JPH11281425A - Pulsation absorbing structure for flow meter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform accurate flow rate measuring by reducing the influence of a pulsating flow. SOLUTION: Pipe members 17 and 18 having fluid paths 15 and 16 smaller in inner diameter than an inlet 12 and an outlet 13 are provided inside the inlet 12 and the outlet 13 such that the fluid paths are set along the flowing-in/ flowing-out direction of fluid. Also, in a main body 11, partition walls 21 and 22 for preventing the flowing of fluid in a specified direction are provided by keeping specified gaps from the pipe member 17 and 18.

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 a flow rate used in an electronic gas meter or the like, and more particularly, to an estimating equation for estimating an integrated flow rate by intermittently measuring a flow velocity in a flow path. The present invention relates to a flowmeter pulsation absorbing structure for reducing the influence of flowmeter pulsation (pressure fluctuation, flow velocity fluctuation).

[0002]

2. Description of the Related Art Conventionally, as a flow meter used for measuring a flow rate of an electronic gas meter or the like, a flow meter of an ultrasonic type or a fluidic type has been widely used. For example, the basic principle of an ultrasonic gas flow meter will be briefly described. As shown in FIG. 3, the ultrasonic flow meter 30 uses an ultrasonic frequency which is arranged at a predetermined distance in a gas flow path. It has two acoustic transducers 31, 32, for example made of piezoelectric transducers, and a measuring duct 33 through which ultrasonic waves propagate.

[0003] The ultrasonic flowmeter 30 first generates an ultrasonic signal from the acoustic transducer 31 on the gas inflow side, receives the ultrasonic signal on the acoustic transducer 32 on the gas outflow side, and converts the ultrasonic signal between the acoustic transducers into gas. The propagation time t1 in the flow direction is measured. Next, the ultrasonic flow meter 3
0 switches both acoustic transducers to generate an ultrasonic signal from the acoustic transducer 32 on the gas outflow side and to receive the ultrasonic signal on the acoustic transducer 31 on the gas inflow side. measure. Further, the ultrasonic flow meter 30 intermittently obtains the flow velocity v of the gas flowing through the measurement duct 33 based on the measured propagation time difference between the two propagation times t1 and t2.
Is multiplied by the cross-sectional area of the measuring duct 33 to determine the instantaneous flow rate. Then, the flow rate is obtained by multiplying the instantaneous flow rate by a sampling time that is a constant measurement interval, and the integrated flow rate obtained by integrating the flow rates is displayed.

[0004]

In a combustor such as a gas heat pump (GHP) that consumes a fluid such as a gas supplied through a flow meter of this type, during operation, pressure fluctuations or fluctuations in the supplied gas occur. Some may cause pulsations such as flow velocity fluctuations. That is, for example, in the installation example of the flow meter shown in FIG. 4A, the gas pressure fluctuates with the operation of the combustor 40, and the pulsation 41 thereof is generated from the downstream side of the flow meter 30.
Propagate inside. This causes a measurement error.

[0005] In the installation example of the flow meter shown in FIG. 4B, of the two flow meters 30A and 30B connected in parallel, the flow meter 30B has a pulsation 41B from the combustor 40B.
Propagates from the downstream side, and pulsations 41A from the combustor 40A propagate from the upstream side. Therefore, the flow meter 3
At 0B, a larger measurement error occurs than in the installation example shown in FIG.

More specifically, referring to FIG. 5, when a pressure fluctuation or the like occurs, the gas flow causes a pulsating flow in which the gas flow rate changes with time due to the fluctuation. The flow velocity v of the gas flow having such a pulsating flow is measured at a constant sampling interval Δt by the flow meter as described above, and the passing flow rate is obtained by multiplying the measured flow velocity v by the sampling time Δt. In this case, the hatched portion in the figure becomes an error. Therefore, the integrated flow rate obtained by integrating the passing flow rates is an integrated value different from the actual gas usage amount.

