抄録
We propose a new method for a clamp-on ultrasonic flowmeter.
A conventional clamp-on ultrasonic flowmeter has a problem that the determination of transit path of ultrasonic waves is complex, because there is a pipe wall on the transit path. In this paper, this problem is studied by a spatial frequency analysis. It is found that the transit path depends on the conditions of incident waves; frequency, incident angle and beam width. It is also found that especially plate mode excitation affects the transit path seriously, and that a wide beam would be very effective in reducing the effect due to the plate mode excitation.
According to the above mentioned result, we propose a new idea of “wide beam model” for determining the transit path, and a new method for an ultrasonic flowmeter employing a wide beam. Some experiments are carried out to confirm that the transit path can be estimated exactly by this new model. The wide beam ultrasonic flowmeter provides a measurement with high accuracy, even if temperature changes in transit path would occur. This new flowmeter can be applied to any fluids whose sound velocities are unknown.
