Spray Targeting Inside a Production-Type Intake Port of a 4-Valve Gasoline Engine

An experimental study was carried out to investigate the spray behavior inside engine intake ports. Production-type intake ports of four-valve gasoline engines were modified for the optical access at directions. The global spray formation process was visualized through laser Mie scattering technique. The spray breakup and atomization processes, spray targeting and fuel dispersing characteristics were investigated as a function of elapse time after fuel injection. The spray interaction with the port wall and port air flow were examined with different types of port fuel injectors including single-stream, multi-stream, and air-shrouded ones. The spray targeting and dispersing characteristics inside two different intake ports were examined. It was found that spray targeting and fuel dispersion inside the intake port are strongly dependent on the spray characteristics, as a result of different injector designs and injector installation positions. Single-stream injector has a good targeting capability but poor fuel dispersing characteristics. It causes a serious wall wetting on the port divider region when applied to a four-valve engine. Dual-stream injector shows an apparent improvement in reducing the port divider fuel wetting. In comparison, four-stream injector can better disperse the fuel across the intake port while with an increased port divider and port floor fuel wetting. The effect of air flow on the spray behavior was not significant for the intake ports examined in this study except for a slight spray acceleration. It was also found that the injector must be matched well with the intake port design. A careful selection of intake port geometry and injector can reduce the fuel wall wetting markedly.