Principle and Design of Ultrasonic Flowmeter

Contents

The invention relates to an ultrasonic flow measuring device, comprising a measuring tube with a straight measuring tube axis, a transmitter for transmitting an acoustic signal on a first signal path, a receiver for receiving the acoustic signal on the first signal path and at least one first reflection surface, wherein in each case the acoustic signal on the first signal path is reflected at least once at the first reflection surface, wherein the acoustic signal incident on the first reflection surface and the acoustic signal reflected at the first reflection surface travel along a straight section of the first signal path.

Background of the Invention

Ultrasonic flow measuring devices are widely used in process and automation technology. They can easily determine the volume flow and/or mass flow in pipelines.

Known ultrasonic flow measuring devices usually work according to the travel time difference principle. The ultrasonic waves are generated by so-called ultrasonic transducers and are received accordingly. For this purpose, the ultrasonic transducers are firmly set in the wall of the relevant pipeline section. There are also clamp-on ultrasonic flow measuring systems. In this case, the ultrasonic transducer is pressed against the outside of the wall of the measuring tube. One of the great advantages of clamp-on ultrasonic flow measuring systems is that the ultrasonic flow measuring system does not come into contact with the measured medium and can be set on existing pipelines.

Multipath systems are also known, which have a plurality of ultrasonic transducer pairs, which in each case form a signal path along which the ultrasonic signal can pass through the measuring tube. In this case, the individual signal paths and the associated ultrasonic transducers are located in mutually parallel planes parallel to the measuring tube axis. The advantage of multipath systems is that they can measure the flow profile of the measured medium in the measuring tube at a plurality of locations and can therefore provide highly accurate measured values ​​for the flow. This can be obtained, among other things, based on the fact that each individual travel time along the different signal paths is weighted differently. However, a disadvantage in the case of multipath systems is their manufacturing costs, due to the need to use a plurality of ultrasonic transducers and, in certain cases, the need to use complex evaluation electronics.

Summary of the invention

The object of the present invention is to provide an ultrasonic flow measurement device which can ensure high-precision flow and effectively reduce manufacturing costs.

The ultrasonic flow measurement device of the present invention comprises a measuring tube for flow measurement having a straight measuring tube axis, at least one first transmitter for sending an acoustic signal on a first signal path, at least one first receiver for receiving the acoustic signal on the first signal path, and at least one first reflection surface, wherein the transmitter, the receiver and the first reflection surface are oriented relative to each other and are arranged in or on the measuring tube so that the acoustic signal on the first signal path from the first transmitter to the first receiver is reflected on the first reflection surface, so that the sum of all lengths of all first segments of the first signal path extending in a first plane parallel to the measuring tube axis and having a non-zero predetermined first spacing from the measuring tube axis projected onto the measuring tube axis has a non-zero predetermined first value, and wherein the sum of all lengths of all second segments of the first signal path extending in a second plane parallel to the measuring tube axis and different from the first plane and having the first spacing from the measuring tube axis projected onto the measuring tube axis has a predetermined first value, wherein the first plane extends in a first half of the measuring tube, and the second plane extends in a second half of the measuring tube, wherein the first half of the measuring tube, more precisely the first plane of the first half, and the second half, more precisely the second plane of the second half of the measuring tube, do not overlap.

In an embodiment of the invention, the transmitter is adapted for receiving an acoustic signal on a first signal path, and the receiver is adapted for sending an acoustic signal on the first signal path. Both the transmitter and the receiver are ultrasonic transducers, in particular ultrasonic transducers having an electromechanical transducer element, such as a piezoelectric transducer element.

At the same time, the acoustic signal is emitted perpendicularly to the membrane of the first ultrasonic transducer as a transmitter and is received perpendicularly to the membrane of the second ultrasonic transducer as a receiver, wherein the two ultrasonic transducers are oriented relative to the reflection surface so that the acoustic signal can be reflected on the reflection surface to the second ultrasonic transducer.

In a first embodiment of the invention, the measuring tube has an elliptical, in particular circular, cross section, wherein the measuring tube axis can also be referred to as main axis, center axis or longitudinal axis. The main flow direction of the medium in the measuring tube coincides with the measuring tube axis.

In another embodiment, the size of the measuring tube is a multiple of the size of the ultrasonic transducer or the transmitter and/or the receiver. Thus, in the case of a circular measuring tube and a disc-shaped transmitter and/or receiver, the diameter of the measuring tube is at least twice, in particular five times, in particular at least ten times, the diameter of the disc of the transmitter and/or receiver. If the measuring tube has, for example, an angular cross section, in particular a rectangular cross section, in particular a square cross section, and/or the ultrasonic transducer as the transmitter and/or receiver has some different shape, for example, the same rectangle, then the surface area of ​​the cross section of the measuring tube lumen is at least four times, or even at least twenty-five times, or even at least a hundred times, the surface area of ​​the ultrasonic transducer.

In other embodiments of the invention, the first reflection surface and/or all other reflection surfaces in or on the measuring tube are arranged relative to the transmitter and the receiver such that the first plane and the second plane intersect a line extending parallel to the measuring tube axis.