Combustion characteristics of a 1-butanol gel fuel droplet in elevated pressure conditions

Abstract

The aim of this study was to determine the combustion characteristics of a 1-butanol gel fuel droplet under elevated temperature and pressure conditions. (1)-Butanol is an excellent candidate for replacing conventional fossil fuels because it is sustainable and has a higher heating value than ethanol and methanol. A 1-butanol gel fuel was produced by adding 10 wt% of distilled water and 2.5 and 3 wt% of hydroxypropyl methylcellulose. The combustion of 1-butanol gel fuel can be divided into three stages: droplet heating, 1-butanol combustion, and crust combustion. Puffing was frequent at 1 bar, but it decreased as the ambient pressure increased. An increase in the ambient temperature reduced the ignition delay and droplet lifetime but slightly increased the effective burning rate owing to droplet inflation at 600 °C. The elevation of the ambient pressure did not significantly affect the ignition delay and effective burning rate, except at 1 bar, because the gel layer around the droplet surface dominated the combustion process by suppressing the evacuation of fuel vapor. The ignition was delayed as the gellant concentration increased when the ambient temperature was 600 °C; however, the gap diminished when the ambient temperature was increased to 700 °C. The effective burning rates were similar in all cases. The overall results demonstrated that the combustion behavior of the gel droplet was insensitive to pressure compared with that of the neat liquid fuel because of the effect of the gel layer at the droplet surface.