JP4582623B2 - Flowmeter - Google Patents

Description

  The present invention relates to a flowmeter for measuring the flow rate of a liquid that is connected in the middle of a flow path that normally flows in a non-full state and flows through the flow path.

Conventionally, a so-called permabolous flume type flow meter is known as this type of flow meter. In this permbolus flume type flow meter, if a portion where the flow becomes a jet is created by providing a constriction in the middle of the flow path, a certain relationship is established between the liquid level and the flow rate upstream of the constriction. Therefore, the flow rate is obtained by measuring the liquid level (see, for example, Non-Patent Document 1).
Yutaka Matsuyama, “Practical flow rate measurement”, 1st edition, Energy Conservation Center, June 15, 1999, p. 191, 194-196

  By the way, the above-described conventional flowmeter can measure the flow rate relatively accurately in the large flow rate region, but has a problem that the flow rate cannot be measured accurately in the small flow rate region.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a flowmeter capable of accurately measuring a flow rate even in a small flow rate region.

In order to achieve the above object, a flow meter according to claim 1 is provided in the middle of a flow path through which a fluid flows, and a flume for creating a limit flow in the fluid, and a fluid level upstream of the flume. A liquid level measuring means for measuring, a magnetic field generating means for generating a magnetic field inside the flume, and a pair of electrodes arranged opposite to each other inside the flume, are generated between the pair of electrodes. thereby possible to measure the flow rate of the fluid at a given flow rate region based on the power, the greater flow rate region than a predetermined flow rate range, in the flow meter the flow rate was measurable on the basis of the liquid level of the fluid, the electromotive force A data processing unit that calculates a flow rate based on the electromotive force when the amount of change per unit time of the fluid level measured by the liquid level measurement unit is smaller than a reference value. Flow rate calculation result In addition to the above, when the amount of change in the fluid level per unit time is greater than the reference value, there is a calculation result selection means that rejects the calculation result of the flow rate based on the electromotive force during that time. Has characteristics.

[Effect of claim 1]
According to the first aspect of the present invention, since the fluid in the flow path becomes a limit flow due to the flume, a certain relationship is established between the flow velocity of the fluid and the liquid level in the flow path. Here, the flow rate of the fluid in the non-full state can be obtained from the product of the flow velocity and the cross-sectional area of the flow. The cross-sectional area of the flow can be obtained from the liquid level.

When the flow rate of the fluid flowing through the flow path is relatively small and included in a predetermined flow rate range, the electromotive force generated between the pair of electrodes due to the passage of the fluid is measured. Since the magnitude of the electromotive force has a fixed relationship with the fluid flow velocity according to the so-called electromagnetic induction law, the flow velocity can be obtained from the electromotive force. Further, as described above, since the fluid flow rate has a fixed relationship with the liquid level, the liquid level can be obtained from the flow rate, and the cross-sectional area of the flow can be obtained. Thereby, even if the inside of a flow path is a non-full state, the flow volume of the fluid can be obtained from an electromotive force. That is, it can function as a so-called non-full water type electromagnetic flow meter. Here, since the non-full-type electromagnetic flow meter has high measurement accuracy from a small flow rate range to a large flow rate range, the flow rate can be accurately measured even in a predetermined flow rate range where the flow rate is relatively small. it can.
On the other hand, when the flow rate of the fluid flowing through the flow path increases and becomes larger than a predetermined flow rate range, the liquid level of the fluid passing through the flume can be measured, and the flow rate can be obtained based on the liquid level. . That is, it can function as a so-called flume type flow meter.

  Here, a non-full-type electromagnetic flow meter needs to be actually adjusted by actually passing water over the entire range of the used flow rate before use. For this reason, in order to be able to measure all the flow areas from a small flow area to a large flow area only with a non-full-type electromagnetic flow meter, the water flow equipment for actual adjustment becomes large-scale.

  On the other hand, the flume type flow meter does not require actual adjustment, and the measurement accuracy in the small flow region is low, but the measurement accuracy in the large flow region is relatively high.

  In the present invention, when the flow rate becomes larger than a predetermined flow rate range, it is possible to switch from the flow rate measurement based on the electromotive force generated between the electrodes to the flow rate measurement based on the liquid level. It suffices to perform only the predetermined flow rate range. Accordingly, it is possible to reduce the scale of the water flow facility for actual measurement adjustment and to reduce the trouble of actual measurement adjustment.

