KR100798211B1 - Restriction flowmeter - Google Patents

Abstract

A fluid-limiting flow meter having a cylinder through which a fluid to be measured flows and a pipe for forming a fluid restricting mechanism installed through the cylinder so as to be orthogonal to its central axis, wherein the pipe has a diameter smaller than the inner diameter of the cylinder. Having a first pressure measuring hole formed at a position above the narrowest cross section, and a second pressure measuring hole formed at the cylinder wall portion upstream of the cylinder diameter more than 1/2 from the narrowest cross section. It features.

Flow meter, differential pressure detector, orifice, venturi, pressure measuring hole, total pressure

Description

Fluid Restricted Flowmeters {RESTRICTION FLOWMETER}

The present invention relates to a fluid restriction flowmeter for measuring the flow rate or flow rate of a fluid in a pipe.

Conventionally, a differential pressure detector is used as one of the measurement instruments for measuring the flow rate in a pipe, which is an orifice or venturi tube having a fluid restriction portion. It is possible to configure a fluid-limiting flow meter that can measure hydrostatic differential pressure using a manometer on the back, allowing measurement of flow rate or flow rate.

Such conventional differential pressure detectors require precise machining as specified in the Japanese Industrial Standard (JIS), and since the measurement accuracy is degraded in a state in which the fluid flow is mixed, a straight line suitable for the upstream and downstream regions of the installed equipment is required. You need to install the pipes. In addition, the differential pressure generated from the differential pressure detector is represented by a single curve as the square of the flow rate and the flow rate flowing in the pipe.

In addition, when the fluid to be measured is a liquid, the orifice wears edge portions due to erosion due to prolonged use, or sludge precipitates before and after the fluid limiting portion, resulting in deterioration of measurement accuracy. .

However, according to the above-described prior art, the installation has been withheld in spite of the necessity of flow rate measurement due to the high price because precise machining is required. In particular, the consumer the building for being the most delay the reduction of CO ₂ problem environment attracting attention these days, even though the need to do the management for energy savings with respect to the heat sink (heat sink) despite not being the most installed as the initial cost of a problem not.

In addition, in the differential pressure detector according to the prior art, it is necessary to install it at a place where the flow of the fluid in the pipe is in a constant state in order to maintain the measurement accuracy. For example, a local resistance such as an R elbow (Note: elbow for piping) is used. In the case of installation in the rear part, it is necessary to install a fairly long straight pipe. Therefore, it is difficult to use it because the installation location is limited at the actual site.

In the differential pressure detector according to the related art, the differential pressure generated when a low pressure range is measured from a low flow rate region to a high flow rate region so that the relationship between the differential pressure generated and the flow rate and flow rate of the flowing fluid is represented by a second curve. The larger the range, the greater the measurement error in the low flow rate range, depending on the performance of the pressure gauge. Moreover, there existed a problem which abrasion of the edge part or deposition of a deposit by long-term use generate | occur | produce, and the measurement precision fell.

In addition, when a pitot tube is used as a conventional differential pressure detector, the total pressure and the hydrostatic pressure are extracted and a differential pressure between them is obtained. Only the speed can be obtained, and in order to calculate the average speed, it is necessary to measure the speed at several places in the same section.

Further, as disclosed in Japanese Patent Application Laid-Open No. 8-210887, a cylindrical member for total pressure detection is provided in the tube member through which the fluid flows perpendicularly to the axis thereof, and the fluid is distributed to the cylindrical member for total pressure detection. The total pressure detection hole opened toward the direction is provided, and an opening is provided in the wall part of the tube member in the upstream, and it is made to perform positive pressure detection.

In this differential pressure detector, however, detection is possible at a plurality of points in the same cross section, but a large differential pressure cannot be detected in a low flow rate region.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and is an inexpensive product that does not require precise machining. Therefore, it is possible to measure high precision even in a turbid flow state, and further, it is possible to measure the differential pressure, flow rate, and It is an object of the present invention to provide a fluid-limited flow meter capable of maintaining stable measurement accuracy over a long period of time, expressed as a plurality of secondary curves.

