Analysis of the pressure fluctuation in the flow field of a large-scale cyclone separator

Flow field in a cyclone separator is not stable and show complex dynamic properties. Dynamic pressure signals were measured at different positions in a large-scale gas-solid cyclone separator such as the vortex finder, outer vortex and inner vortex, using a micro-differential pressure transmitter with different inlet gas velocities and inlet particle concentrations. Power spectral density (PSD) and fast Fourier transform (FFT) were used to analyze the characteristics of these dynamic pressure signals. The results showed that the PSD of the outer vortex was divided into two parts: part 1 in a low frequency region (0-n Hz) with high magnitude and part 2 in a high frequency region (n-50 Hz) with low magnitude. The dominant frequency region was related to outer vortex, and its range and magnitude increased with increased inlet gas velocity. There was a dominant frequency in the vortex finder of the cyclone separator, which was related to inner vortex rotation. The dominant frequency increased with increased inlet gas velocity and decreased with increased particle concentration. Using data processing methods, including an FFT filter and standard deviation, particle effects were found to be focused in lower frequency region parts, while the effects were not linearly depend on the particle concentration. Furthermore, there were special pressure transfer characteristics in the cyclone separator, which resulted in forming the pressure fluctuation. Through PSDs and the coherence analysis of the dynamic pressure in two positions in the vortex space of the cyclone separator, the outer vortex was found to induce a low frequency range pressure fluctuation with high magnitude and the inner vortex induced a new main frequency because of the periodically-rotating flow behavior. Considering the resonance phenomenon, the natural frequency of cyclone separator should be kept away from the frequency of pressure fluctuation, which concentrated below 50 Hz. (C) 2018 Published by Elsevier B.V.