当量比燃烧天然气发动机铑基三效催化器次生污染物研究  

Investigation on Generation of Secondary Pollutant from Rh-Only Three Way Catalytic in a Natural Gas Engine Under Stoichiometric Conditions

作　　者：唐飞[1] 钱叶剑[1] 孟顺 余自洋 边顺 TANG Fei;QIAN Yejian;MENG Shun;YU Ziyang;BIAN Shun(School of Automotive and Transportation Engineering,Hefei University of Technology,Hefei 230009,China)

机构地区：[1]合肥工业大学动力机械及工程系,合肥230009

出　　处：《内燃机工程》2021年第6期70-79,共10页Chinese Internal Combustion Engine Engineering

基　　金：国家自然科学基金项目(51676062)。

摘　　要：建立了一种适用于当量比燃烧天然气发动机的Rh基三效催化器(three-way catalytic converter,TWC)整体模型,研究了排气温度和组分对TWC系统次生污染物N_(2)O和NH_(3)生成特性的影响。结果表明:N_(2)O主要在起燃和低温(400 K~605 K)阶段通过CO还原NO反应生成;高温状态下(>850 K)NH_(3)通过H_(2)还原NO反应生成,H_(2)来源于蒸汽重整(steam reforming,SR)和水煤气变换(water gas-shift,WGS)反应。H_(2)体积分数的增加促进了N_(2)O和NH_(3)生成,高温下N_(2)O会与H_(2)发生还原反应,H_(2)体积分数越高,N_(2)O生成反而越低。H_(2)O和CH_(2)对N_(2)O和NH_(3)生成的影响随着温度变化而变化。在一定范围内,随着O_(2)体积分数增加,NH_(3)生成减少,N_(2)O生成增加;高温下,O_(2)体积分数过高时,N_(2)O生成反而减少。研究还发现,排气中O_(2)体积分数在4000×10^(-6)左右时,排温控制在580 K~850 K,能实现N_(2)O和NH_(3)近零排放。A global model of Rh-only three-way catalytic(TWC)suitable for a stoichiometric natural gas engine was established,and the effects of exhaust temperature and composition on the generation characteristics of side-products N_(2)O and NH_(3) were investigated.The results show that N_(2)O is primarily formed during light-off and low temperature period(400 K~605 K),which proceeds via reduction of NO by CO.NH_(3) is observed at high temperature(>850 K)via reduction of NO by H_(2),and the H_(2) required to produce NH_(3) is generated via steam reforming and water gas-shift reactions over the catalysts.The increase of H_(2) concentration promotes the production of N_(2)O and NH_(3).At high temperature,the N_(2)O production will react with H_(2),and the higher the H_(2) concentration,the lower the N_(2)O generation.The effect of H_(2)O and CH_(2) on the formation of N_(2)O and NH_(3) varies with temperature.Within a certain temperature range,as the O_(2) concentration increases,the NH_(3) production decreases and the N_(2)O production increases.At high temperature,the N_(2)O production decreases when the O_(2) concentration is too high and under 4000×10^(-6) O_(2) concentration,the zero emission of N_(2)O and NH_(3) can be achieved by controlling the exhaust temperature at 580 K~850 K range.

关 键 词：当量比燃烧 天然气发动机 三效催化器 N_(2)O排放 NH_(3)生成 

分 类 号：TK411.5[动力工程及工程热物理—动力机械及工程]