Numerical modeling and investigation of unsteady phenomena in condensing flows of industrial steam turbines

The condensation process in a steam turbine is in reality an essentially unsteady phenomenon. There are differences between steady and time-accurate calculations introduced by the large-scale temperature fluctuations which are caused by the segmentation of blade wakes by successive blade rows. Consequently, it is important to consider the additional losses caused by condensation in unsteady simulations. In this work a time-accurate Eulerian-Lagrangian two-phase model is presented. The algorithm is applied to the compressible Navier-Stokes solver TRACE to predict the influence of spontaneous homogeneous nucleation using source terms for heat, mass and momentum transfer between the phases. In simulations presented in this work the capability of the two-phase model is demonstrated through comparisons with one and two dimensional experiments of nozzles and a cascade blade from literature. Unsteady phenomena are described in detail for an industrial low pressure steam turbine stage.