A one-dimensional numerical model for diesel particulate trap performance study during loading and regeneration

Abstract

A one-dimensional model was developed for honeycomb diesel particulate traps. Quasisteady state conservation equations of mass and momentum were solved by combining the shooting method and Runge-Kutta method to find the flow velocity and particulate thickness. A filtration model based on the ‘unit collector’ filtration theory was used to determine the transient filtration parameters of the porous wall. Transient conservation equations of energy were solved using a fully implicit finite difference method to find the temperature field. Analytical method and experimental data from literature were used to calibrate and validate the model, and good agreement has been achieved. A U-shaped particulate layer thickness distribution was found for a clean trap loading. In the loading process of a catalysed trap, the pressure drop increases with time at the beginning, then decreases and eventually reaches a steady state. This type of trap behaviour has been observed in experiments but cannot be predicted by numerical models assuming uniform particulate layer distribution. The trap regeneration performances were studied using this model. It was found that initially retained particulate matter can be oxidized completely during controlled regeneration, while a small amount of particulate still remains at the entrance of inlet channel after uncontrolled regeneration. Parametric studies have been carried out and these show that the trap geometry does not significantly affect trap regeneration behaviour.