Influence of Trailing Edge Geometry on the Condensing Steam Flow in Low-Pressure Steam Turbine

Abstract

The paper describes the influence of trailing edge geometries on the non-equilibrium homogeneously condensing steam flow in the stationary cascade of turbine blades. The computational fluid dynamics (CFD) simulations were performed with the ANSYS Fluent CFD code using the Eulerian-Eulerian approach. The condensation phenomena were simulated on the basis of the classical nucleation theory, and the steam properties were calculated with the real gas model. Flow turbulence was solved by employing the modified version of the shear-stress transport (SST) k-ω turbulence model. For this study, three trailing edge profiles; that is, conic, semicircular and square were considered. The influence of the trailing edge shapes were discussed together with experimental data available in the literature. The presented results show that the trailing edge geometries influence on the nucleation process, the droplet size, wetness fraction, the shock waves structure generated at trailing edge and its angles, the flow angle, the entropy generation and flow mixing in the wake. The cascade loss coefficients were calculated for the low inlet superheat case and for the high inlet superheat case. The presented results demonstrated that the losses that occur due to the irreversible heat and mass transfer during the condensation process were also influenced due to the trailing edge shapes.