Extraction and Analysis of High Emission Conditions of Heavy Diesel Vehicles Based on Real Road Driving Conditions

In order to explore a method for judging the on-board emission level of heavy-duty diesel vehicles and to study the emission level of heavy-duty diesel vehicles, in this paper, we used OBD system data acquisition terminal to transport five heavy-duty vehicles on actual drive based on the subject of “Research and application of key technologies for emission monitoring in actual operation of heavy-duty diesel vehicles”. By collecting the data and consulting Beijing Local Standard, China VI Standards for heavy duty diesel vehicles and the method of driving cycle construction, AME (Averaging Window Method), NTE (Not-To-Exceed) method and short-trip method were used to analyze the collected data segments respectively. Comparing the segment data obtained by three methods and the proportion of segments exceeding the limit value, it is concluded that the short-trip method can effectively extract the operating segments with emission exceeding the limit. A further analysis of the short trips of 5 vehicles exceeding the emission limit showed that, compared with vehicle speed and acceleration, VSP can better identify vehicle emissions exceeding the standard in the actual driving process, and VSP of the emission exceeding segments was concentrated in the range of 0–2.5 kW/ton. The duration of high emission segments was mainly within 300 s, and the idle proportion of high emission segments was concentrated in 0–5%, the acceleration proportion of more than 80% segments was within 22%, and the distribution law of deceleration proportion and uniform proportion was not obvious. The average speed of high emission segments is mainly distributed at low and medium speeds and the high emission segments with maximum acceleration of 1–1.3 m/s² account for a large proportion, The possible reason is that the lower speed running segment basically appears in the process of vehicle deceleration to zero immediately after a short acceleration. At this time, the acceleration of the vehicle is larger, and the reaction of the post-processing system is delayed, so the exhaust emission cannot be reduced in time.