Abstract: Acoustic emission(AE) technique,based on Hilbert-Huang transform(HHT) analysis,was used to analyze the AE signal received from the wall of a multi-layer slurry stirred tank,in which cation exchange resin was dispersed in water by agitation.IMF 1—5,which considered the characteristic scale(20—230 kHz),was obtained by empirical mode decompositon(EMD),representing the slurry system. A reconstructed AE signal was acquired by IMF 1—5.The energy of the reconstructed signal was found changing regularly with increasing impeller speed in the stirred tank.Then,a criterion to determine the critical suspension speed was presented.When energy began to remain constant after rapidly increasing,the corresponding impeller speed was the critical suspension speed.It was shown that the average absolute relative deviation(AARD) was about 3.83% compared with visual observation. Furthermore,external loop could diminish the critical suspension speed by intensifying axial flow in the tank,which meant that solid suspension was promoted.A predictive equation for calculating the critical suspension speed in a stirred tank with an external loop was proposed,which gave an AARD of 5.78%.Therefore,multi-scale analysis of acoustic signals based on HHT analysis was feasible for determining the critical dispersion speed and had the merit of being sensitive,non-intrusive and accurate.

Key words: Hilbert-Huang transform , external loop, critical suspension speed, acoustic emission

摘要： 基于声发射测量技术，结合Hilbert-Huang变换（HHT），分析搅拌釜壁声发射信号，获得了代表浆液运动的特征频段(20～230 kHz)，以特征频段对声信号进行重构。同时，以重构信号能量为特征参数，根据其随搅拌转速的规律性变化，提出了搅拌釜临界悬浮转速的测量判据，即重构信号能量由上升转向平稳时所对应的搅拌转速为临界悬浮转速。与目测法相比，该方法平均相对误差为3.83%，具有较高的精度。进一步，发现外循环加强了搅拌釜内轴向流动，有利于固体悬浮，从而使临界分散转速变小，并建立了外循环搅拌釜临界悬浮转速的预测关联式，平均相对误差为5.78%。由此获得了一种快速、准确、安全的临界悬浮转速的测量技术，有利于工业生产流程的优化和控制。

关键词: Hilbert-Huang变换 , 外循环, 临界悬浮转速, 声发射