JP2006208404A - Flowmeter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flowmeter improved in measuring accuracy by enhancing a flow straightening effect without increasing pressure loss. <P>SOLUTION: In this flow meter, a pressure loss member 13a made of a wire gauge, which causes uniform pressure loss to the whole sectional area of a basic passage 20A is closely arranged in the downstream end of a plurality of divided passages formed by equally dividing the basic passage 20A. According to this, the flow in the passage is effectively straightened as the pressure loss remains sufficiently minimized. The number of divided passages is increased by adjusting the number of straightening vanes 12A, whereby the flowmeter can respond to a large flow rate. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a flow meter, and more particularly, to a flow meter that is used in a gas meter or the like to enhance a rectifying effect without increasing pressure loss and improve measurement accuracy.

  2. Description of the Related Art Conventionally, a method of inserting a rectifying plate or a rectifying grid into a flow path is widely known in order to bring the flow of a fluid in the vicinity of a flow sensor in the flow path into a rectified state without disturbance. According to this method, a certain amount of rectification effect can be obtained without generating a large pressure loss, but if there is a large flow deviation on the upstream side, it will pass through the rectification plate or rectification grid with this deviation remaining. There are drawbacks. In order to eliminate such a bias, a method of arranging a mesh or the like on the upstream side of the flow path to be rectified is also widely known, but this method conversely generates a turbulence in the flow in the flow path or reduces pressure loss. There is a drawback of increasing.

  Therefore, in order to compensate for these drawbacks, there is a method in which a rectifying plate or a rectifying grid is inserted into the flow path and a mesh or the like is disposed on the upstream side thereof.

  According to this method, it is known that it is difficult to be affected by the upstream flow bias, and that it is possible to obtain a certain amount of rectification effect. To that end, however, pressure loss is reduced by reducing the mesh number. The problem arises that it must be enlarged.

  Therefore, in view of the present situation described above, an object of the present invention is to provide a flowmeter that improves the rectification effect without increasing the pressure loss and improves the measurement accuracy.

  The flowmeter according to claim 1, which has been made to solve the above problem, is provided in a basic flow path in which a fluid to be measured flows and has a constant cross-sectional shape, and has a predetermined length in a direction parallel to the flow of the fluid to be measured. A flow path dividing member that extends only and divides the basic flow path equally to form a plurality of divided flow paths, and is arranged in close contact with the end of the flow path dividing member on the downstream side of the flow path dividing member A pressure loss member made of a wire mesh that causes a uniform pressure loss over the entire cross-section of the basic flow path, and a flow rate sensor disposed so that a measurement surface is exposed to at least one of the divided flow paths. It is characterized by that.

  According to the first aspect of the present invention, a wire mesh that causes an equal pressure loss across the entire cross-section of the basic channel at the downstream end of the plurality of divided channels formed by equally dividing the basic channel 20. By arranging the pressure loss member 13 made of in close contact with each other, rectification in the flow path is effectively performed while the pressure loss is sufficiently small.

  The flowmeter according to claim 2, which has been made to solve the above problem, is provided in a basic flow path in which a fluid to be measured flows and has a constant cross-sectional shape, and has a predetermined length in a direction parallel to the flow of the fluid to be measured. A flow path dividing member that extends only and divides the basic flow path equally to form a plurality of divided flow paths, and is arranged in close contact with the end of the flow path dividing member on the downstream side of the flow path dividing member A pressure loss member made of a wire mesh that causes a uniform pressure loss over the entire cross-section of the basic flow path, and a microflow sensor arranged so that the measurement surface is exposed to the downstream side in the vicinity of the location of the pressure loss member. It is characterized by including.

  According to the second aspect of the present invention, a wire mesh that causes an equal pressure loss to the entire cross section of the basic flow path at the downstream end portions of the plurality of divided flow paths formed by equally dividing the basic flow path 20. The pressure loss member 13 is arranged in close contact, and the microflow sensor 11A is arranged on the downstream side in the vicinity of the location where the pressure loss member 13 is arranged, so that the pressure loss can be kept sufficiently small while the rectifying effect is higher. It is possible to measure the flow rate.

