Influences of a multi-cavity tip on the blade tip and the over tip casing aerothermal performance in a high pressure turbine cascade

Abstract

In modern gas turbine, the over tip leakage flow is inevitably generated in the tip gap of the first stage turbine blade due to the freestanding airfoil. In order to obtain a higher thermal efficiency, the turbine inlet temperature is gradually increased. Therefore, the over tip leakage flow induces significant aerodynamic losses and the blade tip and the over tip casing endure high level of thermal load. In the pursuit of a high-performance turbine engine, cavity tips are widely implemented in the turbine blade to reduce the over tip leakage flow and the thermal load on the blade tip and over tip casing. In the current study, the influences of the multi-cavity squealer tip on the blade tip and the over tip casing aerothermal performance were numerically investigated. Three-dimensional (3D) Reynolds-Averaged Navier-Stokes (RANS) equations and standard k-ω turbulence model were solved to conduct the simulations. The results indicate that the flat tip attains the largest thermal load on the blade tip, over-tip casing and induces the largest total pressure loss. However, the case with a single tip cavity (1CST) achieves the smallest total pressure loss and heat transfer coefficient on the over-tip casing, which are 7.6% and 19.6% lower than the flat tip, respectively. The case with a multi-cavity tip obtains a decreasing heat transfer coefficient on the blade tip. The case with five tip cavities (5CST) achieves the smallest heat transfer coefficient on the blade tip among all simulated cases, which is decreased by 17.5% relative to the flat tip.