Fuel Spray Evolution: Comparison of Experiment and CFD Simulation of Nonevaporating Spray

Abstract

Detailed spray characteristics were obtained for a small-capacity, pressure-swirl atomizer using an Aerometrics phase-Doppler particle analyzer. Measurements included drop size and velocity distributions, liquid volume fluxes, and air velocities at four axial locations, 25, 50, 75, and 100 mm, with complete radial traverses at each location. Drop size results were compared with measurements from a Malvern laser-diffraction instrument, and integrated liquid volume fluxes were compared with measured flow rates to estimate measurement uncertainties. Drop sizes measured by the two independent techniques and area-weighted-averaged over the radial traverses at each of the four axial stations varied on average by less than 4 percent. Integrated volume flux measurements by the phase-Doppler instrument at four axial stations differed from the nozzle flow rate by at most 19 percent, with some of the difference due to evaporation. The phase-Doppler data were used to begin an evaluation of a commercial two-phase, three-dimensional, CFD code (FLUENT). Using a simplified representation of the spray based on velocity measurements 2 mm from the atomizer, it is shown that the model predicts drop trajectories, velocities, and volume fluxes reasonably well, and air entrainment velocities fairly accurately except on the spray centerline. Drop velocity profiles indicate dense spray effects very close to the atomizer that are not properly predicted by the dilute spray model.