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pressure recovery characteristics for a dilute gas-particle suspension flowing vertically downward in a pipe with a sudden expansion: A two-fluid modeling approach

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Particuology 2020年第3期18卷 100-111页

作者： Santosh Kumar Senapati Sukanta Kumar Dash Department of Mechanical Engineering Indian Institute of Technology KharagpurWest Bengal 721302India

This work applies the Eulerian-Eulerian model in conjunction with the kinetic theory of granular flow and inter-particle collisions to study the characteristics of pressure recovery for a dilute gas-particle suspension flowing through a pipe with a sudden expansion at a relatively higher solid *** do so,the numerical procedure was validated against experimental results for relatively small dilute phase flows in a pipe with a sudden expansion;a satisfactory agreement was ***,the effect of the two significant numerical parameters namely,the speculairty coefficient and the coefficient of restitution for particle-particle collisions were investigated and then,for fixed combinations of these parameters the effect of particle-phase volume fraction,particle density,particle size,and inlet slip ratio were *** was concluded that pressure recovery diminishes as the speculairty coefficient increases and the particle-particle coefficient of restitution *** recovery was found to increase with increasing solid volume fraction for coarse particles whereas,for fine particles,a critical volume fraction is obtained above which pressure recovery *** increase in slip ratio is found to diminish pressure ***,at relatively higher solid volume fractions,a critical diameter was found,above and below which pressure recovery decreases.

关键词： Gas-solid flow Sudden expansion pipe Eulerian-Eulerian model pressure recovery Vertically downward flow

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Microjet flow control in an ultra-compact serpentine inlet

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Chinese Journal of Aeronautics 2015年第5期28卷 1381-1390页

作者： Da Xingya Fan Zhaolin Fan Jianchao Zeng Liquan Rui Wei Zhou Run State Key Laboratory of Aerodynamics China Aerodynamics Research and Development Center High Speed Aerodynamics Institute China Aerodynamics Research and Development Center China Aerodynamics Research and Development Center

Microjets are used to control the internal flow to improve the performance of an ultra-compact serpentine inlet. A highly offset serpentine inlet with length-to-diameter ratio of 2.5 is designed and static tests are conducted to analyze the internal flow characteristics in terms of pressure recovery, distortion and flow separation. Flow separation is encountered in the second S-turn, and two strong counter-rotating vortices are formed at the aerodynamic interthce plane （AIP） face which occupy a quarter of the outlet area and result in severe pressure loss and distortion. A flow control model employing a row of microjets in the second turn is designed based on the internal flow characteristics and simplified CFD simulations. Flow control tests are conducted to verify the control effectiveness and understand the characteristics as a function of inlet throat Mach number, injection mass flow ratio, jet Mach number and momentum coefficient. At all test Mach numbers, microjet flow control （MFC） effectively improves the recovery and reduces the distortion intensity. Between inlet throat Mach number 0.2 and 0.5, the strong flow separation in the second S-turn is suppressed at an optimum jet flow ratio of less than 0.65%, resulting in a maximum improvement of 4% for pressure recovery coefficient and a maximum decrease of 75% for circumferential distortion intensity at cruise. However, in order to suppress the flow separation, the injection rate should retain in an effective range. When the injection rate is higher than this range, the flow is degraded and the distortion contour is changed from 90° circumferential distortion pattern to 180° circumferential distortion pattern. Detailed data analysis shows that this optimum flow ratio depends on inlet throat Mach number and the monlcntunl coefficient affects the control effectiveness in a dual stepping manner.

关键词： Active flow control Distortion intensity:Micro jet pressure recovery Serpentine inlet

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Gas-solid flow in a diffuser:Effect of inter-particle and particle-wall collisions

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Particuology 2021年第4期19卷 187-200页

作者： Santosh Kumar Senapati Sukanta K.Dash CFD Laboratory Department of Mechanical EngineeringIndian Institute of Technology KharagpurWest Bengal721302India

