Pressure Fluctuations in Pneumatic Conveying Systems

There exist a direct relationship between the flow patterns and the power spectral density function of the static wall pressure fluctuations and the differential pressure fluctuations. The probability density function was found to be helpful in distinguishing between oscillatory and non-oscillatory flow. In general, the frequency domain analysis was more useful in the classification of the flow patterns than the amplitude domain analysis. The choice of the sampling frequency and the record length is critical for accurate analysis of the signals. For homogeneous flow conditions, the shape of the power spectrum of the pressure fluctuations from the various taps is the same; however, small frequency shifts are observed. For degenerate dune flow, the shapes of the spectrums can be quite different but the total power in the lower frequency ranges is identical. For regular dune flow, the same spectrum is obtained regardless of the tap location. Both static and differential pressure fluctuations could be uniquely identified with the flow patterns, however, their relative performance is not the same over the entire range of the operating conditions. Static pressure transducers were found to detect homogeneous and stratified flows much better.