Sample records for premix membrane emulsification

  1. Polylactide microspheres prepared by premix membrane emulsification - Effects of solvent removal rate

    NARCIS (Netherlands)

    Sawalha, H.I.M.; Purwanti, N.; Rinzema, A.; Schroën, C.G.P.H.; Boom, R.M.


    Polylactide microspheres were prepared by pre-mix membrane emulsification and subsequent extraction of solvent in a coagulation bath, and ultimately to the gas phase. The polymer was dissolved in dichloromethane and emulsified with water or water¿methanol mixtures by repeated passage through a glass

  2. Preparation of stable food-grade double emulsions with a hybrid premix membrane emulsification system

    NARCIS (Netherlands)

    Eisinaite, Viktorija; Juraite, Dovile; Schroën, Karin; Leskauskaite, Daiva


    In this study we demonstrate that food-grade double emulsions can be successfully prepared using a hybrid premix emulsification system. A coarse emulsion containing beetroot juice as inner water phase, sunflower oil as oil phase and 0.5% or 1.0% whey protein isolate solution as outer water phase

  3. Spray dried double emulsions containing procyanidin-rich extracts produced by premix membrane emulsification: effect of interfacial composition. (United States)

    Berendsen, Rikkert; Güell, Carme; Ferrando, Montserrat


    Spray drying of procyanidin-loaded W1/O/W2 emulsions produced by premix membrane emulsification (ME) enabled to produce microcapsules containing procyanidins. The interface of the emulsion droplets prior to spray drying was stabilized with several hydrophilic emulsifiers (whey protein (WPI), WPI-carboxylmethyl cellulose, WPI-gum Arabic, and WPI-chitosan). Their effect on procyanidin encapsulation efficiency, water activity, moisture and oil content, and microcapsule size distribution was investigated. Furthermore, the microstructure and droplet size distribution of redispersed microcapsules were analyzed. Although premix ME produced W1/O/W2 emulsions with a narrow droplet size distribution regardless the hydrophilic emulsifier (main peak of droplet size distribution around 9 μm), microcapsules after spray drying and double emulsions after redispersion showed profound differences in sizes depending on the interfacial composition. WPI-CMC stabilized microcapsules not only showed the highest procyanidin content (5.3 g kg(-1)) but also gave the narrowest particle size distribution with the lowest particle size for both microcapsules and the corresponding emulsions after rehydration (7.7 and 9.9 μm respectively).

  4. Emulsification using microporous membranes

    Directory of Open Access Journals (Sweden)

    Goran T. Vladisavljević


    Full Text Available Membrane emulsification is a process of injecting a pure dispersed phase or pre-emulsion through a microporous membrane into the continuous phase. As a result of the immiscibility of the two phases, droplets of the dispersed phase are formed at the outlets of membrane pores. The droplets formed in the process are removed from the membrane surface by applying cross-flow or stirring of the continuous phase or using a dynamic (rotating or vibrating membrane. The most commonly used membrane for emulsification is the Shirasu Porous Glass (SPG membrane, fabricated through spinodal decomposition in a melt consisting of Japanese volcanic ash (Shirasu, boric acid and calcium carbonate. Microsieve membranes are increasingly popular as an alternative to highly tortuous glass and ceramic membranes. Microsieves are usually fabricated from nickel by photolithography and electroplating or they can be manufactured from silicon nitride via Reactive Ion Etching (RIE. An advantage of microsieves compared to the SPG membrane is in much higher transmembrane fluxes and higher tolerance to fouling by the emulsion ingredients due to the existence of short, straight through pores. Unlike conventional emulsification devices such as high-pressure valve homogenisers and rotor-stator devices, membrane emulsification devices permit a precise control over the mean pore size over a wide range and during the process insignificant amount of energy is dissipated as heat. The drop size is primarily determined by the pore size, but it depends also on other parameters, such as membrane wettability, emulsion formulation, shear stress on the membrane surface, transmembrane pressure, etc.

  5. High throughput production of double emulsions using packed bed premix emulsification

    NARCIS (Netherlands)

    Sahin, S.; Sawalha, H.I.M.; Schroen, C.G.P.H.


    We explored the potential of packed bed premix emulsification for homogenizing coarse food grade W/O/W emulsions, prepared with sunflower oil. Using packed beds with different glass bead sizes (30–90 µm) at different applied pressures (200–600 kPa), emulsions with reasonably uniform droplet size (sp

  6. Droplet break-up mechanism in premix emulsification using

    NARCIS (Netherlands)

    Nazir, A.; Boom, R.M.; Schroën, C.G.P.H.


    Some emulsification techniques based on microstructures are known for the monodispersity of produced droplets, however, they lack in scalability. The techniques that are able to produce emulsions in larger amounts do not usually produce monodispersed droplets. We here report on a specific technique

  7. Membrane emulsification to produce perfume microcapsules (United States)

    Pan, Xuemiao

    Microencapsulation is an efficient technology to deliver perfume oils from consumer products onto the surface of fabrics. Microcapsules having uniform size/mechanical strength, may provide better release performance. Membrane emulsification in a dispersion cell followed by in-situ polymerization was used to prepare narrow size distribution melamine-formaldehyde (MF) microcapsules containing several types of oil-based fragrances or ingredients. Investigated in this study are the parameters impacting to the size and size distribution of the droplets and final MF microcapsules. A pilot plant-scale cross-flow membrane system was also used to produce MF microcapsules, demonstrating that the membrane emulsification process has potential to be scaled up for industrial applications. In this study, health and environmental friendly poly (methyl methacrylate) (PMMA) microcapsules with narrow size distribution were also prepared for the first time using the dispersion cell membrane emulsification system. Characterization methods previously used for thin-shell microcapsules were expanded to analyse microcapsules with thick shells. The intrinsic mechanical properties of thick shells were determined using a micromanipulation technique and finite element analysis (FEM). The microcapsules structure was also considered in the determination of the permeability and diffusivity of the perfume oils in good solvents..

  8. Membrane emulsification with vibrating membranes: A numerical study

    NARCIS (Netherlands)

    Kelder, J.D.H.; Janssen, J.J.M.; Boom, R.M.


    Membrane emulsification of oil in water may be enhanced by mechanically exciting the membrane, thereby enabling the formation of smaller droplets of a narrower size distribution, combined with higher specific production rate. To evaluate this potential, a force balance model was developed that

  9. Linking Findings in Microfluidics to Membrane Emulsification Process Design: The Importance of Wettability and Component Interactions with Interfaces

    Directory of Open Access Journals (Sweden)

    Karin Schroën


    Full Text Available In microfluidics and other microstructured devices, wettability changes, as a result of component interactions with the solid wall, can have dramatic effects. In emulsion separation and emulsification applications, the desired behavior can even be completely lost. Wettability changes also occur in one phase systems, but the effect is much more far-reaching when using two-phase systems. For microfluidic emulsification devices, this can be elegantly demonstrated and quantified for EDGE (Edge-base Droplet GEneration devices that have a specific behavior that allows us to distinguish between surfactant and liquid interactions with the solid surface. Based on these findings, design rules can be defined for emulsification with any micro-structured emulsification device, such as direct and premix membrane emulsification. In general, it can be concluded that mostly surface interactions increase the contact angle toward 90°, either through the surfactant, or the oil that is used. This leads to poor process stability, and very limited pressure ranges at which small droplets can be made in microfluidic systems, and cross-flow membrane emulsification. In a limited number of cases, surface interactions can also lead to lower contact angles, thereby increasing the operational stability. This paper concludes with a guideline that can be used to come to the appropriate combination of membrane construction material (or any micro-structured device, surfactants and liquids, in combination with process conditions.

  10. Preparation of double emulsions by membrane emulsification - a review

    NARCIS (Netherlands)

    Graaf, van der S.; Schroën, C.G.P.H.; Boom, R.M.


    Double emulsions have potential for the production of low calorie food products, encapsulation of medicines and other high value products. The main issue is the difficulty to efficiently produce double emulsions in a well controlled manner due to their shear sensitivity. In membrane emulsification o

  11. Production of crosslinked protein particles through membrane emulsification

    CSIR Research Space (South Africa)

    Kotzé-Jacobs, L


    Full Text Available the disadvantages of stirred reactors for our application. AIM the purpose of this study was to investigate membrane emulsification as a scale-up method for crosslinked bovine serum albumin (BSA) particles. Factors investigated were crosslinker and surfactant...P Initial studies showed that particles produced through membrane emulsion were much larger than the expected size of 2-3 times the mesh size (20 µm) of the membrane (i.e. much larger than 40-60 µm). crosslinker and surfactant concentration were...

  12. Manufacture of poly(methyl methacrylate) microspheres using membrane emulsification. (United States)

    Bux, Jaiyana; Manga, Mohamed S; Hunter, Timothy N; Biggs, Simon


    Accurate control of particle size at relatively narrow polydispersity remains a key challenge in the production of synthetic polymer particles at scale. A cross-flow membrane emulsification (XME) technique was used here in the preparation of poly(methyl methacrylate) microspheres at a 1-10 l h(-1) scale, to demonstrate its application for such a manufacturing challenge. XME technology has previously been shown to provide good control over emulsion droplet sizes with careful choice of the operating conditions. We demonstrate here that, for an appropriate formulation, equivalent control can be gained for a precursor emulsion in a batch suspension polymerization process. We report here the influence of key parameters on the emulsification process; we also demonstrate the close correlation in size between the precursor emulsion and the final polymer particles. Two types of polymer particle were produced in this work: a solid microsphere and an oil-filled matrix microcapsule.This article is part of the themed issue 'Soft interfacial materials: from fundamentals to formulation'.

  13. Energy-Efficient and Environmentally Sound Technique of Emulsification and Phase Inversion for Producing Stable Droplets – Application of Membrane Emulsification to Polymerization: A Review

    Directory of Open Access Journals (Sweden)

    Sultan Ali


    Full Text Available Emulsification plays an important role in the formation of many products such as milk products, pharmaceuticals, lubricants, paints, dyes, and many food items. Their application in industry such as mining, crude oil extraction, pulp and paper, textile, and polymer, is immense. Over the last two decades there has been a growing interest in making emulsions by a new technique known as membrane emulsification. This is because it requires lesser energy as compared to the other conventional turbulence based methods like homogenization and rotor-stator systems, with the added advantage of producing droplets of a given size by just selecting the average pore size of the membrane. It is the distinguished feature of membrane emulsification that the resulting droplet size is controlled primarily by the membrane type and its pore size and not by the generation of turbulent droplet breakup. This article provides a review of the currently available emulsification processes with special focus on polymer emulsification. The main characteristics of emulsification processes including membrane emulsification process and its principles, influence of process parameters, industrial applications as well as an outlook to further improvement of the processes are discussed.

  14. Droplet formation in a T-shaped microchannel junction: A model system for membrane emulsification

    NARCIS (Netherlands)

    Graaf, van der S.; Steegmans, M.L.J.; Sman, van der R.G.M.; Schroën, C.G.P.H.; Boom, R.M.


    Droplet formation was studied in a glass microchip with a small channel containing to-be-dispersed phase perpendicular to a large channel with a cross-flowing continuous phase. This resembles the situation during cross-flow membrane emulsification. In this model system, droplets are formed at a

  15. Interfacial properties and emulsification performance of thylakoid membrane fragments

    NARCIS (Netherlands)

    Tamayo Tenorio, A.; Jong, de E.W.M.; Nikiforidis, K.; Boom, R.M.; Goot, van der A.J.


    Thylakoids membranes are sophisticated, dynamic structures found in plant leaves, composed of protein complexes in a dynamic lipid matrix. The interfacial absorption dynamics and viscoelasticity of thylakoid membranes fragments were measured to assess the properties of the interfacial layer and to e


    Institute of Scientific and Technical Information of China (English)

    Guanghui Ma


    Much attention has in recent years been paid to fine applications of polymer particles, e.g., carrier for enzyme, separation media for protein, DNA and cell, and carrier for drug in Drug Delivery System (DDS). Control of polymer particle size is especially important in such fine applications. For instance, when the particles are used as a carrier of anti-cancer agents, the locations of particles containing anti-cancer agents also depend on the size of the particles. In this paper, various techniques of controlling polymer particle size are described, with emphasis on Shirasu Porous Glass (SPG) membrane emulsification, as carried out in our research group.

  17. Legume Protein Isolates for Stable Acidic Emulsions Prepared by Premix Membrane Emulsification

    NARCIS (Netherlands)

    Ladjal Ettoumi, Yakoub; Berton-Carabin, Claire; Chibane, Mohamed; Schroën, Karin


    Proteins originating from dry legumes are not that much used in food formulations, yet, they are interesting components from a sustainability point of view, and could have interesting functional properties, e.g. for emulsion preparation. Therefore, this work focuses on the potential of the water

  18. Performance of slotted pores in particle manufacture using rotating membrane emulsification

    Institute of Scientific and Technical Information of China (English)

    Qingchun Yuan; Nita Aryanti; Ruozhou Hou; Richard A.Williams


    This paper addresses the use of different slotted pores in rotating membrane emulsification technology.Pores of square and rectangular shapes were studied to understand the effect of aspect ratio (1-3.5) and their orientation on oil droplet formation.Increasing the membrane rotation speed decreased the droplet size,and the oil droplets produced were more uniform using slotted pores as compared to circular geometry.At a given rotation speed,the droplet size was mainly determined by the pore size and the fluid velocity of oil through the pore (pore fluid velocity).The ratio of droplet diameter to the equivalent diameter of the slotted pore increased with the pore fluid velocity.At a given pore fluid velocity and rotation speed,pore orientation significantly influences the droplet formation rate: horizontally disposed pores (with their longer side perpendicular to the membrane axis) generate droplets at double the rate of vertically disposed pores.This work indicates practical benefits in the use of slotted membranes over conventional methods.

  19. Production of Concentrated Pickering Emulsions with Narrow Size Distributions Using Stirred Cell Membrane Emulsification. (United States)

    Manga, Mohamed S; York, David W


    Stirred cell membrane emulsification (SCME) has been employed to prepare concentrated Pickering oil in water emulsions solely stabilized by fumed silica nanoparticles. The optimal conditions under which highly stable and low-polydispersity concentrated emulsions using the SCME approach are highlighted. Optimization of the oil flux rates and the paddle stirrer speeds are critical to achieving control over the droplet size and size distribution. Investigating the influence of oil volume fraction highlights the criticality of the initial particle loading in the continuous phase on the final droplet size and polydispersity. At a particle loading of 4 wt %, both the droplet size and polydispersity increase with increasing of the oil volume fraction above 50%. As more interfacial area is produced, the number of particles available in the continuous phase diminishes, and coincidently a reduction in the kinetics of particle adsorption to the interface resulting in larger polydisperse droplets occurs. Increasing the particle loading to 10 wt % leads to significant improvements in both size and polydispersity with oil volume fractions as high as 70% produced with coefficient of variation values as low as ∼30% compared to ∼75% using conventional homogenization techniques.

  20. Drug release characterization and preparation of Ca-Alginate microparticle drug carrier using membrane emulsification method

    Energy Technology Data Exchange (ETDEWEB)

    You, Jin Oh; Park, Seong Bae; Park, Ham Yong; Haam, Seung Joo; Kim, Jung Hyun; Kim, Woo Sik [Dept. of Chemical Engineering, Yonsei University, Seoul (Korea)


    Conventional alginate bead has been limited to be used as a drug carrier because of its large size. To overcome the disadvantages of conventional large-size alginate drug beads, Ca-alginate microparticles were prepared using membrane emulsification method controlled with the sodium alginate concentration and the pressure of reactor. The optimal monodispersed microparticles were obtained with the concentration of 2 wt % alginate solution and the pressure of 0.4*10{sup 5} Pa. The mean size of our prepared microparticles was about 4 {gamma}m. As the drug solutions, lidocaine{center_dot}HCI(cationic), sodium salicylate(anionic) and 4-acetamidophenol(nonionic) were selected. These three different drugs were loaded in the drug carrier of prepared alginate microparticles. Drug releases were performed in the sodium phosphate buffers of pH 2 and pH 7 and ionic strength of 0.2. The release behavior with the variation of drug charge shoed that of the cationic drug release was retarded more than anionic one due to the ionic interaction between carboxyl group of alginates and positive charge of cationic drug. >From the comparison experiments of the buffers of pH 2 and pH 7, the release was much retarded at pH 2 buffer due to the ionic repulsive force or ionic attractive force between the carboxyl group and the hydroxy or sodium ion in the buffer. Conclusively, the usage of small-size pH sensitive microparticle as a drug carrier has a high potential for the application of drug delivery systems. 19 refs., 9 figs.

  1. Producing monodisperse drug-loaded polymer microspheres via cross-flow membrane emulsification: the effects of polymers and surfactants. (United States)

    Meyer, Robert F; Rogers, W Benjamin; McClendon, Mark T; Crocker, John C


    Cross-flow membrane emulsification (XME) is a method for producing highly uniform droplets by forcing a fluid through a small orifice into a transverse flow of a second, immiscible fluid. We investigate the feasibility of using XME to produce monodisperse solid microspheres made of a hydrolyzable polymer and a hydrophobic drug, a model system for depot drug delivery applications. This entails the emulsification of a drug and polymer-loaded volatile solvent into water followed by evaporation of the solvent. We use a unique side-view visualization technique to observe the details of emulsion droplet production, providing direct information regarding droplet size, dripping frequency, wetting of the membrane surface by the two phases, neck thinning during droplet break off, and droplet deformation before and after break off. To probe the effects that dissolved polymers, surfactants, and dynamic interfacial tension may have on droplet production, we compare our results to a polymer and surfactant-free fluid system with closely matched physical properties. Comparing the two systems, we find little difference in the variation of particle size as a function of continuous phase flow rate. In contrast, at low dripping frequencies, dynamic interfacial tension causes the particle size to vary significantly with drip frequency, which is not seen in simple fluids. No effects due to shear thinning or fluid elasticity are detected. Overall, we find no significant impediments to the application of XME to forming highly uniform drug-loaded microspheres.

  2. Emulsification with microstructured systems : process principles

    NARCIS (Netherlands)

    Zwan, van der E.A.


    The aim of this thesis is to elucidate the underlying processes and mechanisms that determine the droplet size of emulsions produced with microstructured systems, such as premix microstructure homogenization and microchannel emulsification. The ultimate goal is to describe these methods based on det

  3. Antitumor activity of docetaxel-loaded polymeric nanoparticles fabricated by Shirasu porous glass membrane-emulsification technique

    Directory of Open Access Journals (Sweden)

    Yu YN


    Full Text Available Yunni Yu,1,* Songwei Tan,1,2,* Shuang Zhao,1 Xiangting Zhuang,1 Qingle Song,1 Yuliang Wang,1 Qin Zhou,2,3 Zhiping Zhang1,2 1Tongji School of Pharmacy, 2National Engineering Research Center for Nanomedicine, 3College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, People’s Republic of China *These authors contributed equally to this work Abstract: Docetaxel (DTX has excellent efficiency against a wide spectrum of cancers. However, the current clinical formulation has limited its usage, as it causes some severe side effects. Various polymeric nanoparticles have thus been developed as alternative formulations of DTX, but they have been mostly fabricated on a laboratory scale. Previously, we synthesized a novel copolymer, poly(lactide-D-α-tocopheryl polyethylene glycol 1000 succinate (PLA-TPGS, and found that it exhibited great potential in drug delivery with improved properties. In this study, we applied the Shirasu porous glass (SPG membrane-emulsification technique to prepare the DTX-loaded PLA-TPGS nanoparticles on a pilot scale. The effect of several formulation variables on the DTX-loaded nanoparticle properties, including particle size, zeta potential, and drug-encapsulation efficiency, were investigated based on surfactant type and concentration in the aqueous phase, organic/aqueous phase volumetric ratio, membrane-pore size, transmembrane cycles, and operation pressure. The DTX-loaded nanoparticles were obtained with sizes of 306.8 ± 5.5 nm and 334.1 ± 2.7 nm (mean value ± standard deviation, and drug-encapsulation efficiency of 81.8% ± 4.5% and 64.5% ± 2.7% for PLA-TPGS and poly(lactic-co-glycolic acid (PLGA nanoparticles, respectively. In vivo pharmacokinetic study exhibited a significant advantage of PLA-TPGS nanoparticles over PLGA nanoparticles and Taxotere. Drug-loaded PLA-TPGS nanoparticles exhibited 1.78-, 6.34- and 3.35-fold higher values for area under the curve, half-life, and mean

  4. Polycaprolactone multicore-matrix particle for the simultaneous encapsulation of hydrophilic and hydrophobic compounds produced by membrane emulsification and solvent diffusion processes. (United States)

    Imbrogno, A; Dragosavac, M M; Piacentini, E; Vladisavljević, G T; Holdich, R G; Giorno, L


    Co-encapsulation of drugs in the same carrier, as well as the development of microencapsulation processes for biomolecules using mild operating conditions, and the production of particles with tailored size and uniformity are major challenges for encapsulation technologies. In the present work, a suitable method consisting of the combination of membrane emulsification with solvent diffusion is reported for the production of multi-core matrix particles with tailored size and potential application in multi-therapies. In the emulsification step, the production of a W/O/W emulsion was carried out using a batch Dispersion Cell for formulation testing and subsequently a continuous azimuthally oscillating membrane emulsification system for the scaling-up of the process to higher capacities. In both cases precise and gentle control of droplet size and uniformity of the W/O/W emulsion was achieved, preserving the encapsulation of the drug model within the droplet. Multi-core matrix particles were produced in a post emulsification step using solvent diffusion. The compartmentalized structure of the multicore-matrix particle combined with the different chemical properties of polycaprolactone (matrix material) and fish gelatin (core material) was tested for the simultaneous encapsulation of hydrophilic (copper ions) and hydrophobic (α-tocopherol) test components. The best operating conditions for the solidification of the particles to achieve the highest encapsulation efficiency of copper ions and α-tocopherol of 99 (± 4)% and 93(± 6)% respectively were found. The multi-core matrix particle produced in this work demonstrates good potential as a co-loaded delivery system.


    Institute of Scientific and Technical Information of China (English)


    1 IntroductionIn recent years, there has been increaSing interestin the use of microcaPSules (or microspheres) as thecontrolled release carriers of proteins andpolypeptides such as insulin I'l, growth hormone IZIand human bone morphogenetic protein-2 I3] etc. In+.view of their Practical uses in the body' the primaryaim is to prepare small $he and narrow sizedistribution microcaPSules (Or microspheme) withbiocompatible and biodegradable materials becausetheir distribution in the body is strongly dependent on...

  6. Sulforaphane Microcapsules Prepared by Membrane Emulsification Method%膜乳化法制备莱菔硫烷微胶囊的研究

    Institute of Scientific and Technical Information of China (English)

    李椿方; 程华; 梁浩


    研究了膜乳化法制备莱菔硫烷微胶囊的工艺,采用乙酸乙酯作为有机溶剂相,玉米油与乙基纤维素的质量比为6∶4,乙基纤维素浓度5%时,制得的微胶囊对莱菔硫烷的包埋率最高。同时分析了减压蒸发、常温蒸发和溶剂扩散3种溶剂去除方法对所制备微胶囊包埋率和平均粒径的影响,结果表明,减压蒸发法有更好的包埋率,且速度快、耗时短,平均粒径适合,制得的莱菔硫烷微胶囊分散性能好、表面光滑、流动性好。%Sulforaphane microcapsules were prepared by membrane emulsification method under optimal condition. Ethyl acetate was organic solvent phase , the mass ratio of corn oil and ethyl cellulose ethyl cellulose was 6∶4, ethyl cellulose concentration was 5%. The encapsulation efficiency (EE)of the prepared microcapsules was the highest. At the same time, the solvent removal effects to EE of the prepared microcapsules and the average particle size of the vacuum evaporation , room temperature evaporation and solvent diffusion method were evaluated. The results showed that EE of vacuum evaporation method had better than that of other two methods, and the prepared speed was quick, time was short, the average particle size was suitable. The prepared sulforaphane microcapsules had good dispersion performance , smooth surface and good fluidity.

  7. Emulsification with microstructured devices

    NARCIS (Netherlands)

    Maan, A.A.


    Emulsions (dispersions of droplets of one immiscible liquid e.g. oil into the other e.g. water) are important in many industries including foods, cosmetics, pharmaceuticals and petrochemicals. Traditional machines used for emulsification are highly energy inefficient and provide poor control over

  8. Emulsification with microstructured devices

    NARCIS (Netherlands)

    Maan, A.A.


    Emulsions (dispersions of droplets of one immiscible liquid e.g. oil into the other e.g. water) are important in many industries including foods, cosmetics, pharmaceuticals and petrochemicals. Traditional machines used for emulsification are highly energy inefficient and provide poor control over dr

  9. Use of dynamic membranes for the preparation of vitamin E-loaded lipid particles: An alternative to prevent fouling observed in classical cross-flow emulsification

    NARCIS (Netherlands)

    Lauoini, A.; Charcosset, C.; Fessi, H.; Schroën, C.G.P.H.


    Solid lipid particles (SLP) were introduced at the beginning of the 1990s as an alternative to encapsulation systems such as emulsions and liposomes used in cosmetic and pharmaceutical preparations. The present paper investigated for the first time the preparation of SLP based on premix emulsificati

  10. 超声在陶瓷膜处理乳化含油废水中的作用研究%Effect of Ultrasound on the Treatment of Emulsification Wastewater by Ceramic Membranes

    Institute of Scientific and Technical Information of China (English)

    舒莉; 邢卫红; 徐南平


    Ultrasonic field was applied in the treatment of oil emulsification wastewater by ZrO2 ceramic membrane. The permeate flux,rejection ratio in the filtration process and recovery ratio of flux in the membrane cleaning process were measured. Great improvement in the permeate flux and rejection ratio have been observed for the membrane process enhanced by the ultrasonic field. The permeate flux of water through the membrane was about were 8W of ultrasonic power,7cm of ultrasonic probe length introduced into the membrane channel and the same ultrasonic radiation direction as the wastewater flow. The resistance of the membrane process was compared between the cases with and without ultrasound,and the total resistance was reduced 68% by the use of ultrasound.Four methods including water cleaning,water cleaning under sonication,chemical cleaning and chemical cleaning under sonication were used to recover membrane flux. It was found that the flux recovery ratio increased with the increase of ultrasonic cleaning power. In addition,the use of chemical agents combining with ultrasonic irradiation showed a synergistic effect,which resulted in the highest cleaning efficiency and the shorter cleaning time.

  11. 膜乳化法制备尺寸均-P(NIPAM-co-AAc)微球及其羧基分布%Distribution of Carboxyl Groups in Monodispersed Poly(N-Isopropylacylamide-co-Acrylic Acid) Microspheres Prepared by Membrane Emulsification

    Institute of Scientific and Technical Information of China (English)

    司天保; 秦佳; 王玉霞; 马光辉


    Temperature-/pH-responsive monodispersed poly(N-isopropyl acrylamide-co-acrylic acid) [P(NIPAM-co-AAc)] microspheres were prepared by Shirasu porous glass membrane emulsification at room temperature with N,N,N',N'-tetramethylethylenediamine as accelerator and cyclohexane/trichluromethane mixture as oil phase. The monodispersed P(NIPAM-co-AAc) microspheres with controllable diameter could be reproducibly obtained with cyclohexane-trichloromethane mixture (volumetric ratio 7:3) as oil phase and two stage stirring speeds (140 and and 170 r/min) under the membrane emulsification pressure of 2 kPa. Conductometric titration was used to determine the distribution of carboxyl groups in the microspheres. Four-step titration curves of all the P(NIPAM-co-AAc)microspheres with different acrylic acid contents were obtained. With the increase of AAc content, the amounts of both exterior carboxyl and embeded carboxyl groups increased gradually, but the percentage of exterior carboxyl groups increased firstly, then remained at a fixed value. The highest percentage of exterior carboxyl groups was obtained with 15%(ω) acrylic acid in the microspheres.%采用膜乳化法,以环己烷和氯仿混合溶液为油相,在室温下通过加入加速剂TEMED引发聚合反应,制备了一系列不同内烯酸含量的P(NIPAM-co-AAc)微球.结果表明,在压力2 kPa、环己烷/氯仿体积比7:3、第一和第二阶段过膜搅拌速度分别为140和170 r/min的条件下,可制备粒径均一、大小可控、重复性较好的P(NlPAM-co-AAc)微球.用电导滴定法测定微球中羧基分布,所有不同丙烯酸含量的P(NIPAM-co-AAc)微球电导滴定曲线均为4阶梯形状,随其含量增加,微球外层羧基含量和内层包埋的羧基含量均逐渐增加,但外层羧基占总羧基含量比例先增大然后趋于不变,丙烯酸含量为15%时达最大值.

  12. Zeolite imidazolate frameworks 8 as sorbent and its application to sonication-assisted emulsification microextraction combined with vortex-assisted porous membrane-protected micro-solid-phase extraction for fast analysis of acidic drugs in environmental water samples. (United States)

    Ge, Dandan; Lee, Hian Kee


    A novel and fast procedure, sonication-assisted emulsification microextraction combined with vortex-assisted porous membrane protected micro-solid-phase extraction (SAEME-VA-μ-SPE), was developed for the gas chromatography-mass spectrometric determination of acidic drugs from environmental water samples. One advantage of the new procedure is that any solvent immiscible with water can be used as extractant solvent of SAEME and any solid sorbent can be used for μ-SPE in the SAEME-VA-μ-SPE process. In the present work, zeolite imidazolate framework 8 (ZIF-8) was employed as extraction sorbent for μ-SPE and 1-octanol as extractant solvent for SAEME. ZIF-8 has very good thermal, chemical and water stability, which make it a suitable material for the extraction of trace analytes from aqueous samples. Under the optimized extraction conditions, the developed method exhibited low limits of detection (0.01-0.04 ng/ml), good linearity (with r² between 0.9965 and 0.9993) from 0.5 to 50 ng/ml and satisfactory repeatability (between 4.1% and 7.6%). In essence SAEME-VA-μ-SPE is a combination of two different and efficient miniaturized techniques. It was demonstrated to be a fast, accurate, and convenient pretreatment procedure for trace analysis of environmental water samples.

  13. Microfluidic EDGE emulsification: the importance of interface interactions on droplet formation and pressure stability (United States)

    Sahin, Sami; Bliznyuk, Olesya; Rovalino Cordova, Ana; Schroën, Karin


    The fact that interactions of components with interfaces can influence processes is well-known; e.g. deposit accumulation on heat exchangers and membrane fouling lead to additional resistances against heat and mass transfer, respectively. In microfluidic emulsification, the situation is even more complex. Component accumulation at the liquid/liquid interface is necessary for emulsion stability, while undesired at the solid/liquid interface where it may change wettability. For successful emulsification both aspects need to be controlled, and that is investigated in this paper for o/w emulsification with microfluidic EDGE devices. These devices were characterised previously, and can be used to detect small wettability changes through e.g. the pressure stability of the device. We used various oil/emulsifier combinations (alkanes, vegetable oil, surfactants and proteins) and related droplet size and operational pressure stability to component interactions with the solid surface and liquid interface. Surfactants with a strong interaction with glass always favour emulsification, while surfactants that have week interactions with the surface can be replaced by vegetable oil that interacts strongly with glass, resulting in loss of emulsification. Our findings clearly show that an appropriate combination of construction material and emulsion components is needed to achieve successful emulsification in microfluidic EDGE devices.

  14. Fundamentals of premixed turbulent combustion

    CERN Document Server

    Lipatnikov, Andrei


    Lean burning of premixed gases is considered to be a promising combustion technology for future clean and highly efficient gas turbine engines. This book highlights the phenomenology of premixed turbulent flames. The text provides experimental data on the general appearance of premixed turbulent flames, physical mechanisms that could affect flame behavior, and physical and numerical models aimed at predicting the key features of premixed turbulent combustion. The author aims to provide a simple introduction to the field for advanced graduate and postgraduate students. Topics covered include La

  15. CA-gel/PLGA composite microspheres loaded protein by SPG membrane emulsification%SPG 膜乳化法制备载蛋白的 CA-gel/PLGA 复合微球

    Institute of Scientific and Technical Information of China (English)

    钟晨; 罗宇燕; 郭喆霏; 罗永梅; 张永明


    Protein loaded CA-gel /PLGA composite microspheres were prepared by a novel SPG mem-brane emulsification method,which was modified from the traditional preparation method of PLGA micro-spheres.The formation of the sustained-release gel was based on the ionic interaction between Sa and cal-cium ion.The drug loading of composite microspheres was significantly increased from 6.94% to 8.35%,entrapment efficiency was increased from 62.47% to 75.1 6%,and the burst release rate was declined from 42.32% to 30.84%.Drug release test showed that nearly 40.29% of drug was continu-ously and steadily released from the composite microspheres in 2 ~40 days.The drug release curves were corresponded to Peppas-Sahlin equation (R2 >0.99)for both the traditional microspheres and composite microspheres,which means that the release mechanism was mainly diffusion and dissolution.The results from scanning electron microscopy and freezing microtomy demonstrated that the composite microspheres were more compact in structure,and its surface hole number and porosity were smaller than traditional PLGA microspheres.The enhanced fluorescence intensity was observed from the laser confocal scan mi-croscopy,indicating that more protein drugs were wrapped inside composite microspheres.In conclusion, the CA-gel /PLGA composite microspheres can effectively increase drug loading and entrapment efficiency and reduce the burst release.%采用 SPG 膜乳化法,在 PLGA 微球的制备基础上,利用 Sa 与 Ca2+螯合形成难溶于水的 CA-gel 原理,以粒径、载药量、包封率、体外释放行为等作为评价指标,研究制备载蛋白药物的 CA-gel/PLGA 复合微球的新工艺,并对比复合微球和 PLGA 微球的载药释药特性的差异。与 PLGA 微球相比,复合微球的载药量由6.94%增加至8.35%,包封率由62.47%增加至75.16%,突释率由42.32%下降至30.84%。复合微球在经历早期的突释之后以较为均匀的速

  16. Step-emulsification in nanofluidic device

    CERN Document Server

    Li, Z; Pismen, L M; Tabeling, P


    In this paper we present a comprehensive study of the step-emulsification process for high-throughput production of (sub-)$\\mu$m-size monodisperse droplets. The microfluidic device combines a Hele-Shaw nanofluidic cell with a step-like outlet to a deep and wide reservoir. The proposed theory based on Hele-Shaw hydrodynamics provides the quasi-static shape of the free boundary between the disperse liquid phase engulfed by the co-flowing continuous phase prior to transition to oscillatory step-emulsification at low enough capillary number. At the transition the proposed theory anticipates a simple condition for critical capillary number as a function of the Hele-Shaw cell geometry. The transition threshold is in excellent agreement with experimental data. A simple closed-form expression for the size of the droplets generated in step-emulsification regime derived using simple geometric arguments also shows a very good agreement with the experimental results.

  17. Porous microcapsule formation with microsieve emulsification

    NARCIS (Netherlands)

    Wagdare, N.A.; Marcelis, A.T.M.; Boom, R.M.; Rijn, van C.J.M.


    A simple route is presented to prepare core–shell Eudragit microcapsules through a solvent extraction method with the use of microsieve emulsification. Droplets from a solution of Eudragit FS 30D (a commercial copolymer of poly(methyl acrylate-co-methyl methacrylate-co-methacrylic acid) 7:3:1) and h


    Institute of Scientific and Technical Information of China (English)

    Suda Kiatkamjornwong; Roongkan Nuisin; Guang-Hui Ma; Shinzo Omi


    This research studied the initiator efficiency for producing polymeric particles of poly(styrene-co-methyl methacrylate) copolymers by a Shirasu porous glass membrane (SPG) emulsification technique followed by suspension copolymerization. BPO, ADVN, and AIBN were used as initiators and we found that BPO is the most suitable initiator.Copolymers for various feed ratios of styrene/methyl methacrylate were thus synthesized by benzoyl peroxide, and their copolymer particle size, molecular weight distribution and particle size distribution were characterized. Then n-BMA or 2-EHMA was added as the third monomer to decrease the terpolymcr glass transition temperature. This article describes the preparation technique, recipes and polymerization conditions for producing both copolymer and terpolymer particles, particle size changes, the corresponding particle morphologies and glass transition temperatures.

  19. Performance of sonication and microfluidization for liquid-liquid emulsification. (United States)

    Maa, Y F; Hsu, C C


    The purpose of this research was to evaluate and compare liquid-liquid emulsions (water-in-oil and oil-in-water) prepared using sonication and microfluidization. Liquid-liquid emulsions were characterized on the basis of emulsion droplet size determined using a laser-based particle size analyzer. An ultrasonic-driven benchtop sonicator and an air-driven microfluidizer were used for emulsification. Sonication generated emulsions through ultrasound-driven mechanical vibrations, which caused cavitation. The force associated with implosion of vapor bubbles caused emulsion size reduction and the flow of the bubbles resulted in mixing. An increase in viscosity of the dispersion phase improved the sonicator's emulsification capability, but an increase in the viscosity of the dispersed phase decreased the sonicator's emulsification capability. Although sonication might be comparable to homogenization in terms of emulsification efficiency, homogenization was relatively more effective in emulsifying more viscous solutions. Microfluidization, which used a high pressure to force the fluid into microchannels of a special configuration and initiated emulsification via a combined mechanism of cavitation, shear, and impact, exhibited excellent emulsification efficiency. Of the three methodologies, sonication generated more heat and might be less suitable for emulsion systems involving heat-sensitive materials. Homogenization is in general a more effective liquid-liquid emulsification method. The results derived from this study can serve as a basis for the evaluation of large-scale liquid-liquid emulsification in the microencapsulation process.

  20. A Geometric Model for the Dynamics of Microchannel Emulsification

    NARCIS (Netherlands)

    Zwan, van der E.A.; Schroën, C.G.P.H.; Boom, R.M.


    Microchannel emulsification is an interfacial tension driven method to produce monodisperse microdroplets, or microspheres. In this paper we introduce a model for describing the dynamics of microchannel emulsification based on simple time dependent geometric shape analysis. The model is based on mec

  1. Emulsification properties of soy bean protein

    Directory of Open Access Journals (Sweden)



    Full Text Available Chen W, Li X, Rahman MRT, Al-Hajj NQM, Dey KC, Raqib SM. 2014. Emulsification properties of soy bean protein. Nusantara Bioscience 6: 196-202. Emulsion stability and emulsifying ability are two important factors in food industry. Soy protein has the great of interest because of its amphilic structure. β-Conglycinnin and glycinin are main components in soy protein which can be used as emulsifiers in food processing. However, due to its size and molecular weight, the emulsifying ability of soy protein is limited. By chemical, physical and enzymatic modification, the emulsifying ability of soy protein can be improved. The addition of polysaccharides in emulsion is common. The interaction of polysaccharides and proteins are being discussed in this review. In some complex food emulsion, the function of soy protein molecules and emulsifier at the interface need to be investigated in the future study.

  2. Nano-encapsulated PCM via Pickering Emulsification (United States)

    Wang, Xuezhen; Zhang, Lecheng; Yu, Yi-Hsien; Jia, Lisi; Sam Mannan, M.; Chen, Ying; Cheng, Zhengdong


    We designed a two-step Pickering emulsification procedure to create nano-encapsulated phase changing materials (NEPCMs) using a method whose simplicity and low energy consumption suggest promise for scale-up and mass production. Surface-modified amphiphilic zirconium phosphate (ZrP) platelets were fabricated as the Pickering emulsifiers, nonadecane was chosen as the core phase change material (PCM), and polystyrene, the shell material. The resultant capsules were submicron in size with remarkable uniformity in size distribution, which has rarely been reported. Differential scanning calorimetry (DSC) characterization showed that the capsulation efficiency of NEPCMs, and they were found to be thermal stable, as characterized by the DSC data for the sample after 200 thermal cycles. NEPCMs exhibit superior mechanical stability and mobility when compared with the well-developed micro-encapsulated phase change materials (MEPCMs). NEPCMs find useful applications in thermal management, including micro-channel coolants; solar energy storage media; building temperature regulators; and thermal transfer fabrics.

  3. On the regimes of premixing

    Energy Technology Data Exchange (ETDEWEB)

    Angelini, S.; Theofanous, T.G.; Yuen, W.W. [California Univ., Santa Barbara, CA (United States). Center for Risk Studies and Safety


    The conditions of the MAGICO-2000 experiment are extended to more broadly investigate the regimes of premixing, and the corresponding internal structures of mixing zones. With the help of the data and numerical simulations using the computer code PM-ALPHA, we can distinguish extremes of behavior dominated by inertia and thermal effects - we name these the inertia and thermal regimes, respectively. This is an important distinction that should guide future experiments aimed at code verification in this area. Interesting intermediate behaviors are also delineated and discussed. (author)

  4. Computational aspects of premixing modelling

    Energy Technology Data Exchange (ETDEWEB)

    Fletcher, D.F. [Sydney Univ., NSW (Australia). Dept. of Chemical Engineering; Witt, P.J.


    In the steam explosion research field there is currently considerable effort being devoted to the modelling of premixing. Practically all models are based on the multiphase flow equations which treat the mixture as an interpenetrating continuum. Solution of these equations is non-trivial and a wide range of solution procedures are in use. This paper addresses some numerical aspects of this problem. In particular, we examine the effect of the differencing scheme for the convective terms and show that use of hybrid differencing can cause qualitatively wrong solutions in some situations. Calculations are performed for the Oxford tests, the BNL tests, a MAGICO test and to investigate various sensitivities of the solution. In addition, we show that use of a staggered grid can result in a significant error which leads to poor predictions of `melt` front motion. A correction is given which leads to excellent convergence to the analytic solution. Finally, we discuss the issues facing premixing model developers and highlight the fact that model validation is hampered more by the complexity of the process than by numerical issues. (author)

  5. Influence of Emulsification of Composite Collector on Rutile Flotation

    Institute of Scientific and Technical Information of China (English)


    The emulsifiable conditions of composite collector (FP-2) in industry are systematically researched in the paper. It is found that tpyes of the emulsifiers, emulsification temperature, the mixed proportion of FP-2 to emulsifier are the important parameters affecting emulsification effect and rutile flotation targets. When the proportion of FP-2 to emulsifier (E-4) is 100, by means of emulsification of mechanical stirring, the rutile flotation recovery is 85.6% and the grade is 75.3%, which approach the flotation targets of FP-2 used as collector by ultrasonic emulsification unit. The favorable conditions are set up for FP-2 in industry application. By means of XPS measurement,the chemical interaction of composite collector with rutile is found.

  6. Microchannel emulsification using gelatin and surfactant-free coacervate microencapsulation. (United States)

    Nakagawa, Kei; Iwamoto, Satoshi; Nakajima, Mitsutoshi; Shono, Atsushi; Satoh, Kazumi


    In this study, we investigated the use of microchannel (MC) emulsifications in producing monodisperse gelatin/acacia complex coacervate microcapsules of soybean oil. This is considered to be a novel method for preparing monodisperse O/W and W/O emulsions. Generally, surfactants are necessary for MC emulsification, but they can also inhibit the coacervation process. In this study, we investigated a surfactant-free system. First, MC emulsification using gelatin was compared with that using decaglycerol monolaurate. The results demonstrated the potential use of gelatin for MC emulsification. MC emulsification experiments conducted over a range of conditions revealed that the pH of the continuous phase should be maintained above the isoelectric point of the gelatin. A high concentration of gelatin was found to inhibit the production of irregular-sized droplets. Low-bloom gelatin was found to be suitable for obtaining monodisperse emulsions. Finally, surfactant-free monodisperse droplets prepared by MC emulsification were microencapsulated with coacervate. The microcapsules produced by this technique were observed with a confocal laser scanning microscope. Average diameters of the inner cores and outer shells were 37.8 and 51.5 microm; their relative standard deviations were 4.9 and 8.4%.

  7. Study on mechanism of wet air oxidation of emulsification wastewater. (United States)

    Tang, Wen W; Zeng, Xin P; Xiao, Yao M; Gu, Guo W


    Wet air oxidation (WAO) can effectively be used to treat high-concentration, non-biodegradable emulsification wastewater that contains nonionic matters. Gas chromatograph analysis of emulsification wastewater after oxidation indicated that a catalyst increased production of fatty acids but could not promote its oxidation between 160 and 180 degrees C. When the temperature was greater than or equal to 220 degrees C, the catalyst not only increased production of fatty acids initially but effectively promoted its oxidation in later stages and significantly reduced the concentration of residual surfactants. Experiments proved that fatty acids (especially acetic acid) were the primary intermediate products and that oxidation of these acids was the rate-limiting step. During the process of catalytic WAO of emulsification wastewater, active oxygen molecules attacked organic matters resulting in production of fatty acids, ketone, alcohol, hydrocarbon, and oligo-polyether through radical chain reactions.

  8. Impact of the emulsification-diffusion method on the development of pharmaceutical nanoparticles. (United States)

    Quintanar-Guerrero, David; Zambrano-Zaragoza, María de la Luz; Gutierrez-Cortez, Elsa; Mendoza-Munoz, Nestor


    Nanotechnology is having a profound impact in many scientific fields and it has become one of the most important and exciting discipline. Like all technological advances, nanotechnology has its own scientific basis with a broad interdisciplinary effect. Perhaps, we are witnessing an exponential growth of nanotechnology, reflection of this is the important increase in the number of patents, scientific papers and specialized "nano" meetings and journals. The impact in the pharmaceutical area is related to the use of colloidal drug delivery systems as carriers for bioactive agents, in particular, the nanoparticle technology. The term nanoparticles designates solid submicronic particles formed of acceptable materials (e.g. polymers, lipids, etc.) containing an active substance. It includes both nanospheres (matricial systems) and nanocapsules (membrane systems). The knowledge of the nanoparticle preparation methods is a key issue for the formulator involved with drug-delivery research and development. In general, the methods based on preformed polymers, in particular biodegradable polymers, are preferred due to their easy implementation and lower potential toxicity. One of the most widely used methods to prepare polymeric nanoparticles is emulsification-diffusion. This method has been discussed in some reviews that compile research works but has a small number of patents. In this review, the emulsification-diffusion method is discussed from a technological point of view in order to show the operating conditions and formulation variables from data extracted of recent patents and experimental works. The main idea is to provide the reader with a general guide for formulators to make decisions about the usefulness of this method to develop specific nanoparticulate systems. The first part of this review provides an overview of the emulsification-diffusion method to prepare polymeric nanoparticles, while the second part evaluates the influence of preparative variables on the

  9. Design factors for stable lean premix combustion

    Energy Technology Data Exchange (ETDEWEB)

    Richards, G.A.; Yip, M.J.; Gemmen, R.S.


    The Advanced Turbine Systems (ATS) program includes the development of low-emission combustors. Low emissions have already been achieved by premixing fuel and air to avoid the hot gas pockets produced by nozzles without premixing. While the advantages of premixed combustion have been widely recognized, turbine developers using premixed nozzles have experienced repeated problems with combustion oscillations. Left uncontrolled, these oscillations can lead to pressure fluctuations capable of damaging engine hardware. Elimination of such oscillations is often difficult and time consuming - particularly when oscillations are discovered in the last stages of engine development. To address this issue, METC is studying oscillating combustion from lean premixing fuel nozzles. These tests are providing generic information on the mechanisms that contribute to oscillating behavior in gas turbines. METC is also investigating the use of so-called {open_quotes}active{close_quotes} control of combustion oscillations. This technique periodically injects fuel pulses into the combustor to disrupt the oscillating behavior. Recent results on active combustion control are presented in Gemmen et al. (1995) and Richards et al. (1995). This paper describes the status of METC efforts to avoid oscillations through simple design changes.

  10. Phaco-emulsification causes the formation of cavitation bubbles. (United States)

    Svensson, B; Mellerio, J


    There have been reports of complications arising from damage to non-lenticular ocular tissue during the increasingly popular procedure of cataract extraction with phaco-emulsification. One cause of this damage might be the formation of cavitation bubbles. Such bubbles are known to produce free radicals and shock waves. This paper demonstrates directly the formation of cavitation bubbles at the tip of the phaco-probe. It also shows the importance of a smooth probe profile in reducing bubble formation. Recommendations are made for probe and tip design and for the use of minimum power during the surgical procedure of phaco-emulsification.

  11. Chaos in an imperfectly premixed model combustor

    Energy Technology Data Exchange (ETDEWEB)

    Kabiraj, Lipika, E-mail:; Saurabh, Aditya; Paschereit, Christian O. [Hermann Föttinger Institut, Technische Universität Berlin (Germany); Karimi, Nader [School of Engineering, University of Glasgow (United Kingdom); Sailor, Anna [University of Wisconsin-Madison, Madison 53706 (United States); Mastorakos, Epaminondas; Dowling, Ann P. [Department of Engineering, University of Cambridge (United Kingdom)


    This article reports nonlinear bifurcations observed in a laboratory scale, turbulent combustor operating under imperfectly premixed mode with global equivalence ratio as the control parameter. The results indicate that the dynamics of thermoacoustic instability correspond to quasi-periodic bifurcation to low-dimensional, deterministic chaos, a route that is common to a variety of dissipative nonlinear systems. The results support the recent identification of bifurcation scenarios in a laminar premixed flame combustor (Kabiraj et al., Chaos: Interdiscip. J. Nonlinear Sci. 22, 023129 (2012)) and extend the observation to a practically relevant combustor configuration.

  12. Characterization of emulsification at flat microchannel Y junctions

    NARCIS (Netherlands)

    Steegmans, M.L.J.; Schroën, C.G.P.H.; Boom, R.M.


    Y junctions with a large width-to-depth ratio were used for the emulsification of hexadecane in various ethanol¿water mixtures with different static interfacial tension and viscosity. The resulting droplets were monodisperse. To describe droplet size a force-balance model was derived and was found

  13. Preparation of microcapsule-supported palladium catalyst using SPG (Shirasu Porous Glass) emulsification technique

    Institute of Scientific and Technical Information of China (English)

    Ying Liu; Xiu Juan Feng; De Cai Bao; Kai Xiao Li; Ming Bao


    A new method for the preparation of microcapsule-supported palladium catalyst was described.The highly monodisperse crosslinked polystyrene microcapsules containing phosphine ligand were synthesized by the self-assembling of phase separated polymer(SaPSeP)method using diphenyl(4-vinylphenyl)phosphine and divinylbenzene as a monomer and crosslinking agent,respectively,and 2,2'-azobisisobutyronitrile(AIBN)as an initiator within the droplets of oil-in-water(O/W)emulsions,which were prepared by using the Shirasu Porous Glass(SPG)membrane emulsification technique.The prepared microcapsule-supported palladium catalyst exhibited high catalytic activity for Heck reaction and can be reused several times without loss of activity.

  14. Pickering Emulsification to Mass Produce Nanoencapsulated Phase-change-material (United States)

    Wang, Xuezhen; Zhang, Lecheng; Yu, Yi-Hsien; Mannan, S. Sam; Chen, Ying; Cheng, Zhengdong; Cheng's Group Team, Dr.


    Phase changing materials (PCM) have useful applications in thermal management. However, mass production of micro and nano encapsulated PCM has been a challenge. Here, we present a simple and scalable method via a two-step Pickering emulsification method. We have developed interface active nanoplates by asymmetric modification of nanoplates of layered crystal materials. Nanoencapsulated PCM is realized with exfoliated monolayer nanoplates surfactants using very little energy input for emulsification. Further chemical reactions are performed to convert the emulsions into core-shell structures. The resulted capsules are submicron in size with remarkable uniformity in size distribution. DSC characterization showed that the capsulation efficiency of NEPCM was 58.58% and were thermal stable which was characterized by the DSC data for the sample after 200 thermal cycling.

  15. Emulsification of Hydrocarbons by Biosurfactant: Exclusive Use of Agrowaste

    Directory of Open Access Journals (Sweden)

    Olusola Solomon Amodu


    Full Text Available Novel biosurfactant-producing strains were isolated from hydrocarbon-contaminated environments that exclusively utilize agro-waste as their primary carbon source for the expression of biosurfactants. These were quantified using various standardized methods. Among the agro-waste screened, Beta vulgaris (Beetroot proved to be the most suitable substrate, for which the biosurfactants produced by three bacterial isolates–B. licheniformis STK01, B. subtilis STK02, and P. aeruginosa STK03–lowered the surface tension of the culture media to 30.0, 32.98, and 30.37 mN/m, respectively. The biosurfactants achieved considerable emulsification activity, particularly for heavy hydrocarbons, with the highest emulsification indices being 65.5% and 95% for anthracene and lubricant oil, respectively. The emulsion formed with lubricant oil was thermally stable even up to 50 °C for 21 days. The results showed the proficiency of the novel bacterial isolates used, as well as the suitability of solid agro-waste for biosurfactant production, thus suggesting that exclusive utilization of solid agro-waste is a promising option for use in biosurfactant production for environmental remediation. The outstanding emulsification activity and thermal stability demonstrated by the biosurfactants produced showed their potential applications in enhancing bioavailability and bioremediation of recalcitrant and hydrophobic environmental contaminants.

  16. Membraner

    DEFF Research Database (Denmark)

    Bach, Finn


    Notatet giver en kort introduktion til den statiske virkemåde af membraner og membrankonstruktioner......Notatet giver en kort introduktion til den statiske virkemåde af membraner og membrankonstruktioner...


    Institute of Scientific and Technical Information of China (English)

    YANG Zhenzhong; ZHAO Delu; XU Yuanze; XU Mao


    Phase inversion emulsification technique is a recently developed method to achieve waterborne dispersions of polymer resin. It is found that the electrical and rheological properties of the system experience abrupt changes in the vicinity of the phase inversion point (PIP). Before PIP, the system is a Newtonian fluid. At PIP, the continuous phase transforms from polymer resin to water phase with the result that the electrical resistance of the system drops abruptly. Meanwhile, the system at PIP exhibits high viscoelasticity originated from the formation of a physical gel alike structure among the waterborne particles. Besides, the morphology evolution is observed by Scanning Electron Microscopy (SEM).


    Institute of Scientific and Technical Information of China (English)

    Zhen-zhong Yang


    In this review,our recent work in phase inversion emulsification (PIE)for polymer(especially epoxy resin) waterborne dispersions is summarized.Based on experimental results about PIE process,the physical model is proposed which Can guide the synthesis of the waterborne dispersions such as polymer/nanoparticle composite dispersion.In the presence of a latent curing catalyst,PIE can give a crosslinkable epoxy resin waterborne dispersion.The dispersions can form cured transparent coatings with some unique properties such as UV shielding.They are promising in functional coatings,waterborne resin matrices for composites,and sizing for high performance fibers.

  19. Turbulence in laminar premixed V-flames

    Institute of Scientific and Technical Information of China (English)

    ZHANG; Xiaoqian(张孝谦); LEI; Yu(雷宇); WANG; Baorui(王宝瑞); WANG; Yue(王岳); WEI; Minggang(韦明罡)


    Strong velocity fluctuations had been found in the laminar premixed V-flames. These velocity fluctuations are closely related to the chemical reaction. But the effects of the upstream combustible mixture velocity on the velocity fluctuations inside the flame are quite weak. The probability distribution function (PDF) of the velocity in the centre region of the flame appears "flat top" shaped. By analyzing the experiment results the flame-flow interactions are found to affect the flame not only at large scale in the flow field but also at small scale inside the flame. These effects will give rise to flame generated small scale turbulences.

  20. Performance evaluation of organic emulsion liquid membrane on phenol removal

    CERN Document Server

    Ng, Y S; Hashim, M A


    The percentage removal of phenol from aqueous solution by emulsion liquid membrane and emulsion leakage was investigated experimentally for various parameters such as membrane:internal phase ratio, membrane:external phase ratio, emulsification speed, emulsification time, carrier concentration, surfactant concentration and internal agent concentration. These parameters strongly influence the percentage removal of phenol and emulsion leakage. Under optimum membrane properties, the percentage removal of phenol was as high as 98.33%, with emulsion leakage of 1.25%. It was also found that the necessity of carrier for enhancing phenol removal was strongly dependent on the internal agent concentration.

  1. Numerical simulation of laminar premixed combustion in a porous burner

    Institute of Scientific and Technical Information of China (English)

    ZHAO Pinghui; CHEN Yiliang; LIU Minghou; DING Min; ZHANG Genxuan


    Premixed combustion in porous media differs substantially from combustion in free space. The interphase heat transfer between a gas mixture and a porous medium becomes dominant in the premixed combustion process. In this paper, the premixed combustion of CH4/air mixture in a porous medium is numerically simulated with a laminar combustion model. Radiative heat transfer in solids and convective heat transfer between the gas and the solid is especially studied. A smaller detailed reaction mechanism is also used and the results can show good prediction for many combustion phenomena.

  2. Oil-in-water emulsification using confined impinging jets. (United States)

    Siddiqui, Shad W; Norton, Ian T


    A confined impinging jet mixing device has been used to investigate the continuous sunflower oil/water emulsification process under turbulent flow conditions with oil contents between 5% (v/v) and 10% (v/v). Various emulsifiers (Tween20, Span80, Whey Protein, Lecithin and Sodium Dodecylsulphate) varying in molecular weights have been studied. Mean droplet sizes varied with the emulsifiers used and smallest droplets were obtained under fully turbulent flow regime, i.e. at the highest jet flow rate and highest jet Reynolds Number conditions. Sodium Dodecylsulfate (SDS) produced droplets in the range of 3.8 μm while 6 μm droplets were obtained with Whey Protein. Similar droplet sizes were obtained under fully turbulent flow conditions (610 mL/min; Reynolds Number=13,000) for oil content varying between 5% (v/v) and 10% (v/v). To investigate the smallest droplet size possible in the device, the emulsion was passed through the geometry multiple times. Multi-pass emulsification resulted in reduction in droplet size indicating that longer residence in the flow field under high shear condition allowed for breakage of droplets as well as the time for the emulsifier to stabilize the newly formed droplets, decreasing the impact of coalescence. This was confirmed by timescale analysis of the involved process steps for the droplet data obtained via experiments. Dependence of mean droplet size on the o/w interfacial tension and peak energy dissipation was also investigated. Copyright © 2012 Elsevier Inc. All rights reserved.

  3. Premixed flame propagation in vertical tubes

    CERN Document Server

    Kazakov, Kirill A


    Analytical treatment of premixed flame propagation in vertical tubes with smooth walls is given. Using the on-shell flame description, equations describing quasi-steady flame with a small but finite front thickness are obtained and solved numerically. It is found that near the limits of inflammability, solutions describing upward flame propagation come in pairs having close propagation speeds, and that the effect of gravity is to reverse the burnt gas velocity profile generated by the flame. On the basis of these results, a theory of partial flame propagation driven by the gravitational field is developed. A complete explanation is given of the intricate observed behavior of limit flames, including dependence of the inflammability range on the size of the combustion domain, the large distances of partial flame propagation, and the progression of flame extinction. The role of the finite front-thickness effects is discussed in detail. Also, various mechanisms governing flame acceleration in smooth tubes are ide...

  4. Premixes production for synthesis of wear-resistant composite materials (United States)

    Kontsevoi, Yu V.; Meilakh, A. G.; Shubin, A. B.; Pastukhov, E. A.; Dolmatov, A. V.; Sipatov, I. S.


    State of the art line of powder metallurgy is application of initial powders as micro-composites with additional components - premixes. Usage of premixes inhibits segregation of added components and implies the homogeneity of powder charge composition, and finally it has a significant impact on structure formation and properties of end products. The aim of the present work was to design the new production technology of premixes based on iron powder which is layer-by-layer plated by aluminium and copper. We propose to carry out production of Cu-Al-Fe premixes in two stages: cladding of iron powder by aluminium and coating of the obtained composite by copper. The self-developed technique of vibration treatment of iron and aluminium powder mixture was chosen for this purpose. The uniform in thickness and unbroken copper-plating of Fe-Al powders were carried out by chemical technique. Physico-chemical properties and production conditions of premixes-powders were studied, besides optimal parameters of production and further heat-treatment were selected. In the result of the present study the Fe-Al-Cu premixes with laminated structure comprising of iron core, Fe-Al and Cu-Al intermetallide shells were synthesised.

  5. Microencapsulated probiotics using emulsification technique coupled with internal or external gelation process. (United States)

    Song, Huiyi; Yu, Weiting; Gao, Meng; Liu, Xiudong; Ma, Xiaojun


    Alginate-chitosan microcapsules containing probiotics (Yeast, Y235) were prepared by emulsification/external gelation and emulsification/internal gelation techniques respectively. The gel beads by external gelation showed asymmetrical structure, but those by internal gelation showed symmetrical structure in morphology. The cell viability was approximately 80% for these two techniques. However, during cell culture process, emulsification/internal gelation microcapsules showed higher cell growth and lower cell leakage. Moreover, the survival rate of entrapped low density cells with culture (ELDCwc) increased obviously than that directly entrapped high density cells (dEHDC) and free cells when keeping in simulated gastrointestinal conditions. It indicated the growth process of cells in microcapsule was important and beneficial to keep enough active probiotics under harmful environment stress. Therefore, the emulsification/internal gelation technique was the preferred method for application in food or biotechnological industries. Copyright © 2013 Elsevier Ltd. All rights reserved.

  6. Premixer Design for High Hydrogen Fuels

    Energy Technology Data Exchange (ETDEWEB)

    Benjamin P. Lacy; Keith R. McManus; Balachandar Varatharajan; Biswadip Shome


    This 21-month project translated DLN technology to the unique properties of high hydrogen content IGCC fuels, and yielded designs in preparation for a future testing and validation phase. Fundamental flame characterization, mixing, and flame property measurement experiments were conducted to tailor computational design tools and criteria to create a framework for predicting nozzle operability (e.g., flame stabilization, emissions, resistance to flashback/flame-holding and auto-ignition). This framework was then used to establish, rank, and evaluate potential solutions to the operability challenges of IGCC combustion. The leading contenders were studied and developed with the most promising concepts evaluated via computational fluid dynamics (CFD) modeling and using the design rules generated by the fundamental experiments, as well as using GE's combustion design tools and practices. Finally, the project scoped the necessary steps required to carry the design through mechanical and durability review, testing, and validation, towards full demonstration of this revolutionary technology. This project was carried out in three linked tasks with the following results. (1) Develop conceptual designs of premixer and down-select the promising options. This task defined the ''gap'' between existing design capabilities and the targeted range of IGCC fuel compositions and evaluated the current capability of DLN pre-mixer designs when operated at similar conditions. Two concepts (1) swirl based and (2) multiple point lean direct injection based premixers were selected via a QFD from 13 potential design concepts. (2) Carry out CFD on chosen options (1 or 2) to evaluate operability risks. This task developed the leading options down-selected in Task 1. Both a GE15 swozzle based premixer and a lean direct injection concept were examined by performing a detailed CFD study wherein the aerodynamics of the design, together with the chemical kinetics of the

  7. Large eddy simulation of bluff body stabilized premixed and partially premixed combustion (United States)

    Porumbel, Ionut

    Large Eddy Simulation (LES) of bluff body stabilized premixed and partially premixed combustion close to the flammability limit is carried out in this thesis. The main goal of the thesis is the study of the equivalence ratio effect on flame stability and dynamics in premixed and partially premixed flames. An LES numerical algorithm able to handle the entire range of combustion regimes and equivalence ratios is developed for this purpose. The algorithm has no ad-hoc adjustable model parameters and is able to respond automatically to variations in the inflow conditions, without user intervention. Algorithm validation is achieved by conducting LES of reactive and non-reactive flow. Comparison with experimental data shows good agreement for both mean and unsteady flow properties. In the reactive flow, two scalar closure models, Eddy Break-Up (EBULES) and Linear Eddy Mixing (LEMLES), are used and compared. Over important regions, the flame lies in the Broken Reaction Zone regime. Here, the EBU model assumptions fail. In LEMLES, the reaction-diffusion equation is not filtered, but resolved on a linear domain and the model maintains validity. The flame thickness predicted by LEMLES is smaller and the flame is faster to respond to turbulent fluctuations, resulting in a more significant wrinkling of the flame surface when compared to EBULES. As a result, LEMLES captures better the subtle effects of the flame-turbulence interaction, the flame structure shows higher complexity, and the far field spreading of the wake is closer to the experimental observations. Three premixed (φ = 0.6, 0.65, and 0.75) cases are simulated. As expected, for the leaner case (φ = 0.6) the flame temperature is lower, the heat release is reduced and vorticity is stronger. As a result, the flame in this case is found to be unstable. In the rich case (φ = 0.75), the flame temperature is higher, and the spreading rate of the wake is increased due to the higher amount of heat release. The ignition

  8. Encapsulation of brewers yeast in chitosan coated carrageenan microspheres by emulsification/thermal gelation. (United States)

    Raymond, Marie-Christine; Neufeld, Ronald J; Poncelet, Denis


    Brewers yeast was encapsulated in kappa-carrageenan microspheres using an emulsification-thermal gelation approach. Due to heat sensitivity of the yeast at temperatures in excess of 36 degrees C, mixtures of low and high gelation temperature carrageenans were tested to obtain a blend yielding a gelation temperature under 40 degrees C. A 20:80 dispersion of 2% carrageenan sol containing cells, in warm canola oil, produced microspheres upon cooling, with a mean diameter of 450 microm and narrow size dispersion (span of 1.2). Application of a chitosan membrane coat to minimize cell release, increased the mean microsphere diameter to 700 microm, due to the coat thickness and swelling of the microspheres. This diameter was designed so as to minimize mass transfer limitations. Batch fermentations were carried out in a 3 L reactor on a commercial wort medium. Cell loading was 10(7) cells mL(-1) microspheres, and cell "burst" release was observed upon inoculation into fresh medium, whether microspheres were coated or not. The kinetics of intra- and extracapsular cell growth were determined. Increased concentrations of extracapsular free cells could be accounted for by growth in the wort medium, and by ongoing release from the gel microspheres, whether coated or not. Cell release from chitosan-coated carrageenan microspheres was less than that from uncoated microspheres, likely due to retention by the membrane coat. Growth kinetics and alpha-amino nitrogen consumption of encapsulated yeast were higher than that of free cells, and differences in alcohol and ester profiles were also observed, likely due to modified metabolism of the encapsulated yeast.

  9. Microfluidic step-emulsification in a cylindrical geometry (United States)

    Chakraborty, Indrajit; Leshansky, Alexander M.


    The model microfluidic device for high-throughput droplet generation in a confined cylindrical geometry is investigated numerically. The device comprises of core-annular pressure-driven flow of two immiscible viscous liquids through a cylindrical capillary connected co-axially to a tube of a larger diameter through a sudden expansion, mimicking the microfluidic step-emulsifier (1). To study this problem, the numerical simulations of axisymmetric Navier-Stokes equations have been carried out using an interface capturing procedure based on coupled level set and volume-of-fluid (CLSVOF) methods. The accuracy of the numerical method was favorably tested vs. the predictions of the linear stability analysis of core-annular two-phase flow in a cylindrical capillary. Three distinct flow regimes can be identified: the dripping (D) instability near the entrance to the capillary, the step- (S) and the balloon- (B) emulsification at the step-like expansion. Based on the simulation results we present the phase diagram quantifying transitions between various regimes in plane of the capillary number and the flow-rate ratio. MICROFLUSA EU H2020 project.

  10. Premixed flame propagation in vertical tubes (United States)

    Kazakov, Kirill A.


    Analytical treatment of the premixed flame propagation in vertical tubes with smooth walls is given. Using the on-shell flame description, equations for a quasi-steady flame with a small but finite front thickness are obtained and solved numerically. It is found that near the limits of inflammability, solutions describing upward flame propagation come in pairs having close propagation speeds and that the effect of gravity is to reverse the burnt gas velocity profile generated by the flame. On the basis of these results, a theory of partial flame propagation driven by a strong gravitational field is developed. A complete explanation is given of the intricate observed behavior of limit flames, including dependence of the inflammability range on the size of the combustion domain, the large distances of partial flame propagation, and the progression of flame extinction. The role of the finite front-thickness effects is discussed in detail. Also, various mechanisms governing flame acceleration in smooth tubes are identified. Acceleration of methane-air flames in open tubes is shown to be a combined effect of the hydrostatic pressure difference produced by the ambient cold air and the difference of dynamic gas pressure at the tube ends. On the other hand, a strong spontaneous acceleration of the fast methane-oxygen flames at the initial stage of their evolution in open-closed tubes is conditioned by metastability of the quasi-steady propagation regimes. An extensive comparison of the obtained results with the experimental data is made.

  11. Simulations of premixed combustion in porous media (United States)

    Diamantis, D. J.; Mastorakos, E.; Goussis, D. A.


    A numerical model for planar premixed flames of methane in ceramic porous media has been developed to improve the understanding of the structure of such flames. The model successfully reproduces experimental data for both single- and two-layer surface flames. The success is attributed to the detail given to the boundary conditions and the radiation modelling, which was done by solving the radiation transfer equation inside the porous medium without any simplifying models. Surface-stabilized flames yielded SL/SL01 and their energy balance was similar to that of a free flame, which implies that the burning velocity acceleration is due to the reactant preheat. The flame solutions were further analysed with concepts from the computational singular perturbation method to construct reduced mechanisms. For all types of combustion (surface or submerged), an almost identical ordering of chemistry timescales to free flames was found and previously developed reduced mechanisms for free flames were accurate also for the flames inside the porous medium. The results suggest that the thermal exchange between the two phases that is responsible for the flame behaviour remains decoupled from the fast part of the chemistry.


    KAUST Repository

    Mansour, Morkous S.


    A novel double-slit curved wall-jet (CWJ) burner was proposed and employed, which utilizes the Coanda effect by supplying fuel and air as annular-inward jets over a curved surface. We investigated the stabilization characteristics and structure of methane/air, and propane/air turbulent premixed and non-premixed flames with varying global equivalence ratio, , and Reynolds number, Re. Simultaneous time-resolved measurements of particle image velocimetry and planar laser-induced fluorescence of OH radicals were conducted. The burner showed potential for stable operation for methane flames with relatively large fuel loading and overall rich conditions. These have a non-sooting nature. However, propane flames exhibit stable mode for a wider range of equivalence ratio and Re. Mixing characteristics in the cold flow of non-premixed cases were first examined using acetone fluorescence technique, indicating substantial transport between the fuel and air by exhibiting appreciable premixing conditions.PIV measurements revealed that velocity gradients in the shear layers at the boundaries of the annularjets generate the turbulence, enhanced with the collisions in the interaction jet, IJ,region. Turbulent mean and rms velocities were influenced significantly by Re and high rms turbulent velocities are generated within the recirculation zone improving the flame stabilization in this burner.Premixed and non-premixed flames with high equivalence ratio were found to be more resistant to local extinction and exhibited a more corrugated and folded nature, particularly at high Re. For flames with low equivalence ratio, the processes of local quenching at IJ region and of re-ignition within merged jet region maintained these flames further downstream particularly for non-premixed methane flame, revealing a strong intermittency.

