Study On Flow Field Analysis Of Ultrasonic Flowmeter And Flow Measurement Based On Guided Waves

As one of the most widely used measuring tools,ultrasonic flowmeter is widely used in gas and liquid flow measurement,and the demand is increasing these years.The parameter setting for commonly used ultrasonic flowmeter is based on ideal flow pattern.However in actual pipeline,the installation condition for ultrasonic flowmeter can not meet the requirement for ideal flow pattern,so the accuracy of ultrasonic flowmeter is seriously affected.Each year a large amount of manpower and material resource are needed for the installation and removal of ultrasonic flowmeter,therefore the exploration of a new on-line flow measurement method has become the focus of many countries.In this thesis the measurement performance of ultrasonic flowmeter,the adaptability for non-ideal flow measurement and the research for guide wave flow measurement method are studied.The main contents of the thesis are as follows:(1)The study of Fluent simulation of flow distribution in common pipeline conditions.The simulation of flow distribution in a single-bend pipe,double-bend pipe and non-coplane double-bend pipe is analyzed,and the bend pipes are installed upstream of DN80 ultrasonic flowmeter.The flow patterns at different sections of pipes at different inlet velocities are researched,especially for the velocity distribution of horizontal and vertical paths in different sections.Then the influence of different pipes on the measurement accuracy of ultrasonic flowmeter is discussed.(2)Experimental study on measurement stability of multi-phase flow for ultrasonic flowmeter.A special experimental platform is established to achieve the mixing of gas and liquid in the pipe thoroughly.Liquid pasting the pipe is weighed by standard device and then liquid weight is converted into volume value.Finally the volume value is set as a standard value to compare with the measurement result of different experimental UFMs.The adaptability and accuracy of UFMs in different flow conditions are measured by experiments.(3)Research of flow measurement in liquid-filled pipe based on guided longitudinal mode.The dispersion equation of guided longitudinal modes in the pipe filled with flowing liquid is established.The energy distribution of longitudinal modes in liquid-filled pipes at different frequencies is also analyzed by the combination of wave structure analysis.The propagation characteristics of longitudinal modes at different excitation frequencies are studied experimentally,in order to study the relationship between the propagation velocity of longitudinal mode in pipe and liquid flow velocity in pipe.All these works provide a new method for in-service flow measurement in the pipes filled with flowing liquid and theoretical support for the application of ultrasonic guided waves for flow measurement in pipes.