A new approach to detection of vortices using ultrasound |
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| Affiliation: | 1. Faculty of Electrical Engineering, University of Sarajevo, 71000 Sarajevo, Bosnia and Herzegovina;2. Institute of metrology of Bosnia and Herzegovina, 71000 Sarajevo, Bosnia and Herzegovina;1. Department of Mining and Nuclear Engineering, Missouri University of Science and Technology, Fulton Hall, 310 W. 14th Street, Rolla, MO 65409, USA;2. Department of Chemical and Biochemical Engineering, Missouri University of Science and Technology, 110 Bertelsmeyer Hall, 1101 N. State Street, Rolla, MO 65409, USA;3. Leading Edge Non Destructive Testing Technology (LENDT) Group, Industrial Technology Division, Malaysian Nuclear Agency, Bangi, 43000, Kajang, Selangor D.E., Malaysia;1. Chair of Measurement and Sensor System Techniques, Faculty of Electrical and Computer Engineering, Technische Universität Dresden, 01062 Dresden, Germany;2. SolarWorld Innovations GmbH, Berthelsdorfer Str. 111A, 09599 Freiberg, Germany;3. Institute for Nonferrous Metallurgy and Purest Materials, TU Bergakademie Freiberg, Leipziger Str. 34, 09599 Freiberg, Germany;1. Faculty of Engineering, Hokkaido University, N13W8, Sapporo 060-8628, Japan;2. Institute of Food, Nutrition and Health, ETH Zürich, 8092 Zürich, Switzerland |
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| Abstract: | The measurement principle of vortex flowmeter is based on von Karman vortex shedding phenomenon. Frequency of vortices, behind the bluff body, is proportional to the mean flow velocity. There are different ways of detection of vortices, and different sensors are used (presser sensors, capacitive sensors, thermo-resistance sensors, ultrasonic sensors, etc.). Proposed method to vortex identification, presented in this paper is based on simultaneous detection of pair of vortices with opposite circulation, by means of two pairs of ultrasonic transducers. A beam of ultrasound, from ultrasonic transmitter to ultrasonic receiver is transmitted perpendicularly to the vortex street. The received ultrasonic signal is amplitude and phase modulated. Frequency of demodulated signal is equal to the frequency of vortices. This technique allows a number of advantages comparing to conventional solutions: reduction, or elimination of noises caused by installation vibration and disturbances in the flow, higher sensor sensitivity, which as a result leads to a possibility of a reduction of the bluff body size, i.e. reduction of the pressure drop on the flow meter, increase of the measurement range in the low flow region, the possibility of redundant operation of the flow meter, reduced measurement uncertainty, instrument technology improvements, improved reliability of the instrument, assured improved statement of complete uncertainty contributions, improved metrology of the equipment as such and calibration procedures that contribute to measuring capabilities etc. For experimental testing a prototype vortex flowmeter of a nominal inner diameter (ID) 50 mm is developed. A cylindrical bluff body for vortex shedding is used. Ultrasonic transducers based on piezo-crystal PZT-5A, inserted in the wall of the vortex meter casing are utilized. The testing of prototype ultrasonic vortex flowmeter is realized on the calibration station on the water. The results at the testing point to the possibility of measuring flow of liquid fluids at velocities less than 0.5 m/s, with an uncertainty better than ±1%. |
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| Keywords: | Vortex shedding Bluff body Ultrasonic wave Amplitude and phase modulation |
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