Secondary-Drop-Breakup Simulation Integrated With Fuel-Breakup Simulation Near Injector Outlet

The fuel spray of an injector for automobile engines contains multiscale free surfaces: liquid films formed at the fuel-injector outlet, ligaments generated by liquid-film breakup, and droplets generated from the ligaments within the secondary-drop-breakup region. To simulate these multiscale free surfaces, we developed a method that combines two types of simulation. The liquid-film breakup near the injector outlet was simulated by using a particle method, and the secondary-drop breakup after the liquid-film breakup was simulated by using a discrete droplet model (DDM). The injection conditions of DDM were the distributions of droplet diameters and velocities calculated in the liquid-film-breakup simulation. We applied our method to simulate the spray from a collision-type fuel injector. The simulated liquid-film breakup near the injector outlet and behavior of the secondary-drop breakup qualitatively agreed with measurements. Furthermore, the errors of the mean droplet diameters between the simulations and the measurements were less than 12%. This shows that our method is effective for fuel spray simulation.