In addition, the flume used when functioning as a flume type flow meter can also be used when functioning as a non-full type electromagnetic flow meter.
Furthermore, if the amount of change per unit time in the fluid level measured by the fluid level measurement means is smaller than the reference value by the computation result sorting means, the computation result of the flow rate based on the exact electromotive force is adopted. On the other hand, when the amount of change per unit time of the fluid level is larger than the reference value, the calculation result of the flow rate based on the electromotive force that has become inaccurate is rejected. As a result, the calculation result of the inaccurate flow rate is eliminated, and only the calculation result of the accurate flow rate is adopted, so that the measurement result of the flow rate with higher reliability can be obtained.

Hereinafter, an embodiment of the present invention will be described with reference to FIGS.
As shown in FIG. 1, the flow path component 11 provided in the flow meter 10 of the present embodiment has a groove structure opened upward, and the inner space of the flow path component 11 becomes a flow path 12 through which fluid flows. ing. And piping (for example, sewage piping) is connected to both ends of 11, and the flow rate is measured by allowing fluid (for example, sewage) flowing through the piping to pass through the flow path 12.

  The flow path constituting member 11 has a so-called perma bolus flume structure. That is, a throat portion 14 that narrows the inner space of the flow path component 11 is provided in the middle of the flow path component 11 in the axial direction. On the upstream side of the throat portion 14, there is provided a contraction portion 13 that gradually narrows the inner space of the flow path constituting member 11 toward the throat portion 14, and on the downstream side of the throat portion 14 An enlarged portion 15 is provided that gradually widens the inner space of the path constituent member 11. As shown in FIG. 3, a crest portion 60 swelled on the inner side of the flow path component member 11 is provided at the bottom of the throat portion 14 of the flow path component member 11. At the bottom portion, tapered portions 61 and 61 are formed so as to be inclined as they are separated from the crest portion 60. The contracted portion 13, the throat portion 14, and the enlarged portion 15 constitute a “flume” according to the present invention.

  An ultrasonic water level meter 16 corresponding to the “liquid level measuring means” of the present invention is provided upstream of the throat portion 14 of the flow path component member 11 and above the flow path component member 11. The fluid flowing inside the flow path component 11 increases in flow rate as it approaches the throat portion 14 and becomes a limit flow in the throat portion 14. That is, the ultrasonic water level meter 16 measures the liquid level upstream of the throat portion 14 where the flow of the liquid has become a critical flow, and the flow rate of the liquid flowing in the flow path component 11 from this liquid level is measured. It is configured to ask for. That is, the flow meter 10 functions as a so-called flume type flow meter. Here, the reason why the liquid level is measured on the upstream side of the throat portion 14 that has become the limit flow is that the unique relationship between the flow velocity and the liquid level is maintained at this position, This is because the position is stable.

  Now, as shown in FIG. 3, an excitation coil 23 (corresponding to “magnetic field generating means” of the present invention) is built in the bottom portion (crest portion 60) of the throat portion 14 of the flow path component member 11. . The exciting coil 23 generates a magnetic field in a direction crossing the liquid flow in the inner space of the flow path component 11.

  As shown in FIG. 3, a pair of electrodes 24 and 24 are provided above the exciting coil 23 in the throat portion 14 (only one electrode 24 is shown in the figure). As shown in FIG. 2, the electrode 24 has a flat plate shape and is laid on the inner side surfaces 14 </ b> A and 14 </ b> A of the throat portion 14. Has been. The electromotive force generated between the electrodes 24 and 24 when the fluid that has reached the limit flow inside the flow path component 11 (more specifically, the throat portion 14) passes through the magnetic field generated by the excitation coil 23. It is possible to measure the flow rate of the liquid flowing through the flow path 12 from this electromotive force. That is, the flow meter 10 functions as a so-called non-full type electromagnetic flow meter. The electrodes 24 and 24 are attached so as to be flush with the inner side surface 14 </ b> A of the throat portion 14, and the liquid flow is prevented from being disturbed in the throat portion 14.

  Incidentally, the flow meter 10 of the present invention includes a data processing unit 30 as shown in FIG. Values (liquid level and electromotive force) measured by the ultrasonic water level gauge 16 or the electrodes 24 and 24 are taken into the data processing unit 30. The data processing unit 30 obtains the flow rate based on the liquid level or electromotive force and outputs the flow rate to the display unit 34.

