University of California, Bourns College of Engineering, Center for Environmental Research and Technology (CE-CERT), 1084 Columbia Avenue, Riverside, CA 92507, USA.
University of California, Bourns College of Engineering, Center for Environmental Research and Technology (CE-CERT), 1084 Columbia Avenue, Riverside, CA 92507, USA; Department of Chemical and Environmental Engineering, Bourns College of Engineering, University of California, Riverside, CA 92521, USA.
Sci Total Environ. 2021 Aug 25;784:147224. doi: 10.1016/j.scitotenv.2021.147224. Epub 2021 Apr 20.
This study assessed the real-world nitrogen oxide (NOx) emissions from 50 heavy-duty vehicles of different vocations and engine technologies using portable emissions measurement systems (PEMS). This is one of the most comprehensive in-use emissions studies conducted to date, which played a key role in the development of CARB's (California Air Recourses Board) updated EMission FACtor (EMFAC) model, especially for natural gas vehicles. In-use emissions testing was performed on school and transit buses, refuse haulers, goods movement vehicles, and delivery vehicles while were driven over their normal operating routes in the South Coast Air Basin. Engine technologies included diesel engines with and without selective catalytic reduction (SCR) systems, compressed natural gas (CNG) engines and liquified petroleum gas (LPG) engines, and SCR-equipped diesel hybrid electric vehicles. For most vehicles, the in-use NOx emissions were higher than the certification standards for the engine. Diesel vehicles generally showed higher brake-specific NOx emissions compared to the CNG vehicles. NOx emissions were strongly dependent on the SCR temperature, with SCR temperatures below 200 °C resulting in elevate brake-specific NOx. The 0.02 g/bhp-hr certified CNG vehicles showed the largest reductions in NOx emissions. The diesel hybrid electric vehicles showed important distance-specific NOx benefits compared to the conventional diesel vehicles, but higher emissions compared to the CNG and LPG vehicles. Overall, average NOx reductions were 75%, 94%, 65%, 79%, respectively, for the 0.2 CNG, 0.02 CNG, diesel hybrid electric, and LPG vehicles compared to diesel vehicles, due in part to some diesel vehicles with particularly high emissions, indicating that the widespread implementation of advanced technology and alternative fuel vehicles could provide important NOx reductions and a path for meeting air quality targets in California and elsewhere.
本研究使用便携式排放测量系统（PEMS）评估了 50 辆不同职业和发动机技术的重型车辆的实际氮氧化物（NOx）排放。这是迄今为止进行的最全面的实际排放研究之一，对加州空气资源委员会（CARB）更新的排放因子模型（EMFAC）的开发起到了关键作用，特别是对天然气车辆。在南海岸空气盆地，对校车和过境巴士、垃圾清运车、货物运输车辆和送货车辆进行了实际排放测试，这些车辆在正常运行路线上行驶。发动机技术包括带和不带选择性催化还原（SCR）系统的柴油发动机、压缩天然气（CNG）发动机和液化石油气（LPG）发动机以及配备 SCR 的柴油混合动力电动汽车。对于大多数车辆，实际 NOx 排放高于发动机的认证标准。与 CNG 车辆相比，柴油车辆的制动比 NOx 排放通常更高。NOx 排放强烈依赖于 SCR 温度，SCR 温度低于 200°C 会导致制动比 NOx 升高。经认证的 0.02g/bhp-hr CNG 车辆显示出最大的 NOx 减排量。与传统柴油车辆相比，柴油混合动力电动汽车在特定距离内具有重要的 NOx 效益，但与 CNG 和 LPG 车辆相比，排放更高。总体而言，与柴油车辆相比，0.2 CNG、0.02 CNG、柴油混合动力电动汽车和 LPG 车辆的平均 NOx 减排率分别为 75%、94%、65%和 79%，部分原因是一些柴油车辆的排放特别高，这表明广泛实施先进技术和替代燃料车辆可以提供重要的 NOx 减排，并为加州和其他地区实现空气质量目标提供途径。
