The Emission of a Diesel Engine in Different Coolant Temperature During Cold Start at High Altitude 2019-01-0730

The emission of a diesel engine has been received much more attention since the Volkswagen Emission Scandal. The Euro VI emission standard has already included cold start emissions in the legislative emission driving cycles which is the hardest part of emission control. High altitude performance is also considered in the latest regulations which will be stricter in the future. Heating the coolant is one of the most common method to improve the cold start performance. But research focus on the emission of a diesel engine in different coolant temperature at high altitude which up to 4500m has not been seen. The present research investigated the effect of coolant temperature on the diesel engine ‘s performance and exhaust emission (gaseous and particulate emissions) characteristics during the cold start and followed by idle. The engine tests were carried out on a plateau simulation test bench and the coolant temperature was controlled from 20°C to 60°C. The engine started up faster with higher coolant temperature at any altitude. As the coolant temperature increased, the CO and THC emission reached a higher peak and a lower total emission during the first 30 seconds. The CO2 emission did not change obviously at different coolant temperatures. The NOX emission was decreased as the coolant temperature increased, but went much higher when it was up to 60°C, which was just opposite of the particulate number (PN) and particulate number (PN) emission characteristic. At the same coolant temperature, higher gaseous and particulate emissions were observed at higher altitude. The PN and PM diameter distributions were analyzed and the relationship between PN and PM during cold start at different coolant temperature and altitude were established. The cold start performance of the engine with high coolant temperature at high altitude affects the engine transient emission obviously.