  As described above, according to the first aspect of the present invention, the downstream end portion of the plurality of divided channels formed by equally dividing the basic channel 20 is equivalent to the entire cross-section of the basic channel. By disposing the pressure loss member 13 made of a wire mesh that causes pressure loss in close contact, the flow path can be effectively rectified while the pressure loss is sufficiently reduced. As a result, the flow rate can be measured stably and accurately.

  According to the second aspect of the present invention, a wire mesh that causes an equal pressure loss to the entire cross section of the basic flow path at the downstream end portions of the plurality of divided flow paths formed by equally dividing the basic flow path 20. The pressure loss member 13 is arranged in close contact, and the microflow sensor 11A is arranged on the downstream side in the vicinity of the location where the pressure loss member 13 is arranged, so that the pressure loss can be kept sufficiently small while the rectifying effect is higher. It is possible to measure the flow rate.

Hereinafter, embodiments of the present invention will be described with reference to FIGS.
First, application examples of the flowmeter of the present invention will be described. FIG. 1 is an explanatory view showing an application example of the flowmeter of the present invention.

  As shown in FIG. 1, the flow meter 1 of the present embodiment basically includes a flow sensor 11, a rectifying plate 12, and a pressure loss member 13. This configuration will be described later with reference to FIGS.

  This flow meter 1 is applied to, for example, a gas meter 100 and installed in the flow path 2 thereof. The gas meter 100 is connected between an upstream pipe 101A on the gas supply source side and a downstream pipe 102A on the gas consumption source side. The upstream pipe 101A and the downstream pipe 102A have a predetermined interval, and the inlet 101 and the outlet 102 of the gas meter 100 are connected to each other.

  The gas flowing in from the inflow port 101 passes through the flow path 2 inside the gas meter 100 and flows out to the outflow port 102. A flow sensor 11 of the flow meter 1 is attached to a part of the flow path 2, and the gas flow here is measured by the flow sensor 11. This vicinity has, for example, an elongated rectangular parallelepiped shape having a circular, square, or rectangular cross section.

  As the flow sensor 11, for example, a micro flow sensor or an ultrasonic sonar is used. The detection signal from the flow sensor 11 is supplied to the control unit 3 and converted into a digital signal. Based on this digital signal, the control unit 3 obtains the instantaneous flow velocity of the gas flowing through the flow path 2 and multiplies it by a cross-sectional area of the flow path 2 and a coefficient depending on the structure thereof. Find the instantaneous flow rate of the gas flowing through Further, the control unit 3 samples the instantaneous flow rate at a predetermined cycle, and based on the sampling cycle, obtains an integrated flow rate of the gas flowing in the gas pipe and displays it on the display unit 4.

  The gas pressure passing through the flow path 2 is measured by the pressure sensor and the pressure sensor device of the shut-off valve device 5. This gas pressure measurement value is supplied to the control unit 3. The control unit 3 monitors the gas pressure and the gas flow rate described above. When an abnormal value is detected, the control unit 3 controls the pressure sensor and the shutoff valve of the shutoff valve device 5 to close the gas flowing through the flow path 2. Cut off. In addition, the control unit 3 may display an alarm on the display unit 4 when there is an abnormality.

  The control unit 3 is connected to a switch 6 including a reset button and various setting switches for performing a reset operation after the abnormal state is released. In addition, 7 is a power supply which supplies a predetermined drive power supply to each part of the gas meter 100, for example, a CR battery is used.

  Next, several embodiments of the flowmeter of the present invention will be described with reference to FIGS. 2A to 2C are schematic cross-sectional views illustrating a first embodiment of the flowmeter of the present invention. FIGS. 3A to 3C are schematic cross-sectional views showing a second embodiment of the flowmeter of the present invention. 4A to 4C are schematic cross-sectional views showing a third embodiment of the flowmeter of the present invention. 5A to 5C are schematic cross-sectional views showing a fourth embodiment of the flow meter of the present invention. Each of FIGS. (B) and (C) shows the basic flow path including the flow path dividing member as viewed from the upstream side and the downstream side indicated by arrows.

