| The aero-engines are developing in the direction of high efficiency,low fuel consumption and high thrust-to-weight ratio.Compressors,as the core components of aero-engines,need to work under high efficiency,high pressure ratio and high stability conditions.The presence of the tip clearance of the compressor can cause severe tip leakage flow.A large number of studies have shown that the loss in the compressor is mainly caused by the loss of the tip leakage.How to properly regulate the flow of the tip clearance and improve the stability and aerodynamic performance of the aero-engine has always attracted the attention of the academic community.In recent years,the tip winglet has also received extensive attention as a passive control of the gap flow mode.The in-depth study of the effect and mechanism of the application of the tip winglet in the compressor can lay a foundation for the development of the path of controlling the gap flow.Firstly,the numerical analysis of the tip winglets of the transonic fan rotor NASA Rotor 67 with different installation methods(pressure face winglet and suction face winglet)under different working conditions is carried out,and the aerodynamic characteristics are analyzed.It is shown that the four-width pressure face tip winglets increase the flow stability margin of the transonic fan rotor by 28.5%,33.9%,51.1%,and 56.9%,respectively.After the leakage vortex and shock of the transonic fan rotor,the tip leakage vortex is not broken,and the vortex/wave interference is the main cause of instability.The pressure surface winglet reduces the tip leakage vortex strength of the fan rotor,weakens the strength of the leakage vortex and the shock wave interference,and reduces the area of the fluid blocking zone formed by the tip shock/leak vortex interference,thereby improving the fan rotor.The flow capacity of the tip of the blade increases the flow stability margin of the fan rotor.Then,under the condition of variable clearance(0.25%chord of small gap,1.1%chord of design gap,2.25%chord of large gap),the larger the gap,the stronger the leakage strength.In the case of small clearance,the stall of the transonic fan rotor is mainly Due to the vortex/wave interference and the separation of the boundary layer with the larger suction side of the rotor,the pressure surface winglet increases the flow stability margin by 32.9%,and the total pressure ratio and the highest isentropic efficiency are slightly decreased.In the small clearance condition,the mechanism expansion is mainly to weaken the vortex/wave interference,and the tip winglet has little influence on the boundary layer separation of the fan rotor suction surface.In the case of large clearance conditions,the pressure surface winglet increases the flow stability margin by 47.7%,and the total pressure ratio and the highest isentropic efficiency of the fan rotor are reduced.Under the large clearance condition,the principle of the expansion of the tip of the pressure tip is similar to that of the design,that is,by weakening the vortex/wave interference intensity.The larger the tip clearance,the more obvious the effect of the tip of the pressure tip on the vortex/wave interference.Finally,under the condition of variable working condition(100%design speed,80%design speed,60%design speed),the aerodynamic characteristics of the wing tip with/without tip are studied.The research shows that at 100%speed and 80%speed,The leakage vortex is not broken,and the cause of the stall of the fan rotor is mainly due to the interference of the shock wave tip tip region of the fan rotor and the tip leakage vortex,so that the low energy fluid formed by the vortex/interference blocks the flow in the fan rotor passage.At 60%of the rotational speed,the leakage vortex breaks,and the reason for inducing the stall of the transonic fan rotor is that the leakage vortex overflows from the leading edge of the adjacent blade.At 100%speed and 80%speed,the tip wing reduces the intensity of the shock and leakage vortex interference,reducing the low Mach number area after the shock and leakage vortex interference,making the flow in the channel smoother.At 60%of the rotational speed,the expansion of the tip of the pressure surface tip is due to not only weakening the vortex/wave interference strength but also reducing the three-dimensional separation of the tip. |
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