School of Transportation, Southeast University, China.
Department of Civil & Mineral Engineering, University of Toronto, Canada.
Sci Total Environ. 2021 Mar 15;760:143402. doi: 10.1016/j.scitotenv.2020.143402. Epub 2020 Nov 6.
Studies have demonstrated that vehicles with gasoline direct injection (GDI) engines produce significantly higher emissions during a cold start than under hot-stabilized periods. A cold start is typically defined by the temperature of the engine or the catalytic converter; its extended effect on emissions, after the vehicle reaches the warm-up stage, has seldom been investigated. In this study, the influence of the post cold start period on nitrogen oxides (NO) emissions was evaluated using real-world measurements. Vehicle on-board diagnostic data, fuel consumption, and emissions of multiple pollutants were collected on a 2020 GDI sports utility vehicle equipped with a Portable Emission Measurement System (PEMS). A total of 31 trips, with two drives per day, were conducted along arterial roads and highways in Toronto, Canada. The results indicate that during the first trip of the day after an overnight soak, the average NO emission rate was 0.27 g/litre and 0.037 g/km, 384% and 299% higher than the emission rate on the second trip of the day. The amount of trip total NO emissions is positively associated with the length of the catalytic converter warm-up period with correlation coefficient 0.67. We also observe that the catalyst warm-up time is negatively correlated with ambient temperature, and a negative relationship between ambient temperature and NO emissions throughout the trip is depicted with correlation coefficient -0.44. The measured data reveal an extended effect of the cold start on NO emissions even after the temperatures of the engine coolant and catalyst reach a stable level.
研究表明，与热稳定阶段相比，采用汽油直喷（GDI）技术的车辆在冷启动期间会产生更高的排放。通常，冷启动是根据发动机或催化转化器的温度来定义的；在车辆达到预热阶段后，其对排放的延长影响很少被研究。在这项研究中，使用实际测量评估了冷启动后阶段对氮氧化物（NO）排放的影响。使用车载诊断数据、燃料消耗和多种污染物的排放，在配备便携式排放测量系统（PEMS）的 2020 年 GDI 运动型多用途车上进行了收集。总共进行了 31 次行程，每天两次在多伦多的主要道路和高速公路上进行。结果表明，在一夜浸泡后的当天第一次行程中，平均 NO 排放率为 0.27 g/litre 和 0.037 g/km，分别比当天第二次行程的排放率高 384%和 299%。总行程 NO 排放量与催化转化器预热期的长度呈正相关，相关系数为 0.67。我们还观察到，催化剂预热时间与环境温度呈负相关，并且整个行程中环境温度与 NO 排放之间呈负相关，相关系数为-0.44。测量数据显示，即使发动机冷却液和催化剂的温度达到稳定水平，冷启动对 NO 排放的延长影响仍然存在。
