Modelling unsteadinesses and polydispersion in wet steam flows using the quadrature method of moments and a two-equation model

Authors

F. Blonde, M. Stanciu - Electricite de France, Chatou
F. Lebœuf, M. Lance - Ecole Centrale de Lyon, France

Abstract

The efficient prediction of wetness and droplet size in steam turbine flows is still a challenge in Computational Fluid Dynamics nowadays. Most of the time, polydispersed models (i.e. numerous radii are considered) such as the sectional method, involve a large number of transport equations, and can be computationally unstable. In this paper, the polydispersed Quadrature Method of Moments (QMOM) is tested and compared with a classical, monodispersed (i.e. only one representative radius is considered) two-equation model. The use of the QMOM method is a step toward the description of the Particle Size Distribution in a context of large industrial CFD calculations: only a few equations are transported and a coarse distribution is computed. Academic test cases dealing with unsteadiness and shock wave instabilities in nozzles highlight the ability of the QMOM method to handle polydispersion and unsteadiness in flow fields similar to those encountered in steam turbines. The QMOM method has shown a very stable behaviour and proved to be a very good tool for condensation prediction in industrial applications.