JPH08210887A - Differential pressure type flowmeter - Google Patents

Abstract

PURPOSE: To stably measure the flow rate of a fluid with high accuracy by detecting the total pressure of the fluid at holes opened toward the flowing direction of the fluid and static pressure of the fluid at another opening provided through the wall of a pipe on the upstream side. CONSTITUTION: A plurality of total pressure detecting holes 5 of a total pressure detecting tube 6 are opened toward the flowing direction of a fluid flowing through a pipe 4 and a globe valve connected to the front end of the tube 6 is set to a closing state. A static pressure detecting means 3 is provided with an opening and detector which detects the static pressure of the fluid on the inner peripheral surface of the pipe 4. The opening is provided on the upstream side of the holes 5 at a distance which is equal to the 1/2 of the radius of the pipe 4. In such a state, the means 2 detects the total pressure of the fluid and the means 3 detects the static pressure of the fluid. The flow rate of the fluid is found by performing prescribed arithmetic operation based on the detected pressures. Since the opening is provided in the stable region of the fluid, the flow rate can be stably measured with high accuracy.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a differential pressure type flow meter,
More specifically, it relates to a differential pressure type flow meter capable of stably performing highly accurate flow rate measurement.

[0002]

2. Description of the Related Art Conventionally, as a differential pressure type flow meter, a total pressure detecting space having a total pressure detecting hole which opens in the direction of fluid flow, and a partition wall for detecting the total pressure. A static pressure detecting space having a static pressure detecting hole which is isolated from the working space and opens toward the downstream direction of the fluid,
There has been known a differential pressure type flow meter including a tubular total pressure / static pressure detection tube body inside.

FIG. 5 shows an example of a total pressure / static pressure detecting tubular body in such a differential pressure type flow meter.

The total pressure / static pressure detecting pipe 40 is composed of two pipes 41 and 42 each having a semicircular cross section, and the two pipes 4 mentioned above.
1 and 42 are formed by a cylindrical connecting pipe body 43 provided so as to surround the flat surface portions on the peripheral side surfaces of both pipe bodies, the pipe body 41 and the connecting pipe. It has a total pressure detecting hole 44 penetrating the wall surface of the body 43, and a static pressure detecting hole 45 penetrating the wall surfaces of the pipe body 42 and the coupling pipe body 43.

In the differential pressure type flow meter provided with this total pressure / static pressure detecting tube 40, the flow rate is measured as follows. That is, the total pressure / static pressure detection pipe 40 is such that the total pressure / static pressure detection pipe 40 is substantially perpendicular to the fluid flow direction, and the total pressure detection hole 44 is opened in the fluid flow direction. Then, the static pressure detection hole 45 is inserted into the pipe body (not shown) so as to open toward the downstream direction of the fluid flow. The total pressure obtained from the total pressure detection hole 44 and the static pressure obtained from the static pressure detection hole 45 are detected by a pressure detector (not shown). A predetermined calculation is performed based on the detected total pressure and static pressure to calculate the flow rate.

However, for example, if the total pressure / static pressure detection pipe has a circular cross section as shown in FIG. 5, the position of the flow separation point on the peripheral side surface of the total pressure / static pressure detection pipe changes. An unstable region of flow occurs in the downstream side of the total pressure / static pressure detection pipe, that is, in the direction in which the static pressure detection holes are opened. This causes a problem that the static pressure fluctuates or pulsates. Therefore, the static pressure cannot be accurately detected, and the accuracy of flow rate measurement is low.

There is also known a differential pressure type flow meter whose accuracy is improved by suppressing the variation of the separation point.

FIG. 6 shows the total pressure of such a differential pressure type flow meter.
The static pressure detection tube is shown. This total pressure / static pressure detection tube 50
Is a pipe for connecting two pipes 51 and 52 having a triangular cross-section and a pipe having a rhombic cross-section provided so as to surround the two pipes 51 and 52 with the flat portions of both pipes being joined to each other. A total pressure detection hole 54 formed of a body 53 and penetrating the wall surfaces of the pipe body 51 and the coupling pipe body 53, and a static pressure detection penetrating the wall faces of the pipe body 52 and the coupling pipe body 53. And holes 55.

In this total pressure / static pressure detection tube, the position of the peeling point is fixed by making the cross-sectional shape rhombic.

However, in this differential pressure type flow meter, although the accuracy is slightly improved because the position of the separation point does not change, the static pressure is affected by the Karman vortex,
The measurement accuracy was not yet sufficient.

