Turbine Blade Endwall Heat Transfer and Film Cooling Performance With Multigap Jets and Film Holes

Abstract

Due to manufacturing, assembly, and operational conditions, gaps are commonly presented in the turbine components, such as a slashface gap between two adjacent blade endwalls and a slot gap between the stator and rotor. The coolant ejected through these gaps not only limits hot mainstream gas ingestion into the disk cavity but also has the potential to provide endwall film cooling coverage. Nevertheless, the interaction of these gap jets, pre-designed film holes jet, and endwall secondary flows, significantly impacts endwall heat transfer and film cooling performances and leads to a more complicated flow field near the endwall. To further understand the endwall flow physical behaviors in this environment, the combined effects of film holes jet and multi-gap jets (slashface jet and slot jet) were experimentally studied in a transient wind tunnel with a six-blade linear cascade. The endwall heat transfer was measured and recorded by the IR technique at inlet average turbulence intensity (Tu) of 7.5% and an exit Mach number (Maex) of 0.4. In addition, detailed numerical predictions were also performed to discuss the flow physics near the endwall and the multi-gap jet flow behaviors. Results indicated that the slashface jet is an essential contributor to endwall film cooling performance in this endwall configuration. The slashface jet limits the development of the film holes jet, leading to an enhancement of film cooling performance downstream of the film holes.