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Technical Paper

Computational Simulation of the Ceramic Trap Transient Operation

The paper presents a mathematical model for the simulation of the operational characteristics of the trap during transient operation, based on trap inlet conditions of the exhaust gas and trap history. The model incorporates (a) the formulation of flow conditions in the trap (b) the fundamental mass and energy balance of the system (c) the formulation of the oxidation process through chemical kinetics and (d) the description of mass and heat transfer conditions, including the possibility for calculation of trap operation during both particulate accumulation and regeneration phases. The major output of the model comprises ceramic wall and exhaust gas temperature fields in the trap, as functions of time, as well as the loading level of the trap. The application of the simulation model clarifies the critical importance of the wall temperature at trap outlet and forecasts the failure probability of the ceramic material due to overheating, under specific conditions at trap inlet.
Technical Paper

A New Approach to the Oxidizing Behavior of a Porous Ceramic Diesel Particulate Trap

A model simulating the behavior of the porous ceramic trap was developed. The model is based on the assumption that the pore size of the trap combined with the particle size distribution resulting from the trap oxidising activity defines two areas of trap operation: Ci) accumulation when no pass-through is permitted, and (ii) continuous regeneration when pass-through is permitted. The mathematical evaluation of the model demonstrates that regeneration depends on the ratio of space-time and oxidation process time constant. As far as the lower regeneration limit is concerned, temperature is the main parameter, while the upper regeneration limit is imposed by the low space-time. These dependencies have been experimentally confirmed for the couple of a light-duty Daimler-Benz engine and a Corning EX 47 trap. The test data at the regeneration limits have been correlated on the basis of the model and for continuous oxidation of particle mass flow.
Technical Paper

Development of Metal Foam Based Aftertreatment System on a Diesel Passenger Car

An alternative metal foam substrate for exhaust aftertreatment applications has been recently presented and characterized. The present paper focuses on the potential of the metal foam technology as an efficient DOC and CDPF substrates on real-world conditions. The target platform is a mid-size passenger car and the methodology includes both modeling and experiments. The experimental testing starts from small-scale reactor characterization of the basic heat/mass transfer properties and chemical kinetics. The results show that the foam structure exhibits excellent mass-transport properties offering possibilities for precious metal and catalyst volume savings for oxidation catalyst applications. These results are also used to calibrate an advanced 2-dimensional model which is able to predict the transient filtration and reaction phenomena in axial and radial flow systems.
Technical Paper

Metal Foam Substrate for DOC and DPF Applications

A new metal foam material for diesel particulate filtration, trademarked as INCOFOAM® HighTemp, was recently presented. Extensive tests showed the potential of achieving filtration efficiencies of the order of 85% or more at low pressure drop using a radial flow design concept with graded foam porosity. By applying a catalytic washcoat, the foam exhibits enhanced gas mixing and thus higher conversion efficiencies at high space velocities. In addition, due to an excellent soot-catalyst contact, the washcoated foam exhibited high catalytic regeneration rates. The present paper focuses on a novel “cross-flow” design concept for a better filtration/pressure drop trade-off as well as application of the foam as an oxidation catalyst substrate. The experimental testing starts from small-scale reactors and proceeds to real exhaust testing on the engine bench as well as vehicle tests on the chassis dynamometer and on-road testing.
Technical Paper

Performance of Catalyzed Particulate Filters without Upstream Oxidation Catalyst

The possibility to employ a single-brick system with a catalyzed filter (CDPF) for the after-treatment of diesel engines is potentially a promising and cost-effective solution. In the first part of this paper, the effectiveness of a single brick CDPF system towards reducing the gaseous CO and HC emissions is investigated experimentally and computationally. The second part of the paper deals with the behavior of single brick catalyzed filters compared with two brick systems comprising an upstream oxidation catalyst. The main differences of the two systems are highlighted in terms of regeneration efficiency and thermal loading, based on simulation results. The modeling work is based on a 3-dimensional model of the catalyzed filter and an axi-symmetric model of the oxidation catalyst. Model validations are presented based on engine bench testing.