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Numerical investigation on the mechanism of impeller hub corner separation flow and induced energy loss in the bulb tubular pump

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Journal of Hydrodynamics 2023年第2期35卷 252-267页

作者： Long-yue Sun Qiang Pan De-sheng Zhang Rui-jie Zhao B.P.M.(Bart)van Esch Research Center of Fluid Machinery Engineering and Technology Jiangsu UniversityZhenjiang212013China Wenling Fluid Machinery Technology Institute of Jiangsu University Wenling317525China Department of Mechanical Engineering Eindhoven University of TechnologyEindhovenThe Netherlands Shimge Pump Industry(Zhejiang)Co. Ltd.Wenling317525China

Impeller hub corner separation flow(IHCS)has a significant influence on energy conversion of the bulb tubular pump,and its unsteady characteristics are investigated with CFD-based method.The generation mechanism and power loss characteristics of IHCS are investigated by the entropy production method and pressure fluctuation analysis.The main cause can be attributed to the large transverse pressure gradient near the hub at the trailing edge of the impeller,which is aggravated by the circumferential movement trend and the diffuser reverse flow,while the IHCS is significantly weakened with increased flow rate.The undesirable flow behavior is more likely to cause a significant increase in energy loss near the hub region compared to that in the rim region.The relative vortex stretching induced by the velocity gradient is the main cause of the horn-like vortex(HLV),and its intensity and resulting energy loss tend to decrease along the vortex trajectory.The HLV changes the dominant frequency of the pressure fluctuations in the nearby flow field,the value of which increases from 1fr(the blade passing frequency)to 2fr with increased amplitude,mainly due to the lower pressure regions on the impeller suction surface(SS)and HLV vortex core.Due to the effect of rotor-stator interaction(RSI),the HLVs generated between two adjacent impeller blades are cut into several sections by the diffuser vanes and propagate and dissipate along the mainstream direction.

关键词： Bulb tubular pump corner separation entropy production pressure fluctuation visualization analysis

Numerical Study of Dual Sweeping Jet Actuators for corner separation Control in Compressor Cascade

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Journal of Thermal Science 2021年第1期30卷 201-209页

作者： MENG Qinghe DU Xin CHEN Shaowen WANG Songtao School of Energy Science and Engineering Harbin Institute of TechnologyHarbin 150001China

Unsteady behaviors are important issues in flow control of turbomachinery.Pulsed excitation or suction is widely investigated in compressor cascades.This paper presents a discussion on the unsteady flow control realized by dual sweeping jet actuator(SJA)located on the blade suction surface.The unsteady numerical simulations were utilized to study the effect of applying dual SJAs on controlling the corner separation.With the numerical results,the following conclusions could be drawn with current compressor cascade.A maximum total pressure loss coefficient reduction of 6.8%was obtained.The analysis of the flow field pointed out that the regulation mechanisms of the corner separation were different with each SJA.The SJA ahead achieved an interruption of the suction side boundary layer development and the rear SJA enhanced the interaction and entrainment between the excitation stream and the secondary flows.Meanwhile,the different unsteadiness structures of the flow field frequency spectrum compared with single SJA cases were identified.The first peak frequency corresponded to the difference of the two SJAs and the rest frequencies could be regulated to a base frequency and its harmonic frequencies.

关键词： sweeping jet actuator compressor cascade active flow control corner separation

Parameter study on numerical simulation of corner separation in LMFA-NACA65 linear compressor cascade

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Chinese Journal of Aeronautics 2017年第1期30卷 15-30页

作者： Gao Feng Ma Wei Sun Jinjing Jérome Boudet Xavier Ottavy Liu Yangwei Lu Lipeng Shao Liang National Key Laboratory of Science and Technology on Aero-Engine Aero-thermodynamics School of Energy and Power Engineering Beihang University Beijing 100191 China Department of Mechanical Engineering Sciences University of Surrey Guildford GU2 7XH UK School of Aeronautics and Astronautics Shanghai Jiao Tong University Shanghai 200240 China Laboratoire de Mecanique des Fluides et d'Acoustique Ecole Centrale de Lyon Ecully 69134 France

Large-eddy simulation（LES） is compared with experiment and Reynolds-averaged Navier-Stokes（RANS）, and LES is shown to be superior to RANS in reproducing corner separation in the LMFA-NACA65 linear compressor cascade, in terms of surface limiting streamlines,blade pressure coefficient, total pressure losses and blade suction side boundary layer profiles. However, LES is too expensive to conduct an influencing parameter study of the corner separation.RANS approach, despite over-predicting the corner separation, gives reasonable descriptions of the corner separated flow, and is thus selected to conduct a parametric study in this paper. Two kinds of influencing parameters on corner separation, numerical and physical parameters, are analyzed and discussed： second order spatial scheme is necessary for a RANS simulation; incidence angle and inflow boundary layer thickness are found to show the most significant influences on the corner separation among the parameters studied; unsteady RANS with the imposed inflow unsteadiness（inflow angle varying sinusoidally with fluctuating amplitude of 0.92°） does not show any non-linear effect on the corner separation.

