A spray from a GDI multi-hole injector is used to investigate and compare the atomization results from five different fuels in which air has been dissolved to promote the atomization. The spray is injected in ambient air at ambient conditions; five fuels are tested, two gasolines with different distillation curves, and three mono-component fuels, pentane, hexane and N-heptane. The fuel is heated at constant temperature, between 30° and 120°C, and pressurised at 50 bars, a relatively low pressure used to improve the accuracy of the droplet sizing by PDA, thus allowing higher sensibility in detecting small variations of the measured quantity for better comparison among the results.
This work follows and completes a previous study, with similar methodology. The global spray behaviours, like spray penetration and spreading angle, are illustrated by photographic results. Then the atomization is accurately measured by Phase Doppler Anemometry and results are analysed and compared. The spray droplet are measured at 45mm of axial distance from the injector tip in 13 different radial positions; after data post-processing the average velocity and diameters results are plotted, both as time evolution in a fixed position, and as radial profiles during the quasi-steady injection period.
With all fuels and no air dissolved, the temperature increase gives negligible effects up to each fuel initial distillation or boiling point, above which stronger variations are observed, with the typical spray collapse at increasing temperature.
When the fuel injected is saturated with air dissolved in it, the effects observed are very similar to those happening because of flash boiling, but they start and become observable at temperature that are about 20 degrees lower. The major effects are the spray collapse, with a closer shape, generally finer and more homegeneous atomization, and a remarkable lack of larger droplets, which results in a better atomization of the initial droplets of the spray