WorldWideScience

Sample records for blowoff

  1. Lean blowoff detection sensor

    Science.gov (United States)

    Thornton, Jimmy; Straub, Douglas L.; Chorpening, Benjamin T.; Huckaby, David

    2007-04-03

    Apparatus and method for detecting incipient lean blowoff conditions in a lean premixed combustion nozzle of a gas turbine. A sensor near the flame detects the concentration of hydrocarbon ions and/or electrons produced by combustion and the concentration monitored as a function of time are used to indicate incipient lean blowoff conditions.

  2. Lean blowoff of bluff body stabilized flames. Scaling and dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Shanbhogue, Santosh J.; Husain, Sajjad; Lieuwen, Tim [Daniel Guggenheim School of Aerospace Engineering, Georgia Institute of Technology, 270 Ferst Drive, Atlanta, GA 30332 (United States)

    2009-02-15

    This paper overviews the dynamics of bluff body stabilized flames and describes the phenomenology of the blowoff process. The first section of the paper provides an overview of the fluid mechanics of the non-reacting and reacting bluff body wake flow. It highlights the key features of the flow (the boundary layer, separated shear layer, and wake), the flow instabilities that influence each of these features, and the influences of the flame on these instabilities. A key point from these studies is the large differences between the non-reacting wake (dominated by an absolutely unstable, sinuous instability associated with vortex shedding from the bluff body) and the reacting wake of high dilatation ratio flames. The latter are dominated by the lower intensity, convective instability of the shear layer. Very low dilatation ratio flames begin to approach the behavior of the non-reacting wake, as might be expected. Next, the paper presents a compilation of bluff body blowoff data from the literature and shows that the basic Damkoehler correlations developed from prior studies are recovered, but without the need for semi-empirical fits or adjustable constants for chemical time estimation. The third section considers in detail the dynamics and phenomenology of near blowoff flames. It is shown that spatio/temporally localized extinction occurs sporadically on near blowoff flames, manifested as 'holes' in the flame sheet that form and convect downstream. However, these extinction events are distinct from blowoff - in fact, under certain conditions the flame can persist indefinitely with certain levels of local extinction. The number of these events per unit time increase as blowoff is approached, eventually leading to large scale alteration of the wake. We hypothesize that simple Damkoehler number correlations contain the essential physics describing the initial stage of blowoff; i.e., they are correlations for the conditions where local extinction on the flame

  3. In situ window cleaning by laser blowoff through optical fiber

    International Nuclear Information System (INIS)

    The feasibility of a window cleaning system based on the laser blowoff technique is investigated to remove the impurity deposition on vacuum windows of the modified reversed field experiment fusion device. The laser pulse is sent to the window through a fused silica fiber optic (φ=1 mm), then focused on its internal surface, single shot ablating up to ∼5 mm2 of the impurity layer; the focused pulse is scanned across the window to clean its entire surface. The composition of the deposited layer is studied through the secondary ion mass spectrometry and profilometry techniques. Effectiveness of cleaning is analyzed in terms of quality of the cleaned spot, its dimension, repetition rate of the laser, and its wavelength. The energy damage threshold of the fiber optic is also investigated. Three different lasers (microjoule Nd:YAG, Nd:YLF, and ruby) are first tested directly on the window; then only the ruby laser beam is propagated through an optical fiber and tested.

  4. In situ window cleaning by laser blowoff through optical fibera)

    Science.gov (United States)

    Alfier, A.; Barison, S.; Danieli, T.; Giudicotti, L.; Pagura, C.; Pasqualotto, R.

    2008-10-01

    The feasibility of a window cleaning system based on the laser blowoff technique is investigated to remove the impurity deposition on vacuum windows of the modified reversed field experiment fusion device. The laser pulse is sent to the window through a fused silica fiber optic (φ=1mm), then focused on its internal surface, single shot ablating up to ˜5mm2 of the impurity layer; the focused pulse is scanned across the window to clean its entire surface. The composition of the deposited layer is studied through the secondary ion mass spectrometry and profilometry techniques. Effectiveness of cleaning is analyzed in terms of quality of the cleaned spot, its dimension, repetition rate of the laser, and its wavelength. The energy damage threshold of the fiber optic is also investigated. Three different lasers (microjoule Nd:YAG, Nd:YLF, and ruby) are first tested directly on the window; then only the ruby laser beam is propagated through an optical fiber and tested.

  5. The blow-off mechanism of a bluff-body stabilized laminar premixed flame

    KAUST Repository

    Kedia, Kushal S.

    2015-04-01

    © 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.

  6. Blow-off characteristics of turbulent premixed flames in curved-wall Jet Burner

    KAUST Repository

    Mansour, Morkous S.

    2015-08-02

    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.

  7. Electric fields effect on liftoff and blowoff of nonpremixed laminar jet flames in a coflow

    KAUST Repository

    Kim, Minkuk

    2010-01-01

    The stabilization characteristics of liftoff and blowoff in nonpremixed laminar jet flames in a coflow have been investigated experimentally for propane fuel by applying AC and DC electric fields to the fuel nozzle with a single-electrode configuration. The liftoff and blowoff velocities have been measured by varying the applied voltage and frequency of AC and the voltage and the polarity of DC. The result showed that the AC electric fields extended the stabilization regime of nozzle-attached flame in terms of jet velocity. As the applied AC voltage increased, the nozzle-attached flame was maintained even over the blowout velocity without having electric fields. In such a case, a blowoff occurred directly without experiencing a lifted flame. While for the DC cases, the influence on liftoff was minimal. There existed three different regimes depending on the applied AC voltage. In the low voltage regime, the nozzle-detachment velocity of either liftoff or blowoff increased linearly with the applied voltage, while nonlinearly with the AC frequency. In the intermediate voltage regime, the detachment velocity decreased with the applied voltage and reasonably independent of the AC frequency. At the high voltage regime, the detachment was significantly influenced by the generation of discharges. © 2009 The Combustion Institute.

  8. Blow-off momentum from melt and vapor in nuclear deflection scenarios

    Science.gov (United States)

    Howley, Kirsten; Managan, Robert; Wasem, Joseph

    2014-10-01

    For Earth-impacting objects that are large in size or have short warning times nuclear explosives are an effective threat mitigation response. Nuclear-based deflection works by means of conservation of momentum: as material is heated by incoming photons and neutrons it is ejected from the body which imparts momentum to the remaining mass of the asteroid. Predicting the complete response of a particular object is difficult, since the ejecta size and velocity distributions rely heavily on the unknown, complicated internal structure of the body. However, lower bounds on the blow-off momentum can be estimated using the melted and vaporized surface material. In this paper, we model the response of a one-dimensional SiO2 surface to monoenergetic soft X-ray, hard X-ray and neutron sources using Arbitrary Lagrangian-Eulerian radiation/hydrodynamic simulations. Errors in the blow-off momentum due to our hydrodynamic mesh resolution are quantified and inform zone sizing that balances numerical discretization error with computational efficiency. We explore deposited energy densities ranging from 1.1 to 200 times the melt energy density for SiO2, and develop an approximate relation that gives the mesh resolution needed for a desired percent error in the blow-off momentum as a function of deposited energy density and melt depth. Using these mesh constraints, the response of our one-dimensional SiO2 surface to the energy sources is simulated, and lower bounds are placed on the melt/vapor blow-off momentum as a function of deposited energy density and source energy type.

  9. Laser blow-off injection of metal impurities in Tore Supra

    International Nuclear Information System (INIS)

    The results obtained on Tore Supra during the 1992 campaign by means of the laser blow-off impurity injection technique are presented. Ni and Mn puffs are injected in ohmic plasmas and in plasmas heated simultaneously by ion cyclotron resonance heating and lower hybrid radio frequency systems. Using an impurity transport simulation code the radius dependent transport parameters D and V (Diffusion coefficient and inward convection Velocity) are determined for both regimes. The simulations show a reduced transport in the central region and a confinement degradation with additional power. Three particular injections are considered in detail, chosen with quite different sawtooth stabilization periods. Comparison of the experimental values of D and V with the predictions of neo-classical theory is discussed

  10. Sawtooth Activities During Impurity Injection by Laser Blow-off in HL-2A

    Institute of Scientific and Technical Information of China (English)

    DENG Wei; LIU Yi; CUI Zhengying; DONG Yunbo; HUANG Yuan; ZHANG Peng; SUN Ping; FU Bingzhong

    2007-01-01

    In order to study impurity transport and their progression in the plasma,small amount of high-Z impurities were injected into HL-2A ohmic heated plasmas by laser blow-off and traced with good spatial temporal resolution by a soft X-ray camera.An analysis of the evolution of the impurities'radiation distribution in the plasma revealed that impurity transport in the central region was profoundly different from that outside of it.It was found that the sawteeth tended to be inverted on the central soft X-ray chord signals after the impurity injection and the soft X-ray profiles exhibited discontinuities during the movement of the impurities in the plasma central region.Detailed 2D visualization of the evolution of impurities'radiation using computer tomography has provided further understanding of the properties of impurity transport in the HL-2A plasma.

  11. Liftoff and blowoff of a diffusion flame between parallel streams of fuel and air

    Energy Technology Data Exchange (ETDEWEB)

    Fernandez-Tarrazo, Eduardo [I.N.T.A. Area de Propulsion-Edificio R02, Ctra. Ajalvir, km 4, 28850 Torrejon de Ardoz, Madrid (Spain); Vera, Marcos [Area de Mecanica de Fluidos, Universidad Carlos III de Madrid, 28911 Leganes (Spain); Linan, Amable [Departamento de Motopropulsion y Termofluidodinamica, Universidad Politecnica de Madrid, Pza. Cardenal Cisneros 3, 28040 Madrid (Spain)

    2006-01-01

    A numerical analysis is presented to describe the liftoff and blowoff of a diffusion flame in the mixing layer between two parallel streams of fuel (mainly methane diluted with nitrogen) and air emerging from porous walls. The analysis, which takes into account the effects of thermal expansion, assumes a one-step overall Arrhenius reaction, where the activation energy E is allowed to vary to reproduce the variations of the planar flame propagation velocity with the equivalence ratio. First, we describe the steady flame-front structure when stabilized close to the porous wall (attached flame regime). Then, we analyze the case where the flame front is located far away from the porous wall, at a distance x{sub f}' such that, upstream of the flame front, the mixing layer has a self-similar structure (lifted flame regime). For steady lifted flames, the results, given here in the case when the fuel and air streams are injected with the same velocity, relate U{sub f}'/S{sub L}, the front velocity (relative to the upstream flow) measured with the planar stoichiometric flame velocity, with the Damkohler number D{sub m}=({delta}{sub m}/{delta}{sub L}){sup 2}, based on the thickness, {delta}{sub m}, of the nonreacting mixing layer at the flame-front position and the laminar flame thickness, {delta}{sub L}. For large values of D{sub m}, the results, presented here for a wide range of dilutions of the fuel stream, provide values of the front propagation velocity that are in good agreement with previous experimental results, yielding well-defined conditions for blowoff. The calculated flame-front velocity can also be used to describe the transient flame-front dynamics after ignition by an external energy source.

  12. NEAR-BLOWOFF DYNAMICS OF BLUFF-BODY-STABILIZED PREMIXED HYDROGEN/AIR FLAMES IN A NARROW CHANNEL

    KAUST Repository

    Lee, Bok Jik

    2015-06-07

    The flame stability is known to be significantly enhanced when the flame is attached to a bluff-body. The main interest of this study is on the stability of the flame in a meso-scale channel, considering applications such as combustion-based micro power generators. We investigate the dynamics of lean premixed hydrogen/air flames stabilized behind a square box in a two-dimensional meso-scale channel with high-fidelity numerical simulations. Characteristics of both non-reacting flows and reacting flows over the bluff-body are studied for a range of the mean inflow velocity. The flame stability in reacting flows is investigated by ramping up the mean inflow velocity step by step. 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 blowoff limit, there exists a narrow range of the inlet velocity where the flames exhibit periodic local extinction and recovery. Approaching further to blowoff limit, the local extinction and recovery becomes highly transient and a failure of recovery leads blowoff and extinction of the flame kernel.

  13. Optimized in-situ window cleaning system by laser blow-off through optical fiber

    International Nuclear Information System (INIS)

    An optimized in-situ window cleaning system by laser blow-off through optical fiber has been developed on the basis of a feasibility study previously presented. The beam generated from a Q-switched Nd:YAG laser (up to 330mJ output energy, pulse duration 5ns FWHM with 10Hz repetition rate) is launched into a high damage threshold optical fiber (Oe=1mm) through an f=80mm lens kept in a sealed box at 1mbar pressure. The fiber output is focused on the coated surface of a vacuum window previously exposed to the plasma of the RFX-mod experiment. We investigate the energy density threshold necessary to ablate the impurity deposition substrate: above threshold a single laser pulse recovers ∼95% of the window transmission before its exposure to the plasma, while below it the efficiency of the cleaning process is too poor. The system so conceived can clean completely the largest window on RFX-mod (104mm2 surface) in about 20minutes. We also present first results obtained firing the laser directly on a bundle of small core diameter fibers, showing performance similar to those attainable with commercial products.

  14. 排污管裂口失效分析%Failure Analysis on the Blow-off Pipe Rip

    Institute of Scientific and Technical Information of China (English)

    闫纪宪; 曹怀祥; 张号; 宋雪; 武晓; 宋明大; 申孝民

    2015-01-01

    某生物科技有限公司与溶剂罐相连的排污口发生破裂,导致介质泄露,引发爆炸事故。本文通过宏观检查、排污管化学成分分析、金相组织分析、扫描电镜观察、能谱分析、水质分析等方法,对排污管的破裂原因进行了分析。分析结果表明:生产过程中产生的有机酸和水进溶剂罐并在排污封头和排污管内聚集,形成酸性溶液,构成了电化学腐蚀环境。由于焊缝热影响区的自腐蚀电位较其他部位偏低,在电化学腐蚀环境中热影响区的金属作为电化学原电池的阳极,优先发生腐蚀,在焊缝两侧形成腐蚀沟槽,最终穿透管壁发生泄漏。%The blow-off pipe connected with solvent tank was fractured caused an explosion accident with the leak of media in the solvent tank. In this paper, the reason of rupture of blow-off pipe has been confirmed by the methods of macroscopic examination, chemical composition analysis, microstructure analysis, scanning electron microscopy, energy spectrum analysis, and water quality analysis. The result showed that electrochemical corrosion environment was constructed when the organic acid and water were stored in blow-off pipe. The metal of heat affected zone would be as anode of primary electrochemical and generated corrosion because that weld corrosion potential is lower than other parts. And the corrosion groove had been formed and led to organic solvent leakage at last.

  15. Pollutant Emissions and Lean Blowoff Limits of Fuel Flexible Burners Operating on Gaseous Renewable and Fossil Fuels

    Science.gov (United States)

    Colorado, Andres

    : ignition; lean blowoff; and variable air to fuel ratio. Some remarkable results of this dissertation include: • At a fixed fire rate (117kW) the addition of hydrogen to NG raises the emission of NO x for the reactions stabilized with the LSB. Under the same conditions, the addition of H2 to NG will reduce the emission levels of the reactions stabilized with the SSCB. • It was found experimentally that nitrous oxide (N2O) is emitted during ignition and blowoff events. • Ammonia (NH3) is also emitted during ignition and blowoff events. • It was found experimentally that at high concentrations of hydrogen in NG (H2>70%), reactions aerodynamically stabilized with the LSB will emit significant amounts of N2O.

  16. Mechanisms of stabilization and blowoff of a premixed flame downstream of a heat-conducting perforated plate

    KAUST Repository

    Kedia, Kushal S.

    2012-03-01

    The objective of this work is to investigate the flame stabilization mechanism and the conditions leading to the blowoff of a laminar premixed flame anchored downstream of a heat-conducting perforated-plate/multi-hole burner, with overall nearly adiabatic conditions. We use unsteady, fully resolved, two-dimensional simulations with detailed chemical kinetics and species transport for methane-air combustion. Results show a bell-shaped flame stabilizing above the burner plate hole, with a U-shaped section anchored between neighboring holes. The base of the positively curved U-shaped section of the flame is positioned near the stagnation point, at a location where the flame displacement speed is equal to the flow speed. This location is determined by the combined effect of heat loss and flame stretch on the flame displacement speed. As the mass flow rate of the reactants is increased, the flame displacement speed at this location varies non-monotonically. As the inlet velocity is increased, the recirculation zone grows slowly, the flame moves downstream, and the heat loss to the burner decreases, strengthening the flame and increasing its displacement speed. As the inlet velocity is raised, the stagnation point moves downstream, and the flame length grows to accommodate the reactants mass flow. Concomitantly, the radius of curvature of the flame base decreases until it reaches an almost constant value, comparable to the flame thickness. While the heat loss decreases, the higher flame curvature dominates thereby reducing the displacement speed of the flame base. For a stable flame, the gradient of the flame base displacement speed normal to the flame is higher than the gradient of the flow speed along the same direction, leading to dynamic stability. As inlet velocity is raised further, the former decreases while the latter increases until the stability condition is violated, leading to blowoff. The flame speed during blow off is determined by the feedback between the

  17. Effect of inlet and outlet configurations on blow-off and flashback with premixed combustion for methane and a high hydrogen content fuel in a generic swirl burner

    International Nuclear Information System (INIS)

    Highlights: • Correlation of blowoff and flashback using the tangential inlet velocity. • The correlation appears to arise from the exhaust shear flow. • Reynolds Number effects can be important with methane and flashback. • For flashback the correlation was effective for 0.8 ⩽ swirl number ⩽ 2.2. • For blowoff the correlation was effective for 0.8 ⩽ swirl number ⩽ 4. - Abstract: The paper analyses new data for three fuels, natural gas, methane and Coke Oven Gas (COG) in two swirl burners. Flashback and blowoff can be correlated with the inlet tangential velocity, not the inlet mass flow, over a range of swirl numbers from 0.8 to more than 4. Geometry and fuel type are important. The correlation gives best fit for a particular outlet geometry and with higher hydrogen content fuels. The correlation still holds with methane and natural gas, especially with confinement. Analysis of the correlation infers that both blowoff and flashback occurrences are governed by the shear layer surrounding the Central Recirculation Zone (CRZ). The CRZ acts to control the width and strength of the shear flow region. Blowoff was found to occur when the CRZ was extensive and well develop and could be modeled by a well stirred reactor system. Two modes of flashback were found, both of which could be characterized by the same correlation of inlet tangential velocity. The first flashback case occurred at lower swirl numbers when the flame attached to the burner rim and flashed back through the outer boundary layer. At higher swirl numbers the CRZ and associated flame located next to its boundary extended back over the fuel nozzle inside the swirl chamber. Flashback occurred when the flame suddenly moved radially outwards towards the inlets. A clear trend was established for COG; as the swirl number was increased from 0.8 to 1.5 blowoff slightly worsened, whilst flashback improved. Thus higher swirl numbers are tentatively favored for flashback protection for higher

  18. Impurities removal by laser blow-off from in-vacuum optical surfaces on RFX-mod experiment

    International Nuclear Information System (INIS)

    An in situ window cleaning system by laser blow-off through optical fiber has been developed on the basis of a feasibility study previously presented. The beam generated by a Q-switched Nd:YAG laser is launched in a vacuum box into a high damage threshold optical fiber through a lens. The fiber output is focused on the impurities-coated surface of a vacuum window exposed to the plasma of the RFX-mod experiment, and it is remotely controlled with an xy motion system to scan the entire surface. We first investigate the energy density threshold necessary to ablate the deposited impurity substrate on removed dirty windows: above threshold, a single laser pulse recovers ∼95% of the window transmission before its exposure to the plasma, while below it the efficiency of the cleaning process is too poor. The system so conceived was then used to clean the three collection windows of the Main Thomson scattering diagnostic on RFX-mod. We also present results obtained applying the same technique to the SiO-protected Al mirror used for the Zeff diagnostic: an energy threshold for efficient impurity removal without mirror damage is first identified, then ablation tests are executed and analyzed in terms of recovered reflectivity. The SIMS technique is used both with windows and mirror to study the composition of surfaces before and after the ablation

  19. Investigation of impurity transport using laser blow-off technique in the HL-2A Ohmic and ECRH plasmas

    Science.gov (United States)

    Kai, Zhang; Zheng-Ying, Cui; Ping, Sun; Chun-Feng, Dong; Wei, Deng; Yun-Bo, Dong; Shao-Dong, Song; Min, Jiang; Yong-Gao, Li; Ping, Lu; Qing-Wei, Yang

    2016-06-01

    Impurity transports in two neighboring discharges with and without electron cyclotron resonance heating (ECRH) are studied in the HL-2A tokamak by laser blow-off (LBO) technique. The progression of aluminium ions as the trace impurity is monitored by soft x-ray (SXR) and bolometer detector arrays with good temporal and spatial resolutions. Obvious difference in the time trace of the signal between the Ohmic and ECRH L-mode discharges is observed. Based on the numerical simulation with one-dimensional (1D) impurity transport code STRAHL, the radial profiles of impurity diffusion coefficient D and convective velocity V are obtained for each shot. The result shows that the diffusion coefficient D significantly increases throughout the plasma minor radius for the ECRH case with respect to the Ohmic case, and that the convection velocity V changes from negative (inward) for the Ohmic case to partially positive (outward) for the ECRH case. The result on HL-2A confirms the pump out effect of ECRH on impurity profile as reported on various other devices.

