Analysis of reformed EGR on the performance of a diesel particulate filter

The use of a diesel particulate filter (DPF) in combination with an upstream diesel oxidation catalyst (DOC) has been successfully implemented and shown to reduce carbon monoxide (CO), hydrocarbon (HC) and Particulate Matter (PM) diesel exhaust gas emissions. However issues including cost, size and uncontrolled active regeneration under a low temperature window still require attention. This study therefore primarily focuses on the potential benefits of using a single catalytic coated DPF (cDPF) and a combined DOC-cDPF instead of the DOC-DPF aftertreatment system utilising a passive, low temperature regeneration method. Comparisons were made through monitoring exhaust gas compositions from an experimental single cylinder diesel engine as well as measuring the pressure drop across the filters to analyse the accumulation of soot particles. The influence of reformed EGR (REGR), enriched simulated hydrogen (H2) and CO, on DPF and cDPF soot loading was of interest as H2 promotes the NO to NO2 oxidation. Similarly the addition of simulated reformate (added either directly into the engine intake or exhaust manifold) for optimal performance of the aftertreatment systems was examined.The effects of adding REGR resulted in a significant decrease in total engine-out NOx emissions, as well as an increase in both NO2 concentration and NO2/NOx ratio. This resulted in improved filter efficiency and overall loading, especially under a DOC-cDPF aftertreatment configuration system. As a whole, a simultaneous NOx and PM reduction was achieved.

► REGR lowers diesel fuel consumption with simultaneous NOx and PM emission reductions. ► Reduced emissions and improved combustion with REGR enhances aftertreatment activity. ► Enhanced in-cylinder oxidation from diesel-REGR combustion reduces soot emissions. ► Improved NO2/NO ratio promotes low temperature passive DPF regeneration.