JP3398251B2 - Flowmeter - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flow meter for measuring the flow rate of fluid such as gas.

[0002]

2. Description of the Related Art Flowmeters used for gas meters, etc.
There is a device in which the flow velocity of a fluid flowing in a pipe is measured by a flow velocity sensor such as a hot wire anemometer, a flow amount is calculated from the flow velocity, and the flow rate is displayed.

Here, in the conventional flowmeter, as shown in FIG. 4, one flow velocity sensor 1 is arranged in the central portion of the fluid flow passage in the pipe 2 to obtain the flow velocity sensor 1. The flow velocity at the center of the flow path is calculated as the flow rate by the flow rate calculation unit 3 and displayed on the display unit.

[0004]

However, the piping 2
In the case of flow velocity in the middle, the flow velocity distribution on the same cross section may differ due to the difference in pipe shape, the presence of bends, branches, etc., or the size of the flow rate, and the flow line may change in the longitudinal direction of the fluid flow path. is there. For this reason, the conventional flowmeter, which was able to detect only the flow velocity at the center of one cross section of the fluid flow path, could not accurately obtain the measurement value of the flow velocity, and as a result, could accurately measure a wide range of flow rates. There was a problem that I could not do it.

The present invention has been made in view of the above problems, and an object thereof is to have different flow velocity distributions on the same cross section in the fluid flow passage and to change the streamline in the longitudinal direction of the fluid flow passage. Even in any case, it is to provide a flow meter capable of accurately measuring the flow rate.

[0006]

According to a first aspect of the present invention, there is provided a flowmeter comprising: a pipe portion which forms a fluid passage through which a fluid passes ;
With respect to the wall surface of the pipe part so that the detection part faces the fluid flow path
Flow rate sensors that are attached to the fluid flow channel and that detect the flow velocity of the fluid at a plurality of positions in the fluid flow channel including at least two positions that are different in both the longitudinal direction of the fluid flow channel and the direction orthogonal to the longitudinal direction. An average flow velocity calculating means for calculating the average value of the flow velocity at a plurality of positions based on the output signals of the plurality of flow velocity sensors, and a flow rate calculating means for calculating the flow rate of the fluid based on the calculation result of the average flow velocity calculating means. It is a thing.

In this flow meter, the flow velocity of the fluid at a plurality of positions in the fluid flow passage including at least two positions which are different in both the longitudinal direction of the fluid flow passage and the direction orthogonal to the longitudinal direction by the plurality of flow velocity sensors. Is detected, the average value of the flow velocities at a plurality of positions is calculated by the average flow velocity calculation means based on the output signals of these flow velocity sensors, and the flow rate calculation means calculates the flow rate based on the average value of the flow velocities.

[0008] flowmeter according to claim 2 are those in flowmeter of claim 1, wherein the cross section of the tube portion in a rectangular shape.

A flowmeter according to a third aspect is the flowmeter according to the second aspect, wherein the plurality of flow velocity sensors are a plurality of first flow velocity sensors attached to one wall face of the wall faces facing each other of the pipe portion. , A plurality of second walls attached to the other wall
The flow velocity sensor of FIG.

A flowmeter according to a fourth aspect is the flowmeter according to the third aspect, wherein the plurality of first flow velocity sensors and the plurality of second flow velocity sensors are respectively inclined with respect to the longitudinal direction of the pipe portion. In addition, they are arranged along directions that are not parallel to each other.

[0011]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a perspective view showing a flowmeter according to an embodiment of the present invention with a part thereof cut away, and FIG. 2 is a view of the flowmeter of FIG. 1 seen from a longitudinal direction (direction shown by an arrow A in FIG. 1). It is a side view.
The flowmeter according to the present embodiment has a rectangular cross section and a pipe portion 11 forming a fluid flow path through which a fluid such as a gas passes, and a first flow velocity attached to one side wall surface 11a of the pipe portion 11. The flow velocity sensors 12 _{1 to} 12 ₃ as sensors and the flow velocity sensors 13 _{1 to} 13 ₃ as second flow velocity sensors attached to the other side wall surface 11b are provided. The flow velocity sensors 12 _{1 to} 12 ₃ and the flow velocity sensors 13 _{1 to} 13 ₃ are respectively arranged along the directions that are inclined with respect to the longitudinal direction of the tube portion 11 and are not parallel to each other. That is, on one side wall surface 11a, the upstream side flow velocity sensor 12 ₁ is attached to a position above the side wall surface 11a, and the longitudinal center velocity sensor 12 ₂ is attached to a position in the center of the side wall surface 11a, and the downstream side flow sensor 12 ₃ is attached to the lower position of the side wall surface 11a. On the other side wall surface 11b, the upstream side flow velocity sensor 13 ₁ is attached to a position below the side wall surface 11b, and the flow velocity sensor 13 _{2 at the} center in the longitudinal direction is attached.
Is attached to the position of the center of the side wall surface 11b, a flow rate sensor 13 ₃ on the downstream side is attached to the upper position of the side wall surface 11b. The flow velocity sensor 12 ₁ and the flow velocity sensor 1
The position of 3 _{1 in} the longitudinal direction, the position of the flow velocity sensor 12 ₂ and the flow velocity sensor 13 _{2 in} the longitudinal direction, and the position of the flow velocity sensor 12 ₃ and the flow velocity sensor 13 _{3 in} the longitudinal direction are the same. These flow velocity sensors 12 _{1 to} 12 ₃ and 13 _{1 to} 13 ₃ have fluids at a plurality of positions in the fluid flow passage including at least two positions that are different in both the longitudinal direction of the fluid flow passage and the direction orthogonal to the longitudinal direction. The flow velocity of is detected. These flow rate sensors 12 ₁ to 12 ₃ each detector 14 _{1-14 3} and flow rate sensor _{131-134 3} each detector 15 _{1-15 3} Installing so as to face the fluid flow path in the tube 11 Has been.