      In order to achieve the above object, the fluid-limiting flow meter according to the present invention includes a cylinder through which a fluid to be measured flows and a pipe for forming a fluid restricting mechanism installed through the cylinder so as to be orthogonal to its central axis. In a fluid confined flow meter in which the pipe has a diameter smaller than the inner diameter of the cylinder, a first pressure measuring hole formed at a position on the cross section where the cross section perpendicular to the flow direction is narrowed to the maximum, and one of the inner diameter of the cylinder from the narrowest cross section. And a second pressure measuring hole formed in an upstream cylinder wall portion separated by at least two.

      Further, in the above fluid-limited flow meter, the first pressure measuring hole is formed in the cylinder wall portion on the narrowest cross section.

      Further, in the fluid-limited flow meter, the first pressure measuring hole is formed in the wall surface of the pipe on the narrowest cross section.

      In the fluid-limited flow meter, the first pressure measuring hole is formed on the wall surface downstream from the narrowest cross section among the wall surfaces of the pipe.

      In such a fluid-limiting flow meter, a rectification plate is provided inside the cylinder upstream from the second pressure measuring hole at a distance of at least 1/2 of the inner diameter of the cylinder.

      In the fluid-limiting flowmeter as described above, a hollow hollow body having a shell-shaped cutting surface at a position upstream than the narrowest cross-sectional location perpendicular to the flow direction of the fluid in the cylinder. Is provided, the first pressure measuring hole formed in the position on the narrowest cross section, the second pressure measuring hole formed in the wall portion of the cylinder upstream of the hollow body, and the third pressure provided by opening the hole in the flow direction in the hollow body. It is characterized by having a measuring hole.

     In this fluid-limited flow meter, a first pressure measuring hole is formed in the wall portion of the cylinder on the narrowest cross section.

     In this fluid-limited flow meter, the first pressure measuring hole is formed on the wall surface of the pipe on the narrowest cross section or on the wall surface of the pipe downstream from the first pressure measuring hole.

     Further, in the fluid-limited flow meter, by selecting two pressure measuring holes among the first, second, and third pressure measuring holes, and detecting the differential pressure between the selected pressure measuring holes, the pressure gauge is provided in a wide range of flow velocity ranges. It is characterized by obtaining a suitable differential pressure.

     In the fluid-limiting flow meter of the present invention, the pressure detected by each pressure measuring hole, and the relationship between the differential pressure and the flow rate will be described.

The differential pressure detector in the fluid-limited flow meter of the present invention has a structure in which a pipe passes through the cylinder so as to be orthogonal to its central axis, and the passage section is partially narrowed. In this narrowed cross section, the flow velocity increases, so that the positive pressure P ₁ in the first pressure measuring hole formed in the pipe wall on the cross section decreases. When the static pressure detected in the second pressure measuring hole formed in the cylinder wall upstream of 1/2 or more of the cylinder inner diameter from the narrowed end surface is P ₂ , such a pressure drop, that is, differential pressure ΔP (= P ₂ -P ₁ ) Is measured by a pressure gauge and the flow velocity in the cylinder can be obtained by

Ⅴ = K ＊ （2 / ρ ＊ △ P) ^0.5

     Where K is the flow coefficient, ρ is the density of the fluid, and ΔP is the differential pressure generated.

     In the above function, the fluid restriction ratio of the flow path can be appropriately changed by the diameter of the pipe which is provided through, and the flow rate K can be adjusted as in the case of using an orifice.

      For example, when the flow rate is low, it is possible to penetrate through a large diameter pipe to increase the fluid restriction and increase the differential pressure generated.

     On the other hand, when the flow velocity is high, the differential pressure generated by reducing the fluid restriction can be reduced by using a pipe having a small diameter, and the pressure loss can also be suppressed.

     In general, since the pipe for installing the fluid-limited flowmeter has a complicated three-dimensional construction due to space problems, the velocity distribution of the fluid flowing therein shows an unstable flow that is not developed. In this state, in order to measure the flow rate with high accuracy, the conventional differential pressure detector needed to provide a sufficient straight pipe portion in the upper / lower fluid region.

