Call number: LD2668 .T4 1984 H924 / Master of Science

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While most filters are made of pleated fibrous media, almost all existing theories of aerosol filtration are developed for flat media placed perpendicular to the air flow. Expressions developed for flat sheet media do not provide accurate information directly useful for designing a pleated filter, and therefore, most progress made in developing pleated filters is based on empiricism. This study is aimed at establishing an enabling knowledge that allows for a better design and optimization of pleated aerosol filters. This study is focused on developing a predictive simulation method that accounts for the influence of a filter’s micro-scale geometric parameters, such as fiber orientation, as well as its macro-scale features, like pleat shape, in predicting the transient pressure drop and collection efficiency with or without the effects of dust loading. The dual-scale simulation method developed in this work is believed to be the only feasible approach for design and optimization of pleated aerosol filters with the current academic-level computational power. Our study is divided into two major tasks of micro- and macro-scale modeling. Our micro-scale studies are comprised of a series of CFD simulations conducted in virtual 2-D or 3-D fibrous geometries that resemble the internal micro-structure of a fibrous medium. These simulations are intended to isolate the effects of each micro structural parameter and study its influence on the performance of the filter medium. In detail, it is intended to propose a method to predict the performance of micro-structures with fiber size distribution. Also, the effects of micro-structural fiber orientation were investigated. Moreover, we offered methodology to predict the performance of noncircular fibers using available analytical expressions for circular fibers. It is shown that the circumscribed circle for a trilobal shaped fiber gives the best prediction for collection efficiency. In macro-scale simulations, on the other hand, the filter medium is treated as a lumped porous material with its properties obtained via micro-scale simulations. Our results showed that more number of pleats helps better performance of pleated filters, however, if the pleat channel becomes blocked by dust cake then this effect is no longer valid.

by Tai Leong Charn. / Bibliography: leaves R-i-iii / Thesis (M.Phil.)--Chinese University of Hong Kong, 1983

Chok-ki Chan. / Bibliography: leaves 117-122 / Thesis (Ph.D.) - Chinese University of Hong Kong, 1984

Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2004. / Includes bibliographical references (leaves 108-111). Also available in electronic version. Access restricted to campus users.

Thesis (MSc)--University of Stellenbosch, 2008. / Bibliography. Also available via the Internet.

In this thesis, new effective and efficient implementation structures of three-dimensional (3D) spatio-temporal (ST) Finite Impulse Response (FIR) uniform and non-uniform cone and frustum filters using well-known filter banks are investigated. The performance of the proposed implementation structures for 3D ST FIR uniform and non-uniform cone and frustum filters are investigated for 3D broadband beamforming in radio astronomy applications. First, implementations of two 3D ST uniform FIR cone filters are investigated. The 3D cone filters are designed by cascading either the well-known uniform quadrature mirror – cosine-modulated (QM-CM) filter bank or directly designed filter banks (DDFBs), with 2D low-pass circularly-symmetric spatial filters. In addition, two 3D ST uniform FIR frustum filters are derived from the cone filters by implementing partial bands of the filter banks with corresponding 2D spatial filters. The performance of the proposed implementation structures for 3D ST uniform QM-CM and DDFBs cone and frustum filters are evaluated using broadband beamforming signals in radio astronomy applications. The performance of the QM-CM and DDFBs cone and frustum filters shows improvement in terms of Signal-to-Interference-plus-Noise ratio (SINRs) over existing 3D ST cone and frustum filters. In addition to their effective performance, these cone and frustum filters can be efficiently implemented with equivalent or less computational complexity compared to existing methods. Second, implementations of two 3D ST non-uniform cone and frustum filters are explored. These cone and frustum filters are obtained by cascading either QM-CM or DDFBs non-uniform filter banks, with 2D low-pass circularly-symmetric spatial filters. The motivation for the 3D ST non-uniform cone and frustum filters is to achieve better approximation at low temporal frequencies than using the uniform ones. The performance of the 3D ST non-uniform cone and frustum filters is evaluated and compared with the performance of the uniform 3D ST cone and frustum filters. Results indicate that the performance of the proposed 3D ST non-uniform QM-CM and DDFBs cone filters shows some improvement in selective filtering compared to the performance of 3D ST uniform cone filters. / Graduate / 0544 / hussamss@uvic.ca

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