K. Vasudeva Karanth
2009-01-01
Full Text Available The flow between the impeller exit and the diffuser entry (i.e., in the radial gap is generally considered to be complex. With the development of PIV and CFD tools such as moving mesh techniques, it is now possible to arrive at a prudent solution compatible with the physical nature of flow. In this work, numerical methodology involving moving mesh technique is used in predicting the real flow behavior, as exhibited when a target blade of the impeller is made to move past corresponding vane on the diffuser. Many research works have been undertaken using experimental and numerical methods on the impeller-diffuser interactive phenomenon. It is found from the literature that the effect of radial gap between impeller and diffuser on the interaction and on the performance of the fan has not been the focus of attention. Hence numerical analysis is undertaken in this work to explore and predict the flow behavior due to the radial gap. This has revealed the presence of an optimum radial gap which could provide better design characteristics or lower loss coefficient. It is found that there is a better energy conversion by the impeller and enhanced energy transformation by the diffuser, corresponding to optimum radial gap. The overall efficiency also found to increase for relatively larger gap.
Mohammadjavad Hosseini
2017-07-01
Full Text Available A high-performance centrifugal compressor is needed for numerous industry applications nowadays. The radial gap ratio between the impeller and the diffuser vanes plays an important role in the improvement of the compressor performance. In this paper, the effects of the radial gap ratio on a high-pressure ratio centrifugal compressor are investigated using numerical simulations. The performance and the flow field are compared for six different radial gap ratios and five rotational speeds. The minimal radial gap ratio was 1.04 and the maximal was 1.14. Results showed that reducing the radial gap ratio decreases the choke mass flow rate. For the tip-speed Mach number (impeller inlet with Mu < 1, the pressure recovery and the loss coefficients are not sensitive to the radial gap ratio. However, for Mu ≥ 1, the best radial gap ratio is 1.08 for the pressure recovery and the loss coefficients. Furthermore, the impeller pressure ratio and efficiency are reduced by increasing the radial gap ratio. Finally, the compressor efficiency was compared for different radial gap ratios. For Mu < 1, the radial gap ratio does not have noticeable effects. In comparison, the radial gap ratio of 1.08 has the best performance for Mu ≥ 1.
Centrifugal compressor tip clearance and impeller flow
Jaatinen-Varri, Ahti; Tiainen, Jonna; Turunen-Saaresti, Teemu; Gronman, Aki; Ameli, Alireza; Backman, Jari [Laboratory of Fluid Dynamics, LUT School of Energy Systems, Lappeenranta University of Technology, Lappeenranta (Finland); Engeda, Abraham [Turbomachinery Laboratory, Dept. of Mechanical Engineering, Michigan State University, East Lansing (United States)
2016-11-15
Compressors consume a considerable portion of the electricity used in the industrial sector. Hence, improvements in compressor efficiency lead to energy savings and reduce environmental impacts. The efficiency of an unshrouded centrifugal compressor suffers from leakage flow over the blade tips. The effect of tip leakage flow on the passage flow differs between the full and splitter blade passages. In this study, the differences in the flow fields between the full and splitter blade passages were studied numerically in detail. An industrial high-speed compressor with a design pressure ratio of 1.78 was modelled. Numerical studies were conducted with six different tip clearances and three different diffuser widths. The results show that increasing tip clearance considerably increases the reversed flow into the impeller with an unpinched diffuser. The reversed flow then partly mixes into the flow in the same blade passage it entered the impeller and the rest migrates over the blade, mixing with the tip clearance flow. Furthermore, as the reversed and clearance flow mix into the wake, the wake is weakened. As pinch reduces both the reversed flow and clearance flow, the passage wakes are stronger with pinches. However, the pinch is beneficial as the losses at the impeller outlet decrease.
Centrifugal compressor tip clearance and impeller flow
Jaatinen-Varri, Ahti; Tiainen, Jonna; Turunen-Saaresti, Teemu; Gronman, Aki; Ameli, Alireza; Backman, Jari; Engeda, Abraham
2016-01-01
Compressors consume a considerable portion of the electricity used in the industrial sector. Hence, improvements in compressor efficiency lead to energy savings and reduce environmental impacts. The efficiency of an unshrouded centrifugal compressor suffers from leakage flow over the blade tips. The effect of tip leakage flow on the passage flow differs between the full and splitter blade passages. In this study, the differences in the flow fields between the full and splitter blade passages were studied numerically in detail. An industrial high-speed compressor with a design pressure ratio of 1.78 was modelled. Numerical studies were conducted with six different tip clearances and three different diffuser widths. The results show that increasing tip clearance considerably increases the reversed flow into the impeller with an unpinched diffuser. The reversed flow then partly mixes into the flow in the same blade passage it entered the impeller and the rest migrates over the blade, mixing with the tip clearance flow. Furthermore, as the reversed and clearance flow mix into the wake, the wake is weakened. As pinch reduces both the reversed flow and clearance flow, the passage wakes are stronger with pinches. However, the pinch is beneficial as the losses at the impeller outlet decrease
Design and optimization of mixed flow pump impeller blades by varying semi-cone angle
Dash, Nehal; Roy, Apurba Kumar; Kumar, Kaushik
2018-03-01
The mixed flow pump is a cross between the axial and radial flow pump. These pumps are used in a large number of applications in modern fields. For the designing of these mixed flow pump impeller blades, a lot number of design parameters are needed to be considered which makes this a tedious task for which fundamentals of turbo-machinery and fluid mechanics are always prerequisites. The semi-cone angle of mixed flow pump impeller blade has a specified range of variations generally between 45o to 60o. From the literature review done related to this topic researchers have considered only a particular semi-cone angle and all the calculations are based on this very same semi-cone angle. By varying this semi-cone angle in the specified range, it can be verified if that affects the designing of the impeller blades for a mixed flow pump. Although a lot of methods are available for designing of mixed flow pump impeller blades like inverse time marching method, the pseudo-stream function method, Fourier expansion singularity method, free vortex method, mean stream line theory method etc. still the optimized design of the mixed flow pump impeller blade has been a cumbersome work. As stated above since all the available research works suggest or propose the blade designs with constant semi-cone angle, here the authors have designed the impeller blades by varying the semi-cone angle in a particular range with regular intervals for a Mixed-Flow pump. Henceforth several relevant impeller blade designs are obtained and optimization is carried out to obtain the optimized design (blade with optimal geometry) of impeller blade.
Performance prediction and flow field calculation for airfoil fan with impeller inlet clearance
Kang, Shin Hyoung; Cao, Renjing; Zhang, Yangjun
2000-01-01
The performance prediction of an airfoil fan using a commercial code, STAR/CD, is verified by comparing the calculated results with measured performance data and velocity fields of an airfoil fan. The effects of inlet tip clearance on performance are investigated. The calculations overestimate the pressure rise performance by about 10-25 percent. However, the performance reduction due to tip clearance is well predicted by numerical simulations. Main source of performance decrease is not only the slip factor but also impeller efficiency. The reduction in performance is 12-16 percent for 1 percent gap of the diameter. The calculated reductions in impeller efficiency and slip factor are also linearly proportional to the gap size. The span-wise distributions of phase averaged velocity and pressure at the impeller exit are strongly influenced by the radial gap size. The radial component of velocity and the flow angle increase over the passage as the gap increases. The slip factor decreases and the loss increases with the gap size. The high velocity of leakage jet affects the impeller inlet and passage flows. With a larger clearance, the main stream moves to the impeller hub side and high loss region extends from the shroud to the hub
Ben-Nun, R.; Sheintuch, M.; Kysela, Bohuš; Konfršt, Jiří; Fořt, I.
2015-01-01
Roč. 61, č. 4 (2015), s. 1413-1426 ISSN 0001-1541 R&D Projects: GA ČR GAP101/12/2274 Institutional support: RVO:67985874 Keywords : turbulent jet * mixing * radial impeller * stirred tank * Rushton turbine Subject RIV: BK - Fluid Dynamics Impact factor: 2.980, year: 2015
Modeling the Design Flow Coefficient of a Centrifugal Compressor Impeller
A. A. Drozdov
2017-01-01
Full Text Available In calculating gas-dynamic characteristics by the universal modeling method it is necessary to determine a non-incidence flow rate through the blades of an impeller because of its relationship with the magnitude of incidence losses. The flow area decreased by the blades of finite thickness and the blades load have impact on the critical streamline direction. The universal modeling method in primary designing uses for this a scheme of replacing the influence of the blade load by the vortex effect with identical circulation. Finally, calculating the inviscid flow around the blades allows selecting a value of the inlet blade angle. For impellers with small design flow coefficients, the condition of the non-incidence inlet for the primary design and for the calculation of the inviscid flow is significantly different. The calculating correctness of the non-incidence regime for the non-viscous flow was checked earlier by measurements of the flow in the impellers. The paper presents CFD calculations of twenty impellers in a tenfold range of design flow coefficients. To provide correct comparison, it takes into account the differences in the value of the loading factor calculated by the programs of inviscid quasi-three-dimensional calculation and CFD programs. Shows the identity of inlet conditions for both methods. To increase primary design accuracy, the calculation model was refined. The formula for calculating vortex-induced velocity involves an empirical coefficient. The analysis of data for 32 impellers with different blade profiling allowed working out formulas for calculating empirical coefficient, depending on the type of an impeller, the blade load and the width of the throat at an impeller inlet. The new scheme-based calculation with the empirical coefficient is accurate enough for the primary design.
Characterizing the flow of stirred vessels with anchor type impellers
S.M.C. Peixoto
2000-12-01
Full Text Available Despite its importance in chemical industries, there are few works which studies anchor type impellers and only a fraction of the works investigate these systems under a computational approach. The great majority refers to turbine impellers, specially Rushton turbines, under turbulent flow. Anchor impellers are used specially for highly viscous flow, typical of polymer reactions. The viscosity is normally in the range 1000-10000 cp. Since this range of viscosity describe highly viscous flows, the reactions for anchor agitated systems are normally carried out under laminar flow. This work presents a detailed computational fluid dynamics (CFD approach to study the behaviour of stirred vessels using anchor impellers. The axial plane of the tank, which is being modelled, is divided into small control volumes, which collectively is referred to as the mesh, or grid. In each of these cells the momentum balance, energy and mass conservation, which describes the model, are rewritten algebraically using the finite volumes method to relate such variables as velocity, pressure and temperature to values in neighbouring cells. The equations are then solved numerically, and the results yield the flow corresponding to the model. Since the geometry of a vessel with anchor impellers strictly calls for a three dimensional method, an approximation is made to account for the effect of the blades (Kuncewics, 1992. The main objective of this work is to give a detailed description of the flow generated by this axial impeller with a view to indicate ways in which the design and operation of these systems can be improved.
CFD study of leakage flows in shroud cavities of a compressor impeller
Soldatova, K.
2017-08-01
The flow character in a gap between shroud disc of an impeller and a stator surface (shroud cavity) influences disc friction loss, labyrinth seal loss (parasitic losses) and thrust force. Flow calculations inside the shroud cavity of a model of centrifugal compressor stage and its labyrinth seal in a range of flow rates and axial width and radial gap are presented. The results are presented in terms of non-dimensional coefficients of flow, disc friction and seal leakage losses coefficients and pressure coefficient. The distributions meridional and tangential flow velocities correspond to the continuity and equilibrium equations - flow radial circulation exists in wide cavity and is absent in narrow cavities. The radial pressure distributions as measured and calculated are not fully comparable. The possible reason is that CFD-calculated leakage coefficient is less than calculated by A.Stodola formula. The influence of a cavity width on the losses and the thrust force requires a balanced design.
Interaction of impeller and guide vane in a series-designed axial-flow pump
Kim, S; Choi, Y S; Lee, K Y; Kim, J H
2012-01-01
In this paper, the interaction of the impeller and guide vane in a series-designed axial-flow pump was examined through the implementation of a commercial CFD code. The impeller series design refers to the general design procedure of the base impeller shape which must satisfy the various flow rate and head requirements by changing the impeller setting angle and number of blades of the base impeller. An arc type meridional shape was used to keep the meridional shape of the hub and shroud with various impeller setting angles. The blade angle and the thickness distribution of the impeller were designed as an NACA airfoil type. In the design of the guide vane, it was necessary to consider the outlet flow condition of the impeller with the given setting angle. The meridional shape of the guide vane were designed taking into consideration the setting angle of the impeller, and the blade angle distribution of the guide vane was determined with a traditional design method using vane plane development. In order to achieve the optimum impeller design and guide vane, three-dimensional computational fluid dynamics and the DOE method were applied. The interaction between the impeller and guide vane with different combination set of impeller setting angles and number of impeller blades was addressed by analyzing the flow field of the computational results.
M. Younsi
2007-01-01
Full Text Available The aim of this study is to evaluate the influence of design parameters on the unsteady flow in a forward-curved centrifugal fan and their impact on the aeroacoustic behavior. To do so, numerical and experimental studies have been carried out on four centrifugal impellers designed with various geometrical parameters. The same volute casing has been used to study these impellers. The effects on the unsteady flow behavior related to irregular blade spacing, blade count and radial distance between the impeller periphery and the volute tongue have been studied. The numerical simulations of the unsteady flow have been carried out using computational fluid dynamics (CFD tools based on the unsteady Reynolds averaged Navier Stokes (URANS approach. The study is focused on the unsteadiness induced by the aerodynamic interaction between the volute and the rotating impeller blades. In order to predict the acoustic pressure at far field, the unsteady flow variables provided by the CFD calculations have been used as inputs in the Ffowcs Williams-Hawkings equations (FW-H. The experimental part of this work concerns measurement of aerodynamic performance of the fans using a test bench built according to ISO 5801 (1997 standard. In addition to this, pressure microphones have been flush mounted on the volute tongue surface in order to measure the wall pressure fluctuations. The sound pressure level (SPL measurements have been carried out in an anechoic room in order to remove undesired noise reflections. Finally, the numerical results have been compared with the experimental measurements and a correlation between the wall pressure fluctuations and the far field noise signals has been found.
Zou, Zhichao [College of Water Resources and Civil Engineering, China Agricultural University, Beijing 100083 (China); Wang, Fujun, E-mail: wangfj@cau.edu.cn [College of Water Resources and Civil Engineering, China Agricultural University, Beijing 100083 (China); Beijing Engineering Research Center of Safety and Energy Saving Technology for Water Supply Network System, China Agricultural University, Beijing 100083 (China); Yao, Zhifeng [College of Water Resources and Civil Engineering, China Agricultural University, Beijing 100083 (China); Beijing Engineering Research Center of Safety and Energy Saving Technology for Water Supply Network System, China Agricultural University, Beijing 100083 (China); Tao, Ran [College of Water Resources and Civil Engineering, China Agricultural University, Beijing 100083 (China); Xiao, Ruofu [College of Water Resources and Civil Engineering, China Agricultural University, Beijing 100083 (China); Beijing Engineering Research Center of Safety and Energy Saving Technology for Water Supply Network System, China Agricultural University, Beijing 100083 (China); Li, Huaicheng [Shanghai Liancheng (Group) Co., Ltd., Shanghai 201812 (China)
2016-12-15
Highlights: • Conclude the characteristics of transient radial force in the startup process for a large double-suction centrifugal pump. • The overall direction of the radial force during startup process is also confirmed. • A formula used to calculate the transient radial force during startup process is proposed. • A relationship between radial force variation and axial vortex development in blade channel during the startup process is established. The mechanism of the radial force evolution is revealed. - Abstract: Double-suction centrifugal pumps play an important role in the main feedwater systems of nuclear power plant. The impeller radial force in a centrifugal pump varies dramatically during startup at the shut-off condition. In this study, the startup process of a large double-suction centrifugal pump is investigated using CFD. During testing, the impeller speed is accelerated from zero to its rated speed in 1.0 s (marked as t{sub 0}) and is then maintained at the rated speed. The results show that the radial force increase lags behind the impeller speed increase. At 0–0.4t{sub 0}, the radial force is small (approaching zero). At 0.4–1.4t{sub 0}, the radial force increases rapidly. After 1.4t{sub 0}, the average radial force stabilizes and reaches its maximum value of 55,619 N. The observed maximum radial force value during startup is approximately nine times as high as the radial force under rated condition. During startup, the overall radial force direction is proximate to the radial line located 25° from the volute tongue along circumferential direction. A transient radial force formula is proposed to evaluate the changes in radial force during startup. The streamline distribution in impeller passages and the impeller outlet pressure profile varying over time are produced. The relationship between radial force evolution and the varying axial-to-spiral vortex structure is analyzed. The radial force change mechanism is revealed. This research
Zou, Zhichao; Wang, Fujun; Yao, Zhifeng; Tao, Ran; Xiao, Ruofu; Li, Huaicheng
2016-01-01
Highlights: • Conclude the characteristics of transient radial force in the startup process for a large double-suction centrifugal pump. • The overall direction of the radial force during startup process is also confirmed. • A formula used to calculate the transient radial force during startup process is proposed. • A relationship between radial force variation and axial vortex development in blade channel during the startup process is established. The mechanism of the radial force evolution is revealed. - Abstract: Double-suction centrifugal pumps play an important role in the main feedwater systems of nuclear power plant. The impeller radial force in a centrifugal pump varies dramatically during startup at the shut-off condition. In this study, the startup process of a large double-suction centrifugal pump is investigated using CFD. During testing, the impeller speed is accelerated from zero to its rated speed in 1.0 s (marked as t_0) and is then maintained at the rated speed. The results show that the radial force increase lags behind the impeller speed increase. At 0–0.4t_0, the radial force is small (approaching zero). At 0.4–1.4t_0, the radial force increases rapidly. After 1.4t_0, the average radial force stabilizes and reaches its maximum value of 55,619 N. The observed maximum radial force value during startup is approximately nine times as high as the radial force under rated condition. During startup, the overall radial force direction is proximate to the radial line located 25° from the volute tongue along circumferential direction. A transient radial force formula is proposed to evaluate the changes in radial force during startup. The streamline distribution in impeller passages and the impeller outlet pressure profile varying over time are produced. The relationship between radial force evolution and the varying axial-to-spiral vortex structure is analyzed. The radial force change mechanism is revealed. This research provides a scientific
Yang, Ce; Liu, Yixiong; Yang, Dengfeng; Wang, Benjiang
2017-11-01
To achieve the rebalance of flow distributions of double-sided impellers, a method of improving the radius of rear impeller is presented in this paper. It is found that the flow distributions of front and rear impeller can be adjusted effectively by increasing the radius of rear impeller, thus improves the balance of flow distributions of front and rear impeller. Meanwhile, the working conversion mode process of double-sided centrifugal compressor is also changed. Further analysis shows that the flowrates of blade channels in front impeller are mainly influenced by the circumferential distributions of static pressure in the volute. But the flowrates of rear impeller blade channels are influenced by the outlet flow field of bent duct besides the effects of static pressure distributions in the volute. In the airflow interaction area downstream, the flowrate of blade channel is obviously smaller. By increasing the radius of rear impeller, the work capacity of rear impeller is enhanced, the working mode conversion process from parallel working mode of double-sided impeller to the single impeller working mode is delayed, and the stable working range of double-sided compressor is broadened.
Stability of radial swirl flows
Dou, H S; Khoo, B C
2012-01-01
The energy gradient theory is used to examine the stability of radial swirl flows. It is found that the flow of free vortex is always stable, while the introduction of a radial flow will induce the flow to be unstable. It is also shown that the pure radial flow is stable. Thus, there is a flow angle between the pure circumferential flow and the pure radial flow at which the flow is most unstable. It is demonstrated that the magnitude of this flow angle is related to the Re number based on the radial flow rate, and it is near the pure circumferential flow. The result obtained in this study is useful for the design of vaneless diffusers of centrifugal compressors and pumps as well as other industrial devices.
Rotordynamic Forces on Centrifugal Pump Impellers
Franz, R.; Arndt, N.; Caughey, T. K.; Brennen, C. E.; Acosta, A. J.
1987-01-01
The asymmetric flow around an impeller in a volute exerts a force upon the impeller. To study the rotordynamic force on an impeller which is vibrating around its machine axis of rotation, the impeller, mounted on a dynamometer, is made to whirl in a circular orbit within the volute. The measured force is expressed as the sum of a steady radial force and an unsteady force due to the eccentric motion of the impeller. These forces were measured in separate tests on a centrifugal pump with rad...
Mathematical modeling of fluid flow in aluminum ladles for degasification with impeller - injector
Ramos-Gómez, E.; González-Rivera, C.; Ramírez-Argáez, M. A.
2012-09-01
In this work a fundamental Eulerian mathematical model was developed to simulate fluid flow in a water physical model of an aluminum ladle equipped with impeller for degassing treatment. The effect of critical process parameters such as rotor speed, gas flow rate on the fluid flow and vortex formation was analyzed with this model. Commercial CFD code PHOENICS 3.4 was used to solve all conservation equations governing the process for this twophase fluid flow system. The mathematical model was successfully validated against experimentally measured liquid velocity and turbulent profiles in a physical model. From the results it was concluded that the angular speed of the impeller is the most important parameter promoting better stirred baths. Pumping effect of the impeller is increased as impeller rotation speed increases. Gas flow rate is detrimental on bath stirring and diminishes pumping effect of impeller.
Valenzuela, Javier
2001-01-01
A radial flow heat exchanger (20) having a plurality of first passages (24) for transporting a first fluid (25) and a plurality of second passages (26) for transporting a second fluid (27). The first and second passages are arranged in stacked, alternating relationship, are separated from one another by relatively thin plates (30) and (32), and surround a central axis (22). The thickness of the first and second passages are selected so that the first and second fluids, respectively, are transported with laminar flow through the passages. To enhance thermal energy transfer between first and second passages, the latter are arranged so each first passage is in thermal communication with an associated second passage along substantially its entire length, and vice versa with respect to the second passages. The heat exchangers may be stacked to achieve a modular heat exchange assembly (300). Certain heat exchangers in the assembly may be designed slightly differently than other heat exchangers to address changes in fluid properties during transport through the heat exchanger, so as to enhance overall thermal effectiveness of the assembly.
Computer aided hydraulic design of axial flow pump impeller
Sreedhar, B.K.; Rao, A.S.L.K.; Kumaraswamy, S.
1994-01-01
Pumps are the heart of any power plant and hence their design requires great attention. Computers with their potential for rapid computation can be successfully employed in the design and manufacture of these machines. The paper discusses a program developed for the hydraulic design of axial flow pump impeller. The program, written in FORTRAN 77, is interactive and performs the functions of design calculation, drafting and generation of numerical data for blade manufacture. The drafting function, which makes use of the software ACAD, is carried out automatically by means of suitable interface programs. In addition data for blade manufacture is also generated in either the x-y-z or r-θ-z system. (author). 4 refs., 3 figs
Gas–liquid flow in stirred reactors: Trailing vortices and gas accumulation behind impeller blades
Ranade, V.; Deshpande, Vaibhav R.
1999-01-01
In a gas–liquid stirred reactor, gas tends to accumulate in low-pressure regions behind the impeller blades. Such gas accumulation significantly alters impeller performance characteristics. We have computationally investigated gas–liquid flow generated by a Rushton (disc) turbine. Rotating Rushton
Origins of hydrodynamic forces on centrifugal pump impellers
Adkins, Douglas R.; Brennen, Christopher E.
1987-01-01
Hydrodynamic interactions that occur between a centrifugal pump impeller and volute are experimentally and theoretically investigated. The theoretical analysis considers the inability of the blades to perfectly guide the flow through the impeller, and also includes a quasi-one dimensional treatment of the flow in the volute. The disturbance at the impeller discharge and the resulting forces are determined by the theoretical model. The model is then extended to obtain the hydrodynamic force perturbations that are caused by the impeller whirling eccentrically in the volute. Under many operating conditions, these force perturbations were found to be destablizing. Comparisons are made between the theoretical model and the experimental measurements of pressure distributions and radial forces on the impeller. The theoretical model yields fairly accurate predictions of the radial forces caused by the flow through the impeller. However, it was found that the pressure acting on the front shroud of the impeller has a substantial effect on the destablizing hydrodynamic forces.
Prian, Vasily
1951-01-01
An analysis was made of the flow in the rotating passages of a 48-inch diameter radial-inlet centrifugal impeller at a tip speed of 700 feet per second in order to provide more knowledge on the flow...
Study of Pumping Capacity of Pitched Blade Impellers
I. Fořt
2002-01-01
Full Text Available A study was made of the pumping capacity of pitched blade impellers in a cylindrical pilot plant vessel with four standard radial baffles at the wall under a turbulent regime of flow. The pumping capacity was calculated from the radial profile of the axial flow, under the assumption of axial symmetry of the discharge flow. The mean velocity was measured using laser Doppler anemometry in a transparent vessel of diameter T = 400 mm, provided with a standard dished bottom. Three and six blade pitched blade impellers (the pitch angle varied within the interval a Îá24°; 45°ń of impeller/vessel diameter ratio D/T = 0.36, as well as a three blade pitched blade impeller with folded blades of the same diameter, were tested. The calculated results were compared with the results of experiments mentioned in the literature, above all in cylindrical vessels with a flat bottom. Both arrangements of the agitated system were described by the impeller energetic efficiency, i.e, a criterion including in dimensionless form both the impeller energy consumption (impeller power input and the impeller pumping effect (impeller pumping capacity. It follows from the results obtained with various geometrical configurations that the energetic efficiency of pitched blade impellers is significantly lower for configurations suitable for mixing solid-liquid suspensions (low impeller off bottom clearances than for blending miscible liquids in mixing (higher impeller off bottom clearances.
Flow in a centrifugal fan impeller at off-design conditions
Wright, T.; Tzou, K. T. S.; Madhavan, S.
1984-06-01
A fully three-dimensional finite element analysis of inviscid, incompressible blade channel flow is the basis of the present study of both predicted and measured surface velocity and pressure distributions in the internal flow channels of a centrifugal fan impeller, for volume flow rates of 80-125 percent the design flow rate. The experimental results made extensive use of blade and sidewall surface pressure taps installed in a scale model of an airfoil-bladed centrifugal fan impeller. The results obtained illustrate the ability of both flow analyses to predict the dominant features of the impeller flow field, including peak blade surface velocities and adverse gradients at flows far from the design point. Insight is also gained into the limiting channel diffusion values for typical centrifugal cascade performance, together with the influence of viscous effects, as seen in deviations from ideal flow predictions.
High performance hydraulic design techniques of mixed-flow pump impeller and diffuser
Kim, Sung; Lee, Kyoung Yong; Kim, Joon Hyung; Kim, Jin Hyuk; Jung, Uk Hee; Choi, Young Seok
2015-01-01
In this paper, we describe a numerical study about the performance improvement of a mixed-flow pump by optimizing the design of the impeller and diffuser using a commercial computational fluid dynamics (CFD) code and design-of-experiments (DOE). The design variables of impeller and diffuser in the vane plane development were defined with a fixed meridional plane. The design variables were defined by the vane plane development, which indicates the blade-angle distributions and length of the impeller and diffuser. The vane plane development was controlled using the blade-angle in a fixed meridional plane. The blade shape of the impeller and diffuser were designed using a traditional method in which the inlet and exit angles are connected smoothly. First, the impeller optimum design was performed with impeller design variables. The diffuser optimum design was performed with diffuser design variables while the optimally designed impeller shape was fixed. The importance of the impeller and diffuser design variables was analyzed using 2 k factorial designs, and the design optimization of the impeller and diffuser design variables was determined using the response surface method (RSM). The objective functions were defined as the total head (Ht) and the total efficiency (ηt) at the design flow rate. The optimally designed model was verified using numerical analysis, and the numerical analysis results for both the optimum model and the reference model were compared to determine the reasons for the improved pump performance. A pump performance test was carried out for the optimum model, and its reliability was proved by a comparative analysis of the results of the numerical analysis and an experiment using the optimum model.
Optical PIV and LDV Comparisons of Internal Flow Investigations in SHF Impeller
G. Wuibaut
2006-01-01
Full Text Available The paper presents a comparison between two sets of experimental results in a centrifugal flow pump. The tested impeller is the so-called SHF impeller for which many experimental data have been continuously produced to built databases for CFD code validations with various levels of approximation. Measurements have been performed using optical techniques: 2D particle image velocimetry (PIV technique on an air test model and 2D laser doppler velocimetry (LDV technique on a water model, both for different flow rates. For the present study, results obtained by these optical techniques are compared together in terms of phase averaged velocity and velocity fluctuations inside the impeller flow passage for design flow rate.
Numerical analysis of cavitating flow characteristics in impeller of residual heat removal pump
Hong, Feng; Yuan, Jianping; Zhou, Banglun
2016-01-01
In order to investigate internal cavitating flow characteristics of the impeller in residual heat removal pumps, the three-dimensional cavitating flow in a residual heat removal model pump is numerically calculated by using the homogeneous mixture cavitation model based on the Rayleigh-Plesset
Cholemari, Murali R.; Arakeri, Jaywant H.
2005-08-01
We study the stability of surface waves on the radial film flow created by a vertical cylindrical water jet striking a horizontal plate. In such flows, surface waves have been found to be unstable and can cause transition to turbulence. This surface-wave-induced transition is different from the well-known Tollmien-Schlichting wave-induced transition. The present study aims at understanding the instability and the transition process. We do a temporal stability analysis by assuming the flow to be locally two-dimensional but including spatial variations to first order in the basic flow. The waves are found to be dispersive, mostly unstable, and faster than the mean flow. Spatial variation is the major destabilizing factor. Experiments are done to test the results of the linear stability analysis and to document the wave breakup and transition. Comparison between theory and experiments is fairly good and indicates the adequacy of the model.
Damm, F.C.
1975-01-01
The unique gas dynamic laser provides outward radial supersonic flow from a toroidal shaped stacked array of a plurality of nozzles, through a diffuser having ring shaped and/or linear shaped vanes, and through a cavity which is cylindrical and concentric with the stacked array, with the resultant laser beam passing through the housing parallel to the central axis of the diffuser which is coincident with the axis of the gas dynamic laser. Therefore, greater beam extraction flexibility is attainable, because of fewer flow shock disturbances, as compared to the conventional unidirectional flow gas dynamic laser in which unidirectional supersonic flow sweeps through a rectangular cavity and is exhausted through a two-dimensional diffuser. (auth)
Computational Fluid Dynamics (CFD) Analysis for the Reduction of Impeller Discharge Flow Distortion
Garcia, R.; McConnaughey, P. K.; Eastland, A.
1993-01-01
The use of Computational Fluid Dynamics (CFD) in the design and analysis of high performance rocket engine pumps has increased in recent years. This increase has been aided by the activities of the Marshall Space Flight Center (MSFC) Pump Stage Technology Team (PSTT). The team's goals include assessing the accuracy and efficiency of several methodologies and then applying the appropriate methodology(s) to understand and improve the flow inside a pump. The PSTT's objectives, team membership, and past activities are discussed in Garcia1 and Garcia2. The PSTT is one of three teams that form the NASA/MSFC CFD Consortium for Applications in Propulsion Technology (McConnaughey3). The PSTT first applied CFD in the design of the baseline consortium impeller. This impeller was designed for the Space Transportation Main Engine's (STME) fuel turbopump. The STME fuel pump was designed with three impeller stages because a two-stage design was deemed to pose a high developmental risk. The PSTT used CFD to design an impeller whose performance allowed for a two-stage STME fuel pump design. The availability of this design would have lead to a reduction in parts, weight, and cost had the STME reached production. One sample of the baseline consortium impeller was manufactured and tested in a water rig. The test data showed that the impeller performance was as predicted and that a two-stage design for the STME fuel pump was possible with minimal risk. The test data also verified another CFD predicted characteristic of the design that was not desirable. The classical 'jet-wake' pattern at the impeller discharge was strengthened by two aspects of the design: by the high head coefficient necessary for the required pressure rise and by the relatively few impeller exit blades, 12, necessary to reduce manufacturing cost. This 'jet-wake pattern produces an unsteady loading on the diffuser vanes and has, in past rocket engine programs, lead to diffuser structural failure. In industrial
Development of a 3-dimensional flow analysis procedure for axial pump impellers
Kim, Min Hwan; Kim, Jong In; Park, Jin Seok; Huh, Houng Huh; Chang, Moon Hee
1999-06-01
A fluid dynamic analysis procedure was developed using the three-dimensional solid model of an axial pump impeller which was theoretically designed using I-DEAS CAD/CAM/CAE software. The CFD software FLUENT was used in the flow field analysis. The steady-state flow regime in the MCP impeller and diffuser was simulated using the developed procedure. The results of calculation were analyzed to confirm whether the design requirements were properly implemented in the impeller model. The validity of the developed procedure was demonstrated by comparing the calculation results with the experimental data available. The pump performance at the design point could be effectively predicted using the developed procedure. The computed velocity distributions have shown a good agreement with the experimental data except for the regions near the wall. The computed head, however, was over-predicted than the experiment. The design period and cost required for the development of an axial pump impeller can be significantly reduced by applying the proposed methodology. (author). 7 refs., 2 tabs
Study on numerical methods for transient flow induced by speed-changing impeller of fluid machinery
Wu, Dazhuan; Chen, Tao; Wang, Leqin; Cheng, Wentao; Sun, Youbo
2013-01-01
In order to establish a reliable numerical method for solving the transient rotating flow induced by a speed-changing impeller, two numerical methods based on finite volume method (FVM) were presented and analyzed in this study. Two-dimensional numerical simulations of incompressible transient unsteady flow induced by an impeller during starting process were carried out respectively by using DM and DSR methods. The accuracy and adaptability of the two methods were evaluated by comprehensively comparing the calculation results. Moreover, an intensive study on the application of DSR method was conducted subsequently. The results showed that transient flow structure evolution and transient characteristics of the starting impeller are obviously affected by the starting process. The transient flow can be captured by both two methods, and the DSR method shows a higher computational efficiency. As an application example, the starting process of a mixed-flow pump was simulated by using DSR method. The calculation results were analyzed by comparing with the experiment data.
Swarm intelligence based on modified PSO algorithm for the optimization of axial-flow pump impeller
Miao, Fuqing; Kim, Chol Min; Ahn, Seok Young; Park, Hong Seok
2015-01-01
This paper presents a multi-objective optimization of the impeller shape of an axial-flow pump based on the Modified particle swarm optimization (MPSO) algorithm. At first, an impeller shape was designed and used as a reference in the optimization process then NPSHr and η of the axial flow pump were numerically investigated by using the commercial software ANSYS with the design variables concerning hub angle β_h, chord angle β_c, cascade solidity of chord σ_c and maximum thickness of blade H. By using the Group method of data handling (GMDH) type neural networks in commercial software DTREG, the corresponding polynomial representation for NPSHr and η with respect to the design variables were obtained. A benchmark test was employed to evaluate the performance of the MPSO algorithm in comparison with other particle swarm algorithms. Later the MPSO approach was used for Pareto based optimization. Finally, the MPSO optimization result and CFD simulation result were compared in a re-evaluation process. By using swarm intelligence based on the modified PSO algorithm, better performance pump with higher efficiency and lower NPSHr could be obtained. This novel algorithm was successfully applied for the optimization of axial-flow pump impeller shape design
Swarm intelligence based on modified PSO algorithm for the optimization of axial-flow pump impeller
Miao, Fuqing; Kim, Chol Min; Ahn, Seok Young [Pusan National University, Busan (Korea, Republic of); Park, Hong Seok [Ulsan University, Ulsan (Korea, Republic of)
2015-11-15
This paper presents a multi-objective optimization of the impeller shape of an axial-flow pump based on the Modified particle swarm optimization (MPSO) algorithm. At first, an impeller shape was designed and used as a reference in the optimization process then NPSHr and η of the axial flow pump were numerically investigated by using the commercial software ANSYS with the design variables concerning hub angle β{sub h}, chord angle β{sub c}, cascade solidity of chord σ{sub c} and maximum thickness of blade H. By using the Group method of data handling (GMDH) type neural networks in commercial software DTREG, the corresponding polynomial representation for NPSHr and η with respect to the design variables were obtained. A benchmark test was employed to evaluate the performance of the MPSO algorithm in comparison with other particle swarm algorithms. Later the MPSO approach was used for Pareto based optimization. Finally, the MPSO optimization result and CFD simulation result were compared in a re-evaluation process. By using swarm intelligence based on the modified PSO algorithm, better performance pump with higher efficiency and lower NPSHr could be obtained. This novel algorithm was successfully applied for the optimization of axial-flow pump impeller shape design.
Computational fluid dynamics analysis of a mixed flow pump impeller
ATHARVA
International Journal of Engineering, Science and Technology ... From the CFD analysis software and advanced post processing tools the complex flow inside the ... The numerical simulation can provide quite accurate information on the fluid ...
2D and 3D impellers of centrifugal compressors - advantages, shortcomings and fields of application
Galerkin, Y.; Reksrin, A.; Drozdov, A.
2017-08-01
The simplified equations are presented for calculation of inlet dimensions and velocity values for impellers with three-dimensional blades located in axial and radial part of an impeller (3D impeller) and with two-dimensional blades in radial part (2D). Considerations concerning loss coefficients of 3D and 2D impellers at different design flow rate coefficients are given. The tendency of reduction of potential advantages of 3D impellers at medium and small design flow rate coefficients is shown. The data on high-efficiency compressors and stages with 2D impellers coefficients designed by the authors are presented. The reached efficiency level of 88 - 90% makes further increase of efficiency by the application of 3D impellers doubtful. CFD-analysis of stage candidates with medium flow rate coefficient with 3D and 2D impellers revealed specific problems. In some cases the constructive advantage of a 2D impeller is smaller hub ratio. It makes possible the reaching of higher efficiency. From other side, there is a positive tendency of gas turbine drive RPM increase. 3D impellers have no alternative for stages with high flow rate coefficients matching high-speed drive.
Stirling Engine With Radial Flow Heat Exchangers
Vitale, N.; Yarr, George
1993-01-01
Conflict between thermodynamical and structural requirements resolved. In Stirling engine of new cylindrical configuration, regenerator and acceptor and rejector heat exchangers channel flow of working gas in radial direction. Isotherms in regenerator ideally concentric cylinders, and gradient of temperature across regenerator radial rather than axial. Acceptor and rejector heat exchangers located radially inward and outward of regenerator, respectively. Enables substantial increase in power of engine without corresponding increase in diameter of pressure vessel.
Prediction of flow- induced dynamic stress in an axial pump impeller using FEM
Gao, J Y; Hou, Y S; Xi, S Z; Cai, Z H; Yao, P P; Shi, H L
2013-01-01
Axial pumps play an important role in water supply and flood control projects. Along with growing requirements for high reliability and large capacity, the dynamic stress of axial pumps has become a key problem. Unsteady flow is a significant reason which results structural dynamic stress of a pump. This paper reports on a flow-induced dynamic stress simulation in an axial pump impeller at three flow conditions by using FEM code. The pressure pulsation obtained from flow simulation using CFD code was set as the force boundary condition. The results show that the maximum stress of impeller appeared at joint between blade and root flange near trailing edge or joint between blade and root flange near leading edge. The dynamic stress of the two zones was investigated under three flow conditions (0.8Q d , 1.0Q d , 1.1Q d ) in time domain and frequency domain. The frequencies of stress at zones of maximum stress are 22.9Hz and 37.5Hz as the fundamental frequency and its harmonics. The fundamental frequencies are nearly equal to vane passing frequency (22.9 Hz) and 3 times blade passing frequency (37.5Hz). The first dominant frequency at zones of maximum stress is equal to the vane passing frequency due to rotor-stator interaction between the vane and the blade. This study would be helpful for axial pumps in reducing stress, improving structure design and fatigue life
Zhi-Feng Yao
2016-01-01
Full Text Available The turbulent flow in a centrifugal pump impeller is bounded by complex surfaces, including blades, a hub and a shroud. The primary challenge of the flow simulation arises from the generation of a boundary layer between the surface of the impeller and the moving fluid. The principal objective is to evaluate the near-wall solution approaches that are typically used to deal with the flow in the boundary layer for the large-eddy simulation (LES of a centrifugal pump impeller. Three near-wall solution approaches –the wall-function approach, the wall-resolved approach and the hybrid Reynolds averaged Navier–Stoke (RANS and LES approach – are tested. The simulation results are compared with experimental results conducted through particle imaging velocimetry (PIV and laser Doppler velocimetry (LDV. It is found that the wall-function approach is more sparing of computational resources, while the other two approaches have the important advantage of providing highly accurate boundary layer flow prediction. The hybrid RANS/LES approach is suitable for predicting steady-flow features, such as time-averaged velocities and hydraulic losses. Despite the fact that the wall-resolved approach is expensive in terms of computing resources, it exhibits a strong ability to capture a small-scale vortex and predict instantaneous velocity in the near-wall region in the impeller. The wall-resolved approach is thus recommended for the transient simulation of flows in centrifugal pump impellers.
Zoran D Protić
2010-01-01
Full Text Available Geometry analysis of the axial fan impeller, experimentally obtained operating characteristics and experimental investigations of the turbulent swirl flow generated behind the impeller are presented in this paper. Formerly designed and manufactured, axial fan impeller blade geometry (originally designed by Prof. Dr-Ing. Z. Protić† has been digitized using a three-dimensional (3D scanner. In parallel, the same impeller has been modeled by beta version software for modeling axial turbomachines, based on modified classical calculation. These results were compared. Then, the axial fan operating characteristics were measured on the standardized test rig in the Laboratory for Hydraulic Machinery and Energy Systems, Faculty of Mechanical Engineering, University of Belgrade. Optimum blade impeller position was determined on the basis of these results. Afterwards, the impeller with optimum angle, without outlet vanes, was positioned in a circular pipe. Rotational speed has been varied in the range from 500 till 2500rpm. Reynolds numbers generated in this way, calculated for axial velocity component, were in the range from 0,8·105 till 6·105. LDA (Laser Doppler Anemometry measurements and stereo PIV (Particle Image Velocimetry measurements of the 3D velocity field in the swirl turbulent fluid flow behind the axial fan have been performed for each regime. Obtained results point out extraordinary complexity of the structure of generated 3D turbulent velocity fields.
Jamshid M. Nouri
2008-03-01
Full Text Available Mean and rms velocity characteristics of two Newtonian flows at Reynolds numbers of 12,800 (glycerin solution and 48,000 (water and of a non-Newtonian flow (0.2% CMC solution, at a power number similar to the Newtonian glycerin flow in a mixing vessel stirred by a 60° pitched blade impeller have been measured by laser Doppler velocimetry (LDV. The velocity measurements, resolved over 360° and 1.08° of impeller rotation, showed that the mean flow of the two power number matched glycerin and CMC flows were similar to within 3% of the impeller tip velocity and the turbulence intensities generally lower in the CMC flow by up to 5% of the tip velocity. The calculated mean flow quantities showed similar discharge coefficient and pumping efficiency in all three flows and similar strain rate between the two power number matched glycerin and CMC flows; the strain rate of the higher Reynolds number Newtonian flow was found to be slightly higher. The energy balance around the impeller indicated that the CMC flow dissipated up to 9% more of the total input power and converted 7% less into the turbulence compared to the glycerin flow with the same power input which could lead to less effective mixing processes where the micro-mixing is important.
Flow generated by an aerated rushton impeller: two-phase PIV experiments and numerical simulations
Deen, N.G.; Solberg, Tron; Hjertager, H.
2002-01-01
A two-camera PIV technique was used to obtain angle resolved velocity and turbulence data of the flow in a lab-scale stirred tank, equipped with a Rushton turbine. Two cases were investigated: a single-phase flow and a gas-liquid flow. In the former case, the classical radial jet flow pattern
Multi-condition optimization and experimental study of impeller blades in a mixed-flow pump
Houlin Liu
2016-05-01
Full Text Available On the basis of design of experiment and numerical simulation, a reliable optimization method for blades of a mixed-flow pump is proposed with the maximum weighted average efficiency at multi-conditions as optimum objective. First, the performance of the model pump was measured and the test results were used to validate the simulation method. To improve the simulation accuracy, the check of the grid independence and the comparison of different turbulence models were done in detail. Then, the method of design of experiment for key geometrical parameters was used to obtain the optimization scheme. The maximum weighted average efficiency of pump at three operation conditions was chosen as optimum objective. The optimum solution was gotten and confirmed by the experiment. The results demonstrate that efficiency of the mixed-flow pump with optimized impeller increases by 3.9%, and the high-efficiency zone is increased from 0.021 to 0.040.
Numerical Analysis for un-baffled Mixing Tank Agitated by Two Types of Impellers
Ammar Ashour Akesh
2018-02-01
Full Text Available The effect of impeller flow type and rotation speed on the fluid in mixing tank design under standard configurations investigated to analyses the fluid velocity, turbulent intensity and path lines. In this theoretical study, the fluid motion inside the mixing tank was investigated by solving Navier-Stokes equation and standard k-ε turbulent model in 3-dimensions, for incompressible and turbulent flow. Two types of flow with three types of impellers were investigated, axial-flow with (Lightnin200 and generic impellers and radial-flow with (Rushton turbine. All impellers evaluated under rotation velocity variation between 10 – 115 rpm. The results showed a direct proportional relationship between the impeller and turbine rotation speed with the fluid velocity in mixing vessel. Also, this case matches with the turbulent intensity and path lines.
Han, Feng Hui; Mao, Yi Jun; Tan, Ji Jian
2016-01-01
Radial inlets are typical upstream components of multistage centrifugal compressors. Unlike axial inlets, radial inlets generate additional flow loss and introduce flow distortions at impeller inlets. Such distortions negatively affect the aerodynamic performance of compressor stages. In this study, industrial centrifugal compressor stages with different radial inlets are investigated via numerical simulations. Two reference models were built, simulated, and compared with each original compressor stage to analyze the respective and coupling influences of flow loss and inlet distortions caused by radial inlets on the performances of the compressor stage and downstream components. Flow loss and inlet distortions are validated as the main factors through which radial inlets negatively affect compressor performance. Results indicate that flow loss inside radial inlets decreases the performance of the whole compressor stage but exerts minimal effect on downstream components. By contrast, inlet distortions induced by radial inlets negatively influence the performance of the whole compressor stage and exert significant effects on downstream components. Therefore, when optimizing radial inlets, the reduction of inlet distortions might be more effective than the reduction of flow loss. This research provides references and suggestions for the design and improvement of radial inlets
Han, Feng Hui; Mao, Yi Jun [School of Energy and Power Engineering, Xi' an Jiaotong University, Xi' an (China); Tan, Ji Jian [Dept. of Research and Development, Shenyang Blower Works Group Co., Ltd., Shenyang (China)
2016-11-15
Radial inlets are typical upstream components of multistage centrifugal compressors. Unlike axial inlets, radial inlets generate additional flow loss and introduce flow distortions at impeller inlets. Such distortions negatively affect the aerodynamic performance of compressor stages. In this study, industrial centrifugal compressor stages with different radial inlets are investigated via numerical simulations. Two reference models were built, simulated, and compared with each original compressor stage to analyze the respective and coupling influences of flow loss and inlet distortions caused by radial inlets on the performances of the compressor stage and downstream components. Flow loss and inlet distortions are validated as the main factors through which radial inlets negatively affect compressor performance. Results indicate that flow loss inside radial inlets decreases the performance of the whole compressor stage but exerts minimal effect on downstream components. By contrast, inlet distortions induced by radial inlets negatively influence the performance of the whole compressor stage and exert significant effects on downstream components. Therefore, when optimizing radial inlets, the reduction of inlet distortions might be more effective than the reduction of flow loss. This research provides references and suggestions for the design and improvement of radial inlets.
Sung Kim
2014-01-01
Full Text Available This paper describes a numerical study on the improvement of suction performance and hydraulic efficiency of a mixed-flow pump by impellers. The design of these impellers was optimized using a commercial CFD (computational fluid dynamics code and DOE (design of experiments. The design variables of meridional plane and vane plane development were defined for impeller design. In DOE, variables of inlet part were selected as main design variables in meridional plane, and incidence angle was selected in vane plane development. The verification of the experiment sets that were generated by 2k factorial was done by numerical analysis. The objective functions were defined as the NPSHre (net positive suction head required, total efficiency, and total head of the impellers. The importance of the geometric design variables was analyzed using 2k factorial designs. The interaction between the NPSHre and total efficiency, according to the meridional plane and incidence angle, was discussed by analyzing the 2k factorial design results. The performance of optimally designed model was verified by experiments and numerical analysis and the reliability of the model was retained by comparison of numerical analysis and comparative analysis with the reference model.
Retrofit of CD-6 (Smith) impeller in fermentation vessels.
Junker, B H; Mann, Z; Hunt, G
2000-10-01
We extended prior studies on the influence of impeller type on fermentation performance to include a novel low-power-number, high-efficiency radial flow impeller, the CD-6, possessing six curved blades on a disk turbine. Dual impeller combinations of CD-6/CD-6, CD-6/Maxflo T, and CD-6/HE-3 were compared with Rushton/Rushton and Maxflo T/Maxflo T base cases. Qualitative comparisons of unaerated and aerated power draw in both water and glycerol were conducted. These suggested minimal power drops with aeration for dual CD-6 impellers and hybrids containing the CD-6 impeller design. We also examined fermentation performance for Streptomyces and Glarea secondary metabolite fermentations. A qualitative comparison of the data suggested that dual CD-6 impellers and hybrids containing the CD-6 impeller design resulted in reasonable power draws, improved mass transfer rates with airflow increases, and acceptable peak titers. These arrangements may warrant further study under a wider range of production conditions.
Investigation of Two-Phase Flow in AxialCentrifugal Impeller by Hydrodynamic Modeling Methods
V. O. Lomakin
2014-01-01
Full Text Available The article provides a methodology to study the flow in the wet part of the pump with fundamentally new axial-centrifugal impeller by methods of hydrodynamic modeling in the software package STAR CCM +. The objective of the study was to determine the normal and cavitation characteristics of the pump with a new type of wet part, as well as optimization of the geometrical parameters of the pump. Authors solved this problem using an example of the hot coolant pump, which should meet high requirements for cavitation quality and efficiency (hydraulic efficiency up to 87%, critical value of NPSH to 2.2 m.Also, the article focuses on the methods of numerical solution of two-phase flow simulation in a pump that are needed for a more accurate simulation of cavitation in the pump and research work in liquids with high gas content.Hydrodynamic modeling was performed on a computing cluster at the department E-10 of BMSTU for pump flow simulation in unsteady statement of problem using the computational grid size to 1.5 million cells. Simultaneously, the experimental model of the pump was made by 3D printing and tested at the stand in the BMSTU. Test results, which were compared with the calculated data are also given in the article. Inaccuracy of the calculation of pump head does not exceed 5%.The simulation results may be of interest to specialists in the field of hydrodynamic modeling, and for designers of such pumps. The authors also report production of a full-length prototype of the pump in order to conduct further testing for the verification of the data in the article, primarily in terms of cavitation characteristics.
On radial flow between parallel disks
Wee, A Y L; Gorin, A
2015-01-01
Approximate analytical solutions are presented for converging flow in between two parallel non rotating disks. The static pressure distribution and radial component of the velocity are developed by averaging the inertial term across the gap in between parallel disks. The predicted results from the first approximation are favourable to experimental results as well as results presented by other authors. The second approximation shows that as the fluid approaches the center, the velocity at the mid channel slows down which is due to the struggle between the inertial term and the flowrate. (paper)
Yue Hao
2017-01-01
Full Text Available The energy performance and radial force of a mixed flow pump with symmetrical and unsymmetrical tip clearance are investigated in this paper. As the tip clearance increases, the pump head and efficiency both decrease. The center of the radial force on the principal axis is located at the coordinate origin when the tip clearance is symmetrical, and moves to the third quadrant when the tip clearance is unsymmetrical. Analysis results show that the total radial force on the principal axis is closely related to the fluctuation of mass flow rate in each single flow channel. Unsteady simulations show that the dominant frequencies of radial force on the hub and blade correspond to the blade number, vane number, or double blade number because of the rotor stator interaction. The radial force on the blade pressure side decreases with the tip clearance increase because of leakage flow. The unsymmetrical tip clearances in an impeller induce uneven leakage flow rate and then result in unsymmetrical work ability of each blade and flow pattern in each channel. Thus, the energy performance decreases and the total radial force increases for a mixed flow pump with unsymmetrical tip clearance.
A Numerical Study on the Impeller Meridional Curvature of High Pressure Multistage Pump
Kim, Deok Su; Jean, Sang Gyu; Mamatov, Sanjar [Hyosung Goodsprings, Inc., Busan (Korea, Republic of); Park, Warn Gyu [Pusan Nat’l Univ., Busan (Korea, Republic of)
2017-07-15
This paper presents the hydraulic design an impeller and radial diffuser of a high-pressure multistage pump for reverse osmosis. The flow distribution and hydraulic performance for the meridional design of the impeller were analyzed numerically. Optimization was conducted based on the response surface method by varying the hub and shroud meridional curvatures, while maintaining the impeller outlet diameter, outlet width, and eye diameter constant. The analysis results of the head and efficiency with the variation in the impeller meridional profile showed that angle of the front shroud near the impeller outlet (εDs) had the highest effect on head increase, while the hub inlet length (d1i) and shroud curvature (Rds) had the highest effect on efficiency. From the meridional profile variation, an approximately 0.5% increase in efficiency was observed compared with the base model (case 25).
Kawase, M. [Tokushima University, Tokushima (Japan); Fukutomi, J.; Nakase, Y. [Tokushima University, Tokushima (Japan). Faculty of Engineering
2000-03-25
The winnowing fan used for head feeding type combines draw in air along the axis from the inlet of both sides, and then radially discharges it into scroll. Therefore, the internal flow of this fan shows a strong three-dimensionality and the efficiency is low. In order to improve the efficiency and make the axial distribution of discharge flow uniform, the experimental and numerical investigations were carried out. Numerical results using CFD agree well with experimental ones for the mean flow. It is found that this numerical simulation method is useful for investigation of the effect of blade and casing configurations. Moreover unsteady flow conditions in the impeller though rotations are shown. For example, in the impeller, a vortex formed around the leading edge of the blade, grows connect with another one, reduce and disappear. (author)
Study of fluid flow in baffled vessels stirred by a Rushton standard impeller
Chára, Zdeněk; Kysela, Bohuš; Konfršt, Jiří; Fořt, I.
2016-01-01
Roč. 272, č. 3 (2016), s. 614-628 ISSN 0096-3003 R&D Projects: GA ČR GAP101/12/2274 Institutional support: RVO:67985874 Keywords : trailing vortices * rushton impeller * PIV measurements * DES * numerical simulation Subject RIV: BK - Fluid Dynamics Impact factor: 1.738, year: 2016
Gómez, Eudoxio Ramos; Zenit, Roberto; Rivera, Carlos González; Trápaga, Gerardo; Ramírez-Argáez, Marco A.
2013-04-01
In this work, a 3D numerical simulation using a Euler-Euler-based model implemented into a commercial CFD code was used to simulate fluid flow and turbulence structure in a water physical model of an aluminum ladle equipped with an impeller for degassing treatment. The effect of critical process parameters such as rotor speed, gas flow rate, and the point of gas injection (conventional injection through the shaft vs a novel injection through the bottom of the ladle) on the fluid flow and vortex formation was analyzed with this model. The commercial CFD code PHOENICS 3.4 was used to solve all conservation equations governing the process for this two-phase fluid flow system. The mathematical model was reasonably well validated against experimentally measured liquid velocity and vortex sizes in a water physical model built specifically for this investigation. From the results, it was concluded that the angular speed of the impeller is the most important parameter in promoting better stirred baths and creating smaller and better distributed bubbles in the liquid. The pumping effect of the impeller is increased as the impeller rotation speed increases. Gas flow rate is detrimental to bath stirring and diminishes the pumping effect of the impeller. Finally, although the injection point was the least significant variable, it was found that the "novel" injection improves stirring in the ladle.
Ohashi, Hideo; Sakurai, Akira; Nishihama, Jiro
1989-01-01
Lateral fluid forces on two-dimensional centrifugal impellers, which whirl on a circular orbit in a vaneless diffuser, were reported. Experiments were further conducted for the cases in which a three-dimensional centrifugal impeller, a model of the boiler feed pump, whirls in vaneless and vaned diffusers. The influence of the clearance configuration between the casing and front shroud of the impeller was also investigated. The result indicated that the fluid dynamic interaction between the impeller and the guide vanes induces quite strong fluctuating fluid forces to the impeller, but nevertheless its influence on radial and tangential force components averaged over a whirling orbit is relatively small.
A novel permanent maglev impeller TAH: most requirements on blood pumps have been satisfied.
Qian, K X; Zeng, P; Ru, W M; Yuan, H Y
2003-07-01
Based on the development of an impeller total artificial heart (TAH) (1987) and a permanent maglev (magnetic levitation) impeller pump (2002), as well as a patented magnetic bearing and magnetic spring (1996), a novel permanent maglev impeller TAH has been developed. The device consists of a rotor and a stator. The rotor is driven radially. Two impellers with different dimensions are fixed at both the ends of the rotor. The levitation of the rotor is achieved by using two permanent magnetic bearings, which have double function: radial bearing and axial spring. As the rotor rotates at a periodic changing speed, two pumps deliver the pulsatile flow synchronously. The volume balance between the two pumps is realized due to self-modulation property of the impeller pumps, without need for detection and control. Because the hemo-dynamic force acting on the left impeller is larger than that on the right impeller, and this force during systole is larger than that during diastole, the rotor reciprocates axially once a cycle. This is beneficial to prevent the thrombosis in the pump. Furthermore, a small flow via the gap between stator and rotor from left pump into right pump comes to a full washout in the motor and the pumps. Therefore, it seems neither mechanical wear nor thrombosis could occur. The previously developed prototype impeller TAH had demonstrated that it could operate in animal experiments indefinitely, if the bearing would not fail to work. Expectantly, this novel permanent magnetic levitation impeller TAH with simplicity, implantability, pulsatility, compatibility and durability has satisfied the most requirements on blood pumps and will have more extensive applications in experiments and clinics.
Some aspects of radial flow between parallel disks
Tabatabai, M.; Pollard, A.
1985-01-01
Radial flow of air between two closely spaced parallel disks is examined experimentally. A comprehensive review of the previous work performed on similar flow situations is given by Tabatabai and Pollard. The present paper is a discussion of some of the results obtained so far and offers some observations on the decay of turbulence in this flow. (author)
A user's evaluation of radial flow HEPA filters
Purcell, J.A.
1992-07-01
High efficiency particulate air (HEPA) filters of rectangular cross section have been used to remove particulates and the associated radioactivity from air ventilation streams since the advent of nuclear materials processing. Use of round axial flow HEPA filters is also longstanding. The advantages of radial flow filters in a circular configuration have been well demonstrated in UKAEA during the last 5--7 years. An evaluation of radial flow filters for fissile process gloveboxes reveals several substantial benefits in addition to the advantages claimed in UKAEA Facilities. The radial flow filter may be provided in a favorable geometry resulting in improved criticality safety. The filter configuration lends to in-place testing at the glovebox to exhaust duct interface. This will achieve compliance with DOE Order 6430.1A, Section 99.0.2. Preliminary testing at SRS for radial flow filters manufactured by Flanders Filters, Inc. revealed compliance in all the usual specifications for filtration efficiency, pressure differential and materials of construction. An evaluation, further detailed in this report, indicates that the radial flow HEPA filter should be considered for inclusion in new ventilation system designs
Kabalyk, K.; Kryllowicz, W.
2017-09-01
The study aims to work out a set of recommendations for setting a proper distance between the trailing edge of impeller and the interface boundary, which on the one hand would not be too large to overpredict the impeller efficiency and not too short to introduce artificial wake-like flow structures at diffuser inlet on the other. Three individual two-element stages belonging to three different types known as medium- and low-flow coefficient stages are studied. Besides of the design flow coefficient, the focus is on the influence of impeller tip Mach number on the optimal location of the boundary.
