Abstract:

A characteristic frequency band of acoustic emission (AE) signals, which represented the motion of solid particles in a stirred tank was obtained by using wavelet transform and Hurst analysis. Then it was observed that the energy fraction of AE signals at different frequencies changed regularly with increasing impeller speed in the stirred tank. A new method for determining the critical suspension speed was presented based on this regular behavior. When the AE energy fraction in the characteristic frequency band decreased rapidly and began to level off, the corresponding impeller speed was the critical suspension speed. This new method was verified by the water-glass bead system, which showed that the average absolute relative deviation (AARD) was about 3.51% as compared with visual observation. The average relative error between the results from acoustic experiment and Zweitering equation was 3.17%. It is concluded that multi-scale analysis of acoustic signals is feasible for determining the critical suspension speed and has the merit of being sensitive, non-intrusive and accurate.

摘要：

基于声发射测量技术，结合声信号的频谱分析、小波分解和R/S分析，获得了代表颗粒运动的特征信号频段（d₁、d₂频段）。同时，根据声波特征信号频段能量随搅拌转速的规律性变化，以固体颗粒碰撞壁面产生信号高频区域的声能量分率值为特征参数，提出了搅拌釜临界悬浮转速的测量判据，即声能量分率快速减少并开始趋于稳定时所对应的搅拌转速为临界悬浮转速。以水-玻璃珠体系为例，与目测法相比，声波法测量值的平均相对误差为3.51%，具有较高的精度。利用经典的Zweitering临界悬浮转速计算公式对声波法测得的实验数据进行拟合，计算值与测量值之间的平均相对误差为3.17%，表明公式对于临界悬浮转速的计算具有较高的准确性。由此获得了一种快速、准确、安全的搅拌釜反应器临界悬浮转速测量技术，有利于工业生产流程的优化和控制。