This article investigates the role of the specularity coefficient(φ,the extent of the energy dissipation due to particle-wall collisions),inter-particle restitution coefficient(e_(pp),the extent of the energy dissipation due to inter-particle collisions),and four combinations of these variables on the hydrodynamics,and the pressure recovery of the dilute gas-solid suspension in a *** investigation applies the two-fluid modeling approach along with the kinetic theory of the granular *** present investigation’s findings indicate that an increase inφor a reduction in e_(pp) reduces the pressure recovery by weakening the reverse momentum transfer phenomenon,which is recognized as the primary means for the pressure ***,in a gas-solid flow system,a higherφor smaller e_(pp) enhances the particles’trapping in the recirculation *** recirculation zone’s strength and size increase asφincreases or e_(pp) ***,an increase in the wall-particle and inter-particle interactions strengthens the sidewise displacement of the *** effect of the wall-particle and inter-particle interactions are insignificant for extremely small solid loading.

关键词： Gas-solid flow Diffuser Particle-wall collision Inter-particle collision pressure recovery Reattachment length

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Effect of the second-throat on the performance of supersonic-supersonic ejectors

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Science China(Technological Sciences) 2012年第9期55卷 2530-2537页

作者： CHEN Jian WANG ZhenGuo WU JiPing XU WanWu Science and Technology on Scramjet Laboratory National University of Defense TechnologyChangsha 410073China

The pressure matching and recovery performances of the second-throat supersonic-supersonic ejector have been performed experimentally and numerically in the current *** pictures of flow structure in former part of the mixing chamber with varied stagnation pressure ratio of the primary and secondary flows have been taken,and the maximum compression ratios have been ***,the relevant numerical simulations have been *** obtained results show that the pressure matching performance of the second-throat supersonic-supersonic ejector is weaker than that of the constant area one,and the pressure recovery performance of the former is better than that of the *** the ejectors tested in this paper,the stagnation pressure ratios of the second-throat supersonic-supersonic ejector at the limiting condition are approximately 10% lower than those of the constant area one when the contraction angle of the mixing chamber is 4°,and the maximum compression ratio is 12%-30% *** the contraction angle of the mixing chamber is 6°,the pressure matching performance of the second-throat supersonic-supersonic ejector declines sharply,and the pressure recovery performance remains almost the *** the contraction angle of the mixing chamber is 8°,the supersonic-supersonic ejection phenomenon does not take place any longer.

关键词： ejector second-throat pressure matching pressure recovery

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Blockage and distortion effects on a vane-island type diffuser performance of centrifugal pumps for various flow rates

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排灌机械工程学报 2016年第12期34卷 1013-1021页

作者： SI Qiaorui DAZIN Antoine DUPONT Patrick ROUSSETTE Olivier BOIS Gérard National Research Center of Pumps Jiangsu University Laboratoire de Mécanique de Lille (UMR CNRS 8107) Arts et Métiers ParisTech Laboratoire de Mécanique de Lille(UMR CNRS 8107) Ecole Centrale de Lille

Experimental investigation of mean flow velocity and pressure inside the vane-island type diffuser passage of a test centrifugal pump model is presented.A directional three-hole probe was used to investigate hub-to-shroud flow properties at diffuser leading and trailing edge *** addition,the mid-section between suction and pressure sides along the diffuser passage was also *** these measurements were performed at five different flow *** flow structures at the inlet section of the diffuser and along with the passage were analyzed in detail,with a focus on the flow distribution and the pressure recovery evolution of different diffuser *** and distortion effects were analyzed by using existing published particle image velocimetry(PIV)measurements in the outer part of the impeller and around the diffuser throat in order to get a better understanding of the overall performances and local flow structures of such a diffuser *** results show that back flows occur on the shroud region from impeller exit plane up to the semi-vaneless part of the diffuser at low flow *** blockage effects combining with blade thickness geometrical blockage tend to diminish the effects of theoretical high positive *** high flow rates,negative incidence effects induce high local velocity on the pressure side of the diffuser just after the *** aerodynamic blockage associated with low flow distortions are found to have a beneficial effect on pressure recovery for low flow *** the contrary,high flow distortions are found for increased flow rates,resulting in a low pressure recovery inside the semi-vane less part of the diffuser and after the throat.

关键词： vane island diffuser flow structure pressure recovery three-hole probe particle image velocimetry

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