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

Abstract

In the annular gap bubble bed of the scrubbingcooling chamber, the instantaneous signals of local gas holdup and axial liquid velocity were measured using a conductivity probe and a pitot tube under different bubble-breaking plate installation conditions. The detailed information contained in the axial liquid velocity signals was obtained by time-domain analysis ((temporal distribution, skewness, kurtosis), frequency−domain analysis (power spectral density), and time−frequency−domain analysis (short-time Fourier transform, wavelet analysis). The results showed that the local axial liquid velocity has certain temporal nonsmoothness and spatial nonuniformity; liquid phase fluctuations, vortex structure, and bubble aggregation lead to the dominant role of liquid velocity fluctuations in the low-frequency range. The bubble-breaking effect of the bubble-breaking plate contributes to the enhancement of the smoothness and uniformity of the axial liquid velocity distribution, as well as to the attenuation of the power spectrum density, the reduction of 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 is the best-performing bubble-breaking plate installation.