Time Domain, Frequency Domain, and Time-Frequency Domain Analysis of Axial Liquid Velocity Signals under the Influence of Internal Components

In the annular gap bubble bed of the scrubbing-coolingchamber,the instantaneous signals of local gas holdup and axial liquid velocitywere measured using a conductivity probe and a pitot tube under differentbubble-breaking plate installation conditions. The detailed informationcontained in the axial liquid velocity signals was obtained by time-domainanalysis ((temporal distribution, skewness, kurtosis), frequency-domainanalysis (power spectral density), and time-frequency-domainanalysis (short-time Fourier transform, wavelet analysis). The resultsshowed that the local axial liquid velocity has certain temporal nonsmoothnessand spatial nonuniformity; liquid phase fluctuations, vortex structure,and bubble aggregation lead to the dominant role of liquid velocityfluctuations in the low-frequency range. The bubble-breaking effectof the bubble-breaking plate contributes to the enhancement of thesmoothness and uniformity of the axial liquid velocity distribution,as well as to the attenuation of the power spectrum density, the reductionof low-frequency fluctuations, the enhancement of high-frequency fluctuations,the local dynamic complexity, the weakening of coherent vortex structure,and the intensity of the turbulence. Staggering the two plates isthe best-performing bubble-breaking plate installation.