Numerical Study On Gas-particle Two-phase Flow Characteristic In Diesel Particulate Filter

As the diesel emission standards become stricter, diesel particulate filters (DPF) are being the dispensable device for reducing particulate emissions. The flow characteristics of the gas and particulate are the most important factors on the utilization ratio of filter, the regeneration period of filter and the lifespan of filter, so there is a significant value to study the gas-particle two-phase flow characteristic in DPF.This article is based on the Hunan Natural Science Funding Program(06JJ20018)"Numerical Simulation of Gas-particle Two-phase Flow and Combustion During Complex Regeneration in Vehicle Diesel Particulate Filter". The main research works and obtained results are expressed as follows:(1) The DPF is divided into the outside of filter and the insider of filter. Based on porous medium theory and gas-particle two-phase flow theory, the integrated 3-D gas-particle two-phase flow mathematic model which includes the outside of filter and the insider of filter has been established for the first time.(2) The established gas-particle two-phase flow model is solved using FLUENT, and the pressure filed, velocity filed and particulate concentration filed are obtained. The simulation results are in good agreement with experiment results, so the correctness of the model is verified. The results show that the distribution of particulate concentration inside the filter depends on the distribution of velocity in the flared zone, and the eddy in the flared zone is the key to affect the distribution of particulate concentration inside the filter.(3) Based on the gas-particle two-phase flow mathematic model in DPF, the influences of inlet velocity, diameter ratio, divergence angle on the distribution uniformity of velocity are studied, and the influences of inlet velocity, particulate diameter, diameter ratio, divergence angle on the distribution uniformity of particulate concentration are studied. The results show that the smaller the particulate is, the well the distribution uniformity of particulate concentration will be, and reducing inlet velocity, diameter ratio and divergence angle can all improve the distribution uniformity of velocity and particulate concentration.The works provides an important reference to optimize the structural parameters of DPF, and provides an important ground to exactly study on regeneration process of DPF.