JPH0460535B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a structure for detecting a vortex signal with excellent S/N in a vortex flow meter.

Prior Art In Japanese Patent Application No. 58-60333, the present applicant disposed a tubular body 3 behind the vortex generator 2 in a direction crossing the vortex generator 2, as shown in FIG. A vortex flowmeter has been proposed in which at least one pair of pressure guiding holes 31 are bored at a predetermined interval in the axial direction of the tubular body 3. This flowmeter focuses on the fact that the fluid is rectified by applying fluctuating pressure to the tubular body 3 to generate fluid fluctuations, and introducing this fluid fluctuation into the tubular body 3, which has a relatively small flow area. This is what I did. In this way, compared to the case without a tubular body, even turbulent vortices included in the flow in the flow path will not be detected, and noise components mixed in the detection signal will be reduced, resulting in a high S/N ratio. We were able to obtain an excellent detection signal. Detection of already generated vortex signals can be improved using the method described above, but as shown in Japanese Patent Publication No. 55-40804, the detection of vortex signals that have already occurred can be improved using isosceles triangles with an acute angle to the flow direction A. By providing a shaped body and sequentially arranging independent flat plates at desired intervals for the false alarms of this generating body, it was possible to give an amplification effect to the vortex and generate a strong and stable vortex.

Problems with the conventional example However, according to the above-mentioned conventional technology, a stable vortex flowmeter that has not been previously achieved is achieved by means of generating strong and stable vortices and means of detecting the generated vortices with an excellent S/N ratio. However, in order to measure the flow rate over a wider range, it was necessary to obtain a stronger vortex signal and to hold the Strouhal number at a constant value over a wider range. Furthermore, in the above-mentioned Japanese Patent Publication No. 55-40804, it has a positive instrumental error characteristic in a small flow area, so although it is a stable vortex generator, it is unsatisfactory for flowmeters that are required to measure a wider range. It was hot.

Means for Solving the Problems The present invention has been made to solve the above-mentioned problems.
1 was arranged in the axial direction of the tubular body 3, while the vortex generated from the vortex generator separates from the vortex generator as a vortex column three-dimensionally, and effective pressure fluctuation was calculated. In addition to arranging pressure introduction holes in the direction of the vortex column, the vortex generator is configured to improve the characteristics inherent to the vortex generator and obtain a flowmeter with excellent linearity over a wide range of flow rates. This method solves the problems of the prior art by focusing on the vortex frequency ratio that each vortex generating element has.

Specific Example FIG. 1 is a diagram for explaining a specific example of the present invention. In the figure, the same reference numerals are given to the same structures as those of the prior art shown in FIG. 3. Vortex generator 2
, an isosceles triangular vortex generating element 2a which is an upstream vortex generating element, a T-shaped vortex generating element 2b disposed on the downstream side, and a flat plate 2 disposed between these.
c are arranged one after another in such a way that the representative length d faces each other. A tubular body 3 that introduces pressure fluctuations due to the vortex into the wake of the vortex generator 2 arranged in this manner is supported so as to penetrate through the channel wall 1 so as to intersect with the vortex generator 2 . FIG. 1C shows the tubular body 3
This shows the details of the tubular body 3 and the pair of tubular bodies 3.
2 are orthogonally connected and fixed. Note that the end surface of the tube body is closed, and there are a plurality of pressure introduction holes 33.
is open on the straight pipe wall. The fluctuating pressure is introduced into a pair of pressure introduction holes 33, and a corresponding fluid displacement occurs as indicated by the arrow. When detecting this fluid displacement as an ultrasonic modulation signal, a sound absorbing material 34 such as a nonwoven fabric is attached to the inner wall of the tube body 32 in order to prevent disturbance of ultrasonic waves contained in the fluid from entering. Figure 1D
2 shows a perspective view thereof, and the notch 35 is provided so as not to close the pressure guiding hole 33. On the other hand, the vortex generator 2 is given a shape such that the vortex frequency ratio of the vortex generator 2b to the vortex frequency of the vortex generator 2a is 0.7 to 0.9. The flat plates 2c are juxtaposed between them, and each is given a gap of t ₁ , t ₂ , t ₃ , and t ₁
~t ₃ =0.1d~0.4d is selected. The vortex flowmeter of FIG. 1 configured in this way can obtain vortices with excellent linearity due to interference due to differences in vortex frequencies between the vortex generating elements. That is, the downstream vortex generating element 2
Since the vortex generation frequency of b is low, the vortex circulation is strong and dominates the high Reynolds number region, and the difference in vortex frequency generated at low Reynolds numbers occurs between the vortex generation elements 2a and 2b. Due to interference with the vortex,
It regulates the vortex frequency in the low Reynolds number region. The vortex that separates from the vortex generator described above flows down as a vortex column parallel to the axis of the vortex generator, so pressure fluctuations also appear with a tendency to follow this.
The introduced differential pressure is also large and averaged.

