Optimization of a Three-Way Catalytic Converter Through Engine Test-Bench Experiments

Abstract

A three-way catalytic converter model designed in a preceding thesis has been refined and translated from SIMULINK into a script-based MATLAB model, to produce faster, more stable and accurate solutions for the ordinary differential equations (ODE). The model consists of nine ODE’s and are solved using the in-built ode15s solver. The states of the model include O2, CO, C3H6, C3H8, H2, NO, CO2, H2O concentrations and oxygen buffer levels for each slice of the catalyst. The scope of the thesis is to gain an in-depth understanding of the workings within the catalyst by conducting experiments in a test-rig where an engine has been used, so as to mimic the composition of the exhaust in a real driving scenario, which is lacking within the scope of literature. The thesis suggests a variety of methods to collect and analyze data, these include using catalysts of different axial lengths (70, 30 and 15mm) and utilizing a heat-exchanger that allow the temperature dynamics to be studied at higher resolution. The collected data is then used to optimize 30 kinetic parameters in the model with the help of a built-in MATLAB function, lsqnonlin. Results show that good emission predictions can be obtained for certain space velocities, with exceptions in higher temperature regions where the model lacks a mass transfer description.