过滤孔径可调的叠片过滤器设计及其水力性能

Design of adjustable equivalent aperture disc filters and its hydraulic performance

叠片过滤器是微灌系统的关键部件之一,对过滤杂质,减缓滴头堵塞起到重要作用。但叠片过滤器的叠片种类单一、过滤沙粒粒径范围较小,同一叠片无法满足不同杂质粒径的过滤要求。基于此,该研究考虑通过合理改变叠片间松紧度的方式调节叠片间有效过滤面积,设计了一种过滤孔径可调的叠片过滤器并通过试验测试其水力性能。结果表明:1)通过调节叠片松紧度可以获得不同过滤孔径的目标。3种叠片在3种电机压力下可获得7种松紧度,对应的叠片过滤等效孔径分别75、100、125、150、200、250、300μm。2)7种孔径叠片过滤器水头损失动态变化和拦沙量存在差异。以小于75μm沙粒为主的小级配含沙水,75μm叠片的水头损失峰值最大,最大值均稳定在16 m左右。其拦沙量显著大于其他叠片(P<0.05)。以>75~150μm沙粒为主的中级配含沙水,75、100和125μm叠片水头损失均较大,最大值均超过了6 m,100和125μm叠片拦沙量显著大于其他叠片(P<0.05)。以>150~300μm沙粒为主的大级配含沙水,150、200、250和300μm叠片的拦沙量都较大,水头损失也有所增加。3)基于TOPSIS法可实现叠片过滤器孔径的优化配置。小级配含沙水应选择75μm叠片;中级配含沙水浓度较大时应选择125μm叠片,浓度较小时应选择100μm叠片;大级配含沙水浓度较大时应选择250和300μm叠片,浓度较小时应选择150和200μm叠片。研究可为减少过滤器水头损失和微灌系统中不同级配含沙水条件下叠片过滤器的合理选型和使用提供参考。

A disc filter is one of the key components in micro-irrigation systems,and plays an important role in filtering impurities and reducing clogging of emitters.However,the disc filter cannot fully meet the filtration requirements of different impurity particle sizes,due to a single type of discs and a narrow range of sand grain sizes for filtration.In this research,a disc filter with an adjustable filter mesh size was proposed to reasonably change the tightness between discs.The disc filter also met the filtration requirements in the different ranges of impurity particle size,in order to reduce the manufacture and operation costs.A series of tests was carried out on the hydraulic performance of disc filters with different mesh.Five flow rates of 10,15,20,25,and 30 m3/h were then set to test the head loss in the conditions of clear water with different mesh sizes of disc filters.In addition,the head loss and sand interception of disc filters were evaluated with different mesh numbers under different grades and contents.Three grades were selected as the small,medium,and large sandy water with less than 75,75−150,and 150−300μm sand particles and three sand contents of 0.8,1.0,and 1.2 g/L.The results show that:(1)Different objectives of mesh filtration were achieved to adjust the disc tightness.Three types of discs were used to obtain 7 levels of tightness under three motor pressures,corresponding to filter mesh sizes of 50,60,75,100,120,150,and 200.(2)There were some differences in the head loss dynamics and sand interception of the 7 mesh disc filters.In small graded sandy water,the 200-mesh disc piece shared the largest peak head loss,where all maximums were stabilized at about 16 m.The sand interceptions of the 200-mesh disc were 54,73,and 84 g,which were significantly larger than that of others(P<0.05).In intermediate-graded sandy water,the head loss was greater than for 120,150,and 200 mesh discs,with the maximum exceeding 6 m.The sand interceptions for 120 and 150 mesh discs were 72,92,and 103 g,and 81,92,and 95 g,respectively,which were significantly greater than that of the others(P<0.05).In large grades of sandy water,the 50,60,75,and 100 mesh discs all shared greater sand interceptions and increased head loss.(3)The optimization configuration of the filter mesh size was achieved using the TOPSIS.Therefore,a 200-mesh disc should be chosen in small graded sandy water.A 120-mesh disc should be chosen in intermediate-graded sandy water when the content was high,and a 150-mesh disc should be chosen when the content was low.A 50-or 60-mesh disc should be selected in large grades of sandy water when the content was high,and a 75-or 100-mesh disc should be chosen when the concentration was low.The best filtration was achieved to effectively avoid the hidden danger of head loss surge.The finding can provide a strong reference for the rational selection and use of disc filters under different sand contents in micro-irrigation systems,in order to reduce the head loss of the filter.