关键词： corner separation Influencing parameter LES Linear compressor cascade RANS

Numerical study of corner separation in a linear compressor cascade using various turbulence models

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Chinese Journal of Aeronautics 2016年第3期29卷 639-652页

作者： Liu Yangwei Yan Hao Liu Yingjie Lu Lipeng Li Qiushi Collaborative Innovation Center of Advanced Aero-Engine Beihang UniversityBeijing 100083China National Key Laboratory of Science and Technology on Aero-Engine Aero-ThermodynamicsSchool of Energy and Power EngineeringBeihang University

Three-dimensional corner separation is a common phenomenon that significantly affects compressor performance. Turbulence model is still a weakness for RANS method on predicting corner separation flow accurately. In the present study, numerical study of corner separation in a linear highly loaded prescribed velocity distribution （PVD） compressor cascade has been investigated using seven frequently used turbulence models. The seven turbulence models include Spalart Allmaras model, standard k-e model, realizable k-e model, standard k-to model, shear stress transport k co model, v2-fmodel and Reynolds stress model. The results of these turbulence models have been compared and analyzed in detail with available experimental data. It is found the standard k-1： model, realizable k-e model, v2-f model and Reynolds stress model can provide reasonable results for predicting three dimensional corner separation in the compressor cascade. The Spalart-Allmaras model, standard k-to model and shear stress transport k-w model overesti- mate corner separation region at incidence of 0°. The turbulence characteristics are discussed and turbulence anisotropy is observed to be stronger in the corner separating region.

关键词： Compressor cascade corner separation Turbomachinery CFD Turbulence anisotropy Turbulence models

Effects of Plasma Aerodynamic Actuation on corner separation in a Highly Loaded Compressor Cascade

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Plasma Science and Technology 2014年第3期16卷 244-250页

作者：王学德赵小虎李应红吴云赵勤 Science and Technology on Plasma Dynamics Laboratory Air Force Engineering University

This paper reports experimental results on the effects of plasma aerodynamic actua- tion （PAA） on corner separation control in a highly loaded, low speed, linear compressor cascade. Total pressure loss coefficient distribution was adopted to evaluate the corner separation control effect in wind tunnel experiments. Results of pressure measurements and particle image velocime- try （PIV） show that the control effect of pitch-wise PAA on the endwall is much better than that of stream-wise PAA on the suction surface. When both the pitch-wise PAA on the endwall and stream-wise PAA on the suction surface are turned on simultaneously, the control effect is the best among all three PAA types. The mechanisms of nanosecond discharge and microsecond discharge PAA are different in corner separation control. The control effect of microsecond discharge PAA turns out better with the increase of discharge voltage and duty cycle. Compared with microsec- ond discharge PAA, nanosecond discharge PAA is more effective in preventing corner separation when the freestream velocity increases. Frequency is one of the most important parameters in plasma flow control. The optimum excitation frequency of microsecond discharge PAA is 500 Hz, which is different from the frequency corresponding to the case with a Strouhal number of unity.

关键词： plasma aerodynamic actuation corner separation compressor cascade

Topological analysis of plasma flow control on corner separation in a highly loaded compressor cascade

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Acta Mechanica Sinica 2012年第5期28卷 1277-1286页

作者： Xiao-Hu Zhao Yun Wu Ying-Hong Li Xue-De Wang Qin Zhao Science and Technology on Plasma Dynamics Laboratory Air Force Engineering University

In this paper, flow behavior and topology structure in a highly loaded compressor cascade with and without plasma aerodynamic actuation （PAA） are investigated. Streamline pattern, total pressure loss coefficient, outlet flow angle and topological analysis are considered to study the effect and mechanism of the plasma flow control on corner separation. Results presented include the boundary layer flow behavior, effects of three types of PAA on separated flows and performance parameters, topology structures and sequences of singular points with and without PAA. Two separation lines, reversed flow and backflow exist on the suction surface. The cross flow on the endwall is an important element for the comer separation. PAA can reduce the undertuming and overturning as well as the total pressure loss, leading to an overall increase of flow turning and enhancement of aerodynamic performance. PAA can change the topology structure, sequences of singular points and their corresponding separation lines. Types II and III PAA are much more efficient in controlling comer separation and enhancing aerodynamic performances than type I.