     In the flowmeter according to the present invention, a rectifying function is added inside the differential pressure detector to correct the bias of the speed distribution and to significantly reduce the pipe construction restrictions.

     In general, since the measurement error rate of the pressure gauge decreases as the differential pressure increases, the overall error rate including the differential pressure detector and the pressure gauge can be reduced by increasing the detection pressure from the fluid.

When the fluid restriction mechanism is formed of a circular pipe or a right angle pipe, the velocity distribution in the cross section tends to accelerate in the vicinity of the portion where the fluid restriction structure is formed and to decrease as it approaches the cylinder wall. By detecting the pressure P ₃ (<P ₁ ) at the pipe wall surface, the differential pressure with the pressure P ₂ at the second pressure measuring hole becomes large. In this way, it is suitable to provide a pressure measuring hole in the wall surface of the fluid restriction part such as a pipe as a means of reducing the overall error rate.

In addition, by using a porous pipe having a flat rectifying function in an upstream region of the fluid restriction portion, the pressure P ₄ (total pressure) of the fluid can be detected to further improve the differential pressure with other pressures. In consideration of the error of the pressure gauge, it is possible to select a pressure measuring hole so as to obtain a differential pressure according to the flow rate, thereby enabling more appropriate measurement.

     For this purpose, as a porous pipe having a rectifying function, a flat hollow body having a shell-shaped cut surface is suitable, whereby the straight pipe portion of the differential pressure detector up / down region at the time of pipe construction can be shortened. Therefore, there is an effect that can reduce the constraints.

The pressure P ₄ from the perforated pipe, the pressure P ₂ from the pressure measuring hole formed in the cylinder wall in the upstream region of the perforated pipe and the pipe to be installed therethrough, at the cylinder wall surface above the cross section of the fluid restriction portion provided through the pipe. by appropriately combining the pressures P _1, P _3, or pressure, such as pressure from a pressure measurement hole formed in the wall of a pipe of the fluid restriction portion, it is possible to obtain various equations, which is represented by the food on the generated differential pressure and flow rate.

V = Kl ＊ [2 / ρ ＊ （P ₄ -P ₁ )] ^0.5

V = K2 ＊ [2 / ρ ＊ （P ₄ -P ₂ )] ^0.5

V = K3 ＊ [2 / ρ ＊ （P ₄ -P ₃ )] ^0.5

Here, Kl, K2, K3, ... are constants determined by the combination of the detected pressures as the flow coefficient.

As described above, by appropriately combining the pressures from three or more pressure measuring holes, the pressure gauge can measure in the differential pressure region maintaining high accuracy, and as a result, the overall measurement error rate can be reduced.

      In addition, a pipe installed through the pipe can be used as a calorimeter by installing a temperature sensor therein, and since the temperature sensor is built into the pipe, damage of the temperature sensor due to eddy vibration can be avoided. .

Other objects, features and advantages of the present invention will become apparent from the following description of the embodiments of the present invention taken in conjunction with the accompanying drawings.

1 is a perspective view of a fluid-limiting flow meter according to a first embodiment of the present invention.

FIG. 2 is a partial cutaway plan view of the flowmeter shown in FIG. 1. FIG.                 

3 is a perspective view of a fluid-limiting flow meter according to a first embodiment of the present invention with a rectifying plate.

FIG. 4 is a partial cutaway plan view of the fluid limited flow meter shown in FIG. 3. FIG.

Fig. 5 is a perspective view of the same fluid restriction type flow meter provided with the rectifying plate of another embodiment.

FIG. 6 is a partial cutaway plan view of the fluid limited flow meter shown in FIG. 5. FIG.

7 is a perspective view of a fluid-limited flow meter according to another embodiment of the present invention.

FIG. 8 is a partial cutaway front view of the fluid limited flow meter shown in FIG. 7. FIG.

Fig. 9 is a cross-sectional view showing a velocity distribution of a fluid restriction portion in the same fluid restriction type flow meter.

10 is a perspective view of a fluid-limiting flow meter according to another embodiment of the present invention.

FIG. 11 is a partial cutaway view of the fluid-limiting flow meter shown in FIG. 10. FIG.

