An Estimation of Wetness Losses for Nuclear Steam Turbines Using Simplified 1D-2D Models

Abstract

Abstract This paper presents a methodology to estimate wetness losses for steam turbines using simplified models. Several 1D solvers are used to evaluate the steam flow field and the droplet nucleation and growth. The results are used as input data for another 2D solver to calculate droplet trajectories, liquid films on blades and wetness losses. These losses are decomposed in several types and modeled according to the classical approaches of Gyarmathy and Laali: thermodynamic, collected water, centrifuged water, drag of fine and coarse droplets, impact, additional friction and exit kinetic energy losses. All HP and LP nuclear steam turbines currently in operation in the EDF’s nuclear fleet are analyzed using this methodology. Several sensitivity studies are also performed to assess the importance of the various physical laws governing the condensation models, the input data used for wetness losses estimation and the values of the parameters involved in the wetness models. The results show that the wetness losses decomposition is strongly dependent on the type of turbine and that the equivalent Baumann coefficients vary depending on the average wetness mass fraction in each stage. The most important factors influencing the wetness losses evaluation are the droplet size and the deposition rate, all other variations of parameters and models playing a less significant role.