Pumping Capacity of Pitched Blade Impellers in a Tall Vessel with a Draught Tube
J. Brož
2004-01-01
Full Text Available A study was made of the pumping capacity of pitched blade impellers (two, three, four, five and six blade pitched blade impellers with pitch angles α = 35° and 45° coaxially located in a cylindrical pilot plant vessel with cylindrical draught tube provided with a standard dished bottom. The draught tube was equipped with four equally spaced radial baffles above the impeller pumping liquid upwards towards the liquid surface. In all investigated cases the liquid aspect ratio H/T = 1.2 - 1.5, the draught tube / vessel diameter ratios DT /T = 0.2 and 0.4 and the impeller / draught tube diameter ratio D/DT = 0.875. The pumping capacity of the impeller was calculated from the radial profile of the axial component of the mean velocity in the draught tube below the impeller at such an axial distance from the impeller that the rotor does not affect the vorticity of the flow. The mean velocity was measured using a laser Doppler anemometer with forward scatter mode in a transparent draught tube and a transparent vessel of diameter T = 400 mm. Two series of experiments were performed, both of them under a turbulent regime of flow of the agitated liquid. First, the optimum height of the dished bottom was sought, and then the dependences of the dimensionless flow rate criterion and the impeller power number on the number of impeller blades were determined for both pitch angles tested under conditions of optimum ratio HT /DT. It follows from the results of the experiments that the optimum ratio HT /DT = 0.25 when the cross sectional areas of the horizontal flow around the bottom and the vertical inflow to the draught tube are the same. For all the tested pitched blade impellers the impeller power number when α = 45° exceeds the value of this quantity when pitch angle α = 35°, while the flow rate number when α = 35° exceeds this quantity when α = 45°. On the other hand, the absolute values of the impeller power number when the draught tube was
Comparison of Deterministic and Probabilistic Radial Distribution Systems Load Flow
Gupta, Atma Ram; Kumar, Ashwani
2017-12-01
Distribution system network today is facing the challenge of meeting increased load demands from the industrial, commercial and residential sectors. The pattern of load is highly dependent on consumer behavior and temporal factors such as season of the year, day of the week or time of the day. For deterministic radial distribution load flow studies load is taken as constant. But, load varies continually with a high degree of uncertainty. So, there is a need to model probable realistic load. Monte-Carlo Simulation is used to model the probable realistic load by generating random values of active and reactive power load from the mean and standard deviation of the load and for solving a Deterministic Radial Load Flow with these values. The probabilistic solution is reconstructed from deterministic data obtained for each simulation. The main contribution of the work is: Finding impact of probable realistic ZIP load modeling on balanced radial distribution load flow. Finding impact of probable realistic ZIP load modeling on unbalanced radial distribution load flow. Compare the voltage profile and losses with probable realistic ZIP load modeling for balanced and unbalanced radial distribution load flow.
Kawase, M. [Tokushima University, Tokushima (Japan); Fukutomi, J.; Nakase, Y. [Tokushima University, Tokushima (Japan). Faculty of Engineering
2000-03-25
Because of a strong 3-dimensional flow, it is difficult to produce a uniform flow or improve efficiency with winnowing fans. Through experiments with various types of impellers, it was found in an earlier study that a forward-inclined impeller could produce a uniform flow and improve efficiency. It was ten reported in a subsequent study aimed at identifying the mechanism behind this, in which the relationship between velocity and static pressure in an impeller of small inclination angle was examined from the perspective of flow, that flow analysis was effective towards estimating inconsistent flow characteristics. Based on these findings, this project was designed to measure and analyze flow characteristics in a forward-inclined impeller. It was found that forward-inclined impellers have many regions of circulating flow and that the mainstream which moves to the outlet is narrow in effective area. As a result, velocity increases and discharge blow rapidly expands within a short distance. Therefore, good static pressure recovery is obtained. (author)
Radial, sideward and elliptic flow at AGS energies
the sideward flow, the elliptic flow and the radial transverse mass distribution of protons data at. AGS energies. In order to ... data on both sideward and elliptic flow, NL3 model is better at 2 A¡GeV, while NL23 model is at 4–8. A¡GeV. ... port approach RBUU which is based on a coupled set of covariant transport equations for.
Yoshiki Yoshida
2001-01-01
destabilizing in the region of negative precessing speed ratio (-0.3<Ω/ω<0, at the design flow rate; (2 At reduced flow rate, the destabilizing fluid force moments occurred at small positive precessing speed ratio (0.2<Ω/ω<0.4; (3 From the comparison of direct measured fluid force moments with those estimated from the unsteady pressure measured on the front and back casing walls, it was found that the destabilizing moments in the backward precession are mainly caused by the fluid forces on the front surface of the present impeller, where there is large clearance between the back shroud and casing.
The performance of a centrifugal fan with enlarged impeller
Li Chunxi; Song Lingwang; Jia Yakui
2011-01-01
Highlights: → The influence of impeller enlargement is evaluated numerically and experimentally. → Variation equations of the operation points for enlarged impellers are derived. → Impeller enlargement leads to louder fan noise due to reduced impeller-volute gap. - Abstract: The influence of enlarged impeller in unchanged volute on G4-73 type centrifugal fan performance is investigated in this paper. Comparisons are conducted between the fan with original impeller and two larger impellers with the increments in impeller outlet diameter of 5% and 10% respectively in the numerical and experimental investigations. The internal characteristics are obtained by the numerical simulation, which indicate there is more volute loss in the fan with larger impeller. Experiment results show that the flow rate, total pressure rise, shaft power and sound pressure level have increased, while the efficiency have decreased when the fan operates with larger impeller. Variation equations on the performance of the operation points for the fan with enlarged impellers are suggested. Comparisons between experiment results and the trimming laws show that the trimming laws for usual situation can predict the performance of the enlarged fan impeller with less error for higher flow rate, although the situation of application is not in agreement. The noise frequency analysis shows that higher noise level with the larger impeller fan is caused by the reduced impeller-volute gap.
The performance of a centrifugal fan with enlarged impeller
Li Chunxi, E-mail: leechunxi@163.com [School of Energy and Power Engineering, North China Electric Power University, 071003 Baoding, Hebei (China); Song Lingwang [School of Energy and Power Engineering, North China Electric Power University, 071003 Baoding, Hebei (China); Jia Yakui [Hebei Electric Power Design and Research Institute, 050031 Shijiazhuang, Hebei (China)
2011-08-15
Highlights: {yields} The influence of impeller enlargement is evaluated numerically and experimentally. {yields} Variation equations of the operation points for enlarged impellers are derived. {yields} Impeller enlargement leads to louder fan noise due to reduced impeller-volute gap. - Abstract: The influence of enlarged impeller in unchanged volute on G4-73 type centrifugal fan performance is investigated in this paper. Comparisons are conducted between the fan with original impeller and two larger impellers with the increments in impeller outlet diameter of 5% and 10% respectively in the numerical and experimental investigations. The internal characteristics are obtained by the numerical simulation, which indicate there is more volute loss in the fan with larger impeller. Experiment results show that the flow rate, total pressure rise, shaft power and sound pressure level have increased, while the efficiency have decreased when the fan operates with larger impeller. Variation equations on the performance of the operation points for the fan with enlarged impellers are suggested. Comparisons between experiment results and the trimming laws show that the trimming laws for usual situation can predict the performance of the enlarged fan impeller with less error for higher flow rate, although the situation of application is not in agreement. The noise frequency analysis shows that higher noise level with the larger impeller fan is caused by the reduced impeller-volute gap.
Numerical simulation of liquid-metal-flows in radial-toroidal-radial bends
Molokov, S.; Buehler, L.
1993-09-01
Magnetohydrodynamic flows in a U-bend and right-angle bend are considered with reference to the radial-toroidal-radial concept of a self-cooled liquid-metal blanket. The ducts composing bends have rectangular cross-section. The applied magnetic field is aligned with the toroidal duct and perpendicular to the radial ones. At high Hartmann number the flow region is divided into cores and boundary layers of different types. The magnetohydrodynamic equations are reduced to a system of partial differential equations governing wall electric potentials and the core pressure. The system is solved numerically by two different methods. The first method is iterative with iteration between wall potential and the core pressure. The second method is a general one for the solution of the core flow equations in curvilinear coordinates generated by channel geometry and magnetic field orientation. Results obtained are in good agreement. They show, that the 3D-pressure drop of MHD flows in a U-bend is not a critical issue for blanket applications. (orig./HP) [de
Bennecke, W.M.; Wood, S.H.
1992-01-01
An impeller flowmeter was used with a COLOG digital acquisition system to determine existing borehole flows, to compare with previous logging results, and to acquire flow measurements of vertical cross-flow of water in the wells between permeable zones in the open-hole intervals. The direction of flow found was predominantly downward with velocities ranging from 0-30 ft/min. Some flow reversals were noted and attributed to nearby pumping wells. USGS wells 44 and 46 were studied in September, 1991 near the Idaho Chemical Processing Plant (ICPP). The results showed a usual overall flow direction downward with flow entering the wells at around 510 to 600 ft. below the land surface. Water exited these wells at lower levels around 550 to 580 ft. Flow velocities ranged up to 24 ft/min. Using published aquifer parameters, the rate of propagation of a pressure change in an aquifer was calculated for the well CPP-2 turning on and off, at 3100 gpm
Model for radial gas fraction profiles in vertical pipe flow
Lucas, D.; Krepper, E.; Prasser, H.M.
2001-01-01
A one-dimensional model is presented, which predicts the radial volume fraction profiles from a given bubble size distribution. It bases on the assumption of an equilibrium of the forces acting on a bubble perpendicularly to the flow path (non drag forces). For the prediction of the flow pattern this model could be used within an procedure together with appropriate models for local bubble coalescence and break-up. (orig.)
Secondary Flow Phenomena in Rotating Radial Straight Pipes
Cheng, K. C.; Wang, Liqiu
1995-01-01
Flow visualization results for secondary flow phenomena near the exit of a rotating radial-axis straight pipe (length ࡁ = 82 cm, inside diameter d = 3.81 cm, ࡁ/d 21.52) are presented to study the stabilizing (relaminarization) and destabilizing (early transition from laminar to turbulent flow) effects of Coriolis forces for Reynolds numbers Re = 500 ∼ 4,500 and rotating speeds n = 0 ∼ 200 rpm. The flow visualization was realised by smoke injection method. The main features of the trans...
PIV investigation of the flow induced by a passive surge control method in a radial compressor
Guillou, Erwann; Gancedo, Matthieu; Gutmark, Ephraim [University of Cincinnati, Department of Aerospace Engineering, Cincinnati, OH (United States); Mohamed, Ashraf [Honeywell Turbo Technologies, Greater Los Angeles, CA (United States)
2012-09-15
Due to recent emission regulations, the use of turbochargers for force induction of internal combustion engines has increased. Actually, the trend in diesel engines is to downsize the engine by use of turbochargers that operate at higher pressure ratios. Unfortunately, increasing the impeller rotational speed of turbocharger radial compressors tends to reduce their range of operation, which is limited at low mass flow rate by the occurrence of surge. In order to extend the operability of turbochargers, compressor housings can be equipped with a passive surge control device such as a ''ported shroud.'' This specific casing treatment has been demonstrated to enhance the surge margin with minor negative impact on the compressor efficiency. However, the actual working mechanisms of the system remain not well understood. Hence, in order to optimize the design of the ported shroud, it is crucial to identify the dynamic flow changes induced by the implementation of the device to control instabilities. From the full dynamic survey of the compressor performance characteristics obtained with and without ported shroud, specific points of operation were selected to carry out planar flow visualization. At normal working, both standard and stereoscopic particle imaging velocimetry (PIV) measurements were performed to evaluate instantaneous and mean velocity flow fields at the inlet of the compressor. At incipient and full surge, phase-locked PIV measurements were added. As a result, satisfying characterization of the compressor instabilities was provided at different operational speeds. Combining transient pressure data and PIV measurements, the time evolution of the complex flow patterns occurring at surge was reconstructed and a better insight into the bypass mechanism was achieved. (orig.)
PIV investigation of the flow induced by a passive surge control method in a radial compressor
Guillou, Erwann; Gancedo, Matthieu; Gutmark, Ephraim; Mohamed, Ashraf
2012-09-01
Due to recent emission regulations, the use of turbochargers for force induction of internal combustion engines has increased. Actually, the trend in diesel engines is to downsize the engine by use of turbochargers that operate at higher pressure ratios. Unfortunately, increasing the impeller rotational speed of turbocharger radial compressors tends to reduce their range of operation, which is limited at low mass flow rate by the occurrence of surge. In order to extend the operability of turbochargers, compressor housings can be equipped with a passive surge control device such as a "ported shroud." This specific casing treatment has been demonstrated to enhance the surge margin with minor negative impact on the compressor efficiency. However, the actual working mechanisms of the system remain not well understood. Hence, in order to optimize the design of the ported shroud, it is crucial to identify the dynamic flow changes induced by the implementation of the device to control instabilities. From the full dynamic survey of the compressor performance characteristics obtained with and without ported shroud, specific points of operation were selected to carry out planar flow visualization. At normal working, both standard and stereoscopic particle imaging velocimetry (PIV) measurements were performed to evaluate instantaneous and mean velocity flow fields at the inlet of the compressor. At incipient and full surge, phase-locked PIV measurements were added. As a result, satisfying characterization of the compressor instabilities was provided at different operational speeds. Combining transient pressure data and PIV measurements, the time evolution of the complex flow patterns occurring at surge was reconstructed and a better insight into the bypass mechanism was achieved.
Forces on Centrifugal Pump Impellers
Jery, Belgacem; Brennen, Christopher E.; Caughey, Thomas K.; Acosta, Allan
1985-01-01
Forces are exerted on a centrifugal pump impeller, due to the asymmetry of the flow caused by the volute of diffuser, and to the motion of the center of the impeller whenever the shaft whirls. Recent work in the measurement of these forces as a function of the whirl speed to shaft speed ratio, and the influence of the volute, is reviewed. These forces may be decomposed into a steady force, a static stiffness matrix, a damping matrix and an inertia matrix. It is shown that for centrifugal p...
Effects of Impeller-Diffuser Interaction on Centrifugal Compressor Performance
Tan, Choon S.
2003-01-01
This research program focuses on characterizing the effect of impeller-diffuser interactions in a centrifugal compressor stage on its performance using unsteady threedimensional Reynolds-averaged Navier-Stokes simulations. The computed results show that the interaction between the downstream diffuser pressure field and the impeller tip clearance flow can account for performance changes in the impeller. The magnitude of performance change due to this interaction was examined for an impeller with varying tip clearance followed by a vaned or vaneless diffuser. The impact of unsteady impeller-diffuser interaction, primarily through the impeller tip clearance flow, is reflected through a time-averaged change in impeller loss, blockage and slip. The results show that there exists a tip clearance where the beneficial effect of the impeller-diffuser interaction on the impeller performance is at a maximum. A flow feature that consists of tip flow back leakage was shown to occur at design speed for the centrifugal compressor stage. This flow phenomenon is described as tip flow that originates in one passage, flows downstream of the impeller trailing edge and then returns to upstream of the impeller trailing edge of a neighboring passage. Such a flow feature is a source of loss in the impeller. A hypothesis is put forth to show that changing the diffuser vane count and changing impeller-diffuser gap has an analogous effect on the impeller performance. The centrifugal compressor stage was analyzed using diffusers of different vane counts, producing an impeller performance trend similar to that when the impeller-diffuser gap was varied, thus supporting the hypothesis made. This has the implication that the effect impeller performance associated with changing the impeller-diffuser gap and changing diffuser vane count can be described by the non-dimensional ratio of impeller-diffuser gap to diffuser vane pitch. A procedure is proposed and developed for isolating impeller passage
Daniel O. Baun
2003-01-01
Full Text Available A comparison is made between the characteristics of the measured lateral impeller forces and the hydraulic performances of a four- and a five-vane impeller, each operating in a spiral volute, a concentric volute, and a double volute. The pump's rotor was supported in magnetic bearings. In addition to supporting and controlling the rotor motion, the magnetic bearings also served as active load cells and were used to measure the impeller forces acting on the pump's rotor. The lateral impeller force characteristics, as a function of a normalized flow coefficient, were virtually identical in the four- and five-vane impellers in each respective volute type. The measured impeller forces for each volute type were compared with correlations in the literature. The measured forces from the double volute configurations agreed with the forces from a correlation model over the full flow range. Single volute configurations compared well with the predictions of a published correlation at high flow rates, ϕ/ϕn>0.5. Concentric volute configurations compared well with a published correlation at low flow rates, ϕ/ϕn<0.4. The head-versus-flow characteristics of the four-vane impeller in each volute type were stable over a greater flow range than the corresponding characteristics of the five-vane impeller. At higher flow rates in the stable region of the head's characteristic curves near the best efficiency point, the five-vane impeller produced higher head than did the four-vane impeller in each volute type.
Modulation of radial blood flow during Braille character discrimination task.
Murata, Jun; Matsukawa, K; Komine, H; Tsuchimochi, H
2012-03-01
Human hands are excellent in performing sensory and motor function. We have hypothesized that blood flow of the hand is dynamically regulated by sympathetic outflow during concentrated finger perception. To identify this hypothesis, we measured radial blood flow (RBF), radial vascular conductance (RVC), heart rate (HR), and arterial blood pressure (AP) during Braille reading performed under the blind condition in nine healthy subjects. The subjects were instructed to read a flat plate with raised letters (Braille reading) for 30 s by the forefinger, and to touch a blank plate as control for the Braille discrimination procedure. HR and AP slightly increased during Braille reading but remained unchanged during the touching of the blank plate. RBF and RVC were reduced during the Braille character discrimination task (decreased by -46% and -49%, respectively). Furthermore, the changes in RBF and RVC were much greater during the Braille character discrimination task than during the touching of the blank plate (decreased by -20% and -20%, respectively). These results have suggested that the distribution of blood flow to the hand is modulated via sympathetic nerve activity during concentrated finger perception.
Limbach, P; Müller, T; Skoda, R
2015-01-01
Commonly, for the simulation of cavitation in centrifugal pumps incompressible flow solvers with VOF kind cavitation models are applied. Since the source/sink terms of the void fraction transport equation are based on simplified bubble dynamics, empirical parameters may need to be adjusted to the particular pump operating point. In the present study a barotropic cavitation model, which is based solely on thermodynamic fluid properties and does not include any empirical parameters, is applied on a single flow channel of a pump impeller in combination with a time-explicit viscous compressible flow solver. The suction head curves (head drop) are compared to the results of an incompressible implicit standard industrial CFD tool and are predicted qualitatively correct by the barotropic model. (paper)
Jonker, Jan B.; van Essen, T.G.; van Essen, T.G.
1997-01-01
A finite element based method has been developed for computing time-averaged fluid-induced radial excitation forces and rotor dynamic forces on a two-dimensional centrifugal impeller rotating and whirling in a volute casing. In this method potential flow theory is used, which implies the assumption
Disposable MagLev centrifugal blood pump utilizing a cone-shaped impeller.
Hijikata, Wataru; Sobajima, Hideo; Shinshi, Tadahiko; Nagamine, Yasuyuki; Wada, Suguru; Takatani, Setsuo; Shimokohbe, Akira
2010-08-01
To enhance the durability and reduce the blood trauma of a conventional blood pump with a cone-shaped impeller, a magnetically levitated (MagLev) technology has been applied to the BioPump BPX-80 (Medtronic Biomedicus, Inc., Minneapolis, MN, USA), whose impeller is supported by a mechanical bearing. The MagLev BioPump (MagLev BP), which we have developed, has a cone-shaped impeller, the same as that used in the BPX-80. The suspension and driving system, which is comprised of two degrees of freedom, radial-controlled magnetic bearing, and a simply structured magnetic coupling, eliminates any physical contact between the impeller and the housing. To reduce both oscillation of the impeller and current in the coils, the magnetic bearing system utilizes repetitive and zero-power compensators. In this article, we present the design of the MagLev mechanism, measure the levitational accuracy of the impeller and pressure-flow curves (head-quantity [HQ] characteristics), and describe in vitro experiments designed to measure hemolysis. For the flow-induced hemolysis of the initial design to be reduced, the blood damage index was estimated by using computational fluid dynamics (CFD) analysis. Stable rotation of the impeller in a prototype MagLev BP from 0 to 2750 rpm was obtained, yielding a flow rate of 5 L/min against a head pressure in excess of 250 mm Hg. Because the impeller of the prototype MagLev BP is levitated without contact, the normalized index of hemolysis was 10% less than the equivalent value with the BPX-80. The results of the CFD analysis showed that the shape of the outlet and the width of the fluid clearances have a large effect on blood damage. The prototype MagLev BP satisfied the required HQ characteristics (5 L/min, 250 mm Hg) for extracorporeal circulation support with stable levitation of the impeller and showed an acceptable level of hemolysis. The simulation results of the CFD analysis indicated the possibility of further reducing the blood damage of
Kawashima, Ryunosuke; Kanemoto, Toshiaki; Sakamoto, Kengo; Uno, Mitsuo
2010-06-01
The authors have proposed the unique centrifugal pump, in which the impeller dose not have the driving shaft but is driven by the magnetic induction, namely Lorentz force, without the stay. Then, the rotating posture of the impeller is not stable, just like UFO. To make the rotating posture of the impeller stable irrespective of the operating condition, the pressure in the impeller casing was investigated experimentally while the impeller rotates at the steady state, as the preliminarily stage. The pressure, as well known, fluctuates periodically in response to the blade number. Besides, the pressure on the impeller shrouds decreases with the increase of the gap between the front shroud and the suction cover where the water leaks to the suction pipe, and is distorted in the peripheral direction. Such pressure conditions contribute directly to the hydraulic force acting on the impeller. The unstable behaviors of the impeller are induced from the above hydraulic forces, which change unsteadily in the radial and the peripheral directions in the impeller casing. The forces are affected by not only the operating condition but also the rotating posture of the impeller.
Guillou, Erwann
Due to recent emission regulations, the use of turbochargers for force induction of internal combustion engines has increased. Actually, the trend in diesel engines is to downsize the engine by use of turbochargers that operate at higher pressure ratio. Unfortunately, increasing the rotational speed tends to reduce the turbocharger radial compressor range of operation which is limited at low mass flow rate by the occurrence of surge. In order to extent the operability of turbochargers, compressor housings can be equipped with a passive surge control device also known as ported shroud. This specific casing treatment has been demonstrated to enhance surge margin with minor negative impact on the compressor efficiency. However, the actual working mechanisms of the bypass system remain not well understood. In order to optimize the design of the ported shroud, it is then crucial to identify the dynamic flow changes induced by the implementation of the device to control instabilities. Experimental methods were used to assess the development of instabilities from stable, stall and eventually surge regimes of a ported shroud centrifugal compressor. Systematic comparison was conducted with the same compressor design without ported shroud. Hence, the full pressure dynamic survey of both compressors' performance characteristics converged toward two different and probably interrelated driving mechanisms to the development and/or propagation of unsteadiness within each compressor. One related the pressure disturbances at the compressor inlet, and notably the more apparent development of perturbations in the non-ported compressor impeller, whereas the other was attributed to the pressure distortions induced by the presence of the tongue in the asymmetric design of the compressor volute. Specific points of operation were selected to carry out planar flow measurements. At normal working, both standard and stereoscopic particle imaging velocimetry (PIV) measurements were performed
Radially sheared azimuthal flows and turbulent transport in a cylindrical helicon plasma device
Tynan, G R; Burin, M J; Holland, C; Antar, G; Diamond, P H
2004-01-01
A radially sheared azimuthal flow is observed in a cylindrical helicon plasma device. The shear flow is roughly azimuthally symmetric and contains both time-stationary and slowly varying components. The turbulent radial particle flux is found to peak near the density gradient maximum and vanishes at the shear layer location. The shape of the radial plasma potential profile associated with the azimuthal E x B flow is predicted accurately by theory. The existence of the mean shear flow in a plasma with finite flow damping from ion-neutral collisions and no external momentum input implies the existence of radial angular momentum transport from the turbulent Reynolds-stress
Radial collective flow in heavy-ion collisions at intermediate energies
Borderie, B.
1996-11-01
The production of radial collective flow is associated with collisions leading to sources which undergo multifragmentation/explosion processes. After a theoretical survey of possible causes of production of radial flow, methods used to derive experimental values are discussed. Finally, a large set of data is presented which can be used to study and disentangle the different effects leading to radial collective flow. The dominant role of compression in the lower energy domain is emphasized. (author)
JOHN WILLIAM BRANCH
2007-01-01
Full Text Available La creación de modelos de objetos reales es una tarea compleja para la cual se ha visto que el uso de técnicas tradicionales de modelamiento tiene restricciones. Para resolver algunos de estos problemas, los sensores de rango basados en láser se usan con frecuencia para muestrear la superficie de un objeto desde varios puntos de vista, lo que resulta en un conjunto de imágenes de rango que son registradas e integradas en un modelo final triangulado. En la práctica, debido a las propiedades reflectivas de la superficie, las oclusiones, y limitaciones de acceso, ciertas áreas de la superficie del objeto usualmente no son muestreadas, dejando huecos que pueden crear efectos indeseables en el modelo integrado. En este trabajo, presentamos un nuevo algoritmo para el llenado de huecos a partir de modelos triangulados. El algoritmo comienza localizando la frontera de las regiones donde están los huecos. Un hueco consiste de un camino cerrado de bordes de los triángulos en la frontera que tienen al menos un borde que no es compartido con ningún otro triangulo. El borde del hueco es entonces adaptado mediante un B-Spline donde la variación promedio de la torsión del la aproximación del B-spline es calculada. Utilizando un simple umbral de la variación promedio a lo largo del borde, se puede clasificar automáticamente, entre huecos reales o generados por intervención humana. Siguiendo este proceso de clasificación, se usa entonces una versión automatizada del interpolador de funciones de base radial para llenar el interior del hueco usando los bordes vecinos.
Impeller inlet geometry effect on performance improvement for centrifugal pumps
Luo, Xianwu; Zhang, Yao; Peng, Junqi; Xu, Hongyuan; Yu, Weiping
2008-01-01
This research treats the effect of impeller inlet geometry on performance improvement for a boiler feed pump, who is a centrifugal pump having specific speed of 183 m.m 3 min -1 .min -1 and close type impeller with exit diameter of 450 mm. The hydraulic performance and cavitation performance of the pump have been tested experimentally. In order to improve the pump, five impellers have been considered by extending the blade leading edge or applying much larger blade angle at impeller inlet compared with the original impeller. The 3-D turbulent flow inside those pumps has been analyzed basing on RNG k-ε turbulence model and VOF cavitation model. It is noted that the numerical results are fairly good compared with the experiments. Based on the experimental test and numerical simulation, the following conclusions can be drawn: (1) Impeller inlet geometry has important influence on performance improvement in the case of centrifugal pump. Favorite effects on performance improvement have been achieved by both extending the blade leading edge and applying much larger blade angle at impeller inlet: (2) It is suspected that the extended leading edge have favorite effect for improving hydraulic performance, and the much larger blade angle at impeller inlet have favorite effect for improving cavitation performance for the test pump: (3) Uniform flow upstream of impeller inlet is helpful for improving cavitation performance of the pump
Impeller inlet geometry effect on performance improvement for centrifugal pumps
Luo, Xianwu; Zhang, Yao; Peng, Junqi; Xu, Hongyuan [Tsinghua University, Beijing (China); Yu, Weiping [Zhejiang Pump Works, Zhejiang (China)
2008-10-15
This research treats the effect of impeller inlet geometry on performance improvement for a boiler feed pump, who is a centrifugal pump having specific speed of 183 m.m{sup 3}min{sup -1}.min{sup -1} and close type impeller with exit diameter of 450 mm. The hydraulic performance and cavitation performance of the pump have been tested experimentally. In order to improve the pump, five impellers have been considered by extending the blade leading edge or applying much larger blade angle at impeller inlet compared with the original impeller. The 3-D turbulent flow inside those pumps has been analyzed basing on RNG k-{epsilon} turbulence model and VOF cavitation model. It is noted that the numerical results are fairly good compared with the experiments. Based on the experimental test and numerical simulation, the following conclusions can be drawn: (1) Impeller inlet geometry has important influence on performance improvement in the case of centrifugal pump. Favorite effects on performance improvement have been achieved by both extending the blade leading edge and applying much larger blade angle at impeller inlet: (2) It is suspected that the extended leading edge have favorite effect for improving hydraulic performance, and the much larger blade angle at impeller inlet have favorite effect for improving cavitation performance for the test pump: (3) Uniform flow upstream of impeller inlet is helpful for improving cavitation performance of the pump
A visual study of radial inward choked flow of liquid nitrogen.
Hendricks, R. C.; Simoneau, R. J.; Hsu, Y. Y.
1973-01-01
Data and high speed movies were acquired on pressurized subcooled liquid nitrogen flowing radially inward through a 0.0076 cm gap. The stagnation pressure ranged from 0.7 to 4 MN/sq m. Steady radial inward choked flow appears equivalent to steady choked flow through axisymmetric nozzles. Transient choked flows through the radial gap are not uniform and the discharge pattern appears as nonuniform impinging jets. The critical mass flow rate data for the transient case appear different from those for the steady case. On the mass flow rate vs pressure map, the slope and separation of the isotherms appear to be less for transient than for steady radial choked flow.
Preliminary design of RDE feedwater pump impeller
Sri Sudadiyo
2018-01-01
Nowadays, pumps are being widely used in the thermal power generation including nuclear power plants. Reaktor Daya Experimental (RDE) is a proposed nuclear reactor concept for the type of nuclear power plant in Indonesia. This RDE has thermal power 10 MW th , and uses a feedwater pump within its steam cycle. The performance of feedwater pump depends on size and geometry of impeller model, such as the number of blades and the blade angle. The purpose of this study is to perform a preliminary design on an impeller of feedwater pump for RDE and to simulate its performance characteristics. The Fortran code is used as an aid in data calculation in order to rapidly compute the blade shape of feedwater pump impeller, particularly for a RDE case. The calculations analyses is solved by utilizing empirical correlations, which are related to size and geometry of a pump impeller model, while performance characteristics analysis is done based on velocity triangle diagram. The effect of leakage, pass through the impeller due to the required clearances between the feedwater pump impeller and the volute channel, is also considered. Comparison between the feedwater pump of HTR-10 and of RDE shows similarity in the trend line of curve shape. These characteristics curves will be very useful for the values prediction of performance of a RDE feedwater pump. Preliminary design of feedwater pump provides the size and geometry of impeller blade model with 5-blades, inlet angle 14.5 degrees, exit angle 25 degrees, inside diameter 81.3 mm, exit diameter 275.2 mm, thickness 4.7 mm, and height 14.1 mm. In addition, the optimal values of performance characteristics were obtained when flow capacity was 4.8 kg/s, fluid head was 29.1 m, shaft mechanical power was 2.64 kW, and efficiency was 52 % at rotational speed 1750 rpm. (author)
Design of a centrifugal compressor impeller using multi-objective optimization algorithm
Kim, Jin Hyuk; Husain, Afzal; Kim, Kwang Yong; Choi, Jae Ho
2009-01-01
This paper presents a design optimization of a centrifugal compressor impeller with hybrid multi-objective evolutionary algorithm (hybrid MOEA). Reynolds-averaged Navier-Stokes equations with shear stress transport turbulence model are discretized by finite volume approximations and solved on hexahedral grids for flow analyses. Two objectives, i.e., isentropic efficiency and total pressure ratio are selected with four design variables defining impeller hub and shroud contours in meridional contours to optimize the system. Non-dominated Sorting of Genetic Algorithm (NSGA-II) with ε-constraint strategy for local search coupled with Radial Basis Neural Network model is used for multi-objective optimization. The optimization results show that isentropic efficiencies and total pressure ratios of the five cluster points at the Pareto-optimal solutions are enhanced by multi-objective optimization.
Design of a centrifugal compressor impeller using multi-objective optimization algorithm
Kim, Jin Hyuk; Husain, Afzal; Kim, Kwang Yong [Inha University, Incheon (Korea, Republic of); Choi, Jae Ho [Samsung Techwin Co., Ltd., Changwon (Korea, Republic of)
2009-07-01
This paper presents a design optimization of a centrifugal compressor impeller with hybrid multi-objective evolutionary algorithm (hybrid MOEA). Reynolds-averaged Navier-Stokes equations with shear stress transport turbulence model are discretized by finite volume approximations and solved on hexahedral grids for flow analyses. Two objectives, i.e., isentropic efficiency and total pressure ratio are selected with four design variables defining impeller hub and shroud contours in meridional contours to optimize the system. Non-dominated Sorting of Genetic Algorithm (NSGA-II) with {epsilon}-constraint strategy for local search coupled with Radial Basis Neural Network model is used for multi-objective optimization. The optimization results show that isentropic efficiencies and total pressure ratios of the five cluster points at the Pareto-optimal solutions are enhanced by multi-objective optimization.
Interpreting Aerodynamics of a Transonic Impeller from Static Pressure Measurements
Fangyuan Lou
2018-01-01
Full Text Available This paper investigates the aerodynamics of a transonic impeller using static pressure measurements. The impeller is a high-speed, high-pressure-ratio wheel used in small gas turbine engines. The experiment was conducted on the single stage centrifugal compressor facility in the compressor research laboratory at Purdue University. Data were acquired from choke to near-surge at four different corrected speeds (Nc from 80% to 100% design speed, which covers both subsonic and supersonic inlet conditions. Details of the impeller flow field are discussed using data acquired from both steady and time-resolved static pressure measurements along the impeller shroud. The flow field is compared at different loading conditions, from subsonic to supersonic inlet conditions. The impeller performance was strongly dependent on the inducer, where the majority of relative diffusion occurs. The inducer diffuses flow more efficiently for inlet tip relative Mach numbers close to unity, and the performance diminishes at other Mach numbers. Shock waves emerging upstream of the impeller leading edge were observed from 90% to 100% corrected speed, and they move towards the impeller trailing edge as the inlet tip relative Mach number increases. There is no shock wave present in the inducer at 80% corrected speed. However, a high-loss region near the inducer throat was observed at 80% corrected speed resulting in a lower impeller efficiency at subsonic inlet conditions.
Flow rate dependency of critical wall shear stress in a radial-flow cell
Detry, J.G.; Jensen, Bo Boye Busk; Sindic, M.
2009-01-01
In the present work, a radial-flow cell was used to study the removal of starch particle aggregates from several solid substrates (glass, stainless steel, polystyrene and PTFE) in order to determine the critical wall shear stress value for each case. The particle aggregates were formed by aspersion...... of a water or ethanol suspension of starch granules on the surfaces. Depending on the substrate and on the suspending liquid, the aggregates differed in size and shape. Aggregate removal was studied at two flow rates. At the lower flow rate (Re-inlet = 955), the values of critical wall shear stress...... for the different surfaces suggested that capillary forces were, for all of them, playing an important role in aggregate adhesion since aqueous based aggregates were always more difficult to remove. At the higher flow rate (Re-inlet = 2016) the critical wall shear stress increased as a result of the change...
Flow control by combining radial pulsation and rotation of a cylinder in uniform flow
Oualli, H.; Hanchi, S.; Bouabdallah, A.; Gad-El-Hak, M.
2008-11-01
Flow visualizations and hot-wire measurements are carried out to study a circular cylinder undergoing simultaneous radial pulsation and rotation and placed in a uniform flow. The Reynolds number is in the range of 1,000--22,000, for which transition in the shear layers and near wake is expected. Our previous experimental and numerical investigations in this subcritical flow regime have established the existence of an important energy transfer mechanism from the mean flow to the fluctuations. Radial pulsations cause and enhance that energy transfer. Certain values of the amplitude and frequency of the pulsations lead to negative drag (i.e. thrust). The nonlinear interaction between the Magnus effect induced by the steady rotation of the cylinder and the near-wake modulated by the bluff body's pulsation leads to alteration of the omnipresent Kármán vortices and the possibility of optimizing the lift-to-drag ratio as well as the rates of heat and mass transfer. Other useful applications include the ability to enhance or suppress the turbulence intensity, and to avoid the potentially destructive lock-in phenomenon in the wake of bridges, electric cables and other structures.
Ida, Katsumi
2001-01-01
The structure of the radial electric field and toroidal/poloidal flow is discussed for the high temperature plasma in toroidal systems, tokamak and Heliotron type magnetic configurations. The spontaneous toroidal and poloidal flows are observed in the plasma with improved confinement. The radial electric field is mainly determined by the poloidal flow, because the contribution of toroidal flow to the radial electric field is small. The jump of radial electric field and poloidal flow are commonly observed near the plasma edge in the so-called high confinement mode (H-mode) plasmas in tokamaks and electron root plasma in stellarators including Heliotrons. In general the toroidal flow is driven by the momentum input from neutral beam injected toroidally. There is toroidal flow not driven by neutral beam in the plasma and it will be more significant in the plasma with large electric field. The direction of these spontaneous toroidal flows depends on the symmetry of magnetic field. The spontaneous toroidal flow driven by the ion temperature gradient is in the direction to increase the negative radial electric field in tokamak. The direction of spontaneous toroidal flow in Heliotron plasmas is opposite to that in tokamak plasma because of the helicity of symmetry of the magnetic field configuration. (author)
One-dimensional analysis of plane and radial thin film flows including solid-body rotation
Thomas, S.; Hankey, W.; Faghri, A.; Swanson, T.
1989-01-01
The flow of a thin liquid film with a free surface along a horizontal plate which emanates from a pressurized vessel is examined by integrating the equations of motion across the thin liquid layer and discretizing the integrated equations using finite difference techniques. The effects of 0-g and solid-body rotation will be discussed. The two cases of interest are plane flow and radial flow. In plane flow, the liquid is considered to be flowing along a channel with no change in the width of the channel, whereas in radial flow the liquid spreads out radially over a disk, so that the area changes along the radius. It is desired to determine the height of the liquid film at any location along the plate of disk, so that the heat transfer from the plate or disk can be found. The possibility that the flow could encounter a hydraulic jump is accounted for.
Radial Flow in a Multiphase Transport Model at FAIR Energies
Soumya Sarkar
2018-01-01
Full Text Available Azimuthal distributions of radial velocities of charged hadrons produced in nucleus-nucleus (AB collisions are compared with the corresponding azimuthal distribution of charged hadron multiplicity in the framework of a multiphase transport (AMPT model at two different collision energies. The mean radial velocity seems to be a good probe for studying radial expansion. While the anisotropic parts of the distributions indicate a kind of collective nature in the radial expansion of the intermediate “fireball,” their isotropic parts characterize a thermal motion. The present investigation is carried out keeping the upcoming Compressed Baryonic Matter (CBM experiment to be held at the Facility for Antiproton and Ion Research (FAIR in mind. As far as high-energy heavy-ion interactions are concerned, CBM will supplement the Relativistic Heavy-Ion Collider (RHIC and Large Hadron Collider (LHC experiments. In this context our simulation results at high baryochemical potential would be interesting, when scrutinized from the perspective of an almost baryon-free environment achieved at RHIC and LHC.
Blade bowing effects on radial equilibrium of inlet flow in axial compressor cascades
Han XU
2017-10-01
Full Text Available The circumferentially averaged equation of the inlet flow radial equilibrium in axial compressor was deduced. It indicates that the blade inlet radial pressure gradient is closely related to the radial component of the circumferential fluctuation (CF source item. Several simplified cascades with/without aerodynamic loading were numerically studied to investigate the effects of blade bowing on the inlet flow radial equilibrium. A data reduction program was conducted to obtain the CF source from three-dimensional (3D simulation results. Flow parameters at the passage inlet were focused on and each term in the radial equilibrium equation was discussed quantitatively. Results indicate that the inviscid blade force is the inducement of the inlet CF due to geometrical asymmetry. Blade bowing induces variation of the inlet CF, thus changes the radial pressure gradient and leads to flow migration before leading edge (LE in the cascades. Positive bowing drives the inlet flow to migrate from end walls to mid-span and negative bowing turns it to the reverse direction to build a new equilibrium. In addition, comparative studies indicate that the inlet Mach number and blade loading can efficiently impact the effectiveness of blade bowing on radial equilibrium in compressor design.
Computer program for the analysis of the cross flow in a radial inflow turbine scroll
Hamed, A.; Abdallah, S.; Tabakoff, W.
1977-01-01
A computer program was used to solve the governing of the potential flow in the cross sectional planes of a radial inflow turbine scroll. A list of the main program, the subroutines, and typical output example are included.
Improvement of centrifugal pump performance through addition of splitter blades on impeller pump
Kurniawan, Krisna Eka; Santoso, Budi; Tjahjana, Dominicus Danardono Dwi Prija
2018-02-01
The workable way to improve pump performance is to redesign or modify the impellers of centrifugal pump. The purpose of impeller pump modification is to improve pump efficiency, reduce cross flow, reduce secondary incidence flows, and decrease backflow areas at impeller outlets. Number blades and splitter blades in the impeller are three. The outlet blade angle is 20°, and the rotating speed of impeller is 2400 rpm. The added splitter blades variations are 0.25, 0.375, and 0.5 of the original blade length. The splitter blade placements are on the outer side of the impeller. The addition of splitter blades on the outer side of the impeller with 0.5L increases the pump head until 22% and the pump has 38.66% hydraulic efficiency. The best efficiency point of water flow rate pump (Qbep) was 3.02 × 10-3 m3/s.
Law of nonlinear flow in saturated clays and radial consolidation
无
2007-01-01
It was derived that micro-scale amount level of average pore radius of clay changed from 0.01 to 0.1 micron by an equivalent concept of flow in porous media. There is good agreement between the derived results and test ones. Results of experiments show that flow in micro-scale pore of saturated clays follows law of nonlinear flow. Theoretical analyses demonstrate that an interaction of solid-liquid interfaces varies inversely with permeability or porous radius. The interaction is an important reason why nonlinear flow in saturated clays occurs. An exact mathematical model was presented for nonlinear flow in micro-scale pore of saturated clays. Dimension and physical meanings of parameters of it are definite. A new law of nonlinear flow in saturated clays was established. It can describe characteristics of flow curve of the whole process of the nonlinear flow from low hydraulic gradient to high one. Darcy law is a special case of the new law. A mathematical model was presented for consolidation of nonlinear flow in radius direction in saturated clays with constant rate based on the new law of nonlinear flow. Equations of average mass conservation and moving boundary, and formula of excess pore pressure distribution and average degree of consolidation for nonlinear flow in saturated clay were derived by using an idea of viscous boundary layer, a method of steady state in stead of transient state and a method of integral of an equation. Laws of excess pore pressure distribution and changes of average degree of consolidation with time were obtained. Results show that velocity of moving boundary decreases because of the nonlinear flow in saturated clay. The results can provide geology engineering and geotechnical engineering of saturated clay with new scientific bases. Calculations of average degree of consolidation of the Darcy flow are a special case of that of the nonlinear flow.
Optimization and Inverse Design of Pump Impeller
Miyauchi, S; Matsumoto, H; Sano, M; Kassai, N; Zhu, B; Luo, X; Piao, B
2012-01-01
As for pump impellers, the meridional flow channel and blade-to-blade flow channel, which are relatively independent of each other but greatly affect performance, are designed in parallel. And the optimization design is used for the former and the inverse design is used for the latter. To verify this new design method, a mixed-flow impeller was made. Next, we use Tani's inverse design method for the blade loading of inverse design. It is useful enough to change a deceleration rate freely and greatly. And it can integrally express the rear blade loading of various methods by NACA, Zangeneh and Stratford. We controlled the deceleration rate by shape parameter m, and its value became almost same with Tani's recommended value of the laminar airfoil.
Transverse and radial flow in intermediate energy nucleus-nucleus collisions
Vestfall, D. Gary
1997-01-01
We have studied transverse and radial flow in nucleus-nucleus collisions ranging in energy from 15 to 155 MeV/nucleon. We have measured the impact parameter dependence of the balance energy for Ar + Sc and compared the results with Quantum Molecular Dynamics calculations with and without momentum dependence. We have shown that transverse flow and the balance energy dependence on the isospin of the system using the systems 58 Fe + 58 Fe, 58 Ni + 58 Ni, and 58 Mn + 58 Fe. These results are compared with Boltzmann-Uehling-Uehlenbeck calculations incorporating isospin-dependence. We have measured radial flow for Ar + Sc and find that about 50% of the observed energy is related to radial flow. (author)
Gas flows in radial micro-nozzles with pseudo-shocks
Kiselev, S. P.; Kiselev, V. P.; Zaikovskii, V. N.
2017-12-01
In the present paper, results of an experimental and numerical study of supersonic gas flows in radial micro-nozzles are reported. A distinguishing feature of such flows is the fact that two factors, the nozzle divergence and the wall friction force, exert a substantial influence on the flow structure. Under the action of the wall friction force, in the micro-nozzle there forms a pseudo-shock that separates the supersonic from subsonic flow region. The position of the pseudo-shock can be evaluated from the condition of flow blockage in the nozzle exit section. A detailed qualitative and quantitative analysis of gas flows in radial micro-nozzles is given. It is shown that the gas flow in a micro-nozzle is defined by the complicated structure of the boundary layer in the micro-nozzle, this structure being dependent on the width-to-radius ratio of the nozzle and its inlet-to-outlet pressure ratio.
Radial Flow Effects On A Retreating Rotor Blade
2014-05-01
birds , marine life and even insect wings. In some cases such as helicopters, wind turbines and compres- sors, dynamic stall becomes the primary...on dynamic stall and reverse flow as applied to a helicopter rotor in forward flight and a wind turbine operating at a yaw angle. While great...occurring on a retreating blade with a focus on dynamic stall and reverse flow as applied to a helicopter rotor in forward flight and a wind turbine
Ullum, Ulrik; Wright, Jennifer; Dayi, Oguz; Ecder, Ali; Soulaimani, Azzeddine; Piche, Robert; Kamath, Hemant
2006-01-01
Experimental data, which was acquired in two centrifugal pumps and provided by Grundfos A/S, were analysed to determine if rotating stall could be detected from the velocity and pressure time series. The pressure data, which were uniformly acquired in time at high sample rates(10 kHz), were measured simultaneously in four adjacent di.user channels just downstream of the impeller outlet. The velocity data, which were non-uniformly sampled in time at fairly low rates(100 Hz to 3.5 kHz), were acquired either in or downstream of the impeller. Two di.erent methodologies were employed for detection of stall. The first method, which involved direct analysis of raw data, yielded qualitatively useful flow reversal information from the time series for the radial velocity. The second approach, which was based on power spectrum analysis of velocity and pressure data, could detect the onset and identify the frequency of rotating stall to a satisfactory extent in one of the two pumps. Nearly identical stall frequencies were observed in both velocity and pressure power spectra and this rotating stall phenomenon, which occurred at a very low frequency relative to the impeller speed, did not reveal any noticeable degree of sensitivity to the flow rate. In the other pump, where the available data was limited to velocity time series, the power spectrum analysis was successful in detecting stationary stall for a 6 bladed impeller but did not provide conclusive results for the existence of stall in the case of the 7 bladed impeller. Recommendations on the type of experimental data required for accurate detection of stall are provided based upon the present study
Analysis of the cross flow in a radial inflow turbine scroll
Hamed, A.; Abdallah, S.; Tabakoff, W.
1977-01-01
Equations of motion were derived, and a computational procedure is presented, for determining the nonviscous flow characteristics in the cross-sectional planes of a curved channel due to continuous mass discharge or mass addition. An analysis was applied to the radial inflow turbine scroll to study the effects of scroll geometry and the through flow velocity profile on the flow behavior. The computed flow velocity component in the scroll cross-sectional plane, together with the through flow velocity profile which can be determined in a separate analysis, provide a complete description of the three dimensional flow in the scroll.
Radial flow towards well in leaky unconfined aquifer
Mishra, P. K.; Kuhlman, K. L.
2012-12-01
An analytical solution is developed for three-dimensional flow towards a partially penetrating large- diameter well in an unconfined aquifer bounded below by a leaky aquitard of finite or semi-infinite extent. The analytical solution is derived using Laplace and Hankel transforms, then inverted numerically. Existing solutions for flow in leaky unconfined aquifers neglect the unsaturated zone following an assumption of instantaneous drainage due to Neuman. We extend the theory of leakage in unconfined aquifers by (1) including water flow and storage in the unsaturated zone above the water table, and (2) allowing the finite-diameter pumping well to partially penetrate the aquifer. The investigation of model-predicted results shows that aquitard leakage leads to significant departure from the unconfined solution without leakage. The investigation of dimensionless time-drawdown relationships shows that the aquitard drawdown also depends on unsaturated zone properties and the pumping-well wellbore storage effects.
Three-dimensional flow field measurements in a radial inflow turbine scroll using LDV
Malak, M. F.; Hamed, A.; Tabakoff, W.
1986-01-01
The results of an experimental study of the three-dimensional flow field in a radial inflow turbine scroll are presented. A two-color LDV system was used in the measurement of three orthogonal velocity components at 758 points located throughout the scroll and the unvaned portion of the nozzle. The cold flow experimental results are presented for through-flow velocity contours and the cross velocity vectors.
Suzukawa, K [Ube Industries, Ltd., Tokyo (Japan); Hashimoto, T; Osaka, H [Yamaguchi University, Yamaguchi (Japan). Faculty of Engineering
1997-11-25
The 3-D flow field relative to a rotating paddle blade is acquired by synchronizing LDV measurements with the output of a shaft-mounted encoder. This makes it possible to capture the impeller stream velocity field, including the details of the discharge flow region behind the blades. Mean velocities ensemble-averaged between a specific impeller blade pair (over 90deg) show the extent of periodicity and the passage and structure of the discharge flow region. Pumping capacities are determined at both sides of impeller and tip of impeller, and it is shown that the radial jet is a consequence of fluid entrainment into the discharge flow region. Mean velocities taken in a rotating frame of reference reveal a significant periodic variation near the impeller than those taken in a fixed frame. 13 refs., 12 figs., 1 tab.
Impeller Design of a Centrifugal Fan with Blade Optimization
Yu-Tai Lee
2011-01-01
Full Text Available A method is presented for redesigning a centrifugal impeller and its inlet duct. The double-discharge volute casing is a structural constraint and is maintained for its shape. The redesign effort was geared towards meeting the design volute exit pressure while reducing the power required to operate the fan. Given the high performance of the baseline impeller, the redesign adopted a high-fidelity CFD-based computational approach capable of accounting for all aerodynamic losses. The present effort utilized a numerical optimization with experiential steering techniques to redesign the fan blades, inlet duct, and shroud of the impeller. The resulting flow path modifications not only met the pressure requirement, but also reduced the fan power by 8.8% over the baseline. A refined CFD assessment of the impeller/volute coupling and the gap between the stationary duct and the rotating shroud revealed a reduction in efficiency due to the volute and the gap. The calculations verified that the new impeller matches better with the original volute. Model-fan measured data was used to validate CFD predictions and impeller design goals. The CFD results further demonstrate a Reynolds-number effect between the model- and full-scale fans.
Axial and radial velocities in the creeping flow in a pipe
Zuykov Andrey L'vovich
2014-05-01
Full Text Available The article is devoted to analytical study of transformation fields of axial and radial velocities in uneven steady creeping flow of a Newtonian fluid in the initial portion of the cylindrical channel. It is shown that the velocity field of the flow is two-dimensional and determined by the stream function. The article is a continuation of a series of papers, where normalized analytic functions of radial axial distributions in uneven steady creeping flow in a cylindrical tube with azimuthal vorticity and stream function were obtained. There is Poiseuille profile for the axial velocity in the uniform motion of a fluid at an infinite distance from the entrance of the pipe (at x = ∞, here taken equal to zero radial velocity. There is uniform distribution of the axial velocity in the cross section at the tube inlet at x = 0, at which the axial velocity is constant along the current radius. Due to the axial symmetry of the flow on the axis of the pipe (at r = 0, the radial velocities and the partial derivative of the axial velocity along the radius, corresponding to the condition of the soft function extremum, are equal to zero. The authors stated vanishing of the velocity of the fluid on the walls of the pipe (at r = R , where R - radius of the tube due to its viscous sticking and tightness of the walls. The condition of conservation of volume flow along the tube was also accepted. All the solutions are obtained in the form of the Fourier - Bessel. It is shown that the hydraulic losses at uniform creeping flow of a Newtonian fluid correspond to Poiseuille - Hagen formula.
Choo, Y. K.; Civinskas, K. C.
1985-01-01
The three-dimensional inviscid DENTON code is used to analyze flow through a radial-inflow turbine rotor. Experimental data from the rotor are compared with analytical results obtained by using the code. The experimental data available for comparison are the radial distributions of circumferentially averaged values of absolute flow angle and total pressure downstream of the rotor exit. The computed rotor-exit flow angles are generally underturned relative to the experimental values, which reflect the boundary-layer separation at the trailing edge and the development of wakes downstream of the rotor. The experimental rotor is designed for a higher-than-optimum work factor of 1.126 resulting in a nonoptimum positive incidence and causing a region of rapid flow adjustment and large velocity gradients. For this experimental rotor, the computed radial distribution of rotor-exit to turbine-inlet total pressure ratios are underpredicted due to the errors in the finite-difference approximations in the regions of rapid flow adjustment, and due to using the relatively coarser grids in the middle of the blade region where the flow passage is highly three-dimensional. Additional results obtained from the three-dimensional inviscid computation are also presented, but without comparison due to the lack of experimental data. These include quasi-secondary velocity vectors on cross-channel surfaces, velocity components on the meridional and blade-to-blade surfaces, and blade surface loading diagrams. Computed results show the evolution of a passage vortex and large streamline deviations from the computational streamwise grid lines. Experience gained from applying the code to a radial turbine geometry is also discussed.
Kim, Youn-Jea; Kim, Dong-Won
The effects of casing shapes on the performance and the interaction between an impeller and a casing in a small-size turbo-compressor are investigated. Numerical analysis is conducted for the turbo-compressor with circular and single volute casings from the inlet to a discharge nozzle. The optimum design for each element is important to develop the small-size turbo-compressor using alternative refrigerant as a working fluid. Typically, the rotating speed of the compressor is in the range of 40000-45000rpm because of the small size of an impeller diameter. A blade of an impeller has backswept two-dimensional shape due to tip clearance and a vane diffuser has wedge type. In order to predict the flow pattern inside the entire impeller, the vaneless diffuser and the casing, calculations with multiple frames of reference method between the rotating and stationery parts of the domain are carried out. For compressible turbulent flow fields, the continuity and time-averaged three-dimensional Navier-Stokes equations are employed. To evaluate the performance of two types of casings, the static pressure recovery and loss coefficients are obtained with various flow rates. Also, static pressure distributions around casings are studied for different casing shapes, which are very important to predict the distribution of radial load. To prove the accuracy of numerical results, measurements of static pressure around the casing and pressure difference between the inlet and the outlet of the compressor are performed for the circular casing. The comparison of experimental and numerical results is conducted, and reasonable agreement is obtained.
A theory of self-organized zonal flow with fine radial structure in tokamak
Zhang, Y. Z.; Liu, Z. Y.; Xie, T.; Mahajan, S. M.; Liu, J.
2017-12-01
The (low frequency) zonal flow-ion temperature gradient (ITG) wave system, constructed on Braginskii's fluid model in tokamak, is shown to be a reaction-diffusion-advection system; it is derived by making use of a multiple spatiotemporal scale technique and two-dimensional (2D) ballooning theory. For real regular group velocities of ITG waves, two distinct temporal processes, sharing a very similar meso-scale radial structure, are identified in the nonlinear self-organized stage. The stationary and quasi-stationary structures reflect a particular feature of the poloidal group velocity. The equation set posed to be an initial value problem is numerically solved for JET low mode parameters; the results are presented in several figures and two movies that show the spatiotemporal evolutions as well as the spectrum analysis—frequency-wave number spectrum, auto power spectrum, and Lissajous diagram. This approach reveals that the zonal flow in tokamak is a local traveling wave. For the quasi-stationary process, the cycle of ITG wave energy is composed of two consecutive phases in distinct spatiotemporal structures: a pair of Cavitons growing and breathing slowly without long range propagation, followed by a sudden decay into many Instantons that carry negative wave energy rapidly into infinity. A spotlight onto the motion of Instantons for a given radial position reproduces a Blob-Hole temporal structure; the occurrence as well as the rapid decay of Caviton into Instantons is triggered by zero-crossing of radial group velocity. A sample of the radial profile of zonal flow contributed from 31 nonlinearly coupled rational surfaces near plasma edge is found to be very similar to that observed in the JET Ohmic phase [J. C. Hillesheim et al., Phys. Rev. Lett. 116, 165002 (2016)]. The theory predicts an interior asymmetric dipole structure associated with the zonal flow that is driven by the gradients of ITG turbulence intensity.
On Analysis of Stationary Viscous Incompressible Flow Through a Radial Blade Machine
Neustupa, Tomáš
2010-09-01
The paper is concerned with the analysis of the two dimensional model of incompressible, viscous, stationary flow through a radial blade machine. This type of turbine is sometimes called Kaplan's turbine. In the technical area the use is either to force some regular characteristic to the flow of the medium going through the turbine (flow of melted iron, air conditioning) or to gain some energy from the flowing medium (water). The inflow and outflow part of boundary are in general a concentric circles. The larger one represents an inflow part of boundary the smaller one the outflow part of boundary. Between them are regularly spaced the blades of the machine. We study the existence of the weak solution in the case of nonlinear boundary condition of the "do-nothing" type. The model is interesting for study the behavior of the flow when the boundary is formed by mutually disjoint and separated parts.
Detection and effects of pump low-flow operation
Casada, D.A.; Greene, R.H.
1994-01-01
Operating experience and previous studies performed for the Nuclear Plant Aging Research Program have shown that a significant cause of pump problems and failures can result from low-flow operation. Operation at low-flow rates can create unstable flows within the pump impeller and casing. This condition can result in an increased radial and axial thrust on the rotor, which in turn causes higher shaft stresses, increased shaft deflection, and potential bearing and mechanical seal problems. Two of the more serious results of low-flow pump operation are cavitation and recirculation. Both of these conditions can be characterized by crackling sounds that accompany a substantial increase in vibration and noise level, and a reduction in total head and output capacity. Cavitation is the formation and subsequent collapse of vapor bubbles in any flow that is at an ambient pressure less than the vapor pressure of the liquid medium. It is the collapse of these vapor bubbles against the metal surfaces of the impeller or casing that causes surface pitting, erosion, and deterioration. Pump recirculation, reversal of a portion of the flow back through the impeller, can be potentially more damaging than cavitation. If located at the impeller eye, recirculation damages the inlet areas of the casing. At the impeller tips, recirculation alters the outside diameter of the impeller. If recirculation occurs around impeller shrouds, it damages thrust bearings. Recirculation also erodes impellers, diffusers, and volutes and causes failure of mechanical seals and bearings. This paper reports on a utility pump failure cause by low-flow induced phenomena. ORNL has continued to investigate the results of low-flow pump operations by evaluating the types of measurements and diagnostic techniques that are currently used by licensees to detect pump degradation
Influence of the Constitutive Flow Law in FEM Simulation of the Radial Forging Process
Olivier Pantalé
2013-01-01
Full Text Available Radial forging is a widely used forming process for manufacturing hollow products in transport industry. As the deformation of the workpiece, during the process, is a consequence of a large number of high-speed strokes, the Johnson-Cook constitutive law (taking into account the strain rate seems to be well adapted for representing the material behavior even if the process is performed under cold conditions. But numerous contributions concerning radial forging analysis, in the literature, are based on a simple elastic-plastic formulation. As far as we know, this assumption has yet not been validated for the radial forging process. Because of the importance of the flow law in the effectiveness of the model, our purpose in this paper is to analyze the influence of the use of an elastic-viscoplastic formulation instead of an elastic-plastic one for modeling the cold radial forging process. In this paper we have selected two different laws for the simulations: the Johnson-Cook and the Ludwik ones, and we have compared the results in terms of forging force, product's thickness, strains, stresses, and CPU time. For the presented study we use an AISI 4140 steel, and we denote a fairly good agreement between the results obtained using both laws.
Malak, Malak Fouad; Hamed, Awatef; Tabakoff, Widen
1990-01-01
A two-color LDV system was used in the measurement of three orthogonal velocity components at 758 points located throughout the scroll and the unvaned portion of the nozzle of a radial inflow turbine scroll. The cold flow experimental results are presented for the velocity field at the scroll tongue. In addition, a total pressure loss of 3.5 percent for the scroll is revealed from the velocity measurements combined with the static pressure readings. Moreover, the measurement of the three normal stresses of the turbulence has showed that the flow is anisotropic. Furthermore, the mean velocity components are compared with a numerical solution of the potential flow field using the finite element technique. The theoretical prediction of the exit flow angle variation agrees well with the experimental results. This variation leads to a higher scroll pattern factor which can be avoided by controlling the scroll cross sectional area distribution.
Sato, Michiko; Io, Hiroaki; Tanimoto, Mitsuo; Shimizu, Yoshio; Fukui, Mitsumine; Hamada, Chieko; Horikoshi, Satoshi; Tomino, Yasuhiko
2012-01-01
It is recommended that arteriovenous fistula (AVF) blood flow should be more than 425 ml/min before cannulation. However, the relationship between preoperative radial artery flow (RAF) and postoperative AVF blood flow has still not been examined. Sixty-one patients with end-stage kidney disease (ESKD) were examined. They had an AVF prepared at Juntendo University Hospital from July 2006 through August 2007. Preoperative RAF and postoperative AVF blood flows were measured by ultrasonography. AVF blood flow gradually increased after the operation. AVF blood flow was significantly correlated with preoperative RAF. When preoperative RAF exceeded 21.4 ml/min, AVF blood flow rose to more than 425 ml/min. The postoperative AVF blood flow in the group with RAF of more than 20 ml/min was significantly higher than that in those with less than 20 ml/min. Preoperative RAF of less than 20 ml/min had a significantly high risk of primary AVF failure within 8 months compared with that of more than 20 ml/min. It appears that measurement of RAF by ultrasonography is useful for estimating AVF blood flow postoperatively and can predict the risk of complications in ESKD patients.
