Lattice-boltzmann diesel particulate filter sub-grid modeling - A progress report

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.