Experimental and numerical investigations for turbine aerodynamic performance with different pressure side squealers and incidence angles

Tip leakage flow directly affects the aerodynamic performance in the turbine stages. In this research, wind tunnel experiments and numerical calculations are performed for the Original Cavity Tip (OCT), the modified Stepped Cavity Tip (SCT) and Cavity Winglet Tip (CWT) with different pressure squealers under seven incidence angles in a range of ±15°. The shape control effects on the aerodynamic performance are obtained by comparing the loss structure of the exit flow field, the pressure distribution of the casing wall and the surface load of the blades. Experimental results show that SCT structure reduces the total pressure loss by 6.8% and the CWT by 4.1% relative to OCT at 0° incidence angle with an outlet Mach Number 0.92. The variation of the incoming flow angles significantly affects the scale and loss values of the passage vortex, which further affects the leakage flow. Numerical calculations are performed as supplementary detail analysis, specify the interrelationship between leakage and passage vortices.