1997-02-24

Transient Spray Characteristics of a Direct-Injection Spark-Ignited Fuel Injector 970629

This paper describes the transient spray characteristics of a high pressure, single fluid injector, intended for use in a direct-injection spark-ignited (DISI) engine. The injector was a single hole, pintle type injector and was electronically controlled. A variety of measurement diagnostics, including full-field imaging and line-of-sight diffraction based particle sizing were employed for spray characterization. Transient patternator measurements were also performed to obtain temporally resolved average mass flux distributions.
Particle size and obscuration measurements were performed at three locations in the spray and at three injection pressures: 3.45 MPa (500 psi), 4.83 Mpa (700 psi), and 6.21 MPa (900 psi).
Results of the spray imaging experiments indicated that the spray shapes varied with time after the start of injection and contained a leading mass, or slug along the center line of the spray. The penetration of the leading mass was faster than the penetration of the leading edge of the main body. Spray shapes were found to be generally similar over the pressure range examined. As expected, penetration of both the leading mass and the leading edge of the main body increased with injection pressure.
Particle size measurements indicated that the Sauter Mean Diameter (SMD) of the leading mass and leading edge of the main body of the spray were significantly larger than the SMD in other regions of the spray. Peak SMD values were smaller for higher injection pressures, and the change in peak SMD with pressure was more gradual as injection pressure increased.
Transient patternator measurements indicated that transient affects significantly influenced average spatial mass distributions, suggesting that short duration injections are likely to have different spatial distributions from longer duration injections.

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