| Catalytic converter is an assembly to effectively reduce the poisonous emissions from internal combustion engine, which is widely used. As a result of the effect of noble metal catalyst loaded on the substrate, CO, HC and NOx are converted into non-toxic substance. With the rapid development of industrialization, the noble metals have been widely used. The noble metal is very rare and expensive. The catalytic converter must be optimized and improved, in order to improve the conversion rate of pollutants, enhance the noble metal use efficiency, and reduce production costs, and then achieve the purpose of saving energy and emission reduction. In this thesis, the flow field in catalytic converter has been investigated. It have been primarily analyzed that efficiency of structural parameters on the flow distribution in catalytic converter, which lay the foundation for the studies about of lowing light-off temperature and increasing utilization ratio of noble metal.Flow in the catalytic converter is not only accompanied by heat and mass transfer, but also include the complex chemical reactions. The flow conditions have a great impact on heat transfer, mass transfer and chemical reaction. The flow distribution non-uniformity can cause the carrier radial direction gradient of temperature to increase and then lead to the thermal deformation and the damage, thereby reducing the life of the catalytic converter.A significant advantage of the catalytic conversion with dual substrates is that the substrates can be more flexible installed. This paper studies that gap width between the substrate length ratio (front/rear) and cell density have impacts on flow uniformity and conversion efficiency. Two-dimensional model and single-channel model of catalytic converters were simulated by using computational fluid dynamics software FLUENT coupled with chemical reaction simulation software CHEMKIN.It proves in this thesis that the Uniformity index increases with increase of air gap for rear substrate and the trend is reversed for the front substrate. The study on the effect of substrate length ratio reveals that, with a fixed substrate volume, better flow distribution and higher converter efficiency is obtained with a much longer front substrate. As cell density of the front substrate increases, converter efficiency and flow uniformity can be improved, with no further extra pressure loss. |
