JPS62198716A - Vortex flow meter - Google Patents

Abstract

PURPOSE:To measure a flow rate with high accuracy over a wide range by sectioning rectangularly a tube body where fluid flows, providing an obstacle which has a rectangular surface in the tube body, and generating a stable vortex street. CONSTITUTION:The tube body 11 is sectioned rectangularly, the obstacle 16 which has the rectangular surface for reducing the fluid in area to both right and left sides is arranged in the tube body, and an exciter 19 is fitted through an arm 20. Area reduction parts 18L and 18R formed on both right and left sides of the obstacle 16 are made rectangular having constant width (d) without reference to their positions and the obstacle 16 is vibrated by the exciter 19 as shown by an arrow 10 to vary the width (d) of the area reduction part 18L and 18R finely. Consequently, the condition of vortex street generation is the same at the center part and upper and lower end parts of the obstacle 1 and the stable vortex street is generated at its downstream side. Further, the vibration of the obstacle 16 is controlled automatically by using the output of a vortex detector 17 to make the vibration frequency resonate with the generation frequency of the vortex street, thereby generating the large vortex street.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention is a method of arranging an obstacle in a pipe through which fluid flows, generating vortex trains alternately on both sides of the obstacle, and detecting the frequency of the vortex train. This paper relates to a vortex flow meter for measuring flow mountains.

(Prior Art) An eddy current meter has no moving parts, has a small number of parts, and has a simple structure.

FIG. 4 shows the structure of a conventionally known vortex flowmeter. 31
is a tube with a circular cross section, and has 7 flange 32 at both ends.
33 is provided so as to be inserted in the middle of the pipe through which the fluid to be measured flows. An obstacle 34 is arranged at the center of the tube body 31 to restrict the fluid flowing inside the tube body 31 to the left and right sides. 35 is a vortex detector that detects the vortex street frequency generated downstream of the obstacle 34.

FIGS. 5(a) and 5(b) are diagrams for explaining the operating principle of this vortex flowmeter. When the fluid 37 flows as shown by arrows in the figure, the fluid is constricted to both the left and right sides at the position of the obstacle 34. These left and right aperture parts 36L36I? The fluid passing through alternately forms vortices (called Karman vortices) behind the obstacle 34. The frequency of the vortex street formed in this way is f
Assuming that the flow velocity of the fluid at the throttle portions 36L and 36R is V, and the width of the obstacle 34 is β, then f is proportional to v-1.

Therefore, by measuring the frequency f of this vortex street, the flow rate can be determined.

As the vortex detector 35, those using a thermistor, those using a strain gauge, those using an ultrasonic sensor, etc. are known. A detector using a thermistor utilizes the following: generation of vortex → generation of differential pressure → change in flow velocity → change in surge 29 surface temperature → change in resistance of the thermistor. To do this, pipe body 3
1 is provided with a bypass for detecting differential pressure, and a thermistor is disposed within this bypass. A detector using a strain gauge uses the following phenomena: generation of vortex → generation of differential pressure → change in force → generation of strain → change in resistance of the strain gauge. A detector using ultrasonic waves irradiates ultrasonic waves through the tubular body 31 and utilizes the fact that the phase of the received ultrasonic waves is modulated as a result of changes in flow velocity due to vortex generation.

Although FIG. 5(a) shows the case where the obstacle 34 is single-shaped, it is also known that the obstacle 34 is Δ-shaped as shown in FIG. 5(b).

(Problems to be solved by R-mei) In the conventional vortex flowmeter described above, a clean vortex array as shown in FIG. 5 is not actually generated. Furthermore, the vortices that are generated alternately on the left and right sides of the tube do not move straight along the tube, but actually move as shown by the broken line arrows in FIG. 5(a). Therefore, it is difficult to accurately measure the frequency of the vortex street.
Accurate flow measurement over a wide range of flow rates has been difficult.

One of the reasons why a stable vortex train is not formed in conventional vortex flowmeters is that the width of the fluid constriction part is not constant because obstacles with rectangular surfaces are placed inside the tube with a circular cross section. . That is, as shown in FIG.
The narrowed portions 36L and 36R formed between the tube walls have a width as large as dl at the center and as small as d2 at the upper and lower peripheries. Naturally, the conditions for vortex generation are different between the width d1 portion and the width 62 portion, which makes it difficult to generate a stable vortex array.

The present invention has been made in view of the above points, and an object of the present invention is to provide a vortex flow meter that enables stable generation of vortex rows and thereby enables highly accurate flow measurement over a wide range.

(Means for Solving the Problems) The vortex flowmeter according to the present invention has a tube through which fluid flows, whose cross-sectional shape is rectangular, and an obstacle having a rectangular surface is arranged inside the tube. A fluid constriction portion with a constant width is formed on both sides of the At the same time, a control circuit is equipped with an exciter that vibrates the obstruction in the tube so that the width of the fluid constriction part slightly changes, and obtains a vibration frequency that maintains a predetermined relationship with the frequency of the vortex street detected by the vortex detector. Equipped with.

(Function) According to the present invention, since the constricted portions on both sides of the obstacle are formed in a rectangular shape with a constant width, stable vortex rows can be generated. In addition, an exciter that vibrates the obstacle is installed, and a circuit is installed that automatically controls the vibration frequency to maintain a predetermined relationship with the detected vortex street generation frequency. This allows a stable and strong vortex train to be generated.

