Analysis of combustion and exhaust characteristics according to changes in the propane content of LPG

Abstract

Owing to the regulation of CO2 reduction in global transportation system, the number of vehicles using LPG is increasing worldwide and their cleanliness is being highlighted. LPG increases the content of propane (C3) to improve startability during winters; accordingly, the contents of butane (C4) and C3 change continuously depending on the weather. In this study, the spray and combustion process in an engine equipped with the latest LPLI system was analyzed to understand the engine control strategies according to the C3 content, and the change in exhaust emission was also studied. Although the injection quantity of LPG with C3 content of 25% was lower than that of LPG with 5% C3 content at the same fuel pressure, the commercial ECU increased the injection duration to match the number of carbons required for combustion. In addition, the ignition timing was advanced owing to the high-octane number of C3 and the maximum combustion pressure was increased by up to 8.63% owing to the high lower heating value and advanced ignition timing. In addition, BSNOx increased by up to 47.61% owing to the increased maximum combustion pressure, and BSCO and BSCO2 increased by 33.14% and 11.70%, respectively, due to excessive injection.