  In the first embodiment shown in FIGS. 2A to 2C, the basic flow path 20 is a rectangular basic flow path 20A having a rectangular cross section. In the rectangular basic flow path 20A, for example, a microflow sensor 11A as the flow sensor 11 measures the flow velocity of the fluid flowing therethrough. This rectangular shape is constant over a predetermined length.

  The rectangular basic flow path 20A extends as a predetermined length in a direction parallel to the flow of the fluid to be measured, and the rectangular basic flow path 20A is equally divided to form a plurality of divided flow paths. A plurality of rectifying plates 12A are provided. The plurality of rectifying plates 12A are composed of a plurality of, in this example, six rectifying plates 12A arranged at equal intervals in parallel to the ceiling surface and floor surface of the rectangular basic flow path 20A. Each rectifying plate 12A is composed of an equivalent member and an equivalent shape, for example, a rectangular thin plate made of heat-resistant plastic.

  And the rectangular mesh 13A as the pressure-loss member 13 made close to the downstream edge part of this baffle plate 12A is arrange | positioned. The rectangular mesh 13A is configured by knitting a metal elongated wire into a mesh shape. Each mesh has a square shape and forms a mesh surface. This rectangular mesh 13A has an equal pressure loss at any location with respect to the flow velocity per unit area with respect to the cross section of the rectangular basic flow path 20A, that is, equal to the entire cross section of the basic flow path. A pressure loss is generated, and this pressure loss increases monotonously with the flow velocity.

  As the flow sensor 4, for example, a known micro flow sensor 11A is used. This microflow sensor has a measurement surface on which a temperature sensor is arranged on the upstream side and the downstream side with a predetermined interval across a heater on a silicon chip. In such a microflow sensor, when the heat generated by the heater is transmitted to the upstream side and the vicinity of the temperature sensor on the downstream side using the gas passing through the rectangular basic flow path 20A as a medium, the transferred heat is transmitted. An electromotive force corresponding to the temperature is generated in each temperature sensor. The generated electromotive force difference is output to the control unit 3 as a thermoelectromotive force signal corresponding to the flow velocity flowing through the basic flow path 20. Since this thermoelectromotive force signal is an analog value, the control unit 3 converts it into a digital signal. The measurement surface of the microflow sensor 11A is disposed so as to be exposed to at least one of the divided flow paths.

  In such a microflow sensor 11A, the flow rate sensor 4 is arranged so that the measurement surface is exposed in the middle of the divided flow path as shown in the figure. Alternatively, the microflow sensor 11A may be arranged so that its measurement surface is exposed downstream of the rectangular mesh 13A in the vicinity of the arrangement position, that is, near the outlet of the rectangular basic flow path 20A (see FIG. 3). In addition to the micro flow sensor 11A, a known thermopile type is preferably used as the flow sensor 11, but any other sensor may be used as long as it can measure a narrow flow rate.

  In the second embodiment shown in FIGS. 3A to 3C, a rectifying grid 12B is used as the flow path dividing member 12 instead of the rectifying plate 12A of the first embodiment. The rectifying grid 12B is configured by combining a plurality of rectangular thin plates made of heat-resistant plastic made of the same material as the rectifying plate 12A so as to be orthogonal. Both of the split flow dew by this rectifying grid 12B have the same substantially square cross section.

  The other constituent elements are the same as those in the first embodiment, except that in this embodiment, the microflow sensor 11A is located downstream of the rectangular mesh 13A, that is, the rectangular basic flow path 20A. In the vicinity of the outlet, the measurement surface is arranged to be exposed. Of course, as shown in FIG. 2, it may be arranged so that the measurement surface is exposed in the middle of the divided flow path.

  As described above, according to the first and second embodiments, in the divided flow path in which the basic flow path 20 (rectangular basic flow path 20A) is divided equally, the flow path dividing member 12 (the rectifying plate 12A or the rectifying grid). 12B) and the pressure loss member 13 (rectangular mesh 13A), the flow of the basic flow path 20 is rectified so as not to be biased and turbulent. The flow rate is measured. As a result, the flow rate of the entire basic channel 20 can be measured stably and accurately. In particular, according to the first and second embodiments, by adjusting the number of thin plates constituting the rectifying plate 12A and the rectifying grid 12B, it is possible to easily cope with a large flow rate by increasing the division path. .

