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The intention of the presented work was to develop a new simulation tool that fits into a CFD (computational fluid dynamics) workflow and provides information about the soot particle size distribution. Additionally it was necessary to improve and use state-of-the-art measurement techniques in order to be able to gain more knowledge about the behavior of the soot particles and to validate the achieved simulation results. The work has been done as a joint research financed by the European Community under FP5.

The DEXA Cluster consisted of three closely interlinked projects. In 2003 the DEXA Cluster concluded by demonstrating the successful development of critical technologies for Diesel exhaust particulate after-treatment, without adverse effects on NOx emissions and maintaining the fuel economy advantages of the Diesel engine well beyond the EURO IV (2000) emission standards horizon. In the present paper the most important results of the DEXA Cluster projects in the demonstration of advanced particulate control technologies, the development of a simulation toolkit for the design of diesel exhaust after-treatment systems and the development of novel particulate characterization methodologies, are presented. The motivation for the DEXA Cluster research was to increase the market competitiveness of diesel engine powertrains for passenger cars worldwide, and to accelerate the adoption of particulate control technology.

Quantitative measurements of the soot volume fraction and diameter performed by spectroscopic techniques within the combustion chamber of a diesel engine are employed to aid multidimensional simulation of the soot formation and oxidation processes. By changing the start of fuel injection, two different operating conditions are considered, which are characterized by different relative importance of the premixed to the diffusive stage of the combustion process. Both the reduced models by Hiroyasu et al., and the one by Nagle and Strikland- Constable are employed within the numerical simulation. The reason of the peculiar over-prediction of soot concentration of the latter model is discussed and related to the need of furnishing coherent values of the soot particle density and mean diameter.