  13. Soot Formation in Freely-Propagating Laminar Premixed Flames (United States)

    Lin, K.-C.; Hassan, M. I.; Faeth, G. M.


    Soot formation within hydrocarbon-fueled flames is an important unresolved problem of combustion science. Thus, the present study is considering soot formation in freely-propagating laminar premixed flames, exploiting the microgravity environment to simplify measurements at the high-pressure conditions of interest for many practical applications. The findings of the investigation are relevant to reducing emissions of soot and continuum radiation from combustion processes, to improving terrestrial and spacecraft fire safety, and to developing methods of computational combustion, among others. Laminar premixed flames are attractive for studying soot formation because they are simple one-dimensional flows that are computationally tractable for detailed numerical simulations. Nevertheless, studying soot-containing burner-stabilized laminar premixed flames is problematical: spatial resolution and residence times are limited at the pressures of interest for practical applications, flame structure is sensitive to minor burner construction details so that experimental reproducibility is not very good, consistent burner behavior over the lengthy test programs needed to measure soot formation properties is hard to achieve, and burners have poor durability. Fortunately, many of these problems are mitigated for soot-containing, freely-propagating laminar premixed flames. The present investigation seeks to extend work in this laboratory for various soot processes in flames by observing soot formation in freely-propagating laminar premixed flames. Measurements are being made at both Normal Gravity (NG) and MicroGravity (MG), using a short-drop free-fall facility to provide MG conditions.

  14. Visualization of flashback in a premixed burner with swirling flow

    Institute of Scientific and Technical Information of China (English)

    Satoshi; TANIMURA; Masaharu; KOMIYAMA; Kenichiro; TAKEISHI; Yuji; IWASAKI; Kiyonobu; NAKAYAMA


    In this study,the measurement object is a flame propagating in a premixed burner with swirling flow in order to investigate unsteady flame behavior in a gas turbine premixer.During flashback,the flame propagating upstream was visualized with a high-speed camera.Moreover,we established the technique to measure the instantaneous flow fields of unburned fuel-air mixture in a swirling premixed burner using particle image velocimetry(PIV).As a result,the characteristics of flame behavior propagating upstream were examined.And it was found that a low velocity region existed in the vicinity of the flame tip.The relationship between low velocity region and flame behavior was discussed in detail.

  15. Injectable Premixed Cement of Nanoapatite and Polyamide Composite

    Institute of Scientific and Technical Information of China (English)


    A new type of injectable premixed bone cement consisting of nano-hydroxyapatite (n-HA) and polyamide 66(PA66) composite is investigated. This cement can be handled as paste and easily shaped, which can set in air, in physiological saline solution and in blood. The setting time, injectability and compressive strength of the cement largely depend on the ratio of liquid to powder (L/P). Moreover, the content of n-HA in composite also affects the compressive strength and injectability of the cement. The premixed composite cement can remain stable in the package for a long period and harden only after delivery to the defects site. The results suggest that injectable premixed cement has a reasonable setting time, reasonable viscosity for injecting, excellent washout resistance and high mechanical strength, which can be developed for root canal filling, sealing and various bone defects augmentation.

  16. New controllable premixed combustion for dimethyl ether engine

    Institute of Scientific and Technical Information of China (English)


    A new concept of the controllable premixed combustion (CPC) system was proposed for dimethyl ether (DME) to explore a new approach to achieving ultra-low NOX emissions with the zero level of particulate matter exhaust emissions. The DME fuel was injected into the premix chamber by means of the electronically controlled low pressure injection system, then the mixture formation and combustion process were controlled with a control-valve set between the main chamber and the premix chamber. The test bench was constructed based on a single diesel engine. Preliminary studies demonstrated that ultra-low NOX emissions had been realized with zero particulate matter emissions under the optimum specifications of the DME engine, NOX emissions were less than 65 × 10-6. According to the engine combustion analysis, it was found that the control-valve played an important role in the pre-mixture formation and ignition timing.

  17. Mechanical Micronization of Lipoaspirates: Squeeze and Emulsification Techniques. (United States)

    Mashiko, Takanobu; Wu, Szu-Hsien; Feng, Jingwei; Kanayama, Koji; Kinoshita, Kaori; Sunaga, Ataru; Narushima, Mitsunaga; Yoshimura, Kotaro


    Condensation of grafted fat has been considered a key for achieving better outcomes after fat grafting. The authors investigated the therapeutic potential of two mechanical tissue micronizing procedures: squeeze and emulsification. Human aspirated fat was centrifuged (centrifuged fat) and fragmented with an automated slicer (squeezed fat). Alternatively, centrifuged fat was emulsified by repeated transfer between two syringes through a small-hole connecter and then separated by mesh filtration into two portions: residual tissue of emulsified fat and filtrated fluid of emulsified fat. The four products were examined for cellular components. Histologic and electron microscopic analyses revealed that squeezed fat and residual tissue of emulsified fat contained broken adipocytes and fragmented capillaries. Compared with centrifuged fat, the squeezed fat and residual fat products exhibited increased specific gravity and increased numbers of adipose-derived stem/stromal cells and endothelial cells per volume, suggesting successful cell/tissue condensation in both squeezed fat and residual tissue of emulsified fat. Although cell number and viability in the stromal vascular fraction were well maintained in both squeezed fat and residual fat, stromal vascular fraction culture assay showed that adipose-derived stromal cells were relatively damaged in residual tissue of emulsified fat but not in squeezed fat. By contrast, no adipose-derived stromal cells were cultured from filtrated fluid of emulsified fat. The authors' results demonstrated that mechanical micronization is easily conducted as a minimal manipulation procedure, which can condense the tissue by selectively removing adipocytes without damaging key components, such as adipose-derived stromal cells and endothelial cells. Depending on the extent of adipocyte removal, the product may be a useful therapeutic tool for efficient tissue volumization or therapeutic revitalization/fertilization. Therapeutic, V.

  18. Dispersion of oil into water using lecithin-Tween 80 blends: The role of spontaneous emulsification. (United States)

    Riehm, David A; Rokke, David J; Paul, Prakash G; Lee, Han Seung; Vizanko, Brent S; McCormick, Alon V


    Lecithin-rich mixtures of the nontoxic surfactants lecithin and Tween 80 are effective marine oil spill dispersants, but produce much higher oil-water interfacial tension than other, comparably effective dispersants. This suggests interfacial phenomena other than interfacial tension influence lecithin-Tween 80 dispersants' effectiveness. The interface between seawater and dispersant-crude oil mixtures was studied using light microscopy, cryogenic scanning electron microscopy, and droplet coalescence tests. Lecithin:Tween 80 ratio was varied from 100:0 to 0:100 and wt% dispersant in the oil was varied from 1.25 to 10wt%. Tween 80-rich dispersants cause oil-into-water spontaneous emulsification, while lecithin-rich dispersants primarily cause water-into-oil spontaneous emulsification. Possible mechanisms for this spontaneous emulsification are discussed, in light of images of spontaneously emulsifying interfaces showing no bursting microstructures, interfacial gel, or phase inversion, and negligible interfacial turbulence. Dispersant loss into seawater due to oil-into-water spontaneous emulsification may explain why Tween 80-rich dispersants are less effective than lecithin-rich dispersants with comparable interfacial tension, although longer droplet coalescence times observed for Tween 80-rich, self-emulsifying dispersant-oil mixtures may mitigate the effects of dispersant leaching. Conversely, surfactant retention in oil via lecithin-rich dispersants' water-into-oil emulsification may explain why lecithin-Tween 80 dispersants are as effective as dispersants containing other surfactant blends which produce lower interfacial tension.

  19. Physicochemical properties of lecithin-based nanoemulsions obtained by spontaneous emulsification or high-pressure homogenization

    Directory of Open Access Journals (Sweden)

    Roselena S. Schuh


    Full Text Available Nanoemulsions composed of a medium-chain triglyceride oil core stabilized by rapeseed or sunflower lecithins were prepared by spontaneous emulsification and high-pressure homogenization. These nanoemulsions are compared with formulations stabilized by egg lecithin. Nanoemulsions obtained by high-pressure homogenization display larger droplet size (230 to 440 nm compared with those obtained by spontaneous emulsification (190 to 310 nm. The zeta potentials of the emulsions were negative and below -25 mV. Zeta potential inversion occurred between pH 3.0 and 4.0. The results demonstrate the feasibility of preparing lipid emulsions comprising rapeseed or sunflower lecithins by spontaneous emulsification and high-pressure homogenization.

  20. Centrifugal Step Emulsification can Produce Water in Oil Emulsions with Extremely High Internal Volume Fractions

    Directory of Open Access Journals (Sweden)

    Friedrich Schuler


    Full Text Available The high throughput preparation of emulsions with high internal volume fractions is important for many different applications, e.g., drug delivery. However, most emulsification techniques reach only low internal volume fractions and need stable flow rates that are often difficult to control. Here, we present a centrifugal high throughput step emulsification disk for the fast and easy production of emulsions with high internal volume fractions above 95%. The disk produces droplets at generation rates of up to 3700 droplets/s and, for the first time, enables the generation of emulsions with internal volume fractions of >97%. The coefficient of variation between droplet sizes is very good (4%. We apply our system to show the in situ generation of gel emulsion. In the future, the recently introduced unit operation of centrifugal step emulsification may be used for the high throughput production of droplets as reaction compartments for clinical diagnostics or as starting material for micromaterial synthesis.

  1. Emulsification-Induced Homohelicity in Racemic Helical Polymer for Preparing Optically Active Helical Polymer Nanoparticles. (United States)

    Zhao, Biao; Deng, Jinrui; Deng, Jianping


    Optically active nano- and microparticles have constituted a significant category of advanced functional materials. However, constructing optically active particles derived from synthetic helical polymers still remains as a big challenge. In the present study, it is attempted to induce a racemic helical polymer (containing right- and left-handed helices in equal amount) to prefer one predominant helicity in aqueous media by using emulsifier in the presence of chiral additive (emulsification process). Excitingly, the emulsification process promotes the racemic helical polymer to unify the helicity and directly provides optically active nanoparticles constructed by chirally helical polymer. A possible mechanism is proposed to explain the emulsification-induced homohelicity effect. The present study establishes a novel strategy for preparing chirally helical polymer-derived optically active nanoparticles based on racemic helical polymers.

  2. Quantification of extinction mechanism in counterflow premixed flames

    KAUST Repository

    Choi, Sangkyu


    The extinction mechanisms of stretched premixed flames have been investigated numerically for the fuels of CH4, C3H8, H2, CO and for the mixture fuels of CH4+H2 and CO+H2 by adopting symmetric double premixed flames in a counterflow configuration. The local equilibrium temperature concept was used as a measure of energy loss or gain in order to quantify the extinction mechanism by preferential diffusion and/or incomplete reaction. The energy loss ratio from preferential diffusion arising from non-unity Lewis number and the loss ratio from incomplete reaction were calculated at various equivalence ratios near flame extinction. The results showed that the extinction of lean H2, CH4, CH4+H2, CO+H2, and rich C3H8 premixed flames was caused by incomplete reaction due to insufficient reaction time, indicating that the effective Lewis number was smaller than unity, while the effect of preferential diffusion resulted in energy gain. However, the extinction of rich H2, CH4, CH4+H2, CO+H2, and lean C3H8 premixed flames was affected by the combined effects of preferential diffusion and incomplete reaction indicating that the effective Lewis number was larger than unity. In CO premixed flames, incomplete reaction was dominant in both lean and rich cases due to the effective Lewis number close to unity. The effect of H2 mixing to CO is found to be quite significant as compared to CH4+H2 cases, which can alter the flame behavior of CO flames to that of H2.

  3. Effect of viscosities of dispersed and continuous phases in microchannel oil-in-water emulsification

    NARCIS (Netherlands)

    Dijke, van K.C.; Kobayashi, I.; Schroën, C.G.P.H.; Uemura, K.; Nakajima, M.; Boom, R.M.


    Although many aspects of microchannel emulsification have been covered in literature, one major uncharted area is the effect of viscosity of both phases on droplet size in the stable droplet generation regime. It is expected that for droplet formation to take place, the inflow of the continuous phas

  4. Spontaneous oil-in-water emulsification induced by charge-stabilized dispersions of various inorganic colloids

    NARCIS (Netherlands)

    Sacanna, S.|info:eu-repo/dai/nl/311471676; Kegel, W.K.|info:eu-repo/dai/nl/113729464; Philipse, A.P.|info:eu-repo/dai/nl/073532894


    Charge-stabilized dispersions of inorganic colloids are shown to induce spontaneous emulsification of hydrophobic (TPM) molecules to stable oil-in-water emulsions, with monodisperse, mesoscopic oil droplet diameters in the range of 30-150 nm, irrespective of the polydispersity of the starting

  5. Formation of oil-in-water emulsions from natural emulsifiers using spontaneous emulsification: sunflower phospholipids. (United States)

    Komaiko, Jennifer; Sastrosubroto, Ashtri; McClements, David Julian


    This study examined the possibility of producing oil-in-water emulsions using a natural surfactant (sunflower phospholipids) and a low-energy method (spontaneous emulsification). Spontaneous emulsification was carried out by titrating an organic phase (oil and phospholipid) into an aqueous phase with continuous stirring. The influence of phospholipid composition, surfactant-to-oil ratio (SOR), initial phospholipids location, storage time, phospholipid type, and preparation method was tested. The initial droplet size depended on the nature of the phospholipid used, which was attributed to differences in phospholipid composition. Droplet size decreased with increasing SOR and was smallest when the phospholipid was fully dissolved in the organic phase rather than the aqueous phase. The droplets formed using spontaneous emulsification were relatively large (d > 10 μm), and so the emulsions were unstable to gravitational separation. At low SORs (0.1 and 0.5), emulsions produced with phospholipids had a smaller particle diameter than those produced with a synthetic surfactant (Tween 80), but at a higher SOR (1.0), this trend was reversed. High-energy methods (microfluidization and sonication) formed significantly smaller droplets (d < 10 μm) than spontaneous emulsification. The results from this study show that low-energy methods could be utilized with natural surfactants for applications for which fine droplets are not essential.

  6. Lecithin-Based Nano-emulsification Improves the Bioavailability of Conjugated Linoleic Acid. (United States)

    Heo, Wan; Kim, Jun Ho; Pan, Jeong Hoon; Kim, Young Jun


    In this study, we investigated the effects of lecithin-based nano-emulsification on the heat stability and bioavailability of conjugated linoleic acid (CLA) in different free fatty acid (FFA) and triglyceride (TG) forms. CLA nano-emulsion in TG form exhibited a small droplet size (70-120 nm) compared to CLA nano-emulsion in FFA form (230-260 nm). Nano-emulsification protected CLA isomers in TG form, but not in free form, against thermal decomposition during the heat treatment. The in vitro bioavailability test using monolayers of Caco-2 human intestinal cells showed that nano-emulsification increased the cellular uptake of CLA in both FFA and TG forms. More importantly, a rat feeding study showed that CLA content in small intestinal tissues or plasma was higher when CLA was emulsified, indicating an enhanced oral bioavailability of CLA by nano-emulsification. These results provide important information for development of nano-emulsion-based delivery systems that improve thermal stability and bioavailability of CLA.

  7. Advance on Effective Chopping Emulsification Technology in Meat Processing%肉品高效斩拌乳化技术研究进展

    Institute of Scientific and Technical Information of China (English)



    Effective emulsification technology was applied in meat processing to achieve water holding and oil stability in the meat products. The effects of chopping emulsification technology are mainly affected by factors, which was chopping parameters and raw meat materials. Chopping parameters such as chopping temperature, chopping speed, chopping time are crucial factors in chopping emulsification technology. While raw materials such as raw meat type, non-meat proteins, emulsifiers and hydrophilic gums are also important factors directly influencing emulsification. The paper mainly reviewed the advance on chopping emulsification technology in meat processing from aforementioned aspects.

  8. Microchannel arrays with improved accessibility and use for cell studies and emulsification (United States)

    Kikuchi, Yuji; Kikuchi, Hiroko E.; Kuboki, Yoshinori; Nakajima, Mitsutoshi


    Arrays of microgrooves (groove width; 2, 3, 4, 5, 6, 7, 8, 10, 12, and 14 micrometer, groove interval; width x3, x10, and x20, one size and interval per chip) each connecting a center well and a side edge of a silicon substrate were created by photolithography and anisotropic wet etching. A penetrating hole was made by sand blast at the substrate center for the access to the center well. By tightly covering the substrate surface with a glass plate, the microgroove arrays were converted to microchannel arrays having one ends open at the side edges of the substrate. These microchannel arrays were used for cell trapping for microinjection and also used for emulsification. Poplar (Populus alba) protoplasts were used for the test of cell trapping. Cells showed a very large variation in size and irregularity in shape, and, furthermore, the protoplast preparation contained a number of cell membrane fragments and chloroplasts. Despite the cell size and shape variations and obstruction by the admixtures, many cells could be trapped by aspiration at the channel ends because of their openness to the outside free space and also their large multiplicity in parallel. The free space outside the side of the substrate allowed a free manipulation of a glass micropipette under microscopic observation using transmitted illumination. The microscopic observation direction nearly perpendicular to the movement directions of the micropipette further allowed the movement of the pipette tip nearly always in focus. These led to an easy pointing and puncturing. In addition, the cell trapping points in a line made successive approach to adjacent cells easier. Soybean oil containing 1.5 wt% polyoxyethylene(20)sorbitan monoolete as a surfactant was forced to flow into physiological saline filling the outside of the substrate through the microchannels. Regularly sized oil particles were created by this process with a variation coefficient (S.D./mean) 16% of their diameter. This variation, which is

  9. Modification of premixed combustion in shear layers by grid turbulence

    Institute of Scientific and Technical Information of China (English)

    MU Kejin; WANG Yue; ZHANG Zhedian; NIE Chaoqun


    The influence of grid turbulence on the shear layer of a jet and the premixed flames embedded in it was investigated in the present study. The velocity field of the jet was measured by using hot-wire anemometry. It was found that grid turbulence reduced turbulence intensities in the shear layer and suppressed low frcquency fluctuation. Moreover, the energy contained in small-scale fluctuation was increased and turbulence became homogeneous. The results indicate that grid turbulence inhibits the formation of a large-scale coherent structure in the shear layer. Flame temperature was measured by using a compensated free-wire thermocouple. It was found that grid turbulence reduced low frequency fluctuation of thc flame fronts, increased the small-scale wrinkles and elevated the mean temperature of the flame zone. The results show that grid turbulence can enhance and stabilize premixed flames in shear flow.

  10. Premixed Flame Dynamics in Narrow 2D Channels

    CERN Document Server

    Ayoobi, Mohsen


    Premixed flames propagating within small channels show complex combustion phenomena that differ from flame propagation at conventional scales. Available experimental and numerical studies have documented stationary/non-stationary and/or asymmetric modes that depend on properties of the incoming reactant flow as well as channel geometry and wall temperatures. The present work seeks to illuminate mechanisms leading to symmetry-breaking and limit cycle behavior that are fundamental to these combustion modes. Specifically, four cases of lean premixed methane/air combustion -- two equivalence ratios (0.53 and 0.7) and two channel widths (2 and 5mm) -- are investigated in a 2D configuration with constant channel length and bulk inlet velocity, where numerical simulations are performed using detailed chemistry. External wall heating is simulated by imposing a linear temperature gradient as a boundary condition on both walls. In the 2mm-channel, both equivalence ratios produce flames that stabilize with symmetric fla...

  11. Premixed burner experiments: Geometry, mixing, and flame structure issues

    Energy Technology Data Exchange (ETDEWEB)

    Gupta, A.K.; Lewis, M.J.; Gupta, M. [Univ of Maryland, College Park, MD (United States)] [and others


    This research program is exploring techniques for improved fuel-air mixing, with the aim of achieving combustor operations up to stoichiometric conditions with minimal NO x and maximum efficiency. The experimental studies involve the use of a double-concentric natural gas burner that is operable in either premixed or non-premixed modes, and the system allows systematic variation of equivalence ratio, swirl strength shear length region and flow momentum in each annulus. Flame structures formed with various combinations of swirl strengths, flow throughput and equivalence ratios in premixed mode show the significant impact of swirl flow distribution on flame structure emanating from the mixedness. This impact on flame structure is expected to have a pronounced effect on the heat release rate and the emission of NO{sub x}. Thus, swirler design and configuration remains a key factor in the quest for completely optimized combustion. Parallel numerical studies of the flow and combustion phenomena were carried out, using the RSM and thek-{epsilon} turbulence models. These results have not only indicated the strengths and limitations of CFD in performance and pollutants emission predictions, but have provided guidelines on the size and strength of the recirculation produced and the spatio-temporal structure of the combustion flowfield. The first stage of parametric studies on geometry and operational parameters at Morgan State University have culminated in the completion of a one-dimensional flow code that is integrated with a solid, virtual model of the existing premixed burner. This coupling will provide the unique opportunity to study the impact of geometry on the flowfield and vice-versa, with particular emphasis on concurrent design optimization.

  12. Premixed intravenous admixtures: a positive development for hospital pharmacy. (United States)

    Lee, H E


    The development of premixed intravenous admixtures is reviewed in a historical context, and its effects on hospital pharmacy practice are discussed. As pharmaceutical manufacturers introduce more i.v. medications in ready-to-use containers, the same complaints that were voiced by pharmacists about unit dose packaging and ready-to-dispense tablets and capsules are being aired. But premixed i.v. admixtures are a logical extension of the basic unit dose principle of providing a readily identifiable and ready-to-administer dose. The time and cost savings these products offer are needed in hospital pharmacies. Some of the disadvantages of these products--including storage and freezer space and multiplicity of administration systems--are overcome by proper planning and education of personnel. If fewer personnel are now needed to prepare i.v. admixtures, then those personnel should be used to improve patient care in other ways. The use of premixed i.v. admixtures is a positive technological advance in drug packaging. Its advantages outweight its disadvantages, and it will soon be become the universally accepted form of i.v. drug packaging.

  13. Large eddy simulation of unsteady lean stratified premixed combustion

    Energy Technology Data Exchange (ETDEWEB)

    Duwig, C. [Division of Fluid Mechanics, Department of Energy Sciences, Lund University, SE 221 00 Lund (Sweden); Fureby, C. [Division of Weapons and Protection, Warheads and Propulsion, The Swedish Defense Research Agency, FOI, SE 147 25 Tumba (Sweden)


    Premixed turbulent flame-based technologies are rapidly growing in importance, with applications to modern clean combustion devices for both power generation and aeropropulsion. However, the gain in decreasing harmful emissions might be canceled by rising combustion instabilities. Unwanted unsteady flame phenomena that might even destroy the whole device have been widely reported and are subject to intensive studies. In the present paper, we use unsteady numerical tools for simulating an unsteady and well-documented flame. Computations were performed for nonreacting, perfectly premixed and stratified premixed cases using two different numerical codes and different large-eddy-simulation-based flamelet models. Nonreacting simulations are shown to agree well with experimental data, with the LES results capturing the mean features (symmetry breaking) as well as the fluctuation level of the turbulent flow. For reacting cases, the uncertainty induced by the time-averaging technique limited the comparisons. Given an estimate of the uncertainty, the numerical results were found to reproduce well the experimental data in terms both of mean flow field and of fluctuation levels. In addition, it was found that despite relying on different assumptions/simplifications, both numerical tools lead to similar predictions, giving confidence in the results. Moreover, we studied the flame dynamics and particularly the response to a periodic pulsation. We found that above a certain excitation level, the flame dynamic changes and becomes rather insensitive to the excitation/instability amplitude. Conclusions regarding the self-growth of thermoacoustic waves were drawn. (author)

  14. Large Eddy Simulation of High-Speed, Premixed Ethylene Combustion (United States)

    Ramesh, Kiran; Edwards, Jack R.; Chelliah, Harsha; Goyne, Christopher; McDaniel, James; Rockwell, Robert; Kirik, Justin; Cutler, Andrew; Danehy, Paul


    A large-eddy simulation / Reynolds-averaged Navier-Stokes (LES/RANS) methodology is used to simulate premixed ethylene-air combustion in a model scramjet designed for dual mode operation and equipped with a cavity for flameholding. A 22-species reduced mechanism for ethylene-air combustion is employed, and the calculations are performed on a mesh containing 93 million cells. Fuel plumes injected at the isolator entrance are processed by the isolator shock train, yielding a premixed fuel-air mixture at an equivalence ratio of 0.42 at the cavity entrance plane. A premixed flame is anchored within the cavity and propagates toward the opposite wall. Near complete combustion of ethylene is obtained. The combustor is highly dynamic, exhibiting a large-scale oscillation in global heat release and mass flow rate with a period of about 2.8 ms. Maximum heat release occurs when the flame front reaches its most downstream extent, as the flame surface area is larger. Minimum heat release is associated with flame propagation toward the cavity and occurs through a reduction in core flow velocity that is correlated with an upstream movement of the shock train. Reasonable agreement between simulation results and available wall pressure, particle image velocimetry, and OH-PLIF data is obtained, but it is not yet clear whether the system-level oscillations seen in the calculations are actually present in the experiment.

  15. Spectral kinetic energy transfer in turbulent premixed reacting flows. (United States)

    Towery, C A Z; Poludnenko, A Y; Urzay, J; O'Brien, J; Ihme, M; Hamlington, P E


    Spectral kinetic energy transfer by advective processes in turbulent premixed reacting flows is examined using data from a direct numerical simulation of a statistically planar turbulent premixed flame. Two-dimensional turbulence kinetic-energy spectra conditioned on the planar-averaged reactant mass fraction are computed through the flame brush and variations in the spectra are connected to terms in the spectral kinetic energy transport equation. Conditional kinetic energy spectra show that turbulent small-scale motions are suppressed in the burnt combustion products, while the energy content of the mean flow increases. An analysis of spectral kinetic energy transfer further indicates that, contrary to the net down-scale transfer of energy found in the unburnt reactants, advective processes transfer energy from small to large scales in the flame brush close to the products. Triadic interactions calculated through the flame brush show that this net up-scale transfer of energy occurs primarily at spatial scales near the laminar flame thermal width. The present results thus indicate that advective processes in premixed reacting flows contribute to energy backscatter near the scale of the flame.

  16. Effect of acidification on the protection of alginate-encapsulated probiotic based on emulsification/internal gelation. (United States)

    Qu, Fangning; Zhao, Meng; Fang, Yapeng; Nishinari, Katsuyoshi; Phillips, Glyn O; Wu, Zhengjun; Chen, Chen


    The method of emulsification/internal gelation is commonly used to prepare alginate microspheres for lactic acid bacteria (LAB). This paper focused on the influence of acidification parameters, i.e. acid/Ca molar ratio and acidification time, on the physical properties and cell protection efficiency of microspheres and their correlations. With increasing acid/Ca molar ratio and acidification time, the average diameter of microspheres decreased and their mechanical strength increased. Interestingly, wet alginate microspheres shrank in simulated gastric juice (SGJ) while they swelled in bile salts solution (BS). The shrinkage or swelling ratio decreased with increasing mechanical strength. Correlation analysis showed that the encapsulated cell survivals in both SGJ and BS were positively correlated with the mechanical strength of microspheres but negatively with the shrinkage or swelling ratio. BacLight LIVE/DEAD assay suggested that the viability of encapsulated cells in fresh, SGJ-treated and BS-treated microspheres was closely related to cell membrane integrity. Acidification is a key step during microsphere preparation, which strongly affected the physical properties of alginate microspheres, resulting in different cell protection efficiency. The resulting well-protected LAB can be applied in probiotics foods. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry.

  17. 淀粉乳化技术对乳化型香肠品质的影响%Effect of Starch Emulsification on Quality of Emulsification-type Sausages

    Institute of Scientific and Technical Information of China (English)



    The effects of traditional emulsification and starch emulsification on quality indices such as water-holding capacity,cooking loss rate and texture properties of emulsification-type sausages were comparatively investigated.Meanwhile,sensory evaluation was performed on emulsification-type sausages derived from both emulsification methods and their ultra-structures were observed under scanning electron microscope(SEM).The results showed that starch emulsification could result in a marked increase of the water retention,viscoelasticity and chewiness of emulsification-type sausages,and an obvious reduction of the cooking loss rate.Emulsification-type sausage derived from starch emulsification exhibited an increased overall acceptability,uniform and compact internal texture,and evenly distributed fat and water without water or oil permeation.Therefore,the starch emulsification is superior to the traditional emulsification.%比较常规乳化和淀粉乳化两种乳化加工技术对乳化型香肠的保水性、蒸煮损失、质构特性等品质指标的影响;通过感官评定试验和扫描电镜观察结果比较分析了两种加工手段对香肠食用品质及超微结构的影响。结果表明:淀粉乳化技术生产的香肠的保水性显著提高,蒸煮损失率减少,黏弹性和咀嚼性均显著增加;感官评定结果和超微结构图片显示,淀粉乳化技术生产的香肠总体可接受性提高,未有出水出油现象,内部质地变得均匀致密,脂肪和水分呈均匀分布。在加工制作乳化型香肠中,淀粉乳化技术较常规乳化技术在提高产品保水性、减少蒸煮损失、优化产品质构品质方面具有明显的优势。

  18. Emulsification at the Liquid/Liquid Interface: Effects of Potential, Electrolytes and Surfactants. (United States)

    Chowdhury, Mehrin; Kataky, Ritu


    Emulsification of oils at liquid/liquid interfaces is of fundamental importance across a range of applications, including detergency. Adsorption and partitioning of the anionic surface active ions at the interface between two immiscible solutions is known to cause predictable chaos at the transfer potential region of the surfactant. In this work, the phenomenon that leads to the chaotic behaviour shown by sodium dodecylbenzene sulfonate (SDBS) at the water/1,2-dichloroethane interface is applied to commercial surfactants and aqueous/glyceryl trioleate interface. Electrochemical methods, electrocapillary curves, optical microscopy and conductivity measurements demonstrated that at 1.5 mm of SDBS, surfactants are adsorbed at the interface and assemble into micelles, leading to interfacial instability. As the concentration of the anionic surfactant was enhanced to 8 and 13.4 mm, the Marangoni effect and the interfacial emulsification became more prominent. The chaotic behaviour was found to be dependent on the surfactant concentration and the electrolytes present.

  19. Controlled microfluidic emulsification of oil in a clay nanofluid: Role of salt for Pickering stabilization (United States)

    Gholamipour-Shirazi, A.; Carvalho, M. S.; Fossum, J. O.


    Research on emulsions is driven by their widespread use in different industries, such as food, cosmetic, pharmaceutical and oil recovery. Emulsions are stabilized by suitable surfactants, polymers, solid particles or a combination of them. Microfluidic emulsification is the process of droplet formation out of two or more liquids under strictly controlled conditions, without pre-emulsification step. Microfluidic technology offers a powerful tool for investigating the properties of emulsions themselves. In this work stable oil in water emulsions were formed with hydrophilic Laponite RD® nanoparticles adsorbed at the interface of the oil phase and aqueous clay nanofluid in a T junction microfluidic chip. Emulsion stability up to at least 40 days could be observed.

  20. Grafting amphiphilic brushes onto halloysite nanotubes via a living RAFT polymerization and their Pickering emulsification behavior. (United States)

    Hou, Yifan; Jiang, Junqing; Li, Kai; Zhang, Yanwu; Liu, Jindun


    Amphiphilic brushes of poly(4-vinylpyridine)-block-polystyrene (P4VP-b-PS) and polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) are grafted onto halloysite nanotubes (HNTs) via a surface reversible addition-fragmentation chain transfer (RAFT) living polymerization through anchoring R group in RAFT agent S-1-dodecyl-S'-(R,R'-dimethyl-R″-acetic acid) trithiocarbonates (DDMAT). The characterization of TGA, TEM, and GPC show that amphiphilic brushes are successfully grafted onto HNTs in a living manner. To verify the amphiphilicity of HNTs grafted with block copolymers, their Pickering emulsification behavior in water/soybean oil diphase mixture is studied. The results show that modified HNTs can emulsify water/soybean oil diphase mixture and the emulsification performance is dependent on microstructure of amphiphilic brushes such as hydrophilic/hydrophobic segment size and sequence.

  1. A Mutant Strain of a Surfactant-Producing Bacterium with Increased Emulsification Activity

    Institute of Scientific and Technical Information of China (English)

    Liu Qingmei; Yao Jianming; Pan Renrui; Yu Zengliang


    As reported in this paper, a strain of oil-degrading bacterium Sp- 5- 3 was determined to belong to Enterobacteriaceae, which would be useful for microbial enhanced oil recovery(MEOR). The aim of our study was to generate a mutant using low energy N+ beam implantation. With 10 keV of energy and 5.2 × 10TM N+/cm2 of dose - the optimum condition, a mutant,S - 34, was obtained, which had nearly a 5-fold higher surface and a 13-fold higher of emulsification activity than the wild type. The surface activity was measured by two methods, namely, a surface tension measuring instrument and a recording of the repulsive circle of the oil film; the emulsification activity was scaled through measuring the separating time of the oil-fermentation mixture. The metabolic acid was determined as methane by means of gas chromatography.

  2. Optimization of parameters in the emulsification process by two different methods. (United States)

    Carlotti, M E; Pattarino, F; Gasco, M R; Brusasca, P


    Synopsis An O/W emulsion with a lipopeptidic emulsifier was optimized by means of two different methods, specifically by experimental design and by selective variation of the parameters. Two optimized emulsions were obtained; they had similar values of emulsification (time and rate of homogenization) and amounts of components. Résumé Une émulsion O/E, avec un lipopeptide comme tensioactif, a été optimisée par deux méthodes d'optimisation différentes, notamment par l'experimental design et par la variation selective de certain paramètres. Deux émulsions optimisées ont été ainsi obtenues: ces émulsions ont des valeurs d'emulsification (temp et vitesse d'homogénéisation) et des quantités des composantes très proches.


    Institute of Scientific and Technical Information of China (English)

    Zhen-zhong Yang; De-lu Zhao


    The phase inversion emulsification technique (PIET) is an effective physical method for preparing waterborne dispersions of polymer resins. Some results concerning the preparation of bisphenol A epoxy resin waterborne dispersions by PIET in our laboratory were summarized. Electrical properties, rheological behavior and morphological evolution during phase inversion progress were systematically characterized. The effects of the emulsifier concentration and emulsification temperature on phase inversion progress and the structural features of the waterborne particles were studied as well. The deformation and break up of water drops in a shear field were analyzed in terms of micro-rheology, while the interaction and coalescence dynamics of water drops were discussed in terms of DLVO theory and Smoluchowski effective collision theory,respectively. Based on the experimental results and theoretical analysis, a physical model of phase inversion progress was suggested, by which the effects of the parameters on phase inversion progress and the structural features of the waterborne particles were interpreted and predicted.

  4. Standard practice for fluorescent liquid penetrant testing using the hydrophilic Post-Emulsification process

    CERN Document Server

    American Society for Testing and Materials. Philadelphia


    1.1 This practice covers procedures for fluorescent penetrant examination utilizing the hydrophilic post-emulsification process. It is a nondestructive testing method for detecting discontinuities that are open to the surface such as cracks, seams, laps, cold shuts, laminations, isolated porosity, through leaks, or lack of fusion and is applicable to in-process, final, and maintenance examination. It can be effectively used in the examination of nonporous, metallic materials, both ferrous and nonferrous, and of nonmetallic materials such as glazed or fully densified ceramics and certain nonporous plastics and glass. 1.2 This practice also provides a reference: 1.2.1 By which a fluorescent penetrant examination hydrophilic post-emulsification process recommended or required by individual organizations can be reviewed to ascertain their applicability and completeness. 1.2.2 For use in the preparation of process specifications dealing with the fluorescent penetrant examination of materials and parts using the hy...

  5. Lambda-Cyhalothrin Nanosuspension Prepared by the Melt Emulsification-High Pressure Homogenization Method


    Zhenzhong Pan; Bo Cui; Zhanghua Zeng; Lei Feng; Guoqiang Liu; Haixin Cui; Hongyu Pan


    The nanosuspension of 5% lambda-cyhalothrin with 0.2% surfactants was prepared by the melt emulsification-high pressure homogenization method. The surfactants composition, content, and homogenization process were optimized. The anionic surfactant (1-dodecanesulfonic acid sodium salt) and polymeric surfactant (maleic rosin-polyoxypropylene-polyoxyethylene ether sulfonate) screened from 12 types of commercially common-used surfactants were used to prepare lambda-cyhalothrin nanosuspension with ...

  6. Stirring effects and bistability in the iodate-arsenous acid reaction: Premixed vs segregated flows (United States)

    Hannon, L.; Horsthemke, W.


    Using a coalescence-dispersion model of the continuous flow-stirred tank reactor (CSTR), we study the effect of premixed vs nonpremixed reactant flows on chemical bistability. The region of bistability is smaller for segregated feed streams than for a fully premixed feed stream. The transition from flow branch to thermodynamic branch is particularly sensitive to the feed stream configuration.

  7. Dry low NOx combustion system with pre-mixed direct-injection secondary fuel nozzle (United States)

    Zuo, Baifang; Johnson, Thomas; Ziminsky, Willy; Khan, Abdul


    A combustion system includes a first combustion chamber and a second combustion chamber. The second combustion chamber is positioned downstream of the first combustion chamber. The combustion system also includes a pre-mixed, direct-injection secondary fuel nozzle. The pre-mixed, direct-injection secondary fuel nozzle extends through the first combustion chamber into the second combustion chamber.

  8. Emulsification of crude oil by an alkane-oxidizing Rhodococcus species isolated from seawater

    Energy Technology Data Exchange (ETDEWEB)

    Bredholt, H.; Bruheim, P.; Eimhjellen, K. [Norwegian Univ. of Scince and Technology, Trondheim (Norway); Josefsen, K.; Vatland, A. [SINTEF SI, Oslo (Norway). Industrial Chemistry Div.


    A Rhodococcus species, which has proven to be the best of 99 oil-emulsifying bacteria isolated from seawater, was characterized. This bacterium produced very stable oil-in-water emulsions from different crude oils with various content of aliphatic and aromatic compounds, by utilizing C{sub 1}1 and C{sub 3}3 n-alkanes as carbon and energy sources. Bacteria that produce stable emulsions are often able to adhere strongly to hydrocarbons or hydrophobic surfaces. It was at these surfaces that extensive emulsification of the residual oil and accumulation of acidic oxidation products occurred. The acidic products were consumed in a second step. This step was characterized by linear growth and an increasing number of cells growing in the water phase. The most extensive emulsification occurred at the end of the exponential phase. There was no evidence of surfactants at the end of the exponential phase, however, a polymeric compound with emulsifying activity, tightly bound to the oil droplets, was isolated, suggesting that the emulsification resulted from the release of the hydrophobic cell surface discarded during growth limitations. 38 refs., 7 figs.

  9. Centrifugal step emulsification applied for absolute quantification of nucleic acids by digital droplet RPA. (United States)

    Schuler, Friedrich; Schwemmer, Frank; Trotter, Martin; Wadle, Simon; Zengerle, Roland; von Stetten, Felix; Paust, Nils


    Aqueous microdroplets provide miniaturized reaction compartments for numerous chemical, biochemical or pharmaceutical applications. We introduce centrifugal step emulsification for the fast and easy production of monodisperse droplets. Homogenous droplets with pre-selectable diameters in a range from 120 μm to 170 μm were generated with coefficients of variation of 2-4% and zero run-in time or dead volume. The droplet diameter depends on the nozzle geometry (depth, width, and step size) and interfacial tensions only. Droplet size is demonstrated to be independent of the dispersed phase flow rate between 0.01 and 1 μl s(-1), proving the robustness of the centrifugal approach. Centrifugal step emulsification can easily be combined with existing centrifugal microfluidic unit operations, is compatible to scalable manufacturing technologies such as thermoforming or injection moulding and enables fast emulsification (>500 droplets per second and nozzle) with minimal handling effort (2-3 pipetting steps). The centrifugal microfluidic droplet generation was used to perform the first digital droplet recombinase polymerase amplification (ddRPA). It was used for absolute quantification of Listeria monocytogenes DNA concentration standards with a total analysis time below 30 min. Compared to digital droplet polymerase chain reaction (ddPCR), with processing times of about 2 hours, the overall processing time of digital analysis was reduced by more than a factor of 4.

  10. Statistical Analysis of Optimal Ultrasound Emulsification Parameters in Thistle-Oil Nanoemulsions. (United States)

    Miastkowska, Małgorzata A; Banach, Marcin; Pulit-Prociak, Jolanta; Sikora, Elżbieta S; Głogowska, Agata; Zielina, Michał


    Thistle oil (INCI: Silybum marianum seed oil) is known as an anti-oxidant, moisturizing and skin regenerating cosmetic raw material. Nanoemulsions are a new form of cosmetic product showing very good user properties (ease of spreading over the skin with no greasy feeling). Moreover, due to their structure, they can also transport both hydrophilic and hydrophobic active substances to the skin. The aim of this work was the preparation and characterization of nanoemulsions, based on thistle oil. The non-ionic surfactants polysorbate 80 (PEG-20 sorbitan monooleate), decyl glucoside, and a polyglyceryl-4 ester blend were applied to stabilize the nanosystems. All formulations were obtained by a high energy method, using an ultrasonic device (Labsonic U, an ultrasound homogenizer). Variations in the emulsification parameters were tested, including surfactants concentration, pre-emulsification time, ultrasound power and sonication time. On the basis of statistical analysis (experimental design, cluster analysis, classification and regression trees) the best emulsification process parameters were determined. In order to verify the results of statistical analysis, once more an experimental study was conducted. The results obtained confirmed that statistical analysis can be a useful method in determining the conditions for obtaining stable nanoemulsions with desired properties. Formulations obtained with the use of Silybum marianum seed oil were characterized by long-term stability, a low polydispersity index, low viscosity and an average droplet size less than 200 nm.

  11. Water-in-oil emulsification in a non-uniform alternating electric field (United States)

    Choi, Suhwan; Saveliev, Alexei


    The emulsification of a water microdroplet placed in castor oil was performed using a non-uniform alternating electric field formed in the pin-to-plate geometry. A non-uniform electric field of ~40 kV/mm alternating with a frequency of 6.7 kHz was generated near the pin electrode. The applied frequency exceeded charge relaxation frequency of castor oil (0.3 Hz) and was below charge relaxation frequency of deionized water (7.8 kHz) used in the experiments. The emulsification process was captured with a CCD camera. The emulsification process started with entrainment of the water droplet in the high electric filed region near the pin electrode under the dielectrophoretic force. Upon touching the pin, the microdroplet was disintegrated in numerous channels and secondary droplets. The process continued by entrainment of secondary droplets and continuous size reduction. Three droplet breakup mechanisms were identified: drop elongation and capillary breakup, ac electrospraying of individual droplets, chain and bridge formation and decay. The quasi-steady narrow size distribution of emulsified water droplets with diameters close to 1 μm was formed after a few minutes. The generated emulsion was confined near the needle electrode due to the dielectrophoretic force. The emulsion had a well-defined boundary with a shape resembling a pendant drop suspended on the pin electrode.

  12. Drop formation using ferrofluids driven magnetically in a step emulsification device. (United States)

    Kahkeshani, Soroush; Di Carlo, Dino


    We present a microfluidic droplet generation technique, where instead of pumps, only magnetic field gradient strength adjusted by the position of an external magnet is used for controllable emulsification of ferrofluid containing solutions. Uniform droplet generation at frequencies O(1-100) Hz per channel for long periods of time (10s of minutes) were easily achieved. In this method, adding magnetic nanoparticles (10 nm) into aqueous solutions imparts a magnetic body force on the fluid in the presence of an external magnetic field gradient. Consequently, the aqueous fluid moves toward the position of an external magnet and towards a junction with a larger width and height oil filled reservoir. Emulsification occurs at the junction due to a rapid change in surface tension forces due to the abrupt change in channel height. Droplet generation rate could be controlled by adjusting surface tension/viscosity, number of channels, and strength of the magnetic force. The geometry of the channel, rather than flow rates or magnetic force, plays the dominant role in defining the droplet size. In addition, reagents mixed with ferrofluids could also be introduced from two or more separate inlets and mixed prior to emulsification as they move toward the step driven by magnetic force. Mixing reagents on chip and forming droplets all within a small foot-print defined by movement of an external magnet is a unique feature of this method suitable for point-of-care diagnostics and other bioengineering applications.

  13. Probing insulin bioactivity in oral nanoparticles produced by ultrasonication-assisted emulsification/internal gelation. (United States)

    Lopes, Marlene A; Abrahim-Vieira, Bárbara; Oliveira, Claudia; Fonte, Pedro; Souza, Alessandra M T; Lira, Tammy; Sequeira, Joana A D; Rodrigues, Carlos R; Cabral, Lúcio M; Sarmento, Bruno; Seiça, Raquel; Veiga, Francisco; Ribeiro, António J


    Alginate-dextran sulfate-based particles obtained by emulsification/internal gelation technology can be considered suitable carriers for oral insulin delivery. A rational study focused on the emulsification and particle recovery steps was developed in order to reduce particles to the nanosize range while keeping insulin bioactivity. There was a decrease in size when ultrasonication was used during emulsification, which was more pronounced when a cosurfactant was added. Ultrasonication add-on after particle recovery decreased aggregation and led to a narrower nanoscale particle-size distribution. Insulin encapsulation efficiency was 99.3%±0.5%, attributed to the strong pH-stabilizing electrostatic effect between insulin and nanoparticle matrix polymers. Interactions between these polymers and insulin were predicted using molecular modeling studies through quantum mechanics calculations that allowed for prediction of the interaction model. In vitro release studies indicated well-preserved integrity of nanoparticles in simulated gastric fluid. Circular dichroism spectroscopy proved conformational stability of insulin and Fourier transform infrared spectroscopy technique showed rearrangements of insulin structure during processing. Moreover, in vivo biological activity in diabetic rats revealed no statistical difference when compared to nonencapsulated insulin, demonstrating retention of insulin activity. Our results demonstrate that alginate-dextran sulfate-based nanoparticles efficiently stabilize the loaded protein structure, presenting good physical properties for oral delivery of insulin.

  14. Intensifying existing premix therapy (BIAsp 30) with BIAsp 50 and BIAsp 70

    DEFF Research Database (Denmark)

    Brito, Miguel; Ligthelm, Robert Jan; Boemi, Massimo


    In 2009, consensus guidelines were published on intensification of insulin therapy using the premix analog biphasic insulin aspart (BIAsp) 30 in the treatment of type 2 diabetes, based on the recommendations of an international, independent expert panel. The guidelines included recommendations...... switch from a BIAsp 30 to a mid-/high-ratio premix regimen for the vast majority of patients with type 2 diabetes. A panel of independent experts with extensive clinical experience in premix analog therapy met in October 2009 to review the therapeutic role of mid- and high-ratio premixes (BIAsp 50 and 70...... assist physicians in introducing mid-/high-ratio premixes to optimize the insulin therapy of patients with type 2 diabetes who are failing to achieve glycemic targets on a BIAsp 30 BID or TID regimen....

  15. Flashback mechanisms in lean premixed gas turbine combustion

    CERN Document Server

    Benim, Ali Cemal


    Blending fuels with hydrogen offers the potential to reduce NOx and CO2 emissions in gas turbines, but doing so introduces potential new problems such as flashback.  Flashback can lead to thermal overload and destruction of hardware in the turbine engine, with potentially expensive consequences. The little research on flashback that is available is fragmented. Flashback Mechanisms in Lean Premixed Gas Turbine Combustion by Ali Cemal Benim will address not only the overall issue of the flashback phenomenon, but also the issue of fragmented and incomplete research.Presents a coherent review of f

  16. Premixed Combustion of Coconut Oil on Perforated Burner


    I.K.G. Wirawan; I. N. G. Wardana; Rudy Soenoko; Slamet Wahyudi


    Coconut oil premixed combustion behavior has been studied experimentally on perforated burner with equivalence ratio (φ) varied from very lean until very rich. The results showed that burning of glycerol needs large number of air so that the laminar burning velocity (SL) is the highest at very lean mixture and the flame is in the form of individual Bunsen flame on each of the perforated plate hole. As φ is increased the  SL decreases and the secondary Bunsen flame with open tip occurs from φ ...

  17. Setting mechanisms of an acidic premixed calcium phosphate cement



    Premixed calcium phosphate cements (pCPC), where glycerol is used instead of water as mixing liquid, present better handling characteristics than water-based cements. However, the setting mechanisms of pCPC have not been described thoroughly. The aim of this paper is to increase the understanding of the setting mechanism of pCPC. The investigated cement starts to set when glycerol is exchanged with water via diffusion of glycerol out to the surrounding body fluid and water into the material. ...

  18. Response mechanisms of attached premixed flames subjected to harmonic forcing (United States)


    The persistent thrust for a cleaner, greener environment has prompted air pollution regulations to be enforced with increased stringency by environmental protection bodies all over the world. This has prompted gas turbine manufacturers to move from nonpremixed combustion to lean, premixed combustion. These lean premixed combustors operate quite fuel-lean compared to the stochiometric, in order to minimize CO and NOx productions, and are very susceptible to oscillations in any of the upstream flow variables. These oscillations cause the heat release rate of the flame to oscillate, which can engage one or more acoustic modes of the combustor or gas turbine components, and under certain conditions, lead to limit cycle oscillations. This phenomenon, called thermoacoustic instabilities, is characterized by very high pressure oscillations and increased heat fluxes at system walls, and can cause significant problems in the routine operability of these combustors, not to mention the occasional hardware damages that could occur, all of which cumulatively cost several millions of dollars. In a bid towards understanding this flow-flame interaction, this research works studies the heat release response of premixed flames to oscillations in reactant equivalence ratio, reactant velocity and pressure, under conditions where the flame preheat zone is convectively compact to these disturbances, using the G-equation. The heat release response is quantified by means of the flame transfer function and together with combustor acoustics, forms a critical component of the analytical models that can predict combustor dynamics. To this end, low excitation amplitude (linear) and high excitation amplitude (nonlinear) responses of the flame are studied in this work. The linear heat release response of lean, premixed flames are seen to be dominated by responses to velocity and equivalence ratio fluctuations at low frequencies, and to pressure fluctuations at high frequencies which are in the

  19. Jet flow and premixed jet flame control by plasma swirler (United States)

    Li, Gang; Jiang, Xi; Zhao, Yujun; Liu, Cunxi; Chen, Qi; Xu, Gang; Liu, Fuqiang


    A swirler based on dielectric barrier discharge plasma actuators is designed and its effectiveness in both jet flow and premixed jet flame control is demonstrated. In contrast to traditional spanwise-oriented actuators, plasma actuators are placed along the axial direction of the injector to induce a circumferential velocity to the main flow and create a swirl flow without any insertion or moving part. In the DBD plasma swirl injector, the discharge does not ignite the mixture nor does it induce flashback. Flame visualization is obtained by cameras while velocity profiles are obtained by Laser Doppler Anemometry measurements. The results obtained indicate the effectiveness of the new design.

  20. Premixer assembly for mixing air and fuel for combustion

    Energy Technology Data Exchange (ETDEWEB)

    York, William David; Johnson, Thomas Edward; Keener, Christopher Paul


    A premixer assembly for mixing air and fuel for combustion includes a plurality of tubes disposed at a head end of a combustor assembly. Also included is a tube of the plurality of tubes, the tube including an inlet end and an outlet end. Further included is at least one non-circular portion of the tube extending along a length of the tube, the at least one non-circular portion having a non-circular cross-section, and the tube having a substantially constant cross-sectional area along its length

  1. Finite amplitude wave interaction with premixed laminar flames (United States)

    Aslani, Mohamad; Regele, Jonathan D.


    The physics underlying combustion instability is an active area of research because of its detrimental impact in many combustion devices, such as turbines, jet engines, and liquid rocket engines. Pressure waves, ranging from acoustic waves to strong shocks, are potential sources of these disturbances. Literature on flame-disturbance interactions are primarily focused on either acoustics or strong shock wave interactions, with little information about the wide spectrum of behaviors that may exist between these two extremes. For example, the interaction between a flame and a finite amplitude compression wave is not well characterized. This phenomenon is difficult to study numerically due to the wide range of scales that need to be captured, requiring powerful and efficient numerical techniques. In this work, the interaction of a perturbed laminar premixed flame with a finite amplitude compression wave is investigated using the Parallel Adaptive Wavelet Collocation Method (PAWCM). This method optimally solves the fully compressible Navier-Stokes equations while capturing the essential scales. The results show that depending on the amplitude and duration of a finite amplitude disturbance, the interaction between these waves and premixed flames can produce a broad range of responses.

  2. Mixing Model Performance in Non-Premixed Turbulent Combustion (United States)

    Pope, Stephen B.; Ren, Zhuyin


    In order to shed light on their qualitative and quantitative performance, three different turbulent mixing models are studied in application to non-premixed turbulent combustion. In previous works, PDF model calculations with detailed kinetics have been shown to agree well with experimental data for non-premixed piloted jet flames. The calculations from two different groups using different descriptions of the chemistry and turbulent mixing are capable of producing the correct levels of local extinction and reignition. The success of these calculations raises several questions, since it is not clear that the mixing models used contain an adequate description of the processes involved. To address these questions, three mixing models (IEM, modified Curl and EMST) are applied to a partially-stirred reactor burning hydrogen in air. The parameters varied are the residence time and the mixing time scale. For small relative values of the mixing time scale (approaching the perfectly-stirred limit) the models yield the same extinction behavior. But for larger values, the behavior is distictly different, with EMST being must resistant to extinction.


    Directory of Open Access Journals (Sweden)

    M I El Khazen


    Full Text Available In this paper we simulate a turbulent premixed V-shape flame stabilized on a hot wire. The device used is composed of a vertical combustion chamber where the methane-air mixture is convected upwards with a mean velocity of 4ms-1. The flow was simulated running Fluent 6.3, which numerically solved the stationary Favre-averaged mass balance; Navier-Stokes equations; combustion progress variable, and k-ε equations on a two-dimensional numerical mesh. We model gaseous mixture, ignoring Soret and Dufour effects and radiation heat transfer. The progress variable balance equation was closed using Eddy Break Up model. The results of our simulations allow us to analyze the influence of equivalence ratio and the turbulent intensity on the properties of the flame (velocity, fluctuation, progress variable and Thickness of flame.This work gives us an idea on the part which turbulence can play to decrease the risks of extinction and instabilities caused by the lean premixed combustion.

  4. Direct Numerical Simulations of Statistically Stationary Turbulent Premixed Flames

    KAUST Repository

    Im, Hong G.


    Direct numerical simulations (DNS) of turbulent combustion have evolved tremendously in the past decades, thanks to the rapid advances in high performance computing technology. Today’s DNS is capable of incorporating detailed reaction mechanisms and transport properties of hydrocarbon fuels, with physical parameter ranges approaching laboratory scale flames, thereby allowing direct comparison and cross-validation against laser diagnostic measurements. While these developments have led to significantly improved understanding of fundamental turbulent flame characteristics, there are increasing demands to explore combustion regimes at higher levels of turbulent Reynolds (Re) and Karlovitz (Ka) numbers, with a practical interest in new combustion engines driving towards higher efficiencies and lower emissions. The article attempts to provide a brief overview of the state-of-the-art DNS of turbulent premixed flames at high Re/Ka conditions, with an emphasis on homogeneous and isotropic turbulent flow configurations. Some important qualitative findings from numerical studies are summarized, new analytical approaches to investigate intensely turbulent premixed flame dynamics are discussed, and topics for future research are suggested. © 2016 Taylor & Francis.

  5. Ion measurements in premixed methane-oxygen flames

    KAUST Repository

    Alquaity, Awad


    Ions are formed as a result of chemi-ionization processes in combustion systems. Recently, there has been an increasing interest in understanding flame ion chemistry due to the possible application of external electric fields to reduce emissions and improve combustion efficiency by active control of combustion process. In order to predict the effect of external electric fields on combustion plasma, it is critical to gain a good understanding of the flame ion chemistry. In this work, a Molecular Beam Mass Spectrometer (MBMS) is utilized to measure ion concentration profiles in premixed methane-oxygen-argon burner-stabilized flames. Lean, stoichiometric and rich flames at atmospheric pressure are used to study the dependence of ion chemistry on equivalence ratio of premixed flames. The relative ion concentration profiles are compared qualitatively with previous methane-oxygen studies and show good agreement. The relative ion concentration data obtained in the present study can be used to validate and improve ion chemistry models for methane-oxygen flames.

  6. Cathlean: catalytic, hybrid, lean-premixed burner for gas turbines

    Energy Technology Data Exchange (ETDEWEB)

    Carroni, Richard; Griffin, Timothy [Alstom Power Technology Ltd., Baden-Daettwil (Switzerland); Kelsall, Greg [Alstom Power Technology Centre, Whetstone (United Kingdom)


    Cathlean (an EU FP5 project) addresses the research and development of an advanced, ultra-low NO{sub x}, hybrid burner for gas turbines (present and future), that combines catalytic and lean-premix combustion components. Such a hybrid design enables this new technology to be introduced in a lower-risk manner. The catalytic elements serve to pretreat the fuel in order to enhance performance in terms of emissions <3 ppmv NO{sub x} and <10 ppmv CO at 15% O{sub 2} and 50-100% load, for natural gas fuel), part-load stability (reducing the lean blow-out temperature by over 100 deg C) and thermoacoustic phenomena (pulsations << 0.3% of pressure). The principle scientific objective is to quantify the advantages of the hybrid burner in terms of the above-mentioned criteria, relative to traditional, lean-premixed combustors. The present paper describes the technical and organisational aspects of the project, including an outline of state-of-the-art catalytic combustion technology, technical specification of the advanced burner and a description of the methods used to attain project goals. (Author)

  7. Establishing bioequivalence of veterinary premixes (Type A medicated articles). (United States)

    Hunter, R P; Lees, P; Concordet, D; Toutain, P-L


    a) Key issues concerning Premix (Type A medicated articles) Bioequivalence evaluations: 1) This is a complex issue concerning both route of administration and formulation. 2) If the animal is not at the bunk/trough, the animal is not self-administering (eating medicated feed), thus there can be no drug absorption. b) Differing opinions among scientists and regulatory authorities/expert bodies regarding: 1) No harmonization on how to design, conduct, and interpret in vivo studies. 2) Applicability of biowaivers to Type A (premix) products. 3) Why are topdress and complete feed considered differently? Are they different formulations or different routes of administration? 4) Single dose vs. multi-dose studies. 5) What is the final formulation? c) What are the next steps: 1) Harmonize current bioequivalence guidelines through the VICH process. 2) Determine the applicability/non-applicability of the Biopharmaceutical Classification System (BCS). 3) Establish the Total Mixed Ration (i.e. formulation) effects. 4) Define the test subject (individual, pen, etc.).

  8. Simuliranje izotermnega QUEOS preskusa mešalne faze eksplozije pare Q08: Simulation of the isothermal QUEOS steam-explosion premixing experiment Q08:


    Leskovar, Matjaž; Mavko, Borut


    The premixing phase of a steam explosion covers the interaction of the melt jet with the water prior to any steam explosion occuring. To ger a better insight into the hydrodynamic processes during the premixing phase in addition to "hot" premixing experiments, where the water evaporation is significant. "cold" isothermal premixing experiments were also performed. The special feature of isothermal premixing experiments is that three phases are involved - the water, the air and the spheres phas...

  9. Influence of water content on hardening and handling of a premixed calcium phosphate cement. (United States)

    Engstrand, Johanna; Aberg, Jonas; Engqvist, Håkan


    Handling of calcium phosphate cements is difficult, where problems often arise during mixing, transferring to syringes, and subsequent injection. Via the use of premixed cements the risk of handling complications is reduced. However, for premixed cements to work in a clinical situation the setting time needs to be improved. The objective of this study is to investigate the influence of the addition of water on the properties of premixed cement. Monetite-forming premixed cements with small amounts of added water (less than 6.8 wt.%) were prepared and the influence on injectability, working time, setting time and mechanical strength was evaluated. The results showed that the addition of small amounts of water had significant influence on the properties of the premixed cement. With the addition of just 1.7 wt.% water, the force needed to extrude the cement from a syringe was reduced from 107 (±15) N to 39 (±9) N, the compression strength was almost doubled, and the setting time decreased from 29 (±4) min to 19 (±2) min, while the working time remained 5 to 6h. This study demonstrates the importance of controlling the water content in premixed cement pastes and how water can be used to improve the properties of premixed cements.

  10. Emulsification action of longitudinal and torsional ultrasound tips and the effect on treatment of the nucleus during phacoemulsification. (United States)

    Miyoshi, Teruyuki; Yoshida, Hironori


    To compare the results of emulsification of test materials when applying torsional and longitudinal emulsification tips as well as to define emulsification and determine how it occurs by examining the effect of phacoemulsification. Miyoshi Eye Hospital, Fukuyama, Japan. An ultra-high-speed digital video camera was used to record emulsification of chestnuts and human nuclei in a test chamber, simulating real phacoemulsification. The treatment of the nucleus as a result of phacoemulsification was analyzed visually. Visual comparison of video data showed that the test chamber materials were completely desiccated by the torsional phaco device. Longitudinal phacoemulsification resulted in cutting and coring of the test chamber materials, but not total disruption. Visual comparisons showed that complete obliteration and desiccation of the nucleus, or emulsification, occurs only with torsional phacoemulsification. These observations open the way to understanding the best approach to new tip design and surgical strategy development. Neither author has a financial or proprietary interest in any material or method mentioned. Copyright 2010 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

  11. Internal combustion engine using premixed combustion of stratified charges (United States)

    Marriott, Craig D.; Reitz, Rolf D. (Madison, WI


    During a combustion cycle, a first stoichiometrically lean fuel charge is injected well prior to top dead center, preferably during the intake stroke. This first fuel charge is substantially mixed with the combustion chamber air during subsequent motion of the piston towards top dead center. A subsequent fuel charge is then injected prior to top dead center to create a stratified, locally richer mixture (but still leaner than stoichiometric) within the combustion chamber. The locally rich region within the combustion chamber has sufficient fuel density to autoignite, and its self-ignition serves to activate ignition for the lean mixture existing within the remainder of the combustion chamber. Because the mixture within the combustion chamber is overall premixed and relatively lean, NO.sub.x and soot production are significantly diminished.

  12. Coaxial fuel and air premixer for a gas turbine combustor (United States)

    York, William D; Ziminsky, Willy S; Lacy, Benjamin P


    An air/fuel premixer comprising a peripheral wall defining a mixing chamber, a nozzle disposed at least partially within the peripheral wall comprising an outer annular wall spaced from the peripheral wall so as to define an outer air passage between the peripheral wall and the outer annular wall, an inner annular wall disposed at least partially within and spaced from the outer annular wall, so as to define an inner air passage, and at least one fuel gas annulus between the outer annular wall and the inner annular wall, the at least one fuel gas annulus defining at least one fuel gas passage, at least one air inlet for introducing air through the inner air passage and the outer air passage to the mixing chamber, and at least one fuel inlet for injecting fuel through the fuel gas passage to the mixing chamber to form an air/fuel mixture.

  13. Three dimensional dynamic mode decomposition of premixed turbulent jet flames (United States)

    Grenga, Temistocle; Macart, Jonathan; Mueller, Michael


    Analysis of turbulent combustion DNS data largely focuses on statistical analyses. However, turbulent combustion is highly unsteady and dynamic. In this work, Dynamic Mode Decomposition (DMD) will be explored as a tool for dynamic analysis of turbulent combustion DNS data, specifically a series of low Mach number spatially-evolving turbulent planar premixed hydrogen/air jet flames. DMD decomposes data into coherent modes with corresponding growth rates and oscillatory frequencies. The method identifies structures unbiased by energy so is particularly well suited to exploring dynamic processes at scales smaller than the largest, energy-containing scales of the flow and that may not be co-located in space and time. The focus of this work will be on both the physical insights that can potentially be derived from DMD modes and the computational issues associated with applying DMD to large three-dimensional DNS datasets.

  14. Flashback detection sensor for lean premix fuel nozzles (United States)

    Thornton, Jimmy Dean; Richards, George Alan; Straub, Douglas L.; Liese, Eric Arnold; Trader, Jr., John Lee; Fasching, George Edward


    A sensor for detecting the flame occurring during a flashback condition in the fuel nozzle of a lean premix combustion system is presented. The sensor comprises an electrically isolated flashback detection electrode and a guard electrode, both of which generate electrical fields extending to the walls of the combustion chamber and to the walls of the fuel nozzle. The sensor is positioned on the fuel nozzle center body at a location proximate the entrance to the combustion chamber of the gas turbine combustion system. The sensor provides detection of a flashback inside the fuel nozzle, by detecting the current conducted by the flame within a time frame that will prevent damage to the gas turbine combustion system caused by the flashback condition.

  15. A turbulent premixed flame on fractal-grid generated turbulence

    CERN Document Server

    Soulopoulos, Nikos; Beyrau, Frank; Hardalupas, Yannis; Taylor, A M K P; Vassilicos, J Christos


    A space-filling, low blockage fractal grid is used as a novel turbulence generator in a premixed turbulent combustion experiment. In contrast to the power law decay of a standard turbulence grid, the downstream turbulence intensity of the fractal grid increases until it reaches a peak at some distance from the grid before it finally decays. The effective mesh size and the solidity are the same as those of a standard square mesh grid with which it is compared. It is found that, for the same flow rate and stoichiometry, the fractal generated turbulence enhances the burning rate and causes the flame to further increase its area. Using a flame fractal model, an attempt is made to highlight differences between the flames established at the two different turbulent fields.

  16. Sintering Response of Aluminum 6061-TiB2 Composite: Effect of Prealloyed and Premixed Matrix (United States)

    Paidpilli, Mahesh; Gupta, Gaurav Kumar; Upadhyaya, Anish


    In the present study, Al6061-based alloy and composites were produced using powder metallurgy route. Two different kinds of base powders (prealloyed and premixed 6061Al alloy) were mixed with TiB2 particles in compositions ranging from 0 to 15 vol.%, respectively. The processed powders were compacted at 300 MPa and sintered at 620 °C under N2 atmosphere. The microstructural evolution of prealloyed and premixed 6061Al alloy, at different stages of sintering cycle, was studied using scanning electron microscope and EDS analysis. A comparative study was done between prealloyed- and premixed-based composites on the basis of densification, microstructure, hardness, transverse rupture strength and electrical conductivity as a function of TiB2 content. Results indicated that premixed-based composites have better mechanical properties than prealloyed-based composites.

  17. An Investigation of a Hybrid Mixing Model for PDF Simulations of Turbulent Premixed Flames (United States)

    Zhou, Hua; Li, Shan; Wang, Hu; Ren, Zhuyin


    Predictive simulations of turbulent premixed flames over a wide range of Damköhler numbers in the framework of Probability Density Function (PDF) method still remain challenging due to the deficiency in current micro-mixing models. In this work, a hybrid micro-mixing model, valid in both the flamelet regime and broken reaction zone regime, is proposed. A priori testing of this model is first performed by examining the conditional scalar dissipation rate and conditional scalar diffusion in a 3-D direct numerical simulation dataset of a temporally evolving turbulent slot jet flame of lean premixed H2-air in the thin reaction zone regime. Then, this new model is applied to PDF simulations of the Piloted Premixed Jet Burner (PPJB) flames, which are a set of highly shear turbulent premixed flames and feature strong turbulence-chemistry interaction at high Reynolds and Karlovitz numbers. Supported by NSFC 51476087 and NSFC 91441202.

  18. Embedded computer controlled premixing inline injection system for air-assisted variable-rate sprayers (United States)

    Improvements to reduce chemical waste and environmental pollution for variable-rate sprayers used in orchards and ornamental nurseries require inline injection techniques. A microprocessor controlled premixing inline injection system implementing a ceramic piston chemical metering pump and two small...

  19. Extinction conditions of a premixed flame in a channel

    Energy Technology Data Exchange (ETDEWEB)

    Alliche, Mounir [LMP2M, Universite de Medea, Quartier Ain Dheb, 26000 Medea (Algeria); M2P2, UMR CNRS 6181, Universite de Provence, Marseille (France); Haldenwang, Pierre [M2P2, UMR CNRS 6181, Universite de Provence, Marseille (France); Chikh, Salah [LTPMP, Faculte de Genie Mecanique and de Genie des Procedes, USTHB, Bab Ezzouar (Algeria)


    A local refinement method is used to numerically predict the propagation and extinction conditions of a premixed flame in a channel considering a thermodiffusive model. A local refinement method is employed because of the numerous length scales that characterize this phenomenon. The time integration is self adaptive and the solution is based on a multigrid method using a zonal mesh refinement in the flame reaction zone. The objective is to determine the conditions of extinction which are characterized by the flame structure and its properties. We are interested in the following properties: the curvature of the flame, its maximum temperature, its speed of propagation and the distance separating the flame from the wall. We analyze the influence of heat losses at the wall through the thermal conductivity of the wall and the nature of the fuel characterized by the Lewis number of the mixture. This investigation allows us to identify three propagation regimes according to heat losses at the wall and to the channel radius. The results show that there is an intermediate value of the radius for which the flame can bend and propagate provided that its curvature does not exceed a certain limit value. Indeed, small values of the radius will choke the flame and extinguish it. The extinction occurs if the flame curvature becomes too small. Furthermore, this study allows us to predict the limiting values of the heat loss coefficient at extinction as well as the critical value of the channel radius above which the premixed flame may propagate without extinction. A dead zone of length 2-4 times the flame thickness appears between the flame and the wall for a Lewis number (Le) between 0.8 and 2. For small values of Le, local extinctions are observed. (author)

  20. Early structure of LPG partially premixed conically stabilized flames

    KAUST Repository

    Elbaz, Ayman M.


    This paper presents experimental investigation of LPG partially premixed turbulent flames stabilized within a conical nozzle burner under constant degree of partial premixing. The stability limits and mean flame structure are presented based on the mean gas temperature and the concentration of CO, O 2, NO, and HC at the flame early region of reaction. The investigation covered the influence of the nozzle cone angle, the jet exit velocity and the jet equivalence ratio. The stability results show that the flames with cone are more stable than those without cone. For conical stabilized flames, the stability results exhibit three different sensitivity regions between the jet velocity and equivalence ratio. The inflame measurements prove that the flame stability could be attributed to the triple flame structure at the flame leading edge. The data show that the triple flame structure is influenced by cone angle, the jet velocity and the equivalence ratio. The flame is believed to be controlled by the recirculation flow inside the cone. Increasing the cone angle induced higher air entrainment to the reaction zone as depicted by a higher O 2 concentration within the flame leading edge. Increasing the jet velocity to a certain limit enhances the intensity of combustion at the flame leading edge, while excessive increase in jet velocity reduces this intensity. At a fixed jet velocity the higher the equivalence ratio, the higher the amount of fuel diffused and engulfed to the reaction zone, the more delay of the combustion completion and the higher the emission concentrations of the flame. © 2012 Elsevier Inc.

