Flow Mechanism for Stall Margin Improvement via Axial Slot Casing Treatment on a Transonic Axial Compressor

Axial slot CTs were designed and applied on Rotor ۶۷ to understand the physical mechanisms responsible for the improvement of the stall margin. Unsteady Reynolds-averaged Navier-Stokes was applied in addition to steady Reynolds-averaged Navier-Stokes to simulate the flow field of the rotor. The results show that aerodynamic performance and the rotor stability were improved. Stall margin improvement (SMI) improved by ۲۶.۸۵% after the CT covering ۵۰% of the axial tip chord was applied, whereas peak efficiency (PE) decreased the least. The main reason for the rotor stall in the solid casing is the blockage caused by tip leakage flow. After axial slot CTs were applied, the tip leakage flow in the front part of the chord was obviously reduced, and the majority of the blockages in the tip region were removed. The absolute value of the axial momentum before ۴۵% axial chord in CT_۵۰ was reduced by ۵۰%, whereas the maximum tangential momentum value of CT_۵۰ was decreased by ۷۰% relative to the solid casing. CT_۵۰ configuration was located across the shock wave; thus, it can fully utilize the pressure gradient to bleed and remove the blockage region, and the across flow is considerably depressed.

کلیدواژه ها:

Casing treatment ، Performance ، Transonic axial compressor ، Stall mechanism ، Flow field