应用粒子图像测试技术测量球床多孔介质单相流动的流场

Measurement of single phase flow in porous media using PIV technique

多孔介质在生产生活以及科技发展中的应用十分广泛,随着能源、化工、冶金和原子能等领域技术的发展,以及近代工农业生产技术的进步,大量多孔介质的传热传质问题逐渐出现,进一步促进了多孔介质学科的形成和发展,使其成为当今科学技术中令人瞩目的研究热点之一.通过实验获得准确的实验图像和数据,并使用相应软件对实验所得数据和流体流动图像进行深度分析,这样既有真实可靠的实际数据,又有直观的理论的支持,使对多孔介质的研究更为完善.实验结合粒子图像测试技术和折射率匹配技术对叉排排列玻璃球多孔介质填充床内的流体流动转变过程进行流场测试,并提取数据,采用Tecplot软件对提取数据进行处理,得出流体流动机理的转变过程.实验固相为由直径25 mm水晶玻璃球叉排堆积而成的填充床,液相为65%苯甲醇和35%无水乙醇配制的匹配液.液相与固相的折射率都为1.477,成功消除由于折射率不匹配引起的激光光线偏折.实验得到雷诺数为4.7 ≤Re ≤1000时球床内流场图,对比不同雷诺数时流场和流线变化得出:随着雷诺数的增加,流线变得越来越紊乱;当雷诺数在220以上时,球床内漩涡在尺寸变化上出现突跃,在位置和形态变化表现出随机特征,预示进入了稳定的湍流.

Porous media are widely used in the production and living,and also in science and technology.With the development of energy,chemical industry,metallurgy,atomic energy and also with the progress of the modern industrial and agricultural production technology,a large number of heat and mass transfer problems in porous media gradually appear.Further promoting the development of the discipline about the formation and development of porous media becomes one of hot research points in the modern science and technology.It is expected that the accurate experimental picture and data can be obtained through the experiment,and the fluid flow picture and experimental data are analyzed in depth by using the corresponding software,so that the reliable data are obtained and the theory is supported intuitively,making the research of porous media more perfect.The experiment combined with particle image velocimetry technology and refractive index matching technique is conducted to test the transformation process of liquid flow in a random ball porous medium filled bed,and to extract the data.The extracted data are processed by using Tecplot software,and the transformation process of liquid flow mechanism is obtained.Experimental solid phase is a 25 mm-diameter crystal glass ball stacked bed,and liquid phase is the matching liquid prepared with the mixture of the 65% benzyl alcohol and35% anhydrous ethanol.The refractive indexes of liquid phase and solid phase are both 1.477,which can successfully eliminate the laser light bending caused by the nismaching of refractive indexes.The flow field diagram in the pebble bed with Reynolds number Re in a range 4.7≤Re≤1000 is obtained experimentally.The comparisons of variations of flow field and flow lines among the different Reynolds numbers reveal that with the increase of Reynolds number,flow lines become more and more disorder：When the Reynolds number Re exceeds 220,stable swirl flow inside the bed changes suddenly,and manifests a random feature in location and configuration,which forebodes its entrance into stable turbulence phase.