Numerical Simulation On The Optimization Of Fibrous Filtration Media Structure Parameters

Pressure drop, capture efficiency and permeability are the most important parameters of fibrous filter performance.previous studies on the performance of fiber filters have been done for many years. There are several two-dimensional and three-dimensional models in previous studies used to predict the Permeability of the filter, but the actual fiber filters structure was simplified, for example, the fiber arrangement was simplified as inerratic, and most simulation are two-dimensional. If these models are used to predict actual media,the results are disappointing. The distribution of fibre and different diameter fibre combination of fibrous filters play an important role for filter performance. So ,researching three-dimensional flow field in fibrous filter have important meaning for deep researching of filtering mechanism and optimizing filter design parameters and operate parameters.To get more realistic microstructure of fiber filter, A series of different structure parameters of virtual 3-D fibrous filter model was created in this paper. Using the computational fluid dynamics (CFD) software FLUENT6.1 as the platform, fibrous filter model s'internal gas phase flow field with different operating parameters were achieved. The main research work and conclusions including:(1) A variety of filter model through computer program was Created, which mainly including the single-peak fibrous filter (the diameter of fibre is unifonn equal), bimodal fibrous filter (filter is made of two different diameter fibrous with certain proportion) and polydisperse fibrous filter (the distribution of fibre diameter is multiple decentralized state, the normal distribution state was considered in this article.).The three-dimensional fibrous filter models are very similar with real microstructure of filter medium.(2) Three different arrangement single-peak fibrous filter were studied:Equidistant parallel arrangement model, staggered arrangement model and random arrangement model. The results of the study indicate that:the influence of wind velocity to pressure drop of these three kinds filters model the is consistent, the pressure drop linear increase along with the increase of wind velocity.The permeability of filter nonlinear decrease along with the increase of solid volume fraction (SVF). But the random arrangement model is more close to true non-woven microstructure and its result is most close to Davies experimental results. In addition, the non-dimensional pressure drop of these three fibrous filter model was concluded. The error between random arrangement model calculation formula result and Davice calculation result is less than 5%, the error between the other two calculation formula and classical model calculation results are less than 10%.(3) Bimodal fibrous filter model was Created, the pressure drop of the filter model with different operating parameters was calculated and the internal flow field distribution was given.The pressure drop linear increase along with the increase of wind velocity; The permeability of filter nonlinear decrease along with the increase of SVF. The pressure drop decrease along with the increase of coarse fibre percent.(4) Polydisperse fibrous filter model was Created, the pressure drop of the filter model with different operating parameters was calculated and the internal flow field distribution was given. The pressure drop linear increase along with the increase of wind velocity; The permeability of filter nonlinear decrease along with the increase of SVF. Considering the influence of fibrous diameter dispersion on pressure drop, but the impact is not quite apparent. With orthogonal experimental data, the pressure drop formula for steady-state clean filter were achieved which including filtration velocity, filter layer thickness, porosity and dispersion. The pressure drop of polydisperse fibrous filter can be described as local pressure drop of the filter medium, its partial resistance coefficient bocome inverse ratio to Reynolds number, porosity and fibrous diameter, but it bocome direct ratio to the dispersion.