Performance and emission characteristics of a vehicle fueled with enriched biogas and natural gases

摘要

This study aimed to investigate the characteristics of exhaust emissions and the fuel economy of a compressed natural gas (CNG) vehicle fueled with biogas and natural gases. A large CNG vehicle currently used as a city bus in Korea was tested on a chassis dynamometer under the European Transient Cycle (ETC) and the National Institute of Environmental Research (NIER) 06 cycles. One CH_4-enriched biogas (97.6% CH_4) and 5 natural gases with different CH_4 contents (81.6-94.0% CH_4) were used as test fuels. Total hydrocarbons (THC), CO, NO_x and CO_2 emissions in the NIER 06 cycle were higher than those in the ETC cycle for all tested fuels, while the fuel economy in the NIER 06 cycle was 43.7-51.5% lower than that in the ETC cycle. Total VOC emissions increased with increasing CH_4 content in the fuel, with toluene being the highest proportion of the BTEX emissions in both the ETC cycle (72-80%) and the NIER 06 cycle (73-78%). Emissions of elemental/organic carbon exhibited a similar trend to that of nanoparticle emissions. Total organic carbon was mainly comprised of organic compounds at 97-99% (ETC cycle) and 95-99% (NIER 06 cycle). Polycyclic aromatic hydrocarbon emissions in the NIER 06 cycle were 133.3-577.8% higher than in the ETC cycle because of incomplete combustion and an increase in unburned fuel in the NIER 06 cycle, which is a low-speed driving mode. Nanoparticle number concentrations were lowest for M91 among the 6 tested fuels; the total number of particles in the NIER 06 cycle was 33.2-123.8% higher than in the ETC cycle.