Off-design flow analysis of low-pressure steam turbines

In this paper, a method for flow calculation in large steam turbines is presented. The method is based on the through-flow theory and the finite element procedure. It includes some extensions and improvements in the form of a new combination of loss correlation, radial distribution of losses and spanwise mixing, a new procedure for density calculation and an extension to encompass reverse meridional flow. The method is applied to the LP (low-pressure) part of a 165 MW steam turbine for which the flow field and performance over a wide range of mass flow and input pressure are calculated. The flow at far off-design loads, at which flow reversal behind the last stage occurs, and the last stage changes to ventilation are especially analysed. The comparison of numerical results with experimental data shows good correspondence.