Study On Tip Clearance Flow Of Transonic Compressor Rotor

The stable operation of the aero-engine compressor has significant effect on the engine overall performance.Unstable phenomena,such as compressor surge and stall,reduce engine useful life and furthermore cause severe damage,which is one of the most dangerous failure of the engine.Casing treatment is a technology of simple configuration,easy to manufacture and obvious improvement of the compressor stability,which has been widely employed in the aeroengine compressor.In this paper,circumferential casing treatments of three different groove numbers have been designed based on Stage35 axial flow transonic compressor and according to previous related research.By means of numerical simulation,the consistency between the computational prediction and test results has been verified through steady-state calculations of various compressor working condition.The mechanism of the interaction between leakage flow and shock wave has been analyzed in comparison of the datum and circumferential casing treatment.In addition,the influence of the break-up of the leakage vortex on the stability of the compressor has been discussed.The main reason for the casing treatment on the expansion of the compressor stability margin has been investigated.The following conclusions are obtained through numerical simulation,the main reason of the stall of the transonic axial flow compressor is the blade tip stall.Due to the break-up of the tip leakage vortex and the boundary layer separation adjacent to the trailing edge of the blade,the blockage of the cascade passage by the low-velocity flow zone is the direct origin inducing blade tip stall.The structure of the circumferential groove is able to suck and blow the lowvelocity flow in the tip flow duct,which decreases and eliminates the blockage area from the break up of the leakage vortex.The boundary layer separation has been suppressed and the flow capacity of the blade tip passage has been enhanced.The possibility of the stall is decreased to widen the stability margin of the flow field of the compressor rotor tip.The stable operating region of the single-stage Stage35 has been effectively expanded by the introduction of the circumferential groove casing treatment.Among the applied circumferential groove configurations,the effect of the stability expansion has been gradually reinforced as the increase of the number of the groove.The circumferential groove closest to the blade leading edge plays the most important role in terms of the reduction of the area of the low-velocity zone and the improvement of the ability of the interaction between the flow inside the groove and the main flow.