Signal and Performance Analysis of a Vortex Flowmeter

• Main Authors: Yeh-Chieh Feng, 葉建鋒
• Other Authors: Miau-Jiun Jih
• Format: Others
• Language: zh-TW
• Published: 2003
• Online Access: http://ndltd.ncl.edu.tw/handle/46207115360788462047

碩士 === 國立成功大學 === 航空太空工程學系碩博士班 === 91 === In the present study, two T-shaped vortex flowmeters fabricated in laboratory were employed for testing in a gas flow calibration facility and a water pipe flow, respectively. The main purpose was to obtain the uncertainty of the vortex flowmeter in pipe flow measurement. In order to reduce the vortex shedding frequency from the signal obtained, the techniques of FFT and autocorrelation were employed. The calibration curve of St-Red and its corresponding uncertainty were then calculated. On the other hand, the calibration curve of K-Red was also obtained in this study, where K is denoted as the meter factor. A gas vortex flowneter were calibrated using a standard flow measurement system in the Flow Measurement Laboratory, ASTRC NCKU. The velocity range calibrated is from 12.72 to 77.6m/sec, equivalent to a Reynolds number range of 2.56×104 ~ 1.56×105. By using FFT to reduce the vortex frequency, the uncertainty associated with the St-Red curve is ±0.745% and the linearity of the curve is ±1.777%. On the other hand, the uncertainty associated with the K-Red curve obtained is ±0.568﹪and the linearity is ±1.89%. A liquid vortex flowneter was tested in a fully developed pipe flow system in the Department of Aeronautics and Astronautics, NCKU. The velocity range is from 0.446 to 4.5m/sec, equivalent to a Reynolds number range of 5.6×103 ~ 5.29×104. By combining the techniques of FFT and autocorrelation to calculate the vortex frequency, the uncertainty associated with the St-Red curve reduced is ±0.802% and the linearity of the curve is ±0.391%. The T-shaped vortex flowmeters mentioned above have a splitter plate of length equal to 2d. By changing the length of the plate from 2d to 1.56d, the uncertainty of the St-Red curve obtained in the water pipe flow facility is ±0.376% and the linearity is ±0.963%, indicating that the length of the splitter plate affects the total uncertainty and the linearity.