Effect of Injection Pressures and Timings on the Performance Emission and Combustion Characteristics of a Direct Injection Diesel Engine Using Biodiesel-Diesel-Ethanol Blend

The search for new alternate fuels is driven by supply uncertainty of petroleum-based fuel, increasing demand, higher crude oil prices and increasingly stringent environmental regulations. Though biodiesel can be an alternative fuel for diesel engine applications, there are several drawbacks, such as higher production cost, poor low temperature properties, higher viscosity and lower calorific value as compared to petroleum-based diesel fuel. The present investigation mainly concerns the effect of various injection pressures and timings on the performance emission and combustion characteristics of single-cylinder, four-stroke direct-injection diesel engine using biodiesel-diesel-ethanol blend as fuel at a constant speed of 1500 rpm. In this study, a blend of 40% waste cooking palm oil (WCO) methyl ester, 50% diesel and 10% ethanol was selected based on stability test conducted at an ambient temperature of 30°C. The test engine exhibited maximum brake thermal efficiency of 31.2% at an injection pressure of 240 bar and injection timing of 25.5° bTDC. By comparison with diesel, biodiesel-diesel-ethanol blend exhibited reduction in carbon monoxide (CO), carbon dioxide (CO₂) and smoke emission by 0.1% by vol., 0.3% by vol. and 12.5% respectively. Biodiesel-diesel-ethanol blend decreased nitric oxide (NO) emission by 3.5%, while a slight increase in the levels of unburnt hydrocarbon (UBHC) was observed compared to diesel. A maximum cylinder gas pressure of 74.5 bar, heat release rate of 27.8 J/°CA and minimum ignition delay of 12.4°CA was observed with biodiesel-diesel-ethanol blend which was similar to diesel at same operating conditions.