High-Speed Imaging Study on the Effects of Internal Geometry on High-Pressure Gasoline Sprays 2020-01-2111

High-pressure gasoline injection can improve combustion efficiency and lower engine-out emissions; however, the spray characteristics of high-pressure gasoline (>500 bar) are not well known. Effects of different injector nozzle geometry on high-pressure gasoline sprays were studied using a constant volume chamber. Five nozzles with controlled internal flow features including differences in nozzle inlet rounding, conicity, and outlet diameter were investigated. Reference grade gasoline was injected at fuel pressures of 300, 600, 900, 1200, and 1500 bar. The chamber pressure was varied using nitrogen at ambient temperature and pressures of 1, 5, 10, and 20 bar. Spray development was recorded using diffuse backlit shadowgraph imaging methods.

The results extracted to describe the spray development included spray tip penetration distance, spray tip penetration rate, and spray angle and include comparisons of the effects of operating conditions and injector geometry variants on spray development. The gasoline spray development was more sensitive to changes in ambient pressure and less sensitive to changes in injection pressure. Spray angle was a more complex function of operating conditions. Larger nozzle diameter, as well as the combination of a converging nozzle and hydro-erosion rounding, resulted in increased penetration distance and spray angle compared with other geometries. However, the nozzle with the smallest diameter consistently resulted in the lowest spray angle, and the diverging nozzle consistently produced the highest spray angle. The largest outlet diameter consistently had the highest penetration distance. Stochastic changes in the spray angle were quantified and indicate the nozzles may have been experiencing significant cavitation affecting the external flow development.