The Measurement and Sampling of Controlled Regeneration Emissions from a Diesel Wall-Flow Particulate Trap

A diesel exhaust sampling system was specially designed to measure and collect emissions from a ceramic wall-flow particulate trap during periods of controlled electric regeneration with the exhaust emissions bypassing the trap. This resulted in the regeneration emissions being independent of those produced during either baseline (no control) or trap (exhaust filtration) sampling conditions. This system provided data regarding the physical, chemical, and biological character of regeneration emissions relative to baseline and trap emissions. Selected emission levels measured continuously during the regeneration process were also used to define the particle combustion process in the trap core. Variations in hydrocarbons (HC), oxides of nitrogen (NO_x), and particulate volume concentrations during the regeneration process were used to define four stages of the combustion process: preheat; combustion wave formation; combustion wave propagation; and combustion wave extinction. Particle concentrations were shown to be related to the location of the combustion wave front in the trap. Total particulate matter (TPM) mass emission rates from the trap were found to be two to three orders of magnitude lower than those measured at baseline or trap conditions, while peak particulate concentrations were similar to baseline and trap emission rates.