Influence of Density Variation on One-Dimensional Modeling of Exhaust Assisted Catalytic Fuel Reforming

Exhaust gas recirculation has become commonplace within the automobile industry to reduce nitrogen oxide emissions because of its ability to lower the combustion temperature. However, it leads to an increase of particulate matter and degradation in fuel economy. One possible avenue for recovering this efficiency is to use exhaust assisted fuel reforming (EAFR) to generate hydrogen by catalytic means using injected fuel and exhaust and add it to the inlet mixture. Adding hydrogen in this manner has shown an increase in combustion stability and efficiency of the engine while reducing particulate matter production. Many classical works use incompressible fluid flow models in order to simulate the reactive flow in monolithic catalyst. However, such models are not appropriate in the case of EAFR, where exothermic reactions cause a large increase in the temperature and consequently in density. To simulate a catalyst undergoing EAFR reactions, a compressible flow solver was used in order to take into account the changes in density. The presented results show the importance of using proper gas dynamics and heat transfer for modeling a flow with catalytic reactions of high exothermicity.