Characterization of fluidization regimes and their transition in gas-solid fluidization by Hilbert-Huang transform

It is common to characterize fluidized bed dynamics using spectral analysis and non-linear methods such as correlation entropy (Kolmogorov entropy). In this paper, an alternative method, the Hilbert-Huang transform, HHT, a non-linear and non-stationary time series data analysis method is applied to experimental data from two independent setups from the literature, a circulating fluidized bed, CFB and bubbling fluidized bed, BFB. Characterization of four representative regimes for the CFB is realized with the Hilbert spectral analysis, HSA. It is also shown in this work that an entropy based on the HHT is capable of reproducing the flow regime boundaries previously identified using other methods. Linear relationships are observed between the HHT entropy, power spectral density, PSD and average cycle frequency. Likewise for the BFB, the HHT entropy captured the regime change from slugging to turbulent fluidization.