气泡雾化喷嘴气体溢出过程声波信号的时频特征研究

通过自建的气泡雾化喷嘴射流可视化实验平台对射流中气体溢出过程进行了声波信号采集和图像观测。采用自适应最优核(AOK)与希尔伯特-黄变换(HHT)边际谱两种时频分析方法对采集到的声波时频信号进行了处理和分析。结果表明:气泡溢出喷嘴时会导致声波信号AOK时频谱幅值的增加;时频谱幅值随时间的变化可以反映喷孔处气体溢出量的实时变动;声波信号的HHT边际谱能量主要集中在一定频率范围内,且在频率轴上的分布与气液两相压力、气液混合状态等因素有关;边际谱能量关于某一中心频率呈近似对称分布,且该中心频率与气泡压力相关,而与气泡大小关系不大;声波信号的时频分析结果能很好地捕捉到气泡雾化喷嘴射流时气相在溢出过程中的变化。声波信号时频分析方法可作为气泡雾化喷嘴射流研究的一个有效途径。

Time-frequency Characteristics of Acoustic Signal in Gas Flowing Process of Effervescent Spray Nozzle

Adaptive optimal kernel (AOK) and Hilbert-Huang transform (HHT) marginal spectrum methods were introduced to process acoustic signals from effervescent atomizer. The time-frequency results reflected the information of bubble pressure, bubble size and gas liquid mass ratio fluctuation which had significant impacts on spray. The experimental results showed that the outflow moment of bubble could be accurately captured by AOK time-frequency spectrum, and the pulsation of amplitude could reflect the gas-liquid mass ratio fluctuation. The Hilbert marginal spectrum power was concentrated in a short frequency range. The power-frequency distribution was affected by gas-liquid pressure and gas-liquid mixture form. The Hilbert marginal spectrum power was symmetric with the center frequency which was positively correlated with bubble pressure, but little correlated with bubble size. Time-frequency analysis of acoustic signals from effervescent atomizer provides a new tactics for further study of the mechanism for effervescent atomization.