  20. Impurities removal by laser blow-off from in-vacuum optical surfaces on RFX-mod experiment

    Energy Technology Data Exchange (ETDEWEB)

    Alfier, A.; Fassina, A.; Pasqualotto, R.; Cervaro, V.; Lotto, L. [Consorzio RFX, Associazione EURATOM-ENEA sulla Fusione, Corso Stati Uniti 4, 35127 Padova (Italy); Barison, S.; Fiameni, S. [Istituto per l' energetica e le interfasi, C.so Stati Uniti 4, 35127 Padova (Italy); Giudicotti, L. [Consorzio RFX, Associazione EURATOM-ENEA sulla Fusione, Corso Stati Uniti 4, 35127 Padova (Italy); Electrical Engineering Department, Padova University, Via Gradenigo 6/A, 35131, Padova (Italy)

    2010-12-15

    An in situ window cleaning system by laser blow-off through optical fiber has been developed on the basis of a feasibility study previously presented. The beam generated by a Q-switched Nd:YAG laser is launched in a vacuum box into a high damage threshold optical fiber through a lens. The fiber output is focused on the impurities-coated surface of a vacuum window exposed to the plasma of the RFX-mod experiment, and it is remotely controlled with an xy motion system to scan the entire surface. We first investigate the energy density threshold necessary to ablate the deposited impurity substrate on removed dirty windows: above threshold, a single laser pulse recovers {approx}95% of the window transmission before its exposure to the plasma, while below it the efficiency of the cleaning process is too poor. The system so conceived was then used to clean the three collection windows of the Main Thomson scattering diagnostic on RFX-mod. We also present results obtained applying the same technique to the SiO-protected Al mirror used for the Z{sub eff} diagnostic: an energy threshold for efficient impurity removal without mirror damage is first identified, then ablation tests are executed and analyzed in terms of recovered reflectivity. The SIMS technique is used both with windows and mirror to study the composition of surfaces before and after the ablation.

  1. Preliminary study of NO{sub x}, CO, and lean blowoff in a piloted-lean premixed combustor. Part 1: Experimental

    Energy Technology Data Exchange (ETDEWEB)

    Barnes, J.C.; Mello, J.P.; Mellor, A.M. [Vanderbilt Univ., Nashville, TN (United States). Combustion and Propulsion Group; Malte, P.C. [Univ. of Washington, Seattle, WA (United States). Dept. of Mechanical Engineering

    1996-05-01

    In order to validate the models for NO{sub x}, CO, and lean blowoff discussed in part 2 of this paper, the development of an experimental datum base was initiated. Experimental data were collected from an industrial, piloted-lean premixed, natural gas fired, can combustor rig. The experiments were designed in order to minimize testing cost and time. Independent variations of inlet pressure (8 to 14 atm), inlet temperature (550 to 750 K), and residence time (13 and 23 ms) were performed in order to gain insight into the sensitivity of the emissions levels to changes in combustor operating conditions.

  2. 含氨放射性废水吹脱法除氨研究%Treatment of Reactive Process Wastewater With High-Level Ammonia by Blow-off Method

    Institute of Scientific and Technical Information of China (English)

    陈晓彤; 权英; 王阳; 付亘娜; 刘兵; 唐亚平

    2012-01-01

    采用吹脱除氨工艺,对高温气冷堆燃料元件二氧化铀核芯颗粒生产中产生的含氨工艺放射性废液进行了除氨处理研究.分析了废水pH、加碱量、加热和吹脱时间等因素对吹脱除氨效果的影响,于80℃、吹脱3h后,废液的除氨效率可超过95%.对除氨后的废液体系进行了阴离子交换树脂吸附铀的静态实验,结果表明,树脂对铀吸附容量较未除氨时有明显提高.%The ceramic UO2 kernels for nuclear fuel elements of high temperature gas cooled reactors were prepared through sol-gel process with uranyl nitrate, which produces process wastewater containing high-level ammonia and uranium. The blow-off method on a bench scale was investigated to remove ammonia from reactive wastewater. Under the optimized operating conditions, the ammonia can be removed by more than 95%, with little reactive uranium distilled. The effects of pH, heating temperature and stripping time were studied. Static tests with ion-exchange resin indicate that ammonia removal treatment increases uranium accumulation in anion exchange resin.

  3. Giant Impact Induced Atmospheric Blow-Off

    OpenAIRE

    Ahrens, Thomas J.; Shen, Andy H.; Ni, Sidao

    2004-01-01

    Previous calculations indicate that the Earth suffered impacts from objects up to Mars size. Such a giant impact may have produced a temporary ejecta-based ring that accreted to form the Moon. To simulate the surface waves from such events we approximated the cratering source as a buried pressurized sphere. For a 10^27 J impactor we calculated the resulting surface wave using the mode summation method of Sato et al.. For such an impact, the solid Earth free-surface velocity above, and antipod...

  4. Phase separator safety valve blow-off.

    CERN Multimedia

    G. Perinic

    2006-01-01

    The fast discharge of the CMS solenoid leads to a pressure rise in the phase separator. On August 28th, a fast discharge was triggered at a current level of 19.1 kA. The pressure in the phase separator increased up to the set pressure of the safety valve and some helium was discharged. In consequence of this and prevoious similar observations the liquid helium level in the phase separator has been reduced from 60% to 50% and later to 45% in order to reduce the helium inventory in the magnet.

  5. Oxygen and carbon discovered in exoplanet atmosphere `blow-off'

    Science.gov (United States)

    2004-02-01

    Oxygen and carbon discovered in exoplanet atmosphere ‘blow-off’ hi-res Size hi-res: 1096 kb Credits: ESA/Alfred Vidal-Madjar (Institut d’Astrophysique de Paris, CNRS, France) Oxygen and carbon discovered in exoplanet atmosphere ‘blow-off’ This artist’s impression shows an extended ellipsoidal envelope - the shape of a rugby-ball - of oxygen and carbon discovered around the well-known extrasolar planet HD 209458b. An international team of astronomers led by Alfred Vidal-Madjar (Institut d’Astrophysique de Paris, CNRS, France) observed the first signs of oxygen and carbon in the atmosphere of a planet beyond our Solar System for the first time using the NASA/ESA Hubble Space Telescope. The atoms of carbon and oxygen are swept up from the lower atmosphere with the flow of escaping atmospheric atomic hydrogen - like dust in a supersonic whirlwind - in a process called atmospheric ‘blow off’. Oxygen and carbon have been detected in the atmosphere of a planet beyond our Solar System for the first time. Scientists using the NASA/ESA Hubble Space Telescope have observed the famous extrasolar planet HD 209458b passing in front of its parent star, and found oxygen and carbon surrounding the planet in an extended ellipsoidal envelope - the shape of a rugby-ball. These atoms are swept up from the lower atmosphere with the flow of the escaping atmospheric atomic hydrogen, like dust in a supersonic whirlwind. The team led by Alfred Vidal-Madjar (Institut d’Astrophysique de Paris, CNRS, France) reports this discovery in a forthcoming issue of Astrophysical Journal Letters. The planet, called HD 209458b, may sound familiar. It is already an extrasolar planet with an astounding list of firsts: the first extrasolar planet discovered transiting its sun, the first with an atmosphere, the first observed to have an evaporating hydrogen atmosphere (in 2003 by the same team of scientists) and now the first to have an atmosphere containing oxygen and carbon. Furthermore the ‘blow-off’ effect observed by the team during their October and November 2003 observations with Hubble had never been seen before. In honour of such a distinguished catalogue this extraordinary extrasolar planet has provisionally been dubbed 'Osiris'. Osiris was the Egyptian god who lost part of his body - like HD 209458b - after his brother killed and cut him into pieces to prevent his return to life. Oxygen is one of the possible indicators of life that is often looked for in experiments searching for extraterrestrial life (such as those onboard the Viking probes and the Spirit and Opportunity rovers), but according to Vidal-Madjar: “Naturally this sounds exciting - the possibility of life on Osiris - but it is not a big surprise as oxygen is also present in the giant planets of our Solar System, like Jupiter and Saturn.” What, on the other hand was surprising was to find the carbon and oxygen atoms surrounding the planet in an extended envelope. Although carbon and oxygen have been observed on Jupiter and Saturn, it is always in combined form as methane and water deep in the atmosphere. In HD 209458b the chemicals are broken down into the basic elements. But on Jupiter or Saturn, even as elements, they would still remain invisible low in the atmosphere. The fact that they are visible in the upper atmosphere of HD 209458b confirms that atmospheric ‘blow off’ is occurring. The scorched Osiris orbits ‘only’ seven million kilometres from its yellow Sun-like star and its surface is heated to about 1000 degrees Celsius. Whereas hydrogen is a very light element - the lightest in fact - oxygen and carbon are much heavier in comparison. This has enabled scientists to conclude that this phenomenon is more efficient than simple evaporation. The gas is essentially ripped away at a speed of more than 35 000 kilometres an hour. “We speculate that even heavier elements such as iron are blown off at this stage as well,” says team member Alain Lecavelier des Etangs (Institut d'Astrophysique de Paris, CNRS, France). The whole evaporation mechanism is so distinctive that there is reason to propose the existence of a new class of extrasolar planets - the chthonian planets, a reference to the Greek God Khtôn, used for Greek deities from the hot infernal underworld (also used in the French word autochton). The chthonian planets are thought to be the solid remnant cores of ‘evaporated gas giants’, orbiting even closer to their parent star than Osiris. The detection of these planets should soon be within reach of current telescopes both on the ground and in space. The discovery of the fierce evaporation process is, according to the scientists, 'highly unusual', but may indirectly confirm theories of our own Earth’s childhood. “This is a unique case in which such a hydrodynamic escape is directly observed. It has been speculated that Venus, Earth and Mars may have lost their entire original atmospheres during the early part of their lives. Their present atmospheres have their origins in asteroid and cometary impacts and outgassing from the planet interiors,” says Vidal-Madjar.

  6. Minimum fluence for laser blow-off of thin gold films at 248 and 532 nm

    International Nuclear Information System (INIS)

    The minimum 248 nm, 25 ns, and 532 nm, 15 ns laser fluences required to blow off thin gold films from optical quartz have been measured as a function of film thickness. The films apparently blow off when the gold-quartz interface reaches the normal boiling point of gold. Even though the initial reflectivities at the two wavelengths are very different, the actual laser fluences required to blow off the films are very similar. While the reflectivities above the melting point appear to be very low, as expected, large decreases in the reflectivity at 532 nm may also occur prior to film melting

  7. Minimum fluence for laser blow-off of thin gold films at 248 and 532 nm

    Energy Technology Data Exchange (ETDEWEB)

    Baseman, R.J.; Froberg, N.M.; Andreshak, J.C.; Schlesinger, Z. (IBM Thomas J. Watson Research Center, Yorktown Heights, New York 10598 (USA))

    1990-04-09

    The minimum 248 nm, 25 ns, and 532 nm, 15 ns laser fluences required to blow off thin gold films from optical quartz have been measured as a function of film thickness. The films apparently blow off when the gold-quartz interface reaches the normal boiling point of gold. Even though the initial reflectivities at the two wavelengths are very different, the actual laser fluences required to blow off the films are very similar. While the reflectivities above the melting point appear to be very low, as expected, large decreases in the reflectivity at 532 nm may also occur prior to film melting.

  8. Application of light-initiated explosive for simulating x-ray blowoff impulse effects on a full scale reentry vehicle

    International Nuclear Information System (INIS)

    Laboratory nuclear effects testing allows the study of reentry vehicle response to simulated exoatmospheric x-ray encounters. Light-initiated explosive produces the nearly simultaneous impulse loading of a structure by using a spray painted coating of explosive which is detonated by an intense flash of light. A lateral impulse test on a full scale reentry vehicle is described which demonstrates that the light-initiated explosive technique can be extended to the lateral loading of very large systems involving load discontinuities. This experiment required the development of a diagnostic method for verifying the applied impulse, and development of a large light source for simultaneously initiating the explosive over the surface of the vehicle. Acceptable comparison between measured strain response and code predictions is obtained. The structural capability and internal response of a vehicle subjected to an x-ray environment was determined from a light-initiated explosive test

  9. Water Supply Intakes, water blowoff, Published in 2008, 1:24000 (1in=2000ft) scale, Box Elder County.

    Data.gov (United States)

    NSGIC GIS Inventory (aka Ramona) — This Water Supply Intakes dataset, published at 1:24000 (1in=2000ft) scale, was produced all or in part from Other information as of 2008. It is described as 'water...

  10. Landfill Leachate Disposal Method Combined with Lime Coagulation, Blow-off and CO2 Aeration%石灰混凝+吹脱+CO2曝气联合对垃圾渗滤液的处理实验研究

    Institute of Scientific and Technical Information of China (English)

    杨爱江; 李清; 王时亮; 孙哲; 郑婷婷

    2012-01-01

    For the purpose of reducing the ammonia nitrogen and the organic pollutant with high concentration in the landfill leachate, this text used combination treatment with lime coagulation, blow off and CO2 aeration to pretreated the landfill leachate in order to lessen the pollutant load to the biochemical treatment in the later stage. This text used single-factor experiment to discuss the impact of different factors, such as dosing quantity of CaO, aeration time, temperature and the ratio of gas and solid, on the removal efficiency of the ammonia nitrogen, COD and UV254. It also discussed the most efficient reaction condition of the comprehensive treatment effect by orthogonal experiment. The experiment also aerate with CO2 after the orthogonal experiment as to reduce the high pH and the concentration of Ca2+. The results of this experiment indicated that, the removal efficiency of ammonia nitrogen had direct correlativity with each factors. That of COD and UV254 had positive relationship with the dosing quantity of CaO. With the most efficient experiment condition of coagulation-blow off which obtained from the orthogonal experiment, the removal rate of the ammonia nitrogen, COD and UV254 could get 98.8%, 60.2%, 68.7% respectively. After the further aeration with CO2, the pH of the garbage percolate fall to 6.8 from 12.1. The removal rate of the concentration of Ca2+ was 70.3% and that of COD was 65.7%.%为了有效降低垃圾渗滤液中高浓度的氨氮和有机污染物,以便降低后期生化处理的污染负荷,采用石灰混凝+吹脱+CO2曝气联合法对垃圾渗滤液进行预处理,通过单因素实验研究CaO投加量、曝气时间、反应温度及气液比等因素对渗滤液中氨氮、COD以及UV254的去除效果的影响;通过正交实验研究综合处理效果最好的反应条件,并在正交实验后进行CO2曝气,以期降低实验后较高的pH和钙离子浓度.结果表明:氨氮去除率与各单因素呈正相关关系,COD及UV254的去除率与CaO投加量相关性较大.在正交试验得出的最佳混凝吹脱条件下,氨氮、COD、UV254的去除率分别能达到98.8%、60.2%、68.7%.进一步CO2曝气后,垃圾渗滤液pH由12.1降至6.8,钙离子浓度降低70.3%,COD去除率可达65.7%.

  11. Effect of electric fields on the stabilization of premixed laminar bunsen flames at low AC frequency: Bi-ionic wind effect

    KAUST Repository

    Kim, Minkuk

    2012-03-01

    The stabilization characteristics of laminar premixed bunsen flames have been investigated experimentally by applying AC electric fields at low frequency below 60. Hz together with DC in the single electrode configuration. The blowoff velocity has been measured for varying AC voltage and frequency. A transition frequency between low and high frequency regimes has been identified near 40-50. Hz, where AC electric fields have minimal effect on flame stabilization. In the low frequency regime, the blowoff velocity decreased linearly with AC voltage such that the flames became less stable. This was consistent with the DC result, implying the influence of the ionic wind effect. The variation of blowoff velocity with AC frequency showed a non-monotonic behavior in that the velocity decreased and then increased, exhibiting minimum blowoff velocity near 6-8. Hz. Based on the molecular kinetic theory, the developing degree of ionic wind was derived. By considering the ionic wind effects arising from both positive and negative ions in a flame zone, the bi-ionic wind effect successfully explained the non-monotonic behavior of blowoff velocity with AC frequency in the low frequency regime. © 2011 The Combustion Institute.

  12. Stability enhancement of ozone-assisted laminar premixed Bunsen flames in nitrogen co-flow

    KAUST Repository

    Vu, Tran Manh

    2014-04-01

    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.

  13. Dynamics of bluff-body-stabilized premixed hydrogen/air flames in a narrow channel

    KAUST Repository

    Lee, Bok Jik

    2015-06-01

    Two-dimensional direct numerical simulations were conducted for bluff-body stabilized flames of a lean hydrogen/air mixture at near-blowoff conditions in a meso-scale channel. Parametric simulations were conducted by incrementally varying the inflow velocity in the vicinity of the blowoff limit, and the corresponding flame response was monitored. The present study is a showcase of combustion DNS with embedded boundary representation, and full demonstration of the detailed visualization of the near-blowoff flame characteristics. As the inflow velocity approaches blowoff limit, the flame dynamics exhibit a complex sequence of events, such as periodic local extinction and recovery, and regrowth of the bulk flame by the flame segments attached behind the bluff-body. The total extinction is observed as the attached flames shrink down and are no longer able to regrow the bulk flames. Despite the disparity in the physical scale under study, the observed sequence of the extinction pathway shows a strong similarity with experimental observations at larger scale combustion systems. © 2015 The Combustion Institute.

