Pressure drop modelling is a subject of special Due to the fuel penalty resulting from the increased backpressure of the loaded filter, it is necessary interest for the design and control of diesel particulate for the filter to be regenerated. This regeneration filters. Based on previous experience, an improved pressure involves oxidation of the accumulated particulate, drop model is presented. Special emphasis is given on the which may be periodical or continuous, during soot permeability properties and its dependence on temregular engine operation. The initiation and control perature and pressure. With the assumption of uniform of the regeneration process is the main issue in diesel wall flow distribution throughout the channel length, it filter technology, as regeneration should be as safe is possible to derive an analytic expression for pressure as possible to avoid excessive thermal stresses and drop calculation. The main difference with previously profailure of the filter material. Regeneration systems posed analytic expressions lies in the inclusion of gas are based on the use of catalysts (catalytic coatings density dependence on local pressure, which necessitates or fuel-borne catalysts) to lower the reaction teman iterative calculation procedure. The importance of this perature and/or engine measures (e.g. post-injection) improvement is illustrated parametrically. The new model or electrical heating to increase the exhaust gas is validated against experimental data on an engine bench, temperature. using a double filter configuration to ensure constant filter Understanding the flow phenomena contributing soot loading throughout the test.to the pressure drop in particulate filters is of great importance for the emissions engineer. On the one Key words: diesel engine, after-treatment technology, hand, filter design should target the minimization of exhaust emissions, mathematical modelling, pressure drop pressure drop in real-world conditions by careful selection of filter geometry (volume, cell density, wall thickness, porosity). On the other hand, the

The diesel particulate filters (DPFs) technology has impressively advanced especially during the last years, driven by the interest in the reduction of automobile particulate emissions. This paper is concerned with the effect of NO 2 as an active oxidation agent in the regeneration process of the soot accumulated in the particulate filter. Experiments at realistic conditions using a diesel engine equipped with a standard oxidation catalyst and a particulate filter are carried out at a wide range of operating conditions. These results are used to validate an already available mathematical model of the NO 2 -assisted regeneration phenomena in the particulate filter. The combined use of experimental and modeling results provides interesting conclusions regarding the significance and the chemistry of the reaction of soot with NO 2 . The advantages and drawbacks of such an approach compared to standard laboratory synthetic gas studies are discussed. The agreement between experimental and simulation results in terms of engineering interest (rate of soot accumulation or depletion) is quite satisfactory and indicates that such a type of model could be a promising design tool.

Rsprinu availablr diroctlg lrom the publisher Photocopying permitted by liscnv only Q 1998 OPA (OMnsas Publinhen Audntian) Arnrtcrdam B. V. Published under liscnw under the Gordon and B m h Science Publirhm imprint. Prinvd in India.The advent of stricter US. and European exhaust emissions regulations has increased the need for reliable 3-way catalytic converter models supporting the design of demanding exhaust systems for low-emitting vehicles. Although a number of tunable models have been presented in the literature, their efficient performance in actual 3-way applicaions requires further development and validation. The major difficulties posed in such modeling eRorts arise from the complexities in the reaction schemes and the respective rate expressions for the multitude of currently used catalyst formulations. This paper addresses the details of tuning and real world application of a two-dimensional catalytic converter model, which accounts for the HC (hvdrocarbons) and CO oxidation. as well as NO reduction reactions. The model features a &mber of innbvations regarding the catalyst transient behaviour modelling and the reaction kinetics scheme. The advanced oxygen storage submodel presented is capable of accounting for the redox and temoerature deoendence of the oxveen availabilitv under transient ooeration. The ,redox sensitivity of the reaction scheme allows to get clearer insight in the "lambda-window" behavior of 3-way catalysts. It is concluded, that mathematical modelling may successfully describe important aspects of real world three-way catalytic converter operation under dynamic conditions, and thus, is a valid tool in exhaust aftertreatment systems optimization.

