In the development of modern gas turbines the increase of the turbine inlet temperature is restricted by the need to cool the first stages of the turbine. In addition the flow leaving the combustor is thermally inhomogeneous. Since the blade cooling has to be designed for the actual local hot gas temperatures, it is important to know how these temperature inhomogeneities develop and attenuate inside the multistage flow passage.
In this investigation the flow inside a 4-stage turbine, which is set up in a test rig at the Institute of Steam and Gas Turbines, Aachen University of Technology, is calculated with a state-of-the-art fully three-dimensional Navier-Stokes solver based on an accurate finite volume scheme. The stator and rotor rows are coupled via mixing planes. The turbine is a scaled down original turbine with realistic axial gaps.
The homogeneous reference case is qualified by comparison to recent experimental data gathered at the test rig. Therefore, the flow is extensively measured at several locations. In a second step a radial temperature streak is set at the inlet for the same point of operation. The results show the development of the temperature streak through the four stages. With this information the underlying mixing processes are described and analysed. It is found that the hot streak segregation effect is present in all four stages.