车用催化器载体蜂窝孔内CO向催化剂表面质量传输分析

摘要

Chemical reaction of CO is a gas-solid catalytic reaction in catalytic converter. The mass transfer course of CO in honeycomb holes has very important effects on CO conversion ratio. Our study reveals that honeycomb holes surface area, CO density and airspeed make notable impact on CO mass transfer ratio; larger surface area and higher CO density can increase CO mass transfer ratio; the influence of airspeed on CO mass transfer ratio is caused by flow velocity boundary layer or CO density boundary layer. The CO mass transfer coefficient is impacted by flow boundary layer and it linearly increases with airspeed increasing when airspeed value is in a limit scope. Out of this scope the CO mass transfer coefficient increases slowly and tends to steady finally.%催化转化器中CO化学反应属于气固非均相催化反应，在载体蜂窝孔内CO向催化剂固体表面的质量传输过程对CO的转化率有着重要影响。通过研究CO的传质过程发现：传质表面积、流体中CO的浓度和空速3个因素对CO的传质速率有着重要影响；增加载体的有效传质表面积，可以有效地增大传质速率；流体中CO浓度越高则传质速率也越大，但不能以此来提高CO的传质速率，因为目的是为了降低排气中的CO浓度；空速对传质速率的影响是通过速度附面层或浓度附面层对传质系数的影响表现出来的，随着空速的增加传质系数也在不断地增加，在一定范围内二者呈线性关系，当超出这一范围后传质系数的增长速率变慢，并最终趋向于稳定。