Modeling of radial gas fraction profiles for bubble flow in vertical pipes
Lucas, D.; Krepper, E.; Prasser, H.-M. [Forschungszentrum Rossendorf e.V., Institute of Safety Research, Dresden (Germany)
2001-07-01
The paper presents a method for the prediction of radial gas fraction profiles from a given bubble size distribution. The method is based on the assumption of the equilibrium of the forces acting on a bubble perpendicularly to the flow direction. Assuming a large number of bubble size classes radial distributions are calculated separately for all bubble classes. The sum of these distributions is the radial profile of the gas fraction. The results of the model are compared with experimental data for a number of gas and liquid volume flow rates. The experiments were performed at a vertical test loop (inner diameter 50 mm) in FZ-Rossendorf using a wire mesh sensor. The sensor enables the determination of void distributions in the cross section of the loop. A special evaluation procedure supplies bubble size distributions as well as local distributions of bubbles within a predefined interval of bubble sizes. There is a good agreement between experimental and calculated data. In particular the change from wall peaking to core peaking is well predicted. (authors)
Modeling of radial gas fraction profiles for bubble flow in vertical pipes
Lucas, D.; Krepper, E.; Prasser, H.-M.
2001-01-01
The paper presents a method for the prediction of radial gas fraction profiles from a given bubble size distribution. The method is based on the assumption of the equilibrium of the forces acting on a bubble perpendicularly to the flow direction. Assuming a large number of bubble size classes radial distributions are calculated separately for all bubble classes. The sum of these distributions is the radial profile of the gas fraction. The results of the model are compared with experimental data for a number of gas and liquid volume flow rates. The experiments were performed at a vertical test loop (inner diameter 50 mm) in FZ-Rossendorf using a wire mesh sensor. The sensor enables the determination of void distributions in the cross section of the loop. A special evaluation procedure supplies bubble size distributions as well as local distributions of bubbles within a predefined interval of bubble sizes. There is a good agreement between experimental and calculated data. In particular the change from wall peaking to core peaking is well predicted. (authors)
Two dimensional radial gas flows in atmospheric pressure plasma-enhanced chemical vapor deposition
Kim, Gwihyun; Park, Seran; Shin, Hyunsu; Song, Seungho; Oh, Hoon-Jung; Ko, Dae Hong; Choi, Jung-Il; Baik, Seung Jae
2017-12-01
Atmospheric pressure (AP) operation of plasma-enhanced chemical vapor deposition (PECVD) is one of promising concepts for high quality and low cost processing. Atmospheric plasma discharge requires narrow gap configuration, which causes an inherent feature of AP PECVD. Two dimensional radial gas flows in AP PECVD induces radial variation of mass-transport and that of substrate temperature. The opposite trend of these variations would be the key consideration in the development of uniform deposition process. Another inherent feature of AP PECVD is confined plasma discharge, from which volume power density concept is derived as a key parameter for the control of deposition rate. We investigated deposition rate as a function of volume power density, gas flux, source gas partial pressure, hydrogen partial pressure, plasma source frequency, and substrate temperature; and derived a design guideline of deposition tool and process development in terms of deposition rate and uniformity.
Characterization of a Twin-Entry Radial Turbine under Pulsatile Flow Condition
Mahfoudh Cerdoun
2016-01-01
Full Text Available In automotive applications radial gas turbines are commonly fitted with a twin-entry volute connected to a divided exhaust manifold, ensuring a better scavenge process owing to less interference between engines’ cylinders. This paper is concerned with the study of the unsteady performances related to the pulsating flows of a twin-entry radial turbine in engine-like conditions and the hysteresis-like behaviour during the pulses period. The results show that the aerodynamic performances deviate noticeably from the steady state and depend mainly on the time shifting between the actual output power and the isentropic power, which is distantly related to the apparent length. The maximum of efficiency and output shaft power are accompanied by low entropy generation through the shroud entry side, and their instantaneous behaviours tend to follow mainly the inlet total pressure curve. As revealed a billow is created by the interaction between the main flow and the infiltrated flow, affecting the flow incidence at rotor entry and producing high losses.
Radial basis function neural network for power system load-flow
Karami, A.; Mohammadi, M.S.
2008-01-01
This paper presents a method for solving the load-flow problem of the electric power systems using radial basis function (RBF) neural network with a fast hybrid training method. The main idea is that some operating conditions (values) are needed to solve the set of non-linear algebraic equations of load-flow by employing an iterative numerical technique. Therefore, we may view the outputs of a load-flow program as functions of the operating conditions. Indeed, we are faced with a function approximation problem and this can be done by an RBF neural network. The proposed approach has been successfully applied to the 10-machine and 39-bus New England test system. In addition, this method has been compared with that of a multi-layer perceptron (MLP) neural network model. The simulation results show that the RBF neural network is a simpler method to implement and requires less training time to converge than the MLP neural network. (author)
The Optimal Hydraulic Design of Centrifugal Impeller Using Genetic Algorithm with BVF
Xin Zhou
2014-01-01
Full Text Available Derived from idea of combining the advantages of two-dimensional hydraulic design theory, genetic algorithm, and boundary vorticity flux diagnosis, an optimal hydraulic design method of centrifugal pump impeller was developed. Given design parameters, the desired optimal centrifugal impeller can be obtained after several iterations by this method. Another 5 impellers with the same parameters were also designed by using single arc, double arcs, triple arcs, logarithmic spiral, and linear-variable angle spiral as blade profiles to make comparisons. Using Reynolds averaged N-S equations with a RNG k-ε two-equation turbulence model and log-law wall function to solve 3D turbulent flow field in the flow channel between blades of 6 designed impellers by CFD code FLUENT, the investigation on velocity distributions, pressure distributions, boundary vorticity flux distributions on blade surfaces, and hydraulic performance of impellers was presented and the comparisons of impellers by different design methods were demonstrated. The results showed that the hydraulic performance of impeller designed by this method is much better than the other 5 impellers under design operation condition with almost the same head, higher efficiency, and lower rotating torque, which implied less hydraulic loss and energy consumption.
Why is the radial flow in central pA collisions stronger than in AA?
Kalaydzhyan, Tigran; Shuryak, Edward
2014-01-01
Both the transverse size and entropy density per area in central pA collisions is smaller than in central AA, and yet the radial flow is stronger. We propose an explanation to this puzzle. Using a weak attraction between strings through the σ-meson exchange, fitted to the lattice data, we find collective implosion of the “spaghetti” multi-string state. Collectivization of the sigma field of the strings is the QCD analog of the black hole formation occurring in holographic models
Deman, P R; Kaiser, T M; Dirckx, J J; Offeciers, F E; Peeters, S A
2003-09-30
A 48 contact cochlear implant electrode has been constructed for electrical stimulation of the auditory nerve. The stimulating contacts of this electrode are organised in two layers: 31 contacts on the upper surface directed towards the habenula perforata and 17 contacts connected together as one longitudinal contact on the underside. The design of the electrode carrier aims to make radial current flow possible in the cochlea. The mechanical structure of the newly designed electrode was optimised to obtain maximal insertion depth. Electrode insertion tests were performed in a transparent acrylic model of the human cochlea.
Inertia effects in the laminar radial flow of a power law fluid with an electromagnetic field
Chen, C.-K.; Chen, K.-H.; Wu, C.-Y.
1984-01-01
An approximate study of the pressure distribution for the radial flow of a non-newtonian (power law) fluid between two parallel disks in the presence of an axial electrical field is obtained by using the momentum and energy integral methods. For a non-newtonian fluid it is shown that the inertia effect must be considered to be significant for the pressure distribution, especially for the power law fluids with n >= 1. Furthermore, it is seen that the inertia effect will also lower the load capacity of the disks. (Auth.)
Dynamic Characteristics of Rotating Stall in Mixed Flow Pump
Xiaojun Li
2013-01-01
Full Text Available Rotating stall, a phenomenon that causes flow instabilities and pressure hysteresis by propagating at some fraction of the impeller rotational speed, can occur in centrifugal impellers, mixed impellers, radial diffusers, or axial diffusers. Despite considerable efforts devoted to the study of rotating stall in pumps, the mechanics of this phenomenon are not sufficiently understood. The propagation mechanism and onset of rotating stall are not only affected by inlet flow but also by outlet flow as well as the pressure gradient in the flow passage. As such, the complexity of these concepts is not covered by the classical explanation. To bridge this research gap, the current study investigated prerotation generated at the upstream of the impeller, leakage flow at the tip clearance between the casing and the impeller, and strong reserve flow at the inlet of the diffuser. Understanding these areas will clarify the origin of the positive slope of the head-flow performance curve for a mixed flow pump. Nonuniform pressure distribution and adverse pressure gradient were also introduced to evaluate the onset and development of rotating stall within the diffuser.
Moore, Joan G.; Moore, John
1992-01-01
The flow in the NASA Low-Speed Impeller is affected by both curvature and rotation. The flow curves due to the following: (1) geometric curvature, e.g. the curvature of the hub and shroud profiles in the meridional plane and the curvature of the backswept impeller blades; and (2) secondary flow vortices, e.g. the tip leakage vortex. Changes in the turbulence and effective turbulent viscosity in the impeller are investigated. The effects of these changes on three-dimensional flow development are discussed. Two predictions of the flow in the impeller, one with, and one without modification to the turbulent viscosity due to rotation and curvature, are compared. Some experimental and theoretical background for the modified mixing length model of turbulent viscosity will also be presented.
Gilmore, Mark Allen
2017-01-01
Turbulence, and turbulence-driven transport are ubiquitous in magnetically confined plasmas, where there is an intimate relationship between turbulence, transport, instability driving mechanisms (such as gradients), plasma flows, and flow shear. Though many of the detailed physics of the interrelationship between turbulence, transport, drive mechanisms, and flow remain unclear, there have been many demonstrations that transport and/or turbulence can be suppressed or reduced via manipulations of plasma flow profiles. This is well known in magnetic fusion plasmas [e.g., high confinement mode (H-mode) and internal transport barriers (ITB's)], and has also been demonstrated in laboratory plasmas. However, it may be that the levels of particle transport obtained in such cases [e.g. H-mode, ITB's] are actually lower than is desirable for a practical fusion device. Ideally, one would be able to actively feedback control the turbulent transport, via manipulation of the flow profiles. The purpose of this research was to investigate the feasibility of using both advanced model-based control algorithms, as well as non-model-based algorithms, to control cross-field turbulence-driven particle transport through appropriate manipulation of radial plasma flow profiles. The University of New Mexico was responsible for the experimental portion of the project, while our collaborators at the University of Montana provided plasma transport modeling, and collaborators at Lehigh University developed and explored control methods.
Gilmore, Mark Allen [Univ. of New Mexico, Albuquerque, NM (United States)
2017-02-05
Turbulence, and turbulence-driven transport are ubiquitous in magnetically confined plasmas, where there is an intimate relationship between turbulence, transport, instability driving mechanisms (such as gradients), plasma flows, and flow shear. Though many of the detailed physics of the interrelationship between turbulence, transport, drive mechanisms, and flow remain unclear, there have been many demonstrations that transport and/or turbulence can be suppressed or reduced via manipulations of plasma flow profiles. This is well known in magnetic fusion plasmas [e.g., high confinement mode (H-mode) and internal transport barriers (ITB’s)], and has also been demonstrated in laboratory plasmas. However, it may be that the levels of particle transport obtained in such cases [e.g. H-mode, ITB’s] are actually lower than is desirable for a practical fusion device. Ideally, one would be able to actively feedback control the turbulent transport, via manipulation of the flow profiles. The purpose of this research was to investigate the feasibility of using both advanced model-based control algorithms, as well as non-model-based algorithms, to control cross-field turbulence-driven particle transport through appropriate manipulation of radial plasma flow profiles. The University of New Mexico was responsible for the experimental portion of the project, while our collaborators at the University of Montana provided plasma transport modeling, and collaborators at Lehigh University developed and explored control methods.
Detection and effects of pump low-flow operation
Casada, D.A.; Greene, R.H.
1993-01-01
Operating experience and previous studies have shown that a significant cause of pump problems and failures can result from low- flow operation. Operation at low-flow rates can create unstable flows within the pump impeller and casing. This condition can result in an increased radial and axial thrust on the rotor, which in turn causes higher shaft stresses, increased shaft deflection, and potential bearing and mechanical seal problems. Two of the more serious results of low-flow pump operation are cavitation and recirculation. Cavitation is the formation and subsequent collapse of vapor bubbles in any flow that is at an ambient pressure less than the vapor pressure of the liquid medium. It is the collapse of these vapor bubbles against the metal surfaces of the impeller or casing that causes surface pitting, erosion, and deterioration. Pump recirculation more damaging than cavitation. If located at the impeller eye, recirculation damages the inlet areas of the casing. At the impeller tips, recirculation alters the outside diameter of the impeller. If recirculation occurs around impeller shrouds, it damages thrust bearings. Recirculation also erodes impellers, diffusers, and volutes and causes failure of mechanical seals and bearings. This paper reports on a utility pump failure caused by low-flow induced phenomena. ORNL is investigating the results of low-flow pump operations by evaluating the types of measurements and diagnostic techniques that are currently used by licensees to detect pump degradation. A new, enhanced application of motor current and power data analysis has been developed that uses a signal comparison methodology to produce an instability ratio indicative of normal or unstable flow conditions. Examples of this type of low-flow detection technique are presented in this paper along with a brief discussion of the various types of technologies currently being used by licensees to evaluate pump operation and determine possible degradation
Lao, Hai-Ling; Liu, Fu-Hu [Shanxi University, Institute of Theoretical Physics, Shanxi (China); Lacey, Roy A. [Stony Brook University, Departments of Chemistry and Physics, Stony Brook, NY (United States)
2017-03-15
We analyze the transverse-momentum (p{sub T}) spectra of identified particles (π{sup ±}, K{sup ±}, p, and anti p) produced in gold-gold (Au-Au) and lead-lead (Pb-Pb) collisions over a √(s{sub NN}) (center-of-mass energy per nucleon pair) range from 14.5 GeV (one of the Relativistic Heavy Ion Collider (RHIC) energies) to 2.76 TeV (one of the Large Hadron Collider (LHC) energies). For the spectra with a narrow p{sub T} range, an improved Tsallis distribution which is in fact the Tsallis distribution with radial flow is used. For the spectra with a wide p{sub T} range, a superposition of the improved Tsallis distribution and an inverse power law is used. Both the extracted kinetic freeze-out temperature (T{sub 0}) and radial flow velocity (β{sub T}) increase with the increase of √(s{sub NN}), which indicates a higher excitation and larger expansion of the interesting system at the LHC. Both the values of T{sub 0} and β{sub T} in central collisions are slightly larger than those in peripheral collisions, and they are independent of isospin and slightly dependent on mass. (orig.)
Radial basis functions in mathematical modelling of flow boiling in minichannels
Hożejowska Sylwia
2017-01-01
Full Text Available The paper addresses heat transfer processes in flow boiling in a vertical minichannel of 1.7 mm depth with a smooth heated surface contacting fluid. The heated element for FC-72 flowing in a minichannel was a 0.45 mm thick plate made of Haynes-230 alloy. An infrared camera positioned opposite the central, axially symmetric part of the channel measured the plate temperature. K-type thermocouples and pressure converters were installed at the inlet and outlet of the minichannel. In the study radial basis functions were used to solve a problem concerning heat transfer in a heated plate supplied with the controlled direct current. According to the model assumptions, the problem is treated as twodimensional and governed by the Poisson equation. The aim of the study lies in determining the temperature field and the heat transfer coefficient. The results were verified by comparing them with those obtained by the Trefftz method.
Evidence for radial flow of thermal dileptons in high-energy nuclear collisions
Arnaldi, R; Castor, J; Chaurand, B; Cicalò, C; Colla, A; Cortese, P; Damjanovic, S; David, A; De Falco, A; Devaux, A; Ducroux, L; Enyo, H; Fargeix, J; Ferretti, A; Floris, M; Förster, A; Force, P; Guettet, N; Guichard, A; Gulkanian, H R; Heuser, J M; Keil, M; Kluberg, L; Lourenço, C; Lozano, J; Manso, F; Martins, P; Masoni, A; Neves, A; Ohnishi, H; Oppedisano, C; Parracho, P; Pillot, P; Poghosyan, T; Puddu, G; Radermacher, E; Ramalhete, P; Rosinsky, P; Scomparin, E; Seixas, J; Serci, S; Shahoyan, R; Sonderegger, P; Specht, H J; Tieulent, R; Usai, G; Veenhof, R; Wöhri, H K
2008-01-01
The NA60 experiment at the CERN SPS has studied low-mass dimuon production in 158 AGeV In-In collisions. An excess of pairs above the known meson decays has been reported before. We now present precision results on the associated transverse momentum spectra. The slope parameter Teff extracted from the spectra rises with dimuon mass up to the rho, followed by a sudden decline above. While the initial rise is consistent with the expectations for radial flow of a hadronic decay source, the decline signals a transition to an emission source with much smaller flow. This may well represent the first direct evidence for thermal radiation of partonic origin in nuclear collisions.
Aurélien Marsan
2017-01-01
Full Text Available This work is the final step of a research project that aims at evaluating the possibility of delaying the surge of a centrifugal compressor stage using a boundary-layer suction technique. It is based on Reynolds-Averaged Navier-Stokes numerical simulations. Boundary-layer suction is applied within the radial vaned diffuser. Previous work has shown the necessity to take into account the unsteady behavior of the flow when designing the active flow control technique. In this paper, a multislot strategy is designed according to the characteristics of the unsteady pressure field. Its implementation results in a significant increase of the stable operating range predicted by the unsteady RANS numerical model. A hub-corner separation still exists further downstream in the diffuser passage but does not compromise the stability of the compressor stage.
Optimal Power Flow in Multiphase Radial Networks with Delta Connections: Preprint
Zhao, Changhong [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Dall-Anese, Emiliano [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Low, Steven H. [California Institute of Technology
2017-11-27
This paper focuses on multiphase radial distribution networks with mixed wye and delta connections, and proposes a semidefinite relaxation of the AC optimal power flow (OPF) problem. Two multiphase power-flow models are developed to facilitate the integration of delta-connected generation units/loads in the OPF problem. The first model extends traditional branch flow models - and it is referred to as extended branch flow model (EBFM). The second model leverages a linear relationship between per-phase power injections and delta connections, which holds under a balanced voltage approximation (BVA). Based on these models, pertinent OPF problems are formulated and relaxed to semidefinite programs (SDPs). Numerical studies on IEEE test feeders show that SDP relaxations can be solved efficiently by a generic optimization solver. Numerical evidences indicate that solving the resultant SDP under BVA is faster than under EBFM. Moreover, both SDP solutions are numerically exact with respect to voltages and branch flows. It is also shown that the SDP solution under BVA has a small optimality gap, while the BVA model is accurate in the sense that it reflects actual system voltages.
SSME Investment in Turbomachinery Inducer Impeller Design Tools and Methodology
Zoladz, Thomas; Mitchell, William; Lunde, Kevin
2010-01-01
Within the rocket engine industry, SSME turbomachines are the de facto standards of success with regard to meeting aggressive performance requirements under challenging operational environments. Over the Shuttle era, SSME has invested heavily in our national inducer impeller design infrastructure. While both low and high pressure turbopump failures/anomaly resolution efforts spurred some of these investments, the SSME program was a major benefactor of key areas of turbomachinery inducer-impeller research outside of flight manifest pressures. Over the past several decades, key turbopump internal environments have been interrogated via highly instrumented hot-fire and cold-flow testing. Likewise, SSME has sponsored the advancement of time accurate and cavitating inducer impeller computation fluid dynamics (CFD) tools. These investments together have led to a better understanding of the complex internal flow fields within aggressive high performing inducers and impellers. New design tools and methodologies have evolved which intend to provide confident blade designs which strike an appropriate balance between performance and self induced load management.
Study of Flow Patterns in Radial and Back Swept Turbine Rotor under Design and Off-Design Conditions
Samip Shah; Salim Channiwala; Digvijay Kulshreshtha; Gaurang Chaudhari
2016-01-01
Paper details the numerical investigation of flow patterns in a conventional radial turbine compared with a back swept design for same application. The blade geometry of a designed turbine from a 25kW micro gas turbine was used as a baseline. A back swept blade was subsequently designed for the rotor, which departed from the conventional radial inlet blade angle to incorporate up to 25° inlet blade angle. A comparative numerical analysis between the two geometries is presented. While opera...
A numerical model for the design of a mixed flow cryogenic turbine ...
Present day cryogenic gas turbines are in more popular as they meet the growing need for low pressure cycles. This calls for improved methods of turbine wheel design. The present study is aimed at the design of the turbine wheel of mixed flow impellers with radial entry and axial discharge. In this paper, a computer code ...
M. F. Akorede
2017-06-01
Full Text Available The intent of power distribution companies (DISCOs is to deliver electric power to their customers in an efficient and reliable manner – with minimal energy loss cost. One major way to minimise power loss on a given power system is to install distributed generation (DG units on the distribution networks. However, to maximise benefits, it is highly crucial for a DISCO to ensure that these DG units are of optimal size and sited in the best locations on the network. This paper gives an overview of a software package developed in this study, called Power System Analysis and DG Optimisation Tool (PFADOT. The main purpose of the graphical user interface-based package is to guide a DISCO in finding the optimal size and location for DG placement in radial distribution networks. The package, which is also suitable for load flow analysis, employs the GUI feature of MATLAB. Three objective functions are formulated into a single optimisation problem and solved with fuzzy genetic algorithm to simultaneously obtain DG optimal size and location. The accuracy and reliability of the developed tool was validated using several radial test systems, and the results obtained are evaluated against the existing similar package cited in the literature, which are impressive and computationally efficient.
Impellers of low specific speed centrifugal pump based on the draughting technology
Hongxun, C; Peiru, W; Weiwei, L; Wen, J
2010-01-01
The authors analyzed the reasons of low efficiency under different operation condition based on the performance test and CFD numerical simulation approach. And the analysis focuses on the relationship between pump efficiency and inner flow characteristics. In order to improve the internal flow and increase efficiency of the pump, some draughting methods of improving the internal flow structure have been proposed, and some new impellers were developed by these methods. The main geometric parameters of the impellers, such as diameter, width and installation of the size, were consistent with the original impeller. The experimental results show that the efficiency of new impellers was improved significantly. The authors' work has opened up a new direction for further improving the efficiency of the low specific speed centrifugal pump.
Disk mini-adsorbers with radial flow for determination of 234Th concentration in seawater
Gulin, S.B.; Gorelov, Yu.S.; Sidorov, I.G.; Proskurnin, V.Yu.
2013-01-01
A modified method has been developed for measuring the 234 Th concentration in seawater, which is based upon the use of MnO 2 -impregnated disk mini adsorbers with radial flow connected in-line and the direct beta counting of 234 Th and/or its daughter 234m Pa. This allows determining the 234 Th concentration in a relatively small volume of seawater (20-50 L) with the possibility to check the extraction efficiency in every individual sample. The field testing, which was carried out at different areas of Sevastopol Bay during different seasons, has shown applicability of the proposed method to evaluate particle fluxes in marine environments within a wide range of concentrations of suspended matter. (author)
Sakai, Yasumasa; Taki, Hirofumi; Kanai, Hiroshi
2016-07-01
In our previous study, the viscoelasticity of the radial artery wall was estimated to diagnose endothelial dysfunction using a high-frequency (22 MHz) ultrasound device. In the present study, we employed a commercial ultrasound device (7.5 MHz) and estimated the viscoelasticity using arterial pressure and diameter, both of which were measured at the same position. In a phantom experiment, the proposed method successfully estimated the elasticity and viscosity of the phantom with errors of 1.8 and 30.3%, respectively. In an in vivo measurement, the transient change in the viscoelasticity was measured for three healthy subjects during flow-mediated dilation (FMD). The proposed method revealed the softening of the arterial wall originating from the FMD reaction within 100 s after avascularization. These results indicate the high performance of the proposed method in evaluating vascular endothelial function just after avascularization, where the function is difficult to be estimated by a conventional FMD measurement.
Xiaozhang Qu
2016-07-01
Full Text Available A kind of modified epoxy resin sheet molding compounds of the impeller has been designed. Through the test, the non-metal impeller has a better environmental aging performance, but must do the waterproof processing design. In order to improve the stability of the impeller vibration design, the influence of uncertainty factors is considered, and a multi-objective robust optimization method is proposed to reduce the weight of the impeller. Firstly, based on the fluid-structure interaction，the analysis model of the impeller vibration is constructed. Secondly, the optimal approximate model of the impeller is constructed by using the Latin hypercube and radial basis function, and the fitting and optimization accuracy of the approximate model is improved by increasing the sample points. Finally, the micro multi-objective genetic algorithm is applied to the robust optimization of approximate model, and the Monte Carlo simulation and Sobol sampling techniques are used for reliability analysis. By comparing the results of the deterministic, different sigma levels and different materials, the multi-objective optimization of the SMC molding impeller can meet the requirements of engineering stability and lightweight. And the effectiveness of the proposed multi-objective robust optimization method is verified by the error analysis. After the SMC molding and the robust optimization of the impeller, the optimized rate reached 42.5%, which greatly improved the economic benefit, and greatly reduce the vibration of the ventilation system.
Babayigit Osman
2015-01-01
Full Text Available Nowadays, single and multistage centrifugal pumps are widely used in industrial and mining enterprises. One of the most important components of a centrifugal pump is the impeller. The performance characteristics are related to the pump comprising the head and the overall efficiency rely a great deal on the impeller geometry. In this work, effects of blade exit angle change on hydraulic efficiency of a multi stage pump impeller are investigated via Ansys-Fluent computational fluid dynamics software for constant width impeller entrance and exit gates, blade numbers and blade thickness. Firstly, the flow volume of a centrifugal pump impeller is generated and then mesh structure is formed for the full impeller flow volume. Secondly, rotational periodic flow model are adopted in order to examine the effect of periodic flow assumption on the performance predictions. Corresponding to the available experimental data, inlet mass flow rate, outlet static pressure and rotation of impeller are taken as 0.02m3s-1, 450 kPa and 2950 rpm, respectively for the water fluid. No slip boundary condition is exposed to all solid of surface in the flow volume. The continuity and Navier-Stokes equations with the k-ε turbulence model and the standard wall functions are used. During the study, numerical analyses are conducted for the blade exit angle values of 18°, 20°, 25°, 30° and 35°. In consequence of the performed analyses, it is determined that hydraulic efficiency of the pump impeller value is changed between 81.0-84.6%. The most convenient blade exit angle that yields 84.6% hydraulic efficiency at is 18°. The obtained results show that the blade exit angle range has an impact on the centrifugal pump performance describing the pump head and the hydraulic efficiency.
A tracer liquid image velocimetry for multi-layer radial flow in bioreactors.
Gao, Yu-Bao; Liang, Jiu-Xing; Luo, Yu-Xi; Yan, Jia
2015-02-13
This paper presents a Tracer Liquid Image Velocimetry (TLIV) for multi-layer radial flow in bioreactors used for cells cultivation of tissue engineering. The goal of this approach is to use simple devices to get good measuring precision, specialized for the case in which the uniform level of fluid shear stress was required while fluid velocity varied smoothly. Compared to the widely used Particles Image Velocimetry (PIV), this method adopted a bit of liquid as tracer, without the need of laser source. Sub-pixel positioning algorithm was used to overcome the adverse effects of the tracer liquid deformation. In addition, a neighborhood smoothing algorithm was used to restrict the measurement perturbation caused by diffusion. Experiments were carried out in a parallel plates flow chamber. And mathematical models of the flow chamber and Computational Fluid Dynamics (CFD) simulation were separately employed to validate the measurement precision of TLIV. The mean relative error between the simulated and measured data can be less than 2%, while in similar validations using PIV, the error was around 8.8%. TLIV avoided the contradiction between the particles' visibility and following performance with tested fluid, which is difficult to overcome in PIV. And TLIV is easier to popularize for its simple experimental condition and low cost.
An improved design of axially driven permanent maglev centrifugal pump with streamlined impeller.
Qian, K X; Zeng, P; Ru, W M; Yuan, H Y
2007-01-01
In 1839, Earnshaw proved theoretically that it is impossible to achieve a stable equilibrium with a pure permanent maglev. Furthermore, in 1939, Braunbeck deduced that it is only possible to stabilize a super conductive or an electric maglev. In 2000, however, the present authors discovered that stable levitation is achievable by a combination of permanent magnetic and nonmagnetic forces, and its stability can be maintained even with mere passive magnetic forces by use of the gyro-effect. An improved design of permanent maglev impeller pump has been developed. Passive magnetic (PM) bearings support the rotor radially; on its right side, an impeller is fixed and on its left side a motor magnets-assemble is mounted. Unlike a previous prototype design, in which the rotor magnets were driven by a motor via magnetic coupling, a motor coil is installed opposite to the motor magnets disc, producing a rotating magnetic field. At standstill or if the rotating speed is lower than 4000 rpm, the rotor has one axial point contact with the motor coil. The contact point is located at the centre of the rotor. As the rotating speed increases gradually to higher than 4000 rpm, the rotor will be drawn off from the contact point by the hydrodynamic force of the fluid. Then the rotor becomes fully suspended. For radial and peripheral stabilization, a gyro-effect is important, which is realized by designing the motor magnets disc to have large diameter, short length and high rotating speed; for axial stability, an axial rehabilitating force is necessary, which is produced by PM bearings. The rotor demonstrated a full levitation by rotation over 4000 rpm. As a left ventricular assist device, the rotation of the pump has a speed range from 5000 to 8000 rpm. The relation between pressure head and flow rate indicates that there is neither mechanical friction nor hydrodynamic turbulence inside the pump; the former is due to the frictionless maglev and the latter is a result of the
Radial flow in 40Ar+45Sc reactions at E=35-115 MeV/nucleon
Pak, R.; Craig, D.; Gualtieri, E. E.; Hannuschke, S. A.; Lacey, R. A.; Lauret, J.; Llope, W. J.; Stone, N. T. B.; Vander Molen, A. M.; Westfall, G. D.; Yee, J.
1996-10-01
Collective radial flow of light fragments from 40Ar+45Sc reactions at beam energies between 35 and 115 MeV/nucleon has been investigated using the Michigan State University 4π Array. The mean transverse kinetic energy of the different fragment types increases with event centrality and increases as a function of the incident beam energy. Comparison of our measured values of shows agreement with predictions of Boltzmann-Uehling-Uhlenbeck model and WIX multifragmentation model calculations. The radial flow extracted from accounts for approximately half of the emitted particle's energy for the heavier fragments (Z>=4) at the highest beam energy studied.
Axisymmetric flow and heat transfer to modified second grade fluid over a radially stretching sheet
Masood Khan
Full Text Available In the present work, an analysis is made to the two-dimensional axisymmetric flow and heat transfer of a modified second grade fluid over an isothermal non-linear radially stretching sheet. The momentum and energy equations are modelled and the boundary layer equations are derived. The governing equations for velocity and temperature are turned down into a system of ordinary differential equations by invoking appropriate transformations which are then solved numerically via fourth and fifth order Runge-Kutta Fehlberg method. Moreover, the influence of the pertinent parameters namely the generalized second grade parameter, stretching parameter, the power-law index and the generalized Prandtl number is graphically portrayed. It is inferred that the generalized second grade parameter uplifted the momentum boundary layer while lessened the thermal boundary layer. Furthermore, the impact of stretching parameter is more pronounced for the second grade fluid (m = 0 in contrast with the power-law fluid (k = 0. For some special cases, comparisons are made with previously reported results and an excellent agreement is established. Keywords: Modified second grade fluid, Axisymmetric flow, Heat transfer, Non-linear stretching sheet
On axisymmetric flow and heat transfer of Cross fluid over a radially stretching sheet
Khan, Masood; Manzur, Mehwish; ur Rahman, Masood
In this article, an analysis is made on the axisymmetric flow and heat transfer of the Cross fluid over a radially stretching sheet. The present study provides with the boundary layer equations of the Cross fluid in cylindrical polar co-ordinates. The modelled momentum and energy equations are further simplified into non-linear ordinary differential equations by applying suitable similarity transformations. The system of equation is then numerically solved by the help of well-known shooting technique. The velocity and temperature profiles are plotted for some values of the governing parameters such as power-law index, local Weissenberg number and the Prandtl number. It is found that growing values of the power-law index elevated the momentum boundary layer structures while the thermal boundary layer thickness lessened correspondingly. Further, the numerical values of the local skin friction coefficient and the local Nusselt number are tabulated for several set of physical parameters. An outstanding agreement is observed by comparing the present results with the previously reported results in the literature as a special case.
Jinbao Lin
2014-01-01
Full Text Available Carbon-fiber reinforced polymer material impeller is designed for the centrifugal pump to deliver corrosive, toxic, and abrasive media in the chemical and pharmaceutical industries. The pressure-velocity coupling fields in the pump are obtained from the CFD simulation. The stress distribution of the impeller couple caused by the flow water pressure and rotation centrifugal force of the blade is analyzed using one-way fluid-solid coupling method. Results show that the strength of the impeller can meet the requirement of the centrifugal pumps, and the largest stress occurred around the blades root on a pressure side of blade surface. Due to the existence of stress concentration at the blades root, the fatigue limit of the impeller would be reduced greatly. In the further structure optimal design, the blade root should be strengthened.
Radial electric field and ion parallel flow in the quasi-symmetric and Mirror configurations of HSX
Kumar, S. T. A.; Dobbins, T. J.; Talmadge, J. N.; Wilcox, R. S.; Anderson, D. T.
2018-05-01
The radial electric field and the ion mean parallel flow are obtained in the helically symmetric experiment stellarator from toroidal flow measurements of C+6 ion at two locations on a flux surface, using the Pfirsch–Schlüter effect. Results from the standard quasi-helically symmetric magnetic configuration are compared with those from the Mirror configuration where the quasi-symmetry is deliberately degraded using auxiliary coils. For similar injected power, the quasi-symmetric configuration is observed to have significantly lower flows while the experimental observations from the Mirror geometry are in better agreement with neoclassical calculations. Indications are that the radial electric field near the core of the quasi-symmetric configuration may be governed by non-neoclassical processes.
The numerical study of the rake angle of impeller blade in centrifugal compressor
Drozdov, A.; Galerkin, Y.
2017-08-01
Investigated impellers have blade surfaces formed by straight generatrix. Blade profiles on shroud and disc surfaces are optimized by velocity diagram control (inviscid, quasi-three dimensional calculations). The blade profiles at hub and shroud blade-to-blade surfaces must be coordinated. A designer can choose the generatrix position at a trailing edge for it. The position is defined by the rake angle that is the angle between a trailing edge generatrix and a meridional plane. Two stages with 3D impellers, vaneless diffusers and return channels were investigated. Seven candidates of impellers of these stages with rake angles in range plus-minus 30 degrees were designed and investigated by quasi-three-dimensional inviscid calculation. CFD-calculations were made for the stages with these impellers. The optimal rake angle is minus 20 degrees for the high flow rate impeller due to lesser blade surface area and favorable meridian velocity field. Zero rake angle is optimal for the medium flow rate impeller where blade surface area is not so important. The combination of inviscid and viscid calculations is the informative instrument for further studies.
Cano-Andrade, S.; Hernandez-Guerrero, A.; Spakovsky, M.R. von; Damian-Ascencio, C.E.; Rubio-Arana, J.C.
2010-01-01
A numerical solution of the current density and velocity fields of a 3-D PEM radial configuration fuel cell is presented. The energy, momentum and electrochemical equations are solved using a computational fluid dynamics (CFD) code based on a finite volume scheme. There are three cases of principal interest for this radial model: four channels, eight channels and twelve channels placed in a symmetrical path over the flow field plate. The figures for the current-voltage curves for the three models proposed are presented, and the main factors that affect the behavior of each of the curves are discussed. Velocity contours are presented for the three different models, showing how the fuel cell behavior is affected by the velocity variations in the radial configuration. All these results are presented for the case of high relative humidity. The favorable results obtained for this unconventional geometry seems to indicate that this geometry could replace the conventional commercial geometries currently in use.
Choo, Y. K.; Civinskas, K. C.
1985-01-01
The three-dimensional inviscid DENTON code is used to analyze flow through a radial-inflow turbine rotor. Experimental data from the rotor are compared with analytical results obtained by using the code. The experimental data available for comparison are the radial distributions of circumferentially averaged values of absolute flow angle and total pressure downstream of the rotor exit. The computed rotor-exit flow angles are generally underturned relative to the experimental values, which reflect the boundary-layer separation at the trailing edge and the development of wakes downstream of the rotor. The experimental rotor is designed for a higher-than-optimum work factor of 1.126 resulting in a nonoptimum positive incidence and causing a region of rapid flow adjustment and large velocity gradients. For this experimental rotor, the computed radial distribution of rotor-exit to turbine-inlet total pressure ratios are underpredicted due to the errors in the finite-difference approximations in the regions of rapid flow adjustment, and due to using the relatively coarser grids in the middle of the blade region where the flow passage is highly three-dimensional. Additional results obtained from the three-dimensional inviscid computation are also presented, but without comparison due to the lack of experimental data. These include quasi-secondary velocity vectors on cross-channel surfaces, velocity components on the meridional and blade-to-blade surfaces, and blade surface loading diagrams. Computed results show the evolution of a passage vortex and large streamline deviations from the computational streamwise grid lines. Experience gained from applying the code to a radial turbine geometry is also discussed.
Radial flow in 40Ar+45Sc reactions at E=35 endash 115 MeV/nucleon
Pak, R.; Craig, D.; Gualtieri, E.; Hannuschke, S.A.; Lacey, R.A.; Lauret, J.; Llope, W.J.; Stone, N.T.; Vander Molen, A.M.; Westfall, G.; Yee, J.
1996-01-01
Collective radial flow of light fragments from 40 Ar+ 45 Sc reactions at beam energies between 35 and 115 MeV/nucleon has been investigated using the Michigan State University 4π Array. The mean transverse kinetic energy left-angle E t right-angle of the different fragment types increases with event centrality and increases as a function of the incident beam energy. Comparison of our measured values of left-angle E t right-angle shows agreement with predictions of Boltzmann-Uehling-Uhlenbeck model and WIX multifragmentation model calculations. The radial flow extracted from left-angle E t right-angle accounts for approximately half of the emitted particle close-quote s energy for the heavier fragments (Z≥4) at the highest beam energy studied. copyright 1996 The American Physical Society
OFF-DESIGN OPERATION OF IMPELLER OF THE CENTRIFUGAL COMPRESSOR
Saim KOÇAK
2004-02-01
Full Text Available Inducer and discharge dimensions of impellers of centrifugal compressor are determined as a preliminary design. Blockage factor and inducer dimensionless mass flow are exercised in relation with the relative Mach number. The equation which will be based o off-design calculation, related with the discharge relative Mach number are iterated until it will equal to inducer dimensionless mass flow rate. Then discharge relative Mach number for off-design works is obtained. The results calculated in accordance with pressure, temperature and density are seen to be similar with the theoretical parameters.
Wang Xiuli; Yuan Shouqi; Zhu Rongsheng; Yu Zhijun
2013-01-01
The numerical simulation calculation of the transient flow characteristics of nuclear reactor coolant pump in the recessive cavitation transition process in the nuclear reactor coolant pump impeller passage is conducted by CFX, and the transient flow characteristics of nuclear reactor coolant pump in the transition process from reducing the inlet pressure at cavitation-born conditions to NPSHc condition is studied and analyzed. The flow field analysis shows that, in the recessive cavitation transition process, the speed diversification at the inlet is relative to the bubble increasing, and makes the speed near the blade entrance increase when the bubble phase region becomes larger. The bubble generation and collapse will affect the the speed fluctuation near the entrance. The vorticity close to the blade entrance gradually increasing is influenced by the bubble phase, and the collapse of bubble generated by cavitation will reduce the vorticity from the collapse to impeller outlet. Pump asymmetric structure causes the asymmetry of the flow, velocity and outlet pressure distribution within every impeller flow passage, which cause the asymmetry of the transient radial force. From the dimensionless t/T = 0.6, the bubble phase starts to have impact on the impeller transient radial force, and results in the irregular fluctuations. (authors)
[Improved design of permanent maglev impeller assist heart].
Qian, Kunxi; Zeng, Pei; Ru, Weimin; Yuan, Haiyu
2002-12-01
Magnetic bearing has no mechanical contact between the rotor and stator. And a rotary pump with magnetic bearing has therefore no mechanical wear and thrombosis due to bearing. The available magnetic bearings, however, are devised with electric magnets, need complicated control and remarkable energy consumption. Resultantly, it is difficult to apply an electric magnetic bearing to rotary pump without disturbing its simplicity, implantability and reliability. The authors have developed a levitated impeller pump merely with permanent magnets. The rotor is supported by permanent magnetic forces radially. On one side of the rotor, the impeller is fixed; and on the other side of the rotor, the driven magnets are mounted. Opposite to this driven magnets, a driving motor coil with iron corn magnets is fastened to the motor axis. Thereafter, the motor drives the rotor via a rotating magnetic field. By laboratory tests with saline, if the rotor stands still or rotates under 4,000 rpm, the rotor has one-point contact axially with the driving motor coil. The contacting point is located in the center of the rotor. As the rotating speed increases gradually to more than 4,000 rpm, the rotor will detache from the stator axially. Then the rotor will be fully levitated. Since the axial levitation is produced by hydraulic force and the driven magnets have a gyro-effect, the rotor rotates very steadly during levitation. As a left ventricular assist device, the pump works in a rotating speed range of 5,000-8,000 rpm, the levitation of the impeller hence is ensured by practical use of the pump.
Performance Testing Of A Modified Centrifugal Fan With Serrated Blade Impeller
Zaimar
2017-10-01
Full Text Available Changes of shape dimension and component part of impeller might change of characteristic fluid flow so that pressure static in the fan housing changed. Changing some geometric characteristics of the centrifugal fan has more efficiency taking with energy crises into consideration. Several factors that can affect fan performance namely design and type size rotation speed air condition or gas through a fan operating point on the nature of the relationship between a volume of air flow and pressure. The purpose of this research was to test of fan performance of the modified centrifugal fan with the serrated blade impeller. The addition of a percentage of closing the inlet causes the air volumetric rate the airflow energy BHP and total efficiency except for the fan total and static pressure. The experimental test results there are static pressure data and the resulting total pressure is different or distorted 10-17 of deviation from calculation data based on the fan laws. This is possible because of changes in the shape of the blade with serrated on the inside of the impeller. Based on the performance curve shows that the selection of impeller speeds of 800 RPM produces a relatively high air volumetric rate is proportional to the total pressure of the fan and the flow energy so that it is more efficient than other impeller speeds.
Jean Robert P. Rodrigues
2014-09-01
Full Text Available In spite of technological importance of solidification of metallic alloys under radial heat flow, relatively few studies have been carried out in this area. In this work the solidification of Al 4.5 wt% Cu cylinders against a steel massive mold is analyzed and compared with unidirectional solidification against a cooled mold. Initially temperature variations at different positions in the casting and in the mold were measured during solidification using a data acquisition system. These temperature variations were introduced in a numerical method in order to determine the variation of heat transfer coefficient at metal/mold interface by inverse method. The primary and secondary dendrite arm spacing variations were measured through optical microscopy. Comparisons carried out between experimental and numerical data showed that the numerical method describes well the solidification processes under radial heat flux.
S. V. Podbolotov
2018-03-01
Full Text Available The relevance of this work is conditioned by the possibility of expanding the range of efficient operation of the turbine by changing the flow pattern of the fluid flow from stage to stage. The purpose of the work is to establish rational modes of operation of turbo machines with coaxially mounted impellers. Research methodology: in this work, we used a systematic approach, which includes the analysis of the results of mathematical modeling and experimental studies. Results. We carried out the analysis of the influence of operating modes on the pressure developed by the turbine. These operating modes include directions of rotation of impellers and the value of their circumferential speeds. The study analyzed the two options of installation: the rotation of the wheels in one direction and the rotation of the wheels in the opposite direction. The theoretical studies were based on a well-known Euler theory under certain assumptions: the cross section averaged for all flow settings; the motion of impellers was made one-dimensional and axisymmetric; the impellers have an infinite number of infinitely thin blades; the flow of fluid does not have viscosity, and the influence of friction forces is absent. The experimental aerodynamic characteristics of the centrifugal turbo machine with coaxial arrangement of driving wheels were obtained on an especially designed aerodynamic stand. Pressure-flow characteristics obtained theoretically and experimentally are presented. Conclusion. The use of coaxial impellers contributes to developing pressure and allows you to extend the range of efficient operation of centrifugal turbo machines. The most rational mode of operation of coaxially mounted impellers is the counter rotation mode. The increase of pressure developed by the Turbo machinery at work in this mode is proven theoretically and confirmed experimentally. Sufficient convergence of mathematical and experimental studies suggests the reliability of the
Impeller Submergence Depth for Stirred Tanks
Thiyam T. Devi
2011-11-01
Full Text Available Impeller submergence governs the performance of mixing tanks employed in oxygen transfer operation. Present work experimentally investigates the effect of impeller submergence depths on oxygen transfer and corresponding power consumption. It has been found that at higher range of impeller submergence, mixing tanks consume less power and gives higher values of oxygen transfer coefficient. Optimal range of submergence depth is 0.7 to 0.9 times the impeller diameter. Copyright ©2011 BCREC UNDIP. All rights reserved.(Received: 4th March 2011; Revised: 12nd July 2011; Accepted: 14th July 2011[How to Cite: T.T. Devi, A.P. Sinha, M. Thakre, and B. Kumar. (2011. Impeller Submergence Depth for Stirred Tanks. Bulletin of Chemical Reaction Engineering & Catalysis, 6 (2: 123-128. doi:10.9767/bcrec.6.2.826.123-128][How to Link / DOI: http://dx.doi.org/10.9767/bcrec.6.2.826.123-128 || or local: http://ejournal.undip.ac.id/index.php/bcrec/article/view/826] | View in
Sarler, B [Institut Jozef Stefan, Ljubljana (Yugoslavia)
1987-07-01
The basic principles of the boundary element method numerical treatment of the radial flow heat diffusion equation are presented. The algorithm copes the time dependent Dirichlet and Neumann boundary conditions, temperature dependent material properties and regions from different materials in thermal contact. It is verified on the several analytically obtained test cases. The developed method is used for the modelling of unsteady radial heat flow in pressurized water reactor fuel rod. (author)
Kewel, M.; Renner, J.
2017-12-01
The variation of hydraulic properties during sliding events is of importance for source mechanics and analyses of the evolution in effective stresses. We conducted laboratory experiments on samples of Padang granite to elucidate the interrelation between shear displacement on faults and their hydraulic properties. The cylindrical samples of 30 mm diameter and 75 mm length were prepared with a ground sawcut, inclined 35° to the cylindrical axis and accessed by a central bore of 3 mm diameter. The conventional triaxial compression experiments were conducted at effective pressures of 30, 50, and 70 MPa at slip rates of 2×10-4 and 8×10-4 mm s-1. The nominally constant fluid pressure of 30 MPa was modulated by oscillations with an amplitude of up to 0.5 MPa. Permeability and specific storage capacity of the fault were determined using the oscillatory radial-flow method that rests on an analysis of amplitude ratio and phase shift between the oscillatory fluid pressure and the oscillatory fluid flow from and into the fault plane. This method allowed us to continuously monitor the hydraulic evolution during elastic loading and frictional sliding. The chosen oscillation period of 60 s guaranteed a resolution of hydraulic properties for slip increments as small as 20 μm. The determined hydraulic properties show a fairly uniform dependence on normal stress at hydrostatic conditions and initial elastic loading. The samples exhibited stable frictional sliding with modest strengthening with increasing strain. Since not all phase-shift values fell inside the theoretical range for purely radial pressure diffusion during frictional sliding, the records of equivalent hydraulic properties exhibit some gaps. In the phases with evaluable phase-shift values, permeability fluctuates by almost one order of magnitude over slip intervals of as little as 100 μm. We suppose that the observed fluctuations are related to comminution and reconfiguration of asperities on the fault planes
Nagatani, Kosuke; Shihata, Yoshinori; Matsushita, Takahiro; Tsukagoshi, Kazuhiko
2016-01-01
Ionic liquid aqueous two-phase systems were delivered into a capillary tube to achieve tube radial distribution flow (TRDF) or annular flow in a microspace. The phase diagram, viscosity of the phases, and TRDF image of the 1-butyl-3-methylimidazolium chloride and NaOH system were examined. The TRDF was formed with inner ionic liquid-rich and outer ionic liquid-poor phases in the capillary tube. The phase configuration was explained using the viscous dissipation principle. We also examined the distribution of rhodamine B in a three-branched microchannel on a microchip with ionic liquid aqueous two-phase systems for the first time.
M. M. Potsane
2014-01-01
Full Text Available The transport of chemicals through soils to the groundwater or precipitation at the soils surfaces leads to degradation of these resources. Serious consequences may be suffered in the long run. In this paper, we consider macroscopic deterministic models describing contaminant transport in saturated soils under uniform radial water flow backgrounds. The arising convection-dispersion equation given in terms of the stream functions is analyzed using classical Lie point symmetries. A number of exotic Lie point symmetries are admitted. Group invariant solutions are classified according to the elements of the one-dimensional optimal systems. We analyzed the group invariant solutions which satisfy the physical boundary conditions.
Hydraulic efficiency of a Rushton turbine impeller
Chara, Z.; Kysela, B.; Fort, I.
2017-07-01
Based on CFD simulations hydraulic efficiency of a standard Rushton turbine impeller in a baffled tank was determined at a Reynolds number of ReM=33330. Instantaneous values of pressure and velocity components were used to draw up the macroscopic balance of the mechanical energy. It was shown that the hydraulic efficiency of the Rushton turbine impeller (energy dissipated in a bulk volume) is about 57%. Using this result we estimated a length scale in a non-dimensional equation of kinetic energy dissipation rate in the bulk volume as L=D/2.62.
Roshani, G.H.; Nazemi, E.; Roshani, M.M.
2017-01-01
Changes of fluid properties (especially density) strongly affect the performance of radiation-based multiphase flow meter and could cause error in recognizing the flow pattern and determining void fraction. In this work, we proposed a methodology based on combination of multi-beam gamma ray attenuation and dual modality densitometry techniques using RBF neural network in order to recognize the flow regime and determine the void fraction in gas-liquid two phase flows independent of the liquid phase changes. The proposed system is consisted of one 137 Cs source, two transmission detectors and one scattering detector. The registered counts in two transmission detectors were used as the inputs of one primary Radial Basis Function (RBF) neural network for recognizing the flow regime independent of liquid phase density. Then, after flow regime identification, three RBF neural networks were utilized for determining the void fraction independent of liquid phase density. Registered count in scattering detector and first transmission detector were used as the inputs of these three RBF neural networks. Using this simple methodology, all the flow patterns were correctly recognized and the void fraction was predicted independent of liquid phase density with mean relative error (MRE) of less than 3.28%. - Highlights: • Flow regime and void fraction were determined in two phase flows independent of the liquid phase density changes. • An experimental structure was set up and the required data was obtained. • 3 detectors and one gamma source were used in detection geometry. • RBF networks were utilized for flow regime and void fraction determination.
Schuster, Eugenio
2014-05-02
The strong coupling between the different physical variables involved in the plasma transport phenomenon and the high complexity of its dynamics call for a model-based, multivariable approach to profile control where those predictive models could be exploited. The overall objective of this project has been to extend the existing body of work by investigating numerically and experimentally active control of unstable fluctuations, including fully developed turbulence and the associated cross-field particle transport, via manipulation of flow profiles in a magnetized laboratory plasma device. Fluctuations and particle transport can be monitored by an array of electrostatic probes, and Ex B flow profiles can be controlled via a set of biased concentric ring electrodes that terminate the plasma column. The goals of the proposed research have been threefold: i- to develop a predictive code to simulate plasma transport in the linear HELCAT (HELicon-CAThode) plasma device at the University of New Mexico (UNM), where the experimental component of the proposed research has been carried out; ii- to establish the feasibility of using advanced model-based control algorithms to control cross-field turbulence-driven particle transport through appropriate manipulation of radial plasma flow profiles, iii- to investigate the fundamental nonlinear dynamics of turbulence and transport physics. Lehigh University (LU), including Prof. Eugenio Schuster and one full-time graduate student, has been primarily responsible for control-oriented modeling and model-based control design. Undergraduate students have also participated in this project through the National Science Foundation Research Experience for Undergraduate (REU) program. The main goal of the LU Plasma Control Group has been to study the feasibility of controlling turbulence-driven transport by shaping the radial poloidal flow profile (i.e., by controlling flow shear) via biased concentric ring electrodes.
Follin, Sven; Ludvigson, Jan-Erik; Leven, Jakob
2011-09-01
According to the strategy for hydrogeological characterisation within the SKB's site investigation programme, two single-hole test methods are available for testing and parameterisation of groundwater flow models - constant-head injection testing with the Pipe String System (PSS method) and difference flow logging with the Posiva Flow Log (PFL method). This report presents the results of an investigation to assess discrepancies in the results of single-hole transmissivity measurements using these methods in the Forsmark site characterisation. The investigation explores the possibility that the source of the discrepancy observed lies in the assumptions of the flow geometry that are inherent to the methods used for standard constant-head injection well test analysis and difference flow logging analysis, respectively. In particular, the report looks at the generalised radial flow (GRF) concept by Barker (1988) as a means that might explain some of the differences. A confirmation of the actual flow geometries (dimensions) observed during hydraulic injection tests could help to identify admissible conceptual models for the tested system, and place the hydraulic testing with the PSS and PFL test methods in its full hydrogeological context. The investigation analyses 151 constant-head injection tests in three cored boreholes at Forsmark. The results suggest that the transmissivities derived with standard constant-head injection well test analysis methods and with the GRF concept, respectively, are similar provided that the dominating flow geometry during the testing is radial (cylindrical). Thus, having flow geometries with dimensions other than 2 affects the value of the interpreted transmissivity. For example, a flow system with a dimension of 1 may require an order of magnitude or more, higher transmissivity to produce the same flow rates. The median of the GRF flow dimensions of all 151 constant-head injection tests is 2.06 with 33% of the tests in the range 1
Tamilselvan V.
2016-06-01
Full Text Available The radial distribution system is a rugged system, it is also the most commonly used system, which suffers by loss and low voltage at the end bus. This loss can be reduced by the use of a capacitor in the system, which injects reactive current and also improves the voltage magnitude in the buses. The real power loss in the distribution line is the I2R loss which depends on the current and resistance. The connection of the capacitor in the bus reduces the reactive current and losses. The loss reduction is equal to the increase in generation, necessary for the electric power provided by firms. For consumers, the quality of power supply depends on the voltage magnitude level, which is also considered and hence the objective of the problem becomes the multi objective of loss minimization and the minimization of voltage deviation. In this paper, the optimal location and size of the capacitor is found using a new computational intelligent algorithm called Flower Pollination Algorithm (FPA. To calculate the power flow and losses in the system, novel data structure load flow is introduced. In this, each bus is considered as a node with bus associated data. Links between the nodes are distribution lines and their own resistance and reactance. To validate the developed FPA solutions standard test cases, IEEE 33 and IEEE 69 radial distribution systems are considered.
Danilo Donato
2014-01-01
Full Text Available Radial flow perfusion of cell-seeded hollow cylindrical porous scaffolds may overcome the transport limitations of pure diffusion and direct axial perfusion in the realization of bioengineered substitutes of failing or missing tissues. Little has been reported on the optimization criteria of such bioreactors. A steady-state model was developed, combining convective and dispersive transport of dissolved oxygen with Michaelis-Menten cellular consumption kinetics. Dimensional analysis was used to combine more effectively geometric and operational variables in the dimensionless groups determining bioreactor performance. The effectiveness of cell oxygenation was expressed in terms of non-hypoxic fractional construct volume. The model permits the optimization of the geometry of hollow cylindrical constructs, and direction and magnitude of perfusion flow, to ensure cell oxygenation and culture at controlled oxygen concentration profiles. This may help engineer tissues suitable for therapeutic and drug screening purposes.
Fu, Youzhi; Gao, Hang; Wang, Xuanping; Guo, Dongming
2017-05-01
The integral impeller and blisk of an aero-engine are high performance parts with complex structure and made of difficult-to-cut materials. The blade surfaces of the integral impeller and blisk are functional surfaces for power transmission, and their surface integrity has significant effects on the aerodynamic efficiency and service life of an aero-engine. Thus, it is indispensable to finish and strengthen the blades before use. This paper presents a comprehensive literature review of studies on finishing and strengthening technologies for the impeller and blisk of aero-engines. The review includes independent and integrated finishing and strengthening technologies and discusses advanced rotational abrasive flow machining with back-pressure used for finishing the integral impeller and blisk. A brief assessment of future research problems and directions is also presented.
Universality Results for Multi-layer Radial Hele-Shaw Flows
Daripa, Prabir; Gin, Craig; Daripa Research Team
2014-03-01
Saffman-Taylor instability is a well known viscosity driven instability of an interface separating two immiscible fluids. We study linear stability of this displacement process in multi-layer radial Hele-Shaw geometry involving an arbitrary number of immiscible fluid phases. Universal stability results have been obtained and applied to design displacement processes that are considerably less unstable than the pure Saffman-Taylor case. In particular, we derive universal formula which gives specific values of the viscosities of the fluid layers corresponding to smallest unstable band. Other similar universal results will also be presented. The talk is based on ongoing work. Supported by an NPRP Grant # 08-777-1-141 from the Qatar National Research Fund (a member of the Qatar Foundation). The statements made herein are solely the responsibility of the authors.
Serrano, José Ramón; Arnau, Francisco José; García-Cuevas, Luis Miguel; Dombrovsky, Artem; Tartoussi, Hadi
2016-01-01
Highlights: • A procedure for performance maps extrapolation of any radial turbine is presented. • Non measured VGT positions, speeds and blade to jet speed ratios can be extrapolated. • Calibration coefficients that can be fitted with a limited set of map data are used. • Experimental points at high blade to jet speed ratios have been used for validation. • The extrapolation accuracy is good in different map ranges and variables. - Abstract: Turbine performance at extreme off-design conditions is growing in importance for properly computing turbocharged reciprocating internal combustion engines behaviour during urban driving conditions at current and future homologation cycles. In these cases, the turbine operates at very low flow rates and power outputs and at very high blade to jet speed ratios during transitory periods due to turbocharger wheel inertia and the high pulsation level of engine exhaust flow. This paper presents a physically based method that is able to extrapolate radial turbines reduced mass flow and adiabatic efficiency in blade speed ratio, turbine rotational speed and stator vanes position. The model uses a very narrow range of experimental data from turbine maps to fit the necessary coefficients. By using a special experimental turbocharger gas stand, experimental data have been obtained for extremely low turbine power outputs for the sake of model validation. Even if the data used for fitting only covers the turbine normal operation zone, the extrapolation model provides very good agreement with the experiments at very high blade speed ratio points; producing also good results when extrapolating in rotational speed and stator vanes position.
Meng, Chen; Huang, Jianke; Ye, Chunyu; Cheng, Wenchao; Chen, Jianpei; Li, Yuanguang
2015-07-01
In this study, a numerical simulation using computational fluid dynamics (CFD) was used to investigate the hydrodynamic characteristics of circular ponds with three different impellers (hydrofoil, four-pitched-blade turbine, and grid plate). The reliability of the CFD model was validated by particle image velocimetry (PIV). Hydrodynamic analyses were conducted to evaluate the average velocity magnitude along the light direction (Uz), turbulence properties, average shear stress, pressure loss and the volume percentage of dead zone inside circular ponds. The simulation results showed that Uz value of hydrofoil was 58.9, 40.3, and 28.8% higher than those of grid plate with single arm, grid plate with double arms and four-pitched blade turbines in small-scale circular ponds, respectively. In addition, hydrofoil impeller with down-flow operation had outstanding mixing characteristics. Lastly, the results of Chlorella pyrenoidosa cultivation experiments indicated that the biomass concentration of hydrofoil impeller with down-flow operation was 65.2 and 88.8% higher than those of grid plate with double arms and four-pitched-blade turbine, respectively. Therefore, the optimal circular pond mixing system for microalgae cultivation involved a hydrofoil impeller with down-flow operation.
Prediction of Heat Transfer For Turbulent Flow in Rotating Radial Duct
P. Tekriwal
1995-01-01
in the case of low-Re model, the computation time is relatively high and the convergence is rather slow, thus rendering the low-Re model as an unattractive choice for rotating flows at high Reynolds number.
Suzukawa, K [Ube Industries, Ltd., Tokyo (Japan); hashimoto, T [Yamaguchi University, Yamaguchi (Japan); Osaka, H [Yamaguchi University, Yamaguchi (Japan). Faclty of Engineering
1997-12-25
The three dimensional complex turbulent flow fields induced by a four flat blade paddle impeller in agitated vessel were measured by laser Doppler velocimetry. Mixing vessel used was a closed cylindrical tank of 490 mm diameter with a flat bottom and four vertical buffles, giving water volumes of about 1001. The impellers were at the midnight of the water level in the tank. A height of liquid (water) was equal to the vessel diameter. Three components of mean velocity were measured at three vertical sections {theta}=7.5deg, 45deg and 85deg, in several horizontal planes. Mixing Reynolds number NRe was 1.2 times 10{sup 5}. It can be found from the results that circumferential mean velocity profiles show the symmetrical shape in the upper and lower sides of impeller. Secondary velocity components, such as axial and radial velocities, however, were not in symmetry. For this reason, the ratio of circulation flow volume which enter in upper and lower sides of impeller was roughly 7/3. In both the middle and buffle regions, mean flow velocities (flow patterns) were different, dependent of three vertical planes with different circumferential angle measured from buffle. 10 refs., 8 figs., 1 tab.
