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 paper describes experimental studies of water droplet motion in turbine cascades using laser diagnostic techniques (particle image velocimetry/particle tracking velocimetry). The investigations were performed at the experimental installation Wet Steam Circuit – 2 (WSC-2) at the Moscow Power Engineering Institute. The facility allows the study of the flow of superheated, saturated and wet steam over a broad range of velocities. The effect of the steam initial conditions on the behaviour of the coarse droplets downstream of a nozzle blade cascade has been studied for subsonic and supersonic flow. The variation of the average droplet velocities and angles across the blade pitch, and the droplet trajectories have been obtained. The relationship between the slip coefficients of droplets having minimal velocities in the blade trailing-edge plane, the initial steam wetness, and the axial distance downstream of the nozzle blade are suggested as the criteria characterising the coarse droplet motion downstream of the cascade.

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The paper presents the results of experiments on the effect of steam injection on the performance of the wet steam turbine nozzle cascade. The steam injection destroys a liquid film on the surface of the blade and reduces erosion and dangerous droplets after cascade. The results obtained in the vane package cascade which include a slot on the concave surface of the airfoil near the trailing edge of blades. Experimental studies were carried out on wet and superheated steam. A pneumatic measurement system was used to determine the parameters of the main and injection steam. A laser diagnostics system “POLIS” that includes PIV/PTV was used to analyze the impact of heating steam injection on the characteristics of the liquid phase. Profile losses were obtained at different steam parameters and steam injection speeds. The characteristics of the liquid phase behind the trailing edge were obtained in a wide range of operating parameters.