基于便携式排放测试系统的重型柴油车冷启动排放评价方法研究

Study on the evaluation method for cold start emission of heavy-duty diesel vehicle based on PEMS

《重型柴油车污染物排放限值及测量方法(中国第六阶段)》(GB 17691—2018)对整车实际道路行驶排放提出了测试要求,但只以冷却液温度≥70℃,发动机进入热态后的数据评价整车排放水平,而从实际测试结果来看,冷启动排放明显偏高。为分析冷、热状态的污染物排放,选取满足GB 17691—2018中6b阶段技术要求的重型柴油车(N 1、N 2、N 3类各一辆)进行实际行驶排放测试。建议下一阶段标准将冷启动排放引入到整车排放水平评价中,分别以冷却液温度达到30、70℃界定发动机冷、热状态,取消有效功基窗口,以功基窗口法直接计算得到两种不同状态的污染物比排放。参照发动机瞬态循环测试的计算原则,分别赋予冷、热排放0.14、0.86的权重,加权判定整车排放达标与否。

“Limits and measurement methods for emission from diesel-fuelled heavy-duty vehicles(ChinaⅥ)”(GB 17691-2018)has set test requirements on real driving emissions for the vehicle,but only based on the data under hot state when the temperature of the coolant is above 70℃.The actual test results showed that the emissions under the cold start state were significantly higher.In order to analyze the emissions under cold start and hot states,the heavy-duty diesel vehicles(each one from the N 1,N 2 and N 3 categories)that met the technical requirements of the stage 6b of GB 17691-2018 were selected to test the real road driving emissions.It was recommended to introduce cold start emissions into the evaluation of vehicle emission levels in the next phase of the standard.The cold start and hot states of the engine were defined by the coolant temperature of 30,70℃,respectively.Furthermore,instead of valid work-based window,the work-based window method was employed to calculate the specific emissions of the pollutants under the two states directly.According to the calculation principle of the engine transient test cycle,weights of 0.14 and 0.86 were given to the emissions under cold start and hot states,respectively,the weighted results were used to determine the compliance of the emissions with the standard.