Gas–liquid two-phase flowrate measurement in pseudo-slug flow with Venturi

The importance of pseudo-slug flow research is becoming increasingly prominent in the petrochemical field. But the gas–liquid two-phase flowrate measurement in the pseudo-slug flow has not been properly understood and modeled. Based on the differential pressure of Venturi, this study proposes a new pseudo-slug flowrate prediction model. By means of Fast Fourier transform (FFT), the representative frequency range (3.125 Hz < f < 6.25 Hz) is determined. Then, the fourth detail component of the differential pressure after wavelet transform is selected as the flag to distinguish the liquid film region and the pseudo-slug body region. Based on the gas–liquid density ratio, a logarithmic model is established to predict the threshold value. In the liquid film region, the gas–liquid two-phase flow is regarded as wet gas and the flowrate is measured through the over-reading model. In the pseudo-slug body region, the volume gas holdup model is established based on the fluctuation information of the differential pressure. Then the gas–liquid two-phase flowrate can be obtained by solving the Bernoulli equation. Compared to the experiment, the confidence probability of ±10% relative deviation band is 97.78% for the gas, and the confidence probability of ±20% relative deviation band is 95% for the liquid.