微灌砂石过滤器滤帽水力性能试验及内部流场模拟  

Hydraulic performance experiment and internal flow field numerical simulation for underdrain of micro-irrigation sand filter

作　　者：蔡九茂[1] 翟国亮[1] 吕谋超[1] 刘杰云 张文正[1] Cai Jiumao;Zhai Guoliang;Lyu Mouchao;Liu Jieyun;Zhang Wenzheng(Farmland Irrigation Research Institute,Chinese Academy of Agricultural Sciences/Key Laboratory of Water Saving Irrigation Engineering,Ministry of Agriculture and Rural Affairs,Xinxiang 453002,China)

机构地区：[1]中国农业科学院农田灌溉研究所/农业农村部节水灌溉工程重点实验室,新乡453002

出　　处：《农业工程学报》2020年第13期67-74,F0004,共9页Transactions of the Chinese Society of Agricultural Engineering

基　　金：河南省科技攻关项目(2019-288);中国农业科学院基本科研业务费(Y2018PT72、FIRI2017-25、FIRI202002-01)。

摘　　要：微灌用砂石过滤器中,集水滤帽是进行过滤过程集水和反冲洗过程散水的关键部件。为了获得滤帽内部流阻特性,改善砂石过滤器水损较大弊端,该研究对国内市场上常用的梯形集水滤帽进行了室内模型试验,测定了滤帽在不同过滤和反冲洗速度下的压降特性,并采用Fluent(15.0)软件对滤帽过滤和反冲洗过程中的流场分布特征进行了数值模拟,研究了滤帽内外的压降分布规律。结果表明:滤帽压降模拟结果和试验测试结果吻合性较好,相对误差3.54%~6.53%。随着滤速升高,滤帽产生的水头损失较滤层水损增长更为显著,反冲洗过程中的滤帽水损要大于过滤状态;通过对滤帽内部流场分析,滤帽水损主要产生于近滤缝区域和芯柱区域,均是由于过水流道突然缩小导致,在滤层滤速为0.030 m/s时,滤缝和芯柱进口处滤速分别为2.57和4.01m/s。结合以上结果,设计了一种扁平球面滤帽结构,增加了滤缝面积,优化了芯柱结构,缩小了滤帽高宽比,通过数值模拟,表明扁平球面滤帽结构有助于改进过滤和反冲洗效果。研究结果可为滤帽选型和优化改进提供参考。Sand filter is considered to be one of the best choice to prevent clogging in micro-irrigation system.Head losses in media filter are produced by the friction loss due to the internal auxiliary elements of the filter container and the resistance offered by the media layer.The underdrain element is a core component in sand filter.To deeply understand the hydraulic behavior of underdrain,the experimental and numerical investigations were conducted to explore the flow resistance characteristics and flow field distribution in the underdrain.Laboratory experiments of filtering and backwashing were conducted in Farmland Irrigation Research Institute,Chinese Academy of Agricultural Sciences,Xinxiang,China.A trapezoidal underdrain element applied commonly in domestic market was selected in the experiment.It was installed in a scaled sand filter based on a commercial filter with 600 mm internal diameter.The sand filter model were tested at eight filtering velocities ranging from 0.010 to 0.040 m/s,and eight backwashing velocities ranging from 0.005 to 0.040 m/s,which were consist with the actual commercial filter operation.The experimental variables were monitored in real time by a data acquisition system consisted of a flowmeter and pressure transmitter.The internal flow behavior through the filter was simulated using the Computational Fluid Dynamics(CFD)method.A CFD model of the underdrain was developed by ANSYS Fluent 15.0.The geometry of the underdrain and its unstructured mesh were designed by ICEM software.Due to the turbulent flow regime in the underdrain and layer,the realizable k-εturbulence model and the porous medium model were selected for solution.The computing area and the boundary condition of inlet and outlet were proposed.To ensure the reliability of the numerical simulation,the experimental values were compared with the simulated results.The results showed that the simulated values of head loss were in good agreement with the experimental values with the relative errors between 3.54%and 6.53%.The tested

关 键 词：流速 过滤器 水力性能 微灌 砂石过滤器 滤帽 流场模拟 流阻特性 

分 类 号：S275.5[农业科学—农业水土工程]