The flat plate 2c is for introducing the vortex generated by the vortex generating element 2a between the gaps t ₁ and t ₃ to produce an amplifying effect of growing the vortex. In addition to the configuration shown in FIG. 1A, the vortex generating body can be effectively configured by combining a triangular prism, a trapezoid, and a flat plate to the configuration shown in FIG. 2, and adding the above conditions to this configuration.

Effects As described above, according to the present invention, a stable vortex signal with a wide range of vortex generation frequency and excellent linearity proportional to the flow rate can be obtained. Since a strong fluctuating differential pressure can be obtained, a vortex flow meter with an extremely wide flow measurement range including both can be obtained.

[Brief explanation of the drawing]

Figure 1 is a diagram for explaining the vortex flowmeter according to the present invention, where Figure A is a side sectional view and Figure B is a line taken along line B-B of Figure A.
Figure C is a detailed view of the tubular body, Figure D is a detailed view of the nonwoven fabric, Figure 2 is a sectional view showing another embodiment of the vortex generator, and Figure 3 is a conventional vortex flowmeter. It is a figure showing an example. 1... Channel, 2... Vortex generator, 3... Tubular body,
4... Ultrasonic oscillator, 5... Ultrasonic receiver, 32
...Pipe body, 33...Pressure introduction hole, 34...Nonwoven fabric.

Claims (1)

[Scope of Claims] 1. A vortex generator disposed in a flow path facing the flow, and a flow path wall located behind the vortex generator and intersecting the vortex generator substantially perpendicularly to the vortex generator in the axial direction of the flow path. It consists of a tubular body with both ends closed, passing through the tubular body, and an ultrasonic transmitter/receiver disposed opposite to both ends of the tubular body to detect the flow velocity inside the tubular body, and transmitting a vortex signal in a predetermined direction in the axial direction of the tubular body. In a vortex flowmeter that detects an alternating flow of a fluid to be measured that is generated in a tubular body based on fluctuating vortex pressure introduced through a pair of pressure introduction holes that are opened at intervals, 1. A vortex flowmeter characterized in that a tubular body closed at both ends substantially perpendicular to the tubular body is communicated at a predetermined interval in the axial direction of the tubular body, and a plurality of pressure introduction holes are provided in the axial direction of the tubular body. 2. The above-mentioned vortex generating body is characterized in that vortex generating elements each having a cross-sectional shape of an isosceles triangle, a flat plate, and a T-shape with an apex on the flow path axis are sequentially arranged at predetermined intervals. A vortex flowmeter according to claim 1. 3. The above-mentioned vortex generating body is characterized in that vortex generating elements each having a cross-sectional shape having an isosceles triangular shape, a flat plate shape, and a ladder shape with an apex on the flow path axis are sequentially arranged at predetermined intervals. The vortex flowmeter according to item 1. 4 The above-mentioned vortex generator has a vortex frequency ratio of 0.7 between the isosceles triangular vortex generating element disposed on the upstream side and the T-shaped or ladder-shaped vortex generating element disposed on the downstream side, with the former as a reference. The vortex flowmeter according to any one of claims 2 to 3, characterized in that the value is 0.9. 5. The vortex flowmeter according to any one of claims 1 to 4, characterized in that a sound-absorbing material such as a nonwoven fabric is provided inside the inner walls of a pair of tubes that communicate orthogonally with the tubular body. .