Flash boiling macroscopic spray characteristics of multi-hole direct injection injectors with different hole arrangement

Abstract

The spray characteristics of two direct-injection gasoline injectors with different hole arrangement under flash boiling conditions were studied. The spray development and spray characteristics, such as the spray tip penetration, spray angle, rate of collapse, and spray area during the injection process of the two injectors were studied via high-speed shadowgraph techniques. The sprays were divided into three regions based on the rate of collapse at room temperature and atmospheric pressure, that is, the subcooled region, and flash boiling region (transition region and flare flash boiling region). In addition, the spray characteristics of injector N under different superheated degree and ASOI were determined in detail. The experimental results showed that the spray plumes of the injector (N) with small hole spacing easily interacted, causing the earlier collapse of the spray structure. Injector (N) with small hole size had a good effect on atomization, and the effect of flash boiling on spray characteristics was low. The flashing spray characteristics are not only affected by the degree of superheat, but also by the ambient pressure alone. The spray characteristics of injector N and injector W in the transition region are ideal for the GDI engine. This may provide new opportunities for the GDI engine combustion system and injection strategy design.