重型柴油车燃用生物柴油CO_(2)和NO_(x)排放影响因素分析

Study on Influencing Factors CO_(2)and NO_(x)Emissions from Heavy-Duty Diesel Trucks with Biodiesel

文章基于底盘测功机法以及中国货车行驶工况(CHTC-HT)测试了国六燃用生物柴油车CO_(2)和NO_(x)的瞬态实际排放特征,评估了运行工况、冷热启动、环境温度和载荷下对实际排放的影响。在瞬态运行工况下,测试车辆CO_(2)的排放速率与加速度呈显著正相关,低速加速段的NO_(x)的排放速率急剧增加。环境温度和冷热启动影响样车CO_(2)和NO_(x)的排放,CO_(2)的排放主要受到车辆速度和负荷的影响,冷启动阶段、市区、城郊和高速的CO_(2)平均排放速率分别是3.84 g/s、2.69 g/s、4.92 g/s和7.52 g/s。冷启动阶段的NO_(x)排放占整个测试循环排放的62.9%,急加速阶段,多次出现排放NO_(x)的峰值。载荷对CO_(2)的比排放的影响并不十分显著,与空载相比,半载的NO_(x)的平均比排放降低了27.1%。测试车辆在市区、城郊和高速的工况下CO_(2)的平均比排放差异并不显著。市区NO_(x)的平均比排放达到6582.7 mg/(kW·h)(空载)、5547.2 mg/(kW·h)(半载),分别是城郊的1.55倍、高速的6.21倍(空载),城郊的1.71倍、高速的9.94倍(半载)。结果表明需重点关注低温冷启动时期,短时间内选择性催化还原器(SCR)的工作效率的提升;同时,注重控制在低速加速阶段、长期荷载较低和经常市区行驶的生物柴油车辆NO_(x)的排放。

This paper investigates transient emission characteristics of CO_(2)and NO_(x)from diesel vehicles based on chassis dynamometer and China heavy-duty commercial vehicle test cycle for truck(CHTC-HT).The influence of operating modes,cold and hot start,ambient temperature and load on the real-word emission are estimated.Under transient operating conditions,the CO_(2)emission rate of the test vehicle is significantly positively correlated with the acceleration,and the NO_(x)emission rate in the low-speed acceleration section increases sharply.The ambient temperature and cold and hot start affect the CO_(2)and NO_(x)emissions of the sampling vehicle.The CO_(2)emissions are mainly determined by the vehicle speed and load.The average CO_(2)emission rates at the cold start,urban area,suburb and freeway are 3.84 g/s、2.69 g/s、4.92 g/s and 7.52 g/s,respectively.The NO_(x)emission in the cold start accounts for 62.9%of the emission in the whole test cycle,and the peak value of NO_(x)emission occurs repeatedly in the rapid acceleration process.The impact of load on the specific emission of CO_(2)is not very significant.Compared with no-load,the average specific emission of NO_(x)at half load is reduced by 27.1%.The average specific emissions of CO_(2)of test vehicles under urban area,suburb and freeway modes are not significantly different.The average specific emission of urban area NO_(x)is 6582.7 mg/(kW·h)(No-load)and 5547.2 mg/(kW·h)(Half-load),which are 1.55 times of suburb,6.21 times of freeway(No-load),1.71 times of suburb and 9.94 times of freeway(Half-load),respectively.The results show that it is necessary to focus on the improvement of selective catalytic reduction(SCR)efficiency in a short-term during the cold start period at low temperature;Meanwhile,should pay attention to controlling the NO_(x)emission of biodiesel vehicles under low-speed acceleration,long-term lower load and regular urban driving.