Resolution of structure characteristics of AE signals in multiphase flow system—From data to information

Abstract

This investigation was performed to study the underlying structure characteristics of acoustic emission (AE) signals, which could be helpful not only to understand a relatively complete picture of hydrodynamics in multiphase flow systems, but also to extract the most useful information from the original signals with respect to a particular measurement requirement. However, due to AE signals are made up of emission from many acoustic sources at different scales, the resolution of AE signals is often very complicated and appears to be relatively poorly researched. In this study, the structure characteristics of AE signals measured both in gas-solid fluidized bed and liquid-solid stirred tank were researched in detail by resorting to wavelet transform and rescaled range analysis. A general criterion was proposed to resolve AE signals into three physicalrelated characteristic scales, i.e., microscale, mesoscale, and macroscale. Multiscale resolution of AE signals implied that AE signals in microscale represented totally the dynamics of solid phase and could be applied to measure particle-related properties. Furthermore, based on the structure characteristics of AE signals, useful features related to particles motion were extracted to establish two new prediction models, one for on-line measurements of particle size distribution (PSD) and average particle size in gas-solid fluidized bed and the other for on-line measurement of the suspension height in liquid-solid stirred tank. The prediction results indicated that (1) measurements of PSD and average particle size using AE method showed a fairly good agreement with that using sieve method both for laboratory scale and plant scale fluidized beds, and (2) measurements of the suspension height using AE method showed a fairly good agreement with that using visual method. The results thus validated that the extracted features based on analyses of structure characteristics of AE signals were very useful for establishing effective on-line measurement models with respect to some particular applications.

Characterization of flow-induced vibrations in gas–solid fluidized beds: Elements of the theory

“…Among the different measurement techniques included within the "AE" methods, the monitoring of mechanical vibrations using accelerometer transducers is currently receiving considerable attention (He et al, 2009;Leskinen et al, 2010;Wang et al, 2009;Wang et al, 2010). To monitor the performance of a specific fluidized bed application, these previous works typically used the accelerometers to gather knowledge on the so-called fluidization quality.…”

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

“…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 …”

“…Due to real‐time, on‐line, and environmental protection, acoustic emission (AE) technology has broad prospects for application. 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.…”

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

“…Various techniques including pressure/differential pressure, electrostatic, optical fibers have been developed to analyze fluctuation signals and identify flow regimes or characterize the hydrodynamics in gas‐solid flows. However, due to the complex nature of gas‐solid two phase flow systems and various origins of the signals, valuable and meaningful information is very hard to obtain . Li et al have stated that the complicated interactions between gas and solid phases at different scales of time and space are responsible for the complexity of gas‐solid two phase flow.…”