Comparison of gasolines with different distillation curves: effect of the temperature on a GDI spray opening angle

A GDI multi-hole injector was used to investigate the effect of the fuel composition and temperature on the spray angle. Ten different fuels were tested: three pure mono-component hydrocarbons, six different gasolines and one very light fuel with a short distillation curve. The injector and the tested fuel were heated-up at different temperatures ranging from 20 to 120 °C, then the spray was injected in a quiescent bomb. Back light photography was used to capture still images of the spray from which some geometrical parameters could be extracted. Attention was focused on the spray spreading when quasi-steady conditions are reached: its initial and far field angles could be compared to infer information on the effect of the fuel composition on these spray macroscopic parameters. No effects are evident when the fuel temperature is below the distillation curve. Evaporation and flash boiling effects are immediately visible when the fuel temperature increases above the initial point of the distillation curve: the spray width measured close to the injector widens, while it narrows in the far field. For the six tested gasolines the measured angles start to change at similar temperature, they show smooth variation with the temperature increase, and behave very similarly among them with slight or negligible differences. The pure components and the light fuel show a much stepper change when the temperature increases above their boiling point. The comparison put in evidence the limits and differences when using a mono-component fuel to simulate gasoline injection.