The purpose of the ''International Wet Steam Modeling Project'' is to review the ability of computational methods to predict condensing steam flows. The results of numerous wet-steam methods are compared with each other and with experimental data for several nozzle test cases. The spread of computed results is quite noticeable and the present paper endeavours to explain some of the reasons for this. Generally, however, the results confirm that reasonable agreement with experiment is obtained by using classical homogeneous nucleation theory corrected for non-isothermal effects, combined with Young's droplet growth model. Some calibration of the latter is however required. The equation of state is also shown to have a significant impact on the location of the Wilson point, thus adding to the uncertainty surrounding the condensation theory. With respect to the validation of wet-steam models it is shown that some of the commonly used nozzle test cases have design deficiencies which are particularly apparent in the context of two-and three-dimensional computations. In particular, it is difficult to separate out condensation phenomena from boundary layer effects unless the nozzle geometry is carefully designed to provide near-one-dimensional flow.

The analysis presented here deals with two subjects related to the transonic flow in a straight turbine cascade: 1) turbulization of the suction side boundary layer and its subsequent development along the profile 2) influence of side wall boundary layers on cascade flows. The turbulization effect of supersonic compression on the boundary layers which accompany transonic expansion on the suction side of the profile is investigated by independent methods. Both the experimental results and the calculation confirm the loss of stability of the laminar boundary layer and its subsequent transition into turbulence in the region of an adverse pressure gradient. Also the possibility of reverse transition of turbulent boundary layer in a subsequent strong favourable pressure gradient is investigated. The contraction effect of the wind tunnel side wall boundary layers is expressed by means of the AVDR factor over a wide range of flow regimes determined by the incidence angle and the Mach number. A correction of the exit flow angle from the cascade is made to obtain a purely 2D flow although it is apparent that the measured exit angle values and the exit angle obtained for a 2D flow differ considerably.

The flow in the exhaust hood of a condensing steam turbine depends to a considerable extent on the inlet swirl of the flow which changes in tandem with the volumetric flow of steam through the last stage. This study gives a description of experiments which were carried out on the exhaust hood of a 500 MW steam turbine under various conditions, e.g. when there is rated power, when there is an idle run, or when there are various pressures in the condenser. The flow in a model exhaust hood was investigated by means of CFD methods. Computations were performed with the help of the FLUENT 5 code which is based on solving the Navier-Stokes equations while taking the RSM and LES models of turbulence into consideration. The results of the computations are in full conformity with the experiments.