Endwall Flow Separation And Stall Control Strategies In Axial Compressor

There is boundary layer separation in the axial compressor because of the viscosity of the fluid,and the pressure ratio on the compressor of modern aero engine are much more high,so the flow separation in the compressor are much more common.The separation in the endwall can cause lots of problems,such as reduce the stable operating range of the compressor,harm the safety of the engine,increase loss,low down compressor efficiency.Casing treatment(CT)is an effective and simple structured passive methodthat canextend the stability range of the compressor,it is widely used.But there still lack understand of the mechanism of the CT,and many of the design of it rely on experiment.BBEW(Blended blade and endwall)is a new technology that can depress the endwall separation,and there is not much research about it.It will help to understanding the mechanism of the BBEW depress the separation flow in the endwall and optimize the compressor efficiency,if the effect of the rounding radius on the flow separation and loss of the endwall is known.And some guidelines enhance the compressor performance can be provided by using this technology.Under the support of China National Natural Science Fund and in order to understanding the flow separation in the endwall of the compressor and take some related control measures to handle it,this dissertation is carried out according to the following aspects:1.Numerical studied the stall process of a subsonic rotor,first the stall margin improvement effect of different slot CTs are compared,the effect of the CTs on the rotor tip leakage flow is analyzed,the RBACT use the pressure gradient of the rotor tip,so the injection flow of the RBACT can encourage the tip leakage flow,the RBACT can have a larger SMI,but it reduced the rotor efficiency a little.The momentum analyze of the rotor tip region show that the CT slow down the increase of the momentum that perpendicular to the chord,increased the momentum ration of the rotor.2.The mechanisms of the interaction of the inlet guide vane and the CT were experimentally done on a certain high subsonic single-rotor axial compressor test bench at 54%design speed of Northwestern Ploytechnical University.The experimental results show that the SMI of the rotor increase as the inlet guide vaneangle increase,but the total pressure ratio of 80%?90% blade high decrease.The rotor get a better SMI when the BACT applied as the inlet guide vane angle change.The SMI of the rotor increased 2.09% when use inlet guide vane on the basis of BACT,as to RBACT the SMI of the rotor increased 13.95%.3.The stall process of Rotor 67 is Numerical researched,then the SMI of different axial position CTs are compared result show that the effect of CT?50 is the best.The rotor tip flow analysis show that the shock wave move downstream,the angle between the track of tip leakage flow and the chord is decreased,the low speed flow aeradecreased and move downstream,the mass and the speed of the tip leakage flow changed,the intensity of the tip leakage flow weakened.The momentum analyze of the rotor tip region show that CT?50 slow down the increase of the momentum that perpendicular to the chord,increased the momentum ration of the rotor.At last sloped slotted casing treatment with different axial angle are researched,results show that CT2 get the best SMI but with the cost of reduce efficiency.The shock wave move downstream,the axial momentum of the injection from CT2 is much larger,so it inspired the tip leakage flow much,depressed the produce of the low speed flow.Because it use the pressure difference of the rotor tip,consume the energy added to the fluid,so it low down the efficiency of the rotor.4.The numerical method is confirmed by the experimental results of a high loaded cascade,then the numerical research are carried out on the cascade which use BBEW technology.The flow at the endwall and the stall characteristics of the cascade with different leading edge rounding radius,corner rounding radius,and they combination are compared to confirm the effect of the BBEW technology.The endwall flow,area of the low speed flow,the pressure gradient at the endwall,total pressure loss at different radius,the pressure rise of the cascade etc are compared and analyzed,in order to expound the mechanism of the rules of dihedral delay the stall at the corner.Research show that FS5 delay the stall of the cascade and the attack angle is much larger when the cascade in stall.