Temperature excursions during regeneration of diesel particulate filters

A major technological challenge in the operation of diesel particulate filters (DPFs) is prevention of occasional melting of the ceramic filters during regeneration. The dynamic features of the combustion of particulate matter (PM) on a single layer diesel particulate filter were studied using IR imaging. The experiments showed that at stationary feed conditions the soot combustion may proceed in three different modes: either by a single moving hot zone or several hot zones generated at different ignition points or uniform combustion all over the surface. The maximum temperature of the moving fronts was much higher than those attained during uniform combustion. The highest temperature attained under stationary (constant feed) combustion is too low to cause the filter melting (melting temperature ∼1250°C).;We conjecture that high temperature excursions are a counter-intuitive response to a rapid deceleration which decreases the exhaust gas temperature and flow-rate and increases the oxygen concentration. The experiments showed that a step-change of the feed temperature led to a transient temperature exceeding the highest attained under stationary operation with the initial feed temperature. A simultaneous step-change of the feed temperature, flow rate and oxygen concentration in the feed led to a transient temperature that exceeded the highest attained for stationary operation under either the initial or final operation conditions. It was also higher than those generated either by a step change of any single feed input or by a step-change of any pair of feed inputs. The temperature rise depended in a complex way on several factors, such as the direction of movement of the propagating front, the location of the front when the feed was step-changed, and whether the step-change was done either before or after formation of a moving temperature front.;The simulations provided insight about the dependence of the amplitude of the temperature rise on the step change of the operating variables. The understanding generated by the simulations should help develop operation and control protocols that circumvent or at least decrease the probability of the occurrence of the destructive melting of the DPF.