Experimental and theoretical investigation of steam condensation in LP part of a large power turbine

The paper reports the experimental investigations of steam flow with condensation in the blading system of the LP part of a 360 MW turbine. For this purpose special probes were used which provided opportunities for flow visualisation including localisation of the front of condensation, determining distributions of pressure, temperature, velocity and flow angle in the inter-row gaps, measurements of water droplet concentration and sizes The measurements have proved that the condensation process in the LP turbine might be of heterogeneous nature depending on the concentration of chemical impurities in the steam. The obtained results created the basis for CFD flow calculations, which were performed using the time dependent 3-D Reynolds averaged Navier-Stokes (RANS) equations coupled with a two-equations turbulence model (k-co SST) and additional conservation equations for the liquid phase. The set of governing equations was closed by a 'local' real gas equation of state. The condensation phenomena were modeled basing on the classical nucleation theory, which was well suited for modeling technical flows. The heterogeneous condensation on the insoluble and soluble impurities was taken into account. The system of governing equations was solved by means of a finite volume method on a multi-block structured grid. The obtained numerical results and experimental data are compared and discussed.