4. Conclusion
The comparative MSAT emission characteristics from a GDI and dedicated LPG-DI light-duty passenger vehicle were investigated. The fuel supply system and injection control scheme of the base GDI engine were modified for the dedicated LPG-DI vehicle operation. The various in-use vehicle test modes, reflecting real-world driving conditions, were chosen for determining the regulated and unregulated emission factors before and after LPG conversion. The regulated and unregulated gaseous emissions of THC, NOx, PM, PN, and PAHs from the LPG-DI vehicle showed significantly lower emission factors than the GDI vehicle. The low carbon fraction and low heating value in LPG fuel decreased the CO2 emissions and fuel economy by approximately 4–6% and 20%, respectively, compared with those of the GDI vehicle.
The superior vaporization characteristics of LPG fuel in a combustion chamber reduced the fuel-wall impingement and the locally fuel rich region than the gasoline fuel, which resulted in a strong reduction in the PN concentration of over 99% in real-world vehicle driving conditions and the proportions of sub-23 nm particles were 32–35% in gasoline and 50–65% in LPG.
The carbonyl levels with LPG applications were significantly increased by 2–10 times compared to gasoline, mainly because of the partial oxidation of LPG fuel during the combustion process and the different purification mechanism of exhaust gases through a gasoline catalytic converter. In particular, the particle-bound PAHs from the LPG-DI vehicle showed significantly lower emission concentration over GDI vehicles, with reduction of 95%. Most of the MSAT emissions from an in-use vehicle were closely influenced by the driving patterns, exhaust system temperatures, and chemical properties of the fuels in a DISI passenger vehicle.
Acknowledgments
This study was supported by the CEFV (Center for Environmentally Friendly Vehicle) as Global-Top Project of KMOE (Ministry of Environment, Korea) and Korea University Grant. The authors gratefully acknowledge the Transportation Pollution Research Center in the National Institute of Environmental Research for the vehicle tests and emission analyses. We also thank Hyundai Motor Company, Motonic Corporation, and Continental-Automotive Systems Corporation for their technical assistance for the development of LPG-DI vehicle.
4. ConclusionThe comparative MSAT emission characteristics from a GDI and dedicated LPG-DI light-duty passenger vehicle were investigated. The fuel supply system and injection control scheme of the base GDI engine were modified for the dedicated LPG-DI vehicle operation. The various in-use vehicle test modes, reflecting real-world driving conditions, were chosen for determining the regulated and unregulated emission factors before and after LPG conversion. The regulated and unregulated gaseous emissions of THC, NOx, PM, PN, and PAHs from the LPG-DI vehicle showed significantly lower emission factors than the GDI vehicle. The low carbon fraction and low heating value in LPG fuel decreased the CO2 emissions and fuel economy by approximately 4–6% and 20%, respectively, compared with those of the GDI vehicle.The superior vaporization characteristics of LPG fuel in a combustion chamber reduced the fuel-wall impingement and the locally fuel rich region than the gasoline fuel, which resulted in a strong reduction in the PN concentration of over 99% in real-world vehicle driving conditions and the proportions of sub-23 nm particles were 32–35% in gasoline and 50–65% in LPG.The carbonyl levels with LPG applications were significantly increased by 2–10 times compared to gasoline, mainly because of the partial oxidation of LPG fuel during the combustion process and the different purification mechanism of exhaust gases through a gasoline catalytic converter. In particular, the particle-bound PAHs from the LPG-DI vehicle showed significantly lower emission concentration over GDI vehicles, with reduction of 95%. Most of the MSAT emissions from an in-use vehicle were closely influenced by the driving patterns, exhaust system temperatures, and chemical properties of the fuels in a DISI passenger vehicle.AcknowledgmentsThis study was supported by the CEFV (Center for Environmentally Friendly Vehicle) as Global-Top Project of KMOE (Ministry of Environment, Korea) and Korea University Grant. The authors gratefully acknowledge the Transportation Pollution Research Center in the National Institute of Environmental Research for the vehicle tests and emission analyses. We also thank Hyundai Motor Company, Motonic Corporation, and Continental-Automotive Systems Corporation for their technical assistance for the development of LPG-DI vehicle.
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