An object of the present invention is to solve the above-mentioned problems, and to provide a pulsation absorbing structure of a flow meter capable of reducing the influence of a pulsating flow and performing accurate flow measurement.

[0008]

An object of the present invention is to provide a flowmeter for measuring a flow rate of a fluid flowing into or out of a main body through an inlet and an outlet by a measuring unit provided in the main body. In, at least one of the inflow port and the outflow port, a tubular member having a fluid flow path having a smaller inside diameter than the inflow port or the outflow port causes the fluid flow path to follow the inflow or outflow direction of the fluid. The pulsation absorbing structure of a flow meter is provided in such a manner as to be provided as described above, and a partition wall for preventing a flow of a fluid in a specific direction is provided in the main body.

In the pulsation absorbing structure of the flow meter according to the present invention, the pulsating flow propagates from the upstream side or the downstream side of the flow meter to the fluid flowing into or out of the main body via the inlet and the outlet. In some cases, the pulsation of the fluid is attenuated by the presence of the tubular member and the partition that change the flow of the fluid.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An ultrasonic gas flow meter to which a pulsation absorbing structure of a flow meter according to an embodiment of the present invention is applied will be described in detail with reference to FIGS. FIG.
FIG. 2 is a schematic sectional view showing an ultrasonic gas flow meter to which a pulsation absorbing structure of a flow meter according to an embodiment of the present invention is applied;
FIG. 2 is an enlarged cross-sectional view near the inlet of the ultrasonic gas flow meter shown in FIG. 1.

Referring to FIGS. 1 and 2, an ultrasonic gas flow meter 10 includes an inlet 12 and an outlet 13 in a main body 11.
The flow rate of gas flowing in or out of the main body 11 is measured by a measuring and measuring unit 14 provided in the main body 11.

The inflow port 12 and the outflow port 13 are each formed in a substantially cylindrical shape, and have substantially the same inner diameter. Inside the inflow port 12 and the outflow port 13, fluid flow paths 15, 16 are provided.
The substantially cylindrical tubular members 17 and 18 having
5 and 16 are provided along the inflow or outflow direction of the fluid. The fluid flow path 15 of each tubular member 17, 18;
The inner diameter of 16 is smaller than the inner diameters of the inflow port 12 and the outflow port 13 by a predetermined amount (about half in this embodiment).

That is, the inside of the inflow port 12 and the outflow port 13 is formed by each tubular member 17, 18 by each flow path 15, 1.
6 (hereinafter referred to as an inner flow path) and tubular members 17 and 18.
It is divided into outer flow paths 19 and 20 (hereinafter, referred to as outer flow paths), and has a concentric double structure.

In the main body 11, a pair of partitions 21 and 22 are provided at predetermined intervals from the tubular members 17 and 18. That is, each of the partition walls 21 and 22 is provided with a flow of fluid or a fluid from the inner end (the lower end in the figure) of each of the tubular members 17 and 18 in the main body 11 to a position spaced a predetermined distance downward in the figure. Direction perpendicular to the outflow direction (left-right direction in the figure)
It is provided along. On the upper surfaces of the partition walls 21 and 22, an auxiliary partition wall 23 is provided to protrude upward along the extension of the side wall 24 of the inflow port 12 and the outflow port 13. Each of the partition walls 21 and 22 together with each of the auxiliary partition walls 23 prevents the fluid from flowing in a specific direction in the main body 11.

The weighing / measuring unit 14 includes a measuring duct 25 through which ultrasonic waves propagate, and a pair of acoustic transducers 26 and 27 arranged at positions facing each other with a predetermined interval across the measuring duct 25. I have. Each acoustic transducer 26, 27 operates at an ultrasonic frequency, for example,
It is a piezoelectric vibrator.

