Measurements and Assessment of Adiabatic Film Cooling Performance on a Gas Turbine Vane Endwall Using PSP Technique

Abstract

Turbine vanes are typically assembled as a section containing single or double airfoil units in an annular pattern. First stage guide vane assembly results in two common mating interfaces - a gap between combustor and vane endwall while another from the adjacent sections, called slashface. High-pressure coolant could leak through these gaps to reduce the ingestion of hot gas and achieve certain cooling benefit. As vane endwall region flow field is already very complicated due to the presence of highly three-dimensional secondary flows, then a significant influence on endwall cooling can be expected due to the gap leakage flows. The entire study is divided into two parts. The first part of this dissertation investigates the endwall film cooling from gap leakage flows with the multiple rows of discrete film cooling holes inside the passages. The later part studies the film cooling performance of multiple endwall cooling designs including inlet leakage jet. Pressure Sensitive Paint (PSP) technique is used to obtain the detailed film cooling effectiveness distributions on the endwall of a scaled up mid-range industrial turbine vane geometry. Experiments are performed in a blow-down wind tunnel cascade facility at the isentropic exit Mach number of 0.5 corresponding to Reynolds number of 3.8 x 105 based on inlet conditions and axial chord length. Passive turbulence grid is used to generate freestream turbulence level about 19% with an integral length scale of 1.7 cm. The effect of coolant-to-mainstream mass flow ratio and density ratio on the film cooling have been studied. Results indicated that leakage coolants have significant influence on the endwall film cooling and different endwall cooling designs are capable of achieving higher cooling effectiveness with relatively uniform coverage