JP2020159851A - Differential flowmeter - Google Patents

Abstract

To provide a differential flowmeter with which it is possible to measure a more accurate flow rate.SOLUTION: Provided is a differential flowmeter for measuring the flow rate of a fluid flowing in a flow path. The differential flowmeter comprises: a pair of pressure difference generators arranged serially to the flow path, for generating a pressure difference in the fluid; and a flow rate measurement mechanism for measuring the flow rate of a fluid flowing in the flow path on the basis of a first pressure difference which is a difference between the first pressure of a fluid flowing into the pressure difference generator on the upstream side and the second pressure of a fluid flowing out of the pressure difference generator on the upstream side and flowing into the pressure difference generator on the downstream side and a second pressure difference between the second pressure and the third pressure of a fluid flowing out of the pressure difference generator on the downstream side. The pair of pressure difference generators have an internal flow path in mutually different length, and the flow path shapes on the upstream end side in the internal flow paths of both pressure difference generators are set to approximately the same shape loss, as well as the flow path shapes on the downstream end side in the internal flow paths of both pressure difference generators are set to approximately the same shape loss.SELECTED DRAWING: Figure 1

Description

The present invention relates to a differential pressure type flow meter.

In the semiconductor manufacturing process, since it is necessary to accurately grasp the flow rate of the fluid flowing through the flow path, a flow meter is installed in each flow path. For example, in Patent Document 1, as one of the flowmeters, a differential pressure generator installed in a flow path, an upstream pressure gauge for detecting the pressure of a fluid flowing into the differential pressure generator, and a differential pressure generator. A differential pressure type flowmeter including a downstream pressure gauge for detecting the pressure flowing out of the flow meter is disclosed.

By the way, there is the following formula (1) as a theoretical formula for installing a differential pressure generator in the flow path and calculating the volume flow rate Qv and the mass flow rate Qm of the fluid from the differential pressure generated in the differential pressure generator.

Here, d is the diameter of the differential pressure generator, μ is the viscosity of the fluid, and l is the region where the velocity distribution of the fluid flowing into the differential pressure generator from the flow path is completed as a laminar flow through the run-up section (hereinafter). , Also referred to as a laminar flow region), ΔP indicates the differential pressure between the two points, respectively. That is, in this equation (1), only the friction loss in the laminar flow region in the differential pressure generator is considered.

Therefore, in the conventional differential pressure type flow meter, the differential pressure ΔP'is calculated from the pressures detected by both pressure gauges, and the differential pressure ΔP'is used as ΔP to calculate the volumetric flow rate Qv from the equation (1). , Accurate flow rate cannot be obtained.

This is because, when the fluid flowing through the measurement flow path of the upstream pressure gauge flows into the internal flow path of the differential pressure generator, the differential pressure ΔP'obtained by the conventional differential pressure type flow meter flows at the joint. Shape loss caused by the reduction of the path shape, and when the fluid flowing through the internal flow path of the differential pressure generator flows into the measurement flow path of the downstream pressure gauge, it occurs due to the expansion of the flow path shape at the joint. This is because the shape loss and the friction loss generated in the measurement flow path of each pressure gauge are included.

On the other hand, a method of directly measuring the differential pressure ΔP by providing a pressure extraction portion in the laminar flow region of the differential pressure generator is also conceivable, but in order to extract the static pressure from the differential pressure generator, the diameter of the differential pressure generator is used. However, since it is necessary to connect a pressure outlet pipe having a diameter small to some extent, there is a problem that the diameter of the pressure outlet pipe becomes too small and the static pressure cannot be taken out accurately.

Japanese Unexamined Patent Publication No. 2006-153677

Therefore, the main object of the present invention is to obtain a differential pressure type flow meter capable of measuring a more accurate flow rate by using a theoretical formula.

That is, the differential pressure type flow meter according to the present invention is a differential pressure type flow meter that measures the flow rate of a fluid flowing through a flow path, and is installed in series with the flow path to generate a differential pressure in the fluid. A pair of differential pressure generators, a first pressure of a fluid flowing into the differential pressure generator on the upstream side, and a fluid flowing out of the differential pressure generator on the upstream side and flowing into the differential pressure generator on the downstream side. It flows through the flow path based on the first differential pressure, which is the difference between the second pressures, and the second differential pressure, which is the difference between the second pressure and the third pressure of the fluid flowing out from the differential pressure generator on the downstream side. A flow rate measuring mechanism for measuring the flow rate of a fluid is provided, and the pair of differential pressure generators have internal flow paths having different lengths from each other, and the upstream end side of the internal flow paths of the two differential pressure generators. The flow path shape is set to have substantially the same shape loss, and the flow path shape on the downstream end side in the internal flow path of the two differential pressure generators is set to have substantially the same shape loss. It is characterized by being.

