Through flow calculation in axial flow turbines using a quasi-orthogonal solver

Abstract

Application of CFD investigating and analysing axial flow turbomachines has reached, in the last years, a high level of accuracy and thus can be applied quite routinely in the prediction of different kinds of flow. The numerical investigation of axial flow turbine performance is of great interest because of the importance of correct product design and of the behaviour in off-design conditions. In this paper a new formulation of the radial equilibrium equation is presented. This formulation is particularly suitable for turbomachinery numerical investigation, and is applied in a quasiorthogonal through flow solver. All the terms involved in the proposed formulation have been taken into account in order to solve the more general problem. Mesh generation and blade geometrical representation are simplified in order to reduce the pre-processing work. In order to evaluate cascade losses and deviation angle, Ainley- and Mathieson semi-empirical correlations and their correction proposed by Dunham and Came and Kacker and Okapuu have been utilised. The four stages Hannover experimental turbine and the Cambridge one have been analysed in different operating conditions; numerical results have been compared with the experimental ones to evaluate the level of accuracy of the proposed procedure.