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Ethanol direct injection (EDI) is a new technology to use ethanol fuel more efficiently in spark ignition engines. Fuel temperature is one of the key factors which determine the evaporation process of liquid fuel spray, and consequently influence the combustion and emission generation of the engine. To better understand the mixture formation process of the EDI spray and provide experimental data for engine modelling, experiments were conducted in a constant volume chamber in engine-like conditions. The high speed Shadowgraphy imaging technique was used to capture the ethanol spray behaviours. The experiments covered a wide range of fuel temperature, ranged from 275 K (non-evaporating) to 400 K (flash-boiling). Particularly the transition of the ethanol spray from normal-evaporating to flash-boiling was investigated.

Surface tension is important due to its affect on fuel spray and atomization processes. Fuel drops tend to breakup easier at smaller surface tension, which leads to smaller Sauter Mean Diameter of the spray and enhanced evaporation. Despite its importance, there are few data on the surface tension of alcohol + diesel fuels and even less are available on its temperature and concentration dependence. To overcome this limitation, this work reports experimental surface tensions of ethanol, n-butanol and diesel at different temperatures, and the experimental surface tensions of ethanol/n-butanol + diesel mixtures at 7 mass fractions at different temperatures. The experimental data showed that mixture surface tension decreased linearly as temperature increased and it also decreased monotonically while alcohol mass fraction increased. The results were correlated with concentration and temperature using the least square fitting method.