Influence of turbulence modelling on non-equilibrium condensing flows in nozzle and turbine cascade

Abstract

The accurate analysis of a condensing flow plays an important role in the development of high-efficiency steam turbines. This paper presents an investigation of turbulence modelling influence on non-equilibrium condensing steam flows in a Laval nozzle and in a stationary cascade of turbine blades using a commercial computational fluid dynamics (CFD) code. The calculations were conducted by employing 2D compressible Reynolds-averaged Navier–Stokes (RANS) equations coupled with a two equation turbulence model. The condensation phenomena were modelled on the basis of the classical nucleation theory. The standard k–ε turbulence model was modified, and the modifications were implemented in the CFD code. The influence of inlet flow turbulence on condensing process was discussed. The impact of turbulence modelling on wet-steam flow was examined based on the experimental data available in the literature. The cascade loss coefficients were calculated numerically as well. The presented study of losses that occur due to the irreversible heat and mass transfer during the condensation process emphasised the importance of turbulence modelling for wet-steam flows in turbines. The paper demonstrates that the accurate computational prediction of condensing steam flow requires the turbulence to be modelled accurately.