填料塔液泛的声发射测量

利用声发射技术采集填料塔在不同操作状态下壁面处的声发射信号,结合标准差分析、频谱分析和小波分析研究填料塔在不同操作状态时的声发射信号特征,提出填料塔液泛气速的声发射测量判据。以空气-水体系为例考察不同液体流量下的液泛气速,发现声发射信号标准差对液泛气速的预测值与压降法的预测值接近。比较不同操作条件下的声发射信号的功率谱,发现填料塔发生液泛时功率密度最大的峰从50 kHz 和60 kHz 转移到在25 kHz附近;进一步将声发射信号在0~300 kHz 频率范围内做7 尺度小波分解,当气速到达液泛气速时特征信号频段G₁(d₄、d₅)的声发射信号能量分率迅速增大。G₁尺度声发射信号能量分率对液泛气速的预测值与压降法的预测值接近。声发射技术作为一种非侵入式的检测手段,能够实现液泛的实时监控,具有良好的应用前景。

Measurement of flooding gas velocity in packed column by acoustic emission technique

The acoustic emission (AE) signal characteristics under different operation conditions of packed column were investigated by analyzing standard deviation (STD), power spectrum density (PSD) and multi-scale wavelet transform of acoustic emission signals. Criterions to determine the flooding gas velocity were proposed. The influence of liquid flowrate was investigated by air-water experiments. It was found that the prediction of the flooding gas velocity by AE signal STD was close to that by pressure drop. The power spectrum density of acoustic emission signals under different operation conditions showed that the maximal PSD peak transferred from around 50 kHz and 60 kHz to around 25 kHz when the packed column flooding. 7 scales wavelet transform was used to investigate the acoustic emission signals. Energy fraction of G₁ (d₄,d₅) scale had a sharp rise as the gas velocity came to flooding gas velocity. The prediction of flooding gas velocity by G₁ scale energy fraction was close to that by pressure drop. As a non-invasive method, acoustic emission detection can monitor flooding accurately and have a good application prospect.