Evaluation of a DPF Regeneration System and DOC Performance Using Secondary Fuel Injection

An active diesel particulate filter (DPF) regeneration system is evaluated, which applies secondary fuel injection (SFI) directly within the exhaust system upstream of a diesel oxidation catalyst (DOC). Diesel fuel is oxidized in the presence of a proprietary catalyst system, increasing exhaust gas temperatures in an efficient and controlled manner, even during low engine-out gas temperatures. The exotherms produced by secondary fuel injection (SFI) have been evaluated using two different DOC volumes and platinum catalyst loadings. DOC light-off temperatures were measured using SFI under steady-state conditions on an engine dynamometer. A ΔT method was used for the light-off temperature measurements – i.e., the minimum DOC inlet gas temperature at which the exothermic reaction increases the outlet gas temperature 20°C or greater than the inlet temperature. All four of the DOCs tested exhibited similar exothermic behavior in achieving the 650°C target temperature at selected engine operating conditions. Analysis of an engine-tested DOC by X-ray diffraction, as well as the measurement of its conversion efficiencies for oxidation of CO, C₃H₆ and NO using a laboratory flow reactor are also reported.