[3A2] Clamp-on guided wave flow metering
L Smith¹, Z Li² and S Dixon¹
¹University of Warwick, UK
²Harbin Institute of Technology, China
Clamp-on ultrasonic transit time difference flow meters are very useful when it is undesirable to cut into an existing pipeline to install a flow meter. However, the small-diameter thin-walled pipes commonly used in domestic water supplies support ultrasonic guided wave modes that complicate the received signal when compared to measurements on larger-diameter and thicker-walled pipes. In this research, it is shown that the guided waves can be used for high accuracy flow metering, yielding excellent performance even down to very low flow rates as low as 2 ml per second. Recent work on the optimisation of the technique is presented, which utilises a focusing transducer design to suppress unwanted guided wave modes. It is found that although the unwanted modes appear to be suppressed, the new design does not necessarily provide better flow measurement performance. Instead, factors external to the transducer design dominate measurement accuracy, masking any benefit of the focusing transducers. The factors identified to dominate the flow measurement performance are the subject of ongoing research.