Further, the differential pressure type flow meter according to the present invention is a differential pressure type flow meter that measures the flow rate of a fluid flowing through a flow path, and is installed in series with the flow path to generate a differential pressure in the fluid. A pair of differential pressure generators, a first pressure of a fluid flowing into the differential pressure generator on the upstream side, and a fluid flowing out of the differential pressure generator on the upstream side and flowing into the differential pressure generator on the downstream side. It flows through the flow path based on the first differential pressure, which is the difference between the second pressures, and the second differential pressure, which is the difference between the second pressure and the third pressure of the fluid flowing out from the differential pressure generator on the downstream side. A flow rate measuring mechanism for measuring the flow rate of a fluid is provided, and the pair of differential pressure generators have internal flow paths having different lengths from each other, and the upstream end side of the internal flow paths of the two differential pressure generators. It is characterized in that the shape loss caused in the above is canceled with each other and the shape loss generated on the downstream end side in the internal flow path of the two differential pressure generators is canceled with each other.

In such a case, since the flow path shapes on the upstream end side and the downstream end side of the internal flow path of each differential pressure generator are substantially the same, a pair based on the first differential pressure and the second differential pressure. When calculating the differential pressure generated by the differential pressure generator, the shape losses that occur on the upstream end side and the downstream end side of the internal flow path of each differential pressure generator are canceled each other. This makes it possible to calculate the volumetric flow rate more accurately using the theoretical formula. Here, the shape loss refers to the energy loss generated in the fluid flowing through the internal flow path due to the shape change of the internal flow path (specifically, bending of the internal flow path, expansion / contraction of the inner diameter of the internal flow path, etc.). ing.

Specifically, as the pair of differential pressure generators, a capillary having an internal flow path set to substantially the same diameter dimension may be used.

Further, as the differential pressure type flow meter according to the present invention, the first differential pressure and the second differential pressure are calculated after detecting the first pressure, the second pressure and the third pressure by three pressure gauges, respectively. A pressure detection method and a differential pressure detection method in which the first differential pressure and the second differential pressure are directly detected by a differential pressure gauge can be considered.

As a pressure detection method, a first pressure gauge in which the flow rate measuring mechanism is connected to the upstream end of the differential pressure generator on the upstream side and has a pressure extraction unit for taking out the first pressure inside the differential pressure generator, and the above. A second pressure gauge connected between the downstream end of the differential pressure generator on the upstream side and the upstream end of the differential pressure generator on the downstream side and having a pressure take-out portion inside the differential pressure generator, and the downstream side. It may be provided with a third pressure gauge connected to the downstream end of the differential pressure generator on the side and having a pressure extraction portion for taking out the third pressure inside.

In this case, it is preferable that the pressure extraction portions of the first pressure gauge, the second pressure gauge, and the third pressure gauge are set to have substantially the same shape.

In such a case, when calculating the differential pressure generated by the pair of differential pressure generators based on the pressure detected by each pressure gauge, the friction loss generated at the pressure extraction part of each pressure gauge is mutual. It will be canceled. This makes it possible to calculate the volumetric flow rate more accurately using the theoretical formula.

Further, in this case, the pressure extraction portions of the first pressure gauge, the second pressure gauge, and the third pressure gauge communicate with the internal flow path of any of the differential pressure generators and are larger than the internal flow path. It has a measurement flow path with a radial dimension, and the difference between the flow path shape at the junction between the internal flow path of the differential pressure generator on the upstream side and the measurement flow path of the first pressure gauge and the downstream side. The shape of the flow path at the joint between the internal flow path of the pressure generator and the measurement flow path of the second pressure gauge is set to have substantially the same shape loss, and the differential pressure generator on the upstream side At the joint between the internal flow path and the measurement flow path of the second pressure gauge, and at the joint between the internal flow path of the differential pressure generator on the downstream side and the measurement flow path of the third pressure gauge. It is preferable that the shape loss is set to be substantially the same as the shape of the flow path.

In such a case, when calculating the differential pressure generated by the pair of differential pressure generators based on the pressure detected by each pressure gauge, the measurement flow path of each pressure gauge and each differential pressure generator are used. The shape loss that occurs at the joint with the internal flow path of the is canceled each other. This makes it possible to calculate the volumetric flow rate more accurately using the theoretical formula.

Further, as a differential pressure detection method, the pair of differential pressure generators are intermittently arranged with respect to the flow path, and the flow rate measuring mechanism is provided at the upstream end of the differential pressure generator on the upstream side and A first differential pressure gauge that is communicated with each of the flow paths connected to the downstream end and has a differential pressure take-out portion that takes out the first differential pressure inside the flow path, and upstream and downstream sides of the differential pressure generator on the downstream side. It may be provided with a second differential pressure gauge which is communicated with each of the flow paths connected to the above and has a differential pressure take-out portion for taking out the second differential pressure inside.

