Effect of double injection on combustion, performance and emissions of Jatropha water emulsion fueled direct-injection diesel engine

The experimental study was carried out using a four-stroke, high speed, DI (direct-injection) diesel engine with double fuel injections. In this study, Jatropha water emulsion was made by mixing a mass ratio of 10% of water. While fixing the first injection timing, we tested the engine on JWE (Jatropha water emulsion) with various injection timings and quantities of second injections. The acquired data was analyzed for various combustion parameters such as heat release rate, combustion center (timing of 50% of total heat release), ignition delay, and combustion duration; for performance parameters such as in-cylinder temperature, exhaust gas temperature, brake thermal efficiency; and emissions of CO (carbon monoxide), CO2 (carbon dioxide), HC (hydrocarbons), NOx (nitrogen oxides), as well as dust and smoke opacity. When using a large second injection amount, we found a significant reduction in the peaks of the in-cylinder pressure, HRR (heat release rate), and average in-cylinder temperatures. We also found a drastic increase in the ignition delay, combustion duration, and a shift in the combustion center toward the later combustion stage, as well as increased exhaust gas temperatures, and reduced brake thermal efficiency compared with those of the Light oil. A large second injection amount reduced NOx emissions up to 48%, and drastically reduced HC emissions at higher loads of the engine.