Flow rates measurement of air-water slug flow based on dual differential pressures

The flow structure of slug flow is unstable in time and space, leading to large fluctuations in its differential pressure, which affects the accuracy of flow rates measurement. A new method for measuring flow rates of slug flow using a swirler and a Venturi tube is proposed. A new measurement correlation for gas-liquid flow rates is established by introducing the liquid correction coefficient θ_s and gas correction coefficient θ_g, which is used to calculate the water volume fraction or the gas-liquid total volumetric flow rate. When the gas-liquid total volumetric flow rate is known, the prediction error of water volume fraction is less than ± 2. The cyclone transforms the complex flow into a regular gas-liquid annular flow, which not only broadens the gas phase flow measurement range but also improves the flow measurement accuracy. The ratio of axial differential pressure to radial differential pressure δ is introduced to establish the water volume fraction prediction model, and its relative error is less than ± 15. The measurement of the gas-liquid total volume flow rate is achieved by combining the prediction model of water volume fraction with the flow rate measurement correlation, resulting in a relative error of less than ± 12.