Evaluating Performance of Uncoated GPF in Real World Driving Using Experimental Results and CFD modelling 2017-24-0128
Environmental authorities such as EPA, VCA have enforced stringent emissions legislation governing air pollutants released into the atmosphere. Of particular interest is the challenge introduced by the limit on particulate number (PN) counting (#/km) and real driving emissions (RDE) testing; with new emissions legislation being shortly introduced for the gasoline direct injection (GDI) engines, gasoline particulate filters (GPF) are considered the most immediate solution. While engine calibration and testing over the Worldwide harmonized Light vehicles Test Cycle (WLTC) allow for the limits to be met, real driving emission and cold start constitute a real challenge.
The present work focuses on an experimental durability study on road under real world driving conditions. Two sets of experiments were carried out. The first study analyzed a gasoline particulate filter (GPF) (2.4 liter, diameter 5.2” round) installed in the underfloor (UF) position and driven up to 200k km. A 1.6 liter Gasoline Direct Injection (GDI) engine was used for the investigation. Ash accumulation versus mileage and soot loading were of interest. A parallel investigation up to 160k km with same engine (2 identical vehicles on an “average customer driving” cycle) and GPF installed in close-coupled (CC) position was also carried out. Both UF and CC GPF are NGK 360 cpsi (i.e. cells per square inch), 5 mil wall thickness.
As a route to develop a robust 3-D Computational Fluid Dynamics (CFD) model to gather information on the fluid flow and pressure loss characteristics of GPF, a baseline model is introduced in this work. The computational domain refers to full length individual 3-D channels and focuses on two quarters of an inlet and two quarters of an outlet channel with the aim of reducing complexity of the problem and its computational cost. Although this baseline version does not include yet the soot and ash loading models, it can be used for understanding real physical problems and gather insight on velocity and pressure distributions inside filter and its channels.