  1. A non-permselective membrane reactor for chemical processes normally requiring strict stoichiometric feed rates of reactants

    NARCIS (Netherlands)

    Sloot, H.J.; Versteeg, G.F.; Swaaij, W.P.M. van


    A novel type of membrane reactor with separated feeding of the reactants is presented for chemical processes normally requiring strict stoichiometric feed rates of premixed reactants. The reactants are fed in the reactor to the different sides of a porous membrane which is impregnated with a catalys

  2. A non-permselective membrane reactor for chemical processes normally requiring strict stoichiometric feed rates of reactants

    NARCIS (Netherlands)

    Sloot, H.J.; Versteeg, G.F.; Swaaij, W.P.M. van


    A novel type of membrane reactor with separated feeding of the reactants is presented for chemical processes normally requiring strict stoichiometric feed rates of premixed reactants. The reactants are fed in the reactor to the different sides of a porous membrane which is impregnated with a

  3. Controlled tissue emulsification produced by high intensity focused ultrasound shock waves and millisecond boiling. (United States)

    Khokhlova, Tatiana D; Canney, Michael S; Khokhlova, Vera A; Sapozhnikov, Oleg A; Crum, Lawrence A; Bailey, Michael R


    In high intensity focused ultrasound (HIFU) applications, tissue may be thermally necrosed by heating, emulsified by cavitation, or, as was recently discovered, emulsified using repetitive millisecond boiling caused by shock wave heating. Here, this last approach was further investigated. Experiments were performed in transparent gels and ex vivo bovine heart tissue using 1, 2, and 3 MHz focused transducers and different pulsing schemes in which the pressure, duty factor, and pulse duration were varied. A previously developed derating procedure to determine in situ shock amplitudes and the time-to-boil was refined. Treatments were monitored using B-mode ultrasound. Both inertial cavitation and boiling were observed during exposures, but emulsification occurred only when shocks and boiling were present. Emulsified lesions without thermal denaturation were produced with shock amplitudes sufficient to induce boiling in less than 20 ms, duty factors of less than 0.02, and pulse lengths shorter than 30 ms. Higher duty factors or longer pulses produced varying degrees of thermal denaturation combined with mechanical emulsification. Larger lesions were obtained using lower ultrasound frequencies. The results show that shock wave heating and millisecond boiling is an effective and reliable way to emulsify tissue while monitoring the treatment with ultrasound.

  4. Ultrasound-assisted emulsification of cosmetic samples prior to elemental analysis by different atomic spectrometric techniques. (United States)

    Lavilla, I; Cabaleiro, N; Costas, M; de la Calle, I; Bendicho, C


    In this work, ultrasound-assisted emulsification with a probe system is proposed as a rapid and simple sample treatment for atomic spectrometric determinations (Electrothermal Atomic Absorption Spectrometry, Inductively Coupled Plasma Optical Emission Spectrometry, Flame Atomic Absorption Spectrometry and Cold Vapour Atomic Absorption Spectrometry) of trace elements (As, Cd, Cr, Cu, Hg, Mg, Mn, Ni, Sr and Zn) in cosmetic samples such as shampoos, gel (hair gel), crèmes (body milk, hair conditioner) and oil (body oil). The type of dispersion medium, the sample mass-to-dispersion medium volume ratio, as well as the parameters related to the ultrasound-assisted emulsification (sonication amplitude and treatment time) were exhaustively studied. Only 1 min of ultrasonic shaking and a dispersion medium containing 0.5% (w/v) of SDS+3% (v/v) of HNO(3) or HCl allows obtaining a stable emulsion at least for 3 months. Thermal programs, nebulization of emulsions, speed of pumps and concentration of reagents used in cold vapour generation were optimized. Calibration using aqueous standards was feasible in all cases. Calibration by the standard addition method and recovery studies was also applied for validation. Microwave-assisted digestion and Inductively Coupled Plasma Mass Spectrometry were used for comparison purposes. Relative standard deviations from analysis of five independent emulsions were less than 9% in all cases.

  5. Optimization of folic acid nano-emulsification and encapsulation by maltodextrin-whey protein double emulsions. (United States)

    Assadpour, Elham; Maghsoudlou, Yahya; Jafari, Seid-Mahdi; Ghorbani, Mohammad; Aalami, Mehran


    Due to susceptibility of folic acid like many other vitamins to environmental and processing conditions, it is necessary to protect it by highly efficient methods such as micro/nano-encapsulation. Our aim was to prepare and optimize real water in oil nano-emulsions containing folic acid by a low energy (spontaneous) emulsification technique so that the final product could be encapsulated within maltodextrin-whey protein double emulsions. A non ionic surfactant (Span 80) was used for making nano-emulsions at three dispersed phase/surfactant ratios of 0.2, 0.6, and 1.0. Folic acid content was 1.0, 2.0, and 3.0mg/mL of dispersed phase by a volume fraction of 5.0, 8.5, and 12%. The final optimum nano-emulsion formulation with 12% dispersed phase, a water to surfactant ratio of 0.9 and folic acid content of 3mg/mL in dispersed phase was encapsulated within maltodextrin-whey protein double emulsions. It was found that the emulsification time for preparing nano-emulsions was between 4 to 16 h based on formulation variables. Droplet size decreased at higher surfactant contents and final nano-emulsions had a droplet sizenano-emulsions containing folic acid.


    Institute of Scientific and Technical Information of China (English)

    Yuan-ze Xu; Yu-zhe Wu; Jian-mao Yang


    The mechanism of phase inversion emulsification process (PIE) was studied for waterborne dispersion of highly viscous epoxy resin using non-ionic polymeric surfactants. Drop deformation and breakup, rheological properties,conductivity, and particle size measurements reveal the micro-structural transition amid emulsification. It is revealed that strong flow causes water drop to burst with the formation of droplets and huge interface. Phase inversion corresponds to an abrupt rheological transition from a type of viscous melt with weak elasticity to a highly elastic type of aqueous gel. This implies that the phase inversion equivalent to a curvature inversion. Based on this, a geometric model is postulated to correlate process variables to the particle size. The coverage and conformation of the surfactant plays key role for the particle size of the final emulsion. The interactions of thermodynamic and hydrodynamic effects are also discussed. It is concluded that the thermodynamics control the PIE while the hydrodynamics drives the creation of interface and involves every step of PIE.

  7. Ultrasound emulsification: effect of ultrasonic and physicochemical properties on dispersed phase volume and droplet size. (United States)

    Gaikwad, Shashank G; Pandit, Aniruddha B


    Ultrasonic emulsification of oil and water was carried out and the effect of irradiation time, irradiation power and physicochemical properties of oil on the dispersed phase volume and dispersed phase droplet size has been studied. The increase in the irradiation time increases the dispersed phase volume while decreases the dispersed phase droplets size. With an increase in the ultrasonic irradiation power, there is an increase in the fraction of volume of the dispersed phase while the droplet size of the dispersed phase decreases. The fractional volume of the dispersed phase increases for the case of groundnut oil-water system while it is low for paraffin (heavy) oil-water system. The droplet size of soyabean oil dispersed in water is found to be small while that of paraffin (heavy) oil is found to be large. These variations could be explained on the basis of varying physicochemical properties of the system, i.e., viscosity of oil and the interfacial tension. During the ultrasonic emulsification, coalescence phenomenon which is only marginal, has been observed, which can be attributed to the collision of small droplets when the droplet concentration increases beyond a certain number and the acoustic streaming strength increases.

  8. Development of solid lipid nanoparticles (SLNs) of lopinavir using hot self nano-emulsification (SNE) technique. (United States)

    Negi, Jeetendra Singh; Chattopadhyay, Pronobesh; Sharma, Ashok Kumar; Ram, Veerma


    Solid lipid nanoparticles (SLNs) of poor orally bioavailable drug lopinavir were prepared using hot self nano-emulsification (SNE) technique. Hot isotropic mixture of stearic acid, poloxamer and polyethylene glycol was spontaneously self nano-emulsify in hot water and SLNs were formed with subsequent rapid cooling. Self nano-emulsification ability of stearic acid, poloxamer and polyethylene glycol mixture was assessed by ternary phase diagram study. Optimized SLNs were having particle size of 180.6 ± 2.32 nm (PDI=0.133 ± 0.001), 91.5 ± 1.3% entrapment efficiency and zeta potential of -13.4 ± 0.56 mV. SLNs were evaluated by transmission electron microscopy (TEM) and atomic force microscopy (AFM) for morphological study. Further, Differential scanning calorimetry (DSC) and X-ray diffraction (XRD) of SLNs were also performed for checking solid state characterization. Higher oral bioavailability was found for lopinavir loaded SLNs in comparison to bulk lopinavir due to higher lymphatic drug transport (p<0.05). Results indicate that SLNs of higher fatty acids can be successfully prepared by hot SNE technique.

  9. Spontaneous Emulsification of a Metal Drop Immersed in Slag Due to Dephosphorization: Surface Area Quantification (United States)

    Assis, Andre N.; Warnett, Jason; Spooner, Stephen; Fruehan, Richard J.; Williams, Mark A.; Sridhar, Seetharaman


    When a chemical reaction occurs between two immiscible liquids, mass transfer is continuously taking place at the liquid-liquid interface. Several studies have shown that if the species being exchanged between the two liquids are surface-active, a very pronounced decrease in interfacial tension can occur which can lead to a phenomenon called spontaneous emulsification. In steelmaking, this behavior has been observed for several reactions that involve the transfer of impurities from molten steel to a molten-oxide slag but little quantification has been made. This work focuses on spontaneous emulsification due to the dephosphorization of a Fe-P drop immersed in a basic oxygen furnace type slag. An Au-image furnace attached to a confocal scanning laser microscope was used to rapidly heat and cool the samples at different times, and X-ray computerized tomography was used to perform the surface area calculations of the samples where the slag/steel reaction was allowed to occur for distinct times. The results show that the surface area of the metal drop rapidly increases by over one order of magnitude during the first 60 seconds of the reaction while the chemical reaction is occurring at a fast rate. Once the reaction slows down, approximately after 60 seconds, the droplets start to coalesce back together minimizing the surface area and returning to a geometry close to its equilibrium shape.

  10. An original combined multiphase model of the steam-explosion premixing phase


    Leskovar, Matjaž; Mavko, Borut


    In multiphase flow, different distributions can occur that cannot be adequately modeled with just free-surface models or with just multiphase models. Such a distribution of phases occurs for example, in isothermal steam-explosion premixing experiments, where dispersed spheres penetrate the water and the water-air surface remains sharp. A common practice when modeling isothermal premixing experiments is to treat all three phases involved - the water, the air and the spheres phase - equally, wi...

  11. Modeling of complex physics & combustion dynamics in a combustor with a partially premixed turbulent flame


    Shahi, Mina


    To avoid the formation of the high temperature stoichiometric regions in flames in a gas turbine combustor, and hence the formation of nitric oxides, an alternative concept of combustion technology was introduced by means of lean premixed combustion. However, the low emission of nitric oxides and carbon monoxide of the lean premixed combustion of natural gas comes at the cost of increased sensitivity to thermoacoustic instabilities. These are driven by the feedback loop between heat release, ...

  12. Decreasing vitamin premix on chicken carcass composition and blood chemistry in floor and battery cage systems

    Directory of Open Access Journals (Sweden)

    Mahmood Shivazad


    Full Text Available Two experiments were conducted the to compare the effect of a decreasing amount of vitamin premix in diets inbroilers from 29 to 42 days of age on carcass composition and blood chemistry in floor (Experiment 1 and battery cage (Experiment 2 systems. At 35 and 42 days of ages, one bird of each replicate was slaughtered and carcass composition was measured. Blood concentrations of alkaline phosphatase (ALP and Ca were used to diagnose vitamin D3 deficiency and enzymes aspartate amino transferase (AST to identify vitamin E deficiency. Floor raised birds showed that vitamin premix reduction/withdrawal at 29 days of age did not impair body weight (BW, carcass composition, ALP and Ca during the final rearing period. However, diet without vitamin premix (T1 had a higher AST at 42 days of age than the other diets. Birds reared in cages were slightly more sensitive to vitamin premix reduction/withdrawal, probably due to the impracticality of performing coprophagy. Diet without vitamin premix (T1 had a lower BW, carcass breast and thigh yield at 42 days of age; also serum ALP, AST and Ca were impaired. In conclusion, the withdrawal of vitamins is not a reasonable option but it is possible to reduce vitamin premix in finisher broilers’ diets without negative effects on performance and on some metabolic traits during the finisher period with both methods of rearing.

  13. Inerting characteristics of entrained atomized water on premixed methane-air flame

    Institute of Scientific and Technical Information of China (English)

    Cai Feng; Wang Ping; Zhou Jiebo; Li Chao


    A combustion tube experiment platform was designed and used to study the inerting conditions and capacity of entrained atomized water on premixed methane–air flame. The structure of a laminar flame of premixed methane–air gas and the process of interaction between atomized water and flame was recorded, and the rules of combustion velocity, stability and strength rate of laminar flame were experi-mentally studied. The inerting process and mechanism was analyzed, and the characteristics of inerting premixed methane–air gas within explosion limits by atomized water were acquired. The research results show that:for the premixed methane–air gas with a concentration of 7%, the minimum inerting atomized water flux is 20.8 mL/(m2 min);for the premixed methane–air gas with a concentration of 9%, the mini-mum inerting atomized water flux is 32.9 mL/(m2 min);for the premixed methane–air gas with a concen-tration of 11%, the minimum inerting atomized water flux is 44.6 mL/(m2 min). The research results are significant for extinguishing methane flame and inhibiting of methane explosion using atomized water.

  14. Large scale manufacture of magnetic polymer particles using membranes and microfluidic devices

    Institute of Scientific and Technical Information of China (English)

    Qingchun; Yuan; Richard; A.; Williams


    Magnetic polymer particles have found applications in diverse areas such as biomedical treatments, diagnosis and separation technology. These applications require the particles to have controlled sizes and narrow size distributions to gain better control and reproducibility in use. This paper reviews recent developments in the preparation of magnetic polymer particles at nano- and micro-scales by encapsulating magnetic components with dissolved or in situ formed polymers. Particle manufacture using emulsification and embedment methods produces magnetic polymer particles at micro-scale dimensions. However, the production of particles in this range using conventional emulsification methods affords very limited control over particle sizes and polydispersity. We report on alternative routes using membrane and microfluidics emulsification techniques, which have a capability to produce monodisperse emulsions and polymer microspheres (with coefficients of variation of less than 10%) in the range from submicrometer to a few 100 μm. The performance of these manufacturing methods is assessed with a view to future applications.

  15. Self-emulsification of alkaline-dissolved clove bud oil by whey protein, gum arabic, lecithin, and their combinations. (United States)

    Luo, Yangchao; Zhang, Yue; Pan, Kang; Critzer, Faith; Davidson, P Michael; Zhong, Qixin


    Low-cost emulsification technologies using food ingredients are critical to various applications. In the present study, a novel self-emulsification technique was studied to prepare clove bud oil (CBO) emulsions, without specialized equipment or organic solvents. CBO was first dissolved in hot alkaline solutions, added at 1% v/v into neutral solutions with 1% w/v emulsifier composed of whey protein concentrate (WPC), gum arabic, lecithin, or their equal mass mixtures, and adjusted to pH 7.0. The self-emulsification process did not affect UV-vis absorption spectrum, reversed-phase HPLC chromatogram, or antimicrobial activity of CBO against Escherichia coli O157:H7, Listeria monocytogenes Scott A, and Salmonella Enteritidis. The entrapment efficiency after extraction by petroleum ether was determined to be about 80%. Most emulsions were stable during 7 days of storage. Emulsions prepared with WPC had smaller particles, whereas emulsions prepared with emulsifier mixtures had more stable particle dimensions. The studied self-emulsification technique may find numerous applications in the preparation of low-cost food emulsions.

  16. A new coupling of spectrophotometric determination with ultrasound-assisted emulsification dispersive liquid-liquid microextraction of trace silver (United States)

    Wen, Xiaodong; Kong, Lamei; Chen, Meihui; Deng, Qingwen; Zhao, Xia; Guo, Jie


    In this work, a new coupling of spectrophotometric determination with preconcentration method named as ultrasound-assisted emulsification dispersive liquid-liquid microextraction (UAE-DLLME) for trace silver was firstly established. Disperser solvent in traditional DLLME was substituted by ultrasound-assisted emulsification, which could afford more effective emulsification and make the extraction method greener. The extraction was accomplished efficiently in only 3 min during ultrasound-assisted emulsification. Compared to traditional DLLME, the established pretreatment was simpler, greener and more effective. The UAE-DLLME technique was effectively coupled with ordinary spectrophotometer to improve the analytical performance and expand the application of spectrophotometric determination. The factors influencing UAE-DLLME, such as concentration of chelating agent, kind and volume of extractant, pH, conditions of phase separation, ultrasound extraction time and instrumental conditions, were studied in detail. Under the optimal conditions, the limit of detection (LOD) for silver was 0.45 μg L-1, with sensitivity enhancement factor (EF) of 35. The established method was applied to the determination of trace silver in real and certified reference samples with satisfactory analytical results.

  17. Investigation into the Cause of Spontaneous Emulsification of a Free Steel Droplet; Validation of the Chemical Exchange Pathway (United States)

    Spooner, Stephen; Assis, Andre N.; Warnett, Jason; Fruehan, Richard; Williams, Mark A.; Sridhar, Seetharaman


    Small Fe-based droplets have been heated to a molten phase suspended within a slag medium to replicate a partial environment within the basic oxygen furnace (BOF). The confocal scanning laser microscope (CSLM) has been used as a heating platform to interrogate the effect of impurities and their transfer across the metal/slag interface, on the emulsification of the droplet into the slag medium. The samples were then examined through X-ray computer tomography (XCT) giving the mapping of emulsion dispersion in 3D space, calculating the changing of interfacial area between the two materials, and changes of material volume due to material transfer between metal and slag. Null experiments to rule out thermal gradients being the cause of emulsification have been conducted as well as replication of the previously reported study by Assis et al.[1] which has given insights into the mechanism of emulsification. Finally chemical analysis was conducted to discover the transfer of oxygen to be the cause of emulsification, leading to a new study of a system with undergoing oxygen equilibration.

  18. Nanospheres of alginate prepared through w/o emulsification and internal gelation with nanoparticles of CaCO3

    NARCIS (Netherlands)

    Paques, J.P.; Sagis, L.M.C.; Rijn, van C.J.M.; Linden, van der E.


    Gelled nanospheres of alginate are prepared through a single step technique involving emulsification and gelation. CaCO3 nanoparticles, together with glucono delta-lactone (GDL), are dispersed in an alginate solution, which is subsequently dispersed in an oil phase and followed by gelation of the al

  19. Nanospheres of alginate prepared through w/o emulsification and internal gelation with nanoparticles of CaCO3

    NARCIS (Netherlands)

    Paques, J.P.; Sagis, L.M.C.; Rijn, van C.J.M.; Linden, van der E.


    Gelled nanospheres of alginate are prepared through a single step technique involving emulsification and gelation. CaCO3 nanoparticles, together with glucono delta-lactone (GDL), are dispersed in an alginate solution, which is subsequently dispersed in an oil phase and followed by gelation of the

  20. Short communication: Preference for flavored concentrate premixes by dairy cows. (United States)

    Harper, M T; Oh, J; Giallongo, F; Lopes, J C; Weeks, H L; Faugeron, J; Hristov, A N


    Flavor preferences may be used to stimulate feed intake in dairy cows, which may improve use of robotic milking systems and increase feed intake of sick cows. A cafeteria-design experiment was used to determine if dairy cows have flavor preferences. Sixteen lactating Holstein cows averaging 197±32d in milk, 1.9±0.8 lactations, 27.8±4.2kg/d of dry matter intake, and 41.5±7.4kg/d of milk yield were involved in the experiment. Cows were offered 7 flavored concentrate premixes (FCP) and 1 control premix. The FCP flavors were anise, fenugreek, honey, orange, thyme, molasses, and vanilla; the absence of flavor, neutral, acted as a control. The inclusion rate of the flavors in FCP was 250 to 300g/t on an as-is basis. Cows were not adapted to the flavors before the experiment. Cows were housed in a tiestall barn and offered, on each day, 4 different FCP (1kg each) in plastic bins placed in front of each cow. The experiment lasted 6 consecutive days. Each FCP was presented to each cow once every 2d, 2h after the morning feeding. Flavors and position of the bins in front of the cows were randomized. As a result, each flavor was presented to each cow 3 times during the experiment, at 3 different bin locations. Each cow had access to the FCP for 5min from the time they started eating. Eating time and amount eaten were recorded. The vanilla and fenugreek FCP were consumed the most, at 408 and 371g/5-min offering, respectively, whereas the orange and anise FCP were consumed the least, at 264 and 239g/5-min offering, respectively. Similarly, cows spent the most time eating the vanilla and fenugreek FCP at 99 and 75 s/offering, respectively, and the least amount of time eating the orange and anise FCP at 49 and 50 s/offering, respectively. We detected an effect of bin position: the 2 center FCP were consumed more than the outer 2 FCP. Flavor had no effect on consumption rate. In conclusion, relative to the control, concentrate intake was not affected by flavor, but dairy cows

  1. Numerical Investigation of Soot Formation in Non-premixed Flames

    KAUST Repository

    Abdelgadir, Ahmed Gamaleldin


    Soot is a carbon particulate formed as a result of the combustion of fossil fuels. Due to the health hazard posed by the carbon particulate, government agencies have applied strict regulations to control soot emissions from road vehicles, airplanes, and industrial plants. Thus, understanding soot formation and evolution is critical. Practical combustion devices operate at high pressure and in the turbulent regime. Elevated pressures and turbulence on soot formation significantly and fundamental understanding of these complex interactions is still poor. In this study, the effects of pressure and turbulence on soot formation and growth are investigated numerically. As the first step, the evolution of the particle size distribution function (PSDF) and soot particles morphology are investigated in turbulent non-premixed flames. A Direct Simulation Monte Carlo (DSMC) code is developed and used. The stochastic reactor describes the evolution of soot in fluid parcels following Lagrangian trajectories in a turbulent flow field. The trajectories are sampled from a Direct Numerical Simulation (DNS) of an n-heptane turbulent non-premixed flame. Although individual trajectories display strong bimodality as in laminar flames, the ensemble-average PSDF possesses only one mode and a broad tail, which implies significant polydispersity induced by turbulence. Secondly, the effect of the flow and mixing fields on soot formation at atmospheric and elevated pressures is investigated in coflow laminar diffusion flames. The experimental observation and the numerical prediction of the spatial distribution are in good agreement. Based on the common scaling methodology of the flames (keeping the Reynolds number constant), the scalar dissipation rate decreases as pressure increases, promoting the formation of PAH species and soot. The decrease of the scalar dissipation rate significantly contributes to soot formation occurring closer to the nozzle and outward on the flames wings as pressure

  2. Emulsification technique affects oxidative stability of fish oil-in-water emulsions

    DEFF Research Database (Denmark)

    Horn, Anna Frisenfeldt; Nielsen, Nina Skall; Jensen, Louise Helene Søgaard

    In oil-in-water emulsions, lipid oxidation is expected to be initiated at the oil-water interface. The properties of the emulsifier used, and the structure at the interface is therefore expected to be of great importance for lipid oxidation in emulsions. Previous studies have shown that e...... of this study was to compare lipid oxidation in 10% fish oil-in-water emulsions prepared by two different kinds of high pressure homogenizers i.e. a microfluidizer and a two valve high pressure homogenizer. Emulsions were made with equal droplet sizes, and with either 1% sodium caseinate or 1% whey protein.......g. homogenization pressure can affect how proteins locate themselves at the interface of an emulsion. The hypothesis is therefore that emulsions produced with different emulsification equipments differ in their oxidative stability due to differences in the behaviour of the proteins at the interface. The aim...

  3. Emulsification technique affects oxidative stability of fish oil-in-water emulsion

    DEFF Research Database (Denmark)

    Horn, Anna Frisenfeldt; Nielsen, Nina Skall; Jensen, Louise Helene Søgaard

    In oil-in-water emulsions, lipid oxidation is expected to be initiated at the oil-water interface. The properties of the emulsifier used, and the structure at the interface is therefore expected to be of great importance for lipid oxidation in emulsions. Previous studies have shown that e...... of this study was therefore to compare lipid oxidation in 10% fish oil-in-water emulsions prepared by two different kinds of high pressure homogenizers i.e. a microfluidizer and a two valve high pressure homogenizer. Emulsions were made with equal droplet sizes, and with either 1% sodium caseinate or 1% whey.......g. homogenization pressure can affect how proteins locate themselves at the interface of an emulsion. The hypothesis is therefore that emulsions produced with different emulsification equipments differ in their oxidative stability due to differences in the behaviour of the proteins at the interface. The aim...

  4. Optimization of solid lipid nanoparticles prepared by a single emulsification-solvent evaporation method

    Directory of Open Access Journals (Sweden)

    Deep Pooja


    Full Text Available This data article contains the data related to the research article “Characterization, biorecognitive activity and stability of WGA grafted lipid nanostructures for the controlled delivery of rifampicin” (Pooja et al. 2015 [1]. In the present study, SLN were prepared by a single emulsification-solvent evaporation method and the various steps of SLN preparation are shown in a flow chart. The preparation of SLN was optimized for various formulation variables including type and quantity of lipid, surfactant, amount of co-surfactant and volume of organic phase. Similarly, effect of variables related to homogezation, sonication and stirring processes, on the size and surface potential of SLN was determined and optimized.

  5. Emulsification of waste cooking oils and fatty acid distillates as diesel engine fuels: An attractive alternative

    Directory of Open Access Journals (Sweden)

    Eliezer Ahmed Melo Espinosa


    Full Text Available The scope of this paper is to analyze the possibility and feasibility of the use of emulsification method applied to waste cooking oils and fatty acid distillates as diesel engine fuels, compared with other commonly used methods. These waste products are obtained from the refining oil industry, food industry and service sector, mainly. They are rarely used as feedstock to produce biofuels and other things, in spite of constitute a potential source of environmental contamination. From the review of the state of arts, significant decreases in exhaust emissions of nitrogen oxides, cylinder pressure as well as increases of the ignition delay, brake specific fuel consumption, hydrocarbon, smoke opacity, carbon monoxide, particulate matters to emulsified waste cooking oils and fatty acid distillates compared with diesel fuel are reported. In some experiments the emulsified waste cooking oils achieved better performance than neat fatty acid distillates, neat waste cooking oils and their derivatives methyl esters.

  6. Phase behavior, self-assembly, and emulsification of Tween 80/water mixtures with limonene and perfluoromethyldecalin. (United States)

    Sharma, Suraj Chandra; Warr, Gregory G


    The phase behavior, microstructure, and emulsification of polyoxyethylene (20) sorbitan monooleate (Tween 80), water, and d-limonene (LM) or perfluoromethyldecalin (PFMD) has been studied by small-angle X-ray scattering and polarizing optical microscopy. In the Tween 80/water binary system, a micellar solution (L(1)), a hexagonal (H(1)) phase, and a water-swellable isotropic surfactant liquid (L(2)) phase are successively formed at 25 °C. LM can be solubilized into all of the phases formed by Tween 80/water mixtures, whereas no solubilization of PFMD occurs. The L(2) phase was found by small-angle neutron scattering to be bicontinuous with low interfacial curvature. Added water swells and amplifies the pre-existing amphiphilic structure. The stability of oil-in-H(1) complex emulsions is found to be sensitive to changes in structure that accompany solubilization.

  7. Production of micron-sized polymer particles for additive manufacturing by melt emulsification

    Energy Technology Data Exchange (ETDEWEB)

    Fanselow, Stephanie; Schmidt, Jochen; Wirth, Karl-Ernst; Peukert, Wolfgang, E-mail: [Institute of Particle Technology, Friedrich-Alexander-Universität Erlangen-Nürnberg, Cauerstrasse 4, 91058 Erlangen (Germany)


    Melt emulsification is an advanced top-down approach that permits to produce spherical particles and thus widens the availability of polymer feed materials for additive manufacturing. In the process the polymer is molten in a continuous phase and droplet breakup is realized in a rotor-stator-device. The stabilization of the newly formed surfaces is quite challenging. Therefore, a new method to identify an appropriate emulsifier by measuring the interfacial tension between the polymer and continuous phase using a high pressure / high temperature cell is presented. The obtained powders are characterized by scanning electron microscopy (SEM) and by a Zimmermann tensile strength tester to determine the powder flowability. The processability of the polymer powders for additive manufacturing is investigated and demonstrated by building single layers by laser beam melting.

  8. Emulsification/internal gelation as a method for preparation of diclofenac sodium-sodium alginate microparticles. (United States)

    Ahmed, Mahmoud M; El-Rasoul, Saleh Abd; Auda, Sayed H; Ibrahim, Mohamed A


    Emulsification/internal gelation has been suggested as an alternative to extrusion/external gelation in the encapsulation of several compounds including non-steroidal anti-inflammatory drugs such as diclofenac sodium. The objective of the present study was a trial to formulate diclofenac sodium as controlled release microparticles that might be administered once or twice daily. This could be achieved via emulsification/internal gelation technique applying Box-Behnken design to choose these formulae. Box-Behnken design determined fifteen formulae containing specified amounts of the independent variables, which included stirring speed in rpm (X1), drug:polymer ratio (X2) and the surfactant span 80% (X3). The dependent variables studied were cumulative percent release after two hours (Y1), four hours (Y2) and eight hours (Y3). The prepared microparticles were characterized for their production yield, sizes, shapes and morphology, entrapment efficiency and Diclofenac sodium in vitro release as well. The results showed that the production yield of the prepared diclofenac sodium microparticles was found to be between 79.55% and 97.41%. The formulated microparticles exhibited acceptable drug content values that lie in the range 66.20-96.36%. Also, the data obtained revealed that increasing the mixing speed (X1) generally resulted in decreased microparticle size. In addition, scanning electron microscope images of the microparticles illustrated that the formula contains lower span concentration (1%) in combination with lower stirring speed (200 rpm) which showed wrinkled, but smooth surfaces. However, by increasing surfactant concentration, microspheres' surfaces become smoother and slightly porous. Kinetic treatment of the in vitro release from drug-loaded microparticles indicated that the zero order is the drug release mechanism for the most formulae.

  9. Direct numerical simulation of bluff-body-stabilized premixed flames

    KAUST Repository

    Arias, Paul G.


    To enable high fidelity simulation of combustion phenomena in realistic devices, an embedded boundary method is implemented into direct numerical simulations (DNS) of reacting flows. One of the additional numerical issues associated with reacting flows is the stable treatment of the embedded boundaries in the presence of multicomponent species and reactions. The implemented method is validated in two test con gurations: a pre-mixed hydrogen/air flame stabilized in a backward-facing step configuration, and reactive flows around a square prism. The former is of interest in practical gas turbine combustor applications in which the thermo-acoustic instabilities are a strong concern, and the latter serves as a good model problem to capture the vortex shedding behind a bluff body. In addition, a reacting flow behind the square prism serves as a model for the study of flame stabilization in a micro-channel combustor. The present study utilizes fluid-cell reconstruction methods in order to capture important flame-to-solid wall interactions that are important in confined multicomponent reacting flows. Results show that the DNS with embedded boundaries can be extended to more complex geometries without loss of accuracy and the high fidelity simulation data can be used to develop and validate turbulence and combustion models for the design of practical combustion devices.

  10. Simulation studies of premixed ch4/air Microcombustion

    Directory of Open Access Journals (Sweden)

    P.Bala Murali


    Full Text Available A numerical study of CH4-air premixed combustion in the micro combustors with a five step global mechanism is performed by solving the two dimensional governing equations of continuity, momentum and species, coupled with the energy equation. A reference case is defined as the combustion in a cylindrical tube with 1 mm inlet diameter and length 10 times its inlet diameter with a uniform velocity profile at the inlet plane. Different physical and boundary conditions have been applied in order to investigate their respective effects on the flame temperature. The conditions studied in the current paper include the combustor size, geometry and inlet velocities. Downscaling the combustion chamber and higher velocities leaded to reduction in residence time which results in lower combustion efficiency causing insufficient heat generation unable to maintain the self-sustained combustion. The effect of variation in inlet velocity has role in the determining the flame position in combination with given thermal conditions. The results of this paper indicate that these various boundary and physical conditions have effects on the flame temperature to different extent and should be carefully monitored when applied for different applications.

  11. Premixed Combustion of Coconut Oil on Perforated Burner

    Directory of Open Access Journals (Sweden)

    I.K.G. Wirawan


    Full Text Available Coconut oil premixed combustion behavior has been studied experimentally on perforated burner with equivalence ratio (φ varied from very lean until very rich. The results showed that burning of glycerol needs large number of air so that the laminar burning velocity (SL is the highest at very lean mixture and the flame is in the form of individual Bunsen flame on each of the perforated plate hole. As φ is increased the  SL decreases and the secondary Bunsen flame with open tip occurs from φ =0.54 at the downstream of perforated flame. The perforated flame disappears at φ = 0.66 while the secondary Bunsen flame still exist with SL increases following that of hexadecane flame trend and then extinct when the equivalence ratio reaches one or more. Surrounding ambient air intervention makes SL decreases, shifts lower flammability limit into richer mixture, and performs triple and cellular flames. The glycerol diffusion flame radiation burned fatty acids that perform cellular islands on perforated hole.  Without glycerol, laminar flame velocity becomes higher and more stable as perforated flame at higher φ. At rich mixture the Bunsen flame becomes unstable and performs petal cellular around the cone flame front. Keywords: cellular flame; glycerol; perforated flame;secondary Bunsen flame with open tip; triple flame

  12. Hydrogen-hydrocarbon turbulent non-premixed flame structure

    Energy Technology Data Exchange (ETDEWEB)

    Tabet, F. [ANSYS-Benelux, 4 Avenue Pasteur, B-1300 Wavre (Belgium); Sarh, B.; Goekalp, I. [Institut de Combustion, Aerothermique, Reactivite et Environnement (ICARE), Centre National de la Recherche Scientifique (CNRS), 1 C avenue de la recherche scientifique, Orleans 45071 Cedex 2 (France)


    In this study, the structure of turbulent non-premixed CH{sub 4}-H{sub 2}/air flames is analyzed with a special emphasis on mixing and air entrainment. The amount of H{sub 2} in the fuel mixture varies under constant volumetric fuel flow. Mixing is described by mixture fraction and its variance while air entrainment is characterized by the ratio of gas mass flow to fuel mass flow at the inlet section. The flow field and the chemistry are coupled by the flamelet assumption. Mixture fraction and its variance are transported by the computational fluid dynamics (CFD) code. The slow chemistry aspect of NO{sub x} is handled by solving an additional transport equation with a source term derived from flamelet library. The results obtained show an improvement of mixing with hydrogen addition leading to a strong consumption of CH{sub 4} and a high air entrainment into the centerline region. As a global effect of this, the composite fuels burn faster and thereby reduce the residence time which ultimately shortens the flame length and thickness. On the other hand, hydrogen is found to increase NO{sub x} level. (author)

  13. Premixed flame chemistry of a gasoline primary reference fuel surrogate

    KAUST Repository

    Selim, Hatem


    Investigating the combustion chemistry of gasoline surrogate fuels promises to improve detailed reaction mechanisms used for simulating their combustion. In this work, the combustion chemistry of one of the simplest, but most frequently used gasoline surrogates – primary reference fuel 84 (PRF 84, 84 vol% iso-octane and 16 vol% n-heptane), has been examined in a stoichiometric premixed laminar flame. Time-of-flight mass spectrometry coupled with a vacuum ultraviolet (VUV) synchrotron light source for species photoionization was used. Reactants, major end-products, stable intermediates, free radicals, and isomeric species were detected and quantified. Numerical simulations were conducted using a detailed chemical kinetic model with the most recently available high temperature sub-mechanisms for iso-octane and heptane, built on the top of an updated pentane isomers model and AramcoMech 2.0 (C0C4) base chemistry. A detailed interpretation of the major differences between the mechanistic pathways of both fuel components is given. A comparison between the experimental and numerical results is depicted and rate of production and sensitivity analyses are shown for the species with considerable disagreement between the experimental and numerical findings.

  14. Tangential stretching rate (TSR) analysis of non premixed reactive flows

    KAUST Repository

    Valorani, Mauro


    We discuss how the Tangential stretching rate (TSR) analysis, originally developed and tested for spatially homogeneous systems (batch reactors), is extended to spatially non homogeneous systems. To illustrate the effectiveness of the TSR diagnostics, we study the ignition transient in a non premixed, reaction–diffusion model in the mixture fraction space, whose dependent variables are temperature and mixture composition. The reactive mixture considered is syngas/air. A detailed H2/CO mechanism with 12 species and 33 chemical reactions is employed. We will discuss two cases, one involving only kinetics as a model of front propagation purely driven by spontaneous ignition, the other as a model of deflagration wave involving kinetics/diffusion coupling. We explore different aspects of the system dynamics such as the relative role of diffusion and kinetics, the evolution of kinetic eigenvalues, and of the tangential stretching rates computed by accounting for the combined action of diffusion and kinetics as well for kinetics only. We propose criteria based on the TSR concept which allow to identify the most ignitable conditions and to discriminate between spontaneous ignition and deflagration front.

  15. Premixed combustion under electric field in a constant volume chamber

    KAUST Repository

    Cha, Min Suk


    The effects of electric fields on outwardly propagating premixed flames in a constant volume chamber were experimentally investigated. An electric plug, subjected to high electrical voltages, was used to generate electric fields inside the chamber. To minimize directional ionic wind effects, alternating current with frequency of 1 kHz was employed. Lean and rich fuel/air mixtures for both methane and propane were tested to investigate various preferential diffusion conditions. As a result, electrically induced instability showing cracked structure on the flame surface could be observed. This cracked structure enhanced flame propagation speed for the initial period of combustion and led to reduction in flame initiation and overall combustion duration times. However, by analyzing pressure data, it was found that overall burning rates are not much affected from the electric field for the pressurized combustion period. The reduction of overall combustion time is less sensitive to equivalence ratio for methane/air mixtures, whereas the results demonstrate pronounced effects on a lean mixture for propane. The improvement of combustion characteristics in lean mixtures will be beneficial to the design of lean burn engines. Two hypothetical mechanisms to explain the electrically induced instability were proposed: 1) ionic wind initiated hydrodynamic instability and 2) thermodiffusive instability through the modification of transport property such as mass diffusivity. © 2012 IEEE.

  16. Development of a lean premixed burner for hydrogen utilization

    Energy Technology Data Exchange (ETDEWEB)

    Keller, J.O. [Sandia National Lab., Livermore, CA (United States)


    The long-term mandate of the hydrogen program is to develop the technologies needed to establish a hydrogen economy. Although a hydrogen fueled automobile has been established as a demonstration project, there are at least three other end use sectors that are recognized by the H{sub 2} program and that are addressed by this project. These end uses are: (1) power generation from stationary turbines, (2) generation of process heat or steam, and (3) commercial and residential direct use applications. Eliminating carbon from the fuel will remove carbon containing species from the emissions, however, NO{sub x} resulting from thermal NO production cannot be ignored. Thermal NO production is minimized by reducing the peak combustion temperature and the residence time at the peak temperature. NO can be reduced to extremely low levels (a few ppm) by operating sufficiently lean to reduce the peak combustion temperatures below 1700 to 1800 K. The objectives for this project are to: (1) develop an environmentally benign and safe burner operating on hydrogen in a lean premixed mode, (2) provide a facility in which fundamental investigations can be performed to support other programs.

  17. Unstrained and strained flamelets for LES of premixed combustion (United States)

    Langella, Ivan; Swaminathan, Nedunchezhian


    The unstrained and strained flamelet closures for filtered reaction rate in large eddy simulation (LES) of premixed flames are studied. The required sub-grid scale (SGS) PDF in these closures is presumed using the Beta function. The relative performances of these closures are assessed by comparing numerical results from large eddy simulations of piloted Bunsen flames of stoichiometric methane-air mixture with experimental measurements. The strained flamelets closure is observed to underestimate the burn rate and thus the reactive scalars mass fractions are under-predicted with an over-prediction of fuel mass fraction compared with the unstrained flamelet closure. The physical reasons for this relative behaviour are discussed. The results of unstrained flamelet closure compare well with experimental data. The SGS variance of the progress variable required for the presumed PDF is obtained by solving its transport equation. An order of magnitude analysis of this equation suggests that the commonly used algebraic model obtained by balancing source and sink in this transport equation does not hold. This algebraic model is shown to underestimate the SGS variance substantially and the implications of this variance model for the filtered reaction rate closures are highlighted.

  18. Measurements of turbulent premixed flame dynamics using cinema stereoscopic PIV

    Energy Technology Data Exchange (ETDEWEB)

    Steinberg, Adam M.; Driscoll, James F. [University of Michigan, Department of Aerospace Engineering, Ann Arbor, MI (United States); Ceccio, Steven L. [University of Michigan, Department of Mechanical Engineering, Ann Arbor, MI (United States)


    A new experimental method is described that provides high-speed movies of turbulent premixed flame wrinkling dynamics and the associated vorticity fields. This method employs cinema stereoscopic particle image velocimetry and has been applied to a turbulent slot Bunsen flame. Three-component velocity fields were measured with high temporal and spatial resolutions of 0.9 ms and 140{mu}m, respectively. The flame-front location was determined using a new multi-step method based on particle image gradients, which is described. Comparisons are made between flame fronts found with this method and simultaneous CH-PLIF images. These show that the flame contour determined corresponds well to the true location of maximum gas density gradient. Time histories of typical eddy-flame interactions are reported and several important phenomena identified. Outwardly rotating eddy pairs wrinkle the flame and are attenuated at they pass through the flamelet. Significant flame-generated vorticity is produced downstream of the wrinkled tip. Similar wrinkles are caused by larger groups of outwardly rotating eddies. Inwardly rotating pairs cause significant convex wrinkles that grow as the flame propagates. These wrinkles encounter other eddies that alter their behavior. The effects of the hydrodynamic and diffusive instabilities are observed and found to be significant contributors to the formation and propagation of wrinkles. (orig.)

  19. Dynamic-Stability Characteristics of Premixed Methane Oxy-Combustion

    KAUST Repository

    Shroll, Andrew P.


    This work explores the dynamic stability characteristics of premixed CH 4/O 2/CO 2 mixtures in a 50 kW swirl stabilized combustor. In all cases, the methane-oxygen mixture is stoichiometric, with different dilution levels of carbon dioxide used to control the flame temperature (T ad). For the highest T ad\\'s, the combustor is unstable at the first harmonic of the combustor\\'s natural frequency. As the temperature is reduced, the combustor jumps to fundamental mode and then to a low-frequency mode whose value is well below the combustor\\'s natural frequency, before eventually reaching blowoff. Similar to the case of CH 4/air mixtures, the transition from one mode to another is predominantly a function of the T ad of the reactive mixture, despite significant differences in laminar burning velocity and/or strained flame consumption speed between air and oxy-fuel mixtures for a given T ad. High speed images support this finding by revealing similar vortex breakdown modes and thus similar turbulent flame geometries that change as a function of flame temperature. Copyright © 2012 American Society of Mechanical Engineers.

  20. Photon-counting chirped amplitude modulation lidar using a smart premixing method. (United States)

    Zhang, Zijing; Zhang, Jianlong; Wu, Long; Zhang, Yong; Zhao, Yuan; Su, Jianzhong


    We proposed a new premixing method for photon-counting chirped amplitude modulation lidar (PCCAML). Earlier studies used the counting results of the returned signal detected by a Geiger mode avalanche photodiode detector (Gm-APD) to mix with the reference signal, called the postmixing method. We use an alternative method known as the premixing method, in which the reference signal is used to directly modulate the sampling gate width of the Gm-APD, and the mixing of the returned signal and the reference signal is completed before the Gm-APD. This premixing method is more flexible and may perform better than the postmixing method in terms of signal-to-noise ratio by cutting down a separated mixer commonly used in the postmixing lidar system. Furthermore, this premixing method lowers the demand for the sampling frequency of the Gm-APD. It allows the use of a much wider modulation bandwidth to improve the range accuracy and resolution. To the best of our knowledge, this is the first report to use the premixing method in the PCCAML system, which will benefit future lidar applications.

  1. Demonstration of a packed bed membrane reactor for the oxidative dehydrogenation of propane

    NARCIS (Netherlands)

    Kotanjac, Zeljko; van Sint Annaland, M.; Kuipers, J.A.M.


    An experimental demonstration of the oxidative dehydrogenation of propane (ODHP) in a lab-scale packed bed membrane reactor has been performed. Experiments were carried out with both premixed and distributed oxygen feed over a Ga2O3/MoO3 catalyst and compared, and the influence of the gas

  2. An experimental study on premixed charge compression ignition-direct ignition engine fueled with ethanol and gasohol

    Directory of Open Access Journals (Sweden)

    S. Saravanan


    Full Text Available This paper investigates the combustion, performance and emission characteristics of a partial Premixed Charge Compression Ignition-Direct Injection (PCCI-DI Engine with premixed fuels ethanol and gasohol (90% gasoline and 10% ethanol by volume along with direct injection of diesel fuel into the combustion chamber. The experiments were conducted in a four stroke, naturally aspirated, air cooled, constant speed diesel engine with 20% premixed fuels from no load to full load condition. The addition of premixed fuel enhances the air fuel mixture strength and for that the combustion duration is decreased in dual fuel operation. From this experiment it was observed the 70% and 67% reduction in smoke emission from premixed gasohol and ethanol fuel when compared to neat diesel operation. In addition to that, the oxides of nitrogen emissions were reduced to 30% and 24% for premixed gasohol and ethanol fuel. In particular, premixed gasohol reduces the smoke and oxides of nitrogen emissions more than the ethanol and also, significant increase in brake thermal efficiency was noted in 20% premixed gasohol and ethanol in dual fuel mode, when compared to neat diesel operation.

  3. Effect of powder density variation on premixed Ti-6Al-4V and Cu composites during laser metal deposition

    CSIR Research Space (South Africa)

    Erinosho, MF


    Full Text Available This paper reports the effect of powder density variation on the premixed Ti-6Al-4V/Cu and Ti-6A-4V/2Cu Composites. Two sets of experiment were conducted in this study. Five deposits each were made for the two premixed composites. Laser powers were...

  4. The Role of Shearing Energy and Interfacial Gibbs Free Energy in the Emulsification Mechanism of Waxy Crude Oil

    Directory of Open Access Journals (Sweden)

    Zhihua Wang


    Full Text Available Crude oil is generally produced with water, and the water cut produced by oil wells is increasingly common over their lifetime, so it is inevitable to create emulsions during oil production. However, the formation of emulsions presents a costly problem in surface process particularly, both in terms of transportation energy consumption and separation efficiency. To deal with the production and operational problems which are related to crude oil emulsions, especially to ensure the separation and transportation of crude oil-water systems, it is necessary to better understand the emulsification mechanism of crude oil under different conditions from the aspects of bulk and interfacial properties. The concept of shearing energy was introduced in this study to reveal the driving force for emulsification. The relationship between shearing stress in the flow field and interfacial tension (IFT was established, and the correlation between shearing energy and interfacial Gibbs free energy was developed. The potential of the developed correlation model was validated using the experimental and field data on emulsification behavior. It was also shown how droplet deformation could be predicted from a random deformation degree and orientation angle. The results indicated that shearing energy as the energy produced by shearing stress working in the flow field is the driving force activating the emulsification behavior. The deformation degree and orientation angle of dispersed phase droplet are associated with the interfacial properties, rheological properties and the experienced turbulence degree. The correlation between shearing stress and IFT can be quantified if droplet deformation degree vs. droplet orientation angle data is available. When the water cut is close to the inversion point of waxy crude oil emulsion, the interfacial Gibbs free energy change decreased and the shearing energy increased. This feature is also presented in the special regions where

  5. An Investigation of a Hybrid Mixing Timescale Model for PDF Simulations of Turbulent Premixed Flames (United States)

    Zhou, Hua; Kuron, Mike; Ren, Zhuyin; Lu, Tianfeng; Chen, Jacqueline H.


    Transported probability density function (TPDF) method features the generality for all combustion regimes, which is attractive for turbulent combustion simulations. However, the modeling of micromixing due to molecular diffusion is still considered to be a primary challenge for TPDF method, especially in turbulent premixed flames. Recently, a hybrid mixing rate model for TPDF simulations of turbulent premixed flames has been proposed, which recovers the correct mixing rates in the limits of flamelet regime and broken reaction zone regime while at the same time aims to properly account for the transition in between. In this work, this model is employed in TPDF simulations of turbulent premixed methane-air slot burner flames. The model performance is assessed by comparing the results from both direct numerical simulation (DNS) and conventional constant mechanical-to-scalar mixing rate model. This work is Granted by NSFC 51476087 and 91441202.

  6. Tabulated Combustion Model Development For Non-Premixed Flames (United States)

    Kundu, Prithwish

    Turbulent non-premixed flames play a very important role in the field of engineering ranging from power generation to propulsion. The coupling of fluid mechanics and complicated combustion chemistry of fuels pose a challenge for the numerical modeling of these type of problems. Combustion modeling in Computational Fluid Dynamics (CFD) is one of the most important tools used for predictive modeling of complex systems and to understand the basic fundamentals of combustion. Traditional combustion models solve a transport equation of each species with a source term. In order to resolve the complex chemistry accurately it is important to include a large number of species. However, the computational cost is generally proportional to the cube of number of species. The presence of a large number of species in a flame makes the use of CFD computationally expensive and beyond reach for some applications or inaccurate when solved with simplified chemistry. For highly turbulent flows, it also becomes important to incorporate the effects of turbulence chemistry interaction (TCI). The aim of this work is to develop high fidelity combustion models based on the flamelet concept and to significantly advance the existing capabilities. A thorough investigation of existing models (Finite-rate chemistry and Representative Interactive Flamelet (RIF)) and comparative study of combustion models was done initially on a constant volume combustion chamber with diesel fuel injection. The CFD modeling was validated with experimental results and was also successfully applied to a single cylinder diesel engine. The effect of number of flamelets on the RIF model and flamelet initialization strategies were studied. The RIF model with multiple flamelets is computationally expensive and a model was proposed on the frame work of RIF. The new model was based on tabulated chemistry and incorporated TCI effects. A multidimensional tabulated chemistry database generation code was developed based on the 1

  7. Lean premixed flames for low NO{sub x} combustors

    Energy Technology Data Exchange (ETDEWEB)

    Sojka, P.; Tseng, L.; Bryjak, J. [Purdue Univ., West Lafayette, IN (United States)] [and others


    Gas turbines are being used throughout the world to generate electricity. Due to increasing fuel costs and environmental concerns, gas turbines must meet stringent performance requirements, demonstrating high thermal efficiencies and low pollutant emissions. In order for U.S. manufactured gas turbines to stay competitive, their NO{sub x} levels must be below 10 ppm and their thermal efficiencies should approach 60%. Current technology is being stretched to achieve these goals. The twin goals of high efficiency and low NO{sub x} emissions require extending the operating range of current gas turbines. Higher efficiency requires operation at higher pressures and temperatures. Lower NO{sub x} emissions requires lower flame temperatures. Lower flame temperatures can be achieved through partially to fully pre-mixed combustion. However, increased performance and lower emissions result in a set of competing goals. In order to achieve a successful compromise between high efficiency and low NO{sub x} emissions, advanced design tools must be developed. One key design tool is a computationally efficient, high pressure, turbulent flow, combustion model capable of predicting pollutant formation in an actual gas turbine. Its development is the goal of this program. Achieving this goal requires completion of three tasks. The first task is to develop a reduced chemical kinetics model describing N{sub O}x formation in natural gas-air systems. The second task is to develop a computationally efficient model that describes turbulence-chemistry interactions. The third task is to incorporate the reduced chemical kinetics and turbulence-chemistry interaction models into a commercially available flow solver and compare its predictions with experimental data obtained under carefully controlled conditions so that the accuracy of model predictions can be evaluated.

  8. Pdf modeling for premixed turbulent combustion based on the properties of iso-concentration surfaces (United States)

    Vervisch, L.; Kollmann, W.; Bray, K. N. C.; Mantel, T.


    In premixed turbulent flames the presence of intense mixing zones located in front of and behind the flame surface leads to a requirement to study the behavior of iso-concentration surfaces defined for all values of the progress variable (equal to unity in burnt gases and to zero in fresh mixtures). To support this study, some theoretical and mathematical tools devoted to level surfaces are first developed. Then a database of direct numerical simulations of turbulent premixed flames is generated and used to investigate the internal structure of the flame brush, and a new pdf model based on the properties of iso-surfaces is proposed.

  9. Effects of a Premixed Layer on the Richtmyer-Meshkov Instability

    Institute of Scientific and Technical Information of China (English)

    TIAN Bao-Lin; ZHANG Xin-Ting; QI Jin; WNG Shuang-Hu


    The effects of a premixed layer on the Richmyer-Meshkov instability (RMI) are studied by setting a density gradient for the first shocked fluid in the RMI problems.The RMI with initial density gradients are simulated by using a high resolution arbitrary Lagrangian-Eulerian method.The effects of density gradient and gradient width are analyzed on the basis of the simulation results for the shock from a light fluid to a heavy fluid and for the shock from a heavy fluid to a light fluid.Overall,the premixed layer can suppress the perturbation growth,and the detailed effects are different depending on the detailed premixed configuration.The width of the premixed layer has a very light influence on the perturbation,while the density gradient has quite a significant effect on two kinds of RMIs.The instability of a material interface under an acceleration by an incident shock was predicted theoretically by Richtmyer in 1960.Ten years later,Meshkov confirmed experimentally Richtmyer's prediction.Since then,this interfacial instability has been referred as the Richtmyer-Meshkov instability (RMI).[1-11] Such instabilities are observed in supernovae explosions and inertial confinement fusion (ICF),and are thus of great importance to science and technology.Extensive theoretical and experimental studies of the RM instability have been carried out in the last three decades.With the advent of computer technology and increasing computing power,numerical studies of the RM instability have become very common.%The effects of a premixed layer on the Richmyer-Meshkov instability (RMI) are studied by setting a density gradient for the first shocked fluid in the RMI problems. The RMI with initial density gradients are simulated by using a high resolution arbitrary Lagrangian-Eulerian method. The effects of density gradient and gradient width are analyzed on the basis of the simulation results for the shock from a light fluid to a heavy fluid and for the shock from a heavy fluid to a light

  10. Dynamic properties of combustion instability in a lean premixed gas-turbine combustor. (United States)

    Gotoda, Hiroshi; Nikimoto, Hiroyuki; Miyano, Takaya; Tachibana, Shigeru


    We experimentally investigate the dynamic behavior of the combustion instability in a lean premixed gas-turbine combustor from the viewpoint of nonlinear dynamics. A nonlinear time series analysis in combination with a surrogate data method clearly reveals that as the equivalence ratio increases, the dynamic behavior of the combustion instability undergoes a significant transition from stochastic fluctuation to periodic oscillation through low-dimensional chaotic oscillation. We also show that a nonlinear forecasting method is useful for predicting the short-term dynamic behavior of the combustion instability in a lean premixed gas-turbine combustor, which has not been addressed in the fields of combustion science and physics.

  11. Probing insulin bioactivity in oral nanoparticles produced by ultrasonication-assisted emulsification/internal gelation

    Directory of Open Access Journals (Sweden)

    Lopes MA


    Full Text Available Marlene A Lopes,1,2,* Bárbara Abrahim-Vieira,3,* Claudia Oliveira,4,5 Pedro Fonte,6,7 Alessandra M T Souza,3 Tammy Lira,3 Joana A D Sequeira,1,2 Carlos R Rodrigues,3 Lúcio M Cabral,3 Bruno Sarmento,6–8 Raquel Seiça,9 Francisco Veiga,1,2 António J Ribeiro1,4,5 1Faculty of Pharmacy, University of Coimbra, Coimbra, Portugal; 2CNC – Center for Neuroscience and Cell Biology, Coimbra, Portugal; 3Department of Pharmaceutics, Faculty of Pharmacy, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil; 4I3S, Instituto de Investigação e Inovação em Saúde, University of Porto, Porto, Portugal; 5Group Genetics of Cognitive Dysfunction, IBMC – Instituto de Biologia Molecular e Celular, Porto, Portugal; 6REQUIMTE, Department of Chemical Sciences – Applied Chemistry Lab, Faculty of Pharmacy, University of Porto, Porto, Portugal; 7CESPU, Instituto de Investigação e Formação Avançada em Ciências e Tecnologias da Saúde, Gandra, Portugal; 8INEB – Instituto de Engenharia Biomédica, University of Porto, Porto, Portugal; 9IBILI – Institute of Biomedical Research in Light and Image, Faculty of Medicine, University of Coimbra, Coimbra, Portugal *These authors contributed equally to this work Abstract: Alginate–dextran sulfate-based particles obtained by emulsification/internal gelation technology can be considered suitable carriers for oral insulin delivery. A rational study focused on the emulsification and particle recovery steps was developed in order to reduce particles to the nanosize range while keeping insulin bioactivity. There was a decrease in size when ultrasonication was used during emulsification, which was more pronounced when a cosurfactant was added. Ultrasonication add-on after particle recovery decreased aggregation and led to a narrower nanoscale particle-size distribution. Insulin encapsulation efficiency was 99.3%±0.5%, attributed to the strong pH-stabilizing electrostatic effect between insulin and

  12. Feasibility study on microencapsulation of anaerobic Clostridium acetobutylicum ATCC 824 by emulsification method for application in biobutanol production. (United States)

    Rathore, Sweta; Heng, Paul Wan Sia; Chan, Lai Wah


    This work evaluated the feasibility of microencapsulating Clostridium acetobutylicum ATCC 824 cells by emulsification for fermentation to produce biobutanol. The effects of selected emulsification process on viability of the vegetative cells and spores were investigated to enable the selection of appropriate form of bacterium for immobilisation. The spores were found to be more suitable for microencapsulation than the vegetative cells. Design of experiment and mathematical models were then used to evaluate the effects of gellan gum concentration, HLB of surfactant blend, temperature and stirring speed on the properties of the microspheres produced. Using the predicted optimal conditions, the spores were successfully immobilised in spherical microspheres for use in fermentation. The microencapsulated spores were easily revived by heat shock treatment and could produce 8.2 g/l of butanol, which was higher than that generally reported in literature. The microencapsulation method developed provides means of producing reusable microbioreactors for anaerobic spore-forming microorganisms.

  13. Development and Evaluation of an Aqueous Polymeric Dispersion of Eudragit L 100-55 Using Emulsification Technology


    Singh S; Mittal A.; Gupta N.; Chauhan N; Alam S


    Aqueous polymer dispersions (APD) are preferred on environmental and safety grounds. APD offer several advantages over polymers dissolved in organic solvents including lower spraying viscosities, higher solids loading, higher spray rates, no solvent environmental, toxicity, or flammability issues, and reduced energy requirements. The purpose of this work is to prepare and characterize an aqueous-based pseudolatex dispersion of Eudragit L100-55 using emulsification technology wi...

  14. An Underwater Superoleophobic Sepiolite Fibrous Membrane (SFM) for Oil­‐in­‐water Emulsion Separation

    KAUST Repository

    Yao, Pinjiang


    Separating oil/water emulsions is significant for the ecosystem and the petroleum and processing industry. To this end, we prepared an underwater superoleophobic membrane inspired by unique wettability of the fish scales. This membrane was fabricated by a facile vacuum filtration process of sepiolite nanofibers and chitosan, and after the cross-linking via glutaraldehyde, a self-standing membrane was obtained. The as-prepared membrane exhibited excellent capability of separating both the surfactant-free and surfactant-stabilized oil-in-water emulsions with high efficiency. This sepiolite fibrous membrane offers a convenient, reliable and efficient way for the large-scale de-emulsification process.

  15. A study on emulsification of silicon oil by the use of surfactant

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Kwang-Eun; Kim, Young-Hun; Shin, Dong-Cheul; Lee, Sun-Gi; Kim, Kyung-Won; Shin, Sun-Myung; Kang, Hyun-Chan [Dong-A University, Pusan (Korea)


    This study aims to make emulsification of silicone oil by the use of several glycolic nonionic surfactants. Emulsified state of silicone oil was examined through changing conditions of HLB 10, 11, 12, 13, 14, 15, 16, 17 and changing agitating speed and agitating time. The most stable emulsified state of silicone oil was obtained under the conditions of HLB 11, agitating speed 16000 rpm, and agitating time 30 minutes. The surfactant addition ratio to the silicone oil was 5%, 10%, 15%, 20%, 25%, 30% and among the emulsified silicone oils, the most stable state of emulsified silicone oil was obtained at surfactant addition ratio to the silicone oil 25% and it was not separated over 120 minutes. Moreover, it could be known through microscope observation that the stability of emulsified silicone oil increased as the particle size of emulsified silicone oil becomes fine. When the surfactant addition ratio to the silicone oil was 25%, the most stable state as well as the finest size of emulsified silicone oil was obtained. (author). 14 refs., 2 tabs., 10 figs.

  16. Improving emulsification efficacy of lecithin by formulation design. I: Effect of adding a secondary surfactant. (United States)

    Krishna, G; Wood, G C; Sheth, B B


    The objective of this study was to seek improvement in the emulsification efficacy of lecithin by formulation design. A Base Emulsion was developed containing lecithin as the primary emulsifier. The lecithin concentration and method of preparation of the Base Emulsion were optimized to obtain minimum particle size and creaming of the emulsion. Selected hydrophilic and hydrophobic synthetic surfactants were evaluated as secondary emulsifiers for their ability to reduce particle size of the Base Emulsion. The selection of type and concentration of the secondary emulsifier was done by application of the HLB method. The hydrophilic emulsifiers selected were Tween 80, Tween 20, Pluronic F68, and Pluronic F127. The hydrophobic surfactants studied included Span 20, Span 80, Pluronic P103, and Pluronic P123. The median droplet size of the Base Emulsion was 2.7 microns. Addition of the hydrophilic emulsifiers caused an increase in particle size and substantial creaming of the emulsions. Addition of three of four hydrophobic surfactants resulted in particle size reduction, but the emulsions showed substantial creaming. Span 20 was found to be the most effective secondary emulsifier. The median particle size of the emulsion was 1.7 microns. These results suggest that supplementing the hydrophilic attributes of lecithin with an appropriate type and amount of hydrophobic surfactant improves the emulsion properties by applying principles of formulation design.

  17. Effect of emulsification and spray-drying microencapsulation on the antilisterial activity of transcinnamaldehyde. (United States)

    Trinh, Nga-Thi-Thanh; Lejmi, Raja; Gharsallaoui, Adem; Dumas, Emilie; Degraeve, Pascal; Thanh, Mai Le; Oulahal, Nadia


    Spray-dried redispersible transcinnamaldehyde (TC)-in-water emulsions were prepared in order to preserve its antibacterial activity; 5% (w/w) TC emulsions were first obtained with a rotor-stator homogeniser in the presence of either soybean lecithin or sodium caseinate as emulsifiers. These emulsions were mixed with a 30% (w/w) maltodextrin solution before feeding a spray-dryer. The antibacterial activity of TC alone, TC emulsions with and without maltodextrin before and after spray-drying were assayed by monitoring the growth at 30 °C of Listeria innocua in their presence and in their absence (control). Whatever the emulsifier used, antilisterial activity of TC was increased following its emulsification. However, reconstituted spray-dried emulsions stabilised by sodium caseinate had a higher antibacterial activity suggesting that they better resisted to spray-drying. This was consistent with observation that microencapsulation efficiencies were 27.6% and 78.7% for emulsions stabilised by lecithin and sodium caseinate, respectively.

  18. Effects of emulsification and microencapsulation on the oxidative stability of camelina and sunflower oils. (United States)

    O'Dwyer, Sandra P; O'Beirne, David; Eidhin, Deirdre Ní; O'Kennedy, Brendan T


    Oil-in-water (O/W) emulsions were prepared using different concentrations of camelina or sunflower oil. Sodium caseinate was used as the emulsifier and dried glucose syrup as the wall material. Emulsions were subsequently spray dried to yield high-fat powders (71.7-85.0%). Emulsification and microencapsulation of bulk oils decreased their level of lipid oxidation (lipid hydroperoxide and p-Anisidine values, p-Avs). Sunflower oil, O/W emulsions and reconstituted powders generally had lower oxidation products than corresponding camelina oil-based products throughout storage at 15°C. p-Avs of bulk oils remained constant, whereas p-Avs of O/W emulsions and reconstituted powders decreased early in storage, and remained low thereafter. Microencapsulated omega (ω)-3 rich powders were produced, easily reconstituted and showed no signs of deterioration throughout storage. These powders provided functional properties with potential for incorporation into various food systems as a source of beneficial ω-3 fatty acids.

  19. Lambda-Cyhalothrin Nanosuspension Prepared by the Melt Emulsification-High Pressure Homogenization Method

    Directory of Open Access Journals (Sweden)

    Zhenzhong Pan


    Full Text Available The nanosuspension of 5% lambda-cyhalothrin with 0.2% surfactants was prepared by the melt emulsification-high pressure homogenization method. The surfactants composition, content, and homogenization process were optimized. The anionic surfactant (1-dodecanesulfonic acid sodium salt and polymeric surfactant (maleic rosin-polyoxypropylene-polyoxyethylene ether sulfonate screened from 12 types of commercially common-used surfactants were used to prepare lambda-cyhalothrin nanosuspension with high dispersity and stability. The mean particle size and polydispersity index of the nanosuspension were 16.01 ± 0.11 nm and 0.266 ± 0.002, respectively. The high zeta potential value of −41.7 ± 1.3 mV and stable crystalline state of the nanoparticles indicated the excellent physical and chemical stability. The method could be widely used for preparing nanosuspension of various pesticides with melting points below boiling point of water. This formulation may avoid the use of organic solvents and reduce surfactants and is perspective for improving bioavailability and reducing residual pollution of pesticide in agricultural products and environment.

  20. CO2-Controllable Foaming and Emulsification Properties of the Stearic Acid Soap Systems. (United States)

    Xu, Wenlong; Gu, Hongyao; Zhu, Xionglu; Zhong, Yingping; Jiang, Liwen; Xu, Mengxin; Song, Aixin; Hao, Jingcheng


    Fatty acids, as a typical example of stearic acid, are a kind of cheap surfactant and have important applications. The challenging problem of industrial applications is their solubility. Herein, three organic amines-ethanolamine (EA), diethanolamine (DEA), and triethanolamine (TEA)-were used as counterions to increase the solubility of stearic acid, and the phase behaviors were investigated systematically. The phase diagrams were delineated at 25 and 50 °C, respectively. The phase-transition temperature was measured by differential scanning calorimetry (DSC) measurements, and the microstructures were vesicles and planar sheets observed by cryogenic transmission electron microscopy (cryo-TEM) observations. The apparent viscosity of the samples was determined by rheological characterizations. The values, rcmc, for the three systems were less than 30 mN·m(-1). Typical samples of bilayers used as foaming agents and emulsifiers were investigated for the foaming and emulsification assays. CO2 was introduced to change the solubility of stearic acid, inducing the transition of their surface activity and further achieving the goal of defoaming and demulsification.

  1. Research on Dispersed Oil Droplets Breakage and Emulsification in the Dynamic Oil and Water Hydrocyclone

    Directory of Open Access Journals (Sweden)

    Guangdong Guo


    Full Text Available Oil and water dynamic hydrocyclone is one type of facilities that separate two phases or multiple phases applied widely in the fields such as food processing, environmental protection, biological pharmacy, petroleum and chemistry. The dispersed oil droplets in the dynamic oil and water hydrocyclone were often broken into small drops by shear force, which decreased the separation efficiency of dynamic oil-water hydrocyclone greatly. To avoid the breakage of the oil droplets, the turbulence field and the velocity field of the dynamic hydrocyclone were studied by the software of Fluent to analyze the main reason that led to breakage of oil droplets. Results indicated that the deformation of oil droplets was caused by the viscous shear force; the breakage of oil droplets was caused by the Reynolds shear stress and the local pressure fluctuations. The main area that the drops were prone to breakup of the dynamic hydrocyclone is that the rotating grating nearby, the wall boundary layer of the drum and center axis of the drum. Finally, the breakage of oil droplets and emulsification of oil and water in the dynamic hydrocyclone were verified by the experiments.

  2. Computational Fluid Dynamics (CFD-Based Droplet Size Estimates in Emulsification Equipment

    Directory of Open Access Journals (Sweden)

    Jo Janssen


    Full Text Available While academic literature shows steady progress in combining multi-phase computational fluid dynamics (CFD and population balance modelling (PBM of emulsification processes, the computational burden of this approach is still too large for routine use in industry. The challenge, thus, is to link a sufficiently detailed flow analysis to the droplet behavior in a way that is both physically relevant and computationally manageable. In this research article we propose the use of single-phase CFD to map out the local maximum stable droplet diameter within a given device, based on well-known academic droplet break-up studies in quasi-steady 2D linear flows. The results of the latter are represented by analytical correlations for the critical capillary number, which are valid across a wide viscosity ratio range. Additionally, we suggest a parameter to assess how good the assumption of quasi-steady 2D flow is locally. The approach is demonstrated for a common lab-scale rotor-stator device (Ultra-Turrax, IKA-Werke GmbH, Staufen, Germany. It is found to provide useful insights with minimal additional user coding and little increase in computational effort compared to the single-phase CFD simulations of the flow field, as such. Some suggestions for further development are briefly discussed.

  3. Preparation of monodisperse aqueous microspheres containing high concentration of l-ascorbic acid by microchannel emulsification. (United States)

    Khalid, Nauman; Kobayashi, Isao; Neves, Marcos A; Uemura, Kunihiko; Nakajima, Mitsutoshi; Nabetani, Hiroshi


    Monodisperse aqueous microspheres containing high concentrations of l-ascorbic acid with different concentrations of sodium alginate (Na-ALG) and magnesium sulfate (MgSO4) were prepared by using microchannel emulsification (MCE). The continuous phase was water-saturated decane containing a 5% (w/w) hydrophobic emulsifier. The flow rate of the continuous phase was maintained at 10 mL h(-1), whereas the pressure applied to the disperse phase was varied between 3 and 25 kPa. The disperse phase optimized for successfully generating aqueous microspheres included 2% (w/w) Na-ALG and 1% (w/w) MgSO4. At a higher MgSO4 concentration, the generated microspheres resulted in coalescence and subsequent bursting. At a lower MgSO4 concentration, unstable and polydisperse microspheres were obtained. The aqueous microspheres generated from the MCs under optimized conditions had a mean particle diameter (dav) of 14-16 µm and a coefficient of variation (CV) of less than 8% at the disperse phase pressures of 5-15 kPa.

