Flow measurement based on the combination of swirler and differential pressure under slug flow

Abstract

The alternating appearance of elongated bubbles and liquid slugs of slug flow in the pipe causes severe pressure fluctuation. As a result, measuring the flow rate of the slug flow with the throttling unit based differential pressure method is difficult. This paper investigates a new swirler-based flow measurement method in slug flow. The swirler converts the slug flow into a swirling annular flow, and the differential pressure method is used to measure the flow rate. The influences of gas and liquid flow rates on the differential pressure ΔPX across the swirler as well as its downstream axial differential pressure ΔPZ are investigated. ΔPX0.5 increases linearly as the liquid mass flow rate increases, and the slope of the curve increases as the gas mass flow rate increases. The influence of gas mass flow rate on ΔPX0.5 is comparable to that of liquid mass flow rate on ΔPX0.5. ΔPZ0.5 increases linearly with increasing gas/liquid mass flow rate, and the slope of the curve of ΔPZ0.5 with ml differs slightly from the slope of the curve in single-phase water conditions. Based on the research presented above, new empirical correlations of mass flow rate based on ΔPX and ΔPZ are established respectively. The superficial liquid velocity ranges from 0.6 to 2 m per second, while the superficial gas velocity ranges from 2 to 6 m per second. If the gas mass flow rate and ΔPX are known, the relative error of liquid mass flow is less than 3%. The relative error of the gas mass flow rate is less than 10% if the liquid mass flow rate and ΔPX are given. The calculation accuracy of the flow measurement model using ΔPX is better than the calculation accuracy of the flow measurement model using ΔPZ.