Research On The Adaptability Of Ultrasonic Flowmeter In The Non-ideal Flow Field

Ultrasonic flowmeter is gradually taking the place of the traditional flowmeter in the water industry, natural gas transportation and other fields for its unique advantages: non-contact measurement; its cost having little relation with its caliber; high-accuracy; wide range; convenient installation; simple operation etc.However, due to the limit of the installation space and cost, there is always no enough straight front and rear section in complex industrial measurement site, so the accuracy of ultrasonic flowmeter will be affected, which is the same problem that the traditional flowmeter faces.The essential cause of this problem is that ultrasonic flowmeter is designed according to the ideal flow. However, the flow fluid in where ultrasonic flowmeter is often used is not ideal. In order to improve the adaptability of the ultrasonic flowmeter in the non-ideal flow field, the following work has been done:(1) The experiments with AF878 ultrasonic flowmeter of General Electric Company have been performed in the water experimental apparatus of Tianjin University. The measurement performance of the ultrasonic flowmeter in different position downstream a single-elbow pipe is analyzed. The result shows that the ultrasonic flowmeter is affected seriously in the non-ideal flow field.(2) The three dimensional simulation model as the condition of experimental is established based on computational fluid dynamics (CFD) simulation method. The measurement performance of the ultrasonic flowmeter downstream a single-elbow pipe is studied based on CFD simulation method. Through the comparison, the simulated result resembles well the experimental data. So CFD simulation method can be used to study the flow field adaptability of ultrasonic flowmeter.(3) Based on CFD simulation method, the research is carried on to find out how the flow field adaptability of the single-path ultrasonic flowmeter is influenced by its path configuration. The results show that the flow field adaptability of ultrasonic flowmeter has no necessary relation to the length of path and the reflection number of the path; single "Triangle" path ultrasonic flowmeter can are well suited for non-ideal flow field. What’s more, ultrasonic flowmeter with double "Triangle" paths which are orthogonal to each other has a better flow field adaptability. (4) Based on CFD simulation method, the work is carried on to study how the flow field adaptability of the multi-path ultrasonic flowmeter is influenced by its numerical integration method and the path number. The result shows that the measurement errors of multi-path ultrasonic flowmeters based on either Gauss-Jacobi method or OWICS method is nearly same, when their path number is same. However, the flow field adaptability is greatly affected by path numbers: the more paths, the better adaptability it has.(5) Based on CFD simulation result, the study to analyze the change rule of the flow field downstream a single-elbow pipe is carried on. At the same time, three dimensional mathematical models of the flow field are established base on the technology of nonlinear least squares with Matlab software. Finally, through analysis and verification based on numerical calculation method, three dimensional flow field mathematical models can reflect well the actual flow field.