PREDICTION OF EVAPORATING SPRAY IN ANISOTROPICALLY TURBULENT GAS-FLOW

Numerical investigation was conducted for a confined evaporating isopr opyl alcohol spray issuing into a coflowing, heated turbulent air stre am. The Eulerian-Lagrangian stochastic model was used for the spray ca lculations. The gas phase turbulence was modeled using either the isot ropic eddy viscosity model or the second-moment transport model for bo th Reynolds stresses and heat fluxes. Two droplet dispersion models we re studied for the Lagrangian trajectory calculations: the conventiona l particle-eddy encounter model and the time-correlated dispersion mod el. In the time-correlated model, gas phase turbulent velocity fluctua tions were correlated temporally and directionally between two success ive time steps in modeling the droplet dispersion. The droplet evapora tion was accounted for by the infinite-conduction evaporation model, w here the gas-film variable properties were considered using the one-th ird rule. Detailed numerical results of the liquid droplet phase, i.e. , the droplet mean diameters, mass fluxes, mean, and fluctuating veloc ities were presented and discussed by comparison with the experimental data. Results show that the droplet mean properties are generally not sensitive to the gas phase turbulence models and the droplet dispersi on models, all of which can give agreeable predictions with the measur ements except for the droplet mass fluxes, which accumulate persistent ly near the centerline far downstream in all calculations. It is found that the conventional particle-eddy encounter model fails to account for the anisotropy of droplet turbulence, no matter what turbulence mo del is used for the gas phase. The anisotropy of droplet phase turbule nce, however, is well predicted by the time-correlated dispersion mode l in conjunction with the gas phase second-moment transport model.