前置DOC对SCR系统柴油机NO_x排放的影响  

Effect of Pre-DOC on NO_x Emission for SCR Diesel Engine

作　　者：田茂军[1] 朱红国[1] 黄德军[1] 徐辉[1] 李祚兵 

机构地区：[1]中国汽车工程研究院股份有限公司,重庆401122

出　　处：《车用发动机》2015年第4期80-84,共5页Vehicle Engine

摘　　要：对装配前置DOC和无DOC的SCR系统柴油机进行稳态和瞬态试验,研究了前置DOC在不同循环状态下对NOx排放的影响。结果表明:前置DOC能显著提高SCR入口处NO2与NOx的体积比V(NO2)∶V(NOx),加速SCR反应,提高NOx转化效率,改善NOx排放;在ESC非怠速工况下,DOC对V(NO2)∶V(NOx)的影响会随着排气中氧含量和排气温度、空速的提高逐渐降低;温度超过一定范围时,NH3对O2的选择性突然提高,V(NO2)∶V(NOx)对NOx转化效率的影响将减小;DOC内氧化反应产生的热量有限,不足以提高SCR入口处排气温度,而DOC陶瓷载体的储热特性在瞬态循环下会对SCR入口温度产生一定影响,但这并不是改善NOx排放的主要原因。The steady and transient test of diesel engine were carried out under the conditions of pre-DOC and non-DOC and the effect of pre-DOC on NOx emission was studied .The results show that the pre-DOC can obviously increase the V (NO2 ):V (NOx ) volume fraction ratio st SCR entrance ,accelerate the SCR reaction ,raise the conversion efficiency of NOx and improve NOx emission .Effect of DOC on V (NO2 ):V (NOx ) volume fraction ratio decreases with the increase of oxygen content ,ex-haust temperature and air speed in ESC except idle .When the exhaust temperature exceeds a certain range ,the effect of V (NO2 ):V (NOx ) volume fraction ratio on NOx conversion rate decreases due to the sharp increase in the selectivity of NH3 to O2 .The limited heat of DOC reaction is not enough to increase the entrance temperature of SCR ,but the accumulated heat of ceramic substrate can increase the entrance temperature in ETC ,however it is not the main method to improve NOx emission .

关 键 词：柴油机 排放 氮氧化物 柴油机氧化催化器 选择性催化还原 

分 类 号：TK427[动力工程及工程热物理—动力机械及工程]