Further, in this case, it is preferable that the heights of the differential pressure extraction portions of the first differential pressure gauge and the second differential pressure gauge extending from the flow path with respect to the flow path are set to be substantially the same.

In such a case, when the differential pressure generated by the pair of differential pressure generators is calculated based on the differential pressure detected by each differential pressure gauge, the losses generated in the pressure extraction section of each differential pressure gauge are mutually different. It will be canceled. This makes it possible to calculate the volumetric flow rate more accurately using the theoretical formula.

Further, in this case, the differential pressure extraction portion of the first differential pressure gauge and the second differential pressure gauge communicates with the upstream side of the internal flow path of any of the differential pressure generators, and has a diameter larger than that of the internal flow path. It has a first measurement flow path having the above and a second measurement flow path which communicates with the downstream side of the internal flow path of the differential pressure generator and has a diameter larger than that of the internal flow path. The shape of the flow path at the junction between the internal flow path of the differential pressure generator on the side and the first measurement flow path of the first differential pressure gauge, and the internal flow path of the differential pressure generator on the downstream side and the second differential pressure gauge. The shape of the flow path at the joint with the first measurement flow path is set to be substantially the same, and the internal flow path of the differential pressure generator on the upstream side and the first differential pressure gauge are the first. The shape of the flow path at the joint with the two measurement flow paths and the shape of the flow path at the joint between the internal flow path of the differential pressure generator on the downstream side and the second measurement flow path of the second differential pressure gauge are substantially the same. It is more preferable that the shape loss is set to be.

In such a case, when calculating the differential pressure generated by the pair of differential pressure generators based on the differential pressure detected by each differential pressure gauge, the measurement flow path of each differential pressure gauge and each differential pressure generation are generated. The shape losses that occur at the junction with the internal flow path of the body cancel each other out. This makes it possible to calculate the volumetric flow rate more accurately using the theoretical formula. In this case, the second measurement flow path of the first differential pressure gauge and the first measurement flow path of the second differential pressure gauge may be common.

Further, in the differential pressure detection method, a correction pressure gauge for correcting the density of the fluid may be provided.

When calculating the mass flow rate of a fluid, the density of the fluid is used, but in such a case, the density of the fluid can be corrected based on the detection value of the correction pressure gauge, so that it is more accurate. The flow rate can be obtained.

In the differential pressure flowmeter according to the present invention, since it is necessary to arrange the two differential pressure generators in series, the total length of the differential pressure flowmeter becomes long. Therefore, at least a part of the two differential pressure generators may be bent, or a part of the two differential pressure generators may be bent in an annular shape.

With such a thing, the total length of the differential pressure flowmeter can be shortened, which makes it compact.

Further, at least one of the pair of differential pressure generators may be equipped with a temperature sensor that detects the temperature of the fluid flowing through the internal flow path thereof.

With such a case, the viscosity μ of the fluid flowing through the differential pressure generator can be corrected based on the temperature, so that a more accurate flow rate can be measured.

According to the differential pressure type flow meter configured as described above, a more accurate flow rate can be measured by using the theoretical formula.

It is sectional drawing which shows typically the differential pressure type flow meter which concerns on Embodiment 1. FIG. It is sectional drawing which shows typically the differential pressure type flow meter which concerns on Embodiment 2. It is a schematic diagram which shows the differential pressure type flow meter which concerns on other embodiment. It is a schematic diagram which shows the differential pressure type flow meter which concerns on other embodiment.

The differential pressure type flow meter according to the present invention will be described below with reference to the drawings.

The differential pressure type flowmeter according to the present invention is installed in a flow path connected to each device used in the semiconductor manufacturing process. The differential pressure type flowmeter according to the present invention can also be used for flow paths in other fields.

<Embodiment 1> As shown in FIG. 1, the differential pressure type flowmeter 100 according to the present embodiment is installed in series with the flow path L, and a pair that generates a differential pressure in the fluid flowing through the flow path L. The differential pressure generators 10 and 20 and the flow rate measuring mechanism F for measuring the flow rate of the fluid flowing through the flow path L based on the differential pressure generated by the differential pressure generators 10 and 20 are provided.