(Example) The present invention will be explained in detail below.

FIG. 1 shows an example of a vortex flowmeter. Reference numeral 11 is a tube having a rectangular or square cross section.

Seven flanges 14.15 are provided at both ends of the tubular body 11 to connect it to a fluid piping, which normally has a circular cross section, through a shape converting portion 12.13 so as to make it a circular opening. There is. An obstacle 16 having a rectangular surface is arranged in the center of the interior of the tube body 11 to restrict the fluid to both the left and right sides. Arms 20 are attached above and below the obstacle 16,
This arm 20 passes through the side wall of the tubular body 11 and is led out to the outside in an airtight manner. And an exciter 19 is attached to this arm 2o.
is attached, and the vibrator 19 is configured to apply a slight lateral vibration to the obstacle 16. Reference numeral 17 denotes a vortex detector for detecting the generation frequency of a vortex train generated on the downstream side of an obstacle. The vortex detector 17 may be of any type known in the art, such as a thermistor sensor, strain gauge sensor, or ultrasonic sensor. For example, when the fluid to be measured is gas, a thermistor sensor, ultrasonic sensor, etc. are generally suitable, and strain gauge sensors can be applied to both gas and liquid.

FIG. 2 is a diagram showing this vortex flowmeter cut away on the upstream side of the obstruction 16 of the tube body 11. As shown in the figure, since the tubular body 11 is rectangular, the constricted portions 18L and 18R formed on both the left and right sides of the obstacle 16 are rectangular with a constant width d regardless of their position. By applying the vibration shown by the arrow 10 to the obstacle 16 using the vibrator 19, the fluid restricting portions 18L and 18R are
The width d can be slightly changed.

The frequency of the vibration applied to the obstacle 16 by the vibrator 19 is automatically controlled so as to maintain a predetermined relationship with the frequency of occurrence of illness and death, preferably to resonate with the frequency of occurrence of illness and death. This is to cause stable and strong death from disease.

FIG. 3 shows a vibration frequency control circuit using such a vibrator 19. This control circuit converts the vortex street generation frequency f obtained by the vortex detector 17 into the frequency/voltage converter 21. Variable gain amplifier 22. A signal with a frequency f2 shifted by a certain ratio is obtained by the voltage/frequency converter 23, and this is guided to the vibration generator of the vibrator 19 to generate vibration proportional to 2 in frequency. That is, the output frequency f1 of the eddy detector 17 is first converted into a voltage V1 by the frequency/voltage converter 21. This voltage 1 is the variable gain amplifier 22
The voltage/frequency converter 23 converts this into the frequency f2. This signal of frequency f2 is then amplified by the power amplifier 24, and the vibration generator 19, in the case of the figure, is a cylindrical permanent magnet with a coil wound around it.
It is configured to generate vibration proportional to the frequency f2.

According to the configuration of this embodiment, the conditions for the occurrence of disease and death are the same both in the center and at the upper and lower ends of the obstacle 16, so that stable disease and death are formed on the downstream side of the obstacle 16. Further, since the vibration applied to the obstacle 16 is automatically adjusted using the output of the vortex detector 17, the vibration frequency can be easily made to resonate with the frequency at which disease and death occur. As a result, a stronger occurrence of disease and death is possible, and therefore, by detecting the frequency of disease and death, highly accurate flow rate measurement can be performed over a wide 21I amount range.

Note that the present invention is not limited to the above embodiments. For example, the downstream shape of the obstacle may be any shape such as a T-shape or a Δ-shape, as long as it is a rectangular constriction portion with a constant width.

Further, the vortex flowmeter of the present invention can be applied to a calorimeter. This is because, as is well known, the amount of heat can be determined by measuring the temperature at the inlet and outlet sides of the fluid and calculating this and the flow rate.

(Effects of the Invention) As described above, according to the present invention, it is possible to provide a vortex flowmeter that enables stable and severe disease and death, and therefore enables highly accurate flow measurement over a wide range. .

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of an eddy current meter according to an embodiment of the present invention,
Figure 2 is a diagram showing the main part cut away, Figure 3 is a diagram showing the configuration of the vibration frequency lllllK1 circuit section, Figure 4 is a diagram showing an example of a conventional vortex flowmeter, and Figure 5 (a )(b) is a diagram for explaining the principle of operation, and FIG. 6 is a diagram for explaining the problem. DESCRIPTION OF SYMBOLS 11... Pipe body, 12.13... Shape conversion part, 14° 15... 7 lunges, 16... Obstacle, 17... Vortex detector, 18L, 18R... Throttle part, 19...
Exciter, 2o... Arm, 21... Frequency/voltage converter, 22... Variable gain amplifier, 23... Voltage/frequency converter, 24... Power amplifier. Applicant's representative Patent attorney Takehiko Suzue Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] A tube body with a rectangular cross section through which fluid flows, and a fluid constriction section located at the center of the tube body and formed on both sides are square in shape with a constant width regardless of the position, and a vortex is generated downstream of the fluid constriction sections on both sides. an obstacle that generates a row, a vortex detector that detects the generation frequency of the vortex row, an exciter that vibrates the obstacle so that the width of the fluid constriction portion on both sides of the obstacle changes slightly; A vortex flow meter comprising: a control circuit for controlling a vibrator using the output of the vortex detector to obtain a vibration frequency that maintains a predetermined relationship with the frequency of occurrence of a detected vortex street.