Modelling wall-flow diesel particulate filter regeneration processes

This research was aimed at providing a better understanding of regeneration processes in wall-flow diesel particulate filters (DPFs), with emphasis on the combustion of particulate matter (PM). A 1-D model was used to investigate the effects of inherent PM properties on DPF regeneration behaviour. These properties were mean particulate diameter, porosity and bulk density of the PM, as well as the kinetic parameters of PM oxidation, i.e. frequency factor and activation energy. A parametric study showed that the activation energy of the PM oxidation reaction was the most important parameter and this was followed by the associated frequency factor, bulk density and porosity and mean particulate diameter. Due to the importance of the kinetic parameters of the PM oxidation reactions, a new 1-D model with a multi-step reaction scheme that required no tuneable kinetic parameters for the PM oxidation reactions was developed. [Continues.

A diesel particulate filter regeneration model with a multi-step chemical reaction scheme

Diesel particulate filters (DPFs) are considered necessary in order to meet future global diesel engine emissions legislation. Various regeneration methods have been developed to clean DPFs by periodic oxidation of trapped particulate matter (soot). To achieve this goal, it is important to understand the fundamentals of the regeneration process. Previous soot oxidation regeneration models relied on tunable chemical kinetic parameters to achieve agreement between model and experimental results. In the work reported in this paper, a multistep chemical reaction scheme is incorporated in a model to study the thermal regeneration process. The regeneration model does not require tunable parameters and its results compare well with experimental findings. The effects on regeneration of various gas species are also studied, in addition to O2 and N2, such as CO and H2O that are present in the exhaust gas. The model is also used to demonstrate the effects of quenching the regeneration process and its impact on partial filter regeneration

The effects of soot properties on the regeneration behaviour of wall-flow diesel particulate filters

In recent years, significant effort has been put into studying the regeneration process of diesel particulate filters (DPFs) either through experiments or modelling. However, less attention is paid to understanding the important influence of soot properties on the regeneration process. In this paper, for the first time, five fundamental soot properties, namely activation energy, frequency factor of the reaction, soot bulk density, porosity and mean soot particulate diameter, are investigated. Sensitivity analyses are carried out for each of these parameters based on a one-dimensional generalized DPF regeneration model. It is found that activation energy is the most important factor in the regeneration process, followed by frequency factor, bulk density, porosity and mean particulate size. In addition, the results also indicate that the concentration of exhaust gas oxygen has a significant influence on the role played by each parameter. This clearly shows the importance of gas diffusion in the regeneration process

A finite-volume-based two-dimensional wall-flow diesel particulate filter regeneration model

Many existing diesel particulate filter (DPF) models do not sufficiently describe the actual physiochemical processes that occur during the regeneration process. This is due to the various assumptions made in the models. To overcome this shortcoming, a detailed twodimensional DPF regeneration model with a multistep chemical reaction scheme is presented. The model solves the variable density, multicomponent conservation equations by the pressure implicit with splitting of operators (PISO) scheme for inlet and outlet channels as well as the porous soot layer and filter wall. It includes a non-thermal equilibrium (NTE) model for the energy equation for porous media. In addition, for the first time, experiments on the DPF were conducted to determine the interstitial heat transfer coefficient inside the DPF porous wall. The results compare well with an in-house one-dimensional model and subsequently this was used in the new two-dimensional model. By using this detailed two-dimensional model, some interesting observations of the DPF regeneration process were revealed. These included flow reversals and asymmetry in the filter channels