Development and Application of CFD Discrete Phase Single Fiber model

摘要

The classical single fiber theory of particle capture has been extensively used to understand the efficiencies of fibrous filters. There are various correlations available in the literature, some of which have been experimentally validated. The theory assumes constant fiber size, packing density, flow velocity field etc. but for real fibrous filters all these parameters vary through the depth of the media. The flow inside the filter media is very complicated because of the 3D structure of the media. CFD has been used successfully in the recent years for understanding the underlying physics of flow and particle capture in fibrous filters. These studies in most cases have focused on microstructure of the fibrous media and are not applicable to scale of the filtration device. CFD has also been applied to understand the overall performance of the filtration device, mainly for pressure drop using porous zone representation of the media. Because of the different scales involved it is very difficult to include everything right from the 3D microstructure of the fibers to the filter housing in a CFD model. By approximating the media as a porous zone and using a single fiber theory in this porous zone the performance of the entire device can be predicted in principle. This paper describes the development of such a model and its application in predicting the particle separation efficiencies of inertial impactors made at Cummins Filtration.