Stewart, J., Stalker, R., O'Shaughnessy, R., Douglas, R. et al., "Sensitivity Analysis of Full Scale Catalyst Response under Dynamic Testing Conditions - A Method to Develop Further Understanding of Catalytic Converter Behavior Pt.1," SAE Technical Paper 2016-01-0979, 2016, doi:10.4271/2016-01-0979.
Catalyst aging is presently one of the most important aspects in aftertreatment development, with legislation stating that these systems must be able to meet the relevant emissions legislation up to a specified mileage on the vehicle, typically 150,000 miles.The current industry approach for controlling aging cycles is based solely on the detailed specification of lambda (air-fuel mixture concentration ratio), flow rate and temperature without any limitations on gas mixture. This is purely based upon the experience of engine-based aging and does not take into account any variation due to different engine operation. Although accurate for comparative testing on the same engine/engine type, inconsistencies can be observed across different aging methods, engine types and engine operators largely driven by the capability of the technology used.This study investigates the variation in thermal profiles measured along the axial length of a Three Way Catalyst (TWC) monolith for different gas compositions with constant inlet conditions of flow rate, temperature, oxygen concentration and lambda. The purpose of this study is to determine the possible differences in temperature profile due to the variation of carbon monoxide (CO) and hydrocarbon (HC) concentrations while maintaining the same lambda and oxygen concentration. Such differences would subsequently affect the level of aging within the catalyst whilst apparently applying the same test conditions.The experimental data was obtained using a unique full scale aftertreatment testing system (recirculating synthetic gas reactor) with high precision and controllability to vary factors not normally or easily explored in typical Standard Gas Bench, engine testbed or vehicle based testing. The results clearly demonstrate that different temperatures can be generated by varying gas mixture alone and that this variation could cause a difference of 15% in aging at the front edge of the brick based on the BAT calculations.