An Investigation of Abnormal Spray Behaviors of Multi-Hole GDI Injector 2016-01-0848

The main objective of this paper is to investigate the influence of injection pressures and fuel temperatures on the secondary injection spray evolution at the end of injection from a multi-hole gasoline direct injection (GDI) injector by Mie-scattering technique.

The results of this paper show that the overall injection process can be classified into five stages which are injection delay stage, main injection stage, dwell stage, secondary injection stage and ligaments breakup stage respectively. Especially, the secondary injection occurs at the end of main injection, which is abnormal and undesirable spray behaviors. During the injection, big droplets and ligaments are injected through nozzle orifices at low speed.

As the injection pressure increases, the phase of the secondary injection advances, and the injection duration decreases. At medium injection pressures (at 6, 8 MPa), more quantity of fuel are injected as ligaments. At higher injection pressures (above 10 MPa), more droplet clusters can be produced. The secondary injection spray tip penetration is lower than that of main injection. The average increment of penetration in one time step is small. The total tendency of the secondary injection spray tip velocity is declining. The average spray tip velocity of secondary injection decreases by about 60% to 70% as compared with that of the main injection. The spray breakup in the secondary injection stage is within the second wind induced regime at low fuel temperature. As the increase of fuel temperature, the secondary injection produces more atomized droplet clusters and less liquid ligaments, accompanied with injection event phase advance, short injection duration and small amount of injected fuel.