JPS6213606B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a Karman vortex flow meter that can measure flow velocity or flow rate using Karman vortices.

Karman vortex flowmeters, which measure the number of Karman vortices generated alternately by vortex generators arranged in a flow path to determine the flow velocity or flow rate, are basically widely known, but the conventional Karman vortices Vortex flowmeters, for example, have a detection element such as a pressure-sensitive element or a temperature-sensitive element fixed to the surface of a vortex generator disposed in the fluid to be measured, and generate a vortex by an electrical signal from the detection element that is in direct contact with the fluid to be measured. If the detection element is configured to measure the flow rate or flow rate of the fluid to be measured by counting the number of particles, the detection element is easily damaged by foreign matter such as dust in the fluid to be measured, and the flow rate or flow rate of the corrosive fluid may be easily damaged. In the case of measurement, it was necessary to coat the surface of the detection element with a corrosion-resistant material.

Alternatively, if the temperature of the flowing measurement fluid is, for example, -100
℃ or +100℃, etc., the detection element may be made of a thermally insulating material, the vicinity of the detection element may be cooled, or it may be placed inside a vortex generator. This requires careful consideration, which not only makes it expensive, but also causes inconveniences such as the inability to perform accurate measurements.

To solve this problem, the detection element is not placed inside or on the surface of the vortex generator, but is placed outside the pipe to prevent the influence of the fluid to be measured and to introduce pressure fluctuations due to the vortices opened on both sides of the vortex generator. A purge fluid is introduced from inside the vortex generator to the pressure guide port for cleaning, and the purge fluid is injected from the pressure guide port to constantly purge the surface of the vortex generator, thereby removing stuck objects and dust from the vortex generator. Japanese Patent Publication No. 49-32152 discloses a so-called purge-type vortex flowmeter that can regularly generate, grow, and separate Karman vortices while preventing the adhesion of such substances. However, in such prior art, the purge fluid flow structure is formed inside the vortex generator, and the purge fluid injection ports are opened on both sides of the vortex generator as pressure guiding ports, so the vortex generator The structure was complicated, making it unsuitable for low-cost mass production.

The present invention has been made with attention to the above points, and the vortex generating body itself does not have any configuration for conducting purge fluid, but only provides an excellent configuration with an excellent vortex generating function, and It is an object of the present invention to provide a Karman vortex flowmeter which is extremely simple in structure and has excellent accuracy by opening a pair of left and right purge fluid pressure guide ports. That is, basically, instead of the bias flow using the flow of the fluid to be measured according to the invention of Japanese Patent Application No. 52-58443 (Japanese Patent Publication No. 57-24492), which was already proposed by the present applicant, inert gas, For example, a new Karman vortex flowmeter that uses a purge fluid such as nitrogen gas and that can inject the purge fluid from the outside of the vortex generator to both sides of the vortex generator without conducting the inside of the vortex generator. It is on offer.

Furthermore, as described above, by using an inert gas such as nitrogen gas as a purge fluid, the present invention can avoid inconveniences such as chemical reactions caused by contact and mixing with the fluid to be measured, and also can eliminate the disadvantages caused by the vortex generator. The present invention is a novel method in which the purge fluid is made to act under conditions such that the generation, growth, and separation of the Karman vortices caused by the generation, growth, and separation of the Karman vortices can be caused by sensitive pressure changes to act on a detection element disposed outside the pipe through the purge fluid. Karman Vortex Flow Meter is available to you.

Furthermore, the present invention provides a vortex generator with a purge fluid pressure inlet facing the wall surface of the pipe or protruding into the pipe to face both sides of the vortex generator, thereby reducing the pressure of the purge fluid on the surface of the vortex generator. To provide a Karman vortex flowmeter in which a pressure guiding port for the purge fluid is provided at a position where a Karman vortex obtained by a vortex generator can be sufficiently detected while performing a cleaning action such as removing dirt and foreign matter. It is in.

An embodiment of the present invention will be described below with reference to the drawings. 1 is a pipe, 2 is a vortex generator disposed in the pipe 1 for generating a Karman vortex with a desired cross-sectional shape, and 3a and 3b are small vortex generators on both sides of the vortex generator 2. A pressure guiding port is opened opposite to the pipe wall 1a of a separate pipe line 1 and can inject purge fluid, and the purge fluid is injected onto both sides of the vortex generator 2 to eliminate dust and foreign matter on the surfaces. etc. to enable the regular generation, growth, and separation of Karman vortices, and the generation of Karman vortices is used as a pressure change to affect the purge fluid through the pressure guide ports 3a and 3b, thereby purging. It allows the flow rate or flow rate of the fluid to be changed. Incidentally, the pressure guiding ports 3a and 3b may of course be opened on the same plane as the pipe wall 1a, but may also be opened to protrude into the pipe line 1 close to both sides of the vortex generator 2. .

Further, the pressure guiding ports 3a and 3b are opened so as to be adjacent to the upper or lower pipe wall 1a of the vortex generator 2, and the purge fluid is injected from above or below along the flow side of the vortex generator 2 for cleaning. It may also be used to improve effectiveness.

