Numerical Study Of The Effect Of Casing Treatment On Compressor Tip Clearance Flow

The loss of compressor tip clearance flow cannot be ignored and effective approaches should be applied to reduce the unfavorable influences of the low-energy leakage flow micelle.By installing casing treatment to improve the overall performance of the compressor is the focus of many scholars in the study of aerodynamic research field.Casing treatment,a simple and effective means of passive control,which can improve the stability of the compressor stall margin,has been widely used in the field of gas turbine.This paper takes NASA Rotor 37 transonic compressor rotor as the calculated datum model.In order to improve compressor stability,a commercial CFD software was used to conduct numerical predictions.Three-dimensional time-averaged steady-state Navier-Stokes equations have been solved by using the Spalart-Allmaras equation.In this paper,Various depth of circumferential groove for the combined casing treatment and the slot width have been taken in to account for the stability margin of the transonic compressor.Further investigation has been achieved for the effect of the casing treatment on the cascade flow field near the blade tip.The numerical simulation of the transonic cascade flow field has been be obtained.The main sources of compressor stall are the break of the leakage flow vortex at the blade leading edge,which is related to the trace of the leakage flow,and the low-energy flow micelle due to the separation of the boundary layer at the blade trailing edge.By applying casing treatment,the variation of the pressure at both sides of the blade reduced significantly.The driving force of the leakage flow has been weakened.The trace of the leakage flow has been offset from the original position adjacent to the pressure side of the blade to the core region of the cascade because of the combined effect of the main flow,groove flow,the leakage flow and the shock wave.The affected area of the low-speed flow of the leakage vortex becomes small.The installation of the casing treatment of the combined circumferential groove is able to effectively reduce the intensity of the leakage flow at the blade tip clearance,so that the aerodynamic performance at the blade-tip region has been improved.Additionally,for a certain compressor rotor,there exists an optimum groove width,which can maximally increase the stability effect of the compressor.