【摘要】 用计算流体力学(CFD)方法对汽车尾气单级双载体催化转化器流场进行数值模拟,并采用合理的统计公式计算出流动均匀性指数,直观地反映出载体间隙、载体孔密度以及前后载体长度等结构参数对转化器内流动特性的影响.结果表明:载体间隙越大,流动分布越均匀;增加前载体孔密度,气流速度分布得以改善,且催化转化器内的压力损失在可接受范围内;载体间隙不变时,前载体越长,气流速度分布越均匀.以铑催化剂表面的CO-O2反应为例,采用详细反应机理耦合CFD模型,研究了起燃阶段前后载体长度变化对转化率的影响.结果显示,在保持载体总长度不变情况下,前载体越长,催化剂起燃温度越低.更多还原

【Abstract】 The flow field in an automotive catalytic converter with dual substrates was numerically simulated by the computational fluid dynamics method(CFD). Flow uniformity index calculated by reasonable statistical formulas was used to analyze the effects of the gap width between the substrates,cell density,and substrate length ratio(front/rear)on airflow characteristics inside the converter. Results show that flow uniformity is improved as the gap width is increased. Employing a front substrate with high cell density promotes the flow uniformity with acceptable pressure loss. When keeping the constant gap width,the flow uniformity index increases with increase of front substrate length. Furthermore,a detailed kinetic model of CO-O2surface reaction over rhodium coupled with the CFD model was employed to predict the influence of substrate length ratio(front/rear)on conversion efficiency. Simulation results show that with a fixed total length of substrates,faster light-off is achieved with a longer front substrate.更多还原