Numerical Prediction of Transient Conversion Characteristics in a Three-Way Catalytic Converter 982556
This paper deals with oxygen storage effect and NOx conversion reaction modeling.
It was found that the oxygen stored in the catalyst increases with catalytic wall temperature and lean ( or rich ) depth from experiments using a well controlled flow reactor. Oxygen storage-release model (OSR model), incorporated with the NOx reduction reaction and THC or CO oxidation reaction, was established from the experimental results.
Reaction rate parameters for three-way catalyst have been determined from the least data of flow reactor experiments using Evolutionary Algorithm.
Transient temperatures and emissions are predicted using the developed OSR model and the determined reaction rate parameters for three-way catalyst, which are incorporated in the numerical algorithms used in the previous paper to predict flow and temperature field in a catalytic converter.
It was found that the predicted emissions (CO,THC,NOx) for early 120 sec of LA#4 mode test showed good agreement with measured emissions. Oxygen amount, stored in or released from the three-way catalytic converter, is higher in the front area of the converter and lower in the rear. Consequently, fluctuation of the air fuel ratio in the outlet gas from a three-way catalytic converter is greatly reduced by the oxygen storage effect.