The cross-sectional size of the inside of the tube portion 11 is, for example, 10 mm in length (X) and 5 mm in width (Y), and the length of the tube portion 11 is, for example, about 100 to 200 mm.

Flow velocity sensors 12 _{1 to} 12 ₃ and 13 _{1 to} 13
_Although not shown, ₃ has, for example, a heat-generating part and two temperature sensors arranged on the upstream side and the downstream side of the heat-generating part, and has a constant temperature difference detected by the two temperature sensors. The flow rate is calculated from the power supplied to the heat generating section necessary for the above, or the heat generating section is heated with a constant current or constant power, and the flow rate is calculated from the difference in temperature detected by the two temperature sensors. In addition to this, the flow velocity sensor 1
As 2 _{1 to} 12 ₃ and 13 _{1 to} 13 ₃ , for example, there is one heat generating part, and the flow velocity is calculated from the power supplied to the heat generating part necessary to keep the temperature (resistance) of this heat generating part constant. Alternatively, the heat generating portion may be heated with a constant current or constant power, and the flow velocity may be obtained from the temperature (resistance) of the heat generating portion.

FIG. 3 is a block diagram showing the circuit configuration of the flowmeter of this embodiment. As shown in this figure, the flowmeter of the present embodiment has flow velocity sensors 12 _{1 to} 12 ₃ , 13 _{1 to} 13 _3.
An average flow velocity calculator 21 that inputs each detection signal and calculates an average value v _a of the flow velocity at a plurality of positions based on these detection signals, and an average of the flow velocity obtained by the average flow velocity calculator 21. A flow rate calculation unit 22 that calculates the flow rate Q based on the value v _a and a display unit 23 that displays the flow rate obtained by the flow rate calculation unit 22 are provided. The average flow velocity calculator 21 and the flow rate calculator 22 are realized by the microcomputer 20.

Next, the operation of the flowmeter of this embodiment will be described. When the gas a passes through the inside of the pipe portion 11, the flow velocity sensors 12 _{1 to} 12 ₃ and 13 _{1 to} 13 ₃ respectively show the flow velocity of the gas at the mounting positions of the detection portions 14 _{1 to} 14 ₃ and 15 ₁ to 15 _3. To detect. Then, the average value v of the flow velocity is calculated by the average flow velocity calculator 21 based on these detection signals.
_a is calculated, the flow rate is calculated by the flow rate calculation unit 22 based on the average value of the flow rates, and the flow rate is displayed by the display unit 23.

Here, as shown in FIG. 1, the flow velocity sensors 12 _{1 to} 12 ₃ and 13 _{1 to} 13 ₃ are from the flow velocity sensors 12 ₁ and 13 ₁ on the upstream side to the flow velocity sensors 12 ₃ and 13 on the downstream side.
They are arranged at positions different from each other in a fluid flow path (hereinafter referred to as a flow rate measurement region) 30 in a section of length L up to ₃ . Therefore, each of the flow velocity sensors 12 _{1 to} 12 ₃ and 13 ₁
When the flow rate detected by to 13 ₃ and v ₁ to v _6, the flow rate per unit volume in the flow measurement region 30, the average flow rate per unit length in other words is determined by the following equation (1) .

[0018]

[Number 1] _{{(v 1 + v 2 +} v 3 + v 4 + v 5 + v 6) / n} × (1 / L) = v a × (1 / L) [cm / s · cm] ... (1) where, n is the number of flow velocity sensors, and is 6 in this embodiment.

On the other hand, the flow rate Q is [cross-sectional area of the fluid passage] ×
The flow velocity is obtained by multiplying the average value of the flow velocity per unit length represented by the equation (1) by the length L of the flow rate measurement region 30. ) Equation is required. The flow rate calculation unit 22 determines the flow rate Q based on this equation (2).

[0020]

[Number 2] Q = X × Y × L × v a × (1 / L) = X × Y × v a ... (2)

As described above, according to this embodiment, in the flow rate measuring region 30 having the length L, a plurality of positions including at least two different positions in both the longitudinal direction of the fluid flow path and the direction orthogonal to the longitudinal direction. Since the average value of the flow velocity is calculated based on the detection values of the plurality of flow velocity sensors 12 _{1 to} 12 ₃ and 13 _{1 to} 13 ₃ arranged at the positions, and the flow rate is calculated based on the average value of the flow velocity, The flow rate can be accurately measured even when the flow velocity distributions on the same cross section in the fluid flow channel are different and the streamline changes in the longitudinal direction of the fluid flow channel. Therefore, the flow rate can be accurately measured even in the flow rate range in which the streamline changes in the longitudinal direction of the fluid flow path, and as a result, the flow rate can be accurately measured over a wide range from a small flow rate to a large flow rate. it can.

