大颗粒流化床中颗粒反射光纤信号的多重分形特性  

Multifractal Spectrum of Optical Reflection Signals in a Two-Dimensional Fluidized Bed with Coarse Granules

作　　者：李晓光[1] 徐德龙[1] 范海宏[1] 

机构地区：[1]西安建筑科技大学材料科学与工程学院

出　　处：《西安交通大学学报》2005年第11期1259-1263,共5页Journal of Xi'an Jiaotong University

基　　金：国家自然科学基金重点资助项目(50432040)

摘　　要：采用2 mm直径的光纤探头,对颗粒直径为3.66 mm的二维流化床内颗粒的光纤反射信号进行了采集,并利用小波变换极大模值法对该类信号进行了数值分析,结果表明其具备多重分形特征;给出了多重分形谱图.由谱图分析可知:随颗粒雷诺数Rep的增加,床中心处颗粒流动更加规律,而近壁区和中心至壁面半途区的情况正相反;在不同的Rep下,床中心部分颗粒无规则运动程度较高,接近壁面处较低.多重分形谱图分析有望为大颗粒流化床中颗粒运动规律的探测提供一种新的手段.In a two-dimensional fluidized bed with granules of 3.66 mm diameter suspending in gas stream, the optical reflection signals were sampled adopting an optical fiber probe with 2 mm-diameter. The signals were analyzed with wavelet transform maximum modulus （WTMM） method and the results revealed the signals multifractal characteristics. The multifractal singular spectrums （MSS） of the signals were presented. It is shown that the granules move in the bed central region more regularly as the granules＇ Reynolds number increases; in the near-wall and midway regions more significant irregularity of granule motion is detected. For a given value of Reynolds number, the disorder in nature of granule motion in the central region is more remarkable than in the near-wall region. The MSS analysis is expected to offer an effective tool for exploring the particle motion in fluidized bed with coarse granules.

关 键 词：流化床 大颗粒 小波变换极大模值 多重分形 光纤信号 

分 类 号：TQ051.13[化学工程]