Research On Boundary Layer Suction Mechanism And Influence Effect Of Axial Flow Compressor

The modern high-performance aero-engine makes greater demands of compressor,and high efficiency?high stage pressure ratio?wide stable working range are the goals of future axial compressor.In axial compressors,the complex flow phenomena,such as the boundary layer separation flows of blade surface?tip leakage flows of rotor and corner separation flows of stator,have great influence on the efficiency and working stability of the compressors,and limit the improvement of stage pressure ratio.As a new type of flow control technology,the boundary layer suction technology can effectively control the compressor internal flows and improve the compressor load.Therefore,a deep study of boundary layer suction technology is very important to improve the compressor's performance and working stability.The following research works for boundary layer suction technology are conducted in this paper:1.The experimental research of two aspirated cascades of different loading types was conducted.The study shows that for both loading types,boundary layer suction can effectively decrease profile loss and improve the cascade performance on the design conditions;as for off-design conditions,boundary layer suction also improves the cascade performance in varying degrees.For various conditions,as the suction flow rate increases,the width and depth of the wake curve decrease continuously,and moves closer to the blade trailing edge,which implies a weaker separation and a larger flow turning angle.2.Suction surface suction scheme and combined suction scheme were investigated respectively on the experimental cascade,in which there exist both suction surface flow separation and corner separation.The effects of various suction slot size?location and suction flow rate on the performance and flow field of this cascade were studied systematically,and the various internal flow mechanisms of different suction schemes were revealed.The research results show that for part-span suction on blade suction surface,the front suction slot obviously improves the flow field of middle section,however worsens the flow field in the end wall region.For all-span suction on blade suction surface,all the suction schemes can improve the flows along the whole blade height;different suction flow rates correspond to different best suction locations.For various combined suction schemes,the end wall suction slot of the best combined suction scheme in this paper locates near the blade suction surface and behind the intersection position between the suction branch of passage horse vortex and the blade suction surface.3.The end wall boundary layer suction on a counter-rotating compressor in stage environment was investigated.Through the independent shroud casing suction of the front rotor(R1)and rear rotor(R2)and combined shroud casing suction of them,the influences of suction location and suction flow rate on the performance?flow field?stable working range and flow instability mechanisms of the compressor were studied in detail.The research results show that R1 shroud casing suction greatly weakens the strength of the R1 tip leakage flow and improves inlet flow condition of the R2 tip region.R2 shroud casing suction makes the R1 blade loading decrease and the intensity of R2 tip leakage flow is weakened significantly.Combine suction is the superposition of the dependent suctions.For various suction schemes,the stable working range and flow instability mechanisms of the compressor are different.4.The end wall boundary layer suction on a transonic compressor in stage environment was investigated.Through shroud casing suction of rotor,the influences of suction location and suction flow rate on the performance?flow field?stable working range and flow instability mechanisms of the compressor were researched in detail.The study results show that suction can effectively control rotor tip leakage vortex and thereby improve inlet flow condition of downstream stator tip region.Through effectively controlling rotor tip leakage flow,suction broadens the stable working range of compressor and changes the flow instability mechanism.Then taking the rotor as research object,the shroud casing suction was further studied to explore its effectiveness of improving the performance and widening the stable working range with inlet circumferential total pressure distortion.The research results show that under inlet distortion condition,suction can also control tip leakage vortex well,improve the rotor performance,widen its stable working range,and alter the flow instability mechanism.5.The design method of high pressure ratio aspirated compressor was investigated.In order to achieve the design goal of high stage pressure ratio and high efficiency and meanwhile avoid the structural strengthen problems caused by boundary layer suction in the rotating parts,the pressed down ?S? shape shroud casing line was adopted to control the rotor tip leakage flow,and the three-dimensionally aerodynamic optimization was conducted to improve the inner shock wave structure and flow field quality in the rotor;while boundary layer suction was only used in the stator,and meanwhile the stator airfoil was designed by aspirated inverse design to improve the stator performance.Based on this design method,an aspirated compressor which achieves a total pressure ratio of 3.21 and an isentropic efficiency of 87.5% was designed using only 1.5% suction flow rate.