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Modeling and simulation of wall -flow diesel particulate filter during loading and regeneration
The advent of tightened diesel emission regulations has led to the development and implementation of various diesel in-cylinder controls and after-treatment devices. As the most promising after-treatment device in reducing particulate emission from diesel engines, the diesel particulate filter (DPF) was developed in the 1980s and has undergone notable improvements. The objective of this dissertation is to explore complicated physical processes in the DPF during loading and regeneration. In the 1-D model, quasi-steady state conservations of mass and momentum are solved by a shooting method coupled with a Runge-Kutta method. A filtration model based on unit collector filtration theory is used to determine transient filtration behaviors of the porous wall. Transient conservations of energy are solved with fully implicit finite difference method to find the temperature field. The major challenge with DPF is the uncertainty of the regeneration process. The exothermic soot oxidation during regeneration leads to sharp rise in local temperature and temperature gradient, which makes the DPF susceptible to melting and cracking. As an extension of the 1-D model, a quasi 3-D model is developed to locate hot spots in the DPF. The 3-D Navier-Stokes equations are solved using order of magnitude analysis and integral method. The 3-D transient conservation of energy is solved by a modified Alternative-Direction-Implicit (ADI) method to find the temperature distribution, which enables further numerical simulation of thermal stress. A displacement-based finite element method is employed to solve for the 3-D thermal stress induced by high temperature and temperature gradient during DPF regeneration. This finite element model is self-contained and independent of any commercial package. It includes functions of meshing body, assembling global stiffness matrix and force vector, solving final equilibrium equations and post-processing. Finally, parametric studies are carried out with these three models to investigate the impact of DPF geometric designs on performance. Primary attention is paid to pressure drop, peak temperature and thermal stress, which are associated with diesel thermal efficiency and potential DPF failure due to melting and cracking.
Guo, Zhenhua, "Modeling and simulation of wall -flow diesel particulate filter during loading and regeneration" (2006). ETD collection for University of Nebraska - Lincoln. AAI3236910.