12 is a perspective view of a fluid restriction type flow meter according to another embodiment of the present invention.

FIG. 13 is a partial cutaway plan view of the fluid limited flow meter shown in FIG. 12. FIG.

14 is a schematic view showing an example of a piping system to which a fluid-limited flow meter according to the present invention is applied.

FIG. 15 is a diagram showing a relationship between a differential pressure and a flow rate that can be obtained in a fluid-limited flow meter according to the present invention. FIG.

Hereinafter, a fluid limited flow meter according to an embodiment of the present invention will be described with reference to the drawings.

1 is a perspective view of a fluid-limiting flow meter according to an embodiment of the present invention, which has a cylinder 1 having a predetermined length in which a fluid to be measured flows in an arrow direction, and a central axis of the cylinder 1. A pipe (2) is provided so as to orthogonally protrude from the wall portion thereof, and is provided therethrough. The pipe (2) forms a fluid restriction mechanism. The pipe 2 is provided with a first pressure measuring hole 4 formed in the wall of the cylinder 1 at the end face of the cylinder 1 forming the narrowest part, and the first pressure measuring hole is provided. And a second pressure measuring hole 5 formed in the wall of the cylinder 1 upstream from the inner diameter of the cylinder 1 at least 1/2 of the inner diameter of the cylinder 1, and the pressure measuring holes 4 and 5 are provided for pressure acquisition. The connectors 3 and 3 are attached, and both ends of the cylinder 1 are provided with flanges 6 for attaching to a piping system as shown in FIG.

The cylinders 1 and the pipes 2 of these pressure detectors may be made of cast iron, other steels, metals such as brass, or resin, and the like. It may be as it is, and does not require a particularly high precision finish surface.

The piping system shown in FIG. 14 is a conduit piped between the pump 50 and the water intake portion 58 and the waterproof portion 59 of the water storage tank 51 through the valves 55, 56, 57 ( 52, 53, 54, etc., the cylinder 1 of the fluid-limited flowmeter is attached by the flange 6 between the straight pipes 52, 53, and can measure a flow velocity and a flow volume.

In the fluid-limiting flow meter of the above-described configuration, the pressure P ₁ of the fluid flowing in the fluid restriction portion can be detected through the connector 3 as a positive pressure from the first pressure measuring hole 4 on the wall of the cylinder 1. In the second pressure measurement hole 5, the pressure P ₂ can be detected as the positive pressure through the connector 3 in the pressure upstream from the fluid restriction portion of the fluid.

Both pressures at that time are detected with a relationship of P ₁ <P ₂ . The flow velocity and the flow rate can be calculated and calculated by the differential pressures ΔP = P ₂ -P ₁ of these pressures P ₁ and P ₂ .

Next, the fluid-limiting flow meter according to the embodiment of the present invention shown in FIGS. 3 to 6 further includes a single rectifying plate 7 further upstream of the second pressure measuring hole 5 in the cylinder 1. It is installed to eliminate the bias of speed distribution. The detection pressure in each of the measuring holes 4 and 5 is to rectify the inside of the cylinder 1 so as to eliminate the influence of the disturbance of the fluid flow. Thereby, also in the piping system shown in FIG. 14, the length of the straight pipes 52 and 53 for eliminating the bias of a speed distribution to the piping upstream and downstream of a flowmeter can be shortened.

The rectification plate 7 shown in FIG. 3 and FIG. 4 is arrange | positioned so that it may become parallel with the pipe 2 provided through. In the fluid limited flow meter shown in FIGS. 5 and 6, the rectifying plate 7 ′ intersecting the two plates is provided in the cylinder 1, and as shown in FIGS. 3 and 4, the speed distribution is eliminated. In addition, the rectifying plate may have a mesh structure or a honeycomb structure.                 

Next, a fluid limited flow meter according to another embodiment of the present invention will be described with reference to FIGS. 7 to 8. The difference from the fluid-limiting flow meter according to the above embodiment is that the first pressure measuring hole is formed in the wall surface of the pipe 2 'provided through the cylinder 1 instead of being formed in the wall portion of the cylinder 1. In this case, the velocity distribution of the fluid in the narrowest cross section is as shown in Fig. 9, and the pressure can be measured in a higher velocity region than in the case where the first pressure measurement hole is formed in the wall of the cylinder 1. Indicates.

