Modeling Catalytic Regeneration of Wall-Flow Particulate Filters

Abstract

The problem of initiating and controlling the regeneration of diesel particulate filters is the major obstacle in the wide application of trap systems in diesel-powered vehicles. The most promising solution approaches to this problem, in terms of minimization of system cost and of additional fuel consumption, are based on the use of catalysts to lower soot ignition temperatures. Various mechanisms have been invoked so far to explain and model catalytic filter regeneration. However, a significant gap is still observed between experimental findings and modeling predictions. This paper presents an attempt to shorten this gap, starting from the special case of fuel additive assisted trap regeneration. The mechanism proposed is based on a dynamic oxygen storage/release model of the metal oxides accumulated in the trap and is applicable to most types of fuel additives. The mechanism was embodied in an existing zero-dimensional regeneration model. The results of simple, full scale experiments are employed in the process of model development and evaluation. Dimensional analysis is used for the evaluation of the parameters affecting the evolution of catalytic regeneration in a concise form. Methods of the comparative assessment of different fuel additives, based on the theory presented, are discussed. Finally, the application of the mathematical model in the design of regeneration control systems is illustrated in a real-world filter failure scenario.

Catalyzed diesel particulate filter modeling

“…In the early stages of DPF technology and modeling development, most models use a simple approach to describe the PM layer, mostly assuming a constant value for density and permeability (Bissett 1984, Koltsakis and Stamatelos 1996a,b, 1997a. Konstandopoulos and Johnson (1989) were the first to simulate the permeability as a function of porous media theory for an unloaded DPF.…”

Modeling of Diesel Particulate Filter Regeneration: Effect of Fuel-Borne Catalyst

“…Conservation of mass (3) We take into account the gas that flows through the porous walls, and also the fact that the channel is partly obstructed by the deposit layer thickness w.…”

“…A number of papers has already been published on the subject, for several kinds of additives [2,3]. Some of the models only simulate the thermal and chemical processes across the particulate deposit layer, assuming that the gas flow rate is large enough to allow the temperature gradients along the lengths of the channel to be neglected.…”

Modeling and Asymptotic Analysis of Combustion of Solid Fuel Deposited over an Inert Porous Medium

“…We observe that in some processes combustion occurs with the active participation of the combustible porous medium, while in some cases combustion happens considering the same temperature of the phases or, use numerical computations to present their final results. On the other hand, numerous computational studies [23][24][25][26][27][28][29][30][31][32][33] have been published to understand the regeneration process of diesel particulate filters. Even though the models are sophisticated with many degrees of freedom but they require detailed input data such as exhaust gas velocity profiles or complex reaction kinetics.…”

“…It should be noted that Pointikakis and Stamatelos [32] have mentioned in their paper that if we take out the chemical reactions submodel and consider the basic assumptions then the majority of the models in use today could be considered as extension of [23,24]. Since the regeneration of porous diesel particulate filter is important in technological point of view, the authors [27][28][29][30][31][32][33] investigate the oxidation of the deposit mass (or, deposit layer thickness) with respect to the time or axial distance to understand the regeneration process in detail.…”