摘要
滤层孔隙结构直接影响过滤过程中的颗粒沉积和运移效果。为了掌握砂石过滤器不同粒形滤料组成滤层的内部孔隙结构特征,该研究以粒径为1~1.18 mm的普通石英砂(QS1)、天然海砂(SS2)、改性玻璃(MG3)和玻璃微珠(GB4)4种滤料为研究对象,采用CT扫描技术对滤层孔隙模型进行了三维重构,利用VGStudio MAX、Image J等计算机图像处理软件,分析了4种滤层的孔隙率、孔径大小及孔隙形状参数,并结合分形理论确定了4种滤层孔隙结构的计盒分形维数。结果表明:4种滤层的表观孔隙率范围分别为39.7%~44.6%、38.5~42.3%、40.7%~45.6%、34.8%~38.7%,对应体积孔隙率分别为0.422、0.412、0.441、0.366;对应孔径范围分别为75~960、80~760、70~1050、85~930μm,圆度值区间分别为1.59~1.78、1.35~1.54、1.65~2.03、1.20~1.36,扁平度值区间分别为2.62~2.75、2.05~2.20、3.04~3.21、1.94~2.04,计盒维数均值分别为1.621、1.566、1.661、1.446。该研究定量表征了滤层孔隙结构特性,得出不同粒形滤料细观孔隙结构的差异:滤层表观孔隙率呈现“上高下低”分布规律,孔径分布规律表明滤层内均是小孔隙占多数,大孔隙占少数,且孔隙以狭长型为主。随着滤料棱角度增加,表观孔隙率分布越分散,体积孔隙率越大,大孔隙占比也相应增加,最大达到17.24%(MG3),孔隙形状更加偏离球形,表征孔隙结构复杂性的计盒维数相应增加,且分形维数与孔隙率呈负相关关系。滤层孔隙结构研究可为后续研究滤层内颗粒沉积和运移规律奠定基础。
Sand media filters are often among the common filter modes in micro-irrigation system due to its excellent fouling capacity.The sand filter intercepts impurity particles mainly through the filter layer pores.The pore structure of filter layers directly affects the effect of particle deposition and transport during filtration.The objective of this work was to to master the internal pore structure characteristics of sand filter layers composed of different granular filter media.Taking ordinary Quartz Sand(QS1),Sea Sand(SS2),ASM Modified Glass(MG3)and Glass Beads(GB4)with selected grain size1.0~1.18 mm as research objective,this study employs the advanced CT scanning technique to construct the three-dimensional(3D)structure of four filter layers.In combination with image analysis software VGStudio MAX,Image J,et al,the pore structure parameters such as porosity,pore size distribution,pore roundness value and flatness ratio of four filter layers were obtained by processing different filter layer CT slices.In order to investigate the complexity of different layer pore structure,the box-counting fractal dimensions of pore structures were calculated with fractal theory.The research results showed that the apparent porosity range of the four filter layers were 39.7%-44.6%(QS1),38.5%-42.3%(SS2),40.7%-45.6%(MG3),34.8%-38.7%(GB4)and the volume porosities were 42.2%,41.2%,44.1%,36.6%respectively.The pore size intervals were 75-960,80-760,70-1050,85-930μm and the difference was not significant.The calculated pore roundness value ranges were 1.59-1.78,1.35-1.54,1.65-2.03,1.20-1.36,the pore flatness ranges were 2.62-2.75,2.05-2.20,3.04-3.21,1.94-2.04,the fractal dimensions Db of the four filter layers were 1.621,1.566,1.661 and 1.446,respectively.This study quantitatively characterized the pore structure characteristics of the filter layer,and obtained the differences of meso-pore structure of different granular filter media.The apparent porosities of the top filter layers were more higher than that of the bottom layers along the depth of the filter.The pore size distribution law was that small pores(<75μm)accounted for the majority for all the four granular media and the pore shapes were mainly narrow and long type.With the media particle angularity increase,the distribution of the apparent porosity was more dispersed and the volume porosity was higher,the proportion of macro-pores increased accordingly and the maximum value reached 17.24%for MG3.The tendency of pore shape parameters deviation from sphericity was more obvious.The fractal box-counting dimension,which represented the complexity of pore structure,increased with the media angularity accordingly,and fractal dimension was negatively correlated with apparent porosity.The quantitative analysis of filter layers pore structure can overcome the shortage of traditional model experiment and provide a foundation for the subsequent study of particle deposition and migration in the filter layers.
作者
蔡九茂
宋蕾
张文正
翟国亮
许强
李鹏来
Cai Jiumao;Song Lei;Zhang Wenzheng;Zhai Guoliang;Xu Qiang;Li Penglai(Farmland Irrigation Research Institute,Chinese Academy of Agricultural Sciences/Key Laboratory of Water Saving Irrigation Engineering,Ministry of Agriculture and Rural Affair,Xinxiang 453002,China;Anhui FLT Filtering System Co.,Ltd,Ma'anshan 243071,China;Inner Mongolia Longze Water-saving Irrigation Technology Co.,Ltd,Chifeng 024005,China)
出处
《农业工程学报》
EI
CAS
CSCD
北大核心
2022年第19期94-101,共8页
Transactions of the Chinese Society of Agricultural Engineering
基金
河南省重大科技专项项目“小麦全产业链融合发展关键技术研发与示范应用”(221100110700)
新乡市重大科技专项“智慧灌溉系统装备研发”(ZD2020009-03)。
关键词
微灌
CT图像
图像处理
孔隙结构
孔隙率
分形维数
micro-irrigation
CT images
image processing
pore structure
porosity
fractal dimension