  Specifically, the data processing unit 30 includes an arithmetic circuit 31 that calculates a flow rate based on an electromotive force or a liquid level. The data processing unit 30 includes an arithmetic circuit when the flow meter 10 measures the flow rate based on the electromotive force between the electrodes 24 and 24 (functions as a non-full electromagnetic flow meter). A correction circuit 33 (corresponding to the “correction means” of the present invention) that corrects the calculation result by 31 based on the liquid level measured by the ultrasonic water level gauge 16 is provided.

  The correction circuit 33 extracts correction data from a correction data table (not shown) based on the liquid level measurement value obtained by the ultrasonic water level gauge 16 and corrects the calculation result of the calculation circuit 31 using the correction data. That is, the calculation result of the flow rate based on the electromotive force is corrected according to the measured value of the liquid level. This makes it possible to obtain a more accurate flow rate measurement result that eliminates the influence of the liquid level.

  In addition, the data processing unit 30 performs calculation by the arithmetic circuit 31 according to the amount of change in the liquid level measured by the ultrasonic water level meter 16 when the flow meter 10 measures the flow rate based on the electromotive force. A sorting circuit 32 for sorting the results (corresponding to “calculation result sorting means” of the present invention) is provided.

  That is, in the sorting circuit 32, when the change amount per unit time of the liquid level measured by the ultrasonic water level gauge 16 is equal to or less than a preset reference value, the calculation of the flow rate by the arithmetic circuit 31 is performed. The result is adopted and output to the correction circuit 33. On the other hand, when the amount of change in the liquid level per unit time is equal to or greater than the reference value, the calculation result of the flow rate based on the incorrect electromotive force calculated by the calculation circuit 31 is rejected. Thereby, since the calculation result of the inaccurate flow rate is not output from the data processing unit 30 and only the calculation result of the accurate flow rate is output, it is possible to obtain the measurement result of the flow rate with higher reliability.

  Furthermore, the flow meter 10 of the present invention includes a flow rate measurement state based on electromotive force (a state that functions as a non-full type electromagnetic flow meter) and a flow rate measurement state based on a liquid level (a state that functions as a flume flow meter). Switching means 36 for switching between and is provided.

  The switching means 36 gradually increases the flow rate of the liquid flowing through the flow path component 11, and the flow rate measurement result by the data processing unit 30 is, for example, a flow rate at which the flow path component 11 is maximum when the flow path component 11 is not full (hereinafter referred to as “flow rate”). When the flow rate becomes 3% of the flow rate (referred to as the “maximum non-full water flow rate”) (corresponding to “the upper limit flow rate of the predetermined flow rate range” of the present invention), the flow meter 10 is moved from the flow measurement state based on the electromotive force. Switch to the flow rate measurement state based on the liquid level.

That is, the flow meter 10 uses a flow rate of 0 to 3% of the maximum non-full water flow rate of the flow path component 11 (corresponding to the “predetermined flow rate range” of the present invention), so-called non-full electromagnetic flow meter. Therefore, the actual measurement adjustment required in advance for the non-full water type electromagnetic flow meter is only required in a relatively small flow rate range of 0 to 3% of the maximum non-full water flow rate of the flow path component 11. For example, when the maximum non-full water flow rate of the flow path component 11 is 1000 m ³ / h, the actual measurement adjustment may be performed only in the flow rate range from 0 to ³⁰ m ³ / h. Accordingly, it is possible to reduce the scale of the water flow facility for actual measurement adjustment and to reduce the trouble of actual measurement adjustment.

  For example, when the flow meter 10 measures the flow rate based on the liquid level, the flow rate of the liquid flowing through the flow path component 11 gradually decreases, and the flow rate measurement result by the data processing unit 30 is When the maximum non-full water flow rate of the constituent member 11 is, for example, 2% flow rate (corresponding to the “switching flow rate” of the present invention), the switching means 36 measures the flow rate based on the liquid level. Switch from state to flow rate measurement state based on electromotive force.

  As described above, the flow rate of the flow meter 10 from the flow rate measurement state based on the electromotive force to the flow rate measurement state based on the liquid level (3% of the maximum non-full water flow rate of the flow path component 11) and the flow rate measurement based on the liquid level. By providing a difference in flow rate (2% of the maximum non-full water flow rate of the flow path component 11) from the state to the flow rate measurement state based on the electromotive force, the flow rate measurement based on the electromotive force is caused by slight fluctuations in the flow rate. The frequent switching to the flow rate measurement based on the liquid level is prevented. The above is the description of the configuration of the flow meter 10 of the present invention.

