Stability Improvement of a High-Pressure Ratio Centrifugal Compressor by Flow Injection

Abstract

High-pressure ratio centrifugal compressors are required in modern turboshaft engines with the requirements of a high power-to-weight ratio and low fuel consumption. The reduction of the stable flow range is one of the crucial issues when increasing the compressor pressure ratio. As a widespread active flow control method, a steady tip injection was applied to extend the stable flow range and improve the stability of a high-pressure ratio centrifugal compressor with a three-dimensional numerical simulation. By the steady simulation method, this paper investigates the influences of different parameters, such as the injection velocity, injection yaw angle, injection position, and injection tube diameter on the pressure ratio and efficiency and stability of the centrifugal compressor. Further, the research is conducted by comparing a datum compressor and an injection configuration compressor with the relative optimal parameters via an unsteady simulation calculation. The results show that the stable flow range of the compressor is successfully increased from 8.1% to 13.4% when using tip air injection. The analysis of the flow field at the region of the leading edge demonstrates that the injection can decrease the passage shock intensity and reduce the load in the vicinity of the tip clearance. The tip leakage vortex, near the shroud of the leading edge, can also be suppressed. The decreased incidence indicates that the air injection can weaken the flow separation in the impeller, thereby improving the stability of the compressor.