2003-FL-46 Lattice-Boltzmann Diesel Particulate Filter Sub-Grid Modeling – a progress report George G. Muntean, Dave Rector, Darrell Herling, Del Lessor, and Moe Khaleel Pacific Northwest National Laboratory PO Box 999, Richland, WA 99352 Copyright © 2003 Society of Automotive Engineers, Inc. ABSTRACT Aftertreatment modeling capabilities are an important part of the diesel engine manufacturer’s efforts to meet the quickly approaching EPA 2007 heavy-duty emissions regulations. A critical, yet poorly understood, component of particulate filter modeling is the representation of the soot oxidation rate. This term directly influences most of the macroscopic phenomenon of interest, including filtration efficiency, heat transfer, back pressure, and filter regeneration. Intrinsic soot cake properties such as packing density, permeability and heat transfer coefficients remain inadequately characterized (1). The work reported in this paper involves subgrid modeling techniques which may prove useful in resolving these inadequacies. The technique involves the use of a lattice Boltzmann modeling approach. This approach resolves length scales which are orders of magnitude below those typical of a standard computational fluid dynamics (CFD) representation of an aftertreatment device. The improved resolution may allow for the characterization of functionality not previously reported in the literature. This paper presents the first status report of this multiyear project. Descriptions of the modeling technique, the initial kinetics, and the development of the computational domain are provided. In addition, preliminary sample exercises are discussed in order to illustrate how the final model, once refined and validated, may be applied in practice. INTRODUCTION The United States Environmental Protection Agency’s 2007 heavy duty diesel engine exhaust emissions standards mandate a 90% reduction in particulate matter over current levels. The majority opinion in the diesel industry is that these standards are, by implication, mandating exhaust particulate filtration for diesel engines (2). Unfortunately, there is no commercially viable filtration technology which currently exists that can be universally applied to all on-highway heavy duty diesel engines without regard to duty cycle (3). Several key technical hurdles that must be overcome in order for diesel particulate filters to become practical include: filter plugging, thermal failures, size, cost, filtration performance, deactivation and durability. The resolution of these technical issues requires a detailed system level understanding of the interaction between the diesel engine’s exhaust characteristics and the filtration device. Attention must be given to all possible application duty cycles and ambient conditions. Modeling can greatly expedite this process. In order to be effective, three specific modeling tasks must be accomplished. First , detailed combustion and air handling models are needed in order to understand exhaust gas temperatures and constituents. Second , exhaust system models (including a characterization of individual installation requirements) are required for heat and mass transfer effects. This would also incorporate any sensors and/or actuators within the exhaust system. Third , the individual aftertreatment device performance must be adequately characterized. Only then can simulations effectively be produced to help aid in the understanding and prediction of filtration effectiveness, durability, and fuel economy impacts. These system models can be used to optimize the engine control strategies, to help determine the physical dimensions of the catalyst system and to simulate numerous real world applications which may be prohibitively expensive to field test individually. The detailed component models can be used to investigate novel new filtration techniques or to optimize existing substrate geometries for soot oxidation or soot capacity. Regardless of the specific soot filtration or system performance question being pursued, a critical key 1