Sonntag Darrell B, Gao H Oliver, Holmén Britt A
School of Civil and Environmental Engineering, Cornell University, 220 Hollister Hall, Ithaca, New York 14853, USA.
Environ Sci Technol. 2008 Aug 1;42(15):5637-43. doi: 10.1021/es702359x.
A linear mixed model was developed to quantify the variability of particle number emissions from transit buses tested in real-world driving conditions. Two conventional diesel buses and two hybrid diesel-electric buses were tested throughout 2004 under different aftertreatments, fuels, drivers, and bus routes. The mixed model controlled the confounding influence of factors inherent to on-board testing. Statistical tests showed that particle number emissions varied significantly according to the after treatment, bus route, driver, bus type, and daily temperature, with only minor variability attributable to differences between fuel types. The daily setup and operation of the sampling equipment (electrical low pressure impactor) and mini-dilution system contributed to 30-84% of the total random variability of particle measurements among tests with diesel oxidation catalysts. By controlling for the sampling day variability, the model better defined the differences in particle emissions among bus routes. In contrast, the low particle number emissions measured with diesel particle filters (decreased by over 99%) did not vary according to operating conditions or bus type but did vary substantially with ambient temperature.
开发了一种线性混合模型，以量化在实际驾驶条件下测试的公交车辆颗粒物排放的变异性。在2004年全年，对两辆传统柴油公交车和两辆柴油-电动混合动力公交车在不同的后处理、燃料、司机和公交线路条件下进行了测试。该混合模型控制了车载测试中固有因素的混杂影响。统计测试表明，颗粒物排放根据后处理、公交线路、司机、公交车型和日温度的不同而有显著差异，只有极小的变异性可归因于燃料类型之间的差异。在使用柴油氧化催化剂的测试中，采样设备（低压冲击器）和小型稀释系统的日常设置和操作导致颗粒物测量总随机变异性的30%-84%。通过控制采样日的变异性，该模型能更好地界定不同公交线路之间的颗粒物排放差异。相比之下，使用柴油颗粒过滤器测得的低颗粒物排放（减少了99%以上）并不随运行条件或公交车型而变化，但会随环境温度有很大变化。
