Numerical Investigation Of Optimized Schemes Of The Trapezoidal Circumferential Groove Casing Treatment

In the whole rotor passage of compressor,the flow structure in the tip area is the most complex,which has the greatest influence on compressor pressure ratio,efficiency,stability and furthermore the engine performance.In recent years,research on the loss of the flow at the tip clearance has been a hot spot and difficult point for many scholars at home and abroad.As a widely applied simple and effective flow control method,casing treatment technology has been widely used in the field of gas turbines,due to its ability to widen the stability margin of the compressor and to improve the overall performance of compressors effectively.In this paper,the Rotor 37 transonic compressor rotor is treated as the basement for the numerical simulation.Three-dimensional models have been established for various combination types of the trapezoidal groove circumferential casing treatment.The aim of this paper is to improve the stability margin of the engine,to investigate the optimum casing treatment and moreover to study the effect of the casing treatment on the flow field of the tip clearance.In this paper,the commercial CFD software NUMECA has been used to calculate and the Navier-Stokes equations by using the Spalart-Allmaras single equation turbulence model.The numerical simulation results have been obtained by setting the inlet total temperature,the inlet total pressure and outlet back pressure.Through the analysis of the numerical predictions of Rotor 37 rotor,it can be found that the large size low-speed flow mass generated by the shock wave interacted tip leakage vortex has directly affected the operation of the rotor and hence consequently causes stalling.By installing combined-type trapezoidal circumferential groove casing treatment,pressure distribution on both sides of the rotor blade has significantly modified.The driving force of the leakage vortex is weakened noticeably.The core position of the leakage vortex has been offset.The strength of the vortex has been weakened.Its influencing region has become smaller.The blockage of the flow in the cascade passage has also been wakened.Hence,the stability margin has been significantly improved.For the selected schemes of the combined-type casing treatment in this paper,the overall stability margin of the optimized scheme has been increased from 9.65% to 17.42% with a total increase of 7.77% and the efficiency decrease of 1.07%.