Numerical Simulation And Application Study On Three-Way Catalytic Converter With Multi-shapes And Geometry Parameter

The conversion efficiency of Three-way catalytic converter is impacted by the A/F ratio fluctuation in a closed loop control system. In general, the A/F ratio fluctuation can widen the selection window, and the selection window will be wider as the amplitude of A/F ratio fluctuation is larger. In 1970s, it's thought that the A/F ratio fluctuation widen the selection window but lower the maximum of the conversion efficiency. However, in the late of 1980s, researchers founds that the improvement in cocatalyst can help keeping the conversion efficiency in a high level while the selection is widen by the A/F ratio fluctuation. Therefore, the oxygen storage submodel should be taken into account for the three-way catalytic converter mathematic computation. Besides, the advantages of column monolith have been recognized, but as the chassis space is limited, the non-columniform monolith, like elliptic monolith and course-shaped monolith, are also employed for the fixing convenience.Based on the computational fluid dynamics, a 3-D flow model of three-way catalytic converter is built and solved by using an CFD software FLUENT. Three catalytic converters with different inlet diffuser are simulated in the model computation. The chart of the radial velocity distrusting is gained. The simulation results is validated by the experiment data. The flow model is the foundation of multi-dimensional flow and reacting flow study of three-way catalytic converter.Based on the knowledge of microcosmic structure and characteristic of the oxygen storage cocatalyst, the oxygen storage reaction submodel is built and calculated under A/F ratio step-change and A/F ratio excursion working condition. The transient CO outlet trends are accorded with the experimental results, and is still better than that of steady state and quasi-steady state. So the submodel can be used in the study of reaction in catalyst.The reaction model is calculated by FLUENT. Based on the improved model, some geometric parameters were studied for an elliptic monolith catalyst. The impacts of ellipse ratio, length and cross-sectional area of the monolith, cell density and cell thickness are studied, which provide the guidelines for practical design improvements to meet the increasingly stringent emission legislations.