On the validity of the linear Boussinesq hypothesis for selected internal cooling features of gas turbine blades

Abstract

In order to further decrease fuel consumption and pollutant emission of modern, highly efficient gas turbine blades, the internal cooling air consumption needs to be reduced. At the same time, the solid temperature must not exceed a critical level to avoid thermal damage of the turbine blades. Different cooling methods such as impingement cooling, pin fins or ribs are used to increase the internal heat transfer and, thus, to decrease the material temperatures. In order to improve local cooling air consumption the flow field and temperature distribution must be known. High fidelity CFD like LES are extremely difficult or even not feasible for such complex geometries and high Reynolds numbers. Therefore, RANS models must be used accepting a higher degree of inaccuracy. In this study, LES of selected cooling features are conducted for a better understanding of the validity of RANS models which are based on the linear Boussinesq hypothesis. The results given below are part of the research project “Improvement of the Numerical Computation of the Conjugate Heat Transfer in Turbine Blades” supported by the Siemens Clean Energy Center and the German Federal Ministry for Economic Affairs and Energy under grant number 03ET7073F.