  14. Solution for a window coating problem developed in the JT-60U Thomson scattering system

    International Nuclear Information System (INIS)

    For an exact measurement of fusion plasmas with higher electron temperature, the following two methods which can solve a window coating problem were developed in the JT-60U Thomson scattering system. One is an in situ monitoring method which can infer a window transmission with sufficient precision from a known attenuation of the deposited film. The other is an in situ window cleaning method which removes the film on the basis of a laser blow-off technique. As the results of the extensive investigations, the existence of chromatic upper limit has been found in the recovered transmission after the laser blow-off cleaning, however, which gives systematic errors only of less than 3% to the apparent measurement for both electron density and temperature at 10 keV or less. The attenuation itself was unchanged before and after the laser blow-off cleaning. So the first method can be also applicable to the window after the laser blow-off cleaning. A complementary use of both the methods against the window coating problem can be expected to provide the Thomson scattering measurement of high Te plasmas with durable reliability and sufficient precision in the present tokamaks and also the ITER. (author)

  15. Particle-induced thermonuclear fusion

    International Nuclear Information System (INIS)

    A nuclear fusion process for igniting a nuclear fusion pellet in a manner similar to that proposed for laser beams uses, an array of pulsed high energy combined particle beams, focused to bombard the pellet for isentropically compressing it to a Fermi-degenerate state by thermal blow-off and balanced beam momentum transfer. (author)

  16. 76 FR 16641 - Petitions for Modification of Existing Mandatory Safety Standards

    Science.gov (United States)

    2011-03-24

    ... 19.2 SCFM @ 30 psig. (8) The uppermost spray nozzle will be located at a height of not more than 56... Mingo County, West Virginia. Regulation Affected: 30 CFR 75.1101-1(b) (Deluge-type water spray systems... blow-off dust covers for the spray nozzles of a deluge-type water spray system. The petitioner...

  17. Flashback Analysis in Tangential Swirl Burners

    OpenAIRE

    Valera-Medina A.; Syred N.; Abdulsada M.

    2011-01-01

    Premixed lean combustion is widely used in Combustion Processes due to the benefits of good flame stability and blowoff limits coupled with low NOx emissions. However, the use of novel fuels and complex flows have increased the concern about flashback, especially for the use of syngas and highly hydrogen enriched blends. Thus, this paper describes a combined practical and numerical approach to study the phenomenon in order to reduce the effect of flashback in a pilot scale 100 kW tangential s...

  18. A laser device for perforating materials

    Science.gov (United States)

    Domankevitz, Yacov; Kwok, Hoi S.; Copley, John A.

    1995-12-01

    A Nd:YAG laser device for perforating materials was developed. The device generates a modified temporal pulse structure of both free-running and Q-switched laser irradiation. This modified structure enhances drilling efficiency by a factor of 2 compared to free-running irradiation and is achieved by mechanical blow-off of preheated material. Such a device is well suited for compact portable field applications.

  19. Numerical investigation on the combustion characteristics of methane/air in a micro-combustor with a hollow hemispherical bluff body

    International Nuclear Information System (INIS)

    Highlights: • A micro-combustor with a hollow hemisphere bluff body is developed. • Blow-off limit of reactor is expanded 2.5 times by the hollow hemisphere bluff body. • Methane conversion rate of combustor sharply increases at the location of bluff body. • Methane conversion rate is mainly affected by equivalence ratio and inlet velocity. • Recirculation zone expands blow-off limit and increases methane conversion rate. - Abstract: The combustion characteristics of methane in a cube micro-combustor with a hollow hemispherical bluff body were numerically investigated. The blow-off limit, recirculation zone length and methane conversion rate were examined. The results illustrate that the blow-off limit of the micro-combustor with a hollow hemispherical bluff body is 2.5 times higher than that without bluff body, which are 24.5 m/s and 9.5 m/s at the same equivalence ratio (ϕ = 1), respectively. With the use of hollow hemispherical bluff body, methane conversion sharply increases from 0.24% to 17.95% at 3 mm along the inlet-flow direction, where is the location of bluff-body, which is not affected by equivalence ratio and inlet velocity. The recirculation zone size has determined influence on residence time of the mixture gas, which increases with the increase of inlet velocity. Methane conversion rate is determined by equivalence ratio and inlet velocity. Methane conversion rate firstly increases and then decreases when the equivalence ratio and inlet velocity increase, reaching the maximum value (97.84%) at ϕ = 1 and 0.02 m/s. Methane conversion rate sharply increases from 45% to 97.84% when the inlet velocity increases from 0.008 m/s to 0.02 m/s

  20. Simulation of Hohlraum Wall Texture for Improved Performance in Hohlraums

    Energy Technology Data Exchange (ETDEWEB)

    Meyer, Isaac Chartrand [Univ. of California, Berkeley, CA (United States); Urbatsch, Todd James [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Scott, John Mitchell [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-08-15

    The performance of hohlraums for use in NIF (National Ignition Facility) is explored using Cassio: a LANL produced radiation hydrodynamics code that implements implicit Monte Carlo radiation transport. We examine the effect on blowoff of adding texture to the inside of the hohlraum wall. These new designs are compared in simulation against current designs and the data are analyzed for the possible use of such hohlraums in future high energy density physics experiments.

  1. Proton imaging of hohlraum plasma stagnation in inertial-confinement-fusion experiments

    International Nuclear Information System (INIS)

    Proton radiography of the spatial structure and temporal evolution of plasma blowing off from a hohlraum wall reveals how the fill gas compresses the wall blow-off, inhibits plasma jet formation and impedes plasma stagnation in the hohlraum interior. The roles of spontaneously generated electric and magnetic fields in hohlraum dynamics and capsule implosions are demonstrated. The heat flux is shown to rapidly convect the magnetic field due to the Nernst effect, which is shown to be ∼10 times faster than convection by the plasma fluid from expanded wall blow-off (vN ∼ 10v). This leads to inhibition of heat transfer from the gas region in the laser beam paths to the surrounding cold gas, resulting in a local plasma temperature increase. The experiments show that interpenetration of the two materials (gas and wall) occurs due to the classical Rayleigh–Taylor instability as the lighter, decelerating ionized fill gas pushes against the heavier, expanding gold wall blow-off. This experiment provides physics insight into the effects of fill gas on x-ray-driven implosions, and would impact the ongoing ignition experiments at the National Ignition Facility. (paper)

  2. Dust emissions from undisturbed and disturbed, crusted playa surfaces: Cattle trampling effects

    Science.gov (United States)

    Baddock, Matthew C.; Zobeck, Ted M.; Van Pelt, R. Scott; Fredrickson, Ed L.

    2011-06-01

    Dry playa lake beds can be significant sources of fine dust emission. This study used a portable field wind tunnel to quantify the PM 10 emissions from a bare, fine-textured playa surface located in the far northern Chihuahua Desert. The natural, undisturbed crust and its subjection to two levels of animal disturbance (one and ten cow passes) were tested. The wind tunnel generated dust emissions under controlled conditions for firstly an initial blow-off of the surface, followed by two longer runs with sand added to the flow as an abrader material. Dust was measured using a GRIMM particle monitor. For the study playa, no significant differences in PM 10 concentration and emission flux were found between the untrampled surface and following a single animal pass. This was the case for both the initial blow-offs and tests on plots under a steady abrader rate. Significantly higher dust loading was only associated with the effect of 10 animal passes. In the blow-offs, the higher PM 10 yield after 10 passes reflected the greater availability of easily entrainable fine particles. Under abrasion, the effect of the heaviest trampling increased the emission flux by a third and abrasion efficiency by around 50% more than values on the untrampled surface. This enhanced abrasion efficiency persisted for a 30 min period under abrasion before the positive effect of the disturbance was no longer evident. The findings highlight the role of a threshold of disturbance that determines if supply-limited surfaces will exhibit enhanced wind erosion or not after undergoing perturbation.

  3. Efficient ventilation in school buildings. Design guidebook; Ventilation performante dans les ecoles. Guide de conception

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2001-07-01

    This guidebook aims at giving practical advices for the design of ventilation systems for school buildings in order to maintain air quality levels and energy consumptions conformable with the real needs: 1 - the specific problem of schools (various types of rooms, particular indoor pollutions); 2 - main criteria to consider (air quality and hygiene, hygro-thermal comfort, ventilation efficiency, acoustic comfort, energy mastery); 3 - main existing solutions (simple-flux blow-off or blow-in mechanical ventilation systems, dual-flux systems, air conditioning systems); 4 - choice of an adapted solution (selection criteria, global solution for the school); setting-up and follow-up (rules, training, maintenance). (J.S.)

  4. Laser-blow-off experiments on ASDEX

    International Nuclear Information System (INIS)

    In 1985 laser blow-off system was installed on the ASDEX tokamak and in the following period a number of experiments were performed. The idea of these investigations was to study the impurity behaviour under different plasma conditions. New and unexpected results were obtained: 1. Considerable improvement of the impurity confinement time in OH plasmas near to the density limit, 2. influence on ELMs by impurities, 3. strong dependence of the impurity confinement time on the gradient of the plasma current, and 4. different impurity confinement under various heating conditions. (orig.)

  5. Self-consistent removal of sawtooth oscillations from transient plasma data by generalized singular value decomposition

    International Nuclear Information System (INIS)

    This paper addresses the problem of removing sawtooth oscillations from multichannel plasma data in a self-consistent way, thereby preserving transients that have a different physical origin. The technique which does this is called the Generalized Singular Value Decomposition (GSVD), and its properties are discussed. Using the GSVD, we analyze spatially resolved electron temperature measurements from the Tore Supra tokamak, made in transient regimes that are perturbed either by the laser blow-off injection of impurities or by pellet injection. Non-local transport issues are briefly discussed. (author)

  6. Analysis of Lean Premixed/Prevaporized Combustion with KIVA-2

    Science.gov (United States)

    Deur, J. M.; Kundu, K. P.; Darling, D. D.; Cline, M. C.; Micklow, G. J.; Harper, M. R.; Simons, T. A.

    1994-01-01

    Requirements to reduce the emissions of pollutants from gas turbines used in aircraft propulsion and ground based power generation have led to consideration of lean premixed/prevaporized (LPP) combustion concept. This paper describes some of the LPP flame tube analyses performed at the NASA Research Center with KIVA-2, a well-known multi-dimensional CFD code for problems including sprays, turbulence, and combustion. Modifications to KIVA-2's boundary condition and chemistry treatments have been made to meet the needs of the present study. The study itself focuses on two key aspects of the LPP concept, low emissions and flame stability (including flashback and lean blowoff.

  7. Novel spherical hohlraum with cylindrical laser entrance holes and shields

    Energy Technology Data Exchange (ETDEWEB)

    Lan, Ke [Institute of Applied Physics and Computational Mathematics, Beijing 100088 (China); Center for Applied Physics and Technology, Peking University, Beijing 100871 (China); Zheng, Wudi [Institute of Applied Physics and Computational Mathematics, Beijing 100088 (China)

    2014-09-15

    Our recent works [K. Lan et al., Phys. Plasmas 21, 010704 (2014); K. Lan et al., Phys. Plasmas 21, 052704 (2014)] have shown that the octahedral spherical hohlraums are superior to the cylindrical hohlraums in both higher symmetry during the capsule implosion and lower backscatter without supplementary technology. However, both the coupling efficiency from the drive laser energy to the capsule and the capsule symmetry decrease remarkably when larger laser entrance holes (LEHs) are used. In addition, the laser beams injected at angles > 45° transport close to the hohlraum wall, thus the wall blowoff causes the LEH to close faster and results in strong laser plasma interactions inside the spherical hohlraums. In this letter, we propose a novel octahedral hohlraum with LEH shields and cylindrical LEHs to alleviate these problems. From our theoretical study, with the LEH shields, the laser coupling efficiency is significantly increased and the capsule symmetry is remarkably improved in the spherical hohlraums. The cylindrical LEHs take advantage of the cylindrical hohlraum near the LEH and mitigate the influence of the blowoff on laser transport inside a spherical hohlraum. The cylindrical LEHs can also be applied to the rugby and elliptical hohlraums.

  8. Bluff-body stabilized flame dynamics of lean premixed syngas combustion

    Science.gov (United States)

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

    2015-11-01

    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.

  9. Effect of AC electric fields on the stabilization of premixed bunsen flames

    KAUST Repository

    Kim, Minkuk

    2011-01-01

    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.

  10. Dynamics and structure of stretched flames

    Energy Technology Data Exchange (ETDEWEB)

    Law, C.K. [Princeton Univ., NJ (United States)

    1993-12-01

    This program aims to gain fundamental understanding on the structure, geometry, and dynamics of laminar premixed flames, and relate these understanding to the practical issues of flame extinction and stabilization. The underlying fundamental interest here is the recent recognition that the response of premixed flames can be profoundly affected by flame stretch, as manifested by flow nonuniformity, flame curvature, and flame/flow unsteadiness. As such, many of the existing understanding on the behavior of premixed flames need to be qualitatively revised. The research program consists of three major thrusts: (1) detailed experimental and computational mapping of the structure of aerodynamically-strained planar flames, with emphasis on the effects of heat loss, nonequidiffusion, and finite residence time on the flame thickness, extent of incomplete reaction, and the state of extinction. (2) Analytical study of the geometry and dynamics of stretch-affected wrinkled flame sheets in simple configurations, as exemplified by the Bunsen flame and the spatially-periodic flame, with emphasis on the effects of nonlinear stretch, the phenomena of flame cusping, smoothing, and tip opening, and their implications on the structure and burning rate of turbulent flames. (3) Stabilization and blowoff of two-dimensional inverted premixed and stabilization and determining the criteria governing flame blowoff. The research is synergistically conducted through the use of laser-based diagnostics, computational simulation of the flame structure with detailed chemistry and transport, and mathematical analysis of the flame dynamics.

  11. An X-ray survey of ultra-active planet hosts

    Science.gov (United States)

    Schmitt, Jurgen

    2013-10-01

    We propose to obtain snapshot observations of a sample of ultra-active planet hosts. The sample is complete in that it comprises all known transiting systems (not observed/proposed) within 250 pc, orbital periods below 10 days and strong activity as photometric variations in excess of 1% and/or Ca II emission; the sample does include all suitable objects detected by Kepler. The sensitivity of the proposed XMM-Newton observations allows the detection of stars with X-ray luminosities in excess of 10^29 erg/sec. Because of the proximity to their hosts these planets are the prime candidates for the process of planetary atmospheric evaporation through hydrodynamic blow-off. With our study we establish the hosts' high-energy properties and pave the way for meaningful follow-up studies.

  12. Kuiper Prize Lecture - Escape of atmospheres, ancient and modern

    Energy Technology Data Exchange (ETDEWEB)

    Hunten, D.M. (Arizona Univ., Tucson (USA))

    1990-05-01

    A development history is presented for theories concerning planetary atmosphere gas-escape phenomena, which although firmly grounded in the kinetics of gases achieved truly productive results only after spacecraft remote sensing data for both the earth atmosphere and the planets became widely available. The most significant initial advances, encompassing diffusion-limited flow, nonthermal escape mechanisms, bound nonthermal coronas, and mass fractionation during early blowoff, followed from sounding rocket studies of the earth upper atmosphere, Mariner 5 results on hydrogen near Venus, and the nitrogen isotopic composition discovered by Viking in Mars. Attention has more recently been given to the xenon isotopic patterns in various atmospheres, as well as to the puzzling behavior of the Io atmosphere and plasma torus. 126 refs.

  13. Radio chemistry as a diagnostic in laser fusion experiments

    International Nuclear Information System (INIS)

    Nuclear chemistry techniques have been employed in an attempt to measure the density of high compression laser fusion targets. Radioactive 28Al atoms formed in the 28Si(n,p)28Al reaction arising from the interaction of the 14 MeV neutrons with the silicon atoms in the glass microsphere have been counted at Lawrence Livermore Laboratory using a β-γ coincidence method. The detection system that is employed allows activities corresponding to 100 aluminum atoms to be measured. From the observed number of activated atoms, neutron yields, and code calculations, information on the density of the compressed fuel can be obtained. This method is particularly valuable when the target compression becomes great enough to prohibit previously employed diagnostic techniques to be used. In addition, technique which utilizes a radioactive tracer to measure the isotropy of the target debris blowoff will also be discussed

  14. Kuiper Prize Lecture - Escape of atmospheres, ancient and modern

    International Nuclear Information System (INIS)

    A development history is presented for theories concerning planetary atmosphere gas-escape phenomena, which although firmly grounded in the kinetics of gases achieved truly productive results only after spacecraft remote sensing data for both the earth atmosphere and the planets became widely available. The most significant initial advances, encompassing diffusion-limited flow, nonthermal escape mechanisms, bound nonthermal coronas, and mass fractionation during early blowoff, followed from sounding rocket studies of the earth upper atmosphere, Mariner 5 results on hydrogen near Venus, and the nitrogen isotopic composition discovered by Viking in Mars. Attention has more recently been given to the xenon isotopic patterns in various atmospheres, as well as to the puzzling behavior of the Io atmosphere and plasma torus. 126 refs

  15. Influence of partially-stripped impurity ions on the cyclotron absorption of the fast magnetosonic wave in TFR plasmas

    International Nuclear Information System (INIS)

    Injection of vanadium ions by the laser blow-off technique has permitted to modify at will the impurity content in TFR plasmas prior to ion-cyclotron resonance (ICR) heating experiments in the mode conversion regime. The initial rate of increase of the central deuteron temperature has thus been enhanced. By solving the wave propagation equation in the WKB approximation, it has been possible to account for the enhanced dTsub(D)(O)/dt value by wave energy deposition on resonating V21+ ions, provided a fraction (of the order of 1O%) of these ions has been accelerated to the tens of keV range. Previous experimental ICR heating results, in conditions such that the proton cyclotron layer is outside the limiter radius, can be explained by similar resonance processes on intrinsic metal impurity ions

  16. Effect of NLTE Emissivity Models on NIF Ignition Hohlraum Power Requirements

    International Nuclear Information System (INIS)

    NLTE atomic physics model can significantly affect the power requirements and plasma conditions in ignition hohlraums. This is because the emissivity is a significant factor in determining the time dependent coronal temperature of the hot blow-off plasma filling ignition hohlraums, which, in turn, determines the total energy stored in that coronal plasma at any instant. Here we present best estimates of NLTE emissivity using the SCRAM model, including the range of uncertainty, and compare them with the emissivity of the model used to design NIF ignition hohlraums and set the NIF pulse shape, XSN NLTE. We then present pulse shapes derived from hohlraum simulations using an atomic physics model that approximates the SCRAM emissivities. We discuss the differences in coronal energetics and show how this affects the pulse shape and, in particular, the peak power requirement.