The pair of differential pressure generators 10 and 20 are tubular, and specifically, a cylindrical capillary. The pair of differential pressure generators 10 and 20 are set so that the flow path shapes on the upstream end side of the internal flow paths 10a and 20a have substantially the same shape loss as each other, and the internal flow paths 10a, The shape of the flow path on the downstream end side of 20a is set so as to have substantially the same shape loss. Specifically, the pair of differential pressure generators 10 and 20 have internal flow paths 10a and 20a having different lengths, and the diameter dimensions of the internal flow paths 10a and 20a are substantially the same. .. That is, the internal flow paths 10a and 20a of the pair of differential pressure generators 10 and 20 have substantially the same shape other than their lengths. In the present embodiment, a cylindrical capillary is used, but the capillaries are not limited to this, and the cross sections of the internal flow paths 10a and 20a may be a capillary having another shape such as a rectangular shape or an elliptical shape. ..

The pair of differential pressure generators 10 and 20 extend linearly, respectively, and are arranged side by side with respect to the flow path L along the flow direction of the fluid. More specifically, the differential pressure generator 10a having the shorter overall length is arranged on the upstream side of the flow path L, and the differential pressure generator 20a having the longer overall length is arranged on the downstream side of the flow path L. There is.

Specifically, the flow rate measuring mechanism F generates a differential pressure on the downstream side by flowing out of the first pressure, which is the pressure of the fluid flowing into the differential pressure generator 10 on the upstream side, and the differential pressure generator 10 on the upstream side. It is the difference between the first differential pressure, which is the difference between the second pressure, which is the pressure of the fluid flowing into the body 20, and the third pressure, which is the pressure of the fluid flowing out from the second pressure and the differential pressure generator 20 on the downstream side. The flow rate of the fluid flowing through the flow path L is measured based on the second differential pressure.

Then, the flow rate measuring mechanism F is connected to the upstream end of the differential pressure generator 10 on the upstream side, and has a first pressure gauge 30 having a pressure extraction unit 31 for taking out the first pressure inside the first pressure gauge 30 and the upstream side. A second pressure gauge 40 which is connected between the downstream end of the differential pressure generator 10 and the upstream end of the differential pressure generator 20 on the downstream side and has a pressure take-out portion 41 for taking out the second pressure inside. A third pressure gauge 50, which is connected to the downstream end of the differential pressure generator 20 on the downstream side and has a pressure take-out portion 51 for taking out the third pressure, is provided therein. In the following, the first pressure gauge 30, the second pressure gauge 40, and the third pressure gauge 50 are collectively referred to as pressure gauges 30, 40, and 50.

The pressure extraction portions 31, 41, 51 of the pressure gauges 30, 40, 50 communicate with the flow path L and the internal flow paths 10a, 20a of the differential pressure generators 10, 20, and the measurement flow path 31a, in which the fluid flows. It includes 41a, 51a and pressure outlet paths 31b, 41b, 51b that branch off from the measurement flow paths 31a, 41a, 51a. Further, the measurement flow paths 31a, 41a, 51a have a larger diameter dimension (diameter) than the internal flow paths 10a, 20a of the differential pressure generators 10 and 20. Further, the pressure outlet paths 31b, 41b, 51b branch from the measurement flow paths 31a, 41a, 51a and extend, and pressure detection for detecting the pressure taken out by the pressure extraction paths 31b, 41b, 51b on the tip side thereof Parts 32, 42, and 52 are provided. The pressure extraction portions 31b, 41b, 51b of the present embodiment branch off from a position corresponding to the center with respect to the upstream and downstream directions of the measurement flow paths 31a, 41a, 51a.

In each of the pressure gauges 30, 40, 50, the shapes of the pressure extraction portions 31, 41, 51 are set to substantially the same shape. Specifically, the pressure extraction portions 31, 41, 51 of the pressure gauges 30, 40, 50 have substantially the same length and diameter of the measurement flow paths 31a, 41a, 51a and the pressure extraction passages 31b, 41b, 51b. In addition, the branch positions of the pressure outlet paths 31b, 41b, 51b with respect to the measurement flow paths 31a, 41a, 51a are set to be substantially the same.

Then, the shape of the flow path at the joint portion X1 between the internal flow path 10a of the differential pressure generator 10 on the upstream side and the measurement flow path 31a of the first pressure gauge 30, and the internal flow path 20a of the differential pressure generator 20 on the downstream side. And the shape of the flow path at the joint portion X2 between the second pressure gauge 40 and the measurement flow path 41a of the second pressure gauge 40 are set so as to have substantially the same shape loss. That is, the internal flow paths 10a and 20a and the measurement flow paths 31a and 41a are joined so that the flow path shapes of these joint points X1 and X2 are substantially the same.

Further, the shape of the flow path at the junction X3 between the internal flow path 10a of the differential pressure generator 10 on the upstream side and the measurement flow path 41a of the second pressure gauge 40, and the internal flow path 20a of the differential pressure generator 20 on the downstream side. And the shape of the flow path at the joint portion X4 with the measurement flow path 51a of the third pressure gauge 50 are set so as to have substantially the same shape loss. That is, the internal flow paths 10a and 20a and the measurement flow paths 41a and 51a are joined so that the flow path shapes of these joint points X3 and X4 are substantially the same.

