Investigation on the optimization design of non-axisymmetric endwall of a contra-rotating turbine

A high loss can be caused by the secondary flow, which have a crucial impact on the aerodynamic performance of a turbine, especially in a highly-loaded contra-rotating turbine. Aiming at controlling the secondary flows near the endwall region of a contra-rotating turbine, numerical simulation was used to analyze the flow field near the endwall region. An optimized platform was used to study the influence mechanism of the optimized non-axisymmetric endwall (NAEW) profiling on secondary flow, and the endwalls of the three rows were optimized one after another. The results show that, the NAEW profiling of the guide vane weakens the intensity of vortex systems such as passage vortices, reduces the thickness of the regenerated boundary layer near the endwall. As a result, the flow loss of the guide vane is reduced and the incoming flow conditions at the inlet of the high-pressure (HP) rotor is optimized. The intensity of the vortices in the HP rotor and the intensity of the shock wave are also weakened due to the NAEW profiling of the guide vane. The NAEW profiling of the HP rotor further weakens the intensity of the vortices near endwall and the intensity of the shock wave, causing a further improvement for the performance of the contra-rotating turbine. For the NAEW profiling of the low-pressure (LP) rotor, it also changes the structures of the vortices near endwall. After the endwall profiling of the three rows of blades, the isentropic efficiency of the contra-rotating turbine is increased by 0.39 %.