  17. Recent US target-physics-related research in heavy-ion inertial fusion: depostion physics and other discussions

    International Nuclear Information System (INIS)

    Theoretical work on heavy-ion deposition physics continues at several US laboratories. For example, simulations of charge-state evolution during initial phases of beam-target interactions are suggestive that equilibrium charge is reached only after a substantial fraction of the ion range. Thus we expect reduced interactions and energy loss to the blow-off plasma and also to the tampers in the case of tamped targets. Studies of plasma effects of beam-target interactions are still relevant. But recent result of high current density experiments (250 kA/cm2) with a deuteron beam at the Naval Research Laboratory are indicative of classical deposition for finite temperature plasmas. Moreover, presently we expect heavy-ion beams to have even more stable beam-target interactions than deuterons. Further experimental and accompanying theoretical studies would be very useful

  18. Comparison of soil pollution concentrations determined using AAS and portable XRF techniques

    International Nuclear Information System (INIS)

    Past mining activities in the area of Silvermines, Ireland, have resulted in heavily polluted soils. The possibility of spreading pollution to the surrounding areas through dust blow-offs poses a potential threat for the local communities. Conventional environmental soil and dust analysis techniques are very slow and laborious and consequently there is a need for fast and accurate analytical methods, which can provide real-time in situ pollution mapping. Laboratory-based aqua regia acid digestion of the soil samples collected in the area followed by the atomic absorption spectrophotometry (AAS) analysis confirmed very high pollution, especially by Pb, As, Cu, and Zn. In parallel, samples were analyzed using portable X-ray fluorescence radioisotope and miniature tube powered (XRF) NITON instruments and their performance was compared. Overall, the portable XRF instrument gave excellent correlation with the laboratory-based reference AAS method.

  19. Lunar Dust and Dusty Plasma Physics

    Science.gov (United States)

    Wilson, Thomas L.

    2009-01-01

    In the plasma and radiation environment of space, small dust grains from the Moon s surface can become charged. This has the consequence that their motion is determined by electromagnetic as well as gravitational forces. The result is a plasma-like condition known as "dusty plasmas" with the consequence that lunar dust can migrate and be transported by magnetic, electric, and gravitational fields into places where heavier, neutral debris cannot. Dust on the Moon can exhibit unusual behavior, being accelerated into orbit by electrostatic surface potentials as blow-off dust, or being swept away by moving magnetic fields like the solar wind as pick-up dust. Hence, lunar dust must necessarily be treated as a dusty plasma subject to the physics of magnetohydrodynamics (MHD). A review of this subject has been given before [1], but a synopsis will be presented here to make it more readily available for lunar scientists.

  20. Surface temperature transients from pulsed laser heating of UO 2

    Science.gov (United States)

    Yagnik, S. K.; Olander, D. R.

    1988-07-01

    Surface heating of UO 2 by a pulsed laser was investigated theoretically and experimentally. Targets of solid uranium dioxide in vacuum were rapidly heated to peak temperatures of 3700 K, as measured by a fast-response automatic optical pyrometer. The measured target surface temperatures were compared with a one-dimensional heat transport model that accounts for conduction and melting in the solid and ablation and radiation from the surface. Congruent vaporization of UO 2 was assumed. The measured temporal and spatial characteristics of the laser beam as well as temperature-dependent physical and thermodynamic properties of UO 2 are used as input to the calculations. Agreement of the theory with the measurements was further validated by post-irradiation microscopic examination of the target surface. Additional tests were performed to assess qualitatively the attenuation of laser light and thermal radiation from the surface by the vapor blow-off from the target. This effect was found to be insignificant.

  1. Reducing wall plasma expansion with gold foam irradiated by laser

    International Nuclear Information System (INIS)

    The experimental study on the expanding plasma movement of low-density gold foam (∼1% solid density) irradiated by a high power laser is reported in this paper. Experiments were conducted using the SG-III prototype laser. Compared to solid gold with 19.3 g/cc density, the velocities of X-ray emission fronts moving off the wall are much smaller for gold foam with 0.3 g/cc density. Theoretical analysis and MULTI 1D simulation results also show less plasma blow-off, and that the density contour movement velocities of gold foam are smaller than those of solid gold, agreeing with experimental results. These results indicate that foam walls have advantages in symmetry control and lowering plasma fill when used in ignition hohlraum

  2. Reducing wall plasma expansion with gold foam irradiated by laser

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Lu; Ding, Yongkun, E-mail: ding-yk@vip.sina.com; Jiang, Shaoen, E-mail: jiangshn@vip.sina.com; Yang, Jiamin; Li, Hang; Kuang, Longyu; Lin, Zhiwei; Jing, Longfei; Li, Liling; Deng, Bo; Yuan, Zheng; Chen, Tao; Yuan, Guanghui; Tan, Xiulan; Li, Ping [Research Center of Laser Fusion, China Academy of Engineering Physics, P.O. Box 919-986, Mianyang 621900 (China)

    2015-11-15

    The experimental study on the expanding plasma movement of low-density gold foam (∼1% solid density) irradiated by a high power laser is reported in this paper. Experiments were conducted using the SG-III prototype laser. Compared to solid gold with 19.3 g/cc density, the velocities of X-ray emission fronts moving off the wall are much smaller for gold foam with 0.3 g/cc density. Theoretical analysis and MULTI 1D simulation results also show less plasma blow-off, and that the density contour movement velocities of gold foam are smaller than those of solid gold, agreeing with experimental results. These results indicate that foam walls have advantages in symmetry control and lowering plasma fill when used in ignition hohlraum.

  3. Edge Thomson Scattering in RFX-mod: Operation and first measures

    Energy Technology Data Exchange (ETDEWEB)

    Alfier, A; Fassina, A; Pasqualotto, R; Dal Bello, S; Cervaro, V; Lotto, L; Tollin, M, E-mail: alessandro.fassina@igi.cnr.i [Consorzio RFX, Corso Stati Uniti 4, 35157 Padova (Italy)

    2010-05-01

    During the 2009 experimental campaign the Edge Thomson Scattering System started the operations, after a commissioning period. The main modification has been the adoption of interferential filters spectrometers with APD detectors, similar to those used on the main TS. Other improvements were the optimization of the laser input path and of the collection optics, which increased the signal level of about 50 %. With the present setup, temperature and density measures show good compatibility with those of the main TS diagnostic; density data have been calculated after Rotational Raman Scattering calibration, a method which is not affected by impurity deposition on the collection window. Present operational limits of the diagnostic are discussed as well as short terms planned operations, focusing in particular on laser multi-pulse issues and laser sharing with the impurity injection system by laser blow-off.

  4. The MgI line: a new probe of the atmospheres of evaporating exoplanets

    CERN Document Server

    Bourrier, V; Vidal-Madjar, A

    2014-01-01

    Transit observations of HD209458b in the UV revealed signatures of neutral magnesium escaping the planet's upper atmosphere. The absorption detected in the MgI line provides unprecedented information on the physical conditions at the altitude where the atmospheric blow-off takes place. Here we use a 3D model of atmospheric escape to estimate the transit absorption signatures in the MgI line of their host stars. The detectability of these signatures depends on the brightness of the star and the escape rate of neutral magnesium. We identify a sample of potentially evaporating exoplanets that covers a wide range of stellar and planetary properties, and whose extended exospheres might be detected through MgI line observations with current UV facilities, allowing further steps in comparative exoplanetology.

  5. Structures and stabilization of low calorific value gas turbulent partially premixed flames in a conical burner

    Energy Technology Data Exchange (ETDEWEB)

    Yan, B.; Liu, C. [Faculty of Environmental Science and Engineering, Tianjin University, 300072 Tianjin (China); Division of Fluid Mechanics, Lund University, 221 00 Lund (Sweden); Li, B.; Sun, Z.W.; Li, Z.S.; Alden, M. [Division of Combustion Physics, Lund University, 221 00 Lund (Sweden); Baudoin, E.; Bai, X.S. [Division of Fluid Mechanics, Lund University, 221 00 Lund (Sweden); Chen, G. [Faculty of Environmental Science and Engineering, Tianjin University, 300072 Tianjin (China); Mansour, M.S. [Cairo University, Natl Inst Laser Enhanced Sci., Cairo (Egypt)

    2010-04-15

    Experiments are carried out on partially premixed turbulent flames stabilized in a conical burner. The investigated gaseous fuels are methane, methane diluted with nitrogen, and mixtures of CH{sub 4}, CO, CO{sub 2}, H{sub 2} and N{sub 2}, simulating typical products from gasification of biomass, and co-firing of gasification gas with methane. The fuel and air are partially premixed in concentric tubes. Flame stabilization behavior is investigated and significantly different stabilization characteristics are observed in flames with and without the cone. Planar laser induced fluorescence (LIF) imaging of a fuel-tracer species, acetone, and OH radicals is carried out to characterize the flame structures. Large eddy simulations of the conical flames are carried out to gain further understanding of the flame/flow interaction in the cone. The data show that the flames with the cone are more stable than those without the cone. Without the cone (i.e. jet burner) the critical jet velocities for blowoff and liftoff of biomass derived gases are higher than that for methane/nitrogen mixture with the same heating values, indicating the enhanced flame stabilization by hydrogen in the mixture. With the cone the stability of flames is not sensitive to the compositions of the fuels, owing to the different flame stabilization mechanism in the conical flames than that in the jet flames. From the PLIF images it is shown that in the conical burner, the flame is stabilized by the cone at nearly the same position for different fuels. From large eddy simulations, the flames are shown to be controlled by the recirculation flows inside cone, which depends on the cone angle, but less sensitive to the fuel compositions and flow speed. The flames tend to be hold in the recirculation zones even at very high flow speed. Flame blowoff occurs when significant local extinction in the main body of the flame appears at high turbulence intensities. (author)

  6. Diffusion Flame Stabilization

    Science.gov (United States)

    Takahashi, Fumiaki; Katta, Viswanath R.

    2007-01-01

    Diffusion flames are commonly used for industrial burners in furnaces and flares. Oxygen/fuel burners are usually diffusion burners, primarily for safety reasons, to prevent flashback and explosion in a potentially dangerous system. Furthermore, in most fires, condensed materials pyrolyze, vaporize, and burn in air as diffusion flames. As a result of the interaction of a diffusion flame with burner or condensed-fuel surfaces, a quenched space is formed, thus leaving a diffusion flame edge, which plays an important role in flame holding in combustion systems and fire spread through condensed fuels. Despite a long history of jet diffusion flame studies, lifting/blowoff mechanisms have not yet been fully understood, compared to those of premixed flames. In this study, the structure and stability of diffusion flames of gaseous hydrocarbon fuels in coflowing air at normal earth gravity have been investigated experimentally and computationally. Measurements of the critical mean jet velocity (U(sub jc)) of methane, ethane, or propane at lifting or blowoff were made as a function of the coflowing air velocity (U(sub a)) using a tube burner (i.d.: 2.87 mm) (Fig. 1, left). By using a computational fluid dynamics code with 33 species and 112 elementary reaction steps, the internal chemical-kinetic structures of the stabilizing region of methane and propane flames were investigated (Fig. 1, right). A peak reactivity spot, i.e., reaction kernel, is formed in the flame stabilizing region due to back-diffusion of heat and radical species against an oxygen-rich incoming flow, thus holding the trailing diffusion flame. The simulated flame base moved downstream under flow conditions close to the measured stability limit.

  7. Oxy-combustion of high water content fuels

    Science.gov (United States)

    Yi, Fei

    As the issues of global warming and the energy crisis arouse extensive concern, more and more research is focused on maximizing energy efficiency and capturing CO2 in power generation. To achieve this, in this research, we propose an unconventional concept of combustion - direct combustion of high water content fuels. Due to the high water content in the fuels, they may not burn under air-fired conditions. Therefore, oxy-combustion is applied. Three applications of this concept in power generation are proposed - direct steam generation for the turbine cycle, staged oxy-combustion with zero flue gas recycle, and oxy-combustion in a low speed diesel-type engine. The proposed processes could provide alternative approaches to directly utilize fuels which intrinsically have high water content. A large amount of energy to remove the water, when the fuels are utilized in a conventional approach, is saved. The properties and difficulty in dewatering high water content fuels (e.g. bioethanol, microalgae and fine coal) are summarized. These fuels include both renewable and fossil fuels. In addition, the technique can also allow for low-cost carbon capture due to oxy-combustion. When renewable fuel is utilized, the whole process can be carbon negative. To validate and evaluate this concept, the research focused on the investigation of the flame stability and characteristics for high water content fuels. My study has demonstrated the feasibility of burning fuels that have been heavily diluted with water in a swirl-stabilized burner. Ethanol and 1-propanol were first tested as the fuels and the flame stability maps were obtained. Flame stability, as characterized by the blow-off limit -- the lowest O2 concentration when a flame could exist under a given oxidizer flow rate, was determined as a function of total oxidizer flow rate, fuel concentration and nozzle type. Furthermore, both the gas temperature contour and the overall ethanol concentration in the droplets along the

  8. Cavity pressure history of contained nuclear explosions

    International Nuclear Information System (INIS)

    Knowledge of pressure in cavities created by contained nuclear explosions is useful for estimating the possibility of venting radioactive debris to the atmosphere. Measurements of cavity pressure, or temperature, would be helpful in evaluating the correctness of present code predictions of underground explosions. In instrumenting and interpreting such measurements it is necessary to have good theoretical estimates of cavity pressures. In this paper cavity pressure is estimated at the time when cavity growth is complete. Its subsequent decrease due to heat loss from the cavity to the surrounding media is also predicted. The starting pressure (the pressure at the end of cavity growth) is obtained by adiabatic expansion to the final cavity size of the vaporized rock gas sphere created by the explosion. Estimates of cavity size can be obtained by stress propagation computer codes, such as SOC and TENSOR. However, such estimates require considerable time and effort. In this paper, cavity size is estimated using a scheme involving simple hand calculations. The prediction is complicated by uncertainties in the knowledge of silica water system chemistry and a lack of information concerning possible blowoff of wall material during cavity growth. If wall material blows off, it can significantly change the water content in the cavity, compared to the water content in the ambient media. After cavity growth is complete, the pressure will change because of heat loss to the surrounding media. Heat transfer by convection, radiation and conduction is considered, and its effect on the pressure is calculated. Analysis of cavity heat transfer is made difficult by the complex nature of processes which occur at the wall where melting, vaporization and condensation of the gaseous rock can all occur. Furthermore, the melted wall material could be removed by flowing or dripping to the cavity floor. It could also be removed by expansion of the steam contained in the melt (blowoff) and by

  9. Experimental study of the inverse diffusion flame using high repetition rate OH/acetone PLIF and PIV

    KAUST Repository

    Elbaz, Ayman M.

    2015-10-29

    Most previous work on inverse diffusion flames (IDFs) has focused on laminar IDF emissions and the soot formation characteristics. Here, we investigate the characteristics and structure of methane IDFs using high speed planar laser-induced fluorescence (PLIF) images of OH, particle image velocimetry (PIV), and acetone PLIF imaging for non-reacting cases. First, the flame appearance was investigated with fixed methane loading (mass flux) but with varying airflow rates, yielding a central air jet Reynolds number (Re) of 1,000 to 6,000 (when blow-off occurs). Next, it was investigated a fixed central air jet Re of 4500, but with varied methane mass flux such that the global equivalence ratio spanned 0.5 to 4. It was observed that at Re smaller than 2000, the inner air jet promotes the establishment of an inverse diffusion flame surrounded by a normal diffusion flame. However, when the Re was increased to 2500, two distinct zones became apparent in the flame, a lower entrainment zone and an upper mixing and combustion zone. 10 kHz OH-PLIF images, and 2D PIV allow the identification of the fate and spatial flame structure. Many flame features were identified and further analyzed using simple but effective image processing methods, where three types of structure in all the flames investigated here: flame holes or breaks; closures; and growing kernels. Insights about the rate of evolution of these features, the dynamics of local extinction, and the sequence of events that lead to re-ignition are reported here. In the lower entrainment zone, the occurrence of the flame break events is counterbalanced by closure events, and the edge propagation appears to control the rate at which the flame holes and closures propagate. The rate of propagation of holes was found to be statistically faster than the rate of closure. As the flames approach blow-off, flame kernels become the main mechanism for flame re-ignition further downstream. The simultaneous OH-PLIF/Stereo PIV

  10. Reactor container

    International Nuclear Information System (INIS)

    Object: To stand a vapor passage extending through a diaphragm floor from a bottom of a pressure restraining chamber and to position a steam ejecting outlet, which is disposed in pressure restraining water, so as not to directly be directed toward the body of a container and the bottom of the pressure restraining chamber, thereby eliminating influence due to blow-off condensation of steam. Structure: In an arrangement wherein a container is divided by a diaphragm floor into two portions, i.e., an upper drywell and a lower pressure restraining chamber containing pressure restraining water to from a steam communicating duct which communicates said drywell with said pressure restraining chamber, said communicating duct being stood extending through the diaphragm floor from the bottom of the pressure restraining chamber, and a steam ejecting outlet of said communicating duct disposed in pressure restraining water being fitted so as not to directly be directed toward the body of the container and the bottom of the pressure restraining chamber. (Ohara, T.)

  11. Experimental investigation of the interaction of 100 TW laser with solid targets (abstract)

    International Nuclear Information System (INIS)

    We report on the first plasma experiments with the 100 TW laser at LLNL. We have experimentally investigated the interaction of 1 μm, 40 J, 400 fs, 5x1019 W/cm2 laser pulses with multilayer solid targets. Various diagnostics were used to characterize this interaction. An x-ray pinhole camera monitored laser spot size and plasma location on target. Part of the laser beam was split off to probe the density scale length of the preformed plasma. An optical system for Schlieren photography was designed to record the images of plasma with electron density gradients as low as 1021 cm-4 with characteristic scale length of 10 μm. The range of electron densities was 1018 endash 2020 cm-3. CR-39 plastic track detectors were employed to measure the fast ion blowoff from the plasma. Using a foil-filter technique the proton energy spectrum up to 6 MeV was measured. It was found that the high energy tail usually had a narrow (FWHM ∼10 degree) cone of expansion. Energy conversion to the fast ions (above 0.5 MeV) was estimated to be ∼0.3%endash 1% of laser energy. In addition, charge-coupled devices were used for detecting characteristic Kα emission caused by fast (>1 MeV) electrons. (See article by K. Wharton for further discussion of the fast electron measurements.) Estimated fast electron yield ∼3%.copyright 1997 American Institute of Physics

  12. Flashback Analysis in Tangential Swirl Burners

    Directory of Open Access Journals (Sweden)

    Valera-Medina A.

    2011-10-01

    Full Text Available Premixed lean combustion is widely used in Combustion Processes due to the benefits of good flame stability and blowoff limits coupled with low NOx emissions. However, the use of novel fuels and complex flows have increased the concern about flashback, especially for the use of syngas and highly hydrogen enriched blends. Thus, this paper describes a combined practical and numerical approach to study the phenomenon in order to reduce the effect of flashback in a pilot scale 100 kW tangential swirl burner. Natural gas is used to establish the baseline results and effects of different parameters changes. The flashback phenomenon is studied with the use of high speed photography. The use of a central fuel injector demonstrates substantial benefits in terms of flashback resistance, eliminating coherent structures that may appear in the flow channels. The critical boundary velocity gradient is used for characterization, both via the original Lewis and von Elbe formula and via analysis using CFD and investigation of boundary layer conditions in the flame front.

