The effect of speed ratio on the first rotating stall stage in contra-rotating compressor

Since the structure and aerodynamic advantages of contra-rotating technology, it has been considered as an important approach to further improve the thrust-weight ratio of aircraft engine. In the present work, the impact of rotating speed ratio on the first rotating stall stage of a CRAC which consist of two counter-rotating rotors is investigated numerically. To detect the stall margin of CRAC exactly, the back pressure dichotomy method is developed, the grid indepence is verified and the performance is measured. A large number computation is carried out to explore the influence of rotating speed ratio on the performance of contra-rotating compressor. Finally the flow filed near blade tip is analyzed to find the relation between the rotating speed ratio and the first stall rotor. The result shows: (1) The work conditions of ROT1 have a significant impact on the aerodynamic performance of ROT2, while ROT2 play a little impact on the performance of ROT1. (2) At the condition of rotating speed ratio R2:R1≥0.9, the second rotor will be the first stall stage as the mass flow is decreased. (3) When the ROT2 rotating speed is slower than the ROT1, the intensity of tip leakage in ROT2 declines obviously with decreasing the rotating speed ratio, but the intensity of tip leakage in ROT1 has little changes. At the condition of R2:R1<0.9, the first rotor will be the first stall stage.