In consideration of this velocity distribution, the first pressure measuring hole has a detection hole 8a located in the narrowest cross section of the wall of the pipe 2 'and a region downstream from the narrowest cross section as shown by the dotted line in FIG. The detection hole 8b may be formed in the same manner as the detection hole 8c at the most downstream portion as shown by the dotted line in Fig. 8. Further, among the detection holes 8a and 8b, Figs. Pressure measuring holes 8a-8a 'or pressure measuring holes 8b-8b' are respectively provided with detection holes 8a 'and 8b' at positions symmetrical with respect to the center line of the pipe 2 'in the flow line direction in FIG. It may be formed as.

Further, these pressure measuring holes 8a-8a ', 8b-8b', 8c are each detection holes 8a (8a ') in the downstream region of the narrowest cross section of the pipe 2', as shown in FIG. , 8b (8b ') and 8c], two or more locations may be provided at the wall surface of the pipe 2' along the axis of the pipe 2 '.

These detection sphere pressure from [8a (8a '), 8b (8b'), 8c)] , the pipe (2, is obtained from "), the connector (3 of the end portion") as the pressure P ₃ of this detected pressure P ₃ Is detected from the connector 3 'with a relationship of P ₃ <P _2. The flow rates and flow rates can be calculated from the differential pressures ΔP = P ₂ -P ₃ of these pressures P ₂ and P ₃ .

In the fluid limited flow meter shown in FIGS. 7 and 8, the rectifying plates 7 and 7 ′ as shown in FIGS. 3 to 6 may be provided, and the rectifying of the fluid is performed by the installation of the rectifying plates. As a result, the bias of the speed distribution can be corrected.

A fluid limited flow meter according to still another embodiment of the present invention will be described using the fluid limited flow meter shown in FIGS. 10 to 13.

The fluid limited flow meter according to this embodiment is different from that shown in FIGS. 1 to 7 above between the pipes 2 and 2 'and the second pressure measuring hole 5 inside the cylinder 1. The hollow body 10 having a shell shape in the cross section is provided in parallel to the pipes 2 and 2 'so that the hollow body 10 has a rectifying function. Opposing the flow of the fluid, a plurality of pressure measuring holes 11 are formed at the front end along the wall surface of the hollow body 10 perpendicular to the axis of the cylinder 1 at appropriate intervals, and the third pressure measuring hole ( The pressure detected in 11) is obtained as the pressure P ₄ at the upper end portion projecting out of the cylinder 1, and detected as the total pressure.

The pressure P ₄ and the cylinder 1, a second first pressure measurement formed in the wall surface of the cylinder (1) on the pressure P _2, or the cross-sectional flow path is most narrowed to detect from pressure measuring hole 5 of the wall surface of the upstream region From the combination of the pressure P ₁ (<P ₂ ) from the hole 4, the differential pressure ΔP = P ₄ -P ₁ (or ΔP = P ₄ -P ₂ ) can be measured and the flow rate and flow rate can be calculated by calculation. have.

The fluid limited flow meter shown in FIGS. 12 and 13 is provided with a flat hollow body 10 having a shell-shaped cross section shown in FIGS. 10 and 11 in the fluid limited flow meter shown in FIGS. 7 and 8. Similarly, the hollow body 10 has a rectifying function, and as the third pressure measuring hole 11, the pressure measuring hole 11 is opened at the distal end facing the flow, and a plurality of the hollow bodies 10 are perpendicular to the axis of the cylinder 1. It is formed in the hollow body 10 at appropriate intervals. The third pressure measuring hole 11 can detect the pressure P ₄ as the total pressure.

This pressure P ₄ and the pressure P ₂ detected from the second pressure measuring hole 5 on the wall of the cylinder 1 in the upstream region, or the pressure detection hole 8a on the wall of the pipe 2 provided through the cylinder 1 8a '), 8b (8b' ), 8c] by any one of the detected pressure from P ₃ (<Pl) wareul combinations and measured the determined differential pressure, flow rate and flow rate can be obtained by calculation.

