Open Channel Flow Measurement Using an Electromagnetic Submersible Flowmeter

The purpose of the article was to develop and verify a method for measuring flow rate in open channels using an immersion electromagnetic flow meter (EPZ) and an ultrasonic probe. The proposed solution is based on the use of classic submersible electromagnetic flow meters of the Promag W 400 type, originally designed for closed pipelines. The key element of the method is the location of the EPZ at the point of the open channel with the average flow velocity, determined empirically by the mill method. The measurement is complemented by ultrasonic measurement of the height of the liquid mirror, allowing the determination of the cross-sectional area of the flow. A calculation algorithm was developed to determine the total flow based on the local measurement and correction factors. Tests carried out at a municipal wastewater treatment plant showed that the developed method makes it possible to achieve a measurement accuracy of 5% relative to the mill method. In addition, the possibility of increasing the accuracy of flow measurement by increasing the homogeneity of the flow velocity field with the help of channel tapers or appropriate shaping of the measurement section was indicated. The presented solution is a practical and economical alternative to conventional methods of flow measurement in open channels, while allowing full calibration of the device.