Temperature rise during stationary and dynamic regeneration of a diesel particulate filter

Abstract

The development of a safe regeneration procedure which circumvents large temperature excursions during the exothermic regeneration is the current major technological challenge in the operation of diesel particulate filters. The cause of this local hot zone formation is still an open question. The maximum temperature attained under stationary (constant) feed conditions regeneration is not sufficiently high to cause the local melting. The counterintuitive temperature rise in an adiabatic packed-bed reactor following a sudden decrease in the feed temperature suggests that a high transient temperature in a diesel particulate filter (DPF) could be the response to a transient change of the operating conditions, such as a shift from normal driving mode to idle. Here, we review recent experimental measurements by a high speed infrared camera of the transient spatial and temporal temperature rise during stationary and dynamic regeneration of a soot layer deposited on a single layer Cordierite DPF. The experiments confirmed that the response to a simultaneous step change of the feed conditions (temperature, flow rate and oxygen concentration) leads to a transient temperature that exceeds the highest attained under stationary operation with either the initial or final operation conditions. The amplitude of the temperature excursion during step changes of the three feed conditions depended in a complex way on the location at which ignition occurred, when the step change was done and whether the step change was conducted after or before a moving front was established. A surprising finding was that the temperature rise following a simultaneous change of the three input variables was rather close to the sum of the three responses to a step change of only one of the three feed conditions.