A STANDING-WAVE FLOW MEASUREMENT SYSTEM FOR SMALL-DIAMETER PIPES USING LONG ACOUSTIC-WAVES

An exploratory investigation, using laboratory fabricated acoustic com ponents, of standing-wave flow measurement techniques for liquids and gases in pipes of diameter up to about 25 mm was undertaken, using lon g acoustic waves. The results show a linear sensitivity based on the ' 'sing-around'' technique, often associated with contrapropagating time -of-flight flowmeters. A repeatability test at a volume flow rate of 1 .5 l per minute indicates that, within the 95% confidence limit, only 5% of the readings will lie outside the range of 1.1-1.9 l per minute. The transducer used in the above investigation comprises a section of the pipe wall which acts as part of a resonating transmitter or detec tor of long waves in a fluid. The measurement cell is closed and gener ates a known standing-wave pattern. The results obtained suggest that, in the future, the initial accuracy obtained in this study can be sig nificantly enhanced with further improvements to the transducers, the measurement cell, the electronics, and test procedures, on which work is continuing, to produce a device competitive with those using other technologies.