Evaporation of a 1-Butanol Gel Fuel Droplet under Elevated Pressure Conditions

In this study, the evaporation characteristics of a gel fuel droplet under elevated temperatures and pressures were studied. 1-Butanol was selected as the base fuel because it is eco-friendly and has a calorific value similar to that of hydrocarbon-based fuels. In the experiment, 2.5 and 3 wt % hydroxypropyl methylcellulose (HPMC) was added as a gellant to generate the gel fuel. The viscosity of the gel fuel significantly increased compared to that of the 1-butanol fuel, and it decreased as the shear rate increased, which is referred to as the shear-thinning behavior. The evaporation of the 1-butanol gel fuel was divided into three periods, which were categorized as droplet heating, puffing, and crust formation. The behavior of each period changed as the ambient conditions changed. The elevation of the ambient temperature and gellant concentration boosted the intensity of puffing, whereas puffing was suppressed under higher-ambient-pressure conditions. When the ambient temperature increased from 600 to 700 °C, the evaporation rate of the gel fuels increased due to the increase in heat supply from the ambient temperature. Nevertheless, an increase in the ambient pressure and mass concentration of the gellant did not significantly affect the evaporation rate of the gel fuel.