Analysis of the Mixing Process in a 1.5 Stage Turbine With Coolant Ejection

Abstract

The addition of cooling fluid into the main flow affects the aerodynamic performance of the blading and causes changes of the overall flow capacity and efficiency of a turbine. Computing systems which consider all those effects are necessary for the performance prediction of cooled multistage turbines. The throughflow method presented here is based on the finite element method and includes models for the radial distribution of losses, for the spanwise mixing and for different cooling configurations, e.g. convection cooling with trailing edge outlet and film cooling. The reliability of the method is verified by comparisons with experimental data of a 1.5 stage cold air turbine with nitrogen ejection in front of the first stator. Because the coolant is ejected at different radii in order to observe the flow path, the radial mixing process is of special importance for this test case. Due to the reliable models used in the throughflow method the mixing between main flow and coolant at the ejection locus and the radial mixing process downstream is well predicted.