Research On Measurement Model Of Wet Gas Using Z-gas Ultrasonic Flowmeter

Wet gas is widely present in the process of industrial production, including thewellhead produced gas, coal bed methane, wet saturated water vapor etc. The onlinenon-separation measurement technology of wet gas flow is not very mature, and thegoal of this paper is to improve the accuracy of wet gas flow online measurement.This study analyzes the over-reading generation mechanism and the real flowexperiment data. There gets wet gas flow measurement over-reading properties of theZ-gas ultrasonic flowmeter and the long throat venturi tube. The Z-gas ultrasonicflowmeter over-reading theoretical model expression is deduced. This paper uses theZ-gas ultrasonic flowmeter and the long throat venturi tube to measure wet gas. Themain research works of this dissertation are as follow:The wet gas flow measurement experiment using the Z-gas ultrasonic flowmeter.It analyses the pressure, superficial gas velocity and the L-M parameter on the virtualhigh impact. The conclusion is that the L-M parameter is the main influence factor ofthe over-reading, and it can be established over-reading prediction model based onvoid fraction. Through comparing with five over-reading prediction effect of differentvoid fraction models, this paper proposes the over-reading prediction model based onthe Armand-Massina model.Comparing of the study of Z and V gas ultrasonic flowmeter, the conclusion isthat when Z-gas ultrasonic flowmeter used for wet gas flow measurement, theover-reading is larger, and the measurement repeatability is better, and the maxsuitable quality liquid rate is about65%. The quality liquid rate less than50%, theprecision of over-reading prediction for V-gas ultrasonic flowmeter is higher. In thewet gas flow measurement, the over-reading prediction model of V-gas ultrasonicflowmeter is based on Spedding&Chen model, the prediction accuracy in rang of-2%to+3%. The over-reading prediction model of Z-gas ultrasonic flowmeter isbased on Armand-Massina model, and the average error value of over-readingprediction is4.30%, and the root mean square error of relative error is3.28%.The wet gas experiment is done using the long throat Venturi tube with structureoptimization. Analysing the effect between the superficial gas velocity and theover-reading, it establishes a corresponding over-reading model, according to thedifferent velocity range. Through the calculation of the model, the relative error of gas phase flow rate is in±5%. At last, the experiment is continued using the Z-gasultrasonic flowmeter and the long throat venturi tube. This study establishes acalculation model of gas phase flow according to the velocity range and a calculationmodel of liquid phase flow. The data is validated that the relative error of gas phaseflow measurement is in±4%, and the full scale error of liquid phase flowmeasurement is mainly distributed within±10%.