Fundamental Study on Particle Filtration Process and Gasoline Particulate Filter (GPF) Modeling

Yang, Y. Fundamental Study on Particle Filtration Process and Gasoline Particulate Filter (GPF) Modeling. University of Wisconsin-Madison, 2018.

Porous materials are widely used to separate mixtures such as gas/solid and liquid/solid, with the desired characteristics being low pressure drop and high separation. In the automotive exhaust aftertreatment area, two types of filtration are commonly studied, deep bed filtration and cake filtration. Deep bed filtration is filtration inside the porous material, while cake filtration is filtration by the particulate cake layer, which generally has both high filtration efficiency and high pressure drop. The unit collector concept was developed to model the porous material statistically and with lower computational cost. The standard unit collector model with spherical collectors was found to have high fidelity in predicting Diesel Particulate Filter (DPF) performance, where cake filtration is dominant. Nevertheless, the deep bed filtration process is still difficult to capture, due to its complexity and the continuous wall structure changes that occur during deposition. The development of a model that can capture the changes in the microstructure and properties of the porous material is extremely helpful to understand the filtration process and could be used in real device design.

In the current study, the unit collector model is successfully extended to the deep bed filtration area. A Pore Filtration Model (PFM) is developed using the constricted tube concept, which has the advantages of lower computational cost and higher accuracy, as the collector. A complete solution is provided in the current study, including the model development process, validation, and performance. Data from a spark ignition direct injection (SIDI) engine is used to validate the model for significantly different particulate conditions occurring under four different operating conditions.

Details of the modeling process, including individual unit collector analysis, and the combination of constricted tube collectors, are presented. The differences in the overall filtration efficiency from the experimental measurements and the simulations are within 3%. Comparisons of the spherical collector and the constricted tube collector through both theoretical analysis and simulation results confirm the advantage of the PFM.

Besides the model development process, the PFM performance is also investigated. The effect of the geometry of the constricted tube collector on the filtration efficiency is examined. The simulation study indicates porous materials with high porosity and narrow pores have high filtration efficiency. Additionally, the filtration is analyzed for various operating conditions with an objective of understanding the real filtration circumstances.