气液搅拌釜泛点转速的声波测量

Identification of flooding-loading transition in stirred vessel based on acoustic method

通过对采集的搅拌釜中声信号的频谱分析、小波分解和R/S分析,获得了代表气液体系运动的特征信号频段(d4、d5、d6频段),针对声波特征信号频段能量随搅拌转速的规律性变化,提出了搅拌釜泛点转速的声波测量判据,即声能量分率快速增加并开始趋于稳定时所对应的搅拌转速为泛点转速。以空气-水体系为例,考察了不同通气量和静液位高度下的泛点转速,发现泛点转速随通气量的增加而增加,随静液位高度的增加而减小。与目测法相比,声波法测量值的平均相对误差为2.62%,优于传统的功耗法。由此获得了一种快速、准确、安全的搅拌釜反应器泛点转速测量技术,具有良好的工业应用前景。

The characteristic scale （G1） of acoustic emission （AE） signals that represent the interactions between bubbles and liquid phase in a stirred tank was obtained by using AE measurement based on wavelet transform and R/S analysis. Since the energy fraction of AE signals in G1 scale change regularly with the impeller speed, a criterion to determine the flooding-loading flow regime transition is presented. When the AE energy fraction in the characteristic frequency scales increased rapidly and began to remain constant, the corresponding impeller speed was the minimum speed to prevent flooding （Nf）. Furthermore, the influences of aeration rate and total liquid depth on the criterion were investigated by airwater experiments. It was found that Nf increased with increasing aeration rate but decreased with increasing total liquid depth. By comparing experimental results from AE measurement with those from visual observation, the average relative errors of AE method were no more than 2.62%, better than the power consumption method. Finally, it is concluded that multi-scale analysis of acoustic signals is feasible for determining the flooding-loading flow regime transition and is sensitive, non-intrusive and accurate.