Next, the operation and effect of the flow meter 10 of this embodiment will be described.
FIG. 5 shows a conceptual diagram when the flow meter 10 of the present invention is installed in the sewer. In the figure, reference numeral 100 denotes a sewage treatment plant. From the sewage treatment plant 100, a sewage main 101 extends over a plurality of local governments (A city, B town, C town, D town). An extended sewage pipe 102 is connected. And the flowmeter 10 of this invention is installed in the boundary part of each entrance (A city, B town, C town, D town) among the entrance of the sewage treatment plant 100 and each local government (A city, B town, C town, D town) among these sewage mains 101, and these some Based on the measurement value of the flow meter 10, the sewage discharge amount for each local government is calculated.

  Here, since the maximum non-full water flow rate of the flow channel component 11 is determined based on the maximum flow rate when the sewer diffusion rate is achieved 100%, the flow channel component member immediately after the start of the operation of the sewage treatment plant 100. The flow rate of the sewage flowing to 11 is extremely small relative to the maximum non-full water flow rate.

  Now, the sewage flowing into the flow meter 10 from the sewage main pipe 101 becomes a limit flow in the throat portion 14 of the flow path component 11. When the sewage flowing through the sewage main pipe 101 is less than 3% of the maximum non-full water flow rate of the flow path component 11, the flow meter 10 functions as a flow rate measurement state based on electromotive force (non-full water electromagnetic flow meter). State). That is, the flow rate of sewage is determined based on the electromotive force generated between the electrodes 24 and 24 when the sewage that has become a critical flow at the throat portion 14 passes through the magnetic field. Thereby, even if the flow volume of the sewage which flows into the sewage main pipe 101 (flow path component 11) is comparatively small, a flow volume can be calculated | required accurately.

  When the flow rate of sewage flowing into the sewage main pipe 101 increases with the increase in the sewerage penetration rate and becomes a flow rate of 3% or more of the maximum non-full water flow rate of the flow path component 11, the flow rate is changed by the switching means 36. The meter 10 switches to a flow rate measurement state based on the liquid level (a state in which it functions as a flume type flow meter). That is, the level of the sewage that passes through the flow path component 11 is measured by the ultrasonic water level meter 16, and the flow rate is obtained from the level.

  After the flow meter 10 is switched to the flow rate measurement state based on the liquid level, the flow rate of sewage decreases, for example, when the flow rate of the flow path component 11 becomes 2.5% of the maximum non-full water flow rate, The switching means 36 holds the flow meter 10 in the flow rate measurement state based on the liquid level, and does not switch to the flow rate measurement state based on the electromotive force.

  When the flow rate of sewage further decreases and becomes a flow rate of 2% of the maximum non-full water flow rate of the flow path component 11, the flow meter 10 is switched again to the flow rate measurement state based on the electromotive force by the switching means 36. That is, the flow meter 10 can be switched to an optimal measurement state according to the flow rate of sewage.

  Thus, according to the present embodiment, when the flow rate is relatively small and less than 3% of the maximum non-full water flow rate of the flow path component 11, the flow meter 10 is a so-called non-full electromagnetic flow meter. The flow rate is measured based on the electromotive force generated between the electrodes 24 and 24. Further, when the flow rate increases and becomes 3% or more of the maximum non-full water flow rate of the flow path component member 11, the flow meter 10 measures the flow rate based on the liquid level measurement result by the ultrasonic water level meter 16. As a result, the flow rate can be accurately measured from the small flow rate range to the large flow rate range. Further, the actual adjustment required before use for the non-full type electromagnetic flow meter is only required in a small flow rate range (0 to 3% of the maximum non-full flow rate of the flow path component 11). Accordingly, it is possible to reduce the scale of the facility for actual measurement adjustment and to reduce the trouble of actual measurement adjustment.

  In addition, when switching between flow rate measurement based on electromotive force and flow rate measurement based on liquid level, it is not necessary to change the structure of the flow meter 10, so that a person needs to work in the sewage main pipe 101 for switching. There is no need to stop the flow of sewage. That is, even when the measurement state is switched, the liquid can continue to flow through the flow path component member 11, and the flow rate can be continuously measured.

