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Trends towards lower vehicle fuel consumption and smaller environmental impact will increase the share of Diesel hybrids and Diesel Range Extended Vehicles (REV). Because of the Diesel engine presence and the ever tightening soot particle emissions, these vehicles will still require soot particle emissions control systems. Ceramic wall-flow monoliths are currently the key players in the Diesel Particulate Filter (DPF) market, offering certain advantages compared to other DPF technologies such as the metal based DPFs. The latter had, in the past, issues with respect to filtration efficiency, available filtration area and, sometimes, their manufacturing cost, the latter factor making them less attractive for most of the conventional Diesel engine powered vehicles. Nevertheless, metal substrate DPFs may find a better position in vehicles like Diesel hybrids and REVs in which high instant power consumption is readily offered enabling electrical filter regeneration.

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.

The pore structure of DPF (Diesel Particulate Filter) is one of the key factors in contributing the fuel consumption and the emission control performance of a vehicle. The pressure loss of mini samples (1 in. in diameter, 2 in. in length) with various pore structures was measured at relatively low filtration velocity (< 5 cm/sec). Then the obtained data were evaluated by using an index of “permeability”. As a result, among the parameters which characterize the pore structure, it was found that the size of the pore diameter and the sharpness of pore distribution were the most contributing factors in reducing pressure loss which in turn is related to the fuel consumption performance when the cell structure was fixed. On the other hand, it was found that the gas permeability was not affected significantly by any parameter when the catalyst was coated because the coating caused a broadening of the pore distribution.

This paper describes the durability of the filtration layer integrated into Diesel Particulate Filters (DPFs) that we have developed to ensure low pressure loss and high filtration efficiency performances which also meet emission regulations. DPF samples were evaluated in regards to their performance deterioration which is brought about by ash loading and uncontrolled regeneration cycles, respectively. Ash was synthesized by using a diesel fuel/lubrication oil mixture and was trapped up to a level which corresponded to a 240,000km run, into the DPFs both with and without the filtration layer. Afterwards, aged-DPFs were measured with respect to their permeability, pressure loss, filtration efficiency, as well as soot oxidation speed using suitable analytical methods. Consequently, it has been confirmed that there was no noteworthy deterioration of the performances in the DPF with the filtration layer.

Upcoming (2005) particulate matter standards for diesel powered vehicles are likely to require the deployment of aftertreatment devices, such as particulate filters to ensure emissions compliance. A major challenge in the development of diesel filter systems has been the achievement of filter regeneration by the oxidation of the collected particulate matter in a reliable and cost-effective manner. Recently the emergence of the so-called continuously regenerating trap (CRT™) in conjunction with the future availability of very low-sulphur diesel fuel, represents a promising solution to the diesel particulate control problem. In the present study, design and selection criteria are devised, regarding the sizing of wall flow diesel particulate filters for application in CRT™ systems, employing a range of analytical and 3-D CFD tools validated against experimental data.

As use of Particulate Filters (PFs) is growing not only for diesel but also for gasoline powered vehicles, the need for better understanding of deposit structure, growth dynamics and evolution arises. In the present paper we address a number of deposit growth and restructuring phenomena within particulate filters with the aim to improve particulate filter soot load estimation. To this end we investigate the dynamic factors that quantify the amount of particles that are stored within the wall and the restructuring of soot deposits. We demonstrate that particle accumulation inside the porous wall is dynamically controlled by the dimensionless Peclet number and provide a procedure for the estimation of parameters of interest such as the loaded filter wall permeability, the wall-stored soot mass at the onset of cake filtration.

Diesel particulate filters (DPFs) equipped with diesel vehicles have become indispensable components to capture the soot emitted from the engines from a viewpoint of both human health and global warming problems as well as the prevailing regulations. Meanwhile, the pressure drop caused by them leads to a direct increase of fuel consumption. In order to reduce it guaranteeing the sufficient soot filtration efficiency, we have developed the new concept of asymmetric plugging layout for the DPF design, so-called Valuable Plugging Layout (VPL), on the basis of octosquare (OS) structure and have clarified the advantage of the pressure drop reduction both experimentally and theoretically. The VPL-DPF consists of two kinds of octagonal/square inlet channels and octagonal outlet channels, and there are thought to be five filtration velocity modes as well as four kinds of soot deposit layers on each side of the inlet channel walls.