现实工况下挖掘机尾气排放特征分析

Characterization of Tailpipe Emissions from in-use Excavators

为量化挖掘机在实际施工作业中尾气排放特征,研究选取成都市不同建设工地在用的8台挖掘机,利用便携式尾气测量系统对其进行现实工况下的尾气排放测量,测试按挖掘机的不同作业特点分怠速、行走和作业进行.测量的尾气排放污染物包括CO、HC、NO和PM_(2.5).结果表明,挖掘机的尾气排放随工况的不同而不同,怠速时NO排放平稳,行走和作业时排放速率波动较大.满足不同尾气排放标准的挖掘机,其尾气排放也有所不同,例如,国Ⅱ阶段的挖掘机与国Ⅰ阶段的挖掘机相比,其在怠速、行走、作业工况下尾气排放的NO分别减小8%、35%和5%,PM_(2.5)分别降低88%、87%和80%.另外,本研究中挖掘机尾气排放的实测结果与我国非道路机械尾气排放因子技术指南中推荐的用于排放清单估算的排放因子相比,也均有显著不同.这说明,开展非道路机械尾气排放现实工况下的测量,对于提高尾气排放清单精准度具有重要作用.

In this paper, the objective is to characterize real-world tailpipe emissions for excavators. Eight excavators in several construction sites in Chengdu were selected in this study. A portable emission measurement system (PEMS) was used for real-world emissions measurements (i. e., CO, HC, NO, and PM2.5) for three predefined operation modes:idling, moving, and working. The results showed that the tailpipe emissions of excavators vary depending on the operation mode as well as the equipment. NO emissions were relatively stable when the engine was idling compared to when the excavator was moving or doing actual work. In addition, excavators that complied to different emissions standards also exhibited different emissions, with those that met higher emission standards producing fewer emissions. For example, when comparing excavators complying with Stage Ⅱ emission standards to those complying with Stage Ⅰ emission standards, the NO and PM2.5 emissions appeared to decrease. On average, the NO emissions decreased by 8%, 35%, and 5%, and the PM2.5 emissions decreased by 88%, 87%, and 80% for the idling, moving, and working modes, respectively. Furthermore, the studies showed significant differences existed between the emissions factors in the real-world measurements and those recommended by national guidance. This indicated that real-world emission measurements of non-road equipment will play a key role in emissions inventory development. This study demonstrated that PEMS can be used to characterize real-world emissions from non-road equipment.