Effect of non-axisymmetric endwall and periodic upstream wakes on the aero-thermal dynamics in turbine cascade

Abstract

The thermal management and heat transfer behavior considering both the contoured endwall and upstream wakes were seldom investigated. In the present work, the experimental measurements of aero-thermal characteristics regarding to a high-pressure turbine cascade with flat and non-axisymmetric endwall, which was optimized with the aim of minimum aerodynamic losses, were carried out. The numerical analysis of the cascade flow with and without upstream wakes and contoured endwall was performed. Then the field synergy theory and entropy production rate concerning heat transfer were introduced. Furthermore, the combining influence of incoming wakes and secondary flow at endwall on the heat transfer characteristics was investigated. Results show that the non-axisymmetric endwall suppresses the passage vortex by weakening the cross flow and surface vortex with concave profiling. And the underturning effect of yaw angle at the cascade exit is reduced due to lower spanwise positon of passage vortex and weaker secondary flow. The positive influence of contoured endwall on losses induced by temperature gradients is mainly localized at the passage downstream, and the leading edge area for contoured endwall, however, has the potential of overheating due to significantly strengthened horse shoe vortex at suction side. The periodic wakes scatter and suppress the negative influence of the contoured endwall on the heat transfer at the leading edge by mixing with the horse shoe vortex. And when wakes and passage vortex meet, the risk of overheating at the rear part of the cascade is reduced. The present work may guide shed now lights into the application of cooling technique on the high-pressure turbine cascade.