  4. Effect of added surfactant on interfacial tension and spontaneous emulsification in alkali/acidic oil systems

    Energy Technology Data Exchange (ETDEWEB)

    Rudin, J.; Bernard, C.; Wasan, D.T. (Illinois Inst. of Tech., Chicago, IL (United States). Dept. of Chemical Engineering)


    An experimental investigation of the buffered surfactant-enhanced alkaline flooding system chemistry was undertaken to determine the influence of various species present on interfacial tension as a function of pH and ionic strength. Phase behavior tests that monitor the extent of emulsification are sufficient to determine the region of low interfacial tension. Optimization of interfacial tension by adjustment of the ionic strength alone may not necessarily provide the lowest interfacial tension under the best conditions. The pH should be simultaneously optimized along with ionic strength to allow better control over attainment of low interfacial tension. The dominant mechanism by which added surfactant aids in the reduction of interfacial tension is the formation of mixed micelles with the ionized acid. Although added surfactant partitioning from the influence of the un-ionized acid and ionic strength will affect interfacial behavior, the formation of mixed micelles plays a dominant role. Middle-phase formation is possible with a low acid oil using a petroleum sulfonate at a proper pH and ionic strength.

  5. Acceleration of disproportionation of aromatic alcohols through self-emulsification of reactants in water. (United States)

    Zhang, Binbin; Song, Jinliang; Liu, Huizhen; Han, Buxing; Jiang, Tao; Fan, Honglei; Zhang, Zhaofu; Wu, Tianbin


    Exploration of new and effective routes to conduct organic reactions in water using the special properties of water/organics is of great importance. In this work, we performed the disproportionation of various aromatic alcohols in water and in different organic solvents. It was demonstrated that the disproportionation reactions of the alcohols were accelerated more effectively in water than organic-solvent-based or solvent-free reactions. A series of control experiments were conducted to study the mechanism of the accelerated reaction rate in water. It was shown that the reactants could emulsify the reactant/water systems at the reaction conditions owing to their amphiphilic nature. The regularly orientated reactant molecules at the water/reactant droplet interface improved the contact probability of the reactive groups and the Pd nanocatalysts, which is one of the main reasons for the enhanced reaction rate in water. Controlling the self-emulsification of amphiphilic reactant/water systems has great application potential for optimizing the rate and/or selectivity of many organic reactions.

  6. Phaco-emulsification in completely vitrectomized eyes: Intraoperative analysis of modified phaco sleeve

    Directory of Open Access Journals (Sweden)

    Rajesh S Joshi


    Full Text Available Purpose: The purpose was to evaluate the results of modified sleeve in phacoemulsification of cataract in completely vitrectomised eyes, Materials and Methods: Twenty-five previously completely vitrectomized eyes of 23 patients having visually significant cataract were included. After through evaluation they underwent phaco-emulsification by phaco chop with a modified sleeve via temporal clear corneal incision. The modified sleeve was made by creating a small round port of approximate 1 × 1 mm size at the proximate end of the sleeve in line with the already existing ports. This port faced the posterior capsule while performing phacoemulsification. Patients were observed for any intraoperative complications. Result: The most common indication for pars plana vitrectomy in our study group was vitreous hemorrhage due to diabetic retinopathy [13 out of 25 eyes (52%]. Intraoperative findings included miosis [seen in 3 (12% eyes] and posterior capsular plaque [seen in 2(8% eyes]. No other significant intraoperative complications (posterior capsular tear, dropped nucleus were observed. Average effective phaco time was 33 sec. (±15.11. Conclusion: Though cataract surgery in postvitrectomized eyes is a challenging situation, modified sleeve prevents anterior chamber fluctuation and avoids complications arising out of it, making the surgery safe.

  7. Dissolved carbon dioxide flotation: an effective way for phase separation in emulsification microextraction method. (United States)

    Molaei, Saeideh; Saleh, Abolfazl; Ghoulipour, Vanik; Seidi, Shahram


    Dissolved carbon dioxide flotation after emulsification microextraction (DCF-EME) technique coupled with gas chromatography-electron capture detection (GC-ECD) was introduced for preconcentration and determination of six organochlorine pesticides (OCPs) in seawater samples. DCF-EME method is based on the rapid and simple phase separation of low density organic solvent from the aqueous phase via introducing of a saturated NaHCO3 solution (9.6% w/v) into the acidified sample solution (0.1M of HCl) containing analytes. Thanks to the in situ generation of carbon dioxide (CO2) bobbles intensified by ultrasound radiation, the dispersed extraction solvent was collected to the surface of the aqueous sample and then was narrowed to the capillary part of a special home-made extraction cell for facile retrieving. Under the optimal conditions, the limits of detection were at the range of 2.6-9.2 ng L(-1) and preconcentration factors were varied between 271 and 307 for different OCPs. The applicability of the developed method was evaluated by the extraction and determination of the target analytes from Caspian seawater samples.

  8. Development of a nutraceutical nano-delivery system through emulsification/internal gelation of alginate. (United States)

    Mokhtari, Samira; Jafari, Seid Mahdi; Assadpour, Elham


    Alginate nano/microspheres are produced by emulsification/internal gelation of sodium alginate dispersed within vegetable oils containing surfactant, followed by CaCl2 addition resulting in hardened particles. In this work, the impact was evaluated of alginate, CaCl2, oil and surfactant content on the size and encapsulation efficiency of nanocarriers containing peppermint phenolic extract and prepared by a low energy internal gelation technique. The results revealed that size of nanoparticles decreased at higher oil and surfactant contents, higher molarity of CaCl2 and lower alginate concentrations. Also, it was found that the encapsulation efficiency was inversely proportional to the size of nanoparticles, and the impact of alginate concentration and surfactant content was markedly higher than the other two factors. The composition of 0.5% alginate, 400ml oil, 0.05M CaCl2 and 100ml surfactant was recognized as the optimized treatment with a reasonable encapsulation efficiency of 5.6% and a nanoparticle size of 785nm. Copyright © 2017 Elsevier Ltd. All rights reserved.

  9. A simulation of a bluff-body stabilized turbulent premixed flame using LES-PDF (United States)

    Kim, Jeonglae; Pope, Stephen


    A turbulent premixed flame stabilized by a triangular cylinder as a flame-holder is simulated. The computational condition matches the Volvo experiments (Sjunnesson et al. 1992). Propane is premixed at a fuel lean condition of ϕ = 0 . 65 . For this reactive simulation, LES-PDF formulation is used, similar to Yang et al. (2012). The evolution of Lagrangian particles is simulated by solving stochastic differential equations modeling transport of the composition PDF. Mixing is modeled by the modified IEM model (Viswanathan et al. 2011). Chemical reactions are calculated by ISAT and for the good load balancing, PURAN distribution of ISAT tables is applied (Hiremath et al. 2012). To calculate resolved density, the two-way coupling (Popov & Pope 2013) is applied, solving a transport equation of resolved specific volume to reduce statistical noise. A baseline calculation shows a good agreement with the experimental measurements in turbulence statistics, temperature, and minor species mass fractions. Chemical reaction does not significantly contribute to the overall computational cost, in contrast to non-premixed flame simulations (Hiremath et al. 2013), presumably due to the restricted manifold of the purely premixed flame in the composition space.

  10. Influence of particle size on hardening and handling of a premixed calcium phosphate cement. (United States)

    Aberg, Jonas; Engstrand, Johanna; Engqvist, Håkan


    Premixed calcium phosphate cements (pCPC) have been developed to circumvent problems related to mixing and transfer of cements in the operating room. In addition, by using pCPC the short working times generally associated with conventional water-mixed cements are avoided. In this work, the influence of particle size on handling and hardening characteristics of a premixed monetite cement has been assessed. The cements were evaluated with respect to their injectability, setting time and compressive strength. It was found that cements with smaller particle sizes were more difficult to inject and had higher compressive strength. Regarding setting time, no clear trend could be discerned. The addition of granules made the cements easier to inject, but setting time was prolonged and lower strengths were obtained. The main findings of this work demonstrate that particle size can be used to control handling and physical properties of premixed cements and that previous knowledge from water-based CPC, regarding effects of particle size, is not directly applicable to premixed CPC.

  11. Acute toxicity study of Vilocym Premix (herbal growth promoter for Livestockin Wistar Albino Rat

    Directory of Open Access Journals (Sweden)

    A.H. Ahmad


    Full Text Available An experimental study with the objective of safety evaluation of Vilocym Premix, herbal growth promoter for Livestock (supplied by Ayurvet Ltd., Baddi, India, was done as per standard guidelines of OECD-423 for acute toxicity testing. Vilocym Premix is a scientifically developed combination of herbs that contains herbal ingredients namely Azadirachta indica, Curcuma longa & many more alongwith natural zeolites. The study was done in 3 males and 3 female Wistar Albino rats, which were administered an initial dose of 50 mg/kg body weight followed by dose rates of 300, 500 & 5000 mg/kg body weight of test compound. The animals were observed for signs of convulsions, tremors, circling, depression, excitement and mortality. Body weight was recorded at 0,7th and 14th day and plasma total protein, albumin; AST and ALT were measured after 3rd day of experiment. No abnormal sign of symptoms were observed in any of the animal fed with Vilocym Premix at the dose rate of 50, 300, 500 & 5000 mg/kg. No mortality was observed indicating safety of herbal premix. [Vet. World 2009; 2(3.000: 100-102

  12. Numerical and experimental investigation of NO{sub x} formation in lean premixed combustion of methane

    Energy Technology Data Exchange (ETDEWEB)

    Bengtsson, K.; Benz, P.; Marti, T.; Schaeren, R.; Schlegel, A. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)


    A high pressure jet-stirred reactor has been built and employed to investigate NO{sub x} formation in lean premixed combustion of methane/air. Experimental results are compared with numerical predictions using the model of a perfectly stirred reactor and elementary reaction mechanisms. Four reaction mechanisms are considered with respect to NO{sub x} formation. (author) 3 figs., 6 refs.

  13. Turbulent combustion modelling of a confined premixed jet flame including heat loss effects using tabulated chemistry

    NARCIS (Netherlands)

    Gövert, S.; Mira, D.; Kok, J.B.W.; Vázquez, M.; Houzeaux, G.


    The present work addresses the coupling of a flamelet database, to a low-Mach approximation of the Navier–Stokes equations using scalar controlling variables. The model is characterized by the chemistry tabulation based on laminar premixed flamelets in combination with an optimal choice of the react

  14. Autoignition and flame stabilisation processes in turbulent non-premixed hot coflow flames

    NARCIS (Netherlands)

    Oldenhof , E.


    This dissertation examines stabilisation processes in turbulent non-premixed jet flames, created by injecting gaseous fuel into a co-flowing stream of hot, low-oxygen combustion products. Being able to predict whether and how a flame achieves stable and reliable combustion is a matter of great pract

  15. Transient combustion modeling of an oscillating lean premixed methane/air flam

    NARCIS (Netherlands)

    Withag, J.A.M.; Kok, Jacobus B.W.; Syed, Khawar


    The main objective of the present study is to demonstrate accurate low frequency transient turbulent combustion modeling. For accurate flame dynamics some improvements were made to the standard TFC combustion model for lean premixed combustion. With use of a 1D laminar flamelet code, predictions

  16. A non-adiabatic flamelet progress–variable approach for LES of turbulent premixed flames

    NARCIS (Netherlands)

    Cecere, Donato; Giacomazzi, Eugenio; Picchia, Franca R.; Arcidiacono, Nunzio; Donato, Filippo; Verzicco, Roberto


    A progress variable/flame surface density/probability density function method has been employed for a Large Eddy Simulation of a CH4/Air turbulent premixed bluff body flame. In particular, both mean and variance of the progress variable are transported and subgrid spatially filtered gradient contrib

  17. Experimental Investigation of Turbulence-Chemistry Interaction in High-Reynolds-Number Turbulent Partially Premixed Flames (United States)


    AFRL-AFOSR-VA-TR-2016-0277 Experimental Investigation of Turbulence- Chemistry Interaction in High-Reynolds-Number Turbulent Partially Premixed...4. TITLE AND SUBTITLE [U] Experimental investigation of turbulence- chemistry interaction in high-Reynolds-number 5a. CONTRACT NUMBER turbulent...flames. Mixture fraction is an important variable in understanding and modeling turbulent mixing and turbulence- chemistry interaction, two key

  18. Preparation of ZnO-Al2O3 Particles in a Premixed Flame

    DEFF Research Database (Denmark)

    Jensen, Joakim Reimer; Johannessen, Tue; Wedel, Stig


    Zinc oxide (ZnO) and alumina (Al2O3) particles are synthesized by the combustion of their volatilized acetylacetonate precursors in a premixed air-methane flame reactor. The particles are characterized by XRD, transmission electron microscopy, scanning mobility particle sizing and by measurement ...

  19. Rare earth metals appliance for magnetic admixtures recovery from mineral premixes

    Directory of Open Access Journals (Sweden)

    A. A. Shevtsov


    Full Text Available The analysis of the material composition metallomagnetic admixtures of mineral premix. It is shown that the dressed metallomagnetic impurity includes low-magnetic particles with low magnetic susceptibility. Removing these particles from the product stream in process of magnetic separation using high-energy rare earth magnets is a challenging task.

  20. The flow field structure of highly stabilized partially premixed flames in a concentric flow conical nozzle burner with coflow

    KAUST Repository

    Elbaz, Ayman M.


    The stability limits, the stabilization mechanism, and the flow field structure of highly stabilized partially premixed methane flames in a concentric flow conical nozzle burner with air co-flow have been investigated and presented in this work. The stability map of partial premixed flames illustrates that the flames are stable between two extinction limits. A low extinction limit when partial premixed flames approach non-premixed flame conditions, and a high extinction limit, with the partial premixed flames approach fully premixed flame conditions. These two limits showed that the most stable flame conditions are achieved at a certain degree of partial premixed. The stability is improved by adding air co-flow. As the air co-flow velocity increases the most stable flames are those that approach fully premixed. The turbulent flow field of three flames at 0, 5, 10 m/s co-flow velocity are investigated using Stereo Particle Image Velocimetry (SPIV) in order to explore the improvement of the flame stability due to the use of air co-flow. The three flames are all at a jet equivalence ratio (Φj) of 2, fixed level of partial premixing and jet Reynolds number (Rej) of 10,000. The use of co-flow results in the formation of two vortices at the cone exit. These vortices act like stabilization anchors for the flames to the nozzle tip. With these vortices in the flow field, the reaction zone shifts toward the reduced turbulence intensity at the nozzle rim of the cone. Interesting information about the structure of the flow field with and without co-flow are identified and reported in this work.

  1. Subfilter Scale Combustion Modelling for Large Eddy Simulation of Turbulent Premixed Flames (United States)

    Shahbazian, Nasim

    Large eddy simulation (LES) is a powerful computational tool for modelling turbulent combustion processes. However, for reactive flows, LES is still under significant development. In particular, for turbulent premixed flames, a considerable complication of LES is that the flame thickness is generally much smaller than the LES filter width such that the flame front and chemical reactions cannot be resolved on the grid. Accurate and robust subfilter-scale (SFS) models of the unresolved turbulence-chemistry interactions are therefore required and studies are needed to evaluate and improve them. In this thesis, a detailed comparison and evaluation of five different SFS models for turbulence- chemistry interactions in LES of premixed flames is presented. These approaches include both flamelet- and non-flamelet-based models, coupled with simple or tabulated chemistry. The mod- elling approaches considered herein are: algebraic- and transport-equation variants of the flame surface density (FSD) model, the presumed conditional moment (PCM) with flame prolongation of intrinsic low-dimensional manifold (FPI) tabulated chemistry, or PCM-FPI approach, evaluated with two different presumed probability density function (PDF) models; and conditional source-term estimation (CSE) approach. The predicted LES solutions are compared to the existing laboratory-scale experimental observation of Bunsen-type turbulent premixed methane-air flames, corresponding to lean and stoichiometric conditions lying from the upper limit of the flamelet regime to well within the thin reaction zones regime of the standard regimes diagram. Direct comparison of different SFS approaches allows investigation of stability and performance of the models, while the weaknesses and strengths of each approach are identified. Evaluation of algebraic and transported FSD models highlights the importance of non-equilibrium transport in turbulent premixed flames. The effect of the PDF type for the reaction progress

  2. The application of near-infrared spectroscopy for the quality control analysis of rocket propellant fuel pre-mixes. (United States)

    Judge, Michael D


    The viability of near-infrared (NIR) spectroscopy as a technique for the quality control analysis of ingredient concentrations in a rocket propellant fuel liquid pre-mix was investigated. The pre-mix analyzed consisted of a polybutadiene pre-polymer, a plasticizer and two antioxidants. It was determined that NIR spectroscopy offered a fast and convenient method of verifying the percentage level of all four ingredients while requiring no sample preparation. The NIR methodology exhibited a high level of accuracy and precision. There was also a clear indication that the technique allowed monitoring of antioxidant depletion in the pre-mix on ageing.

  3. Development of Criteria for Flameholding Tendencies within Premixer Passages for High Hydrogen Content Fuels

    Energy Technology Data Exchange (ETDEWEB)

    Lewis, Elliot Sullivan- [Univ. of California, Irvine, CA (United States); McDonell, Vincent G. [Univ. of California, Irvine, CA (United States)


    Due to increasingly stringent air quality requirements stationary power gas turbines have moved to lean-premixed operation, which reduces pollutant emissions but can result in flashback. Flashback can cause serious damage to the premixer hardware. Curtailing flashback can be difficult with hydrocarbon fuels and becomes even more challenging when hydrogen is used as the fuel. The two main approaches for coping with flashback are either to design a combustor that is resistant to flashback, or to design a premixer that will not anchor a flame if flashback occurs. Even with a well-designed combustor flashback can occur under certain circumstances, thus it is necessary to determine how to avoid flameholding within the premixer passageways of a gas turbine. To this end, an experiment was designed that would determine the flameholding propensities at elevated pressures and temperatures of three different classes of geometric features commonly found in gas turbine premixers, with both natural gas and hydrogen fuel. Experiments to find the equivalence ratio at blow off were conducted within an optically accessible test apparatus with four flameholders: 0.25 and 0.50 inch diameter cylinders, a reverse facing step with a height of 0.25 inches, and a symmetric airfoil with a thickness of 0.25 inches and a chord length of one inch. Tests were carried out at temperatures between 300 K and 750 K, at pressures up to 9 atmospheres. Typical bulk velocities were between 40 and 100 m/s. The effect of airfoil’s angle of rotation was also investigated. Blow off for hydrogen flames was found to occur at much lower adiabatic flame temperatures than natural gas flames. Additionally it was observed that at high pressures and high turbulence intensities, reactant velocity does not have a noticeable effect on the point of blow off due in large part to corresponding increases in turbulent flame speed. Finally a semi empirical correlation was developed that predicts flame extinction for both

  4. Development of Criteria for Flameholding Tendencies within Premixer Passages for High Hydrogen Content Fuels

    Energy Technology Data Exchange (ETDEWEB)

    Lewis, Elliot; McDonell, Vincent


    Due to increasingly stringent air quality requirements stationary power gas turbines have moved to lean-premixed operation, which reduces pollutant emissions but can result in flashback. Flashback can cause serious damage to the premixer hardware. Curtailing flashback can be difficult with hydrocarbon fuels and becomes even more challenging when hydrogen is used as the fuel. The two main approaches for coping with flashback are either to design a combustor that is resistant to flashback, or to design a premixer that will not anchor a flame if flashback occurs. Even with a well-designed combustor flashback can occur under certain circumstances, thus it is necessary to determine how to avoid flameholding within the premixer passageways of a gas turbine. To this end, an experiment was designed that would determine the flameholding propensities at elevated pressures and temperatures of three different classes of geometric features commonly found in gas turbine premixers, with both natural gas and hydrogen fuel. Experiments to find the equivalence ratio at blow off were conducted within an optically accessible test apparatus with four flameholders: 0.25 and 0.50 inch diameter cylinders, a reverse facing step with a height of 0.25 inches, and a symmetric airfoil with a thickness of 0.25 inches and a chord length of one inch. Tests were carried out at temperatures between 300 K and 750 K, at pressures up to 9 atmospheres. Typical bulk velocities were between 40 and 100 m/s. The effect of airfoil’s angle of rotation was also investigated. Blow off for hydrogen flames was found to occur at much lower adiabatic flame temperatures than natural gas flames. Additionally it was observed that at high pressures and high turbulence intensities, reactant velocity does not have a noticeable effect on the point of blow off due in large part to corresponding increases in turbulent flame speed. Finally a semi empirical correlation was developed that predicts flame extinction for both

  5. Production of BCG alginate-PLL microcapsules by emulsification/internal gelation. (United States)

    Esquisabel, A; Hernández, R M; Igartua, M; Gascón, A R; Calvo, B; Pedraz, J L


    A biocompatible emulsification method for microencapsulation of live cells and enzymes within a calcium alginate matrix applied to Bacillus Calmette-Guérin (BCG) has been developed. Small-diameter alginate beads (microcapsules) were formed via internal gelation of an alginate solution emulsified within vegetable oil. Five different oils (sesame, sweet almond, perhydrosqualene, camomile and jojoba) were used. The rheological analysis of the oils showed a Newtonian behaviour, with viscosities = 30.0, 37.7, 51.2, 59.3 and 67.1 mPa.s for perhydrosqualene, jojoba, camomile, sesame and sweet almond oil respectively. The particle size of the microcapsules obtained ranged from 30.3 microns for the microcapsules prepared with sweet almond oil to 57.0 microns for those made with perhydrosqualene. The mean particle diameter obtained was found to be dependent on the viscosity of the oil employed, according to the equation: phi (micron) = 76.6-0.628 eta (mPa.s) (r2 = 0.943). The encapsulated BCG was identified by the Difco TB stain set K, followed by observation under optical microscopy. Freeze-drying of the microcapsules was carried out to ensure their stability during storage. Two batches of microcapsules (those prepared with sesame and jojoba oil) and four types of cryoprotectors (glucose, trehalose, mannitol and sorbitol), at three concentration levels (5, 10 and 20% w/v) were studied. The parameters evaluated were particle size, physical appearance, reconstitution of lyophilizates and microscopical evaluation. For both batches of microcapsules the best results were obtained with trehalose 5%, showing particle sizes of 42.1 microns in the case of the microcapsules prepared with sesame oil, and of 45.3 microns for those prepared with jojoba.

  6. Patients' preferences for positioning during phaco-emulsification under topical-intracameral anaesthesia. (United States)

    Tsatsos, Michael; Chong, Loy; Eke, Tom


    In many eye departments it is routine to ask patients to lie completely flat for cataract surgery. However, many patients prefer not to lie completely flat, if given the choice. It is our practice to ensure patients are in a comfortable position before commencing surgery. We conducted a prospective observational study of our routine practice comprising 125 consecutive cataract operations conducted by a single surgeon with local anaesthesia (occasional phaco under general anaesthetic was not included). All patients were initially positioned lying flat on the reclining chair and were given the option of staying in that position throughout the operation or having the chair-back raised until they were comfortable. Only 27% (34 patients of 125 total) were happy to lie flat (angle between 0 degrees and 5 degrees ). The majority of our patients (62%--78 patients) preferred to sit up slightly, with the chair-back 10 degrees to 25 degrees above the horizontal; 8% (10 patients) of the patients were sited at an angle of 30 degrees to 35 degrees and 2% (three patients) needed to be sited at 35 degrees or more. Patients who sat up above 30 degrees generally had a medical reason such as orthopnoea (3%--four patients), back pain (5%--six patients), anxiety (2%--two patients), Meniere's disease (1%--one patient). Patients who sat up below 25 degrees chose this position for comfort or preference. Our results show that patient preferences for positioning during cataract phaco-emulsification under topical-intracameral anaesthesia should increase overall patient satisfaction without the need to compromise safety.

  7. Effects of buttermilk powders on emulsification properties and acid tolerance of cream. (United States)

    Ihara, Keiichi; Ochi, Hiroshi; Saito, Hitoshi; Iwatsuki, Keiji


    Emulsifying properties and acid tolerance are 2 of the most important characteristics of cream. The effects of the buttermilk component, especially its phospholipids, on the emulsifying properties and acid tolerance of cream were investigated in this study. Two buttermilks with differing phospholipid contents and skimmed milk were used to evaluate the effects of phospholipids on the aforementioned parameters. The mean diameter of fat globules and the cream viscosity were used as indicators of emulsifying properties. Acid tolerance was evaluated by studying the effect of citric acid on the maximum viscosity of cream. This was tested by adding 400 μL of 10% (w/w) citric acid solution to cream every minute and simultaneously measuring pH and viscosity. In 45% and 40% fat cream systems, buttermilk, and especially that with higher phospholipid content, improved the emulsifying properties and acid tolerance of the cream. The components of buttermilk could alter the properties of the surface of fat globules, thereby altering the emulsification properties of the cream. However, neither of the tested buttermilks affected the emulsifying properties and acid tolerance of lower-fat (35% and 30%) cream systems. Emulsifying components exist in proportionately larger amounts in lower-fat creams, which could render the emulsifying properties resistant to change. The number of fat globules may also influence acid-induced changes in viscosity. The addition of phospholipids or lysophospholipids did not improve the acid tolerance of creams, a finding that may be attributable to the formation of complexes of phospholipids and protein. The findings presented herein demonstrate the ability to improve the acid tolerance of cream using materials derived from milk. Implementing these findings appropriately may result in a high-quality cooking cream.

  8. Preparation and characteristics of nanostructured lipid carriers for control-releasing progesterone by melt-emulsification. (United States)

    Yuan, Hong; Wang, Lei-Lei; Du, Yong-Zhong; You, Jian; Hu, Fu-Qiang; Zeng, Su


    Nanostructured lipid carriers (NLC) made from mixtures of solid and spatially incompatible liquid lipids were prepared by melt-emulsification. Their drug loading capacity and releasing properties of progesterone were compared with those of solid lipid nanoparticles (SLN), and the NLC prepared by solvent diffusion method. Monostearin (MS) and stearic acid (SA) were used as solid lipid, whilst the oleic acid (OA) was used as liquid lipid. Properties of carriers such as the particle size and its distribution, drug loading, drug encapsulation efficiency and drug release behavior were investigated. As a result, the drug encapsulation efficiencies were improved by adding the liquid lipid into the solid lipid of nanoparticles. The drug release behavior could be adjusted by the addition of liquid lipid, and the NLC with higher OA content showed the faster rate of drug releasing. NLC had higher efficiency of encapsulation and slower rate of drug release than those of NLC prepared by solvent diffusion method. On the other hand, the NLC with higher drug loading was obtained, though the drug encapsulation efficiency was decreased slightly due to the increase of the amount of drug. The NLC modified with polyethylene glycol (PEG) was also prepared by using polyethylene glycol monostearate (PEG-SA). It was observed that the incorporation of PEG-SA reduced the drug encapsulation efficiency, but increased the rate of drug release. A sample with almost complete drug release in 24h was obtained by modifying with 1.30mol% PEG-SA. It indicated that the modified NLC was a potential drug delivery system for oral administration.

  9. Experimental data regarding the characterization of the flame behavior near lean blowout in a non-premixed liquid fuel burner

    Directory of Open Access Journals (Sweden)

    Maria Grazia De Giorgi


    The data are related to the research article “Image processing for the characterization of flame stability in a non-premixed liquid fuel burner near lean blowout” in Aerospace Science and Technology [1].

  10. Analysis of biosurfactants from industrially-viable Pseudomonas strain isolated from crude oil suggests how rhamnolipids congeners affect on emulsification property and antimicrobial activity

    Directory of Open Access Journals (Sweden)

    Palashpriya eDas


    Full Text Available Rhamnolipid biosurfactants produced mainly by Pseudomonas sp. had been reported to possess a wide range of potential industrial application. These biosurfactants are produced as monorhamnolipid (MRL and di-rhamnolipid (DRL congeners. The present study deals with rhamnolipid biosurfactants produced by three bacterial isolates from crude oil. Biosurfactants produced by one of the strains (named as IMP67 was found to be very efficacious based on its critical micelle concentration (CMC value and hydrocarbon emulsification property. Strikingly, antimicrobial and anti-biofilm potential of this biosurfactant were higher than biosurfactants produced by other two strains. Thin layer chromatography (TLC analysis and rhamnose quantification showed that the rhamnolipids of IMP67 had more MRL congeners than biosurfactants of the other two strains. Emulsification and antimicrobial actions were affected by manual change of MRL and DRL congener proportions. Increase of MRL proportion enhanced emulsification index and antimicrobial property to Gram negative bacteria. This result indicated that the ratio of MRL and DRL affect the emulsification potentials of rhamnolipids, and suggested that high emulsification potentials might enhance rhamnolipids to penetrate the cell wall of Gram negative bacteria. In consistent, rhamnolipids of IMP67 reduced the MIC of some antibiotics against bacteria, suggesting the potential of biosurfactant as antibiotics synergist.

  11. Analysis of biosurfactants from industrially viable Pseudomonas strain isolated from crude oil suggests how rhamnolipids congeners affect emulsification property and antimicrobial activity. (United States)

    Das, Palashpriya; Yang, Xin-Ping; Ma, Luyan Z


    Rhamnolipid biosurfactants produced mainly by Pseudomonas sp. had been reported to possess a wide range of potential industrial application. These biosurfactants are produced as monorhamnolipid (MRL) and di-rhamnolipid (DRL) congeners. The present study deals with rhamnolipid biosurfactants produced by three bacterial isolates from crude oil. Biosurfactants produced by one of the strains (named as IMP67) was found to be very efficacious based on its critical micelle concentration value and hydrocarbon emulsification property. Strikingly, antimicrobial, and anti-biofilm potential of this biosurfactant were higher than biosurfactants produced by other two strains. Thin layer chromatography analysis and rhamnose quantification showed that the rhamnolipids of IMP67 had more MRL congeners than biosurfactants of the other two strains. Emulsification and antimicrobial actions were affected by manual change of MRL and DRL congener proportions. Increase of MRL proportion enhanced emulsification index and antimicrobial property to Gram negative bacteria. This result indicated that the ratio of MRL and DRL affected the emulsification potentials of rhamnolipids, and suggested that high emulsification potentials might enhance rhamnolipids to penetrate the cell wall of Gram negative bacteria. In line with this finding, rhamnolipids of IMP67 also reduced the MIC of some antibiotics against bacteria, suggesting their synergistic role with the antibiotics.

  12. The Effect of Premixed Schedule on the Crystal Formation of Calcium Phosphate Cement-chitosan Composite with Added Tetracycline

    Institute of Scientific and Technical Information of China (English)

    Jing MAO; Yan LIU; Bin ZHOU; Liyun YAO


    In this study, calcium phosphate cements (CPC) were prepared by mixing cement powders of tetracalcium phosphate (TTCP) with a cement liquid of phosphate acid saline solution. Tetracycline (TTC)-CPC, chitosan-CPC and chitosan-TTC-CPC were investigated with different premixed schedule. It was demonstrate that both TTC and chitosan worked on the phase transition and crystal characteristics. TTCP mixed with phosphate acid saline solution had similar features of Fourier transform-infrared spectrometry (FT-IR) no matter it was mixed with chitosan or TTC or both. TTC premixed with cement liquid or powder had significant different features of FT-IR and 876 cm-1seemed to be a special peak for TTC when TTC was premixed with cement liquid. This was also supported by XRD analysis, which showed that TTC premixed with cement liquid improved phase transition of TTCP to OCP. Chitosan, as organic additive, regulates the regular crystal formation and inhibits the phase transition of TTCP to OCP, except when it is mingled with cement liquid premixed with TTC in field scanning electron microscope. It was concluded that the premixed schedule influences the crystal formation and phase transition, which may be associated with its biocompatibility and bioactivities in vivo.

  13. Evaluation of protein structural changes and water mobility in chicken liver paste batters prepared with plant oil substituting pork back-fat combined with pre-emulsification. (United States)

    Xiong, Guoyuan; Han, Minyi; Kang, Zhuangli; Zhao, Yingying; Xu, Xinglian; Zhu, Yingying


    Protein structural changes and water mobility properties in chicken liver paste batters prepared with plant oil (sunflower and canola oil combinations) substituting 0-40% pork back-fat combined with pre-emulsification were studied by Raman spectroscopy and low-field nuclear magnetic resonance (NMR). Results showed that pre-emulsifying back-fat and plant oil, including substituting higher than 20% back-fat with plant oil increased the water- and fat-binding (pproperties, formed more even and fine microstructures, and gradually decreased the NMR relaxation times (T21a, T21b and T22), which was related to the lower fluid losses in chicken liver paste batters. Raman spectroscopy revealed that compared with a control, there was a decrease (poil combined with pre-emulsification. Pre-emulsification and plant oil substitution changed tryptophan and tyrosine doublet hydrophobic residues in chicken liver paste batters.

  14. Optimization of Copper Removal from Aqueous Solutions Using Emulsion Liquid Membranes with Benzoylacetone as a Carrier

    Directory of Open Access Journals (Sweden)

    Loreto León


    Full Text Available The presence of heavy metals in aqueous solutions above certain limits represents a serious threat to the environment due to their toxicity and non-degradability. Thus, the removal of these metals from contaminated waters has received increasing attention during recent decades. This paper describes the removal of Cu(II from aqueous solutions by emulsion liquid membranes, through a carrier-facilitated counter-transport mechanism, using benzoylacetone as the carrier and HCl as the stripping agent (protons as counter-ions. To optimize the Cu(II removal process, the effect of the following operating parameters on the on the stability of the emulsion liquid membrane and on the Cu(II removal efficiency was studied: feed pH, HCl concentration in the permeate phase, carrier and emulsifier concentration in the membrane phase, feed phase/emulsion phase and permeate phase/membrane phase volume ratios, emulsification time and speed in the primary emulsion preparation and stirring speed in the whole feed phase/emulsion phase system. Typical membrane transport parameters, such as flux and permeability, were also determined. Optimal Cu(II removal conditions were: 5.5 feed pH, 10 kg/m3 benzoylacetone concentration in the membrane phase, 18.250 kg/m3 HCl concentration in the permeate phase, 50 kg/m3 Span 80 concentration in the membrane phase, 200 rpm stirring rate, 5 min emulsification time, 2700 rpm emulsification rate, 2:1 feed:emulsion volume ratio and 1:1 permeate:membrane volume ratio. In these optimal conditions, 80.3% of Cu(II was removed in 15 min with an apparent initial flux and permeability of 0.3384 kg·m−3·min−1 and 0.3208 min−1, respectively.

  15. An experimental and kinetic modeling study of premixed nitroethane flames at low pressure

    DEFF Research Database (Denmark)

    Zhang, Kuiwen; Zhang, Lidong; Xie, Mingfeng


    An experimental and kinetic modeling study is reported on three premixed nitroethane/oxygen/argon flames at low pressure (4.655kPa) with the equivalence ratios (Φ) of 1.0, 1.5 and 2.0. Over 30 flame species were identified with tunable synchrotron vacuum ultraviolet photoionization mass spectrome......An experimental and kinetic modeling study is reported on three premixed nitroethane/oxygen/argon flames at low pressure (4.655kPa) with the equivalence ratios (Φ) of 1.0, 1.5 and 2.0. Over 30 flame species were identified with tunable synchrotron vacuum ultraviolet photoionization mass...... predictions have shown satisfactory agreement with the experimental results. Basing on the rate-of-production analysis, the reaction pathways that feature the combustion of nitroethane were revealed, including the primary decomposition of C–N bond fission, the oxidation of C2 and C1 hydrocarbons...

  16. Laminar premixed methane/air flame extinction characteristics influenced by co-flow water mists

    Institute of Scientific and Technical Information of China (English)

    LIU XuanYa; LU ShouXiang; ZHU YingChun; LIU Yi


    Based on the tubular burner, the burning velocities, flame stretch and inhibition rules influenced by co-flow water mists were studied using a high-speed schlieren system. Moreover, the variation rules of the flame critical extinction in our burner equipment were also obtained by analyzing the process and mechanism of flame extinction and inhibition. It is shown that the flame stretch is related to the fuel concentration, co-flow fluxes and water mist diameters. For droplets with a larger diameter, the smaller the co-flow fluxes, the more obvious the flame stretch. When the water mist loading rate is rather smaller, for fuel-rich premixed flame with Le>1, the flame with larger burning rate tends to backfire more easily. Under the same water mist conditions, for fuel-lean premixed flame with Le<1, the smaller the gas concentration, the easier the flame is extinct.

  17. Effects Of Ignition on Premixed Vortex Rings: A Simultaneous PLIF and PIV Investigation (United States)

    Meyer, T. R.; Gord, J. R.; Katta, V. R.; Gogineni, S. P.


    Preliminary studies of reacting, premixed vortex rings have shown that flame propagation is highly sensitive to ignition timing, equivalence ratio, and vortex strength. A variety of divergent phenomena have been observed, such as interior/exterior flame propagation, vortex-induced flame bridging across the jet column, and the formation of unburned pockets. In the current work, planar laser-induced fluorescence (PLIF) of acetone and OH is performed to study the non-reacting and reacting regions, respectively, and particle image velocimetry (PIV) is used to study the effects of reaction on the flow field. The flow field consists of well-characterized vortex rings of premixed methane and air generated at the exit of an axisymmetric nozzle using a solenoid-driven piston. Ignition is initiated at various phases of vortex development and propagation. Results are compared with corresponding numerical simulations from a time-dependent computational fluid dynamics code with chemistry.

  18. Analysis of the flamelet concept in the numerical simulation of laminar partially premixed flames

    Energy Technology Data Exchange (ETDEWEB)

    Consul, R.; Oliva, A.; Perez-Segarra, C.D.; Carbonell, D. [Centre Tecnologic de Transferencia de Calor (CTTC), Universitat Politecnica de Catalunya (UPC), Colom 11, E-08222, Terrassa, Barcelona (Spain); de Goey, L.P.H. [Eindhoven University of Technology, Department of Mechanical Engineering, P.O. Box 513, 5600 MB Eindhoven (Netherlands)


    The aim of this work is to analyze the application of flamelet models based on the mixture fraction variable and its dissipation rate to the numerical simulation of partially premixed flames. Although the main application of these models is the computation of turbulent flames, this work focuses on the performance of flamelet concept in laminar flame simulations removing, in this way, turbulence closure interactions. A well-known coflow methane/air laminar flame is selected. Five levels of premixing are taken into account from an equivalence ratio {phi}={infinity} (nonpremixed) to {phi}=2.464. Results obtained using the flamelet approaches are compared to data obtained from the detailed solution of the complete transport equations using primitive variables. Numerical simulations of a counterflow flame are also presented to support the discussion of the results. Special emphasis is given to the analysis of the scalar dissipation rate modeling. (author)

  19. Development of lean premixed low-swirl burner for low NO{sub x} practical application

    Energy Technology Data Exchange (ETDEWEB)

    Yegian, D.T.; Cheng, R.K.


    Laboratory experiments have been performed to evaluate the performance of a premixed low-swirl burner (LSB) in configurations that simulate commercial heating appliances. Laser diagnostics were used to investigate changes in flame stabilization mechanism, flowfield, and flame stability when the LSB flame was confined within quartz cylinders of various diameters and end constrictions. The LSB adapted well to enclosures without generating flame oscillations and the stabilization mechanism remained unchanged. The feasibility of using the LSB as a low NO{sub x} commercial burner has also been verified in a laboratory test station that simulates the operation of a water heater. It was determined that the LSB can generate NO{sub x} emissions < 10 ppm (at 3% O{sub 2}) without significant effect on the thermal efficiency of the conventional system. The study has demonstrated that the lean premixed LSB has commercial potential for use as a simple economical and versatile burner for many low emission gas appliances.

  20. Recent Advances in Understanding of Thermal Expansion Effects in Premixed Turbulent Flames (United States)

    Sabelnikov, Vladimir A.; Lipatnikov, Andrei N.


    When a premixed flame propagates in a turbulent flow, not only does turbulence affect the burning rate (e.g., by wrinkling the flame and increasing its surface area), but also the heat release in the flame perturbs the pressure field, and these pressure perturbations affect the turbulent flow and scalar transport. For instance, the latter effects manifest themselves in the so-called countergradient turbulent scalar flux, which has been documented in various flames and has challenged the combustion community for approximately 35 years. Over the past decade, substantial progress has been made in investigating (a) the influence of thermal expansion in a premixed flame on the turbulent flow and turbulent scalar transport within the flame brush, as well as (b) the feedback influence of countergradient scalar transport on the turbulent burning rate. The present article reviews recent developments in this field and outlines issues to be solved in future research.

  1. NO{sub x} formation in lean premixed combustion of methane at high pressures

    Energy Technology Data Exchange (ETDEWEB)

    Bengtsson, K.U.M.; Griebel, P.; Schaeren, R. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)


    High pressure experiments in a jet-stirred reactor have been performed to study the NO{sub x} formation in lean premixed combustion of methane/air mixtures. The experimental results are compared with numerical predictions using four well known reaction mechanisms and a model which consists of a series of two perfectly stirred reactors and a plug flow reactor. (author) 2 figs., 7 refs.

  2. Premixed Combustion of Kapok (ceiba pentandra) seed oil on Perforated Burner


    I.K.G. Wirawan; I. N. G. Wardana; Rudy Soenoko; Slamet Wahyudi


    Availability of fossil fuels in the world decrease gradually due to excessive fuel exploitation. This situations push researcher to look for alternative fuels as a source of renewable energy, one of them is kapok (ceiba pentandra) seed oil. The aim this study was to know the behavior of laminar burning velocity, secondary Bunsen flame with open tip, cellular and triple flame. Premixed combustion of kapok seed oil was studied experimentally on perforated burner with equivalence ratio (φ) varie...

  3. Exploring Soot Particle Concentration and Emissivity by Transient Thermocouples Measurements in Laminar Partially Premixed Coflow Flames

    Directory of Open Access Journals (Sweden)

    Gianluigi De Falco


    Full Text Available Soot formation in combustion represents a complex phenomenon that strongly depends on several factors such as pressure, temperature, fuel chemical composition, and the extent of premixing. The effect of partial premixing on soot formation is of relevance also for real combustion devices and still needs to be fully understood. An improved version of the thermophoretic particle densitometry (TPD method has been used in this work with the aim to obtain both quantitative and qualitative information of soot particles generated in a set of laminar partially-premixed coflow flames characterized by different equivalence ratios. To this aim, the transient thermocouple temperature response has been analyzed to infer particle concentration and emissivity. A variety of thermal emissivity values have been measured for flame-formed carbonaceous particles, ranging from 0.4 to 0.5 for the early nucleated soot particles up to the value of 0.95, representing the typical value commonly attributed to mature soot particles, indicating that the correct determination of the thermal emissivity is necessary to accurately evaluate the particle volume fraction. This is particularly true at the early stage of the soot formation, when particle concentration measurement is indeed particularly challenging as in the central region of the diffusion flames. With increasing premixing, an initial increase of particles is detected both in the maximum radial soot volume fraction region and in the central region of the flame, while the further addition of primary air determines the particle volume fraction drop. Finally, a modeling analysis based on a sectional approach has been performed to corroborate the experimental findings.

  4. Quantification of trace metals in infant formula premixes using laser-induced breakdown spectroscopy (United States)

    Cama-Moncunill, Raquel; Casado-Gavalda, Maria P.; Cama-Moncunill, Xavier; Markiewicz-Keszycka, Maria; Dixit, Yash; Cullen, Patrick J.; Sullivan, Carl


    Infant formula is a human milk substitute generally based upon fortified cow milk components. In order to mimic the composition of breast milk, trace elements such as copper, iron and zinc are usually added in a single operation using a premix. The correct addition of premixes must be verified to ensure that the target levels in infant formulae are achieved. In this study, a laser-induced breakdown spectroscopy (LIBS) system was assessed as a fast validation tool for trace element premixes. LIBS is a promising emission spectroscopic technique for elemental analysis, which offers real-time analyses, little to no sample preparation and ease of use. LIBS was employed for copper and iron determinations of premix samples ranging approximately from 0 to 120 mg/kg Cu/1640 mg/kg Fe. LIBS spectra are affected by several parameters, hindering subsequent quantitative analyses. This work aimed at testing three matrix-matched calibration approaches (simple-linear regression, multi-linear regression and partial least squares regression (PLS)) as means for precision and accuracy enhancement of LIBS quantitative analysis. All calibration models were first developed using a training set and then validated with an independent test set. PLS yielded the best results. For instance, the PLS model for copper provided a coefficient of determination (R2) of 0.995 and a root mean square error of prediction (RMSEP) of 14 mg/kg. Furthermore, LIBS was employed to penetrate through the samples by repetitively measuring the same spot. Consequently, LIBS spectra can be obtained as a function of sample layers. This information was used to explore whether measuring deeper into the sample could reduce possible surface-contaminant effects and provide better quantifications.

  5. Simulations and experiments on the ignition probability in turbulent premixed bluff-body flames (United States)

    Sitte, Michael Philip; Bach, Ellen; Kariuki, James; Bauer, Hans-Jörg; Mastorakos, Epaminondas


    The ignition characteristics of a premixed bluff-body burner under lean conditions were investigated experimentally and numerically with a physical model focusing on ignition probability. Visualisation of the flame with a 5 kHz OH* chemiluminescence camera confirmed that successful ignitions were those associated with the movement of the kernel upstream, consistent with previous work on non-premixed systems. Performing many separate ignition trials at the same spark position and flow conditions resulted in a quantification of the ignition probability Pign, which was found to decrease with increasing distance downstream of the bluff body and a decrease in equivalence ratio. Flows corresponding to flames close to the blow-off limit could not be ignited, although such flames were stable if reached from a richer already ignited condition. A detailed comparison with the local Karlovitz number and the mean velocity showed that regions of high Pign are associated with low Ka and negative bulk velocity (i.e. towards the bluff body), although a direct correlation was not possible. A modelling effort that takes convection and localised flame quenching into account by tracking stochastic virtual flame particles, previously validated for non-premixed and spray ignition, was used to estimate the ignition probability. The applicability of this approach to premixed flows was first evaluated by investigating the model's flame propagation mechanism in a uniform turbulence field, which showed that the model reproduces the bending behaviour of the ST-versus-u‧ curve. Then ignition simulations of the bluff-body burner were carried out. The ignition probability map was computed and it was found that the model reproduces all main trends found in the experimental study.

  6. Low and High Temperature Combustion Chemistry of Butanol Isomers in Premixed Flames and Autoignition Systems

    Energy Technology Data Exchange (ETDEWEB)

    Sarathy, S M; Pitz, W J; Westbrook, C K; Mehl, M; Yasunaga, K; Curran, H J; Tsujimura, T; Osswald, P; Kohse-Hoinghaus, K


    Butanol is a fuel that has been proposed as a bio-derived alternative to conventional petroleum derived fuels. The structural isomer in traditional 'bio-butanol' fuel is n-butanol, but newer conversion technologies produce iso-butanol as a fuel. In order to better understand the combustion chemistry of bio-butanol, this study presents a comprehensive chemical kinetic model for all the four isomers of butanol (e.g., 1-, 2-, iso- and tert-butanol). The proposed model includes detailed high temperature and low temperature reaction pathways. In this study, the primary experimental validation target for the model is premixed flat low-pressure flame species profiles obtained using molecular beam mass spectrometry (MBMS). The model is also validated against previously published data for premixed flame velocity and n-butanol rapid compression machine and shock tube ignition delay. The agreement with these data sets is reasonably good. The dominant reaction pathways at the various pressures and temperatures studied are elucidated. At low temperature conditions, we found that the reaction of alphahydroxybutyl with O{sub 2} was important in controlling the reactivity of the system, and for correctly predicting C{sub 4} aldehyde profiles in low pressure premixed flames. Enol-keto isomerization reactions assisted by HO{sub 2} were also found to be important in converting enols to aldehydes and ketones in the low pressure premixed flames. In the paper, we describe how the structural features of the four different butanol isomers lead to differences in the combustion properties of each isomer.

  7. Microwave and conventional sintering of premixed and prealloyed Cu-12Sn bronze

    Directory of Open Access Journals (Sweden)

    Sethi G.


    Full Text Available The aim of the present investigation is to study the sintering behavior of the Cu-12Sn bronze system in both, a microwave furnace as well as a conventional furnace. The powders prepared by premixed and prealloyed routes were sintered in the range of solid state, transient and supersolidus liquid phase sintering conditions. The comparative analysis is based on the sintered density, densification parameter, hardness, macrostructures and microstructures of the samples.

  8. Numerical simulation of pollutant emission and flame extinction in lean premixed systems (United States)

    Eggenspieler, Gilles

    Premixed and partially-premixed combustion and pollutant emissions in full-scale gas turbines has been numerically investigated using a massively-parallel Large-Eddy Simulation Combustion Dynamics Model. Through the use of a flamelet library approach, it was observed that CO (Carbon Oxide) and NO (Nitric Oxide) emission can be predicted and match experimental results. The prediction of the CO emission trend is shown to be possible if the influence of the formation of UHC (Unburnt HydroCarbons) via flame extinction is taken into account. Simulations were repeated with two different combustion approach: the G-equation model and the Linear-Eddy Mixing (LEM) Model. Results are similar for these two set of numerical simulations. The LEM model was used to simulate flame extinction and flame lift-off in a dump combustion chamber. The LEM model is compared to the G-equation model and it was found that the LEM model is more versatile than the G-equation model with regard to accurate simulation of flame propagation in all turbulent premixed combustion regimes. With the addition of heat losses, flame extinction was observed for low equivalence ratio. Numerical simulation of flame propagation with transient inflow conditions were also carried out and demonstrated the ability of the LEM model to accurately simulate flame propagation in the case of a partially-premixed system. In all simulations where flame extinction and flame lift-off was simulated, release of unburnt fuel in the post-flame region through flame extinction was not observed.

  9. Nonlinear hydrodynamic and thermoacoustic oscillations of a bluff-body stabilised turbulent premixed flame (United States)

    Lee, Chin Yik; Li, Larry Kin Bong; Juniper, Matthew P.; Cant, Robert Stewart


    Turbulent premixed flames often experience thermoacoustic instabilities when the combustion heat release rate is in phase with acoustic pressure fluctuations. Linear methods often assume a priori that oscillations are periodic and occur at a dominant frequency with a fixed amplitude. Such assumptions are not made when using nonlinear analysis. When an oscillation is fully saturated, nonlinear analysis can serve as a useful avenue to reveal flame behaviour far more elaborate than period-one limit cycles, including quasi-periodicity and chaos in hydrodynamically or thermoacoustically self-excited system. In this paper, the behaviour of a bluff-body stabilised turbulent premixed propane/air flame in a model jet-engine afterburner configuration is investigated using computational fluid dynamics. For the frequencies of interest in this investigation, an unsteady Reynolds-averaged Navier-Stokes approach is found to be appropriate. Combustion is represented using a modified laminar flamelet approach with an algebraic closure for the flame surface density. The results are validated by comparison with existing experimental data and with large eddy simulation, and the observed self-excited oscillations in pressure and heat release are studied using methods derived from dynamical systems theory. A systematic analysis is carried out by increasing the equivalence ratio of the reactant stream supplied to the premixed flame. A strong variation in the global flame structure is observed. The flame exhibits a self-excited hydrodynamic oscillation at low equivalence ratios, becomes steady as the equivalence ratio is increased to intermediate values, and again exhibits a self-excited thermoacoustic oscillation at higher equivalence ratios. Rich nonlinear behaviour is observed and the investigation demonstrates that turbulent premixed flames can exhibit complex dynamical behaviour including quasiperiodicity, limit cycles and period-two limit cycles due to the interactions of various

  10. Direct Numerical Simulation of a Cavity-Stabilized Ethylene/Air Premixed Flame (United States)

    Chen, Jacqueline; Konduri, Aditya; Kolla, Hemanth; Rauch, Andreas; Chelliah, Harsha


    Cavity flame holders have been shown to be important for flame stabilization in scramjet combustors. In the present study the stabilization of a lean premixed ethylene/air flame in a rectangular cavity at thermo-chemical conditions relevant to scramjet combustors is simulated using a compressible reacting multi-block direct numerical simulation solver, S3D, incorporating a 22 species ethylene-air reduced chemical model. The fuel is premixed with air to an equivalence ratio of 0.4 and enters the computational domain at Mach numbers between 0.3 and 0.6. An auxiliary inert channel flow simulation is used to provide the turbulent velocity profile at the inlet for the reacting flow simulation. The detailed interaction between intense turbulence, nonequilibrium concentrations of radical species formed in the cavity and mixing with the premixed main stream under density variations due to heat release rate and compressibility effects is quantified. The mechanism for flame stabilization is quantified in terms of relevant non-dimensional parameters, and detailed analysis of the flame and turbulence structure will be presented. We acknowledge the sponsorship of the AFOSR-NSF Joint Effort on Turbulent Combustion Model Assumptions and the DOE Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and Biosciences.

  11. DNS of turbulent premixed slot flames with mixture inhomogeneity: a study of NOx formation (United States)

    Luca, Stefano; Attili, Antonio; Bisetti, Fabrizio


    A set of Direct Numerical Simulations of three-dimensional methane/air lean flames in a spatially developing turbulent slot burner are performed. The flames are in the thin-reaction zone regimes and the jet Reynolds number is 5600. This configuration is of interest since it displays turbulent production by mean shear as in real devices. The gas phase hydrodynamics are modeled with the reactive, unsteady Navier-Stokes equations in the low Mach number limit. Combustion is treated with finite-rate chemistry. The jet is characterized by a non-uniform equivalence ratio at the inlet and varying levels of incomplete premixing for the methane/air mixture are considered. The global equivalence ratio is 0.7 and temperature is 800 K. All simulations are performed at 4 atm. The instantaneous profiles of the mass fractions of methane and air at the inlet are sampled from a set of turbulent channel simulations that provide realistic, fully turbulent fields. The data are analyzed to study the influence of partial premixing on the flame structure. Particular focus is devoted to the assessment of heat release rate fluctuations and NOx formation. In particular, the effects of partial premixing on the production rates for the various pathways to NOx formation are investigated.

  12. Optimization of instant dalia dessert pre-mix production by using response surface methodology. (United States)

    Jha, Alok; Shalini, B N; Patel, Ashok Ambalal; Singh, Mithilesh; Rasane, Prasad


    Dalia, a wheat-based, particulate containing dairy dessert is popularly consumed as a breakfast food and is also considered as a health food. Though popular throughout Northern parts of the country, its limited shelf-life even under refrigeration imposes severe restrictions on its organized manufacture and marketing. In order to promote dalia dessert as a marketable product, in the present study, a process was developed for manufacture of instant dalia pre-mix, as a dry product with long shelf-life, which could be attractively packaged and easily reconstituted for consumption. During the investigation, the effect of different levels of milk solids and wheat solids was studied on dalia pre-mix quality by employing a central composite rotatable design (CCRD). The suggested formulation had 17.82 % milk solids and 2.87 % wheat solids. This formulation was found to be most appropriate for manufacture of instant dalia pre-mix with predicted sensory scores (Max. 100) of 85.35, 41.98 and 67.27 for mouthfeel, consistency and flavor, respectively; the viscosity of the product was 941.0 cp.

  13. Conditional budgets of second-order statistics in nonpremixed and premixed turbulent combustion (United States)

    Macart, Jonathan F.; Grenga, Temistocle; Mueller, Michael E.


    Combustion heat release modifies or introduces a number of new terms to the balance equations for second-order turbulence statistics (turbulent kinetic energy, scalar variance, etc.) compared to incompressible flow. A major modification is a significant increase in viscosity and dissipation in the high-temperature combustion products, but new terms also appear due to density variation and gas expansion (dilatation). Previous scaling analyses have hypothesized that dilatation effects are important in turbulent premixed combustion but are unimportant in turbulent nonpremixed combustion. To explore this hypothesis, a series of DNS calculations have been performed in the low Mach number limit for spatially evolving turbulent planar jet flames of hydrogen and air in both premixed and nonpremixed configurations. Unlike other studies exploring the effects of heat release on turbulence, the turbulence is not forced, and detailed chemical kinetics are used to describe hydrogen-air combustion. Budgets for second-order statistics are computed conditioned on progress variable in the premixed flame and on mixture fraction in the nonpremixed flame in order to locate regions with respect to the flame structure where dilatation effects are strongest.

  14. Combined Influence of Strain and Heat Loss on Turbulent Premixed Flame Stabilization

    KAUST Repository

    Tay-Wo-Chong, Luis


    The present paper argues that the prediction of turbulent premixed flames under non-adiabatic conditions can be improved by considering the combined effects of strain and heat loss on reaction rates. The effect of strain in the presence of heat loss on the consumption speed of laminar premixed flames was quantified by calculations of asymmetric counterflow configurations (“fresh-to-burnt”) with detailed chemistry. Heat losses were introduced by setting the temperature of the incoming stream of products on the “burnt” side to values below those corresponding to adiabatic conditions. The consumption speed decreased in a roughly exponential manner with increasing strain rate, and this tendency became more pronounced in the presence of heat losses. An empirical relation in terms of Markstein number, Karlovitz Number and a non-dimensional heat loss parameter was proposed for the combined influence of strain and heat losses on the consumption speed. Combining this empirical relation with a presumed probability density function for strain in turbulent flows, an attenuation factor that accounts for the effect of strain and heat loss on the reaction rate in turbulent flows was deduced and implemented into a turbulent combustion model. URANS simulations of a premixed swirl burner were carried out and validated against flow field and OH chemiluminescence measurements. Introducing the effects of strain and heat loss into the combustion model, the flame topology observed experimentally was correctly reproduced, with good agreement between experiment and simulation for flow field and flame length.

  15. Influence of polymer addition on the mechanical properties of a premixed calcium phosphate cement. (United States)

    Engstrand, Johanna; Persson, Cecilia; Engqvist, Håkan


    Premixed calcium phosphate cements can reduce handling complications that are associated with the mixing of cements in the operating room. However, to extend the clinical indication of ceramic cements their mechanical properties need to be further improved. The incorporation of a polymeric material with intrinsically high tensile properties could possibly assist in increasing the mechanical properties of calcium phosphate cement. In this study polymer microparticles made from poly(lactid-co-glycolide) plasticised with poly(ethylene glycol) 400 (PLGA/PEG microparticles) were added in amounts of up to 5 wt% to a premixed acidic calcium phosphate cement. The PLGA/PEG microparticles added undergo a shape transformation at 37 °C, which could give a better integration between polymer microparticles and ceramic cement compared with polymer microparticles lacking this property. The results showed that the incorporation of 1.25 wt% PLGA/PEG microparticles increased the compressive strength by approximately 20% up to 15.1 MPa while the diametral tensile strength was kept constant. The incorporation of PLGA/PEG microparticles increased the brushite to monetite ratio after setting compared with pure ceramic cements. In conclusion, small amounts of PLGA/PEG microparticles can be incorporated into premixed acidic calcium phosphate cement and increase their mechanical properties, which could lead to increased future applications.

  16. Influence of polymer addition on the mechanical properties of a premixed calcium phosphate cement (United States)

    Engstrand, Johanna; Persson, Cecilia; Engqvist, Håkan


    Premixed calcium phosphate cements can reduce handling complications that are associated with the mixing of cements in the operating room. However, to extend the clinical indication of ceramic cements their mechanical properties need to be further improved. The incorporation of a polymeric material with intrinsically high tensile properties could possibly assist in increasing the mechanical properties of calcium phosphate cement. In this study polymer microparticles made from poly(lactid-co-glycolide) plasticised with poly(ethylene glycol) 400 (PLGA/PEG microparticles) were added in amounts of up to 5 wt% to a premixed acidic calcium phosphate cement. The PLGA/PEG microparticles added undergo a shape transformation at 37 °C, which could give a better integration between polymer microparticles and ceramic cement compared with polymer microparticles lacking this property. The results showed that the incorporation of 1.25 wt% PLGA/PEG microparticles increased the compressive strength by approximately 20% up to 15.1 MPa while the diametral tensile strength was kept constant. The incorporation of PLGA/PEG microparticles increased the brushite to monetite ratio after setting compared with pure ceramic cements. In conclusion, small amounts of PLGA/PEG microparticles can be incorporated into premixed acidic calcium phosphate cement and increase their mechanical properties, which could lead to increased future applications. PMID:24270588

  17. Understanding premixed flame chemistry of gasoline fuels by comparing quantities of interest

    KAUST Repository

    Selim, Hatem


    Gasoline fuels are complex mixtures that vary in composition depending on crude oil feedstocks and refining processes. Gasoline combustion in high-speed spark ignition engines is governed by flame propagation, so understanding fuel composition effects on premixed flame chemistry is important. In this study, the combustion chemistry of low-pressure, burner-stabilized, premixed flames of two gasoline fuels was investigated under stoichiometric conditions. Flame speciation was conducted using vacuum-ultraviolet synchrotron photoionization time-of-flight molecular beam mass spectroscopy. Stable end-products, intermediate hydrocarbons, and free radicals were detected and quantified. In addition, several isomeric species in the reaction pool were distinguished and quantified with the help of the highly tunable synchrotron radiation. A comparison between the products of both flames is presented and the major differences are highlighted. Premixed flame numerical simulations were conducted using surrogate fuel kinetic models for each flame. Furthermore, a new approach was developed to elucidate the main discrepancies between experimental measurements and the numerical predictions by comparing quantities of interest. © 2016.

  18. Gravitational Influences on Flame Propagation through Non-Uniform, Premixed Gas Systems (United States)

    Miller, Fletcher J.; Easton, John; Ross, Howard D.; Marchese, Anthony; Perry, David; Kulis, Michael


    Flame propagation through non-uniformly premixed (or layered) gases has importance both in useful combustion systems and in unintentional fires. As summarized previously, non-uniform premixed gas combustion receives scant attention compared to the more usual limiting cases of diffusion or uniformly premixed flames, especially regarding the role gravity plays. This paper summarizes our progress on furthering the knowledge of layered combustion, in which a fuel concentration gradient exists normal to the direction of flame spread. We present experimental and numerical results for flame spread through propanol-air layers formed near the flash point temperature (25 C) or near the stoichiometric temperature (33 C). Both the model and experimental results show that the removal of gravity results in a faster spreading flame, by as much as 80% depending on conditions. This is exactly the opposite effect as that predicted by an earlier model reported. We also found that having a gallery lid results in faster flame spread, an effect more pronounced at normal gravity, demonstrating the importance of enclosure geometry. Also reported here is the beginning of our spectroscopic measurements of fuel vapor.

  19. Linear Stability Analysis of Laminar Premixed Fuel-Rich Double-Spray Flames

    Directory of Open Access Journals (Sweden)

    Noam Weinberg


    Full Text Available This paper considers the stability of a double-spray premixed flame formed when both fuel and oxidizer are initially present in the form of sprays of evaporating liquid droplets. To simplify the inherent complexity that characterizes the analytic solution of multi-phase combustion processes, the analysis is restricted to fuel-rich laminar premixed double-spray flames, and assumes a single-step global chemical reaction mechanism. Steady-state solutions are obtained and the sensitivity of the flame temperature and the flame propagating velocity to the initial liquid fuel and/or oxidizer loads are established. The stability analysis revealed an increased proneness to cellular instability induced by the presence of the two sprays, and for the fuel-rich case considered here the influence of the liquid oxidizer was found to be more pronounced than that of the liquid fuel. Similar effects were noted for the neutral pulsating stability boundaries. The impact of unequal latent heats of vaporization is also investigated and found to be in keeping with the destabilizing influence of heat loss due to droplet evaporation. It should be noted that as far as the authors are aware no experimental evidence is available for (at least validation of the predictions. However, they do concur in a general and reasonable fashion with independent experimental evidence in the literature of the behavior of single fuel spray laminar premixed flames.

  20. Bluff-body stabilized flame dynamics of lean premixed syngas combustion (United States)

    Im, Hong G.; Kim, Yu Jeong; Lee, Bok Jik; Kaust Team


    Recently, syngas combustion has been actively investigated for the potential application to integrated gasification combined cycle (IGCC) systems. While lean premixed combustion is attractive for both reduced emission and enhanced efficiency, flame instability becomes often an issue. Bluff-bodies have been adopted as effective flame holders for practical application of premixed flames. In the present study, high-fidelity direct numerical simulations are conducted to investigate the dynamics of lean premixed syngas flames stabilized on a bluff-body, in particular at the near blow-off regime of the flame. A two-dimensional domain of 4 mm height and 20 mm length with a flame holder of a 1 mm-by-1 mm square geometry is used. For a syngas mixture with the equivalence ratio of 0.5 and the CO:H2 ratio of 1, several distinct flame modes are identified as the inflow velocity approaches to the blowoff limit. The sequences of extinction pathway and combustion characteristics are discussed.

  1. Soot Formation in Laminar Premixed Methane/Oxygen Flames at Atmospheric Pressure (United States)

    Xu, F.; Lin, K.-C.; Faeth, G. M.


    Flame structure and soot formation were studied within soot-containing laminar premixed mc1hane/oxygen flames at atmospheric pressure. The following measurements were made: soot volume fractions by laser extinction, soot temperatures by multiline emission, gas temperatures (where soot was absent) by corrected fine-wire thermocouples, soot structure by thermophoretic sampling and transmission electron microscope (TEM), major gas species concentrations by sampling and gas chromatography, and gas velocities by laser velocimetry. Present measurements of gas species concentrations were in reasonably good agreement with earlier measurements due to Ramer et al. as well as predictions based on the detailed mechanisms of Frenklach and co-workers and Leung and Lindstedt: the predictions also suggest that H atom concentrations are in local thermodynamic equilibrium throughout the soot formation region. Using this information, it was found that measured soot surface growth rates could be correlated successfully by predictions based on the hydrogen-abstraction/carbon-addition (HACA) mechanisms of both Frenklach and co-workers and Colket and Hall, extending an earlier assessment of these mechanisms for premixed ethylene/air flames to conditions having larger H/C ratios and acetylene concentrations. Measured primary soot particle nucleation rates were somewhat lower than the earlier observations for laminar premixed ethylene/air flames and were significantly lower than corresponding rates in laminar diffusion flames. for reasons that still must be explained.

  2. Soot Formation in Laminar Premixed Methane/Oxygen Flames at Atmospheric Pressure. Appendix H (United States)

    Xu, F.; Lin, K.-C.; Faeth, G. M.; Urban, D. L. (Technical Monitor); Yuan, Z.-G. (Technical Monitor)


    Flame structure and soot formation were studied within soot-containing laminar premixed methanefoxygen flames at atmospheric pressure. The following measurements were made: soot volume fractions by laser extinction, soot temperatures by multiline emission, gas temperatures (where soot was absent) by corrected fine-wire thermocouples, soot structure by thermophoretic sampling and transmission electron microscope (TEM), major gas species concentrations by sampling and gas chromatography, and gas velocities by laser velocimetry. Present measurements of gas species concentrations were in reasonably good agreement with earlier measurements due to Ramer et al. as well as predictions based on the detailed mechanisms of Frenklach and co-workers and Leung and Lindstedt; the predictions also suggest that H atom concentrations are in local thermodynamic equilibrium throughout the soot formation region. Using this information, it was found that measured soot surface growth rates could be correlated successfully by predictions based on the hydrogenabstraction/carbon-addition (HACA) mechanisms of both Frenklach and co-workers and Colket and Hall, extending an earlier assessment of these mechanisms for premixed ethylene/air flames to conditions having larger H/C ratios and acetylene concentrations. Measured primary soot particle nucleation rates were somewhat lower than the earlier observations for laminar premixed ethylene/air flames and were significantly lower than corresponding rates in laminar diffusion flames, for reasons that still must be explained.

  3. White organic light-emitting diodes with an ultra-thin premixed emitting layer

    CERN Document Server

    Jeon, T; Tondelier, Denis; Bonnassieux, Yvan; Forget, Sebastien; Chenais, Sebastien; Ishow, Elena


    We described an approach to achieve fine color control of fluorescent White Organic Light-Emitting Diodes (OLED), based on an Ultra-thin Premixed emitting Layer (UPL). The UPL consists of a mixture of two dyes (red-emitting 4-di(4'-tert-butylbiphenyl-4-yl)amino-4'-dicyanovinylbenzene or fvin and green-emitting 4-di(4'-tert-butylbiphenyl-4-yl)aminobenzaldehyde or fcho) premixed in a single evaporation cell: since these two molecules have comparable structures and similar melting temperatures, a blend can be evaporated, giving rise to thin films of identical and reproducible composition compared to those of the pre-mixture. The principle of fine color tuning is demonstrated by evaporating a 1-nm-thick layer of this blend within the hole-transport layer (4,4'-bis[N-(1-naphtyl)-N-phenylamino]biphenyl (\\alpha-NPB)) of a standard fluorescent OLED structure. Upon playing on the position of the UPL inside the hole-transport layer, as well as on the premix composition, two independent parameters are available to finel...

  4. The role of reactant unmixedness, strain rate, and length scale on premixed combustor performance

    Energy Technology Data Exchange (ETDEWEB)

    Samuelsen, S.; LaRue, J.; Vilayanur, S. [Univ. of California, Irvine, CA (United States)] [and others


    Lean premixed combustion provides a means to reduce pollutant formation and increase combustion efficiency. However, fuel-air mixing is rarely uniform in space and time. This nonuniformity in concentration will lead to relative increases in pollutant formation and decreases in combustion efficiency. The nonuniformity of the concentration at the exit of the premixer has been defined by Lyons (1981) as the {open_quotes}unmixedness.{close_quotes} Although turbulence properties such as length scales and strain rate are known to effect unmixedness, the exact relationship is unknown. Evaluating this relationship and the effect of unmixedness in premixed combustion on pollutant formation and combustion efficiency are an important part of the overall goal of US Department of Energy`s Advanced Turbine Systems (ATS) program and are among the goals of the program described herein. The information obtained from ATS is intended to help to develop and commercialize gas turbines which have (1) a wide range of operation/stability, (2) a minimal amount of pollutant formation, and (3) high combustion efficiency. Specifically, with regard to pollutants, the goals are to reduce the NO{sub x} emissions by at least 10%, obtain less than 20 PPM of both CO and UHC, and increase the combustion efficiency by 5%.