  13. Optimization of a premixed low-swirl burner for industrial applications

    International Nuclear Information System (INIS)

    This study was motivated by recent tests results showing that a 5cm i.d. low-swirl burner (LSB) stabilizes ultra-lean premixed turbulent flames up to 600kW. A parametric study has been performed to determine the optimum ultra-lean LSB configuration, i.e. one that will achieve low NOx and flame stability, for thermal input between 15kW to 150kW. Using Laser Doppler Velocimetry (LDV), non-reacting centerline velocity and rms fluctuation profiles were measured, and were found to show self-similar behavior. This self-similarity may explain why the flame remains stationary relative to the burner exit despite a change in bulk flow velocity from 5 to 90m/s. The recess distance of the swirler affects the shape of the mean and rms velocity profiles. Lean blow-off limits were also determined for various recess distances, and an optimum exit length was found that provides stable operation for ultra-lean flames

  14. Gas-filled hohlraum study on Shenguang-III prototype

    Science.gov (United States)

    Yang, Dong; Li, Sanwei; Li, Zhichao; Yi, Rongqing; Guo, Liang; Jiang, Xiaohua; Liu, Shenye; Yang, Jiamin; Jiang, Shaoen; Ding, Yongkun; Hao, Liang; Zhang, Huasen; Zhao, Yiqing; Zou, Shiyang; Huo, Wenyi; Li, Xin

    2015-11-01

    Experimental studies on gas-filled hohlraum were performed extensively in recent years on Shenguang-III prototype laser facility. These experiments employed Au hohlraums within C5H12 gas fill heated by smoothing beams. In the first round of experiments, although the low-Z gas fill impeded the blow-off plasma ablated from hohlraum wall, the x-ray flux from the LEH decreased dramatically compared with the vacuum hohlraum. Further analysis of several ways of energy deposition including heating the gas-fill, extra scattered light and ablating the LEH membrane, revealed that too much laser energy were wasted in exploding the LEH membrane if we use a 1 ns square pulse. After we introduced a low power prepulse to intentionally exploding the membrane, the behavior of the x-ray flux from the gas-filled hohlraum is identical with the vacuum hohlraum. In subsequent studies, the motion of x-ray spot and corona plasma has also been studied using the gas-filled hohlraum. We obtained high quality data of the gas/wall interface and the boundary of the ablated wall near the LEH. The result agrees with that in simulation. However, there is a discrepancy between the experiment and the simulation in the spatial feature of the ablated wall near the LEH extracted from M-band x-ray image.

  15. Taking into account steam generator tube failure accidents in the design of safety systems for the N4 reactor (PWR 1400)

    International Nuclear Information System (INIS)

    Owing to the frequency with which they occur on PWRs, steam generator tube failure accidents have been the subject of a comprehensive review in France. Many modifications have been incorporated into the new PWR 1400 reactors so as to take this kind of accident more fully into account. The aim of these modifications is to control as well as possible the discharge of steam to the atmosphere, on the one hand, by making the atmospheric dump system an engineered safety feature, and on the other hand, by keeping to a minimum the risk of stressing the steam generator blow-off valves. Other modifications have been made to the turbine trip and to the startup of the emergency feedwater system, with a view to limiting the risk of an uncontrolled discharge into the atmosphere. The approach adopted represents an example of the integration of feedback into the design of safety systems and makes it possible to improve the level of safety in relation not only to steam generator tube failure accidents, but to all accidents which would necessitate rapid cooling by the secondary system. (author). 1 fig., 2 tabs

  16. 带侧边微孔射流扰动火焰结构特性%Flame Structure of a Jet Flame with Penetration of Side Micro-jets

    Institute of Scientific and Technical Information of China (English)

    曹玉春; 吴金星; 米建春; 周钰

    2008-01-01

    In this paper, an innovative jet lifted flame with side micro-jets has been proposed and its effects on the flame structure have also been investigated. Due to the changes of the initial combustion conditions, mixing and aerodynamics which resulted from the perturbation of the side micro-jets, such a lifted jet flame has different flame structure compared with the common premixed flame. Results demonstrate that use of the micro-jets can control, to a certain extent, the flame structure, including the flame length, lift-off distance and blow-off limit. With the same fuel and air flow rate, the flame length with the side micro-jets will decrease about 5% 40% as the air volume ratio a increases from 58%-76%. Compared with the common diffusion flame, the jet flame with the side micro-jets demonstrates to be easier to be a momentum-dominated flame. The flame length with 2 micro-jets is about 5% less than with 6 micro-jets under the same fuel and air flow rate. With the same α, the fewer number of the controlled jets lead to the flame with relatively shorter length, not easier to be blown off and higher NOx emission. With certain fuel flow rate, the critical air volume ratio is largest for the flame with 3 micro-jets, which is more difficult to be blown off than the cases with 2,4 or 6 micro-jets.

  17. Impurity transport in ohmically heated TFTR plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Stratton, B.C.; Fonck, R.J.; Hulse, R.A.; Ramsey, A.T.; Timberlake, J.; Efthimion, P.C.; Fredrickson, E.; Grek, B.; Hill, K.W.; Johnson, D.W.

    1988-11-01

    Impurity transport in ohmically heated TFTR plasmas is studied by computer modeling of VUV line emissions from impurities injected using the laser-blowoff technique. The results are sensitive to uncertainties in the ionization and recombination rates used in the modeling; as a result, only a spatially averaged diffusion coefficient and parameterized convective velocity can be measured. Measurements of these transport parameters are presented for deuterium and helium discharges with I/sub p/ = 0.8-2.5 MA, /bar n/sub e// = 0.6-6.0/times/10/sup 19/ m/sup -3/, and Z/sub eff/ = 2-6. Diffusion coefficients are found to be in the 0.5-1.5 m/sup 2//s range, considerably larger than neoclassical values. Nonzero inward convective velocities are necessary to fit the data in most cases. No dependence of the diffusion coefficient on injected element, working gas species, or plasma current is found, but at a given current, the diffusion coefficient is smaller by approximately a factor of two in plasmas near the density limit than in discharges with /bar n/sub e//<3/times/10/sup 19/ m/sup -3/. 31 refs., 9 figs., 3 tabs.

  18. Water Environment Protection in Yangzhou Section of Yangtze River%长江扬州段水环境保护研究

    Institute of Scientific and Technical Information of China (English)

    华迎春; 陈勤; 任晓梅; 高荣

    2001-01-01

    It is an urgent task at present to utilize resources of Yangtze River scientifically and reasonably and implement continuous development in the economic region along the river.This paper makes a special research on the status and evolution trend of water environment in Yangzhou section of the Yangtze River and puts forward a measure concerned to bring it under control by total amount control,especially make a breakthrough on pollution analysis and control countermeasure for non-point source based on a vast amount of monitoring data and basic material collected.The evaluation and forecast methods,determination of patternin flow & water quality and design condition,calculation on pollution effect in key section and mixed area of blowoff port etc.used in this paper have higher learning and practical value.It is significant for the protection of water environment and ecological environment,and provides basis for the research on water environment protection of Yangtze River and inspiration for water quality protection.This technology has good value in application and dissemination.

  19. Ion transport studies on the PLT tokamak during neutral beam injection

    International Nuclear Information System (INIS)

    Radial transport of ions during co- and counter-neutral beam heating in the PLT tokamak has been studied, using molybdenum and scandium ions as tracer elements. The time evolution of the radial profiles of several ionization stages of both elements, injected by laser blowoff during the neutral beam heating, were measured under three significantly different beam-plasma combinations. No noticeable differences in the radial profiles attributable to the beam direction were observed. However, a given injected amount resulted in considerably larger interior concentrations of the tracer element in the counter-beam heating cases, suggesting larger penetration of the plasma periphery. Computer simulation with the MIST code suggests a net inward drift of the order 103 cm/sec superposed to a diffusion coefficient of the order 104 cm2/sec for both scandium and molybdenum ions. Injection of larger amounts of the tracer element, sufficient to cause measurable central electron temperature changes, resulted in dramatic changes in ion-state distributions, making some appear peaked in the center while others disappeared. This effect could be produced with both co- and counter-beam heating, but with lesser amounts in the latter case. It is interpreted as rearrangement of the ionization balance, rather than any preferential accumulation of the injected element

  20. Density clamping phenomena in electron cyclotron resonance heated plasmas on Heliotron E

    International Nuclear Information System (INIS)

    Particle transport and related phenomena are investigated in currentless electron cyclotron resonance heated plasmas. It is observed that during the initial phase the density stops rising and then starts to decay, in spite of continuous gas puffing. The delay time between the breakdown time and the time at which the density starts to decay depends inversely on rf power. The density profile changes drastically, becoming flat or hollow at this time. This density profile change becomes more significant as the rf power is increased. In order to sustain the density at some level the external particle source should be increased with increasing rf power. Here it is found that the particle confinement time decreases with increasing power. The substantial increase in the particle outflux from the main plasma causes the scrape-off plasma to have a steep gradient. As a result, the amplitudes of density and magnetic fluctuations are enhanced with increasing rf power. When the cyclotron resonance layer is shifted outside the half radius, it is found that the density profile changes from hollow to centrally peaked. This result shows that the density profile is a function of the power deposition profile. It is also shown that the behavior of impurity ions (injected by the laser blow-off technique) is similar to that of the bulk particles. (author)

  1. Combustion Characteristics of Butane Porous Burner for Thermoelectric Power Generation

    Directory of Open Access Journals (Sweden)

    K. F. Mustafa

    2015-01-01

    Full Text Available The present study explores the utilization of a porous burner for thermoelectric power generation. The porous burner was tested with butane gas using two sets of configurations: single layer porcelain and a stacked-up double layer alumina and porcelain. Six PbSnTe thermoelectric (TE modules with a total area of 54 cm2 were attached to the wall of the burner. Fins were also added to the cold side of the TE modules. Fuel-air equivalence ratio was varied between the blowoff and flashback limit and the corresponding temperature, current-voltage, and emissions were recorded. The stacked-up double layer negatively affected the combustion efficiency at an equivalence ratio of 0.20 to 0.42, but single layer porcelain shows diminishing trend in the equivalence ratio of 0.60 to 0.90. The surface temperature of a stacked-up porous media is considerably higher than the single layer. Carbon monoxide emission is independent for both porous media configurations, but moderate reduction was recorded for single layer porcelain at lean fuel-air equivalence ratio. Nitrogen oxides is insensitive in the lean fuel-air equivalence ratio for both configurations, even though slight reduction was observed in the rich region for single layer porcelain. Power output was found to be highly dependent on the temperature gradient.

  2. A Comparison of the Characteristics of Planar and Axisymmetric Bluff-Body Combustors Operated under Stratified Inlet Mixture Conditions

    Directory of Open Access Journals (Sweden)

    G. Paterakis

    2013-01-01

    Full Text Available The work presents comparisons of the flame stabilization characteristics of axisymmetric disk and 2D slender bluff-body burner configurations, operating with inlet mixture stratification, under ultralean conditions. A double cavity propane air premixer formed along three concentric disks, supplied with a radial equivalence ratio gradient the afterbody disk recirculation, where the first flame configuration is stabilized. Planar fuel injection along the center plane of the leading face of a slender square cylinder against the approach cross-flow results in a stratified flame configuration stabilized alongside the wake formation region in the second setup. Measurements of velocities, temperatures, OH∗ and CH∗ chemiluminescence, local extinction criteria, and large-eddy simulations are employed to examine a range of ultralean and close to extinction flame conditions. The variations of the reacting front disposition within these diverse reacting wake topologies, the effect of the successive suppression of heat release on the near flame region characteristics, and the reemergence of large-scale vortical activity on approach to lean blowoff (LBO are investigated. The cross-correlation of the performance of these two popular flame holders that are at the opposite ends of current applications might offer helpful insights into more effective control measures for expanding the operational margin of a wider range of stabilization configurations.

  3. Single-pulse laser effects measurements at 248 nm

    International Nuclear Information System (INIS)

    We have measured induced impulse and mass loss from exposures of a number of materials to 50 ns, KrF (0.248 μm) laser pulses as a function of incident laser fluence, ambient atmospheric pressure, and angle of incidence. The energy on target was normally about 100 J but was varied down to about 10 J and the beam diameter on target was varied from about 0.1 to 38 mm providing incident laser fluences of from about 104 J/m2 to about 1010 J/m2. Calculations indicate that for fluences in these experiments below about 107 J/m2, the blowoff hydrodynamics is predominately one dimensional. The ambient atmospheric pressure was varied from about 105 Pa of dry air to a vacuum of less than 10-2 Pa; the angle of incidence was varied from normal incidence to 100 from grazing incidence. In a few cases, the pressure was measured as a function of time, sometimes concurrently with impulse. A number of plasma physics measurements were also performed concurrently

  4. Spectroscopic measurement of impurity transport coefficients and penetration efficiencies in Alcator C-Mod plasmas

    Science.gov (United States)

    Graf, M. A.; Rice, J. E.; Terry, J. L.; Marmar, E. S.; Goetz, J. A.; McCracken, G. M.; Bombarda, F.; May, M. J.

    1995-01-01

    Impurity transport coefficients and the penetration efficiencies of intrinsic and injected impurities through the separatrix of diverted Alcator C-Mod discharges have been measured using x-ray and vacuum ultraviolet (VUV) spectroscopic diagnostics. The dominant low Z intrinsic impurity in C-Mod is carbon which is found to be present in concentrations of less than 0.5%. Molybdenum, from the plasma facing components, is the dominant high Z impurity and is typically found in concentrations of about 0.02%. Trace amounts of medium and high Z nonrecycling impurities can be injected at the midplane using the laser blow-off technique and calibrated amounts of recycling, gaseous impurities can be introduced through fast valves either at the midplane or at various locations in the divertor chamber. A five chord crystal x-ray spectrometer array with high spectral resolution is used to provide spatial profiles of high charge state impurities. An absolutely calibrated, grazing incidence VUV spectrograph with high time resolution and a broad spectral range allows for the simultaneous measurement of many impurity lines. Various filtered soft x-ray diode arrays allow for spatial reconstructions of plasma emissivity. The observed brightnesses and emissivities from a number of impurity lines are used together with the mist transport code and a collisional-radiative atomic physics model to determine charge state density profiles and impurity transport coefficients. Comparisons of the deduced impurity content with the measured Zeff and total radiated power of the plasma are made.

  5. Outgassing History and Escape of the Martian Atmosphere and Water Inventory

    CERN Document Server

    Lammer, H; Karatekin, Ö; Morschhauser, A; Niles, P B; Mousis, O; Odert, P; Möstl, U V; Breuer, D; Dehant, V; Grott, M; Gröller, H; Hauber, E; Pham, L B S

    2015-01-01

    The evolution and escape of the martian atmosphere and the planet's water inventory can be separated into an early and late evolutionary epoch. The first epoch started from the planet's origin and lasted $\\sim$500 Myr. Because of the high EUV flux of the young Sun and Mars' low gravity it was accompanied by hydrodynamic blow-off of hydrogen and strong thermal escape rates of dragged heavier species such as O and C atoms. After the main part of the protoatmosphere was lost, impact-related volatiles and mantle outgassing may have resulted in accumulation of a secondary CO$_2$ atmosphere of a few tens to a few hundred mbar around $\\sim$4--4.3 Gyr ago. The evolution of the atmospheric surface pressure and water inventory of such a secondary atmosphere during the second epoch which lasted from the end of the Noachian until today was most likely determined by a complex interplay of various nonthermal atmospheric escape processes, impacts, carbonate precipitation, and serpentinization during the Hesperian and Amazon...

  6. Soft x-ray tomography during ELMs and impurity injection in JET

    International Nuclear Information System (INIS)

    The soft x-ray diagnostic at JET views the plasma from six directions with a total of 215 lines of sight. The good coverage of the plasma makes it possible to make detailed tomographic reconstructions of the soft x-ray emission during various conditions. We discuss one of the tomography methods applied at JET: a grid-based constrained optimization method that uses anisotropic smoothness on flux surfaces as regularization. This method has made it possible to study in detail the transport of heavy trace impurities injected into the plasma by laser blow-off. Impurity injection experiments in hot-ion H mode and optimized-shear plasmas are presented and discussed. The addition of a number of features to the algorithm, notably a non-negativity constraint, has made it possible to reconstruct very localized soft x-ray emission from the wall during ELMs. The detectors suffer damage from the neutrons produced in DD fusion reactions. This damage influences the sensitivity of the detectors, which makes it necessary to cross-calibrate the cameras. A method based on tomographic reconstructions has been developed to achieve the cross-calibration. (author)

  7. Soft X ray tomography during ELMs and impurity injection in JET

    International Nuclear Information System (INIS)

    The soft X ray diagnostic at JET views the plasma from six directions with a total of 215 lines of sight. The good coverage of the plasma makes it possible to make detailed tomographic reconstructions of the soft X ray emission during various conditions. One of the tomography methods applied at JET is discussed: a grid based constrained optimization method that uses anisotropic smoothness on flux surfaces as regularization. This method has made it possible to study in detail the transport of heavy trace impurities injected into the plasma by laser blow-off. Impurity injection experiments in hot ion H mode and optimized shear plasmas are presented and discussed. The addition of a number of features to the algorithm, notably a non-negativity constraint, has made it possible to reconstruct very localized soft X ray emission from the wall during edge localized modes (ELMs). The detectors suffer damage from the neutrons produced in deuterium-deuterium (DD) fusion reactions. This damage influences the sensitivity of the detectors, which makes it necessary to cross-calibrate the cameras. A method based on tomographic reconstructions has been developed to achieve the cross-calibration. (author)

  8. Responses of wind erosion to disturbance in a desert scrub grassland: grass vs. bush cover, and a snapshot into recovery

    Science.gov (United States)

    Baddock, M.; Zobeck, T. M.; D'Odorico, P.; van Pelt, S.; Ravi, S.; Over, T. M.; Bhattachan, A.

    2010-12-01

    The mixture of grass and bush vegetation that typifies many desert scrublands is a distinctive feature of the northern Chihuahuan Desert, where it represents a change in land cover driven by shrub encroachment. In such environments, the redistribution of nutrients by aeolian transport has been recognized as an important biophysical process, with a role in sustaining shrub presence. Investigation of disturbances in these landscapes (e.g. fire and grazing) will enable better understanding of their dust emission behavior with changing climate, perturbance regime and management scenarios. Here we use a portable wind tunnel to investigate the impact of fire and animals on soil erodibilty and dust emissions from different vegetation types in the Sevilleta Wildlife Refuge, central New Mexico. Plots were selected that were a) predominantly creosote bush or b) predominantly grass covered. Dust emission was measured for these surfaces both before and after a prescribed burn was conducted. The grass plots were also clipped and artificially trampled to simulate grazing. PM10 concentrations and emission rates from the test surfaces are shown for initial blow-off experiments as the wind tunnel flow accelerates to a target velocity, plus the steady state emission flux produced under constant wind flow with an added abrader sand. An adjacent area burned 8 months previously also allowed investigation of the change in erodibility of the soil for a known time after fire. Our preliminary results indicate the extent that dust emission is changed by the introduced disturbances, and their differing effect on creosote bush and grass dominated covers.

  9. Design of a cone target for fast ignition

    Directory of Open Access Journals (Sweden)

    Sunahara Atsushi

    2013-11-01

    Full Text Available We propose a new type of target for the fast ignition of inertial confinement fusion. Pre-formed plasma inside a cone target can significantly reduce the energy coupling efficiency from the ultra-high intense short-pulse laser to the imploded core plasma. Also, in order to protect the tip of the cone and reduce generation of pre-formed plasma, we propose pointed shaped cone target. In our estimation, the shock traveling time can be delayed 20–30 ps by lower-Z material with larger areal density compared to the conventional gold flat tip. Also, the jet flow can sweep the blow-off plasma from the tip of the cone, and the implosion performance is not drastically affected by the existence of pointed tip. In addition, the self-generated magnetic field is generated along the boundary of cone tip and surrounding CD or DT plasma. This magnetic field can confine fast electrons and focus to the implosion core plasma. Resultant heating efficiency is improved by 30% compared to that with conventional gold flat tip.

