Numerical Simulation And Experimental Study Of Double Swirl Fiber Ball Filter

Fiber filter has the advantages of fast filtration speed,high filtration precision and high tolerance to water quality,becoming a typical deep filtration equipment.At present,the research on filters mainly focuses on the structure optimization of new fiber filter materials and filters with large axial diameter ratio.There are few studies on the performance of filters with similar axial diameter ratio.There is no report of backwashing by double-swirl stirring method.In this paper,the filtration and backwashing process of the filter with the same axial diameter ratio is studied by CFD and experiment,so as to optimize the filter structure,and then the influence of process parameters on the backwashing efficiency is studied,which provides theoretical guidance for the selection of production process parameters.In this paper,a two-swirl fiber ball filter from a factory is used as the prototype,and a model that conforms to the actual production is established.The influence of the flow distribution system on the filtration performance and the backwash nozzle system on the backwash performance is studied.The structural parameters of the above system are optimized,and the filtration and backwash experiments are carried out as follows:Using the porous media model and the multiphase flow model,the influences of flow distribution system,filter bed height and filling density on filtration behavior were analyzed.The results showed that the more uniform the filter bed fouling distribution,the smaller the difference in radial filtration resistance of the filter bed,and the better the"tightness"of the filter bed.The optimized parameters of the flow distribution system were as follows:the diameter of the outlet was 15mm-20mm,and the number of the outlet was 10-12.The influences of backwash duration,nozzle structure,backwash mode and backwash intensity on backwash characteristics were studied by using a multiphase flow model.The results showed that a circular"DNA"-like double helix rotating flow field was formed in the annular region near the filter wall,and a single spiral rotating flow field along the axis was formed in the region near the filter axis.The optimized nozzle parameters are as follows:nozzle Angle 70°,number of nozzles 60,nozzle diameter30mm,upper and lower spacing 270mm.Double swirl backwash is adopted,which is 43%more efficient than bottom backwash,and the backwash strength is 0.6m~3/(m~2·min).The experimental platform of filtration and backwashing was built.The results showed that the pressure loss of the filter bed was more uniform in the radial direction after optimizing the water outlet.Considering the backwashing efficiency and energy consumption,the gas-water combined backwashing process with the strength of backwashing water 0.6m~3/(m~2·min)and the strength of backwashing gas 0.8m~3/(m~2·min)was selected to improve the backwashing effect.