流化床压力脉动信号时间延迟相关性

DELAY TIME CORRELATION OF TIME OF PRESSURE FLUCTUATIONS IN BUBBLING FLUIDIZED BED

对鼓泡流化床压力脉动信号用FFT变换进行分解,得到0-10Hz、10-20 Hz、20-30 Hz、30-40 Hz、40-50Hz、50-60Hz和大于60Hz的信号.分别用自相关函数和互信息函数研究了各个频段信号的线性相关性和非线性相关性.首次通过理论证实了鼓泡流化床压力脉动信号中30 Hz以上信号不存在线性相关性,40 Hz以上信号不存在非线性相关性.由于40 Hz以上信号不存在前后相关性,可以认为其为噪声信号.研究指出通过流化床压力脉动信号研究流化床内部信息时,应考虑40 Hz以下信号,而不是以前认为的20 Hz以下信号.

The signals of pressure in a bubbling fluidized bed, 0.30 m in diameter and 3.8 m in height were decomposed into signals of different frequency band including 0-10 Hz, 10-20 Hz, 20-30 Hz, 30- 40 Hz, 40-50 Hz, 50-60 Hz and more than 60 Hz by Fourier transform. The linear and nonlinear correlation characteristics of signals of different frequency band were studied using auto-correlation function and mutual information function, respectively. The signals of more than 30 Hz in frequency are confirmed to be not of linear correlation and the signals of more than 40 Hz in frequency to be not of nonlinear correlation. Therefore, the signals of more than 40 Hz in frequency could be considered as noise for no correlation in any time interval. Meanwhile, the signals of less than 40 Hz in frequency should be considered rather than 20 Hz as before if more details on fluidized bed are to be obtained by studying pressure signals.