Study On Phase Volume Fraction Detection Of Gas-liquid Two-phase Flow Based On Near-infrared Absorbance Feature

In recent years, with the continuous development of the oil industry and the increase inenergy, multiphase flow measurement techniques without separation become more and moreimportant. The phase holdup measurement of multiphase flow is of great significance forsingle-phase flow measurement, process control, as well as the operating reliability ofproduction equipment.Compared with other fields such as food where the near-infrared spectral absorptioncharacteristics are used maturely, for the multiphase flow, its application is still relativelyweak. Near-infrared light which has characteristic both of ray method and optical method, isnot visible, can penetrate plexiglass tubes and fluid. The absorption coefficient of water isdifferent with that of gas, as a result, under certain wavelength it can distinguish liquid phaseand gas phase in gas-liquid two-phase flow. Meanwhile, the near-infrared light is sosignificantly affected by the gas-liquid interface that it can reflect the fluctuations of thegas-liquid interface very well. For different holdup, the cross-section occupied by two phasesis different, and the attenuation intensity of the near-infrared is also different. What’s more,some tiny bubbles can strongly affect the attenuation intensity, directly leading detectionresult.The paper analyzed the near-infrared permeability of plexiglass and water in static stateon the near-infrared spectral scanning device, and found three wavelength bands suit theexperiment:960nm~1000nm,1220nm~1330nm,1500nm~1600nm. Besides, combined withoptical probes dynamic experiments are explored on the multiphase flow experiment platform,discovering that the difference between different flow patterns and different aqueous phasevolume fraction is very obvious, which laid the foundation for the single-wavelength probeschoice. At last, the probes’ wavelength is determined970nm and1550nm.Based on the static experiment on the plexiglass tube section, the relationship of waterthickness and measured voltage value of optical fiber intensity under corresponding probe isdetermined, fully comply with Lambert-Beer law. Through the experiment, we found that the 1550nm detector is much more suitable for the aqueous layer thickness less than10mm. Theaqueous phase volume fraction can finally estimated by the aqueous thickness, measuredvoltage value.Compared the aqueous phase volume fraction of calculated value and the actual valueabout the18operating conditions under slug flow and bubbly flow, we found the averagevalue can be used only. The measured error in slug flow conditions is less than60%, and thatin bubbly flow conditions is less than10%, improving the accuracy and operation is muchmore convenient.