Investigations on the effect of Piston Squish Area on Performance and Emission Characteristics of LPG fuelled Lean Burn SI Engine 2016-28-0123

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%. The HC emission level at 30% squish area is less compared to other areas. At mid equivalence ratios the NO emission increased in 30% and 25% when compared to 35% and 40% due to increase in temperature and pressure. But NO emissions at maximum power in 25% and 30% were lower compared to 35% and 40% squish area. The Co-efficient of Variation (COV) of Indicated Mean Effective pressure (IMEP) increased sharply when the lean limit is reached. The heat release pattern shows that the rate of heat release was lowered at lean condition. On the whole it is concluded that 30% squish area is best suitable in terms of performance and emissions for LPG fuelled lean burn SI engine.