Relationship between pneumatic conveying flow regimes and acoustic signals based on DWT and HHT analysis

To clarify the relationship between flow regimes and acoustic signals in pneumatic conveying, the acoustic signal of pneumatic conveying process was non-intrusively collected. Frequency and energy characteristics of acoustic signals were analyzed by using the discrete wavelet transform (DWT) and the Hilbert-Huang transform (HHT) to reveal the flow regime transformation during pneumatic conveying. Results show that the effective acoustic signal of pneumatic conveying is mainly concentrated in the region of 0 to 37.5 Hz, and the amplitude of the acoustic signal is positively correlated with the discharge pressure. The flow regime changes from plug flow to dune flow and suspended flow with the increase in acoustic signal amplitude in. The summarized Hilbert spectrum energy of the acoustic signal during the steady conveying stage is mainly concentrated in the range of 0 to 20 Hz. The energy of the Intrinsic Mode Function (IMF) components shows a trend of first decreasing and then increasing with the discharge pressure, which corresponds to plug flow, dune flow, and suspended flow regimes, respectively.