A Numerical Study of Two-Phase Transonic Steam Flow through Convergence-Divergence Nozzles with Different Rates of Expansion

During the transonic flow of steam in a divergence nozzle, flow first supercools and then nucleates to become a two-phase droplet flow. This phenomenon especially occurs in the last stages of steam turbines and affects the performance. In this research, a numerical scheme for two-phase flow in nozzle passages is developed. An Eulerian Eulerian reference frame is used for both phases. The Shear Stress Transport turbulence model is used to model the Reynolds stresses appeared in the averaged Navier-Stokes equations. The SIMPLE algorithm is used to solve the discritized equations and a homogenous nucleation model applied for the mass transfer in the transonic conditions. In this paper three nozzles with different rate of expansion are employed to be under study. Overall (static to total); pressure ratio and droplet size through the results are compared with the experimental data and good agreements are observed. Also, the two-phase results are compared with the dry steam simulation in the same pressure condition and the differences of pressure and Mach profiles for these types are the case of discussion.

کلیدواژه ها:

Nucleation ، Two-Phase Flow ، Nozzles ، CFD ، Eulerian-Eulerian )