Numerical Simulation and Experimental Research about Shock Wave in 1+1/2 Counter-Rotating Turbine

Abstract

To investigate the internal distribution regularities of shock wave structure in 1+1/2 (without low pressure guide vane) counter-rotating turbine, both steady and unsteady numerical simulation about a designed 1+1/2 counter-rotating turbine are conducted, and experimental research about the shock wave structure of high pressure guide vane, high pressure rotor and low pressure rotor was also conducted by using the schlieren apparatus under different working conditions. The numerical simulation divides into two parts: steady and unsteady calculation. The result of steady simulation under designed condition shows that there appears supersonic flow and shock wave at the exit of root in high pressure guide vane, while supersonic flow appears at the entire passage of the blade outlet in both the high pressure rotor and low pressure rotor, together with strong shock wave and complex wave structures. From the point of the unsteady results, the unsteady effect has few influence on the flow field of high pressure guide vane, but the wake of the high pressure guide leaves periodically sweeps through the front edge of the high pressure blade and there presents strong unsteady effect on flow field of high pressure rotor. Then, to deeply research the characteristics of the shock wave structure, 50% height section of the blade of the three types of blades are extracted respectively to make plane cascades which are conducted blowing experiments in supersonic wind tunnel. During the experiment schlieren display technology is used to record the shock wave structure changing process in three cascade flow passage under the design Angle of attack when pressure ratio changes from 1.7 to 2.5. The final photograph were analyzed by comparing with the CFD results. Results show that with the increase of expansion ratio, the wave structures in both high and low pressure blade channel move toward the exit and the caudal interference between the outer tail wave and is strengthened gradually. The results show that the current design of high pressure blade and low pressure blade show better advantages for controlling the structure of the shock wave.