The flow rate measuring mechanism F further includes a calculation unit 60. The calculation unit 60 is connected to the pressure gauges 30, 40, and 50, respectively. The arithmetic unit 60 is composed of a so-called computer equipped with a CPU, a memory, an A / D / D / A converter, an input / output means, etc., and a program stored in the memory is executed to execute various devices. The function is realized by collaborating. Specifically, it exerts a function of calculating the flow rate of the fluid flowing in the flow path L based on the pressures detected by the pressure gauges 30, 40, and 50.

Next, the measurement principle of the differential pressure type flow meter 100 according to the present embodiment will be described.

First, the first pressure is P ₁ , the second pressure is P ₂ , the third pressure is P ₃ , and the friction loss generated on the downstream side Y1 of the measurement flow path 31a of the first pressure gauge 30 is ΔPf _{p1 out.} The friction loss generated in Y2 downstream of the pressure outlet path 41b in the measurement flow path 41a of the second pressure gauge 40 is ΔP _fp2out , and the friction loss occurs in Y3 upstream of the pressure outlet passage 41b in the measurement flow path 41a of the second pressure gauge 40. The generated friction loss is ΔP _fp2in , the friction loss generated on the upstream side Y4 of the pressure outlet path 51b in the measurement flow path 51a of the third pressure gauge 50 is ΔP _fp3in , and the shape loss due to the reduction of the flow path shape at the joint portion X1 is ΔP. _sc1 , the shape loss due to the expansion of the flow path shape at the junction X3 is ΔP _se1 , the shape loss due to the reduction of the flow path shape at the junction X2 is ΔP _sc2 , and the shape loss due to the expansion of the flow path shape at the junction X4 is If ΔP _se2 , the friction loss in the laminar flow region of the differential pressure generator 10 on the upstream side is ΔP _fc1 , and the friction loss in the laminar flow region of the differential pressure generator 20 on the downstream side is ΔP _fc2 , then the first differential pressure ΔP ₁₂ And the second differential pressure ΔP ₂₃ can be expressed by the following equations (2) and (3), respectively.

Here, since the pressure extraction portions 31, 41, 51 of the pressure gauges 30, 40, and 50 have substantially the same shape, the friction loss that occurs on the downstream side Y1 of the measurement flow path 31a of the first pressure gauge 30 and? Pf _P1OUT, the friction loss [Delta] P _Fp2out occurring downstream Y2 of the second pressure gauge 40 of the measuring channel 41a is substantially the same, friction loss [Delta] P occurs upstream Y3 of the second pressure gauge 40 of the measuring channel 41a _Fp2in And the friction loss ΔP _fp3in generated on the upstream side Y4 of the measurement flow path 51a of the third pressure gauge 50 are substantially the same. Further, since the flow path shapes of the joint portion X1 and the joint portion X2 are substantially the same, the shape loss ΔP _sc1 generated at the joint portion X1 and the shape loss ΔP _sc2 generated at the joint portion X2 are substantially the same. Further, since the flow channel shape of the joint X3 and joint X4 is in substantially the same shape, the shape loss [Delta] P _se1 occurring joint X3 and shape loss [Delta] P _se2 occurring joint X4 is substantially the same.

Therefore, when the difference between the first differential pressure ΔP ₁₂ and the second differential pressure ΔP ₂₃ is calculated based on the equations (2) and (3), other than the friction loss generated in the laminar flow region of the differential pressure generators 10 and 20. The following equation (4) is obtained, excluding the friction loss and shape loss of.
That is, from only the pressure value detected by each pressure gauge, a value including only the friction loss in the laminar flow region can be obtained.

Then, by substituting this ΔP _{23 −} ΔP ₁₂ into the equation (1) as ΔP, a more accurate flow rate of the fluid flowing through the flow path L can be calculated.

The calculation unit 60 includes a first pressure P1 detected by the first pressure gauge 30, a second pressure P2 detected by the second pressure gauge 40, and a third pressure P3 detected by the third pressure gauge 50. ΔP is calculated based on the equation (4), and the flow rate of the fluid flowing through the flow path L is calculated using the equation (1).

<Embodiment 2> The differential pressure type flow meter 100 according to the present embodiment is a modified example of the flow rate measuring mechanism F in the first embodiment. Specifically, as shown in FIG. 2, the flow rate measuring mechanism F according to the present embodiment is connected to the upstream end and the downstream end of the differential pressure generator 10 on the upstream side, and the first differential pressure is applied to the inside thereof. It has a first differential pressure gauge 70 having a differential pressure extraction unit 71 to be taken out, and a differential pressure extraction unit 81 connected to the upstream side and the downstream side of the differential pressure generator 20 on the downstream side and taking out the second differential pressure inside. It is provided with a second differential pressure gauge 80. In the following, the first differential pressure gauge 70 and the second differential pressure gauge 80 are collectively referred to as the differential pressure gauges 70 and 80.

