Numerical study on the flow field characteristics and efficiency losses in nuclear power turbines based on the non-equilibrium condensation model

摘要: The steam turbine is one of the most critical energy conversion components in power generation systems. Unlike thermal power plants, nuclear steam turbines operate in the wet steam region in most of their stages, with the inlet steam often near saturation, resulting in more severe non-equilibrium condensation. This study aims to investigate the non-equilibrium condensation flow characteristics and efficiency of a nuclear steam turbine. Firstly, a suitable condensation model was selected and validated by comparing it with the existing experimental data on nozzles. Then, a thermodynamic analysis of non-equilibrium condensation in a nine-stage nuclear turbine was performed using the Euler–Euler method. Due to the saturated inlet conditions and a maximum supercooling of only 7 K, nucleation was suppressed by pre-existing droplets, and condensation was dominated by droplet growth. Furthermore, the effects of steam extraction ports and shaft seals on condensation were examined. Results indicate that although extraction promotes nucleation, the extracted flow, accounting for approximately 17.4% of the inlet mass flow, removes part of the droplets, thereby reducing overall humidity. Finally, internal efficiency and various types of losses were analyzed. The turbine efficiency decreased from 91% to around 80%, with wet steam loss being the most significant, reaching about 15% at the last stage. The findings provide insights for improving the design and operation of nuclear steam turbines, enhancing their economic performance and operational reliability.