Measurements of the Evaporation Behavior of the Film of Fuel Blends

The formation of fuel film in the combustion cylinder affects the mixing process of the air and the fuel, and the process of the combustion propagation in engines. Some models of film evaporation have been developed to predict the evaporation behavior of the film, but rarely experimental results have been produced, especially when the temperature is high. In this study, the evaporation behavior of the film of different species of oil and their blends at different temperature are observed. The 45 μL films of isooctane, 1-propanol, 1-butanol, 1-pentanol, and their blends were placed on a quartz glass substrate in the closed temperature-controlled chamber. The shape change of the film during evaporation was monitored by a high-speed camera through the window of the chamber. First, the binary blends film of isooctane and one of the other three oils were evaporated at 30 °C, 50 °C, 70 °C and 90 °C. Secondly, the pure films of isooctane, 1-propyl alcohol, 1-butanol and 1-pentanol were evaporated at 90 °C. Finally, after the data processing in Matlab, the data of the volume change, average thickness, and maximum thickness were obtained. The results also showed that there would be three evaporation periods according to different volumetric evaporation rates. With the increase of temperature, the first period would have a higher percentage of the whole evaporating volume of film. The evaporation behaviors were similar for Pr50 (50% isooctane and 50% 1-propanol) when the temperatures are 70 °C and 90 °C. Additionally, the evaporation behaviors were similar for Pr50 and B50 (50% isooctane and 50% 1-butanol) when the temperature is at 90 °C. Although there were small differences of the boiling points between 1-propanol and isooctane, the isooctane evaporated faster because of its higher vapor pressure and lower latent heat.