A SIMPLIFIED METHOD WITH LOCAL CORRELATIONS FOR THE ANALYSIS OF MULTISTAGE AXIAL TURBINES

摘要

A new through flow method, formulated in terms of pressure rather than velocity, for the analysis of multistage axial turbines is presented. It is designed to provide reliable radial distributions of circumferentially averaged values for the fundamental unknowns. This form of the radial equilibrium equation can represent also sharp velocity gradients in radial direction and interpret very realistic situations as discussed in the following applications. This result is more difficult to achieve if radial equilibrium is written in terms of velocity since this one approaches zero close to the wall. In order to demonstrate this statement, an experimental gas turbine, extensively analysed in literature, has been calculated and the results obtained by means of the proposed method have been compared with those circumferentially averaged derived from a 3D viscous calculation. Two stages of an industrial steam turbine have also been calculated with local semi-empirical correlations available in the open literature. Radial distributions of the fundamental quantities are successfully compared, in every station, with the mean circumferential values evaluated with a 3D viscous calculation. The differences are due to the approximations of the correlations employed.