The impact of soybean methyl ester (SME) on the injection mass curve, exhaust emissions, engine performance, and exhaust gas temperatures of a common-rail direct injection diesel engine have been investigated. In this study, 30% SME blended diesel fuel (BD30) has been used as a fuel in the engine and results of the investigation were compared to those obtained using petroleum diesel fuel. The results of the investigation show that the change in injection mass curve when using BD30 instead of diesel was insignificant. A combustion analysis shows BD30 has a shorter ignition delay at part-load operating condition where heavy exhaust gas recirculation (EGR) rate is used. This difference in behavior is due to the oxygen contents and lower stoichiometric air-fuel ratio of BD30, which leads to higher O2 concentration in the exhaust gas. At part-load operating conditions, BD30 results showed 53% reduction in smoke at the expense of 18% increase in NOx emission. The full load engine power for BD30 was decreased by 2.1∼3.8% using EMS (engine management system) configurations without torque adjustment to compensated reduction in calorific value of BD30. When the engine power was so adjusted that BD30 produced the same power as diesel fuel, a lower exhaust gas temperature was observed at full load operating condition. Considering that the LHV (lower heating value) of BD30 is 2.6% lower than that of diesel fuel, there may be no factors that cause deterioration of thermal efficiency on using BD30 under all operating conditions.

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