Investigation of Combustion Rates and Injection and Ignition Onset of Heated Rapeseed Oil in Direct-Injection Turbodiesel Engines

This paper reports on the experimental investigation of the combustion of heated rapeseed oil in a typical tractor engine, which was operated alternately on heated rapeseed oil and diesel fuel without any adjustments of the injection pump. At intermediate to high engine rpm and loads, onset of combustion occurred earlier on rapeseed oil. This was correlated with increased emissions of nitrogen oxide and earlier onset of pressure rise in the injector, and independent of fuel temperature. At low rpm and loads, the onset of the combustion occurred later on rapeseed oil and was correlated with elevated emissions of hydrocarbons; this deterioration was exacerbated by prolonged low-load operation and by low fuel temperatures. It appears that there is a possible link among later onset of combustion, low temperatures of combustion chamber surfaces, formation of deposits, and increased emissions, suggesting that certain regions of the engine operating map need to be identified and operation of the engine on rapeseed oil in such regions avoided or improved.