Study On Gas Ultrasonic Flowmeter Based On Component Compensation

As a new type of flowmeter,the gas ultrasonic flowmeter has many advantages like noncontract,high-precision and widely applicable,so it was used in the measurement of various gas flows extensively.In contrast with traditional flow meters,ultrasonic flow meters has certain advantages in terms of measurement accuracy,but there are still some problems that need to be solved,so the research on gas ultrasonic flow meters was of great significance.Based on the measurement principle of the time-difference method,this paper analyzed the influence of different components on the flowmeter measurement,proposed a flow coefficient correction based on component compensation,and completed the development of a DN100 four-channel gas ultrasonic flowmeter.First,by analyzing the physical characteristics of the mixed gas in the pipeline,the influence of different components of the gas on the flow state of the flow field was studied.The physical model of the DN100 four-channel gas ultrasonic flowmeter and its pipeline was established using ICEM CFD.Fluent calculation software was used for numerical simulation to simulate the flow state of the fluid in the pipeline,under the circumstance of air medium and the natural gas medium.The flow field velocity distribution state of different gas components at different flow points were obtained through CFD numerical simulation calculation.And the flow coefficient k at different flow rates of different components was used to compensate the flow measurement of the ultrasonic flowmeter.Second,the design of the hardware circuit and software program of the DN100 fourchannel gas ultrasonic flowmeter prototype has been completed.In the hardware,MSP430FR6047 has came into use as the main control chip,to complete the design of not only the system power circuit,transducer excitation circuit,channel switching circuit,isolation circuit,but also the design of signal conditioning circuit,temperature measurement circuit,pressure measurement circuit and human-computer interaction circuit.As for software,the modular programming idea was adopted to complete the software design of the four-channel ultrasonic flowmeter system.The next was to study the temperature and pressure compensation of multi-component mixed gas and complete the mutual conversion between working condition flow rate and standard condition flow rate.The high-precision AGA8-92 DC compression factor calculation method was adopted,and the temperament parameters of the multi-component mixed gas were analyzed to realize temperature and pressure compensation.Finally,the DN100 four-channel gas ultrasonic flowmeter prototype was verified.In the low zone flow range,the maximum indication error was 1.21%,and the repeatability was 0.125.And the maximum indication error was 0.86%,the repeatability was 0.058 in the high zone flow range.The performance of the prototype fit the bill of the 1.0-level instrument.