Experimental investigation on the aerodynamic performance of a transonic turbine rotor with non-axisymmetric endwall

To demonstrate the effectiveness of non-axisymmetric endwall (NAE) and elucidate its underlying flow fundamentals, a transonic aerodynamic test platform was designed and constructed for an annular cascade. The loss characteristics and flow field structures were measured for a meticulously -designed NAE model and a baseline axisymmetric endwall at various exit Mach numbers (0.6 to 0.95). The static pressure distributions in front of and behind the endwall are found to be relatively similar between the two models. However, the NAE model exhibits a lower endwall static pressure behind the cascade than the baseline model. Along the 10% span section, the NAE model reduces the pressure loads within the range of 20% to 60% of the axial chord compared to the baseline model. This redistribution of pressure loads leads to a notable reduction in the transverse pressure gradient near the endwall, substantially mitigating secondary flow losses. At an outlet Mach number of 0.8, the area -averaged total pressure loss coefficient can be reduced by 14.0% with the implementation of NAE. Additionally, an exquisite oil flow visualization technique is employed to provide visual insights into the flow fundamentals. The flow trajectory within the cascade channel of the NAE model exhibits a much closer proximity to the pressure side, effectively hindering the growth of passage vortex. The meticulous measurements of loss distribution and flow structure provide compelling evidence to validate the aerodynamic benefits of NAE design under transonic conditions.