Fuel effects on diesel odour from an IDI CFR engine

A single–cylinder CFR indirect injection (IDI) diesel engine was modified and instrumented to incorporate odour research utilising the Diesel Odour Analysis System. The effect on odour levels of some important fuel properties including volatility, cetane number and aromaticity were determined over the load range of the engine. Although fuels of high cetane number resulted in reduced ignition delay and reduced hydrocarbon and carbon monoxide emissions, no significant reduction in the odour level was noticed. Similarly, the combined effect of decrease in cetane number (from 52 to 36) and increase in aromaticity (from 21 to 47 per cent) in a typical diesel fuel had an insignificant effect on the odour level. Only fuel volatility correlated well with odour levels over normal engine operating conditions; decreases in fuel volatility (higher 90 per cent distillation point temperature) were associated with increased odour levels. Sources of odour generation during the engine combustion process are discussed and related to the observed fuel effects behaviour. The application of the results to other engine and burner systems is discussed.