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Comparisons between 1D simulations and experiments on a mini scale SiC filter are presented. First of all, experiments with regeneration for different loading mass and soot composition enabled us to derive an improved pressure drop correlation. The assumption of constant particulate layer permeability proves unable to predict the influence of the gas temperature on the pressure drop. This discrepancy seems to be linked to the high Knudsen number of the flow in the particulate layer. A new correlation is proposed. This correlation contains four adjustable constants which have been determined on a single experimental run. Without modifying these constants, other cases have been correctly simulated. Obviously, more work is needed to substantiate this approach. In a second step, regenerations with and without additive (Cerium) for two different soot compositions have been simulated and compared with experimental results.

Computer Aided Engineering (CAE) Methodologies are increasingly being applied to assist the design of 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 in view of the capabilities of recently developed mathematical models. The design of diesel exhaust systems must cope with three major aftertreatment categories: (i) diesel oxidation catalysts, (ii) diesel particulate filters and (iii) de-NOx catalytic converters. An integrated CAE methodology that could assist the design of all these classes of systems is described in this paper.

The design of a diesel particulate trap system to fit a specific vehicular application requires significant expenditure, due to the high degree of interaction between the vehicle operation and trap behavior. The assistance of modeling in the design process is already well established. This paper presents the basic principles of a Computer Aided Engineering methodology aimed to assist the selection of the basic parameters of a Diesel Particulate Trap System by reducing the number of the necessary experimental tests. The computational modules currently supporting the CAE methodology are based on fundamental mathematical models, incorporating a small number of semi-empirical relations derived by experimental data on trap loading and catalytic regeneration, exhaust system heat transfer and trap backpressure effect on fuel consumption.

The purpose of this paper is to investigate a new, universally applicable technique to protect the filter from overheating that could overcome the need for trap bypassing; namely, the trap protection by limiting A/F ratio during regeneration. The technique is supported by control of A/F ratio, leading to an indirect control of exhaust oxygen content and consequently trap regeneration rate. Realisation of the above-mentioned, very simple idea, so as to work effectively in the multitude of possible trap failure scenarios occuring during vehicle driving, is shown to be a fairly complicated task. The new method of trap protection, now being at the stage of initial investigations, is expected to lead to a safe and reliable system with wide applicability, without the need to bypass the trap at any circumstances. As such, it will also be attractive for passenger car applications, supported by the recent advances in wide application of electronic fuel control.

In view of recent and future US and european regulations the design optimization of 3-way catalytic converters (3WCC) should also account for catalyst durability. The purpose of this paper is to extend the authors' approach for 3WCC modeling and evaluation in the direction of covering some aspects of ageing behavior. After a brief examination of the commonly accepted ageing mechanisms, a new methodology for the assessment of catalyst durability is formulated. This methodology takes into account the effect of thermal loading, high-temperature oxidation and poisoning of the catalyst. Based on the approach presented, along with the 3WCC and other related models and computer codes already in-use by the authors, a comparative assesment of engine bench ageing cycles may be computationally supported. Correlation of vehicle ageing cycles with engine bench cycles may also be accomplished as illustrated by a case study.

The modeling of transient phenomena occurring inside an automotive 3-way catalytic converter poses a significant challenge to the emissions control engineer. Since the significant progress that has been observed with steady-state models cannot be directly exploited in this direction, it is necessary to develop a fully transient model and computer code incorporating dynamic behaviour of the three way catalytic converter in a relatively simple and effective way. The Laboratory of Applied Thermodynamics (LAT), Aristotle University Thessaloniki, is cooperating with the Engine Direction of FIAT Research Center, in the development of a computer code fulfilling these objectives, within the framework of an EEC Brite EuRam cost shared project. The CRF and LAT modeling approaches, along with the underlying philosophy and experimental work, are presented in this paper.

This paper presents the experience gained by testing a trap system on a turbocharged bus engine. The trap is placed before the turbo in order to fully exploit the high regeneration potential of the turbocharged engine. This of course necessitates a new consideration of the turbocharging system, in order to keep a good turbocharger response. The quick temperature response of the light-weight exhaust manifold installed with the system, partially offsets in this respect the thermal inertia of the ceramic trap. The effects of the use of Cerium or Copper-based fuel additives enhancing regeneration capability are presented, in order to allow preliminary assessment of optimization capabilities for the final version of the system to be used with the bus. Regeneration of this system is effected through the application of exhaust throttling before the trap. The bypass technique is also applied for trap protection.

Exhaust temperature response is very important in the design of exhaust aftertreatment systems. Analysis of this response is made in this paper by means of heat transfer calculations at the exhaust system, leading to a model that predicts exhaust system and exhaust temperature response. Thus, the effect of differences in design of exhaust system components may be studied for optimization purposes. The model is readily extended to predict heating response of ceramic honeycomb filters. An approximate method for quick computation of exhaust system response based on the response of individual components, is also presented to facilitate the computations.