基于实际道路测试的轻型汽油车甲烷排放因子模型构建与评估

Development and evaluation of methane emission factor model for light-duty gasoline vehicles based on on-road driving tests

针对目前机动车温室气体甲烷(CH4)排放因子缺乏的问题,利用便携式尾气测量系统(Portable Emission Measurement System,PEMS)对13辆轻型汽油车开展实际道路车载测试,获得汽油车CH4排放因子及排放特征.结果表明,轻型汽油车CH4排放因子随着国标加严而下降,国6轻型汽油车CH4排放因子相较于国1车辆下降了约94.5%.基于CH4逐秒排放特征分析发现,在实际行驶工况下CH4排放变动剧烈,排放峰值通常出现在高速或高加速工况.同时,研究发现CH4排放因子与燃烧效率(MCE)、机动车比功率(VSP)呈现显著相关性,通过CH4与MCE、VSP的关系构建了轻型汽油车不同标准下的基于MCE及基于VSP的排放因子模型.以一辆国4汽油车实测值对模型进行验证与评估,该车CH4排放因子的实测值为(3.9±0.6)mg·km^(-1),基于MCE、VSP的模型模拟值分别为(3.3±0.1)、(3.5±0.5)mg·km^(-1),模型的准确性可达84.6%、89.7%.其中,基于MCE的模型结果可用于宏观层面机动车CH4排放估算,基于VSP的模型结果可用于微观层面机动车CH4排放估算,研究结果可为不同尺度机动车温室气体CH4排放清单提供数据支撑.

Given the lack of methane(CH4)emission factors(EFs)from motor vehicles,this study employed a commercial portable emission measurement system(PEMS)to carry out on-road emission tests using 13 light-duty gasoline vehicles.The emission characteristics and EFs of CH4 emitted from these vehicles were investigated.Our results showed that the CH4 EFs decreased with the tightening of emission standards overall,and the China 6 EFs was about 94.5%lower than that of China 1 ones.The second-by-second measurements indicated that CH4 emission was significantly affected by the driving conditions,i.e.,the high peaks generally occurred at the high speed or the strong acceleration conditions.Meanwhile,this study found that the CH4 EFs had a good correlation with the modified combustion efficiency(MCE)and the vehicle specific power(VSP).Therefore,the CH4 EFs model was established based on VSP and MCE under different emission standards.The model was further verified and evaluated by the measured value of a China 4 gasoline vehicle.The results showed that the measured value of this vehicle was(3.9±0.6)mg·km^(-1),and the simulated value of VSP and MCE based models were(3.5±0.5)mg·km^(-1) and(3.3±0.1)mg·km^(-1),with the accuracies of 84.6%and 89.7%,respectively.The MCE and VSP models can be used to simulate the vehicular CH4 emissions at macro-and micro-levels,respectively,and the corresponding results will support for the developments of CH4 emission inventories at different regional scales.