关键词: 纤维过滤器, 格子Boltzmann气固两相流模型, 优化, 压降, 捕集效率

Abstract: Fibrous filter with the advantage of high capture efficiency of sub-micro particles is widely used in coal-fired power plants, mineral engineering, cement industry and other fields.The filtration process is very complex because of various capture mechanisms and the interactions among airflow, particles and fibers.Up to now, many researchers have investigated the filtration process of fibrous filter, especially the single fiber condition.A series of theories or equations have been presented to calculate pressure drop and filtration efficiency for the single fiber.By contrast, studies for multi-fiber condition are fewer than the single fiber condition.The existing studies of multi-fiber filtration process often focus on the factors(velocity of airflow, volume fraction, particle diameter, etc.)which may affect capture efficiency.It is worth noting that, the ultimate purpose for the study of filtration process should be optimization of fiber configuration for multi-fiber filter, and then a filter with high capture efficiency and low pressure drop can be obtained.However, there is no report about optimization for fiber configuration.In this paper, the lattice Boltzmann-cell automata(LB-CA)probability model was used to simulate the filtration process of multi-fiber filter.The pressure drop and capture efficiency with different mechanisms and fiber configurations were investigated, and the results obtained from the LB-CA model were in good agreement with existing results.The quality factor defined as ratio of capture efficiency and pressure drop was also introduced to weigh the fibrous filters.In order to present the optimization method for different particles, the capture ability of each fiber was first defined and calculated.Parallel model and staggered model for fiber configuration were presented.The quality factor of the staggered model was greater than that of the parallel model because of higher capture efficiency although its pressure drop was also larger.Through comparison of capture ability of fibers in different positions, it was found that the fore fibers were more efficient than the rear ones, especially in the inertial impaction capture mechanism.In the diffusional and interception mechanisms, the similar situation also existed but the contribution of rear fibers could not be neglected.The results showed that a filter with diminishing volume fraction along the depth direction might perform well in the filtration process with the diffusional and interception mechanisms; in the inertial impaction mechanism, the row number of fibers should not exceed two.

Key words: fibrous filter, lattice Boltzmann two-phase flow model, optimize, pressure drop, capture efficiency