Price, Daniel J.; Cuello, Nicolás; Pinte, Christophe; Mentiplay, Daniel; Casassus, Simon; Christiaens, Valentin; Kennedy, Grant M.; Cuadra, Jorge; Sebastian Perez, M.; Marino, Sebastian; Armitage, Philip J.; Zurlo, Alice; Juhasz, Attila; Ragusa, Enrico; Laibe, Guillaume; Lodato, Giuseppe
2018-06-01
We present 3D hydrodynamical models of the HD 142527 protoplanetary disc, a bright and well-studied disc that shows spirals and shadows in scattered light around a 100 au gas cavity, a large horseshoe dust structure in mm continuum emission, together with mysterious fast radial flows and streamers seen in gas kinematics. By considering several possible orbits consistent with the observed arc, we show that all of the main observational features can be explained by one mechanism - the interaction between the disc and the observed binary companion. We find that the spirals, shadows, and horseshoe are only produced in the correct position angles by a companion on an inclined and eccentric orbit approaching periastron - the `red' family from Lacour et al. Dust-gas simulations show radial and azimuthal concentration of dust around the cavity, consistent with the observed horseshoe. The success of this model in the HD 142527 disc suggests other mm-bright transition discs showing cavities, spirals, and dust asymmetries may also be explained by the interaction with central companions.
Investigation on the Flow in a Rotor-Stator Cavity with Centripetal Through-Flow
Bo Hu
2017-10-01
Full Text Available Daily and Nece distinguished four flow regimes in an enclosed rotor-stator cavity, which are dependent on the circumferential Reynolds number and dimensionless axial gap width. A diagram of the different flow regimes including the respective mean profiles for both tangential and radial velocity was developed. The coefficients for the different flow regimes have also been correlated. In centrifugal pumps and turbines, the centripetal through-flow is quite common from the outer radius of the impeller to the impeller eye, which has a strong influence on the radial pressure distribution, axial thrust and frictional torque. The influence of the centripetal through-flow on the cavity flow with different circumferential Reynolds numbers and dimensionless axial gap width is not sufficiently investigated. It is also quite important to convert the 2D Daily and Nece diagram into 3D by introducing the through-flow coefficient. In order to investigate the impact of the centripetal through-flow, a test rig is designed and built up at the University of Duisburg-Essen. The design of the test rig is described. The impact of the above mentioned parameters on the velocity profile, pressure distribution, axial thrust and frictional torque are presented and analyzed in this paper. The 3D Daily and Nece diagram introducing the through-flow coefficient is also organized in this paper.
Wave structure in the radial film flow with a circular hydraulic jump
Rao, A.; Arakeri, J. H.
A circular hydraulic jump is commonly seen when a circular liquid jet impinges on a horizontal plate. Measurements of the film thickness, jump radius and the wave structure for various jet Reynolds numbers are reported. Film thickness measurements are made using an electrical contact method for regions both upstream and downstream of the jump over circular plates without a barrier at the edge. The jump radius and the separation bubble length are measured for various flow rates, plate edge conditions, and radii. Flow visualization using high-speed photography is used to study wave structure and transition. Waves on the jet amplify in the film region upstream of the jump. At high flow rates, the waves amplify enough to cause three-dimensional breakdown and what seems like transition to turbulence. This surface wave induced transition is different from the traditional route and can be exploited to enhance heat and mass transfer rates.
Wave structure in the radial film flow with a circular hydraulic jump
Rao, A.; Arakeri, J.H. [Indian Inst. of Science, Bangalore (India). Dept. of Mechanical Engineering
2001-11-01
A circular hydraulic jump is commonly seen when a circular liquid jet impinges on a horizontal plate. Measurements of the film thickness, jump radius and the wave structure for various jet Reynolds numbers are reported. Film thickness measurements are made using an electrical contact method for regions both upstream and downstream of the jump over circular plates without a barrier at the edge. The jump radius and the separation bubble length are measured for various flow rates, plate edge conditions, and radii. Flow visualization using high-speed photography is used to study wave structure and transition. Waves on the jet amplify in the film region upstream of the jump. At high flow rates, the waves amplify enough to cause three-dimensional breakdown and what seems like transition to turbulence. This surface wave induced transition is different from the traditional route and can be exploited to enhance heat and mass transfer rates. (orig.)
Subchannel flow analysis in Candu and ACR pressure tubes with radial and axial diameter variation
Catana, A.; Prodea, L. [RAAN, Institute for Nuclear Research, Arges (Romania); Danila, N.; Prisecaru, I.; Dupleac, D. [Bucharest Univ. Politehnica(Romania)
2007-07-01
The Candu (Canada Deuterium Uranium) and ACR (Advanced Candu Reactor) are pressure tubes (PT) heavy water moderated reactors. Candu are heavy water and ACR are light water cooled reactors. The pressure tube is filled with 12 bundles, each consisting of 37 respectively 43 fuel rods. One Candu reactor is in operation at Cernavoda, Romania since 1996. ACR is a proposed advanced Candu. PT diameter variation has a significant impact on the thermal-hydraulic parameters. Almost all thermal-hydraulic parameters change, but some of them have a greater significance. In this work we have considered a set of radial and axial PT diameter variations both for Candu-600 and ACR-700 reactors using various types of fuel bundles. We can conclude the following: 1) some thermal-hydraulic parameters are significantly influenced: critical heat flux (CHF), pressure drop, or void fraction; 2) the most significant parameter CHF is worsening which reduces the safety margin; 3) some fuel types present a better thermal-hydraulic behavior; and 4) fuel bundles with fresh fuel or low burnup have a worse thermal-hydraulic behaviour than those at average burn-up.
Subchannel flow analysis in Candu and ACR pressure tubes with radial and axial diameter variation
Catana, A.; Prodea, L.; Danila, N.; Prisecaru, I.; Dupleac, D.
2007-01-01
The Candu (Canada Deuterium Uranium) and ACR (Advanced Candu Reactor) are pressure tubes (PT) heavy water moderated reactors. Candu are heavy water and ACR are light water cooled reactors. The pressure tube is filled with 12 bundles, each consisting of 37 respectively 43 fuel rods. One Candu reactor is in operation at Cernavoda, Romania since 1996. ACR is a proposed advanced Candu. PT diameter variation has a significant impact on the thermal-hydraulic parameters. Almost all thermal-hydraulic parameters change, but some of them have a greater significance. In this work we have considered a set of radial and axial PT diameter variations both for Candu-600 and ACR-700 reactors using various types of fuel bundles. We can conclude the following: 1) some thermal-hydraulic parameters are significantly influenced: critical heat flux (CHF), pressure drop, or void fraction; 2) the most significant parameter CHF is worsening which reduces the safety margin; 3) some fuel types present a better thermal-hydraulic behavior; and 4) fuel bundles with fresh fuel or low burnup have a worse thermal-hydraulic behaviour than those at average burn-up
The effect of impeller type on silica sol formation in laboratory scale agitated tank
Nurtono, Tantular; Suprana, Yayang Ade; Latif, Abdul; Dewa, Restu Mulya; Machmudah, Siti; Widiyastuti, Winardi, Sugeng
2016-02-01
The multiphase polymerization reaction of the silica sol formation produced from silicic acid and potassium hydroxide solutions in laboratory scale agitated tank was studied. The reactor is equipped with four segmental baffle and top entering impeller. The inside diameter of reactor is 9 cm, the baffle width is 0.9 cm, and the impeller position is 3 cm from tank bottom. The diameter of standard six blades Rushton and three blades marine propeller impellers are 5 cm. The silicic acid solution was made from 0.2 volume fraction of water glass (sodium silicate) solution in which the sodium ion was exchanged by hydrogen ion from cation resin. The reactor initially filled with 286 ml silicic acid solution was operated in semi batch mode and the temperature was kept constant in 60 °C. The 3 ml/minute of 1 M potassium hydroxide solution was added into stirred tank and the solution was stirred. The impeller rotational speed was varied from 100 until 700 rpm. This titration was stopped if the solution in stirred tank had reached the pH of 10-The morphology of the silica particles in the silica sol product was analyzed by Scanning Electron Microscope (SEM). The size of silica particles in silica sol was measured based on the SEM image. The silica particle obtained in this research was amorphous particle and the shape was roughly cylinder. The flow field generated by different impeller gave significant effect on particle size and shape. The smallest geometric mean of length and diameter of particle (4.92 µm and 2.42 µm, respectively) was generated in reactor with marine propeller at 600 rpm. The reactor with Rushton impeller produced particle which the geometric mean of length and diameter of particle was 4.85 µm and 2.36 µm, respectively, at 150 rpm.
The three-dimensional compressible flow in a radial inflow turbine scroll
Hamed, A.; Tabakoff, W.; Malak, M.
1984-01-01
This work presents the results of an analytical study and an experimental investigation of the three-dimensional flow in a turbine scroll. The finite element method is used in the iterative numerical solution of the locally linearized governing equations for the three-dimensional velocity potential field. The results of the numerical computations are compared with the experimental measurements in the scroll cross sections, which were obtained using laser Doppler velocimetry and hot wire techniques. The results of the computations show a variation in the flow conditions around the rotor periphery which was found to depend on the scroll geometry.
Roshani, G.H.; Nazemi, E.; Roshani, M.M.
2017-01-01
In this paper, a novel method is proposed for predicting the density of liquid phase in stratified regime of liquid-gas two phase flows by utilizing dual modality densitometry technique and artificial neural network (ANN) model of radial basis function (RBF). The detection system includes a 137 Cs radioactive source and two NaI(Tl) detectors for registering transmitted and scattered photons. At the first step, a Monte Carlo simulation model was utilized to obtain the optimum position for the scattering detector in dual modality densitometry configuration. At the next step, an experimental setup was designed based on obtained optimum position for detectors from simulation in order to generate the required data for training and testing the ANN. The results show that the proposed approach could be successfully applied for predicting the density of liquid phase in stratified regime of gas-liquid two phase flows with mean relative error (MRE) of less than 0.701. - Highlights: • Density of liquid phase in stratified regime of two phase flows was predicted. • Combination of dual modality densitometry technique and ANN was utilized. • Detection system includes a 137 Cs radioactive source and two NaI(Tl) detectors. • MCNP simulation was done to obtain the optimum position for the scattering detector. • An experimental setup was designed to generate the required data for training the ANN.
Ghobadi, Narges; Ogino, Chiaki; Yamabe, Kaoru; Ohmura, Naoto
2017-01-01
A Fullzone (FZ) impeller was used in the first study of the characteristics involved in the fermentation of Aspergillus oryzae. Both the experimental and simulation results of this study revealed novel findings into the positive relationship between the global-axial mixing patterns of a FZ impeller and fermentation efficiency. The mixing results when using the FZ impeller compared with a double Rushton turbine (DRT) impeller indicated that the culture mixed by the FZ resulted in a more homogeneous medium with higher values for oxygen mass transfer, cell growth rate, and alpha amylase activity. The simulation of fluid flow was done in a laminar regime using a two-fluid model. According to the simulation results, the maximum shear stress when using the DRT was higher than that with the FZ at the same power input (P in ). A high degree of local shear stress and the shear rate near the turbine blade of the DRT resulted in cell damage and a reduction in the enzyme activity, biomass, pellet diameter, and dissolved oxygen concentration. Calculations using the Brown equation showed that the maximum and average shear rates during mixing with the FZ impeller were lower than that when using the DRT. Therefore, the use of an FZ impeller, particularly at low P in , enhanced the cultivation of A. oryzae. Copyright © 2016 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.
Zhu, Bing; Chen, Hongxun; Wei, Qun
2014-06-01
This paper is to study the cavitating characteristics in a low specific speed centrifugal pump with gap structure impeller experimentally and numerically. A scalable DES numerical method is proposed and developed by introducing the von Karman scale instead of the local grid scale, which can switch at the RANS and LES region interface smoothly and reasonably. The SDES method can detect and grasp unsteady scale flow structures, which were proved by the flow around a triangular prism and the cavitation flow in a centrifugal pump. Through numerical and experimental research, it's shown that the simulated results match qualitatively with tested cavitation performances and visualization patterns, and we can conclude that the gap structure impeller has a superior feature of cavitation suppression. Its mechanism may be the guiding flow feature of the small vice blade and the pressure auto-balance effect of the gap tunnel.
Performance Testing Of A Modified Centrifugal Fan With Serrated Blade Impeller
Zaimar; Mursalim; H. Abbas; Supratomo
2017-01-01
Changes of shape dimension and component part of impeller might change of characteristic fluid flow so that pressure static in the fan housing changed. Changing some geometric characteristics of the centrifugal fan has more efficiency taking with energy crises into consideration. Several factors that can affect fan performance namely design and type size rotation speed air condition or gas through a fan operating point on the nature of the relationship between a volume of air flow and pressur...
Unsteady axisymmetric flow and heat transfer over time-dependent radially stretching sheet
Azeem Shahzad
2017-03-01
Full Text Available This article address the boundary layer flow and heat transfer of unsteady and incompressible viscous fluid over an unsteady stretching permeable surface. First of all modeled nonlinear partial differential equations are transformed to a system of ordinary differential equations by using similarity transformations. Analytic solution of the reduced problem is constructed by using homotopy analysis method (HAM. To validate the constructed series solution a numerical counterpart is developed using shooting algorithm based on Runge-Kutta method. Both schemes are in an excellent agreement. The effects of the pertinent parameters on the velocity and energy profile are shown graphically and examined in detail.
Liu, Rong; Chen, Xue; Ding, Zijing
2018-01-01
We consider the motion of a gravity-driven flow down a vertical fiber subjected to a radial electric field. This flow exhibits rich dynamics including the formation of droplets, or beads, driven by a Rayleigh-Plateau mechanism modified by the presence of gravity as well as the Maxwell stress at the interface. A spatiotemporal stability analysis is performed to investigate the effect of electric field on the absolute-convective instability (AI-CI) characteristics. We performed a numerical simulation on the nonlinear evolution of the film to examine the transition from CI to AI regime. The numerical results are in excellent agreement with the spatiotemporal stability analysis. The blowup behavior of nonlinear simulation predicts the formation of touchdown singularity of the interface due to the effect of electric field. We try to connect the blowup behavior with the AI-CI characteristics. It is found that the singularities mainly occur in the AI regime. The results indicate that the film may have a tendency to form very sharp tips due to the enhancement of the absolute instability induced by the electric field. We perform a theoretical analysis to study the behaviors of the singularities. The results show that there exists a self-similarity between the temporal and spatial distances from the singularities.
Nguyen, Q H; Choi, S B; Lee, Y S; Han, M S
2013-01-01
This paper focuses on the optimal design of a compact and high damping force engine mount featuring magnetorheological fluid (MRF). In the mount, a MR valve structure with both annular and radial flows is employed to generate a high damping force. First, the configuration and working principle of the proposed MR mount is introduced. The MRF flows in the mount are then analyzed and the governing equations of the MR mount are derived based on the Bingham plastic behavior of the MRF. An optimal design of the MR mount is then performed to find the optimal structure of the MR valve to generate a maximum damping force with certain design constraints. In addition, the gap size of MRF ducts is empirically chosen considering the ‘lockup’ problem of the mount at high frequency. Performance of the optimized MR mount is then evaluated based on finite element analysis and discussions on performance results of the optimized MR mount are given. The effectiveness of the proposed MR engine mount is demonstrated via computer simulation by presenting damping force and power consumption. (paper)
Nguyen, Q. H.; Choi, S. B.; Lee, Y. S.; Han, M. S.
2013-11-01
This paper focuses on the optimal design of a compact and high damping force engine mount featuring magnetorheological fluid (MRF). In the mount, a MR valve structure with both annular and radial flows is employed to generate a high damping force. First, the configuration and working principle of the proposed MR mount is introduced. The MRF flows in the mount are then analyzed and the governing equations of the MR mount are derived based on the Bingham plastic behavior of the MRF. An optimal design of the MR mount is then performed to find the optimal structure of the MR valve to generate a maximum damping force with certain design constraints. In addition, the gap size of MRF ducts is empirically chosen considering the ‘lockup’ problem of the mount at high frequency. Performance of the optimized MR mount is then evaluated based on finite element analysis and discussions on performance results of the optimized MR mount are given. The effectiveness of the proposed MR engine mount is demonstrated via computer simulation by presenting damping force and power consumption.
Kevin D. Ballard
2014-01-01
Full Text Available Background. Blocking nitric oxide (NO and vasodilator prostanoids (PN does not consistently reduce flow-mediated dilation (FMD in young adults. The impact of aging on the contribution of NO and PG to FMD is unknown. Methods. FMD was measured in older adults (n=10, 65±3 y after arterial infusion of saline, N(G-monomethyl-L-arginine (L-NMMA, and ketorolac + L-NMMA. Data were compared to published data in young adults. Results. L-NMMA reduced FMD in older adults (8.9±3.6 to 5.9±3.7% although this was not statistically significant (P=0.08 and did not differ (P=0.74 from the reduction observed in young adults (10.0±3.8 to 7.6±4.7%; P=0.03. Blocking PN did not affect FMD in young or older adults. In older adults, L-NMMA reduced (n=6; range = 36–123% decrease, augmented (n=3; 10–122% increase, or did not change FMD (n=1; 0.4% increase. After PN blockade, FMD responses were reduced (n=2, augmented (n=6, or unaffected (n=1. Conclusions. NO or PN blockade did not consistently reduce FMD in healthy older adults, suggesting the existence of redundant vasodilator phenotypes as observed previously in young adults.
Chaotic characteristics enhanced by impeller of perturbed six-bent-bladed turbine in stirred tank
Deyu Luan
Full Text Available The fundamental way of improving the mixing efficiency is to induce the chaotic flow in a stirred vessel. The impeller form plays an important role for changing the structure of flow field and realizing chaotic mixing. Based on the velocity time series acquired by the experiment of particle image velocimetry (PIV, with the software Matlab, the macro-instability (MI, largest Lyapunov exponent (LLE, and Kolmogorov entropy in the water stirred tank is investigated respectively with the impeller of perturbed six-bent-bladed turbine (6PBT. The results show that the MI characteristics are obvious and two peak values of MI frequency are observed at the speed N = 60 rpm. With the increasing speed (more than 100 rpm, the peak characteristics of MI frequency disappear and a multi-scale wavelet structure of characterizing the chaotic flow field appears. Moreover, under the speed N = 60 rpm, the LLE is less than 0 and Kolmogorov entropy is 0, which means that the flow field is in the periodic moving state. As the speed is increased to more than 100 rpm, the LLE and Kolmogorov entropy are all more than 0, which indicates that the flow field goes into the chaotic mixing. When the speed reaches up to about 210 rpm, both of the LLE and Kolmogorov entropy achieve the optimum values, which will result in an excellent chaos with the highest mixing efficient. So it is feasible that the MI frequency, the LLE and the Kolmogorov entropy can be used to analyze the flow field characteristics in a stirred tank. The research results promote the understanding of the chaotic mixing mechanism and provide a theoretical reference for the development of new type impeller. Keywords: Macro-instability, The largest Lyapunov exponent, Kolmogorov entropy, The impeller of perturbed six-bent-bladed turbine, Chaotic mixing, PIV
Girka, Igor O.; Pavlenko, Ivan V.; Thumm, Manfred
2018-05-01
Azimuthal surface waves are electromagnetic eigenwaves of cylindrical plasma-dielectric waveguides which propagate azimuthally nearby the plasma-dielectric interface across an axial external stationary magnetic field. Their eigenfrequency in particular can belong to the electron cyclotron frequency range. Excitation of azimuthal surface waves by rotating relativistic electron flows was studied in detail recently in the case of the zeroth radial mode for which the waves' radial phase change within the layer where the electrons gyrate is small. In this case, just the plasma parameters cause the main influence on the waves' dispersion properties. In the case of the first and higher radial modes, the wave eigenfrequency is higher and the wavelength is shorter than in the case of the zeroth radial mode. This gain being of interest for practical applications can be achieved without any change in the device design. The possibility of effective excitation of the higher order radial modes of azimuthal surface waves is demonstrated here. Getting shorter wavelengths of the excited waves in the case of higher radial modes is shown to be accompanied by decreasing growth rates of the waves. The results obtained here are of interest for developing new sources of electromagnetic radiation, in nano-physics and in medical physics.
Numerical Investigations of Unsteady Flow in a Centrifugal Pump with a Vaned Diffuser
Olivier Petit
2013-01-01
Full Text Available Computational fluid dynamics (CFD analyses were made to study the unsteady three-dimensional turbulence in the ERCOFTAC centrifugal pump test case. The simulations were carried out using the OpenFOAM Open Source CFD software. The test case consists of an unshrouded centrifugal impeller with seven blades and a radial vaned diffuser with 12 vanes. A large number of measurements are available in the radial gap between the impeller and the diffuse, making this case ideal for validating numerical methods. Results of steady and unsteady calculations of the flow in the pump are compared with the experimental ones, and four different turbulent models are analyzed. The steady simulation uses the frozen rotor concept, while the unsteady simulation uses a fully resolved sliding grid approach. The comparisons show that the unsteady numerical results accurately predict the unsteadiness of the flow, demonstrating the validity and applicability of that methodology for unsteady incompressible turbomachinery flow computations. The steady approach is less accurate, with an unphysical advection of the impeller wakes, but accurate enough for a crude approximation. The different turbulence models predict the flow at the same level of accuracy, with slightly different results.
High-speed flow visualization in a pump-turbine under off-design operating conditions
Hasmatuchi, V; Roth, S; Botero, F; Avellan, F; Farhat, M
2010-01-01
The flow hydrodynamics in a low specific speed radial pump-turbine reduced scale model is experimentally investigated under off-design operating conditions in generating mode. Wall pressure measurements, in the stator, synchronized with high-speed flow visualizations in the vaneless space between the impeller and the guide vanes using air bubbles injection are performed. When starting from the best efficiency point and increasing the runner speed, a significant increase of the pressure fluctuations is observed mainly in channels between wicket gates. The spectral analysis shows a rise of one stall cell, rotating with about 70% of the impeller frequency, at runaway, which further increases as the zero discharge condition is approached. Then a specific image processing technique is detailed and applied to create a synthetic instantaneous view of the flow pattern on the entire guide vanes circumference for an operating point in turbine-brake mode, where backflow and vortices accompany the stall passage.
Schmidt, J.; Piret, C.; Zhang, N.; Kadlec, B. J.; Liu, Y.; Yuen, D. A.; Wright, G. B.; Sevre, E. O.
2008-12-01
The faster growth curves in the speed of GPUs relative to CPUs in recent years and its rapidly gained popularity has spawned a new area of development in computational technology. There is much potential in utilizing GPUs for solving evolutionary partial differential equations and producing the attendant visualization. We are concerned with modeling tsunami waves, where computational time is of extreme essence, for broadcasting warnings. In order to test the efficacy of the GPU on the set of shallow-water equations, we employed the NVIDIA board 8600M GT on a MacBook Pro. We have compared the relative speeds between the CPU and the GPU on a single processor for two types of spatial discretization based on second-order finite-differences and radial basis functions. RBFs are a more novel method based on a gridless and a multi- scale, adaptive framework. Using the NVIDIA 8600M GT, we received a speed up factor of 8 in favor of GPU for the finite-difference method and a factor of 7 for the RBF scheme. We have also studied the atmospheric dynamics problem of swirling flows over a spherical surface and found a speed-up of 5.3 using the GPU. The time steps employed for the RBF method are larger than those used in finite-differences, because of the much fewer number of nodal points needed by RBF. Thus, in modeling the same physical time, RBF acting in concert with GPU would be the fastest way to go.
Li, R N; Wang, H Y; Han, W; Shen, Z J; Ma, W
2013-01-01
The screw centrifugal pump is used as an object, and the unsteady numerical simulation of solid-liquid two-phase flow is carried out under different flow rate conditions in one circle by choosing the two-phase flow of sand and water as medium, using the software FLUENT based on the URANS equations, combining with sliding mesh method, and choosing the Mixture multiphase flow model and the SIMPLE algorithm. The results show that, with the flow rate increasing, the change trends for the pressure on volute outlet are almost constant, the fluctuation trends of the impeller axial force have a little change, the pressure and the axial force turn to decrease on the whole, the radial force gradually increases when the impeller maximum radius passes by half a cycle near the volute outlet, and the radial force gradually decreases when the maximum radius passes by the other half a cycle in a rotation cycle. The distributions of the solid particles are very uneven under a small flow rate condition on the face. The solid particles under a big flow rate condition are distributed more evenly than the ones under a small flow rate condition on the back. The theoretical basis and reference are provided for improving its working performance
A numerical study on an optimum design of a Cross-flow type Power Turbine (CPT)
Ha, Jin Ho; Kim, Chul Ho
2008-01-01
A wind turbine is one of the most popular energy conversion systems to generate electricity from the natural renewable energy source and an axial-flow type wind turbine is commonly used system for the generation electricity in the wind farm nowadays. In this study, a cross-flow type turbine has been studied for the application of wind turbine for electricity generation. The target capacity of the electric power generation of the model wind turbine developing in this project is 12volts-150A/H(about 1.8Kw). The important design parameters of the model turbine impeller are the inlet and exit angle of the turbine blade, number of blade, hub/tip ratio and exit flow angle of the housing. In this study, the radial equilibrium theorem was used to decide the inlet and exit angle of the model impeller blade and CFD technique was incorporated to have performance analysis of the design model power turbine for the optimum design of the geometry of the Cross-flow Power Turbine impeller and Casing. In CFD, Navier-Stokes equation is solved with the SIMPLEC method in a general coordinates system. Realizable k-ε turbulent model with MARS scheme was used for evaluating torque of each blade in the Cross-flow Power Turbine (CPT). From the result, the designed CPT with 24 impeller blades at α=40 .deg. and β=85 .deg. of turbine blade angle was estimated to generate 1.2Nm of the indicated torque and 200watts of the indicated power. On the basis of the rules of similarity, the generating power capacity of the real size CPT that is eight times longer than the model impeller is predicted to have an 1.6kW of the output power (about 12V-130A/H or 24V-65A/H)
Fannian Meng; Quanlin Dong; Yan Wang; Pengfei Wang; Chunxi Zhang
2013-01-01
A numerical optimum study on three-dimensional unsteady viscous flow in a centrifugal fan with backward-curved blades was performed. The influence of the inlet angle, the outlet blade angle and blade number on aerodynamic performance of the centrifugal fan was analyzed concerning the whole impeller-volute configuration. Response Surface Methodology (RSM) based on a three-level, three -variable Box-Behnken Design (BBD) was used to evaluate the interactive effects of factors such as inlet blade...
Large eddy simulation of a pitched blade impeller mixed vessel - Comparison with LDA measurements
Vlček, P.; Kysela, Bohuš; Jirout, T.; Fořt, I.
2016-01-01
Roč. 108, April (2016), s. 42-48 ISSN 0263-8762. [15th European Conference on Mixing. St. Petersburg, 28.06.2016-03.07.2016] Institutional support: RVO:67985874 Keywords : CFD * LES * mixed vessel * pitched six-blade impeller * ensemble averaged mean velocity * flow rate Subject RIV: BK - Fluid Dynamics OBOR OECD: Fluids and plasma physics (including surface physics) Impact factor: 2.538, year: 2016 http://www.sciencedirect.com/science/article/pii/S0263876216000836
Strength and dynamic characteristics analyses of wound composite axial impeller
Wang, Jifeng; Olortegui-Yume, Jorge; Müller, Norbert
2012-03-01
A low cost, light weight, high performance composite material turbomachinery impeller with a uniquely designed blade patterns is analyzed. Such impellers can economically enable refrigeration plants to use water as a refrigerant (R718). A strength and dynamic characteristics analyses procedure is developed to assess the maximum stresses and natural frequencies of these wound composite axial impellers under operating loading conditions. Numerical simulation using FEM for two-dimensional and three-dimensional impellers was investigated. A commercially available software ANSYS is used for the finite element calculations. Analysis is done for different blade geometries and then suggestions are made for optimum design parameters. In order to avoid operating at resonance, which can make impellers suffer a significant reduction in the design life, the designer must calculate the natural frequency and modal shape of the impeller to analyze the dynamic characteristics. The results show that using composite Kevlar fiber/epoxy matrix enables the impeller to run at high tip speed and withstand the stresses, no critical speed will be matched during start-up and shut-down, and that mass imbalances of the impeller shall not pose a critical problem.
Hein, O.
1999-07-01
Due to rotation (Coriolis forces) in a coolant channel a secondary flow is superimposed to the basic flow. This leads to a change in the local heat transfer over the surface of the coolant channel as well as a change in the overall value of the heat transfer. Also the pressure loss over the channel length will change by rotation. By means of computational fluid dynamics (Finite Element Method) it was achieved to figure out the interaction between changing fluid flow and heat transfer. To validate the results obtained by a numerical flow simulation, a new measurement technique was developed. A laser-two-focus velocimeter has been combined with a rotation prism which allows continued measurements in a rotating scaled up channel. (orig.) [German] Bedingt durch die Rotationsbewegung eines Kuehlkanals wird die Grundstroemung von einem Sekundaerwirbel ueberlagert (Corioliskraefte). Durch diese Einfluesse aendert sich sowohl der lokale Waermeuebergang ueber der Kanaloberflaeche als auch die globalen Waermeuebertragungsraten ueber dem gesamten Kanal. Ebenfalls aendert sich durch die Rotation der Druckverlust ueber der Kanallaenge. Durch eine numerische Stroemungssimulation (Finite-Element-Methode) war es moeglich, einen detaillierten Zusammenhang zwischen dem veraenderten Stroemungsverhalten und dem Waermeuebertragungsverhalten darzustellen. Um die numerisch gewonnenen Ergebnisse experimentell abzusichern, wurde eine neuartige Messtechnik entwickelt. Ein Laser-2-Fokus-Velozimeter wurde mit einem Bilddrehprisma kombiniert, und dies erlaubte eine kontinuierliche Messung in einem rotierenden vergroesserten Modellkanal. (orig.)
Zhao, Hewei; Yang, Shengchang; Guo, Xudong; Peng, Congjiao; Gu, Xiaoxuan; Deng, Chuanyuan; Chen, Luzhen
2018-02-01
Mangrove species have developed uniquely efficient water-use strategies in order to survive in highly saline and anaerobic environments. Herein, we estimated the stand water use of two diffuse-porous mangrove species of the same age, Sonneratia apetala Buch. Ham and Sonneratia caseolaris (L.) Engl., growing in a similar intertidal environment. Specifically, to investigate the radial patterns of axial sap flow density (Js) and understand the anatomical traits associated with them, we measured axial sap flow density in situ together with micromorphological observations. A significant decrease of Js was observed for both species. This result was accompanied by the corresponding observations of wood structure and blockages in xylem sapwood, which appeared to influence and, hence, explained the acute radial reductions of axial sap flow in the stems of both species. However, higher radial resistance in sapwood of S. caseolaris caused a steeper decline of Js radially when compared with S. apetala, thus explaining the latter's more efficient use of water. Without first considering acute reductions in Js into the sapwood from the outer bark, a total of ~55% and 51% of water use would have been overestimated, corresponding to average discrepancies in stand water use of 5.6 mm day-1 for S. apetala trees and 2.5 mm day-1 for S. caseolaris trees. This suggests that measuring radial pattern of Js is a critical factor in determining whole-tree or stand water use. © The Author(s) 2018. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.
Kang, Hyun Su; Oh, Jeongsu; Han, Jeong Sam
2014-01-01
This paper discusses a one-way fluid structural interaction (FSI) analysis and shape optimization of the impeller blades for a 15,000 HP centrifugal compressor using the response surface method (RSM). Because both the aerodynamic performance and the structural safety of the impeller are affected by the shape of its blades, shape optimization is necessary using the FSI analysis, which includes a structural analysis for the induced fluid pressure and centrifugal force. The FSI analysis is performed in ANSYS Workbench: ANSYS CFX is used for the flow field and ANSYS Mechanical is used for the structural field. The response surfaces for the FSI results (efficiency, pressure ratio, maximum stress, etc.) generated based on the design of experiments (DOE) are used to find an optimal shape for the impeller blades, which provides the maximum aerodynamic performance subject to the structural safety constraints
Kang, Hyun Su [Sungkyunkwan University, Suwon (Korea, Republic of); Oh, Jeongsu [Daejoo Machinery Co., Daegu (Korea, Republic of); Han, Jeong Sam [Andong National University, Andong (Korea, Republic of)
2014-06-15
This paper discusses a one-way fluid structural interaction (FSI) analysis and shape optimization of the impeller blades for a 15,000 HP centrifugal compressor using the response surface method (RSM). Because both the aerodynamic performance and the structural safety of the impeller are affected by the shape of its blades, shape optimization is necessary using the FSI analysis, which includes a structural analysis for the induced fluid pressure and centrifugal force. The FSI analysis is performed in ANSYS Workbench: ANSYS CFX is used for the flow field and ANSYS Mechanical is used for the structural field. The response surfaces for the FSI results (efficiency, pressure ratio, maximum stress, etc.) generated based on the design of experiments (DOE) are used to find an optimal shape for the impeller blades, which provides the maximum aerodynamic performance subject to the structural safety constraints.
Kang, Nan; Zhang, Jing; Yu, Xiaotong; Ma, Yuewen
2017-01-01
We performed middle cerebral artery occlusion (MCAO) in rats to investigate the effect and some of the underlying mechanisms of radial extracorporeal shock wave therapy (rESWT) in cerebral ischemia rats. We measured neurological function and cerebral blood flow (CBF) using a full-field laser perfusion imager and brain infarct volume on days 3, 12, and 30. Immunofluorescence, western blot, and real-time polymerase chain reaction (PCR) techniques were used to detect the expression of vascular endothelial growth factor (VEGF), neuron-specific enolase (NSE), nestin, Wnt3a, and β-catenin in the ischemic hemisphere. The dose of rESWT used on the head revealed remarkable advantages over sham rESWT, as demonstrated by improved neurological function scores, increased CBF, and reduced brain infarct volume. Furthermore, applying rESWT to the head and limbs enhanced short-term neurological function. Our results confirmed that rESWT can induce VEGF expression over an extended period with a profound effect, which may be the primary reason for CBF recovery. High NSE and nestin expression levels suggest that rESWT enhanced the number of neurons and neural stem cells (NSCs). Wnt3a and β-catenin expression were up-regulated in the ischemic hemisphere, indicating that rESWT promoted NSC proliferation and differentiation via the Wnt/β-catenin pathway. Overall, our findings suggest that an appropriate rESWT dose delivered to the head of rats helps restore neurological function and CBF, and additional application of rESWT to the limbs is more effective than treating the head alone.
Radial loads and axial thrusts on centrifugal pumps
Anon.
1986-01-01
The proceedings of a seminar organised by the Power Industries Division of the IMechE are presented in this text. Complete contents: Review of parameters influencing hydraulic forces on centrifugal impellers; The effect of fluid forces at various operation conditions on the vibrations of vertical turbine pumps; A review of the pump rotor axial equilibrium problem - some case studies; Dynamic hydraulic loading on a centrifugal pump impeller; Experimental research on axial thrust loads of double suction centrifugal pumps; A comparison of pressure distribution and radial loads on centrifugal pumps; A theoretical and experimental investigation of axial thrusts within a multi-stage centrifugal pump
Numerical Calculation of the Flow in a Centrifugal Compressor Volute
Seong, Seon Mo; Kang, Shin Hyoung; Cho, Kyung Seok; Kim, Woo June
2007-01-01
Flows in the centrifugal compressor volute with circular cross section are numerically investigated. The computational domain contained inlet passage, impeller, radial and axial diffuser, and volute. The volute grid for the calculation utilized a multi-block arrangement to form a butterfly grid and flow calculations are performed using commercial CFD software, CFX-TASCflow. The centrifugal compressor of this study has the inlet passage like steps and axial diffuser after radial diffuser because of the shape of the motor cooling fins and installation constraints. Due to this feature the swirling flow pattern is different from the other investigations. The loss in through the inlet passage was considerable and the flow inside volute is very complex and three dimensional with strong vortex and recirculation through volute tongue
Numerical investigation of degas performance on impeller of medium-consistency pump
Hong Li
2015-12-01
Full Text Available Medium-consistency technology is known as the process with high efficiency and low pollution. The gas distribution was simulated in the medium-consistency pump with different degas hole positions. Rheological behaviors of pulp suspension were obtained by experimental test. A modified Herschel–Bulkley model and the Eulerian gas–liquid two-phase flow model were utilized to approximately represent the behaviors of the medium-consistency pulp suspension. The results show that when the relative position is 0.53, the gas volume ratio is less than 0.1% at the pump outlet and 9.8% at the vacuum inlet, and the pump head is at the maximum. Because of the different numbers of the impeller blades and turbulence blades and the asymmetric volute structure, the gas is distributed unevenly in the impeller. In addition, the pump performance was tested in experiment and the results are used to validate computational fluid dynamics outcomes.
Analysis on the influence of the pump start transient performance with different inertia impeller
Tang, Y; Cheng, J; Liu, E H; Tang, L D
2012-01-01
Centrifugal pump start-up time is very short, in the boot process, the instantaneous head and flow will have an impact role to the pipeline, and however the moment of inertia is one of the main factors affecting centrifugal pump boot acceleration. We analyzed the pump start-up transient characteristics with the different moment of inertia of the impeller corresponding to the different materials, there are three different moment of inertia of the impeller have been selected. At first, we use the 'Flowmaster' fluid system simulation software do the outer characteristics simulation to the selected-model, get the time - flow and the time - speed curve. Then, do the experiments research in the process when pump start-up, and compare with the simulation result. At last use the outer characteristics simulation result as the boundary, using the ANASYS CFX software do the transient simulation to the three groups with different inertia pump impeller, and draw the pressure distribution picture. In according to the analysis, we can confirm that the impact of inertia is one of the factors in the stability during the pump star, and we can get that the greater moment of inertia, the longer the boot stable. We also can get that combined Flowmaster with ANSYS can solved engineering practice problem in fluid system conveniently, and take it easy to solve the similar problem.
Abbasfard, Hamed; Hashemi, Seyed Hamid; Rahimpour, Mohammad Reza; Jokar, Seyyed Mohammad; Ghader, Sattar
2013-01-01
The nitric acid plant of a domestic petrochemical complex is designed to annually produce 56,400 metric tons (based on 100% nitric acid). In the present work, radial-flow spherical bed reactor (RFSBR) for selective catalytic reduction of nitric oxides (NO(x)) from the stack of this plant was modelled and compared with the conventional radial-flow reactor (CRFR). Moreover, the proficiency of a radial-flow (water or nitrogen) membrane reactor was also compared with the CRFR which was found to be inefficient at identical process conditions. In the RFSBR, the space between the two concentric spheres is filled by a catalyst. A mathematical model, including conservation of mass has been developed to investigate the performance of the configurations. The model was checked against the CRFR in a nitric acid plant located at the domestic petrochemical complex. A good agreement was observed between the modelling results and the plant data. The effects of some important parameters such as pressure and temperature on NO(x) conversion were analysed. Results show 14% decrease in NO(x) emission annually in RFSBR compared with the CRFR, which is beneficial for the prevention of NO(x) emission, global warming and acid rain.
Knežević Darko M.
2016-01-01
Full Text Available In control hydraulic components (servo valves, LS regulators, etc. there is a need for precise mathematical description of fluid flow through radial clearances between the control piston and body of component at zero overlap, small valve opening and small lengths of overlap. Such a mathematical description would allow for a better dynamic analysis and stability analysis of hydraulic systems. The existing formulas in the literature do not take into account the change of the physical properties of the fluid with a change of thermodynamic state of the fluid to determine the flow rate through radial clearances in hydraulic components at zero overlap, a small opening, and a small overlap lengths, which leads to the formation of insufficiently precise mathematical models. In this paper model description of fluid flow through radial clearances at zero overlap is developed, taking into account the changes of physical properties of hydraulic fluid as a function of pressure and temperature. In addition, the experimental verification of the mathematical model is performed.
Computational fluid dynamics modeling of gas dispersion in multi impeller bioreactor.
Ahmed, Syed Ubaid; Ranganathan, Panneerselvam; Pandey, Ashok; Sivaraman, Savithri
2010-06-01
In the present study, experiments have been carried out to identify various flow regimes in a dual Rushton turbines stirred bioreactor for different gas flow rates and impeller speeds. The hydrodynamic parameters like fractional gas hold-up, power consumption and mixing time have been measured. A two fluid model along with MUSIG model to handle polydispersed gas flow has been implemented to predict the various flow regimes and hydrodynamic parameters in the dual turbines stirred bioreactor. The computational model has been mapped on commercial solver ANSYS CFX. The flow regimes predicted by numerical simulations are validated with the experimental results. The present model has successfully captured the flow regimes as observed during experiments. The measured gross flow characteristics like fractional gas hold-up, and mixing time have been compared with numerical simulations. Also the effect of gas flow rate and impeller speed on gas hold-up and power consumption have been investigated. (c) 2009 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.
Investigation of CFD calculation method of a centrifugal pump with unshrouded impeller
Wu, Dazhuan; Yang, Shuai; Xu, Binjie; Liu, Qiaoling; Wu, Peng; Wang, Leqin
2014-03-01
Currently, relatively large errors are found in numerical results in some low-specific-speed centrifugal pumps with unshrouded impeller because the effect of clearances and holes are not accurately modeled. Establishing an accurate analytical model to improve performance prediction accuracy is therefore necessary. In this paper, a three-dimensional numerical simulation is conducted to predict the performance of a low-specific-speed centrifugal pump, and the modeling, numerical scheme, and turbulent selection methods are discussed. The pump performance is tested in a model pump test bench, and flow rate, head, power and efficiency of the pump are obtained. The effect of taking into consideration the back-out vane passage, clearance, and balance holes is analyzed by comparing it with experimental results, and the performance prediction methods are validated by experiments. The analysis results show that the pump performance can be accurately predicted by the improved method. Ignoring the back-out vane passage in the calculation model of unshrouded impeller is found to generate better numerical results. Further, the calculation model with the clearances and balance holes can obviously enhance the numerical accuracy. The application of disconnect interface can reduce meshing difficulty but increase the calculation error at the off-design operating point at the same time. Compared with the standard k-ɛ, renormalization group k-ɛ, and Spalart-Allmars models, the Realizable k-ɛ model demonstrates the fastest convergent speed and the highest precision for the unshrouded impeller flow simulation. The proposed modeling and numerical simulation methods can improve the performance prediction accuracy of the low-specific-speed centrifugal pumps, and the modeling method is especially suitable for the centrifugal pump with unshrouded impeller.
The effect of impeller type on silica sol formation in laboratory scale agitated tank
Nurtono, Tantular; Suprana, Yayang Ade; Latif, Abdul; Dewa, Restu Mulya; Machmudah, Siti; Widiyastuti,, E-mail: widi@chem-eng.its.ac.id; Winardi, Sugeng [Chemical Engineering Department, Institute of Technology Sepuluh Nopember, Surabaya 60111 (Indonesia)
2016-02-08
The multiphase polymerization reaction of the silica sol formation produced from silicic acid and potassium hydroxide solutions in laboratory scale agitated tank was studied. The reactor is equipped with four segmental baffle and top entering impeller. The inside diameter of reactor is 9 cm, the baffle width is 0.9 cm, and the impeller position is 3 cm from tank bottom. The diameter of standard six blades Rushton and three blades marine propeller impellers are 5 cm. The silicic acid solution was made from 0.2 volume fraction of water glass (sodium silicate) solution in which the sodium ion was exchanged by hydrogen ion from cation resin. The reactor initially filled with 286 ml silicic acid solution was operated in semi batch mode and the temperature was kept constant in 60 °C. The 3 ml/minute of 1 M potassium hydroxide solution was added into stirred tank and the solution was stirred. The impeller rotational speed was varied from 100 until 700 rpm. This titration was stopped if the solution in stirred tank had reached the pH of 10-The morphology of the silica particles in the silica sol product was analyzed by Scanning Electron Microscope (SEM). The size of silica particles in silica sol was measured based on the SEM image. The silica particle obtained in this research was amorphous particle and the shape was roughly cylinder. The flow field generated by different impeller gave significant effect on particle size and shape. The smallest geometric mean of length and diameter of particle (4.92 µm and 2.42 µm, respectively) was generated in reactor with marine propeller at 600 rpm. The reactor with Rushton impeller produced particle which the geometric mean of length and diameter of particle was 4.85 µm and 2.36 µm, respectively, at 150 rpm.
Mass transfer and power characteristics of stirred tank with Rushton and curved blade impeller
Thiyam Tamphasana Devi
2017-04-01
Full Text Available Present work compares the mass transfer coefficient (kLa and power draw capability of stirred tank employed with Rushton and curved blade impeller using computational fluid dynamics (CFD techniques in single and double impeller cases. Comparative analysis for different boundary conditions and mass transfer model has been done to assess their suitability. The predicted local kLa has been found higher in curved blade impeller than the Rushton impeller, whereas stirred tank with double impeller does not show variation due to low superficial gas velocity. The global kLa predicted has been found higher in curved blade impeller than the Rushton impeller in double and single cases. Curved blade impeller also exhibits higher power draw capability than the Rushton impeller. Overall, stirred tank with curved blade impeller gives higher efficiency in both single and double cases than the Rushton turbine
Tasawar Hayat
Full Text Available Peristaltic transport of Williamson fluid in a curved geometry is modeled. Problem formulation is completed by complaint walls of channel. Radial magnetic field in the analysis is taken into account. Resulting problem formulation is simplified using long wavelength and low Reynolds number approximations. Series solution is obtained for small Weissenberg number. Influences of different embedded parameters on the axial velocity and stream function are examined. As expected the velocity in curved channel is not symmetric. Axial velocity is noticed decreasing for Hartman number. Trapped bolus increases for Hartman and curvature parameters. Keywords: Williamson fluid, Curved channel, Radial magnetic field, Complaint walls
Shi, Weidong; Zhou, Ling; Lu, Weigang; Pei, Bing; Lang, Tao
2013-01-01
The existing research of the deep-well centrifugal pump mainly focuses on reduce the manufacturing cost and improve the pump performance, and how to combine above two aspects together is the most difficult and important topic. In this study, the performances of the deep-well centrifugal pump with four different impeller outlet widths are studied by the numerical, theoretical and experimental methods in this paper. Two stages deep-well centrifugal pump equipped with different impellers are simulated employing the commercial CFD software to solve the Navier-Stokes equations for three-dimensional incompressible steady flow. The sensitivity analyses of the grid size and turbulence model have been performed to improve numerical accuracy. The flow field distributions are acquired and compared under the design operating conditions, including the static pressure, turbulence kinetic energy and velocity. The prototype is manufactured and tested to certify the numerical predicted performance. The numerical results of pump performance are higher than the test results, but their change trends have an acceptable agreement with each other. The performance results indicted that the oversize impeller outlet width leads to poor pump performances and increasing shaft power. Changing the performance of deep-well centrifugal pump by alter impeller outlet width is practicable and convenient, which is worth popularizing in the engineering application. The proposed research enhances the theoretical basis of pump design to improve the performance and reduce the manufacturing cost of deep-well centrifugal pump.
Impeller Design of a Centrifugal Fan with Blade Optimization
Lee, Yu-Tai; Ahuja, Vineet; Hosangadi, Ashvin; Slipper, Michael E.; Mulvihill, Lawrence P.; Birkbeck, Roger; Coleman, Roderick M.
2011-01-01
A method is presented for redesigning a centrifugal impeller and its inlet duct. The double-discharge volute casing is a structural constraint and is maintained for its shape. The redesign effort was geared towards meeting the design volute exit pressure while reducing the power required to operate the fan. Given the high performance of the baseline impeller, the redesign adopted a high-fidelity CFD-based computational approach capable of accounting for all aerodynamic losses. The present eff...
Hathaway, Michael D.; Chriss, Randall M.; Strazisar, Anthony J.; Wood, Jerry R.
1995-01-01
A laser anemometer system was used to provide detailed surveys of the three-dimensional velocity field within the NASA low-speed centrifugal impeller operating with a vaneless diffuser. Both laser anemometer and aerodynamic performance data were acquired at the design flow rate and at a lower flow rate. Floor path coordinates, detailed blade geometry, and pneumatic probe survey results are presented in tabular form. The laser anemometer data are presented in the form of pitchwise distributions of axial, radial, and relative tangential velocity on blade-to-blade stream surfaces at 5-percent-of-span increments, starting at 95-percent-of-span from the hub. The laser anemometer data are also presented as contour and wire-frame plots of throughflow velocity and vector plots of secondary velocities at all measurement stations through the impeller.
Liu, Q Z; Yang, K; Li, D Y; Gong, R Z
2013-01-01
The fluid pressure fluctuation generated by unsteady flow is a very important factor to induce vibration of the centrifugal pump. The relative movement between impeller and volute generates an unsteady interaction which affects not only the overall pump performance, but is also responsible for pressure fluctuations. Pressure fluctuations interact with the volute casing or even with the circuit and give rise to dynamic effects over the mechanical parts, which are one of the most important sources of vibration and hydraulic noise. To investigate the flow characteristic in the centrifugal pump, the unsteady flow is simulated by CFD methods in this paper. Unsteady flow characteristic in the centrifugal pump is obtained considering the impeller-volute interaction in the whole flow field. Based on the unsteady flow simulation, amplitude-frequency characteristics of the pressure fluctuation in the centrifugal pump are obtained through setting up monitoring point at the impeller outlet. The research shows that the frequency component include the blade passing frequency as the main component, the multiplication of blade passing frequency, and the harmonic interference due to the unsteady flow
Optimal Design of a Centrifugal Compressor Impeller Using Evolutionary Algorithms
Soo-Yong Cho
2012-01-01
Full Text Available An optimization study was conducted on a centrifugal compressor. Eight design variables were chosen from the control points for the Bezier curves which widely influenced the geometric variation; four design variables were selected to optimize the flow passage between the hub and the shroud, and other four design variables were used to improve the performance of the impeller blade. As an optimization algorithm, an artificial neural network (ANN was adopted. Initially, the design of experiments was applied to set up the initial data space of the ANN, which was improved during the optimization process using a genetic algorithm. If a result of the ANN reached a higher level, that result was re-calculated by computational fluid dynamics (CFD and was applied to develop a new ANN. The prediction difference between the ANN and CFD was consequently less than 1% after the 6th generation. Using this optimization technique, the computational time for the optimization was greatly reduced and the accuracy of the optimization algorithm was increased. The efficiency was improved by 1.4% without losing the pressure ratio, and Pareto-optimal solutions of the efficiency versus the pressure ratio were obtained through the 21st generation.
Yamagishi, Osamu
2018-04-01
Radial wavenumber dependencies of the residual zonal potential for E × B flow in a circular, large aspect ratio tokamak is investigated by means of the collisionless gyrokinetic simulations of Rosenbluth-Hinton (RH) test and the semi-analytic approach using an analytic solution of the gyrokinetic equation Rosenbluth and Hinton (1998 Phys. Rev. Lett. 80 724). By increasing the radial wavenumber from an ion Larmor radius scale {k}r{ρ }i≲ 1 to an electron Larmor radius scale {k}r{ρ }e≲ 1, the well-known level ˜ O[1/(1+1.6{q}2/\\sqrt{r/{R}0})] is retained, while the level remains O(1) when the wavenumber is decreased from the electron to the ion Larmor radius scale, if physically same adiabatic assumption is presumed for species other than the main species that is treated kinetically. The conclusion is not modified by treating both species kinetically, so that in the intermediate scale between the ion and electron Larmor radius scale it seems difficult to determine the level uniquely. The toroidal momentum conservation property in the RH test is also investigated by including an initial parallel flow in addition to the perpendicular flow. It is shown that by taking a balance between the initial parallel flow and perpendicular flows which include both E × B flow and diamagnetic flow in the initial condition, the mechanical toroidal angular momentum is approximately conserved despite the toroidal symmetry breaking due to the finite radial wavenumber zonal modes. Effect of electromagnetic potentials is also investigated. When the electromagnetic potentials are applied initially, fast oscillations which are faster than the geodesic acoustic modes are introduced in the decay phase of the zonal modes. Although the residual level in the long time limit is not modified, this can make the time required to reach the stationary zonal flows longer and may weaken the effectiveness of the turbulent transport suppression by the zonal flows.
Effect of attack angle on flow characteristic of centrifugal fan
Wu, Y.; Dou, H. S.; Wei, Y. K.; Chen, X. P.; Chen, Y. N.; Cao, W. B.
2016-05-01
In this paper, numerical simulation is performed for the performance and internal flow of a centrifugal fan with different operating conditions using steady three-dimensional incompressible Navier-Stokes equations coupled with the RNG k-e turbulent model. The performance curves, the contours of static pressure, total pressure, radial velocity, relative streamlines and turbulence intensity at different attack angles are obtained. The distributions of static pressure and velocity on suction surface and pressure surface in the same impeller channel are compared for various attack angles. The research shows that the efficiency of the centrifugal fan is the highest when the attack angle is 8 degree. The main reason is that the vortex flow in the impeller is reduced, and the jet-wake pattern is weakened at the impeller outlet. The pressure difference between pressure side and suction side is smooth and the amplitude of the total pressure fluctuation is low along the circumferential direction. These phenomena may cause the loss reduced for the attack angle of about 8 degree.
Quanyan Tian
2017-12-01
Full Text Available Global climate change is likely to change precipitation patterns with consequences for tree water use and growth in semi-arid areas. However, little is known about the effects of variability in precipitation on growth- and water-related physiological processes of native trees in dry areas of northwestern China. In this study, sap flow and stem radial variability in four Qinghai spruce trees (Picea crassifolia were monitored in the Qilian Mountains, China. Tree water deficit (ΔW and basal area increment (BAI were calculated using stem radial variation; water-use efficiency (WUE was then estimated as the ratio of BAI and sap flow (Jt. The results showed that sap flow density (Js increased logarithmically with increasing ΔW when ΔW < 50 μm, and then gradually stabilized. Multiple factor generalized additive models (GAM showed that Js was closely related to all measured environmental variables except for daily mean temperature and relative air humidity. ΔW was related to the minimum daily temperature and soil water content. WUE exhibited higher values in early July. Low WUE was observed under conditions of prolonged dry weather, but it quickly increased during rainy days. WUE decreased after precipitation events due to high transpiration. We concluded that, in these semi-arid areas, precipitation is the most important controlling factor in tree growth and transpiration.
Brandao, Jose Geraldo Trani; Tomazini, Jose Elias [UNESP, Guaratingueta, SP (Brazil). Faculdade de Engenharia. Dept. de Mecanica]. E-mails: brandao@feg.unesp.br; tomazini@feg.unesp.br
2000-07-01
This work reports the static calibration of a device used for measurements of the hydraulic efforts resulting from the interaction between the flow and the turbomachinery rotor, simulating the various operation conditions. The device was developed by the Stuttgart University. A calibration process is described for allowing a real correspondence among real efforts acting on the rotor model and the the measured efforts. The used device consists of load three dimension piezoelectric sensors.
Neverov, V. V.; Kozhukhov, Y. V.; Yablokov, A. M.; Lebedev, A. A.
2017-08-01
Nowadays the optimization using computational fluid dynamics (CFD) plays an important role in the design process of turbomachines. However, for the successful and productive optimization it is necessary to define a simulation model correctly and rationally. The article deals with the choice of a grid and computational domain parameters for optimization of centrifugal compressor impellers using computational fluid dynamics. Searching and applying optimal parameters of the grid model, the computational domain and solver settings allows engineers to carry out a high-accuracy modelling and to use computational capability effectively. The presented research was conducted using Numeca Fine/Turbo package with Spalart-Allmaras and Shear Stress Transport turbulence models. Two radial impellers was investigated: the high-pressure at ψT=0.71 and the low-pressure at ψT=0.43. The following parameters of the computational model were considered: the location of inlet and outlet boundaries, type of mesh topology, size of mesh and mesh parameter y+. Results of the investigation demonstrate that the choice of optimal parameters leads to the significant reduction of the computational time. Optimal parameters in comparison with non-optimal but visually similar parameters can reduce the calculation time up to 4 times. Besides, it is established that some parameters have a major impact on the result of modelling.
CFD Modelling of a Pump as Turbine (PAT with Rounded Leading Edge Impellers for Micro Hydro Systems
Ismail Mohd Azlan
2017-01-01
Full Text Available A Pump as Turbine (PAT is one of micro hydro system components that is used to substitute a commercially available turbine due to its wide availability and low acquisition cost. However, PAT have high hydraulic losses due to differences in pump-turbine operation and hydraulic design. The fluid flowing inside the PAT is subjected to hydraulic losses due to the longer flow passage and unmatched fluid flow within the wall boundaries. This paper presents the effect of rounding the impeller leading edges of the pump on turbine performance. A CFD model of a PAT was designed to simulate virtual performance for the analysis. The aim of this study is to observe the internal hydraulic performance resulting from the changes in the performance characteristics. Highest efficiency was recorded at 17.0 l/s, an increase of 0.18%. The simulation results reveal that there is an improvement in hydraulic performance at overflow operation. The velocity vector visualization shows that there is a reduction in wake and consequently less flow separation along impeller flow passages. However, adjusting the sensitive impeller inlet geometry will also alter the velocity inlet vector and consequently change the velocity triangles for the turbo machinery system.
Follin, Sven (SF GeoLogic AB (Sweden)); Ludvigson, Jan-Erik; Leven, Jakob (Geosigma AB (Sweden))
2011-09-15
According to the strategy for hydrogeological characterisation within the SKB's site investigation programme, two single-hole test methods are available for testing and parameterisation of groundwater flow models - constant-head injection testing with the Pipe String System (PSS method) and difference flow logging with the Posiva Flow Log (PFL method). This report presents the results of an investigation to assess discrepancies in the results of single-hole transmissivity measurements using these methods in the Forsmark site characterisation. The investigation explores the possibility that the source of the discrepancy observed lies in the assumptions of the flow geometry that are inherent to the methods used for standard constant-head injection well test analysis and difference flow logging analysis, respectively. In particular, the report looks at the generalised radial flow (GRF) concept by Barker (1988) as a means that might explain some of the differences. A confirmation of the actual flow geometries (dimensions) observed during hydraulic injection tests could help to identify admissible conceptual models for the tested system, and place the hydraulic testing with the PSS and PFL test methods in its full hydrogeological context. The investigation analyses 151 constant-head injection tests in three cored boreholes at Forsmark. The results suggest that the transmissivities derived with standard constant-head injection well test analysis methods and with the GRF concept, respectively, are similar provided that the dominating flow geometry during the testing is radial (cylindrical). Thus, having flow geometries with dimensions other than 2 affects the value of the interpreted transmissivity. For example, a flow system with a dimension of 1 may require an order of magnitude or more, higher transmissivity to produce the same flow rates. The median of the GRF flow dimensions of all 151 constant-head injection tests is 2.06 with 33% of the tests in the range 1
Ran Tao
2014-01-01
Full Text Available RANS simulation is widely used in the flow prediction of centrifugal pumps. Influenced by impeller rotation and streamline curvature, the eddy viscosity models with turbulence isotropy assumption are not accurate enough. In this study, Spalart-Shur rotation/curvature correction was applied on the SST k-ω turbulence model. The comparative assessment of the correction was proceeded in the simulations of a centrifugal pump impeller. CFD results were compared with existing PIV and LDV data under the design and low flow rate off-design conditions. Results show the improvements of the simulation especially in the situation that turbulence strongly produced due to undesirable flow structures. Under the design condition, more reasonable turbulence kinetic energy contour was captured after correction. Under the low flow rate off-design condition, the prediction of turbulence kinetic energy and velocity distributions became much more accurate when using the corrected model. So, the rotation/curvature correction was proved effective in this study. And, it is also proved acceptable and recommended to use in the engineering simulations of centrifugal pump impellers.
