Computational studies of air-assisted spray impingement on a flat plate

Fuel impingement and film formation are critical issues for the goal of reducing hydrocarbon emissions from automotive gasoline direct injection engines. This computational study compares fuel impingement from a simulated air-assisted spray with that of a simulated spray from a swirl atomizer. Impingement occurs on a flat plate in a low ambient pressure case that approximates an early-injection condition and in a high ambient pressure case that approximates a late-injection condition. The simulated results suggest that the air-assisted injector produces substantially less fuel film and impingement than the swirl atomizer because of faster vaporization of smaller droplets and slower penetration. Although the swirl atomizer produces more splashing, much of the splashed fuel mass returns to the plate. More detailed numerical studies of the air-assisted injector were also conducted to ascertain the effects of turning the vaporization model off, employing a very fine grid, having angled impingement and changing the injector design to increase the initial spray angle.