On the choice of variables and matching criteria for the steady simulation of transonic axial turbine stages

Abstract

A transonic axial turbine stage is computed by solving the time-averaged Navier-Stokes equations in the turbulent flow regime. The stator and rotor rows are interfaced using a mixing plane. The sensitivity of the stator-rotor coupling to the boundary conditions and mixing strategies is investigated. The mass or area tangential averaging is found to have slight impact on the stator-rotor match. The relative and absolute formulation of the rotor inlet boundary condition is found to alter the match of the two rows. The computations indicate that both relative and absolute boundary conditions should be used to estimate and control part of the uncertainty in the stator-rotor match, which can be greatly reduced by an iterative procedure, based on the stator exit pressure. The area averaging allows a unique matching point to be estimated for both absolute and relative properties.