  5. Novel coupling of surfactant assisted emulsification dispersive liquid-liquid microextraction with spectrophotometric determination for ultra trace nickel (United States)

    Deng, Qingwen; Chen, Meihui; Kong, Lamei; Zhao, Xia; Guo, Jie; Wen, Xiaodong


    In this work, dispersive liquid-liquid microextraction (DLLME) was improved and the preconcentration method named as surfactant assisted emulsification dispersive liquid-liquid microextraction (SAE-DLLME) was established for ultra trace nickel preconcentration and spectrophotometric determination. Non-ionic surfactant Triton X-100 (TX-100) was used as emulsifier and Triton X-114 (TX-114) was investigated as comparison. Disperser solvent was substituted by surfactant, which could afford more effective emulsification and make the extraction relatively greener. The extraction was accomplished efficiently in only 1 min during manual shaking. Compared to traditional DLLME, the developed SAE-DLLME pretreatment was simple, rapid and effective. The improved extraction technique was firstly coupled with traditional spectrophotometer to improve the analytical performance and expand the application of spectrophotometric determination. The influence factors relevant to SAE-DLLME including extraction parameters and instrumental conditions, were studied in detail. Under the optimal conditions, the limit of detection (LOD) for nickel was 0.24 μg L-1, with sensitivity enhancement factor (EF) of 23.

  6. Preparation and characterization of paclitaxel nanosuspension using novel emulsification method by combining high speed homogenizer and high pressure homogenization. (United States)

    Li, Yong; Zhao, Xiuhua; Zu, Yuangang; Zhang, Yin


    The aim of this study was to develop an alternative, more bio-available, better tolerated paclitaxel nanosuspension (PTXNS) for intravenous injection in comparison with commercially available Taxol(®) formulation. In this study, PTXNS was prepared by emulsification method through combination of high speed homogenizer and high pressure homogenization, followed by lyophilization process for intravenous administration. The main production parameters including volume ratio of organic phase in water and organic phase (Vo:Vw+o), concentration of PTX, content of PTX and emulsification time (Et), homogenization pressure (HP) and passes (Ps) for high pressure homogenization were optimized and their effects on mean particle size (MPS) and particle size distribution (PSD) of PTXNS were investigated. The characteristics of PTXNS, such as, surface morphology, physical status of paclitaxel (PTX) in PTXNS, redispersibility of PTXNS in purified water, in vitro dissolution study and bioavailability in vivo were all investigated. The PTXNS obtained under optimum conditions had an MPS of 186.8 nm and a zeta potential (ZP) of -6.87 mV. The PTX content in PTXNS was approximately 3.42%. Moreover, the residual amount of chloroform was lower than the International Conference on Harmonization limit (60 ppm) for solvents. The dissolution study indicated PTXNS had merits including effect to fast at the side of raw PTX and sustained-dissolution character compared with Taxol(®) formulation. Moreover, the bioavailability of PTXNS increased 14.38 and 3.51 times respectively compared with raw PTX and Taxol(®) formulation.

  7. Microchannel emulsification study on formulation and stability characterization of monodisperse oil-in-water emulsions encapsulating quercetin. (United States)

    Khalid, Nauman; Kobayashi, Isao; Neves, Marcos A; Uemura, Kunihiko; Nakajima, Mitsutoshi; Nabetani, Hiroshi


    The study used microchannel emulsification (MCE) to encapsulate quercetin in food grade oil-in-water (O/W) emulsions. A silicon microchannel plate (Model WMS 1-2) comprised of 10,300 discrete 10×104μm microslots was connected to a circular microhole with an inner diameter of 10μm. 1% (w/w) Tween 20 was used as optimized emulsifier in Milli-Q water, while 0.4mgml(-1) quercetin in different oils served as a dispersed phase. The MCE was carried by injecting the dispersed phase at 2mlh(-1). Successful emulsification was conducted below the critical dispersed phase flux, with a Sauter mean diameter of 29μm and relative span factor below 0.25. The O/W emulsions remained stable in terms of droplet coalescence at 4 and 25°C for 30days. The encapsulation efficiency of quercetin in the O/W emulsions was 80% at 4°C and 70% at 25°C during the evaluated storage period.

  8. Preparation and characterization of alginate-gelatin microencapsulated Bacillus subtilis SL-13 by emulsification/internal gelation. (United States)

    Tu, Liang; He, Yanhui; Yang, Hongbing; Wu, Zhansheng; Yi, Lijuan


    Gelatin was blended with sodium alginate (NaALG) to obtain a novel microbial fungicide, and dispersed micron Bacillus subtilis SL-13 microspheres prepared by emulsification/internal gelation method. Microscopic examination revealed that microcapsules were nearly spherical in shape. Fourier transform infrared spectroscopy, differential scanning calorimetry, and X-ray diffraction confirmed that the electrostatic interaction was occurred when gelatin added into NaALG. The maximum encapsulation efficiency was 93.44% at a gelatin concentration of 1.5%. Particle size, swelling, and biodegradation of beads increased with gelatin content increase. Furthermore, the viability of encapsulated SL-13 could be preserved at more than 10(8) CFU/mL after 120 d storage at 25 °C. The number of viable cells released from microcapsules presented an initial rapid increase followed by a gradual increase, and reached the maximum as 10(10) CFU/mL on day 35. Thus, it is feasible to prepare uniform, rounded shape, and well-dispersed micron microcapsules of SL-13 via emulsification/internal gelation using NaALG and gelatin composites. This encapsulation strategy could be considered as a potential alternative to future applications in the agricultural industry.

  9. The effects of maternal dietary vitamin premixes, canthaxanthin, and 25-hydroxycholecalciferol on the performance of progeny ducklings. (United States)

    Ren, Z Z; Wang, J P; Zeng, Q F; Ding, X M; Bai, S P; Luo, Y H; Su, Z W; Xuan, Y; Zhang, K Y


    This trial studied the effects of maternal dietary vitamin premixes, and the mixture of canthaxanthin (CX) and 25-hydroxycholecalciferol (25-OH-D3) on the performance of progeny ducklings. Four maternal diets were used under a 2 × 2 factorial arrangement with 2 kinds of vitamin premixes (Regular and High; High premix had higher levels of all vitamins except K3 than the Regular premix), and with or without the addition of the mixture of CX (6 mg/kg) and 25-OH-D3 (0.069 mg/kg). Cherry Valley duck breeders (38-wk-old) were fed with corn-wheat flour-soybean meal-based diets for 8 wk, and then eggs were collected and hatched. Healthy ducklings (equal number of female and male) from each maternal group were randomly selected and received the same commercial starter (1 to 14 d) and grower (15 to 35 d) pellet diet for 35 d. Maternal High vitamin premix increased shank pigmentation (1 d, P = 0.001), BW (1 d, P growth performance and antioxidant status of ducklings.

  10. A randomised cross-over trial in healthy adults indicating improved absorption of omega-3 fatty acids by pre-emulsification

    Directory of Open Access Journals (Sweden)

    Tang James


    Full Text Available Abstract Background The health benefits of increased intakes of omega-3 fatty acids are well established but palatability often presents a problem. The process of emulsification is used in the food industry to provide a wider spectrum of use, often with the result of increased consumption. Moreover, as emulsification is an important step in the digestion and absorption of fats, the pre-emulsification process may enhance digestion and absorption. In this study the levels of plasma fatty acid and triacylglycerol (TAG following the ingestion of either an oil mixture or an emulsified oil mixture have been compared. Methods In this randomised cross-over study, 13 volunteers received the oil mixture and 11 received the oil emulsion as part of an otherwise fat free meal. Blood samples were collected at 0, 1.5, 3, 4.5, 6, 7.5 and 9 hours after ingestion of oil, separated and stored at -20°C. Plasma triacylglycerols were assessed spectrophotometrically and fatty acids were determined by gas chromatography. Following a washout period of twenty days the procedure was repeated with the assignments reversed. Results The postprandial plasma TAG and the C18:3 (n-6, C18:3(n-3, C20:5(n-3 and C22:6 (n-3 polyunsaturated fatty acid (PUFA levels for the emulsified oil group were increased significantly (P = 0.0182; P = 0.0493; P = 0.0137; P Conclusion Pre-emulsification of an oil mixture prior to ingestion increases the absorption of longer chain more highly unsaturated fatty acids (especially eicosapentaenoic acid and docosahexaenoic acid but does not affect absorption of shorter chain less saturated fatty acids, suggesting that pre-emulsification of fish oils may be a useful means of boosting absorption of these beneficial fatty acids. Trial registration: Current Controlled Trials ISRCTN43202606

  11. Influence of viscosity and uronic acid composition of alginates on the properties of alginate films and microspheres produced by emulsification. (United States)

    Lee, Huey Ying; Chan, Lai Wah; Dolzhenko, Anton V; Heng, Paul Wan Sia


    This study investigated the influence of viscosity and uronic acid composition of alginates on the properties of alginate films and microspheres produced by emulsification. Tensile properties of films were determined while the yield, size, drug contents and release characteristics of the microspheres were examined. Tensile properties of calcium alginate matrix were significantly affected by the orientation and arrangement of the polymer chains. High viscosity alginates gave rise to higher yields and bigger microspheres. Generally, microspheres with high drug content and slower rate of drug release had high Ca2+ contents and were produced from alginates of higher viscosity. Within an alginate microsphere batch, small sized microsphere fractions had higher drug contents but showed faster drug release rates. Microspheres having a defined size range revealed great dependence of encapsulation efficiency and drug release rates on viscosity and extent of Ca2+-alginate interaction. Viscosity appeared to exert a predominant influence on the microsphere properties.


    Institute of Scientific and Technical Information of China (English)


    This paper presents a theory on premix fuel combustion at nearisosceles triangle type rate of heat release,describes the measures taken for the combustion system,points out its many theoretical advantages,and that it can solve effectively the problems of rough running,fuel consumption and exhaust emission.Two squish lip type combustion chambers are designed to match separately with multiple holes injector and conical spray type injector in order to achieve premix combustion at near isosceles triangle type rate of heat release.Experimental studies on two single cylinder diesel engines showed that premix combustion at isosceles triangle type rate of heat release resulted in longer ignition delay period,larger amount of fuel injected into cylinder during the ignition delay period,lower maximum pressure,better fuel economy,and better exhaust emission.

  13. Membrane dynamics

    DEFF Research Database (Denmark)

    Bendix, Pól Martin


    Current topics include membrane-protein interactions with regard to membrane deformation or curvature sensing by BAR domains. Also, we study the dynamics of membrane tubes of both cells and simple model membrane tubes. Finally, we study membrane phase behavior which has important implications...... for the lateral organization of membranes as wells as for physical properties like bending, permeability and elasticity...

  14. Study on the oscillating phenomena of electrical potential across a liquid membrane

    Institute of Scientific and Technical Information of China (English)

    Jin Zhang Gao; Hong Xia Dai; Hua Chen; Jie Ren; Wu Yang


    The electrical oscillations across a liquid membrane in water/oil/water system was studied with octanol as oil phase by introducing two opposite charged surfactants in oil and aqueous phase, respectively. The sustained and rhythmic oscillation was observed. To a certain extent, the features of the oscillation (e.g. induction time, frequency, life time and orientation of the pulse pikes) strongly depend on the property of surfactant, dissolved in octanol. The mechanism may be explained by the formation and destruction of dual-ion surfactant membrane accompanying with emulsification at the interface and considering the coupling effect of diffusion and associated reaction in the vicinity of the interface.

  15. Determination of ionophore coccidiostat salinomycine in premixes and poultry feeding stuffs by liquid chromatography after post-column derivatisation

    Directory of Open Access Journals (Sweden)

    Kostadinović Ljiljana M.


    Full Text Available Coccidiosis is a common parasitic disease of broiler chickens caused by single-celled protozoan parasites of the genus Eimeria which are commonly referred to as coccidian. This is an infective disease of the digestive tract which is most frequent with poultry, causing a decrease in daily increment, prolonged fattening, poorer skin pigmentation, slower feed conversion and increased mortality. The disease is caused by Protozoas from the genera of Eimeria, Isospora and Cryptospora, and it is manifested by damaging the intestine epithelial cells, less frequently the bile duct and renal tubuli. Coccidiosis is traditionally controlled by chemotherapy. There are many anticoccidial preparations which are used in the prevention of coccidiosis. We are chose a polyether monocarboxylic acid - salinomycine. Salinomycin is monovalent carboxyl-polyether ionophores. Salinomycin, produced by Streptomyces albus, destroys the cell membranes and causes their lysis. Salinomycin and other ionophoric antibiotics combine with a number of mono and divalent cations and in the form of bi-complexes make it possible to transfer metal ions through lipid hydrophobic membrane, and when they are added to diet, they change bioavailability, gut uptake and absorption and reserves of nutrient tissues. In this paper has been developed and validated process of Liquid chromatography determination of ionophoric coccidiostat salinomycin with UV spectrophotometric detection and post-column derivatisation with dimethylaminobenzaldehyde (DMAB. The method is based on extraction of salinomycin in animal feed samples using mixture acetonitrile-water (80:20, v/v and purification of extracts obtained by the filter 0,2 μm Acrodisc® PSF. The relative standard deviation (RSD for reproducibility and accuracy varied from 2,4 to 8,8% and from 2,6% to 8,8%, respectively and the values for the relative recovery rate ranged from 89 to 98%. The limit of detection (LOD and limit of quantification (LOQ

  16. Comparison of Performance and Leg Bone Characteristics of Broiler Fed Different Levels of Vitamin Premix in Floor and

    Directory of Open Access Journals (Sweden)

    H. Moravej


    Full Text Available Two experiments were carried out in order to comparison of the effect of different levels of vitamin premix in two raising systems of floor and cage on performance and leg bone characteristics of broiler chickens which were fed with adjusted diet base on wheat and barley during 29 to 42 days. The treatments were composed of 0, 33.33, 66.66 and 100 percent of vitamin premix (according to the recommendation of vitamin premix Producer Company which used from 29 to 42 days. Experiment in floor was carried out by using 288 male broiler chickens (Ross 308 with 4 treatments and 4 replicates in a completely randomized design in floor system. Experiment in cage battery system was carried out by using 80 male broiler chickens with 4 treatments and 4 replicates in raising cage. Feed intake and body weight gain of each replicate were calculated during two weeks of the experiment. During these two weeks, in experiment in floor, two broiler chickens were measured and in experiment in cage battery system one broiler chickens slaughtered and breast, thigh, percentage of abdominal fat and liver were measured. After slaughtered, right leg of each bird was used for determine ash, calcium, phosphorus and strength. The results of the experiment in floor showed that vitamin premix withdrawal at 29 days of age did not impair carcass characteristics and leg bone characteristics during the final rearing period. The results of battery cage system showed that withdrawal of vitamin premix from the diet of experimental birds; were induced negative effect on productive performance, weights of thigh, and breast and leg bone characteristics during 36-42 day of ages. Therefore, it seems that there is the possibility of vitamin premix levels reduction up to the approximate 33% level in finisher period while in the floor system; it is possible to withdraw vitamin supplements in broilers’ finisher diets and in this way the costs of poultry industry will reduce.

  17. Study of low-pressure premixed laminar n-heptane+ propane/oxygen/nitrogen flames

    Institute of Scientific and Technical Information of China (English)

    YU Wu; WEI LiXia; MA ZhiHao; HUANG ZuoHua; YUAN Tao; TIAN ZhenYu; LI YuYang


    Low-pressure premixed laminar n-heptane+propane/oxygen/nitrogen flames were investigated with tunable synchrotron vacuum ultraviolet (VUV) photoionization and molecular-beam sampling mass spectrometry. Three flames with different mass percentage of propane in the fuel blends of 0%, 10%, and 20% were studied. The combustion intermediates were identified by comparing the measured IEs with those values in literatures. Mole fraction profiles of the main species were compared among the three flames. The experimental results provide detailed data in understanding the combustion of n-heptane and n-heptane/propane blends in engine. They are also helpful in establishing and verifying the kinetic models.

  18. An experimental and kinetic modeling study of premixed nitromethane flames at low pressure

    DEFF Research Database (Denmark)

    Zhang, Kuiwen; Li, Yuyang; Yuan, Tao


    An experimental and modeling study is reported on three premixed nitromethane/oxygen/argon flames at low pressure (4.655kPa) with equivalence ratios (ϕ) of 1.0, 1.5 and 2.0. Flame species were identified with tunable synchrotron vacuum ultraviolet photoionization. The mole fraction profiles of more...... against experimental results of all three flames. The computed predictions showed satisfactory agreement with the experimental results. Based on a rate-of-production analysis, reaction pathway diagrams were obtained to describe the hydrocarbon oxidation process and nitrogenous species chemistry...

  19. Flame holding tolerant fuel and air premixer for a gas turbine combustor (United States)

    York, William David; Johnson, Thomas Edward; Ziminsky, Willy Steve


    A fuel nozzle with active cooling is provided. It includes an outer peripheral wall, a nozzle center body concentrically disposed within the outer wall in a fuel and air pre-mixture. The fuel and air pre-mixture includes an air inlet, a fuel inlet and a premixing passage defined between the outer wall in the center body. A gas fuel flow passage is provided. A first cooling passage is included within the center body in a second cooling passage is defined between the center body and the outer wall.

  20. Influence of rarefaction wave on premixed flame structure and propagation behavior

    Institute of Scientific and Technical Information of China (English)

    CHEN Xianfeng; SUN Jinhua; LU Shouxiang; CHU Guanquan; YAO Liyin; LIU Yi


    To explore the influence of rarefaction wave on the structure and propagation behavior of the premixed propane/air flame in a rectangle combustion pipe, the techniques of high speed Schlieren photograph method, pressure measurement and so on are used to study the interaction processes between rarefaction wave and flame. Two cases of rarefaction wave-flame interaction were performed in the experiment. The experimental result shows that both the rarefaction waves can cause the flame transition from laminar to turbulent combustion quickly. The cowflow rarefaction wave decreases the flame speed, while the counterflow rarefaction wave leads the flame propagation speed to increasing on the whole, accompanied with sharp vibration.

  1. Premixing hydrogen burners for surface refinement of glass; Vormischende Wasserstoffbrenner zur Oberflaechenbearbeitung von Glas

    Energy Technology Data Exchange (ETDEWEB)

    Goerisch, Matthias [Linde AG, Linde Gas Deutschland, Nuernberg (Germany)


    As a result, inter alia, of unceasing globalisation, European glass producers in practically all sectors - flat glass, container glass, crystal glass and special glasses - are faced with ever tougher competition from Asia. In the 2012 to 2015 period and beyond, the principal focuses in the manufacture of glass products will again be on reducing overall production costs and increasing process efficiency wherever possible, on greater productivity and on enhanced product (surface) quality. To meet these challenges in the field of surface refinement and flame polishing of glass products as efficiently as possible, Linde AG/Linde Gases Division has developed premixing Hydropox {sup registered} burner technology for hydrogen/oxygen fuels. (orig.)

  2. Understanding and predicting soot generation in turbulent non-premixed jet flames.

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Hai (University of Southern California, Los Angeles, CA); Kook, Sanghoon; Doom, Jeffrey; Oefelein, Joseph Charles; Zhang, Jiayao; Shaddix, Christopher R.; Schefer, Robert W.; Pickett, Lyle M.


    This report documents the results of a project funded by DoD's Strategic Environmental Research and Development Program (SERDP) on the science behind development of predictive models for soot emission from gas turbine engines. Measurements of soot formation were performed in laminar flat premixed flames and turbulent non-premixed jet flames at 1 atm pressure and in turbulent liquid spray flames under representative conditions for takeoff in a gas turbine engine. The laminar flames and open jet flames used both ethylene and a prevaporized JP-8 surrogate fuel composed of n-dodecane and m-xylene. The pressurized turbulent jet flame measurements used the JP-8 surrogate fuel and compared its combustion and sooting characteristics to a world-average JP-8 fuel sample. The pressurized jet flame measurements demonstrated that the surrogate was representative of JP-8, with a somewhat higher tendency to soot formation. The premixed flame measurements revealed that flame temperature has a strong impact on the rate of soot nucleation and particle coagulation, but little sensitivity in the overall trends was found with different fuels. An extensive array of non-intrusive optical and laser-based measurements was performed in turbulent non-premixed jet flames established on specially designed piloted burners. Soot concentration data was collected throughout the flames, together with instantaneous images showing the relationship between soot and the OH radical and soot and PAH. A detailed chemical kinetic mechanism for ethylene combustion, including fuel-rich chemistry and benzene formation steps, was compiled, validated, and reduced. The reduced ethylene mechanism was incorporated into a high-fidelity LES code, together with a moment-based soot model and models for thermal radiation, to evaluate the ability of the chemistry and soot models to predict soot formation in the jet diffusion flame. The LES results highlight the importance of including an optically-thick radiation

  3. Characterization of complexities in combustion instability in a lean premixed gas-turbine model combustor. (United States)

    Gotoda, Hiroshi; Amano, Masahito; Miyano, Takaya; Ikawa, Takuya; Maki, Koshiro; Tachibana, Shigeru


    We characterize complexities in combustion instability in a lean premixed gas-turbine model combustor by nonlinear time series analysis to evaluate permutation entropy, fractal dimensions, and short-term predictability. The dynamic behavior in combustion instability near lean blowout exhibits a self-affine structure and is ascribed to fractional Brownian motion. It undergoes chaos by the onset of combustion oscillations with slow amplitude modulation. Our results indicate that nonlinear time series analysis is capable of characterizing complexities in combustion instability close to lean blowout.

  4. QUEOS, an experimental investigation of the premixing phase with hot spheres

    Energy Technology Data Exchange (ETDEWEB)

    Meyer, L. [Forschungszentrum Karlsruhe GmbH Technik und Umwelt (Germany). Inst. fuer Neutronenphysik und Reaktortechnik


    A second series of experiments with hot spheres to investigate the premixing phase of a steam explosion has been performed in the QUEOS facility at FZK. The diameter of the sphere jet plunging into the water has been reduced from 180 mm to 100 mm and larger masses have been employed. Both changes led to longer pours, compared to the short pours in the first series. The data of seven experiments are presented using three types of spheres at 1800 K and total volumes of approximately two and four liters, respectively. High speed films were taken, pressures, water temperatures and the steaming rate were measured. (author)

  5. Determination of liquid-fuel prevaporization and premixing in gas-turbine combustion chambers (United States)

    Mrugalla, J.

    A semiempirical mathematical model of the evaporation and distribution of liquid fuel in the prevaporization-premixing zone of a stationary gas turbine is developed, and the predictions obtained are compared with published experimental data and with the results of photographic, suction-probe, two-focus-laser-velocimeter, and light-scattering measurements on water sprays from 65-deg hollow-cone nozzles in a wind tunnel operating at 64 m/s. Good agreement is obtained, and the applicability of the model to the design of turbine combustion chambers giving lower NO(x) and CO emissions is indicated.


    Institute of Scientific and Technical Information of China (English)

    Yao Chunde; Yao Guangtao; Song Jinou; Wang Yinshan


    Numerical simulations of pilot fuel spray and compressing ignition for pre-mixed natural gas ignited by pilot diesel are described. By means of these modeling, the dual fuel and diesel fuel ignition mechanism of some phenomena investigated on an optional engine by technology of high-speed CCD is analyzed. It is demonstrated that the longer delay of ignition in dual fuel engine is not mainly caused by change of the mixture thermodynamics parameters. The analysis results illustrate that the ignition of pre-mixed natural gas ignited by pilot diesel taking place in dual fuel engine is a process of homogenous charge compression ignition.

  7. Deposition and consolidation of porous ceramic films for membrane separation

    DEFF Research Database (Denmark)

    Elmøe, Tobias Dokkedal; Tricoli, Antonio; Johannessen, Tue

    The deposition of porous ceramic films for membrane separation can be done by several processes such as thermophoresis [1], dip-coating [2] and spray pyrolysis [3]. Here we present a high-speed method, in which ceramic nano-particles form a porous film by filtration on top of a porous ceramic...... substrate [4]. Ceramic nano-particles are generated in a flame, using either a premixed (gas) flame, in which a metal-oxide precursor is evaporated in an N2 stream, which is combusted with methane and air, or using a flame spray pyrolysis, in which a liquid metal-oxide precursor is sprayed through a nozzle...

  8. Effect of Inhibitors on Biogas Laminar Burning Velocity and Flammability Limits in Spark Ignited Premix Combustion

    Directory of Open Access Journals (Sweden)

    Willyanto Anggono


    Full Text Available Biogas is the natural byproduct of the decomposition of vegetation or animal manure, of which there are almost in exhaustable supplies in the world, and which does not contribute CO2 or other greenhouse gases to global warming or climate change. Biogas contains 66.4% flammable gas (CH4 and 33.6% inhibitors (CO2 and N2. This study focuses on the effects of inhibitors on biogas laminar burning velocity and flammability limits in spark ignited premix combustion. Spherically expanding laminar premixed flames, freely propagating from spark ignition sources in initially quiescent biogas–air mixtures, are continuously recorded by a high-speed digital camera. Initially, all the experiments in this paper were performed using inhibitorless biogas (biogas without inhibitors at room temperature, at reduced pressure (0.5 atm and at various equivalence ratios (ϕ from the lower flammable limit to the upper flammable limit. The results are compared with those from biogas (containing inhibitors flames at reduced pressure, inhibitorless biogas flames at atmospheric pressure (1 atm, and biogas flames at atmospheric pressure to emphasize the effect of inhibitors on biogas laminar burning velocity and flammability limits. Compared to an inhibitorless biogas-air mixtures, in the biogas-air mixtures, the presence of inhibitors cause a reduction in the laminar burning velocity and the flammable limits become narrower.

  9. The anchoring mechanism of a bluff-body stabilized laminar premixed flame

    KAUST Repository

    Kedia, Kushal S.


    The objective of this work is to investigate the mechanism of the laminar premixed flame anchoring near a heat-conducting bluff-body. We use unsteady, fully resolved, two-dimensional simulations with detailed chemical kinetics and species transport for methane-air combustion. No artificial flame anchoring boundary conditions were imposed. Simulations show a shear-layer stabilized flame just downstream of the bluff-body, with a recirculation zone formed by the products of combustion. A steel bluff-body resulted in a slightly larger recirculation zone than a ceramic bluff-body; the size of which grew as the equivalence ratio was decreased. A significant departure from the conventional two-zone flame-structure is shown in the anchoring region. In this region, the reaction zone is associated with a large negative energy convection (directed from products to reactants) resulting in a negative flame-displacement speed. It is shown that the premixed flame anchors at an immediate downstream location near the bluff-body where favorable ignition conditions are established; a region associated with (1) a sufficiently high temperature impacted by the conjugate heat exchange between the heat-conducting bluff-body and the hot reacting flow and (2) a locally maximum stoichiometry characterized by the preferential diffusion effects. © 2014 The Combustion Institute.

  10. Microjet Injection Strategies for Mitigating Dynamics in a Lean Premixed Swirl-Stabilized Combustor

    KAUST Repository

    LaBry, Zachary


    Combustion dynamics remain a challenge in the development of low-emission, air-breathing combustors for power generation and aircraft propulsion. In this paper, we presenta parametric study on the use of microjet injectors for suppressing or mitigating the combustion dynamics that energize the thermoacoustic instability in a swirl-stabilized, premixed combustor. Microjet injectors consist of small inlet ports intended to inject flow with high momentum at relatively low mass flow rates into the flame-anchoring region. The microjets were configured to inject flow either axially, into the outer recirculation zone, or radially into the inner recirculation zone. Additionally, different injectors were tested with different relative senses of swirl (signs of angular momentum)with respect to the main flow: co-swirling, not swirling, or counter-swirling. We observed that injecting air or premixed fuel/air into the inner recirculation zone via counter-swirling radial microjets, we were able to reduce the overall sound pressure level in the combustor by over 20 dB in the lean end of the operating range. Other injector configurations were not observed to positively influence the combust or stability. Detailed PIV measurements are used to examine possible mechanisms of how the microjets impact the combustion dynamics, and the technology implications of our experiments are discussed.

  11. Soot Particle Size Distribution Functions in a Turbulent Non-Premixed Ethylene-Nitrogen Flame

    KAUST Repository

    Boyette, Wesley


    A scanning mobility particle sizer with a nano differential mobility analyzer was used to measure nanoparticle size distribution functions in a turbulent non-premixed flame. The burner utilizes a premixed pilot flame which anchors a C2H4/N2 (35/65) central jet with ReD = 20,000. Nanoparticles in the flame were sampled through a N2-filled tube with a 500- μm orifice. Previous studies have shown that insufficient dilution of the nanoparticles can lead to coagulation in the sampling line and skewed particle size distribution functions. A system of mass flow controllers and valves were used to vary the dilution ratio. Single-stage and two-stage dilution systems were investigated. A parametric study on the effect of the dilution ratio on the observed particle size distribution function indicates that particle coagulation in the sampling line can be eliminated using a two-stage dilution process. Carbonaceous nanoparticle (soot) concentration particle size distribution functions along the flame centerline at multiple heights in the flame are presented. The resulting distributions reveal a pattern of increasing mean particle diameters as the distance from the nozzle along the centerline increases.

  12. A simple one-step chemistry model for partially premixed hydrocarbon combustion

    Energy Technology Data Exchange (ETDEWEB)

    Fernandez-Tarrazo, Eduardo [Instituto Nacional de Tecnica Aeroespacial, Madrid (Spain); Sanchez, Antonio L. [Area de Mecanica de Fluidos, Universidad Carlos III de Madrid, Leganes 28911 (Spain); Linan, Amable [ETSI Aeronauticos, Pl. Cardenal Cisneros 3, Madrid 28040 (Spain); Williams, Forman A. [Department of Mechanical and Aerospace Engineering, University of California San Diego, La Jolla, CA 92093-0411 (United States)


    This work explores the applicability of one-step irreversible Arrhenius kinetics with unity reaction order to the numerical description of partially premixed hydrocarbon combustion. Computations of planar premixed flames are used in the selection of the three model parameters: the heat of reaction q, the activation temperature T{sub a}, and the preexponential factor B. It is seen that changes in q with equivalence ratio f need to be introduced in fuel-rich combustion to describe the effect of partial fuel oxidation on the amount of heat released, leading to a universal linear variation q(f) for f>1 for all hydrocarbons. The model also employs a variable activation temperature T{sub a}(f) to mimic changes in the underlying chemistry in rich and very lean flames. The resulting chemistry description is able to reproduce propagation velocities of diluted and undiluted flames accurately over the whole flammability limit. Furthermore, computations of methane-air counterflow diffusion flames are used to test the proposed chemistry under nonpremixed conditions. The model not only predicts the critical strain rate at extinction accurately but also gives near-extinction flames with oxygen leakage, thereby overcoming known predictive limitations of one-step Arrhenius kinetics. (author)

  13. Enstrophy transport conditional on local flow topologies in different regimes of premixed turbulent combustion

    KAUST Repository

    Papapostolou, Vassilios


    Enstrophy is an intrinsic feature of turbulent flows, and its transport properties are essential for the understanding of premixed flame-turbulence interaction. The interrelation between the enstrophy transport and flow topologies, which can be assigned to eight categories based on the three invariants of the velocity-gradient tensor, has been analysed here. The enstrophy transport conditional on flow topologies in turbulent premixed flames has been analysed using a Direct Numerical Simulation database representing the corrugated flamelets (CF), thin reaction zones (TRZ) and broken reaction zones (BRZ) combustion regimes. The flame in the CF regime exhibits considerable flame-generated enstrophy, and the dilatation rate and baroclinic torque contributions to the enstrophy transport act as leading order sink and source terms, respectively. Consequently, flow topologies associated with positive dilatation rate values, contribute significantly to the enstrophy transport in the CF regime. By contrast, enstrophy decreases from the unburned to the burned gas side for the cases representing the TRZ and BRZ regimes, with diminishing influences of dilatation rate and baroclinic torque. The enstrophy transport in the TRZ and BRZ regimes is governed by the vortex-stretching and viscous dissipation contributions, similar to non-reacting flows, and topologies existing for all values of dilatation rate remain significant contributors.

  14. Combustion characteristics of lemongrass (Cymbopogon flexuosus oil in a partial premixed charge compression ignition engine

    Directory of Open Access Journals (Sweden)

    Avinash Alagumalai


    Full Text Available Indeed, the development of alternate fuels for use in internal combustion engines has traditionally been an evolutionary process in which fuel-related problems are met and critical fuel properties are identified and their specific limits defined to resolve the problem. In this regard, this research outlines a vision of lemongrass oil combustion characteristics. In a nut-shell, the combustion phenomena of lemongrass oil were investigated at engine speed of 1500 rpm and compression ratio of 17.5 in a 4-stroke cycle compression ignition engine. Furthermore, the engine tests were conducted with partial premixed charge compression ignition-direct injection (PCCI-DI dual fuel system to profoundly address the combustion phenomena. Analysis of cylinder pressure data and heat-release analysis of neat and premixed lemongrass oil were demonstrated in-detail and compared with conventional diesel. The experimental outcomes disclosed that successful ignition and energy release trends can be obtained from a compression ignition engine fueled with lemongrass oil.

  15. Turbulent non-premixed combustion driven by the Richtmyer-Meshkov instability (United States)

    Varshochi, Hilda; Ramaprabhu, Praveen; Attal, Nitesh


    We report on 3D high resolution numerical simulations of a non-premixed, reacting Richmyer-Meshkov (RM) instability performed using the FLASH code. In the simulations, a Mach 1.6 shock traverses a diffuse, corrugated material interface separating Hydrogen at 1000 K and Oxygen at 300 K, so that local misalignments between pressure and density gradients induce baroclinic vorticity at the contact line. The vorticity deposition drives the RM instability, which in turn results in combustion and flame formation. We study the evolution of the interface and the flame as the resulting RM instability grows through linear, nonlinear and turbulent stages. We develop a detailed understanding of the effects of heat release and combustion on the underlying flow properties by comparing our results with a baseline non-reacting RM flow. We document the properties of the instability (growth rates, pdfs, spectra) and the flame (scalar dissipation rate, flame surface area, heat release rate) as well as the nature of the coupling between the two. Our findings are relevant to supernovae detonation, knocking in IC engines and scramjet performance, while the underlying flow problem defined here represents a novel canonical framework to understand the broader class of non-premixed turbulent flames.

  16. Forced and self-excited oscillations in a natural gas fired lean premixed combustor

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Daesik; Park, Sung Wook


    An experimental study of the flame response in a premixed gas turbine combustor has been conducted at room temperature and under atmospheric pressure inlet conditions using natural gas. The fuel is premixed with the air upstream of a choked inlet to avoid equivalence ratio fluctuations. Therefore the observed flame response is only the result of the imposed velocity fluctuations, which are produced using a variable-speed siren. Also, a variable length combustor is designed for investigating characteristics of self-excited instabilities. Measurements are made of the velocity fluctuation in the mixing section using hot wire anemometry and of the heat release fluctuation in the combustor using chemiluminescence emission. The results are analyzed to determine the phase and gain of the flame transfer function. The results show that the gain of flame transfer function is closely associated both with inlet flow forcing conditions such as frequency and amplitude of modulation as well as the operating conditions such as equivalence ratio. In order to predict the operating conditions where the combustor goes stable or unstable at given combustor and nozzle designs, time-lag analysis was tried using convection time delay measured from the phase information of the transfer function. The model prediction was in very good agreement with the self-excited instability measurement. However, spatial heat release distribution became more significant in long flames than in short flames and also had an important influence on the system damping procedure. (author)

  17. Combustion Characteristics for Turbulent Prevaporized Premixed Flame Using Commercial Light Diesel and Kerosene Fuels

    Directory of Open Access Journals (Sweden)

    Mohamed S. Shehata


    Full Text Available Experimental study has been carried out for investigating fuel type, fuel blends, equivalence ratio, Reynolds number, inlet mixture temperature, and holes diameter of perforated plate affecting combustion process for turbulent prevaporized premixed air flames for different operating conditions. CO2, CO, H2, N2, C3H8, C2H6, C2H4, flame temperature, and gas flow velocity are measured along flame axis for different operating conditions. Gas chromatographic (GC and CO/CO2 infrared gas analyzer are used for measuring different species. Temperature is measured using thermocouple technique. Gas flow velocity is measured using pitot tube technique. The effect of kerosene percentage on concentration, flame temperature, and gas flow velocity is not linearly dependent. Correlations for adiabatic flame temperature for diesel and kerosene-air flames are obtained as function of mixture strength, fuel type, and inlet mixture temperature. Effect of equivalence ratio on combustion process for light diesel-air flame is greater than for kerosene-air flame. Flame temperature increases with increased Reynolds number for different operating conditions. Effect of Reynolds number on combustion process for light diesel flame is greater than for kerosene flame and also for rich flame is greater than for lean flame. The present work contributes to design and development of lean prevaporized premixed (LPP gas turbine combustors.

  18. Influence of obstacle-produced turbulence on development of premixed flames

    Institute of Scientific and Technical Information of China (English)

    YU; Lixin(余立新); SUN; Wenchao(孙文超); WU; Chengkang(吴承康)


    An investigation into influence of obstructions on premixed flame propagation has been carried out in a semi-open tube.It is found that there exists flame acceleration and rising overpressure along the path of flame due to obstacles.According to the magnitude of flame speeds,the propagation of flame in the tube can be classified into three regimes:the quenching,the choking and the detonation regimes.In premixed flames near the flammability limits,the flame is observed first to accelerate and then to quench itself after propagating past a certain number of obstacles.In the choking regime,the maximum flame speeds are somewhat below the combustion product sound speeds,and insensitive to the blockage ratio.In the more sensitive mixtures,the transition to detonation (DDT) occurs when the equivalence ratio increases.The transition is not observed for the less sensitive mixtures.The dependence of overpressure on blockage ratio is not monotonous.Furthermore,a numerical study of flame acceleration and overpressure with the unsteady compressible flow model is performed,and the agreement between the simulation and measurements is good.``

  19. Direct simulation and modeling of flame-wall interaction for premixed turbulent combustion

    Energy Technology Data Exchange (ETDEWEB)

    Poinsot, T.J.; Haworth, D.C.; Bruneaux, G. (CNRS, Toulouse (France). Inst. de Mecanique des Fluides de Toulouse General Motors Research, Warren, MI (United States) Inst. Francais du Petrole, Rueil Malmaison (France))


    The interaction between turbulent premixed flames and walls is studied using a two-dimensional full Navier-Stokes solver with simple chemistry. The effects of wall distance on the local and global flame structure are investigated. Quenching distances and maximum wall heat fluxes during quenching are computed in laminar cases and are found to be comparable to experimental and analytical results. For turbulent cases, it is shown that quenching distances and maximum heat fluxes remain of the same order as for laminar flames. Based on simulation results, a law-of-the-wall'' model is derived to describe the interaction between a turbulent premixed flame and a wall. This model is constructed to provide reasonable behavior of flame surface density near a wall under the assumption that flame -- wall interaction takes place at scales smaller than the computational mesh. It can be implemented in conjunction with any of several recent flamelet models based on a modeled surface density equation, with no additional constraints on mesh size or time step. Preliminary tests of this model are presented for the case of a spark-ignited piston engine.

  20. Emission characteristics and axial flame temperature distribution of producer gas fired premixed burner

    Energy Technology Data Exchange (ETDEWEB)

    Bhoi, P.R. [Department of Mechanical Engineering, L and T-Sargent and Lundy Limited, L and T Energy Centre, Near Chhani Jakat Naka, Baroda 390 002 (India); Channiwala, S.A. [Department of Mechanical Engineering, Sardar Vallabhbhai National Institute of Technology, Deemed University, Ichchhanath, Surat 395 007, Gujarat (India)


    This paper presents the emission characteristics and axial flame temperature distribution of producer gas fired premixed burner. The producer gas fired premixed burner of 150 kW capacity was tested on open core throat less down draft gasifier system in the present study. A stable and uniform flame was observed with this burner. An instrumented test set up was developed to evaluate the performance of the burner. The conventional bluff body having blockage ratio of 0.65 was used for flame stabilization. With respect to maximum flame temperature, minimum pressure drop and minimum emissions, a swirl angle of 60 seems to be optimal. The experimental results also showed that the NO{sub x} emissions are inversely proportional to swirl angle and CO emissions are independent of swirl angle. The minimum emission levels of CO and NO{sub x} are observed to be 0.167% and 384 ppm respectively at the swirl angle of 45-60 . The experimental results showed that the maximum axial flame temperature distribution was achieved at A/F ratio of 1.0. The adiabatic flame temperature of 1653 C was calculated theoretically at A/F ratio of 1.0. Experimental results are in tune with theoretical results. It was also concluded that the CO and UHC emissions decreases with increasing A/F ratio while NO{sub x} emissions decreases on either side of A/F ratio of 1.0. (author)

  1. Considerations and calculations on the breakup of jets and drops of melt related to premixing

    Energy Technology Data Exchange (ETDEWEB)

    Buerger, M.; Berg, E. von; Buck, M. [Inst. fuer Kernenergetik und Energiesysteme (IKE), Univ. of Stuttgart, Pfaffenwaldring 31, 70569 Stuttgart (Germany)


    Various descriptions of jet and drop breakup are applied in premixing codes, presently. The main task is to check these descriptions over a wide range of conditions in order to assure extrapolation capabilities for the codes. Jet breakup under non-boiling conditions is relatively well described by IKEJET, based on Conte/Miles (CM) instability description and a relatively detailed stripping model, in contrast to using Kelvin/Helmholtz (KH) theory. Remaining open questions are elaborated. Especially, thick jet behavior with dominance of stripping even at small relative velocities must be distinguished from thin jets with coarse breakup. The application of IKEJET to cases with jet breakup under strong film boiling yielded significantly too little fragmentation. As a possible explanation line, multiphase effects on the wave growth and stripping are considered, due to entrainment of melt and water. Parametric checking calculations are performed with a strongly simplified approach for PREMIX and FARO experiments in order to reveal main effects and the possible physical explanation features as a basis for extended modelling. The results indicate that jet breakup may be essentially sufficient to explain the experimental behavior. Rather coalescence than further drop breakup may be expected. This is also indicated by calculations with IKE drop breakup models. (author)

  2. DNS and modeling of the interaction between turbulent premixed flames and walls (United States)

    Poinsot, T. J.; Haworth, D. C.


    The interaction between turbulent premixed flames and walls is studied using a two-dimensional full Navier-Stokes solver with simple chemistry. The effects of wall distance on the local and global flame structure are investigated. Quenching distances and maximum wall heat fluxes during quenching are computed in laminar cases and are found to be comparable to experimental and analytical results. For turbulent cases, it is shown that quenching distances and maximum heat fluxes remain of the same order as for laminar flames. Based on simulation results, a 'law-of-the-wall' model is derived to describe the interaction between a turbulent premixed flame and a wall. This model is constructed to provide reasonable behavior of flame surface density near a wall under the assumption that flame-wall interaction takes place at scales smaller than the computational mesh. It can be implemented in conjunction with any of several recent flamelet models based on a modeled surface density equation, with no additional constraints on mesh size or time step.

  3. Polymeric microspheres with N-methyl-D-glucamine ligands for boron removal from water solution by adsorption-membrane filtration process. (United States)

    Wolska, Joanna; Bryjak, Marek; Kabay, Nalan


    Polymeric microspheres with N-methyl-D-glucamine (NMDG) ligands have been tested in the adsorption-membrane filtration process for boron removal from aqueous solutions. The chelating resins were synthesized by reacting NMDG with the vinylbenzyl chloride-styrene-1,4-divinylbenzene (VBC/S/DVB) copolymer at the reflux temperature and in the microwave reactor. VBC/S/DVB spheres with a gel structure that contained 6 wt% DVB were obtained by membrane emulsification followed by suspension polymerization. By selecting the optimal emulsification and polymerization parameters, it was possible to obtain 25-microm-diameter particles with a narrow size distribution. Resins obtained by microwave modification showed the higher boron adsorption capacity.

  4. CFD Analysis of Fuel Atomization, Secondary Droplet Breakup and Spray Dispersion in the Premix Duct of a LPP Combustor

    NARCIS (Netherlands)

    Schmehl, R.; Maier, G.; Wittig, S.


    The two phase flow in the premix duct of a LPP combustor is computed using a Lagrangian droplet tracking method. To reproduce the characteristic spray structure of an air-assisted pressure-swirl atomizer, a sheet spray model is de-rived from measured sheet parameters and combined with an advanced co

  5. The Impact of Variable Inlet Mixture Stratification on Flame Topology and Emissions Performance of a Premixer/Swirl Burner Configuration

    Directory of Open Access Journals (Sweden)

    P. Koutmos


    Full Text Available The work presents the assessment of a low emissions premixer/swirl burner configuration utilizing lean stratified fuel preparation. An axisymmetric, single- or double-cavity premixer, formed along one, two, or three concentric disks promotes propane-air premixing and supplies the combustion zone at the afterbody disk recirculation with a radial equivalence ratio gradient. The burner assemblies are operated with a swirl co-flow to study the interaction of the recirculating stratified flame with the surrounding swirl. A number of lean and ultra-lean flames operated either with a plane disk stabilizer or with one or two premixing cavity arrangements were evaluated over a range of inlet mixture conditions. The influence of the variation of the imposed swirl was studied for constant fuel injections. Measurements of turbulent velocities, temperatures, OH* chemiluminescence and gas analysis provided information on the performance of each burner set up. Comparisons with Large Eddy Simulations, performed with an 11-step global chemistry, illustrated the flame front interaction with the vortex formation region under the influence of the variable inlet mixture stratifications. The combined effort contributed to the identification of optimum configurations in terms of fuel consumption and pollutants emissions and to the delineation of important controlling parameters and limiting fuel-air mixing conditions.

  6. Error analysis of large-eddy simulation of the turbulent non-premixed sydney bluff-body flame

    NARCIS (Netherlands)

    Kempf, A.M.; Geurts, B.J.; Oefelein, J.C.


    A computational error analysis is applied to the large-eddy simulation of the turbulent non-premixed Sydney bluff-body flame, where the error is defined with respect to experimental data. The errorlandscape approach is extended to heterogeneous compressible turbulence, which is coupled to combustion

  7. The global, centralized approach of the GAIN Premix Facility has made oil fortification in Indonesia more affordable. (United States)

    Jallier, Vincent; Guyondet, Christophe; Provent, Adeline; Laillou, Arnaud; Soekirman; Moench-Pfanner, Regina


    Access to high-grade micronutrients is a recurring challenge that often threatens the long-term sustainability of food fortification programs. To assess the efficiency of the Global Alliance for Improved Nutrition (GAIN) Premix Facility in procuring quality, affordable vitamin A for fortification of edible oil in Indonesia. A global approach to procurement of standard items was used by combining volumes across various demand streams in order to reduce the total cost of acquisition through economies of scale. The GAIN Premix Facility undertook a detailed analysis of vitamin A requirements across its existing customer base, which served as a basis for developing a reliable demand forecast. A consolidated, competitive tender was launched that resulted in the setting up of a long-term commercial agreement with the selected supplier to lock in the most competitive price for a given period of time. The direct benefit to oil manufacturers of fortifying with vitamin A is that the cost of fortification went down significantly compared with prices they would have been offered had they ordered vitamin A individually. In Indonesia, this consolidated procurement approach has allowed a 14.5% decrease in the unit price of vitamin A. The GAIN Premix Facility demonstrated its effectiveness in acting as a global procurement platform by aggregating demand across different customers and leveraging improved prices through increased volumes. Building on the success of this effort, the GAIN Premix Facility is replicating this global approach for procurement of other standard items being procured across fortification programs worldwide.

  8. Research on Cellular Instabilities of Lean Premixed Syngas Flames under Various Hydrogen Fractions Using a Constant Volume Vessel

    Directory of Open Access Journals (Sweden)

    Hong-Meng Li


    Full Text Available An experimental study of the intrinsic instabilities of H2/CO lean (φ = 0.4 to φ = 1.0 premixed flames at different hydrogen fractions ranging from 0% to 100% at elevated pressure and room temperature was performed in a constant volume vessel using a Schlieren system. The unstretched laminar burning velocities were compared with data from the previous literature and simulated results. The results indicate that excellent agreements are obtained. The cellular instabilities of syngas-air flames were discussed and critical flame radii were measured. When hydrogen fractions are above 50%, the flame tends to be more stable as the equivalence ratio increases; however, the instability increases for flames of lower hydrogen fractions. For the premixed syngas flame with hydrogen fractions greater than 50%, the decline in cellular instabilities induced by the increase in equivalence ratio can be attributed to a reduction of diffusive-thermal instabilities rather than increased hydrodynamic instabilities. For premixed syngas flames with hydrogen fractions lower than 50%, as the equivalence ratio increases, the cellular instabilities become more evident because the enhanced hydrodynamic instabilities become the dominant effect. For premixed syngas flames, the enhancement of cellular instabilities induced by the increase in hydrogen fraction is the result of both increasing diffusive-thermal and hydrodynamic instabilities.

  9. NO formation in the burnout region of a partially premixed methane-air flame with upstream heat loss

    NARCIS (Netherlands)

    Mokhov, A.V.; Levinsky, H.B.


    Measurements of temperature and NO concentration in laminar, partially premixed methane-air flames stabilized on a ceramic burner in coflow are reported. The NO concentration and temperature were determined by laser- induced fluorescence (LIF) and coherent anti-Stokes Raman scattering: (CARS), respe

  10. Diode laser absorption measurement and analysis of HCN in atmospheric-pressure, fuel-rich premixed methane/air flames

    NARCIS (Netherlands)

    Gersen, Sander; Mokhov, A. V.; Levinsky, H. B.


    Measurements of HCN in flat, fuel-rich premixed methane/air flames at atmospheric pressure are reported. Quartz-microprobe sampling followed by wavelength modulation absorption spectroscopy with second harmonic detection was used to obtain an overall measurement uncertainty of better than 20% for

  11. Inclusion of preferential diffusion in simulations of premixed combustion of hydrogen/methane mixtures with flamelet generated manifolds

    NARCIS (Netherlands)

    Swart,; Bastiaans, R.J.M.; Oijen, J.A. van; Goey, L.P.H. de; Cant, R.S.


    In this paper we study the possibility to account for preferential diffusion effects in lean turbulent premixed flames in numerical predictions with reduced chemistry. We studied the situation when hydrogen is added to methane at levels of 20% and 40% by volume in the fuel, at lean combustion (φ=

  12. Simultaneous determination of cork taint and Brett character responsible compounds in wine using ultrasound-assisted emulsification microextraction with solidification of floating organic drop. (United States)

    Pizarro, C; Sáenz-González, C; Pérez-del-Notario, N; González-Sáiz, J M


    In this study, ultrasound-assisted emulsification microextraction combined with solidification of floating organic drop method (USAEME-SFOD) has been proposed as a novel approach for the sensitive determination of haloanisoles and volatile phenols in wines. For this purpose, the influence of the different parameters affecting the procedure (type and volume of extraction solvent, temperature, time and ionic strength) was evaluated in order to optimise the efficiency of the process. Subsequently, the linearity, detection and quantification limits, precision, recoveries and applicability to real samples were studied, obtaining excellent method performance results. Moreover, USAEME-SFOD was compared with other liquid-liquid microextraction methods such as dispersive liquid-liquid microextraction (DLLME) and ultrasound-assisted emulsification microextraction (USAEME). This comparison study proved the suitability of USAEME-SFOD as an alternative to previously reported methods for the simultaneous determination of cork taint and Brett character responsible compounds in wines.

  13. 磺化聚砜改性超滤膜的制备及性能%Preparation amd Performance Research of the Sulfonated Polysulfone Modified Ultrafiltration Membrane

    Institute of Scientific and Technical Information of China (English)

    董晓静; 胡小玲; 管萍; 岳红; 张新丽


    Using sulfonated polysulfone for raw material and complex additive. Adopting the method of the posture transform to preparation sulfonated polysulfone modified ultrafihmtion memebrane. It''s aperture is 400 - 500A°.Structure and separate capability have been investigated. Result show that the sulfonated polysulfone modified ultrafiltration membrane can separate solubility protein in the ferment solution of the erythromycin. Problem of the emulsification in the extraction process of the erythromycin have been resolved.

  14. Encapsulation de la vitamine E dans des vecteurs pharmaceutiques inhalables préparés par des contacteurs à membrane


    Laouini, Abdallah


    The present study investigated the preparation of pharmaceutical drug carriers encapsulating the vitamin E and intended for pulmonary administration after nebulisation. Vitamin E, a physiological antioxidant, could be used to prevent cigarette smoke toxicity since several pulmonary disorders are mainly caused by oxidative stress phenomena. The methods used for the drug carriers’ preparation were based on the membrane emulsification principle. In these methods, the to-be-dispersed phase was in...

  15. Membrane reactor. Membrane reactor

    Energy Technology Data Exchange (ETDEWEB)

    Shindo, Y.; Wakabayashi, K. (National Chemical Laboratory for Industry, Tsukuba (Japan))


    Many reaction examples were introduced of membrane reactor, to be on the point of forming a new region in the field of chemical technology. It is a reactor to exhibit excellent function, by its being installed with membrane therein, and is generally classified into catalyst function type and reaction promotion type. What firstly belongs to the former is stabilized zirconia, where oxygen, supplied to the cathodic side of membrane with voltage, impressed thereon, becomes O {sup 2 {minus}} to be diffused through the membrane and supplied, as variously activated oxygenous species, on the anodic side. Examples with many advantages can be given such as methane coupling, propylene oxidation, methanating reaction of carbon dioxide, etc. Apart, palladium film and naphion film also belong to the former. While examples of the latter comprise, among others, decomposition of hydrogen sulfide by porous glass film and dehydrogenation of cyclohexane or palladium alloy film, which are expected to be developed and materialized in the industry. 33 refs., 8 figs.

  16. Computational Enhancements for Direct Numerical Simulations of Statistically Stationary Turbulent Premixed Flames

    KAUST Repository

    Mukhadiyev, Nurzhan


    Combustion at extreme conditions, such as a turbulent flame at high Karlovitz and Reynolds numbers, is still a vast and an uncertain field for researchers. Direct numerical simulation of a turbulent flame is a superior tool to unravel detailed information that is not accessible to most sophisticated state-of-the-art experiments. However, the computational cost of such simulations remains a challenge even for modern supercomputers, as the physical size, the level of turbulence intensity, and chemical complexities of the problems continue to increase. As a result, there is a strong demand for computational cost reduction methods as well as in acceleration of existing methods. The main scope of this work was the development of computational and numerical tools for high-fidelity direct numerical simulations of premixed planar flames interacting with turbulence. The first part of this work was KAUST Adaptive Reacting Flow Solver (KARFS) development. KARFS is a high order compressible reacting flow solver using detailed chemical kinetics mechanism; it is capable to run on various types of heterogeneous computational architectures. In this work, it was shown that KARFS is capable of running efficiently on both CPU and GPU. The second part of this work was numerical tools for direct numerical simulations of planar premixed flames: such as linear turbulence forcing and dynamic inlet control. DNS of premixed turbulent flames conducted previously injected velocity fluctuations at an inlet. Turbulence injected at the inlet decayed significantly while reaching the flame, which created a necessity to inject higher than needed fluctuations. A solution for this issue was to maintain turbulence strength on the way to the flame using turbulence forcing. Therefore, a linear turbulence forcing was implemented into KARFS to enhance turbulence intensity. Linear turbulence forcing developed previously by other groups was corrected with net added momentum removal mechanism to prevent mean

  17. Nano-liter droplet libraries from a pipette: step emulsificator that stabilizes droplet volume against variation in flow rate. (United States)

    Dutka, Filip; Opalski, Adam S; Garstecki, Piotr


    Many modern analytical assays, for example, droplet digital PCR, or screening of the properties of single cells or single mutated genes require splitting a liquid sample into a number of small (typically ca. nano-liter in volume) independent compartments or droplets. This calls for a method that would allow splitting small (microliter) samples of liquid into libraries of nano-liter droplets without any dead volume or waste. Step emulsification allows for facile protocols that require delivery of only the sample liquid, yet they typically exhibit dependence of the droplet size on the rate at which the sample is injected. Here, we report a novel microfluidic junction that reduces the dependence of the volume of droplets on the rate of injection. We also demonstrate generation of tightly monodisperse nanoliter droplets by introduction of solely the dispersed phase into the system from an automatic pipette. The method presented here can readily be used and can replace the sophisticated devices typically used to generate libraries of nano-liter droplets from liquid samples.

  18. Formulation and characterization of esterified xylo-oligosaccharides-stabilized oil-in-water emulsions using microchannel emulsification. (United States)

    Udomrati, Sunsanee; Khalid, Nauman; Gohtani, Shoichi; Nakajima, Mitsutoshi; Uemura, Kunihiko; Kobayashi, Isao


    A series of amphiphilically esterified xylo-oligosaccharides (xylo esters) with different fatty acids residues - decanoic acid (C-10), lauric acid (C-12) and palmitic acid (C-16) - were enzymatically modified at 60°C for 4h. These xylo esters were used as emulsifiers to formulate oil-in-water (O/W) emulsions by microchannel emulsification (MCE). Grooved and straight-through MCE was used to investigate the droplet generation and/or emulsion stability. Xylo ester-stabilized oil droplets were generated smoothly from microchannels arranged linearly or two dimensionally, while xylo ester-stabilized emulsions were less monodispersed owing to low surface activity of the xylo esters. The combined use of xylo esters (2.5% (w/w)) and Tween series (0.1% (w/w)) in the continuous phase can improve the monodispersity of the resultant oil. Successful droplet generation was achieved with the straight-through MCE using 2.5% (w/w) xylo laurate and 0.1% (w/w) Tween 20. The optimized combination of xylo laurate and Tween 20 inhibited coalescence and oiling off more efficiently than the droplets solely stabilized by Tween 20 during 30days of storage.

  19. Continuous synthesis of drug-loaded nanoparticles using microchannel emulsification and numerical modeling: effect of passive mixing. (United States)

    Ortiz de Solorzano, Isabel; Uson, Laura; Larrea, Ane; Miana, Mario; Sebastian, Victor; Arruebo, Manuel


    By using interdigital microfluidic reactors, monodisperse poly(d,l lactic-co-glycolic acid) nanoparticles (NPs) can be produced in a continuous manner and at a large scale (~10 g/h). An optimized synthesis protocol was obtained by selecting the appropriated passive mixer and fluid flow conditions to produce monodisperse NPs. A reduced NP polydispersity was obtained when using the microfluidic platform compared with the one obtained with NPs produced in a conventional discontinuous batch reactor. Cyclosporin, an immunosuppressant drug, was used as a model to validate the efficiency of the microfluidic platform to produce drug-loaded monodisperse poly(d,l lactic-co-glycolic acid) NPs. The influence of the mixer geometries and temperatures were analyzed, and the experimental results were corroborated by using computational fluid dynamic three-dimensional simulations. Flow patterns, mixing times, and mixing efficiencies were calculated, and the model supported with experimental results. The progress of mixing in the interdigital mixer was quantified by using the volume fractions of the organic and aqueous phases used during the emulsification-evaporation process. The developed model and methods were applied to determine the required time for achieving a complete mixing in each microreactor at different fluid flow conditions, temperatures, and mixing rates.

  20. Numerical Investigation of Cell Encapsulation for Multiplexing Diagnostic Assays Using Novel Centrifugal Microfluidic Emulsification and Separation Platform

    Directory of Open Access Journals (Sweden)

    Yong Ren


    Full Text Available In the present paper, we report a novel centrifugal microfluidic platform for emulsification and separation. Our design enables encapsulation and incubation of multiple types of cells by droplets, which can be generated at controlled high rotation speed modifying the transition between dripping-to-jetting regimes. The droplets can be separated from continuous phase using facile bifurcated junction design. A three dimensional (3D model was established to investigate the formation and sedimentation of droplets using the centrifugal microfluidic platform by computational fluid dynamics (CFD. The simulation results were compared to the reported experiments in terms of droplet shape and size to validate the accuracy of the model. The influence of the grid resolution was investigated and quantified. The physics associated with droplet formation and sedimentation is governed by the Bond number and Rossby number, respectively. Our investigation provides insight into the design criteria that can be used to establish centrifugal microfluidic platforms tailored to potential applications, such as multiplexing diagnostic assays, due to the unique capabilities of the device in handling multiple types of cells and biosamples with high throughput. This work can inspire new development of cell encapsulation and separation applications by centrifugal microfluidic technology.

  1. 氧化蜡乳化工艺研究%Study on emulsification process of oxidized paraffin

    Institute of Scientific and Technical Information of China (English)

    陈娆; 王冬美; 孙彩兰; 安磊


    Studied on the emulsification process of oxidized paraffin. The influence factors about the properties of the oxidized paraffin emulsion are the emulsifier formula, the stirring speed, the emulsifying temperature, the emulsifying time. The results show that the concentration of emulsifier A, emulsifier B, emulsifier C are 4%, 3~3.5%, 1%, the stirring speed is 1 000~1 200 r/min, the emulsifying time is 20~25 min, the emulsifying temperature is 85~90 ℃ , we can get excellent performance of oxidized paraffin microemulsion.%对氧化蜡的乳化工艺进行研究。考察了乳化剂配方、搅拌速度、乳化温度、乳化时间对氧化蜡乳液性能的影响。结果表明:石蜡通过氧化改性,当乳化剂A、乳化剂B、助乳化剂C的浓度分别为4%、3.0~3.5%、1.0%,搅拌转速为1000~1200 r/min、乳化时间为20~25 min、乳化温度为85~90℃时能得到性能优良的氧化蜡微乳液。

  2. Biobased Membrane

    NARCIS (Netherlands)

    Koenders, E.A.B.; Zlopasa, J.; Picken, S.J.


    The present invention is in the field of a composition for forming a bio-compatible membrane applicable to building material, such as concrete, cement, etc., to a meth od of applying said composition for forming a bio-compatible membrane, a biocompatible membrane, use of said membrane for various pu

  3. Membrane fusion

    DEFF Research Database (Denmark)

    Bendix, Pól Martin


    At Stanford University, Boxer lab, I worked on membrane fusion of small unilamellar lipid vesicles to flat membranes tethered to glass surfaces. This geometry closely resembles biological systems in which liposomes fuse to plasma membranes. The fusion mechanism was studied using DNA zippering...... between complementary strands linked to the two apposing membranes closely mimicking the zippering mechanism of SNARE fusion complexes....

  4. Experimental Study of Pre-mixed Flames on a Multi-Hole Matrix Burner

    Directory of Open Access Journals (Sweden)

    Vasudevan Raghavan


    Full Text Available This paper deals with an experimental investigation of the flame characteristics of premixed Liquefied Petroleum Gas (LPG - air mixtures with different equivalence ratios on a multi-hole matrix burner. Lowest possible fuel-lean mixing conditions are envisaged. Results show that the flame pattern changes into four different types which are oscillatory flames in the middle region, flames with oscillations along the centerline, flames with very little oscillations and stable flames from all the holes. Species concentration measurements are performed with the help of  gas analyzer and the results show that the concentrations of carbon-monoxide and oxygen decreases, whereas that of carbon-dioxide and nitric oxide increases with increase in the volumetric flow rate of LPG and air mixture. In addition to this, temperature measurements are carried out using a K-type thermocouple over the burner surface at different heights. Temperature contours for each plane have been presented.

  5. Evaluation of Sintering Behavior of Premix Al-Zn-Mg-Cu Alloy Powder

    Directory of Open Access Journals (Sweden)

    Haris Rudianto


    Full Text Available Sintering of light aluminium alloys powder has been investigated as a way to substitute steels in automotive and aerospace industries. Premix Al-5.5Zn-2.5Mg-0.5Cu composite powder called Alumix 431D was analyzed in this research. Sintering was carried out under ultra high purity nitrogen gas and before reaching sintering temperature, green samples were delubricated at 400°C for 30 min. The powder possesses high sinterability by reaching 96% relative density at 580°C sintering temperature. Formation of liquid phase seems to support achieving high sintering density. Optimum mechanical properties also were obtained under those conditions. T6 heat treatment was done to improve the mechanical properties by formation of precipitation strengthening, and MgZn2 appears to be dominant strengthening precipitate. X-ray diffraction, optical microscopy, and SEM-EDS were used to characterize powder, and sintered and heat treated samples.

  6. Resolvent methods for steady premixed flame shapes governed by the Zhdanov-Trubnikov equation

    CERN Document Server

    Borot, Gaëtan; Joulin, Guy


    Using pole decompositions as starting points, the one parameter (-1 =< c < 1) nonlocal and nonlinear Zhdanov-Trubnikov (ZT) equation for the steady shapes of premixed gaseous flames is studied in the large-wrinkle limit. The singular integral equations for pole densities are closely related to those satisfied by the spectral density in the so-called O(n) matrix model, with n = -2(1 + c)/(1 - c). They can be solved via the introduction of complex resolvents and the use of complex analysis. We retrieve results obtained recently for -1 =< c =< 0, and we explain and cure their pathologies when they are continued naively to 0 < c < 1. Moreover, for any -1 =< c < 1, we derive closed-form expressions for the shapes of steady isolated flame crests, and then bicoalesced periodic fronts. These theoretical results fully agree with numerical resolutions. Open problems are evoked.

  7. Numerical Study on Laminar Burning Velocity and Flame Stability of Premixed Methane/Ethylene/Air Flames

    Institute of Scientific and Technical Information of China (English)

    陈珊珊; 蒋勇; 邱榕; 安江涛


    A numerical study on premixed methane/ethylene/air flames with various ethylene fractions and equivalence ratios was conducted at room temperature and atmospheric pressure. The effects of ethylene addition on laminar burning velocity, flame structure and flame stability under the condition of lean burning were investigated. The results show that the laminar burning velocity increases with ethylene fraction, especially at a large equivalence ratio. More ethylene addition gives rise to higher concentrations of H, O and OH radicals in the flame, which significantly promotes chemical reactions, and a linear correlation exists between the laminar burning velocity and the maximum H + OH concentration in the reaction zone. With the increase of ethylene fraction, the adiabatic flame temperature is raised, while the inner layer temperature becomes lower, contributing to the enhancement of combustion. Markstein length and Markstein number, representative of the flame stability, increase as more ethylene is added, indicating the tendency of flame stability to improve with ethylene addition.

  8. Microstructure of premixed propane/air flame in the transition from laminar to turbulent combustion

    Institute of Scientific and Technical Information of China (English)

    CHEN XianFeng; SUN JinHua; LIU Yi; LIU XuanYa; CHEN SiNing; LU ShouXiang


    In order to explore the flame structure and propagation behavior of premixed propane/air in the transition from laminar to turbulent combustion, the high speed camera and Schlieren images methods were used to record the photograph of flame propagation process in a semi-vented pipe. Meanwhile, the super-thin thermocouple and ionization current probe methods were applied to detect the temperature distribution and reaction intensity of combustion reaction. The characteristics of propane/air flame propagation and microstructure were analyzed in detail by the experimental results coupled with chemical reaction thermodynamics. In the test, the particular tulip flame behavior and the formation process in the laminar-turbulent transition were disclosed clearly. From the Schlieren images and iron current results, one conclusion can be drawn that the small-scale turbulent combustion also appeared in laminar flame, which made little influence on the flame shape, but increased the flame thickness obviously.

  9. Novel analytical model for predicting the combustion characteristics of premixed flame propagation in lycopodium dust particles

    Energy Technology Data Exchange (ETDEWEB)

    Bidabadi, Mehdi; Rahbari, Alireza [Iran University of Science and Technology, Tehran (Iran, Islamic Republic of)


    This paper presents the effects of the temperature difference between gas and particle, different Lewis numbers, and heat loss from the walls in the structure of premixed flames propagation in a combustible system containing uniformly distributed volatile fuel particles in an oxidizing gas mixture. It is assumed that the fuel particles vaporize first to yield a gaseous fuel, which is oxidized in a gas phase. The analysis is performed in the asymptotic limit, where the value of the characteristic Zeldovich number is large. The structure of the flame is composed of a preheat zone, reaction zone, and convection zone. The governing equations and required boundary conditions are applied in each zone, and an analytical method is used for solving these equations. The obtained results illustrate the effects of the above parameters on the variations of the dimensionless temperature, particle mass friction, flame temperature, and burning velocity for gas and particle

  10. Stabilization of premixed lean methane-air combustion using dielectric barrier discharge with low pollutant emissions (United States)

    Ono, Ryo; Ogura, Kazuaki; Mogi, Toshio


    Catalytic combustion is a promising technology to stabilize lean combustion with low pollutant emissions. Catalytic combustion has been applied to gas turbine combustors; however, some drawbacks of this technology remain to be addressed. In this work, a new concept is demonstrated to overcome the problems of catalytic combustion by using dielectric barrier discharge (DBD) instead of a catalyst. A premixed lean methane-air mixture preheated to 400 °C with an equivalence ratio of 0.45 is flowed through the DBD reactor under atmospheric pressure. Almost complete combustion is achieved with a DBD power of 0.7% of the net calorific value of the mixture. The exhaust emissions are NO = 20 ppm, NO2 = 2 ppm, CO = 2 ppm, and HC \\cong 0 ppm. This work demonstrates that DBD-assisted combustion is a potential alternative to catalytic combustion.

  11. Identifying combustion intermediates in premixed MTBE/gasoline/oxygen flame probed via synchrotron radiation

    Institute of Scientific and Technical Information of China (English)

    YAO Chunde; QI Fei; LI Jing; LI Qi; JI Qing; HUANG Chaoqun; WEI Lixia; WANG Jing; TIAN Zhenyu; LI Yuyang


    Molecular-beam sampling mass spectrometry (MBMS) combined with tunable synchrotron radiation photoionization technique offers obvious advantages for the study of flame chemistry over other techniques because of the precision measurement of the combustion intermediates and products in flame.In this paper,the results to identify combustion intermediates in low-pressure premixed gasoline/oxygen flame with the synchrotron radiation were reported.Based on the results obtained,the formation process of five products and the difference between gasoline/oxygen and MTBE/gasoline/oxygen flame were emphatically analyzed.The results achieved provide data basis for the analysis of intermediates and radicals in flame,and are helpful to establish the kinetic modeling of gasoline/oxygen and MTBE/gasoline/oxygen flames.

  12. Flow topologies in different regimes of premixed turbulent combustion: A direct numerical simulation analysis (United States)

    Wacks, Daniel H.; Chakraborty, Nilanjan; Klein, Markus; Arias, Paul G.; Im, Hong G.


    The distributions of flow topologies within the flames representing the corrugated flamelets, thin reaction zones, and broken reaction zone regimes of premixed turbulent combustion are investigated using direct numerical simulation data of statistically planar turbulent H2-air flames with an equivalence ratio ϕ =0.7 . It was found that the diminishing influence of dilatation rate with increasing Karlovitz number has significant influences on the statistical behaviors of the first, second, and third invariants (i.e., P ,Q , and R ) of the velocity gradient tensor. These differences are reflected in the distributions of the flow topologies within the flames considered in this analysis. This has important consequences for those topologies that make dominant contributions to the scalar-turbulence interaction and vortex-stretching terms in the scalar dissipation rate and enstrophy transport equations, respectively. Detailed physical explanations are provided for the observed regime dependences of the flow topologies and their implications on the scalar dissipation rate and enstrophy transport.

