Representing Polydispersed Droplet Behavior in Nucleating Steam Flow With the Quadrature-Method-of-Moments

Abstract

This paper applies the Quadrature-Method-of-Moments (QMOM) to the polydispersed droplets spectrum typical in low pressure steam turbines. Various modes of nonequilibrium phase transition are present in steam turbines, starting with primary and secondary homogeneous nucleation as the main source of moisture followed by heterogeneous nucleation and surface entrainment sources. The range of phase transition possibilities leads to a wide range of droplet sizes, which are present under various combinations of inertial and thermal nonequilibrium. Given the extensive prevalence of CFD in turbomachinery design, it is of interest to develop an efficient modeling approach for polydispersed droplet flows that avoids solving an excessive number of equations to represent the droplet size distribution. Methods based on QMOM have shown promise in this regard in other applications areas of two-phase flow, and this paper attempts to quantify its potential for steam turbine applications by applying the method to supersonic nozzle studies with homogeneous and heterogeneous phase transitions.