Contribution to the understanding of filtration and pressure drop phenomena in wall-flow DPFs

Abstract

From the last decades of the 20th century, internal combustion engines have undergone a continuous improvement process aimed to the increase of their efficiency and decrease of the pollutants emissions. The reduction of the availability of fossil fuel and the increase of human-made pollution observed in the last decades is leading worldwide to more stringent emission standards that make the engine manufacturers to constantly look for fuel consumption and emission reductions while keeping engine performance.To comply with current and incoming emission regulations, the exhaust line of internal combustion engines has been gradually complicated by the presence of aftertreatment systems. Among them, the particulate filter is the device in charge of abating the emission of soot in the atmosphere. Concerning compression ignition engines, diesel particulate filters (DPF) were first commercially utilized in significant numbers in passenger car and heavy-duty engines since the beginning of the 21st century. Euro 6 emission standards limits the emitted particulate matter from direct injection engines, thus extending the use of particulate filters also to direct injection gasoline engines.A deep knowledge of the phenomena happening inside the DPF is required for the correct understanding of the behaviour of this system and its interaction with the engine. The precise knowledge of the filtration and pressure drop processes is mandatory for the design of the particulate filter and is also essential to wisely think up and analyse solutions aimed to limit the negative impact of the filter on the fuel consumption maintaining its capability of retaining soot particles.Thus, the present work pretends to provide a contribution to the understanding of these phenomena in wall-flow DPFs. The problem has been faced on a computational and experimental basis. A notable part of the work was dedicated to the development and validation of a one-dimensional DPF filtration model to be coupled with the existing pressure drop model. The model was implemented in OpenWAM™, the open-source gas dynamics software for internal combustion engines and components computation developed at CMT -Motores Térmicos.The developed computational tool was applied to the assessment of the aftertreatment (DOC&DPF) volume downsizing potential in post-and pre-turbo aftertreatment configuration. The study is completed with experimental analysis to support theoretical insights discussing how the soot deposition profile and the particulate layer properties impact on the DPF pressure drop.i ResumenDesde las últimas décadas del siglo XX, se ha producido un proceso de mejora continua de los motores de combustión interna alternativos con el fin de aumentar su eficiencia y reducir las emisiones contaminantes. La reducción de la disponibilidad de combustibles fósiles y el incremento de la polución de origen antropogénico observados en las ultimas décadas ha provocado el progresivo endurecimiento de las normativas anticontaminación a nivel mundial obligando a los fabri...

On the Impact of Particulate Matter Distribution on Pressure Drop of Wall-Flow Particulate Filters

“…This distance, which will be referred to as the onset of the soot mass distribution (δ pl ) from now on, has been also varied in order to determine its impact on the pressure drop. This study is based on the conclusions obtained from Scanning Electron Microscope (SEM) analysis [34]. Figure 3 shows SEM pictures corresponding to two different samples of DPF #B, which was loaded with 44.6 g. The pictures show the cross-section of an inlet channel at two different distances from the monolith entrance.…”