222 / 2019-08-30 10:42:33

Study and simulation of the filtration performance of the gas fibrous filters for the sea salt aerosols in the marine atmosphere

CFD-DEM; Sea salt aerosols；Random 3-D fiber model; Filtration performance

计算流体力学、多场耦合、生物力学、动力学等 > 多场耦合模拟

With the development of marine resources exploration, more and more attention is paid to the working environment of the offshore platform and ships. Salt mist, water mist, oil mist and solid particles, which can be concluded as sea salt aerosols, plays a very important role in electrical and electronic equipment corrosion. High efficiency air filters have been widely applied to remove harmful atmospheric aerosols. Therefore, in this work, the filtration efficiency and pressure drop of the gas fibrous filters are studied through theoretical analysis and simulation. Different from most previous 2-D model studies, random 3-D structures of fibrous filter element is established to explore the filtration efficiency and pressure drop of the gas fibrous filters for the sea salt aerosols in the marine atmosphere. The computational fluid dynamics(CFD) technology coupled with the discrete element method(DEM) is applied to simulate the filtration process combining airflow, particles, fibers and the interactions between them. At the beginning of each time step of the CFD-DEM coupling, the flow field is calculated to converge in CFD. Then the flow information is transferred to DEM and the particle-fluid interaction forces are calculated. Meanwhile, the dynamic information of particles (e.g., positions and velocity) are obtained by solving the equations of translation and rotation. Thus the flow field is updated considering the influence of the particles by using the obtained information and the simulation enters the next time step. As many electrical and electronic components have been used in pneumatic systems, it is necessary to conduct research on gas fibrous filters working in marine atmosphere. Due to most research on gas filters are concentrated on atmospheric environment, the correlations between filtration performance and air pressure are investigated. Meantime, the correlations between filtration performance and fiber structures, particle parameters and fluid properties are investigated. The simulation results are validated by comparing with semi-analytical models. The results clearly show the particle collision and aggregation phenomena, as well as particle detachment from fiber. At the beginning of the filtration, particles are captured by fibers and gradually formed particle dendrites, and most particles are captured on the surface of the filter, but small particles were easier to penetrate fibers and dendrites. It was found that, for the size of particles ranging from 2-8μm which represents the particle size distribution of the sea salt aerosols, decrease of particles diameter improved the filtration efficiency and the decrease of fiber diameter resulted in great fluctuation of pressure drop.