Frydrychowicz, A; Roldan-Alzate, A; Winslow, E; Consigny, D; Campo, C A; Motosugi, U; Johnson, K M; Wieben, O; Reeder, S B
2017-12-01
Objectives of this study were to compare radial time-resolved phase contrast magnetic resonance imaging (4D Flow-MRI) with perivascular ultrasound (pvUS) and to explore a porcine model of acute pre-hepatic portal hypertension (PHTN). Abdominal 4D Flow-MRI and pvUS in portal and splenic vein, hepatic and both renal arteries were performed in 13 pigs of approximately 60 kg. In six pigs, measurements were repeated after partial portal vein (PV) ligature. Inter- and intra-reader comparisons and statistical analysis including Bland-Altman (BA) comparison, paired Student's t tests and linear regression were performed. PvUS and 4D Flow-MRI measurements agreed well; flow before partial PV ligature was 322 ± 30 ml/min in pvUS and 297 ± 27 ml/min in MRI (p = 0.294), and average BA difference was 25 ml/min [-322; 372]. Inter- and intra-reader results differed very little, revealed excellent correlation (R 2 = 0.98 and 0.99, respectively) and resulted in BA differences of -5 ml/min [-161; 150] and -2 ml/min [-28; 25], respectively. After PV ligature, PV flow decreased from 356 ± 50 to 298 ± 61 ml/min (p = 0.02), and hepatic arterial flow increased from 277 ± 36 to 331 ± 65 ml/min (p = n.s.). The successful in vivo comparison of radial 4D Flow-MRI to perivascular ultrasound revealed good agreement of abdominal blood flow although with considerable spread of results. A model of pre-hepatic PHTN was successfully introduced and acute responses monitored. • Radial 4D Flow-MRI in the abdomen was successfully compared to perivascular ultrasound. • Inter- and intra-reader testing demonstrated excellent reproducibility of upper abdominal 4D Flow-MRI. • A porcine model of acute pre-hepatic portal hypertension was successfully introduced. • 4D Flow-MRI successfully monitored acute changes in a model of portal hypertension.
Nakamura, Manami; Makabe, Takeshi; Ichikawa, Masaki; Hatakeyama, Ryohei; Sugimori, Hiroyuki; Sakata, Motomichi
2013-01-01
Vessel wall imaging using radial scanning does not use a blood flow suppression pulse with gated acquisition. It has been proposed that there may not be a flow void effect if the flow rate is slow; however, this has yet to be empirically tested. To clarify the relationship between the signal intensity of the vessel lumen and the blood flow rate in a flow phantom, we investigated the usefulness of vessel wall imaging at 3.0 tesla (T). We measured the signal intensity while changing the flow rate in the flow phantom. Radial scanning at 1.5 T showed sufficient flow voids at above medium flow rates. There was no significant difference in lumen signal intensity at the carotid artery flow rate. The signal intensity of the vessel lumen decreased sufficiently using the radial scan method at 3.0 T. We thus obtained sufficient flow void effects at the carotid artery flow rate. We conclude this technique to be useful for evaluating plaque if high contrast can be maintained for fixed tissue (such as plaque) and the vessel lumen. (author)
Detonation in supersonic radial outflow
Kasimov, Aslan R.; Korneev, Svyatoslav
2014-01-01
We report on the structure and dynamics of gaseous detonation stabilized in a supersonic flow emanating radially from a central source. The steady-state solutions are computed and their range of existence is investigated. Two-dimensional simulations
Energy Harvesting from Fluid Flow in Water Pipelines for Smart Metering Applications
Hoffmann, D; Willmann, A; Göpfert, R; Becker, P; Folkmer, B; Manoli, Y
2013-01-01
In this paper a rotational, radial-flux energy harvester incorporating a three-phase generation principle is presented for converting energy from water flow in domestic water pipelines. The energy harvester together with a power management circuit and energy storage is used to power a smart metering system installed underground making it independent from external power supplies or depleting batteries. The design of the radial-flux energy harvester is adapted to the housing of a conventional mechanical water flow meter enabling the use of standard components such as housing and impeller. The energy harvester is able to generate up to 720 mW when using a flow rate of 20 l/min (fully opened water tab). A minimum flow rate of 3 l/min is required to get the harvester started. In this case a power output of 2 mW is achievable. By further design optimization of the mechanical structure including the impeller and magnetic circuit the threshold flow rate can be further reduced
Energy Harvesting from Fluid Flow in Water Pipelines for Smart Metering Applications
Hoffmann, D.; Willmann, A.; Göpfert, R.; Becker, P.; Folkmer, B.; Manoli, Y.
2013-12-01
In this paper a rotational, radial-flux energy harvester incorporating a three-phase generation principle is presented for converting energy from water flow in domestic water pipelines. The energy harvester together with a power management circuit and energy storage is used to power a smart metering system installed underground making it independent from external power supplies or depleting batteries. The design of the radial-flux energy harvester is adapted to the housing of a conventional mechanical water flow meter enabling the use of standard components such as housing and impeller. The energy harvester is able to generate up to 720 mW when using a flow rate of 20 l/min (fully opened water tab). A minimum flow rate of 3 l/min is required to get the harvester started. In this case a power output of 2 mW is achievable. By further design optimization of the mechanical structure including the impeller and magnetic circuit the threshold flow rate can be further reduced.
Flow measurements in a model centrifugal pump by 3-D PIV
Yang, H; Xu, H R; Liu, C
2012-01-01
PIV (Particle Image Velocimetry), as an non-intrusive flow measurements technology, is widely used to investigate the flow fields in many areas. 3-D (three Dimensional) PIV has seldom been used to measure flow field in rotational impeller of centrifugal pump due to the difficulty of calibration in samll space. In this article, a specially manufactured water tank was used to perform the calibration for 3-D PIV measurement. The instantaneous absolute velocity in one impeller passage was obtained by merging of three sub zones and the relative velocity was acquired by velocity decomposition. The result shows that, when the pump runs at the condition of design flow rate, the radial component velocity W r appears a concave distribution except the condition of R=45 mm. With the increase of radius, the circumference location of the minimum radial component velocity W r moves from the pressure side to the suction side. At the same time, the tangential component velocity W θ on the suction side decreases gradually with the increase of radius, while the component on the pressure side increases gradually. The secondary flow in different radius section has also been shown. At last, the error of PIV measurements was analyzed, which shows that the test results are accurate and the measured data is reliable.
Rapid Speed Modulation of a Rotary Total Artificial Heart Impeller.
Kleinheyer, Matthias; Timms, Daniel L; Tansley, Geoffrey D; Nestler, Frank; Greatrex, Nicholas A; Frazier, O Howard; Cohn, William E
2016-09-01
Unlike the earlier reciprocating volume displacement-type pumps, rotary blood pumps (RBPs) typically operate at a constant rotational speed and produce continuous outflow. When RBP technology is used in constructing a total artificial heart (TAH), the pressure waveform that the TAH produces is flat, without the rise and fall associated with a normal arterial pulse. Several studies have suggested that pulseless circulation may impair microcirculatory perfusion and the autoregulatory response and may contribute to adverse events such as gastrointestinal bleeding, arteriovenous malformations, and pump thrombosis. It may therefore be beneficial to attempt to reproduce pulsatile output, similar to that generated by the native heart, by rapidly modulating the speed of an RBP impeller. The choice of an appropriate speed profile and control strategy to generate physiologic waveforms while minimizing power consumption and blood trauma becomes a challenge. In this study, pump operation modes with six different speed profiles using the BiVACOR TAH were evaluated in vitro. These modes were compared with respect to: hemodynamic pulsatility, which was quantified as surplus hemodynamic energy (SHE); maximum rate of change of pressure (dP/dt); pulse power index; and motor power consumption as a function of pulse pressure. The results showed that the evaluated variables underwent different trends in response to changes in the speed profile shape. The findings indicated a possible trade-off between SHE levels and flow rate pulsatility related to the relative systolic duration in the speed profile. Furthermore, none of the evaluated measures was sufficient to fully characterize hemodynamic pulsatility. © 2016 International Center for Artificial Organs and Transplantation and Wiley Periodicals, Inc.
Frydrychowicz, A. [University of Wisconsin - Madison, Department of Radiology, School of Medicine and Public Health, E3/366 Clinical Science Center, Madison, WI (United States); University Hospital Schleswig-Holstein, Campus Luebeck, Clinic for Radiology and Nuclear Medicine, Luebeck (Germany); University of Luebeck, Luebeck (Germany); Roldan-Alzate, A. [University of Wisconsin - Madison, Department of Radiology, School of Medicine and Public Health, E3/366 Clinical Science Center, Madison, WI (United States); University of Wisconsin, Department of Mechanical Engineering, Madison (United States); Winslow, E. [University of Wisconsin, Department of Surgery, Madison (United States); Consigny, D.; Campo, C.A.; Motosugi, U. [University of Wisconsin - Madison, Department of Radiology, School of Medicine and Public Health, E3/366 Clinical Science Center, Madison, WI (United States); Johnson, K.M. [University of Wisconsin, Department of Medical Physics, Madison (United States); Wieben, O. [University of Wisconsin - Madison, Department of Radiology, School of Medicine and Public Health, E3/366 Clinical Science Center, Madison, WI (United States); University of Wisconsin, Department of Medical Physics, Madison (United States); Reeder, S.B. [University of Wisconsin - Madison, Department of Radiology, School of Medicine and Public Health, E3/366 Clinical Science Center, Madison, WI (United States); University of Wisconsin, Department of Medical Physics, Madison (United States); University of Wisconsin, Department of Biomedical Engineering, Madison (United States); University of Wisconsin, Department of Medicine, Madison (United States); University of Wisconsin, Department of Emergency Medicine, Madison (United States)
2017-12-15
Objectives of this study were to compare radial time-resolved phase contrast magnetic resonance imaging (4D Flow-MRI) with perivascular ultrasound (pvUS) and to explore a porcine model of acute pre-hepatic portal hypertension (PHTN). Abdominal 4D Flow-MRI and pvUS in portal and splenic vein, hepatic and both renal arteries were performed in 13 pigs of approximately 60 kg. In six pigs, measurements were repeated after partial portal vein (PV) ligature. Inter- and intra-reader comparisons and statistical analysis including Bland-Altman (BA) comparison, paired Student's t tests and linear regression were performed. PvUS and 4D Flow-MRI measurements agreed well; flow before partial PV ligature was 322 ± 30 ml/min in pvUS and 297 ± 27 ml/min in MRI (p = 0.294), and average BA difference was 25 ml/min [-322; 372]. Inter- and intra-reader results differed very little, revealed excellent correlation (R {sup 2} = 0.98 and 0.99, respectively) and resulted in BA differences of -5 ml/min [-161; 150] and -2 ml/min [-28; 25], respectively. After PV ligature, PV flow decreased from 356 ± 50 to 298 ± 61 ml/min (p = 0.02), and hepatic arterial flow increased from 277 ± 36 to 331 ± 65 ml/min (p = n.s.). The successful in vivo comparison of radial 4D Flow-MRI to perivascular ultrasound revealed good agreement of abdominal blood flow although with considerable spread of results. A model of pre-hepatic PHTN was successfully introduced and acute responses monitored. (orig.)
P. Hasal
2002-01-01
Full Text Available Experimental data obtained by measuring the tangential component of force affecting radial baffles in a flat-bottomed cylindrical mixing vessel stirred with pitched blade impellers is analysed. The maximum mean tangential force is detected at the vessel bottom. The mean force value increases somewhat with decreasing impeller off-bottom clearance and is noticeably affected by the number of impeller blades. Spectral analysis of the experimental data clearly demonstrated the presence of its macro-instability (MI related low-frequency component embedded in the total force at all values of impeller Reynolds number. The dimensionless frequency of the occurrence of the MI force component is independent of stirring speed, position along the baffle, number of impeller blades and liquid viscosity. Its mean value is about 0.074. The relative magnitude (QMI of the MI-related component of the total force is evaluated by a combination of proper orthogonal decomposition (POD and spectral analysis. Relative magnitude QMI was analysed in dependence on the frequency of the impeller revolution, the axial position of the measuring point in the vessel, the number of impeller blades, the impeller off-bottom clearance, and liquid viscosity. Higher values of QMI are observed at higher impeller off-bottom clearance height and (generally QMI decreases slightly with increasing impeller speed. The QMI value decreases in the direction from vessel bottom to liquid level. No evident difference was observed between 4 blade and 6 blade impellers. Liquid viscosity has only a marginal impact on the QMI value.
Radial lean direct injection burner
Khan, Abdul Rafey; Kraemer, Gilbert Otto; Stevenson, Christian Xavier
2012-09-04
A burner for use in a gas turbine engine includes a burner tube having an inlet end and an outlet end; a plurality of air passages extending axially in the burner tube configured to convey air flows from the inlet end to the outlet end; a plurality of fuel passages extending axially along the burner tube and spaced around the plurality of air passage configured to convey fuel from the inlet end to the outlet end; and a radial air swirler provided at the outlet end configured to direct the air flows radially toward the outlet end and impart swirl to the air flows. The radial air swirler includes a plurality of vanes to direct and swirl the air flows and an end plate. The end plate includes a plurality of fuel injection holes to inject the fuel radially into the swirling air flows. A method of mixing air and fuel in a burner of a gas turbine is also provided. The burner includes a burner tube including an inlet end, an outlet end, a plurality of axial air passages, and a plurality of axial fuel passages. The method includes introducing an air flow into the air passages at the inlet end; introducing a fuel into fuel passages; swirling the air flow at the outlet end; and radially injecting the fuel into the swirling air flow.
Jianchi Xin
2016-03-01
Full Text Available In engineering practice, most centrifugal compressors use variable inlet guide vanes which can provide pre-whirl and control volume flow rates. As the impeller of a centrifugal compressor passes through the wakes created from the guide vanes, the aerodynamic parameters change significantly. The concept of adding dual slots at the trailing-edge of the guide vanes is proposed for reducing the aerodynamic load on the compressor impeller blades. In this article, the steady and unsteady performances of the new guide vanes are analysed under two compressor operating conditions (winter and design conditions. The results show that the average amplitude of the impeller passing frequency at the leading edge has a 13% decrease under the winter condition, especially at the middle and root parts. Moreover, the dual slots structure has no effect on the overall compressor performance.
Pitched blade impeller - an option for mixing in continuous actinide reconversion process
Tripathi, V.M.; Suresh Kumar, K.; Sreekumar, G.; Sugilal, G.
2016-01-01
In nuclear fuel cycle, current methodology for Pu reconversion involves Pu(IV)-oxalate precipitation as a semi continuous/batch process mode for a predetermined volume of Pu(NO 3 ) 4 solution in a long single column with a marine propeller type stirrer. In this process the slurry is being drained from bottom of the vessel leading to a possibility of accumulation of precipitate in the vessel which is an unfavorable condition for continuous process. As continuous reconversion process is a requirement to meet high through put of reprocessing plants, the conventional process has to be improvised with reference to its slurry exit point through overflow line. Although marine propeller type stirrer ensures an axial flow, it is not a choice for uniform solid suspension in a reactor vessel. A better alternate for complete suspension of solid in tall reactor is pitched blade turbine. Moreover pitched blade impellers are effective in low bottom clearance which ensures a thorough mixing of reactants. Present study focuses on feasibility of pitched blade impeller for mixing of reactants in a continuous actinide oxalate precipitation reactor with over flow line
Aizaki, Hideki; Nagamori, Seishi; Matsuda, Mami; Kawakami, Hayato; Hashimoto, Osamu; Ishiko, Hiroaki; Kawada, Masaaki; Matsuura, Tomokazu; Hasumura, Satoshi; Matsuura, Yoshiharu; Suzuki, Tetsuro; Miyamura, Tatsuo
2003-01-01
Lack of efficient culture systems for hepatitis C virus (HCV) has been a major obstacle in HCV research. Human liver cells grown in a three-dimensional radial-flow bioreactor were successfully infected following inoculation with plasma from an HCV carrier. Subsequent detection of increased HCV RNA suggested viral replication. Furthermore, transfection of HCV RNA transcribed from full-length cDNA also resulted in the production and release of HCV virions into supernatant. Infectivity was shown by successful secondary passage to a new culture. Introduction of mutations in RNA helicase and polymerase regions of HCV cDNA abolished virus replication, indicating that reverse genetics of this system is possible. The ability to replicate and detect the extracellular release of HCV might provide clues with regard to the persistent nature of HCV infection. It will also accelerate research into the pathogenicity of HCV, as well as the development of prophylactic agents and new therapy
Physical aspects of liquid-impelled loop reactors
Sonsbeek, van H.
1992-01-01
The liquid-impelled loop reactor (LLR) is a reactor that consists of two parts : the main tube and the circulation tube. Both parts are in open connection at the bottom and at the top. The reactor is filled with a liquid phase: the continuous phase. Another liquid phase is injected in the
CFD simulation of the discharge flow from standard Rushton impeller
Kysela, Bohuš; Konfršt, Jiří; Fořt, I.; Chára, Zdeněk
2014-01-01
Roč. 2014, January (2014), s. 1-7 ISSN 1687-8078 R&D Projects: GA ČR GAP101/12/2274 Institutional support: RVO:67985874 Keywords : Rushton turbine * mixing * ensemble-average mean velocity * fluctuating velocity * LDA/LDV * velocity profiles Subject RIV: BK - Fluid Dynamics
Hermansky, Jozef; Zavodsky, Martin
2014-01-01
A coolant flow through the reactor is usually determined after annual outages at Slovak NPP (VVER 440) in two distinct ways. First method is determination on the basis of the secondary system parameters - measurement of thermal balances. The value achieved by this method is used as the input parameter in the Table of allowed reactor operation modes. The second method draws from the primary system parameters - measurement of primary system hydraulic characteristics. Flow nozzles used for the measurement of feed water flow behind high pressure heaters were replaced at both Bohunice Units during outages in 2008. The feed water flow behind high pressure heaters is one of the main parameters used for the determination of coolant flow through the reactor by the first method. Compared to the measurement executed during previous fuel cycles, the calculated coolant flow through the reactor decreased considerably after the change of flow nozzles. The imaginary change of coolant flow through the reactor at Unit 3 was -1,6 %; and at Unit 4 -2,6 %. This change was not proved by the parallel measurement of primary system hydraulic characteristics. Later it was found out that the original flow nozzles used for 25 years were substantially deposited (original inner diameter of the nozzles was reduced by about 0,6-0,9 mm). Therefore feed water flow measurement was untrustworthy within the recent years. On the findings stated above, Bohunice NPP has decided to increase coolant flow through the reactor by changing the reactor coolant pumps impeller wheels. The modification of impellers wheels is planned within years 2012 to 2014. During the outages in 2013 two impeller wheels were replaced at both units. Nowadays Unit 4 is operated with all 6 new impeller wheels and Unit 3 with four new impeller wheels. Modification of last two impeller wheels at Unit 3 will be performed during the outage in 2014. On account of impeller wheels modification, non-standard measurement of PS hydraulic
Cheng, X R; Li, R N; Gao, Y; Guo, W L
2013-01-01
A commercial CFD code has been used to predict the performance of a screw centrifugal pump with pump-out vanes, especially when changing regularity of impeller axial force based on the solid-liquid two-phase flow. The Unsteady Reynolds Averaged Navier-Stokes (URANS) approach has been applied to solve the unsteady, incompressible, three-dimensional turbulent. The SIMPLEC algorithm, standard wall functions and mix two-phase flow model were applied. The RNG k ε-model was used to account the turbulence effects. By changing the number of impeller pump-out vanes and width, six different screw centrifugal pump numerical simulation projects were given, and each scheme in the different solid volume fraction were calculated respectively. The change rules of axial force, velocity and pressure distribution of flow field were obtained on the different condition and different volume fraction. The results showed that the axial forces values based solid-fluid two-phase greater than based single-phase clear water, but both changing regularity of the axial force were consistent; as same condition, the same solid-phase volume concentration, with the increase of pump-out vanes number or width, the impeller axial force increased as well. Meanwhile the number of the pump-out vanes and the width of pump-out vanes in balancing the impeller axial force, there are the most optimal value
Kan, Kan; Liu, Huiwen; Yang, Chunxia [Hohai University, Nanjing (China); Zheng, Yuan [National Engineering Research Center of Water Resources Efficient Utilization and Engineering Safety, Nanjing (China); Fu, Shifeng; Zhang, Xin [Power China Huadong Engineering Corporation, Hangzhou (China)
2017-04-15
Current research on the stability of tubular pumps is mainly concerned with the transient hydrodynamic characteristics. However, the structural response under the influence of fluid-structure interaction hasn't been taken fully into consideration. The instability of the structure can cause vibration and cracks, which may threaten the safety of the unit. We used bidirectional fluid-structure interaction to comprehensively analyze the dynamic stress characteristics of the impeller blades of the shaft extension tubular pump device. Furthermore, dynamic stress of impeller blade of shaft extension tubular pump device was solved under different lift conditions of 0° blade angle. Based on Reynolds-average N-S equation and SST k-ω turbulence model, numerical simulation was carried out for three-dimensional unsteady incompressible turbulent flow field of the pump device whole flow passage. Meanwhile, the finite element method was used to calculate dynamic characteristics of the blade structure. The blade dynamic stress distribution was obtained on the basis of fourth strength theory. The research results indicate that the maximum blade dynamic stress appears at the joint between root of inlet side of the blade suction surface and the axis. Considering the influence of gravity, the fluctuation of the blade dynamic stress increases initially and decreases afterwards within a rotation period. In the meantime, the dynamic stress in the middle part of inlet edge presents larger relative fluctuation amplitude. Finally, a prediction method for dynamic stress distribution of tubular pump considering fluid-structure interaction and gravity effect was proposed. This method can be used in the design stage of tubular pump to predict dynamic stress distribution of the structure under different operating conditions, improve the reliability of pump impeller and analyze the impeller fatigue life.
Effects of radial diffuser hydraulic design on a double-suction centrifugal pump
Hou, H. C.; Zhang, Y. X.; Xu, C.; Zhang, J. Y.; Li, Z. L.
2016-05-01
device and is good to transform the dynamic energy to pressure energy. Then through the hydraulic loss analysis of each pump component for all diffusers, it shows that the impeller takes up the biggest part of the whole loss about 8.19% averagely, the radial diffuser about 3.70% and the volute about 1.65%. The hydraulic loss of impeller is dominant at the large flow rate while the radial diffuser is at the small flow rate. Among all diffusers, the ES profile diffuser generates the least loss and combined to the distribution of velocity vector and turbulent kinetic energy for two kinds of diffusers it also shows that ES profile is fit to apply in radial diffuser. This research can offer a significant reference for the radial diffuser hydraulic design of such centrifugal pumps.
Preliminary Design of Compressor Impeller for innovative Sodium Cooled Fast Reactor
Lee, Jekyoung; Cho, Seongkuk; Lee, Jeong Ik [KAIST, Daejeon (Korea, Republic of); Cha, Jae Eun [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)
2015-05-15
For nuclear power plant application, applying S-CO{sub 2} Brayton cycle to Sodium cooled Fast Reactors and Small Modular Reactors are currently considered and active research is being performed by various research institutions and universities. As a part of research activities on the SCO{sub 2} Brayton cycle development for a nuclear power system, KAIST joint research team is currently working on an innovative Sodium cooled Fast Reactor (iSFR) development which utilizes S-CO{sub 2} Brayton cycle as its power conversion system. Various research subjects including reactor physics, thermo-hydraulics, material, cycle analysis and system integration are being considered as research issues currently. However, technical issues rising from dramatic change of thermodynamic property of CO{sub 2} near the critical point still remain as problems to be solved. As a result, 3D impeller model generation based on 1D mean stream line analysis results was successfully performed for non-airfoil blades. Since 3D model generation module works successfully, KAIST{sub T}MD can support 3D CFD analysis for internal flow structure in the designed impeller. Compressor loss mechanisms are complex phenomena and these are difficulties to be modeled while considering each loss mechanism separately.
Study of blades inclination influence of gate impeller with a non-Newtonian fluid of Bingham
Rahmani Lakhdar
2016-01-01
Full Text Available A large number of chemical operations, biochemical or petrochemical industry is very depending on the rheological fluids nature. In this work, we study the case of highly viscous of viscoplastic fluids in a classical system of agitation: a cylindrical tank with plate bottom without obstacles agitated by gate impeller agitator. We are interested to the laminar, incompressible and isothermal flows. We devote to a numerical approach carried out using an industrial code CFD Fluent 6.3.26 based on the method of finites volumes discretization of Navier - Stokes equations formulated in variables (U.V.P. The threshold of flow related to the viscoplastic behavior is modeled by a theoretical law of Bingham. The results obtained are used to compare between the five configurations suggested of power consumption. We study the influence of inertia by the variation of Reynolds number.
Detonation in supersonic radial outflow
Kasimov, Aslan R.
2014-11-07
We report on the structure and dynamics of gaseous detonation stabilized in a supersonic flow emanating radially from a central source. The steady-state solutions are computed and their range of existence is investigated. Two-dimensional simulations are carried out in order to explore the stability of the steady-state solutions. It is found that both collapsing and expanding two-dimensional cellular detonations exist. The latter can be stabilized by putting several rigid obstacles in the flow downstream of the steady-state sonic locus. The problem of initiation of standing detonation stabilized in the radial flow is also investigated numerically. © 2014 Cambridge University Press.
LUIZ CARLOS MIRANDA
1999-11-01
Full Text Available O trabalho foi desenvolvido com o objetivo de avaliar a evolução física do processo de remoção de água das sementes em secador estacionário, com cilindro central perfurado e distribuição radical de ar. A pesquisa foi conduzida com sementes de soja, variando o fluxo (26,9, 28,4 e 33,2 m³/minuto/t e a temperatura do ar insuflado (42, 46 e 50ºC, considerando a posição das sementes (17, 34 e 51 cm em relação ao cilindro de insuflação e o tempo de secagem (zero a doze horas, com intervalos de duas horas. Foram caracterizados o ar ambiente, o ar insuflado, as temperaturas e os teores de água da massa, as velocidades e curvas de secagem. As avaliações realizadas destacaram vantagens físicas operacionais da combinação de 28,4 m³/minuto/t com 46ºC e o contrário, com a combinação de 26,9 m³/minuto/t com 42ºC.The purpose of this research was to study several physical parameters of soybean seed drying submitted to stationary process with radial air distribution by combining different air flows (26.9, 28.4 and 33.2 m³/minute/ton and temperatures (42, 46 and 50ºC, considering seed positions in the seed mass (17, 34 and 51 cm in relation to the insuflation cylinder and drying periods (zero to twelve hours with two-hour intervals. Environmental air, insuflation air, seed temperatures, moisture content of seeds, drying speed and drying curves were characterized. Considering the evaluated parameters during the drying process, the physical advantages of the combination of 28.4 m³/minute/ton with 46ºC, and the desadvantage of the combination of 26.9 m³/minute/ton with 42ºC were observed.
Vortex Whistle in Radial Intake
Tse, Man-Chun
2004-01-01
In a radial-to-axial intake with inlet guide vanes (IGV) at the entry, a strong flow circulation Gamma can be generated from the tangential flow components created by the IGVs when their setting exceed about halfclosing (approx. 45 deg...
On-line PWR RHR pump performance testing following motor and impeller replacement
DiMarzo, J.T.
1996-01-01
On-line maintenance and replacement of safety-related pumps requires the performance of an inservice test to determine and confirm the operational readiness of the pumps. In 1995, major maintenance was performed on two Pressurized Water Reactor (PWR) Residual Heat Removal (RHR) Pumps. A refurbished spare motor was overhauled with a new mechanical seal, new motor bearings and equipped with pump's 'B' impeller. The spare was installed into the 'B' train. The motor had never been run in the system before. A pump performance test was developed to verify it's operational readiness and determine the in-situ pump performance curve. Since the unit was operating, emphasis was placed on conducting a highly accurate pump performance test that would ensure that it satisfied the NSSS vendors accident analysis minimum acceptance curve. The design of the RHR System allowed testing of one train while the other was aligned for normal operation. A test flow path was established from the Refueling Water Storage Tank (RWST) through the pump (under test) and back to the RWST. This allowed staff to conduct a full flow range pump performance test. Each train was analyzed and an expression developed that included an error vector term for the TDH (ft), pressure (psig), and flow rate (gpm) using the variance error vector methodology. This method allowed the engineers to select a test instrumentation system that would yield accurate readings and minimal measurement errors, for data taken in the measurement of TDH (P,Q) versus Pump Flow Rate (Q). Test results for the 'B' Train showed performance well in excess of the minimum required. The motor that was originally in the 'B' train was similarly overhauled and equipped with 'A' pump's original impeller, re-installed in the 'A' train, and tested. Analysis of the 'A' train results indicate that the RHR pump's performance was also well in excess of the vendors requirements
On-line PWR RHR pump performance testing following motor and impeller replacement
DiMarzo, J.T.
1996-12-01
On-line maintenance and replacement of safety-related pumps requires the performance of an inservice test to determine and confirm the operational readiness of the pumps. In 1995, major maintenance was performed on two Pressurized Water Reactor (PWR) Residual Heat Removal (RHR) Pumps. A refurbished spare motor was overhauled with a new mechanical seal, new motor bearings and equipped with pump`s `B` impeller. The spare was installed into the `B` train. The motor had never been run in the system before. A pump performance test was developed to verify it`s operational readiness and determine the in-situ pump performance curve. Since the unit was operating, emphasis was placed on conducting a highly accurate pump performance test that would ensure that it satisfied the NSSS vendors accident analysis minimum acceptance curve. The design of the RHR System allowed testing of one train while the other was aligned for normal operation. A test flow path was established from the Refueling Water Storage Tank (RWST) through the pump (under test) and back to the RWST. This allowed staff to conduct a full flow range pump performance test. Each train was analyzed and an expression developed that included an error vector term for the TDH (ft), pressure (psig), and flow rate (gpm) using the variance error vector methodology. This method allowed the engineers to select a test instrumentation system that would yield accurate readings and minimal measurement errors, for data taken in the measurement of TDH (P,Q) versus Pump Flow Rate (Q). Test results for the `B` Train showed performance well in excess of the minimum required. The motor that was originally in the `B` train was similarly overhauled and equipped with `A` pump`s original impeller, re-installed in the `A` train, and tested. Analysis of the `A` train results indicate that the RHR pump`s performance was also well in excess of the vendors requirements.
Li, Xiao; Zhang, Jiang; Tan, Ya-Li; Li, Zhi-Hong; Yu, Xue-Feng; Xia, Jian-Ye; Chu, Ju; Ge, You-Qun
2013-01-01
In this work, the flow field in the existing fermentor with radial-flow impellers (C1) was studied using the computational fluid dynamics (CFD) software package Fluent, then the fermentor with radial-axial flow impellers (C2) was constructed and was compared with the C1 fermentor by CFD and experimental research. The simulation results revealed that the flow field in C2 fermentor had characteristics such as higher turbulent kinetic energy, gas holdup and shear rates. Metabolic variables of Streptomyces lincolnensis in the two fermentors such as carbon and nitrogen source consumption rates, specific growth rates (μ), hyphae morphologies, and lincomycin productivities were further explored. The correlation analysis between the experimental measurements and the simulation results indicated that the hyphae clustering and dry cell weight (DCW) decreasing at production stage were eliminated in C2 fermentor, which had higher gas volumetric mass transfer coefficient (K(L)a), dissolved oxygen (DO) concentration and consumption rates of nutrient materials. When C2 was employed in the fermentor, the specific growth rate of S. lincolnensis at growth stage was higher, and the maintenance metabolism together with secondary metabolism at production stage was kept at higher levels. As a result, the yield of lincomycin was achieved 7039 μg ml(-1) when the 60 m(3) industrial fermentor was equipped with C2, which was increased by 46% compared to that obtained in the C1 fermentor. Copyright © 2012 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.
Zhai, L L; Wu, P; Jiang, Q L; Wang, L Q
2012-01-01
In engineering practice, part of the multi-stage centrifugal pumps is designed without space guide vanes due to the size restrictions and the volute is distorted much in shape. In these pumps, tangential velocity of the fluid at the outlet of the first-stage impeller is so great that it has caused a prerotation problem which will affect the inlet flow conditions of the secondary impeller leading to serious efficiency and head decline of the secondary impeller. The head problem of the second stage in multi-stage centrifugal pumps caused by prerotation at the entrance of the second stage was analyzed and the internal hydraulic performance was optimized by setting clapboards in the volute in this paper. CFD numerical simulation method combined with experiment was applied to predict the effect of internal clapboards on the performance of the centrifugal pump. The original prototype was transformed according to the simulation result and tested to verify the optimization work. The experiment result shows that hydraulic performance is remarkably improved compared with the original one and the prerotation problem is basically solved.
Experimental investigation of a direct driven radial compressor for domestic heat pumps
Schiffmann, J. [Fischer Engineering Solutions AG, Birkenweg 3, CH-3360 Herzogenbuchsee (Switzerland); Favrat, D. [Ecole Polytechnique Federale de Lausanne, EPFL STI IGM LENI, Station 9, CH-1015 Lausanne (Switzerland)
2009-12-15
The presence of oil in domestic heat pumps is an obstacle toward higher efficiency, particularly for enhanced surface evaporators and for advanced concepts based on two-stage cycles. Very compact direct driven radial compressors supported on oil-free bearings represent a promising alternative. This paper presents the derivation of the specifications, the choice for an appropriate refrigerant fluid and the design of a proof of concept prototype with the various tradeoffs between the impeller characteristics to follow the seasonal heat demand, the bearing and rotordynamics for a stable operation. Heat pump simulation results, the design of the impeller as well as the layout of the experimental facility and first experimental results are presented. An impeller with a tip diameter of 20 mm has been tested at rotational speeds of up to 210 krpm reaching pressure ratios in excess of 3.3 and efficiencies above 78%. The refrigerant chosen for this first experimental approach is HFC 134a. (author)
Simple Impeller Systems for Maintenance of Oil Palm Culture Aggregates
Tarmizi, A.H.; Zaiton, R.; Rosli, M.Y.
2016-01-01
Scaling up of liquid culture systems generally involves moving from the use of simple shake flasks to bioreactors or specialised vessels; this is costly. A new innovation called the Two-in-One MPOB Simple Impeller (2-in-1 MoSLIM) was developed using commonly available Schott bottles in the laboratory. This system provided simultaneous aeration and agitation (two-in-one) in a single device for tissue propagation in liquid culture. The 2-in-1 MoSLIM produced cell aggregates with fresh weight increments of two- to six-fold over 30-40 days. This system was a convenient alternative compared to the conventional shake flask system. Multiplication of cultures in the 2-in-1 MoSLIM did not require any shaker or a big space area. This system with a working volume of 300 - 700 ml used a simple impeller and a pump for agitation and aeration purposes. However, with the 2-in-1 MoSLIM, media replenishment remained a tedious task. To overcome this, modifications were made to the system to enable media replenishment on-site without the need of a sterile hood. The adaptation of 2-in-1 MoSLIM with an earlier innovation, Fast Transfer Technique (MoFaTT) in Liquid Culture System, resulted in the development of the Simple Impeller with Fast Transfer Technique (SLIM-FaTT) system. This new system can be applied to the liquid culture system of any crop with a potential towards automation. (author)
K. Majidi
2000-01-01
Full Text Available The flow field in volute and circular casings interacting with a centrifugal impeller is obtained by numerical analysis. In the present study, effects of the volute and circular casings on the flow pattern have been investigated by successively combining a volute casing and a circular casing with a single centrifugal impeller. The numerical calculations are carried out with a multiple frame of reference to predict the flow field inside the entire impeller and casings. The impeller flow field is solved in a rotating frame and the flow field in the casings in a stationary frame. The static pressure and velocity in the casing and impeller, and the static pressures and secondary velocity vectors at several cross-sectional planes of the casings are calculated. The calculations show that the curvature of the casings creates pressure gradients that cause vortices at cross-sectional planes of the casings.
Thrombotic Depositions on Right Impeller of Double-Ended Centrifugal Total Artificial Heart In Vivo.
Karimov, Jamshid H; Horvath, David J; Okano, Shinji; Goodin, Mark; Sunagawa, Gengo; Byram, Nicole; Moazami, Nader; Golding, Leonard A R; Fukamachi, Kiyotaka
2017-05-01
The development of total artificial heart devices is a complex undertaking that includes chronic biocompatibility assessment of the device. It is considered particularly important to assess whether device design and features can be compatible long term in a biological environment. As part of the development program for the Cleveland Clinic continuous-flow total artificial heart (CFTAH), we evaluated the device for signs of thrombosis and biological material deposition in four animals that had achieved the intended 14-, 30-, or 90-day durations in each respective experiment. Explanted CFTAHs were analyzed for possible clot buildup at "susceptible" areas inside the pump, particularly the right pump impeller. Depositions of various consistency and shapes were observed. We here report our findings, along with macroscopic and microscopic analysis post explant, and provide computational fluid dynamics data with its potential implications for thrombus formation. © 2016 International Center for Artificial Organs and Transplantation and Wiley Periodicals, Inc.
Design of Stirrer Impeller with Variable Operational Speed for a Food Waste Homogenizer
Idris A. Kayode; Emmanuel O. B. Ogedengbe; Marc A. Rosen
2016-01-01
A conceptualized impeller called KIA is designed for impact agitation of food waste in a homogenizer. A comparative analysis of the performance of KIA is made with three conventional impeller types, Rushton, Anchor, and Pitched Blade. Solid–liquid mixing of a moisture-rich food waste is simulated under various operational speeds, in order to compare the dispersions and thermal distributions at homogenous slurry conditions. Using SolidWorks, the design of the impellers employs an Application P...
Aksenov, A. A.; Danilishin, A. M.; Dubenko, A. M.; Kozhukov, Y. V.
2017-08-01
Design modernization of the centrifugal compressor stage test bench with three dimensional impeller blades was carried out for the possibility of holding a series of experimental studies of different 3D impeller models. The studies relates to the problem of joint work of the impeller and the stationary channels of the housing when carrying out works on modernization with the aim of improving the parameters of the volumetric capacity or pressure in the presence of design constraints. The object of study is the experimental single end centrifugal compressor stage with the 3D impeller. Compressor stage consists of the 3D impeller, vaneless diffuser (VLD), outlet collector - folded side scroll and downstream pipe. The drive is a DC motor 75 kW. The increase gear (multiplier) was set between the compressor and DC motor, gear ratio is i = 9.8. To obtain the characteristics of the compressor and the flow area the following values were measured: total pressure, static pressure, direction (angles) of the stream in different cross sections. Additional pneumometric probes on the front wall of the VLD of the test bench have been installed. Total pressure probes and foster holes for the measurement of total and static pressure by the new drainage scheme. This allowed carrying out full experimental studies for two elements of centrifugal compressor stage. After the experimental tests the comprehensive information about the performance of model stage were obtained. Was measured geometric parameters and the constructed virtual model of the experimental bench flow part with the help of Creo Parametric 3.0 and ANSYS v. 16.2. Conducted CFD calculations and verification with experimental data. Identifies the steps for further experimental and virtual works.
Neuropathy - radial nerve; Radial nerve palsy; Mononeuropathy ... Damage to one nerve group, such as the radial nerve, is called mononeuropathy . Mononeuropathy means there is damage to a single nerve. Both ...
Mihelc, Kevin M; Frankowski, Brian J; Lieber, Samuel C; Moore, Nathan D; Hattler, Brack G; Federspiel, William J
2009-01-01
Respiratory assist using an intravenous catheter may be a potential treatment for patients suffering from acute or acute-on-chronic lung failure. The objective of this study was to evaluate a novel respiratory catheter that uses an impeller within the fiber bundle to enhance gas exchange efficiency, thus requiring a smaller fiber bundle and insertional size (25 Fr) and permitting simple percutaneous insertion. Bench testing of gas exchange in deionized water was used to evaluate eight impeller designs. The three best performing impeller designs were evaluated in acute studies in four calves (122 + or - 10 kg). Gas exchange increased significantly with increasing impeller rotation rate. The degree of enhancement varied with impeller geometry. The maximum gas exchange efficiency (exchange per unit surface area) for the catheter with the best performing impeller was 529 + or - 20 ml CO(2)/min/m(2) and 513 + or - 21 ml CO(2)/min/m(2) for bench and animal studies, respectively, at a rotation rate of 20,000 rpm. Absolute CO(2) exchange was 37 and 36 ml CO(2)/min, respectively. Active mixing by rotating impellers produced 70% higher gas exchange efficiency than pulsating balloon catheters. The sensitivity of gas exchange to impeller design suggests that further improvements can be made by computational fluid dynamics-based optimization of the impeller.
Experimental Study of Unshrouded Impeller Pump Stage Sensitivity to Tip Clearance
Williams, Robert W.; Zoladz, Thomas; Storey, Anne K.; Skelley, Stephen E.
2002-01-01
This viewgraph presentation provides information on an experiment. Its objective is to experimentally determine unshrouded impeller performance sensitivity to tip clearance. The experiment included: Determining impeller efficiency at scaled operating conditions in water at MSFC's Pump Test Equipment (PTE) Facility; Testing unshrouded impeller at three different tip clearances; Testing each tip clearance configuration at on- and off-design conditions, and collecting unsteady- and steady-state data in each configuration; Determining impeller efficiency directly using drive line torquemeter and pump inlet and exit total pressure measurements.
Reyes, J. Leonardo; Lubczynski1, Maciek W.
2010-05-01
Sap flow measurement is a key aspect for understanding how plants use water and their impacts on the ecosystems. A variety of sensors have been developed to measure sap flow, each one with its unique characteristics. When the aim of a research is to have accurate tree water use calculations, with high temporal and spatial resolution (i.e. scaled), a sensor with high accuracy, high measurement efficiency, low signal-to-noise ratio and low price is ideal, but such has not been developed yet. Granier's thermal dissipation probes (TDP) have been widely used in many studies and various environmental conditions because of its simplicity, reliability, efficiency and low cost. However, it has two major flaws when is used in semi-arid environments and broad-stem tree species: it is often affected by high natural thermal gradients (NTG), which distorts the measurements, and it cannot measure the radial variability of sap-flux density in trees with sapwood thicker than two centimeters. The new, multi point heat field deformation sensor (HFD) is theoretically not affected by NTG, and it can measure the radial variability of the sap flow at different depths. However, its high cost is a serious limitation when simultaneous measurements are required in several trees (e.g. catchment-scale studies). The underlying challenge is to develop a monitoring schema in which HFD and TDP are combined to satisfy the needs of measurement efficiency and accuracy in water accounting. To assess the level of agreement between TDP and HFD methods in quantifying sap flow rates and temporal patterns on Quercus ilex (Q.i ) and Quercus pyrenaica trees (Q.p.), three measurement schemas: standard TDP, TDP-NTG-corrected and HFD were compared in dry season at the semi-arid Sardon area, near Salamanca in Spain in the period from June to September 2009. To correct TDP measurements with regard to radial sap flow variability, a radial sap flux density correction factor was applied and tested by adjusting TDP
Pump impeller failures - a compendium of case studies
Van Bennekom, A
2001-04-01
Full Text Available surface material. It should also be noted that this stress is above the yield strengths of many materials and as such some localised plastic deformation could also be expected. The exact mechanism by which collapse of the bubbles transmits the localised... metal to cavitation damage, it appears as though the degree of degradation is related to the pitting resistance rather than the general corrosion resistance of the material [4]. The presence of pits on the surface of the impeller also causes disruption...
Crittenden, P. E.; Balachandar, S.
2018-03-01
The radial one-dimensional Euler equations are often rewritten in what is known as the geometric source form. The differential operator is identical to the Cartesian case, but source terms result. Since the theory and numerical methods for the Cartesian case are well-developed, they are often applied without modification to cylindrical and spherical geometries. However, numerical conservation is lost. In this article, AUSM^+ -up is applied to a numerically conservative (discrete) form of the Euler equations labeled the geometric form, a nearly conservative variation termed the geometric flux form, and the geometric source form. The resulting numerical methods are compared analytically and numerically through three types of test problems: subsonic, smooth, steady-state solutions, Sedov's similarity solution for point or line-source explosions, and shock tube problems. Numerical conservation is analyzed for all three forms in both spherical and cylindrical coordinates. All three forms result in constant enthalpy for steady flows. The spatial truncation errors have essentially the same order of convergence, but the rate constants are superior for the geometric and geometric flux forms for the steady-state solutions. Only the geometric form produces the correct shock location for Sedov's solution, and a direct connection between the errors in the shock locations and energy conservation is found. The shock tube problems are evaluated with respect to feature location using an approximation with a very fine discretization as the benchmark. Extensions to second order appropriate for cylindrical and spherical coordinates are also presented and analyzed numerically. Conclusions are drawn, and recommendations are made. A derivation of the steady-state solution is given in the Appendix.
Roshani, G H; Karami, A; Salehizadeh, A; Nazemi, E
2017-11-01
The problem of how to precisely measure the volume fractions of oil-gas-water mixtures in a pipeline remains as one of the main challenges in the petroleum industry. This paper reports the capability of Radial Basis Function (RBF) in forecasting the volume fractions in a gas-oil-water multiphase system. Indeed, in the present research, the volume fractions in the annular three-phase flow are measured based on a dual energy metering system including the 152 Eu and 137 Cs and one NaI detector, and then modeled by a RBF model. Since the summation of volume fractions are constant (equal to 100%), therefore it is enough for the RBF model to forecast only two volume fractions. In this investigation, three RBF models are employed. The first model is used to forecast the oil and water volume fractions. The next one is utilized to forecast the water and gas volume fractions, and the last one to forecast the gas and oil volume fractions. In the next stage, the numerical data obtained from MCNP-X code must be introduced to the RBF models. Then, the average errors of these three models are calculated and compared. The model which has the least error is picked up as the best predictive model. Based on the results, the best RBF model, forecasts the oil and water volume fractions with the mean relative error of less than 0.5%, which indicates that the RBF model introduced in this study ensures an effective enough mechanism to forecast the results. Copyright © 2017 Elsevier Ltd. All rights reserved.
Pressure fluctuation characteristics of flow field of mixed flow nuclear primary pump
Wang Chunlin; Yang Xiaoyong; Li Changjun; Jia Fei; Zhao Binjuan
2013-01-01
In order to research the pressure fluctuation characteristics of flow field of mixed flow nuclear primary pump, this study used the technique of ANSYS-Workbench and CFX fluid solid heat coupling to do numerical simulation analysis for model pump. According to the situation of pressure fluctuation of time domain and frequency domain, the main cause of pressure fluctuation was discussed. For different flow, the pressure fluctuations were compared. This study shows it is feasible that large eddy simulation method is used for the research of pressure fluctuation. The pressure fluctuation amplitudes of four sections are increasing from wheel hub to wheel rim. The pressure fluctuation of inlet and outlet of impeller depends on the rotational frequency of impeller. Along with the fluid flowing away from the impeller, the effect of the impeller on the fluid pressure fluctuation weakens gradually. Comparing the different results of three flow conditions, the pressure fluctuation in design condition flow is superior to the others. (authors)
PIV pictures of stream field predict haemolysis index of centrifugal pump with streamlined impeller.
Qian, K X; Feng, Z G; Ru, W M; Zeng, P; Yuan, H Y
2007-01-01
Previously it has been found by pump haemolysis testing that the flow rate has a remarkable effect on index of haemolysis (IH), while pressure head does not affect IH. Recent investigation with particle image velocimetry (PIV) technology has demonstrated that IH is directly related to the flow pattern of stream field in impeller vane channels. PIV is a visible approach showing the real flow status in the pump. The different positions of a tracer particle in two PIV pictures taken at 20 micros intervals decide the velocity value and direction. The velocity vectors of many particles draw the flow pattern of the stream field. The same pictures are taken at 2, 4 and 6 l min(-1) flow rates while the pressure head is kept unchanged at 100 mmHg; then the pictures are taken at 4 l min(-1) flow with different pressure heads of 80, 100 and 120 mmHg. Results reveal that the flow rate of 4 l min(-1) (IH = 0.030) has the best stream field, and neither turbulence nor separation can be seen. In other flow rates (IH: 0.048 - 0.082), there is obviously second flow. Meanwhile, no significant difference can be seen among the PIV pictures of different pressure heads pumped, which agrees with the results of haemolysis testing showing that pressure has no effect on pump haemolysis. It may be concluded that the haemolysis property of a centrifugal pump can be assessed approximately by PIV pictures, which are much easier to take than haemolysis tests.
Sarler, B; Alujevic, A [Univerza B. Kardelja, Institut ' Jozef Stefan' , Ljubljana (Yugoslavia)
1988-07-01
The basic principles of self-adaptive algorithm for treatment of transient nonlinear nonhomogeneous radial heat flow, based on direct Boundary Element method formulation, are presented. The indicators of discretization error are developed, together with binary-tree strategy for manipulation with time domain mesh, assuring automatic optimisation of calculation procedure with respect to predetermined error. The developed method is particularly suitable for use in a spectrum of extremely nonlinear cases, occurring in thermal analyses of reactor components.(author)
Peters, Jacob M; Gravish, Nick; Combes, Stacey A
2017-06-15
Honey bees ( Apis mellifera ) are remarkable fliers that regularly carry heavy loads of nectar and pollen, supported by a flight system - the wings, thorax and flight muscles - that one might assume is optimized for aerial locomotion. However, honey bees also use this system to perform other crucial tasks that are unrelated to flight. When ventilating the nest, bees grip the surface of the comb or nest entrance and fan their wings to drive airflow through the nest, and a similar wing-fanning behavior is used to disperse volatile pheromones from the Nasonov gland. In order to understand how the physical demands of these impeller-like behaviors differ from those of flight, we quantified the flapping kinematics and compared the frequency, amplitude and stroke plane angle during these non-flight behaviors with values reported for hovering honey bees. We also used a particle-based flow visualization technique to determine the direction and speed of airflow generated by a bee performing Nasonov scenting behavior. We found that ventilatory fanning behavior is kinematically distinct from both flight and scenting behavior. Both impeller-like behaviors drive flow parallel to the surface to which the bees are clinging, at typical speeds of just under 1 m s -1 We observed that the wings of fanning and scenting bees frequently contact the ground during the ventral stroke reversal, which may lead to wing wear. Finally, we observed that bees performing Nasonov scenting behavior sometimes display 'clap-and-fling' motions, in which the wings contact each other during the dorsal stroke reversal and fling apart at the start of the downstroke. We conclude that the wings and flight motor of honey bees comprise a multifunctional system, which may be subject to competing selective pressures because of its frequent use as both a propeller and an impeller. © 2017. Published by The Company of Biologists Ltd.
Maria C Marcondes
2010-04-01
Full Text Available O trabalho objetivou avaliar dois tipos de colhedoras, de fluxo radial e axial, em relação à qualidade física e fisiológica de sementes de duas cultivares de soja, BRS 184 e BRS 133, colhidas em dois horários, às 10 e 18 horas. A colhedora de fluxo radial trabalhou a 5,0 km h-1 , com o cilindro batedor a 750 rotações por minuto (rpm. A colhedora de fluxo axial trabalhou a 8,0 km h-1, e rotor com 650 rpm. Para a avaliação da qualidade física e fisiológica das sementes, foram realizados testes de germinação, envelhecimento acelerado, tetrazólio, dano mecânico (hipoclorito, umidade de campo e laboratório, sementes quebradas (bandinha e pureza. A colheita realizada às 18 horas, com grau de umidade menor que 12%, ocasionou maiores danos mecânicos nas sementes da cultivar BRS 184. A colhedora de sistema de fluxo axial resultou em sementes de melhor qualidade fisiológica para a cultivar BRS 184, e em menores percentuais de sementes quebradas e maior pureza para ambas as cultivares, comparativamente à colhedora de sistema de trilha com fluxo radial.This experiment aimed to evaluate two types of harvest combines, the radial flow and axial flow rotary, regarding the physical and physiological seed quality of BRS 184 and BRS 133 soybeans cultivars, harvested in two periods of the day, at 10 a.m. and 6 p.m. The conventional combine worked moving at 5.0 km h-1, cylinder speed at 750 rotations per minute (rpm. The axial rotary combine worked moving at 8.0 km h, rotorspeed at 650 rpm. The germination test, vigour test, tetrazolium, mechanical (hypochlorite damage, field and laboratory humidity test, broken seeds test and purity test were used to evaluate the physical and physiological quality of the seeds. The experiment performed at 6 pm, with a humidity level inferior to 12%, presented greater mechanical damages in BRS 184 seeds. The axial flow rotary harvest presented better seed physiological quality for BRS 184 cultivar, less
Laser cleaning of sulfide scale on compressor impeller blade
Tang, Q.H.; Zhou, D.; Wang, Y.L.; Liu, G.F.
2015-01-01
Highlights: • The effects of sulfide layers and fluence values on the mechanism of laser cleaning were experimentally established. • The specimen surface with sulfide scale becomes slightly smoother than that before laser cleaning. • The mechanism of laser cleaning the sulfide scale of stainless steel is spallation without oxidization. • It would avoid chemical waste and dust pollution using a fiber laser instead of using nitric acids or sandblasting. - Abstract: Sulfide scale on the surface of a compressor impeller blade can considerably reduce the impeller performance and its service life. To prepare for subsequent remanufacturing, such as plasma spraying, it needs to be removed completely. In the corrosion process on an FV(520)B stainless steel, sulfide scale is divided into two layers because of different outward diffusion rates of Cr, Ni and Fe. In this paper, the cleaning threshold values of the upper and inner layers and the damage threshold value of the substrate were investigated using a pulsed fiber laser. To obtain experimental evidence, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and 3D surface profilometry were employed to investigate the two kinds of sulfide layers on specimens before, during, and after laser cleaning.
Pump, sodium, inducer, intermediate size (ISIP) (impeller/inducer/diffuser retrofit)
Paradise, D.R.
1978-01-01
This specification defines the requirements for the Intermediate-Size Inducer Pump (ISIP), which is to be made by replacing the impeller of the FFTF Prototype Pump with a new inducer, impeller, diffuser, seal, and necessary adapter hardware. Subsequent testing requirements of the complete pump assembly are included
Cavitation erosion scaling: tests on a pump impeller in water and in sodium
Dorey, J.M.; Rascalou, T.
1992-01-01
Tests to quantify cavitation agressivity carried out in water and in sodium (400 deg) on a model pump impeller are presented. The polished samples method has been used. It can be now applied to curved surfaces such as impeller blades with the help of new measurement devices. Results are discussed regarding scaling laws for fluid-to-fluid transposition
Blade design loads on the flow exciting force in centrifugal pump
Xu, Y; Yang, A L; Langand, D P; Dai, R
2012-01-01
The three-dimensional viscous flow field of two centrifugal pumps, which have the same volute, design head, design flow rate and rotational speed but the blade design load, are analyzed based on large eddy simulation. The comparisons are implemented including the hydraulic efficiencies, flow field characteristics, pressure pulsations and unsteady forces applied on the impellers to investigate the effect of the design blade load on hydraulic performance and flow exciting force. The numerical results show that the efficiency of the pump, the impeller blade of which has larger design load, is improved by 1.1%∼2.9% compared to the centrifugal pump with lower blade design load. The pressure fluctuation of the pump with high design load is more remarkable. Its maximum amplitude of coefficient of static pressure is higher by 43% than the latter. At the same time the amplitude of unsteady radial force is increased by 11.6% in the time domain. The results also imply that the blade design load is an important factor on the excitation force in centrifugal pumps.
Comparative PIV and LDA studies of Newtonian and non-Newtonian flows in an agitated tank.
Story, Anna; Jaworski, Zdzisław; Simmons, Mark J; Nowak, Emilia
2018-01-01
The paper presents results of an experimental study of the fluid velocity field in a stirred tank equipped with a Prochem Maxflo T (PMT) type impeller which was rotating at a constant frequency of N = 4.1 or 8.2 s -1 inducing transitional ( Re = 499 or 1307) or turbulent ( Re = 2.43 × 10 4 ) flow of the fluid. The experiments were performed for a Newtonian fluid (water) and a non-Newtonian fluid (0.2 wt% aqueous solution of carboxymethyl cellulose, CMC) exhibiting mild viscoelastic properties. Measurements were carried out using laser light scattering on tracer particles which follow the flow (2-D PIV). For both the water and the CMC solution one primary and two secondary circulation loops were observed within the fluid volume; however, the secondary loops were characterized by much lower intensity. The applied PMT-type impeller produced in the Newtonian fluid an axial primary flow, whilst in the non-Newtonian fluid the flow was more radial. The results obtained in the form of the local mean velocity components were in satisfactory agreement with the literature data from LDA. Distribution of the shear rate in the studied system was also analyzed. For the non-Newtonian fluid an area was computed where the elastic force dominates over the viscous one. The area was nearly matching the region occupied by the primary circulation loop.
L2F and LDV velocimetry measurement and analysis of the 3-D flow field in a centrifugal compressor
Fagan, John R., Jr.; Fleeter, Sanford
1989-01-01
The flow field in the Purdue Research Centrifugal Compressor is studied using a laser two-focus (L2F) velocimeter. L2F data are obtained which quantify: (1) the compressor inlet flow field; (2) the steady-state velocity field in the impeller blade passages; and (3) the flow field in the radial diffuser. The L2F data are compared with both laser Doppler velocimetry (LDV) data and predictions from three-dimensional inviscid and viscous flow models. In addition, a model is developed to calculate the effect on the measurement volume geometry of refraction by curved windows. Finally, the advantages and disadvantages of using the L2F for turbomachinery measurements is discussed in terms of measurement accuracy, ease of use, including sample time per correlated event and the ability to make measurements in regions of high noise due to stray radiation from wall reflections.
Diego Abreu-López
2017-04-01
Full Text Available A mathematical model was developed to describe the hydrodynamics of a batch reactor for aluminum degassing utilizing the rotor-injector technique. The mathematical model uses the Eulerian algorithm to represent the two-phase system including the simulation of vortex formation at the free surface, and the use of the RNG k-ε model to account for the turbulence in the system. The model was employed to test the performances of three different impeller designs, two of which are available commercially, while the third one is a new design proposed in previous work. The model simulates the hydrodynamics and consequently helps to explain and connect the performances in terms of degassing kinetics and gas consumption found in physical modeling previously reported. Therefore, the model simulates a water physical model. The model reveals that the new impeller design distributes the bubbles more uniformly throughout the ladle, and exhibits a better-agitated bath, since the transfer of momentum to the fluids is better. Gas is evenly distributed with this design because both phases, gas and liquid, are dragged to the bottom of the ladle as a result of the higher pumping effect in comparison to the commercial designs.
Ramirez-Argaez, M. A.; Conteras, F.; Gonzalez, C.
2006-01-01
In this work a fundamental Eulerian mathematical model was developed to study fluid flow and mixing phenomena in aluminium ladles equipped with impeller for deshidrogenization treatment. The effect of critical process parameters such as rotor speed, depth of immersion, gas flow rate, and type of rotor on the mixing behavior and vortex formation was analyzed with this model. The model simulates operation with and without gas injection and it was developed on the commercial CFD code PHOENICS 3.4 in order to solve all conservation equations governing the process, i. e. continuity, 3D turbulent Navier-Stockers and the kε turbulence model for a two-phase fluid flow problem using the Inter Phase Slip Algorithm (IPSA). (Author). 20 refs
Unsteady flow measurements in centrifugal compressors
Bammert, K.; Mobarak, A.; Rautenberg, M.
1976-01-01
Centrifugal compressors and blowers are often used for recycling the coolant gas in gas-cooled reactors. To achieve the required high pressure ratios, highly loaded centrifugal compressors are built. The paper deals with unsteady flow measurements on highly loaded centrifugal impellers. Measurements of the approaching flow have been done with hot wires. The method of measurement enabled us to get the velocity distribution across the pitch ahead of the inducer. The static pressure signals along the shroud line has been discussed on the basis of some theoretical considerations. Accordingly the form of flow in the impeller and the wave flow or separation zones in the impeller can now be better interpreted. The importance of the unsteady nature of the relative flow, especially at impeller exit, is clearly demonstrated. Measurements with high responsive total pressure probes in the vicinity of impeller exit and the subsequent calculations have shown, that the instantaneous energy transfer at a certain point after the impeller may differ by more than 30% from the Euler work. Lastly, unsteady pressure measurements along the shroud line have been performed during surge and rotating stall. The surge signal have been analyzed in more detail and the mechanism of flow rupture and pressure recovery during a surge cycle is thoroughly discussed. (orig.) [de
Irnawan, Roni; Silva, Filipe Miguel Faria da; Bak, Claus Leth
2017-01-01
This paper deals with a radial offshore multi-terminal HVDC (MTDC) transmission system which is formed by interconnection several existing offshore wind farm (OWF) HVDC links with a shore-to-shore (StS) HVDC link. A challenge arises when deciding the steady-state DC voltage operating level...
Optimization of a Continuous Hybrid Impeller Mixer via Computational Fluid Dynamics
N. Othman
2014-01-01
Full Text Available This paper presents the preliminary steps required for conducting experiments to obtain the optimal operating conditions of a hybrid impeller mixer and to determine the residence time distribution (RTD using computational fluid dynamics (CFD. In this paper, impeller speed and clearance parameters are examined. The hybrid impeller mixer consists of a single Rushton turbine mounted above a single pitched blade turbine (PBT. Four impeller speeds, 50, 100, 150, and 200 rpm, and four impeller clearances, 25, 50, 75, and 100 mm, were the operation variables used in this study. CFD was utilized to initially screen the parameter ranges to reduce the number of actual experiments needed. Afterward, the residence time distribution (RTD was determined using the respective parameters. Finally, the Fluent-predicted RTD and the experimentally measured RTD were compared. The CFD investigations revealed that an impeller speed of 50 rpm and an impeller clearance of 25 mm were not viable for experimental investigations and were thus eliminated from further analyses. The determination of RTD using a k-ε turbulence model was performed using CFD techniques. The multiple reference frame (MRF was implemented and a steady state was initially achieved followed by a transient condition for RTD determination.