[Other Embodiments]
The present invention is not limited to the above-described embodiment. For example, the embodiments described below are also included in the technical scope of the present invention, and various other than the following can be made without departing from the scope of the invention. It can be changed and implemented.
(1) In the above embodiment, the flow path component member 11 has a groove shape, but may have a cylindrical shape.

(2) In the above embodiment, the flow rate at which the flow meter 10 switches from the flow rate measurement state based on the electromotive force to the flow rate measurement state based on the liquid level is 3% of the maximum non-full water flow rate of the flow path component 11. However, the flow rate is not limited to this as long as the flow rate is included in 2 to 5% of the maximum non-full water flow rate of the flow path component member 11.

(3) In the above-described embodiment, the flow rate at which the flow meter 10 switches from the flow rate measurement state based on the liquid level to the flow rate measurement state based on the electromotive force is a flow rate of 2% of the flow rate when the flow path component member 11 is full. However, the flow meter 10 is not limited to this as long as the flow rate is smaller than the flow rate at which the flow rate measurement state based on the electromotive force is switched to the flow rate measurement state based on the liquid level.

(4) In the above-described embodiment, the flow path component 11 has a perma bolus flume structure. However, the flow path component 11 may have a so-called partial flume structure as long as the flow rate can be measured based on the liquid level. Also good.

  Moreover, it is not restricted to what is called a flume structure, You may comprise the dam structure like the flow-path structural member 90 shown in FIG. That is, a structure in which a weir plate 92 having a notch 93 on the upper side is provided in the middle of the channel 91 having a rectangular cross section so as to be perpendicular to the fluid flow. The dam plate may be a so-called triangular dam shown in FIG. 6, a square dam or a full-width dam.

(5) In the above-described embodiment, the ultrasonic water level gauge 16 is disposed above the flow path 12, but may be disposed at the bottom upstream of the throat portion 14 of the flow path component 11.

(6) In the above embodiment, the ultrasonic water level gauge 16 is used as the liquid level measuring means, but other liquid level measuring means may be used. For example, as shown in FIG. 7A, a pressure-type water level meter 70 that measures the water level by water pressure may be provided at the bottom of the flow path 12 on the upstream side of the throat portion 14. Further, as shown in FIG. 7B, the bottoms of the flow path component member 11 and the water level detection tank 81 provided separately from the flow path component member 11 are communicated with each other by a water conduit 82, and the water level detection tank 81 is connected. A so-called float-type water level meter 80 that detects the water level in the flow path component 11 based on the position of the float 83 floating on the surface may be used.

The perspective view of the flowmeter which concerns on one Embodiment of this invention. Front section of flow meter Side cross section of flow meter Block diagram showing the electrical configuration of the flow meter Conceptual diagram showing an installation example of a flow meter in the sewer Front sectional view of a flowmeter according to another embodiment (4) (A) Side sectional view and (B) Front sectional view of a flowmeter according to another embodiment (6)

Explanation of symbols

10 Flow meter 12 Flow path 16 Ultrasonic water level meter (liquid level measuring means)
23 Excitation coil (magnetic field generating means)
24, 24 Electrode 30 Data processor 32 Sorting circuit (Calculation result sorting means)
33 Correction circuit (correction means)
36 switching means 70 pressure type water level gauge (liquid level measuring means)
80 Float type water level gauge (liquid level measuring means)

Claims (1)

A flume provided in the middle of the flow path through which the fluid flows to create a limiting flow in the fluid;
A liquid level measuring means for measuring the liquid level of the fluid upstream of the flume;
Magnetic field generating means for generating a magnetic field inside the flume;
A pair of electrodes opposed to each other inside the flume,
Based on the electromotive force generated between the pair of electrodes, the flow rate of the fluid in a predetermined flow rate range can be measured,
Wherein the predetermined larger flow area than the flow rate range, in the flow meter the flow rate was measurable on the basis of the liquid level of the fluid,
A data processing unit that calculates a flow rate based on the electromotive force,
The data processing unit employs a flow rate calculation result based on the electromotive force when a change amount per unit time of the fluid level measured by the fluid level measuring unit is smaller than a reference value. ,
When the amount of change per unit time of the fluid level of the fluid is larger than the reference value, it is provided with calculation result selection means for rejecting the calculation result of the flow rate based on the electromotive force during that time. A flow meter.

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