The Influence Of Tangent Air Injection To The Aerodynamic Performance Of Highly-Loaded Compressor Cascades

The trend to reduce compressor size and weight by reducing the number of stages leads to higher amounts of diffusion per stage, which will cause large endwall loss in the compressor, or even largely reduce compressor efficiency and surge margin. Since the improvement in the aerodynamic performance of aero-engines depends on further increases in efficiency of each component, especially compressor and turbine, many researchers are addressing this issue through the use of varying flow control techniques, such as compound lean blade or air injection.In this paper, an extensive numerical study has been performed to investigate the effects of air injection on the performance of the straight blade compressor cascade and compound lean compressor cascade as well. Air injection was implemented via the hole/slot between the pressure and suction surfaces at appropriate locations. Injected air due to the pressure difference between the pressure and suction surfaces was used to energize the low energy fluid within the endwall/suction corner to increase its ability to overcome the adverse pressure gradient so as to avoid or delay flow separation. First, single-hole configurations with different hole diameters, at different axial or radial locations were simulated in the straight blade cascade. Second, the mechanism of multi-hole configurations were studied in the straight blade cascade, thus the concept of injection slot was developed. Third, the mechanism of injection slot on the performance improvement of straight blade cascade and compound lean blade cascade were discussed in detail.The numerical results show that the aerodynamic performance of compressor cascade changes significantly with the variation of the single-hole diameter, its axial and radial locations. The optimum hole diameter, or the optimum axial or radial hole location, therefore exists. When the three parameters are in a good match, for example, the hole with a diameter of 2~4mm placed at 70% of the axial chord between 10% and 15% of the blade height, the capacity of through-flow is increased 1.4%, and the outlet total pressure loss is reduced 17%. The blade loading and the axial diffusion range are also increased...