Further, in the conventional differential pressure type flow meter,
When the flow rate of a fluid containing dust is continuously measured for a long time, dust is accumulated or adheres to the inner wall surface in the static pressure detection space, and in some cases, the static pressure detection hole is clogged.
Then, there is a problem in that the accuracy of measurement is significantly reduced. Moreover, since the total pressure / static pressure detection tube body in the conventional differential pressure type flow meter has a complicated cross-sectional shape as shown in FIG. 5 or 6, it is impossible to remove contaminants such as adhered substances. It was extremely difficult.

For the purpose of removing such adhering substances, compressed air is sent into the static pressure detecting space,
A method has been proposed in which the adhering substances and the like are blown off from the static pressure detecting holes to the outside, but even with this method, the dust stuck to the inner wall surface cannot be removed. There is also a problem that a special device for feeding compressed air is required, which complicates the device configuration.

Further, the material for forming the total pressure / static pressure detection tube body in the conventional differential pressure type flow meter is limited to the material which can be processed into a complicated shape, and therefore, the bending strength against the flow of the fluid and sufficient It has not been possible to inexpensively manufacture a total pressure / static pressure detection tube having excellent resonance resistance, heat resistance, and corrosion resistance.

The present invention has been completed based on such circumstances. That is, an object of the present invention is to provide a differential pressure type flow meter capable of stably performing highly accurate flow rate measurement. A further object of the present invention is to provide a differential pressure type flow meter having a simple structure. A further object of the present invention is to provide a differential pressure type flow meter which can easily remove stuck dust and the like. Further, an object of the present invention is to provide a differential pressure type flow meter which has an extremely simple structure and facilitates maintenance work such as cleaning. A further object of the present invention is to provide a differential pressure type flow meter capable of stably measuring the flow rate for a long period of time. An object of the present invention is to provide a differential pressure type flow meter that achieves any or all of the above objects.

[0015]

According to the present invention for solving the above-mentioned problems, there is provided a total-pressure detecting means having a total-pressure detecting hole opened in a fluid flow direction, and a total-pressure detecting hole. A differential pressure type flow meter, comprising: a static pressure detecting means having an opening on an inner wall of the tubular body, which is upstream of an opening position, and the invention according to claim 2 provides the opening. Is the differential pressure type flow meter according to claim 1, wherein the total pressure detection hole is opened at a position farther than the same length as the radius of the tubular body from the opening position to the upstream side.
The invention according to claim 3 is the differential pressure type flowmeter according to claim 1 or 2, wherein the total pressure detecting holes are plural, and the invention according to claim 4 is for the fluid to flow. Total pressure detection having a total pressure detection hole that penetrates through the pipe body and opens in the fluid flow direction on the peripheral side surface and has a cleaning member insertable inside Means and
A differential pressure type flow meter, comprising: a static pressure detecting means having an opening on an inner wall of the tubular body, the upstream side of the total pressure detecting tubular body.

The differential pressure type flow meter of the present invention will be described in detail below.

The differential pressure type flow meter of the present invention has total pressure detecting means and static pressure detecting means.

The total pressure detecting means has a function of detecting the total pressure of the fluid flowing in the pipe body, and has a total pressure detecting hole opened in the flowing direction of the fluid in the pipe body. The number of the total pressure detection holes is at least 1 or more, and preferably a plurality. The shape and size of the opening of the total pressure detection hole are not particularly limited, and can be appropriately determined according to the diameter of the pipe through which the fluid flows and the type and properties of the fluid flowing through the pipe. . The shape of the opening of the total pressure detection hole is not particularly limited, and may be, for example, a circle or an ellipse, or a polygon such as a triangle, a quadrangle, or a rhombus. It is preferably circular.

In a preferred mode of the total pressure detecting means in the present invention, the total pressure detecting means is inserted into the pipe body so as to be orthogonal to the flow direction of the fluid in the pipe body and opens in the flow direction of the fluid. It is possible to show a mode in which a total pressure detecting cylinder having a working hole on the peripheral side surface is provided. In this case, it is more preferable that a plurality of total pressure detecting holes, which are open in the fluid flow direction, are formed in one line or a plurality of lines on the circumferential side surface of the pressure detecting cylinder.

On the other hand, the static pressure detecting means has a function of detecting the static pressure of the fluid flowing in the tubular body, and has an opening in the inner wall of the tubular body upstream of the total pressure detecting means. It becomes. The size and shape of the opening are not particularly limited, and can be appropriately determined according to the diameter of the pipe through which the fluid flows, the type and properties of the fluid flowing through the pipe, and the like. The static pressure detecting means in the present invention is not particularly limited in its structure, shape, etc. as long as the static pressure can be measured at this opening.

