JPH11281435A - Pulsation absorbing structure for flow meter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a good pulsation absorbing structure for a flow meter, which is capable of facilitating accurate flow rate measuring at low costs by reducing the influence of pulsation in the flow meter of an estimation type. SOLUTION: An ultrasonic flow meter 100 is provided with a case main body 2 having a gas flow passage for communicating an inlet 5a and an outlet with each other, a flow rate measuring section 8 arranged between upstream and downstream side chambers 3a and 3b in the case main body 2, shielding plates 4a and 4b provided in the inlet 5a and the outlet 5b respectively communicated with the upstream and downstream side chambers 3a and 3b and displaced by pulsation propagated in the inlet 3a and the outlet 3b so as to change the opening area of the flow passage.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pulsation absorbing structure of a flow meter used as an electronic gas meter or the like.
The flow rate of a guess-type equation that intermittently measures the flow velocity of the fluid in the flow path and estimates the passing flow rate of the fluid that has passed through the flow path by multiplying the measured flow velocity by the cross-sectional area of the flow path and the intermittent time. The present invention relates to a pulsation absorbing structure for reducing the influence of pulsation (pressure fluctuation, flow velocity fluctuation) on a meter.

[0002]

2. Description of the Related Art In recent years, a flow meter used in an electronic gas meter or the like includes a measuring means for intermittently measuring a physical quantity which changes according to a flow velocity of a fluid in a flow path, and a flow rate measured by the measuring means. There is known an inferential flow meter that includes a flow rate measuring unit that measures a passing flow rate of a fluid that has passed through the flow path by multiplying the flow area by multiplying the cross-sectional area of the flow path by the intermittent time. In addition, such a speculative flow meter uses an ultrasonic flow meter that uses an acoustic transducer or the like, which is an element that transmits and receives ultrasonic waves in a fluid, as a measuring means, and a pressure fluctuation of a fluid in a flow path. There is a fluidic type flow meter that uses a fluidic element for detecting the flow rate.

FIG. 6 shows the basic structure of an ultrasonic flowmeter 20 used as an electronic gas meter.
The ultrasonic flowmeter 20 includes a case main body 24 that forms a gas flow path that communicates the inflow port 26 and the outflow port 27, and a flow measurement unit 28 that is a measuring unit disposed in the case main body 24. Have. The flow rate measuring unit 28 includes an upstream chamber 20 a and a downstream chamber 2 in the case main body 24.
0b, and a straight tube-shaped measurement duct 22 which also functions as a gas flow measurement flow path and an ultrasonic wave propagation channel, and a pair of opposedly disposed opposite ends of the measurement duct 22 at a predetermined distance. Sound transducers 21 and 23 are provided. The acoustic transducers 21, 23 comprise, for example, piezoelectric vibrators operating at ultrasonic frequencies.

[0004] The gas flowing into the upstream chamber 20a from the inlet 26 of the case body 24 reaches the downstream chamber 20b through the measuring duct 22, and the outlet 2
Outflow from 7. Therefore, an ultrasonic signal is generated from the acoustic transducer 21 on the upstream chamber 20a side and received by the acoustic transducer 23 on the downstream chamber 20b side, and the propagation time of the ultrasonic signal in the gas flow direction between the acoustic transducers 21 and 23 is determined. to measure the t _1.

Next, both acoustic transducers 21,
By switching the 23, to generate an ultrasonic signal from the downstream chamber 20b side of the acoustic transducer 23, the upstream chamber 20a side gas flow direction by receiving the acoustic transducer 21 of measuring the propagation time t ₂ in the reverse direction . The flow velocity V of the gas flowing in the measurement duct 22 is intermittently obtained based on the difference between the two measured propagation times t ₁ and t ₂ , and the flow velocity V is multiplied by the cross-sectional area of the measurement duct 22. To find the instantaneous flow rate. Further, the instantaneous flow rate is multiplied by a sampling time, which is a constant measurement interval, to obtain a passing flow rate, and the passing flow rates are integrated to obtain an integrated flow rate.
An electronic gas meter can be configured by displaying the integrated flow rate obtained by the flow rate measuring means (not shown) on a display means (not shown) provided on the outer surface of the case main body 24.

[0006]

Among combustors that consume gas supplied through an electronic gas meter, some gas burners, such as gas governors and gas heat pumps (GHPs), apply pressure fluctuations and flow velocity fluctuations to supply gas during use. Some cause pulsation. Then, for example, as shown in FIG.
When the pulsation 25 propagates from the downstream side of the ultrasonic flowmeter 20 into the flowmeter, the gas flow in the measurement duct 22 may be a pulsating flow.

