Application of Pre-DPF Water Injection Technique for Pressure Drop Limitation

Wall-flow diesel particulate filters have become the most effective system for particulate matter abatement in Diesel engines being required for current and future emission standards fulfillment. Despite the high filtration efficiency that wall-flow DPFs exhibit their use involves a noticeable impact in fuel consumption because of the increase of the exhaust back-pressure. Additionally, the fuel economy penalty increases as the DPF becomes soot/ash loaded. This constraint demands the approach and development of new solutions to reduce the DPF pressure drop.

This paper focuses on the improvement of the ratio between the pressure drop and the loading by means of pre-DPF water injection. A proper management of the water injection events is able to completely remove the dependence between these magnitudes. The test campaign and the discussion of the experimental results address how the DPF pressure drop reduction leads to benefits in engine fuel consumption. The lack of dependence between the pressure drop and the particulate matter loading also involves other advantages concerning regeneration management based on critical soot mass loading or optimization of the DPF maintenance because of ash loading. The advantage in pressure drop arises from the collected soot restructuring due to water drag along the inlet channels. Nevertheless, the analysis of the DPF response reveals that the transient soot emission during water injection events is negligible and that the overall filtration capability of the substrate is unaffected. Concerning the regeneration process, the experimental results demonstrate that the DPF performance during active and passive processes is kept.