  13. Explosive Combustion of a Neutron Star into a Quark Star: the non-premixed scenario

    CERN Document Server

    Ouyed, Rachid; Jaikumar, Prashanth


    We review aspects of the hydrodynamical combustion of nuclear matter to strange quark matter in a neutron star. Numerical studies on non-premixed combustion that consistently include hydrodynamical flows in a reactive-diffusive setup show that in 1D, the conversion (burning) front moves at sub-sonic speeds and stops short of converting the entire star to SQM, essentially due to advective forces. However, in the process, we also find that neutrino cooling of the interface causes it to wrinkle, laying a platform for a deflagrative-to-detonative transition (DDT). We outline progress on improvements in the burning code (Burn-UD: that will ultimately reveal the mechanism that can explode the outermost layers of even a dense compact object like a neutron star.

  14. LES-Modeling of a Partially Premixed Flame using a Deconvolution Turbulence Closure (United States)

    Wang, Qing; Wu, Hao; Ihme, Matthias


    The modeling of the turbulence/chemistry interaction in partially premixed and multi-stream combustion remains an outstanding issue. By extending a recently developed constrained minimum mean-square error deconvolution (CMMSED) method, to objective of this work is to develop a source-term closure for turbulent multi-stream combustion. In this method, the chemical source term is obtained from a three-stream flamelet model, and CMMSED is used as closure model, thereby eliminating the need for presumed PDF-modeling. The model is applied to LES of a piloted turbulent jet flame with inhomogeneous inlets, and simulation results are compared with experiments. Comparisons with presumed PDF-methods are performed, and issues regarding resolution and conservation of the CMMSED method are examined. The author would like to acknowledge the support of funding from Stanford Graduate Fellowship.

  15. Effect of fuel type on equivalence ratio measurements using chemiluminescence in premixed flames (United States)

    Orain, Mikaël; Hardalupas, Yannis


    Local temporally-resolved measurements of chemiluminescent intensity from OH ∗, CH ∗ and C ∗2 radicals were obtained in premixed counterflow flames operating with propane and prevaporised fuels (isooctane, ethanol and methanol), for different equivalence ratios and strain rates. The results quantified independently the effects of fuel type, strain rate and equivalence ratio on chemiluminescent emissions from flames. The ability of chemiluminescent intensity from OH ∗, CH ∗ and C ∗2 radicals to indicate heat release rate depends strongly on fuel type. The intensity ratio OH ∗/CH ∗ has a monotonic decrease with equivalence ratio for all fuels and can be used to measure equivalence ratio of the reacting mixture. For propane and isooctane, the OH ∗/CH ∗ ratio remains independent of flame strain rate, whereas some dependence is observed for ethanol and methanol.

  16. Flowfield characterization of a piloted lean premixed injector by particle image velocimetry (United States)

    Berdanier, Catherine G. P.

    Limiting atmospheric pollution, especially nitrous oxides, is an important endeavor for aviation technology companies. Technology-driving regulations from the International Civil Aviation Organization's (ICAO) Committee of Aviation Environmental Protection (CAEP) standards spur the combustion research and development community to find innovative engine technologies to decrease emissions in the coming years. As engine technologies are developed, testing is necessary to verify combustion models and expected flow patterns. Optical diagnostics provide a unique opportunity to visualize flowfields in complex practical combustor systems. For this thesis, Particle Image Velocimetry (PIV) was employed to characterize the flowfield in a piloted lean premixed injector under non-combusting conditions. Planes of PIV data were acquired at five spanwise locations and two streamwise locations, at two different pressure conditions in order to characterize the flowfields and structures throughout the optically accessible flowpath. Average velocity maps and time-resolved vector fields at these planes were analyzed for this thesis.

  17. An experimental investigation of the interaction between a Karman vortex street and a premixed laminar flame (United States)

    Namer, I.


    The interaction of a premixed C2H4-air flame with a Karman vortex street was studied. Laser Doppler anemometry was used for velocity measurements and Rayleigh scattering was used to measure total gas density. A reference hot wire was used to enable phase-locked ensemble averaging to be performed on the data. The velocity measurements for vortex shedding cylinder Reynolds numbers indicated that the vortex street and, hence, the flow field upstream of the flame is deflected by the flame. This is due to the pressure drop across the flame which is necessary to accelerate the flow behind the flame. The vortices were not observed behind the flame. The combination of dilation and increased dissipation consumed the vortices. Density statistics obtained from Rayleigh scattering measurements were compared with predictions by the Bray-Moss-Libby (B-M-L) model which neglects intermediate states. Density fluctuations were overpredicted by the B-M-L model by a small amount.

  18. Dynamics of premixed flames in a narrow channel with a step-wise wall temperature

    Energy Technology Data Exchange (ETDEWEB)

    Kurdyumov, Vadim N. [Department of Energy, CIEMAT, Avda. Complutense 22, 28040 Madrid (Spain); Pizza, Gianmarco [Aerothermochemistry and Combustion Systems Laboratory, Swiss Federal Institute of Technology, Zurich CH-8092 (Switzerland); Combustion Research, Paul Scherrer Institute, Villigen CH-5232 (Switzerland); Frouzakis, Christos E. [Aerothermochemistry and Combustion Systems Laboratory, Swiss Federal Institute of Technology, Zurich CH-8092 (Switzerland); Mantzaras, John [Combustion Research, Paul Scherrer Institute, Villigen CH-5232 (Switzerland)


    The effect of channel height, inflow velocity and wall temperature on the dynamics and stability of unity Lewis number premixed flames in channels with specified wall temperature is investigated with steady and transient numerical simulations using a two-dimensional thermo-diffusive model. The simplified model is capable of capturing many of the transitions and the combustion modes observed experimentally and in direct numerical simulations in micro- and meso-scale channels, and indicates that the thermal flame/wall interaction is the mechanism leading to the observed flame instabilities. Finally, an ad-hoc one-dimensional model based on the flame-sheet approximation is tested in its capacity to reproduce some of the flame dynamics of the two-dimensional thermo-diffusive model. (author)

  19. Emissions measurements for a lean premixed propane/air system at pressures up to 30 atmospheres (United States)

    Roffe, G.


    A series of experiments was conducted in which the emissions of a lean premixed system of propane and air were measured at pressures of 5, 10, 20 and 30 atm in a flametube apparatus. Measurements were made for inlet temperatures between 600K and 1000K and combustor residence times from 1.0 to 3.0 msec. A schematic of the test rig is presented along with graphs showing emissions measurements for nitric oxide, carbon monoxide, and UHC as functions of bustor residence time for various equivalence ratios, entrance temperatures and pressures; typical behavior of emissions as a function of equivalence ratio for a fixed residence time. Correlations of nitric oxide emission index with adiabatic flame temperature for a fixed residence time of 2 msec and pressures from 5 to 30 atm; and adiabatic flame temperature corresponding to CO breakpoint conditions for 2 msec residence time as a function of inlet temperature.

  20. Identification of oxygenated ions in premixed flames of dimethyl ether and oxygen

    DEFF Research Database (Denmark)

    Frøsig Østergaard, L.; Egsgaard, H.; Hammerum, S.


    dimethyl ether, (CH3)(2)OH+. The flame-ion m/z 61 is a mixture of the trimethyloxonium ion, (CH3)(3)O+ and lesser amounts of protonated methyl formate and/or protonated ethyl methyl ether. The viability of an ionic mechanism to soot formation for dimethyl ether-oxygen flames is discussed on the background......The structure of characteristic flame-ions in premixed flames of dimethyl ether and oxygen was studied by ion-molecule reactions with ammonia and collision activation with argon. The results obtained show that the flame-ions m/z 45 and m/z 47 are the methoxymethyl cation, CH3OCH2+, and protonated...... of ions present in the dimethyl ether flames and the reactivity of the ions....

  1. Flow topologies in different regimes of premixed turbulent combustion: A direct numerical simulation analysis

    KAUST Repository

    Wacks, Daniel H.


    The distributions of flow topologies within the flames representing the corrugated flamelets, thin reaction zones, and broken reaction zone regimes of premixed turbulent combustion are investigated using direct numerical simulation data of statistically planar turbulent H-2-air flames with an equivalence ratio phi = 0.7. It was found that the diminishing influence of dilatation rate with increasing Karlovitz number has significant influences on the statistical behaviors of the first, second, and third invariants (i.e., P, Q, and R) of the velocity gradient tensor. These differences are reflected in the distributions of the flow topologies within the flames considered in this analysis. This has important consequences for those topologies that make dominant contributions to the scalar-turbulence interaction and vortex-stretching terms in the scalar dissipation rate and enstrophy transport equations, respectively. Detailed physical explanations are provided for the observed regime dependences of the flow topologies and their implications on the scalar dissipation rate and enstrophy transport.

  2. Cyclic Combustion Variations in Dual Fuel Partially Premixed Pilot-Ignited Natural Gas Engines

    Energy Technology Data Exchange (ETDEWEB)

    Srinivasan, K. K. [Mississippi State Univ., MS (United States). Dept. of Mechanical Engineering; Krishnan, S. R. [Mississippi State Univ., MS (United States). Dept. of Mechanical Engineering; Qi, Y. [Caterpillar, Inc., Peoria, IL (United States)


    Dual fuel pilot ignited natural gas engines are identified as an efficient and viable alternative to conventional diesel engines. This paper examines cyclic combustion fluctuations in conventional dual fuel and in dual fuel partially premixed low temperature combustion (LTC). Conventional dual fueling with 95% (energy basis) natural gas (NG) substitution reduces NOx emissions by almost 90%t relative to straight diesel operation; however, this is accompanied by 98% increase in HC emissions, 10 percentage points reduction in fuel conversion efficiency (FCE) and 12 percentage points increase in COVimep. Dual fuel LTC is achieved by injection of a small amount of diesel fuel (2-3 percent on an energy basis) to ignite a premixed natural gas₋air mixture to attain very low NOx emissions (less than 0.2 g/kWh). Cyclic variations in both combustion modes were analyzed by observing the cyclic fluctuations in start of combustion (SOC), peak cylinder pressures (Pmax), combustion phasing (Ca50), and the separation between the diesel injection event and Ca50 (termed "relative combustion phasing" ). For conventional dual fueling, as % NG increases, Pmax decreases, SOC and Ca50 are delayed, and cyclic variations increase. For dual fuel LTC, as diesel injection timing is advanced from 20° to 60° BTDC, the relative combustion phasing is identified as an important combustion parameter along with SoC, Pmax, and CaPmax. For both combustion modes, cyclic variations were characterized by alternating slow and fast burn cycles, especially at high %NG and advanced injection timings. Finally, heat release return maps were analyzed to demonstrate thermal management strategies as an effective tool to mitigate cyclic combustion variations, especially in dual fuel LTC.

  3. Study and modeling of finite rate chemistry effects in turbulent non-premixed flames (United States)

    Vervisch, Luc


    The development of numerical models that reflect some of the most important features of turbulent reacting flows requires information about the behavior of key quantities in well defined combustion regimes. In turbulent flames, the coupling between turbulent and chemical processes is so strong that it is extremely difficult to isolate the role played by one individual physical phenomenon. Direct numerical simulation (hereafter DNS) allows us to study in detail the turbulence-chemistry interaction in some restricted but completely defined situations. Globally, non-premixed flames are controlled by two limiting regimes: the fast chemistry case, where the turbulent flame can be pictured as a random distribution of local chemical equilibrium problems; and the slow chemistry case, where the chemistry integrates in time the turbulent fluctuations. The Damkoehler number, ratio of a mechanical time scale to chemical time scale, is used to distinguish between these regimes. Today most of the industrial computer codes are able to perform predictions in the hypothesis of local equilibrium chemistry using a presumed shape for the probability density function (pdt) of the conserved scalar. However, the finite rate chemistry situation is of great interest because industrial burners usually generate regimes in which, at some points, the flame is undergoing local extinction or at least non-equilibrium situations. Moreover, this variety of situations strongly influences the production of pollutants. To quantify finite rate chemistry effect, the interaction between a non-premixed flame and a free decaying turbulence is studied using DNS. The attention is focused on the dynamic of extinction, and an attempt is made to quantify the effect of the reaction on the small scale mixing process. The unequal diffusivity effect is also addressed. Finally, a simple turbulent combustion model based on the DNS observations and tractable in real flow configurations is proposed.

  4. A flame particle tracking analysis of turbulence–chemistry interaction in hydrogen–air premixed flames

    KAUST Repository

    Uranakara, Harshavardhana A.


    Interactions of turbulence, molecular transport, and energy transport, coupled with chemistry play a crucial role in the evolution of flame surface geometry, propagation, annihilation, and local extinction/re-ignition characteristics of intensely turbulent premixed flames. This study seeks to understand how these interactions affect flame surface annihilation of lean hydrogen–air premixed turbulent flames. Direct numerical simulations (DNSs) are conducted at different parametric conditions with a detailed reaction mechanism and transport properties for hydrogen–air flames. Flame particle tracking (FPT) technique is used to follow specific flame surface segments. An analytical expression for the local displacement flame speed (Sd) of a temperature isosurface is considered, and the contributions of transport, chemistry, and kinematics on the displacement flame speed at different turbulence-flame interaction conditions are identified. In general, the displacement flame speed for the flame particles is found to increase with time for all conditions considered. This is because, eventually all flame surfaces and their resident flame particles approach annihilation by reactant island formation at the end of stretching and folding processes induced by turbulence. Statistics of principal curvature evolving in time, obtained using FPT, suggest that these islands are ellipsoidal on average enclosing fresh reactants. Further examinations show that the increase in Sd is caused by the increased negative curvature of the flame surface and eventual homogenization of temperature gradients as these reactant islands shrink due to flame propagation and turbulent mixing. Finally, the evolution of the normalized, averaged, displacement flame speed vs. stretch Karlovitz number are found to collapse on a narrow band, suggesting that a unified description of flame speed dependence on stretch rate may be possible in the Lagrangian description.

  5. The i-V curve characteristics of burner-stabilized premixed flames: detailed and reduced models

    KAUST Repository

    Han, Jie


    The i-V curve describes the current drawn from a flame as a function of the voltage difference applied across the reaction zone. Since combustion diagnostics and flame control strategies based on electric fields depend on the amount of current drawn from flames, there is significant interest in modeling and understanding i-V curves. We implement and apply a detailed model for the simulation of the production and transport of ions and electrons in one-dimensional premixed flames. An analytical reduced model is developed based on the detailed one, and analytical expressions are used to gain insight into the characteristics of the i-Vcurve for various flame configurations. In order for the reduced model to capture the spatial distribution of the electric field accurately, the concept of a dead zone region, where voltage is constant, is introduced, and a suitable closure for the spatial extent of the dead zone is proposed and validated. The results from the reduced modeling framework are found to be in good agreement with those from the detailed simulations. The saturation voltage is found to depend significantly on the flame location relative to the electrodes, and on the sign of the voltage difference applied. Furthermore, at sub-saturation conditions, the current is shown to increase linearly or quadratically with the applied voltage, depending on the flame location. These limiting behaviors exhibited by the reduced model elucidate the features of i-V curves observed experimentally. The reduced model relies on the existence of a thin layer where charges are produced, corresponding to the reaction zone of a flame. Consequently, the analytical model we propose is not limited to the study of premixed flames, and may be applied easily to others configurations, e.g.~nonpremixed counterflow flames.

  6. Chemiluminescence-based multivariate sensing of local equivalence ratios in premixed atmospheric methane-air flames

    Energy Technology Data Exchange (ETDEWEB)

    Tripathi, Markandey M.; Krishnan, Sundar R.; Srinivasan, Kalyan K.; Yueh, Fang-Yu; Singh, Jagdish P.


    Chemiluminescence emissions from OH*, CH*, C2, and CO2 formed within the reaction zone of premixed flames depend upon the fuel-air equivalence ratio in the burning mixture. In the present paper, a new partial least square regression (PLS-R) based multivariate sensing methodology is investigated and compared with an OH*/CH* intensity ratio-based calibration model for sensing equivalence ratio in atmospheric methane-air premixed flames. Five replications of spectral data at nine different equivalence ratios ranging from 0.73 to 1.48 were used in the calibration of both models. During model development, the PLS-R model was initially validated with the calibration data set using the leave-one-out cross validation technique. Since the PLS-R model used the entire raw spectral intensities, it did not need the nonlinear background subtraction of CO2 emission that is required for typical OH*/CH* intensity ratio calibrations. An unbiased spectral data set (not used in the PLS-R model development), for 28 different equivalence ratio conditions ranging from 0.71 to 1.67, was used to predict equivalence ratios using the PLS-R and the intensity ratio calibration models. It was found that the equivalence ratios predicted with the PLS-R based multivariate calibration model matched the experimentally measured equivalence ratios within 7%; whereas, the OH*/CH* intensity ratio calibration grossly underpredicted equivalence ratios in comparison to measured equivalence ratios, especially under rich conditions ( > 1.2). The practical implications of the chemiluminescence-based multivariate equivalence ratio sensing methodology are also discussed.

  7. Flame kernel generation and propagation in turbulent partially premixed hydrocarbon jet

    KAUST Repository

    Mansour, Mohy S.


    Flame development, propagation, stability, combustion efficiency, pollution formation, and overall system efficiency are affected by the early stage of flame generation defined as flame kernel. Studying the effects of turbulence and chemistry on the flame kernel propagation is the main aim of this work for natural gas (NG) and liquid petroleum gas (LPG). In addition the minimum ignition laser energy (MILE) has been investigated for both fuels. Moreover, the flame stability maps for both fuels are also investigated and analyzed. The flame kernels are generated using Nd:YAG pulsed laser and propagated in a partially premixed turbulent jet. The flow field is measured using 2-D PIV technique. Five cases have been selected for each fuel covering different values of Reynolds number within a range of 6100-14400, at a mean equivalence ratio of 2 and a certain level of partial premixing. The MILE increases by increasing the equivalence ratio. Near stoichiometric the energy density is independent on the jet velocity while in rich conditions it increases by increasing the jet velocity. The stability curves show four distinct regions as lifted, attached, blowout, and a fourth region either an attached flame if ignition occurs near the nozzle or lifted if ignition occurs downstream. LPG flames are more stable than NG flames. This is consistent with the higher values of the laminar flame speed of LPG. The flame kernel propagation speed is affected by both turbulence and chemistry. However, at low turbulence level chemistry effects are more pronounced while at high turbulence level the turbulence becomes dominant. LPG flame kernels propagate faster than those for NG flame. In addition, flame kernel extinguished faster in LPG fuel as compared to NG fuel. The propagation speed is likely to be consistent with the local mean equivalence ratio and its corresponding laminar flame speed. Copyright © Taylor & Francis Group, LLC.

  8. Combustion characteristics of pulverized coal and air/gas premixed flame in a double swirl combustor

    Energy Technology Data Exchange (ETDEWEB)

    Kamal, M.M. [Ain Shams University, Cairo (Egypt). Faculty of Education


    An experimental work was performed to investigate the co-firing of pulverized coal and premixed gas/air streams in a double swirl combustor. The results showed that the NOx emissions are affected by the relative rates of thermal NOx formation and destruction via the pyrolysis of the fuel-N species in high temperature fuel-rich zones. Various burner designs were tested in order to vary the temperature history and the residence time across both coal and gas flames inside the furnace. It was found that by injecting the coal with a gas/air mixture as a combined central jet surrounded by a swirled air stream, a double flame envelope develops with high temperature fuel-rich conditions in between the two reaction zones such that the pyrolysis reactions to N{sub 2} are accelerated. A further reduction in the minimum NOx emissions, as well as in the minimum CO concentrations, was reported for the case where the coal particles are fed with the gas/air mixture in the region between the two swirled air streams. On the other hand, allocating the gas/air mixture around the swirled air-coal combustion zone provides an earlier contact with air and retards the NOx reduction mechanism in such a way that the elevated temperatures around the coal particles allow higher overall NOx emissions. The downstream impingement of opposing air jets was found more efficient than the impinging of particle non-laden premixed flames for effective NOx reduction. In both cases, there is an upstream flow from the stagnation region to the coal primary combustion region, but with the case of air impingement, the hot fuel-rich zone develops earlier. The optimum configuration was found by impinging all jets of air and coal-gas/air mixtures that pronounced minimum NOx and CO concentrations of 310 and 480ppm, respectively.

  9. Soot Formation in Laminar Premixed Ethylene/Air Flames at Atmospheric Pressure. Appendix G (United States)

    Xu, F.; Sunderland, P. B.; Faeth, G. M.; Urban, D. L. (Technical Monitor)


    Soot formation was studied within laminar premixed ethylene/air flames (C/O ratios of 0.78-0.98) stabilized on a flat-flame burner operating at atmospheric pressure. Measurements included soot volume fractions by both laser extinction and gravimetric methods, temperatures by multiline emission, soot structure by thermophoretic sampling and transmission electron microscopy, major gas species concentrations by sampling and gas chromatography, concentrations of condensable hydrocarbons by gravimetric sampling. and velocities by laser velocimetry. These data were used to find soot surface growth rates and primary soot particle nucleation rates along the axes of the flames. Present measurements of soot surface growth rates were correlated successfully by predictions based on typical hydrogen-abstraction/carbon-addition (HACA) mechanisms of Frenklach and co-workers and Colket and Hall. These results suavest that reduced soot surface growth rates with increasing residence time seen in the present and other similar flames were mainly caused by reduced rates of surface activation due to reduced H atom concentrations as temperatures decrease as a result of radiative heat losses. Primary soot particle nucleation rates exhibited variations with temperature and acetylene concentrations that were similar to recent observations for diffusion flames; however, nucleation rates in the premixed flames were significantly lower than in, the diffusion flames for reasons that still must be explained. Finally, predictions of yields of major gas species based on mechanisms from both Frenklach and co-workers and Leung and Lindstedt were in good agreement with present measurements and suggest that H atom concentrations (relevant to HACA mechanisms) approximate estimates based on local thermodynamic equilibrium in the present flames.

  10. Rayleigh/Raman/LIF measurements in a turbulent lean premixed combustor

    Energy Technology Data Exchange (ETDEWEB)

    Nandula, S.P.; Pitz, R.W. [Vanderbilt Univ., Nashville, TN (United States); Barlow, R.S. [Sandia National Labs., Livermore, CA (United States)] [and others


    Much of the industrial electrical generation capability being added worldwide is gas-turbine engine based and is fueled by natural gas. These gas-turbine engines use lean premixed (LP) combustion to meet the strict NO{sub x} emission standards, while maintaining acceptable levels of CO. In conventional, diffusion flame gas turbine combustors, large amount of NO{sub x} forms in the hot stoichiometric zones via the Zeldovich (thermal) mechanism. Hence, lean premixed combustors are rapidly becoming the norm, since they are specifically designed to avoid these hot stoichiometric zones and the associated thermal NO, However, considerable research and development are still required to reduce the NO{sub x} levels (25-40 ppmvd adjusted to 15% O{sub 2} with the current technology), to the projected goal of under 10 ppmvd by the turn of the century. Achieving this objective would require extensive experiments in LP natural gas (or CH{sub 4}) flames for understanding the combustion phenomena underlying the formation of the exhaust pollutants. Although LP combustion is an effective way to control NO{sub x}, the downside is that it increases the CO emissions. The formation and destruction of the pollutants (NO{sub x} and CO) are strongly affected by the fluid mechanics, the finite-rate chemistry, and their (turbulence-chemistry) interactions. Hence, a thorough understanding of these interactions is vital for controlling and reducing the pollutant emissions. The present research is contributing to this goal by providing a detailed nonintrusive laser based data set with good spatial and temporal resolutions of the pollutants (NO and CO) along with the major species, temperature, and OH. The measurements reported in this work, along with the existing velocity data on a turbulent LP combustor burning CH{sub 4}, would provide insight into the turbulence-chemistry interactions and their effect on pollutant formation.

  11. The Effect of Premixed Al-Cu Powder on the Stir Zone in Friction Stir Welding of AA3003-H18 (United States)

    Abnar, B.; Kazeminezhad, M.; Kokabi, A. H.


    In this research, 3-mm-thick AA3003-H18 non-heat-treatable aluminum alloy plates were joined by friction stir welding (FSW). It was performed by adding pure Cu and premixed Cu-Al powders at various rotational speeds of 800, 1000, and 1200 rpm and constant traveling speeds of 100 mm/min. At first, the powder was filled into the gap (0.2 or 0.4 mm) between two aluminum alloy plates, and then the FSW process was performed in two passes. The microstructure, mechanical properties, and formation of intermetallic compounds were investigated in both cases of using pure Cu and premixed Al-Cu powders. The results of using pure Cu and premixed Al-Cu powders were compared in the stir zone at various rotational speeds. The copper particle distribution and formation of Al-Cu intermetallic compounds (Al2Cu and AlCu) in the stir zone were desirable using premixed Al-Cu powder into the gap. The hardness values were significantly increased by formation of Al-Cu intermetallic compounds in the stir zone and it was uniform throughout the stir zone when premixed Al-Cu powder was used. Also, longitudinal tensile strength from the stir zone was higher when premixed Al-Cu powder was used instead of pure Cu powder.

  12. Continuous synthesis of drug-loaded nanoparticles using microchannel emulsification and numerical modeling: effect of passive mixing

    Directory of Open Access Journals (Sweden)

    Ortiz de Solorzano I


    Full Text Available Isabel Ortiz de Solorzano,1,2,* Laura Uson,1,2,* Ane Larrea,1,2,* Mario Miana,3 Victor Sebastian,1,2 Manuel Arruebo1,2 1Department of Chemical Engineering and Environmental Technologies, Institute of Nanoscience of Aragon (INA, University of Zaragoza, 2CIBER de Bioingeniería, Biomateriales y Nanomedicina (CIBER-BBN, Centro de Investigación Biomédica en Red, Madrid, 3ITAINNOVA, Instituto Tecnológico de Aragón, Materials & Components, Zaragoza, Spain *These authors contributed equally to this work Abstract: By using interdigital microfluidic reactors, monodisperse poly(d,l lactic-co-glycolic acid nanoparticles (NPs can be produced in a continuous manner and at a large scale (~10 g/h. An optimized synthesis protocol was obtained by selecting the appropriated passive mixer and fluid flow conditions to produce monodisperse NPs. A reduced NP polydispersity was obtained when using the microfluidic platform compared with the one obtained with NPs produced in a conventional discontinuous batch reactor. Cyclosporin, an immunosuppressant drug, was used as a model to validate the efficiency of the microfluidic platform to produce drug-loaded monodisperse poly(d,l lactic-co-glycolic acid NPs. The influence of the mixer geometries and temperatures were analyzed, and the experimental results were corroborated by using computational fluid dynamic three-dimensional simulations. Flow patterns, mixing times, and mixing efficiencies were calculated, and the model supported with experimental results. The progress of mixing in the interdigital mixer was quantified by using the volume fractions of the organic and aqueous phases used during the emulsification–evaporation process. The developed model and methods were applied to determine the required time for achieving a complete mixing in each microreactor at different fluid flow conditions, temperatures, and mixing rates. Keywords: microchannel emulsification, high-throughput synthesis, drug-loaded polymer

  13. Ultrasonic emulsification of parenteral valproic acid-loaded nanoemulsion with response surface methodology and evaluation of its stability. (United States)

    Tan, Suk Fei; Masoumi, Hamid Reza Fard; Karjiban, Roghayeh Abedi; Stanslas, Johnson; Kirby, Brian P; Basri, Mahiran; Basri, Hamidon Bin


    Response surface methodology (RSM) was used to optimize the formulation of a nanoemulsion for central delivery following parenteral administration. A mixture of medium-chain triglyceride (MCT) and safflower seed oil (SSO) was determined as a sole phase from the emulsification properties. Similarly, a natural surfactant (lecithin) and non-ionic surfactant (Tween 80) (ratio 1:2) were used in the formulation. A central composite design (CCD) with three-factor at five-levels was used to optimize the processing method of high energy ultrasonicator. Effects of pre-sonication ultrasonic intensity (A), sonication time (B), and temperature (C) were studied on the preparation of nanoemulsion loaded with valproic acid. Influence of the aforementioned specifically the effects of the ultrasonic processing parameters on droplet size and polydispersity index were investigated. From the analysis, it was found that the interaction between ultrasonic intensity and sonication time was the most influential factor on the droplet size of nanoemulsion formulated. Ultrasonic intensity (A) significantly affects the polydispersity index value. With this optimization method, a favorable droplet size of a nanoemulsion with reasonable polydispersity index was able to be formulated within a short sonication time. A valproic acid loaded nanoemulsion can be obtained with 60% power intensity for 15 min at 60 °C. Droplet size of 43.21±0.11 nm with polydispersity index of 0.211 were produced. The drug content was then increased to 1.5%. Stability study of nanoemulsion containing 1.5% of valproic acid had a good stability as there are no significant changes in physicochemical aspects such as droplet size and polydispersity index. With the characteristisation study of pH, viscosity, transmission electron microscope (TEM) and stability assessment study the formulated nanoemulsion has the potential to penetrate blood-brain barrier in the treatment of epilepsy.

  14. Effect of glycerol on formation, stability, and properties of vitamin-E enriched nanoemulsions produced using spontaneous emulsification. (United States)

    Saberi, Amir Hossein; Fang, Yuan; McClements, David Julian


    Oil-in-water nanoemulsions are finding increasing use as delivery systems to encapsulate lipophilic bioactive components in functional food, personal care, and pharmaceutical products. We investigated the influence of a water-soluble cosolvent (glycerol) on the formation, stability, and properties of vitamin E acetate-loaded nanoemulsions (VE-NEs) prepared by spontaneous emulsification. VE-NEs were formed by titration of a mixture of vitamin E acetate, carrier oil (MCT) and non-ionic surfactant (Tween 80) into an aqueous glycerol solution with continuous mixing. Cosolvent concentration had an appreciable effect on the particle size produced, with the smallest mean droplet diameters (dglycerol. Nanoemulsions (dglycerol levels. The turbidity of the NEs decreased at high glycerol concentrations due to the reduction in droplet size and refractive index contrast. The long-term stability of the VE-NEs was strongly influenced by glycerol concentration and storage temperature. VE-NEs containing 40% glycerol were relatively stable to droplet growth when stored at 5 and 20°C, but a rapid increase in droplet size and turbidity occurred during storage at 37°C. Temperature scanning experiments (20-80-20°C) indicated that a steep and irreversible increase in turbidity occurred during heating, which was around 70°C in the absence of glycerol and 60°C in the presence of 40% glycerol. Droplet instability was attributed to an increase in the rate of Ostwald ripening and/or coalescence as the temperature was increased, associated with dehydration of the non-ionic surfactant head-group leading to a reduction in phase inversion temperature. Dilution (100×) of VE-NEs containing glycerol with water considerably improved their stability to droplet growth, especially at high storage temperatures. This study provides important information about the effect of glycerol on the formation, stability and physical properties of VE-enriched NEs suitable for food, personal care, and

  15. 改性石蜡的乳化研究%Research on Emulsification of Modification Paraffin Wax

    Institute of Scientific and Technical Information of China (English)

    付雪; 诸林; 朱蠡庆


    以58#全精炼石蜡为原料,采用无催化技术进行氧化,氧化温度130℃,氧化时间2h,氧化后的石蜡物性与天然蜂蜡相近.将氧化后的石蜡进行乳化,研究了乳化剂用量、乳化温度、乳化时间、搅拌速度等参数对乳液粒径的影响.结果表明:在乳化温度为90℃,乳化时间为40 min,搅拌速度为1 000 r/min,使用硬脂酸与三乙醇胺复配的乳化剂时,获得了乳化效果最佳的乳化蜡.%The 58# fully refined paraffin wax was oxidized without catalyst,When reaction temperature is 130 ℃,oxidized time is 2 h,and the physical properties of reaction product are similar to the natural bee-wax.In the experiment of oxidized paraffin wax emulsion,the affecting parameters of emulsion particle size,such as variety and dosage of the emulsifier,emulsifying temperature,emulsifying time,stirring speed were investigated.Experimental results demonstrate the optimal parameter for paraffin emulsification,the best emulsified wax was obtained when emulsifying temperature is 90 ℃,and emulsifying time is 40 min,stirring speed 1 000 r/min,and the stearic acid and triethanolamine as compound emulsifier.

  16. [The application of artificial protein premixes for nutritive support of patients with chronic renal insufficiency, being treated by perinateal dialysis]. (United States)

    Pichugina, I S; Vetchinnikova, O N; Vereshchagina, V M; Gapparov, M M; Vatazin, A V


    As a result of a survey of 56 patients with chronic renal insufficiency, who undergone hemodialysis, it was established, that clinical condition of patients, biochemical and hematological blood indices as well as results of anthropometric research improve upon application of artificial balanced high-protein premixes -"Nutrinil" and "Nutrien-Nefro". Irrespective of way of administration - introperitoneal ("Nutrinil" solution) or enteral ("Nutrien-Nefro" mixture) protein-energetic insufficiency diminishes or totally disappears, body weight, fat and muscle content of the body weight, as well as indices of whole protein, albumine, lymphocytes, haemoglobin, pH approache the norm. Intraperitoneal way of administration of artificial protein premixes increase patients adherence to this procedure, though enteral way of their administration is more preferable from economic point of view.

  17. Effects of Non-Equilibrium Plasmas on Low-Pressure, Premixed Flames. Part 1: CH* Chemiluminescence, Temperature, and OH (United States)


    chemistry. Qualitative imaging of CH* chemiluminescence indicates that during plasma discharge, the luminous flame zone is shifted upstream towards...The same research group also has observed an increase in premixed methane/air flame blow-off velocities by more than a factor of two by the...resolution and rotational line-specific features . Due to the large number of test cases (see Table 2) and the desire for spatially-resolved

  18. Numerical simulation of nitrogen oxide formation in lean premixed turbulent H2/O2/N2 flames

    DEFF Research Database (Denmark)

    Day, Marc S.; Bell, John B.; Gao, Xinfeng


    Lean premixed hydrogen flames are thermodiffusively unstable and burn in cellular structures. Within these cellular structures the flame is locally enriched by preferential diffusion of hydrogen, leading to local hotspots that burn more intensely than an idealized flat steady flame at comparable...... examination of the reaction chemistry in these unsteady flames shows that at richer conditions the predominant path taken to convert nitrogen gas to nitric oxide is via NNH. For leaner flames a path through nitrous oxide becomes increasingly important....

  19. Extractive probe/TDLAS measurements of acetylene in atmospheric-pressure fuel-rich premixed methane/air flames

    Energy Technology Data Exchange (ETDEWEB)

    Gersen, S.; Mokhov, A.V.; Levinsky, H.B. [Laboratory for High Temperature Gas Kinetics, University of Groningen (Netherlands)


    The profiles of C{sub 2}H{sub 2} mole fractions were measured in flat atmospheric-pressure rich-premixed methane/air flames using microprobe gas sampling followed by tunable diode laser absorption spectroscopy (TDLAS), and compared the results with predictions of one-dimensional flame calculations. Acetylene concentrations are also determined by spontaneous Raman scattering to quantify possible uncertainties due to chemical reactions on the probe surface or acceleration of the combustion products into the probe.

  20. Petroleum and derivatives emulsification by bacterial consortium of sea meeds from Enseada do Forno-Armacao de Buzios (RJ); Emulsificacao de petroleo e seus derivados pelos consorcios bacterianos de algas da Enseada do Forno-Armacao dos Buzios (RJ)

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Frederico S. da; Crapez, Mirian A.C.; Krepsky, Natascha; Fontana, Luiz F.; Baptista-Neto, Jose Antonio [Universidade Federal Fluminense (UFF), Niteroi, RJ (Brazil)]. E-mail:


    Constant petroleum spill over natural habitats made necessary alternatives for environmental damage mitigation and recuperation. Bio surfactants can be used as an alternative for oil spill once they reduce surface oil tension, making them soluble in water or can make it available from the sediments. Bacterial consortia were isolated and bio amplified from Caulerpa (C), Laurencia (L) and Dictyota (D) algae biofilm. Bacterial carbon (CB); surface tension (TS); Emulsification index (E{sub 24}) and non-aqueous (A) and aqueous (B) emulsification of gasoline, kerosene and Arabian Light were estimated in 0, 7, 15 and 30 days of incubation. Results show a decrease of Laurencia and Caulerpa CB. However, Dictyota showed an increase at CB. Laurencia TS showed no significant reduction at days 7 and 15. For Dictyota and Caulerpa there was a increase at day 7 and reduction at day 15. E{sub 24} was higher than 70% for all the three substances and consortia tested. Laurencia bacteria consortia presented emulsification B for Arabian Light and emulsification A for gasoline and kerosene. Caulerpa consortia emulsified all compounds. All bacterial consortia isolated were surfactant producer, with emulsification A and B, being indicated for recuperation of environments contaminated with oil and its derivatives compounds. (author)

  1. Membranous nephropathy (United States)

    ... page: // Membranous nephropathy To use the sharing features on this page, please enable JavaScript. Membranous nephropathy is a kidney disorder that leads to changes ...

  2. Microencapsulation by Membrane Emulsification of Biophenols Recovered from Olive Mill Wastewaters

    Directory of Open Access Journals (Sweden)

    Emma Piacentini


    Full Text Available Biophenols are highly prized for their free radical scavenging and antioxidant activities. Olive mill wastewaters (OMWWs are rich in biophenols. For this reason, there is a growing interest in the recovery and valorization of these compounds. Applications for the encapsulation have increased in the food industry as well as the pharmaceutical and cosmetic fields, among others. Advancements in micro-fabrication methods are needed to design new functional particles with target properties in terms of size, size distribution, and functional activity. This paper describes the use of the membrane emulsification method for the fine-tuning of microparticle production with biofunctional activity. In particular, in this pioneering work, membrane emulsification has been used as an advanced method for biophenols encapsulation. Catechol has been used as a biophenol model, while a biophenols mixture recovered from OMWWs were used as a real matrix. Water-in-oil emulsions with droplet sizes approximately 2.3 times the membrane pore diameter, a distribution span of 0.33, and high encapsulation efficiency (98% ± 1% and 92% ± 3%, for catechol and biophenols, respectively were produced. The release of biophenols was also investigated.

  3. Experimental and Numerical Study of Jet Controlled Compression Ignition on Combustion Phasing Control in Diesel Premixed Compression Ignition Systems

    Directory of Open Access Journals (Sweden)

    Qiang Zhang


    Full Text Available In order to directly control the premixed combustion phasing, a Jet Controlled Compression Ignition (JCCI for diesel premixed compression ignition systems is investigated. Experiments were conducted on a single cylinder natural aspirated diesel engine without EGR at 3000 rpm. Numerical models were validated by load sweep experiments at fixed spark timing. Detailed combustion characteristics were analyzed based on the BMEP of 2.18 bar. The simulation results showed that the high temperature jets of reacting active radical species issued from the ignition chamber played an important role on the onset of combustion in the JCCI system. The combustion of diesel pre-mixtures was initiated rapidly by the combustion products issued from the ignition chamber. Moreover, the flame propagation was not obvious, similar to that in Pre-mixed Charge Compression Ignition (PCCI. Consequently, spark timing sweep experiments were conducted. The results showed a good linear relationship between spark timing in the ignition chamber and CA10 and CA50, which indicated the ability for direct combustion phasing control in diesel PCCI. The NOx and soot emissions gradually changed with the decrease of spark advance angle. The maximum reduction of NOx and soot were both over 90%, and HC and CO emissions were increased.

  4. The effect of stratification on premixed swirl-flame flashback by using porous center-body injection (United States)

    McCaslin, Andrew; Ranjan, Rakesh; Clemens, Noel


    Boundary layer flashback must be prevented in order to stably operate stationary gas turbines. One strategy to avoid flashback is to create equivalence-ratio stratification, such as by reducing the fuel/air ratio in the boundary layer below the flammability limit. Typically, stratification is achieved by using radially non-uniform fuel injection. The goal of the current study is to reduce the propensity of flashback in a premixed annular swirl combustor that uses a premix section with center-body. A porous metal center-body (10 micron pore size) is used to bleed air directly into the boundary layer and thus locally reduce the equivalence ratio. Planar laser-induced fluorescence imaging of anisole-seeded flow is carried out to assess the stratification in the flow. Time-resolved PIV and chemiluminescence imaging are used to investigate flashback at atmospheric pressure conditions. A comparative study between fully premixed and stratified flame flashback is conducted to determine how stratification influences flashback physics. This work was sponsored by the DOE NETL under Grant DEFC2611-FE0007107. This source of funding is gratefully acknowledged.

  5. CFD Studies of Combustion in Direct Injection Single Cylinder Diesel Engine Using Non-Premixed Combustion Model

    Directory of Open Access Journals (Sweden)

    S Gavudhama Karunanidhi


    Full Text Available In this study the simulation process of non-premixed combustion in a direct injection single cylinder diesel engine has been described. Direct injection diesel engines are used both in heavy duty vehicles and light duty vehicles. The fuel is injected directly into the combustion chamber. The fuel mixes with the high pressure air in the combustion chamber and combustion occurs. Due to the non-premixed nature of the combustion occurring in such engines, non-premixed combustion model of ANSYS FLUENT 14.5 can be used to simulate the combustion process. A 4-stroke diesel engine corresponds to one fuel injector hole without considering valves was modeled and combustion simulation process was studied. Here two types of combustion chambers were compared. Combustion studies of both chambers:- shallow depth and hemispherical combustion chambers were carried out. Emission characteristics of both combustion chambers had also been carried out. The obtained results are compared. It has been found that hemispherical combustion chamber is more efficient as it produces higher pressure and temperature compared to that of shallow depth combustion chamber. As the temperature increases the formation of NOx emissions and soot formation also get increased.

  6. The premixing and propagation phases of fuel-coolant interactions: a review of recent experimental studies and code developments

    Energy Technology Data Exchange (ETDEWEB)

    Antariksawan, A.R. [Reactor Safety Technology Research Center of BATAN (Indonesia); Moriyama, Kiyofumi; Park, Hyun-sun; Maruyama, Yu; Yang, Yanhua; Sugimoto, Jun


    A vapor explosion (or an energetic fuel-coolant interactions, FCIs) is a process in which hot liquid (fuel) transfers its internal energy to colder, more volatile liquid (coolant); thus the coolant vaporizes at high pressure and expands and does works on its surroundings. Traditionally, the energetic fuel-coolant interactions could be distinguished in subsequent stages: premixing (or coarse mixing), triggering, propagation and expansion. Realizing that better and realistic prediction of fuel-coolant interaction consequences will be available understanding the phenomenology in the premixing and propagation stages, many experimental and analytical studies have been performed during more than two decades. A lot of important achievements are obtained during the time. However, some fundamental aspects are still not clear enough; thus the works are directed to that direction. In conjunction, the model/code development is pursuit. This is aimed to provide a scaling tool to bridge the experimental results to the real geometries, e.g. reactor pressure vessel, reactor containment. The present review intends to collect the available information on the recent works performed to study the premixing and propagation phases. (author). 97 refs.

  7. Cellular burning in lean premixed turbulent hydrogen-air flames: Coupling experimental and computational analysis at the laboratory scale (United States)

    Day, M. S.; Bell, J. B.; Cheng, R. K.; Tachibana, S.; Beckner, V. E.; Lijewski, M. J.


    One strategy for reducing US dependence on petroleum is to develop new combustion technologies for burning the fuel-lean mixtures of hydrogen or hydrogen-rich syngas fuels obtained from the gasification of coal and biomass. Fuel-flexible combustion systems based on lean premixed combustion have the potential for dramatically reducing pollutant emissions in transportation systems, heat and stationary power generation. However, lean premixed flames are highly susceptible to fluid-dynamical combustion instabilities making robust and reliable systems difficult to design. Low swirl burners are emerging as an important technology for meeting design requirements in terms of both reliability and emissions for next generation combustion devices. In this paper, we present simulations of a lean, premixed hydrogen flame stabilized on a laboratory-scale low swirl burner. The simulations use detailed chemistry and transport without incorporating explicit models for turbulence or turbulence/chemistry interaction. Here we discuss the overall structure of the flame and compare with experimental data. We also use the simulation data to elucidate the characteristics of the turbulent flame interaction and how this impacts the analysis of experimental measurements.

  8. Firing membranes

    NARCIS (Netherlands)

    Kappert, Emiel Jan


    Thermal processing is commonly employed to alter the chemistry and microstructure of membrane layers. It can shape, strengthen, and give functionality to a membrane. A good understanding of the processes taking place during the thermal processing of a membrane material allows for optimization and tu

  9. Studies on the formation of polymeric nano-emulsions obtained via low-energy emulsification and their use as templates for drug delivery nanoparticle dispersions. (United States)

    Calderó, G; Montes, R; Llinàs, M; García-Celma, M J; Porras, M; Solans, C


    Ethylcellulose nanoparticles have been obtained from O/W nano-emulsions of the water/polyoxyethylene 10 oleyl ether/[ethyl acetate+4wt% ethylcellulose] system by low energy-energy emulsification at 25°C. Nano-emulsions with droplet sizes below 200nm and high kinetic stability were chosen for solubilising dexamethasone (DXM). Phase behaviour, conductivity and optical analysis studies of the system have evidenced for the first time that both, the polymer and the drug play a role on the structure of the aggregates formed along the emulsification path. Nano-emulsion formation may take place by both, phase inversion and self-emulsification. Spherical polymeric nanoparticles containing surfactant, showing sizes below 160nm have been obtained from the nano-emulsions by organic solvent evaporation. DXM loading in the nanoparticles was high (>90%). The release kinetics of nanoparticle dispersions with similar particle size and encapsulated DXM but different polymer to surfactant ratio were studied and compared to an aqueous DXM solution. Drug release from the nanoparticle dispersions was slower than from the aqueous solution. While the DXM solution showed a Fickian release pattern, the release behaviour from the nanoparticle dispersions was faster than that expected from a pure Fickian release. A coupled diffusion/relaxation model fitted the results very well, suggesting that polymer chains undergo conformational changes enhancing drug release. The contribution of diffusion and relaxation to drug transport in the nanoparticle dispersions depended on their composition and release time. Surfactant micelles present in the nanoparticle dispersion may exert a mild reservoir effect. The small particle size and the prolonged DXM release provided by the ethylcellulose nanoparticle dispersions make them suitable vehicles for controlled drug delivery applications.

  10. Micro-Mixing Lean-Premix System for Ultra-Low Emission Hydrogen/Syngas Combustion

    Energy Technology Data Exchange (ETDEWEB)

    Erlendur Steinthorsson; Brian Hollon; Adel Mansour


    The focus of this project was to develop the next generation of fuel injection technologies for environmentally friendly, hydrogen syngas combustion in gas turbine engines that satisfy DOE's objectives of reducing NOx emissions to 3 ppm. Building on Parker Hannifin's proven Macrolamination technology for liquid fuels, Parker developed a scalable high-performing multi-point injector that utilizes multiple, small mixing cups in place of a single conventional large-scale premixer. Due to the small size, fuel and air mix rapidly within the cups, providing a well-premixed fuel-air mixture at the cup exit in a short time. Detailed studies and experimentation with single-cup micro-mixing injectors were conducted to elucidate the effects of various injector design attributes and operating conditions on combustion efficiency, lean stability and emissions and strategies were developed to mitigate the impact of flashback. In the final phase of the program, a full-scale 1.3-MWth multi-cup injector was built and tested at pressures from 6.9bar (100psi) to 12.4bar (180psi) and flame temperatures up to 2000K (3150 F) using mixtures of hydrogen and natural gas as fuel with nitrogen and carbon dioxide as diluents. The injector operated without flash back on fuel mixtures ranging from 100% natural gas to 100% hydrogen and emissions were shown to be insensitive to combustor pressure. NOx emissions of 3-ppm were achieved at a flame temperature of 1750K (2690 F) when operating on a fuel mixture containing 50% hydrogen and 50% natural gas by volume with 40% nitrogen dilution and 1.5-ppm NOx was achieved at a flame temperature of 1680K (2564 F) using only 10% nitrogen dilution. NOx emissions of 3.5-ppm were demonstrated at a flame temperature of 1730K (2650 F) with only 10% carbon dioxide dilution. Finally, 3.6-ppm NOx emissions were demonstrated at a flame temperature over 1600K (2420 F) when operating on 100% hydrogen fuel with 30% carbon dioxide dilution. Superior

  11. Effect of Dimethyl Ether Mixing on Soot Size Distribution in Premixed Ethylene Flame

    KAUST Repository

    Li, Zepeng


    As a byproduct of incomplete combustion, soot attracts increasing attentions as extensive researches exploring serious health and environmental effects from soot particles. Soot emission reduction requires a comprehensive understanding of the mechanism for polycyclic aromatic hydrocarbons and of soot formation and aging processes. Therefore, advanced experimental techniques and numerical simulations have been conducted to investigate this procedure. In order to investigate the effects of dimethyl ether (DME) mixing on soot particle size distribution functions (PSDFs), DME was mixed in premixed ethylene/oxygen/argon at flames at the equivalence ratio of 2.0 with a range of mixing ratio from 0% to 30% of the total carbon fed. Two series of atmospheric pressure flames were tested in which cold gas velocity was varied to obtain different flame temperatures. The evolution of PSDFs along the centerline of the flame was determined by burner stabilized stagnation probe and scanning mobility particle sizer (SMPS) techniques, yielding the PSDFs for various separation distances above the burner surface. Meanwhile, the flame temperature profiles were carefully measured by a thermocouple and the comparison to that of simulated laminar premixed burner-stabilized stagnation flame was satisfactory. Additionally, to understand the chemical role of DME mixing in soot properties, characterization measurements were conducted on soot samples using thermo-gravimetric analysis (TGA) and elemental analysis (EA). Results of the evolution of PSDFs and soot volume fraction showed that adding DME into ethylene flame could reduce soot yield significantly. The addition of DME led to the decrease of both the soot nucleation rate and the particle mass growth rate. To explain the possible mechanism for the observation, numerical simulations were performed. Although DME addition resulted in the slight increase of methyl radicals from pyrolysis, the decrease in acetylene and propargyl radicals

  12. Correspondence Between Uncoupled Flame Macrostructures and Thermoacoustic Instability in Premixed Swirl-Stabilized Combustion

    KAUST Repository

    Taamallah, Soufien


    In this paper, we conduct an experimental investigation of a confined premixed swirl-stabilized dump combustor similar to those found in modern gas turbines. We operate the combustor with premixed methane-air in the lean range of equivalence ratio ϕ ∈ [0.5–0.75]. First, we observe different dynamic modes in the lean operating range, as the equivalence ratio is raised, confirming observations made previously in a similar combustor geometry but with a different fuel [1]. Next we examine the correspondence between dynamic mode transitions and changes in the mean flame configuration or macrostructure. We show that each dynamic mode is associated with a specific flame macrostructure. By modifying the combustor length without changing the underlying flow, the resonant frequencies of the geometry are altered allowing for decoupling the heat release fluctuations and the acoustic field, in a certain range of equivalence ratio. Mean flame configurations in the modified (short) combustor and for the same range of equivalence ratio are examined. It is found that not only the same sequence of flame configurations is observed in both combustors (long and short) but also that the set of equivalence ratio where transitions in the flame configuration occur is closely related to the onset of thermo-acoustic instabilities. For both combustor lengths, the flame structure changes at similar equivalence ratio whether thermo-acoustic coupling is allowed or not, suggesting that the flame configuration holds the key to understanding the onset of self-excited thermo-acoustic instability in this range. Finally, we focus on the flame configuration transition that was correlated with the onset of the first dynamically unstable mode ϕ ∈ [0.61–0.64]. Our analysis of this transition in the short, uncoupled combustor shows that it is associated with an intermittent appearance of a flame in the outer recirculation zone (ORZ). The spectral analysis of this “ORZ flame flickering”

  13. Membrane Biophysics

    CERN Document Server

    Ashrafuzzaman, Mohammad


    Physics, mathematics and chemistry all play a vital role in understanding the true nature and functioning of biological membranes, key elements of living processes. Besides simple spectroscopic observations and electrical measurements of membranes we address in this book the phenomena of coexistence and independent existence of different membrane components using various theoretical approaches. This treatment will be helpful for readers who want to understand biological processes by applying both simple observations and fundamental scientific analysis. It provides a deep understanding of the causes and effects of processes inside membranes, and will thus eventually open new doors for high-level pharmaceutical approaches towards fighting membrane- and cell-related diseases.

  14. Basal insulin therapy strategy is superior to premixed insulin therapy in the perioperative period blood glucose management

    Institute of Scientific and Technical Information of China (English)

    HUANG Qing-xian; LOU Fu-chen; WANG Ping; LIU Qian; WANG Kun; ZHANG Li; ZHU Lei


    Background The probability and risk of operations increase in patients with type 2 diabetes mellitus.For diabetic patients,blood glucose control is a key factor to improving the prognosis of surgery.During perioperative period,insulin therapy is usually advised to be used for surgical patients with type 2 diabetes.However,the insulin regimen which one is better remains controversial.In this study,we estimated the efficacy,safety and advantage of different insulin therapy strategy during perioperative period.Methods A total of 1086 cases of surgical patients with type 2 diabetes mellitus enrolled in the present study.According to the glucose level at admission,all patients were divided into relatively high glucose group (group A,fasting blood glucose (FBG) <13.9 mmol/L) and higher glucose group (group B,FBG >13.9 mmol/L).Patients in group A randomly accepted premixed insulin twice a day,or basal insulin plus oral medications,and were divided into group A1 and A2 respectively.Patients in group B randomly received premixed insulin twice daily,basal insulin plus oral hypoglycemic agents,or basal insulin plus preprandial insulin,and were divided into group B1,B2 and B3 respectively.The data of the preoperative preparation time,the daily doses of insulin used in different periods,postoperative incision healed installments,hypoglycemic events,the total hospitalization time,postoperative complications were all collected and statistically analyzed.Results Compared the main outcome measures in groups treated by premixed insulin therapy,both in preoperative preparation and postoperative period,the daily insulin dosage and the frequency of hypoglycemic events were decreased in groups treated by basal insulin therapy (P <0.05).The preoperative preparation time and the total hospitalization time in groups with basal insulin therapy were shorter than that in groups with premixed insulin therapy (P <0.05).The incision healing rate of stage Ⅰ,Ⅱ and Ⅲ among different

  15. Application of membrane technology to food industry; Shokuhin kogyo bun'ya ni okeru maku riyo

    Energy Technology Data Exchange (ETDEWEB)

    Kamata, T.; Nakajima, M. [Univ. of Tsukuba, Tsukuba (Japan)


    In the food industry, the membrane technologies are used practically for concentration of fruit juice and milk, etc. as reverse osmosis, for decolorization and desalination of liquid seasoning as nanofiltration, for bacteria elimination, etc. as micro-filtration, for recovery and purification of the protein as ultra-filtration, and for kitchen salt manufacturing and desalination as electrodialysis. In this paper, the state of utilization of membranes and the trend of recent research and development in the food industry are described. At first, a utilization of membranes in the dairy industry field, the fruit juice processing field, the alcoholic beverage field, the seasoning field, the honey purification field, the protein field and the fats and oils processing field are described. Next, as a film emulsification technology, a preparing process of W/O emulsion in which the pressurized water phase is penetrated through a hydrophobic membrane into the oil phase of the opposite side, and a preparing process of W/O emulsion in which the pressurized oil phase is penetrated through a hydrophilic film are described. The emulsification technology using the micro-channel made of the silicon chip, which is developed by the author is introduced. (NEDO)

  16. 3D velocity measurements in a premixed flame by tomographic PIV (United States)

    Tokarev, M. P.; Sharaborin, D. K.; Lobasov, A. S.; Chikishev, L. M.; Dulin, V. M.; Markovich, D. M.


    Tomographic particle image velocimetry (PIV) has become a standard tool for 3D velocity measurements in non-reacting flows. However, the majority of the measurements in flows with combustion are limited to small resolved depth compared to the size of the field of view (typically 1 : 10). The limitations are associated with inhomogeneity of the volume illumination and the non-uniform flow seeding, the optical distortions and errors in the 3D calibration, and the unwanted flame luminosity. In the present work, the above constraints were overcome for the tomographic PIV experiment in a laminar axisymmetric premixed flame. The measurements were conducted for a 1 : 1 depth-to-size ratio using a system of eight CCD cameras and a 200 mJ pulsed laser. The results show that camera calibration based on the triangulation of the tracer particles in the non-reacting conditions provided reliable accuracy for the 3D image reconstruction in the flame. The modification of the tomographic reconstruction allowed a posteriori removal of unwanted bright objects, which were located outside of the region of interest but affected the reconstruction quality. This study reports on a novel experience for the instantaneous 3D velocimetry in laboratory-scale flames by using tomographic PIV.

  17. Rich methane premixed laminar flames doped by light unsaturated hydrocarbons - Part I : allene and propyne

    CERN Document Server

    Gueniche, Hadj-Ali; Dayma, Guillaume; Fournet, Ren{é}; Battin-Leclerc, Fr{é}d{é}rique


    The structure of three laminar premixed rich flames has been investigated: a pure methane flame and two methane flames doped by allene and propyne, respectively. The gases of the three flames contain 20.9% (molar) of methane and 33.4% of oxygen, corresponding to an equivalence ratio of 1.25 for the pure methane flame. In both doped flames, 2.49% of C3H4 was added, corresponding to a ratio C3H4/CH4 of 12% and an equivalence ratio of 1.55. The three flames have been stabilized on a burner at a pressure of 6.7 kPa using argon as dilutant, with a gas velocity at the burner of 36 cm/s at 333 K. The concentration profiles of stable species were measured by gas chromatography after sampling with a quartz microprobe. Quantified species included carbon monoxide and dioxide, methane, oxygen, hydrogen, ethane, ethylene, acetylene, propyne, allene, propene, propane, 1,2-butadiene, 1,3-butadiene, 1-butene, isobutene, 1-butyne, vinylacetylene, and benzene. The temperature was measured using a PtRh (6%)-PtRh (30%) thermocou...

  18. Diffusion air effects on the soot axial distribution concentration in a premixed acetylene/air flame

    Energy Technology Data Exchange (ETDEWEB)

    Fassani, Fabio Luis; Santos, Alex Alisson Bandeira; Goldstein Junior, Leonardo [Universidade Estadual de Campinas, SP (Brazil). Faculdade de Engenharia Mecanica. Dept. de Engenharia Termica e de Fluidos]. E-mails:;;; Ferrari, Carlos Alberto [Universidade Estadual de Campinas, SP (Brazil). Inst. de Fisica. Dept. de Eletronica Quantica]. E-mail:


    Soot particles are produced during the high temperature pyrolysis or combustion of hydrocarbons. The emission of soot from a combustor, or from a flame, is determined by the competition between soot formation and its oxidation. Several factors affect these processes, including the type of fuel, the air-to-fuel ratio, flame temperature, pressure, and flow pattern. In this paper, the influence of the induced air diffusion on the soot axial distribution concentration in a premixed acetylene/air flame was studied. The flame was generated in a vertical axis burner in which the fuel - oxidant mixture flow was surrounded by a nitrogen discharge coming from the annular region between the burner tube and an external concentric tube. The nitrogen flow provided a shield that protected the flame from the diffusion of external air, enabling its control. The burner was mounted on a step-motor driven, vertical translation table. The use of several air-to-fuel ratios made possible to establish the sooting characteristics of this flame, by measuring soot concentration along the flame height with a non-intrusive laser light absorption technique. (author)

  19. Effect of pointed and diffused air injection on premixed flame confined in a Rijke tube

    Directory of Open Access Journals (Sweden)

    Nilaj N. Deshmukh


    Full Text Available The coupling between pressure fluctuations and unsteady heat release in a combustion systems results in acoustic oscillations inside the combustion system. These acoustic oscillations, when grow sufficiently, may cause serious structural damage thereby reducing the lifespan of jet engines, gas turbines, and industrial burners. The aim of the first part of study is to define acoustically stable and unstable regions. The second part is focused on studying the effect of change in pressure field near the flame on the amplitude and frequency of the oscillations of instability. This study is carried out for three-burner positions and equivalence ratio of 0.7 by varying heat supply and total flow rate. The results show two acoustically unstable regions for 0.1 and 0.2 burner positions and only one acoustically unstable region for 0.25 burner position. The effect of pointed injection and diffused injection over a premixed flame on the sound pressure level was studied. The results show for burner position of x/L = 0.2 there is 25 dB suppression is possible using pointed injection at higher total flow rate. The experiment of diffused injection shows sound amplification more than 12 dB was observed.

  20. Soot reduction under DC electric fields in counterflow non-premixed laminar ethylene flames

    KAUST Repository

    Park, Daegeun


    The effects of DC electric fields on non-premixed ethylene flames in a counterflow burner were studied experimentally with a focus on the reduction of soot particles. The experiment was conducted by connecting a high voltage terminal and a ground terminal to a lower (fuel) and upper (oxidizer) nozzle, respectively. We applied direct current (DC) potentials in a range of -5 kV < Vdc < 5 kV. Uniform electric fields were then generated in the gap between the two nozzles. The experimental conditions were selected to cover both soot formation (SF) and soot formation oxidation (SFO) flames. The flames subjected to the negative electric fields moved toward the fuel nozzle because of an ionic wind due to the Lorentz force acting on the positive ions in the flames. In addition, the yellow luminosity significantly decreased, indicating changes in the sooting characteristics. To analyze the sooting characteristics under the electric fields, planar laser induced incandescence (PLII) and fluorescence (PLIF) techniques were used to visualize the soot, polycyclic aromatic hydrocarbons (PAHs), and OH radicals. The sooting limits in terms of the fuel and oxygen mole fractions were measured. No substantial soot formation due to the effects of the DC electric fields for the tested range of voltages and reactant mole fractions could be identified. The detailed flame behaviors and sooting characteristics under the DC electric fields are discussed. Copyright © Taylor & Francis Group, LLC.

  1. The effect of nitrogen on biogas flame propagation characteristic in premix combustion (United States)

    Anggono, Willyanto; Suprianto, Fandi D.; Hartanto, Tan Ivan; Purnomo, Kenny; Wijaya, Tubagus P.


    Biogas is one of alternative energy and categorized as renewable energy. The main sources of biogas come from animal waste, garbage, and household waste that are organic waste. Primarily, over 50% of this energy contains methane (CH4). The other substances or inhibitors are nitrogen and carbon dioxide. Previously, carbon dioxide effect on biogas combustion is already experimented. The result shows that carbon dioxide reduces the flame propagation speed of biogas combustion. Then, nitrogen as an inhibitor obviously also brings some effects to the biogas combustion, flame propagation speed, and flame characteristics. Spark ignited cylinder is used for the premixed biogas combustion research. An acrylic glass is used as the material of this transparent cylinder chamber. The cylinder is filled with methane (CH4), oxygen (O2), and nitrogen (N2) with particular percentage. In this experiment, the nitrogen composition are set to 0%, 5%, 10%, 20%, 30%, 40%, and 50%. The result shows that the flame propagation speed is reduced in regard to the increased level of nitrogen. It can also be implied that nitrogen can decrease the biogas combustion rate.

  2. Measurements of Positively Charged Ions in Premixed Methane-Oxygen Atmospheric Flames

    KAUST Repository

    Alquaity, Awad B. S.


    Cations and anions are formed as a result of chemi-ionization processes in combustion systems. Electric fields can be applied to reduce emissions and improve combustion efficiency by active control of the combustion process. Detailed flame ion chemistry models are needed to understand and predict the effect of external electric fields on combustion plasmas. In this work, a molecular beam mass spectrometer (MBMS) is utilized to measure ion concentration profiles in premixed methane–oxygen argon burner-stabilized atmospheric flames. Lean and stoichiometric flames are considered to assess the dependence of ion chemistry on flame stoichiometry. Relative ion concentration profiles are compared with numerical simulations using various temperature profiles, and good qualitative agreement was observed for the stoichiometric flame. However, for the lean flame, numerical simulations misrepresent the spatial distribution of selected ions greatly. Three modifications are suggested to enhance the ion mechanism and improve the agreement between experiments and simulations. The first two modifications comprise the addition of anion detachment reactions to increase anion recombination at low temperatures. The third modification involves restoring a detachment reaction to its original irreversible form. To our knowledge, this work presents the first detailed measurements of cations and flame temperature in canonical methane–oxygen-argon atmospheric flat flames. The positive ion profiles reported here may be useful to validate and improve ion chemistry models for methane-oxygen flames.

  3. Effects of Radiative and Diffusive Transport Processes on Premixed Flames near Flammability Limits (United States)

    Abbud-Madrid, Angel; Ronney, Paul D.


    A study of the mechanisms of flammability limits and the dynamics of flame extinguishment in premixed gas flames is described, a novel feature of which is the use of diluent gases having a wide range of radiative and diffusive transport properties. This feature enables an assessment of the importance of volumetric heat losses and Lewis number effects on these mechanisms. Additionally, effects of flame dynamics and flame front curvature are studied by employing spherically expanding flames obtained in a microgravity environment whereby natural convection is eliminated. New diagnostics include chamber pressure measurements and the first reported species concentration measurements in a microgravity combustion experiment. The limit mechanisms and extinguishment phenomena are found to be strongly influenced by the combined effects of radiant heat loss, Lewis number and flame curvature. Two new and as yet not well understood phenomena are reported: 'double flames' in rich H2-O2-CO2 mixtures and an 'inverse flammability region' in rich C3H8-O2-CO2 mixtures.

  4. Impact of flame-wall interaction on premixed flame dynamics and transfer function characteristics

    KAUST Repository

    Kedia, K.S.


    In this paper, we numerically investigate the response of a perforated-plate stabilized laminar methane-air premixed flame to imposed inlet velocity perturbations. A flame model using detailed chemical kinetics mechanism is applied and heat exchange between the burner plate and the gas mixture is incorporated. Linear transfer functions, for low mean inlet velocity oscillations, are analyzed for different equivalence ratio, mean inlet velocity, plate thermal conductivity and distance between adjacent holes. The oscillations of the heat exchange rate at the top of the burner surface plays a critical role in driving the growth of the perturbations over a wide range of conditions, including resonance. The flame response to the perturbations at its base takes the form of consumption speed oscillations in this region. Flame stand-off distance increases/decreases when the flame-wall interaction strengthens/weakens, impacting the overall dynamics of the heat release. The convective lag between the perturbations and the flame base response govern the phase of heat release rate oscillations. There is an additional convective lag between the perturbations at the flame base and the flame tip which has a weaker impact on the heat release rate oscillations. At higher frequencies, the flame-wall interaction is weaker and the heat release oscillations are driven by the flame area oscillations. The response of the flame to higher amplitude oscillations are used to gain further insight into the mechanisms. © 2010 Published by Elsevier Inc. on behalf of The Combustion Institute. All rights reserved.

  5. Lagrangian analysis of premixed turbulent combustion in hydrogen-air flames (United States)

    Darragh, Ryan; Poludnenko, Alexei; Hamlington, Peter


    Lagrangian analysis has long been a tool used to analyze non-reacting turbulent flows, and has recently gained attention in the reacting flow and combustion communities. The approach itself allows one to separate local molecular effects, such as those due to reactions or diffusion, from turbulent advective effects along fluid pathlines, or trajectories. Accurate calculation of these trajectories can, however, be rather difficult due to the chaotic nature of turbulent flows and the added complexity of reactions. In order to determine resolution requirements and verify the numerical algorithm, extensive tests are described in this talk for prescribed steady, unsteady, and chaotic flows, as well as for direct numerical simulations (DNS) of non-reacting homogeneous isotropic turbulence. The Lagrangian analysis is then applied to DNS of premixed hydrogen-air flames at two different turbulence intensities for both single- and multi-step chemical mechanisms. Non-monotonic temperature and fuel-mass fraction evolutions are found to exist along trajectories passing through the flame brush. Such non-monotonicity is shown to be due to molecular diffusion resulting from large spatial gradients created by turbulent advection. This work was supported by the Air Force Office of Scientific Research (AFOSR) under Award No. FA9550-14-1-0273, and the Department of Defense (DoD) High Performance Computing Modernization Program (HPCMP) under a Frontier project award.

  6. Combustion chemistry of alcohols: Experimental and modeled structure of a premixed 2-methylbutanol flame

    KAUST Repository

    Lucassen, Arnas


    This paper presents a detailed investigation of 2-methylbutanol combustion chemistry in low-pressure premixed flames. This chemistry is of particular interest to study because this compound is potentially a lignocellulosic-based, next-generation biofuel. The detailed chemical structure of a stoichiometric low-pressure (25 Torr) flame was determined using flame-sampling molecular-beam mass spectrometry. A total of 55 species were identified and subsequently quantitative mole fraction profiles as function of distance from the burner surface were determined. In an independent effort, a detailed flame chemistry model for 2-methylbutanol was assembled based on recent knowledge gained from combustion chemistry studies for butanol isomers ([Sarathy et al. Combust. Flame 159 (6) (2012) 2028-2055]) and iso-pentanol (3-methylbutanol) [Sarathy et al. Combust. Flame 160 (12) (2013) 2712-2728]. Experimentally determined and modeled mole fraction profiles were compared to demonstrate the model\\'s capabilities. Examples of individual mole fraction profiles are discussed together with the most significant fuel consumption pathways to highlight the combustion chemistry of 2-methylbutanol. Discrepancies between experimental and modeling results are used to suggest areas where improvement of the kinetic model would be needed. © 2014.

  7. Determination of EDTA in feed and premix formulations by HPLC-DAD. (United States)

    Chiumiento, Francesco; D'Aloise, Antonio; Marchegiani, Francesca; Melai, Valeria


    A simple analytical method for the quantitative determination of ethylenediaminetetraacetic acid (EDTA) in feed and premix formulations was developed and validated. The method involves an extraction with an acidic ferric chloride solution, to quantitatively convert EDTA species in the samples into the Fe(III)-EDTA complex, and its subsequent detection by Ion-Pair-Reversed Phase-High Performance Liquid Chromatography-Diode Array Detection (IP-RP-HPLC-DAD). A robust validation procedure was performed according to the Decision 2002/657/EC at concentrations ranging from 25 to 100 mg kg(-1) on sample. Good recoveries (85.6-92.8%) were obtained; repeatability of the method was in the range of 1.3-8.0%, with an intermediate precision ranging from 6.0% to 8.6%, both of them expressed as relative standard deviation (RSD). No interfering species hindered the straightforward detection of EDTA. Hence, the proposed method can be adopted for an effective and rapid routine analysis of products for livestock.