Thus, the pressure measuring hole is the second pressure measuring hole 5, the first pressure measuring hole 4, the detection holes 8a, 8b, 8c of the pipe 2, or the third of the hollow body 10 having a flat shape. An example showing the relationship between the differential pressure and the velocity of the fluid is shown in FIG. 15 by selecting and combining the pressure from the pressure measuring hole 11.

Curves I, I, and I shown in Fig. 15 show the relationship between the respective differential pressure versus the flow rate between the pressure measuring holes, respectively. Curve I is a hollow body having a positive pressure and a flat shape from the first pressure measuring hole which is any one of the pressure detecting holes 8a (8a '), 8b (8b') and 8c of the pipes 2 and 2 '. The relationship between the differential pressure from the total pressure obtained from the third pressure measuring hole 11 and the flow velocity of the fluid is shown in (10), and the curve II is formed in the narrowest cross section of the wall of the cylinder 1. Similar to the positive pressure from the pressure measuring hole 4, the fluid for the differential pressure from the second pressure measuring hole 5 formed upstream of the hollow hollow body 10 of the cylinder 1 in a similar manner. The curve II1 shows a positive pressure from the second pressure measuring hole 5 of the cylinder 1 and a third pressure measuring hole 11 of the hollow body 10 of the flat shape. Shows the relationship between the flow rate and the differential pressure with respect to the total pressure from Since the pressure from the third pressure measuring hole 11 of the hollow body 10 of the flat shape is measured as the total pressure, it is the highest and the other pressure measuring holes 4, 5, 8a (8a '), 8b (8b'), 8c] The positive pressure is measured at each of the second pressure measuring holes 5, the first pressure measuring holes 4, and the measuring holes 8a (8a ') and 8b (in the pipes 2 and 2'). 8b ') and 8c], the lower static pressures are detected in the order of the positive pressures detected in this order, so by selecting two of these pressure measuring holes, a differential pressure suitable for the flow velocity of the fluid to be measured can be obtained. By using the above equation, the flow rate and flow rate can be obtained by calculation.

Specifically, as is clear from Fig. 15, in consideration of the measurement range and the error of the pressure gauge and the like, for example, when the maximum measurement range of the pressure gauge is 10 Kpa, the curve (I) shows the flow rate of the fluid of 2 m / s or less. It is effective in the measurement, and the curve II is effective for the measurement of the fluid whose flow velocity is 2 m / s-4 m / s, and the curve III is effective for the measurement of the fluid whose flow velocity is 4 m / s or more. In this way, when a measurement error of a pressure gauge or the like is taken into consideration and a curve capable of obtaining a large differential pressure within a flow rate range to be measured is selected, a highly accurate flow rate calculation is possible. In addition, although the flow velocity shows only up to 4 m / s, the curve III shown in FIG. 15 can obtain a differential pressure with a substantially identical curve.

Thus, on the basis of the curves I, II and II, the first pressure in the narrowest cross section of the cylinder 1 shown in FIGS. 10 to 13 is considered, taking into account the relationship between the differential pressure and the speed with little influence of the measurement error of the pressure gauge. The third pressure measuring holes 11 of the pressure measuring holes 4 and the pressure measuring holes 8a (8a ', 8b (8b') and 8c formed in the pipe 2 and the flat hollow body 10, respectively. When any two pressure measuring holes are selected and the pressure from both measuring holes is detected to obtain a differential pressure, the flow rate and flow rate of the fluid can be calculated by the differential pressure.

The fluid applicable to the fluid-limiting flowmeter as described above is not specifically defined, but it is natural that the fluid can be applied to a liquid such as water or a gas such as air, but to a fluid mixed with impurities such as sand and mud. It can also be used.

The fluid limited flow meter according to the present invention as described above exhibits the following effects.

Fluid-limited flowmeters can be formed using universal cylinders and pipes, regardless of material, and do not require precise machining, so they can be provided as inexpensive flowmeters.

