A Study Of Numerical Simulation On Condensative Steam Flow In The End Stage Of Turbine

In the large-scale turbine equipment, which using vapor as working-medium, much phenomenon of the condensed steam flow always exist in the end stage of turbine. The condensed steam breaks the thermodynamic equilibrium of the state of former flow. Due to returning to the thermodynamic equilibrium, much latent heat release accompanied internal dissipation and affects the power performance. This rapid expansion of steam bring to non-equilibrium condensation flowing, which be deemed to the important problem that cause the efficiency of turbine to decline. Furthermore, the droplet which the vapor condensation, impinge against the blade follow the parent vapor leading to water erosion. The severe water-erosion results in the break of blade, which a certain extent safety is impacted to turbine machine. Therefore, in the modern large-scale power plant and nuclear power station, the question of two-phase flow mainly lies in two sides: on one hand, the humidity of wet-steam lowers the working efficiency of turbine's end stage; on the other hand, the droplets that exist in the wet-steam bring about the water-erosion that impinge against the blade of turbine's last stage.In this thesis, first of all, the basis parameter of vapor and grid-building for 2-dimension model are introduced. Through analyzing the process of condensed steam flow, based on the classical nucleate theory, the wet-steam flow in the plane cascade has been simulated. The results show the major area of steam condensed and the flow feature in the whole flow field. The comparison between numerical result and experimental data indicated that the method be feasible and could be used to simulate the flow accurately, provided the basic reference for optimizing design and reducing the damage of impingement.Secondly, the flow of condensation steam was compared with the flow of ideal gas. From the contrasted results, it can be found the difference between the condensative steam flowing and ideal-gas flowing. And, it also can be found out that it is inevitable to condense for steam flowing under the supersonic state. At the same time, the major areas which formed second drips have been displayed in the solved results.Finally, the flow of condensation steam in the 3-dimension model has been simulated. And some knowledge of grid topology is also introduced. The nucleation of condensative steam in the whole flowing field has been displayed. Furthermore, the characteristic of two-phase complex flow is analyzed. In the stationary blade's passage, the flowing status is stable relatively. The steam expanding is comparatively relaxing and the nucleation area of steam is small. In the moving blade's passage, the expanding of steam is tempestuous relatively because of dual-velocity effect; the degree of condensation of steam is considerably distinct.