不同浸车时长下轻型汽油车尾气VOCs排放特征及臭氧生成潜势

Tailpipe VOC Emissions and Ozone Formation Potential from Light-Duty Gasoline Vehicles Under Different Soak Durations

  • 摘要: 汽车浸车时长(即“停车时间”)与再次启动时油气雾化程度、三元催化器(TWC)工作温度等密切相关,进而影响尾气排放。为探明浸车时长对汽车尾气VOCs排放的影响,本研究基于整车转毂排放测试系统,开展典型国Ⅵ轻型汽油车在不同浸车时长(t<0.5 h、1.5 h<t<4 h和t>6 h)下的尾气排放测试,对尾气中VOCs进行采样和组分分析,并利用最大增量反应活性法(MIR)测算其臭氧生成潜势(OFP)。结果表明,随着浸车时长从t<1.5 h增加到t>6 h,汽油车尾气VOCs平均排放因子由10.9 mg/km增加至30.6 mg/km,OFP由26.1 mgO3/km增加至109.4 mgO3/km,其中烯烃、芳香烃等高活性物种排放占比显著增加。当浸车时长t>1.5 h,前589 s(启动阶段)排放的VOCs占全工况(1800s)的75%以上,OFP相对贡献占全工况85%以上。建议结合我国汽车使用特征,构建考虑浸车时长参数的精细化VOCs排放清单,并针对长浸车工况下冷启动阶段的高VOCs高排放特性,开发精准控制技术。

     

    Abstract: Vehicle soak duration (i.e., ‘parking time’) is closely related to fuel vaporization efficiency and the operating temperature of the three-way catalytic converter (TWC) during restart, thereby influencing tailpipe emissions. To investigate the impact e of soak duration on VOC emissions from gasoline vehicles, this study performed chassis dynamometer- tests on two representative China VI light-duty gasoline vehicles under three soak conditions (t < 0.5 h, 1.5 h < t < 4 h, and t > 6 h). Tailpipe VOCs were sampled and analyzed, and their ozone formation potential (OFP) was calculated using the Maximum Incremental Reactivity (MIR) method. Results showed that as soak duration increased from t < 1.5 h to t > 6 h, the average VOC emission factor increased from 10.9 mg/km to 30.6 mg/km, and the OFP rose from 26.1 mgO3/km to 109.4 mgO3/km. The proportion of highly reactive species such as olefins and aromatics also increased significantly. When soak duration exceeded 1.5 h, VOCs emitted during the first 589 s (start-up phase) accounted for over 75% of total emissions in the 1800 s test cycle, and contributed more than 85% of the total OFP. It is recommended to develop a refined VOC emission inventory that incorporates soak duration parameters based on typical vehicle usage patterns in China, and to promote emission control technologies for cold-start conditions following long soak periods.

     

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