In such a fluid-limiting flow meter, since the rectifying plate is provided at the uppermost part of the cylinder, it is possible to eliminate the bias of the velocity distribution and to reduce the number of straight pipes that eliminate the bias of the velocity distribution in the upstream and downstream regions of the cylinder. Measurements can be performed with high precision even in this narrow environment.

In addition, when the fluid is a liquid, since there are few edges and stagnations due to the structure, the wear due to corrosion and the deposition of deposits are small, and the measurement at high precision can be maintained for a long time.

In the differential pressure detector according to the prior art, since the relationship between the generated differential pressure, the flow velocity of the flowing fluid, and the flow rate is represented by a single square curve, surveying is performed from a low flow rate region to a high flow rate region with a single pressure gauge. In this case, there is a problem in that the range of generated differential pressure is large and the measurement error is large in the low flow rate region due to the performance of the pressure gauge. However, the present invention can provide a structure having three or more pressure detection units, and thus the pressure for obtaining the differential pressure. Since a plurality of combinations of measurement holes can be obtained, the overall error rate including the pressure gauge can be reduced, and high precision measurement can be performed in a wide range of flow rates and flow rates.

Although the said description was made about the Example, this invention is not limited to that, It is clear to those skilled in the art that various changes and correction can be made within the idea of this invention and the range of an attached claim.

The fluid-limiting flow meter according to the present invention is provided with a fluid pressure measuring device that does not require high precision machining, and enables a wide range of measurement of flow rate and flow rate by performing a wide range of pressure measurement with high accuracy to obtain a differential pressure.

Claims (10)

A cylinder through which the fluid to be measured flows, and In a fluid-limiting flow meter having a pipe for forming a fluid restriction mechanism installed through the cylinder orthogonal to its central axis, the pipe having a diameter smaller than the inner diameter of the cylinder, A first pressure measuring hole formed in a position above the narrowest cross section, perpendicular to the flow direction, and And a second pressure measuring hole formed in the wall portion of the cylinder upstream of at least 1/2 of the cylinder inner diameter from the narrowest end surface. The fluid-limited flow meter according to claim 1, wherein the first pressure measuring hole is formed in a wall of the cylinder on the narrowest cross section. The fluid-limited flow meter according to claim 1 or 2, wherein the first pressure measuring hole is formed on a wall surface of the pipe on the narrowest cross section. The fluid-limited flow meter according to claim 3, wherein the first pressure measuring hole is formed on a wall surface downstream from the narrowest end surface at the wall surface of the pipe. The fluid-limiting flow meter according to claim 3, wherein a rectifying plate is provided upstream of the cylinder inner diameter from the second pressure measuring hole at least 1/2 of the inner diameter of the cylinder. A cylinder through which the fluid to be measured flows, and In a fluid limited flow meter having a pipe installed so as to be perpendicular to the central axis of the cylinder, the pipe having a diameter smaller than the inner diameter of the cylinder, A flat hollow body having a shell-shaped cutting surface is provided at a position upstream from the narrowest cross-sectional position perpendicular to the flow direction of the fluid in the cylinder, A first pressure measuring hole formed at a position above the narrowest cross section, a second pressure measuring hole formed at a wall portion of the cylinder upstream of the hollow body, and a third formed by opening a hole in the fluid flow direction in the hollow body A fluid limited flow meter having a pressure measuring hole. 7. A fluid restricted flow meter according to claim 6, wherein said first pressure measuring hole is formed in a wall of said cylinder on said narrowest cross section. The fluid restriction type as claimed in claim 6, wherein the first pressure measuring hole is formed on the wall surface of the pipe on the narrowest cross section or on the wall surface of the pipe downstream from the first pressure measuring hole. Flow meter. The pressure measuring hole according to any one of claims 6 to 8, wherein any one of the first, second and third pressure measuring holes is selected, and the differential pressure between the selected pressure measuring holes is selected. And a differential pressure suitable for a pressure gauge in a wide range of flow rates. The fluid-limiting flow meter according to claim 4, wherein a rectifying plate is provided upstream of the cylinder inner diameter at least 1/2 of the inner diameter of the cylinder from the second pressure measuring hole.

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