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Rising energy demands, ecological deterioration and diminution of fossil fuels has necessitated the researchers to search for alternatives. With alternate fuels like Liquefied Petroleum Gas (LPG), hydrogen and alcohol based fuels, it is easier to substitute with the present engine without many alterations. Excellent chemical properties of these fuels make them favorable for lean burn operation which makes it a cost effective option to achieve goals of better fuel economy and controlled emissions. In this regard, experimental studies were carried out to examine the effects of LPG with different proportions of alcohols like ethanol and methanol (5, 10 and 20%) on the performance, emission and combustion characteristics of a single cylinder SI engine operated at a constant speed of 1500 rpm with a optimized compression ratio of 10.5:1 under full throttle opening conditions at varying equivalence ratio.

Experiments were conducted to study the effects of piston squish area on the performance, emissions and combustion characteristics of a Liquefied Petroleum Gas (LPG) fuelled lean burn Spark Ignition (SI) engine at a compression ratio of 10:1 under 25% throttle condition. A single cylinder diesel engine was modified to operate as LPG fuelled SI engine at a constant speed of 1500 rpm. The test was conducted at different squish areas of 25, 30, 35 and 40% on the total piston area at different equivalence ratios maintaining a constant squish velocity of 4 m/s. The ignition timing was set to MBT (Minimum advance for best Torque). It has been found that there is no significant change in lean limit in all the squish areas. An appreciable difference in brake power and brake thermal efficiency was noticed between equivalence ratios 0.7 and 0.9. The piston with 30% squish area showed good results followed by 25, 35 and 40%.