Emission Comparison of Light-Duty in-Use Flexible-Fuel Vehicles Fuelled with Gasoline and Compressed Natural Gas Based on the ECE 15 Driving Cycle

This paper presents an exhaust emission comparison for light-duty in-use compressed natural gas (CNG)-gasoline flexible-fuel vehicles under the ECE 15 driving cycle protocol. The aim of this study is to provide a scientific basis for determining the level of emissions reduction for gasoline vehicles fuelled with CNG. The emission characteristics of gasoline and CNG under the ECE 15 driving cycle are experimentally measured and parabolic fits to the data are performed to obtain the relationship between CO, HC, and NO x emission levels and vehicle mileage. As the mileage exceeds 200 000 km, changes in the level of emissions gradually begin to become apparent. When the mileage exceeds 300 000 km, the level of emission of pollutants increases dramatically. Compared to the emission levels measured for gasoline, the values for CNG are, averagely, reduced 30.34 per cent for CO, 15.30 per cent for HC, and 7.22 per cent for NO x , respectively. No obvious differences in the emission level at a given mileage can be found for the three vehicle types used in this study.