Comparison of gasoline and mono-component fuels: effect of the temperature on the atomization of a GDI spray

A spray from a GDI multi-hole injector operated in ambient air at known conditions is used to investigate and compare the atomization results from five different fuels: two gasolines with different distillation curves, and three mono-component fuels, pentane, hexane and N-heptane. The analysis is focussed on the effect of the fuel temperatures between 30°C and 120°C. The spray is studied with different experimental techniques to better understand the different behaviours. 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 analyzed and compared. The spray droplet are measured at 45mm 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. For each pure component, the temperature increase gives negligible effects up to its boiling point, above which stronger variations are observed in all the investigated parameters. The typical structure change with the spray collapse at increasing temperature is easily visible from photographic comparison. From PDA, atomization effects are more evident and easy to quantify and compare: the velocity profile clearly shifts towards the centre of the collapsing spray, while the droplet velocity and size decreases. Both gasolines show this same behaviour too, starting from a temperature slightly above their distillation initial point, that is also very close to the boiling point of hexane. All the results from both gasolines are very similar to those from hexane at the same temperatures, thus highlighting the importance of a correct model fuel choice when evaporation phenomena become important on the spray development.