Fuel injectors for automobile engines atomize fuel into 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. We previously developed a fuel spray simulation combining the liquid-film breakup near the injector outlet with the air/fuel mixture. The liquid-film breakup was simulated by a particle method. The fuel-droplet behavior in the air/fuel mixture region was simulated by a discrete droplet model (DDM). In this study, we applied our method to simulate fuel sprays from a fuel injector with collision jets. The simulation results were compared with the measurements—the mean diameter of droplet in spray, D32, was 35 percent larger than measured D32. We also studied the effects of DDM injection conditions on the spray distribution in the air/fuel mixture region—diameter distributions of injected DDM-droplets were given by the liquid-film breakup simulation, or by Nukiyama-Tanazawa’s theory. The diameter distribution of droplets near the injector outlet was found to affect the spray distribution within the air/fuel mixture region, mainly around the leading edge of spray.

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