Secondary Flow, Turbulence, and Film Cooling Measurements in a Gas Turbine Vane Passage Downstream of a Novel Combustor-turbine Interface

Abstract

Gas turbines are essential in electrical power generation and aircraft applications. One way to increase the efficiency of a gas turbine engine is to increase the combustor exit temperature. However, temperatures higher than the melting point of turbines located downstream can result in serious thermal failures. Therefore, these high temperatures create a need to design aggressive cooling schemes for engine sections to prevent component damage. However, owing to the complexity of the flow in the engine, it is essential to understand how coolant flows interact with engine passage flow. This thesis discusses three experimental studies relating to the cooling of gas turbines:(1) Evolution of secondary flows: Due to the geometry of turbine vanes, various undesired flows are developed in the vane passage, which are termed as secondary flows. The flowrates of the injected coolants affect the way in which these secondary flows are generated and transported. A detailed description of the vane passage secondary flowfield for a variety of coolant flowrates is provided and discussed. (2) Film cooling performance: The injected coolant forms a film on the surfaces to be cooled to protect them from failure. The cooling performance of a novel coolant injection scheme is reported in this study. Coolant transport is recorded using temperature and velocity measurements. The cooling performance on the vane passage surfaces is discussed using these transport measurements and compared with injection scheme currently used in the engine. (3) Decay of turbulence: Vane geometry leads to changes in turbulence features of the flow, which are known to affect the cooling of the vane surfaces. Such changes to turbulence were measured and discussed. Numerical simulations using Reynolds-averaged Navier-Stokes turbulence models were also performed for the same vane geometry. A comparison between the computed and the measured parameters is also presented. The results of these studies are meant to help gas turbine designers in reducing the amount of required coolant which would lead to an increase in the gas turbine efficiency.