  10. Monochromatic x-ray radiography of laser-driven spherical targets using high-energy, picoseconds LFEX laser

    Science.gov (United States)

    Sawada, Hiroshi; Fujioka, S.; Lee, S.; Arikawa, Y.; Shigemori, K.; Nagatomo, H.; Nishimura, H.; Sunahara, A.; Theobald, W.; Perez, F.; Patel, P. K.; Beg, F. N.

    2015-11-01

    Formation of a high density fusion fuel is essential in both conventional and advanced Inertial Confinement Fusion (ICF) schemes for the self-sustaining fusion process. In cone-guided Fast Ignition (FI), a metal cone is attached to a spherical target to maintain the path for the injection of an intense short-pulse ignition laser from blow-off plasma created when nanoseconds compression lasers drive the target. We have measured a temporal evolution of a compressed deuterated carbon (CD) sphere using 4.5 keV K-alpha radiography with the Kilo-Joule, picosecond LFEX laser at the Institute of Laser Engineering. A 200 μm CD sphere attached to the tip of a Au cone was directly driven by 9 Gekko XII beams with 300 J/beam in a 1.3 ns Gaussian pulse. The LFEX laser irradiated on a Ti foil to generate 4.51 Ti K-alpha x-ray. By varying the delay between the compression and backlighter lasers, the measured radiograph images show an increase of the areal density of the imploded target. The detail of the quantitative analyses to infer the areal density and comparisons to hydrodynamics simulations will be presented. This work was performed with the support and under the auspices of the NIFS Collaboration Research program (NIFS13KUGK072). H.S. was supported by the UNR's International Activities Grant program.

  11. Lessons from two field tests on pipeline damage detection using acceleration measurement

    Science.gov (United States)

    Shinozuka, Masanobu; Lee, Sungchil; Kim, Sehwan; Chou, Pai H.

    2011-04-01

    Early detection of pipeline damages has been highlighted in water supply industry. Water pressure change in pipeline due to a sudden rupture causes pipe to vibrate and the pressure change propagates through the pipeline. From the measurement of pipe vibration the rupture can be detected. In this paper, the field test results and observations are provided for implementing next generation of SCADA system for pipeline rupture detection. Two field tests were performed on real buried plastic and metal pipelines for rupture detection. The rupture was simulated by introducing sudden water pressure drop caused by water blow-off and valve control. The measured acceleration data at the pipe surfaces were analyzed in both time and frequency domain. In time domain, the sudden narrow increase of acceleration amplitude was used as an indication of rupture event. For the frequency domain analysis, correlation function and the short time Fourier Transform technique were adopted to trace the dominant frequency shift. The success of rupture detection was found to be dependent on several factors. From the frequency analysis, the dominant frequency of metal water pipe was shifted by the water pressure drop, however, it was hard to identify from the plastic pipeline. Also the influence of existing facility such as airvac on pipe vibrations was observed. Finally, several critical lessons learned in the viewpoint of field measurement are discussed in this paper.

  12. Energy and impurity transport in the Alcator C tokamak

    International Nuclear Information System (INIS)

    Energy and impurity confinement times, tausub(E) and tausub(I), have been investigated in Ohmically heated Alcator C discharges in the following parameter range: density n-bar20 m-3, current Isub(p)20 m-3, the results of size-scaling experiments are summarized by the relation tausub(E) is proportional to asup(0.8) Rsup(2.3). At high density, the inferred ion thermal conductivity chisub(i) apparently exceeds the neoclassical value of Hinton and Hazeltine by a factor which varies from 2 to about 4 depending on geometry and plasma parameters. Other interpretations of the data are, however, possible. Impurity confinement has also been studied in these discharges using the laser blow-off technique. The principal new results concerning tausub(I) are (1) independence of the charge and mass of the injected impurity ion; (2) a linear dependence on asub(l); (3) a rapid deterioration as a function of the amplitude of the m=2,3 tearing modes; and (4) an approximately linear dependence on the effective charge. (author)

  13. Predictive analysis of optical ablation in several dermatological tumoral tissues

    Science.gov (United States)

    Fanjul-Vélez, F.; Blanco-Gutiérrez, A.; Salas-García, I.; Ortega-Quijano, N.; Arce-Diego, J. L.

    2013-06-01

    Optical techniques for treatment and characterization of biological tissues are revolutionizing several branches of medical praxis, for example in ophthalmology or dermatology. The non-invasive, non-contact and non-ionizing character of optical radiation makes it specially suitable for these applications. Optical radiation can be employed in medical ablation applications, either for tissue resection or surgery. Optical ablation may provide a controlled and clean cut on a biological tissue. This is particularly relevant in tumoral tissue resection, where a small amount of cancerous cells could make the tumor appear again. A very important aspect of tissue optical ablation is then the estimation of the affected volume. In this work we propose a complete predictive model of tissue ablation that provides an estimation of the resected volume. The model is based on a Monte Carlo approach for the optical propagation of radiation inside the tissue, and a blow-off model for tissue ablation. This model is applied to several types of dermatological tumoral tissues, specifically squamous cells, basocellular and infiltrative carcinomas. The parameters of the optical source are varied and the estimated resected volume is calculated. The results for the different tumor types are presented and compared. This model can be used for surgical planning, in order to assure the complete resection of the tumoral tissue.

  14. Production of high-Q ions by laser bombardment method

    International Nuclear Information System (INIS)

    The expanding plasma produced when an intense pulse of laser radiation is focused in vacuum onto a solid target has been used as a source of highly stripped ions for collision cross-section measurements. Usable fluxes of carbon nuclei at energies of a few hundred eV/charge have been obtained by irradiation of graphite with pulses of CO2 laser radiation at a focused power density of 3 x 1010 W/cm2. Bombardment of aluminum and iron targets at comparable power levels have yielded ions of maximum charges of 9 and 16, respectively. A time-of-flight apparatus has been constructed to utilize the laser source for measurement of electron capture cross sections for highly stripped ions in gases at energies in the few hundred eV/charge range. Apertures collimate an ion beam from the plasma blowoff, and an electrostatic analyzer selects ions from the expanding plasma which have the same energy per charge. The beam is directed through a gas target cell, charge analyzed once more by deceleration, and detected by a channel plate electron multiplier used in a current amplification mode. Electron capture cross sections have been measured for C/sup +q/ ions, q = 3, 4, 5 in H2 at energies ranging from 150 to 1160 eV/charge

  15. Active Control for Statistically Stationary Turbulent PremixedFlame Simulations

    Energy Technology Data Exchange (ETDEWEB)

    Bell, J.B.; Day, M.S.; Grcar, J.F.; Lijewski, M.J.

    2005-08-30

    The speed of propagation of a premixed turbulent flame correlates with the intensity of the turbulence encountered by the flame. One consequence of this property is that premixed flames in both laboratory experiments and practical combustors require some type of stabilization mechanism to prevent blow-off and flashback. The stabilization devices often introduce a level of geometric complexity that is prohibitive for detailed computational studies of turbulent flame dynamics. Furthermore, the stabilization introduces additional fluid mechanical complexity into the overall combustion process that can complicate the analysis of fundamental flame properties. To circumvent these difficulties we introduce a feedback control algorithm that allows us to computationally stabilize a turbulent premixed flame in a simple geometric configuration. For the simulations, we specify turbulent inflow conditions and dynamically adjust the integrated fueling rate to control the mean location of the flame in the domain. We outline the numerical procedure, and illustrate the behavior of the control algorithm on methane flames at various equivalence ratios in two dimensions. The simulation data are used to study the local variation in the speed of propagation due to flame surface curvature.

  16. Laser cutting of bone tissue under bulk water with a pulsed ps-laser at 532 nm

    Science.gov (United States)

    Tulea, Cristian-Alexander; Caron, Jan; Gehlich, Nils; Lenenbach, Achim; Noll, Reinhard; Loosen, Peter

    2015-10-01

    Hard-tissue ablation was already investigated for a broad variety of pulsed laser systems, which cover almost the entire range of available wavelengths and pulse parameters. Most effective in hard-tissue ablation are Er:YAG and CO2 lasers, both utilizing the effect of absorption of infrared wavelengths by water and so-called explosive vaporization, when a thin water film or water-air spray is supplied. The typical flow rates and the water layer thicknesses are too low for surgical applications where bleeding occurs and wound flushing is necessary. We studied a 20 W ps-laser with 532 nm wavelength and a pulse energy of 1 mJ to effectively ablate bones that are submerged 14 mm under water. For these laser parameters, the plasma-mediated ablation mechanism is dominant. Simulations based on the blow-off model predict the cut depth and cross-sectional shape of the incision. The model is modified considering the cross section of the Gaussian beam, the incident angle, and reflections. The ablation rate amounts to 0.2 mm3/s, corresponding to an increase by at least 50% of the highest values published so far for ultrashort laser ablation of hard tissue.

  17. Laser cutting of bone tissue under bulk water with a pulsed ps-laser at 532 nm.

    Science.gov (United States)

    Tulea, Cristian-Alexander; Caron, Jan; Gehlich, Nils; Lenenbach, Achim; Noll, Reinhard; Loosen, Peter

    2015-10-01

    Hard-tissue ablation was already investigated for a broad variety of pulsed laser systems, which cover almost the entire range of available wavelengths and pulse parameters. Most effective in hard-tissue ablation are Er:YAG and CO2 lasers, both utilizing the effect of absorption of infrared wavelengths by water and so-called explosive vaporization, when a thin water film or water–air spray is supplied. The typical flow rates and the water layer thicknesses are too low for surgical applications where bleeding occurs and wound flushing is necessary. We studied a 20 W ps-laser with 532 nm wavelength and a pulse energy of 1 mJ to effectively ablate bones that are submerged 14 mm under water. For these laser parameters, the plasma-mediated ablation mechanism is dominant. Simulations based on the blow-off model predict the cut depth and cross-sectional shape of the incision. The model is modified considering the cross section of the Gaussian beam, the incident angle, and reflections. The ablation rate amounts to 0.2  mm3/s, corresponding to an increase by at least 50% of the highest values published so far for ultrashort laser ablation of hard tissue. PMID:26469563

  18. Impurity accumulation in plasma regimes with high energy confinement

    Science.gov (United States)

    Ran, L. B.; Roberts, D. E.; Yang, H. R.; Dodel, G.; Gentle, K.; Von Goeler, S.; Holzhauer, E.; Hübner, K.; Keilhacker, M.; Korotkov, A.; Luce, T. C.; Miura, Y.; Tsois, N.; Würz, H.; Fussmann, G.; Hofmann, J.; Janeschitz, G.; Krieger, K.; Müller, E. R.; Nolte, R.; Röhr, H.; Steuer, K. H.; Becker, G.; Bomba, B.; Bruhns, H.; Büchl, K.; Carlson, A.; Eberhagen, A.; Fahrbach, H.-U.; Gehre, O.; Gernhardt, J.; Giannone, L.; Von Gierke, G.; Glock, E.; Gruber, O.; Haas, G.; Herrmann, H.; Kaesdorf, S.; Karger, F.; Kaufmann, M.; Klüber, O.; Kornherr, M.; Lackner, K.; Lang, R.; Lee, P.; Lisitano, G.; Mast, F.; Mayer, H. M.; McCormick, K.; Meisel, D.; Mertens, V.; Murmann, H.; Neuhauser, J.; Niedermeyer, H.; Noterdaeme, J. M.; Poschenrieder, W.; Preis, R.; Rapp, H.; Rudyj, A.; Sandmann, W.; Schneider, F.; Schnider, U.; Siller, G.; Simmet, E.; Speth, E.; Söldner, F.; Stäbler, A.; Steinmetz, K.; Stroth, U.; Vollmer, O.; Zasche, D.

    1989-04-01

    Investigations of impurity accumulation phenomena in ASDEX are reviewed. There are four different operating regimes where pronounced accumulation is observed and these regimes are also characterized by improved energy confinement. In particular, medium-Z metallic ions are involved in accumulation processes whereas low-Z ions appear almost unaffected. The rapid accumulation observed in the case of metallic ions may be explained by neoclassical inward drifts if we assume that the anomalous diffusion is sufficiently suppressed, some indication of this being found from laser blow-off studies. The present results, however, can only be partly explained by neoclassical theory, according to which accumulation of low-Z impurities should also occur. The temporal behaviour of accumulation and the retarding effect of proton dilution for collision dominated transport are also discussed. Finally, we conclude that the full benefits of improved energy confinement can be achieved only if the impurity influxes are kept to a sufficiently low level. Expressed in terms of concentrations under low confinement conditions we have to postulate, for ASDEX, concentrations ≲ 10 -4 for metals and ≲ 2% for all light impurities.

  19. Photo-ionization of planetary winds: case study HD209458b

    CERN Document Server

    Schneiter, E M; D'Angelo, C S Villarreal; Velazquez, P F; Raga, A C; Costa, A

    2016-01-01

    Close-in hot Jupiters are exposed to a tremendous photon flux that ionizes the neutral escaping material from the planet leaving an observable imprint that makes them an interesting laboratory for testing theoretical models. In this work we present 3D hydrodynamic simulations with radiation transfer calculations of a close-in exoplanet in a blow-off state. We calculate the Ly-$\\alpha$ absorption and compare it with observations of HD 209458b an previous simplified model results.Our results show that the hydrodynamic interaction together with a proper calculation of the photoionization proccess are able to reproduce the main features of the observed Ly-$\\alpha$ absorption, in particular at the blue-shifted wings of the line. We found that the ionizing stellar flux produce an almost linear effect on the amount of absorption in the wake. Varying the planetary mass loss rate and the radiation flux, we were able to reproduce the $10\\%$ absorption observed at $-100~\\mathrm{km~s^{-1}}$.

  20. Recent trends of hydraulic snubbers for nuclear power station

    International Nuclear Information System (INIS)

    One of the important safety measures for nuclear power stations is aseismatic measure. The vibration due to earthquakes, the pulsation of fluid, the blow-off of safety valves, the whipping of pipes due to break and so on should be taken into consideration. The recent trends of the hydraulic vibration dampers for pipings are described. The vibration dampers must not restrain the gradual move due to thermal expansion, but exert restraining force to violent move due to earthquakes and others. Fixed restrainers and spring type restrainers are simple and sure, but there is some fear of restraining thermal expansion with them. In nuclear power stations, hydraulic suppressors are mostly employed. The poppet valves in a control valve box do not close in case of the motion slower than 0.1 cm/sec, therefore resistance does not arise. In case of the motion of 0.1 - 0.4 cm/sec, the poppet valves close and stop the motion of a piston. In the motion faster than 0.4 cm/sec, the poppet valves close without fail, and the resistance of nominal capacity is produced. The hydraulic vibration dampers are prescribed in the subsection NF, Section III, ASME Boiler and Pressure Vessel Code. The problems are the radiation resistance and the degeneration due to temperature and secular change of actuating oil and seal material. The bleed rate of the hydraulic vibration dampers is important for preventing the troubles. (Kako, I.)

  1. Impurity transport in ohmically heated TFTR plasmas

    International Nuclear Information System (INIS)

    Impurity transport in ohmically heated TFTR plasmas is studied by computer modeling of VUV line emissions from impurities injected using the laser-blowoff technique. The results are sensitive to uncertainties in the ionization and recombination rates used in the modeling; as a result, only a spatially averaged diffusion coefficient and parameterized convective velocity can be measured. Measurements of these transport parameters are presented for deuterium and helium discharges with I/sub p/ = 0.8-2.5 MA, /bar n/sub e// = 0.6-6.0/times/1019 m-3, and Z/sub eff/ = 2-6. Diffusion coefficients are found to be in the 0.5-1.5 m2/s range, considerably larger than neoclassical values. Nonzero inward convective velocities are necessary to fit the data in most cases. No dependence of the diffusion coefficient on injected element, working gas species, or plasma current is found, but at a given current, the diffusion coefficient is smaller by approximately a factor of two in plasmas near the density limit than in discharges with /bar n/sub e//19 m-3. 31 refs., 9 figs., 3 tabs

  2. Active control for turbulent premixed flame simulations

    Energy Technology Data Exchange (ETDEWEB)

    Bell, John B.; Day, Marcus S.; Grcar, Joseph F.; Lijewski, Michael J.

    2004-03-26

    Many turbulent premixed flames of practical interest are statistically stationary. They occur in combustors that have anchoring mechanisms to prevent blow-off and flashback. The stabilization devices often introduce a level of geometric complexity that is prohibitive for detailed computational studies of turbulent flame dynamics. As a result, typical detailed simulations are performed in simplified model configurations such as decaying isotropic turbulence or inflowing turbulence. In these configurations, the turbulence seen by the flame either decays or, in the latter case, increases as the flame accelerates toward the turbulent inflow. This limits the duration of the eddy evolutions experienced by the flame at a given level of turbulent intensity, so that statistically valid observations cannot be made. In this paper, we apply a feedback control to computationally stabilize an otherwise unstable turbulent premixed flame in two dimensions. For the simulations, we specify turbulent in flow conditions and dynamically adjust the integrated fueling rate to control the mean location of the flame in the domain. We outline the numerical procedure, and illustrate the behavior of the control algorithm. We use the simulations to study the propagation and the local chemical variability of turbulent flame chemistry.

  3. Characteristics of autoignited laminar lifted flames in heated coflow jets of carbon monoxide/hydrogen mixtures

    KAUST Repository

    Choi, Byungchul

    2012-06-01

    The characteristics of autoignited lifted flames in laminar jets of carbon monoxide/hydrogen fuels have been investigated experimentally in heated coflow air. In result, as the jet velocity increased, the blowoff was directly occurred from the nozzle-attached flame without experiencing a stabilized lifted flame, in the non-autoignited regime. In the autoignited regime, the autoignited lifted flame of carbon monoxide diluted by nitrogen was affected by the water vapor content in the compressed air oxidizer, as evidenced by the variation of the ignition delay time estimated by numerical calculation. In particular, in the autoignition regime at low temperatures with added hydrogen, the liftoff height of the autoignited lifted flames decreased and then increased as the jet velocity increased. Based on the mechanism in which the autoignited laminar lifted flame is stabilized by ignition delay time, the liftoff height can be influenced not only by the heat loss, but also by the preferential diffusion between momentum and mass diffusion in fuel jets during the autoignition process. © 2012 The Korean Society of Mechanical Engineers.

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

    KAUST Repository

    Shroll, Andrew P.

    2012-01-01

    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.

  5. INSTRUMENTATION FOR SURVEYING ACOUSTIC SIGNALS IN NATURAL GAS TRANSMISSION LINES

    Energy Technology Data Exchange (ETDEWEB)

    John L. Loth; Gary J. Morris; George M. Palmer; Richard Guiler; Deepak Mehra

    2003-09-01

    In the U.S. natural gas is distributed through more than one million miles of high-pressure transmission pipelines. If all leaks and infringements could be detected quickly, it would enhance safety and U.S. energy security. Only low frequency acoustic waves appear to be detectable over distances up to 60 km where pipeline shut-off valves provide access to the inside of the pipeline. This paper describes a Portable Acoustic Monitoring Package (PAMP) developed to record and identify acoustic signals characteristic of: leaks, pump noise, valve and flow metering noise, third party infringement, manual pipeline water and gas blow-off, etc. This PAMP consists of a stainless steel 1/2 inch NPT plumbing tree rated for use on 1000 psi pipelines. Its instrumentation is designed to measure acoustic waves over the entire frequency range from zero to 16,000 Hz by means of four instruments: (1) microphone, (2) 3-inch water full range differential pressure transducer with 0.1% of range sensitivity, (3) a novel 3 inch to 100 inch water range amplifier, using an accumulator with needle valve and (4) a line-pressure transducer. The weight of the PAMP complete with all accessories is 36 pounds. This includes a remote control battery/switch box assembly on a 25-foot extension chord, a laptop data acquisition computer on a field table and a sun shield.

