JPH0456246B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel method of vortex detection in a vortex flowmeter.

BACKGROUND ART Conventionally, as one of the vortex detection methods for a vortex flowmeter, a method has been proposed in which a flow hole passing through both sides of a vortex generator is detected as a displacement of a flowing fluid based on a fluctuating differential pressure caused by a vortex.

However, in this method, since the flow holes penetrate both sides of the vortex generator, the vortex strength becomes weaker, and as a result, the Strouhal number changes. In other words, the instrumental error characteristics of the flowmeter change depending on the size of the flow hole, and furthermore, this results in a decrease in accuracy.

The present invention has been made in view of the above points, and the purpose of the present invention is to increase the vortex strength in a vortex flow meter. By drilling a through hole that communicates with the fluid only on one side of the generator and detecting the fluid fluctuation of the compressible fluid flowing into and out of this cavity by the vortex fluctuation differential pressure, it is possible to detect the flow through the vortex generator. do not have,
The purpose is to detect stable eddy signals.

This will be explained below using figures.

Figure 1 shows the concept of the basic technology of the present invention. ○A is a plan view, 1 is a flow tube, 2 is a vortex generator, and 3 is a hole bored parallel to the axis of the vortex generator. chamber, which penetrates the vortex generator. 4 penetrates the vortex generator from the side near one end of the vortex generator to form the empty chamber 3
This is a conduction hole that communicates with the Reference numerals 5 and 6 denote an ultrasonic transmitter and an ultrasonic receiver, which are disposed at the end of the vortex generator to face each other with a cavity 3 interposed therebetween. coupled to the device. Although the through hole 4 is opened in the side surface near one end of the vortex generating body in FIG. To explain the operation with reference to the figures above, the alternating vortices generated by the vortex generator disposed in the fluid flow generate an alternating differential pressure corresponding to the vortex generation on the side surface of the vortex generator. The vortex generated by the vortex generator is generated along with the vortex generator. Therefore, there is a pressure difference between the left and right sides of the vortex generating body 2 in the front view ◯◯ of FIG.

The pressure within the chamber 3 is the static pressure of the fluid when there is no flow, but the eddy fluctuation differential pressure is added via the through hole 4 when the fluid is flowing. When the fluid is a gas, it is compressed and expanded due to this fluctuating pressure difference, causing fluid displacement within the cavity 3 and a change in density. The ultrasonic wave transmitted from the ultrasonic wave transmitter 5 is affected by the propagation speed due to fluid displacement and density change. That is, a phase change occurs.

If the conduction hole 4 is located at the center of the vortex generator, the fluid displacements will cancel each other out with respect to the ultrasonic wave transmitter 5, but a change in density will occur, resulting in a phase change. Furthermore, even if the conduction hole 4 is located on the opposite side of the ultrasonic transmitter 5, that is, on the side of the ultrasonic receiver 6 in Fig. Phase changes occur because the influences are different.

Looking at the modulation of the ultrasonic propagation velocity based on density changes as described above, it is clear that not only one but a plurality of through holes 4 may be opened on one side of the vortex generator.

FIG. 2 shows a case where this idea is expanded, and in order to obtain the same effect by opening a plurality of through holes 4 in succession, the through holes 4 are made into slits communicating with the empty chamber 3. According to this method, it is possible to eliminate the problem that the communication port is blocked by dust or mist flowing into the empty chamber 3 through the communication port 4. Although it has been described above that the vortex is detected as a phase change based on a change in ultrasonic propagation velocity as a fluid displacement and a density change due to the fluid displacement, any method that can detect these state quantity changes may be used.

As described above, according to the present invention, a stable vortex flow can be obtained, and therefore highly accurate measurement can be performed. In addition, since it detects fluid fluctuations such as fluid displacement and density changes introduced into the vortex generator from one side of the vortex generator, the detection element can be configured integrally with the vortex generator, and since fluid fluctuations are detected, piping It is not affected by external vibrations such as the vibrations of Therefore, it is possible to provide an inexpensive, lightweight, and highly accurate vortex flowmeter without reducing the accuracy of the flowmeter.

[Brief explanation of the drawing]

Figure 1 is a diagram explaining the principle of the present invention, where ○A is a plan view of the flow in the direction of the arrow, and ○B is the AA of diagram ○A.
FIG. FIG. 2 shows another embodiment of the invention,
○A is a plan view, and ○B is a BB sectional view of Figure ○A. still,
Common numbers indicate the same numbers in both Figures 1 and 2. 1...flow tube, 2...vortex generator, 3...empty chamber, 4
...Conduction hole, 5, 6...Ultrasonic transducer, 7...
Slits.

Claims (1)

[Claims] 1. In a vortex flow meter that utilizes the fact that the vortex frequency generated from a vortex generator disposed in a flow tube opposite to the flow is proportional to the flow rate, the vortex generator A cavity parallel to the axis of the body is bored, a conduction hole is provided only on one side of the vortex generating body, and the conduction hole and the cavity are communicated with each other to detect periodic pressure fluctuations due to the generation of vortices in the fluid to be measured. A vortex flow meter characterized by detecting fluctuations in fluid flowing into and out of the chamber. 2. The vortex flowmeter according to claim 1, wherein a plurality of said through holes are provided in parallel to the axis of the vortex generator. 3. The vortex flowmeter according to claim 1, wherein the through hole is a slit hole parallel to the axis of the vortex generator. 4. The vortex flowmeter according to any one of claims 1 to 3, wherein fluid fluctuations in the fluid to be measured flowing in and out of the chamber are detected as changes in density. 5. The vortex flowmeter according to claim 4, wherein a change in the density of the fluid to be measured flowing into and out of the chamber is detected as a modulation signal of the propagation velocity of an ultrasonic wave propagating within the chamber.