When measuring the gas flow rate, the measurement / measurement unit 14 generates an ultrasonic signal from the acoustic transducer 26 on the gas inflow side (the left side in the figure) and converts the ultrasonic signal into the gas outflow side (the right side in the figure). ) Is received by the acoustic transducer 27). At this time, the propagation time t1 of the ultrasonic signal between the acoustic transducers 26 and 27 in the gas flow direction (right direction in the figure) is measured.

Next, the weighing / measuring unit 14 switches between the two acoustic transducers 26 and 27 to generate an ultrasonic signal from the acoustic transducer 27 on the gas outflow side, and to transmit the ultrasonic signal to the acoustic transducer 26 on the gas inflow side. To receive. At this time, the propagation time t2 in the direction opposite to the gas flow direction (left direction in the figure) is measured.

Further, the weighing / measuring unit 14 calculates the propagation time t.
The flow velocity v of the gas flowing in the measurement duct 25 is intermittently obtained based on the propagation time difference of 1, t2. Then, an instantaneous flow rate is obtained by multiplying a constant determined by the cross-sectional area of the measurement duct 25 and the temperature, pressure, and gas quality (density, viscosity) by the flow velocity v. Thereafter, a passing flow rate is obtained by multiplying the instantaneous flow rate by a sampling time that is a fixed measurement interval, and the passing flow rate is integrated to obtain an integrated flow rate.

The operation of the present embodiment will be described. In the above-described gas flow meter 10 of the present embodiment, the pulsating flow propagates to the fluid flowing into or out of the main body 11 through the inflow port 12 and the outflow port 13, for example, from the upstream side or the downstream side of the flow meter. In some cases, tubular members 17, 18 that change the flow of fluid
The presence of the partitions 21 and 22 attenuates pulsations (hereinafter simply referred to as pulsations) such as pressure fluctuations and flow velocity fluctuations.

That is, for example, at the inlet 12, the gas before measurement flows downward into the main body 11 through the inner flow path 15 and the outer flow path 19 (steady flow). At this time, the gas that has passed through the inner flow path 15 exits from the lower end of the tubular member 17 and hits the partition 21 to disturb the flow and attenuate the pulsation. Further, a part of the gas bounced back to the partition 21 goes into the outer flow path 19 and flows upward in the outer flow path 19. Due to this backflow, collision occurs with the gas flowing downward in the outer flow path 19 in the vicinity indicated by the broken circle in FIG. 2, and the pulsation is further attenuated.

For example, the gas after measurement goes around the left end of the partition wall 22 on the right side in FIG.
a, and passes between the tip of the auxiliary partition 23 of the partition 22 and the left side surface of the tubular member 18 in the outlet 13. This causes the gas to be disturbed and dampen pulsation. Further, the gas that has hit the tubular member 18 flows into the outer flow path 20 and also flows into the inner flow path 16 bypassing the lower end of the tubular member 18. And, each flow path 16, 20
Flows upward and flows out of the main body 11.

Further, for example, when the pulsating flow propagates from the downstream side (outlet 13 side) of the gas flowmeter 10 into the gas flowmeter 10, the pulsating flow propagates from the outlet 13 into the main body 11. Happens. That is, at the outlet 13, the pulsating flow from the downstream side of the gas flow meter 10 propagates downward into the main body 11 via the inner flow path 16 and the outer flow path 20. At this time, the pulsation propagating through the inner flow path 16 hits the upper surface of the partition wall 22 from the lower end of the tubular member 18 and is disturbed and attenuated. Further, the pulsating flow bounced back by the partition wall 22 wraps around the outer flow path 20 and
Propagates in the opposite direction (upward in the figure). Due to the propagation in the opposite direction, a collision occurs with the pulsation propagating downward in the outer flow path 20 and is further attenuated. (See Fig. 2)

In addition to the propagation of the pulsating flow from the downstream side of the gas flow meter 10, even if a reverse flow of the gas occurs from the downstream side of the gas flow meter 10, for example, the downstream side of the gas flow meter 10 described above. As in the case of the propagation of the pulsating flow from, the pulsation of the gas flowing backward at the outlet 13 is attenuated.

