Flow regime identification in gas-solid two-phase fluidization via acoustic emission technique

Abstract

To explore flow regime transition processes in gas-solid two-phase fluidization, a non-intrusive, real-time and environment-friendly acoustic emission technique and an auxiliary pressure fluctuation method were applied in this work. Particle activity and collision intensity in the bed are obtained through standard deviation analysis. On that basis, it is found that the acoustic signal measurements can more effectively reflect the transition velocities among major flow regimes, including uc (from bubbling to turbulent fluidization), uk (from turbulent to fast fluidization), and uFD (from fast fluidization to dense phase pneumatic conveying). Meanwhile, the multi-scale resolution of acoustic signals during regime transitions can be obtained through Hurst and wavelet analyses. To be specific, micro-scale signals reflect the inter-particle collision and the particle-wall collision, meso-scale signals indicate the interactions and behaviors of particle clusters and gas phase, and macro-scale signals represent the average flow behavior. According to the comparison of experimental results, the experimental values of transition velocities obtained from acoustic signal measurement are closer to corresponding empirical values. In other words, the integration of standard deviation and multi-scale analyses with acoustic signal measurement can effectively identify flow regime transitions in real-time.