The center of the opening of the static pressure detecting means is farther from the opening position of the total pressure detecting hole of the total pressure detecting means toward the upstream side than the same length as the radius of the tubular body. It is desirable to be opened in. At such a position, an accurate static pressure without pulsation can be measured irrespective of the shape of the total pressure detection means, and therefore extremely highly accurate flow rate measurement can be stably performed. Particularly preferred is a position where the center of the opening is located at the same distance as the radius of the tubular body from the opening position of the total pressure detecting hole toward the upstream side.

The fluid whose flow rate is measured by the differential pressure type flow meter of the present invention is not particularly limited, and even if it is a gas,
It may be liquid. Further, it may be a mixed fluid containing solid particles or the like.

[0023]

The differential pressure type flow meter of the present invention operates as follows. That is, the total pressure detecting means is provided in the pipe body so that the total pressure detecting hole faces the flow direction of the fluid.

The fluid flowing in the pipe body applies pressure to the fluid in the total pressure detecting hole through the total pressure detecting hole opened in the fluid flowing direction. On the other hand, the pressure is also applied by the fluid to the inside of the opening formed on the inner wall of the tubular body on the upstream side of the total pressure detecting means.

The pressure applied to the fluid in the total pressure detecting hole and the pressure applied to the opening formed on the inner wall of the pipe body on the upstream side of the total pressure detecting means. Each is detected. Then, the flow rate is obtained by a predetermined calculation based on the detected total pressure and static pressure.

[0026]

The present invention will be described in detail below with reference to examples. It is needless to say that the present invention is not limited to the embodiments and various design changes can be made within the range in which the object of the present invention can be achieved.

(First Embodiment) The differential pressure type flow meter of the present invention will be described in detail below with reference to the drawings. FIG.
FIG. 3 is a partial cross-sectional explanatory view showing a differential pressure type flow meter which is an embodiment of the present invention.

The differential pressure type flow meter 1 of this embodiment comprises a total pressure detecting means 2 and a static pressure detecting means 3.

The total pressure detecting means 2 has a plurality of total pressure detecting holes 5 penetrating the tube body 4 having an inner diameter L and opening in the fluid flow direction on the peripheral side surface. An opened total pressure detecting cylinder 6 having a circular cross section, a first fixing means 8 for fixing the base side end portion 7 of the total pressure detecting cylinder 6 on the outer peripheral surface of the pipe 4, and the total fixing member 8. Second end for fixing the end portion 9 of the pressure detecting cylinder 6 on the outer peripheral surface of the pipe body 4
And fixing means 10.

The total pressure detecting cylinder 6 penetrates the first through hole 11 and the second through hole 12 provided in the pipe body 4, and the central axis line of the total pressure detecting cylinder 6 is the above-mentioned. The pipe body 4 is penetrated so as to be orthogonal to the central axis of the pipe body 6.

A plurality of total pressure detecting holes 5 provided on the peripheral side surface of the total pressure detecting cylindrical body 6 are arranged at predetermined intervals on the peripheral side surface and are parallel to the central axis of the total pressure detecting cylindrical body 6. They are arranged in a line. The plurality of total pressure detection holes 5 are provided in the tubular body 4 when the total pressure detection tubular body 6 is inserted into the tubular body 4.
It is provided all over the part located inside.

At the end of the total pressure detecting cylinder 6 on the side of the first through hole 11, that is, at the end 7 on the base side, the total pressure detecting cylinder 6 is provided.
A pressure detector (not shown) that detects the pressure of the fluid inside.
Is provided.

As shown in FIG. 2, the first fixing means 8 has a flange portion 14 welded to the outer peripheral surface of the tube body 4 at one end and a bolt insertion hole 13 at the other end.
Further, it has a cylindrical first fixing member 15 into which the total pressure detecting cylinder 6 can be inserted. Further, the first fixing member 15 is provided on the end portion of the total pressure detecting cylinder 6 on the side where the pressure detector is provided, that is, on the outer peripheral surface of the base-side end portion 7.
A flange 17 for fixing, which also has a bolt insertion hole 16 at a position corresponding to the bolt insertion hole 13,
Is provided.

The total pressure detecting cylinder 6 is fixed by the first fixing means 8 between the flange portion 14 of the first fixing member 15 and the fixing flange 17 of the total pressure detecting cylinder 6. This is performed by interposing a ring-shaped seal member 18 having an inner diameter substantially equal to the outer diameter of the total pressure detecting cylinder 6 and tightening it with bolts 19 and nuts 20 from both sides.

