Characteristic Study of Wet Steam Condensation With Different Mathematical Models in High-Pressure and Low-Pressure Nozzles

Abstract Turbines play a critical role as the primary energy conversion devices in the conventional island of nuclear power plants, efficiently transforming the thermal energy of steam into mechanical energy. They hold a significant position in the power generation system. While thermal power turbines often generate wet steam in the final stages, nuclear power turbines, particularly those in pressurized water reactor (PWR) units, exhibit distinct characteristics. The lower steam parameters produced in the steam generators result in the majority of the working fluid entering the turbine as either saturated steam or steam with a certain degree of moisture. Consequently, compared to thermal power turbines, a substantial portion of the entire turbine set in nuclear power turbines operates within the wet steam region, exacerbating the phenomenon of spontaneous condensation of wet steam. Previous research has predominantly focused on the last stages of both thermal and nuclear power turbines, with limited attention given to the non-equilibrium condensation of wet steam in high-pressure conditions during turbine operation. Nozzles and blades, due to their structural similarity to the turbine flow path, are commonly employed as representative components for mathematical modeling and characteristic studies of turbines. In this study, the Euler-Euler two-phase flow mathematical model was adopted, and the nucleation and droplet models were selected and modified. The IWSEP nozzle and Gyarmathy nozzle were used to simulate wet steam flow under low and high inlet pressures, respectively. Through numerical simulations, the results were compared with previous simulation outcomes and experimental data. Additionally, by exploring the impact of different nucleation and droplet growth models, the study investigated the influence of mathematical models on wet steam condensation. The research yielded insights into the evolution patterns of the flow field inside the nozzle under different condensation models. The results indicate that the numerical prediction method established in this study can be applied to the primary droplet prediction in both high and low-pressure nozzles. This is advantageous in reducing heat losses attributed to wet steam condensation, providing a theoretical foundation and basis for the practical operation of turbines.