  8. Effects of temperature, moisture and choline chloride on vitamin A stability in broiler premix

    Institute of Scientific and Technical Information of China (English)

    SUN Haixia; SHAN Anshan; SHI Baoming


    A 2×2×2 factorial design was adopted to study the effects of temperature, moisture and choline chloride on vitamin A stability in premix. The results indicated that temperature, moisture and choline chloride damaged vitamin A significantly. The regression equations of vitamin A disappearance rate and storage time were as follows: in room temperature (18±3) ℃, y=14.368Ln(x)+ 4.1425,R2=978; in high temperature (4℃), y=22.24Ln(x)+13.27, R2=O.9918; in low moisture (2%-3%), y=10.408Ln(x)+9.5418, R2=O.9322; in high moisture (8%-9%), y=26.199Ln(x)+7.8741, R2=0.9949; in the condition of choline chloride free, y=9.5125Ln(x)+ 8.9869, R2=O.9826; supplemented with choline chloride, y=27.094Ln(x)+8.4276, R2=0.9984. Temperature had highly significant interaction with moisure and choline chloride on destruction of vitamin A, respectively from the periods of two months storage. However, from the period of the first month storage, the interaction of moisture and choline chloride, as well as the interaction of temperature, moisture and choline destroyed vitamin A remarkably.

  9. Numerical Study of Pollutant Emissions in a Jet Stirred Reactor under Elevated Pressure Lean Premixed Conditions

    Directory of Open Access Journals (Sweden)

    Karim Mazaheri


    Full Text Available Numerical study of pollutant emissions (NO and CO in a Jet Stirred Reactor (JSR combustor for methane oxidation under Elevated Pressure Lean Premixed (EPLP conditions is presented. A Detailed Flow-field Simplified Chemistry (DFSC method, a low computational cost method, is employed for predicting NO and CO concentrations. Reynolds Averaged Navier Stokes (RANS equations with species transport equations are solved. Improved-coefficient five-step global mechanisms derived from a new evolutionary-based approach were taken as combustion kinetics. For modeling turbulent flow field, Reynolds Stress Model (RSM, and for turbulence chemistry interactions, finite rate-Eddy dissipation model are employed. Effects of pressure (3, 6.5 bars and inlet temperature (408–573 K over a range of residence time (1.49–3.97 ms are numerically examined. A good agreement between the numerical and experimental distribution of NO and CO was found. The effect of decreasing the operating pressure on NO generation is much more than the effect of increase in the inlet temperature.

  10. Numerical study of premixed HCCI engine combustion and its sensitivity to computational mesh and model uncertainties (United States)

    Kong, Song-Charng; Reitz, Rolf D.


    This study used a numerical model to investigate the combustion process in a premixed iso-octane homogeneous charge compression ignition (HCCI) engine. The engine was a supercharged Cummins C engine operated under HCCI conditions. The CHEMKIN code was implemented into an updated KIVA-3V code so that the combustion could be modelled using detailed chemistry in the context of engine CFD simulations. The model was able to accurately simulate the ignition timing and combustion phasing for various engine conditions. The unburned hydrocarbon emissions were also well predicted while the carbon monoxide emissions were under predicted. Model results showed that the majority of unburned hydrocarbon is located in the piston-ring crevice region and the carbon monoxide resides in the vicinity of the cylinder walls. A sensitivity study of the computational grid resolution indicated that the combustion predictions were relatively insensitive to the grid density. However, the piston-ring crevice region needed to be simulated with high resolution to obtain accurate emissions predictions. The model results also indicated that HCCI combustion and emissions are very sensitive to the initial mixture temperature. The computations also show that the carbon monoxide emissions prediction can be significantly improved by modifying a key oxidation reaction rate constant.

  11. Hydrodynamic aspects of premixed flame stripes in two-dimensional stagnation-point flows

    Energy Technology Data Exchange (ETDEWEB)

    Lee, H.; Sohrab, S.H. [Northwestern Univ., Evanston, IL (United States). Dept. of Mechanical Engineering


    The behavior of cellular premixed flames of rich butane-air in the two-dimensional stagnation-point flow configuration has been investigated. It is found that the stretching of the cellular flame results in the alignment f the ridge (extinction) and the trough (combustion) zones of the individual cells such as to form a series of parallel flame stripes. The number of flame stripes as a function of the equivalence ratio for three different mean velocities at the nozzle have been determined. Through the introduction of a generalized form of the stream function periodic velocity fields are obtained as the exact solutions of the Euler equation for the nonreactive finite-jet two-dimensional stagnation flow. The predicted periodic velocity profiles are confirmed by the experimental observation of the streamlines in nonreactive flow made visible by laser-sheet lighting. The observed average size of the flame stripes is found to be in good agreement with the predicted value. Similar periodic velocity profiles are also obtained for the viscous flow within the laminar boundary layer by treatment of the unsteady vorticity equation first described by Taylor. The results support an earlier prediction by Williams that cellular flame structures that are affected mainly by diffusive-thermal phenomena may in fact be initiated by the hydrodynamic instability.

  12. Interplay of Darrieus-Landau instability and weak turbulence in premixed flame propagation (United States)

    Creta, Francesco; Lamioni, Rachele; Lapenna, Pasquale Eduardo; Troiani, Guido


    In this study we investigate, both numerically and experimentally, the interplay between the intrinsic Darrieus-Landau (DL) or hydrodynamic instability of a premixed flame and the moderately turbulent flow field in which the flame propagates. The objective is threefold: to establish, unambiguously, through a suitably defined marker, the presence or absence of DL-induced effects on the turbulent flame, to quantify the DL effects on the flame propagation and morphology and, finally, to asses whether such effects are mitigated or suppressed as the turbulence intensity is increased. The numerical simulations are based on a deficient reactant model which lends itself to a wealth of results from asymptotic theory, such as the determination of stability limits. The skewness of the flame curvature probability density function is identified as an unambiguous morphological marker for the presence or absence of DL effects in a turbulent environment. In addition, the turbulent propagation speed is shown to exhibit a distinct dual behavior whereby it is noticeably enhanced in the presence of DL instability while it is unchanged otherwise. Furthermore, increasing the turbulence intensity is found to be mitigating with respect to DL-induced effects such as the mentioned dual behavior which disappears at higher intensities. Experimental propane and/or air Bunsen flames are also investigated, utilizing two distinct diameters, respectively, above and below the estimated DL cutoff wavelength. Curvature skewness is still clearly observed to act as a marker for DL instability while the turbulent propagation speed is concurrently enhanced in the presence of the instability.

  13. Control of the low-load region in partially premixed combustion (United States)

    Ingesson, Gabriel; Yin, Lianhao; Johansson, Rolf; Tunestal, Per


    Partially premixed combustion (PPC) is a low temperature, direct-injection combustion concept that has shown to give promising emission levels and efficiencies over a wide operating range. In this concept, high EGR ratios, high octane-number fuels and early injection timings are used to slow down the auto-ignition reactions and to enhance the fuel and are mixing before the start of combustion. A drawback with this concept is the combustion stability in the low-load region where a high octane-number fuel might cause misfire and low combustion efficiency. This paper investigates the problem of low-load PPC controller design for increased engine efficiency. First, low-load PPC data, obtained from a multi-cylinder heavy- duty engine is presented. The data shows that combustion efficiency could be increased by using a pilot injection and that there is a non-linearity in the relation between injection and combustion timing. Furthermore, intake conditions should be set in order to avoid operating points with unfavourable global equivalence ratio and in-cylinder temperature combinations. Model predictive control simulations were used together with a calibrated engine model to find a gas-system controller that fulfilled this task. The findings are then summarized in a suggested engine controller design. Finally, an experimental performance evaluation of the suggested controller is presented.

  14. Direct numerical simulations of turbulent non-premixed methane-air flames modeled with reduced kinetics (United States)

    Card, J. M.; Chen, J. H.; Day, M.; Mahalingam, S.


    Turbulent non-premixed stoichiometric methane-air flames modeled with reduced kinetics have been studied using the direct numerical simulation approach. The simulations include realistic chemical kinetics, and the molecular transport is modeled with constant Lewis numbers for individual species. The effect of turbulence on the internal flame structure and extinction characteristics of methane-air flames is evaluated. Consistent with earlier DNS with simple one-step chemistry, the flame is wrinkled and in some regions extinguished by the turbulence, while the turbulence is weakened in the vicinity of the flame due to a combination of dilatation and an increase in kinematic viscosity. Unlike previous results, reignition is observed in the present simulations. Lewis number effects are important in determining the local stoichiometry of the flame. The results presented in this work are preliminary but demonstrate the feasibility of incorporating reduced kinetics for the oxidation of methane with direct numerical simulations of homogeneous turbulence to evaluate the limitations of various levels of reduction in the kinetics and to address the formation of thermal and prompt NO(x).

  15. Dynamics of bluff-body-stabilized lean premixed syngas flames in a meso-scale channel

    KAUST Repository

    Lee, Bok Jik


    Direct numerical simulations are conducted to investigate the dynamics of lean premixed syngas flames stabilized by a bluff-body in a meso-scale channel at near blow-off conditions, in order to provide fundamental insights into the physical mechanisms responsible for the critical phenomena. Flames in a two-dimensional meso-scale channel with a square flame holder are adopted as the model configuration, and a syngas mixture at an equivalence ratio of 0.5 with the CO:H ratio of 1 is considered. As the inlet velocity is increased, the initially stable steady flames undergo a transition to an unsteady mode of regular asymmetric fluctuation. When the inlet velocity is further increased, the flame is eventually blown off. Between the regular fluctuation mode and blow-off limit, there exists a narrow range of the inlet velocity where the flames exhibit periodic local extinction and recovery. Approaching further to the blow-off limit, the recovery mode fails to occur but the flame survives as a short kernel attached to the base of the bluff-body, until it is completely extinguished as the attached flames are gradually shrunk towards the bluff-body. The results are systematically compared with the hydrogen flame results reported in our earlier study. Examination of the characteristic time scales of relevant processes provided understanding of key mechanisms responsible for the observed differences, thereby allowing improved description of the local extinction and re-ignition dynamics that are critical to flame stabilization.

  16. Dynamics of flow-soot interaction in wrinkled non-premixed ethylene-air flames (United States)

    Arias, Paul G.; Lecoustre, Vivien R.; Roy, Somesh; Luo, Zhaoyu; Haworth, Daniel C.; Lu, Tianfeng; Trouvé, Arnaud; Im, Hong G.


    A two-dimensional simulation of a non-premixed ethylene-air flame was conducted by employing a detailed gas-phase reaction mechanism considering polycyclic aromatic hydrocarbons, an aerosol-dynamics-based soot model using a method of moments with interpolative closure, and a grey gas and soot radiation model using the discrete transfer method. Interaction of the sooting flame with a prescribed decaying random velocity field was investigated, with a primary interest in the effects of velocity fluctuations on the flame structure and the associated soot formation process for a fuel-strip configuration and a composition with mature soot growth. The temporally evolving simulation revealed a multi-layered soot formation process within the flame, at a level of detail not properly described by previous studies based on simplified soot models utilizing acetylene or naphthalene precursors for initial soot inception. The overall effect of the flame topology on the soot formation was found to be consistent with previous experimental studies, while a unique behaviour of localised strong oxidation was also noted. The imposed velocity fluctuations led to an increase of the scalar dissipation rate in the sooting zone, causing a net suppression in the soot production rate. Considering the complex structure of the soot formation layer, the effects of the imposed fluctuations vary depending on the individual soot reactions. For the conditions under study, the soot oxidation reaction was identified as the most sensitive to the fluctuations and was mainly responsible for the local suppression of the net soot production.

  17. Supplementary Material for: Measurements of Positively Charged Ions in Premixed Methane-Oxygen Atmospheric Flames

    KAUST Repository

    Alquaity, Awad B. S.


    Cations and anions are formed as a result of chemi-ionization processes in combustion systems. Electric fields can be applied to reduce emissions and improve combustion efficiency by active control of the combustion process. Detailed flame ion chemistry models are needed to understand and predict the effect of external electric fields on combustion plasmas. In this work, a molecular beam mass spectrometer (MBMS) is utilized to measure ion concentration profiles in premixed methane–oxygen argon burner-stabilized atmospheric flames. Lean and stoichiometric flames are considered to assess the dependence of ion chemistry on flame stoichiometry. Relative ion concentration profiles are compared with numerical simulations using various temperature profiles, and good qualitative agreement was observed for the stoichiometric flame. However, for the lean flame, numerical simulations misrepresent the spatial distribution of selected ions greatly. Three modifications are suggested to enhance the ion mechanism and improve the agreement between experiments and simulations. The first two modifications comprise the addition of anion detachment reactions to increase anion recombination at low temperatures. The third modification involves restoring a detachment reaction to its original irreversible form. To our knowledge, this work presents the first detailed measurements of cations and flame temperature in canonical methane–oxygen-argon atmospheric flat flames. The positive ion profiles reported here may be useful to validate and improve ion chemistry models for methane-oxygen flames.

  18. Markstein Numbers of Negatively-Stretched Premixed Flames: Microgravity Measurements and Computations (United States)

    Ibarreta, Alfonso F.; Driscoll, James F.; Feikema, Douglas A.; Salzman, Jack (Technical Monitor)


    The effect of flame stretch, composed of strain and curvature, plays a major role in the propagation of turbulent premixed flames. Although all forms of stretch (positive and negative) are present in turbulent conditions, little research has been focused on the stretch due to curvature. The present study quantifies the Markstein number (which characterizes the sensitivity of the flame propagation speed to the imposed stretch rate) for an inwardly-propagating flame (IPF). This flame is of interest because it is negatively stretched, and is subjected to curvature effects alone, without the competing effects of strain. In an extension of our previous work, microgravity experiments were run using a vortex-flame interaction to create a pocket of reactants surrounded by an IPF. Computations using the RUN-1DL code of Rogg were also performed in order to explain the measurements. It was found that the Markstein number of an inwardly-propagating flame, for both the microgravity experiment and the computations, is significantly larger than that of an outwardly-propagating flame. Further insight was gained by running the computations for the simplified (hypothetical) cases of one step chemistry, unity Lewis number, and negligible heat release. Results provide additional evidence that the Markstein numbers associated with strain and curvature have different values.

  19. Modeling and numerical simulation of a pilot-stabilized turbulent premixed flame

    Energy Technology Data Exchange (ETDEWEB)

    Benarous, Abdallah [Hassiba Benbouali University, Chlef (Algeria); Abdelkrim, Liazid [National Polytechnic School, Oran (Algeria); Karmed, Djamel [Poitiers University, Chasseneuil Cedex (France)


    The present paper is devoted to the numerical modeling of turbulent reactive flows subjected to spatial variations of equivalence ratio. In such situations, the description of the local thermochemistry requires at least two variables. The mixture fraction and the fuel mass fraction are respectively chosen to describe the composition of the fresh mixture and the chemical reaction progress. In the present contribution, a generalization of the Libby-Williams (LW) approach to four delta probability density function (Pdf) is presented. Transport equations for the first and second-order (variance) of mean scalar quantities are numerically solved. Moreover, the so-called LW-P model solves an additional transport equation for the cross-correlation between the reactive and the passive scalars. The model is applied to the calculation of a turbulent lean-premixed flow of methane and air stabilized by a near-stoichiometric pilot-flame. Numerical results regarding flow dynamics and flame structure are compared with the experimental data of a laboratory-scale burner-chamber device.

  20. Pulsed Current-Voltage-Induced Perturbations of a Premixed Propane/Air Flame

    Directory of Open Access Journals (Sweden)

    Jacob. B. Schmidt


    Full Text Available The effect of millisecond wide sub-breakdown pulsed voltage-current induced flow perturbation has been measured in premixed laminar atmospheric pressure propane/air flame. The flame equivalence ratios were varied from 0.8 to 1.2 with the flow speeds near 1.1 meter/second. Spatio-temporal flame structure changes were observed through collection of CH (A-X and OH (A-X chemiluminescence and simultaneous spontaneous Raman scattering from N2. This optical collection scheme allows us to obtain a strong correlation between the measured gas temperature and the chemiluminescence intensity, verifying that chemiluminescence images provide accurate measurements of flame reaction zone structure modifications. The experimental results suggest that the flame perturbation is caused by ionic wind originating only from the radial positive space-charge distribution in/near the cathode fall. A net momentum transfer acts along the annular space discharge distribution in the reaction zone at or near the cathode fall which modifies the flow field near the cathodic burner head. This radially inward directed body force appears to enhance mixing similar to a swirl induced modification of the flame structure. The flame fluidic response exhibit a strong dependence on the voltage pulse width ≤10 millisecond.

  1. Direct numerical simulation of stationary lean premixed methane-air flames under intense turbulence

    Energy Technology Data Exchange (ETDEWEB)

    Sankaran, Ramanan [ORNL; Hawkes, Evatt R [Sandia National Laboratories (SNL); Yoo, Chun S [Sandia National Laboratories (SNL); Chen, Jacqueline H [Sandia National Laboratories (SNL); Lu, Tianfeng [Princeton University; Law, Chung K [Princeton University


    Direct numerical simulation of a three-dimensional spatially- developing turbulent Bunsen flame has been performed at three different turbulence intensities. The simulations are performed using a reduced methane-air chemical mechanism which is specifically tailored for the lean premixed conditions simulated here. A planar-jet turbulent Bunsen flame configuration is used in which turbulent preheated methane-air mixture at 0.7 equivalence ratio issues through a central jet and is surrounded by a hot laminar coflow of burned products. The turbulence characteristics at the jet inflow are selected such that combustion occurs in the thin reaction zones (TRZ) regime. At the lowest turbulence intensity the conditions fall on the boundary between the TRZ regime and the corrugated flamelet regime. At the highest turbulence intensity the conditions correspond to the boundary between the TRZ regime and the broken reaction zones regime. The data from the three simulations is analyzed to understand the effect of turbulent stirring on the flame structure and thickness. Statistical analysis of the data shows that the thermal preheat layer of the flame is thickened due to the action of turbulence, but the reaction zone is not significantly affected.

  2. Electron temperature measurement in a premixed flat flame using the double probe method

    Energy Technology Data Exchange (ETDEWEB)

    Wild, J.; Kudrna, P.; Tichy, M. [Charles University in Prague, Faculty of Mathematics and Physics, V Holesovickach 2, 180 00 Praha 8 (Czech Republic); Nevrly, V.; Strizik, M.; Bitala, P.; Filipi, B. [VSB - Technical University of Ostrava, Faculty of Safety Engineering, Lumirova 13, 700 30 Ostrava-Vyskovice (Czech Republic); Zelinger, Z. [J. Heyrovsky Institute of Physical Chemistry, v.v.i., Academy of Sciences of the Czech Republic, Dolejskova 3, 182 23 Praha 8 (Czech Republic)


    The electron temperatures T{sub e} were measured using a double probe in a premixed methane flame produced by a calibration burner according to Hartung et al. The experiment was performed at atmospheric pressure. In contrast to other authors, we have managed to find typical nonlinearities corresponding to the retarding electron current region and to calculate electron temperatures using a suitable fit on the basis of the measured characteristics. A Pt-Rh thermocouple was used to measure temperatures T{sub h} corresponding to ''heavy'' species. Our results indicate that the flame plasma can be considered to be weakly non-isothermic - T{sub e} = (2400-4000) K, T{sub h} = (1400-1600) K. On the basis of measurement of the saturated ion current, the number density of the charged particles was estimated at (0.3-3.8) . 10{sup 17} m{sup -3}. The trends in T{sub e} and T{sub h} in dependence on the positions of the probes and thermocouple in the flame differ substantially; this fact has not yet been explained (copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  3. Effect of an external electric field on the propagation velocity of premixed flames

    KAUST Repository

    Sánchez-Sanz, Mario


    © 2014 The Combustion Institute. Published by Elsevier Inc. All rights reserved. There have been many experimental investigations into the ability of electric fields to enhance combustion by acting upon ion species present in flames [1]. In this work, we examine this phenomenon using a one-dimensional model of a lean premixed flame under the influence of a longitudinal electric field. We expand upon prior two-step chain-branching reaction laminar models with reactions to model the creation and consumption of both a positively-charged radical species and free electrons. Also included are the electromotive force in the conservation equation for ion species and the electrostatic form of the Maxwell equations in order to resolve ion transport by externally applied and internally induced electric fields. The numerical solution of these equations allows us to compute changes in flame speed due to electric fields. Further, the variation of key kinetic and transport parameters modifies the electrical sensitivity of the flame. From changes in flame speed and reactant profiles we are able to gain novel, valuable insight into how and why combustion can be controlled by electric fields.

  4. Asymptotic Analysis of Transport Properties and Burning Velocities for Premixed Hydrocarbon Flames

    Institute of Scientific and Technical Information of China (English)

    J.Y. Law; H.K. Ma


    Based on premixed flame, the theoretical model of transport properties with temperature variation was established inside a preheated zone. Lewis number of the deficient-to-stoichiometric hydrocarbon/air mixture has been theoretically predicted over a wide range of preheated temperature. These predictions are compared with the experimental data on transport properties that exist in the literature. The response of the burning velocity to flame stretch can be parameterized by the laminar flame speed and Markstein length. Therefore, if the laminar flame speed and Markstein number could be accurately simulated by using an analytic expression of characterized temperature, equivalence ratio, and Lewis number, the results are applicable to the prediction of methane,acetylene, ethylene, ethane, and propane flames. Expanding previous studies on the extinction ofpremixed flames under the influence of stretch and incomplete reaction, the results were further classified and rescaled. Finally, it could be inferred that parameter Pq, the rescaled extinction Karlovitz number could be used to explain the degree of flame quench.

  5. Impact of chemical kinetic model reduction on premixed turbulent flame characteristics (United States)

    Fillo, Aaron; Niemeyer, Kyle


    The use of detailed chemical kinetic models for direct numerical simulations (DNS) is prohibitively expensive. Current best practice for the development of reduced models is to match laminar burning parameters such as flame speed, thickness, and ignition delay time to predictions of the detailed chemical kinetic models. Prior studies using reduced models implicitly assumed that matching the homogeneous and laminar properties of the detailed model will result in similar behavior in a turbulent environment. However, this assumption has not been tested. Fillo et al. recently demonstrated experimentally that real jet fuels with similar chemistry and laminar burning parameters exhibit different turbulent flame speeds under the same flow conditions. This result raises questions about the validity of current best practices for the development of reduced chemical kinetic models for turbulent DNS. This study will investigate the validity of current best practices. Turbulent burning parameters, including flame speed, thickness, and stretch rate, will be compared for three skeletal mechanisms of the Princeton POSF 4658 mechanism, reduced using current best practice methods. DNS calculations of premixed, high-Karlovitz flames will be compared to determine if these methods are valid. This material is based upon work supported by the National Science Foundation under Grant No. 1314109-DGE.

  6. The flame anchoring mechanism and associated flow structure in bluff-body stabilized lean premixed flames (United States)

    Michaels, Dan; Shanbhogue, Santosh; Ghoniem, Ahmed


    We present numerical analysis of a lean premixed flame anchoring on a heat conducting bluff-body. Different mixtures of CH4/H2/air are analyzed in order to systematically vary the burning velocity, adiabatic flame temperature and extinction strain rate. The study was motivated by our experimental measurements in a step combustor which showed that both the recirculation zone length and stability map under acoustically coupled conditions for different fuels and thermodynamic conditions collapse using the extinction strain rate. The model fully resolves unsteady two-dimensional flow with detailed chemistry and species transport, and without artificial flame anchoring boundary conditions. The model includes a low Mach number operator-split projection algorithm, coupled with a block-structured adaptive mesh refinement and an immersed boundary method for the solid body. Calculations reveal that the recirculation zone length correlates with the flame extinction strain rate, consistent with the experimental evidence. It is found that in the vicinity of the bluff body the flame is highly stretched and its leading edge location is controlled by the reactants combustion characteristics under high strain. Moreover, the flame surface location relative to the shear layer influences the vorticity thus impacting the velocity field and the recirculation zone. The study sheds light on the experimentally observed collapse of the combustor dynamics using the reactants extinction strain rate.

  7. Large scale Direct Numerical Simulation of premixed turbulent jet flames at high Reynolds number (United States)

    Attili, Antonio; Luca, Stefano; Lo Schiavo, Ermanno; Bisetti, Fabrizio; Creta, Francesco


    A set of direct numerical simulations of turbulent premixed jet flames at different Reynolds and Karlovitz numbers is presented. The simulations feature finite rate chemistry with 16 species and 73 reactions and up to 22 Billion grid points. The jet consists of a methane/air mixture with equivalence ratio ϕ = 0 . 7 and temperature varying between 500 and 800 K. The temperature and species concentrations in the coflow correspond to the equilibrium state of the burnt mixture. All the simulations are performed at 4 atm. The flame length, normalized by the jet width, decreases significantly as the Reynolds number increases. This is consistent with an increase of the turbulent flame speed due to the increased integral scale of turbulence. This behavior is typical of flames in the thin-reaction zone regime, which are affected by turbulent transport in the preheat layer. Fractal dimension and topology of the flame surface, statistics of temperature gradients, and flame structure are investigated and the dependence of these quantities on the Reynolds number is assessed.

  8. Investigation on Effect of Air Velocity in Turbulent Non-Premixed Flames

    Directory of Open Access Journals (Sweden)

    Namazian Zafar


    Full Text Available In this study, the turbulent non-premixed methane-air flame is simulated to determine the effect of air velocity on the length of flame, temperature distribution and mole fraction of species. The computational fluid dynamics (CFD technique is used to perform this simulation. To solve the turbulence flow, k-ε model is used. In contrast to the previous works, in this study, in each one of simulations the properties of materials are taken variable and then the results are compared. The results show that at a certain flow rate of fuel, by increasing the air velocity, similar to when the properties are constant, the width of the flame becomes thinner and the maximum temperature is higher; the penetration of oxygen into the fuel as well as fuel consumption is also increased. It is noteworthy that most of the pollutants produced are NOx, which are strongly temperature dependent. The amount of these pollutants rises when the temperature is increased. As a solution, decreasing the air velocity can decrease the amount of these pollutants. Finally, comparing the result of this study and the other work, which considers constant properties, shows that the variable properties assumption leads to obtaining more exact solution but the trends of both results are similar.

  9. Interest of 50% nitrous oxide and oxygen premix sedation in gerodontology

    Directory of Open Access Journals (Sweden)

    Emmanuel Nicolas


    Full Text Available Emmanuel Nicolas1,2, Claire Lassauzay1,21CHU de Clermont-Ferrand, 63000 Clermont-Ferrand, France; 2Université Clermont 1, EA 3847, Faculty of Dentistry, 63000 Clermont-Ferrand, FranceAbstract: Elderly patients presenting cardiovascular, respiratory, or neurological disorders require a specific dental care approach, especially patients presenting Alzheimer’s disease. Sedative procedures can prevent dental care-induced stress, even when there is effective pain control, but they have to be adapted to accommodate age-induced physiological modifications, age-related pathologies, and the concomitant treatments. In many situations, routine sedative prescriptions for dental care, such as benzodiazepine or antihistaminics, are not recommended for these patients. Nitrous oxide inhalation together with a specific behavioral threshold is currently the only sedative procedure adapted to cognitively-impaired elderly patients. Nitrous oxide is able to curb stress and its cardiovascular consequences, improve oxygenation, and optimize cooperation during dental care, making not only rehabilitation treatments but also routine dental care a viable option.Keywords: nitrous oxide, oxygen, premix, sedation, gerodontology, dental care

  10. Melt water interaction tests. PREMIX tests PM10 and PM11

    Energy Technology Data Exchange (ETDEWEB)

    Kaiser, A.; Schuetz, W.; Will, H. [Forschungszentrum Karlsruhe Inst. fuer Reaktorsicherheit, Karlsruhe (Germany)


    A series of experiments is being performed in the PREMIX test facility in which the mixing behaviour is investigated of a hot alumina melt discharged into water. The major parameters have been: the melt mass, the number of nozzles, the distance between the nozzle and the water, and the depth of the water. The paper describes the last two tests in which 20 kg of melt were released through one and three nozzles, respectively, directly into the water whose depth was 500 mm. The melt penetration and the associated phenomena of mixing are described by means of high-speed films and various measurements. The steam production and, subsequently, the pressure increased markedly only after the melt had reached the bottom of the pool. Spreading of the melt across the bottom caused violent boiling in both tests. Whereas the boiling lasted for minutes in the single-jet test, a steam explosion occurred in the triple-jet test about one second after the start of melt penetration. (author)

  11. Tip opening of premixed bunsen flames: Extinction with negative stretch and local Karlovitz number

    KAUST Repository

    Vu, Tranmanh


    The characteristics of tip openings in premixed bunsen flames have been studied experimentally by measuring OH radicals from laser-induced fluorescence and tip curvatures from chemiluminescent images. Results showed that the tip opening occurred at a constant equivalence ratio and was independent of the jet velocity in propane/air mixtures. The observation of a local extinction phenomenon of the negatively stretched flame due to the flame curvature could not be consistently explained based on flame stretch or the Karlovitz number, since they varied appreciably with the jet velocity. The concept of the local Karlovitz number (KaL) was introduced, which is defined as the ratio of the characteristic reaction time in the normal direction for a stretched flame to the characteristic flow time in the tangential direction for the stretched flame. The local Karlovitz number maintained a constant value under tip opening conditions, irrespective of the jet velocity. Tip opening occurred at a reasonably constant local Karlovitz number of about ~1.72 when the nitrogen dilution level in propane and n-butane fuels was varied.

  12. Blow-off characteristics of turbulent premixed flames in curved-wall Jet Burner

    KAUST Repository

    Mansour, Morkous S.


    This study concerns the flame dynamics of a curved-wall jet (CWJ) stabilized turbulent premixed flame as it approaches blow-off conditions. Time resolved OH planar laser-induced fluorescence (PLIF) delineated reaction zone contours and simultaneously stereoscopic particle image velocimetry (SPIV) quantified the turbulent flow field features. Ethylene/air flames were stabilized in CWJ burner to determine the sequence of events leading to blowoff. For stably burning flames far from blowoff, flames are characterized with a recirculation zone (RZ) upstream for flame stabilization followed by an intense turbulent interaction jet (IJ) and merged-jet regions downstream; the flame front counterparts the shear layer vortices. Near blowoff, as the velocity of reactants increases, high local stretch rates exceed the extinction stretch rates instantaneously resulting in localized flame extinction along the IJ region. As Reynolds number (Re) increases, flames become shorter and are entrained by larger amounts of cold reactants. The increased strain rates together with heat loss effects result in further fragmentation of the flame, eventually leading to the complete quenching of the flame. This is explained in terms of local turbulent Karlovitz stretch factor (K) and principal flow strain rates associated with C contours. Hydrogen addition and increasing the RZ size lessen the tendency of flames to be locally extinguished.

  13. Effect of AC electric fields on the stabilization of premixed bunsen flames

    KAUST Repository

    Kim, Minkuk


    The stabilization characteristics of laminar premixed bunsen flames have been investigated experimentally for stoichiometric methane-air mixture by applying AC voltage to the nozzle with the single-electrode configuration. The detachment velocity either at blowoff or partial-detachment has been measured by varying the applied voltage and frequency of AC. The result showed that the detachment velocity increased with the applied AC electric fields, such that the flame could be nozzle-attached even over five times of the blowoff velocity without having electric fields. There existed four distinct regimes depending on applied AC voltage and frequency. In the low voltage regime, the threshold condition of AC electric fields was identified, below which the effect of electric fields on the detachment velocity is minimal. In the moderate voltage regime, the flame base oscillated with the frequency synchronized to AC frequency and the detachment velocity increased linearly with the applied AC voltage and nonlinearly with the frequency. In the high voltage regime, two different sub-regimes depending on AC frequency were observed. For relatively low frequency, the flame base oscillated with the applied AC frequency together with the half frequency and the variation of the detachment velocity was insensitive to the applied voltage. For relatively high frequency, the stabilization of the flame was significantly affected by the generation of streamers and the detachment velocity decreased with the applied voltage. © 2010 Published by Elsevier Inc. on behalf of The Combustion Institute. All rights reserved.

  14. Experimental study of the effects of flameholder geometry on emissions and performance of lean premixed combustors (United States)

    Roffe, G.; Venkataramani, K. S.; Duerr, R. M.


    Emissions of NOx, CO and unburned hydrocarbons (UHC) are reported for a lean premixed propane-air system at inlet conditions of 800K and 1 MPa using twelve flameholder designs. The flameholders tested represent six design concepts with two values of blockage for each concept. Data were obtained at reference velocities of 35 m/s, 25 m/s and 20 m/s at combustor stations 10 cm and 30 cm downstream of the flameholders. Flameholder pressure drop was found to be a principal determinant of emissions performance. Designs producing larger pressure drops also produced less NOx, CO and UHC emissions. The lean stability limit equivalence ratio was found to be approximately 0.35 for all designs. Flashback velocities (axial components in the flameholder passages) varied between 30 m/s and 40 m/s. A perforated plate flameholder was operated with a velocity as low as 23 m/s through the perforations at equivalence ratio 0.7 without producing flashback.

  15. Temperature response of an acoustically forced turbulent lean premixed flame: A quantitative experimental determination

    KAUST Repository

    Chrystie, Robin


    Temperature measurements have been taken on an acoustically forced lean premixed turbulent bluff-body stabilized flame. The burner used in this study is a test-bed to investigate thermoacoustic instability in gas-turbine engines at the University of Cambridge. Numerous experiments have been performed on the burner, one of which used two-line OH planar laser induced fluorescence to measure temperature. Here, we employ vibrational coherent anti-Stokes Raman scattering (CARS) of nitrogen as an alternative to measure temperature, circumventing the limitations of the former method. The use of nitrogen CARS avoids the problem of probing regions of the flame with low OH concentrations that resulted in erroneous temperature. Such an application of CARS showed that the results from previous efforts were systematically biased up to 47% close to the bluff-body. We also critically review the limitations of CARS used in our experiments, pertaining to spatial resolution and associated biasing further downstream from the bluff-body. Using the more accurate results from this work, more up-to-date computational fluid dynamical (CFD) models of the burner can be validated, with the aim of improved understanding and prediction of thermoacoustic instability in gas turbines. © 2013 Copyright Taylor and Francis Group, LLC.

  16. Addition of Zinc Improves the Physical Stability of Insulin in the Primary Emulsification Step of the Poly(lactide-co-glycolide Microsphere Preparation Process

    Directory of Open Access Journals (Sweden)

    Chandrasekar Manoharan


    Full Text Available In this study, the effect of zinc on insulin stability during the primary emulsification step of poly(lactide-co-glycolide microspheres preparation by the water-in-oil-in-water (w/o/w double emulsion solvent evaporation technique was evaluated. Insulin was emulsified at homogenization speeds of 5000 and 10,000 rpm. Insulin was extracted from the primary w/o emulsion by a method previously reported from our laboratory and analyzed by comprehensive analytical techniques. The differential scanning calorimetry thermograms of insulin with zinc showed a single peak around 83 °C with calorimetric enthalpy values similar to native insulin. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE of extracted insulin showed a single intense band around 6 kDa, demonstrating the preservation of primary structure. High performance liquid chromatography (HPLC analysis revealed that no degradation products were formed during the homogenization process. Insulin aggregates residing at the w/o interfaces were found to be of non-covalent nature. In addition, observation of a single characteristic peak for insulin at m/z 5808 in the matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF mass spectrum confirmed the absence of insulin degradation products and covalent dimers. Presence of zinc preserved the secondary structure of insulin as indicated by circular dichroism. In conclusion, these results show that with the addition of zinc, insulin stability can be improved during the primary emulsification step.

  17. Development of a home-made extraction device for vortex-assisted surfactant-enhanced-emulsification liquid-liquid microextraction with lighter than water organic solvents. (United States)

    Yang, Zhong-Hua; Wang, Peng; Zhao, Wen-ting; Zhou, Zhi-Qiang; Liu, Dong-Hui


    We have developed a novel vortex-assisted surfactant-enhanced-emulsification liquid-liquid microextraction using the low density solvent for the determination of eight organophosphorus pesticides (OPPs) in water samples. The key point of this method is the application of a special home-made extraction device. The influence parameters relevant to this method were systemically investigated and the optimum conditions were as follow: 35μL of toluene was used as extraction solvent and 0.2mmol L-1 Triton X-100 was chosen as the surfactant to enhance the emulsification. Under the optimum experimental conditions, the limit of detections (LODs) of the method was ranged between 0.01 and 0.05μgL(-1) and the relative standard deviations (RSDs) were 2.9-8.1%. The calibration curve was linear in the range of 0.1-50.0μgL(-1), with the correlation coefficients (r) varying from 0.9949 to 0.9991. Finally, the developed method has been successfully applied to the determination of eight organophosphorus pesticides in river, reservoir and well water samples with recoveries between 82.1% and 98.7%.

  18. Vortex-assisted surfactant-enhanced-emulsification liquid-liquid microextraction for the determination of triazine herbicides in water samples by microemulsion electrokinetic chromatography. (United States)

    Li, Ran-Hong; Liu, Dong-Hui; Yang, Zhong-Hua; Zhou, Zhi-Qiang; Wang, Peng


    A novel method based on the combination of microemulsion electrokinetic chromatography (MEEKC) and vortex-assisted surfactant-enhanced-emulsification liquid-liquid microextraction (VSLLME) was developed for the determination of five triazine herbicides (simazine, atrazine, ametryn, prometryn, and terbutryn) in water samples. The five triazine herbicides were baseline separated by using the microemulsion buffer containing a 10 mmol/L borate buffer at pH 9.5, 2.5% (w/v) SDS as surfactant, 0.8% (w/v) ethyl acetate as oil phase, and 6.0% (w/v) 1-butanol as cosurfactant. The optimum extraction conditions of VSLLME were as follows: 100 μL chloroform was used as extraction solvent, 5.0 × 10⁻⁵ mol/L Tween-20 was chosen as the surfactant to enhance the emulsification, and the extraction process was carried out by vortex mixing for 3 min. Under these optimum experimental conditions, the calibration curve was linear in the range of 2.0-200.0 ng/mL, with the correlation coefficients (r²) varying from 0.9927 to 0.9958. The detection limits of the method varied from 0.41 to 0.62 ng/mL. The purposed method was applied to the determination of five triazine herbicides in real water samples, and the recoveries were between 80.6 and 107.3%.

  19. Ultrasound-assisted emulsification microextraction for the determination of ephedrines in human urine by capillary electrophoresis with direct injection. Comparison with dispersive liquid-liquid microextraction. (United States)

    Alshana, Usama; Göğer, Nilgün G; Ertaş, Nusret


    Ultrasound-assisted emulsification microextraction and dispersive liquid-liquid microextraction were compared for extraction of ephedrine, norephedrine, and pseudoephedrine from human urine samples prior to their determination by capillary electrophoresis. Formation of a microemulsion of the organic extract with an aqueous solution (at pH 3.2) containing 10% methanol facilitated the direct injection of the final extract into the capillary. Influential parameters affecting extraction efficiency were systematically studied and optimized. In order to enhance the sensitivity further, field-amplified sample injection was applied. Under optimum extraction and stacking conditions, enrichment factors of up to 140 and 1750 as compared to conventional capillary zone electrophoresis were obtained resulting in limits of detection of 12-33 μg/L and 1.0-2.8 μg/L with dispersive liquid-liquid microextraction and ultrasound-assisted emulsification microextraction when combined with field-amplified sample injection. Calibration graphs showed good linearity for urine samples by both methods with coefficients of determination higher than 0.9973 and percent relative standard deviations of the analyses in the range of 3.4-8.2% for (n = 5). The results showed that the use of ultrasound to assist microextraction provided higher extraction efficiencies than disperser solvents, regarding the hydrophilic nature of the investigated analytes.

  20. Ionic liquid-based ultrasound-assisted emulsification microextraction coupled with high performance liquid chromatography for the determination of four fungicides in environmental water samples. (United States)

    Liang, Pei; Wang, Fang; Wan, Qin


    A highly efficient and environmentally friendly sample preparation method termed ionic liquid-based ultrasound-assisted emulsification microextraction (IL-USAEME) combined with high performance liquid chromatography has been developed for the determination of four fungicides (azoxystrobin, diethofencarb, pyrimethanil and kresoxim-methyl) in water samples. In this novel approach, ionic liquid (IL) was used as extraction solvent in place of the organic solvent used in conventional USAEME assay, and there is no need for using organic dispersive solvent which is typically required in the common dispersive liquid-liquid microextraction method. Various parameters that affect the extraction efficiency, such as the kind and volume of IL, ultrasound emulsification time, extraction temperature and salt addition were investigated and optimized. Under the optimum extraction condition, the linearities of calibration curves were in the range from 3 to 5000 ng mL(-1) for target analytes with the correlation coefficient higher than 0.9992. The enrichment factors and the limits of detection were in the range of 88-137 and 0.73-2.2 ng mL(-1), depending on the analytes. The environmental water samples were successfully analyzed using the proposed method, and the relative recoveries at fortified levels of 50 and 100 ng mL(-1) were in the range of 83.9%-116.2%.

  1. Effect of Addition of Soybean Oil and Gamma-Ray Cross-linking on the Nanoporous HDPE Membrane

    Directory of Open Access Journals (Sweden)

    Jong-Seok Park


    Full Text Available A nanoporous high-density polyethylene (HDPE membrane was prepared by a wet process. Soybean oil and dibutyl phthalate (DBP were premixed as codiluents, and gamma-rays were used for the cross-linking of HDPE. The pore volume of the nanoporous HDPE membranes with soybean oil was affected by the extracted amount of oil. The tensile strength of the membrane improved with an increasing absorbed dose up to 60 kGy, but decreased at 80 kGy due to severe degradation. The ionic conductivity of the nanoporous HDPE membrane did not really change with an increasing absorbed dose because the pores had already been formed before the gamma-ray radiation. Finally, the electrochemical stability of the HDPE membrane increased when the absorbed dose increased up to 60 kGy.

  2. Upscaling microstructured emulsification devices

    NARCIS (Netherlands)

    Sahin, S.


    Emulsions, which are dispersions of two immiscible liquids (e.g. oil and water), are part of our daily life through many products that we use such as milk, mayonnaise, salad dressings, ice cream, lotions, shampoos, medicines, wall paints, etc. Many quality attributes of these products such as

  3. Emulsification with microstructures

    NARCIS (Netherlands)

    Dijke, van K.C.


    A dispersion is a multiphase product in which at least one phase is dispersed into another phase. In emulsions, those phases are immiscible liquids, for example oil and water. Many products which we use in everyday life are emulsions. One can think of ointments, paints, or sun protection cream, but

  4. Emulsification with microstructures

    NARCIS (Netherlands)

    Dijke, van K.C.


    A dispersion is a multiphase product in which at least one phase is dispersed into another phase. In emulsions, those phases are immiscible liquids, for example oil and water. Many products which we use in everyday life are emulsions. One can think of ointments, paints, or sun protection cream, but

  5. Upscaling microstructured emulsification devices

    NARCIS (Netherlands)

    Sahin, S.


    Emulsions, which are dispersions of two immiscible liquids (e.g. oil and water), are part of our daily life through many products that we use such as milk, mayonnaise, salad dressings, ice cream, lotions, shampoos, medicines, wall paints, etc. Many quality attributes of these products such as stabil

  6. Marine sponge cyclic peptide theonellamide A disrupts lipid bilayer integrity without forming distinct membrane pores. (United States)

    Espiritu, Rafael Atillo; Cornelio, Kimberly; Kinoshita, Masanao; Matsumori, Nobuaki; Murata, Michio; Nishimura, Shinichi; Kakeya, Hideaki; Yoshida, Minoru; Matsunaga, Shigeki


    Theonellamides (TNMs) are antifungal and cytotoxic bicyclic dodecapeptides derived from the marine sponge Theonella sp. These peptides specifically bind to 3β-hydroxysterols, resulting in 1,3-β-D-glucan overproduction and membrane damage in yeasts. The inclusion of cholesterol or ergosterol in phosphatidylcholine membranes significantly enhanced the membrane affinity of theonellamide A (TNM-A) because of its direct interaction with 3β-hydroxyl groups of sterols. To better understand TNM-induced membrane alterations, we investigated the effects of TNM-A on liposome morphology. (31)P nuclear magnetic resonance (NMR) and dynamic light scattering (DLS) measurements revealed that the premixing of TNM-A with lipids induced smaller vesicle formation. When giant unilamellar vesicles were incubated with exogenously added TNM-A, confocal micrographs showed dynamic changes in membrane morphology, which were more frequently observed in cholesterol-containing than sterol-free liposomes. In conjunction with our previous data, these results suggest that the membrane action of TNM-A proceeds in two steps: 1) TNM-A binds to the membrane surface through direct interaction with sterols and 2) accumulated TNM-A modifies the local membrane curvature in a concentration-dependent manner, resulting in dramatic membrane morphological changes and membrane disruption.

  7. Sphingomyelinase D activity in model membranes: structural effects of in situ generation of ceramide-1-phosphate

    DEFF Research Database (Denmark)

    Stock, Roberto; Brewer, Jonathan R.; Wagner, Kerstin;


    The toxicity of Loxosceles spider venom has been attributed to a rare enzyme, sphingomyelinase D, which transforms sphingomyelin to ceramide-1-phosphate. The bases of its inflammatory and dermonecrotic activity, however, remain unclear. In this work the effects of ceramide-1-phosphate on model...... membranes were studied both by in situ generation of this lipid using a recombinant sphingomyelinase D from the spider Loxosceles laeta and by pre-mixing it with sphingomyelin and cholesterol. The systems of choice were large unilamellar vesicles for bulk studies (enzyme kinetics, fluorescence spectroscopy...

  8. The Effect of Different Levels of Minerals and Vitamins Premixes on Performance of Laying Hens fed by Wheat and Corn Base Diets

    Directory of Open Access Journals (Sweden)

    A. Nobakht


    Full Text Available This experiment was conducted to evaluate effects of different levels of mineral and vitamin premixes with wheat and corn base diets on performance and egg traits of laying hens. Experiment carried out as 2*5 factorial include wheat and corn base diets and 5 levels of minerals and vitamin premixes (0, 0.25, 0.35, 0.45 and 0.55 percentage in a completely randomized design with 360 Hi-Line (W36 laying hens from 65 to 77 weeks in 10 treatments, 3 replicates and 12 hens in each replicate for 12 weeks. The results showed that diets composition, level of mineral and vitamin premixes, and interaction between them significantly affected the performance and egg traits of laying hens (P

  9. A photo-tunable membrane based on inter-particle crosslinking for decreasing diffusion rates

    KAUST Repository

    Li, Song


    Functional polymeric membranes are widely used to adjust and control the diffusion of molecules. Herein, photosensitive poly(hydroxycinnamic acid) (PHCA) microspheres, which were fabricated by an emulsification solvent-evaporation method, were embedded into an ethyl cellulose matrix to fabricate composite membranes with a photo-tunable property. The photoreaction of PHCA is based on the [2 + 2] cycloaddition of cinnamic moieties upon irradiation with 365 nm light. Intra-particle crosslinking in PHCA microspheres was confirmed in the solution phase, while inter-particle crosslinking between adjacent PHCA microspheres dominated the solid membrane phase. The inter-particle crosslinking turned down the permeability of the composite membranes by 74%. To prove the applicability of the designed system, the composite membrane was coated on a model drug reservoir tablet. Upon irradiating the tablet with UV light, the original permeability decreased by 57%, and consequently the diffusion rate of the cargo (Rhodamine B) from the tablet slowed down. Most importantly, the tablet showed sustained release for over 10 days. This controllability can be further tuned by adjusting the membrane thickness. Composite membranes showed excellent processing reproducibility together with consistent mechanical properties. These results demonstrate that the incorporation of photosensitive PHCA microspheres in polymeric membranes provides a promising photo-tunable material for different applications including coating and separation. This journal is © The Royal Society of Chemistry 2015.

  10. Premixed Combustion of Kapok (ceiba pentandra seed oil on Perforated Burner

    Directory of Open Access Journals (Sweden)

    I.K.G. Wirawan


    Full Text Available Availability of fossil fuels in the world decrease gradually due to excessive fuel exploitation. This situations push researcher to look for alternative fuels as a source of renewable energy, one of them is kapok (ceiba pentandra seed oil. The aim this study was to know the behavior of laminar burning velocity, secondary Bunsen flame with open tip, cellular and triple flame. Premixed combustion of kapok seed oil was studied experimentally on perforated burner with equivalence ratio (φ varied from 0.30 until 1.07. The results showed that combustion of glycerol requires a large amount of air so that laminar burning velocity (SL is the highest at very lean mixture (φ =0.36 in the form of individual Bunsen flame on each of the perforated plate hole.  Perforated and secondary Bunsen flame both reached maximum SL similar with that of ethanol and higher than that of hexadecane. Slight increase of φ decreases drastically SL of perforated and secondary Bunsen flame. When the mixture was enriched, secondary Bunsen and perforated flame disappears, and then the flame becomes Bunsen flame with open tip and triple flame (φ = 0.62 to 1.07. Flame was getting stable until the mixture above the stoichiometry. Being isolated from ambient air, the SL of perforated flame, as well as secondary Bunsen flame, becomes equal with non-isolated flame. This shows the decreasing trend of laminar burning velocity while φ is increasing. When the mixture was enriched island (φ = 0.44 to 0.48 and petal (φ = 0.53 to 0.62 cellular flame take place. Flame becomes more unstable when the mixture was changed toward stoichiometry.

  11. Dynamics of flow–soot interaction in wrinkled non-premixed ethylene–air flames

    KAUST Repository

    Arias, Paul G.


    A two-dimensional simulation of a non-premixed ethylene–air flame was conducted by employing a detailed gas-phase reaction mechanism considering polycyclic aromatic hydrocarbons, an aerosol-dynamics-based soot model using a method of moments with interpolative closure, and a grey gas and soot radiation model using the discrete transfer method. Interaction of the sooting flame with a prescribed decaying random velocity field was investigated, with a primary interest in the effects of velocity fluctuations on the flame structure and the associated soot formation process for a fuel-strip configuration and a composition with mature soot growth. The temporally evolving simulation revealed a multi-layered soot formation process within the flame, at a level of detail not properly described by previous studies based on simplified soot models utilizing acetylene or naphthalene precursors for initial soot inception. The overall effect of the flame topology on the soot formation was found to be consistent with previous experimental studies, while a unique behaviour of localised strong oxidation was also noted. The imposed velocity fluctuations led to an increase of the scalar dissipation rate in the sooting zone, causing a net suppression in the soot production rate. Considering the complex structure of the soot formation layer, the effects of the imposed fluctuations vary depending on the individual soot reactions. For the conditions under study, the soot oxidation reaction was identified as the most sensitive to the fluctuations and was mainly responsible for the local suppression of the net soot production. © 2015 Taylor & Francis

  12. Heat release and flame structure measurements of self-excited acoustically-driven premixed methane flames

    Energy Technology Data Exchange (ETDEWEB)

    Kopp-Vaughan, Kristin M.; Tuttle, Steven G.; Renfro, Michael W. [Department of Mechanical Engineering, University of Connecticut, 191 Auditorium Rd, U-3139, Storrs, CT 06269 (United States); King, Galen B. [School of Mechanical Engineering, Purdue University, West Lafayette, IN 47907 (United States)


    An open-open organ pipe burner (Rijke tube) with a bluff-body ring was used to create a self-excited, acoustically-driven, premixed methane-air conical flame, with equivalence ratios ranging from 0.85 to 1.05. The feed tube velocities corresponded to Re = 1780-4450. Coupled oscillations in pressure, velocity, and heat release from the flame are naturally encouraged at resonant frequencies in the Rijke tube combustor. This coupling creates sustainable self-excited oscillations in flame front area and shape. The period of the oscillations occur at the resonant frequency of the combustion chamber when the flame is placed {proportional_to}1/4 of the distance from the bottom of the tube. In this investigation, the shape of these acoustically-driven flames is measured by employing both OH planar laser-induced fluorescence (PLIF) and chemiluminescence imaging and the images are correlated to simultaneously measured pressure in the combustor. Past research on acoustically perturbed flames has focused on qualitative flame area and heat release relationships under imposed velocity perturbations at imposed frequencies. This study reports quantitative empirical fits with respect to pressure or phase angle in a self-generated pressure oscillation. The OH-PLIF images were single temporal shots and the chemiluminescence images were phase averaged on chip, such that 15 exposures were used to create one image. Thus, both measurements were time resolved during the flame oscillation. Phase-resolved area and heat release variations throughout the pressure oscillation were computed. A relation between flame area and the phase angle before the pressure maximum was derived for all flames in order to quantitatively show that the Rayleigh criterion was satisfied in the combustor. Qualitative trends in oscillating flame area were found with respect to feed tube flow rates. A logarithmic relation was found between the RMS pressure and both the normalized average area and heat release rate

  13. Stability enhancement of ozone-assisted laminar premixed Bunsen flames in nitrogen co-flow

    KAUST Repository

    Vu, Tran Manh


    Ozone (O3) is known as one of the strongest oxidizers and therefore is widely used in many applications. Typically in the combustion field, a combination of non-thermal plasma and combustion systems have been studied focusing on the effects of ozone on flame propagation speeds and ignition characteristics. Here, we experimentally investigated the effects of ozone on blowoff of premixed methane/air and propane/air flames over a full range of equivalence ratios at room temperature and atmospheric pressure by using a co-flow burner and a dielectric barrier discharge. The results with ozone showed that a nozzle exit jet velocity at the moment of flame blowoff (blowoff velocity) significantly increased, and flammability limits for both fuel-lean and rich mixtures were also extended. Ozone had stronger effects of percent enhancement in the blowoff velocity for off-stoichiometric mixtures, while minimum enhancements could be observed around stoichiometric conditions for both fuels showing linear positive dependence on a tested range of ozone concentration up to 3810ppm. Through chemical kinetic simulations, the experimentally observed trends of the enhancement in blowoff velocity were identified as a result of the modification of the laminar burning velocity. Two ozone decomposition pathways of O3+N2→O+O2+N2 and O3+H→O2+OH were identified as the most controlling steps. These reactions, coupled with fuel consumption characteristics of each fuel determined the degree of promotion in laminar burning velocities, supporting experimental observations on blowoff velocities with ozone addition. © 2013 The Combustion Institute.


    Directory of Open Access Journals (Sweden)

    V. A. Afanas’ev


    Full Text Available Summary. The article describes validation and development of technology of vitamin, mineral and complex premixes with the introduction of vegetable oil and a set of equipment for its implementation. The two-component mixture was used for research. Crushed wheat was used as the main component, and the metal admixture with magnetic properties, vitamin B2 and salt of micronutrients MnSO4 as key components. Quality of the final mixture was determined by the homogeneity test. Trace components dosing accuracy was determined by dosing vitamins B5 , E, A, and trace-element salts MnSO4 , FeSO4 , CuSO4 . Also introduction of vegetable oil in the filler was researched. When the oil was entering the mixer in an amount of 2 % homogeneity of the filler and oil mixture was 94 %. The oil fine spray was provided by special nozzles design. A pilot mixer consisting of a body having a lower portion of the shape of the double trough and lid is developed for conducting research in mixing vitamins, salts of trace elements with the filler. Inside the case, there are two horizontal shafts, rotating in opposite directions. Each shaft has four rows of blades. In the upper part of the mixer above paddle shafts manifold with injectors is located. The studies found that the accuracy of dosing vitamins B5 , E and A in amounts of 0,02 and 0,2%, does not exceed 1 % of a set weight of component; accuracy of dosing of trace components salts MnSO4, FeSO4, CuSO4 in amounts of 0,2 % does not exceed 1 % of a set weight of component; high quality of mixing provided by a mixer design that implements the fluidized mixing method.

  15. Unsteady Flame Embedding (UFE) Subgrid Model for Turbulent Premixed Combustion Simulations

    KAUST Repository

    El-Asrag, Hossam


    We present a formulation for an unsteady subgrid model for premixed combustion in the flamelet regime. Since chemistry occurs at the unresolvable scales, it is necessary to introduce a subgrid model that accounts for the multi-scale nature of the problem using the information available on the resolved scales. Most of the current models are based on the laminar flamelet concept, and often neglect the unsteady effects. The proposed model\\'s primary objective is to encompass many of the flame/turbulence interactions unsteady features and history effects. In addition it provides a dynamic and accurate approach for computing the subgrid flame propagation velocity. The unsteady flame embedding approach (UFE) treats the flame as an ensemble of locally one-dimensional flames. A set of elemental one dimensional flames is used to describe the turbulent flame structure at the subgrid level. The stretched flame calculations are performed on the stagnation line of a strained flame using the unsteady filtered strain rate computed from the resolved- grid. The flame iso-surface is tracked using an accurate high-order level set formulation to propagate the flame interface at the coarse resolution with minimum numerical diffusion. In this paper the solver and the model components are introduced and used to investigate two unsteady flames with different Lewis numbers in the thin reaction zone regime. The results show that the UFE model captures the unsteady flame-turbulence interactions and the flame propagation speed reasonably well. Higher propagation speed is observed for the lower than unity Lewis number flame because of the impact of differential diffusion.

  16. Transition from pulled to pushed premixed turbulent flames due to countergradient transport (United States)

    Sabelnikov, V. A.; Lipatnikov, A. N.


    The influence of countergradient transport on the speed of a statistically stationary, planar, 1D premixed flame that propagates in frozen turbulence is studied theoretically and numerically by considering the normalised magnitude NB of the countergradient flux to be an input parameter. Spectra of admissible flame speeds are analytically determined and explicit travelling wave solutions are found for two algebraic relations widely used to close the mean rate of product creation. A problem of selecting the physically relevant solution that is approached for sufficiently steep initial conditions is addressed. It is argued that, if NB is larger than an analytically determined critical number NcrB, then the type of the physically relevant solution is drastically changed. If NB pulled wave type, i.e. its speed is controlled by processes localised to the leading edge of the flame brush and can be determined within the framework of a linear analysis at the leading edge. If NB > NcrB, the physically relevant solution is of pushed wave type, i.e. its speed is controlled by processes in the entire flame brush. Analytical expressions for the speed of the physically relevant solution as a function of NB and the density ratio are obtained. For NB > NcrB, the mean flame brush thickness and the spatial profile of the Favre-averaged combustion progress variable are also determined analytically. These results are validated by numerical simulations. Both analytical expressions and numerical data indicate that (i) both turbulent flame speed and thickness are decreased when NB is increased and (ii) the direction of total scalar flux (i.e. the sum of countergradient and gradient contributions) is strongly affected not only by NB, but also by the shape of the dependence of the mean rate of product creation on the mean combustion progress variable.

  17. A detailed kinetic modeling study of toluene oxidation in a premixed laminar flame

    Energy Technology Data Exchange (ETDEWEB)

    Tian, Z; Pitz, W J; Fournet, R; Glaude, P; Battin-Leclerc, F


    An improved chemical kinetic model for the toluene oxidation based on experimental data obtained in a premixed laminar low-pressure flame with vacuum ultraviolet (VUV) photoionization and molecular beam mass spectrometry (MBMS) techniques has been proposed. The present mechanism consists of 273 species up to chrysene and 1740 reactions. The rate constants of reactions of toluene, decomposition, reaction with oxygen, ipso-additions and metatheses with abstraction of phenylic H-atom are updated; new pathways of C{sub 4} + C{sub 2} species giving benzene and fulvene are added. Based on the experimental observations, combustion intermediates such as fulvenallene, naphtol, methylnaphthalene, acenaphthylene, 2-ethynylnaphthalene, phenanthrene, anthracene, 1-methylphenanthrene, pyrene and chrysene are involved in the present mechanism. The final toluene model leads to an overall satisfactory agreement between the experimentally observed and predicted mole fraction profiles for the major products and most combustion intermediates. The toluene depletion is governed by metathese giving benzyl radicals, ipso-addition forming benzene and metatheses leading to C{sub 6}H{sub 4}CH{sub 3} radicals. A sensitivity analysis indicates that the unimolecular decomposition via the cleavage of a C-H bond has a strong inhibiting effect, while decomposition via C-C bond breaking, ipso-addition of H-atom to toluene, decomposition of benzyl radicals and reactions related to C{sub 6}H{sub 4}CH{sub 3} radicals have promoting effect for the consumption of toluene. Moreover, flow rate analysis is performed to illustrate the formation pathways of mono- and polycyclic aromatics.

  18. Lagrangian coherent structures during combustion instability in a premixed-flame backward-step combustor (United States)

    Sampath, Ramgopal; Mathur, Manikandan; Chakravarthy, Satyanarayanan R.


    This paper quantitatively examines the occurrence of large-scale coherent structures in the flow field during combustion instability in comparison with the flow-combustion-acoustic system when it is stable. For this purpose, the features in the recirculation zone of the confined flow past a backward-facing step are studied in terms of Lagrangian coherent structures. The experiments are conducted at a Reynolds number of 18600 and an equivalence ratio of 0.9 of the premixed fuel-air mixture for two combustor lengths, the long duct corresponding to instability and the short one to the stable case. Simultaneous measurements of the velocity field using time-resolved particle image velocimetry and the C H* chemiluminescence of the flame along with pressure time traces are obtained. The extracted ridges of the finite-time Lyapunov exponent (FTLE) fields delineate dynamically distinct regions of the flow field. The presence of large-scale vortical structures and their modulation over different time instants are well captured by the FTLE ridges for the long combustor where high-amplitude acoustic oscillations are self-excited. In contrast, small-scale vortices signifying Kelvin-Helmholtz instability are observed in the short duct case. Saddle-type flow features are found to separate the distinct flow structures for both combustor lengths. The FTLE ridges are found to align with the flame boundaries in the upstream regions, whereas farther downstream, the alignment is weaker due to dilatation of the flow by the flame's heat release. Specifically, the FTLE ridges encompass the flame curl-up for both the combustor lengths, and thus act as the surrogate flame boundaries. The flame is found to propagate upstream from an earlier vortex roll-up to a newer one along the backward-time FTLE ridge connecting the two structures.

  19. Methane combustion in catalytic premixed burners; Combustione del metano in bruciatori catalitici premiscelati

    Energy Technology Data Exchange (ETDEWEB)

    Cerri, I.; Saracco, G.; Specchia, V. [Turin Politecnico, Turin (Italy). Dipt. di scienza dei materiali ed ingegneria chimica


    Catalytic premixed burners for domestic boiler applications were developed with the aim of achieving a power modularity from 10 to 100% and pollutant emissions limited to NO{sub x} (<)75 ppmv, CO(<)100 ppmv, HC(<)10 ppmv. The catalyst played a strategic role in reducing the CO and HC emissions, particularly when operating at superficial heat power lower than 800 kw/m{sup 2}, where the combustion took place entirely inside the burner heating it to incandescence and allowing a decrease in the flame temperature and NO{sub x} emissions. Such results were confirmed through further tests carried out in a commercial industrial-scale boiler equipped with the conical panels. All the results, by varying the excess air and the heat power employed, are presented and discussed. [Italian] Sono stati sviluppati bruciatori catalitici premiscelati con l'intento di raggiungere una modulazione della potenza termica dal 10 al 100% con una limitata generazione di emissioni inquinanti. Il catalizzatore ha giocato un ruolo strategico nel ridurre le missioni di CO e HC, specialmente per carichi termici inferiori a 800 kw/m{sup {sup }}, valori per i quali la combustione si realizza all'interno del apnnello che, raggiungendo le condizioni radianti, permette la riduzione della temperatura di fiamma e quindi dei livelli di NO{sub x}. Tali risultati sono stati poi confermati da ulteriori prove realizzate in una caldaia commerciale di scala industriale su due pannelli conici. Tutti i risultati, al variare dell'eccesso d'aria e della potenza termica impiegata, vengono presentati e discussi.

  20. The blow-off mechanism of a bluff-body stabilized laminar premixed flame

    KAUST Repository

    Kedia, Kushal S.


    © 2014 The Combustion Institute. The objective of this work is to investigate the dynamics leading to blow-off of a laminar premixed flame stabilized on a confined bluff-body using high fidelity numerical simulations. We used unsteady, fully resolved, two-dimensional simulations with detailed chemical kinetics and species transport for methane-air combustion. The flame-wall interaction between the hot reactants and the heat conducting bluff-body was accurately captured by incorporating the conjugate heat exchange between them. Simulations showed a shear-layer stabilized flame just downstream of the bluff-body, with a recirculation zone formed by the products of combustion. The flame was negatively stretched along its entire length, primarily dominated by the normal component of the strain. Blow-off was approached by decreasing the mixture equivalence ratio, at a fixed Reynolds number, of the incoming flow. A flame is stable (does not undergo blow-off) when (1) flame displacement speed is equal to the flow speed and (2) the gradient of the flame displacement speed normal to its surface is higher than the gradient of the flow speed along the same direction. As the equivalence ratio is reduced, the difference between the former and the latter shrinks until the dynamic stability condition (2) is violated, leading to blow-off. Blow-off initiates at a location where this is first violated along the flame. Our results showed that this location was far downstream from the flame anchoring zone, near the end of the recirculation zone. Blow-off started by flame pinching separating the flame into an upstream moving (carried within the recirculation zone) and a downstream convecting (detached from the recirculation zone) flame piece. Within the range of operating conditions investigated, the conjugate heat exchange with the bluff-body had no impact on the flame blow-off.

  1. Flow structures in a lean-premixed swirl-stabilized combustor with microjet air injection

    KAUST Repository

    LaBry, Zachary A.


    The major challenge facing the development of low-emission combustors is combustion instability. By lowering flame temperatures, lean-premixed combustion has the potential to nearly eliminate emissions of thermally generated nitric oxides, but the chamber acoustics and heat release rate are highly susceptible to coupling in ways that lead to sustained, high-amplitude pressure oscillations, known as combustion instability. At different operating conditions, different modes of instability are observed, corresponding to particular flame shapes and resonant acoustic modes. Here we show that in a swirl-stabilized combustor, these instability modes also correspond to particular interactions between the flame and the inner recirculation zone. Two stable and two unstable modes are examined. At lean equivalence ratios, a stable conical flame anchors on the upstream edge of the inner recirculation zone and extends several diameters downstream along the wall. At higher equivalence ratios, with the injection of counter-swirling microjet air flow, another stable flame is observed. This flame is anchored along the upstream edge of a stronger recirculation zone, extending less than one diameter downstream along the wall. Without the microjets, a stationary instability coupled to the 1/4 wave mode of the combustor shows weak velocity oscillations and a stable configuration of the inner and outer recirculation zones. Another instability, coupled to the 3/4 wave mode of the combustor, exhibits periodic vortex breakdown in which the core flow alternates between a columnar mode and a vortex breakdown mode. © 2010 Published by Elsevier Inc. on behalf of The Combustion Institute. All rights reserved.

  2. Straining and wrinkling processes during turbulence-premixed flame interaction measured using temporally-resolved diagnostics

    Energy Technology Data Exchange (ETDEWEB)

    Steinberg, Adam M.; Driscoll, James F. [Department of Aerospace Engineering, The University of Michigan, Ann Arbor, MI 48109 (United States)


    The dynamical processes of flame surface straining and wrinkling that occur as turbulence interacts with a premixed flame were measured using cinema-stereoscopic PIV (CS-PIV) and orthogonal-plane cinema-stereoscopic PIV (OPCS-PIV). These diagnostics provided temporally resolved measurements of turbulence-flame interaction at frame rates of up to 3 kHz and spatial resolutions as small as 280{mu} m. Previous descriptions of flame straining and wrinkling have typically been derived based on a canonical interaction between a pair of counter-rotating vortices and a planar flame surface. However, it was found that this configuration did not properly represent real turbulence-flame interaction. Interactions resembling the canonical configuration were observed in less than 10% of the recorded frames. Instead, straining and wrinkling were generally caused more geometrically complex turbulence, consisting of large groups of structures that could be multiply curved and intertwined. The effect of the interaction was highly dependent on the interaction geometry. Furthermore, even when the turbulence did exist in the canonical geometry, the straining and wrinkling of the flame surface were not well characterized by the vortical structures. A new mechanistic description of the turbulence-flame interaction was therefore identified and confirmed by the measurements. In this description, flame surface straining is caused by coherent structures of fluid-dynamic strain-rate (strain-rate structures). The role of vortical structures is to curve existing flame surface, creating wrinkles. By simultaneously considering both forms of turbulent structure, turbulence-flame interactions in both the canonical configuration and more complex geometries could be understood. (author)

  3. Characteristics of premixed flames stabilized in an axisymmetric curved-wall jet burner with tip modification

    KAUST Repository

    Kim, Daejoong


    The stabilization characteristics of premixed flames in an axisymmetric curved-wall jet burner have been experimentally investigated. This burner utilized the Coanda effect on top of a burner tip. The initially spherical burner tip was modified to a flat tip and a concave tip in order to improve flame stabilization by providing enough space for flow recirculation above the burner tip region. The flow characteristics have been visualized using a schlieren technique. Small-scale turbulence structure has been observed mainly in the interaction jet region (located downstream of the recirculation region) for large jet velocity (Reynolds number >11,500). An appreciable amount of air entrainment was exhibited from the half-angle of the jet spread, approximately 20. The averaged planar laser-induced fluorescence images of the flames for this large velocity demonstrated that the strong signal of OH radicals, representing reaction zones, existed in the recirculation zone, while it was weak in the interaction jet region due to intermittency and local extinction by the generation of small scale turbulence. The OH radical signals strengthened again in the merged jet region (downstream of the interaction jet region). In extreme cases of Reynolds number over 19,000, a unique flame exhibiting OH radicals only in the recirculation zone was observed for the concave tip. The flame stabilization has been mapped by varying jet velocity and equivalence ratio, and the result showed that the stabilization characteristics were improved appreciably from the initial spherical tip design, especially for rich mixtures. The flow fields measured by a laser Doppler velocimetry confirmed the existence of recirculation zone and the expansion of the recirculation zones for the modified tips. The temperature profile measured by a coherent anti-Stokes Raman spectroscopy exhibited an intermittent nature, especially near the recirculation zone.

  4. Conical quarl swirl stabilized non-premixed flames: flame and flow field interaction

    KAUST Repository

    Elbaz, Ayman M.


    The flame-flow field interaction is studied in non-premixed methane swirl flames stabilized in quartz quarl via simultaneous measurements of the flow field using a stereo PIV and OH-PLIF at 5 KHz repetition rate. Under the same swirl intensity, two flames with different fuel jet velocity were investigated. The time-averaged flow field shows a unique flow pattern at the quarl exit, where two recirculation vortices are formed; a strong recirculation zone formed far from the quarl exit and a larger recirculation zone extending inside the quarl. However, the instantaneous images show that, the flow pattern near the quarl exit plays a vital role in the spatial location and structure of the reaction zone. In the low fuel jet velocity flame, a pair of vortical structures, located precisely at the corners of the quarl exit, cause the flame to roll up into the central region of low speed flow, where the flame sheet then tracks the axial velocity fluctuations. The vorticity field reveals a vortical structure surrounding the reaction zones, which reside on a layer of low compressive strain adjacent to that vortical structure. In the high fuel jet velocity flame, initially a laminar flame sheet resides at the inner shear layer of the main jet, along the interface between incoming fresh gas and high temperature recirculating gas. Further downstream, vortex breakdown alters the flame sheet path toward the central flame region. The lower reaction zones show good correlation to the regions of maximum vorticity and track the regions of low compressive strain associated with the inner shear layer of the jet flow. In both flames the reactions zones conform the passage of the large structure while remaining inside the low speed regions or at the inner shear layer.

