Singer Brett C, Kirchstetter Thomas W, Harley Robert A, Kendall Gary R, Hesson James M
a Department of Civil and Environmental Engineering , University of California , Berkeley , California , USA.
b Technical Services Division , Bay Area Air Quality Management District , San Francisco , California , USA.
J Air Waste Manag Assoc. 1999 Feb;49(2):125-135. doi: 10.1080/10473289.1999.10463785.
The temporary ineffectiveness of motor vehicle emission controls at startup causes emission rates to be much higher for a short period after starting than during fully warmed, or stabilized, vehicle operation. Official motor vehicle emission inventories estimate that excess emissions during cold-start operation contribute a significant fraction of all hydrocarbon, carbon monoxide (CO), and nitrogen oxide (NO) emissions from California vehicles. In an effort to verify these estimates under real-world conditions, vehicle emissions were measured in an underground parking garage in Oakland, CA, during March 1997. Hot stabilized emissions were measured as vehicles arrived at the garage in the morning, and cold-start emissions were measured as vehicles exited in the afternoon; the incremental, or excess, emissions associated with vehicle starting were calculated by difference. Composite emissions from ~135 vehicles were sampled during each of six morning and six afternoon periods. Measured stabilized exhaust emissions were 19 ± 2 g nonmethane hydrocarbons (NMHC), 223 ± 17 g CO, and 8.6 ± 1.3 g NO per gal of gasoline consumed. Cold-start emissions of 69 ± 2 g NMHC/gal, 660 ± 15 g CO/gal, and 27.8 ± 1.2 g NO/gal were measured for vehicles spending an average of ~60 sec in the garage after starting in the afternoon. Using second-by-second emissions data from California's light-duty vehicle surveillance program, average fuel use during cold start was estimated to be ~0.07 gal, and the cold-start period was estimated to last for ~200 sec. When cold-start emission factors measured in the garage were scaled to represent the full 200-sec cold-start period, incremental start emission factors of 2.1 g NMHC, 16 g CO, and 2.1 g NO per vehicle start were calculated. These emission factors are lower than those used by California's motor vehicle emission inventory model (MVEI 7G) by 45% for NMHC, 65% for CO, and 12% for NO. This suggests that the importance of cold-start emissions may be overstated in current emission inventories. Overall, the composition of volatile organic compound (VOC) emissions measured during cold start was similar to that of hot stabilized VOC emissions. However, the weight fractions of unburned fuel and acetylene were higher during cold start than during hot stabilized driving.
机动车排放控制装置在启动时的暂时失效，导致车辆启动后的短时间内排放率远高于车辆完全预热或稳定运行期间。官方机动车排放清单估计，冷启动运行期间的过量排放占加利福尼亚州车辆所有碳氢化合物、一氧化碳（CO）和氮氧化物（NO）排放的很大一部分。为了在实际条件下验证这些估计，1997年3月在加利福尼亚州奥克兰的一个地下停车场对车辆排放进行了测量。当车辆上午抵达停车场时测量热稳定排放，下午车辆离开时测量冷启动排放；通过差值计算与车辆启动相关的增量或过量排放。在六个上午时段和六个下午时段中的每个时段，对约135辆车的综合排放进行了采样。测得的稳定尾气排放为每消耗一加仑汽油排放19±2克非甲烷碳氢化合物（NMHC）、223±17克CO和8.6±1.3克NO。对于下午启动后在停车场平均停留约60秒的车辆，测得的冷启动排放为69±2克NMHC/加仑、660±15克CO/加仑和27.8±1.2克NO/加仑。利用加利福尼亚轻型车辆监测计划中逐秒的排放数据，估计冷启动期间的平均燃油消耗量约为0.07加仑，冷启动期估计持续约200秒。当将在停车场测得的冷启动排放因子按比例换算以代表完整的200秒冷启动期时，计算出每辆车启动时的增量启动排放因子为2.1克NMHC、16克CO和2.1克NO。这些排放因子比加利福尼亚机动车排放清单模型（MVEI 7G）使用的排放因子低，NMHC低45%，CO低65%，NO低12%。这表明冷启动排放在当前排放清单中的重要性可能被高估了。总体而言，冷启动期间测得的挥发性有机化合物（VOC）排放成分与热稳定VOC排放相似。然而，冷启动期间未燃烧燃料和乙炔的重量分数高于热稳定行驶期间。
