Numerical Study On Dynamic Process Of Flow Field In Blade Tip Region Of Axial Compressor Rotor

Up to now,there is no clear conclusion about the flow nature of the compressor under the condition of unstable rotating stall.It is very important to study the internal flow to broaden the stable operating range of the compressor and to improve the active control technology of stalling.In order to reveal the cause of stalling inception and further study the development process of the stalling cell,a transonic rotor was studied in this paper,and the multi-annulus and full annulus numerical simulation of both steady and unsteady were carried out.The signal characteristics of the compressor flow field were studied by using several signal processing methods,such as frequency domain analysis,time-frequency analysis and wavelet analysis and the unsteady flow caused by the tip leakage vortex in the transonic rotor and the wall flow separation were analyzed in detail.Through the steady and unsteady calculation of a ten-annulus transonic rotor,the flow field structure and related details of the compressor as demonstrated by the unsteady calculation results under two different numerical methods were studied.Before entering the stall state,it was found that the instability occurs in the tip region at first by analyzing the calculation results of these two numerical methods and the bubble broken of the tip leakage vortex played an important role in choking and instability of the compressor flow field.The two numerical methods had significant differences in computational stability when the compressor was brought into stall development due to the reduced outlet corrected flow rate given by the outlet,from which a numerical method suitable for this study was derived.Through the steady and unsteady calculation of full-annulus transonic rotor,the signal characteristics and flow field details of the compressor during dynamic stall were analyzed.Before the formation of stalling inception,the flow field of the compressor during stalling development was as follows: low pressure cells appear on the leading edge of multiple blades in the compressor,which was caused by the crushing of tip leakage vortex.In the initial stage of stalling,the spike signal monitored in the flow field was caused by the circumferential propagation of the low pressure cells and they induced the flow separation on the pressure surface of the blades,resulting in the blockage of the flow field and the increase of flow loss.During the stalling stage,the flow separation of the blades in the tip region aggravated and the low-pressure fluid in the stalling cells came from the low-energy fluid generated by the flow separation of the blade surface...