Experimental investigation of the combustion of vegetable oils in diesel engine at low engine loads

Vegetable oils are being increasingly used as fuel in diesel engines in passenger vehicles, with various results. One of the associated problems is excessive emissions of organic compounds at very low engine loads. Aside from an undesirable increase in emissions, such compounds also contribute to the formation of deposits in the engine and in the catalytic reactor. In this study, a typical turbodiesel engine, adapted for operation on vegetable oils, was fitted with fast-response in-cylinder pressure measurement system. The engine was operated on an engine dynamometer at low loads typical for urban driving at several coolant and fuel temperatures. Results will be presented and discussed. Engine and rapeseed oil fuelling system setup, comparison of combustion timing of diesel fuel and rapeseed oil, indicated in-cylinder pressure for diesel fuel and rapeseed oil for different speeds and loads, indicated in-cylinder pressure at original and modified injection timing, comparison of nox and CO2 concentrations at original injection timing, emissions from rapeseed oil relative to diesel fuel at different speeds and loads, effect of injection timing optimization on peak indicated pressure, effect of injection timing optimization on nox and CO concentrations, Brake-specific fuel consumption, are presented in the paper.