先进后处理对重型车超细颗粒排放的影响

Effect of Advanced Aftertreatment for PM and NOx Reduction on Heavy-Duty Vehicle Engine Ultrafine Particle Emissions under Different Working Conditions

本文在重型底盘测功机上基于C-WTVC和中国重型商用车辆行驶工况(CHTC),研究了环境温度、工况因素以及先进后处理等关键参数对重型整车气态污染物、超细颗粒物(包括>23 nm和 23 nm的颗粒影响较小,对10~23 nm的颗粒影响显著,这与硝酸铵和硫酸铵的生成条件有关,使用含硫量低的燃料和润滑油可以降低 < 23 nm颗粒数。从总颗粒数上看,10~23 nm部分占总颗粒数的比重较高,包含10~23 nm部分时C-WTVC和CHTC工况在低环境温度时尚可满足当前法规限值,但当环境温度升高,尤其是CHTC工况,总颗粒数会大幅超过限值要求。CHTC低速段时间长,加速工况多是NOx排放和百公里油耗高于C-WTVC的主要原因,低速段急加速工况是今后降低NOx的研究重点,高速段是改善燃油经济性的研究重点。

The paper analyzes the differences between China Heavy-duty Commercial Vehicle Test Cycle (CHTC) and C-WTVC based on cycle characteristic parameters. The heavy-duty diesel vehicles were tested using a chassis dynamometer to character-ize the effect of the ambient temperature, cycle characteristics and aftertreament on the gaseous pollutants and the occurrence of nucleation. Results showed that the occurrence of a nucleation mode could be predicted based on the level of catalyst, the temperature, and the sulfur/ammonia in the aftertreatment. Reducing the sulfur level in fuels and lubricating oil can effectively prevent na-noparticle formation related to particle filters. Ambient temperature has no influence on the >23 nm particle number emissions, but has significant effect on particles of 10~23 nm, this is related to the formation of ammonium nitrate and ammonium sulfate. The 10~23 nm part accounts for a high proportion of the total particle number. Including the 10~23 nm part, the C-WTVC and CHTC can meet the current regulations at low ambient temperature, but when the ambient temperature rises, especially CHTC, the total particle number will greatly exceed the limit. CHTC’s NOx and fuel con-sumption are higher than that of C-WTVC due to its longer low-speed period and more acceleration and deceleration conditions. CHTC’s low-speed acceleration cycles are the focus of research to re-duce NOx emissions, and the high speed cycles are the focus of research to improve fuel economy.