Development and Experimental Validation of a NOx Trap Model for Diesel Exhaust

This paper presents a mathematical model for the simulation of NO_x traps during the storage and the regeneration phases. The objective is to validate the model under realistic exhaust gas conditions during NO_x storage and release phases.

The model is based on a previous modeling platform developed by Aristotle University which simulates the behavior of 3-way catalysts. The previous model is extended to include the additional reactions taking place on a NO_x trap, with particular emphasis on the calculation of thermodynamic equilibrium effects. Moreover, the model includes the necessary reactions to simulate catalyst sulfation and de-sulfation processes. In parallel, a set of measurements are conducted under well controlled conditions with real diesel exhaust to study the storage and release phenomena under various operating conditions. The experimental data are used to calibrate the reaction kinetics and validate the model.

The complexity of the modeling problem arises from the lack of sufficient knowledge regarding the processes affecting the status of Ba during real-world operation. Nevertheless, the accuracy of the model is acceptable at least in the temperature range between 200 and 400°C, which is more relevant for diesel applications. The model is quite useful to study the “saturation” and regeneration processes within the NO_x trap as function of position. Further work is required to improve the model accuracy in a wider range of conditions.