Development of Air-Assisted Injection System for MPI Gasoline Engine 981056
The spray characteristics of air-assisted fuel injection system and its effects on the combustion of port-injection type gasoline engine were investigated in this study. In order to supply assistant air for the atomization of injected fuel, several types of air-assisted injection adapter, which is not only easy to make and equip but also good for low-cost mass production, were designed and manufactured.
The atomization characteristics of a multi-point type injector inserted into the adapter such as spray pattern, droplet distributions were evaluated using particle size analyzing system. Droplet sizes of fuel injection were decreased with assistant air supplied, and fine spray under 60mm of SMD was acquired on the conditions of air-assist pressure over 0.4bar.
And the lean combustion performance of an MPI engine equipped with one of those adapters was tested on the dynamometer. Lean combustion limit defined by air-to-fuel ratio for cycle-by-cycle stability showed the maximum value when the assistant air pressure is 0.8bar, and HC, CO emissions were decreased over that pressure.
From these results, it is concluded that the air-assisted injection adapters applied in this study have enough effects on fuel atomization, so that those can be useful for idle stability, lean combustion, etc.