Numerical Investigation of a Two-stage Counter-rotating Turbine with Transition Modeling and Prediction Improvement with Time-accurate Calculations

Accurate numerical simulations depend on the correct prediction of all relevant flow phenomena. For many aeronautical devices such as turbomachinery the behavior of boundary layers, wall-shear-stress and wall heat transfer are significant for the performance. Turbulence and transition influence such flow characteristics. Onset and extent of transition can therefore be of high importance for the design process. Three-dimensional steady-state and time-accurate simulations of a two-stage turbine with transition modeling have been performed. The configuration consists of a transonic high pressure turbine stage followed by an S-shaped turning mid turbine frame and a counter-rotating low pressure turbine rotor. The inhouse Reynolds-averaged Navier-Stokes solver has been applied to this configuration with the correlation based γ − Reθ transition model developed by Menter et al. which was added to the SST turbulence model. The results are discussed to evaluate the accuracy gain through time-accurate simulations and its effect on transition phenomena. An analysis of the overall efficiency of the turbine and the efficiency losses in the blade and vane rows are also presented.