Abstract The current study investigates the nonvolatile particle number emissions of three bi-fuel passenger cars (Euro 6b, 6d-temp), which operate on compressed natural gas (CNG), as a primary fuel, and gasoline as a secondary one. The CNG fuel was injected into the engine using port fuel injection (PFI) while the gasoline fuel was either by PFI or by direct injection (GDI). A novel exhaust gas sampling and dilution system was employed for the determination of solid particle number (SPN) emissions at 10 nm (SPN>10nm) and 2.5 nm (SPN>2.5 nm). The vehicles were tested in the laboratory over different test cycles where the CNG solid particle number emissions greater than 23 nm (SPN>23nm) were an order of magnitude lower than GDI and PFI gasoline emissions. However, when the size threshold was lowered to 10 nm or 2.5 nm, emissions were similar for both fuels. Particularly, SPN>2.5 nm emissions of the Euro 6 b vehicle exceeded the Euro 6 emission standard for both fuels while the SPN>23nm emissions were between 40 and 2.8 times lower than the limit for CNG and gasoline, respectively. Particle size distributions show a significant number of particles reside below the regulated limit of 23 nm, even lower than 10 nm. The results have significant implications in setting a particle number limit for alternative fuel vehicles while indicating that the current size threshold (23 nm) is insufficient for particle emission testing. Copyright © 2020 American Association for Aerosol Research

中文翻译：

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专注于亚 23nm 的 CNG 车辆的粒子排放测量

摘要 当前的研究调查了三辆双燃料客车（Euro 6b，6d-temp）的非挥发性颗粒数排放，这些客车以压缩天然气 (CNG) 作为主要燃料，以汽油作为次要燃料。CNG 燃料通过进气道燃料喷射 (PFI) 注入发动机，而汽油燃料则通过 PFI 或直接喷射 (GDI) 注入发动机。一种新型废气采样和稀释系统用于测定 10 nm (SPN>10nm) 和 2.5 nm (SPN>2.5 nm) 处的固体颗粒数 (SPN) 排放。这些车辆在实验室进行了不同测试周期的测试，其中大于 23 纳米（SPN>23 纳米）的 CNG 固体颗粒数排放量比 GDI 和 PFI 汽油排放量低一个数量级。然而，当尺寸阈值降低到 10 nm 或 2.5 nm 时，两种燃料的排放量相似。特别是，Euro 6 b 车辆的 SPN>2.5 nm 排放量超过了两种燃料的 Euro 6 排放标准，而 SPN>23nm 排放量分别比 CNG 和汽油的排放限值低 40 至 2.8 倍。粒度分布显示大量颗粒低于规定的 23 纳米，甚至低于 10 纳米。结果对设定替代燃料汽车的颗粒数量限制具有重要意义，同时表明当前的尺寸阈值（23 nm）不足以进行颗粒排放测试。版权所有 © 2020 美国气溶胶研究协会 23nm 的排放量分别比 CNG 和汽油的限值低 40 到 2.8 倍。粒度分布显示大量颗粒低于 23 nm 的规定限值，甚至低于 10 nm。结果对设定替代燃料汽车的颗粒数量限制具有重要意义，同时表明当前的尺寸阈值（23 nm）不足以进行颗粒排放测试。版权所有 © 2020 美国气溶胶研究协会 23nm 的排放量分别比 CNG 和汽油的限值低 40 到 2.8 倍。粒度分布显示大量颗粒低于规定的 23 纳米，甚至低于 10 纳米。结果对设定替代燃料汽车的颗粒数量限制具有重要意义，同时表明当前的尺寸阈值（23 nm）不足以进行颗粒排放测试。版权所有 © 2020 美国气溶胶研究协会 结果对设定替代燃料汽车的颗粒数量限制具有重要意义，同时表明当前的尺寸阈值（23 nm）不足以进行颗粒排放测试。版权所有 © 2020 美国气溶胶研究协会 结果对设定替代燃料汽车的颗粒数量限制具有重要意义，同时表明当前的尺寸阈值（23 nm）不足以进行颗粒排放测试。版权所有 © 2020 美国气溶胶研究协会