气固搅拌流化床压力脉动的小波分析

Wavelets analysis of pressure fluctuation in agitated fluidized bed

在内径188mm、静床高400mm的搅拌流化床中,采用GeldartD类颗粒为实验物料,通过小波分析研究了不同气速和搅拌桨转速下搅拌流化床的压力脉动行为.实验发现,搅拌桨的转动作用促使在普通流化床中不易散式流态化的D类颗粒形成了散式流态化.随着气速的增加,第1尺度的小波能量特征值在某一个气速范围内发生急剧变化,进而提出了将该气速范围的下限和上限分别定义为临界鼓泡速度和充分鼓泡速度的判据.随搅拌转速的增加,散式流态化的气速操作范围线性增加.在鼓泡流态化状态下,气速是流化床气泡行为的主导因素,搅拌桨转速的增加对气泡产生的频率无明显影响但可使气泡的直径变小.

In an agitated fluidized bed using Geldart D particles as fluidized materials with a static bed height of 400 mm and an inner diameter of 188 mm, the pressure fluctuation signals at different rotation speeds of stirrer blade and gas velocities were analyzed with the wavelet analysis method for investigating the influence of agitation of stirrer blade on the fluidization behavior. The pressure fluctuation signals were decomposed into 9 scales by Dau2 wavelet. Experimental results indicated that the wavelet energy characteristics of Scale 1 detailed signal changed sharply in a certain range of gas velocity. Then the criteria of the minimum bubbling velocity and full bubbling velocity were developed. The Geldart D particles showed particulate fluidization due to the rotation of stirrer blade. The minimum bubbling velocity and full bubbling velocity increased linearly with increasing rotation speeds of stirrer blade, while the fluidized bed transformed from bubbling fluidization to particulate fluidization. Gas velocity was the major cause for the pressure fluctuation in the bubbling fluidization regime and increasing rotation speed of stirrer blade had little effect on the bubble frequency, but made the bubble size smaller obviously.