Effect of FFA of Jatropha Curcas L Oil on Performance and Emissions of a DI Diesel Engine

Oil with high free fatty acid (FFA) content may not be an appropriate contestant for biodiesel production due to poor process yield. The high FFA content (≻1%) will cause soap formation and the separation of products will be exceedingly difficult, and as a result, it has low yield of biodiesel product. In order to increase the process yield, pretreatment setup is required. This involves additional cost and will increase overall fuel price. Hence crude vegetable oils having high FFA can be blended with diesel for effectual employment in diesel engines. In this context, Jatropha Curcas L, non-edible tree-based oil with higher FFA content, can be considered as one of the prominent blending sources for diesel. The primary objective of the present work is to analyze the effect of FFA content of crude Jatropha Curcas L oil (CJO) on performance and emission characteristics of a direct injection (DI) diesel engine. The effect of FFA on some of the critical fuel properties was also investigated.
In the present study, the CJO with five different FFA percentages (5.1, 7.6, 10.1, 12.7, and 14.9 %) were collected and blended in the ratio of 80:20 (diesel:CJO) on volume basis. The effect of FFA content on density, viscosity, cetane number, heating value, volatility characteristics, and oxidative stability was investigated. From the measurements it was observed that the density, viscosity, and distillation temperatures were found to increase with increase in FFA content in the blend; while cetane number, heating value, and oxidative stability were observed to decrease with increase in FFA content. As compared to diesel, density, kinematic viscosity, and distillation temperatures were higher for such blends and the difference in magnitude ranges by 3 to 7.5% for density, 2.2 to 4.6 times in kinematic viscosity, and by 24 to 58°C in T50 temperature. However, cetane number of the blends increased while the heating value decreased when compared to diesel. The cetane number of blends was found to be higher by 4.3 to 19.1%; whereas heating value was observed to be decreased by 3 to 7.9% as compared to diesel. To study the performance and emissions, tests were carried out in a DI diesel engine at different loads. The effect of FFA content on brake specific fuel consumption, brake thermal efficiency, oxides of nitrogen, and smoke was investigated. It is found that the brake thermal efficiency and smoke decrease; while oxides of nitrogen increases with increase in FFA content. The magnitude ranges by 0.33 to 2.04% in brake thermal efficiency, 5.4 to 27% in smoke, and 3.4 to 21.7% in oxides of nitrogen for blends as compared to diesel. From the present study, it can be concluded that the blend of CJO (80:20 diesel:CJO) up to 5.1% FFA content can be considered as a potential blending agent for diesel fuel.
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