An Experimental and Analytical Investigation of the Spray Structure from Automotive Port Injectors 941873

Port fuel injection system in gasoline engines is receiving an increasing attention for its potential advantages in meeting the constrains of simultaneous reduction in fuel consumption and exhaust emission, and maintaining a good engine performance. The structure of port injector spray dominates the mixture preparation process and strongly affect the subsequent engine combustion characteristics over a wide range of operating conditions in port-injection gasoline engines. In this paper, an experimental and analytical study is made to characterize the breakup mechanism and atomization process of the non-air-assisted port injector sprays in gasoline engines. The liquid sprays resulted from various types of current and development-type automotive fuel injectors were visualized using planar laser-induced fluorescence imaging technique. A comparison was made on the spray structure of the single hole and multi-hole injectors. The radial distributions of the droplet size and velocity and volume flux were characterized by a PDPA system. Multi-dimensional internal CFD and external spray calculation methods were combined to correlate the droplet size, spray angle and several other spray parameters of multi-hole port injectors with the injector design. Through this work, it was found that the multi-hole injector produces a finer spray with a wide spray angle and less dominant liquid phase compared with single hole injector which however, shows a very good pointing ability. Moreover, the turbulent primary breakup mechanism, rather than the aero-dynamic secondary one is identified to dominate atomization process of sprays for the low-pressure multi-hole injectors. By correlating to the internal CFD calculation result with an injection velocity distribution and an initial disturbance level directly linked to the turbulent energy, the multi-hole compound injector spray is successfully simulated. Therefore, the spray structure can be optimized through the injector design to meet the fundamental requirements of the gasoline engines.