Optimisation of Karanja/Jatropha-Methanol emulsification variables and their engine evaluation

Vegetable oil based emulsified fuels have emerged as an attractive option for existing diesel engines. The issues such as higher viscosity and exhaust emissions such as oxides of nitrogen (NOX), particulate matter (PM) are associated with straight vegetables oils (SVO), which can be potentially eliminated by making SVO emulsions, without worrying about PM-NOx trade-off. In this study, emulsions were prepared, where methanol was used as a dispersed phase and SVOs (Jatropha and Karanja) were used as continuous phase. A non-ionic commercial surfactant 'Sorbitan monooleate' also known as 'Span®80' was added and the mixture was stirred by a mechanical stirrer to produce emulsified fuel. Effect of several process variables such as surfactant concentration, stirrer speed and stirring duration on emulsion stability were optimised. The optimum surfactant concentration, stirrer speed, and stirring duration were determined for Methanol-Jatropha/Karanja emulsions. Emulsified fuels had important fuel properties comparable to baseline mineral diesel. These emulsions were blended with diesel in 1:3 proportions and evaluated in a single cylinder diesel engine for their performance and emissions characteristics. Performance and emission characteristics of emulsified blends followed a trend, which was related to methanol concentration in the dispersed phase of the emulsions.