Optimization of a continuous hybrid impeller mixer via computational fluid dynamics.
Othman, N; Kamarudin, S K; Takriff, M S; Rosli, M I; Engku Chik, E M F; Meor Adnan, M A K
2014-01-01
This paper presents the preliminary steps required for conducting experiments to obtain the optimal operating conditions of a hybrid impeller mixer and to determine the residence time distribution (RTD) using computational fluid dynamics (CFD). In this paper, impeller speed and clearance parameters are examined. The hybrid impeller mixer consists of a single Rushton turbine mounted above a single pitched blade turbine (PBT). Four impeller speeds, 50, 100, 150, and 200 rpm, and four impeller clearances, 25, 50, 75, and 100 mm, were the operation variables used in this study. CFD was utilized to initially screen the parameter ranges to reduce the number of actual experiments needed. Afterward, the residence time distribution (RTD) was determined using the respective parameters. Finally, the Fluent-predicted RTD and the experimentally measured RTD were compared. The CFD investigations revealed that an impeller speed of 50 rpm and an impeller clearance of 25 mm were not viable for experimental investigations and were thus eliminated from further analyses. The determination of RTD using a k-ε turbulence model was performed using CFD techniques. The multiple reference frame (MRF) was implemented and a steady state was initially achieved followed by a transient condition for RTD determination.
Data on mixing of viscous fluids by helical screw impellers in cylindrical vessels
Houari Ameur
2016-09-01
Full Text Available In this article, the data assembled regarding the mixing of Newtonian and shear thinning fluids by screw impellers in a cylindrical tank is disclosed. The data summarizing some information on the efficiency of such impellers are obtained via 3D calculations of velocities and viscous dissipation in the whole vessel volume. The data presented herein may be useful for those who want to outline the mixing characteristics in terms of fluid circulation and power consumption for this kind of impellers, therefore, avoiding a great effort for achieving a high number of experiments. Keyword: Mixing, Helical screw agitator, Power consumption, Fluid circulation, Cylindrical tanks
Dirk Hagelstein
2000-01-01
Full Text Available The increased use of small gas turbines and turbochargers in different technical fields has led to the development of highly-loaded centrifugal compressors with extremely thin blades. Due to high rotational speed and the correspondingly high centrifugal loads, the shape of the impeller hub must also be optimized. This has led to a reduction of the thickness of the impeller disc in the outlet region. The thin parts of the impeller are very sensitive and may be damaged by the excitation of dangerous blade vibrations.
Performance prediction of centrifugal compressor impellers using quasi-three-dimensional analysis
Ahn, S. J.; Kim, K. Y.; Oh, H. W.
2001-01-01
This-paper presents analysis of the flows through three different types of radial compressor by using quasi-three-dimensional analysis method. The method obtains two-dimensional solution for velocity distribution on meridional plane, and then calculates approximately the static pressure distributions on blade surfaces. Finite difference method is used for the solutions of governing equations. The compressors have low level compression-ratio and 12 straight radial blades with no sweepback. The results are compared with experimental data and the results of inviscid analysis with finite element method. It can be concluded that the agreement is good for the cases where viscous effects are not dominant
Bertin H.
2006-11-01
Full Text Available Les instabilités de déplacements miscibles radiaux en milieu poreux dues à un contraste de mobilité sont étudiées de manière théorique et expérimentale. Dans une première partie, la mise au point d'un modèle numérique bidimensionnel permet la visualisation mathématique d'une configuration instable. A partir des équations aux perturbations linéarisées, l'étude nous permet d'évaluer l'influence de chacun des paramètres conditionnant la stabilité d'un tel écoulement. Ces résultats, dans la gamme des paramètres étudiés, nous permettent d'établir un critère d'instabilité. La deuxième partie, expérimentale, nous permet de visualiser, grâce à une méthode optique basée sur l'effet Christiansen, des instabilités dues au contraste de mobilité (développement notable de digitations. L'interprétation des résultats expérimentaux est comparée aux prédictions théoriques. The instabilities of radial miscible displacements in porous media due to a mobility contrast are examined theoretically and experimentally. The first part describes a two-dimensional numerical model used for the mathematical visualization of an unstable configuration. On the basis of linearized perturbation equations, we can evaluate the influence of each parameter governing the stability of the displacement. In the range of parameters investigated, these results enable an instability criterion to be established. The second part is experimental. An optical method based on the Christiansen effect is used to visualize instabilities due to mobility contrast (appreciable development of fingerings. The interpretation of the experimental results is compared to theoretical predictions.
2013-01-01
In this study, a miniature stirred tank bioreactor was designed for treatment of waste gas containing benzene, toluene and xylene. Oxygen mass transfer characteristics for various twin and single-impeller systems were investigated for 6 configurations in a vessel with 10 cm of inner diameter and working volume of 1.77L. Three types of impellers, namely, Rushton turbine, Pitched 4blades and Pitched 2blades impellers with downward pumping have been used. Deionized water was used as a liquid phase. With respect to other independent variables such as agitation speed, aeration rate, type of sparger, number of impellers, the relative performance of these impellers was assessed by comparing the values of (KLa) as a key parameter. Based on the experimental data, empirical correlations as a function of the operational conditions have been proposed, to study the oxygen transfer rates from air bubbles generated in the bioreactor. It was shown that twin Rushton turbine configuration demonstrates superior performance (23% to 77% enhancement in KLa) compared with other impeller compositions and that sparger type has negligible effect on oxygen mass transfer rate. Agitation speeds of 400 to 800 rpm were the most efficient speeds for oxygen mass transfer in the stirred bioreactor. PMID:23369581
Design of Stirrer Impeller with Variable Operational Speed for a Food Waste Homogenizer
Idris A. Kayode
2016-05-01
Full Text Available A conceptualized impeller called KIA is designed for impact agitation of food waste in a homogenizer. A comparative analysis of the performance of KIA is made with three conventional impeller types, Rushton, Anchor, and Pitched Blade. Solid–liquid mixing of a moisture-rich food waste is simulated under various operational speeds, in order to compare the dispersions and thermal distributions at homogenous slurry conditions. Using SolidWorks, the design of the impellers employs an Application Programming Interface (API which acts as the canvas for creating a graphical user interface (GUI for automation of its assembly. A parametric analysis of the homogenizer, at varying operational speeds, enables the estimation of the critical speed of the mixing shaft diameter and the deflection under numerous mixing conditions and impeller configurations. The numerical simulation of the moisture-rich food waste (approximated as a Newtonian carrot–orange soup is performed with ANSYS CFX v.15.0. The velocity and temperature field distribution of the homogenizer for various impeller rotational speeds are analyzed. It is anticipated that the developed model will help in the selection of a suitable impeller for efficient mixing of food waste in the homogenizer.
Ju, Yaping; Zhang, Chuhua
2016-03-01
Blade fouling has been proved to be a great threat to compressor performance in operating stage. The current researches on fouling-induced performance degradations of centrifugal compressors are based mainly on simplified roughness models without taking into account the realistic factors such as spatial non-uniformity and randomness of the fouling-induced surface roughness. Moreover, little attention has been paid to the robust design optimization of centrifugal compressor impellers with considerations of blade fouling. In this paper, a multi-objective robust design optimization method is developed for centrifugal impellers under surface roughness uncertainties due to blade fouling. A three-dimensional surface roughness map is proposed to describe the nonuniformity and randomness of realistic fouling accumulations on blades. To lower computational cost in robust design optimization, the support vector regression (SVR) metamodel is combined with the Monte Carlo simulation (MCS) method to conduct the uncertainty analysis of fouled impeller performance. The analyzed results show that the critical fouled region associated with impeller performance degradations lies at the leading edge of blade tip. The SVR metamodel has been proved to be an efficient and accurate means in the detection of impeller performance variations caused by roughness uncertainties. After design optimization, the robust optimal design is found to be more efficient and less sensitive to fouling uncertainties while maintaining good impeller performance in the clean condition. This research proposes a systematic design optimization method for centrifugal compressors with considerations of blade fouling, providing a practical guidance to the design of advanced centrifugal compressors.
An experimental description of the flow in a centrifugal compressor from alternate stall to surge
Moënne-Loccoz, V.; Trébinjac, I.; Benichou, E.; Goguey, S.; Paoletti, B.; Laucher, P.
2017-08-01
The present paper gives the experimental results obtained in a centrifugal compressor stage designed and built by SAFRAN Helicopter Engines. The compressor is composed of inlet guide vanes, a backswept splittered unshrouded impeller, a splittered vaned radial diffuser and axial outlet guide vanes. Previous numerical simulations revealed a particular S-shape pressure rise characteristic at partial rotation speed and predicted an alternate flow pattern in the vaned radial diffuser at low mass flow rate. This alternate flow pattern involves two adjacent vane passages. One passage exhibits very low momentum and a low pressure recovery, whereas the adjacent passage has very high momentum in the passage inlet and diffuses efficiently. Experimental measurements confirm the S-shape of the pressure rise characteristic even if the stability limit experimentally occurs at higher mass flow than numerically predicted. At low mass flow the alternate stall pattern is confirmed thanks to the data obtained by high-frequency pressure sensors. As the compressor is throttled the path to instability has been registered and a first scenario of the surge inception is given. The compressor first experiences a steady alternate stall in the diffuser. As the mass flow decreases, the alternate stall amplifies and triggers the mild surge in the vaned diffuser. An unsteady behavior results from the interaction of the alternate stall and the mild surge. Finally, when the pressure gradient becomes too strong, the alternate stall blows away and the compressor enters into deep surge.
Radial electric fields for improved tokamak performance
Downum, W.B.
1981-01-01
The influence of externally-imposed radial electric fields on the fusion energy output, energy multiplication, and alpha-particle ash build-up in a TFTR-sized, fusing tokamak plasma is explored. In an idealized tokamak plasma, an externally-imposed radial electric field leads to plasma rotation, but no charge current flows across the magnetic fields. However, a realistically-low neutral density profile generates a non-zero cross-field conductivity and the species dependence of this conductivity allows the electric field to selectively alter radial particle transport
Pai, C N; Shinshi, T; Shimokohbe, A
2010-01-01
Evaluation of the hydraulic forces in a magnetically levitated (maglev) centrifugal blood pump is important from the point of view of the magnetic bearing design. Direct measurement is difficult due to the absence of a rotor shaft, and computational fluid dynamic analysis demands considerable computational resource and time. To solve this problem, disturbance force observers were developed, using the radial controlled magnetic bearing of a centrifugal blood pump, to estimate the radial forces on the maglev impeller. In order to design the disturbance observer, the radial dynamic characteristics of a maglev impeller were evaluated under different working conditions. It was observed that the working fluid affects the additional mass and damping, while the rotational speed affects the damping and stiffness of the maglev system. Based on these results, disturbance force observers were designed and implemented. The designed disturbance force observers present a bandwidth of 45 Hz. In non-pulsatile conditions, the magnitude of the estimated radial thrust increases in proportion to the flowrate, and the rotational speed has little effect on the force direction. At 5 l/min against 100 mmHg, the estimated radial thrust is 0.95 N. In pulsatile conditions, this method was capable of estimating the pulsatile radial thrust with good response.
Blanck, Harvey F.
2012-01-01
Naturally occurring gravity currents include events such as air flowing through an open front door, a volcanic eruption's pyroclastic flow down a mountainside, and the spread of the Bhopal disaster's methyl isocyanate gas. Gravity currents typically have a small height-to-distance ratio. Plastic models were designed and constructed with a…
Schiffmann, J. [Fischer Engineering Solutions AG, Birkenweg 3, CH-3360 Herzogenbuchsee (Switzerland); Favrat, D. [Ecole Polytechnique Federale de Lausanne, EPFL STI IGM LENI, Station 9, CH-1015 Lausanne (Switzerland)
2010-01-15
The main driver for small scale turbomachinery in domestic heat pumps is the potential for reaching higher efficiencies than volumetric compressors currently used and the potential for making the compressor oil-free, bearing a considerable advantage in the design of advanced multi-stage heat pump cycles. An appropriate turbocompressor for driving domestic heat pumps with a high temperature lift requires the ability to operate on a wide range of pressure ratios and mass flows, confronting the designer with the necessity of a compromise between range and efficiency. The present publication shows a possible way to deal with that difficulty, by coupling an appropriate modeling tool to a multi-objective optimizer. The optimizer manages to fit the compressor design into the possible specifications field while keeping the high efficiency on a wide operational range. The 1D-tool used for the compressor stage modeling has been validated by experimentally testing an initial impeller design. The excellent experimental results, the agreement with the model and the linking of the model to a multi-objective optimizer will allow to design radial compressor stages managing to fit the wide operational range of domestic heat pumps while keeping the high efficiency level. (author)
Methods and apparatus for radially compliant component mounting
Bulman, David Edward [Cincinnati, OH; Darkins, Jr., Toby George; Stumpf, James Anthony [Columbus, IN; Schroder, Mark S [Greenville, SC; Lipinski, John Joseph [Simpsonville, SC
2012-03-27
Methods and apparatus for a mounting assembly for a liner of a gas turbine engine combustor are provided. The combustor includes a combustor liner and a radially outer annular flow sleeve. The mounting assembly includes an inner ring surrounding a radially outer surface of the liner and including a plurality of axially extending fingers. The mounting assembly also includes a radially outer ring coupled to the inner ring through a plurality of spacers that extend radially from a radially outer surface of the inner ring to the outer ring.
An Enhanced Factor Analysis of Performance Degradation Assessment on Slurry Pump Impellers
Shilong Sun
2017-01-01
Full Text Available Slurry pumps, such as oil sand pumps, are widely used in industry to convert electrical energy to slurry potential and kinetic energy. Because of adverse working conditions, slurry pump impellers are prone to suffer wear, which may result in slurry pump breakdowns. To prevent any unexpected breakdowns, slurry pump impeller performance degradation assessment should be immediately conducted to monitor the current health condition and to ensure the safety and reliability of slurry pumps. In this paper, to provide an alternative to the impeller health indicator, an enhanced factor analysis based impeller indicator (EFABII is proposed. Firstly, a low-pass filter is employed to improve the signal to noise ratios of slurry pump vibration signals. Secondly, redundant statistical features are extracted from the filtered vibration signals. To reduce the redundancy of the statistic features, the enhanced factor analysis is performed to generate new statistical features. Moreover, the statistic features can be automatically grouped and developed a new indicator called EFABII. Data collected from industrial oil sand pumps are used to validate the effectiveness of the proposed method. The results show that the proposed method is able to track the current health condition of slurry pump impellers.
Duan, Shengbing; Ni, Weijia; Luo, Hongzhen; Shi, Zhongping; Liu, Fan; Yuan, Guoqiang; Zhao, Yanli
2013-01-01
Cephalosporin C (CPC) fermentation by Acremonium chrysogenum is an extremely high oxygen-consuming process and oxygen transfer rate in a bioreactor directly affects fermentation performance. In this study, fluid dynamics and oxygen transfer in a 7 L bioreactor with different impellers combinations were simulated by computational fluid dynamics (CFD) model. Based on the simulation results, two impeller combinations with higher oxygen transfer rate (K_La) were selected to conduct CPC fermentations, aiming at achieving high CPC concentration and low accumulation of major by-product, deacetoxycephalosporin (DAOC). It was found that an impeller combination with a higher K_La and moderate shear force is the prerequisite for efficient CPC production in a stirred bioreactor. The best impeller combination, which installed a six-bladed turbine and a four-pitched-blade turbine at bottom and upper layers but with a shortened impellers inter-distance, produced the highest CPC concentration of 35.77 g/L and lowest DAOC/CPC ratio of 0.5%
Duan, Shengbing; Ni, Weijia; Luo, Hongzhen; Shi, Zhongping; Liu, Fan [Jiangnan University, Wuxi (China); Yuan, Guoqiang; Zhao, Yanli [CSPC Hebei Zhongrun Pharmaceutical Co. Ltd., Shijiazhuang (China)
2013-05-15
Cephalosporin C (CPC) fermentation by Acremonium chrysogenum is an extremely high oxygen-consuming process and oxygen transfer rate in a bioreactor directly affects fermentation performance. In this study, fluid dynamics and oxygen transfer in a 7 L bioreactor with different impellers combinations were simulated by computational fluid dynamics (CFD) model. Based on the simulation results, two impeller combinations with higher oxygen transfer rate (K{sub L}a) were selected to conduct CPC fermentations, aiming at achieving high CPC concentration and low accumulation of major by-product, deacetoxycephalosporin (DAOC). It was found that an impeller combination with a higher K{sub L}a and moderate shear force is the prerequisite for efficient CPC production in a stirred bioreactor. The best impeller combination, which installed a six-bladed turbine and a four-pitched-blade turbine at bottom and upper layers but with a shortened impellers inter-distance, produced the highest CPC concentration of 35.77 g/L and lowest DAOC/CPC ratio of 0.5%.
Properties of made by different methods of RP impeller foundry patterns
G. Budzik
2007-04-01
Full Text Available This article presents the tests of properties of foundry patterns of turbocharger turbine impeller. Impellers prototypes were predestinated for casting by method losing patterns. There were carried out tests of these prototypes made by different methods of Rapid Prototyping (RP. Two impeller were made by growth methods: stereolitography (SLA and three dimensional printing (3DP. One prototype was made by the method of Vacuum Casting as a wax casting. Tests were executed in the Department of Machine Design of Rzeszow University of Technology in cooperation with WSK PZL Rzeszow and Car Technology Krakow. First impeller was carried out by method of stereolitography on SLA 250 plant. That pattern was also used to carry out silicon matrix for casting of wax pattern. Next pattern was printed by three dimensional printer Z510 from the powder ZP14. Good removability of the pattern from the mould is particularly essential for impellers of small turbines with blades of small thickness of their section. All pattern were tested on their removability from the ceramic mould. The best melting properties had the wax pattern. Patterns made from resin SL5170 (SLA and powder ZP14 (3DP were removed in the process of burning but about 1% of soot was left in the mould.
Optical Flow-Field Techniques Used for Measurements in High-Speed Centrifugal Compressors
Skoch, Gary J.
1999-01-01
The overall performance of a centrifugal compressor depends on the performance of the impeller and diffuser as well as on the interactions occurring between these components. Accurate measurements of the flow fields in each component are needed to develop computational models that can be used in compressor design codes. These measurements must be made simultaneously over an area that covers both components so that researchers can understand the interactions occurring between the two components. Optical measurement techniques are being used at the NASA Lewis Research Center to measure the velocity fields present in both the impeller and diffuser of a 4:1 pressure ratio centrifugal compressor operating at several conditions ranging from design flow to surge. Laser Doppler Velocimetry (LDV) was used to measure the intrablade flows present in the impeller, and the results were compared with analyses obtained from two three-dimensional viscous codes. The development of a region of low throughflow velocity fluid within this high-speed impeller was examined and compared with a similar region first observed in a large low-speed centrifugal impeller at Lewis. Particle Image Velocimetry (PIV) is a relatively new technique that has been applied to measuring the diffuser flow fields. PIV can collect data rapidly in the diffuser while avoiding the light-reflection problems that are often encountered when LDV is used. The Particle Image Velocimeter employs a sheet of pulsed laser light that is introduced into the diffuser in a quasi-radial direction through an optical probe inserted near the diffuser discharge. The light sheet is positioned such that its centerline is parallel to the hub and shroud surfaces and such that it is parallel to the diffuser vane, thereby avoiding reflections from the solid surfaces. Seed particles small enough to follow the diffuser flow are introduced into the compressor at an upstream location. A high-speed charge-coupled discharge (CCD) camera is
Radial nerve dysfunction (image)
The radial nerve travels down the arm and supplies movement to the triceps muscle at the back of the upper arm. ... the wrist and hand. The usual causes of nerve dysfunction are direct trauma, prolonged pressure on the ...
Dong, Shuhao; Zhu, Ping; Xu, Xiaoying; Li, Sha; Jiang, Yongxiang; Xu, Hong
2015-07-01
Agitator is one of the essential factors to realize high efficient fermentation for high aerobic and viscous microorganisms, and the influence of different impeller combination on the fermentation process is very important. Welan gum is a microbial exopolysaccharide produced by Alcaligenes sp. under high aerobic and high viscos conditions. Computational fluid dynamics (CFD) numerical simulation was used for analyzing the distribution of velocity, shear rate and gas holdup in the welan fermentation reactor under six different impeller combinations. The best three combinations of impellers were applied to the fermentation of welan. By analyzing the fermentation performance, the MB-4-6 combination had better effect on dissolved oxygen and velocity. The content of welan was increased by 13%. Furthermore, the viscosity of production were also increased.
Yongxue Zhang
2014-02-01
Full Text Available A hydraulic design method of three-dimensional blade was presented to design the blades of the rotodynamic multiphase pump. Numerical simulations and bench test were conducted to investigate the performance of the example impeller designed by the presented method. The results obtained from the bench test were in good agreement with the simulation results, which indicated the reasonability of the simulation. The distributions of pressure and gas volume fraction were analyzed and the results showed that the designed impeller was good for the transportation of mixture composed of gas and liquid. In addition, the advantage of the impeller designed by the presented method was suitable for using in large volume rate conditions, which were reflected by the comparison of the head performance between this three-dimensional design method and another one.
A prediction of 3-D viscous flow and performance of the NASA Low-Speed Centrifugal Compressor
Moore, John; Moore, Joan G.
1990-01-01
A prediction of the three-dimensional turbulent flow in the NASA Low-Speed Centrifugal Compressor Impeller has been made. The calculation was made for the compressor design conditions with the specified uniform tip clearance gap. The predicted performance is significantly worse than that predicted in the NASA design study. This is explained by the high tip leakage flow in the present calculation and by the different model adopted for tip leakage flow mixing. The calculation gives an accumulation of high losses in the shroud/pressure-side quadrant near the exit of the impeller. It also predicts a region of meridional backflow near the shroud wall. Both of these flow features should be extensive enough in the NASA impeller to allow detailed flow measurements, leading to improved flow modeling. Recommendations are made for future flow studies in the NASA impeller.
Numerical simulation of 3-D turbulent flow through entire stage in a multistage centrifugal pump
Huang, S.; Islam, M.F.; Liu, P.
2005-01-01
A three-dimensional turbulent flow through a multistage centrifugal pump is numerically simulated using a commercial CFD software package. The simulation and analysis include flow fields in rotating impeller and stationary diffuser and is completed in a multiple reference frame. The standard k-ε turbulence model is applied. The analysis of the simulation reveals that the reverse flows exist in the zone near the impeller exit and diffuser entrance, resulting in flow field asymmetric and unsteady. There is a considerable interference on velocity field at impeller exit due to the interaction between impeller blades and diffuser vanes. The hydraulic performance is connected and evaluated with the 3-D computational flow field. The current computation is verified by comparing predicted and measured head. (author)
Bhattacharyya, Trambak; Khuntia, Arvind; Pareek, Pooja; Sahoo, Raghunath; Cleymans, Jean
2016-01-01
We expand the Tsallis distribution in a Taylor series of powers of (q - 1), where q is the Tsallis parameter, assuming q is very close to 1. This helps in studying the degree of deviation of transverse momentum spectra and other thermodynamic quantities from a thermalized Boltzmann distribution. After checking thermodynamic consistency, we provide analytical results for the Tsallis distribution in the presence of collective flow up to the first order of (q - 1). The formulae are compared with the experimental data. (orig.)
Bhattacharyya, Trambak; Khuntia, Arvind; Pareek, Pooja; Sahoo, Raghunath [Indian Institute of Technology Indore, Discipline of Physics, School of Basic Sciences, Simrol (India); Cleymans, Jean [University of Cape Town, UCT-CERN Research Centre and Department of Physics, Rondebosch (South Africa)
2016-02-15
We expand the Tsallis distribution in a Taylor series of powers of (q - 1), where q is the Tsallis parameter, assuming q is very close to 1. This helps in studying the degree of deviation of transverse momentum spectra and other thermodynamic quantities from a thermalized Boltzmann distribution. After checking thermodynamic consistency, we provide analytical results for the Tsallis distribution in the presence of collective flow up to the first order of (q - 1). The formulae are compared with the experimental data. (orig.)
Vargyas, M.; Csörgo, T.; Vértési, Robert
2013-01-01
Roč. 11, č. 5 (2013), s. 553-559 ISSN 1895-1082 Institutional support: RVO:61389005 Keywords : brookhaven RHIC Coll * heavy ion * dilepton production * collective flow * phase transition Subject RIV: BG - Nuclear, Atomic and Molecular Physics, Colliders Impact factor: 1.077, year: 2013 http://download.springer.com/static/pdf/562/art%253A10.2478%252Fs11534-013-0249-6.pdf?auth66=1383750813_546c1ca442190c6f9388aa55e3c54340&ext=.pdf
Usta, Ilker [Wood Products Industrial Engineering, Hacettepe University, 06532-Beytepe, Ankara (Turkey)
2006-08-15
This paper discusses the effects of wood drying upon treatability (as determined by preservative uptake and gain-in-weight retention) of European silver fir on the two moisture content (MC) levels which were designed to be above and below the fibre saturation point (FSP). The treatability behaviour was investigated for individual flow pathways: longitudinal (L, along the stem), tangential (T, along the growth rings) and radial (R, along the rays), and also for the triplex (t, cumulative of all three directions: all faces left open). As the FSP was observed 32.7%, MC of the experimental samples-for each flow path-nominated to around 50% and 9% by recommended kiln drying schedule using a conventional kiln. The samples were then treated with a 2.5% concentration of commercial Tanalith C of CCA (chromium/copper/arsenic) via a mild schedule of full-cell impregnation process using a model pressure treatment plant. Treatability of European silver fir was noticed in different behaviour in either flow paths before and after drying. According to the experimental results, MC regulate the preservative uptake (as the percentage of void volume filled with preservative, VVF%) along the grain (L) and VVF% was improved by kiln drying process effectively, however, it was seemed to be contradictory across the grain (in both T and R). In the cumulative form (t), treatability-in either above or below the FSP-was appeared to be slightly greater than that for L due to support of the longitudinal flow. Therefore, it could be suggested that wood material which is subjected to be used in constructional purposes has to be initially dried to below the FSP, and - for efficient preservative treatment - it has to be treated with all faces unsealed (free from any pre-coating and/or painting). This shall be more ideal which in turn influences the quality of treated wood allowing better performance in its service life. (author)
Jairo Andrés Acosta Rojas
2007-12-01
Full Text Available En la digitalización 3D del rodete del compresor centrífugo de un turbo cargador HT3B, se evaluaron numerosas metodologías que permitieran reproducir su geometría satisfactoriamente, de modo que a partir del modelo virtual obtenido se pudiera llevar a cabo una simulación computacional de flujo en el compresor centrífugo. Tras analizar dichas metodologías se decidió que la toma de tomografías axiales computarizadas era la más indicada, a pesar de que requirió previamente la construcción de un modelo en acrílico del rodete. Una vez se contó con las tomografías axiales computarizadas del rodete, se procedió a construir el modelo virtual del mismo usando un programa CAD 3D, integrando una metodología analítica para la generación de la geometría de los álabes del rodete de un compresor centrífugo, con la información metrológica adquirida a través de las tomografías. El modelo virtual del rodete presentó características aptas para el posterior trabajo de simulación, demostrando que el procedimiento planteado constituye una alternativa viable para la digitalización 3D de piezas mecánicas de alta complejidad.In the 3D digitizing of an HT3B turbocharger's centrifugal compressor's impeller, several methodologies were evaluated, reproducing its shape in such a way, that the obtained virtual model could be used to perform a computational flow simulation in the whole centrifugal compressor. After analyzing these methodologies, computerized axial tomographies were chosen as the most suitable methodology, despite requiring the previous construction of an impeller's acrylic-made model. Once the impeller's computerized axial tomographies had been taken, the generation of the virtual model was performed by software CAD 3D, by integrating an analytic methodology for the impeller's vanes' geometrical shape generation, with the metrological information extracted from the tomographies. The virtual model generated presented
Numerical simulation of radial compressor stage
Syka, T.; Luňáček, O.
2013-04-01
Article describes numerical simulations of air flow in radial compressor stage in NUMECA CFD software. In simulations geometry variants with and without seals are used. During tasks evaluating was observed seals influence on flow field and performance parameters of compressor stage. Also is described CFDresults comparison with results from design software based on experimental measurements and monitoring of influence of seals construction on compressor stage efficiency.
Numerical simulation of radial compressor stage
Luňáček O.; Syka T.
2013-01-01
Article describes numerical simulations of air flow in radial compressor stage in NUMECA CFD software. In simulations geometry variants with and without seals are used. During tasks evaluating was observed seals influence on flow field and performance parameters of compressor stage. Also is described CFDresults comparison with results from design software based on experimental measurements and monitoring of influence of seals construction on compressor stage efficiency.
Numerical simulation of radial compressor stage
Luňáček O.
2013-04-01
Full Text Available Article describes numerical simulations of air flow in radial compressor stage in NUMECA CFD software. In simulations geometry variants with and without seals are used. During tasks evaluating was observed seals influence on flow field and performance parameters of compressor stage. Also is described CFDresults comparison with results from design software based on experimental measurements and monitoring of influence of seals construction on compressor stage efficiency.
Smith, Karl H.
2002-01-01
A radial wedge flange clamp comprising a pair of flanges each comprising a plurality of peripheral flat wedge facets having flat wedge surfaces and opposed and mating flat surfaces attached to or otherwise engaged with two elements to be joined and including a series of generally U-shaped wedge clamps each having flat wedge interior surfaces and engaging one pair of said peripheral flat wedge facets. Each of said generally U-shaped wedge clamps has in its opposing extremities apertures for the tangential insertion of bolts to apply uniform radial force to said wedge clamps when assembled about said wedge segments.
Review on stress corrosion and corrosion fatigue failure of centrifugal compressor impeller
Sun, Jiao; Chen, Songying; Qu, Yanpeng; Li, Jianfeng
2015-03-01
Corrosion failure, especially stress corrosion cracking and corrosion fatigue, is the main cause of centrifugal compressor impeller failure. And it is concealed and destructive. This paper summarizes the main theories of stress corrosion cracking and corrosion fatigue and its latest developments, and it also points out that existing stress corrosion cracking theories can be reduced to the anodic dissolution (AD), the hydrogen-induced cracking (HIC), and the combined AD and HIC mechanisms. The corrosion behavior and the mechanism of corrosion fatigue in the crack propagation stage are similar to stress corrosion cracking. The effects of stress ratio, loading frequency, and corrosive medium on the corrosion fatigue crack propagation rate are analyzed and summarized. The corrosion behavior and the mechanism of stress corrosion cracking and corrosion fatigue in corrosive environments, which contain sulfide, chlorides, and carbonate, are analyzed. The working environments of the centrifugal compressor impeller show the behavior and the mechanism of stress corrosion cracking and corrosion fatigue in different corrosive environments. The current research methods for centrifugal compressor impeller corrosion failure are analyzed. Physical analysis, numerical simulation, and the fluid-structure interaction method play an increasingly important role in the research on impeller deformation and stress distribution caused by the joint action of aerodynamic load and centrifugal load.
Effects of impeller diameter and rotational speed on performance of pump running in turbine mode
Jain, Sanjay V.; Swarnkar, Abhishek; Motwani, Karan H.; Patel, Rajesh N.
2015-01-01
Highlights: • Experiments done between 900 and 1500 rpm with original, 10% and 20% trimmed impellers. • The performance of PAT was found better in speed range of 1000–1200 rpm. • Blade rounding led to 3–4% rise in efficiency at rated speed with existing impeller. • Correlation developed has predicted η BEP within ±10% of experimental results. - Abstract: The major limitations of mini/micro hydropower schemes is the higher cost of small capacity hydro turbines. Also, it is very cumbersome, time consuming and expensive to develop the site specific turbines corresponding to local site conditions in mini/micro hydro range. In such plants, small centrifugal pumps can be used in turbine mode by running in the reverse direction. The efficiency of pump as turbines (PATs) is usually lower than the conventional hydro turbines; however, there may be substantial decrease in the capital cost of the plant. Hydropower plants usually runs at part load for several months in a year due to insufficient water availability for the power generation. The application range of PAT can be widened if its part load and/or maximum efficiency can be improved. In the present study, experimental investigations are carried out on centrifugal pump running in turbine mode to optimize its geometric and operational parameters e.g. impeller diameter and rotational speed. The experiments were performed in the wide range of rotational speeds varying from 900 to 1500 rpm with original (∅ 250 mm), 10% trimmed (∅ 225 mm) and 20% trimmed (∅ 200 mm) impellers. Impeller trimming led to improvement in efficiency at part load operating conditions. The performance of PAT was found better at the lower speeds than that at the rated speed. The effects of blade rounding were studied in all the cases and it led to 3–4% rise in efficiency at rated speed with the original impeller. The empirical correlation is also developed for prediction of efficiency in terms of impeller diameter and rotational
Pei, Ji; Wang, Wen Jie; Yuan, Shouqi [National Research Center of Pumps, Jiangsu University, Zhenjiang (China)
2016-11-15
A wide operating band is important for a pump to safely perform at maximum efficiency while saving energy. To widen the operating range, a multi-point optimization process based on numerical simulations in order to improve impeller performance of a centrifugal pump used in nuclear plant applications is proposed by this research. The Reynolds average Navier Stokes equations are utilized to perform the calculations. The meridional shape of the impeller was optimized based on the following four parameters; shroud arc radius, hub arc radius, shroud angle, and hub angle as the design variables. Efficiencies calculated under 0.6Qd, 1.0Qd and 1.62Qd were selected as the three optimized objectives. The Design of experiment method was applied to generate various impellers while 35 impellers were generated by the Latin hypercube sampling method. A Response surface function based on a second order function was applied to construct a mathematical relationship between the objectives and design variables. A multi-objective genetic algorithm was utilized to solve the response surface function to obtain the best optimized objectives as well as the best combination of design parameters. The results indicated that the pump performance predicted by numerical simulation was in agreement with the experimental performance. The optimized efficiencies based on the three operating conditions were increased by 3.9 %, 6.1 % and 2.6 %, respectively. In addition, the velocity distribution, pressure distribution, streamline and turbulence kinetic energy distribution of the optimized and reference impeller were compared and analyzed to illustrate the performance improvement.
Pei, Ji; Wang, Wen Jie; Yuan, Shouqi
2016-01-01
A wide operating band is important for a pump to safely perform at maximum efficiency while saving energy. To widen the operating range, a multi-point optimization process based on numerical simulations in order to improve impeller performance of a centrifugal pump used in nuclear plant applications is proposed by this research. The Reynolds average Navier Stokes equations are utilized to perform the calculations. The meridional shape of the impeller was optimized based on the following four parameters; shroud arc radius, hub arc radius, shroud angle, and hub angle as the design variables. Efficiencies calculated under 0.6Qd, 1.0Qd and 1.62Qd were selected as the three optimized objectives. The Design of experiment method was applied to generate various impellers while 35 impellers were generated by the Latin hypercube sampling method. A Response surface function based on a second order function was applied to construct a mathematical relationship between the objectives and design variables. A multi-objective genetic algorithm was utilized to solve the response surface function to obtain the best optimized objectives as well as the best combination of design parameters. The results indicated that the pump performance predicted by numerical simulation was in agreement with the experimental performance. The optimized efficiencies based on the three operating conditions were increased by 3.9 %, 6.1 % and 2.6 %, respectively. In addition, the velocity distribution, pressure distribution, streamline and turbulence kinetic energy distribution of the optimized and reference impeller were compared and analyzed to illustrate the performance improvement
Sirenomelia with radial dysplasia.
Kulkarni, M L; Abdul Manaf, K M; Prasannakumar, D G; Kulkarni, Preethi M
2004-05-01
Sirenomelia is a rare anomaly usually associated with other multiple malformations. In this communication the authors report a case of sirenomelia associated with multiple malformations, which include radial hypoplasia also. Though several theories have been proposed regarding the etiology of multiple malformation syndromes in the past, the recent theory of primary developmental defect during blastogenesis holds good in this case.
Radially truncated galactic discs
Grijs, R. de; Kregel, M.; Wesson, K H
2000-01-01
Abstract: We present the first results of a systematic analysis of radially truncatedexponential discs for four galaxies of a sample of disc-dominated edge-onspiral galaxies. Edge-on galaxies are very useful for the study of truncatedgalactic discs, since we can follow their light distributions out
Radial transfer effects for poloidal rotation
Hallatschek, Klaus
2010-11-01
Radial transfer of energy or momentum is the principal agent responsible for radial structures of Geodesic Acoustic Modes (GAMs) or stationary Zonal Flows (ZF) generated by the turbulence. For the GAM, following a physical approach, it is possible to find useful expressions for the individual components of the Poynting flux or radial group velocity allowing predictions where a mathematical full analysis is unfeasible. Striking differences between up-down symmetric flux surfaces and asymmetric ones have been found. For divertor geometries, e.g., the direction of the propagation depends on the sign of the ion grad-B drift with respect to the X-point, reminiscent of a sensitive determinant of the H-mode threshold. In nonlocal turbulence computations it becomes obvious that the linear energy transfer terms can be completely overwhelmed by the action of the turbulence. In contrast, stationary ZFs are governed by the turbulent radial transfer of momentum. For sufficiently large systems, the Reynolds stress becomes a deterministic functional of the flows, which can be empirically determined from the stress response in computational turbulence studies. The functional allows predictions even on flow/turbulence states not readily obtainable from small amplitude noise, such as certain transport bifurcations or meta-stable states.
Lavaud, F.
2001-09-01
My thesis relates to central collisions of Au+Au at energies going from 40 to 100 MeV/A. It was pursued in the scope of an analysis of the collection and the interpretation of data obtained though the 4. campaign of measures from the INDRA multidetector. The first part for this study, related to the data collection, enabled me to rebuild the kinetic energies and the charge of the fragments detected thanks to data issued from ionisation chamber and silicon detectors of INDRA. For the first time, it has been possible to demonstrate and correct the non-linear effects appearing in INDRA's acquisition chain. At the end of this study, I focussed on the selection of central collisions. For that purpose, and in order not to dodge the resulting interpretations on physics, I used two different methods: selection in impact parameter and PCA. A comparative study of those mathematical tools has been performed, showing instructive results. The interpretation of the results requires the use of different codes, which in turn imply the validity of the hypothesis which need to be made (thermodynamic equilibrium, existence of a 'freeze-out' volume). The use of statistical models (SMM, MMMC) enabled to extract the size of the emitter system, named 'single source', as well as its excitation energy. The anisotropy of the fragments kinetic energy distributions enabled, depending on the incident energy of the collision, first to demonstrate the deformation of the source and second to rebuild the existing thermal and collective energies. A second comparison of the data has been performed, this time using dynamic models (QMD, CMD). At the conclusion of this study, remarks on the validity of such approaches as SMM or MMMC could be made, questioning the fundaments of the physical interpretation of the collective flow which commonly made. (author)
Variable stator radial turbine
Rogo, C.; Hajek, T.; Chen, A. G.
1984-01-01
A radial turbine stage with a variable area nozzle was investigated. A high work capacity turbine design with a known high performance base was modified to accept a fixed vane stagger angle moveable sidewall nozzle. The nozzle area was varied by moving the forward and rearward sidewalls. Diffusing and accelerating rotor inlet ramps were evaluated in combinations with hub and shroud rotor exit rings. Performance of contoured sidewalls and the location of the sidewall split line with respect to the rotor inlet was compared to the baseline. Performance and rotor exit survey data are presented for 31 different geometries. Detail survey data at the nozzle exit are given in contour plot format for five configurations. A data base is provided for a variable geometry concept that is a viable alternative to the more common pivoted vane variable geometry radial turbine.
Nilsson, Martin
2007-01-01
The demands for ride comfort quality in today's long haulage trucks are constantly growing. A part of the ride comfort problems are represented by internal vibrations caused by rotating mechanical parts. This thesis work focus on the vibrations generated from radial runout on the wheels. These long haulage trucks travel long distances on smooth highways, with a constant speed of 90 km/h resulting in a 7 Hz oscillation. This frequency creates vibrations in the cab, which can be found annoying....
Coufal, David
2017-01-01
Roč. 319, 15 July (2017), s. 1-27 ISSN 0165-0114 R&D Projects: GA MŠk(CZ) LD13002 Institutional support: RVO:67985807 Keywords : fuzzy systems * radial functions * coherence Subject RIV: BA - General Mathematics OBOR OECD: Computer sciences, information science, bioinformathics (hardware development to be 2.2, social aspect to be 5.8) Impact factor: 2.718, year: 2016
Radial Field Piezoelectric Diaphragms
Bryant, R. G.; Effinger, R. T., IV; Copeland, B. M., Jr.
2002-01-01
A series of active piezoelectric diaphragms were fabricated and patterned with several geometrically defined Inter-Circulating Electrodes "ICE" and Interdigitated Ring Electrodes "ICE". When a voltage potential is applied to the electrodes, the result is a radially distributed electric field that mechanically strains the piezoceramic along the Z-axis (perpendicular to the applied electric field). Unlike other piezoelectric bender actuators, these Radial Field Diaphragms (RFDs) strain concentrically yet afford high displacements (several times that of the equivalent Unimorph) while maintaining a constant circumference. One of the more intriguing aspects is that the radial strain field reverses itself along the radius of the RFD while the tangential strain remains relatively constant. The result is a Z-deflection that has a conical profile. This paper covers the fabrication and characterization of the 5 cm. (2 in.) diaphragms as a function of poling field strength, ceramic thickness, electrode type and line spacing, as well as the surface topography, the resulting strain field and displacement as a function of applied voltage at low frequencies. The unique features of these RFDs include the ability to be clamped about their perimeter with little or no change in displacement, the environmentally insulated packaging, and a highly repeatable fabrication process that uses commodity materials.
Perceived radial translation during centrifugation
Bos, J.E.; Correia Grácio, B.J.
2015-01-01
BACKGROUND: Linear acceleration generally gives rise to translation perception. Centripetal acceleration during centrifugation, however, has never been reported giving rise to a radial, inward translation perception. OBJECTIVE: To study whether centrifugation can induce a radial translation
Flow Simulation and Performance Prediction of Centrifugal Pumps ...
With the aid of computational fluid dynamics, the complex internal flows in water pump impellers can be well predicted, thus facilitating the product development process of pumps. In this paper a commercial CFD code was used to solve the governing equations of the flow field. A 2-D simulation of turbulent fluid flow is ...
Experimental feasibility study of radial injection cooling of three-pad radial air foil bearings
Shrestha, Suman K.
Air foil bearings use ambient air as a lubricant allowing environment-friendly operation. When they are designed, installed, and operated properly, air foil bearings are very cost effective and reliable solution to oil-free turbomachinery. Because air is used as a lubricant, there are no mechanical contacts between the rotor and bearings and when the rotor is lifted off the bearing, near frictionless quiet operation is possible. However, due to the high speed operation, thermal management is one of the very important design factors to consider. Most widely accepted practice of the cooling method is axial cooling, which uses cooling air passing through heat exchange channels formed underneath the bearing pad. Advantage is no hardware modification to implement the axial cooling because elastic foundation structure of foil bearing serves as a heat exchange channels. Disadvantage is axial temperature gradient on the journal shaft and bearing. This work presents the experimental feasibility study of alternative cooling method using radial injection of cooling air directly on the rotor shaft. The injection speeds, number of nozzles, location of nozzles, total air flow rate are important factors determining the effectiveness of the radial injection cooling method. Effectiveness of the radial injection cooling was compared with traditional axial cooling method. A previously constructed test rig was modified to accommodate a new motor with higher torque and radial injection cooling. The radial injection cooling utilizes the direct air injection to the inlet region of air film from three locations at 120° from one another with each location having three axially separated holes. In axial cooling, a certain axial pressure gradient is applied across the bearing to induce axial cooling air through bump foil channels. For the comparison of the two methods, the same amount of cooling air flow rate was used for both axial cooling and radial injection. Cooling air flow rate was
Finite volume modeling of the solidification of an axial steel cast impeller
M. Copur
2014-04-01
Full Text Available In the foundry industry, obtaining the solidification contours in cast geometries are extremely important to know the last location(s to solidify in order to define the correct feeding path and the number of risers. This paper presents three-dimensional simulation of transient conduction heat transfer within an axial impeller, made of AISI 1016 steel, poured and solidified in chemically bonded mold and core medium, by using FVM technique and ANSYS CFX. Specific heat, density and thermal conductivity of AISI 1016 steel, mold and Core materials are considered as functions of temperatures. In this transient thermal analysis, the convection heat transfer phenomenon is also considered at the outer surfaces of the mold. In order to shorten the run-time, the nonlinear transient analysis has been made for 600/3600 segment of the impeller, core and mold. The solidification contours of the impeller as well as isothermal lines in core and mold have been obtained in 3-D. The cooling curves of diff erent points are also shown in the result section.
The Strength Calculation of the Pump Shaft with a Worn Impeller
Nikolay P. Ovchinnikov
2017-12-01
Full Text Available Introduction: This paper presents the study of the impeller wear influence on stress-strain state of a centrifugal pump shaft. In agro-industrial sector, centrifugal pumps are used for watering various agricultural crops. During pumping water, a centrifugal pump impeller is usually a subject to influence of various irreversible physical-and-mechanical and physical-and-chemical processes that can result in a certain reduction in its mass. Materials and Methods: We used a comprehensive approach including the analysis of a sufficient number domestic and foreign publications on the research topic and parametric studies conducted on a laboratory-pumping unit. We had modern vibration-based diagnostic equipment, the mathematical models of loading a pump shaft and a finite-element modeling in APM Win Machine software (Beam module. Results: The comparison of the maximum equivalent dynamic stresses obtained according to the proposed method with existing methods for carrying out the checking strength calculation of a centrifugal pump shaft showed that account of the impeller wear significantly changes picture of stress-strain state shaft. Discussion and Conclusions: The amendments proposed by the author in checking strength calculation of a centrifugal pump shaft will allow estimating its stress-strain state in certain production situations.
Houlin Liu
2014-01-01
Full Text Available The impeller outlet width of centrifugal pumps is of significant importance for numbers of effects. In the paper, these effects including the performance, pressure pulsations, hydraulically generated vibration, and noise level are investigated. For the purpose, two approaches were used to predict the vibration and sound radiation of the volute under fluid excitation force. One approach is the combined CFD/FEM analysis for structure vibration, and then the structure response obtained from the FEM analysis is treated as the boundary condition for BEM analysis for sound radiation. The other is the combined CFD/FEM/BEM coupling method. Before the numerical methods were used, the simulation results were validated by the vibration acceleration of the monitoring points on the volute. The vibration and noise were analyzed and compared at three flow conditions. The analysis of the results shows that the influences of the sound pressure of centrifugal pumps on the structure appear insignificant. The relative outlet width b2* at nq(SI = 26.7 in this paper should be less than 0.06, based on an overall consideration of the pump characteristics, pressure pulsations, vibration and noise level.
Radial reflection diffraction tomography
Lehman, Sean K.
2012-12-18
A wave-based tomographic imaging method and apparatus based upon one or more rotating radially outward oriented transmitting and receiving elements have been developed for non-destructive evaluation. At successive angular locations at a fixed radius, a predetermined transmitting element can launch a primary field and one or more predetermined receiving elements can collect the backscattered field in a "pitch/catch" operation. A Hilbert space inverse wave (HSIW) algorithm can construct images of the received scattered energy waves using operating modes chosen for a particular application. Applications include, improved intravascular imaging, bore hole tomography, and non-destructive evaluation (NDE) of parts having existing access holes.
Do ray cells provide a pathway for radial water movement in the stems of conifer trees?
David M. Barnard; Barbara Lachenbruch; Katherine A. McCulloh; Peter Kitin; Frederick C. Meinzer
2013-01-01
The pathway of radial water movement in tree stems presents an unknown with respect to whole-tree hydraulics. Radial profiles have shown substantial axial sap flow in deeper layers of sapwood (that may lack direct connection to transpiring leaves), which suggests the existence of a radial pathway for water movement. Rays in tree stems include ray tracheids and/or ray...
Elert, M.
1999-05-01
The 'Aespoe task force on modelling of groundwater flow and transport of solutes' is a forum for the international organisations supporting the Aespoe HRL Project. The purpose of the Task Force is to interact in the area of conceptual and numerical modelling of groundwater flow and solute transport in fractured rock. Task 4 of the Aespoe Modelling Task Force consists of modelling exercises in support of the TRUE-1 tracer tests. In this report, the modelling work performed within Tasks 4C and 4D is evaluated, which comprised predictive modelling of the radially converging tracer tests and dipole tracer tests performed within the TRUE-1 tests using non-sorbing tracers. The tests were performed between packed off boreholes penetrating a water-conducting geological feature with a simple structure (Feature A). These tests are to a great extent preparatory steps for the subsequent tests with sorbing radioactive tracers. In Tasks 4E and 4F of the Aespoe Modelling Task Force predictive modelling of the sorbing tracer tests is performed. Eight modelling teams representing seven organisations have performed predictive modelling using different modelling approaches and models. The modelling groups were initially given data from the site characterisation and data on the experimental set-up of the tracer tests. Based on this information model predictions were performed of drawdown, tracer mass recovery and tracer breakthrough. The performed predictions shows that the concept of Feature A as a singular well-connected feature with limited connectivity to its surroundings is quite adequate for predictions of drawdown in boreholes and conservative tracer breakthrough. Reasonable estimates were obtained using relatively simple models. However, more elaborate models with calibration or conditioning of transmissivities and transport apertures are required for more accurate predictions. The general flow and transport processes are well understood, but the methodology to derive the
Elert, M. [Kemakta Konsult AB, Stockholm (Sweden)
1999-05-01
The `Aespoe task force on modelling of groundwater flow and transport of solutes` is a forum for the international organisations supporting the Aespoe HRL Project. The purpose of the Task Force is to interact in the area of conceptual and numerical modelling of groundwater flow and solute transport in fractured rock. Task 4 of the Aespoe Modelling Task Force consists of modelling exercises in support of the TRUE-1 tracer tests. In this report, the modelling work performed within Tasks 4C and 4D is evaluated, which comprised predictive modelling of the radially converging tracer tests and dipole tracer tests performed within the TRUE-1 tests using non-sorbing tracers. The tests were performed between packed off boreholes penetrating a water-conducting geological feature with a simple structure (Feature A). These tests are to a great extent preparatory steps for the subsequent tests with sorbing radioactive tracers. In Tasks 4E and 4F of the Aespoe Modelling Task Force predictive modelling of the sorbing tracer tests is performed. Eight modelling teams representing seven organisations have performed predictive modelling using different modelling approaches and models. The modelling groups were initially given data from the site characterisation and data on the experimental set-up of the tracer tests. Based on this information model predictions were performed of drawdown, tracer mass recovery and tracer breakthrough. The performed predictions shows that the concept of Feature A as a singular well-connected feature with limited connectivity to its surroundings is quite adequate for predictions of drawdown in boreholes and conservative tracer breakthrough. Reasonable estimates were obtained using relatively simple models. However, more elaborate models with calibration or conditioning of transmissivities and transport apertures are required for more accurate predictions. The general flow and transport processes are well understood, but the methodology to derive the
Radial semiconductor drift chambers
Rawlings, K.J.
1987-01-01
The conditions under which the energy resolution of a radial semiconductor drift chamber based detector system becomes dominated by the step noise from the detector dark current have been investigated. To minimise the drift chamber dark current attention should be paid to carrier generation at Si/SiO 2 interfaces. This consideration conflicts with the desire to reduce the signal risetime: a higher drift field for shorter signal pulses requires a larger area of SiO 2 . Calculations for the single shaping and pseudo Gaussian passive filters indicate that for the same degree of signal risetime sensitivity in a system dominated by the step noise from the detector dark current, the pseudo Gaussian filter gives only a 3% improvement in signal/noise and 12% improvement in rate capability compared with the single shaper performance. (orig.)
1983-01-01
There were 37 (normal) + 3 (special) Radial Field magnets in the ISR to adjust vertically the closed orbit. Gap heights and strengths were 200 mm and .12 Tm in the normal magnets, 220 mm and .18 Tm in the special ones. The core length was 430 mm in both types. Due to their small length as compared to the gap heights the end fringe field errors were very important and had to be compensated by suitably shaping the poles. In order to save on cables, as these magnets were located very far from their power supplies, the coils of the normal type magnets were formed by many turns of solid cpper conductor with some interleaved layers of hollow conductor directly cooled by circulating water
Stone, M.B.; Abernathy, D.L.; Niedziela, J.L.; Overbay, M.A.
2015-01-01
We have designed, installed, and commissioned a scattered beam radial collimator for use at the ARCS Wide Angular Range Chopper Spectrometer at the Spallation Neutron Source. The collimator has been designed to work effectively for thermal and epithermal neutrons and with a range of sample environments. Other design considerations include the accommodation of working within a high vacuum environment and having the ability to quickly install and remove the collimator from the scattered beam. The collimator is composed of collimating blades (or septa). The septa are 12 micron thick Kapton foils coated on each side with 39 microns of enriched boron carbide ( 10 B 4 C with 10 B > 96%) in an ultra-high vacuum compatible binder. The collimator blades represent an additional 22 m 2 of surface area. In the article we present collimator's design and performance and methodologies for its effective use
Study of the turbulent flow structure around a standard Rushton impeller
Kysela, Bohuš; Konfršt, Jiří; Fořt, I.; Kotek, M.; Chára, Zdeněk
2014-01-01
Roč. 35, č. 1 (2014), s. 137-147 ISSN 0208-6425 R&D Projects: GA ČR GAP101/12/2274 Institutional support: RVO:67985874 Keywords : Rushton turbine * mixing * ensemble-average mean velocity * fluctuation velocity LDA/LDV * PIV * velocity profiles Subject RIV: BK - Fluid Dynamics Impact factor: 0.653, year: 2014
Nishida, Masahiro; Yamane, Takashi; Tsukamoto, Yuki; Ito, Kazuyuki; Konishi, Yoshiaki; Masuzawa, Toru; Tsukiya, Tomonori; Endo, Seiko; Taenaka, Yoshiyuki
To clarify the correlation between high-shear flow and hemolysis in blood pumps, detail shear velocity distribution was quantified by an experimental method with a model centrifugal blood pump that has a series data of hemolysis tests and computational fluid dynamic analyses. Particular attention was paid to the shear velocity near the casing surface in the volute where the high shear causes in circumferentially wide region that is considerable to cause high hemolysis. Three pump models were compared concern with the radial gap width between the impeller and casing (the radial volute width) also with the outlet position whereas the impeller geometry was identical. These casing geometries were as follows: model 1-the gap width is standard 3mm and the outlet locates to make a smooth geometrical connection with the volute, model 2-the gap width is small 0.5mm and the outlet locates to make the smooth geometrical connection with the volute, and model 3-the gap width is small 0.5mm and the outlet locates to hardly make the smooth geometrical connection with the volute but be similar radial position with that of model 1. Velocity was quantified with a particle tracking velocimetry that is one of the quantitative flow visualization techniques, and the shear velocity was calculated. Results showed that all large shear velocity existed within the layers of about 0.1mm from the casing surface and that those layers were hardly affected by a vane passage even if the gap width is 0.5mm. They also showed that the maximum shear velocity appeared on the casing surface, and the shear velocities of models 2 and 3 were almost twice as large as that of model 1. This finding is in full corresponding with the results of hemolysis tests which showed that the hemolysis levels of both models 2 and 3 were 1.5 times higher than that of model 1. These results suggest that detailed high-shear evaluation near the casing surface in the volute is one of the most important keys in estimating the
Antiproton compression and radial measurements
Andresen, G B; Bowe, P D; Bray, C C; Butler, E; Cesar, C L; Chapman, S; Charlton, M; Fajans, J; Fujiwara, M C; Funakoshi, R; Gill, D R; Hangst, J S; Hardy, W N; Hayano, R S; Hayden, M E; Humphries, A J; Hydomako, R; Jenkins, M J; Jorgensen, L V; Kurchaninov, L; Lambo, R; Madsen, N; Nolan, P; Olchanski, K; Olin, A; Page R D; Povilus, A; Pusa, P; Robicheaux, F; Sarid, E; Seif El Nasr, S; Silveira, D M; Storey, J W; Thompson, R I; Van der Werf, D P; Wurtele, J S; Yamazaki, Y
2008-01-01
Control of the radial proﬁle of trapped antiproton clouds is critical to trapping antihydrogen. We report detailed measurements of the radial manipulation of antiproton clouds, including areal density compressions by factors as large as ten, achieved by manipulating spatially overlapped electron plasmas. We show detailed measurements of the near-axis antiproton radial proﬁle, and its relation to that of the electron plasma. We also measure the outer radial proﬁle by ejecting antiprotons to the trap wall using an octupole magnet.
Radial-piston pump for drive of test machines
Nizhegorodov, A. I.; Gavrilin, A. N.; Moyzes, B. B.; Cherkasov, A. I.; Zharkevich, O. M.; Zhetessova, G. S.; Savelyeva, N. A.
2018-01-01
The article reviews the development of radial-piston pump with phase control and alternating-flow mode for seismic-testing platforms and other test machines. The prospects for use of the developed device are proved. It is noted that the method of frequency modulation with the detection of the natural frequencies is easily realized by using the radial-piston pump. The prospects of further research are given proof.
Modal behavior of a reduced scale pump-turbine impeller. Part 1: Experiments
Escaler, X; Huetter, J K; Egusquiza, E; Farhat, M; Avellan, F
2010-01-01
An experimental investigation has been carried out to quantify the effects of surrounding fluid on the modal behavior of a reduced scale pump-turbine impeller. The modal properties of the fluid-structure system have been obtained by Experimental Modal Analysis (EMA) with the impeller suspended in air and inside a water reservoir. The impeller has been excited with an instrumented hammer and the response has been measured by means of miniature accelerometers. The Frequency Response Functions (FRF's) have been obtained from a large number of impacting positions in order to ensure the identification of the main mode shapes. As a result, the main modes of vibration have been well characterized both in air and in water in terms of natural frequency, damping ratio and mode shape. The first mode is the 2 Nodal Diameter (ND), the second one is the 0ND and the following ones are the 3ND coupled with the 1ND. The visual observation of the animated mode shapes and the level of the Modal Assurance Criterion (MAC) have permitted to correlate the homologous modes of vibration of the fluid-structure system in air and in water. From this comparison the added mass effect on the natural frequencies and the fluid effect on the damping ratios have been quantified for the most significant modes. With the surrounding water, the natural frequencies decrease in average by 10%. On the other hand, the damping ratios increase in average by 0.5%. In any case, the damping ratio appears to decrease with the frequency value of the mode.
Radial expansion and multifragmentation
Angelique, J.C.; Bizard, G.; Bougault, R.; Brou, R.; Buta, A.; Colin, J.; Cussol, D.; Durand, D.; Kerambrun, A.; Le Brun, C.; Lecolley, J.F.; Lopez, O.; Louvel, M.; Meslin, C.; Nakagawa, T.; Patry, J.P.; Peter, J.; Popescu, R.; Regimbart, R.; Steckmeyer, J.C.; Tamain, B.; Vient, E.; Yuasa-Nakagawa, K.; Wieloch, A.
1998-01-01
The light systems 36 Ar + 27 Al and 64 Zn + nat Ti were measured at several bombarding energies between ∼ 35 and 95 MeV/nucleon. It was found that the predominant part of the cross section is due to binary collisions. In this paper the focus is placed on the properties of the quasi-projectile nuclei. In the central collisions the excitation energies of the quasi-projectile reach values exceeding largely 10 MeV/nucleon. The slope of the high energy part of the distribution can give only an upper limit of the apparent temperature (the average temperature along the decay chain). The highly excited quasi-projectile may get rapidly fragmented rather than sequentially. The heavy fragments are excited and can emit light particles (n, p, d, t, 3 He, α,...) what perturbs additionally the spectrum of these particles. Concerning the expansion energy, one can determine the average kinetic energies of the product (in the quasi-projectile-framework) and compare with simulation values. To fit the experimental data an additional radial expansion energy is to be considered. The average expansion energy depends slightly on the impact parameter but it increases with E * / A, ranging from 0.4 to 1,2 MeV/nucleon for an excitation energy increasing from 7 to 10.5 MeV/nucleon. This collective radial energy seems to be independent of the fragment mass, what is possibly valid for the case of larger quasi-projectile masses. The origin of the expansion is to be determined. It may be due to a compression in the interaction zone at the initial stage of the collision, which propagates in the quasi-projectile and quasi-target, or else, may be due, simply, to the increase of thermal energy leading to a rapid fragment emission. The sequential de-excitation calculation overestimates light particle emission and consequently heavy residues, particularly, at higher excitation energies. This disagreement indicates that a sequential process can not account for the di-excitation of very hot nuclei
Stability of a radial immiscible drive
Bataille, J
1968-11-01
The stability of the displacement front between 2 immiscible fluids of radial flow between 2 parallel plates (Hele-Shaw model) is studied mathematically by superposing onto the circular displacement front a sinusoidal perturbation. The equations are reduced to dimensionless variables, and it is shown that the stable and unstable domains in a plot: dimensionless viscosity vs. dimensionless time are separated by a polygonal contour, each side of the contour being characterized by the (integer) number of perturbations along the circumference. There is a critical reduced time below which the perturbations are amortized but beyond which they are amplified. Experimental results have been in fair general agreement with theoretical results, the divergence between them being attributable to neglecting capillary phenomena, which may become very important at large radial distances. One test with miscible fluids has shown that even in this case, there is a critical time or an equivalent critical radius.
