Lean Nox Trap Storage Model for Diesel Engine Aftertreatment Control and Diagnosis

Abstract

NOx emissions are a great concern to the environment. One major NOx emission source is from off-road and highway vehicles powered with diesel engines. Diesel engines offer significant benefits in fuel economy and low-speed torque performance. However, these benefits come at the expense of increased aftertreatment complexity. A lean NOx trap (LNT) is one effective way to reduce emissions to meet strict EPA regulations. Based on the chemical kinetics analysis of the LNT adsorption mechanism and mass transfer process, a storage model was proposed to estimate the mass of NOx adsorbed inside an LNT during lean periods based on other available signals. The model includes exhaust gas mass flow rate, in-bed temperature, inflow NOx concentrations, and NOx adsorption capacity of the LNT. Model validation shows close agreement between predictions and experimental data. This storage model can be used for LNT regeneration control and fault detection.