  6. Short-wavelength, direct-drive laser fusion experiments at the Laboratory for Laser Energetics

    International Nuclear Information System (INIS)

    Measurements are reported of absorption, hot electron generation, preheat, thermal transport and irradiation uniformity in direct-drive, spherical target experiments conducted with six 351-nm wavelength beams of the OMEGA symmetric irradiation facility. On-target energy in excess of 400 J, pulses of 650 ps duration and uniform irradiation at an intensity in the range of 1013 to 1015 W/cm2 characterize the laser conditions for these experiments. Absorption varied from 100%, for Ti targets at an intensity of 1013 W/cm2, to 60% at an intensity of 2 x 1015 W/cm2. The suprathermal electron fraction was found to be less than 3 x 10-3 of the absorbed energy in these experiments. Higher ablation pressures were measured than in comparable 1054-nm experiments. At a laser intensity of 1015 W/cm2 an ablation pressure of 100 Mbar was deduced from plasma blowoff measurements. Measurement and calculation of the irradiation uniformity indicate that the 24 beam OMEGA, 351-nm laser should be capable of producing the required drive uniformity to compress targets to 200 times liquid DT density with less than 2000 joules of laser energy

  7. Characteristics of autoignited laminar lifted flames in heated coflow jets of carbon monoxide/hydrogen mixtures

    International Nuclear Information System (INIS)

    The characteristics of autoignited lifted flames in laminar jets of carbon monoxide/hydrogen fuels have been investigated experimentally in heated coflow air. In result, as the jet velocity increased, the blowoff was directly occurred from the nozzle attached flame without experiencing a stabilized lifted flame, in the non autoignited regime. In the autoignited regime, the autoignited lifted flame of carbon monoxide diluted by nitrogen was affected by the water vapor content in the compressed air oxidizer, as evidenced by the variation of the ignition delay time estimated by numerical calculation. In particular, in the autoignition regime at low temperatures with added hydrogen, the liftoff height of the autoignited lifted flames decreased and then increased as the jet velocity increased. Based on the mechanism in which the autoignited laminar lifted flame is stabilized by ignition delay time, the liftoff height can be influenced not only by the heat loss, but also by the preferential diffusion between momentum and mass diffusion in fuel jets during the autoignition process

  8. Lightweight Target Generates Bright, Energetic X-Rays

    Energy Technology Data Exchange (ETDEWEB)

    Hazi, A

    2006-01-25

    solid targets is only a fraction of 1 percent. Solid targets have low efficiencies because much of the laser energy is deposited far from the target's x-ray emitting region, and the energy is carried by the relatively slow process of thermal conduction. ''The laser beam ablates material from the massive target, and that material moves away from the target's surface'', says Fournier. With a nanosecond pulse or longer, the laser interacts with the blow-off plasma rather than the remaining bulk sample. As a result, much of the laser's energy goes into the kinetic energy of the blow-off material, not into heating the bulk of the foil.

  9. Fusion research in Hungary

    International Nuclear Information System (INIS)

    Hungarian fusion research started in the 1970s, when the idea of installing a small tokamak experiment emerged. In return to computer equipment a soviet tokamak was indeed sent to Hungary and started to operate as MT-1 at the Central Research Institute for Physics (KFKI) in 1979. Major research topics included diagnostic development, edge plasma studies and investigation of disruptions. Following a major upgrade in 1992 (new vacuum vessel, active position control and PC network based data acquisition system) the MT-1M tokamak was used for the study of transport processes with trace impurity injection, micropellet ablation studies, X-ray tomography and laser blow-off diagnostic development. Although funding ceased in the middle of the 90's the group was held alive by collaborations with EU fusion labs: FZ -Juelich, IPP-Garching and CRPP-EPFL Lausanne. In 1998 the machine was dismantled due to reorganization of the Hungarian Academy of Sciences. New horizons opened to fusion research from 1999, when Hungary joined EURATOM and a fusion Association was formed. Since then fusion physics studies are done in collaboration with major EU fusion laboratories, Hungarian researchers also play an active role in JET diagnostics upgrade and ITER design. Major topics are pellet ablation studies, plasma turbulence diagnosis using Beam Emission Spectroscopy and other techniques, tomography and plasma diagnostics using various neutral beams. In fusion relevant technology R and D Hungary has less records. Before joining EURATOM some materials irradiation studies were done at the Budapest Research Reactor at KFKI-AEKI. The present day fusion technology programme focuses still on irradiation studies, nuclear material database and electromagnetic testing techniques. Increasing the fusion technology research activities is a difficult task, as the competition in Hungarian industry is very strong and the interest of organizations in long-term investments into R and D is rather weak and

  10. A quasi-adiabatic laminar flat flame burner for high temperature calibration

    International Nuclear Information System (INIS)

    Flat flame burners were developed for many purposes. In this study, a new flat flame burner for the high temperature calibration of combustion product species and temperature is presented. The burner is operated on methane/air mixtures. Equivalence ratios can be varied from φ = 0.65 to φ = 1.5. A flat, laminar, premixed flame stabilizes above the flame holder that is manufactured from porous material and differently to other designs is not water cooled. Unlike most other realizations, the flame burns detached by 1.5–2.5 mm from the flame holder. This is realized by adjusting the exit speed to a value very close to the burning velocity of the corresponding equivalence ratio. As the control range between flame blow-off and attachment to the flame holder is very narrow, this strategy requires spatially very uniform porous materials and a precise mass flow control. Heat losses to the flame holder necessary for flame stabilization are minimized furthermost by these detached flames. This becomes manifested by a temperature rise of the flame holder by less than 10 K and an almost homogeneous temperature distribution within the flame holder. In consequence, flame temperatures measured by Rayleigh thermometry are observed to be close to adiabatic flame temperatures. Differences between adiabatic and measured temperatures depend on the equivalence ratio and range from 35 K to 50 K. By comparison with 1D-flame simulations with and without radiation models, it is shown that these temperature losses are mainly due to radiation but not to heat conduction to the flame holder. For this reason, flames stabilized on this burner are termed quasi-adiabatic as they exhibit exhaust gas temperatures very similar to freely propagating flames

  11. ENERGY SAVING AT OPERATION OF OUTDOOR SWIMMING POOLS

    Directory of Open Access Journals (Sweden)

    V. F. Ivin

    2013-09-01

    Full Text Available Purpose. Energy saving is a major problem in modern power engineering and various energy-consuming devices. They include outdoor swimming pools. In order to maintain them in working condition, especially in winter period, it takes significant amount of thermal energy. Task of heat loss substantial decrease in open swimming pools is considered in the article (on DNURT example. Methodology. The method of determining the mass and heat loss on the basis of criteria equations of heat and mass transfer theory is used. Findings. Calculations of the actual DNURT pool heat loss for different seasons, as for natural convection both for air forced motion above the free water surface are performed. It is shown that for the adiabatic evaporation conditions of water from the pool in winter during blow-off with wind the heat loss can be up to 2 kW/m2 on surface. To reduce these losses it is offered to cover water surface in a pool with a special material with low thermal conductivity on the basis of porous polyethylene during the time when the pool is not used for other purposes. It is shown that the implementation of these standards will reduce the actual heat loss, at least 5-6 times. Originality. The solution of important environmental and energy problem thanks to reducing heat losses by the pool in different times of a year and correspondingly lower emissions of power generating enterprises. Practical value. It is shown that the coating surface of the pool with poorly heat-conducting and easy to install coating will let, at a minimum, to reduce the actual heat loss on 5-6 times and reduce the emissions of power plants generating energy for pool heating.

  12. Simulations of flashing experiments in TOPFLOW facility with TRACE code

    International Nuclear Information System (INIS)

    Highlights: • Two decompression experiments performed at TOPFLOW are simulated with a TRACE code. • The depressurization triggers flashing of the slightly undersaturated liquid water. • Pressure, temperature and void fractions are compared with measurements. • Prediction of the choked flow is the most critical parameter of simulations. • Good agreement with measurements at high initial pressure (i.e. 65 and 40 bars). - Abstract: The decompression experiments performed at TOPFLOW facility in 2010 have been reproduced using the latest best-estimate thermohydraulic system code TRACE (V 5.0 Patch 3). The main component of TOPFLOW facility was about 8 m long vertical tube with an inner diameter of 195.3 mm. The evaporation of liquid water to steam caused by depressurization was simulated using two different procedures: from stagnant water and during circulating of water in tubes. The liquid water was almost saturated at initial pressure values of 1.0, 2.0, 4.0 and 6.5 MPa. Our approach applies one-dimensional code to simulate all the important parts of the facility not just the vertical test section, where the measurements were taken. The obtained simulated pressure, temperature and void fractions are compared with measured values. The simulations of the first procedure (stagnant water at beginning) are in a good agreement with measurements, especially for the cases with longer transients and higher initial pressure, however, choked flow model through the blow-off valve had to be adjusted. There is a short transient (about 2 s) after the fast opening valve opens, which was not reproduced correctly with TRACE. The simulations of the second procedure (circulating water in a loop) correctly predict pressure and temperature decrease, but underpredict void fraction. No modification of the default TRACE choked flow model was needed for procedure B

  13. Field Effects of Buoyancy on Lean Premixed Turbulent Flames

    Science.gov (United States)

    Cheng, R. K.; Johnson, M. R.; Greenberg, P. S.; Wernet, M. P.

    2003-01-01

    The study of field effects of buoyancy on premixed turbulent flames is directed towards the advancement of turbulent combustion theory and the development of cleaner combustion technologies. Turbulent combustion is considered the most important unsolved problem in combustion science and laboratory studies of turbulence flame processes are vital to theoretical development. Although buoyancy is dominant in laboratory flames, most combustion models are not yet capable to consider buoyancy effects. This inconsistency has impeded the validation of theories and numerical simulations with experiments. Conversely, the understanding of buoyancy effects is far too limited to help develop buoyant flame models. Our research is also relevant to combustion technology because lean premixed combustion is a proven method to reduce the formation of oxides of nitrogen (NOx). In industrial lean premixed combustion systems, their operating conditions make them susceptible to buoyancy thus affecting heat distribution, emissions, stability, flashback and blowoff. But little knowledge is available to guide combustion engineers as to how to avoid or overcome these problems. Our hypothesis is that through its influence on the mean pressure field, buoyancy has direct and indirect effects on local flame/turbulence interactions. Although buoyancy acts on the hot products in the farfield the effect is also felt in the nearfield region upstream of the flame. These changes also influence the generation and dissipation of turbulent kinetic energy inside the flame brush and throughout the flowfield. Moreover, the plume of an open flame is unstable and the periodic fluctuations make additional contributions to flame front dynamics in the farfield. Therefore, processes such as flame wrinkling, flow acceleration due to heat release and flame- generated vorticity are all affected. Other global flame properties (e.g. flame stabilization limits and flame speed) may all be coupled to buoyancy. This

  14. Flame macrostructures, combustion instability and extinction strain scaling in swirl-stabilized premixed CH4/H2 combustion

    KAUST Repository

    Shanbhogue, S.J.

    2016-01-01

    © 2015 The Combustion Institute. In this paper, we report results from an experimental investigation on transitions in the average flame shape (or microstructure) under acoustically coupled and uncoupled conditions in a 50 kW swirl stabilized combustor. The combustor burns CH4/H2 mixtures at atmospheric pressure and temperature for a fixed Reynolds number of 20,000 and fixed swirl angle. For both cases, essentially four different flame shapes are observed, with the transition between flame shapes occurring at the same equivalence ratio (for the same fuel mixture) irrespective of whether the combustor is acoustically coupled or uncoupled. The transition equivalence ratio depends on the fuel mixture. For the baseline case of pure methane, the combustor is stable close to the blowoff limit and the average flame in this case is stabilized inside the inner recirculation zone. As the equivalence ratio is raised, the combustor transitions to periodic oscillations at a critical equivalence ratio of φ=0.65. If hydrogen is added to the mixture, the same transition occurs at lower equivalence ratios. For all cases that we investigated, flame shapes captured using chemiluminescence imaging show that the transition to harmonic oscillations in the acoustically coupled cases is preceded by the appearance of the flame in the outer recirculation zone. We examine the mechanism associated with the transition of the flame between different shapes and, ultimately, the propagation of the flame into the outer recirculation zone as the equivalence ratio is raised. Using the extinction strain rates for each mixture at different equivalence ratios, we show that these transitions in the flame shape and in the instability (in the coupled case) for different fuel mixtures collapse as a function of a normalized strain rate : κextDU∞. We show that the results as consistent with a mechanism in which the flame must overcome higher strains prevailing in the outer recirculation zone, in order

  15. LLE review, Volume 77. Quarterly report, October--December 1998

    Energy Technology Data Exchange (ETDEWEB)

    Regan, S.P. [ed.

    1998-12-31

    This volume of the LLE Review, covering the period October--December 1998, includes two articles addressing issues applicable to direct-drive ICF on the National Ignition Facility (NIF): laser-plasma interactions and laser-irradiation uniformity. Additional highlights of the research presented in this issue are: (1) P.B. Radha and S. Skupsky present a novel charged-particle diagnostic that performs simultaneous {rho}R measurements of the fuel, shell, and ablator regions of a compressed ICF target, consisting of an inner DT fuel region, a plastic (CH) shell, and an ablator (CD), by measuring the knock-on deuteron spectrum. (2) F. Dahmani, S. Burns, J. Lambropoulos, S. Papernov, and A. Schmid report results from stress-inhibited laser-driven crack propagation and stress-delayed damage-initiation experiments in fused silica at 351 nm. Research is underway presently to determine the ramifications of these findings for large-aperture systems, such as OMEGA. (3) V. Goncharov presents an analytic theory of the ablative Richtmyer-Meshkov instability, which shows that the main stabilizing mechanism of the ablation-front perturbations is the dynamic overpressure of the blowoff plasma with respect to the target material. The perturbation evolution during the shock transit time is studied to determine the initial conditions for the Rayleigh-Taylor phase of the instability and to analyze the level of laser imprint on ICF direct-drive targets. (4) J.M. Larkin, W.R. Donaldson, T.H. Foster, and R.S. Knox examine the triplet state of rose bengal, a dye used in photodynamic therapy, that is produced by 1,064-nm excitation of T{sub 1}. (5) R. Adam, M. Currie, R. Sobolewski, O. Harnack, and M. Darula report measurements of the picosecond photoresponse of a current-biased YBCO microbridge coupled to a bicrystal YBCO Josephson junction.

  16. HXD2型机车风源净化系统的合理配置浅析%Analysis of Reasonable Allocation of Wind Source Purifying System of HXD2 Locomotive

    Institute of Scientific and Technical Information of China (English)

    李映晨; 宋瑶; 黄思俊

    2013-01-01

      The reasonable allocation of internal parts of locomotive wind source purifying system has a directly impact on air quality of loco⁃motive wind source purifying system. The article described that allocation and selection of internal parts of locomotive wind source purifying system such as filter, blow-off valve, dryer etc which affect the air quality. Dryer selection and regeneration air consumption rate was de⁃scribed particularly. Through the results of dryer type test, improving that the allocation of HXD2 locomotive wind source system is reason⁃able, and the existing air quality of wind source system meet the air using requirements.%  机车风源净化系统内各部件的配置合理性,直接影响机车风源空气质量的好坏。介绍了影响空气质量的机车风源系统内各部件(如过滤器、排污阀、干燥器等)的布局原则与选择方法,侧重介绍空气干燥器的选型和再生耗气率计算。通过HXD2机车干燥器的型式试验结果,验证了其风源净化系统的配置合理性,并能满足HXD2机车的空气质量要求。

  17. XUV-exposed, non-hydrostatic hydrogen-rich upper atmospheres of terrestrial planets. Part I: atmospheric expansion and thermal escape.

    Science.gov (United States)

    Erkaev, Nikolai V; Lammer, Helmut; Odert, Petra; Kulikov, Yuri N; Kislyakova, Kristina G; Khodachenko, Maxim L; Güdel, Manuel; Hanslmeier, Arnold; Biernat, Helfried

    2013-11-01

    The recently discovered low-density "super-Earths" Kepler-11b, Kepler-11f, Kepler-11d, Kepler-11e, and planets such as GJ 1214b represent the most likely known planets that are surrounded by dense H/He envelopes or contain deep H₂O oceans also surrounded by dense hydrogen envelopes. Although these super-Earths are orbiting relatively close to their host stars, they have not lost their captured nebula-based hydrogen-rich or degassed volatile-rich steam protoatmospheres. Thus, it is interesting to estimate the maximum possible amount of atmospheric hydrogen loss from a terrestrial planet orbiting within the habitable zone of late main sequence host stars. For studying the thermosphere structure and escape, we apply a 1-D hydrodynamic upper atmosphere model that solves the equations of mass, momentum, and energy conservation for a planet with the mass and size of Earth and for a super-Earth with a size of 2 R(Earth) and a mass of 10 M(Earth). We calculate volume heating rates by the stellar soft X-ray and extreme ultraviolet radiation (XUV) and expansion of the upper atmosphere, its temperature, density, and velocity structure and related thermal escape rates during the planet's lifetime. Moreover, we investigate under which conditions both planets enter the blow-off escape regime and may therefore experience loss rates that are close to the energy-limited escape. Finally, we discuss the results in the context of atmospheric evolution and implications for habitability of terrestrial planets in general. PMID:24251443

  18. Fouling Process and Control Measures for 50 MW Turbo Generator Set of Combined Heat and Power%热电联供50 MW汽轮发电机组结垢处理及管理措施

    Institute of Scientific and Technical Information of China (English)

    汪学峰

    2012-01-01

      介绍了自备发电站热电联供装置50 MW汽轮发电机组汽轮机叶片结垢的原因和危害,采用低温低压饱和湿蒸汽清洗去除叶片结垢,在生产运行中加强蒸汽、凝结水品质监督,使热电联供发电机组汽轮机叶片结垢、积盐情况得到了明显改善,因蒸汽、凝结水品质原因引起的非计划停机、停炉、停电等设备事故没有发生,提高了热电联供汽轮发电机组的运行效率,保障了机组高效、安全、稳定、经济运行。%  Introduction was made to the cause and harm of steam turbine blade fouling of 50 MW turbo generator set of combined heat and power providing for power plant. Low-temperature and low-saturation moist steam was adopted to remove the blade foul-ing. During production run, the quality supervision of steam and condensation water was strengthened to improve the situation of steam turbine blade fouling and salt accumulating of 50 MW turbo generator set of combined heat and power, so that there was no equipment breakdown such as unplanned shut-down, blow-off and power failure caused by the quality of steam and condensation water, which raised the operating efficiency of turbo generator set of combined heat and power, and ensured high-efficiency, safe, stable and economic operation.

