Flow control mechanisms of a combined approach using blade slot and vortex generator in compressor cascade

Abstract

Experiments proved the performance gains in a high-load cascade using a new combined flow control approach, but lack of clear explanations on flow interactions between the configurations and the cascade flow. A detailed discussion is conducted here to further reveal the flow control mechanisms based on experimental and numerical results. An overview of experimental studies is firstly presented to conclude the flow control benefits and to put forward the questions for the simulations. Cascade flow fields observed by experiments show that the combined approach works by two aspects: the slot produces high-speed jets to re-energize the suction side separated flows and reattach them to the suction surface; the vortex generator (VG) creates a counter-rotating vortex into cascade passage to further reduce the end-wall cross flows. Thus, both the two main sources of separations in cascade flow are considerably suppressed. The corner separation is suppressed by delaying the passage vortex (PV): The VG counter-balances and deflects the PV while the slot jet further limits its pitch-wise width. Coupling the effects of two devices, the cascade flow structure is improved and main vortices are significantly reduced in size and intensity, result in greater separation control effects than the individuals in the high-load cascade.