05/02815 CFD simulation of the effect of upstream flow distribution on the light-off performance of a catalytic converter

Abstract

A method is described by which a CFD code known as FLUENT, may be adapted to model the reactions that take place inside catalyst structures. To test the CFD code, simulations of gas flow in a circular tube are performed and compared with analytical solutions. Then the coupled processes of diffusion and chemical reaction, combined with heat and mass transfer effects are modelled in a catalyst pellet. To illustrate the technique, the catalytic combustion of propane is simulated in spherical and cylindrical shaped pellets, at gas temperatures from 500 to 700 K and at atmospheric pressure. To help validate the approach adopted, the results of the CFD simulations are compared with solutions obtained from a one-dimensional model using MATLAB. It is shown that the CFD simulations provide comparable results with MATLAB, and that the CFD code can provide valuable additional information about temperature and concentration gradients in and around the catalyst pellet—this is not available in a simple one-dimensional approach. It is discussed how the technique could be extended to model reactions in a packed bed which would be a valuable design tool.