Hot zones formation in Diesel Particulate Filters (DPFs)
Dan Luss, Univesity of Houston
Experience has shown that the exothermic combustion of the deposited particulate matter (PM) in a diesel particulate filter leads in some cases to unexpected temperature excursions, which can melt the common Cordierite ceramic filter. Circumventing the melting of the filter is the most demanding technological challenge in the operation of a DPF. Previous explanations of the cause of the temperature excursions were that a rapid shift in the driving mode to idle decreases the removal rate of the heat generated by the PM combustion. Moreover, the shift to idle increases the oxygen concentration which further increases the reaction rate and heat release. Our simulations and experiments reveal that a large temperature rise may be caused just by the reduction of the exhaust gas temperature. Even larger temperature excursions may be generated when in addition to a temperature decrease either the exhaust flow rate is decreased or the oxygen concentration is increased.