The second fixing means 10 is inserted from the first through hole 11 and the distal end portion of the total pressure detecting cylindrical body 6 penetrating the pipe body 4 by penetrating the second through hole 12. , Are fixed on the outer peripheral surface of the tubular body 4. FIG.
It is a schematic sectional drawing which shows the 2nd fixing means 10 in this Example.

The second fixing means 10 is a cylindrical body which is open at both ends and allows the total pressure detecting cylindrical body 6 to be inserted therethrough, and one end of which is provided on the outer peripheral surface of the tubular body 4 through the opening. 2 a second fixing member 22 that is welded to the outer peripheral surface of the tubular body 4 so as to surround the opening of the through hole 12 and has a female screw portion 21 on the inner peripheral surface of the other end, and the total pressure detection A cylindrical body having an inner diameter slightly larger than the outer diameter of the working cylinder 6, having a male screw portion 23 threadedly engaged with the second fixing member 22 on one outer peripheral surface and a screw thread on the other outer peripheral surface. The gripping member 25 having the male screw portion 24 that slightly reduces the inner diameter when fitted together, and the total pressure detecting cylinder 6 can be inserted, and the female member screwed into the male screw portion 24 of the gripping member 25 can be inserted. And a tightening member 27 having a screw portion 26 on the inner peripheral surface.

To fix the total pressure detecting cylinder 6 by the second fixing means 10, the tightening member 27 is held by the gripping member 2.
5 is screwed into the male screw portion 24, and the total pressure detecting cylinder 6 is tightened from the outer peripheral direction on the inner peripheral surface of the grip member 25.

In this embodiment, the total pressure detecting cylinder 6 is fixed at both ends of the base side end 7 and the tip side end 9, but in the present invention only the base side end is provided. The cylinder for detecting total pressure may be fixed.

That is, when the tip of the total pressure detecting cylinder is inserted into the tube through the insertion hole provided on the outer peripheral surface of the tube, the tip does not reach the inner wall of the tube on the opposite side. The pressure may be detected. In this case, in principle, the tip of the total pressure detecting cylinder is closed. in this way,
When the total pressure is to be detected when the tip does not reach the inner wall of the tube on the opposite side, the total pressure detecting cylinder is formed in an L-shape so that the tip is oriented in the fluid flow direction. It is also possible to open the tip without closing it and use this as the total pressure detecting hole. In this case, it is preferable not to form the total pressure detecting hole on the peripheral side surface of the total pressure detecting cylinder.

The total pressure detecting cylinder 6 in this embodiment
An opening / closing means is provided at the tip of the. FIG. 4 is a cross-sectional view showing the ball valve 28 which is the opening / closing means in this embodiment. The spherical valve 28 is a tubular body that is open at both ends, and has a mounting portion 29 to which the tip of the total pressure detecting tubular body 6 can be mounted at one end opening thereof, and an inner peripheral surface at the center of the inner peripheral surface. Cylindrical spherical valve body 30 having a concave groove formed by making a round
And a sphere 32 having an insertion hole 31 that is accommodated in a space formed by being surrounded by the concave groove.
The spherical body 32 rotates in conjunction with the lever 33 shown in FIG. 1, and the spherical valve can be opened and closed by operating the lever 33. In addition, when the spherical valve 28 is open,
It is shown in FIG.

When the spherical valve 28 is opened, a passage having an inner diameter substantially equal to the inner diameter of the total pressure detecting cylinder 6 is formed in the spherical valve 28, and the total pressure detecting cylinder 6 is formed. A cleaning member such as a wire brush can be inserted therein.

Further, instead of such a spherical valve, a cleaning member may be formed so as to be insertable by covering the tip of the total pressure detecting cylinder with a removable cover.

As shown in FIGS. 1 and 2, the static pressure detecting means 3 is provided with an opening 34 that opens to the inner peripheral surface of the tubular body 4, and the center of the opening 34 is the total area. The pressure detecting means is provided at a position having the same distance as the radius L / 2 of the tubular body 4 from the position of the total pressure detecting hole 5 toward the upstream side. The static pressure detecting means 3 is a pressure detector (not shown) for detecting static pressure at the opening 34.
Be equipped with.

The measurement of the flow rate by this differential pressure type flow meter will be described.

The total pressure detecting means 2 and the static pressure detecting means 3 are arranged and fixed as shown in FIG. At this time, all of the plurality of total pressure detecting holes 5 in the total pressure detecting cylinder 6 are opened toward the flow direction of the fluid flowing in the tube body 4, and the total pressure detecting cylinder 6 is formed. The spherical valve 28 attached to the tip of the is closed. The flow direction of the fluid in the tubular body 4 is indicated by an arrow in the figure.

