Comparative study of Euler/Euler and Euler/Lagrange approaches simulating evaporation in a turbulent gas-liquid flow

摘要

This study deals with the Reynolds-averaged Navier-Stokes simulation of evaporation in a turbulent gas- liquid flow in a three-dimensional duct, focussing on the results obtained by a four-equation turbulence model within the framework of the Euler/Euler approach for multiphase flow calculations: in addition to the two-equation k-ε model describing the turbulence of the continuous (C) phase, the computational model employs transport equations for the turbulence kinetic energy of the disperse (D) phase and for the velocity covariance q =〈{(u{sub}i){sup}D }{sup}D{(u{sub}I){sup}C }{sup}C〉{sup}D. In the present study, the evaporation model according to Abramzon and Sirignano (Int. J. Heat Mass Transfer 1989; 32:1605-1618) has been extended by introducing an additional transport equation for a newly defined quantity a{top}-, defined as the phase-interface surface fraction. This allows the change in the drop diameter to be quantified in terms of a probability density function. The source term in the equation describing the dynamics of the volumetric fraction of the dispersed phase α{sup}D is related to the evaporation time scale τ{sub}Γ. The performance of the new model is evaluated by performing a comparative analysis of the results obtained by simulating a polydispersed spray in a three-dimensional duct configuration with the results of the Euler/Lagrange calculations performed in parallel. Prior to these calculations, some selected (solid) particle-laden flow configurations were computationally examined with respect to the validation of the background, four-equation, eddy-viscosity-based turbulence model.