The differential pressure extraction portions 71 and 81 of the differential pressure gauges 70 and 80 are the first measurement flow paths 71a and 81a in which the fluid flows in communication with the upstream sides of the internal flow paths 10a and 20a of the differential pressure generators 10 and 20. The second measurement flow paths 71b and 81b, and the first measurement flow paths 71a and 81a and the second measurement flow paths 71b, in which the fluid flows in communication with the downstream sides of the internal flow paths 10a and 20a of the differential pressure generators 10 and 20. , 81b, and the pressure outlet paths 71c and 81c extending from the 81b. The first measurement flow paths 71a and 81a and the second measurement flow paths 71b and 81b have a larger diameter than the internal flow paths 10a and 20a of the differential pressure generators 10 and 20. Further, the pressure outlet passages 71c and 81c are branched from the first measurement passages 71a and 81a and the second measurement passages 71b and 81b, and are taken out by the pressure outlet passages 71c and 81c to the tip side thereof. Differential pressure detection units 72 and 82 for detecting the differential pressure of the pressure are provided. In the present embodiment, the second measurement flow path 71b of the first differential pressure gauge 70 and the first measurement flow path 81a of the second differential pressure gauge 80 are commonly used, and from this common measurement flow path. A part of the pressure take-out path 71c of the first differential pressure gauge 70 and a part of the pressure take-out path 81c of the second differential pressure gauge 80 are commonly used.

The differential pressure extraction portions 71 and 81 of the differential pressure gauges 70 and 80 have a height h (the length of a portion extending in the orthogonal direction from the flow path L) of the differential pressure extraction paths 71c and 81c from the flow path L. It is set to be the same. Specifically, the height h from the flow path L of the differential pressure extraction paths 71c and 81c located on both sides of the differential pressure detection units 72 and 82 (the length of the portion extending in the orthogonal direction from the flow path L). Are set to be approximately the same. Further, the height h (the length of the portion extending in the orthogonal direction from the flow path L) from the flow path L of the differential pressure take-out path 71c and the differential pressure take-out path 81c is set to be substantially the same. As a result, the differential pressure detection units 72 and 82 are all arranged at substantially the same height from the flow path L. Further, the branch positions of the pressure outlet paths 71c with respect to the first measurement flow paths 71a and 81a and the second measurement flow paths 71b and 81b are set to be substantially the same.

Then, the shape of the flow path at the junction X1 between the internal flow path 10a of the differential pressure generator 10 on the upstream side and the first measurement flow path 71a of the first differential pressure gauge 70, and the internal flow of the differential pressure generator 20 on the downstream side. The shape of the flow path at the joint portion X2 between the path 20a and the first measurement flow path 81a of the second differential pressure gauge 80 is set so as to have substantially the same shape loss. That is, the internal flow paths 10a and 20a and the first measurement flow paths 71a and 81a are joined so that the flow path shapes of these joint points X1 and X2 are substantially the same.

Further, the shape of the flow path at the junction X3 between the internal flow path 10a of the differential pressure generator 10 on the upstream side and the second measurement flow path 71b of the first differential pressure gauge 70, and the internal flow of the differential pressure generator 20 on the downstream side. The shape of the flow path at the joint portion X4 between the path 20a and the second measurement flow path 81b of the second differential pressure gauge 80 is set so as to have substantially the same shape loss. That is, the internal flow paths 10a and 20a and the second measurement flow paths 71b and 81b are joined so that the flow path shapes of these joint points X3 and X4 are substantially the same.

Even in such a case, ΔP should be calculated based on the difference between the first differential pressure P ₁₂ detected by the first differential pressure gauge 70 and the second differential pressure P ₂₃ detected by the second differential pressure gauge 80. As a result, the shape loss that occurs at the joints X1, X2, X3, and X4, the friction loss that occurs in the first measurement flow path 71a and the second measurement flow path 71b of the first differential pressure gauge 70, and the first of the second differential pressure gauge 80 A differential pressure including only the friction loss in the laminar flow region is obtained, excluding the friction loss generated in the measurement flow path 81a and the second measurement flow path 81b.

