不同负载条件下国Ⅱ重型柴油货车的实际道路排放特征

摘要

重型柴油车排放已经成为中国城市与区域大气污染的重要来源.为研究负载条件对重型柴油车实际道路排放的影响, 利用车载排放测试 (PEMS) 方法对2辆国Ⅱ重型柴油货车开展实际道路排放测试, 分析不同负载 (空载、半载和满载) 条件下的尾气污染物排放特征.基于机动车比功率 (VSP) 方法分析了不同速度区间的气态污染物 (NOx、CO和总碳氢化合物 (THC) ) 排放特征, 同时通过滤膜采样方法对尾气PM2.5及其碳质组分 (有机碳 (OC) 和元素碳 (EC) ) 进行了定量分析.结果显示, 2辆国Ⅱ重型柴油货车气态污染物排放因子与负载呈现显著的正相关关系, 半载和满载时NOx、CO和THC排放因子相对于空载分别升高18％～41％、6％～67％、37％～125％.但2辆重型柴油货车的PM2.5排放因子并未随负载增加而呈现相同的变化规律.在PM2.5中碳质组分排放约占61％～97％ (质量分数) , 其中EC排放因子随负载的增加而增大.%Heavy-duty diesel vehicles have been identified as one of the most important contributors to urban and regional air pollution in China.In order to investigate the impact from payloads on the real-world emissions of heavy-duty diesel vehicles, two ChinaⅡ heavy-duty diesel trucks with three different payloads (empty, half and full payload) were tested by using aportable emission measurement system (PEMS) .Emission characteristics of these gaseous pollutants (NOx, CO and total hydrocarbons (THC) ) at different velocity were explored based on vehicle specific power (VSP) method, and a filter sampling method was used to quantify PM2.5 and its carbonaceous components (organic carbon (OC) and elemental carbon (EC) ) .A positive correction was found obviously between the gaseous pollutant emissions and payloads in this study.The NOx, CO and THC emission factors of the two tested heavy duty diesel trucks with half and full payloads were 18％-41％, 6％-67％and 37％-125％ higher than those with empty payload, respectively.However, for the PM2.5 emission factors, the two heavy-duty diesel trucks presented different changes with the increasing payloads.The carbonaceous components accounted for about 61％-97％ (mass ratio) of PM2.5, in which, EC emission factors increased with the increasing payloads.