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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.

This paper presents a computational model of the transient behaviour of trap systems. The model is applicable to various driving scenarios, vehicle, engine, and trap types, as well as different trap regeneration and protection techniques. The model is synthesized from existing submodels covering the vehicle kinematics, diesel engine operation, trap operational characteristics, and the trap regeneration and protection hardware performance. The model is applied to a parametric investigation of the transient operation of the Laboratory of Applied Thermodynamics (LAT) trap oxidiser system fitted on a Mercedes 200D passenger car. The major tasks of the investigation were (a) the evaluation of the control philosophies as regards their influence on vehicle driveability, fuel consumption, and by-pass operation time, (b) the evaluation of protection techniques such as lambda-control and trap by-passing with the trap subjected to a number of failure scenarios.

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.

The effect of three oxidation catalysts (Honeycat DEP 290, Engelhard PTX 623, Herapur 20L) and one catalytic trap oxidizer (Johnson Matthey JM 13/II) on the emissions of a RABA (M.A.N. Licensed) heavy-duty diesel engine has been comparatively studied. Tests were conducted according to EPA 13 mode test to measure CO, total HC, NOx and total particulate matter emitted by the engine with and without devices. The test results were also correlated to the total emissions of the Athenian buses through new weighing factors of an “Athenian 13 mode test”. The engine tests for all four devices resulted in: (1) considerable reduction of the engines CO and total HC emissions - being already low (2) practicaly no difference in NOx emissions and (3) increase of the total particulate emissions at high load modes.

A regeneration system for the ceramic trap oxidiser is presented, based on the exhaust gas throttling of the engine. The trottling process, producing 1.5-3.0 bar overpressure, leads to a modified power flow in the engine, resulting in higher enthalpy exhaust gas, at the expense of the net power output of the engine. Thus exhaust temperature is raised over the lower regeneration limit (550°C) for a wide range of engine operation modes including also high speed-no-load modes. The effects of throttling on exhaust gas thermodynamic state and engine operational characteristics (volumetric efficiency, mean effective pressure, power output, consumption) are theoretically and experimentally analysed. An optimised regeneration system by exhaust throttling is described. This system includes: regulated throttling orifice for minimum net power output loss and reduction of fuel injected for acceptable smoke emission of the engine under high backpressure conditions.

The oxidizing behavior of the ceramic diesel particulate trap Corning EX 47 is examined under forced regeneration by exhaust gas throttling, based on a trap loading model, assuming soot accumulation from channel outlet towards inlet. The required conditions which may lead to an extended life of the trap are investigated. It is deduced that regeneration of a trap, even totally loaded, is possible, provided that exhaust temperature does not exceed 650°C and mass flow through the trap is higher than a lower critical value.