  In the third embodiment shown in FIGS. 4A to 4C, the basic flow path 20 is a cylindrical basic flow path 20B having a circular cross section. For example, an ultrasonic sonar 11B as the flow rate sensor 11 measures the flow velocity of the fluid flowing through the cylindrical basic flow path 20B. This cylindrical shape is constant over a predetermined length.

  This rectangular basic flow path 20A extends in a predetermined length in a direction parallel to the flow of the fluid to be measured, and the basic flow path 20 is equally divided to form a plurality of flow path dividing members 12 that form a plurality of divided flow paths. A prismatic honeycomb structure 12C is provided. In this example, the polygonal columnar honeycomb structure 12C is a regular hexagonal columnar honeycomb structure partitioned by a heat-resistant plastic thin plate, and the outer peripheral portion of the structure does not conform to the shape of the inner wall of the cylindrical basic flow path 20B. Filled with heat-resistant plastic. Further, the plurality of regular hexagonal honeycombs which are the diversion paths all have the same shape. These ensure that the fluid flows evenly through the plurality of diversion paths.

  And the circular mesh 13B as the pressure loss member 13 produced in close contact with the downstream end of the polygonal column honeycomb structure 12C is disposed. The circular mesh 13B is configured by knitting a metal elongated wire into a mesh shape. Each mesh has a square shape and forms a mesh surface. This can also be obtained by processing the rectangular mesh 13A shown in FIG. 2 into a circle. Similarly to the rectangular mesh 13A, the circular mesh 13B generates an equivalent pressure loss at any location with respect to the flow rate per unit area with respect to the cross section of the cylindrical basic flow path 20B. Is assumed to increase monotonically with flow velocity.

  As the flow sensor 4, for example, a known ultrasonic sonar 11B is used. Here, the detection elements of the pair of ultrasonic sonars 11B are arranged so that the detection elements are exposed in the vicinity of the inlet and the outlet of at least one of the divided flow paths. Using the ultrasonic signal arrival time of the pair of ultrasonic sonars 11B, the flow velocity of the fluid passing through the divided flow path is measured. This ultrasonic signal arrival time is converted into an average flow velocity or flow rate of the entire basic flow path 20 by the control unit 3. As the flow rate sensor 11, it is preferable to use an ultrasonic sonar 11B for ease of installation with respect to the divided flow path as described above. However, any other type can be used as long as it can measure a narrow flow rate. There may be.

  In the fourth embodiment shown in FIGS. 5A to 5C, a cylindrical honeycomb structure 12D is used as the flow path dividing member 12 instead of the rectifying plate 12A of the second embodiment. This cylindrical honeycomb structure 12D is configured by bundling a plurality of circular tubes made of heat-resistant plastic. The plurality of circular pipes all have the same shape, and each form a shunt path. Since the outer peripheral portion of the structural body 12D does not conform in shape to the inner wall of the cylindrical basic flow path 20B, it is supplemented with heat-resistant plastic. In addition, the respective shunt paths are similarly compensated. As a result, the fluid flows evenly through the plurality of diversion paths. Other structural requirements are the same as those of the third embodiment shown in FIG.

  As described above, according to the third and fourth embodiments, in the divided flow channel in which the basic flow channel 20 (cylindrical basic flow channel 20B) is divided equally, the flow channel dividing member 12 (polygonal honeycomb structure 12C). Alternatively, the flow rate sensor 11 (ultrasonic sonar 11B, etc.) is flown by the cylindrical honeycomb structure 12D) and the pressure loss member 13 (circular mesh 13B) so that the flow of the basic flow path 20 is not biased and turbulent. To measure a stable average flow rate. As a result, the flow rate of the entire basic channel 20 can be measured stably and accurately. In particular, according to the third and fourth embodiments, by arranging the pair of ultrasonic sonars 11B as the flow rate sensor 11 in the vicinity of the inlet and the outlet of the divided flow path, the flow detection accuracy can be further improved. There is. Moreover, since it can be easily applied to the cylindrical basic flow path 20B, the applicable range of diversion measurement is expanded. For example, there is an effect that it can be easily applied not only to the inside of the gas meter but also to a gas pipe having a circular cross section that is widely distributed.

