Combustion and Exhaust Emissions Characteristics of a Dual-Fuel Compression Ignition Engine Operated with Diesel Fuel and Liquefied Petroleum Gas

The paper reports on the utilization of liquefied petroleum gas (LPG) as a primary fuel with diesel as an ignition pilot fuel in a direct injection diesel engine. A detailed account on brake-specific fuel consumption (BSFC), exhaust emissions, and combustion characteristic parameters in a wide range of engine load conditions with different LPG substitution ratios (SR) has been presented. From the results it was observed that, at low engine loads, the peak cylinder pressure, pressure rise rate, and heat release rate decreased with the increase of LPG SR, and at high engine loads, these parameters of dual fuel with a LPG SR of 25% were highest. The ignition delay period increased with the increase of LPG SR, and the combustion duration also increased with the increase of LPG SR at low engine loads, but firstly increased and then decreased at high engine loads. At each engine load, there existed a LPG SR at which the BSFC was lowest. The BSFC of dual fuel was higher than that of diesel fuel at low engine loads and lower at high engine loads. With the increase of LPG SR, hydrocarbon and carbon monoxide emissions evidently increased, but smoke emission decreased. Nitrogen oxide emissions of dual fuel were lower than those of diesel fuel and hardly varied with the increase of LPG SR.