Effects of Sloped Trench Casing Treatment Combined with Air Injection on Aerodynamic Performance 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 performance, a three-dimensional numerical simulation was carried out. Three air injection configurations were set to reflect the influence of injected flow velocity and injected mass flow rate. Results show that sloped trench casing treatment combined with air injection could improve the stall margin, total pressure ratio, and adiabatic efficiency of the compressor simultaneously. Moreover, injected flow velocity has a more significant influence on the effectiveness of extending stability than the injected mass flow rate. The optimal configuration obtains the stall margin improvement of 8.37% by using only 0.69% of the whole annulus mass flow rate. Based on a detailed analysis of the rotor flow field, it is found that the high-speed jet causes axial momentum of the incoming flow upstream the rotor blade tip to increase and load of the forepart chord of the rotor blade tip to reduce. The blockage in the tip region of the rotor passage is thus suppressed effectively, which results in the stall margin of the compressor enhanced.