  19. Simulations of flashing experiments in TOPFLOW facility with TRACE code

    Energy Technology Data Exchange (ETDEWEB)

    Mikuž, Blaž, E-mail: blaz.mikuz@ijs.si [Jozef Stefan Institute, Reactor Engineering Division, Jamova cesta 39, 1000 Ljubljana (Slovenia); Tiselj, Iztok [Jozef Stefan Institute, Reactor Engineering Division, Jamova cesta 39, 1000 Ljubljana (Slovenia); Beyer, Matthias; Lucas, Dirk [Institute of Fluid Dynamics, Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstraße 400, 01328 Dresden (Germany)

    2015-03-15

    Highlights: • Two decompression experiments performed at TOPFLOW are simulated with a TRACE code. • The depressurization triggers flashing of the slightly undersaturated liquid water. • Pressure, temperature and void fractions are compared with measurements. • Prediction of the choked flow is the most critical parameter of simulations. • Good agreement with measurements at high initial pressure (i.e. 65 and 40 bars). - Abstract: The decompression experiments performed at TOPFLOW facility in 2010 have been reproduced using the latest best-estimate thermohydraulic system code TRACE (V 5.0 Patch 3). The main component of TOPFLOW facility was about 8 m long vertical tube with an inner diameter of 195.3 mm. The evaporation of liquid water to steam caused by depressurization was simulated using two different procedures: from stagnant water and during circulating of water in tubes. The liquid water was almost saturated at initial pressure values of 1.0, 2.0, 4.0 and 6.5 MPa. Our approach applies one-dimensional code to simulate all the important parts of the facility not just the vertical test section, where the measurements were taken. The obtained simulated pressure, temperature and void fractions are compared with measured values. The simulations of the first procedure (stagnant water at beginning) are in a good agreement with measurements, especially for the cases with longer transients and higher initial pressure, however, choked flow model through the blow-off valve had to be adjusted. There is a short transient (about 2 s) after the fast opening valve opens, which was not reproduced correctly with TRACE. The simulations of the second procedure (circulating water in a loop) correctly predict pressure and temperature decrease, but underpredict void fraction. No modification of the default TRACE choked flow model was needed for procedure B.

  20. Combustion Control and Diagnostics Sensor Testing in a Thermal Barrier Coated Combustor

    Energy Technology Data Exchange (ETDEWEB)

    Chorpening, B.T.; Dukes, M.G.; Robey, E.H.; Thornton, J.D.

    2007-05-01

    The combustion control and diagnostics sensor (CCADS) continues to be developed as an in-situ combustion sensor, with immediate application to natural gas fired turbines. In-situ combustion monitoring is also expected to benefit advanced power plants of the future, fueled by coal-derived syngas, liquified natural gas (LNG), hydrogen, or hydrogen blend fuels. The in-situ monitoring that CCADS provides can enable the optimal operation of advanced, fuel-flexible turbines for minimal pollutant emissions and maximum efficiency over the full operating range of an advanced turbine. Previous work has demonstrated CCADS as a useful sensor for in-situ monitoring of natural gas combustion, including detection of important combustion events such as flashback and lean blowoff, in experimental combustors without thermal barrier coatings (TBC). Since typical TBC materials are electrical insulators at room temperature, and CCADS operation requires conduction of electrical current to the walls of the combustor, a TBC on the combustion liner was identified as a potential barrier to CCADS operation in commercial application. This paper reports on CCADS experiments in a turbulent lean premixed combustor with a yttria-stabilized zirconia (YSZ) thermal barrier coating on the combustor wall. The tests were conducted at 0.1 MPa (1 atm), with a 15V excitation voltage on the CCADS electrodes. The results confirm that for a typical thermal barrier coating, CCADS operates properly, and the total measured average resistance is close to that of an uncoated combustor. This result is consistent with previous materials studies that found the electrical resistance of typical TBC materials considerably decreases at combustor operating temperatures.

  1. High precision laser sclerostomy

    Science.gov (United States)

    Góra, W. S.; Urich, A.; McIntosh, L.; Carter, R. M.; Wilson, C. G.; Dhillon, B.; Hand, D. P.; Shephard, J. D.

    2015-03-01

    Ultrafast lasers offer a possibility of removing soft ophthalmic tissue without introducing collateral damage at the ablation site or in the surrounding tissue. The potential for using ultrashort pico- and femtosecond pulse lasers for modification of ophthalmic tissue has been reported elsewhere and has resulted in the introduction of new, minimally invasive procedures into clinical practice. Our research aims to define the most efficient parameters to allow for the modification of scleral tissue without introducing collateral damage. Our experiments were carried out on hydrated porcine sclera in vitro. Porcine sclera, which has similar collagen organization, histology and water content (~70%) to human tissue was used. Supporting this work we present a 2D finite element blow-off model which employs a one-step heating process. It is assumed that the incident laser radiation that is not reflected is absorbed in the tissue according to the Beer-Lambert law and transformed into heat energy. The experimental setup uses an industrial picosecond laser (TRUMPF TruMicro 5x50) with 5.9 ps pulses at 1030 nm, with pulse energies up to 125 μJ and a focused spot diameter of 35 μm. Use of a beam steering scan head allows flexibility in designing complicated scanning patterns. In this study we have demonstrated that picosecond pulses are capable of removing scleral tissue without introducing any major thermal damage which offers a possible route for minimally invasive sclerostomy. In assessing this we have tested several different scanning patterns including single line ablation, square and circular cavity removal.

  2. Up-down and in-out asymmetries monitoring based on broadband radiation detectors

    International Nuclear Information System (INIS)

    chamber to monitor up-down and in-out radiation asymmetries that are observed in transitions to different confinement regimes. Preliminary data obtained under several plasma operation scenarios (ECRH-NBI transition, ECR power modulation, laser blow-off impurity injection and edge biasing experiments) reveal different degrees of up-down and in-out radiation asymmetries. (author)

  3. Experimental analysis of a porous burner operating on kerosene–vegetable cooking oil blends for thermophotovoltaic power generation

    International Nuclear Information System (INIS)

    Highlights: • Blends of kerosene–VCO fuels are successfully demonstrated for TPV power system. • Axial temperature distributions inside the combustion chamber are discussed. • Efficiencies are greatly affected by the change in fuel–air equivalence ratio. • CO and NOx emissions are affected by a change in fuel–air equivalence ratio. - Abstract: An experimental work was conducted to evaluate the performance and combustion characteristics of a porous burner for the cogeneration of heat and TPV applications. The main component comprised a novel tubular combustor that is designed to operate on several mixtures of gravity-fed liquid fuels and is integrated into an array of gallium antimonide (GaSb) TPV cells. Four mixtures of kerosene–vegetable cooking oil (VCO) were prepared and evaluated, as follows: 100% kerosene (100 kerosene), 90%/10% kerosene–VCO (90/10 KVCO), 75%/25% kerosene–VCO (75/25 KVCO), and 50%/50% kerosene–VCO (50/50 KVCO). The fuel–air equivalence ratios were varied from the rich blow-off condition to the lean region, and the corresponding electrical output and combustion characteristics were assessed. The maximum electrical efficiency of 1.03% was achieved using 50/50 KVCO, but the maximum radiant efficiency of 31.5% was obtained by using 100 kerosene. Experimental results indicated that increased fuel–air equivalence ratio adversely affected thermal efficiency. However, this shortcoming offsets the achievement of radiant power and efficiency. The thermal efficiency peaked at around stoichiometric mixture for all tested fuel blends. The combustion characteristics of the burner were clarified by analyzing the axial temperature profiles and emissions of carbon monoxide (CO) and nitrogen oxides (NOx). The temperature at the surface of the porous alumina was significantly higher than the developed flame temperature and the temperature at the exit of the burner. The CO emission fluctuated between 220 and 380 ppm in the lean region

  4. Analytical Analysis of the Effect of the Radiation Pressure on Planetary Exospheres: Application to Earth, Mars, Titan and Hot Jupiters

    Science.gov (United States)

    Beth, A.; Garnier, P.; Toublanc, D.; Dandouras, I. S.; Mazelle, C. X.

    2014-12-01

    force and stellar gravity. We show the influence of the radiation pressure on the equipotentials of the Circular Restricted Three Body Problem. We also demonstrate that the hot Jupiter HD 209458b is actually in a blow-off regime induced by the radiation pressure, which allows us to propose an alternative scenario for the evolution of its atmosphere.

  5. Report on the NOK's request for the removal of time limits on the licence for the operation of the Beznau II nuclear power plant

    International Nuclear Information System (INIS)

    concerned, no significant effect can be expected because of the distance of at least 6 km. As far as the analyses of possible incidents are concerned, the scenario 'rupture of a fresh steam pipe' leads to the highest radiological exposition in the neighbourhood. The worst case is the destruction of the fresh steam blow-off system and damage to components with radioactive contents. Its source term was estimated and the dose on the neighbour German regions was calculated. Even in the worst case, the legal dose limit of the German radiological ordinance was not exceeded

  6. Combustion characteristics of hydrogen/air mixture in a micro-combustor with cavities%微型凹腔燃烧器内氢气/空气的预混燃烧特性

    Institute of Scientific and Technical Information of China (English)

    万建龙; 程哲; 范爱武; 刘伟

    2013-01-01

    Premixed combustion of a hydrogen/air mixture in a planar micro-channel with cavities was numerically simulated by FLUENT with detailed chemical reaction mechanism. The equivalence ratio of the mixture was 0. 5. Effects of the inlet mixture velocity and length-depth ratio of the cavities on the temperature field, combustion efficiency and exhaust gas temperature were investigated. The results show that with the increase of inlet velocity, the flame front shifts downstream and becomes longer and narrower, and the temperature of outer wall becomes more uniform. Moreover, for the same length-depth ratio, the combustion efficiency decreases with the increase of inlet velocity; however, the exhaust gas temperature first increases and then decreases with the increase of inlet velocity. Furthermore, the blow-off limit is extended as the length-depth ratio is increased from 1 to 3, and then remained unchanged when width-depth ratio is raised from 3 to 4.%使用计算流体动力学软件FLUENT,并采用详细的化学反应机理,对当量比为0.5的氢气/空气预混气在带凹腔的平板型微通道内的燃烧特性进行了数值模拟.探讨了进气速度和凹腔的长深比对微通道内的温度场、燃烧效率和排烟温度的影响.计算结果表明:随着进气速度的增大,火焰被吹向下游,并且使火焰变得狭长,这会使得壁温分布更加均匀;在同一长深比下,燃烧效率随着进气速度的增加而降低,而排烟温度随着进气速度的增大先升高后降低;当长深比从1增大到3时,增大凹腔的长深比能拓展吹熄极限;长深比从3增大到4时,其吹熄极限相同.

  7. Experimental characterization of methane inverse diffusion flame

    KAUST Repository

    Elbaz, Ayman M.

    2014-06-26

    This article presents 10-kHz images of OH-PLIF simultaneously with 2-D PIV measurements in an inverse methane diffusion flame. Under a constant fuel flow rate, the central air jet Re was varied, leading to air to fuel velocity ratio, Vr, to vary from 8.3 to 66.5. Starting from Vr = 20.7, the flame is commonly characterized by three distinct zones. The length of the lower fuel entrainment region is inversely proportional to Vr. The flames investigated resemble a string shear layer confining this zone, and converging into the second distinct region, the flame neck zone. The third region is the rest of the flame, which spreads in a jet-like manner. The inverse diffusion flames exhibit varying degrees of partial premixing, depending upon on the velocity ratio Vr, and this region of partial premixing evolves into a well-mixed reaction zone along the flame centerline. The OH distribution correlated with the changes in the mean characteristics of the flow through reduction in the local Reynolds number due to heat release. The existence of a flame suppresses or laminarizes the turbulence at early axial locations and promotes fluctuations at the flame tip for flames with Vr < 49.8. In addition, the flame jet width can be correlated to the OH distribution. In upstream regions of the flames, the breaks in OH are counterbalanced by flame closures and are governed by edge flame propagation. These local extinctions were found to occur at locations where large flow structures were impinging on the flame and are associated with a locally higher strain rate or correlated to the local high strain rates at the flame hole edges without this flow impinging. Another contributor to re-ignition was found to be growing flame kernels. As the flames approach global blow-off, these kernels become the main mechanism for re-ignition further downstream of the flames. At low Vr, laminarization within the early regions of the flame provides an effective shield, preventing the jet flow from

  8. Unusual occurrences during the whole operation of BN-250 NPP

    International Nuclear Information System (INIS)

    Unusual occurrences during the whole operation BN-350 NPP. 1. Oil ingress in high pressure receiver for the not reveled reason, 12.05.1994. 2. lncrease of water radioactivity of circulating water supply system due to heat exchanger leak of spent fuel assembly washing out system, 17.09.1993. 3. Lack of passableness of sodium drain header of primary circuit reveled during inspection on scheduled preventative maintenance, 28.11.1996. 4. Destruction of the blow-off line of MCP-6 due to corrosion damage of the pipeline while unit was being operated at rated power, 23.04.1993. 5. Lack of passableness of blow-down pipeline connecting reactor gas cover with gas-type pressurizer while unit was being operated at rated power, 17.11.1994. 6. Sodium ingress in blow-down pipeline of loop-5 intermediate heat exchanger while loop-5 was being fed of sodium during scheduled preventative maintenance, 27.06.1994. 7. Resistance deterioration of electro heating zones of loop-4 due to heat exchanger leak and water ingress in air-pipeline of primary circuit boxes recirculating air system, 02.05.1997. 8. Resistance deterioration of electro heating zones of sodium drain header of secondary circuit was sopped in the water for the extinguishing the fire of blowing ventilation oil-strainer, 23.12.1994. 9. Sodium ingress in gas-type pressurizer through pipeline of primary sodium cleanup system and blow-down pipeline of failed MCP-2 while primary sodium cleanup system was being connected to the primary circuit, 17.08.1976. As a rule, the main reactor systems are scrutinized more carefully than the auxiliary reactor systems and the order actions are existed for eliminating and mitigating of consequences of main reactor system fails. Therefore the auxiliary reactor system fails may impact on the main reactor systems through places of its contact in significant measure. The influence of auxiliary reactor system fails on main reactor systems and its possible consequences for behavior of the main

  9. Effects of Buoyancy on Laminar and Turbulent Premixed V-Flame

    Science.gov (United States)

    Cheng, Robert K.; Bedat, Benoit

    1997-01-01

    Turbulent combustion occurs naturally in almost all combustion systems and involves complex dynamic coupling of chemical and fluid mechanical processes. It is considered as one of the most challenging combustion research problems today. Though buoyancy has little effect on power generating systems operating under high pressures (e.g., IC engines and turbines), flames in atmospheric burners and the operation of small to medium furnaces and boilers are profoundly affected by buoyancy. Changes in burner orientation impacts on their blow-off, flash-back and extinction limits, and their range of operation, burning rate, heat transfer, and emissions. Theoretically, buoyancy is often neglected in turbulent combustion models. Yet the modeling results are routinely compared with experiments of open laboratory flames that are obviously affected by buoyancy. This inconsistency is an obstacle to reconciling experiments and theories. Consequently, a fundamental understanding of the coupling between turbulent flames and buoyancy is significant to both turbulent combustion science and applications. The overall effect of buoyancy relates to the dynamic interaction between the flame and its surrounding, i.e., the so-called elliptical problem. The overall flame shape, its flowfield, stability, and mean and local burning rates are dictated by both upstream and downstream boundary conditions. In steady propagating premixed flames, buoyancy affects the products region downstream of the flame zone. These effects are manifested upstream through the mean and fluctuating pressure fields to influence flame stretch and flame wrinkling. Intuitively, the effects buoyancy should diminish with increasing flow momentum. This is the justification for excluding buoyancy in turbulent combustion models that treats high Reynolds number flows. The objectives of our experimental research program is to elucidate flame-buoyancy coupling processes in laminar and turbulent premixed flames, and to

  10. Novel method for determining DDT in vapour and particulate phases within contaminated indoor air in a malaria area of South Africa

    Energy Technology Data Exchange (ETDEWEB)

    Naude, Yvette, E-mail: yvette.naude@up.ac.za [Department of Chemistry, University of Pretoria, Private Bag X20, Hatfield 0028, Pretoria (South Africa); Rohwer, Egmont R., E-mail: egmont.rohwer@up.ac.za [Department of Chemistry, University of Pretoria, Private Bag X20, Hatfield 0028, Pretoria (South Africa)

    2012-06-12

    Highlights: Black-Right-Pointing-Pointer We present a novel denuder for the determination of DDT in contaminated indoor air. Black-Right-Pointing-Pointer Single step concentration of vapour phase on PDMS, particulate phase on filter. Black-Right-Pointing-Pointer Solvent-free green technique, sample extraction not required. Black-Right-Pointing-Pointer Ratios of airborne p,p Prime -DDD/p,p Prime -DDT and of o,p Prime -DDT/p,p Prime -DDT are unusual. Black-Right-Pointing-Pointer Insecticidal efficacy of technical DDT may be compromised. - Abstract: The organochlorine insecticide DDT (1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane) is still used for malaria vector control in certain areas of South Africa. The strict Stockholm Convention on Persistent Organic Pollutants (POPs) allows spraying on the inside of traditional dwellings with DDT. In rural villages contaminated dust presents an additional pathway for exposure to DDT. We present a new method for the determination of DDT in indoor air where separate vapour and particulate samples are collected in a single step with a denuder configuration of a multi-channel open tubular silicone rubber (polydimethylsiloxane (PDMS)) trap combined with a micro quartz fibre filter. The multi-channel PDMS trap section of the denuder concentrates vapour phase insecticide whereas particle associated insecticide is transferred downstream where it is collected on a micro-fibre filter followed by a second multi-channel PDMS trap to capture the blow-off from the filter. The multi-channel PDMS trap and filter combination are designed to fit a commercial thermal desorber for direct introduction of samples into a GC-MS. The technique is solvent-free. Analyte extraction and sample clean-up is not required. Two fractions, vapour phase and particulate phase p,p Prime -DDT, o,p Prime -DDT; p,p Prime -DDD, o,p Prime -DDD; p,p Prime -DDE and o,p Prime -DDE in 4 L contaminated indoor air, were each quantitatively analysed by GC-MS using

  11. Periglacial landforms on Mars as evidence of undersurface ice

    Science.gov (United States)

    Sik, A.

    1. Introduction By the methods of comparative planetology we can acquire new information not only from other planets, but from the Earth as well. The purpose of my research is to compare the periglacial environment of Mars and Earth, their forms and geomorphological processes. Hereby we might could refine our understanding of the paleoclimatic changes on these two planets, the history of near-surface water on Mars and the possibility of Martian life. I used the high resolution narrow angle images of Mars Global Surveyor's Mars Oriber Camera [1] to define landforms and the profiles of Mars Oriber Laser Altimeter [2] to characterize the relief on the examined terrains. Because of the "difficulties" of real field work on the surface of Mars, I obtained these kind of data during a periglacial research expedition of my university, carried out in the summer of 2000. 2. Short history of water on Mars After the formation of the planet, Mars had a stable and thick atmosphere, probably dominated by carbon-dioxide, water-vapour and nitrogen. So during the first part of its history, called "wet Mars period", planet Mars had active water-cycle and as a part of it, water-related erosion landforms had taken shape. This can be the explanation of the seashore-like, regionally identical altitude lines which separates different surface regions, the river channels and the inner crater pond sediments widely general on the surface. But as a result of more mechanisms, about 3,5 billion years ago this era ended. The main reasons probably were some giant impact events, produced a kind of atmospheric blow-off and resulted huge impact forms, like Hellas- and Argyre- basins. Another factor of it was the loss of global magnetic field, so the charged particles of solar wind was able to erode the outer part of the atmosphere. Besides, the low escape velocity caused by the small mass of the planet enabled gas molecules of the Martian atmosphere to leave for the interplanetary space. For all these