The purpose of this investigation is to evaluate the feasibility of rapeseed oil and palm oil for diesel fuel substitution in a naturally aspirated D.I. diesel engine, and also to find means to reduce the carbon deposit buildup in vegetable oil combustion.
In the experiments, the engine performance, exhaust gas emissions, and carbon deposits were measured for a number of fuels: rapeseed oil, palm oil, methylester of rapeseed oil, and these fuels blended with ethanol or diesel fuel with different fuel temperatures.
It was found that both of the vegetable oil fuels generated an acceptable engine performance and exhaust gas emission levels for short term operation, but they caused carbon deposit buildups and sticking of piston rings after extended operation. Practical solutions to overcome the problems were: increasing the fuel temperature to over 200 °C, blending 25 vol% diesel fuel in the vegetable oil, blending 20 vol% ethanol in the fuel, or converting the vegetable oils into methylesters.