<Other Embodiments> In each of the above embodiments, linear capillaries are used as the pair of differential pressure generators 10 and 20, but as shown in FIGS. 3 (a) and 3 (b), for example. In addition, a shape in which the middle of the capillaries 10 and 20 is bent in a U shape, or a shape in which the middle of the capillaries 10 and 20 is bent in an annular shape may be used as shown in FIG. Here, in the embodiments shown in FIGS. 3A, 3B, and 4, the capillary 10 (upstream differential pressure generator 10) and the capillary 20 (downstream differential pressure generator 20) are When looking at a portion other than the linear portion, it has bent portions having the same shape as each other. For example, in the embodiment shown in FIGS. 3 (a) and 3 (b), the capillary 10 and the capillary 20 are provided with portions that are bent in a U shape and a pair of L shapes, respectively. In the embodiments shown, the capillary 10 and the capillary 20 include portions that are bent in an annular shape with respect to each other. Further, in the embodiments shown in FIGS. 3 (a), 3 (b) and 4, the capillaries 10 and 20 have different lengths of linear portions from each other, whereby both capillaries 10 and 20 are used. The total length of is different. For example, in the embodiments shown in FIGS. 3A and 4, the capillary 10 and the capillary 20 are either one or both of the upstream end portions 10b and 20b and the downstream end portions 10c and 20c (both in both embodiments). ) Have different lengths, and in the embodiment shown in FIG. 3B, the capillary 10 and the capillary 20 have different lengths from each other in the intermediate portions 10d and 20d. It has become. With such a device, the total length of the entire device can be shortened while maintaining the total length of the capillary. In the embodiment shown in FIG. 3B, the distance between the first pressure gauge 30 and the second pressure gauge 40 and the distance between the second pressure gauge 40 and the third pressure gauge 50 are the same. ing.

Further, in each of the above-described embodiments, the capillary is used as the pair of differential pressure generators 10 and 20, but as the pair of differential pressure generators, a restrictor in which a laminar flow element is arranged in the internal flow path is used. You may.

Further, in the second embodiment, a pressure gauge for detecting the pressure of the fluid flowing through the flow path L may be further provided. In this case, the pressure gauge may be provided on the upstream side of the first differential pressure gauge 70 or on the downstream side of the second differential pressure gauge 80 so as not to interfere with the differential pressure measurement. This makes it possible to correct the density of the fluid based on the pressure detected by the pressure gauge. Then, a more accurate value can be obtained by calculating the mass flow rate Qm by the following equation (5).
Note that ρ indicates the density of the fluid.

Further, in each of the above-described embodiments, a temperature sensor may be provided for the pair of differential pressure generators 10 and 20. In this case, the viscosity μ and the density ρ of the fluid can be corrected based on the temperature measured by the temperature sensor.

In addition, the present invention is not limited to each of the above-described embodiments, and it goes without saying that various modifications can be made without departing from the spirit of the present invention.

100 Differential pressure type flow meter 10 Upstream differential pressure generator 10a Internal flow path 20 Downstream differential pressure generator 20a Internal flow path 30 First pressure gauge 31 Differential pressure extraction unit 31a Measurement flow path 40 Second pressure gauge 41 Difference Pressure take-out part 41a Measurement flow path 50 Third pressure gauge 51 Differential pressure take-out part 51a Measurement flow path 70 First differential pressure gauge 71a First measurement flow path 71b Second measurement flow path 71c Pressure take-out passage 80 Second differential pressure gauge 81a First Measurement flow path 81b Second measurement flow path 81c Pressure outlet path X1, X2, X3, X4 Connection point

Claims (13)

