A method for measuring and correcting the cross-section phase holdup of gas-liquid two-phase annular flow in a circular pipe

Abstract

The invention discloses a method for measuring and correcting gas-liquid phase annular flow cross-section phase content in a circular pipe. The method includes the following steps: 1) performing shooting on gas-liquid phase annular flow in a circular pipe through a combination of a photography device (1) and a light source (3) to obtain a grey-scale map containing a liquid film and a gas core; 2)performing digital image processing on the grey-scale map so that a binarized image containing the liquid film and the gas core can be obtained; 3) calculating the percentage of the number of white pixels to the total number of black and white pixels in the binarized image to obtain a liquid film phase content imaging value alpha <1, imaging>; 4) establishing a theoretical model of the quantitative relation of prediction of tube wall thickness and the liquid film phase content imaging value and a true value; 5) performing correcting on the liquid film phase content imaging value alpha <1, imaging> by utilizing the liquid film phase content optical imaging theoretical model established by step 4) to obtain a liquid film phase content true value alpha <1, true>; and 6) obtaining a gas core phase content true value alpha <g, true> by subtracting the liquid film phase content true value alpha <1, true> from 1. The method can realize non-intrusive and highly accurate detection of the gas-liquid phase annular flow cross-section phase content in the circular pipe.

Description

technical field [0001] The invention belongs to the technical field of gas-liquid two-phase annular flow parameter measurement, and in particular relates to a method for measuring and correcting phase holdup of a gas-liquid two-phase annular flow section in a circular pipe. Background technique [0002] Gas-liquid two-phase annular flow is an important and widely used two-phase flow in the engineering field. The annular flow in the pipe is mainly composed of the liquid film on the pipe wall and the central mist-like high-speed gas core. In the annular flow, there is a strong mass, momentum and energy transfer between the liquid film on the pipe wall and the gas core. Accurate measurement of the gas-liquid phase holdup is not only the basis for obtaining parameters such as gas-liquid phase separation velocity and flow rate, but also for the in-depth study of the annular flow. The flow and heat transfer properties of the stream play an important role. According to different m...

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Problems solved by technology

The quick-closing valve method approximately replaces the cross-section phase holdup by measuring the volume phase holdup, which is mainly used for the calibration of the measuring device and cannot meet the requirements of real-time and on-line measurement

The conductometric method is simple, reliable, and low in cost, but it is only suitable for the measurement of conductive liquids. The intrusion of the conductometric probe into the fluid will also cause certain interference to the flow field, resulting in measurement deviations

The optical method has high measurement accuracy, but the optical measurement equipment is generally expensive, the operation process is complicated, and there are strict requirements on the cleanliness of the measured medium and the application environment

In addition, the data measured by the quick-closing valve method, conductivity method, and optical method are mostly single-point, constant or timed average values, which cannot measure the instantaneous phase holdup distribution on the entire flow section.

Process tomography has the advantages of non-invasive measurement, but because the feedback signal of tomography is greatly affected by the phase distribution, and the measurement results are highly dependent on the accuracy of the image reconstruction algorithm, it can only be used in the measurement range with low gas content. Guaranteed measurement results

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