Further, according to this embodiment, a plurality of flow sensors 12 ₁ to 12 _{3, 131-134 3,} since the attachment to the wall of the tube portion 11 so as to face the fluid flow path, a small flow rate Even if the cross-sectional area of the flow path is made small in order to improve the measurement accuracy in the region, a plurality of flow velocity sensors 12 _{1 to} 12 ₃ ,
13 _{1 to} 13 ₃ can be provided, and the measurement accuracy in the small flow rate region can be improved. Further, since the cross section of the pipe part 11 is rectangular, the wall surface area of the pipe part 11 can be increased when the cross section of the pipe part has the same cross-sectional area as compared with the case where the cross section of the pipe part is circular. Since the wall surface of the portion 11 becomes flat, the number of flow velocity sensors can be increased and the attachment becomes easy.

As long as the flowmeter shown in FIG. 1 is unitized so that it can be connected to other pipes, a unitized flowmeter is simply installed at the location where the flow rate is to be measured. It is possible to easily measure the flow rate without performing the complicated work of mounting the sensor.

The present invention is not limited to the above-described embodiments. For example, the cross-section of the tube portion 11 is preferably rectangular, but is not limited to this. Also,
When the cross-sectional area of the pipe portion 11 is large, the plurality of flow velocity sensors may not be attached to the wall surface of the pipe portion 11, but may be arranged inside the wall surface of the pipe portion 11 by the guide member.

The present invention is not limited to measuring the flow rate of gas such as gas, but can be applied to a flow meter for measuring the flow rate of liquid.

[0026]

As described above, according to the flowmeter of the first aspect, the inside of the fluid flow path including at least two different positions in both the longitudinal direction of the fluid flow path and the direction orthogonal to the longitudinal direction. A plurality of flow velocity sensors for detecting the flow velocity of the fluid at a plurality of positions are provided, and the average value of the flow velocity at the plurality of positions is calculated by the average flow velocity calculating means based on the output signals of these flow velocity sensors, and the flow velocity calculating means calculates the flow velocity. Since the flow rate is calculated based on the average value, the flow rate can be accurately calculated even if the flow velocity distribution on the same cross section in the fluid flow path is different and the streamline changes in the longitudinal direction of the fluid flow path. The effect is that it can be measured.

Further, according to the flowmeter of any one of claims 2 to 4, the pipe section has a rectangular cross section so that each of the plurality of flow velocity sensors faces the fluid passage. Since it was attached to the wall surface of the pipe part, in addition to the above effects,
Even if the cross-sectional area of the flow path is reduced in order to improve the measurement accuracy in the small flow rate range, a plurality of flow velocity sensors can be provided, and there is an effect that the measurement accuracy can be improved especially in the small flow rate range.

[Brief description of drawings]

FIG. 1 is a perspective view showing a flow meter according to an embodiment of the present invention with a part thereof cut away.

FIG. 2 is a side view of the flow meter of FIG. 1 viewed from a longitudinal direction.

FIG. 3 is a block diagram showing a circuit configuration of the flow meter of FIG.

FIG. 4 is a sectional view for explaining the measurement principle of a conventional flowmeter.

[Explanation of symbols]

11 Pipe parts 12 _{1 to} 12 ₃ , 13 _{1 to} 13 ₃ Flow velocity sensor 14 _{1 to} 14 ₃ , 15 ₁ to 15 ₃ Detection part 21 Average flow velocity calculation part 22 Flow rate calculation part 23 Display part

Claims (4)

(57) [Claims] 1. A pipe part forming a fluid flow path through which a fluid passes, and a wall surface of the pipe part so that each detection part faces the fluid flow path.
A plurality of flow velocity sensors that are attached to the fluid flow channel and that detect the flow velocity of the fluid at a plurality of positions in the fluid flow channel including at least two positions that are different in both the longitudinal direction of the fluid flow channel and the direction orthogonal to the longitudinal direction. An average flow velocity calculating means for calculating an average value of the flow velocity at a plurality of positions based on the output signals of the plurality of flow velocity sensors, and a flow rate calculating means for calculating the flow rate of the fluid based on the calculation result of the average flow velocity calculating means. A flow meter characterized by having and. 2. A flowmeter according to claim 1, wherein the tube portion in cross-section a rectangular. 3. The plurality of flow velocity sensors are a plurality of first flow velocity sensors attached to one wall face of the wall faces of the pipe section, and a plurality of second flow velocity sensors attached to the other wall face. 3. The flowmeter according to claim 2, comprising: 4. The plurality of first flow velocity sensors and the plurality of second flow velocity sensors are arranged along directions that are inclined with respect to the longitudinal direction of the pipe portion and are not parallel to each other. The flowmeter according to claim 3, wherein