Experimental analysis of liquid LPG injection on the combustion, performance and emissions in a spark ignition engine

In this study, the investigation of engine combustion, performance and emissions of liquid liquefied petroleum gas (LPG) injection was carried out using a four-stroke 1.6 L spark-ignition (SI) engine. The experiments were performed at 3,000 rpm and at four throttle positions (TP): 25%, 50%, 75% and 100%, and the results were compared with reference fuel, unleaded petrol (ULP). Analysis of combustion showed that the LPG has higher in-cylinder pressure and rate of pressure rise (ROPR) as the TP increased with respect to the ULP. The results also indicated that the rate of heat release (ROHR) and mass fraction burn (MFB) of LPG had risen earlier than ULP as the TP increased. In view of combustion stability, LPG has better stability at all TPs with lower variance, that is in the range of 2.6% to 13.1% than that of the ULP. Torque and brake mean effective pressure (BMEP) results revealed that LPG has higher value as compared with ULP. The brake specific fuel consumption (BSFC) of liquid LPG injection was found to be averagely lower than that of the ULP. Concurrently, the emissions of nitrogen oxides (NO_x), hydrocarbon (HC) and carbon monoxide (CO) of liquid LPG injection were recorded to be higher than that of the ULP. (paper)