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Initiation of the regeneration of porous ceramic diesel particulate filters at low exhaust gas temperatures and the subsequent control of the soot oxidation rate is necessary in order to allow a wide applicability of filter systems in diesel-powered vehicles. The use of catalysts in this respect, in particular catalytic fuel additives, has been proven to be successful, leading to a minimization of the system's cost and additional fuel consumption. Better understanding and modeling of the catalytic activity at low temperatures necessitates that one takes into account the oxidation not only of dry particulate but also of the volatile hydrocarbons adsorbed on the particulate. In this paper, the oxidation of the hydrocarbons adsorbed on the particulate is modeled, to allow a better understanding of the filter regeneration behavior at very low temperatures (150−300 °C). A simplified reaction scheme and tunable kinetics are employed in the description of adsorbed hydrocarbon oxidation. The mechanism is incorporated in an existing mathematical model, and specific computational case studies are invoked to explain and to model regeneration at low temperatures. The results compare well with experimental evidence and indicate certain directions for further research to better understand this complex process which is essential to the successful application of diesel particulate filters.

Precious metal catalysts for NO x reduction in lean diesel engine exhaust conditions are characterized by a narrow temperature range of efficient operation and require high availability of reducing species in significant concentration. Consequently, there exists a large optimization potential in the design and control of lean-NO x catalytic conversion systems. A mathematical model of the transport and chemical phenomena in platinum-based lean-NO x catalysts was formulated, based on the experience with analogous models for gasoline three-way catalysts. A simplified four-reaction scheme is employed, considering the oxidation of CO, H2 and hydrocarbons (HCs), as well as the reaction between NO x and HCs. Results are compared with previously published laboratory and engine data in order to assess the capacity of this approach in representing real-world behaviour of Pt-based lean-NO x catalysts. Initial results illustrate the power and flexibility of the model, which is able to predict the NO x conversion characteristics in model gas tests as well as in full-scale engine tests with reasonable accuracy.

Computer aided engineering (CAE) methodologies are increasingly being applied to assist the design of spark-ignition (SI) engine exhaust aftertreatment systems in view of the stage III and IV emissions standards. Following this trend, the design of diesel exhaust aftertreatment systems is receiving more attention owing to the capabilities of recently developed mathematical models. The design of diesel exhaust systems must cope with three major aftertreatment categories: diesel oxidation catalysts, diesel particulate filters and de-NOx catalytic converters. An integrated CAE methodology that could assist the design of all these classes of systems is described in this paper. It employs the following computational tools: a computer code for modelling transient exhaust system heat transfer, a computer code for modelling the transient operation of a diesel oxidation or a de-NOx catalytic converter, a database containing chemical kinetics data for a variety of oxidation and de-NOx catalyst formulations and a computer code for modelling the loading and regeneration behaviour of a wall-flow filter, assisted by catalytic fuel additives. Application of the CAE methodology, which helps the exhaust aftertreatment system design engineer to meet the future emissions standards, is highlighted by referring to a number of representative case studies.

Forced by strict emission standards, interest in the reduction of particulate emissions becomes increasingly higher. Although the technology of diesel particulate lters ( DPFs) has advanced impressively, especially during recent years, considerable technological challenges remain unsolved. The technology of NO 2 -assisted continuously regenerating diesel lters in conjunction with the upcoming availability of low sulphur diesel fuel represents a promising solution, especially for heavy duty engines. In the present paper, a transient modelling approach for the combined catalyst and DPF system is presented. This combined model is used to predict the regeneration performance of NO 2 -assisted regeneration systems in the transient conditions of a legislated European driving cycle. Although the model is based on global and approximate reaction schemes, the results illustrate the applicability of simulation tools in the process of optimizing certain important design parameters of the system, such as catalyst and particulate lter sizing and positioning, and catalyst activity requirements. It is expected that such engineering models will be valuable tools in the selection and design of such kind of systems, minimizing the testing eVort and the associated costs.