1996-02-01

A Study of the Regeneration Process in Diesel Particulate Traps Using a Copper Fuel Additive 960136

The goals of this research are to understand the regeneration process in ceramic (Cordierite) monolith traps using a copper fuel additive and to investigate the various conditions that lead to trap regeneration failure. The copper additive lowers the trap regeneration temperature from approximately 500 °C to 375 °C and decreases the time necessary for regeneration. Because of these characteristics, it is important to understand the effect of the additive on regeneration when excessive particulate matter accumulation occurs in the trap.
The effects of particulate mass loading on regeneration temperatures and regeneration time were studied for both the controlled (engine operated at full load rated speed) and uncontrolled (trap regeneration initiated at full load rated speed after which the engine was cut to idle) conditions. The trap peak temperatures were higher for the uncontrolled than the controlled regeneration. The higher peak trap temperatures were predominantly controlled by the effect of the exhaust flow rates on the energy transfer processes. The total regeneration time was faster for the controlled regeneration compared to the uncontrolled regeneration. All traps passed the controlled regeneration tests having maximum temperatures less than 900 °C. During the uncontrolled regeneration tests, trap failure occurred at 135 and 139 g particulate matter loadings. The maximum temperatures were in excess of 1150 °C.
The pressure drop across the trap was modeled using the one dimensional Darcy's law which accounted for the pressure drop due to the ceramic wall and the particulate layer. The experimental results for the substrate correlate well with the empirical substrate pressure drop models available in the literature. The models also enable an estimate to be made regarding trap mass loading. These data along with the laboratory data have indicated that mass loadings greater than 110 g followed by high temperature operation and subsequent engine idling can result in trap failures during regeneration. The particulate layer permeability was calculated using the one-dimensional Darcy's equation and found to be approximately 3x10-14 m2 (an order of magnitude lower than that of the substrate).

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