Effects of Sloped Trench Casing Treatment Combined with Air Injection on Stall Triggering Factor of a 1.5 Stage Axial Flow Compressor

Abstract

A new mode, sloped trench casing treatment combined with air injection, was designed and introduced in a 1.5 stage axial compressor. To reveal the effects of this mode on the aerodynamic stability, a three-dimensional numerical simulation was carried out. Results show that sloped trench casing treatment combined with air injection could improve the stable operating range, total pressure ratio, and adiabatic efficiency of the compressor simultaneously. The optimal configuration obtains the stable range extension of 26.47% by using only 0.69% of the whole annulus mass flow rate. Based on a comparison of the stall routes, it is found that the smooth casing compressor occurring stall is caused by a blockage cell formed mainly by the low-velocity tip leakage flow. However, the stall of the sloped trench casing compressor with air injection is caused by a considerable blockage cell formed jointly by the low-velocity tip leakage flow and separated flow on the suction surface of the middle-upper span of the rotor blade. The latter’s contribution cannot be neglected.