基于PEMS的重型柴油车低负荷和冷起动工况排放特性研究

Emission Characteristics of Heavy-Duty Diesel Vehicles under Low Load and Cold Start Conditions Based on PEMS

使用便携式排放测试系统(portable emission measurement system,PEMS)对3辆重型柴油车进行道路排放测试,以发动机负荷率及CO_(2)排放率作为发动机低负荷或高负荷工况划分依据,结合比排放、瞬态排放等对低负荷工况CO,CO_(2),NO_(x)和PN_(23)及冷起动过程排放特性进行分析,并探究低负荷工况下PN_(10)比排放变化规律。研究结果表明:使用CO_(2)排放率作为划分依据的低负荷工况更具代表性,低负荷工况下CO,CO_(2),NO_(x)和PN_(23)比排放值较高,CO,NO_(x)和PN_(23)易超出标准限值,冷起动过程存在大量高CO和NO_(x)比排放的低负荷工况点,且将PN计数粒径范围下限由23 nm降低至10 nm后低负荷工况下PN_(10)比排放将会翻倍。

By using a portable emission measurement system(PEMS),the road-based emission tests were conducted on three heavy-duty diesel vehicles.The engine load rate and CO_(2)emission rate were used as the reference for dividing the engine into low load or high load conditions.Combined with specific emissions,transient emissions and etc,the emission characteristics of CO,CO_(2),NO_(x),PN_(23)under low load conditions and during cold start process were analyzed,and the variation law of PN_(10)specific emissions under low load conditions was explored.The research results indicate that the low load condition based on CO_(2)emission rate is more representative.Under low load conditions,the specific emissions of CO,CO_(2),NO_(x),and PN_(23)are higher,and CO,NO_(x),and PN_(23)are prone to exceed the standard limits.There are a large number of low load working points with high CO and NO_(x)specific emissions during the cold start process.Furthermore,reducing the lower limit of PN counting particle size from 23 nm to 10 nm will result in a doubling of PN_(10)specific emissions under low load conditions.