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Reducing the emissions and fuel consumption are no longer future goals; instead they are the demands of the day. People are concerned about rising fuel costs and effects of emissions on the environment. Diesel engines are the major contributors to the increased levels of pollutants. In the present work an attempt is made for effective utilization of diesel engine with reduced fuel consumption, smoke density and NOx emissions. This is achieved by some minor modifications in diesel engine so as to run it as LPG-Diesel Dual-fuel engine with LPG (Liquefied Petroleum Gas) (70% Butane + 30% Propane) induction at air intake. The important aspect of LPG-Diesel dual-fuel engine is that, it shows significant reduction in smoke density, NOx emission and improved brake thermal efficiency with reduced energy consumption. An existing 4-S, single cylinder, naturally aspirated, water-cooled, direct injection, C.I. engine test rig was used for the experimental purpose.

Dual fuel engines suffer from problems of poor brake thermal efficiency and high UBHC emission, particularly at low outputs. Pilot fuel quantity and the intake temperature are the two important parameters which control the combustion process in duel fuel engines. In the present experimental work, the effects of LPG intake temperature, pilot fuel quantity and injection timing, on improving the performance of LPG-Diesel dual fuel have been studied. The experiments were conducted on a computer interfaced LPG-Diesel duel fuel engine and the results have been analyzed. Results at 75% of load indicated that an ignition timing of 27° before TDC, gives low emission and high thermal efficiency. At higher LPG intake temperature UBHC and CO levels are low, and improvement in brake thermal efficiency were observed. A marginal increase in NOx level was found with increase in LPG intake temperature.