关键词： Plasma aerodynamic actuation - Compressor Cascade Topology structure corner separation

Influence of Endwall Air Injection with Discrete Holes on corner separation of a Compressor Cascade

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Journal of Thermal Science 2021年第5期30卷 1684-1704页

作者： CAO Zhiyuan GAO Xi ZHANG Xiang ZHANG Fei LIU Bo School of Power and Energy Northwestern Polytechnical UniversityXi’an710072China

The aim of this study is to reveal the influence mechanism of endwall air injection with distributed holes on the corner separation of a highly loaded compressor cascade,so as to promote the application of injection in aero-engines.Single-hole and double-hole endwall injection schemes featuring different axial locations,pitchwise locations,injection mass rates and injection directions,were designed and investigated.Results showed that the corner separation was eliminated by endwall injection;the optimal single-hole injection scheme achieved an endwall loss coefficient reduction of 29.7%,with injection coefficient as low as 0.48%.The optimal axial location of single-hole endwall injection was at 82%axial chord,being the center of corner separation.However,as injection hole was located at upstream of it,endwall injection resulted in severer corner separation.The mid-span flow field was deteriorated after endwall injection,which was due to 3D flow effects,i.e.,AVDR(axial velocity density ratio)effect and low-momentum fluid spanwise migration effect.The optimal injection was achieved at low injection angle and from close to the suction surface on pitchwise.Double-hole injection exhibited inferior performance compared with single-hole,which was due to the interaction of the two injection streams and mixing of injection streams with the bulk stream.

关键词： compressor cascade corner separation flow control air injection endwall discrete hole injection

Influence of sub boundary layer vortex generator height and attack angle on cross-flows in the hub region of compressors

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Chinese Journal of Aeronautics 2022年第8期35卷 30-44页

作者： Hao FU Ling ZHOU Lucheng JI School of Aerospace Engineering Beijing Institute of TechnologyBeijing 100081China Institute for Aero Engine Tsinghua UniversityBeijing 100084China

It has been recently shown that Sub Boundary layer Vortex Generator(SBVG,abbreviated as VG hereafter)can suppress the Cross-Flow(CF),and therefore,can eliminate corner separation and increase aerodynamic loading when installed on the end wall inside middle-load compressor passages.However,when VGs are applied in high-load compressors,it is difficult to achieve ideal results.This is because the definition of the VG attack angle in the presence of CF in existing research is confusing,and the stronger CF in high-load compressors worsens the problem and results in an improper design and optimization range of VG attack angle.Therefore,this paper clarifies the definition of the VG attack angle in the presence of CF and reveals the CF controlling mechanism of VG on a flat plate.The differences in the flow phenomena around a VG both with and without CF are also studied.The numerical results show that a larger height or attack angle of the VG generates a greater CF suppression effect.However,the cross velocity increases when surmounting the primary vortex induced by the VG,except that this enhanced CF is less conspicuous for larger VG heights.Compared to the cases without CF,the VG suffers an additional loss because of the stronger separation and primary vortex loss caused by the CF.

关键词： Compressors corner separation Cross-flow Flat plate Vortex generator

Comparison of Flow Mechanism of Blade Sweep between a Transonic Single Rotor and a Rotor in Stage Environment

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Journal of Thermal Science 2022年第5期31卷 1804-1819页

作者： CAO Zhiyuan GAO Xi LIANG Yuyuan HUANG Ping LEI Peng LIU Bo School of Power and Energy Northwestern Polytechnical UniversityXi’an710072China AECC Sichuan Gas Turbine Research Establishment Chengdu610599China

In order to reveal the different effect mechanisms of blade sweep on the aerodynamic performance when a transonic rotor operates alone or in fan stage environment,two series of forward and backward swept rotors were designed and utilized in the first stage of the dual-stage NASA CR-120859 fan.Results show that,the influence of sweep on the single rotor and the whole stage is different,indicating swept designs for rotor alone may not be suitable for the stage operations.The distinct effect of sweep is account for the difference of the flow field characteristic and stall mechanism of the single rotor and the rotor in the stage environment.The single rotor is tip limited and its stall mechanism is shock/tip leakage vortex(TLV)interaction,whereas the fan stage is hub limited and its stall mechanism is the severe corner separation at stage hub region.For the single rotor,forward sweep increases the stall margin(SM)for all sweep schemes,while backward sweep reduces it in general.For the fan stage,however,backward swept rotor significantly increases stall margin and the stall mechanism is changed to shock/TLV interaction.On the contrary,forward sweep reduces stall margin in general.The flow mechanism is that forward sweep reduces blade loading at tip region near leading edge(LE)and causes the shock to move downstream.Both the variations improve flow field at tip region,while backward sweep exerts an opposite effect.At hub region,backward sweep reduces radial flow tendency by varying radial pressure gradient,causing reduction of corner separation at rotor hub,while forward sweep enhances corner separation.Moreover,with increasing of swept height and swept angle,the chock mass flow,peak efficiency and total pressure ratio of forward sweep are reduced in general,while an opposite effect can be found for backward sweep.

关键词： sweep tip leakage flow shock corner separation transonic fan