Abstract
This work describes the visualization of spray structure and the spray characteristics of a high pressure gasoline injector. The global spray structure of a high pressure gasoline injector was investigated when fuel was injected for a injection duration of 1 msec at pressures of 5 MPa and 7 MPa. Also quantitative spray characteristics were measured by using a phase Doppler particle analyzer (PDPA) and particle image velocimetry (PIV) system. A ring shape vortex was observed at the later stage of injection in which the air entrainment into the spray is expected to promote an air/fuel mixing process. The peripheral droplets which coalesced with the inside droplets in the axial direction were entrained with air vortices. The spray tip penetration and spray width with time were linearly proportional to the time and injection pressure. The spray tip velocities were estimated to be 42 m/s and 47 m/s and the spray cone angle were about 52° and 54° at injection pressures of 5 MPa and 7 MPa respectively. It was shown that the spray droplets at 7 MPa of injection pressure were disintegrated into the smaller droplets and had slightly higher velocity than those of 5 MPa. From the PIV measurement the spray developed 0.4 msec later at an injection pressure of 5 MPa compared to that of 7 MPa.