The role of rhodium sulfate on the bond angles of triglyceride molecules and their effect on the combustion characteristics of crude jatropha oil droplets

[Display omitted] •Rhodium sulfate as a liquid catalyst was blended with crude jatropha oil.•Rhodium sulfate enlarges the bond angle of the triglyceride.•Increased bond angles cause atoms to get extra space to move and more reactive.•Increased bond angles weaken the bonds molecules so that easily breaks and burns.•Rhodium sulfate improves the properties and combustion performance. The alternative fuels were developed from a blended fuel with crude jatropha oil (CJO) and rhodium sulfate as a homogeneous combustion catalyst. In this study, the performances of blended fuel droplets were investigated experimentally under normal gravity conditions. Combustion characteristics were observed by igniting droplets at the thermocouple junction, and the droplet combustion was observed using a high-speed camera. To this end, understanding how the molecular structure (bonding and angular properties of triglyceride carbon chains) of the fuel affects the combustion characteristics is crucial. The results showed that CJO had 53 rotatable and 111 nonrotatable bonds. This makes CJO more rigid and nonpolar. The interaction of the catalyst with triglycerides changes the molecular chain bond angle so that the atoms get extra space to move, thereby increasing the electron mobility. This makes the fuel molecule more reactive so that the viscosity and flash point are reduced and the fuel is easily ignited. Moreover, the results also showed that the catalyst improved combustion performance, where droplet ignition times were shorter at higher temperatures, and fuel droplets had higher burning rates and combustion temperatures.