不同行驶工况下轻型柴油车瞬时排放的CMEM模拟对比研究

A Comparison Study on Instantaneous Emission Simulation by CMEM for Light-Duty Diesel Vehicles with Different Driving Cycles

近年来,我国机动车保有量迅猛增加,标准的行驶工况已难以准确反映机动车在实际道路上的行驶状况。采用CMEM模型研究不同标准工况下车辆排放的差异,旨在为城市交通环境管理与规划提供技术支持。以轻型柴油车为研究对象,给出了模型关于柴油机的结构和主要输入参数,并将模拟得到的车辆在实际道路上的瞬时排放结果与实测数据进行了验证。检验结果表明,THC、CO、NOx排放量的相对误差分别为14.2%、3.7%、32.7%,其相关系数分别达到0.73、0.72、0.87,表明CMEM模型能够较好地反映车辆在实际道路上排放的瞬时变化。对车辆在日本10-15工况、欧洲ECE工况、美国FTP城区工况及中国上海城市主干道路况上的排放和燃油经济性进行了计算。CMEM模拟结果发现,污染物排放水平随着车速的提高而下降,特别是超低速段（0～10 km/h）向低速段（10～20 km/h）过渡时,污染物排放水平的变化显著。车辆的加速过程在污染物排放过程中起主导性作用,其对污染物排放的贡献率在30%以上,个别甚至超过了70%。中国上海城市主干道工况的怠速过程对THC和CO的贡献率分别接近40%和30%,其CO排放因子分别是欧、美、日的1.3、1.5、1.4倍;THC排放因子分别是欧、美、日的1.5、2.1、1.9倍;NOx排放因子分别是欧、美、日的1.2、1.3、1.3倍。模拟车辆在中国上海城市主干道上的燃油经济性最差,仅为9.56 km/L。国外行驶工况不能真实地反映我国机动车在实际道路上的行驶状况。

CMEM （comprehensive modal emissions model） for calculating time based instant emissions from light-duty diesel vehicles and its input parameters were introduced. On-board test data were used to validate the simulation results. The verification showed that relative errors of the emissions of total hydrocarbon, carbon monoxide （CO） and nitrogen oxides （NOx） were 14.2%, 3.7% and 32.7% whilst their correlation coefficients reaching 0.73, 0.72 and 0.87, respectively. It revealed that the simulation of instantaneous emissions from lightduty diesel vehicles by CMEM well reflected the transient changes in the real driving cycle in Shanghai. The simulation of instantaneous emissions and fuel economies with the test cycles of ECE 15-mode, FTP-mode, Japanese 10-15-mode and the Shanghai arterial road showed that the emissions declined along with the rise of vehicle speed, especially during the transition from the ranges of 0 - 10 km/hr to 10 -20 km/hr. The accelerating course dominated tt^e whole emissions, contributing to more than 30%, or even over 70% for exception. The contributions of idle condition in the cycle of Shanghai arterial road to the emissions of total hydrocarbon and CO were nearing 40% and 30%, respectively, whilst comparing its emission factors with that of the cycles of ECE-15, FTP and Japanese 10-15 being 1.3, 1.5 and 1.4 times for CO, 1.5, 2.1 and 1.9 times for total hydrocarbon, and 1.2, 1.3 and 1.3 times for NOx, respectively. The fuel economy for simulated vehicles on the Shanghai arterial road was only 9156 km/L. It has been concluded that the foreign driving cycles are not suitable for the Shanghai real-road situation.