A differential pressure type flow meter that measures the flow rate of fluid flowing through the flow path.
A pair of differential pressure generators that are installed in series with the flow path and generate a differential pressure in the fluid.
The difference between the first pressure of the fluid flowing into the differential pressure generator on the upstream side and the second pressure of the fluid flowing out of the differential pressure generator on the upstream side and flowing into the differential pressure generator on the downstream side. Flow rate measurement to measure the flow rate of the fluid flowing through the flow path based on the 1 differential pressure and the 2nd differential pressure which is the difference between the 2nd pressure and the 3rd pressure of the fluid flowing out from the differential pressure generator on the downstream side. Equipped with a mechanism
The pair of differential pressure generators have internal flow paths of different lengths, and the flow path shapes on the upstream end side of the internal flow paths of the two differential pressure generators have substantially the same shape loss. A differential pressure type flow meter characterized in that the shape of the flow path on the downstream end side in the internal flow path of the two differential pressure generators is set to have substantially the same shape loss. A differential pressure type flow meter that measures the flow rate of fluid flowing through the flow path.
A pair of differential pressure generators that are installed in series with the flow path and generate a differential pressure in the fluid.
The difference between the first pressure of the fluid flowing into the differential pressure generator on the upstream side and the second pressure of the fluid flowing out of the differential pressure generator on the upstream side and flowing into the differential pressure generator on the downstream side. Flow rate measurement to measure the flow rate of the fluid flowing through the flow path based on the 1 differential pressure and the 2nd differential pressure which is the difference between the 2nd pressure and the 3rd pressure of the fluid flowing out from the differential pressure generator on the downstream side. Equipped with a mechanism
The pair of differential pressure generators have internal flow paths of different lengths, and the shape loss generated on the upstream end side of the internal flow paths of the two differential pressure generators is canceled by each other, and both of them. A differential pressure type flowmeter characterized in that shape losses occurring on the downstream end side in the internal flow path of the differential pressure generator are configured to cancel each other. The differential pressure type flow meter according to claim 1 or 2, wherein the pair of differential pressure generators are capillaries having internal flow paths set to substantially the same diameter. The flow rate measuring mechanism
A first pressure gauge connected to the upstream end of the differential pressure generator on the upstream side and having a pressure extraction unit for taking out the first pressure inside the first pressure gauge.
A second pressure gauge connected between the downstream end of the differential pressure generator on the upstream side and the upstream end of the differential pressure generator on the downstream side and having a pressure take-out portion inside the differential pressure generator.
The difference according to any one of claims 1 to 3, further comprising a third pressure gauge connected to the downstream end of the differential pressure generator on the downstream side and having a pressure extraction unit for taking out the third pressure inside. Pressure type flow meter. The differential pressure type flow meter according to any one of claims 1 to 4, wherein the pressure extraction portions of the first pressure gauge, the second pressure gauge, and the third pressure gauge are set to substantially the same shape. A measurement in which the pressure extraction section of the first pressure gauge, the second pressure gauge, and the third pressure gauge communicates with the internal flow path of any of the differential pressure generators and has a diameter dimension larger than that of the internal flow path. It has a flow path and
The shape of the flow path at the junction between the internal flow path of the differential pressure generator on the upstream side and the measurement flow path of the first pressure gauge, and the internal flow path of the differential pressure generator on the downstream side and the second pressure gauge. The shape loss is set to be substantially the same as the shape of the flow path at the joint with the measurement flow path of.
The shape of the flow path at the junction between the internal flow path of the differential pressure generator on the upstream side and the measurement flow path of the second pressure gauge, and the internal flow path of the differential pressure generator on the downstream side and the third pressure gauge. The differential pressure type flow meter according to claim 5, wherein the shape loss of the flow path at the joint with the measurement flow path is substantially the same. The flow rate measuring mechanism
A first differential pressure gauge connected to the upstream end and the downstream end of the differential pressure generator on the upstream side and having a differential pressure take-out portion inside the first differential pressure generator.
Either of claims 1 or 2, which is connected to the upstream side and the downstream side of the differential pressure generator on the downstream side, and includes a second differential pressure gauge having a differential pressure take-out portion for taking out the second differential pressure inside. Differential pressure type flow meter described in Crab. The differential pressure type flow meter according to claim 7, wherein the heights of the differential pressure extraction portions of the first differential pressure gauge and the second differential pressure gauge extending from the flow path with respect to the flow path are set to be substantially the same. The first measurement in which the differential pressure extraction portion of the first differential pressure gauge and the second differential pressure gauge communicates with the upstream side of the internal flow path of any of the differential pressure generators and has a diameter dimension larger than that of the internal flow path. It has a flow path and a second measurement flow path that communicates with the downstream side of the internal flow path of the differential pressure generator and has a diameter larger than that of the internal flow path.
The shape of the flow path at the junction between the internal flow path of the differential pressure generator on the upstream side and the first measurement flow path of the first differential pressure gauge, the internal flow path of the differential pressure generator on the downstream side, and the second. The shape loss is set so that the shape of the flow path at the joint with the first measurement flow path of the differential pressure gauge is substantially the same.
The shape of the flow path at the junction between the internal flow path of the differential pressure generator on the upstream side and the second measurement flow path of the first differential pressure gauge, and the internal flow path of the differential pressure generator on the downstream side and the second measurement flow path. The differential pressure type flow meter according to claim 8, wherein the shape loss of the flow path at the joint with the second measurement flow path of the differential pressure gauge is set to be substantially the same. The differential pressure type flowmeter according to any one of claims 7 to 9, further comprising a correction pressure gauge for correcting the density of the fluid. The differential pressure type flow meter according to any one of claims 1 to 10, wherein at least a part of the two differential pressure generators is bent. The differential pressure type flow meter according to any one of claims 11, wherein a part of both differential pressure generators is bent in an annular shape. The differential pressure type flow meter according to any one of claims 1 to 12, wherein a temperature sensor for detecting the temperature of the fluid flowing through the internal flow path thereof is installed in at least one of the pair of differential pressure generators.