Temperature Excursions during Soot Combustion in a Diesel Particulate Filter (DPF)

A major technological challenge in the operation of diesel particulate filters (DPFs) is prevention of the occasional melting of the ceramic filters during regeneration (combustion of accumulated particulate matter). The cause of this melting is still an established question. Experiments and simulations indicate that during stationary regeneration (fixed feed conditions) the temperature rise is not sufficiently high to cause this melting. We conjecture that the melting is due to a transient temperature excursion caused by a rapid shift of a car from normal driving to idle during regeneration. Infrared imaging was used to follow the response of the spatiotemporal temperature on a planar DPF to sudden changes in the feed conditions. As conjectured, the peak transient temperature was higher than that corresponding to stationary operation under either the initial or final conditions. The amplitude of the temperature excursion was sensitive to the direction in which the temperature front moved and to the period between the initiation of the temperature front and the change in the feed conditions.