Krausche, S.; Ohlsson, Johan
1998-04-01
The objective of this work was to develop a program dealing with design point calculations of radial turbine machinery, including both compressor and turbine, with as few input data as possible. Some simple stress calculations and turbine metal blade temperatures were also included. This program was then implanted in a German thermodynamics program, Gasturb, a program calculating design and off-design performance of gas turbines. The calculations proceed with a lot of assumptions, necessary to finish the task, concerning pressure losses, velocity distribution, blockage, etc., and have been correlated with empirical data from VAT. Most of these values could have been input data, but to prevent the user of the program from drowning in input values, they are set as default values in the program code. The output data consist of geometry, Mach numbers, predicted component efficiency etc., and a number of graphical plots of geometry and velocity triangles. For the cases examined, the error in predicted efficiency level was within {+-} 1-2% points, and quite satisfactory errors in geometrical and thermodynamic conditions were obtained Examination paper. 18 refs, 36 figs
Kang, Hyun Soo; Kim, Youn Jae [Sungkyunkwan University, Suwon (Korea, Republic of)
2016-09-15
In this study, a method for optimal design of impeller for centrifugal compressor under the influence of Fluid-structure interaction (FSI) and Response surface method (RSM) was studied. Numerical simulation was conducted using ANSYS Multi-physics with various configurations of impeller geometry. Each of the design parameters was divided into 3 levels. Total 45 design points were planned by Central composite design (CCD) method, which is one of the Design of experiment (DOE) techniques. Response surfaces generated based on the DOE results were used to find the optimal shape of impeller for high aerodynamic performance. The whole process of optimization was conducted using ANSYS Design xplorer (DX). Through the optimization, structural safety and aerodynamic performance of centrifugal compressor were improved.
Kang, Hyun Soo; Kim, Youn Jae
2016-01-01
In this study, a method for optimal design of impeller for centrifugal compressor under the influence of Fluid-structure interaction (FSI) and Response surface method (RSM) was studied. Numerical simulation was conducted using ANSYS Multi-physics with various configurations of impeller geometry. Each of the design parameters was divided into 3 levels. Total 45 design points were planned by Central composite design (CCD) method, which is one of the Design of experiment (DOE) techniques. Response surfaces generated based on the DOE results were used to find the optimal shape of impeller for high aerodynamic performance. The whole process of optimization was conducted using ANSYS Design xplorer (DX). Through the optimization, structural safety and aerodynamic performance of centrifugal compressor were improved
Ultrafast X-ray tomography for two-phase flow analysis in centrifugal pumps
Schaefer, Thomas; Hampel, Uwe; Technische Univ. Dresden
2017-01-01
The unsteady behavior of gas-liquid two-phase flow in a centrifugal pump impeller has been visualized, using ultrafast X-ray tomography. Based on the reconstructed tomographic images an evaluation and detailed analysis of the flow conditions has been done. Here, the high temporal resolution of the tomographic images offered the opportunity to get a deep insight into the flow to perform a detailed description of the transient gas-liquid phase distribution inside the impeller. Significant properties of the occurring two-phase flow and characteristic flow patterns have been disclosed. Furthermore, the effects of different air entrainment conditions have been investigated and typical phase distributions inside the impeller have been shown.
Ultrafast X-ray tomography for two-phase flow analysis in centrifugal pumps
Schaefer, Thomas [Helmholtz-Zentrum Dresden-Rossendorf, Dresden (Germany). Inst. of Fluid Dynamics; Hampel, Uwe [Helmholtz-Zentrum Dresden-Rossendorf, Dresden (Germany). Inst. of Fluid Dynamics; Technische Univ. Dresden (Germany). AREVA Endowed Chair of Imaging Techniques in Energy and Process Engineering
2017-07-15
The unsteady behavior of gas-liquid two-phase flow in a centrifugal pump impeller has been visualized, using ultrafast X-ray tomography. Based on the reconstructed tomographic images an evaluation and detailed analysis of the flow conditions has been done. Here, the high temporal resolution of the tomographic images offered the opportunity to get a deep insight into the flow to perform a detailed description of the transient gas-liquid phase distribution inside the impeller. Significant properties of the occurring two-phase flow and characteristic flow patterns have been disclosed. Furthermore, the effects of different air entrainment conditions have been investigated and typical phase distributions inside the impeller have been shown.
Sanders, J.P.; Heestand, R.L.; Young, H.C.
1987-01-01
Three gas-bearing circulators are installed in series in a high-pressure, high-temperature loop to provide helium flow up to 0.47 m 3 /s at a total head of 78 kJ/kg. The design pressure is 10.7 MPa, and temperatures of 1000 0 C can be obtained in the test section. The inlet temperature to the circulators is limited to 450 0 C. During a routine examination of the circulator, deep V-shaped grooves were found in the stationary surface of this cavity. At the same time, a very fine, dark particulate was observed in crevices of the housing. At first it was assumed that the grooves were formed by particulate erosion; however, examination of the grooves and discussions with persons experienced with large circulator operation changed this opinion. Erosion caused by particulate is characteristically rounded on the bottom and has a greater width to depth aspect than the V-shaped grooves, which were observed. Analysis of the particulate indicated that it was essentially the material of the housing that had undergone reactions with impurities in the circulating gas. It was subsequently concluded that the impeller housing had not been heat treated in a sufficiently oxidizing atmosphere after machining to form an adherent oxide coating. This suboxide coating was eroded by the shear forces in the gas. The exposed layer of metal was then further oxidized by the impurities in the gas, and these layers of oxide were successively eroded to produce the grooves. This erosion problem was eliminated by machining a ring of the same material, heat treating it to form an adherent stable oxide, and bolting it in place in the cavity
Orthogonal decomposition as a design tool: With application to a mixing impeller
Sloan, Benjamin [Iowa State Univ., Ames, IA (United States)
2013-01-01
Digital manufacturing eliminates the expense and time required to develop custom products. By utilizing this technology, designers can quickly create a customized product specifically for their performance needs. But the timescale and expense from the engineering design workflows used to develop these customized products have not been adapted from the workflows used in mass production. In many cases these customized designs build upon already successful mass-produced products that were developed using conventional engineering design workflows. Many times as part of this conventional design process significant time is spent creating and validating high fidelity models that accurately predict the performance of the final design. These existing validated high fidelity models used for the mass-produced design can be reused for analysis and design of unknown products. This thesis explores the integration of reduced order modeling and detailed analysis into the engineering design workflow developing a customized design using digital manufacturing. Specifically, detailed analysis is coupled with proper orthogonal decomposition to enable the exploration of the design space while simultaneously shaping the model representing the design. This revised workflow is examined using the design of a laboratory scale overhead mixer impeller. The case study presented here is compared with the design of the Kar Dynamic Mixer impeller developed by The Dow Chemical Company. The result of which is a customized design for a refined set of operating conditions with improved performance.
Computer Aided Simulation Machining Programming In 5-Axis Nc Milling Of Impeller Leaf
Huran, Liu
At present, cad/cam (computer-aided design and manufacture) have fine wider and wider application in mechanical industry. For the complex surfaces, the traditional machine tool can no longer satisfy the requirement of such complex task. Only by the help of cad/cam can fulfill the requirement. The machining of the vane surface of the impeller leaf has been considered as the hardest challenge. Because of their complex shape, the 5-axis cnc machine tool is needed for the machining of such parts. The material is hard to cut, the requirement for the surface finish and clearance is very high, so that the manufacture quality of impeller leaf represent the level of 5-axis machining. This paper opened a new field in machining the complicated surface, based on a relatively more rigid mathematical basis. The theory presented here is relatively more systematical. Since the lack of theoretical guidance, in the former research, people have to try in machining many times. Such case will be changed. The movement of the cutter determined by this method is definite, and the residual is the smallest while the times of travel is the fewest. The criterion is simple and the calculation is easy.
Muhammad Syahid
2017-03-01
Full Text Available Aluminium alloy can be applied for a turbine impeller of Organic Rankine Cycle power plant that operates at temperatures below 150 oC. Aluminum turbine impeller can enhance efficiency of turbine due to light weight material. Al alloys was used for impeller due to good mechanical properties. Turbine impeller commonly produced by machining but which is time-consuming and less efficient because of material removal. . It can be replace by Investment casting to produce impeller turbine due to their complex geometry and precision. This study identifies effect Cu content of Al-9Zn-4Mg-xCu on the microstructure and mechanical properties of turbine impeller produce by investment casting. The study also identifies casting defect of turbine impeller. The structures consisted of α-Al, MgZn2, CuMgAl2 and CuAl2. Higher Cu content is the higher hardness value due to CuAl2 phase. Visual examination showed that the turbine impeller was free of macro defects and misruns
Radial retinotomy in the macula.
Bovino, J A; Marcus, D F
1984-01-01
Radial retinotomy is an operative procedure usually performed in the peripheral or equatorial retina. To facilitate retinal attachment, the authors used intraocular scissors to perform radial retinotomy in the macula of two patients during vitrectomy surgery. In the first patient, a retinal detachment complicated by periretinal proliferation and macula hole formation was successfully reoperated with the aid of three radial cuts in the retina at the edges of the macular hole. In the second patient, an intraoperative retinal tear in the macula during diabetic vitrectomy was also successfully repaired with the aid of radial retinotomy. In both patients, retinotomy in the macula was required because epiretinal membranes, which could not be easily delaminated, were hindering retinal reattachment.
Dedicated radial ventriculography pigtail catheter
Vidovich, Mladen I., E-mail: miv@uic.edu
2013-05-15
A new dedicated cardiac ventriculography catheter was specifically designed for radial and upper arm arterial access approach. Two catheter configurations have been developed to facilitate retrograde crossing of the aortic valve and to conform to various subclavian, ascending aortic and left ventricular anatomies. The “short” dedicated radial ventriculography catheter is suited for horizontal ascending aortas, obese body habitus, short stature and small ventricular cavities. The “long” dedicated radial ventriculography catheter is suited for vertical ascending aortas, thin body habitus, tall stature and larger ventricular cavities. This new design allows for improved performance, faster and simpler insertion in the left ventricle which can reduce procedure time, radiation exposure and propensity for radial artery spasm due to excessive catheter manipulation. Two different catheter configurations allow for optimal catheter selection in a broad range of patient anatomies. The catheter is exceptionally stable during contrast power injection and provides equivalent cavity opacification to traditional femoral ventriculography catheter designs.
Fathonah, N. N.; Nurtono, T.; Kusdianto; Winardi, S.
2018-03-01
Single phase turbulent flow in a vessel agitated by side entering inclined blade turbine has simulated using CFD. The aim of this work is to identify the hydrodynamic characteristics of a model vessel, which geometrical configuration is adopted at industrial scale. The laboratory scale model vessel is a flat bottomed cylindrical tank agitated by side entering 4-blade inclined blade turbine with impeller rotational speed N=100-400 rpm. The effect of the impeller diameter on fluid flow pattern has been investigated. The fluid flow patterns in a vessel is essentially characterized by the phenomena of macro-instabilities, i.e. the flow patterns change with large scale in space and low frequency. The intensity of fluid flow in the tank increase with the increase of impeller rotational speed from 100, 200, 300, and 400 rpm. It was accompanied by shifting the position of the core of circulation flow away from impeller discharge stream and approached the front of the tank wall. The intensity of fluid flow in the vessel increase with the increase of the impeller diameter from d=3 cm to d=4 cm.
Rhee, Chang Kyu; Lee, Min Ku; Park, Jin Ju
2008-09-01
Many components of pump impeller of nuclear power plants is generally made of stainless steel and Al-bronze with superior corrosion resistance to sea water. However, they should be replaced by one- to five-year period because of material damage by a very big cavitation impact load, even though their designed durability is twenty years. Especially, in case of Young-Gwang nuclear power plant located at the west sea, damage of components of pump impeller is so critical due to the additional damage by solid particle erosion and hence their replacement period is very short as several months compared to other nuclear power plants. In addition, it is very difficult to maintain and repair the components of pump impeller since there is no database on the exact durability and damage mechanism. Therefore, in this study, fabrication technology of new advanced materials modified by dispersion of nano-carbide and -oxide ceramics into the matrix is developed first. Secondly, technology to estimate the dynamic damage by solid particle erosion is established and hence applied to the prediction of the service life of the components of pump impeller
Ueki, H.; Ishida, M.; Sakaguchi, D.; Sun, Z. [Nagasaki University, Nagasaki (Japan). Faculty of Engineering
2000-07-25
A ring groove arrangement is proposed to suppress unstable flow or surge in a centrifugal blower. The ring groove arrangement connects the upstream position of impeller inlet and the inducer throat tip through a bypass. The recirculation flow 'vas formed by the pressure difference between the two positions, and the recirculation flow rate was changed by increasing the ring groove widths. The inlet recirculation results in a decrease in the flow rate of unstable flow inception, and an up to 800 improvement in stall limit was obtained by the ring groove arrangement at a small expense of the delivery pressure drop. The improvement of stall limit in the present experiment seems to be mainly due to decrease in flow incidence based on the inlet recirculation flow. Tre flow incidence decreases more as the recirculation flow rate increases, thus resulting in a larger improvement in stall limit. (author)
Kaneko, Masanao; Tsujita, Hoshio; Hirano, Toshiyuki
2013-04-01
A single stage ultra micro centrifugal compressor constituting ultra micro gas turbine is required to operate at high rotational speed in order to achieve the pressure ratio which establishes the gas turbine cycle. As a consequence, the aerodynamic losses can be increased by the interaction of a shock wave with the boundary layer on the blade surface. Moreover, the centrifugal force which exceeds the allowable stress of the impeller material can act on the root of blades. On the other hand, the restrictions of processing technology for the downsizing of impeller not only relatively enlarge the size of tip clearance but also make it difficult to shape the impeller with the three-dimensional blade. Therefore, it is important to establish the design technology for the impeller with the two-dimensional blade which possesses the sufficient aerodynamic performance and enough strength to bear the centrifugal force caused by the high rotational speed. In this study, the flow in two types of impeller with the two-dimensional blade which have different meridional configuration was analyzed numerically. The computed results clarified the influence of the meridional configuration on the loss generations in the impeller passage.
Sanders, J.P.; Heestand, R.L.; Young, H.C.
1988-01-01
Three gas-bearing circulators are installed in series in a high-pressure, high-temperature loop to provide helium flow up to 0.47 m 3 /s at a total head of 78 kJ/kg. The design pressure is 10.7 MPa, and temperatures of 1000 deg. C can be obtained in the test section. The inlet temperature to the circulators is limited to 450 deg. C. The 200-kW motor for each circulator is enclosed in the pressure boundary, and the motor is cooled by circulating the gas within the cavity over a water-cooled coil. The full operating speed is 23,500 rpm. A full-flow filter, absolute for particulate above 10 μm, is installed upstream of the circulator to protect the gas bearing surfaces. The minimum clearances between these surfaces during operation are in the range of 15 to 30 μm. During a routine examination of the circulator, deep V-shaped grooves were found in the stationary surface of this cavity. At the same time, a very fine, dark particulate was observed in crevices of the housing. At first it was assumed that the grooves were formed by particulate erosion; however, examination of the grooves and discussions with persons experienced with large circulator operation changed this opinion. Erosion caused by particulate is characteristically rounded on the bottom and has a greater width to depth aspect than the V-shaped grooves, which were observed. Analysis of the particulate indicated that it was essentially the material of the housing that had undergone reactions with impurities in the circulating gas. It was subsequently concluded that the impeller housing had not been heat treated in a sufficiently oxidizing atmosphere after machining to form an adherent oxide coating. This suboxide coating was eroded by the shear forces in the gas. The exposed layer of metal was then further oxidized by the impurities in the gas, and these layers of oxide were successively eroded to produce the grooves. This erosion problem was eliminated by machining a ring of the same material, heat
Effectiveness of meta-models for multi-objective optimization of centrifugal impeller
Bellary, Sayed Ahmed Imran; Samad, Abdus; Husain, Afzal
2014-01-01
The major issue of multiple fidelity based analysis and optimization of fluid machinery system depends upon the proper construction of low fidelity model or meta-model. A low fidelity model uses responses obtained from a high fidelity model, and the meta-model is then used to produce population of solutions required for evolutionary algorithm for multi-objective optimization. The Pareto-optimal front which shows functional relationships among the multiple objectives can produce erroneous results if the low fidelity models are not well-constructed. In the present research, response surface approximation and Kriging meta-models were evaluated for their effectiveness for the application in the turbomachinery design and optimization. A high fidelity model such as CFD technique along with the metamodels was used to obtain Pareto-optimal front via multi-objective genetic algorithm. A centrifugal impeller has been considered as case study to find relationship between two conflicting objectives, viz., hydraulic efficiency and head. Design variables from the impeller geometry have been chosen and the responses of the objective functions were evaluated through CFD analysis. The fidelity of each metamodel has been discussed in context of their predictions in entire design space in general and near optimal region in particular. Exploitation of the multiple meta-models enhances the quality of multi-objective optimization and provides the information pertaining to fidelity of optimization model. It was observed that the Kriging meta-model was better suited for this type of problem as it involved less approximation error in the Pareto-optimal front.
Effectiveness of meta-models for multi-objective optimization of centrifugal impeller
Bellary, Sayed Ahmed Imran; Samad, Abdus [Indian Institute of Technology Madras, Chennai (India); Husain, Afzal [Sultan Qaboos University, Al-Khoudh (Oman)
2014-12-15
The major issue of multiple fidelity based analysis and optimization of fluid machinery system depends upon the proper construction of low fidelity model or meta-model. A low fidelity model uses responses obtained from a high fidelity model, and the meta-model is then used to produce population of solutions required for evolutionary algorithm for multi-objective optimization. The Pareto-optimal front which shows functional relationships among the multiple objectives can produce erroneous results if the low fidelity models are not well-constructed. In the present research, response surface approximation and Kriging meta-models were evaluated for their effectiveness for the application in the turbomachinery design and optimization. A high fidelity model such as CFD technique along with the metamodels was used to obtain Pareto-optimal front via multi-objective genetic algorithm. A centrifugal impeller has been considered as case study to find relationship between two conflicting objectives, viz., hydraulic efficiency and head. Design variables from the impeller geometry have been chosen and the responses of the objective functions were evaluated through CFD analysis. The fidelity of each metamodel has been discussed in context of their predictions in entire design space in general and near optimal region in particular. Exploitation of the multiple meta-models enhances the quality of multi-objective optimization and provides the information pertaining to fidelity of optimization model. It was observed that the Kriging meta-model was better suited for this type of problem as it involved less approximation error in the Pareto-optimal front.
Modelling and analysis of radial thermal stresses and temperature ...
user
it acts as an insulating medium and prevents the heat flow, hence the need of providing insulation coating on valves is ... geometry metal components (piston, liner and cylinder head) and found a satisfactory .... model. Step8: Find the radial thermal stress at all the nodal point with the use of temperature ..... Cast iron St. 70.
Hazeltine, R.D.
1988-12-01
The boundary layer arising in the radial vicinity of a tokamak limiter is examined, with special reference to the TEXT tokamak. It is shown that sheath structure depends upon the self-consistent effects of ion guiding-center orbit modification, as well as the radial variation of E /times/ B-induced toroidal rotation. Reasonable agreement with experiment is obtained from an idealized model which, however simplified, preserves such self-consistent effects. It is argued that the radial sheath, which occurs whenever confining magnetic field-lines lie in the plasma boundary surface, is an object of some intrinsic interest. It differs from the more familiar axial sheath because magnetized charges respond very differently to parallel and perpendicular electric fields. 11 refs., 1 fig
Sharp Dissection versus Electrocautery for Radial Artery Harvesting
Marzban, Mehrab; Arya, Reza; Mandegar, Mohammad Hossein; Karimi, Abbas Ali; Abbasi, Kiomars; Movahed, Namvar; Abbasi, Seyed Hesameddin
2006-01-01
Radial arteries have been increasingly used during the last decade as conduits for coronary artery revascularization. Although various harvesting techniques have been described, there has been little comparative study of arterial damage and patency. A radial artery graft was used in 44 consecutive patients, who were randomly divided into 2 groups. In the 1st group, the radial artery was harvested by sharp dissection and in the 2nd, by electrocautery. These groups were compared with regard to radial artery free flow, harvest time, number of clips used, complications, and endothelial damage. Radial artery free flow before and after intraluminal administration of papaverine was significantly greater in the electrocautery group (84.3 ± 50.7 mL/min and 109.7 ± 68.5 mL/min) than in the sharp-dissection group (52.9 ± 18.3 mL/min and 69.6 ± 28.2 mL/ min) (P =0.003). Harvesting time by electrocautery was significantly shorter (25.4 ± 4.3 min vs 34.4 ± 5.9 min) (P =0.0001). Electrocautery consumed an average of 9.76 clips, versus 22.45 clips consumed by sharp dissection. The 2 groups were not different regarding postoperative complications, except for 3 cases of temporary paresthesia of the thumb in the electrocautery group; histopathologic examination found no endothelial damage. We conclude that radial artery harvesting by electrocautery is faster and more economical than harvesting by sharp dissection and is associated with better intraoperative flow and good preservation of endothelial integrity. PMID:16572861
Axial and radial water transport and internal water storage in tropical forest canopy trees.
Shelley A. James; Frederick C. Meinzer; Guillermo Goldstein; David Woodruff; Timothy Jones; Teresa Restom; Monica Mejia; Michael Clearwater; Paula. Campanello
2003-01-01
Heat and stable isotope tracers were used to study axial and radial water transport in relation to sapwood anatomical characteristics and internal water storage in four canopy tree species of a seasonally dry tropical forest in Panama. Anatomical characteristics of the wood and radial profiles of sap flow were measured at the base, upper trunk, and crown of a single...
A PROTOTYPICAL HYDRODYNAMIC MINI GENERATOR OF ELECTRIC ENERGY TO BE USED IN THE CHANNEL FLOW
Roman KACZYŃSKI
2014-03-01
Full Text Available This work presents the numerical analysis and scientific research of prototypical solutions for mini generators of electric energy to be assembled in small diameter pipelines. Additionally, this papers presents the construction of a test stand stimulating similar flow to the actual flow allowing testing various geometry of impellers at variable conditions. In order to optimize the impellers geometry of hydro generators the cfd analysis has been used. The characteristics of miniature stepper motors working as electric energy generators have also been assigned.
Radial head dislocation during proximal radial shaft osteotomy.
Hazel, Antony; Bindra, Randy R
2014-03-01
The following case report describes a 48-year-old female patient with a longstanding both-bone forearm malunion, who underwent osteotomies of both the radius and ulna to improve symptoms of pain and lack of rotation at the wrist. The osteotomies were templated preoperatively. During surgery, after performing the planned radial shaft osteotomy, the authors recognized that the radial head was subluxated. The osteotomy was then revised from an opening wedge to a closing wedge with improvement of alignment and rotation. The case report discusses the details of the operation, as well as ways in which to avoid similar shortcomings in the future. Copyright © 2014 American Society for Surgery of the Hand. Published by Elsevier Inc. All rights reserved.
Rayleigh-Taylor instability of cylindrical jets with radial motion
Chen, Xiang M. [GE Nuclear, Wilmington, NC (United States); Schrock, V.E.; Peterson, P.F. [Univ. of California, Berkeley, CA (United States)
1995-09-01
Rayleigh-Taylor instability of an interface between fluids with different densities subjected to accelleration normal to itself has interested researchers for almost a century. The classic analyses of a flat interface by Rayleigh and Taylor have shown that this type of instability depends on the direction of acceleration and the density differences of the two fluids. Plesset later analyzed the stability of a spherically symmetric flows (and a spherical interface) and concluded that the instability also depends on the velocity of the interface as well as the direction and magnitude of radial acceleration. The instability induced by radial motion in cylindrical systems seems to have been neglected by previous researchers. This paper analyzes the Rayleigh-Taylor type of the spherical case, the radial velocity also plays an important role. As an application, the example of a liquid jet surface in an Inertial Confinement Fusion (ICF) reactor design is analyzed.
Characterization of magnetically impelled arc butt welded T11 tubes for high pressure applications
R. Sivasankari
2015-09-01
Full Text Available Magnetically impelled arc butt (MIAB welding is a pressure welding process used for joining of pipes and tubes with an external magnetic field affecting arc rotation along the tube circumference. In this work, MIAB welding of low alloy steel (T11 tubes were carried out to study the microstructural changes occurring in thermo-mechanically affected zone (TMAZ. To qualify the process for the welding applications where pressure could be up to 300 bar, the MIAB welds are studied with variations of arc current and arc rotation time. It is found that TMAZ shows higher hardness than that in base metal and displays higher weld tensile strength and ductility due to bainitic transformation. The effect of arc current on the weld interface is also detailed and is found to be defect free at higher values of arc currents. The results reveal that MIAB welded samples exhibits good structural property correlation for high pressure applications with an added benefit of enhanced productivity at lower cost. The study will enable the use of MIAB welding for high pressure applications in power and defence sectors.
Mechanical Properties and Chemical Resistance of New Composites for Oil Pump Impellers
Dilyus I. Chukov
2018-05-01
Full Text Available In this paper, a new class of high-performance composites and a method of their production based on the carbonization of an elastomeric matrix are proposed. The use of elastomeric matrix makes it possible to manufacture products with complex shapes, while the subsequent carbonization can significantly improve their properties by changing the chemical nature of the elastomeric matrix. Such an approach can reduce the products’ machining cost, especially for composites reinforced with super hard fillers such as silicon carbide at high filling degrees. Low-temperature carbonization makes it possible to obtain composites with mechanical behavior similar to that of ceramics. In contrast to classical elastomeric materials, the nitrile butadiene rubber (NBR-based compounds were highly filled (300 parts per hundred rubber-PHR with different carbon fillers and silicon carbide; then cured and carbonized at low-temperature 360 °C with the carbonization cycle of 12 h. The feasibility of the production method was validated through the manufacturing of products with complex shapes—impellers for electric centrifugal pumps. It was found that the carbonized composites have good chemical resistance and low water absorption. The composites have high Shore D hardnesses (93–96, ultimate tensile strengths (62–85 MPa, Young’s moduli (17–24 GPa, and compressive strengths (155–181 MPa.
RADIAL STABILITY IN STRATIFIED STARS
Pereira, Jonas P.; Rueda, Jorge A.
2015-01-01
We formulate within a generalized distributional approach the treatment of the stability against radial perturbations for both neutral and charged stratified stars in Newtonian and Einstein's gravity. We obtain from this approach the boundary conditions connecting any two phases within a star and underline its relevance for realistic models of compact stars with phase transitions, owing to the modification of the star's set of eigenmodes with respect to the continuous case
Velocidades radiales en Collinder 121
Arnal, M.; Morrell, N.
Se han llevado a cabo observaciones espectroscópicas de unas treinta estrellas que son posibles miembros del cúmulo abierto Collinder 121. Las mismas fueron realizadas con el telescopio de 2.15m del Complejo Astronómico El Leoncito (CASLEO). El análisis de las velocidades radiales derivadas del material obtenido, confirma la realidad de Collinder 121, al menos desde el punto de vista cinemático. La velocidad radial baricentral (LSR) del cúmulo es de +17 ± 3 km.s-1. Esta velocidad coincide, dentro de los errores, con la velocidad radial (LSR) de la nebulosa anillo S308, la cual es de ~20 ± 10 km.s-1. Como S308 se encuentra físicamente asociada a la estrella Wolf-Rayet HD~50896, es muy probable que esta última sea un miembro de Collinder 121. Desde un punto de vista cinemático, la supergigante roja HD~50877 (K3Iab) también pertenecería a Collinder 121. Basándonos en la pertenencia de HD~50896 a Collinder 121, y en la interacción encontrada entre el viento de esta estrella y el medio interestelar circundante a la misma, se estima para este cúmulo una distancia del orden de 1 kpc.
Numerical analysis of the internal flow field in screw centrifugal blood pump based on CFD
Han, W.; Han, B. X.; Y Wang, H.; Shen, Z. J.
2013-12-01
As to the impeller blood pump, the high speed of the impeller, the local high shear force of the flow field and the flow dead region are the main reasons for blood damage. The screw centrifugal pump can effectively alleviate the problems of the high speed and the high shear stress for the impeller. The softness and non-destructiveness during the transfer process can effectively reduce the extent of the damage. By using CFD software, the characteristics of internal flow are analyzed in the screw centrifugal pump by exploring the distribution rules of the velocity, pressure and shear deformation rate of the blood when it flows through the impeller and the destructive effects of spiral blades on blood. The results show that: the design of magnetic levitation solves the sealing problems; the design of regurgitation holes solves the problem of the flow dead zone; the magnetic levitated microcirculation screw centrifugal pump can effectively avoid the vortex, turbulence and high shear forces generated while the blood is flowing through the pump. Since the distribution rules in the velocity field, pressure field and shear deformation rate of the blood in the blood pump are comparatively uniform and the gradient change is comparatively small, the blood damage is effectively reduced.
RTOD- RADIAL TURBINE OFF-DESIGN PERFORMANCE ANALYSIS
Glassman, A. J.
1994-01-01
The RTOD program was developed to accurately predict radial turbine off-design performance. The radial turbine has been used extensively in automotive turbochargers and aircraft auxiliary power units. It is now being given serious consideration for primary powerplant applications. In applications where the turbine will operate over a wide range of power settings, accurate off-design performance prediction is essential for a successful design. RTOD predictions have already illustrated a potential improvement in off-design performance offered by rotor back-sweep for high-work-factor radial turbines. RTOD can be used to analyze other potential performance enhancing design features. RTOD predicts the performance of a radial turbine (with or without rotor blade sweep) as a function of pressure ratio, speed, and stator setting. The program models the flow with the following: 1) stator viscous and trailing edge losses; 2) a vaneless space loss between the stator and the rotor; and 3) rotor incidence, viscous, trailing-edge, clearance, and disk friction losses. The stator and rotor viscous losses each represent the combined effects of profile, endwall, and secondary flow losses. The stator inlet and exit and the rotor inlet flows are modeled by a mean-line analysis, but a sector analysis is used at the rotor exit. The leakage flow through the clearance gap in a pivoting stator is also considered. User input includes gas properties, turbine geometry, and the stator and rotor viscous losses at a reference performance point. RTOD output includes predicted turbine performance over a specified operating range and any user selected flow parameters. The RTOD program is written in FORTRAN IV for batch execution and has been implemented on an IBM 370 series computer with a central memory requirement of approximately 100K of 8 bit bytes. The RTOD program was developed in 1983.
Radial Transport and Meridional Circulation in Accretion Disks
Philippov, Alexander A. [Department of Astrophysical Sciences, Princeton University, Ivy Lane, Princeton, NJ 08540 (United States); Rafikov, Roman R., E-mail: sashaph@princeton.edu [Institute for Advanced Study, Einstein Drive, Princeton, NJ 08540 (United States)
2017-03-10
Radial transport of particles, elements and fluid driven by internal stresses in three-dimensional (3D) astrophysical accretion disks is an important phenomenon, potentially relevant for the outward dust transport in protoplanetary disks, origin of the refractory particles in comets, isotopic equilibration in the Earth–Moon system, etc. To gain better insight into these processes, we explore the dependence of meridional circulation in 3D disks with shear viscosity on their thermal stratification, and demonstrate a strong effect of the latter on the radial flow. Previous locally isothermal studies have normally found a pattern of the radial outflow near the midplane, switching to inflow higher up. Here we show, both analytically and numerically, that a flow that is inward at all altitudes is possible in disks with entropy and temperature steeply increasing with height. Such thermodynamic conditions may be typical in the optically thin, viscously heated accretion disks. Disks in which these conditions do not hold should feature radial outflow near the midplane, as long as their internal stress is provided by the shear viscosity. Our results can also be used for designing hydrodynamical disk simulations with a prescribed pattern of the meridional circulation.
Devices and methods of operation thereof for providing stable flow for centrifugal compressors
Skoch, Gary J. (Inventor); Stevens, Mark A. (Inventor); Jett, Thomas A. (Inventor)
2008-01-01
Centrifugal compressor flow stabilizing devices and methods of operation thereof are disclosed that act upon the flow field discharging from the impeller of a centrifugal compressor and modify the flow field ahead of the diffuser vanes such that flow conditions contributing to rotating stall and surge are reduced or even eliminated. In some embodiments, shaped rods and methods of operation thereof are disclosed, whereas in other embodiments reverse-tangent air injection devices and methods are disclosed.
Radial electric field and transport near the rational surface and the magnetic island in LHD
Ida, K.; Inagaki, S.; Tamura, N.
2002-10-01
The structure of the radial electric field and heat transport at the magnetic island in the Large Helical Device is investigated by measuring the radial profile of poloidal flow with charge exchange spectroscopy. The convective poloidal flow inside the island is observed when the n/m=1/1 external perturbation field becomes large enough to increase the magnetic island width above a critical value (15-20% of minor radius) in LHD. This convective poloidal flow results in a non-flat space potential inside the magnetic island. The sign of the curvature of the space potential depends on the radial electric field at the boundary of the magnetic island. The heat transport inside the magnetic island is studied with a cold pulse propagation technique. The experimental results show the existence of the radial electric field shear at the boundary of the magnetic island and a reduction of heat transport inside the magnetic island. (author)
Exceptional circles of radial potentials
Music, M; Perry, P; Siltanen, S
2013-01-01
A nonlinear scattering transform is studied for the two-dimensional Schrödinger equation at zero energy with a radial potential. Explicit examples are presented, both theoretically and computationally, of potentials with nontrivial singularities in the scattering transform. The singularities arise from non-uniqueness of the complex geometric optics solutions that define the scattering transform. The values of the complex spectral parameter at which the singularities appear are called exceptional points. The singularity formation is closely related to the fact that potentials of conductivity type are ‘critical’ in the sense of Murata. (paper)
Neural network analysis of head-flow curves in deep well pumps
Goelcue, Mustafa
2006-01-01
In impellers with splitter blades, the difficulty in calculation of the flow area of the impeller is because of the unknown flow rate occurring in the two separate areas when the splitter blades are added. Experimental studies were made to investigate the effects of splitter blade length on deep well pump performance for different numbers of blades. Head-flow curves of deep well pump impellers with splitter blades were investigated using artificial neural networks (ANNs). Gradient descent (GD), Gradient descent with momentum (GDM) and Levenberg-Marquardt (LM) learning algorithms were used in the networks. Experimental studies were completed to obtain training and test data. Blade number (z), non-dimensional splitter blade length (L-bar ) and flow rate (Q) were used as the input layer, while the output is head (H m ). For the testing data, the root mean squared error (RMSE), fraction of variance (R 2 ) and mean absolute percentage error (MAPE) were found to be 0.1285, 0.9999 and 1.6821%, respectively. With these results, we believe that the ANN can be used for prediction of head-flow curves as an appropriate method in deep well pump impellers with splitter blades.
Booster Pump Performance Analysis Towards Rotation Of Impeller For CSD Dredger Type
Tony Bambang Musriyadi
2017-12-01
Full Text Available Dredger are a vessel for lift materials from sub surface to another place above the water surface. Dredger divided into some types such Suction Dredger, Bucket Dredger, Backhoe Dredger, and Water Injection Dredger. Cutter Suction Dredger is equipped with a rotating cutter head, for cutting and fragmenting hard soils. The soil is sucked up by means of dredge pumps, and discharged through a floating pipeline and pipes on shore, to a deposit area. In some cases, the material is discharged into split hopper barges that are moored alongside the Cutter Suction Dredger. These split hopper barges unload the soil at the deposit area. The most important part of dredger are the pump unit, NPSH is needed to figure the pump performance ability and how the efficiency number of the pump. Booster pump performance analysist are needed to mantain the pump's performance and efficiency. This thesis are describe about drawing process and computerized simulation at Ansys Software for pump performance with 3 different fluid types and 5 variations of impeller rotation. The number of NPSHa are 6.8 m and 2.8 for the NPSHr. Based on the pure water state, the lowest RPM value of 300 was obtained with V = 1.1366 m / s and Q = 1227.52 m3 / h, the highest RPM value of 600 with the result v = 1.1259 m / s and Q = 1215.97 m3 / h. Then the pumps used in this final project are more efficiently used for fluid types which tend to be condensed from the liquid, and less efficient for use in the state of pure water fluid
Radial-Electric-Field Piezoelectric Diaphragm Pumps
Bryant, Robert G.; Working, Dennis C.; Mossi, Karla; Castro, Nicholas D.; Mane, Pooma
2009-01-01
In a recently invented class of piezoelectric diaphragm pumps, the electrode patterns on the piezoelectric diaphragms are configured so that the electric fields in the diaphragms have symmetrical radial (along-the-surface) components in addition to through-the-thickness components. Previously, it was accepted in the piezoelectric-transducer art that in order to produce the out-of-plane bending displacement of a diaphragm needed for pumping, one must make the electric field asymmetrical through the thickness, typically by means of electrodes placed on only one side of the piezoelectric material. In the present invention, electrodes are placed on both sides and patterned so as to produce substantial radial as well as through-the-thickness components. Moreover, unlike in the prior art, the electric field can be symmetrical through the thickness. Tests have shown in a given diaphragm that an electrode configuration according to this invention produces more displacement than does a conventional one-sided electrode pattern. The invention admits of numerous variations characterized by various degrees of complexity. Figure 1 is a simplified depiction of a basic version. As in other piezoelectric diaphragm pumps of similar basic design, the prime mover is a piezoelectric diaphragm. Application of a suitable voltage to the electrodes on the diaphragm causes it to undergo out-of-plane bending. The bending displacement pushes a fluid out of, or pulls the fluid into, a chamber bounded partly by the diaphragm. Also as in other diaphragm pumps in general, check valves ensure that the fluid flows only in through one port and only out through another port.
Cubas, Selma A; Foresti, Eugenio; Rodrigues, José Alberto D; Ratusznei, Suzana M; Zaiat, Marcelo
2011-01-01
The influence of impeller type and stirring frequency on the performance of a mechanically stirred anaerobic sequencing batch reactor containing immobilized biomass on an inert support (AnSBBR--Anaerobic Sequencing Batch Biofilm Reactor) was evaluated. The biomass was immobilized on polyurethane foam cubes placed in a stainless-steel basket inside a glass cylinder. Each 8-h batch run consisted of three stages: feed (10 min), reaction (460 min) and discharge (10 min) at 30 °C. Experiments were performed with four impeller types, i.e., helical, flat-blade, inclined-blade and curved-blade turbines, at stirring frequencies ranging from 100 to 1100 rpm. Synthetic wastewater was used in all experiments with an organic-matter concentration of 530±37 mg/L measured as chemical oxygen demand (COD). The reactor achieved an organic-matter removal efficiency of around 87% under all investigated conditions. Analysis of the four impeller types and the investigated stirring frequencies showed that mass transfer in the liquid phase was affected not only by the applied stirring frequency but also by the agitation mode imposed by each impeller type. The best reactor performance at all stirring frequencies was obtained when agitation was provided by the flat-blade turbine impeller. Copyright Â© 2010 Elsevier Ltd. All rights reserved.
Karon, D. M.; Patel, S. K.; Zoladz, T. F.
2016-01-01
In 2009 and 2010, Concepts NREC prepared for and performed a series of tests on a 52% scale of a version of the Pratt & Whitney Rocketdyne J-2X Oxidizer Turbopump under a Phase III SBIR with NASA MSFC. The test article was a combined inducer and impeller, tested as a unit. This paper presents an overview of the test rig and facility, instrumentation, signal conditioning, data acquisition systems, testing approach, measurement developments, and lessons learned. Results from these tests were presented in the form of two papers at the previous JANNAF joint propulsion conference, in December of 2011.
Ratkovich, Nicolas Rios; Chan, C.C.V.; Bentzen, Thomas Ruby
2012-01-01
in an MBR. Nevertheless, proper experimental validation is required to validate CFD simulation. In this work experimental measurements of shear stress induced by impellers at a membrane surface were made with an electrochemical approach and the results were used to validate CFD simulations. As good results...... appealing for full-scale applications. It has been widely demonstrated that the filtration performances in MBRs can be improved by understanding the shear stress over the membrane surface. Modern tools such as Computational Fluid Dynamics (CFD) can be used to diagnose and understand the shear stress...
Rayleigh-Taylor instability of cylindrical jets with radial motion
Chen, X.M.; Schrock, V.E.; Peterson, P.F.
1997-01-01
Rayleigh-Taylor instability of an interface between fluids with different densities subjected to acceleration normal to itself has interested researchers for almost a century. The classic analyses of a flat interface by Rayleigh and Taylor have shown that this type of instability depends on the direction of acceleration and the density differences of the two fluids. Plesset later analyzed the stability of a spherically symmetric flows (and a spherical interface) and concluded that the instability also depends on the velocity of the interface as well as the direction and magnitude of radial acceleration. The instability induced by radial motion in cylindrical systems seems to have been neglected by previous researchers. This paper analyzes the Rayleigh-Taylor type of instability for a cylindrical surface with radial motions. The results of the analysis show that, like the spherical case, the radial velocity also plays an important role. As an application, the example of a liquid jet surface in an Inertial Confinement Fusion (ICF) reactor design is analyzed. (orig.)
Numerical Modelling of Non-Newtonian Fluid in a Rotational Cross-Flow MBR
Bentzen, Thomas Ruby; Ratkovic, Nicolas Rios; Rasmussen, Michael R.
2011-01-01
Fouling is the main bottleneck of the widespread of MBR systems. One way to decrease and/or control fouling is by process hydrodynamics. This can be achieved by the increase of liquid crossflow velocity. In rotational cross-flow MBR systems, this is attained by the spinning of e.g. impellers. Val...
Radial smoothing and closed orbit
Burnod, L.; Cornacchia, M.; Wilson, E.
1983-11-01
A complete simulation leading to a description of one of the error curves must involve four phases: (1) random drawing of the six set-up points within a normal population having a standard deviation of 1.3 mm; (b) random drawing of the six vertices of the curve in the sextant mode within a normal population having a standard deviation of 1.2 mm. These vertices are to be set with respect to the axis of the error lunes, while this axis has as its origins the positions defined by the preceding drawing; (c) mathematical definition of six parabolic curves and their junctions. These latter may be curves with very slight curvatures, or segments of a straight line passing through the set-up point and having lengths no longer than one LSS. Thus one gets a mean curve for the absolute errors; (d) plotting of the actually observed radial positions with respect to the mean curve (results of smoothing)
Ulnar nerve entrapment complicating radial head excision
Kevin Parfait Bienvenu Bouhelo-Pam
Full Text Available Introduction: Several mechanisms are involved in ischemia or mechanical compression of ulnar nerve at the elbow. Presentation of case: We hereby present the case of a road accident victim, who received a radial head excision for an isolated fracture of the radial head and complicated by onset of cubital tunnel syndrome. This outcome could be the consequence of an iatrogenic valgus of the elbow due to excision of the radial head. Hitherto the surgical treatment of choice it is gradually been abandoned due to development of radial head implant arthroplasty. However, this management option is still being performed in some rural centers with low resources. Discussion: The radial head plays an important role in the stability of the elbow and his iatrogenic deformity can be complicated by cubital tunnel syndrome. Conclusion: An ulnar nerve release was performed with favorable outcome. Keywords: Cubital tunnel syndrome, Peripheral nerve palsy, Radial head excision, Elbow valgus
Zhang, Fan, E-mail: zhangfan4060@gmail.com; Yuan, Shouqi; Fu, Qiang; Tao, Yi
2015-11-15
Highlights: • The transient flow characteristics of the charging pump with the first stage impeller in the HPSI process have been investigated numerically by CFD. • The hydraulic performance of the charging pump during the HPSI are discussed, andthe absolute errors between the simulated and measured results are analyzed in the paper. • Pressure fluctuation in the impeller and flow pattern in the impeller were studied in the HPSI process. It is influenced little at the beginning of the HPSI process while fluctuates strongly in the end of the HPSI process. - Abstract: In order to investigate the transient flow characteristics of the centrifugal charging pump during the transient transition process of high pressure safety injection (HPSI) from Q = 148 m{sup 3}/h to Q = 160 m{sup 3}/h, numerical simulation and experiment are implemented in this study. The transient flow rate, which is the most important factor, is obtained from the experiment and works as the boundary condition to accurately accomplish the numerical simulation in the transient process. Internal characteristics under the variable operating conditions are analyzed through the transient simulation. The results shows that the absolute error between the simulated and measured heads is less than 2.26% and the absolute error between the simulated and measured efficiency is less than 2.04%. Pressure fluctuation in the impeller is less influenced by variable flow rate in the HPSI process, while flow pattern in the impeller is getting better and better with the flow rate increasing. As flow rate increases, fluid blocks on the tongue of the volute and it strikes in this area at large flow rate. Correspondingly, the pressure fluctuation is intense and vortex occurs gradually during this period, which obviously lowers the efficiency of the pump. The contents of the current work can provide references for the design optimization and fluid control of the pump used in the transient process of variable operating
Zhang, Fan; Yuan, Shouqi; Fu, Qiang; Tao, Yi
2015-01-01
Highlights: • The transient flow characteristics of the charging pump with the first stage impeller in the HPSI process have been investigated numerically by CFD. • The hydraulic performance of the charging pump during the HPSI are discussed, andthe absolute errors between the simulated and measured results are analyzed in the paper. • Pressure fluctuation in the impeller and flow pattern in the impeller were studied in the HPSI process. It is influenced little at the beginning of the HPSI process while fluctuates strongly in the end of the HPSI process. - Abstract: In order to investigate the transient flow characteristics of the centrifugal charging pump during the transient transition process of high pressure safety injection (HPSI) from Q = 148 m"3/h to Q = 160 m"3/h, numerical simulation and experiment are implemented in this study. The transient flow rate, which is the most important factor, is obtained from the experiment and works as the boundary condition to accurately accomplish the numerical simulation in the transient process. Internal characteristics under the variable operating conditions are analyzed through the transient simulation. The results shows that the absolute error between the simulated and measured heads is less than 2.26% and the absolute error between the simulated and measured efficiency is less than 2.04%. Pressure fluctuation in the impeller is less influenced by variable flow rate in the HPSI process, while flow pattern in the impeller is getting better and better with the flow rate increasing. As flow rate increases, fluid blocks on the tongue of the volute and it strikes in this area at large flow rate. Correspondingly, the pressure fluctuation is intense and vortex occurs gradually during this period, which obviously lowers the efficiency of the pump. The contents of the current work can provide references for the design optimization and fluid control of the pump used in the transient process of variable operating conditions.
Numerical simulation of internal flow in mixed-flow waterjet propulsion
Wu, T T; Pan, Z Y; Zhang, D Q; Jia, Y Y
2012-01-01
In order to reveal the internal flow characteristic of a mixed-flow waterjet propulsion, a mixed-flow waterjet propulsion under different conditions was simulated based on multi-reference frame(MRF), the standard k − ε turbulent model and SIMPLEC algorithm. The relationship between pump performance instability and internal flow was obtained. The numerical results showed that characteristic instability occurred at 0.65-0.67Q BEP , the reason is that the backflow on the vaned diffuser hub-side blocks the downstream flow from the impeller. Therefore, the flow separates on the pressure surface of the impeller outlet and a strong vortex is generated, then the characteristic instability appeared due to the instability of internal flow. Backflow was found in diffuser passage at 0.65 Q BEP and 0.85 Q BEP , as flow rate decreases, the backflow region and velocity increases. Pressure fluctuation at diffuser inlet and diffuser passages was severe at at 0.65 Q BEP . According to the numerical simulation, the mixed-flow waterjet propulsion has characteristic instability at partial flow rate condition.
Elert, M.; Svensson, Haakan [Kemakta Konsult AB, Stockholm (Sweden)
2001-05-01
The Aespoe Task Force on Modelling of Groundwater Flow and Transport of Solutes is a forum for the international organisations supporting the Aespoe HRL Project. The purpose of the Task Force is to interact in the area of conceptual and numerical modelling of groundwater flow and solute transport in fractured rock. Task 4 of the Aespoe Modelling Task Force consists of modelling exercises in support of the TRUE-1 tracer tests. In this report, the modelling work performed within Tasks 4E and 4F is evaluated, which comprised predictive modelling of the tracer tests (STT-1, STT-1b and STT-2) performed within the TRUE-1 project using sorbing and non-sorbing tracers. The tests were made between packed off boreholes penetrating a water-conducting geological feature with a simple structure (Feature A). Nine modelling teams representing eight organisations have performed predictive modelling of the tracer tests using different modelling approaches and models. The modelling groups were initially given data from the site characterisation, data from preliminary tracer tests performed with non-sorbing tracers and data on the experimental set-up of the sorbing tracer tests. Based on this information, model predictions were made of drawdown, tracer mass recovery and tracer breakthrough. For the predictions of the STT-1b and STT-2 tests results from previous tracer tests with sorbing tracer were also available. The predictions of the sorbing tracer breakthrough in the initial tracer test (STT-1) generally underestimated the breakthrough time, suggesting the need to include additional processes and evaluate the application of the laboratory data. As a result of model calibration and modification the predictions were considerably improved for the latter tracer tests (STT-1b and STT-2). Task 4E and 4F have proved to be very valuable in increasing the understanding of non-sorbing tracer transport in fractured rock. There is a general consensus on the major processes responsible for
Modelling of radial electric field profile for different divertor configurations
Rozhansky, V; Kaveeva, E; Voskoboynikov, S; Counsell, G; Kirk, A; Meyer, H; Coster, D; Conway, G; Schirmer, J; Schneider, R
2006-01-01
The impact of divertor configuration on the structure of the radial electric field has been simulated by the B2SOLPS5.0 transport fluid code. It is shown that the change in the parallel flows in the scrape-off layer, which are transported through the separatrix due to turbulent viscosity and diffusivity, should result in variation of the radial electric field and toroidal rotation in the separatrix vicinity. The modelling predictions are compared with the measurements of the radial electric field for the low field side equatorial mid-plane of ASDEX Upgrade in lower, upper and double-null (DN) divertor configurations. The parallel (toroidal) flows in the scrape-off layer and mechanisms for their formation are analysed for different geometries. It is demonstrated that a spike in the electric field exists at the high field side equatorial mid-plane in the connected DN divertor configuration. Its origin is connected with different potential drops between the separatrix vicinity and divertor plates in the two disconnected scrape-off layers, while the separatrix should be at almost the same potential. The spike might be important for additional turbulent suppression
A large-strain radial consolidation theory for soft clays improved by vertical drains
Geng, X; Yu, H-S
2017-01-01
A system of vertical drains with combined vacuum and surcharge preloading is an effective solution for promoting radial flow, accelerating consolidation. However, when a mixture of soil and water is deposited at a low initial density, a significant amount of deformation or surface settlement occurs. Therefore, it is necessary to introduce large-strain theory, which has been widely used to manage dredged disposal sites in one-dimensional theory, into radial consolidation theory. A governing eq...
A large strain radial consolidation theory for soft clays improved by vertical drains\\ud
Geng, Xueyu; Yu, Hai-sui
2017-01-01
A system of vertical drains with combined vacuum and surcharge preloading is an effective 10 solution for promoting radial flow, accelerating consolidation. However, when a mixture of soil and\\ud 11 water is deposited at a low initial density, a significant amount of deformation or surface settlement 12 occurs. Therefore, it is necessary to introduce large strain theory, which has been widely used to manage\\ud 13 dredged disposal sites in one-dimensional theory, into radial consolidation theo...
Radial head button holing: a cause of irreducible anterior radial head dislocation
Shin, Su-Mi; Chai, Jee Won; You, Ja Yeon; Park, Jina [Seoul National University Seoul Metropolitan Government Boramae Medical Center, Department of Radiology, Seoul (Korea, Republic of); Bae, Kee Jeong [Seoul National University Seoul Metropolitan Government Boramae Medical Center, Department of Orthopedic Surgery, Seoul (Korea, Republic of)
2016-10-15
''Buttonholing'' of the radial head through the anterior joint capsule is a known cause of irreducible anterior radial head dislocation associated with Monteggia injuries in pediatric patients. To the best of our knowledge, no report has described an injury consisting of buttonholing of the radial head through the annular ligament and a simultaneous radial head fracture in an adolescent. In the present case, the radiographic findings were a radial head fracture with anterior dislocation and lack of the anterior fat pad sign. Magnetic resonance imaging (MRI) clearly demonstrated anterior dislocation of the fractured radial head through the torn annular ligament. The anterior joint capsule and proximal portion of the annular ligament were interposed between the radial head and capitellum, preventing closed reduction of the radial head. Familiarity with this condition and imaging findings will aid clinicians to make a proper diagnosis and fast decision to perform an open reduction. (orig.)
Dunca, G; Isbasoiu, E C; Muntean, S
2010-01-01
The paper presents the 3D numerical analysis of the flow into a hydraulic passage of the two stages and double entry storage pump. One of the reasons for choosing this machinery was that, even from the beginning of its operation, high levels of noise and vibration were recorded. According to the literature, these can be considered as effects of the impeller-stator phenomenon. After only 100 hours of operation, the pump' first stator blades was bend and the second stator blades was broken. As a rehabilitation solution, 100 mm of the chord were cut from the stator blades, near the leading edge. After the rehabilitation, a decrease of the noise and vibration levels during pump operation was observed. In order to analyse the pump behaviour, three measurements campaigns were conducted, after the rehabilitation. Yet, the experimental results were not very conclusive. A more detailed experimental analysis on a real turbo machine is very difficult and expensive. Thus, in order to obtain more detailed information regarding the impeller-stator phenomenon inside the analysed pump, a numerical analysis was realized. The impeller-stator (between the first impeller and first stator as well as between second impeller and second stator) and stator-impeller (between the first stator and second impeller) interactions are taken into account with mixing interface method. The hydrodynamic field from the inlet to the outlet is obtained. As a result, the pressure rise and hydraulic efficiency are computed at best efficiency point. These values are validated against experimental data measured into the storage pump. Comparing the numerical results obtained for the two geometries of the stators, it can be seen that they have different behaviour during the pump's operation. It can be considered that, although the same geometry modification was realized for both the stators, the effects on the flow parameters are different, only for the second stator being possible to observe a net
Choi, Young Do; Kurokawa, Junichi; Lee, Young Ho
2005-01-01
In the very low specific speed range (n s < 0.25, non-dimensional), the efficiency of centrifugal pump designed by a conventional method is very low in common. Therefore, positive-displacement pumps have long been used widely. Recently, since the centrifugal pumps are becoming higher in rotational speed and smaller in size, there experts to develop a new centrifugal pump with a high performance to replace the positive-displacement pumps. The purpose of this study is to investigate the internal flow characteristics of a very low specific speed centrifugal pump and to examine the effect of internal flow pattern on pump performance. The results show that the theoretical head definition of semi-open impeller should be revised by the consideration of high slip factor in the semi-open impeller, and the leakage flow through the tip clearance results in a large effect on the impeller internal flow. Strong reverse flow at the outlet of semi-open impeller reduces the absolute tangential velocity considerably, and the decreased absolute tangential velocity increases the slip factor with the reduction of theoretical head
Manipulation of viscous fingering in a radially tapered cell geometry
Bongrand, Grégoire; Tsai, Peichun Amy
2018-06-01
When a more mobile fluid displaces another immiscible one in a porous medium, viscous fingering propagates with a partial sweep, which hinders oil recovery and soil remedy. We experimentally investigate the feasibility of tuning such fingering propagation in a nonuniform narrow passage with a radial injection, which is widely used in various applications. We show that a radially converging cell can suppress the common viscous fingering observed in a uniform passage, and a full sweep of the displaced fluid is then achieved. The injection flow rate Q can be further exploited to manipulate the viscous fingering instability. For a fixed gap gradient α , our experimental results show a full sweep at a small Q but partial displacement with fingering at a sufficient Q . Finally, by varying α , we identify and characterize the variation of the critical threshold between stable and unstable displacements. Our experimental results reveal good agreement with theoretical predictions by a linear stability analysis.
Yannick Bousquet
2014-01-01
Full Text Available This study concerns a 2.5 pressure ratio centrifugal compressor stage consisting of a splittered unshrouded impeller and a vaned diffuser. The aim of this paper is to investigate the modifications of the flow structure when the operating point moves from peak efficiency to near stall. The investigations are based on the results of unsteady three-dimensional simulations, in a calculation domain comprising all the blade. A detailed analysis is given in the impeller inducer and in the vaned diffuser entry region through time-averaged and unsteady flow field. In the impeller inducer, this study demonstrates that the mass flow reduction from peak efficiency to near stall leads to intensification of the secondary flow effects. The low momentum fluid accumulated near the shroud interacts with the main flow through a shear layer zone. At near stall condition, the interface between the two flow structures becomes unstable leading to vortices development. In the diffuser entry region, by reducing the mass flow, the high incidence angle from the impeller exit induces a separation on the diffuser vane suction side. At near stall operating point, vorticity from the separation is shed into vortex cores which are periodically formed and convected downstream along the suction side.
Photoelectric Radial Velocities, Paper XIX Additional Spectroscopic ...
ian velocity curve that does justice to the measurements, but it cannot be expected to have much predictive power. Key words. Stars: late-type—stars: radial velocities—spectroscopic binaries—orbits. 0. Preamble. The 'Redman K stars' are a lot of seventh-magnitude K stars whose radial velocities were first observed by ...
Radial velocities of RR Lyrae stars
Hawley, S.L.; Barnes, T.G. III
1985-01-01
283 spectra of 57 RR Lyrae stars have been obtained using the 2.1-m telescope at McDonald Observatory. Radial velocities were determined using a software cross-correlation technique. New mean radial velocities were determined for 46 of the stars. 11 references
Concepts of radial and angular kinetic energies
Dahl, Jens Peder; Schleich, W.P.
2002-01-01
We consider a general central-field system in D dimensions and show that the division of the kinetic energy into radial and angular parts proceeds differently in the wave-function picture and the Weyl-Wigner phase-space picture, Thus, the radial and angular kinetic energies are different quantities...
Design optimization of flow channel and performance analysis for a new-type centrifugal blood pump
Ji, J. J.; Luo, X. W.; Y Wu, Q.
2013-12-01
In this paper, a new-type centrifugal blood pump, whose impeller is suspended inside a pump chamber with hydraulic bearings, is presented. In order to improve the hydraulic performance of the pump, an internal flow simulation is conducted to compare the effects of different geometrical parameters of pump flow passage. Based on the numerical results, the pumps can satisfy the operation parameters and be free of hemolysis. It is noted that for the pump with a column-type supporter at its inlet, the pump head and hydraulic efficiency decreases compared to the pump with a step-type support structure. The performance drop is caused by the disturbed flow upstream impeller inlet. Further, the unfavorable flow features such as reverse flow and low velocity in the pump may increases the possibility of thrombus. It is also confirmed that the casing shape can little influence pump performance. Those results are helpful for design optimization in blood pump development.
Centrifugal pump’s impeller optimization using methods of calculation hydrodynamics
Grigoriev, S.; Mayorov, S.; Polyakov, R.
2017-08-01
The paper features the results of the fluid flow calculation in the channels of varying geometry of the centrifugal pump for the service water in the methanol production chain. Modeling of the flow in ANSYS CFX allowed developing recommendations on adjusting the impeller’s profile, significantly decrease the cavitation wear and increase the lifetime by several times.
Helander, P.; Hazeltine, R.D.; Catto, P.J.
