Investigations Of The Tip Leakage Flow And Vortex Breakdown In A Transonic Compressor Rotor With Detached-eddy Simulation Method

For an axial compressor,tip leakage flow is unavoidable,and is closely related to the loss and stall characteristics of the rotor.It has a direct impact on the overall performance and the surge margin of the whole compressor,so it is particularly important in the compressor design and analysis process.In this paper,the tip leakage flow phenomenon as well as the application of detachededdy simulation method in the field of transonic compressors were studied.Detachededdy simulations of a transonic rotor were conducted at different working conditions with their reliability verified by the Reynolds time-averaged simulations as well as the experimental data.The flow structures,unsteady characteristics of the tip leakage flow as well as its interacting process with shock waves were obtained.The detailed structure and mechanism of leakage vortex breakdown under certain operating conditions were revealed.The results show that,compared with traditional Reynolds time-averaged simulations,detached-eddy simulations can better capture the flow details of the tip region of the transonic compressor.The structure of the tip leakage flow is closely related to the operating conditions.From near choke point to near stall point,the interface between the tip leakage flow and the mainstream gradually moves upstream with the angle between the tip leakage vortex and the chord increasing.The area of high entropy region in leakage flow increases gradually as well.At near stall point,strong unsteadiness is found above 80% span due to the interaction between the tip leakage vortex and the shock.The characteristic frequencies of the tip leakage flow are 0.64 BPF and 1.80 BPF.In addition,this paper confirms that the spiral-type vortex breakdown occurs at near stall point,and the detailed breakdown structure of the tip leakage vortex is captured for the first time in numerical simulations.This paper reveals that the breakdown shares the characteristics of shock-induced vortex breakdown.In addition,a criterion for normal shock/vortex interaction is applied to the interaction between the tip leakage vortex and the bow shock in present transonic rotor.It is successfully predicted that the leakage vortex breakdown occurs only at near stall point,but not at near choke point and peak efficiency point.Through this study,the applicability of the detached-eddy simulation method in the field of transonic compressors is explored.The mechanisms and structures of the tip leakage flow in transonic compressors are analyzed in more detail.The unsteady characteristics and breakdown phenomena of the tip leakage vortex are further understood.This study could provide a theoretical basis for the control methods aimed at reducing the impact of the tip leakage flow in transonic compressors.