Turbulent Flow Pressure Losses in Gasoline Particulate Filters

Gasoline Particulate Filter (GPF) technology is the key method of meeting the new regulations for particulate matter emissions from gasoline cars. Computer-Aided Engineering is widely used for the design of such systems; thus the development of accurate models for GPFs is crucial. Most existing pressure loss models require experimental calibration of several parameters. These experiments are performed at room temperatures, or on an engine test bench, where gas properties cannot be fully controlled. This article presents pressure loss measurements for clean GPF cores performed with uniform airflow and temperatures up to 680°C. The flow regime in GPF is shown to be different to that in the Diesel Particulate Filters (DPF) due to high flow rates and temperatures. Therefore, most of the existing models are not suitable for design of the new generation of aftertreatment devices. To isolate pressure loss contributions from different sources, unplugged filter cores are tested. A new model to describe pressure losses in GPFs is proposed and validated, taking into account turbulent friction losses and pressure variation along the filter channels. It is shown that friction losses are dominant in clean GPFs, thus shorter filters with high cross-sectional area may need to be considered - at least for the uncoated GPF applications - which provide high filtration area while maintaining short channel length and lower pressure loss. It is suggested how the developed “0D” (zero-dimensional) model can be implemented in three dimensions using the porous medium approach. Thus, collected data and the proposed models will facilitate the development and design of new aftertreatment systems for modern powertrains, especially engines with Gasoline Direct Injection. The method of separating and assessing the pressure losses from different sources gives an insight into properties of several types of flows (laminar flows with contraction/expansion, slip flows, flows with suction/injection) and opens new avenues for investigation of such flows.