Diesel Filter Materials

W. Addy Majewski

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Abstract: Diesel filter materials should be characterized by high filtration efficiencies, high maximum operating temperatures, low thermal expansion, resistance to thermal stress, and chemical resistance to metal oxides (ash) present in diesel particulates. A number of materials have been under development, including ceramic wall-flow monoliths, ceramic fibers, or sintered metals.

Material Requirements

The filter substrate is the key component of the diesel filter system, affecting both its performance and durability. Its task is to physically capture solid particulates and hold them until they can be removed in the regeneration process (periodic or continuous). Design targets for diesel particulate filter materials include the following:

Depending on the regeneration method, diesel filter materials may be exposed to very high temperatures, significantly in excess of 1000°C, as well as rapid temperature changes. These thermal conditions are caused by the release of heat during rapid oxidation of soot accumulated in the filter. Since the distribution of soot is not necessarily uniform throughout the filter, the thermal stress frequently has a local character. Thermal phenomena, both high temperature and thermal stress, are responsible for most instances of filter failure, such as melting or cracking.