  5. Two-dimensional simulations of steady perforated-plate stabilized premixed flames

    KAUST Repository

    Altay, H. Murat


    The objective of this work is to examine the impact of the operating conditions and the perforated-plate design on the steady, lean premixed flame characteristics. We perform two-dimensional simulations of laminar flames using a reduced chemical kinetics mechanism for methane-air combustion, consisting of 20 species and 79 reactions. We solve the heat conduction problem within the plate, allowing heat exchange between the gas mixture and the solid plate. The physical model is based on a zero-Mach-number formulation of the axisymmetric compressible conservation equations. The results suggest that the flame consumption speed, the flame structure, and the flame surface area depend significantly on the equivalence ratio, mean inlet velocity, the distance between the perforated-plate holes and the plate thermal conductivity. In the case of an adiabatic plate, a conical flame is formed, anchored near the corner of the hole. When the heat exchange between themixture and the plate is finite, the flame acquires a Gaussian shape stabilizing at a stand-off distance, that grows with the plate conductivity. The flame tip is negatively curved; i.e. concave with respect to the reactants. Downstream of the plate, the flame base is positively curved; i.e. convex with respect to the reactants, stabilizing above a stagnation region established between neighboring holes. As the plate\\'s thermal conductivity increases, the heat flux to the plate decreases, lowering its top surface temperature. As the equivalence ratio increases, the flame moves closer to the plate, raising its temperature, and lowering the flame stand-off distance. As the mean inlet velocity increases, the flame stabilizes further downstream, the flame tip becomes sharper, hence raising the burning rate at that location. The curvature of the flame base depends on the distance between the neighboring holes; and the flame there is characterized by high concentration of intermediates, like carbon monoxide. © 2010 Taylor

  6. [The use of monensin premix in dairy cows: simple and essential steps for ensuring its proper use]. (United States)

    Dubuc, Jocelyn; Baril, Jean; DesCôteaux, Luc


    The use of monensin premix in dairy cows: Simple and essential steps for ensuring its proper use. Dietary monensin, containing monensin sodium as active ingredient, is frequently used on dairy farms in Canada. Although the use of monensin is safe, some overdose situations have been reported following consumption of higher than recommended doses. A regular monitoring of bulk tank milk fat percentage should be performed to ensure quick detection of a potential overdose situation. Diarrhea and sudden drop in dry matter intake are other potential clinical signs of monensin overdose. Quick detection of such cases will allow rapid correction of the situation.(Translated by the authors).

  7. Evaluation of three formulations of fenbendazole (10% suspension, 0.5% pellets, and 20% premix) against nematode infections in cattle. (United States)

    Blagburn, B L; Hanrahan, L A; Hendrix, C M; Lindsay, D S


    Anthelmintic efficacies of 3 formulations of fenbendazole were evaluated in cattle naturally parasitized with nematodes: a 10% oral suspension, 0.5% pellets as a top dressing on feed, and a 20% premix. All formulations of fenbendazole were greater than 99% effective in removing adults of Haemonchus contortus, Ostertagia spp, Cooperia spp, and Oesophagostomum radiatum. Fenbendazole was greater than 96% effective in removing adults of Strongyloides papillosus and greater than 85% effective in the removal of Trichuris sp. Fenbendazole was greater than 96% effective against immature nematodes, which were thought to be primarily Cooperia spp. Adverse reactions were not observed in calves treated with the 3 formulations of fenbendazole.

  8. A Novel Reagentless Biosensor Constructed by Layer-by-Layer Assembly of HRP and Nile Blue Premixed with Polyanion

    Institute of Scientific and Technical Information of China (English)

    Shao Ming YANG; Yang Mei LI; Xiu Ming JIANG; Xian Fu LIN


    A novel reagentless biosensor constructed by the organic dye nile blue (NB) and horseradish peroxidase (HRP) has been fabricated via layer-by-layer (LBL) self-assembly technique. NB premixed with polyanion poly (sodium-p-styrenesulfonate) (PSS) acts as the mediator between the immobilized HRP and the electrode surface. The response of the biosensor to hydrogen peroxide has been investigated. The linear range of the biosensor to hydrogen peroxide was from 0.20 mmol/L to 7.03 mmol/L with a sensitivity of 8.45μA/(mmol/L).

  9. Description of premixing with the MC3D code including molten jet behavior modeling. Comparison with FARO experimental results

    Energy Technology Data Exchange (ETDEWEB)

    Berthoud, G.; Crecy, F. de; Meignen, R.; Valette, M. [CEA-G, DRN/DTP/SMTH, 17 rue des Martyrs, 38054 Grenoble Cedex 9 (France)


    The premixing phase of a molten fuel-coolant interaction is studied by the way of mechanistic multidimensional calculation. Beside water and steam, corium droplet flow and continuous corium jet flow are calculated independent. The 4-field MC3D code and a detailed hot jet fragmentation model are presented. MC3D calculations are compared to the FARO L14 experiment results and are found to give satisfactory results; heat transfer and jet fragmentation models are still to be improved to predict better final debris size values. (author)

  10. Breakup of jet and drops during premixing phase of fuel coolant interactions

    Energy Technology Data Exchange (ETDEWEB)

    Haraldsson, Haraldur Oskar


    During the course of a hypothetical severe accident in a light water reactor, molten liquid may be introduced into a volatile coolant, which, under certain conditions, results in explosive interactions. Such fuel-coolant interactions (FCI) are characterised by an initial pre-mixing phase during which the molten liquid, metallic or oxidic in nature, undergoes a breakup (fragmentation) process which significantly increase the area available for melt-coolant contact, and thus energy transfer. Although substantial progress in the understanding of phenomenology of the FCI events has been achieved in recent years, there remain uncertainties in describing the primary and secondary breakup processes. The focus of this work is on the melt jet and drop breakup during the premixing phase of FCI. The objectives are to gain insight into the premixing phase of the FCI phenomena, to determine what fraction of the melt fragments and determine the size distribution. The approach is to perform experiments with various simulant materials, at different scales, different conditions and with variation of controlling parameters affecting jet and drop breakup processes. The analysis approach is to investigate processes at different level of detail and complexity to understand the physics, to rationalise experimental results and to develop and validate models. In the first chapter a brief introduction and review of the status of the FCI phenomena is performed. A review of previous and current experimental projects is performed. The status of the experimental projects and major findings are outlined. The first part of the second chapter deals with experimental investigation of jet breakup. Two series of experiments were performed with low and high temperature jets. The low temperature experiments employed cerrobend-70 as jet liquid. A systematic investigation of thermal hydraulic conditions and melt physical properties on the jet fragmentation and particle debris characteristics was

  11. Glycemic control with insulin glargine plus insulin glulisine versus premixed insulin analogues in real-world practices: a cost-effectiveness study with a randomized pragmatic trial design. (United States)

    Levin, Philip A; Zhang, Quanwu; Mersey, James H; Lee, Francis Y; Bromberger, Lee A; Bhushan, Madhu; Bhushan, Rajat


    Cost can be an important consideration, along with safety and efficacy, in deciding the most appropriate treatment for patients with type 2 diabetes. Both basal-bolus and premixed insulin analogue regimens are widely used in clinical practice; however, limited information is available regarding cost-effectiveness. The goal of this study was to compare glycemic control, cost-effectiveness, and quality of life effects of insulin glargine plus insulin glulisine (glargine/glulisine) versus premixed insulin analogues in real-world clinical practice. Adults with type 2 diabetes (glycosylated hemoglobin [HbA(1c)] ≥7.0%) at 3 US endocrinology centers were randomly assigned to receive either glargine/glulisine or premixed insulin analogues and continued treatment following the centers' usual practice. HbA(1c), weight, insulin dose, concomitant oral antidiabetic drug (OAD) usage, and hypoglycemia were evaluated at baseline and 3, 6, and 9 months. Medication costs, including costs for all insulin or OAD regimens, were estimated using published wholesale acquisition costs. A total of 197 patients were randomized to receive glargine/glulisine therapy (n = 106) or premixed analogue therapy (n = 91). Overall, the mean age was 56 years, the mean duration of diabetes was 13 years, with a mean HbA(1c) of 9.25% and mean BMI of 35.8 kg/m(2) at baseline. Patients randomized to receive glargine/glulisine had a greater mean HbA(1c) reduction from baseline (-2.3%) than patients receiving a premixed analogue regimen (-1.7%). Adjusted mean follow-up HbA(1c) was 6.9% versus 7.5%, respectively (difference, -0.59%; P < 0.01). The glargine/glulisine group also used a lower mean number of OADs (0.86 vs 1.14; difference, -0.28; P = 0.04) but had a higher weight (240 vs 235 lb; difference, 4.55 lb; P = 0.03) than the premixed analogue group at follow-up. There were no significant differences in daily insulin dose and rates of hypoglycemia. Overall medication costs per 1.0% reduction in HbA(1c

  12. Sphingomyelinase D activity in model membranes: structural effects of in situ generation of ceramide-1-phosphate

    DEFF Research Database (Denmark)

    Stock, Roberto; Brewer, Jonathan R.; Wagner, Kerstin


    membranes were studied both by in situ generation of this lipid using a recombinant sphingomyelinase D from the spider Loxosceles laeta and by pre-mixing it with sphingomyelin and cholesterol. The systems of choice were large unilamellar vesicles for bulk studies (enzyme kinetics, fluorescence spectroscopy...... sphingomyelin were examined. The findings indicate that: 1) ceramide-1-phosphate (particularly lauroyl ceramide-1-phosphate) can be incorporated into sphingomyelin bilayers in a concentration-dependent manner and generates coexistence of liquid disordered/solid ordered domains, 2) the activity...... of sphingomyelinase D is clearly influenced by the supramolecular organization of its substrate in membranes and, 3) in situ ceramide-1-phosphate generation by enzymatic activity profoundly alters the lateral structure and morphology of the target membranes....

  13. Vortex-assisted surfactant-enhanced emulsification liquid-liquid microextraction for the determination of carbamates in juices by micellar electrokinetic chromatography tandem mass spectrometry. (United States)

    Moreno-González, David; Huertas-Pérez, José F; García-Campaña, Ana M; Gámiz-Gracia, Laura


    A new method based on vortex-assisted surfactant-enhanced-emulsification liquid-liquid microextraction has been developed for the extraction of carbamate pesticides in juice samples prior to their determination by micellar electrokinetic chromatography coupled to tandem mass spectrometry. This sample treatment allowed the satisfactory extraction and the extract clean-up of 25 carbamates from different fruit and vegetal juices (banana, tomato, and peach). In this study, the addition of ammonium perfluorooctanoate in the aqueous sample in combination with vortex agitation, provided very clean extracts with short extraction times. Under optimized conditions, recoveries of the proposed method for these pesticides from fortified juice samples ranged from 81% to 104%, with relative standard deviations lower than 15%. Limits of quantification were between 2.3µgkg(-)(1) and 4.7µgkg(-)(1), showing the high sensitivity of this fast and simple method.

  14. Methods of Soft Tissue Emulsification Using a Mechanism of Ultrasonic Atomization Inside Gas or Vapor Cavities and Associated Systems and Devices (United States)

    Sapozhnikov, Oleg A. (Inventor); Bailey, Michael R. (Inventor); Crum, Lawrence A. (Inventor); Khokhlova, Tatiana D. (Inventor); Khokhlova, Vera A. (Inventor); Simon, Julianna C. (Inventor); Wang, Yak-Nam (Inventor)


    The present technology is directed to methods of soft tissue emulsification using a mechanism of ultrasonic atomization inside gas or vapor cavities, and associated systems and devices. In several embodiments, for example, a method of non-invasively treating tissue includes pulsing ultrasound energy from the ultrasound source toward the target site in tissue. The ultrasound source is configured to emit high intensity focused ultrasound (HIFU) waves. The target site comprises a pressure-release interface of a gas or vapor cavity located within the tissue. The method continues by generating shock waves in the tissue to induce a lesion in the tissue at the target site. The method additionally includes characterizing the lesion based on a degree of at least one of a mechanical or thermal ablation of the tissue.

  15. Ultrasound-assisted emulsification microextraction for determination of 2,4,6-trichloroanisole in wine samples by gas chromatography tandem mass spectrometry. (United States)

    Fontana, Ariel R; Patil, Sangram H; Banerjee, Kaushik; Altamirano, Jorgelina C


    A fast and effective microextraction technique is proposed for preconcentration of 2,4,6-trichloroanisole (2,4,6-TCA) from wine samples prior gas chromatography tandem mass spectrometric (GC-MS/MS) analysis. The proposed technique is based on ultrasonication (US) for favoring the emulsification phenomenon during the extraction stage. Several variables influencing the relative response of the target analyte were studied and optimized. Under optimal experimental conditions, 2,4,6-TCA was quantitatively extracted achieving enhancement factors (EF) > or = 400 and limits of detection (LODs) 0.6-0.7 ng L(-1) with relative standard deviations (RSDs) or = 0.9995. Validation of the methodology was carried out by standard addition method at two concentrations (10 and 50 ng L(-1)) achieving recoveries >80% indicating satisfactory robustness of the method. The methodology was successfully applied for determination of 2,4,6-TCA in different wine samples.

  16. Nanoformulation of poly(ethylene glycol) polymerized organic insect repellent by PIT emulsification method and its application for Japanese encephalitis vector control. (United States)

    Balaji, A P B; Mishra, Prabhakar; Suresh Kumar, R S; Mukherjee, Amitava; Chandrasekaran, Natarajan


    The utilization of increased dosage of insect repellents to overcome mosquito resistance has raised environmental concerns globally. In accord to this, we have formulated an efficacious, water-dispersive, nanometric formulation of a poor water-soluble insect repellent, diethylphenylacetamide (DEPA) by poly(ethylene glycol) (PEG) polymerization followed by PIT emulsification method. The critical micelle concentration of PEG in the spontaneously emulsified conventional DEPA droplets was determined, based on the droplets physical stability. Subjecting them to PIT emulsification yielded monodispersed polymeric nanomicelles of DEPA (Nano DEPA) with hydrodynamic mean diameter of 153.74 nm. The high-resolution scanning and transmission electron microscopic studies revealed the characteristic core-shell structure of micelle. The comparative efficacy of Bulk DEPA and Nano DEPA was evaluated by larvicidal and WHO cone bioassay against the Japanese encephalitis vector Culex tritaeniorhynchus. The median lethal concentrations (48 h) for 3rd instars C. tritaeniorhynchus larvae were found to be 0.416 mg/L for Bulk DEPA and 0.052 mg/L for Nano DEPA, respectively. The median knockdown concentrations (60 min) for the two to three-day-old, sucrose-fed, female adult mosquitoes were 5.372% (v/v) and 3.471% (v/v) for Bulk and Nano DEPA, respectively. Further investigation by histopathological and biochemical studies propound that Nano DEPA exerted better bioefficacy as comparative to its bulk form even at minimal exposure concentrations. Hence, Nano DEPA will serve as an effective alternate in controlling the vector expansion with reduced dosage.

  17. A study of the effects of phenolic de-emulsifier solutions in xylene on the de-emulsification of a Nigerian crude oil emulsion

    Directory of Open Access Journals (Sweden)

    Vincent Enontiemonria Efeovbokhan


    Full Text Available The research and development of de-emulsifiers for separating water from crude oil emulsions usually result in varying degrees of success, depending on the location and the type of crude being treated. This makes de-emulsifiers crude oil specific and thus gives rise to the continuous search for more and effective de-emulsifiers that can meet the specific needs of each locality. In this study, base-catalyzed phenol formaldehyde resins were formulated at varying formaldehyde to phenol ratios (1.2:1–1.8:1; the assessment was carried out by the bottle test method at varied de-emulsifier concentrations (vol/vol in xylene acting as solvent diluent. The bottle test was carried out at an optimum temperature of 70 °C, dosage of 50 ppm and residence times of 10 and 20 min. A factorial design was done to determine the best combination of the de-emulsification conditions for the resolution of the Nigerian crude oil emulsion. The results were analyzed and optimized using Minitab 16 utilizing a Pareto chart, normal effects, main effects and interaction plots. From the analysis carried out, it was found that the most effective formulated de-emulsifier was obtained at formaldehyde to phenol (F:P mole ratio of 1.8:1, 80% de-emulsifier concentration in xylene and residence time of 20 min. This de-emulsifier obtained a water separation efficiency of 79% compared to the commercial de-emulsifier which gave 71% efficiency. Thus the solution of P:F de-emulsifiers in xylene enhances the de-emulsification of the Nigerian crude oil emulsions.

  18. Sub-grid scale combustion models for large eddy simulation of unsteady premixed flame propagation around obstacles. (United States)

    Di Sarli, Valeria; Di Benedetto, Almerinda; Russo, Gennaro


    In this work, an assessment of different sub-grid scale (sgs) combustion models proposed for large eddy simulation (LES) of steady turbulent premixed combustion (Colin et al., Phys. Fluids 12 (2000) 1843-1863; Flohr and Pitsch, Proc. CTR Summer Program, 2000, pp. 61-82; Kim and Menon, Combust. Sci. Technol. 160 (2000) 119-150; Charlette et al., Combust. Flame 131 (2002) 159-180; Pitsch and Duchamp de Lageneste, Proc. Combust. Inst. 29 (2002) 2001-2008) was performed to identify the model that best predicts unsteady flame propagation in gas explosions. Numerical results were compared to the experimental data by Patel et al. (Proc. Combust. Inst. 29 (2002) 1849-1854) for premixed deflagrating flame in a vented chamber in the presence of three sequential obstacles. It is found that all sgs combustion models are able to reproduce qualitatively the experiment in terms of step of flame acceleration and deceleration around each obstacle, and shape of the propagating flame. Without adjusting any constants and parameters, the sgs model by Charlette et al. also provides satisfactory quantitative predictions for flame speed and pressure peak. Conversely, the sgs combustion models other than Charlette et al. give correct predictions only after an ad hoc tuning of constants and parameters.

  19. Adjoint-based sensitivity of flames to ignition parameters in non-premixed shear-flow turbulence (United States)

    Capecelatro, Jesse; Bodony, Daniel; Freund, Jonathan


    The adjoint of the linearized and perturbed compressible flow equations for a mixture of chemically reacting ideal gases is used to assess the sensitivity of ignition in non-premixed shear-flow turbulence. Direct numerical simulations are used to provide an initial prediction, and the corresponding space-time discrete-exact adjoint is used to provide a sensitivity gradient for a specific quantity of interest (QoI). Owing to the ultimately binary outcome of ignition (i.e., it succeeds or fails after some period), a QoI is defined that both quantifies ignition success and varies smoothly near its threshold based on the heat release parameter in a short-time horizon during the ignition process. We use the resulting gradient to quantify the flow properties and model parameters that most affect the initiation of a sustained flame. A line-search algorithm is used to identify regions of high ignition probability and map the boundary between successful and failed ignition. The approach is demonstrated on a non-premixed turbulent shear layer and on a reacting jet-in-crossflow.

  20. CSP-based chemical kinetics mechanisms simplification strategy for non-premixed combustion: An application to hybrid rocket propulsion

    KAUST Repository

    Ciottoli, Pietro P.


    A set of simplified chemical kinetics mechanisms for hybrid rocket applications using gaseous oxygen (GOX) and hydroxyl-terminated polybutadiene (HTPB) is proposed. The starting point is a 561-species, 2538-reactions, detailed chemical kinetics mechanism for hydrocarbon combustion. This mechanism is used for predictions of the oxidation of butadiene, the primary HTPB pyrolysis product. A Computational Singular Perturbation (CSP) based simplification strategy for non-premixed combustion is proposed. The simplification algorithm is fed with the steady-solutions of classical flamelet equations, these being representative of the non-premixed nature of the combustion processes characterizing a hybrid rocket combustion chamber. The adopted flamelet steady-state solutions are obtained employing pure butadiene and gaseous oxygen as fuel and oxidizer boundary conditions, respectively, for a range of imposed values of strain rate and background pressure. Three simplified chemical mechanisms, each comprising less than 20 species, are obtained for three different pressure values, 3, 17, and 36 bar, selected in accordance with an experimental test campaign of lab-scale hybrid rocket static firings. Finally, a comprehensive strategy is shown to provide simplified mechanisms capable of reproducing the main flame features in the whole pressure range considered.

  1. Laminar partially premixed flame stability - application to domestic burner; Stabilite de flammes laminaires partiellement premelangees. Application aux bruleurs domestiques

    Energy Technology Data Exchange (ETDEWEB)

    Lacour, C.


    Phenomena responsible of partially premixed laminar flame stabilisation are investigated on a rich premixed burner configuration. The structure and aerodynamic of the flame generated by a cooking model burner are characterized by Planar Laser Induced Fluorescence of OH radical and Particle Image Velocimetry. The flame behaviour is studied from a stable reference case toward blow-out by varying the flow inlet conditions, the burner geometry and its thermal properties. The flame can be considered as two neighbour and independent reactive zones, each consisting of a double edge flame. The upper double flame stabilisation is similar to the one of a Bunsen burner with a flame-holder attached base and a flame tip stabilized in the flow according to the ratio of the flow velocity and flame speed of the rich pre-mixture. The bottom double flame is stabilized at the crossing point of the stoichiometric flame speed. The flame is finally blown out when there is no more crossing point. (author)

  2. Experimental study on the effects of the number of heat exchanger modules on thermal characteristics in a premixed combustion system

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Byeonghun; Lee, Chang-Eon [Inha University, Incheon (Korea, Republic of); Kum, Sung Min [Halla University, Wonju (Korea, Republic of); Lee, Seungro [Chonbuk National University, Jeonju (Korea, Republic of)


    The effects of the number of heat exchanger modules on thermal characteristics were experimentally studied in a premixed combustion system with a cross-flow staggered-tube heat exchanger. The various heat exchanger modules, from 4 to 8, combined with a premixed burner were tested to investigate the performance of the heat exchanger through the surface area of the heat exchanger at various equivalence ratios. Additionally, the performance of the heat exchanger was analyzed by applying entropy generation theory to the heat exchanger system. As a result, although the heat transfer rate increases with the increase of the equivalence ratio, the NOx and CO concentrations also increase due to the increasing flame temperature. In addition, the entropy generation increases with an increase of the equivalence ratio. Furthermore, the heat transfer rate and the effectiveness are increased with the increase of the number of the heat exchanger modules. Also, the effectiveness is sharply increased when the number of the heat exchanger modules is increased from 4 to 5. Consequently, the optimal operating conditions regarding pollutant emission, effectiveness and entropy generation in this experimental range are 0.85 for the equivalence ratio and 8 for the number of heat exchanger modules.

  3. Turbulence-flame interactions in DNS of a laboratory high Karlovitz premixed turbulent jet flame (United States)

    Wang, Haiou; Hawkes, Evatt R.; Chen, Jacqueline H.


    In the present work, direct numerical simulation (DNS) of a laboratory premixed turbulent jet flame was performed to study turbulence-flame interactions. The turbulent flame features moderate Reynolds number and high Karlovitz number (Ka). The orientations of the flame normal vector n, the vorticity vector ω and the principal strain rate eigenvectors ei are examined. The in-plane and out-of-plane angles are introduced to quantify the vector orientations, which also measure the flame geometry and the vortical structures. A general observation is that the distributions of these angles are more isotropic downstream as the flame and the flow become more developed. The out-of-plane angle of the flame normal vector, β, is a key parameter in developing the correction of 2D measurements to estimate the corresponding 3D quantities. The DNS results show that the correction factor is unity at the inlet and approaches its theoretical value of an isotropic distribution downstream. The alignment characteristics of n, ω and ei, which reflect the interactions of turbulence and flame, are also studied. Similar to a passive scalar gradient in non-reacting flows, the flame normal has a tendency to align with the most compressive strain rate, e3, in the flame, indicating that turbulence contributes to the production of scalar gradient. The vorticity dynamics are examined via the vortex stretching term, which was found to be the predominant source of vorticity generation balanced by dissipation, in the enstrophy transport equation. It is found that although the vorticity preferentially aligns with the intermediate strain rate, e2, the contribution of the most extensive strain rate, e1, to vortex stretching is comparable with that of the intermediate strain rate, e2. This is because the eigenvalue of the most extensive strain rate, λ1, is always large and positive. It is confirmed that the vorticity vector is preferentially positioned along the flame tangential plane, contributing

  4. Multi-zone modelling of partially premixed low-temperature combustion in pilot-ignited natural-gas engines

    Energy Technology Data Exchange (ETDEWEB)

    Krishnan, S. R.; inivasan, K. K.


    Detailed results from a multi-zone phenomenological simulation of partially premixed advanced-injection low-pilot-ignited natural-gas low-temperature combustion are presented with a focus on early injection timings (the beginning of (pilot) injection (BOI)) and very small diesel quantities (2-3 per cent of total fuel energy). Combining several aspects of diesel and spark ignition engine combustion models, the closed-cycle simulation accounted for diesel autoignition, diesel spray combustion, and natural-gas combustion by premixed turbulent flame propagation. The cylinder contents were divided into an unburned zone, several pilot fuel zones (or 'packets') that modelled diesel evaporation and ignition, a flame zone for natural-gas combustion, and a burned zone. The simulation predicted the onset of ignition, cylinder pressures, and heat release rate profiles satisfactorily over a wide range of BOIs (20-60° before top dead centre (before TDC)) but especially well at early BOIs. Strong coupling was observed between pilot spray combustion in the packets and premixed turbulent combustion in the flame zone and, therefore, the number of ignition centres (packets) profoundly affected flame combustion. The highest local peak temperatures (greater than 2000 K) were observed in the packets, while the flame zone was much cooler (about 1650 K), indicating that pilot diesel spray combustion is probably the dominant source of engine-out emissions of nitrogen oxide (NOx). Further, the 60° before TDC BOI yielded the lowest average peak packet temperatures (about 1720 K) compared with the 20° before TDC BOI (about 2480 K) and 40° before TDC BOI (about 2700 K). These trends support experimental NOx trends, which showed the lowest NOx emissions for the 60°, 20°, and 40° before TDC BOIs in that order. Parametric studies showed that increasing the intake charge temperature, pilot quantity, and natural-gas equivalence ratio all led to

  5. Effect of the composition of the hot product stream in the quasi-steady extinction of strained premixed flames

    Energy Technology Data Exchange (ETDEWEB)

    Coriton, Bruno; Smooke, Mitchell D.; Gomez, Alessandro [Department of Mechanical Engineering, Yale Center for Combustion Studies, Yale University, New Haven, CT 06520-8286 (United States)


    The extinction of premixed CH{sub 4}/O{sub 2}/N{sub 2} flames counterflowing against a jet of combustion products in chemical equilibrium was investigated numerically using detailed chemistry and transport mechanisms. Such a problem is of relevance to combustion systems with non-homogeneous air/fuel mixtures or recirculation of the burnt gases. Contrary to similar studies that were focused on heat loss/gain, depending on the degree of non-adiabaticity of the system, the emphasis here was on the yet unexplored role of the composition of counterflowing burnt gases in the extinction of lean-to-stoichiometric premixed flames. For a given temperature of the counterflowing products of combustion, it was found that the decrease of heat release with increase in strain rate could be either monotonic or non-monotonic, depending on the equivalence ratio {phi}{sub b} of the flame feeding the hot combustion product stream. Two distinct extinction modes were observed: an abrupt one, when the hot counterflowing stream consists of either inert gas or equilibrium products of a stoichiometric premixed flame, and a smooth extinction, when there is an excess of oxidizing species in the combustion product stream. In the latter case four burning regimes can be distinguished as the strain rate is progressively increased while the heat release decreases smoothly: an adiabatic propagating flame regime, a non-adiabatic propagating flame regime, the so-called partially-extinguished flame regime, in which the location of the peak of heat release crosses the stagnation plane, and a frozen flow regime. The flame structure was analyzed in detail in the different burning regimes. Abrupt extinction was attributed to the quenching of the oxidation layer with the entire H-OH-O radical pool being comparably reduced. Under conditions of smooth extinction, the behavior is different and the concentration of the H radical decreases the most with increasing strain rate, whereas OH and O remain

  6. Primordial membranes

    DEFF Research Database (Denmark)

    Hanczyc, Martin M; Monnard, Pierre-Alain


    Cellular membranes, which are self-assembled bilayer structures mainly composed of lipids, proteins and conjugated polysaccharides, are the defining feature of cell physiology. It is likely that the complexity of contemporary cells was preceded by simpler chemical systems or protocells during the...

  7. Robotic membranes

    DEFF Research Database (Denmark)

    Ramsgaard Thomsen, Mette


    , Vivisection and Strange Metabolisms, were developed at the Centre for Information Technology and Architecture (CITA) at the Royal Danish Academy of Fine Arts in Copenhagen as a means of engaging intangible digital data with tactile physical material. As robotic membranes, they are a dual examination...

  8. Experimental study of the structure of rich premixed 1,3-butadiene/CH4/O2/Ar flame

    CERN Document Server

    Gueniche, Hadj-Ali; Fournet, René; Battin-Leclerc, Frédérique


    The structure of a laminar rich premixed 1,3-C4H6/CH4/O2/Ar flame have been investigated. 1,3-Butadiene, methane, oxygen and argon mole fractions are 0.033; 0.2073; 0.3315, and 0.4280, respectively, for an equivalent ratio of 1.80. The flame has been stabilized on a burner at a pressure of 6.7 kPa (50 Torr). The concentration profiles of stable species were measured by gas chromatography after sampling with a quartz probe. Quantified species included carbon monoxide and dioxide, methane, oxygen, hydrogen, ethane, ethylene, acetylene, propyne, allene, propene, cyclopropane, 1,3-butadiene, butenes, 1-butyne, vinylacetylene, diacetylene, C5 compounds, benzene, and toluene. The temperature was measured thanks to a thermocouple in PtRh (6%)-PtRh (30%) settled inside the enclosure and ranged from 900 K close to the burner up to 2100 K.

  9. Concept for premixed combustion of hydrogen-containing fuels in gas turbines; Konzept zur vorgemischten Verbrennung wasserstoffhaltiger Brennstoffe in Gasturbinen

    Energy Technology Data Exchange (ETDEWEB)

    Mayer, Christoph


    One of the main challenges for future gas turbines and their combustion systems is to provide fuel flexibility. The fuel range is expected to reach from the lowly reactive natural gas to highly reactive hydrogen-containing syngases. The objective of the project in which this work was pursued is to develop such a combustion system. The burner has to ensure premixed operation with an aerodynamically stabilized flame. The focus of this work is on characterizing and optimizing the operational safety of the system, but also on ensuring sufficientmixing and lowemissions. A burner and fuel injection design is achieved that leads not only to emissions far below the permissible values, but also to flashback safety for hydrogen combustion that comes close to the theoretically achievable maximum at atmospheric pressure conditions. In this design flashback due to combustion-induced vortex breakdown and wall boundary layer flashback is avoided. Flashback only takes place when the flow velocity reaches the flame velocity.

  10. Implementation variations of adiabatic steady PPDF flamelet model in turbulent H2/air non-premixed combustion simulation

    Directory of Open Access Journals (Sweden)

    Qiong Li


    Full Text Available Implementation of the adiabatic steady PPDF flamelet model involves a lot of variations including different scalar dissipation rate calculation methods and different mass diffusion models of the opposed jet flame. Four different look-up tables have been generated with the combinations of two different scalar dissipation rate calculation methods and two different mass diffusion models of the opposed jet flame. Simulation of a turbulent non-premixed H2 jet flame is used to discriminate the accuracy of different implementation methods by comparison with experimental data. It is observed that the turbulent flamelets are very close to their equilibrium states and the simulation result is not sensitive to the choice of dissipation rate calculation method. However, the choice of mass diffusion model has significant influence on the simulation result and excluding the Lewis number effect should be enforced for the opposed jet flame simulation.

  11. Effect of vorticity flip-over on the premixed flame structure: First experimental observation of type I inflection flames

    CERN Document Server

    El-Rabii, Hazem


    Premixed flames propagating in horizontal tubes are observed to take on shape convex towards the fresh mixture, which is commonly explained as a buoyancy effect. A recent rigorous analysis has shown, on the contrary, that this process is driven by the balance of vorticity generated by a curved flame front with the baroclinic vorticity, and predicted existence of a regime in which the leading edge of the flame front is concave. We report first experimental realization of this regime. Our experiments on ethane and n-butane mixtures with air show that flames with an inflection point on the front are regularly produced in lean mixtures, provided that a sufficiently weak ignition is used. The observed flame shape perfectly agrees with the theoretically predicted.


    Institute of Scientific and Technical Information of China (English)

    Jinling Li; Suyuan Yu


    A laminar premixed Propane/Air flame with a fuel equivalence ratio of 2.1 was employed for analysis of soot particles. Zeroth-order Iognormal distributions (ZOLD) were used in the analysis of experimental distribution phenomena at different residence times during soot formation in the flame. Rayleigh's theory and Mie's scattering theory were combined with agglomerate analysis using scattering and extinction data to determine the following soot characteristics: agglomerate parameters, volumetric fractions, mass flow rates and surface growth rate. Soot density measurements were carried out to determine density variations at different stages of growth. The measured results show that metric fraction and mass flow rate indicate that the surface growth rate of soot particles exceeds the oxidation rates in the flame studied. The data obtained in this work would be used to study soot oxidation rate under flaming condition.

  13. A New Type of Steady and Stable, Laminar, Premixed Flame in Ultra-Lean, Hydrogen-Air Combustion

    Energy Technology Data Exchange (ETDEWEB)

    Grcar, Joseph F; Grcar, Joseph F


    Ultra-lean, hydrogen-air mixtures are found to support another kind of laminar flame that is steady and stable beside flat flames and flame balls. Direct numerical simulations are performed of flames that develop into steadily and stably propagating cells. These cells were the original meaning of the word"flamelet'' when they were observed in lean flammability studies conducted early in the development of combustion science. Several aspects of these two-dimensional flame cells are identified and are contrasted with the properties of one-dimensional flame balls and flat flames. Although lean hydrogen-air flames are subject to thermo-diffusive effects, in this case the result is to stabilize the flame rather than to render it unstable. The flame cells may be useful as basic components of engineering models for premixed combustion when the other types of idealized flames are inapplicable.

  14. Calculation and analysis of the mobility and diffusion coefficient of thermal electrons in methane/air premixed flames

    KAUST Repository

    Bisetti, Fabrizio


    Simulations of ion and electron transport in flames routinely adopt plasma fluid models, which require transport coefficients to compute the mass flux of charged species. In this work, the mobility and diffusion coefficient of thermal electrons in atmospheric premixed methane/air flames are calculated and analyzed. The electron mobility is highest in the unburnt region, decreasing more than threefold across the flame due to mixture composition effects related to the presence of water vapor. Mobility is found to be largely independent of equivalence ratio and approximately equal to 0.4m 2V -1s -1 in the reaction zone and burnt region. The methodology and results presented enable accurate and computationally inexpensive calculations of transport properties of thermal electrons for use in numerical simulations of charged species transport in flames. © 2012 The Combustion Institute.

  15. A Detailed Chemical Kinetic Reaction Mechanism for Oxidation of Four Small Alkyl Esters in Laminar Premixed Flames

    Energy Technology Data Exchange (ETDEWEB)

    Westbrook, C K; Pitz, W J; Westmoreland, P R; Dryer, F L; Chaos, M; Osswald, P; Kohse-Hoinghaus, K; Cool, T A; Wang, J; Yang, B; Hansen, N; Kasper, T


    A detailed chemical kinetic reaction mechanism has been developed for a group of four small alkyl ester fuels, consisting of methyl formate, methyl acetate, ethyl formate and ethyl acetate. This mechanism is validated by comparisons between computed results and recently measured intermediate species mole fractions in fuel-rich, low pressure, premixed laminar flames. The model development employs a principle of similarity of functional groups in constraining the H atom abstraction and unimolecular decomposition reactions in each of these fuels. As a result, the reaction mechanism and formalism for mechanism development are suitable for extension to larger oxygenated hydrocarbon fuels, together with an improved kinetic understanding of the structure and chemical kinetics of alkyl ester fuels that can be extended to biodiesel fuels. Variations in concentrations of intermediate species levels in these flames are traced to differences in the molecular structure of the fuel molecules.

  16. Characterization of temperature non-uniformity over a premixed CH4-air flame based on line-of-sight TDLAS (United States)

    Zhang, Guangle; Liu, Jianguo; Xu, Zhenyu; He, Yabai; Kan, Ruifeng


    A novel technique for characterizing temperature non-uniformity has been investigated based on measurements of line-of-sight tunable diode laser absorption spectroscopy. It utilized two fiber-coupled distributed feedback diode lasers at wavelengths around 1339 and 1392 nm as light sources to probe the field at multiple absorptions lines of water vapor and applied a temperature binning strategy combined with Gauss-Seidel iteration method to explore the temperature non-uniformity of the field in one dimension. The technique has been applied to a McKenna burner, which produced a flat premixed laminar CH4-air flame. The flame and its adjacent area formed an atmospheric field with significant non-uniformity of temperature and water vapor concentration. The effect of the number of temperature bins on column-density and temperature results has also been explored.

  17. Determination of the Burning Velocity Domain of a Statistically Stationary Turbulent Premixed Flame in Presence of Counter-Gradient Transport

    Directory of Open Access Journals (Sweden)

    V. A. Sabel'nikov


    Full Text Available The present study aims at providing a complete picture of the various propagation scenarios that a statistically stationary turbulent premixed flame may possibly undergo. By explicitly splitting the scalar turbulent flux between its gradient and counter-gradient contributions, the scalar governing equation is rewritten as an ordinary differential equation in the phase space. Then, an analysis of the characteristic equations in the vicinity of the reactants and products side is carried out. The domain of existence of the propagation velocity is then determined and positioned over the relevant Bray number range. It is shown in particular that when a counter-gradient transport at the cold leading edge of the flame is dominant, there still exists a possibility of observing a steady regime of propagation. This conclusion is compatible with recent experimental data and observations based on the analysis of direct numerical simulations.

  18. Decreasing the emissions of a partially premixed gasoline fueled compression ignition engine by means of injection characteristics and EGR

    Directory of Open Access Journals (Sweden)

    Nemati Arash


    Full Text Available This paper is presented in order to elucidate some numerical investigations related to a partially premixed gasoline fuelled engine by means of three dimensional CFD code. Comparing with the diesel fuel, gasoline has lower soot emission because of its higher ignition delay. The application of double injection strategy reduces the maximum heat release rate and leads to the reduction of NOx emission. For validation of the model, the results for the mean in-cylinder pressure, H.R.R., NOx and soot emissions are compared with the corresponding experimental data and show good levels of agreement. The effects of injection characteristics such as, injection duration, spray angle, nozzle hole diameter, injected fuel temperature and EGR rate on combustion process and emission formation are investigated yielding the determination of the optimal point thereafter. The results indicated that optimization of injection characteristics leads to simultaneous reduction of NOx and soot emissions with negligible change in IMEP.

  19. Analysis of fuel spray characteristics for premixed lean diesel combustion; Kihaku yokongo diesel kikan ni okeru nenryo funmu kaiseki

    Energy Technology Data Exchange (ETDEWEB)

    Sasaki, S.; Harada, a.; Miyamoto, T.; Akagawa, H.; Tsujimura, K.


    Premixed lean diesel combustion (PREDIC) makes it possible to achieve low NOx emission. It is an important factor to make the homogeneous spray formation for PREDIC. In this paper presents I the effect of the spray dispersion on emission characteristic were analyzed with the spray observation and engine test. Pintle type nozzle, which has different feature from orifice type nozzle, are used to form the hollow cone spray. As a result, the pintle type nozzle having grooves to generate the swirl flow, makes the reduced penetration in comparison with the hole nozzle under low ambient gas pressure. And it could improve THC, CO emissions at low NOx emission condition. 7 refs., 12 figs., 1 tab.

  20. Dynamic behavior of thermoacoustic combustion oscillations in a lean premixed gas-turbine model combustor with and without active control (United States)

    Tsujimoto, Ryosuke; Domen, Shohei; Okuno, Yuta; Nakagaki, Yoshitake; Gotoda, Hiroshi


    We experimentally study the dynamic behavior of thermoacoustic combustion oscillations in a laboratory-scale lean premixed gas-turbine model combustor with and without active control. We adopt the delayed feedback control method based on the concept of chaos control to suppress thermoacoustic combustion oscillations. The unstable periodic orbits in the attractor of uncontrolled thermoacoustic combustion oscillations are led to the desired orbits with a small diameter of the attractor when the perturbation is switched on, resulting in the notable suppression of thermoacoustic combustion oscillations. Color-recurrence plots (Gotoda et al., Phys. Rev. E 89, 022910 (2014)) are used for characterizing the complexity of the combustion state with and without delayed feedback control.

  1. On the effects of fuel properties and injection timing in partially premixed compression ignition of low octane fuels

    KAUST Repository

    Naser, Nimal


    A better understanding on the effects of fuel properties and injection timing is required to improve the performance of advanced engines based on low temperature combustion concepts. In this work, an experimental and computational study was conducted to investigate the effects of physical and chemical kinetic properties of low octane fuels and their surrogates in partially premixed compression ignition (PPCI) engines. The main objective was to identify the relative importance of physical versus chemical kinetic properties in predicting practical fuel combustion behavior across a range of injection timings. Two fuel/surrogate pairs were chosen for comparison: light naphtha (LN) versus the primary reference fuel (PRF) with research octane number of 65 (PRF 65), and FACE (fuels for advanced combustion engines) I gasoline versus PRF 70. Two sets of parametric studies were conducted: the first varied the amount of injected fuel mass at different injection timings to match a fixed combustion phasing, and the second maintained the same injected fuel mass at each injection timing to assess resulting combustion phasing changes. Full-cycle computational fluid dynamic engine simulations were conducted by accounting for differences in the physical properties of the original and surrogate fuels, while employing identical chemical kinetics. The simulations were found to capture trends observed in the experiments, while providing details on spatial mixing and chemical reactivity for different fuels and injection timings. It was found that differences in physical properties become increasingly important as injection timing was progressively delayed from premixed conditions, and this was rationalized by analysis of mixture stratification patterns resulting from injection of fuels with different physical properties. The results suggest that accurate descriptions of both physical and chemical behavior of fuels are critical in predictive simulations of PPCI engines for a wide range of

  2. Stabilization of a premixed methane-air flame with a high repetition nanosecond laser-induced plasma (United States)

    Yu, Yang; Li, Xiaohui; An, Xiaokang; Yu, Xin; Fan, Rongwei; Chen, Deying; Sun, Rui


    Laser-induced plasma ignition has been applied in various combustion systems, however, work on flame stabilization with repetitive laser-induced plasma (LIP) is rather limited. In this paper, stabilization of a premixed methane-air flame with a high repetition nanosecond LIP is reported. The plasma energy coupling and the temporal evolution of the flame kernels generated by the LIPs are investigated with different laser repetition rates, i.e., 1 Hz, 100 Hz and 250 Hz, respectively. The plasma energy coupling is not affected in the air flow and in the premixed methane-air flow with the applied laser repetition rates. Continuous combustion flame stabilization has been achieved with LIPs of 100 Hz and 250 Hz, in terms of catch-up and merging of the consecutive flame kernels. The flame kernel formed by the last LIP does not affect the evolution of the newly formed flame kernel by the next LIP. The catch-up distance, defined as the distance from the LIP initiation site to the flame kernel catch-up position, is estimated for different laser repetition rates based on the temporal evolution of the flame kernels. A higher laser repetition rate will lead to a shorter catch-up distance which is beneficial for flame stabilization. The up limit for the laser repetition rate to realize effective flame stabilization is determined from the critical inter-pulse delay defined from the onset of the LIP to the return of the initially contraflow propagating lower front to the LIP initiation site. The up limit is 377 Hz under the flow conditions of this work (equivalence ratio of 1, flow speed of 2 m/s, and Reynolds number of 1316).

  3. Buoyancy induced limits for nanoparticle synthesis experiments in horizontal premixed low-pressure flat-flame reactors (United States)

    Weise, C.; Faccinetto, A.; Kluge, S.; Kasper, T.; Wiggers, H.; Schulz, C.; Wlokas, I.; Kempf, A.


    Premixed low-pressure flat-flame reactors can be used to investigate the synthesis of nanoparticles. The present work examines the flow field inside such a reactor during the formation of carbon (soot) and iron oxide (from Fe(CO)5) nanoparticles, and how it affects the measurements of nanoparticle size distribution. The symmetry of the flow and the impact of buoyancy were analysed by three-dimensional simulations and the nanoparticle size distribution was obtained by particle mass spectrometry (PMS) via molecular beam sampling at different distances from the burner. The PMS measurements showed a striking, sudden increase in particle size at a critical distance from the burner, which could be explained by the flow field predicted in the simulations. The simulation results illustrate different fluid mechanical phenomena which have caused this sudden rise in the measured particle growth. Up to the critical distance, buoyancy does not affect the flow, and an (almost) linear growth is observed in the PMS experiments. Downstream of this critical distance, buoyancy deflects the hot gas stream and leads to an asymmetric flow field with strong recirculation. These recirculation zones increase the particle residence time, inducing very large particle sizes as measured by PMS. This deviation from the assumed symmetric, one-dimensional flow field prevents the correct interpretation of the PMS results. To overcome this problem, modifications to the reactor were investigated; their suitability to reduce the flow asymmetry was analysed. Furthermore, 'safe' operating conditions were identified for which accurate measurements are feasible in premixed low-pressure flat-flame reactors that are transferrable to other experiments in this type of reactor. The present work supports experimentalists to find the best setup and operating conditions for their purpose.

  4. In situ emulsification microextraction using a dicationic ionic liquid followed by magnetic assisted physisorption for determination of lead prior to micro-sampling flame atomic absorption spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Shokri, Masood; Beiraghi, Asadollah [Faculty of Chemistry, Kharazmi University, Tehran (Iran, Islamic Republic of); Seidi, Shahram, E-mail: [Department of Analytical Chemistry, Faculty of Chemistry, K.N. Toosi University of Technology, Tehran (Iran, Islamic Republic of)


    For the first time, a simple and efficient in situ emulsification microextraction method using a dicationic ionic liquid followed by magnetic assisted physisorption was presented to determine trace amounts of lead. In this method, 400 μL of 1.0 mol L{sup −1} lithium bis (trifluoromethylsulfonyl) imide aqueous solution, Li[NTf{sub 2}], was added into the sample solution containing 100 μL of 1.0 mol L{sup −1} 1,3-(propyl-1,3-diyl) bis (3-methylimidazolium) chloride, [pbmim]Cl{sub 2}, to form a water immiscible ionic liquid, [pbmim][NTf{sub 2}]{sub 2}. This new in situ formed dicationic ionic liquid was applied as the acceptor phase to extract the lead-ammonium pyrrolidinedithiocarbamate (Pb-APDC) complexes from the sample solution. Subsequently, 30 mg of Fe{sub 3}O{sub 4} magnetic nanoparticles (MNPs) were added into the sample solution to collect the fine droplets of [pbmim][NTf{sub 2}]{sub 2}, physisorptively. Finally, MNPs were eluted by acetonitrile, separated by an external magnetic field and the obtained eluent was subjected to micro-sampling flame atomic absorption spectrometry (FAAS) for further analysis. Comparing with other microextraction methods, no special devices and centrifugation step are required. Parameters influencing the extraction efficiency such as extraction time, pH, concentration of chelating agent, amount of MNPs and coexisting interferences were studied. Under the optimized conditions, this method showed high extraction recovery of 93% with low LOD of 0.7 μg L{sup −1}. Good linearity was obtained in the range of 2.5–150 μg L{sup −1} with determination coefficient (r{sup 2}) of 0.9921. Relative standard deviation (RSD%) for seven repeated measurements at the concentration of 10 μg L{sup −1} was 4.1%. Finally, this method was successfully applied for determination of lead in some water and plant samples. - Highlights: • A dicationic ionic liquid was used as the extraction solvent, for the first time. • A

  5. Application of ultrasound-assisted emulsification microextraction based on applying low-density organic solvent for the determination of organochlorine pesticides in water samples. (United States)

    Zhang, Yufeng; Lee, Hian Kee


    In this study, a polyethylene Pasteur pipette-based ultrasound-assisted emulsification microextraction (USAEME) applying low-density organic solvent was successfully developed for the extraction of trace levels of organochlorine pesticides (OCPs) in water samples and followed by gas chromatography-mass spectrometry (GC-MS) analysis. In this approach, a polyethylene Pasteur squeeze-type pipette was employed as a convenient extraction device and ultrasound radiation was applied to accelerate the emulsification of low-density organic solvent in aqueous solutions to enhance the microextraction efficiency of OCPs in water samples. Thirty microliters of extraction solvent (isooctane), of lower density than water, were injected into the aqueous sample solution held in the pipette. The latter was then immersed in an ultrasound water bath to form an emulsion. After 30s extraction, phase separation was achieved by centrifugation. The upper layer (isooctane) was collected and analyzed by GC-MS. No disperser solvent was required in this procedure. Significantly, fast analysis and high extraction efficiency were achieved. Another feature of the procedure was the use of the pipette as the extraction device, which permitted less dense than water organic solvent to be used as extraction solvent. This method broadens the applicability of USAEME to a wider range of solvent. Additionally, carry-over problems were avoided with the use of the disposable pipette. Parameters affecting the efficiency of polyethylene Pasteur pipette-based USAEME, such as the extraction solvent, extraction solvent volume, extraction and centrifugation time, ionic strength and extraction temperature were investigated. Under the optimum conditions, the proposed method provided good enrichment factors (EFs) in the range of 128 and 328, with relative standard deviations (RSDs) ranging from 2.7% to 12.4%. The limits of detection were in the range of 0.8 and 10ng/L depending on the analytes. The linearities were

  6. Rapid, highly efficient extraction and purification of membrane proteins using a microfluidic continuous-flow based aqueous two-phase system. (United States)

    Hu, Rui; Feng, Xiaojun; Chen, Pu; Fu, Meng; Chen, Hong; Guo, Lin; Liu, Bi-Feng


    Membrane proteins play essential roles in regulating various fundamental cellular functions. To investigate membrane proteins, extraction and purification are usually prerequisite steps. Here, we demonstrated a microfluidic aqueous PEG/detergent two-phase system for the purification of membrane proteins from crude cell extract, which replaced the conventional discontinuous agitation method with continuous extraction in laminar flows, resulting in significantly increased extraction speed and efficiency. To evaluate this system, different separation and detection methods were used to identify the purified proteins, such as capillary electrophoresis, SDS-PAGE and nano-HPLC-MS/MS. Swiss-Prot database with Mascot search engine was used to search for membrane proteins from random selected bands of SDS-PAGE. Results indicated that efficient purification of membrane proteins can be achieved within 5-7s and approximately 90% of the purified proteins were membrane proteins (the highest extraction efficiency reported up to date), including membrane-associated proteins and integral membrane proteins with multiple transmembrane domains. Compared to conventional approaches, this new method had advantages of greater specific surface area, minimal emulsification, reduced sample consumption and analysis time. We expect the developed method to be potentially useful in membrane protein purifications, facilitating the investigation of membrane proteomics.

  7. Controlled in meso phase crystallization--a method for the structural investigation of membrane proteins.

    Directory of Open Access Journals (Sweden)

    Jan Kubicek

    Full Text Available We investigated in meso crystallization of membrane proteins to develop a fast screening technology which combines features of the well established classical vapor diffusion experiment with the batch meso phase crystallization, but without premixing of protein and monoolein. It inherits the advantages of both methods, namely (i the stabilization of membrane proteins in the meso phase, (ii the control of hydration level and additive concentration by vapor diffusion. The new technology (iii significantly simplifies in meso crystallization experiments and allows the use of standard liquid handling robots suitable for 96 well formats. CIMP crystallization furthermore allows (iv direct monitoring of phase transformation and crystallization events. Bacteriorhodopsin (BR crystals of high quality and diffraction up to 1.3 Å resolution have been obtained in this approach. CIMP and the developed consumables and protocols have been successfully applied to obtain crystals of sensory rhodopsin II (SRII from Halobacterium salinarum for the first time.

  8. Mechanical and water-holding properties and microstructures of soy protein isolate emulsion gels induced by CaCl2, glucono-δ-lactone (GDL), and transglutaminase: influence of thermal treatments before and/or after emulsification. (United States)

    Tang, Chuan-He; Chen, Ling; Foegeding, Edward Allen


    The mechanical properties, water-holding capacities (WHC), and microstructures of emulsion gels, induced by glucono-δ-lactone (GDL), CaCl(2), and microbial transglutaminase (MTGase) from unheated and heated soy protein isolate (SPI)-stabilized emulsions (at protein concentration 5%, w/v; oil volume fraction, 20%, w/v), were investigated and compared. The influence of thermal pretreatments (at 90 °C for 5 min) before and/or after emulsification was evaluated. Considerable differences in mechanical, water-holding, and microstructural properties were observed among various emulsion gels. The thermal pretreatment after emulsification increased the strength of the emulsion gels induced by GDL and CaCl(2), whereas in the case of MTGase, thermal pretreatments before and/or after emulsification on the contrary greatly inhibited gel network formation. The application of the enzyme coagulant exhibited much higher potential to form SPI-stabilized emulsion gels with higher mechanical strength than that of the other two coagulants. The WHC of the emulsion gels seemed to be not directly related to their gel network strength. Confocal laser scanning microscope analyses indicated that the network microstructure of the formed emulsion gels, mainly composed of aggregated protein-stabilized oil droplets and protein aggregate clumps, varied with the type of applied coagulants and emulsions. The differences in microstructure were basically consistent with the differences in mechanical properties of the gels. These results could provide valuable information for the formation of cold-set soy protein-stabilized emulsion gels.

  9. Interactions between poly(ethylene glycol) and protein in dichloromethane/water emulsions. 2. Conditions required to obtain spontaneous emulsification allowing the formation of bioresorbable poly(D,L lactic acid) microparticles. (United States)

    Malzert-Fréon, Aurélie; Schönhammer, Karin; Benoît, Jean-Pierre; Boury, Frank


    From microscopic observations, it was established that an oil-in-water emulsion with droplets of a size in the micrometer range can spontaneously form at room temperature without additional external stirring as soon as a solvent that is only partly miscible to water-like dichloromethane (DCM) is put in contact with an aqueous mixture of polyethylene glycol (PEG) and a protein. Experimental results show that emulsification only occurs if the system simultaneously includes PEG with middle chain, an organic solvent partly miscible to water and for which PEG affinity is sufficiently high, and a protein. From adsorption kinetics, it appears that this spontaneous emulsification process is related to the rapid diffusion of DCM towards water through the formation of interfacial turbulences, once the accumulation of PEG close to the DCM/water interface occurs. The oil droplets formed would be then stabilized by adsorbed protein molecules. Since the presence of polylactic acid in the organic phase did not prevent the emulsion formation, we studied the feasibility of formulating microparticles using this polymer. From results, it appears that microcapsules with a polymeric shell, with a homogeneous size of about 50 microm and able to encapsulate a model hydrophobic drug, such as amiodarone, can be obtained by using this spontaneous emulsification method.

  10. Diffusion of Acetic Acid Across Oil/Water Interface in Emulsification-Internal Gelation Process for Preparation of Alginate Gel Beads

    Institute of Scientific and Technical Information of China (English)

    LIU Xiu-dong; YU Wei-ting; LIN Jun-zhang; MA Xiao-jun; YUAN Quan


    Alginate has been widely used in cell microencapsulation and drug delivery systems in the form of gel beads or microcapsules. Although an alternative novel emulsification-internal gelation technology has been established and both the properties and the potential applications of the beads in drug delivery systems have been studied, the mechanism has not been well understood compared with the traditional droplet method( external gelation technology). On the basis of our previous knowledge that the novel technology is composed of complicatedly consecutive processes with multistep diffusion and re action, and the diffusion of acetic acid across oil/water interface being the prerequisite that determines the occurrence and rate for the reactions and the structures and properties of final produced gel beads, a special emphasis was placed on the diffusion process. With the aid of diffusion modeling and simple experimental design, the diffusion rate constant and diffusion coefficient of acetic acid across oil/water interface were determined to be in the orders of magnitude of 10-6 and 10-16, respectively. This knowledge will be of particular importance in understanding and interpreting the formation, structure of the gel beads and the relationship between the structure and properties and guiding the preparation and quality control of the gel beads.

  11. Ionic liquid-based totally organic solvent-free emulsification microextraction coupled with high performance liquid chromatography for the determination of three acaricides in fruit juice. (United States)

    Zhang, Jiaheng; Liang, Zhe; Guo, Hao; Gao, Peng; Lu, Runhua; Zhou, Wenfeng; Zhang, Sanbing; Gao, Haixiang


    A novel, totally organic solvent-free emulsification microextraction (TEME) technique using ionic liquids (ILs) is proposed in this study. Seven bis(trifluoromethylsulfonyl)imide ionic liquids were synthesized. After comparing the physicochemical properties of the ionic liquids and their application to microextraction experiments, 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C6MIM][NTf2]), which has moderate surface tension and viscosity, was selected as the extraction solvent. The dispersion of ILs and mass transfer were accelerated by ultrasound irradiation and temperature control processes. Therefore, no dispersive organic solvent was needed. Several variables, such as ionic liquid volume, duration of the ultrasound extraction, dispersion temperature, ionic strength and centrifugation time were investigated and optimized. Under the optimum conditions, the calibration curve was linear in the range of 0.1-600 μg L(-1) for chlorfenapyr and fenpyroximate and 0.5-600 μg L(-1) for spirodiclofen, with correlation coefficients of 0.9994-0.9999. The enrichment factors were between 261 and 285. The limits of detection (LODs) were 0.02-0.06 μg L(-1). Real fruit juice samples (at fortified levels of 10 μg L(-1) and 30 μg L(-1)) were successfully analyzed using the proposed method. The relative recoveries and enrichment factors were in the range of 92-104%. Copyright © 2013 Elsevier B.V. All rights reserved.

  12. Vortex-assisted emulsification semimicroextraction for the analytical control of restricted ingredients in cosmetic products: determination of bronopol by liquid chromatography. (United States)

    Miralles, Pablo; Bellver, Raquel; Chisvert, Alberto; Salvador, Amparo


    Vortex-assisted emulsification semimicroextraction is proposed as a one-step solution-extraction procedure for sample preparation in cosmetic products. The procedure allows rapid preparation based on dispersion of the sample in a mixture of 1 mL of n-hexane and 0.5 mL of ethanol, followed by the addition of 0.5 mL of water and centrifugation to obtain two separated phases. This procedure provides good sample clean-up with minimum dilution and is very useful for the determination of ingredients with restricted concentrations, such as bronopol. The procedure was applied to the determination of bronopol by liquid chromatography with UV detection. The best chromatographic separation was obtained by using a C18 column set at 40 °C and performing a stepwise elution with a mixture of ethanol/aqueous 1 % acetic acid solution as mobile phase pumped at 0.5 mL min(-1). The detection wavelength was set at 250 nm and the total run time required was 12 min. The method was successfully applied to 18 commercial cosmetic samples including creams, shampoos, and bath gels. Good recoveries and repeatability were obtained, with a limit of detection of 0.9 μg mL(-1), which makes the method suitable for the analytical control of cosmetic products. Moreover, it could be considered environmentally friendly, because water, ethanol, and only a low volume of n-hexane are used as solvents.

  13. Determination of Lead in Water Samples Using a New Vortex-Assisted, Surfactant-Enhanced Emulsification Liquid-Liquid Microextraction Combined with Graphite Furnace Atomic Absorption Spectrometry. (United States)

    Peng, Guilong; He, Qiang; Lu, Ying; Mmereki, Daniel; Pan, Weiliang; Tang, Xiaohui; Zhou, Guangming; Mao, Yufeng; Su, Xaioxuan


    A low toxic solvent-based vortex-assisted surfactant-enhanced emulsification liquid-liquid microextraction (LT-VSLLME) combined with graphite furnace atomic absorption spectrometry was developed for the extraction and determination of lead (Pb) in water samples. In the LT-VSLLME method, the extraction solvent was dispersed into the aqueous samples by the assistance of vortex agitator. Meanwhile, the addition of a surfactant, which acted as an emulsifier, could enhance the speed of the mass-transfer from aqueous samples to the extraction solvent. The influences of analytical parameters, including extraction solvent type and its volume, surfactant type and its volume, pH, concentration of chelating agent, salt effect and extraction time were investigated. Under the optimized conditions, a good relative standard deviation of 3.69% at 10 ng L(-1) was obtained. The calibration graph showed a linear pattern in the ranges of 5-30 ngL(-1), with a limit of detection of 0.76 ng L(-1). The linearity was obtained by five points in the concentration range of 5-30 ngL(-1). The enrichment factor was 320. The procedure was applied to wastewater and river water, and the accuracy was assessed through the analysis of the recovery experiments.

  14. New chitosan salt in gastro-resistant oral formulation could interfere with enteric bile salts emulsification of diet fats: preliminary laboratory observations and physiologic rationale. (United States)

    Fratter, Andrea; Frare, Carmen; Uras, Giovanni; Bonini, Mauro; Casari Bariani, Enrico; Ragazzo, Barbara; Gaballo, Paolo; Longobardi, Pasquale; Codemo, Carlo; Paoli, Antonio


    Chitosan (CH) is a polymer of glucosamine that is extracted from the shells of several sea fruits. It is well recognized as a nutritional supplement that is used to reduce body weight and blood lipid levels, but its clinical efficacy has not been clearly demonstrated. The true mechanism of action and physiological processes involved in these properties of CH are not yet understood or explained. The most accepted theories assume that CH reduces dietary fat absorption by trapping the fat in the gastric lumen. The very low pH of the gastric lumen induces CH jellification and, therefore, entrapment of the fats. This article describes the most plausible mechanism by which CH interferes with fat absorption in the first part of the enteric tract while interacting with cholic acids. We emphasize the weak points of the classic CH-containing formulations, which are unable to prove this theory. We also report preliminary experimental data of a new CH salt-containing formulation that is capable of effectively interfering with bile salt emulsification processes and, as a result, reducing dietary fat absorption.

  15. Ultrasound-assisted temperature-controlled ionic liquid emulsification microextraction coupled with capillary electrophoresis for the determination of parabens in personal care products. (United States)

    Ma, Teng; Li, Zheng; Jia, Qiong; Zhou, Weihong


    We developed a CE and ultrasound-assisted temperature-controlled ionic liquid emulsification microextraction method for the determination of four parabens (methyl paraben, ethyl paraben, propyl paraben, and butyl paraben) in personal care products including mouthwash and toning lotion. In the proposed extraction procedure, ionic liquid (IL, 1-octyl-3-methylimidazolium hexafluorophosphate) was used as extraction solvent, moreover, no disperser solvent was needed. Parameters affecting the extraction efficiency including volume of IL, heating temperature, ultrasonic time, extraction time, sample pH, ionic strength, and centrifugation time were optimized. Under the optimized conditions, the method was found to be linear over the range of 3-500 ng/mL with coefficient of determination (R(2) ) in the range of 0.9990-0.9998. The LODs and LOQs for the four parabens were 0.45-0.72 ng/mL and 1.50-2.40 ng/mL, respectively. Intraday and interday precisions (RSDs, n = 5) were in the range of 5.4-6.8% and 7.0-8.7%, respectively. The recoveries of parabens at different spiked levels ranged from 71.9 to 119.2% with RSDs less than 9.5%. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Influence of extraction pH on the foaming, emulsification, oil-binding and visco-elastic properties of marama protein. (United States)

    Gulzar, Muhammad; Taylor, John Rn; Minnaar, Amanda


    Marama bean protein, as extracted previously at pH 8, forms a viscous, adhesive and extensible dough. To obtain a protein isolate with optimum functional properties, protein extraction under slightly acidic conditions (pH 6) was investigated. Two-dimensional electrophoresis showed that pH 6 extracted marama protein lacked some basic 11S legumin polypeptides, present in pH 8 extracted protein. However, it additionally contained acidic high molecular weight polypeptides (∼180 kDa), which were disulfide crosslinked into larger proteins. pH 6 extracted marama proteins had similar emulsification properties to soy protein isolate and several times higher foaming capacity than pH 8 extracted protein, egg white and soy protein isolate. pH 6 extracted protein dough was more elastic than pH 8 extracted protein, approaching the elasticity of wheat gluten. Marama protein extracted at pH 6 has excellent food-type functional properties, probably because it lacks some 11S polypeptides but has additional high molecular weight proteins. © 2017 Society of Chemical Industry. © 2017 Society of Chemical Industry.

  17. Ultrasound-Assisted Surfactant-Enhanced Emulsification Micro-Extraction Followed by HPLC for Determination of Preservatives in Water, Beverages and Personal Care Products. (United States)

    Jan-E, Sudarat; Santaladchaiyakit, Yanawath; Burakham, Rodjana


    An ultrasound-assisted surfactant-enhanced emulsification micro-extraction (UASEME) procedure has been developed for pre-concentration of benzoic acid (BA) and paraben preservatives, including methylparaben, ethylparaben, propylparaben and butylparaben, prior to high-performance liquid chromatography-ultraviolet (HPLC-UV) analysis. Separations were performed on a Lichrospher RP-18 endcapped 5 µm, using an isocratic mobile phase of 40% acetonitile, at a flow rate of 1 mL min(-1) The selected UASEME conditions comprised the use of 10 mL sample extract, 125 µL 1-octanol as extraction solvent and 0.05 mmol L(-1) Tween 20 as emulsifier, 0.5% sodium chloride, ultrasonication time of 6 min and centrifugation time of 10 min. Method performance demonstrated wide linear range between 0.5 and 7,000 µg L(-1) (R(2) > 0.9903) and limits of detection between 0.03 and 10 µg L(-1), which providing the enrichment factors of 15-184. The method precision (relative standard deviation) was HPLC-UV has been successfully applied to determine four paraben preservatives in various sample matrices such as water, beverages and personal care products. The recoveries in the range of 70-138.1% were obtained. However, BA could not be determined in real sample extracts. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please email:

  18. Measurement of selected polychlorinated biphenyls (PCBs) in water via ultrasound assisted emulsification-microextraction (USAEME) using low-density organic solvents. (United States)

    Yurdakok-Dikmen, Begum; Kuzukiran, Ozgur; Filazi, Ayhan; Kara, Erdem


    Despite bans and restrictions for their adverse health effects including endocrine disruption, due to their stability in the environment, polychlorinated biphenyls (PCBs) are still of concern for their residues in several matrices. This study employed low-density ultrasound-assisted emulsification-microextraction (USAEME) to measure selected PCBs (28, 52, 101, 118, 138, 153, and 180) in water samples for gas chromatography-mass spectrometry analysis. Among tested solvents (isooctane, chloroform, hexane, and cyclohexane), 200 μL isooctane resulted in the highest yield for a 10 mL sample. The optimized method was validated and yielded recoveries of 87.29-92.83% with the limit of detection and limit of quantification (LOQ) values 3-12 ng/L and 10-40 ng/L, respectively. Twelve tap water samples collected in September 2014 were screened using this simple, rapid, and validated method. PCB concentrations in two samples were above the LOQ values; one sample contained 1,380 ng/L of PCB 118, 530 ng/L of PCB 138, and 152 ng/L of PCB 153, and the other contained 444 ng/L of PCB 138. Despite the city water supply being clean and the municipality employing all available measures to ensure clean water supply, the general public must be made aware of the regular maintenance of local water pipelines and storage tanks for the prevention of PCB contamination.

  19. Determination of selected polychlorinated biphenyls in water samples by ultrasound-assisted emulsification-microextraction and gas chromatography-mass-selective detection. (United States)

    Ozcan, Senar; Tor, Ali; Aydin, Mehmet Emin


    Ultrasound-assisted emulsification-microextraction (USAEME) procedure was developed for the determination of selected polychlorinated biphenyls (PCBs) in 10 mL of water samples by gas chromatography-mass-selective detection. After determination of the most suitable solvent and extraction time, several other parameters including solvent volume, centrifugation time and ionic strength of the sample were optimized using a 2(3) factorial experimental design. The optimized USAEME procedure used 200 microL of chloroform as extraction solvent, 10 min of extraction with no ionic strength adjustment at 25 degrees C and 5 min of centrifugation at 4000 rpm. The limits of detection ranged from 14 ngL(-1) (for PCB153) to 30 ngL(-1) (for PCB101). Recoveries of PCBs from fortified distilled water are over 80% for three different fortification levels between 0.1 and 5 microgL(-1) and relative standard deviations of the recoveries are below 10%. The performance of the proposed method was compared with those involving traditional liquid-liquid extraction (LLE) and solid phase extraction (SPE) on the real water samples (i.e., tap and well water as well as domestic and industrial wastewaters, etc.) and comparable efficiencies were obtained. The proposed USAEME procedure has been demonstrated to be viable, simple, rapid and easy to use for residue analysis of PCBs in water samples.

  20. Ultrasound-assisted emulsification-microextraction combined with graphite furnace atomic absorption spectrometry for the determination of trace lead in water

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Hongmei; Zhang, Yu; Qiu, Bocheng; Li, Wenhua [College of Science, Nanjing Agricultural University, Nan Jing (China)


    The ultrasound-assisted emulsification-microextraction (USAEME) method was combined with graphite furnace atomic absorption spectrometry (GFAAS) for the determination of trace Pb using dithizone (H{sup 2}DZ) as chelating reagent. Some effective parameters influenced the detection and microextraction, such as ashing temperature and atomization temperature, pH, extraction solvent, sample volume, extraction time, and extraction temperature were selected and optimized. After extraction, the calibration curves for Pb was in the concentration range of 0.1-10 ng mL{sup -1}, and the linear equation was y = 0.097 x + 0.023 (R = 0.99). Under the optimized conditions, the detection limit of the method was 20 pg mL{sup -1} with an enrichment factor of 70 and the relative standards deviation (RSD) for seven determinations of 1 ng mL{sup -1} Pb was 11%. The proposed method was successfully applied to determine trace Pb in Yueya Lake water, pond water, and spiked samples. Furthermore, a certified reference material of Environment Water (GBW08607) was analyzed and the determined value was in good agreement with the certified value, which showed the accuracy, recovery, and applicability of the reported method. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)