Mesh Refinement and Inlet Turbulence Intensity in the Numerical Evaluation of Cooling Effectiveness: A Systematic Study on an Industrial Gas Turbine

In this study, the influence of grid resolution and inflow turbulence on the prediction of gas temperature distribution around HP-turbine blades and the effectiveness of cooling flows are assessed by means of a comparative, systematic study with increasing grid resolution, starting from a typical RANS-mesh with progressive refinement, by means of scale-resolving simulations. The investigation is focused on a three-stage industrial gas turbine in the mid-range output class, whereby we restrict our analysis to the first stage, where most of the external cooling flow is injected, this regions being characterized by the highest temperature fluctuations. The extent of these variations and their unsteady characteristics need to be determined to verify if they have a measurable influence on the material temperature. As the interaction of turbulence with cooling flows is a key element in the prediction of cooling effectiveness, turbulence levels play a major role in addition to the grid resolution. Therefore, special attention is paid to the accurate description of turbulence scaling laws and correlations at the turbine inflow. The results of the investigation provide insight in a viable modelling and simulation tool which can be adopted during design cycles and reveals valuable details of the unsteady aerothermal stresses on the HP turbine blades.