Study On The Injection Characteristics Of A Multi-hole Injector Using Various Alcohol-Gasoline Blends

Bio-ethanol and bio-butanol used in gasoline engines not only decrease the dependence on fossil fuel, but also reduce the emissions from gasoline engines. Spray characteristics have close relation to the combustion processes and emissions of gasoline direct injection(GDI) engines. Hence, it is significant to investigate the spray characteristics and fuel injection rates of baseline gasoline, alcohol-gasoline blends containing 10% and 30% volume fraction ethanol, and 10% and 30% volume fraction n-butanol on an injection rate measurement set-up and a constant volume chamber. The conclusions are drawn as following.The amount of alcohol-gasoline blends during one injection is larger than that of gasoline under the condition of a long injection pulse or a high injection pressure. Under high injection pressure, spray penetrations increase and the differences in sprays from each injection at the same time after fuel injection increase.The spray penetrations of alcohol-gasoline blends are close to those of gasoline at high ambient pressures. The spray cone angles of various fuels at the initial stage of injection are much influenced by the ambient pressure in the chamber. At low ambient pressure, the spray cone angles of gasoline are greater than those of alcohol-gasoline blends. On the contrary, at high ambient pressure, the spray cone angles of alcohol-gasoline blends are bigger than those of gasoline except that case using the blends containing 30% volume fraction ethanol.The amount of different fuel droplets vaporized increases with increased ambient temperature under different ambient pressures. However, spray penetration and cone angle of different fuels are slightly affected by the ambient temperature in the chamber.In the case of low ambient pressure, significant spray collapse for the alcohol-gasoline blends with high temperature is observed, spray plume contracts towards the axis of the injector, but the spray of gasoline collapses less. Furthermore, the spray of ethanol-gasoline blends collapses at the lowest fuel temperature, while spray of gasoline collapses at the highest fuel temperature. With increasing fuel temperature, spray penetrations of different fuels initially reduce and then increase, while the spray cone angles of various fuels gradually decrease. As for the change in spray cone angles, ethanol-gasoline blends decrease most while gasoline does least. In the case of high ambient pressure, fuel temperature only has little effect on the spray characteristics.The influence of fuel temperature on the spray characteristics of different fuels is affected much significantly than that of ambient temperature. In particular, alcohol-gasoline blends are easily affected by fuel temperature as compared to gasoline.