4a and 4b are branch pipes leading to the pressure guiding ports 3a and 3b, which communicate with a conduit 5 such as a thin tube at a trifurcated pipe portion 6. 7a and 7b are desired detection elements capable of detecting minute changes in the flow rate or flow velocity of the purge fluid, and are provided in the branch pipes 4a and 4b, respectively.Furthermore, throttle valves 8a and 8b are provided in both the branch pipes 4a and 4b. They are arranged symmetrically. In the illustrated embodiment, the detection element 7
A7b shows a case in which two circuits are provided, but in such a case, the amount of change can be increased by an amplification circuit 9 such as a bridge circuit, but it is also possible to omit the number by assuming only one circuit. . Note that the detection element 7 is preferably an element that can be changed into an electrical quantity, but is not necessarily limited thereto.

Further, a pressure reducing valve 10, a pressure gauge 11, a valve 12, and flow meters 13 and 14 such as an area type flow meter are disposed in the middle of the thin tube 5 in order from the upstream side, and nitrogen gas, for example, is supplied from a purge fluid source not shown. It is possible to supply an inert gas such as gas.

That is, the supply pressure of the purge fluid can be freely adjusted using the pressure reducing valve 10, and the opening degree of the valve 12 can be adjusted using the flow meter 13 to maintain an appropriate flow rate.

With the configuration described above, when the fluid to be measured flows in the direction of the arrow in the pipe 1, two rows of Karman vortices are generated alternately on the downstream side of the vortex generator 2.

On the other hand, the purge fluid supplied from the purge fluid source passes through the pressure reducing valve 0, the valve 12, the flow meter 13, and the valve 14 of the thin tube 5, and then enters the two-way branch pipe 4 from the trifurcated pipe portion 6.
The vortex generating body 2 flows through the pressure guiding ports 3a and 3b which are branched into the flow paths a and 4b, pass through the detection elements 7a and 7b, and open to the pipe line 1.
It is ejected towards both sides of the

Thus, the purge fluid ejected from the pressure guiding ports 3a, 3b constantly flows through the branch pipes 4a, 4b at a desired flow rate or flow velocity, but alternating Karman vortices are formed behind both sides of the vortex generator 2. When this occurs, the Karman vortex imparts a pressure change to the purge fluid, which changes the flow rate or flow velocity of the purge fluid flowing in the branch pipes 4a, 4. The arranged detection elements 7a,
The pressure change is sensitively captured by 7b and amplified so that it can be detected and counted, and therefore the flow rate or flow velocity of the fluid to be measured can be measured.

Therefore, the pressure of the purge fluid and the flow rate of the purge fluid need to be operated in an optimal state corresponding to the flow rate of the fluid to be measured. For example, if the flow rate Q of the fluid to be measured is 260 m ³ /h or 130 m ³ /h. For h, purge fluid pressure Pb = 300mm/Aq, flow rate q = 2l/min or Pb =
Two examples of 300mm/Aq and q=2l/min are shown in Figure 2 a and b.
As shown in the figure, the waveform is irregular and noise etc. are detected, which is not desirable. In contrast, Figure 3 a and b
As shown in , for Q = 260m ³ /h, Pb = 300mm /
For Aq, q=0.5l/min or Q=130m ³ /h
In the case of Pb=300 mm/Aq and q=0.5 l/min, Karman vortices are regularly detected and can be said to be extremely preferable.

Since the present invention is constructed as described above, even if the fluid to be measured is dirty, low-temperature, or high-temperature fluid, the detection element is provided outside the pipe, and the purge fluid does not flow into the fluid to be measured. Since the fluid to be measured does not have any influence on the detection element, it can be used appropriately and effectively regardless of the type or temperature of the fluid to be measured, and the purge fluid constantly acts on the vortex generator to clean the surface. Because it is purified, it is possible to prevent the adhesion of dust, filth, foreign matter, etc., and it is possible to obtain regular Karman vortex generation without any trouble in measuring dirty fluids such as exhaust gas and smoke flow. Since it does not have any other functions other than the vortex generation function such as vortex detection function, it has many advantages such as simple structure, suitable for low-cost mass production, and wide range of applications regardless of gas or liquid. It has the following.

[Brief explanation of the drawing]

Fig. 1 is an overall functional explanatory diagram showing one embodiment of the Karman vortex flowmeter according to the present invention, Figs. A graph showing the state of Karman vortex detection in the relative relationship with . 1... Pipeline, 2... Vortex generator, 3a, 3b...
Pressure guiding port, 4a, 4b...branch pipe, 5...purge fluid thin tube, 7a, 7b...detection element, 10...pressure reducing valve, 13...flow meter.

Claims (1)

[Claims] 1 A conduit through which the gas to be measured flows, a vortex generator disposed within the conduit, a pressure guiding port opened near the pipe wall corresponding to both sides of the vortex generating body, and the pressure guiding port a branch pipe connected to and provided outside the pipe line, a conduit connected to the branch pipe, and a detection element provided in the branch pipe;
an inert gas source outside the pipeline connected to the conduit, a flow meter and a pressure gauge connected to the conduit, a first valve provided between the detection element and the pressure guiding port of the branch pipe, and the branch pipe. It consists of a second valve provided upstream of the detection element of the pipe and a third valve provided near the flowmeter, and the inert gas source is controlled by operating the first to third valves. A Karman vortex flowmeter characterized in that the pressure and flow rate of the fluid supplied from the pipe into the pipe are controlled.