Keywords: biodiesel, fatty acid composition, combustion, diesel engines, engine emissions, engine performance, biofuels
Combustion, performance and emission characteristics of a DI CI engine using biodiesel with varied fatty acid composition
Five Biodiesel produced from different vegetable oils were tested on a diesel engine to study the effect of biodiesel fatty acid composition specifically unsaturated composition on the engine combustion. The results from fuel analysis show that biodiesel (93% unsaturated fatty acid ester composition) with 55% linolenic ester has a higher density of 0.89 kg/m³, lower viscosity of 3.8 cSt, heating value of 39 MJ/kg and cetane number of 49. The engine combustion results exhibits a longer premixed and shorter diffusion burning phase with higher peak pressure of 72 bars and higher cumulative heat release compared to other fatty ester composition. The performance and emission results show that emits more oxides of nitrogen of 16.83 g/kWh and exhibits higher thermal efficiency of 29.76% compared to diesel of 12.83 g/kWh and 28.41% respectively. Biodiesel with 45% saturated ester and 55% unsaturated ester composition shows a NOX neutral fuel with a penalty of 1.75% in thermal efficiency. No significant differences in unburnt hydrocarbon (UBHC), carbon monoxide (CO) and smoke emissions among the biodiesel fuels were noticed except linseed oil methyl ester.