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Multiple Regression Analysis of OSC Characteristics under Transient TWC Conditions
Abstract:
Three Way Catalysts (TWC) contain oxygen storage components (OSC) to enhance HC, CO oxidation and NOx reduction performance under standard operating conditions where there is rapid perturbation of the air-to-fuel ratio (A/F). The OSC function is required to storage and to release oxygen, however the optimum storage capacity and release rate to maximize HC, CO and NOx conversion varies as a function of engine operating conditions, such as A/F perturbation frequency, amplitude and temperature. At the same time it is necessary for the vehicle on board diagnostics (OBD) systems to monitor that the catalyst OSC is functioning correctly. Detailed understanding of how OSC characteristics can simultaneously match gas performance and OBD functionality are not well known.
In this study, several TWC catalysts were prepared with different types of OSC materials such that oxygen storage capacity and activation energy for oxygen release could be varied over a wide range. Five independent variables; OSC species, OSC loading in the catalyst, temperature, A/F amplitude and A/F frequency were controlled and fourteen dependent variables such as gas performance, oxygen sensor response, etc, were measured. Statistical analysis was performed using the multi-objective analysis software, modeFRONTIER.