Effect of different exhaust parameters on conversion efficiency enhancement of a Pd–Rh three-way catalytic converter for heavy-duty natural gas engines

Abstract

In this work, the influence of exhaust parameters on the conversion performance of the Pd–Rh three-way catalytic converter (TWC) for heavy-duty natural gas engines is investigated by CFD simulation. A mathematical model adopting an empirical global reaction mechanism for the Pd–Rh TWC is established and validated. The results indicate that the increase of exhaust CO concentration is beneficial to remove the CH4 and NO emissions. As the exhaust CO concentration increases from 0.7 % (stoichiometric condition) to 1.3 % at 623K, the conversion efficiencies of CH4 and NO increase by 8.1 % and 41.8 %, respectively. In GRA, the most important influencing factor on the conversion efficiencies of CH4 and CO is the exhaust O2 concentration. For the NO conversion efficiency, the primary and secondary relationships of the three factors are exhaust CO concentration＞exhaust flow rate＞exhaust O2 concentration. The orthogonal experiment analysis indicates that Case 7 shows better total conversion performance (CH4: 97.6 %; CO: 100 %; NO: 62.2 %) than other cases. Compared with the stoichiometric condition at 623K, the conversion efficiencies of CH4 and NO are improved by 97.8 % and 3.8 %.