  The pressure loss of the pressure loss member 13 in each of the examples shown in FIGS. 2 to 5 is sufficient even if the pressure loss member 13 is half that of the pressure loss member 13 when arranged upstream of the flow path dividing member 12 as in the prior art. Experiments have confirmed that there is a rectifying effect. Further, it is more effective to disperse and dispose two pressure loss members having a pressure loss half that of the pressure loss member 13 on the upstream side and the downstream side of the flow path dividing member 12 instead of the pressure loss member 13. However, in this case, it is desirable that the pressure loss member is in close contact with the flow path dividing member 12 on the downstream side, and the pressure loss member is separated slightly upstream from the flow path dividing member 12 on the upstream side. For reference, FIGS. 6 and 7 show the relationship between the distance between the current plate and the mesh in the variation and the influence of the presence or absence of the downstream mesh in the variation, respectively. In the figure, the horizontal axis indicates the flow rate, and the vertical axis indicates the variation.

  As described above, according to the present embodiment, the wire mesh that causes an equal pressure loss to the entire cross-section of the basic channel at the downstream end of the plurality of divided channels formed by equally dividing the basic channel 20. By arranging the pressure-loss member 13 made of in close contact with each other, it is possible to effectively rectify the flow path while keeping the pressure loss sufficiently small. As a result, the flow rate can be measured stably and accurately.

It is explanatory drawing which shows the example of application of the flowmeter of this invention. 2A to 2C are schematic cross-sectional views illustrating a first embodiment of the flowmeter of the present invention. FIGS. 3A to 3C are schematic cross-sectional views showing a second embodiment of the flowmeter of the present invention. 4A to 4C are schematic cross-sectional views showing a third embodiment of the flowmeter of the present invention. 5A to 5C are schematic cross-sectional views showing a fourth embodiment of the flow meter of the present invention. It is a graph which shows the relationship between the baffle plate and the distance of a mesh in variation. It is a graph which shows the influence of the downstream mesh presence in dispersion.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Gas meter 2 Flow path 3 Control part 4 Display part 5 Pressure sensor and shut-off valve apparatus 6 Switch 7 Power supply 11 Flow sensor 11A Micro flow sensor (flow sensor)
11B ultrasonic sonar (flow sensor)
12 Flow path dividing member 12A Current plate (flow path dividing member)
12B Rectification grid (channel dividing member)
12C Polygonal honeycomb structure (channel dividing member)
12D Cylindrical honeycomb structure (channel dividing member)
13 Pressure loss member 13A Rectangular mesh (pressure loss member)
13B Circular mesh (pressure loss member)
20 Basic channel 20A Rectangular basic channel (Basic channel)
20B Cylindrical basic channel (basic channel)
101 Inlet 102 Outlet

Claims (2)

Provided in a basic flow path in which a fluid to be measured flows and has a constant cross-sectional shape, extends by a predetermined length in a direction parallel to the flow of the fluid to be measured, divides the basic flow path equally, and a plurality of divided flow paths A flow path dividing member that forms
A pressure loss member made of a metal mesh that is arranged in close contact with the end of the flow path dividing member on the downstream side of the flow path dividing member and generates an equal pressure loss over the entire cross section of the basic flow path;
A flow sensor arranged to expose the measurement surface to at least one of the divided flow paths;
A flow meter characterized by including. Provided in a basic flow path in which a fluid to be measured flows and has a constant cross-sectional shape, extends by a predetermined length in a direction parallel to the flow of the fluid to be measured, divides the basic flow path equally, and a plurality of divided flow paths A flow path dividing member that forms
A pressure loss member made of a metal mesh that is arranged in close contact with the end of the flow path dividing member on the downstream side of the flow path dividing member and generates an equal pressure loss over the entire cross section of the basic flow path;
A microflow sensor arranged so that the measurement surface is exposed to the downstream side in the vicinity of the place where the pressure loss member is arranged;
A flow meter characterized by including.

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