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Evaluation of heavy-duty vehicle emission controls with a decade of California real-world observations
Journal of the Air & Waste Management Association ( IF 2.1 ) Pub Date : 2021-08-23 , DOI: 10.1080/10962247.2021.1890277
Chris Ruehl 1 , Chandan Misra 2 , Seungju Yoon 1 , Jeremy D Smith 3 , Mark Burnitzki 4 , Shaohua Hu 4 , John Collins 1 , Yi Tan 1 , Tao Huai 4 , Jorn Herner 1
Affiliation  

ABSTRACT

Over the past decade, efforts to reduce emissions of particulate matter (PM) and oxides of nitrogen (NO + NO2, or NOx) from heavy-duty diesel vehicles (HDDVs) have led to the widespread adoption of both Diesel Particulate Filters (DPFs) to control PM and Selective Catalytic Reduction (SCR) to control NOx. We evaluated the performance of DPFs and SCR with 13,327 real-world fuel-based Black Carbon (BC) and NOx emission factors from 9,167 unique heavy-duty vehicles (primarily HDDVs) measured at four sites in California (two ports, two highways) from 2011 to 2018. BC emission factors have decreased by 90% during the past decade. At the same time, BC distributions have become increasingly skewed toward “high-emitters” – e.g., the portion of the HDDV fleet responsible for half of all BC emissions has decreased from ~16% to ~3%. NOx emission factors have also decreased over the past decade, but by only 31%. They remain roughly five times greater than in-use thresholds.We examined changes in BC and NOx emissions with engine age. BC emissions from DPF-only trucks decreased slightly but insignificantly, by 6 ± 15 mg/kg fuel per year, while for DPF+SCR trucks they increased by 5 ± 3. These changes are less than 5% of in-use thresholds. The annual increase in NOx emissions with age was much greater: 1.44 ± 0.28 g/kg for older SCR trucks without on-board diagnostic (OBD) capabilities and 0.48 ± 0.35 for newer trucks with OBD, roughly 20– 50% of in-use thresholds. Paired t-tests on the over 600 vehicles that were observed in multiple campaigns were consistent with these results. Observed changes in BC emissions with age were best fit with a “gross emitter” model assuming an annual DPF failure rate of 0.83 ± 0.01% for DPF-only trucks and 0.56 ± 0.01% for DPF+SCR trucks.Implications: These observations of real-world HDV emission factors have several major implications for regulatory efforts to reduce them. The increasing importance of a relatively small number of high BC emitters suggests that widespread sampling of the on-road fleet will be necessary to identify these vehicles. On the other hand, the much more ubiquitous deterioration in NOx control measures may be better addressed by incorporating on-board diagnostic systems, with telematic data transfer when possible, into inspection and maintenance programs. These NOx observations also highlight the need for strengthening heavy-duty SCR durability demonstration requirements.



中文翻译:

用十年的加利福尼亚真实世界观察评估重型车辆排放控制

摘要

在过去的十年中,为减少重型柴油车 (HDDV)的颗粒物 (PM) 和氮氧化物 (NO + NO 2或 NO x )排放的努力导致两种柴油微粒过滤器得到广泛采用( DPFs) 来控制 PM 和选择性催化还原 (SCR) 来控制 NO x。我们用 13,327 种真实世界的燃料基黑碳 (BC) 和 NO x评估了 DPF 和 SCR 的性能2011 年至 2018 年在加利福尼亚州的四个地点(两个港口、两条高速公路)测量的 9,167 辆独特的重型车辆(主要是 HDDV)的排放因子。BC 排放因子在过去十年中下降了 90%。与此同时,BC 分布越来越倾向于“高排放者”——例如,占所有 BC 排放量一半的 HDDV 车队部分已从约 16% 下降到约 3%。NO x排放因子在过去十年中也有所下降,但仅下降了 31%。它们仍然是使用阈值的大约五倍。我们检查了 BC 和 NO x 的变化排放与发动机老化。仅 DPF 卡车的 BC 排放量略有下降,但不显着,每年减少 6 ± 15 mg/kg 燃料,而 DPF + SCR 卡车的 BC 排放量增加了 5 ± 3。这些变化不到使用阈值的 5%。随着车龄的增长,每年 NO x排放量的增加要大得多:没有车载诊断 (OBD) 功能的旧式 SCR 卡车为 1.44 ± 0.28 g/kg,具有 OBD 功能的新型卡车为 0.48 ± 0.35,大约占总排放量的 20-50%。使用阈值。在多个活动中观察到的超过 600 辆车的配对t检验与这些结果一致。观察到的 BC 排放随车龄的变化最适合“总排放量”模型,假设每年 DPF 故障率仅 DPF 卡车为 0.83 ± 0.01%,DPF + SCR 卡车为 0.56 ± 0.01%。影响:这些对现实世界 HDV 排放因子的观察对减少它们的监管工作有几个主要影响。相对少数高 BC 排放者的重要性日益增加,这表明有必要对公路车队进行广泛抽样以识别这些车辆。在另一方面,在NO的更加普遍存在的恶化X的控制措施,可以更好地诊断系统包含板载寻址,同时远程信息数据传送时可能的,成的检查和维护程序。这些 NO x观察结果还强调了加强重型 SCR 耐久性演示要求的必要性。

更新日期:2021-10-06
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