1996-01-01
The orderings in the kinetic equations commonly used to study the plasma core of a tokamak do not allow a balance between parallel ion streaming and radial diffusion, and are, therefore, inappropriate in the plasma edge. Different orderings are required in the edge region where radial transport across the steep gradients associated with the scrape-off layer is large enough to balance the rapid parallel flow caused by conditions close to collecting surfaces (such as the Bohm sheath condition). In the present work, we derive and solve novel kinetic equations, allowing for such a balance, and construct distinctive transport laws for impure, collisional, edge plasmas in which the perpendicular transport is (i) due to Coulomb collisions of ions with heavy impurities, or (ii) governed by anomalous diffusion driven by electrostatic turbulence. In both the collisional and anomalous radial transport cases, we find that one single diffusion coefficient determines the radial transport of particles, momentum and heat. The parallel transport laws and parallel thermal force in the scrape-off layer assume an unconventional form, in which the relative ion-impurity flow is driven by a combination of the conventional parallel gradients, and new (i) collisional or (ii) anomalous terms involving products of radial derivatives of the temperature and density with the radial shear of the parallel velocity. Thus, in the presence of anomalous radial diffusion, the parallel ion transport cannot be entirely classical, as usually assumed in numerical edge computations. The underlying physical reason is the appearance of a novel type of parallel thermal force resulting from the combined action of anomalous diffusion and radial temperature and velocity gradients. In highly sheared flows the new terms can modify impurity penetration into the core plasma
Study of flow instability in a centrifugal fan based on energy gradient theory
Xiao, Meina; Dou, Hua-Shu; Ma, Xiaoyang; Xiao, Qing; Chen, Yongning; He, Haijiang; Ye, Xinxue
2016-01-01
Flow instability in a centrifugal fan was studied using energy gradient theory. Numerical simulation was performed for the three dimensional turbulent flow field in a centrifugal fan. The flow is governed by the three-dimensional incompressible Navier-Stokes equations coupled with the RNG k-ε turbulent model. The finite volume method was used to discretize the governing equations and the Semiimplicit method for pressure linked equation (SIMPLE) algorithm is employed to iterate the system of the equations. The interior flow field in the centrifugal fan and the distribution of the energy gradient function K are obtained at different flow rates. According to the energy gradient method, the area with larger value of K is the place where the flow loses stability easier. The results show that instability is easier to generate in the regions of impeller outlet and volute tongue. The air flow near the hub is more stable than that near the shroud. That is due to the influences of variations of the velocity and the inlet angle along the axial direction. With the decrease of the flow rate, instability zone in a blade channel moves to the impeller inlet from the outlet and the unstable regions in different channels develop in opposite direction to the rotation of impeller
Design and Numerical Simulation of Radial Inflow Turbine Volute
Shah, Samip P.; Channiwala, S. A.; Kulshreshtha, D. B.; Chaudhari, Gaurang
2014-12-01
The volute of a radial inflow turbine has to be designed to ensure that the desired rotor inlet conditions like absolute Mach number, flow angle etc. are attained. For the reasonable performance of vaneless volute turbine care has to be taken for reduction in losses at an appropriate flow angle at the rotor inlet, in the direction of volute, whose function is to convert gas energy into kinetic energy and direct the flow towards the rotor inlet at an appropriate flow angle with reduced losses. In literature it was found that the incompressible approaches failed to provide free vortex and uniform flow at rotor inlet for compressible flow regimes. So, this paper describes a non-dimensional design procedure for a vaneless turbine volute for compressible flow regime and investigates design parameters, such as the distribution of area ratio and radius ratio as a function of azimuth angle. The nondimensional design is converted in dimensional form for three different volute cross sections. A commercial computational fluid dynamics code is used to develop numerical models of three different volute cross sections. From the numerical models, losses generation in the different volutes are identified and compared. The maximum pressure loss coefficient for Trapezoidal cross section is 0.1075, for Bezier-trapezoidal cross section is 0.0677 and for circular cross section is 0.0438 near tongue region, which suggested that the circular cross section will give a better efficiency than other types of volute cross sections.
Effects of the radial electric field in a quasisymmetric stellarator
Landreman, Matt; Catto, Peter J
2011-01-01
Recent calculations have shown that a radial electric field can significantly alter the neoclassical ion heat flux, ion flow, bootstrap current and residual zonal flow in a tokamak, even when the E x B drift is much smaller than the ion thermal speed. Here we show the novel analytical methods used in these calculations can be adapted to a quasisymmetric stellarator. The methods are based on using the conserved helical momentum ψ * instead of the poloidal or toroidal flux as a radial coordinate in the kinetic equation. The banana-regime calculations also employ a model collision operator that keeps only the velocity-space derivatives normal to the trapped-passing boundary, even as this boundary is shifted and deformed by the E x B drift. We prove the isomorphism between quasisymmetric stellarators and tokamaks extends to the finite-E x B generalizations of both banana-regime and plateau-regime neoclassical theory and the residual zonal flow. The plateau-regime results may be relevant to the HSX stellarator, and both the plateau- and banana-regime results can be used to validate stellarator transport codes.
Physics suggests that the interplay of momentum, continuity, and geometry in outward radial flow must produce density and concomitant pressure reductions. In other words, this flow is intrinsically auto-expansive. It has been proposed that this process is the key to understanding...
Hewes, R.C.; Miller, T.R.
1988-01-01
To profile optimally each portion of the meniscus, the authors use the multiangle, multisection feature of a General Electric SIGNA 1.5-T imager to produce radial images centered on each meniscus. A total of 12-15 sections are imaged at 10 0 -15 0 intervals of each meniscus, yielding perpendicular images of the entire meniscus, comparable with the arthrographic tangential views. The authors review their technique and demonstrate correlation cases between the radial gradient recalled acquisition in a steady state sequences, sagittal and coronal MR images, and arthrograms. Radial images should be a routine part of knee MR imaging
Radial pattern of nuclear decay processes
Iskra, W.; Mueller, M.; Rotter, I.; Technische Univ. Dresden
1994-05-01
At high level density of nuclear states, a separation of different time scales is observed (trapping effect). We calculate the radial profile of partial widths in the framework of the continuum shell model for some 1 - resonances with 2p-2h nuclear structure in 16 O as a function of the coupling strength to the continuum. A correlation between the lifetime of a nuclear state and the radial profile of the corresponding decay process is observed. We conclude from our numerical results that the trapping effect creates structures in space and time characterized by a small radial extension and a short lifetime. (orig.)
Optimal Operation of Radial Distribution Systems Using Extended Dynamic Programming
Lopez, Juan Camilo; Vergara, Pedro P.; Lyra, Christiano
2018-01-01
An extended dynamic programming (EDP) approach is developed to optimize the ac steady-state operation of radial electrical distribution systems (EDS). Based on the optimality principle of the recursive Hamilton-Jacobi-Bellman equations, the proposed EDP approach determines the optimal operation o...... approach is illustrated using real-scale systems and comparisons with commercial programming solvers. Finally, generalizations to consider other EDS operation problems are also discussed.......An extended dynamic programming (EDP) approach is developed to optimize the ac steady-state operation of radial electrical distribution systems (EDS). Based on the optimality principle of the recursive Hamilton-Jacobi-Bellman equations, the proposed EDP approach determines the optimal operation...... of the EDS by setting the values of the controllable variables at each time period. A suitable definition for the stages of the problem makes it possible to represent the optimal ac power flow of radial EDS as a dynamic programming problem, wherein the 'curse of dimensionality' is a minor concern, since...
Radial basis function and its application in tourism management
Hu, Shan-Feng; Zhu, Hong-Bin; Zhao, Lei
2018-05-01
In this work, several applications and the performances of the radial basis function (RBF) are briefly reviewed at first. After that, the binomial function combined with three different RBFs including the multiquadric (MQ), inverse quadric (IQ) and inverse multiquadric (IMQ) distributions are adopted to model the tourism data of Huangshan in China. Simulation results showed that all the models match very well with the sample data. It is found that among the three models, the IMQ-RBF model is more suitable for forecasting the tourist flow.
Scaling laws for radial foil bearings
Honavara Prasad, Srikanth
The effects of fluid pressurization, structural deformation of the compliant members and heat generation in foil bearings make the design and analysis of foil bearings very complicated. The complex fluid-structural-thermal interactions in foil bearings also make modeling efforts challenging because these phenomena are governed by highly non-linear partial differential equations. Consequently, comparison of various bearing designs require detailed calculation of the flow fields (velocities, pressures), bump deflections (structural compliance) and heat transfer phenomena (viscous dissipation in the fluid, frictional heating, temperature profile etc.,) resulting in extensive computational effort (time/hardware). To obviate rigorous computations and aid in feasibility assessments of foil bearings of various sizes, NASA developed the "rule of thumb" design guidelines for estimation of journal bearing load capacity. The guidelines are based on extensive experimental data. The goal of the current work is the development of scaling laws for radial foil bearings to establish an analytical "rule of thumb" for bearing clearance and bump stiffness. The use of scale invariant Reynolds equation and experimentally observed NASA "rule of thumb" yield scale factors which can be deduced from first principles. Power-law relationships between: a. Bearing clearance and bearing radius, and b. bump stiffness and bearing radius, are obtained. The clearance and bump stiffness values obtained from scaling laws are used as inputs for Orbit simulation to study various cases. As the clearance of the bearing reaches the dimensions of the material surface roughness, asperity contact breaks the fluid film which results in wear. Similarly, as the rotor diameter increases (requiring larger bearing diameters), the load capacity of the fluid film should increase to prevent dry rubbing. This imposes limits on the size of the rotor diameter and consequently bearing diameter. Therefore, this thesis aims
A method for measuring the velocity flow field in the vicinity of a moving cascade
Bammert, K.; Mobarak, A.
1977-01-01
Centrifugal compressors and blowers are often used for recycling the coolant gas in gas-cooled reactors. To achieve the required pressure ratios, highly loaded centrifugal compressors are built. The paper deals with a method of measuring the flow field in the vicinity of a moving impeller or cascade with hot wires. The relative flow pattern induced ahead of a cascade or impeller or the rotating wakes behind a moving cascade (which is important for loss evaluation) could be now measured with the help of a single hot wire. The wire should be rotated about the axis of the probe for 3 different inclinations with respect to the approaching flow. The method has been used for measuring the flow field in the vicinity of the inducer of a highly loaded centrifugal compressor. The results and the accuracy of the method are discussed and the mean values have been compared with the theoretically estimated velocities. (orig.) [de
Possible Suppression of Magnetorotational Instability by Rapid Radial Flow
Abramowicz, M. A.; Horák, Jiří; Kluzniak, W.
2013-01-01
Roč. 63, č. 2 (2013), s. 267-273 ISSN 0001-5237 R&D Projects: GA ČR(CZ) GAP209/11/2004 Institutional support: RVO:67985815 Keywords : accretion disks * magnetohydrodynamics * black hole physics Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 1.955, year: 2013
Simulation of cylindrical Pierce diodes with radial flow
Alves, M.V.; Gnavi, G.; Gratton, F.T.; Buenos Aires Univ.
1996-01-01
In this paper we study the electron instability and the non linear behaviour of cylindrical Pierce's diodes by particle simulation. We ignore here the ion contribution (ions are fixed at a 1/r density and given a very large mass) to give perspicuity to the electron dynamics, and to facilitate comparison with existing theory. (author). 8 refs., 10 figs
Radial pseudoaneurysm following diagnostic coronary angiography
Shankar Laudari
2015-06-01
Full Text Available The radial artery access has gained popularity as a method of diagnostic coronary catheterization compared to femoral artery puncture in terms of vascular complications and early ambulation. However, very rare complication like radial artery pseudoaneurysm may occur following cardiac catheterization which may give rise to serious consequences. Here, we report a patient with radial pseudoaneurysm following diagnostic coronary angiography. Adequate and correct methodology of compression of radial artery following puncture for maintaining hemostasis is the key to prevention.DOI: http://dx.doi.org/10.3126/jcmsn.v10i3.12776 Journal of College of Medical Sciences-Nepal, 2014, Vol-10, No-3, 48-50
Radial transport with perturbed magnetic field
Hazeltine, R. D. [Institute for Fusion Studies, University of Texas at Austin, Austin, Texas 78712 (United States)
2015-05-15
It is pointed out that the viscosity coefficient describing radial transport of toroidal angular momentum is proportional to the second power of the gyro-radius—like the corresponding coefficients for particle and heat transport—regardless of any geometrical symmetry. The observation is widely appreciated, but worth emphasizing because some literature gives the misleading impression that asymmetry can allow radial moment transport in first-order.
Radial transport with perturbed magnetic field
Hazeltine, R. D.
2015-01-01
It is pointed out that the viscosity coefficient describing radial transport of toroidal angular momentum is proportional to the second power of the gyro-radius—like the corresponding coefficients for particle and heat transport—regardless of any geometrical symmetry. The observation is widely appreciated, but worth emphasizing because some literature gives the misleading impression that asymmetry can allow radial moment transport in first-order
Stability of radial and non-radial pulsation modes of massive ZAMS models
Odell, A.P.; Pausenwein, A.; Weiss, W.W.; Hajek, A.
1987-01-01
The authors have computed non-adiabatic eigenvalues for radial and non-radial pulsation modes of star models between 80 and 120 M solar with composition of chi=0.70 and Z=0.02. The radial fundamental mode is unstable in models with mass greater than 95 M solar , but the first overtone mode is always stable. The non-radial modes are all stable for all models, but the iota=2 f-mode is the closest to being driven. The non-radial modes are progressively more stable with higher iota and with higher n (for both rho- and g-modes). Thus, their results indicate that radial pulsation limits the upper mass of a star
21 CFR 866.4800 - Radial immunodiffusion plate.
2010-04-01
...) MEDICAL DEVICES IMMUNOLOGY AND MICROBIOLOGY DEVICES Immunology Laboratory Equipment and Reagents § 866.4800 Radial immunodiffusion plate. (a) Identification. A radial immunodiffusion plate for clinical use...
Kapadia, Jugal Y; Pierce, Kathryn C; Poupore, Amy K; Throckmorton, Amy L
2010-01-01
To provide hemodynamic support to patients with a failing single ventricle, we are developing a percutaneously inserted, magnetically levitated axial flow blood pump designed to augment pressure in the cavopulmonary circulation. The device is designed to serve as a bridge-to-transplant, bridge-to-recovery, bridge-to-hemodynamic stability, or bridge-to-surgical reconstruction. This study evaluated the hydraulic performance of three blood pump prototypes (a four-bladed impeller, a three-bladed impeller, and a three-bladed impeller with a four-bladed diffuser) whose designs evolved from previous design optimization phases. Each prototype included the same geometric protective cage of filaments, which stabilize the rotor within the housing and protect the housing wall from the rotating blades. All prototypes delivered pressure rises over a range of flow rates and rotational speeds that would be sufficient to augment hemodynamic conditions in the cavopulmonary circulation. The four-bladed impeller outperformed the two remaining prototypes by >40%; this design was able to generate a pressure rise of 4-28 mm Hg for flow rates of 0.5-10 L/min at rotational speeds of 4,000-7,000 RPM. Successful development of this blood pump will provide clinicians with a feasible therapeutic option for mechanically supporting the failing Fontan.
Guo, En Min; Kim, Kwang Yong
2004-01-01
This work developed improved slip factor model and correction method to predict flow through impeller in forward-curved centrifugal fan. Both steady and unsteady three-dimensional CFD analyses were performed to validate the slip factor model and the correction method. The results show that the improved slip factor model presented in this paper could provide more accurate predictions for forward-curved centrifugal impeller than the other slip factor models since the present model takes into account the effect of blade curvature. The correction method is provided to predict mass-averaged absolute circumferential velocity at the exit of impeller by taking account of blockage effects induced by the large-scale backflow near the front plate and flow separation within blade passage. The comparison with CFD results also shows that the improved slip factor model coupled with the present correction method provides accurate predictions for mass-averaged absolute circumferential velocity at the exit of impeller near and above the flow rate of peak total pressure coefficient
A mini axial and a permanent maglev radial heart pump.
Qian, Kun-Xi; Ru, Wei-Min; Wang, Hao; Jing, Teng
2007-05-31
The implantability and durability have been for decades the focus of artificial heart R&D. A mini axial and a maglev radial pump have been developed to meet with such requirements.The mini axial pump weighing 27g (incl.5g rotor) has an outer diameter of 21mm and a length of 10mm in its largest point, but can produce a maximal blood flow of 6l/min with 50mmHg pressure increase. Therefore, it is suitable for the patients of 40-60kg body weight. For other patients of 60-80kg or 80-100kg body weight, the mini axial pumps of 23mm and 25mm outer diameter had been developed before, these devices were acknowledged to be the world smallest LVADs by Guinness World Record Center in 2004.The permanent maglev radial pump weighing 150g is a shaft-less centrifugal pump with permanent magnetic bearings developed by the author. It needs no second coil for suspension of the rotor except the motor coil, different from all other maglev pumps developed in USA, Japan, European, etc. Thus no detecting and controlling systems as well as no additional power supply for maglev are necessary. The pump can produce a blood flow up to as large as 10l/min against 100mmHg pressure.An implantable and durable blood pump will be a viable alternative to natural donor heart for transplantation.
Water Flow Performance of a Superscale Model of the Fastrac Liquid Oxygen Pump
Skelley, Stephen; Zoladz, Thomas
2001-01-01
As part of the National Aeronautics and Space Administration's ongoing effort to lower the cost of access to space, the Marshall Space Flight Center has developed a rocket engine with 60,000 pounds of thrust for use on the Reusable Launch Vehicle technology demonstrator slated for launch in 2000. This gas generator cycle engine, known as the Fastrac engine, uses liquid oxygen and RP-1 for propellants and includes single stage liquid oxygen and RP-1 pumps and a single stage supersonic turbine on a common shaft. The turbopump design effort included the first use and application of new suction capability prediction codes and three-dimensional blade generation codes in an attempt to reduce the turbomachinery design and certification costs typically associated with rocket engine development. To verify the pump's predicted cavitation performance, a water flow test of a superscale model of the Fastrac liquid oxygen pump was conducted to experimentally evaluate the liquid oxygen pump's performance at and around the design point. The water flow test article replicated the flow path of the Fastrac liquid oxygen pump in a 1.582x scale model, including scaled seal clearances for correct leakage flow at a model operating speed of 5000 revolutions per minute. Flow entered the 3-blade axial-flow inducer, transitioned to a shrouded, 6- blade radial impeller, and discharged into a vaneless radial diffuser and collection volute. The test article included approximately 50 total and static pressure measurement locations as well as flush-mounted, high frequency pressure transducers for complete mapping of the pressure environment. The primary objectives of the water flow test were to measure the steady-state and dynamic pressure environment of the liquid oxygen pump versus flow coefficient, suction specific speed, and back face leakage flow rate. Initial results showed acceptable correlation between the predicted and experimentally measured pump head rise at low suction specific speeds
Schiele, O.; Florjancic, D.
1976-01-01
A nuclear steam supply system is described wherein each of a plurality of centrifugal pumps begins to operate with full cavitation in response to an abrupt drop of system pressure in the event of leakage. This is achieved by influencing the net positive suction head of each pump over the entire range of fluid flow and/or by influencing the net positive suction head upstream of the pumps. The first mode of causing the pumps to operate with full cavitation includes an appropriate selection of the inlet angle and/or inlet diameter of the pump impeller, the provision of auxiliary impellers which are located upstream of the pumps and can circulate the fluid in or counter to the direction of rotation of the respective pump impellers, or the provision of suitably curved guide vanes in the pumps. The second mode include interrupting the admission of undercooled fluid into the system upstream of the pumps
Hsu, Y.Y.
1974-01-01
The following papers related to two-phase flow are summarized: current assumptions made in two-phase flow modeling; two-phase unsteady blowdown from pipes, flow pattern in Laval nozzle and two-phase flow dynamics; dependence of radial heat and momentum diffusion; transient behavior of the liquid film around the expanding gas slug in a vertical tube; flooding phenomena in BWR fuel bundles; and transient effects in bubble two-phase flow. (U.S.)
Anomalies of radial and ulnar arteries
Rajani Singh
Full Text Available Abstract During dissection conducted in an anatomy department of the right upper limb of the cadaver of a 70-year-old male, both origin and course of the radial and ulnar arteries were found to be anomalous. After descending 5.5 cm from the lower border of the teres major, the brachial artery anomalously bifurcated into a radial artery medially and an ulnar artery laterally. In the arm, the ulnar artery lay lateral to the median nerve. It followed a normal course in the forearm. The radial artery was medial to the median nerve in the arm and then, at the level of the medial epicondyle, it crossed from the medial to the lateral side of the forearm, superficial to the flexor muscles. The course of the radial artery was superficial and tortuous throughout the arm and forearm. The variations of radial and ulnar arteries described above were associated with anomalous formation and course of the median nerve in the arm. Knowledge of neurovascular anomalies are important for vascular surgeons and radiologists.
New Method for Mesh Moving Based on Radial Basis Function Interpolation
De Boer, A.; Van der Schoot, M.S.; Bijl, H.
2006-01-01
A new point-by-point mesh movement algorithm is developed for the deformation of unstructured grids. The method is based on using radial basis function, RBFs, to interpolate the displacements of the boundary nodes to the whole flow mesh. A small system of equations has to be solved, only involving
Self-consistent model for the radial current generation during fishbone activity
Lutsenko, V.V.; Marchenko, V.S.
2002-01-01
Line broadened quasilinear burst model, originally developed for the bump-on-tail instability [H. L. Berk et al., Nucl. Fusion 35, 1661 (1995)], is extended to the problem of sheared flow generation by the fishbone burst. It is supposed that the radial current of the resonant fast ions can be sufficient to create the transport barrier
Peleman, P.; Xu, Y.; Spolaore, M.; Brotánková, Jana; Devynck, P.; Stöckel, Jan; Van Oost, G.; Boucher, C.
363-365, č. 17 (2007), s. 638-642 ISSN 0022-3115. [ Plasma Surface Interactions in Controlled Fusion Devices/17th./. Hefei, 22.05.2007-26.05.2007] Institutional research plan: CEZ:AV0Z20430508 Keywords : Relaxations * Edge transport * Plasma flow * Radial electric fields Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 1.643, year: 2007
Ida, Katsumi; Miura, Yukitoshi; Itoh, Sanae
1994-10-01
Radial structures of plasma rotation and radial electric field are experimentally studied in tokamak, heliotron/torsatron and stellarator devices. The perpendicular and parallel viscosities are measured. The parallel viscosity, which is dominant in determining the toroidal velocity in heliotron/torsatron and stellarator devices, is found to be neoclassical. On the other hand, the perpendicular viscosity, which is dominant in dictating the toroidal rotation in tokamaks, is anomalous. Even without external momentum input, both a plasma rotation and a radial electric field exist in tokamaks and heliotrons/torsatrons. The observed profiles of the radial electric field do not agree with the theoretical prediction based on neoclassical transport. This is mainly due to the existence of anomalous perpendicular viscosity. The shear of the radial electric field improves particle and heat transport both in bulk and edge plasma regimes of tokamaks. (author) 95 refs
Manufacturing of Precision Forgings by Radial Forging
Wallner, S.; Harrer, O.; Buchmayr, B.; Hofer, F.
2011-01-01
Radial forging is a multi purpose incremental forging process using four tools on the same plane. It is widely used for the forming of tool steels, super alloys as well as titanium- and refractory metals. The range of application goes from reducing the diameters of shafts, tubes, stepped shafts and axels, as well as for creating internal profiles for tubes in Near-Net-Shape and Net-Shape quality. Based on actual development of a weight optimized transmission input shaft, the specific features of radial forging technology is demonstrated. Also a Finite Element Model for the simulation of the process is shown which leads to reduced pre-processing effort and reduced computing time compared to other published simulation methods for radial forging. The finite element model can be applied to quantify the effects of different forging strategies.
Core radial electric field and transport in Wendelstein 7-X plasmas
Pablant, N. A.; Langenberg, A.; Alonso, A.; Beidler, C. D.; Bitter, M.; Bozhenkov, S.; Burhenn, R.; Beurskens, M.; Delgado-Aparicio, L.; Dinklage, A.; Fuchert, G.; Gates, D.; Geiger, J.; Hill, K. W.; Höfel, U.; Hirsch, M.; Knauer, J.; Krämer-Flecken, A.; Landreman, M.; Lazerson, S.; Maaßberg, H.; Marchuk, O.; Massidda, S.; Neilson, G. H.; Pasch, E.; Satake, S.; Svennson, J.; Traverso, P.; Turkin, Y.; Valson, P.; Velasco, J. L.; Weir, G.; Windisch, T.; Wolf, R. C.; Yokoyama, M.; Zhang, D.; W7-X Team
2018-02-01
The results from the investigation of neoclassical core transport and the role of the radial electric field profile (Er) in the first operational phase of the Wendelstein 7-X (W7-X) stellarator are presented. In stellarator plasmas, the details of the Er profile are expected to have a strong effect on both the particle and heat fluxes. Investigation of the radial electric field is important in understanding neoclassical transport and in validation of neoclassical calculations. The radial electric field is closely related to the perpendicular plasma flow (u⊥) through the force balance equation. This allows the radial electric field to be inferred from measurements of the perpendicular flow velocity, which can be measured using the x-ray imaging crystal spectrometer and correlation reflectometry diagnostics. Large changes in the perpendicular rotation, on the order of Δu⊥˜ 5 km/s (ΔEr ˜ 12 kV/m), have been observed within a set of experiments where the heating power was stepped down from 2 MW to 0.6 MW. These experiments are examined in detail to explore the relationship between heating power temperature, and density profiles and the radial electric field. Finally, the inferred Er profiles are compared to initial neoclassical calculations based on measured plasma profiles. The results from several neoclassical codes, sfincs, fortec-3d, and dkes, are compared both with each other and the measurements. These comparisons show good agreement, giving confidence in the applicability of the neoclassical calculations to the W7-X configuration.
The Matlab Radial Basis Function Toolbox
Scott A. Sarra
2017-03-01
Full Text Available Radial Basis Function (RBF methods are important tools for scattered data interpolation and for the solution of Partial Differential Equations in complexly shaped domains. The most straight forward approach used to evaluate the methods involves solving a linear system which is typically poorly conditioned. The Matlab Radial Basis Function toolbox features a regularization method for the ill-conditioned system, extended precision floating point arithmetic, and symmetry exploitation for the purpose of reducing flop counts of the associated numerical linear algebra algorithms.
Radial velocity observations of VB10
Deshpande, R.; Martin, E.; Zapatero Osorio, M. R.; Del Burgo, C.; Rodler, F.; Montgomery, M. M.
2011-07-01
VB 10 is the smallest star known to harbor a planet according to the recent astrometric study of Pravdo & Shaklan [1]. Here we present near-infrared (J-band) radial velocity of VB 10 performed from high resolution (R~20,000) spectroscopy (NIRSPEC/KECK II). Our results [2] suggest radial velocity variability with amplitude of ~1 km/s, a result that is consistent with the presence of a massive planet companion around VB10 as found via long-term astrometric monitoring of the star by Pravdo & Shaklan. Employing an entirely different technique we verify the results of Pravdo & Shaklan.
Plasma Signatures of Radial Field Power Dropouts
Lucek, E.A.; Horbury, T.S.; Balogh, A.; McComas, D.J.
1998-01-01
A class of small scale structures, with a near-radial magnetic field and a drop in magnetic field fluctuation power, have recently been identified in the polar solar wind. An earlier study of 24 events, each lasting for 6 hours or more, identified no clear plasma signature. In an extension of that work, radial intervals lasting for 4 hours or more (89 in total), have been used to search for a statistically significant plasma signature. It was found that, despite considerable variations between intervals, there was a small but significant drop, on average, in plasma temperature, density and β during these events
Reble, a radially converging electron beam accelerator
Ramirez, J.J.; Prestwich, K.R.
1976-01-01
The Reble accelerator at Sandia Laboratories is described. This accelerator was developed to provide an experimental source for studying the relevant diode physics, beam propagation, beam energy deposition in a gas using a radially converging e-beam. The nominal parameters for Reble are 1 MV, 200 kA, 20 ns e-beam pulse. The anode and cathode are concentric cylinders with the anode as the inner cylinder. The radial beam can be propagated through the thin foil anode into the laser gas volume. The design and performance of the various components of the accelerator are presented
Mihai Leonida NICULESCU
2013-03-01
Full Text Available In this paper, Proper Orthogonal Decomposition (POD is applied to the analysis of the unsteady rotor-stator interaction in a low-pressure centrifugal compressor. Numerical simulations are carried out through finite volumes method using the Unsteady Reynolds-Averaged Navier-Stokes Equations (URANS model. Proper Orthogonal Decomposition allows an accurate reconstruction of flow field using only a small number of modes; therefore, this method is one of the best tools for data storage. The POD results and the data obtained by the Adamczyk decomposition are compared. Both decompositions show the behavior of unsteady rotor-stator interaction, but the POD modes allow quantifying better the numerical errors.
Kurten, U.; van Sint Annaland, M.; Kuipers, J.A.M.
2004-01-01
A two-dimensional, pseudohomogeneous reactor model was presented to describe the radial and axial concentration profiles in a packed-bed membrane reactor and the local velocity field while accounting for the influences due to the distributive membrane flow and the radial porosity profile. The effect
A Review Relevant to Turbomachinery Flows
James P. Johnston
1998-01-01
“buoyancy” currents in cases where density gradients occur. Turbulence modification involves reduction (stabilization or increase (destabilization of turbulent Reynolds stresses by Coriolis forces; effects which areof special importance for the understanding and prediction of flows in radial and mixed flow pump and compressor rotors. Stabilization/destabilization effects are discussed by a selective review of the basic research literature on flows in straight, radial, rotating channels and diffusers.
On helicon wave induced radial plasma transport
Petrzilka, V.
1993-04-01
Estimates of helicon wave induced radial plasma transport are presented. The wave induced transport grows or decreases in dependence on the sign of the azimuthal wave number; these changes in transport may play an important role in helicon wave plasma sources. (author) 5 figs., 18 refs
Revealing the radial modes in vortex beams
Sephton, Bereneice C
2016-10-01
Full Text Available Light beams that carry orbital angular momentum are often approximated by modulating an initial beam, usually Gaussian, with an azimuthal phase variation to create a vortex beam. Such vortex beams are well defined azimuthally, but the radial profile...
Measurement of Wear in Radial Journal Bearings
Ligterink, D.J.; Ligterink, D.J.; de Gee, A.W.J.
1996-01-01
this article, the measurement of wear in radial journal bearings is discussed, where a distinction is made between stationary and non-stationary contact conditions. Starting with Holm/Archard's wear law, equations are derived for the calculation of the specific wear rate k of the bearing material as
Radial interchange motions of plasma filaments
Garcia, O.E.; Bian, N.H.; Fundamenski, W.
2006-01-01
on a biperiodic domain perpendicular to the magnetic field. It is demonstrated that a blob-like plasma structure develops dipolar vorticity and electrostatic potential fields, resulting in rapid radial acceleration and formation of a steep front and a trailing wake. While the dynamical evolution strongly depends...
Spectral problem for the radial Schroedinger equation
Vshivtsev, A.S.; Tatarintsev, A.V.; Prokopov, A.V.; Sorokin, V. N.
1998-01-01
For the first time, a procedure for determining spectra on the basis of generalized integral transformations is implemented for a wide class of radial Schroedinger equations. It is shown that this procedure works well for known types of potentials. Concurrently, this method makes it possible to obtain new analytic results for the Cornell potential. This may prove important for hadron physics
Computing modal dispersion characteristics of radially Asymmetric ...
We developed a matrix theory that applies to with non-circular/circular but concentric layers fibers. And we compute the dispersion characteristics of radially unconventional fiber, known as Asymmetric Bragg fiber. An attempt has been made to determine how the modal characteristics change as circular Bragg fiber is ...
Pate, G
2011-10-01
A survey was conducted of medication administered during radial artery cannulation for coronary angiography in 2009 in Ireland; responses were obtained for 15 of 20 centres, in 5 of which no radial access procedures were undertaken. All 10 (100%) centres which provided data used heparin and one or more anti-spasmodics; verapamil in 9 (90%), nitrate in 1 (10%), both in 2 (20%). There were significant variations in the doses used. Further work needs to be done to determine the optimum cocktail to prevent radial artery injury following coronary angiography.
Torrent, Daniel; Sánchez-Dehesa, José
2009-08-07
We demonstrate that metamaterials with anisotropic properties can be used to develop a new class of periodic structures that has been named radial wave crystals. They can be sonic or photonic, and wave propagation along the radial directions is obtained through Bloch states like in usual sonic or photonic crystals. The band structure of the proposed structures can be tailored in a large amount to get exciting novel wave phenomena. For example, it is shown that acoustical cavities based on radial sonic crystals can be employed as passive devices for beam forming or dynamically orientated antennas for sound localization.
Solar updraft power generator with radial and curved vanes
Hafizh, Hadyan; Hamsan, Raziff; Zamri, Aidil Azlan Ahmad; Keprawi, Mohamad Fairuz Mohamad; Shirato, Hiromichi
2018-02-01
Solar radiation is the largest source of energy available on earth and the solar updraft power generator (SUPG) is a renewable energy facility capable of harnessing its abundant power. Unlike the conventional wind turbines that harness natural wind in the atmosphere and often encounter with the intermittent issue or even complete cut-off from airflow, the SUPG creates artificial wind as a result of solar-induced convective flows. However, the SUPG has an inherent low total efficiency due to the conversion of thermal energy into pressure energy. Acknowledging the low efficiency and considering its potential as a renewable energy facility, the current work aims to increase the total efficiency by installing a series of guide walls inside the collector. Two types of guide walls were used i.e. radial and curved vanes. The result with curved vanes showed that the updraft velocity is higher compare to those without vanes. About 18% and 64% improvement of updraft velocity and mechanical power were attained respectively. Furthermore, it was observed that the role of radial vanes configuration was more to produce a smooth updraft velocity profile rather than increasing the total efficiency.
Experimental Characterization of Piezoelectric Radial Field Diaphragms for Fluidic Control
Bryant, R. G.; Kavli, S. E.; Thomas, R. A., Jr.; Darji, K. J.; Mossi, K. M.
2004-01-01
NASA has recently developed a new piezoelectric actuator, the Radial Field Diaphragm or RFD. This actuator uses a radially-directed electric field to generate concentric out-of-plane (Z-axis) motion that allows this packaged device to be used as a pump or valve diaphragm. In order to efficiently use this new active device, experimental determination of pressure, flow rate, mechanical work, power consumption and overall efficiency needs to be determined by actually building a pump. However, without an optimized pump design, it is difficult to assess the quality of the data, as these results are inherent to the actual pump. Hence, separate experiments must be conducted in order to generate independent results to help guide the design criteria and pump quality. This paper focuses on the experiments used to generate the RFD's operational parameters and then compares these results to the experimentally determined results of several types of ball pumps. Also discussed are how errors are inherently introduced into the experiments, the pump design, experimental hardware and their effects on the overall system efficiency.
Experimental and computational investigation of the NASA low-speed centrifugal compressor flow field
Hathaway, Michael D.; Chriss, Randall M.; Wood, Jerry R.; Strazisar, Anthony J.
1993-01-01
An experimental and computational investigation of the NASA Lewis Research Center's low-speed centrifugal compressor (LSCC) flow field was conducted using laser anemometry and Dawes' three-dimensional viscous code. The experimental configuration consisted of a backswept impeller followed by a vaneless diffuser. Measurements of the three-dimensional velocity field were acquired at several measurement planes through the compressor. The measurements describe both the throughflow and secondary velocity field along each measurement plane. In several cases the measurements provide details of the flow within the blade boundary layers. Insight into the complex flow physics within centrifugal compressors is provided by the computational fluid dynamics analysis (CFD), and assessment of the CFD predictions is provided by comparison with the measurements. Five-hole probe and hot-wire surveys at the inlet and exit to the impeller as well as surface flow visualization along the impeller blade surfaces provided independent confirmation of the laser measurement technique. The results clearly document the development of the throughflow velocity wake that is characteristic of unshrouded centrifugal compressors.
Calculation of hydrostatic radial bearing for main circulating pump of 500 BIKS type
Hnatek, T.; Sojka, P.
1978-01-01
Computer calculations of the radial hydrostatic bearing were performed for the main circulating pump of the 500 BIKS type designed for WWER reactors. The calculations were based on the Reynolds equation of thin layer hydrodynamic pressure in turbulent flow. Relations were derived for orifice reducer flow. In contrast to previous calculations conducted for laminar flow, the results are more accurate because the nature of bearing lubrication evidently is turbulent. The required loading of 21,700 N in normal pump operation is fully compensated at a full eccentricity of 0.77. Operating tests of the pump also confirmed that the actual radial forces on the rotor did not attain the desired loading. On the other hand, thanks to the bearing brass design, the bearing is capable of short-time operation with limit eccentricity, ie., at start, in deceleration and in emergency conditions. (Z.M.)
Application of two turbulence models for computation of cavitating flows in a centrifugal pump
He, M; Guo, Q; Zhou, L J; Wang, X; Wang, Z W
2013-01-01
To seek a better numerical method to simulate the cavitating flow field in a centrifugal pump, the applications between RNG k- ε and LES turbulence model were compared by using the Zwart-Gerber-Belamri cavitation model. It was found that both the models give almost the same results with respect to pump performance and cavitation evolutions including growth, local contraction, stability and separation in the impeller passage. But the LES model can not only capture the pump suction recirculation and the low frequency fluctuation caused by it, but also combine the changes of the shaft frequency amplitude acting on the impeller with the cavitation unstable characteristics. Thus the LES model has more advantages than RNG k- ε model in calculating the unsteady cavitating flow in a centrifugal pump
Investigation of the Hydrodynamics of Sweep Blade in Hi-Speed Axial Fuel Pump Impeller
Ran Tao
2013-01-01
Full Text Available Fuel pump is a crucial component in aircraft engine ignition system. For the hi-speed axial fuel pumps, rotating stall triggers vortex and affects the operation stability and security. Sweep blade is widely used to solve the stability problems in aerodynamics field. Investigation on the hydrodynamics was conducted in this study. Based on the typical straight blade pump, positive and negative sweep blade pumps were modeled. With the large eddy simulation method, CFD simulations were conducted to calculate and analyze the flow characteristics in the pump models. To verify the simulation, experiments were also launched on the hydraulic test rig. Results show that the vortex occurs at the suction surface of blade and gathers near the blade tip region. Positive sweep blade is effective to reduce the hydraulic losses by driving the stalled fluid into the mid-part of blade. By applying the positive sweep blade on the axial fuel pump, the instability operating region will be diminished. Adopting sweep blade provides an effective means for stability and security of axial fuel pumps.
Effectiveness of meta-models for multi-objective optimization of centrifugal impeller
Bellary, Sayed Ahmed Imran; Samad, Abdus [Indian Institute of Technology Madras, Chennai (India); Husain, Afzal [Sultan Qaboos University, Al-Khoudh (Oman)
2014-12-15
Transverse secondary gas injection into an axisymmetric supersonic nozzle under standard atmosphere pressure is investigated to get the performance of thrust vectoring control. An analytical model was established based on the transverse injection flow. Three dimensional CFD methods were performed with different transverse secondary injection models. To validate the ability of the numerical model, numerical results were compared with the analytical and experimental results. Overall pressure distributions show quite good match with the analytical and experimental results. The Mach number contours in different injection positions were obtained. Reflection of the bow shock occurred for xj/L = 0.6, not for xj/L = 0.9. Nozzle pressure ratio is also the key factor for shock vector control. Based on this data, thrust vectoring efficiency and system thrust ratio have been considered. Finally, the pressure distributions in different momentum flux ratios were studied in CFD and analytical models. The separating point of boundary layer is moving upstream with the increasing of momentum flux ratio. The result will provide the reference to the further development of shock vector control.
The structural and phase state formed in construction titanium alloy by radial forging
Shlyakhova, Galina V.; Danilov, Vladimir I.; Orlova, Dina V.; Zuev, Lev B. [Institute of Strength Physics and Materials Science SB RAS, Tomsk (Russian Federation); Zavodchikov, Aleksandr S. [Perm State Technical University, Perm (Russian Federation)
2011-07-01
The feasibility of rod manufacture from construction titanium alloy using radial forging on a high duty machine SXK16 was investigated. The investigations were carried on for titanium rod samples using the methods of metallography, electron transmission microscophy and X-ray analysis. The results obtained are described herein. It is found that radial forging results in the formation of homogeneous fine-grained structure.Using radial forging process, high-quality items are produced. As-worked material has submicrocrystalline globular structure and an optimal α:β phase ratio. Besides, the technology is more cost-effective relative to conventional flow charts. Key words: forging, titanium alloy, fine-grain structure, substructure, pore size.
Interplay between Mach cone and radial expansion in jet events
Tachibana, Y., E-mail: tachibana@nt.phys.s.u-tokyo.ac.jp [Theoretical Research Division, Nishina Center, RIKEN, Wako 351-0198 (Japan); Department of Engineering, Nishinippon Institute of Technology, Fukuoka 800-0344 (Japan); Department of Physics, Sophia University, Tokyo 102-8554 (Japan); Hirano, T., E-mail: hirano@sophia.ac.jp [Department of Physics, Sophia University, Tokyo 102-8554 (Japan)
2016-12-15
We study the hydrodynamic response to jet propagation in the expanding QGP and investigate how the particle spectra after the hydrodynamic evolution of the QGP reflect it. We perform simulations of the space-time evolution of the QGP in gamma-jet events by solving (3+1)-dimensional ideal hydrodynamic equations with source terms. Mach cone is induced by the jet energy deposition and pushes back the radial flow of the expanding background. Especially in the case when the jet passage is off-central one, the number of particles emitted in the direction of the push back decreases. This is the signal including the information about the formation of the Mach cone and the jet passage in the QGP fluid.
Interplay between Mach cone and radial expansion in jet events
Tachibana, Y.; Hirano, T.
2016-01-01
We study the hydrodynamic response to jet propagation in the expanding QGP and investigate how the particle spectra after the hydrodynamic evolution of the QGP reflect it. We perform simulations of the space-time evolution of the QGP in gamma-jet events by solving (3+1)-dimensional ideal hydrodynamic equations with source terms. Mach cone is induced by the jet energy deposition and pushes back the radial flow of the expanding background. Especially in the case when the jet passage is off-central one, the number of particles emitted in the direction of the push back decreases. This is the signal including the information about the formation of the Mach cone and the jet passage in the QGP fluid.
Microinstabilities in a radially contracting inhomogeneous cylindrical plasma slab
Deutsch, R.; Kaeppeler, H.J.
1980-07-01
In order to study the development of microinstabilities in a collapsing cylindrical plasma sheath, corresponding to the situations in a z-pinch or a plasma focus, the dispersion relation for electromagnetic perturbations is derived with the aid of a newly established slab-model for an inhomogeneous, radially contracting plasma. In contrast to previously used slab-models, the orientation of the electric field is in direction of the cylinder axis and the azimuthal magnetic field is induced by the current flowing through the cylindrical plasma slab. The Vlasov equation is used together with the Krook collision term in order to include the influence of collisions. The results of this theory presented in this report will be used to calculate the growth of drift instabilities in the compression phase of a plasma focus, and shall serve as a basis for further development of a more general dispersion relation including runaway-effects. (orig.)
Zhang, Y X; Su, M; Hou, H C; Song, P F
2013-01-01
This research adopts the quasi three-dimensional hydraulic design method for the impeller of high specific speed mixed-flow pump to achieve the purpose of verifying the hydraulic design method and improving hydraulic performance. Based on the two families of stream surface theory, the direct problem is completed when the meridional flow field of impeller is obtained by employing iterative calculation to settle the continuity and momentum equation of fluid. The inverse problem is completed by using the meridional flow field calculated in the direct problem. After several iterations of the direct and inverse problem, the shape of impeller and flow field information can be obtained finally when the result of iteration satisfies the convergent criteria. Subsequently the internal flow field of the designed pump are simulated by using RANS equations with RNG k-ε two-equation turbulence model. The static pressure and streamline distributions at the symmetrical cross-section, the vector velocity distribution around blades and the reflux phenomenon are analyzed. The numerical results show that the quasi three-dimensional hydraulic design method for high specific speed mixed-flow pump improves the hydraulic performance and reveal main characteristics of the internal flow of mixed-flow pump as well as provide basis for judging the rationality of the hydraulic design, improvement and optimization of hydraulic model
Optimization of a radially cooled pebble bed reactor - HTR2008-58117
Boer, B.; Kloosterman, J. L.; Lathouwers, D.; Van Der Hagen, T. H. J. J.; Van Dam, H.
2008-01-01
By altering the coolant flow direction in a pebble bed reactor from axial to radial, the pressure drop can be reduced tremendously. In this case the coolant flows from the outer reflector through the pebble bed and finally to flow paths in the inner reflector. As a consequence, the fuel temperatures are elevated due to the reduced heat transfer of the coolant. However, the power profile and pebble size in a radially cooled pebble bed reactor can be optimized to achieve lower fuel temperatures than current axially cooled designs, while the low pressure drop can be maintained. The radial power profile in the core can be altered by adopting multi-pass fuel management using several radial fuel zones in the core. The optimal power profile yielding a flat temperature profile is derived analytically and is approximated by radial fuel zoning. In this case, the pebbles pass through the outer region of the core first and each consecutive pass is located in a fuel zone closer to the inner reflector. Thereby, the resulting radial distribution of the fissile material in the core is influenced and the temperature profile is close to optimal. The fuel temperature in the pebbles can be further reduced by reducing the standard pebble diameter from 6 cm to a value as low as I cm. An analytical investigation is used to demonstrate the effects on the fuel temperature and pressure drop for both radial and axial cooling. Finally, two-dimensional numerical calculations were performed, using codes for neutronics, thermal-hydraulics and fuel depletion analysis, in order to validate the results for the optimized design that were obtained from the analytical investigations. It was found that for a radially cooled design with an optimized power profile and reduced pebble diameter (below 3.5 cm) both a reduction in the pressure drop (Δp = -2.6 bar), which increases the reactor efficiency with several percent, and a reduction in the maximum fuel temperature (ΔT = -50 deg. C) can be achieved
Modified echo peak correction for radial acquisition regime (RADAR).
Takizawa, Masahiro; Ito, Taeko; Itagaki, Hiroyuki; Takahashi, Tetsuhiko; Shimizu, Kanichirou; Harada, Junta
2009-01-01
Because radial sampling imposes many limitations on magnetic resonance (MR) imaging hardware, such as on the accuracy of the gradient magnetic field or the homogeneity of B(0), some correction of the echo signal is usually needed before image reconstruction. In our previous study, we developed an echo-peak-shift correction (EPSC) algorithm not easily affected by hardware performance. However, some artifacts remained in lung imaging, where tissue is almost absent, or in cardiac imaging, which is affected by blood flow. In this study, we modified the EPSC algorithm to improve the image quality of the radial aquisition regime (RADAR) and expand its application sequences. We assumed the artifacts were mainly caused by errors in the phase map for EPSC and used a phantom on a 1.5-tesla (T) MR scanner to investigate whether to modify the EPSC algorithm. To evaluate the effectiveness of EPSC, we compared results from T(1)- and T(2)-weighted images of a volunteer's lung region using the current and modified EPSC. We then applied the modified EPSC to RADAR spin echo (SE) and RADAR balanced steady-state acquisition with rewound gradient echo (BASG) sequence. The modified EPSC reduced phase discontinuity in the reference data used for EPSC and improved visualization of blood vessels in the lungs. Motion and blood flow caused no visible artifacts in the resulting images in either RADAR SE or RADAR BASG sequence. Use of the modified EPSC eliminated artifacts caused by signal loss in the reference data for EPSC. In addition, the modified EPSC was applied to RADAR SE and RADAR BASG sequences.
Modified echo peak correction for radial acquisition regime (RADAR)
Takizawa, Masahiro; Ito, Taeko; Itagaki, Hiroyuki; Takahashi, Tetsuhiko; Shimizu, Kanichirou; Harada, Junta
2009-01-01
Because radial sampling imposes many limitations on magnetic resonance (MR) imaging hardware, such as on the accuracy of the gradient magnetic field or the homogeneity of B 0 , some correction of the echo signal is usually needed before image reconstruction. In our previous study, we developed an echo-peak-shift correction (EPSC) algorithm not easily affected by hardware performance. However, some artifacts remained in lung imaging, where tissue is almost absent, or in cardiac imaging, which is affected by blood flow. In this study, we modified the EPSC algorithm to improve the image quality of the radial acquisition regime (RADAR) and expand its application sequences. We assumed the artifacts were mainly caused by errors in the phase map for EPSC and used a phantom on a 1.5-tesla (T) MR scanner to investigate whether to modify the EPSC algorithm. To evaluate the effectiveness of EPSC, we compared results from T 1 -and T 2 -weighted images of a volunteer's lung region using the current and modified EPSC. We then applied the modified EPSC to RADAR spin echo (SE) and RADAR balanced steady-state acquisition with rewound gradient echo (BASG) sequence. The modified EPSC reduced phase discontinuity in the reference data used for EPSC and improved visualization of blood vessels in the lungs. Motion and blood flow caused no visible artifacts in the resulting images in either RADAR SE or RADAR BASG sequence. Use of the modified EPSC eliminated artifacts caused by signal loss in the reference data for EPSC. In addition, the modified EPSC was applied to RADAR SE and RADAR BASG sequences. (author)
Anthony G. Dixon
2017-10-01
Full Text Available The effective medium approach to radial fixed bed dispersion models, in which radial dispersion of mass is superimposed on axial plug flow, is based on a constant effective dispersion coefficient, DT. For packed beds of a small tube-to-particle diameter ratio (N, the experimentally-observed decrease in this parameter near the tube wall is accounted for by a lumped resistance located at the tube wall, the wall mass transfer coefficient km. This work presents validated computational fluid dynamics (CFD simulations to obtain detailed radial velocity and concentration profiles for eight different computer-generated packed tubes of spheres in the range 5.04 ≤ N ≤ 9.3 and over a range of flow rates 87 ≤ Re ≤ 870 where Re is based on superficial velocity and the particle diameter dp. Initial runs with pure air gave axial velocity profiles vz(r averaged over the length of the packing. Then, simulations with the tube wall coated with methane yielded radial concentration profiles. A model with only DT could not describe the radial concentration profiles. The two-parameter model with DT and km agreed better with the bed-center concentration profiles, but not with the sharp decreases in concentration close to the tube wall. A three-parameter model based on classical two-layer mixing length theory, with a wall-function for the decrease in transverse radial convective transport in the near-wall region, showed greatly improved ability to reproduce the near-wall concentration profiles.
Evidence for forcing-dependent steady states in a turbulent swirling flow.
Saint-Michel, B; Dubrulle, B; Marié, L; Ravelet, F; Daviaud, F
2013-12-06
We study the influence on steady turbulent states of the forcing in a von Karman flow, at constant impeller speed, or at constant torque. We find that the different forcing conditions change the nature of the stability of the steady states and reveal dynamical regimes that bear similarities to low-dimensional systems. We suggest that this forcing dependence may be applicable to other turbulent systems.
Hydrodynamic simulation of elliptic flow
Kolb, P F; Ruuskanen, P V; Heinz, Ulrich W
1999-01-01
We use a hydrodynamic model to study the space-time evolution transverse to the beam direction in ultrarelativistic heavy-ion collisions with nonzero impact parameters. We focus on the influence of early pressure on the development of radial and elliptic flow. We show that at high energies elliptic flow is generated only during the initial stages of the expansion while radial flow continues to grow until freeze-out. Quantitative comparisons with SPS data from semiperipheral Pb+Pb collisions suggest the applicability of hydrodynamical concepts already $\\approx$ 1 fm/c after impact.
WWER radial reflector modeling by diffusion codes
Petkov, P. T.; Mittag, S.
2005-01-01
The two commonly used approaches to describe the WWER radial reflectors in diffusion codes, by albedo on the core-reflector boundary and by a ring of diffusive assembly size nodes, are discussed. The advantages and disadvantages of the first approach are presented first, then the Koebke's equivalence theory is outlined and its implementation for the WWER radial reflectors is discussed. Results for the WWER-1000 reactor are presented. Then the boundary conditions on the outer reflector boundary are discussed. The possibility to divide the library into fuel assembly and reflector parts and to generate each library by a separate code package is discussed. Finally, the homogenization errors for rodded assemblies are presented and discussed (Author)
Oculoauriculovertebral spectrum with radial anomaly in child.
Taksande, Amar; Vilhekar, Krishna
2013-01-01
Oculoauriculovertebral spectrum (OAVS) or Goldenhar syndrome is a wide spectrum of congenital anomalies that involves structures arising from the first and second branchial arches. It is characterized by a wide spectrum of symptoms and physical features. These abnormalities mainly involve the cheekbones, jaws, mouth, ears, eyes, or vertebrae. Other conditions with ear and/or radial involvement, such as, the Nager syndrome, Holt-Oram syndrome, Radial-renal syndrome, facioauriculoradial dysplasia, Fanconi anemia, and Vertebral, Anal atresia, Cardiac, Trachea, Esophageal, Renal, and Limb (VACTERL) association should be considered for differential diagnosis. Here we report a child who had facial asymmetry, microsomia, microtia, congenital facial nerve palsy, conductive hearing loss, skin tags, iris coloboma, and preaxial polydactyly.
Oculoauriculovertebral spectrum with radial anomaly in child
Amar Taksande
2013-01-01
Full Text Available Oculoauriculovertebral spectrum (OAVS or Goldenhar syndrome is a wide spectrum of congenital anomalies that involves structures arising from the first and second branchial arches. It is characterized by a wide spectrum of symptoms and physical features. These abnormalities mainly involve the cheekbones, jaws, mouth, ears, eyes, or vertebrae. Other conditions with ear and/or radial involvement, such as, the Nager syndrome, Holt-Oram syndrome, Radial-renal syndrome, facioauriculoradial dysplasia, Fanconi anemia, and Vertebral, Anal atresia, Cardiac, Trachea, Esophageal, Renal, and Limb (VACTERL association should be considered for differential diagnosis. Here we report a child who had facial asymmetry, microsomia, microtia, congenital facial nerve palsy, conductive hearing loss, skin tags, iris coloboma, and preaxial polydactyly.
Linear radial pulsation theory. Lecture 5
Cox, A.N.
1983-01-01
We describe a method for getting an equilibrium stellar envelope model using as input the total mass, the envelope mass, the surface effective temperature, the total surface luminosity, and the composition of the envelope. Then wih the structure of the envelope model known, we present a method for obtaining the raidal pulsation periods and growth rates for low order modes. The large amplitude pulsations observed for the yellow and red giants and supergiants are always these radial models, but for the stars nearer the main sequence, as for all of our stars and for the white dwarfs, there frequently are nonradial modes occuring also. Application of linear theory radial pulsation theory is made to the giant star sigma Scuti variables, while the linear nonradial theory will be used for the B stars in later lectures
Douma, M.; Ligierko, G.; Angelov, I.
2008-10-01
The need for information has increased exponentially over the past decades. The current systems for constructing, exploring, classifying, organizing, and searching information face the growing challenge of enabling their users to operate efficiently and intuitively in knowledge-heavy environments. This paper presents SpicyNodes, an advanced user interface for difficult interaction contexts. It is based on an underlying structure known as a radial map, which allows users to manipulate and interact in a natural manner with entities called nodes. This technology overcomes certain limitations of existing solutions and solves the problem of browsing complex sets of linked information. SpicyNodes is also an organic system that projects users into a living space, stimulating exploratory behavior and fostering creative thought. Our interactive radial layout is used for educational purposes and has the potential for numerous other applications.
Bahadormanesh, Nikrouz; Rahat, Shayan; Yarali, Milad
2017-01-01
Highlights: • A multi-objective optimization for radial expander in Organic Rankine Cycles is implemented. • By using firefly algorithm, Pareto front based on the size of turbine and thermal efficiency is produced. • Tension and vibration constrains have a significant effect on optimum design points. - Abstract: Organic Rankine Cycles are viable energy conversion systems in sustainable energy systems due to their compatibility with low-temperature heat sources. In the present study, one dimensional model of radial expanders in conjunction with a thermodynamic model of organic Rankine cycles is prepared. After verification, by defining thermal efficiency of the cycle and size parameter of a radial turbine as the objective functions, a multi-objective optimization was conducted regarding tension and vibration constraints for 4 different organic working fluids (R22, R245fa, R236fa and N-Pentane). In addition to mass flow rate, evaporator temperature, maximum pressure of cycle and turbo-machinery design parameters are selected as the decision variables. Regarding Pareto fronts, by a little increase in size of radial expanders, it is feasible to reach high efficiency. Moreover, by assessing the distribution of decision variables, the variables that play a major role in trending between the objective functions are found. Effects of mechanical and vibration constrains on optimum decision variables are investigated. The results of optimization can be considered as an initial values for design of radial turbines for Organic Rankine Cycles.
Experimental study of the influence of flow passage subtle variation on mixed-flow pump performance
Bing, Hao; Cao, Shuliang
2014-05-01
In the mixed-flow pump design, the shape of the flow passage can directly affect the flow capacity and the internal flow, thus influencing hydraulic performance, cavitation performance and operation stability of the mixed-flow pump. However, there is currently a lack of experimental research on the influence mechanism. Therefore, in order to analyze the effects of subtle variations of the flow passage on the mixed-flow pump performance, the frustum cone surface of the end part of inlet contraction flow passage of the mixed-flow pump is processed into a cylindrical surface and a test rig is built to carry out the hydraulic performance experiment. In this experiment, parameters, such as the head, the efficiency, and the shaft power, are measured, and the pressure fluctuation and the noise signal are also collected. The research results suggest that after processing the inlet flow passage, the head of the mixed-flow pump significantly goes down; the best efficiency of the mixed-flow pump drops by approximately 1.5%, the efficiency decreases more significantly under the large flow rate; the shaft power slightly increases under the large flow rate, slightly decreases under the small flow rate. In addition, the pressure fluctuation amplitudes on both the impeller inlet and the diffuser outlet increase significantly with more drastic pressure fluctuations and significantly lower stability of the internal flow of the mixed-flow pump. At the same time, the noise dramatically increases. Overall speaking, the subtle variation of the inlet flow passage leads to a significant change of the mixed-flow pump performance, thus suggesting a special attention to the optimization of flow passage. This paper investigates the influence of the flow passage variation on the mixed-flow pump performance by experiment, which will benefit the optimal design of the flow passage of the mixed-flow pump.
Radial oxygen gradients over rat cortex arterioles
Galler, Michael
2011-01-01
Purpose: We present the results of the visualisation of radial oxygen gradients in rats’ cortices and their use in neurocritical management. Methods: PO2 maps of the cortex of 10 wistar rats were obtained with a camera (SensiMOD, PCO, Kehlheim, Germany). Those pictures were analyzed and edited by a custom-made software. We chose a vessel for examination. A matrix, designed to evaluate the cortical O2 partial pressure, was placed vertically to the artery and afterwards multiple regio...
Variational method for integrating radial gradient field
Legarda-Saenz, Ricardo; Brito-Loeza, Carlos; Rivera, Mariano; Espinosa-Romero, Arturo
2014-12-01
We propose a variational method for integrating information obtained from circular fringe pattern. The proposed method is a suitable choice for objects with radial symmetry. First, we analyze the information contained in the fringe pattern captured by the experimental setup and then move to formulate the problem of recovering the wavefront using techniques from calculus of variations. The performance of the method is demonstrated by numerical experiments with both synthetic and real data.
Moment approach to tandem mirror radial transport
Siebert, K.D.; Callen, J.D.
1986-02-01
A moment approach is proposed for the study of tandem mirror radial transport in the resonant plateau regime. The salient features of the method are described with reference to axisymmetric tokamak transport theory. In particular, the importance of momentum conservation to the establishment of the azimuthal variations in the electrostatic potential is demonstrated. Also, an ad hoc drift kinetic equation is solved to determine parallel viscosity coefficients which are required to close the moment system
Radial excitations in nucleon-nucleon scattering
Silvestre-Brac, B.; Carbonell, J.; Gignoux, C.
1986-01-01
In the non-relativistic constituent quark model, the role of the radial excitations of the nucleon is studied within a resonating group approach of the nucleon-nucleon scattering. It is shown that, rather than the inclusion of new channels, it is important to include mixed-symmetry spin-isospin components in the nucleon wave function. It is also found that during the collision there is no significant deformation of the nucleon. (orig.)
Learning Methods for Radial Basis Functions Networks
Neruda, Roman; Kudová, Petra
2005-01-01
Roč. 21, - (2005), s. 1131-1142 ISSN 0167-739X R&D Projects: GA ČR GP201/03/P163; GA ČR GA201/02/0428 Institutional research plan: CEZ:AV0Z10300504 Keywords : radial basis function networks * hybrid supervised learning * genetic algorithms * benchmarking Subject RIV: BA - General Mathematics Impact factor: 0.555, year: 2005
Hybrid Continuous-Flow Total Artificial Heart.
Fox, Carson; Chopski, Steven; Murad, Nohra; Allaire, Paul; Mentzer, Robert; Rossano, Joseph; Arabia, Francisco; Throckmorton, Amy
2018-05-01
Clinical studies using total artificial hearts (TAHs) have demonstrated that pediatric and adult patients derive quality-of-life benefits from this form of therapy. Two clinically-approved TAHs and other pumps under development, however, have design challenges and limitations, including thromboembolic events, neurologic impairment, infection risk due to large size and percutaneous drivelines, and lack of ambulation, to name a few. To address these limitations, we are developing a hybrid-design, continuous-flow, implantable or extracorporeal, magnetically-levitated TAH for pediatric and adult patients with heart failure. This TAH has only two moving parts: an axial impeller for the pulmonary circulation and a centrifugal impeller for the systemic circulation. This device will utilize the latest generation of magnetic bearing technology. Initial geometries were established using pump design equations, and computational modeling provided insight into pump performance. The designs were the basis for prototype manufacturing and hydraulic testing. The study results demonstrate that the TAH is capable of delivering target blood flow rates of 1-6.5 L/min with pressure rises of 1-92 mm Hg for the pulmonary circulation and 24-150 mm Hg for the systemic circulation at 1500-10 000 rpm. This initial design of the TAH was successful and serves as the foundation to continue its development as a novel, more compact, nonthrombogenic, and effective therapeutic alternative for infants, children, adolescents, and adults with heart failure. © 2018 International Center for Artificial Organs and Transplantation and Wiley Periodicals, Inc.