Simulation of Diffuser Flow Using an Euler Solver With a Distributed Loss Model

Abstract

The flow inside a diffuser which serves as outlet of the last turbine stage is strongly influenced by the tip leakage jet of the last blade row. For the computation of diffuser flow a quasi 3D Euler solver with a simple model for the approximation of viscous effects was developed. A body force which is calculated as a function of velocity gradients normal to the streamwise direction is included in the Euler equations. Computational cost for calculations using this method remains low, permitting its use as a design tool for turbine diffusers. Comparison of numerical results with experimental data for an annular axial radial diffuser at the outlet of a steam turbine model is presented. Flowfields for different tip clearances show a strong dependence of the pressure recovery on the tip leakage jet. Numerical results agree well with measurements.