Research On Wet-gas Flowrate Measurement Method Based On A Combined Ultrasonic Measuring Technology

With the development of industry,people’s demand for non-separating measurement of wet-gas is getting higher and higher.Since the non-separating measurement methods of wet-gas are only mastered by a few companies in the world and are not disclosed as the trade secrets,therefore,a new combined wet-gas flowrate non-separating measurement method based on the ultrasonic measuring technology is proposed in this paper.The research contents are mainly carried out in the following aspects:In terms of the measuring principle and measuring system,a new combined wet-gas flowrate non-separating measurement method is proposed based on the traditional ultrasonic gas flowmeter and the ultrasonic liquid film thickness measurement technology.The principle and feasibility of this method are analyzed.Based on this combined method,a wet-gas flowrate non-separating measurement system has been designed and built,including the tube and probe section,the hardware circuit section and the data acquisition section.By designing these sections,the wet-gas flowrate measurement system can work well over a wide range of wet-gas measurement conditions.In terms of the gas velocity calculation,the traditional ultrasonic receiving signal processing method is no longer suitable in the wet-gas measurement,therefore,the gas ultrasonic receiving signals under various operating conditions are analyzed and studied in this article.A new gas ultrasonic receiving signal processing method based on the DBscan clustering algorithm which are suitable for wet-gas measurement is proposed.The repeatability and reliability of this method have been verified by three real-flow experiments.In terms of the void fraction calculation,in order to make up for the deficiency of the traditional void fraction calculation model based on the liquid film thickness,including the plane model,the double-ring model and so on,the distribution of liquid film thickness in the horizontal pipes have been studied.Based on the liquid film thickness data measured under various operating conditions in real-flow experiments,a new void fraction calculation model for the stratified wavy flow and annular flow conditions is proposed: The Closed Curve Model.The reproducibility and reliability of this model have been verified by three real-flow experiments.Based on the calculation results of gas velocity and void fraction introduced above,the wet-gas flowrate measurement values under various operating conditions in the real-flow experiments are calculated.A correction formula for the wet-gas flowrate measurement values has been established.By correcting the wet-gas flowrate measurement values under each operating condition in the three real-flow experiments using the above correction formula,the measurement errors of wet-gas flowrate measurement values are all kept within 8%,besides,the repeatability of the wet-gas flowrate measurement values under all operating conditions are kept within 0.75%.Different wet-gas flowrate measurement methods have been compared,it shows that the combined wet-gas flowrate measurement method based on the ultrasonic measuring technology proposed in this paper can basically reach the international advanced measurement level and is an ideal wet-gas flowrate measurement method.