Applying Particle/Grid Hybrid Method to Fuel Spray With Collision Jet for Automobile Engines

A fuel spray contains multi-scale free surfaces: liquid films formed at the fuel-injector outlet, ligaments generated by the liquid-film breakup, and droplets generated from the ligaments within the air/fuel mixture region. To simulate multi-scale free surfaces, we previously developed a fuel spray simulation combining the liquid-film breakup with the air/fuel mixture. In this study, we modified a part of the liquid-film breakup simulation that uses a particle/grid hybrid method. The procedures combining a particle method and a grid method were changed to obtain more accurate prediction. First, a simple benchmark test, collapse of a water column as investigated by Martine and Moyce, was used to verify the modified simulation method; the behavior of the water column better agreed with measurements than that by the original method. Next, we applied the modified method to simulate the collision jets from three kinds of nozzles. The simulation results were verified by comparison with measurements; the predicted liquid-film breakup qualitatively agreed well with measurements. Furthermore, the errors of mean droplet-diameters between the simulations and the measurements were less than 12%. Therefore, we found that the modified method was effective for spray simulation.