As described above, according to the pulsation absorbing structure of the flow meter of the present embodiment, the tubular members 17, 1 having the fluid channels 15, 16 smaller in inner diameter than the inlet 12 and the outlet 13 are provided.
8 are provided inside the inflow port 12 and the outflow port 13,
5 and 16 are provided along the inflow or outflow direction of the fluid. Further, in the main body 11, partition walls 21 and 22 for preventing a flow of a fluid in a specific direction are provided.
18 and at a predetermined interval.

Therefore, for example, the pulsation propagating from the upstream side or the downstream side of the gas flow meter 10 can be attenuated near the inflow port 12 and the outflow port 13. This can reduce the effect of pulsating flow on gas flow measurement,
Accurate flow measurement can be performed. In addition, it is possible to cope with the manufacturing by changing the shape of the current component, and the cost can be reduced.

It should be noted that the present invention is not limited to the above embodiment, but can be embodied in other modes by making appropriate changes. For example, in the above embodiment, the inflow port 12 and the
By providing tubular members 17 and 18 having fluid flow paths 15 and 16 having a smaller inner diameter than the outlet 13, the inlet 12
And the inside of the outlet 13 has a concentric double structure, but a second tubular member (not shown) having a fluid passage smaller in inner diameter than the fluid passages 15, 16 of the tubular members 17, 18.
And the inside of the inflow port 12 and the outflow port 13 may have a concentric triple structure. Further, by further overlapping the tubular member, the inside of the inflow port 12 and the
A concentric multi-layer structure may be used.

Further, the above embodiment is particularly suitable for the principle and structure of a guess type gas flow meter including an ultrasonic type, and a remarkable effect can be expected. Although the embodiment has been described, the invention is not limited to this. That is, the present invention is not limited to gas and can be applied to a flow meter that measures the flow rate of any other fluid, and is not limited to the ultrasonic type, and can be applied to other inferential type flow meters or actual measurement type flow meters. it can. In these cases, the same high effects as described above can be expected.

[0028]

As described above, according to the pulsation absorbing structure of the flow meter of the present invention, at least one of the inflow port and the outflow port has a fluid flow having a smaller inside diameter than the inflow port or the outflow port. A tubular member having a passage is provided so as to extend the fluid flow path in the inflow or outflow direction of the fluid, and a partition for preventing the flow of the fluid in a specific direction is provided in the main body at a predetermined distance from the tubular member. It is provided at a distance. Therefore, when measuring the flow rate of the fluid, the influence of the pulsating flow can be reduced, and accurate flow rate measurement can be performed.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an ultrasonic gas flow meter to which a pulsation absorbing structure of a flow meter according to an embodiment of the present invention is applied.

FIG. 2 is an enlarged sectional view of the vicinity of an inlet of the ultrasonic gas flow meter shown in FIG.

FIG. 3 is a schematic sectional view showing a conventional ultrasonic gas flow meter.

FIG. 4 is a schematic view showing an installation example of a conventional gas flow meter.

FIG. 5 is a graph showing a change in gas flow velocity.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Flow meter (ultrasonic gas flow meter) 11 Main body 12 Inflow port 13 Outflow port 14 Measuring unit 15, 16 Inner flow path (fluid flow path) 17, 18 Tubular member 19, 20 Outer flow path 21, 22 Partition wall 23 Auxiliary bulkhead 25 Measurement duct 26, 27 Transducer

Claims (1)

[Claims] 1. A flow meter for measuring a flow rate of a fluid flowing into or out of a main body through an inlet and an outlet by a measuring unit provided in the main body, wherein at least one of the inlet and the outlet is provided. On one side, a tubular member having a fluid flow path having a smaller inside diameter than the inflow port or the outflow port is provided so as to align the fluid flow path in the inflow or outflow direction of the fluid, and in the main body. Is a pulsation absorbing structure of a flow meter, wherein a partition wall for blocking a flow of a fluid in a specific direction is provided.