STUDIES OF GASOLINE DIRECT-INJECTION SPRAYS AT ELEVATED AMBIENT GAS TEMPERATURES AND PRESSURES

This paper studies the influence of ambient conditions on full flow-field, temporally resolved fuel spray characteristics. The gasoline sprays from a direct-injection (DI) injector are examined for varying ambient air densities, air temperature, and fuel temperatures of practical relevance. The data presented and analyzed in this paper have been obtained utilizing temporally resolved phase Doppler anemometry and high-speed imaging (utilizing Mie-scattering) of the spray. The sprays were characterized in an established high-temperature, high-pressure constant volume rig with large optical access. Results are analyzed and discussed in comparison with the "benchmark" spray characterized at atmospheric conditions. Analysis of the injection event is subdivided into three dominant phases: early, mid, and late phase development, corresponding to the transient injection rate characteristic from a gasoline DI rate tube. In particular, the influence of each ambient parameter on the spray structure and spray quality is analyzed in terms of primary atomization, secondary droplet breakup, coalescence, and droplet vaporization. A test matrix is carefully chosen to enable decoupling of these primary spray phenomena. Elevated fuel temperature is shown to have a significant influence on primary atomization, primarily due to variation of liquid properties. This dataset is extremely useful for computational fluid dynamics model appraisal, while spatial integration of the data enables comparison with previous empirical correlations for first-order approximations of global parametric trends.