振动流化床中流动结构的混沌分析

在内径90mm、静床高800mm的高床层流化床中，用动态压力传感器检测了不同气速条件下普通流化床和振动流化床中沿轴向的压力脉动信号，通过小波变换对信号除噪后，用混沌理论对信号进行了分析.通过关联维数和Kolmogorov熵定量表征振动流化床中的流动结构特征.结果表明:压力脉动信号的关联维数和Kolmogorov熵能够描述振动流化床中的流化状态；振动流化床中床层的流动结构存在两个区，在近分布板区域为射流区，床层主体部分为均匀流化区.

CHARACTERIZATION OF FLOW REGIMES IN VIBRATED FLUIDIZED BED USING CHAOTIC ANALYSIS

In a fluidized bed with a high static bed height of 800mm and an inner diameter of 90mm, axial pressure fluctuations are measured at different gas velocities in a vibrated fluidized bed (VFB) and a non-vibrated fluidized bed. The noises in the signals are filtered by wavelet transform. The characteristics of the pressure fluctuations in the VFB and the non-vibrated fluidized bed are analyzed by using chaotic theory. It is shown that the correlation dimension and Kolmogorov entropy can be used to characterize the fluidization state in the VFB. There is a jet regime near the air distributor of the VFB, in which the pressure fluctuations are chaotic. When gas velocity is near the minimum bubbling velocity, the correlation dimension and Kolmogorov entropy of the pressure fluctuations in the jet fluidization region reach the minimum. At lower or higher gas velocities, the values of the correlation dimension and Kolmogorov entropy are high due to the particles' or bubbles' random disturbance on pressure fluctuation. Above the jet fluidization region, the formation and coalition of bubbles are restrained due to the shear effect of vibration wave on the bed. The fluidization in the main part of the VFB is homogenous. In this region,pressure fluctuation is periodic. The correlation dimension is in the range of 1-1.5.Kolmogorov entropy approaches to zero.