重型柴油机双SCR系统转化效率影响因素研究

Study on factors affecting conversion efficiency of double SCR system of heavy duty diesel engine

为了研究国六重型柴油机选择性催化还原(slective catalytic reduction,SCR)系统NO_( x)转化效率的影响因素,文章运用AVL BOOST仿真软件对催化器内的化学反应过程进行了数值仿真和试验验证。结果表明:SCR催化器最佳反应温度范围在180~550℃,催化器转化效率达到95%以上;通过前置氧化型催化转化器(diesel oxidation catalyst,DOC)可以在排气中增加NO_(2)的质量分数,可以提高催化器转化效率且使NO_( x)转化效率保持在较高水平,也可以除去尾气中大部分的CO和HC,达到排放标准;安装混合器后各个工况下NO_( x)转化效率均有10%左右的提高,尤其在低温180℃时SCR催化器的转化效率有13%左右的提高。

In order to study the factors affecting the NO_( x) conversion efficiency of the selective catalytic reduction(SCR)system of the ChinaⅥheavy duty diesel engine,the numerical simulation and experimental verification of the chemical reaction process in the catalytic converter were carried out by using AVL BOOST simulation software.The results show that the optimum reaction temperature range of SCR catalyst is 180550℃,and the catalytic converter conversion efficiency is over 95%;the pre-oxidation type diesel oxidation catalyst(DOC)can increase the mass fraction of NO_(2) in the exhaust gas,improve the catalyst conversion efficiency,keep the NO_( x) conversion efficiency at a high level,and remove most of the CO and HC in the exhaust gas to meet emission standards;after installing the mixer,the NO_( x) conversion efficiency increased by about 10%under various working conditions,especially at a low temperature of 180℃,the conversion efficiency of the SCR catalyst increased by about 13%.