Study on vehicle evaporative emission characteristics and purge strategy based on China VI measurement methods

Abstract

In this study, several experiments were conducted based on China VI measurement methods to analyze the vehicle evaporative emission characteristics and purge strategy. The results showed that the diurnal breathing emissions from the atmospheric fuel system were 157.2 mg, with 88.5 % of the carbon canister bleeding emissions, and the main species emitted were alkanes. The diurnal breathing emissions from the sealed fuel system were 82.2 mg, with 97.1 % of the permeation emissions, and the main species emitted were aromatic and alkane hydrocarbons. There is a significant negative correlation between the vehicle refueling emission and the adsorption capacity of the carbon canister, but no significant correlation with the purge volume. The carbon canister refueling working capacity (ORVR BWC) is only 53 %–72 % of the regular working capacity (BWC). Tires, interior and exterior trims are the main background emission sources of the vehicle, accounting for 29 % and 25.1 % respectively. Baking pretreatment is an effective way to reduce background emissions. Compared to gasoline vehicles, hybrid electric vehicles (HEVs) equipped with atmospheric fuel systems compensate for the lack of purge time by increasing the purge rate. Vehicles equipped with sealed fuel systems can be freed from reliance on the purge strategy. It is a technological trend for vehicles to be equipped with sealed fuel systems, and future evaporative emission control should focus on permeation emissions, refueling emissions and background emissions.