How vehicle and fuel specifications affect evaporative and refuelling emissions from petrol vehicles.

Evaporative and refuelling emissions are a major source of volatile organic compound (VOC) contamination, contributing to ground-level ozone formation in China. To meet increasingly stringent evaporative emission control requirements, a growing number of newly certified vehicles have adopted onboard refuelling vapour recovery systems and updated canisters. This study aimed to evaluate the impact of vehicle and fuel specifications on evaporative and refuelling emissions from China-6 light-duty vehicles (LDVs). Two groups of experiments were conducted. In the first group, 28 tests were performed on China-6 LDVs and 24 on China-5 LDVs. The results showed that emissions from China-6 LDVs were significantly lower than those from China-5 LDVs in terms of total hydrocarbon emissions and diurnal losses over 0-24 h, with lower variability. In the second group, seven petrol fuel samples with varying aromatic formulations, ethanol contents, and vapour pressures were tested. Evaporative emissions and refuelling emissions were measured following China-6 procedures, while speciated VOCs were also quantified. The results showed that higher molecular weight aromatics more effectively suppressed evaporative emissions than toluene. Both E5 and E10 fuels increased vapour leakage during the diurnal-loss stage. Diurnal loss and refuelling emissions increased significantly with rising fuel Reid vapor pressure, particularly after the canister breakthrough on the second day. Speciated VOC analysis revealed that light alkanes dominated the escaped fuel vapour.