Combustion, performance and emissions of Shorea robusta methyl ester blends in a diesel engine

This research work reports the preparation of Sal methyl ester (SME) and exhaustive trials of its blends in a single-cylinder four-stroke diesel engine for evaluation of combustion, performance and emission characteristics. The appraised performance parameters include brake thermal efficiency and brake specific energy consumption. In addition, engine emissions like carbon monoxide, unburnt hydrocarbon and smoke were found to be significantly reduced. Combustion parameters like in-cylinder gas pressure, rate of pressure rise, ignition delay (ID), rate of heat release, cumulative heat release and mass fraction burnt (MFB) were also evaluated. The results revealed that the cumulative heat release of SME10 was marginally higher than baseline data, even though blends above SME20 were lower in comparison to diesel. The total combustion duration (calculated at MFB of 0.05 to 0.95) was early at the initial stage, and reduced ignition delay (up to 2.8 degrees CA) for biodiesel was observed on further addition of SME volume fraction in the blend. Finally, the combustion study exposed an increasing trend in percentage heat release in the diffusion phase with further SME addition, leading to smoother engine operation. Conclusions specified that SME - diesel blends up to 40% (v/v) can be used in a diesel engine without modification.