Numerical simulation of secondary flow control on high-speed compressor cascade with synthetic jets

A simulation study on the use of synthetic jets for the corner separation control on a high-speed compressor cascade was conducted. The mechanisms of the active flow control on delaying flow separation and reducing flow losses were analyzed in detail. Results showed that the space-time structure of the flow field in the blade passage was improved significantly with a maximum loss reduction of 19.8%, while the static pressure rise increment of 8.8% was gained. By periodically adding or removing fluid to or from the boundary layer, synthetic jets could effectively control the corner separation. In the blowing phase, synthetic jets remarkably increased the energy level of the blade suction surface boundary layer and the corner region, while the accumulation of high entropy and low energy fluid towards the corner region was effectively suppressed in the suction phase. The above two contributed to enhancing the resistance to streamwise adverse pressure gradient and thus reducing flow separation. It was worthy to mention that the flow control effect during the suction phase was much more pronounced. Both jet angle and jet momentum were important parameters for the flow control effect. When the jet convected tangentially downstream, the flow control was very efficient in injecting high momentum fluid into the boundary layer, accounting mainly for the resistance to streamwise adverse pressure gradient. In addition, increasing the jet momentum could further improve the cascade time-averaged aerodynamic performance. Factorial design studies indicated that the effect of jet angle was much more pronounced than that of jet momentum, while there was no evidence to support the interaction between jet angle and jet momentum.