Two-Phase Computational Fluid Dynamics Analysis Applied to Prefilming Pure-Airblast Atomizer

A portion of an effort to effectively integrate two-phase, 3D CFD analyses into the design process for fuel atomizers is presented. The primary focus is to assess the utility of using two-phase CFD analyses to guide effectively the design process for the fuel swirler and prefilmer for a pure-airblast atomizer. The study is limited to analysis of the fuel flow under conditions where there is no air pressure drop across the nozzle. Breakup of the liquid sheet is not addressed. Items of interest are 1) film thickness and its circumferential variation at the exit of the prefilmer, 2) velocity components of the fuel film at the exit of the prefilmer, 3) spraycone angle, and 4) leading-edge fuel recirculation /backflow. The Fluent version 5.5 CFD package is used for all analyses. Two-phase flow is modeled using Fluent's implementation of the volume-of-fluid method. Computational results are presented for a baseline experimental fuel swirler that backflows fuel through the inner-air circuit and a modified geometry, guided by CFD, that all but eliminates the backflowing. The CFD results compare favorably with experimental data on film velocity, film thickness, spray-cone angle, and leading-edge recirculation /backflow. (Author)