In such a state, the total pressure detecting means 2 detects the total pressure, and the static pressure detecting means 3 detects the static pressure. The total pressure detecting cylindrical body 6 in the total pressure detecting means 2 has a plurality of total pressure detecting holes 5 which are opened on the peripheral side surface located in the tube body 4 in the fluid flowing direction.
Are arranged in a line, it is possible to obtain averaging according to the velocity distribution of the fluid flow in the pipe body 4.

The flow rate of the fluid is obtained by performing a predetermined calculation process based on the total pressure detected by the total pressure detecting means 2 and the static pressure detected by the static pressure detecting means 3.

In this differential pressure type flow meter, since the opening portion 34 of the static pressure measuring means 3 is provided in the stable region of the fluid, the static pressure is detected in the stable region of the flow, whereby the accuracy is improved. High and stable flow rate measurement is realized. Further, since there is no opening for detecting the total pressure or the static pressure in the unstable region of the flow, clogging due to dust is unlikely to occur.

Further, in the differential pressure type flow meter in this embodiment, the spherical valve 28 provided at the tip of the total pressure detecting cylinder 6 is opened, and the wire brush is inserted in the total pressure detecting cylinder 6. Cleaning tools such as can be inserted. Thus, even if dust adheres to or accumulates on the inner wall of the total pressure detecting cylinder 6 or if the total pressure detecting hole is clogged, the contaminant can be easily removed. Similarly, when the tip end opening of the total pressure detecting cylinder 6 is covered with a detachable lid, the lid is removed and the inside of the total pressure detecting cylinder 6 is cleaned with a cleaning tool such as a wire brush. Can be washed.

[0050]

According to the differential pressure type flow meter of the present invention, it is possible to provide a differential pressure type flow meter capable of stably performing highly accurate flow rate measurement.

According to the differential pressure type flow meter of the present invention, it is possible to provide a differential pressure type flow meter which can easily remove dust stuck in the total pressure detecting member.

According to the differential pressure type flow meter of the present invention, a highly accurate flow rate measurement can be stably performed, and a contaminant substance adhering to the total pressure detecting means can be easily removed. Can be provided.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional explanatory view showing a differential pressure type flow meter which is an embodiment of the present invention.

FIG. 2 is a first diagram of a differential pressure type flow meter of the present invention.
It is a partial cross section explanatory drawing which shows a fixing means.

FIG. 3 is a second view of the differential pressure type flow meter of the present invention.
It is sectional explanatory drawing which shows a fixing means.

FIG. 4 is a schematic sectional view showing an outline of a spherical valve in the embodiment.

FIG. 5 is a cross-sectional view showing a specific example of a conventional differential pressure type flow meter.

FIG. 6 is a cross-sectional view showing another specific example of the conventional differential pressure type flow meter.

[Explanation of symbols]

1 ... Differential pressure type flow meter, 2 ... Total pressure detection means, 3 ...
-Static pressure detecting means, 4 ... Tube, 5 ... Total pressure detecting hole, 6 ... Total pressure detecting cylinder, 7 ... Base side end, 8
... First fixing means, 9 ... Tip end, 10 ...
2nd fixing means, 11 ... 1st through-hole, 12 ... 2nd
Through hole, 13 ... Bolt insertion hole, 14 ... Flange portion, 15 ... First fixing member, 16 ... Bolt insertion hole, 17 ... Fixing collar portion, 18 ... Seal member Two
1 ... Second fixing member, 25 ... Gripping member, 27 ...
-Tightening member, 28 ... spherical valve, 34 ... opening.

Claims (4)

[Claims] 1. A total pressure detecting means having a total pressure detecting hole that opens in a fluid flow direction, and an opening on an inner wall of the tubular body upstream of an opening position of the total pressure detecting hole. And a static pressure detecting means having a section. 2. The opening according to claim 1, wherein the opening is formed at a position farther from the opening position of the total pressure detecting hole toward the upstream side than the same length as the radius of the tubular body. Differential pressure type flow meter. 3. The differential pressure type flow meter according to claim 1, wherein the total pressure detecting holes are plural. 4. A total pressure formed on a peripheral side surface of which a total pressure detecting hole penetrating through a pipe through which the fluid flows and opening toward the flowing direction of the fluid, and having a cleaning member inserted therein. A total pressure detecting means having a detecting cylinder, and a static pressure detecting means having an opening on the inner wall of the pipe upstream of the total pressure detecting cylinder. Differential pressure type flow meter.