Multi‐scale analysis of acoustic emission signals in dense‐phase pneumatic conveying of pulverized coal at high pressure

Abstract

in Wiley Online Library (wileyonlinelibrary.com) Acoustic emission technique in conjunction with multiscale processing method has been utilized to investigate the flow behavior of the dense-phase pneumatic conveying system at high pressure. A clearly defined classification of microscale, mesoscale, and macroscale signals has been put forward with the aid of wavelet transform and V statistics analysis. The detailed signals d 1 -d 4 , d 5 -d 7 , d 8 -d 10 were recomposed into the microscale, mesoscale, and macroscale signals, respectively, which represent microscale particle-wall interactions, mesoscale interaction between gas phase and solid phase (such as bubbles, plugs, dunes), and macroscale flow-induced pipe vibration. Further analysis shows that as the mass flow rate of pulverized coal increases, the energy fraction (energy of detailed signal divided by the energy of original signal) of microscale signals decreases while that of mesoscale signals increases, which indicates that particles are more likely to move as particle aggregates than individual particles when mass flow rate increases.

Flow regime identification in horizontal pneumatic conveying by nonintrusive acoustic emission detection

“…He et al found that in the pneumatic conveying process, frequency analysis of acoustic signals generated by particle‐wall contacts could be further used to characterize the particle conveying behaviors from a microscopic perspective. Using db2 wavelet function to decompose the original signal (900 kHz) by 10‐scales wavelet transform, signals with different frequency ranges can be obtained and the energy fraction of each scale stands for the percentage of signals located in this frequency range.…”

“…According to He et al, acoustic energies in different scales were generated by different kinds of particle‐wall contact patterns. Collision signals generated by vertical particle‐wall contacts were mainly distributed in the d 1 ‐d 3 scales, while friction signals generated by parallel particle‐wall contacts mainly located in the d 4 ‐d 5 scales.…”

“…The time‐domain processing method mainly included SD and acoustic energy, and the frequency‐domain analysis included Fourier transform and wavelet analysis. Aforementioned methods have been widely used to analyze acoustic signals in gas–solid systems such as fluidized bed, pneumatic conveying, and so on. The results obtained can be used to qualitatively and quantitatively characterize the feature of particle motions.…”

“…The results obtained can be used to qualitatively and quantitatively characterize the feature of particle motions. Detailed description of these methods can be found in the literatures …”

“…By AE techniques, a great deal of information related to particle motions can be obtained . He et al has adopted AE detection in dilute‐phase conveying process to investigate particle‐wall contact patterns and measure the solid mass flux. Furthermore, they also combined AE technology with multiscale analysis methods to study the gas–solid two‐phase fluid mechanics behavior in high‐pressure dense‐phase pneumatic conveying of pulverized coal and detect the mass flux of pulverized coal.…”