Diesel Active-Flow Aftertreatment Control on a Heated Flow Bench

Abstract

Empirical investigations were carried out to explore the influence of parameters such as exhaust flow temperature, exhaust flow rate, and supplemental fuel amount on diesel aftertreatment devices. A heated flow-bench system was utilized in combination with a diesel lean NOx trap (LNT) and/or a diesel particulate filter (DPF). The heated flow bench had the capability of producing stable gas temperatures and pressure drop across these aftertreatment devices. Preliminary pressure drop diagnostics were conducted with unloaded substrates meant for LNT and DPF applications. Subsequently, the DPF was loaded with varying amounts of liquid water or liquid diesel fuel and pressure drop diagnostic tests were repeated to determine if the presence of liquid substances within the substrate could be detected. With the presence of a liquid substance, the DPF exhibited relatively flat and undetectable pressure drop variation up to a critical loading level. Once this level was reached, there was a sharp and sudden increase in pressure drop. Further tests investigated the effects of exhaust flow rate and supplemental fuel amount on raising the LNT substrate temperature as required for the LNT de-NOx regeneration process. The results suggested that the maximum substrate temperature was primarily dependant on the fuel amount. Although the exhaust flow rate had very little effect on the substrate’s maximum temperature, it was significant in determining how quickly the maximum temperature was reached.