Comprehensive evaluation method for hydraulic performance and filtering quality of laminated filter

Abstract: Laminated filter has the characteristics of screen filter and sand filter, and can achieve three-dimensional filtration. The structure size of laminated filter is the most important parameter affecting the filter performance. In this study, we established a comprehensive evaluation method of laminated filter performance. Experiment was carried out at Tongzhou Test Station of China Agricultural University. A total of 5 kinds of laminated filters commonly used were selected. The hydraulic and filtration performance of laminated filters were tested under different sediment concentration (0.02%, 0.03% and 0.04%) and flow rate (25, 30, 35 m3/h). Dynamic change of head loss with time, clogging uniformity index, amount of intercepting sediment and median particle size of intercepted sediment were analyzed. Based on the performance test, the 3 single performance indices (amount of intercepting sediment, median particle size of intercepted sediment and clogging uniformity index) related to the size parameters of laminates were selected through correlation analysis. By means of stepwise regression analysis and principal component analysis, the multivariate linear regression equations between 3 single performance indices and 6 laminated structural parameters (single laminate thickness, the number of laminations, length of the flow channel, the number of flow channels, the apex angle of triangle outside flow channel, the height of triangle outer section of flow channel ) were established respectively. And the regression equation of 3 single performance indices was used to establish the comprehensive evaluation function of laminated filter performance by direct weighting method. The results showed that there were great differences among the 5 laminated filters in head loss, amount of intercepting sediment, median particle size of intercepted sediment and clogging uniformity index. The evaluation value of comprehensive evaluative function established in this paper for 5 kinds of laminated filters was ordered by filter V(3.11), smaller than filter II(7.08), filter I(7.22), filter III(7.88) and filter IV(8.63). The smaller evaluation value indicated better comprehensive performance of laminated filters. According to the analysis of the test data, the evaluation results were in line with the actual situation, and could comprehensively and reasonably evaluate and compare the performances of laminated filters. In addition, the numerical value of the index also reflected the difference of the structure and size of the 5 kinds of laminated filters, which showed difference in clogging uniformity index, amount of intercepting sediment and median particle size of intercepted sediment. According to the design requirements of laminated filters, there was a certain constraint relationship between the structural size parameters of laminated filters. It was difficult to improve the hydraulic performance and sediment disposal capacity of the filter at the same time only by changing the value of a certain parameter. Therefore, the geometric structure and size of laminated filter should be considered comprehensively in order to optimize some performance parameters of laminated filter. This evaluation method cannot only be used to assess performance of laminated filter, but also provide information for improving the size of laminated filter structure and further optimizing the performance of filter.