Further, in the case of LPG collective supply or city gas supply as shown in FIG. 7 (b), a plurality of flow meters 20A and 20B are connected to the main supply pipe 31 in a branched manner, so that the upstream flow rate is controlled. The pulsation 25A generated by the combustor 30A connected to the meter 20A may be transmitted to the downstream flow meter 20B through the gas flow in the flow meter 20A and the branch supply pipe 31a. In addition, for example, in the downstream flow meter 20B,
Pulsation 25B from combustor 30B connected to self
And a combustor 30A connected to an upstream flow meter 20A.
And the pulsation 25A from the
A pulsating flow in the flow meter 20B may be further intensified due to the influences of A and 25B. If such a pulsating flow becomes violent and the fluctuation period of the pulsation at the inlet of the flow meter and the fluctuation period of the pulsation at the outlet greatly deviate, backflow may occur in the flow meter in some cases.

In such a flow meter of the guessing type, when a pulsating flow occurs in the gas flow in the measuring duct 22 due to the pulsation generated by the combustor, good measurement cannot be performed in the flow measuring unit 28. In particular, when a backflow occurs in the measurement duct 22, the calculation of the integrated flow rate of the flowmeter is adversely affected. That is, when a pulsating flow occurs in the gas flow in the measurement duct 22, the flow velocity V of the gas flow is measured at a constant sampling interval Δt as shown in FIG. 8, and the measured flow velocity V is multiplied by the sampling time Δt. When the passing flow rate is obtained, the hatched portion in the figure becomes an error, and the integrated flow rate obtained by integrating the passing flow rates is an integrated value that is considerably different from the actual gas usage.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-mentioned problems, and a good flow meter capable of reducing the influence of pulsation in a guess-type flow meter and realizing accurate flow measurement easily and at low cost. Is to provide a pulsation absorbing structure.

[0010]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an electronic apparatus comprising: a case body having a flow path communicating an inlet and an outlet; and an upstream chamber and a downstream chamber in the case body. A pulsation absorbing structure of a flow meter, which is disposed, and includes a measurement unit that intermittently measures a physical quantity that changes in accordance with the flow velocity of the fluid in the flow path, wherein the inflow port and the inflow port respectively communicate with the upstream and downstream chambers. A pulsation of a flow meter, wherein at least one of the outlets is provided with a shielding means that can be displaced so as to change an opening area of the flow path by pulsations propagated from the inlet and the outlet. Achieved by an absorbing structure.

According to the above configuration, the pulsation propagated from the upstream side or the downstream side of the flow meter is absorbed by entering the case main body and displacing the shielding means. In addition, the shielding means changes the opening area of the flow path communicating with the upstream and downstream chambers, thereby preventing the measurement means from being affected by pulsation.

Preferably, the shielding means is configured to be displaced in a direction in which the opening area of the flow path is enlarged by the flow of the fluid in the flow path, thereby minimizing an increase in pressure loss. Pulsation can be absorbed. or,
Preferably, the shielding means includes a shielding plate that is cantilevered by the case main body and can be flexibly deformed. Preferably, the shielding means includes a telescopic elastic member having one end fixed to the case body, and a shielding plate fixed to the other end of the elastic member.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A pulsation absorbing structure of a flow meter according to an embodiment of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a schematic sectional view of an ultrasonic flowmeter 100 provided with a pulsation absorbing structure according to a first embodiment of the present invention.

The ultrasonic flow meter 100 shown in FIG. 1 is used as an electronic gas meter. The ultrasonic flow meter 100 has a substantially rectangular parallelepiped case body 2 having a gas flow path connecting an inlet 5a and an outlet 5b. , The upstream chamber 3 in the case body 2.
a, which is provided at the flow inlet 8a and the outlet 5b communicating with the upstream and downstream chambers 3a, 3b, respectively. Shielding plates 4a and 4b, which are displaceable so as to change the opening area of the flow path by pulsation transmitted from the outlet 5a and the outlet 5b, are provided.

The flow rate measuring section 8 communicates the upstream chamber 3a and the downstream chamber 3b in the case main body 2 partitioned by the partition wall, the gas flow measuring flow path and the ultrasonic wave propagation pipe. And a pair of acoustic transducers 21 and 13 disposed opposite to each other at a predetermined distance from both ends of the measurement duct 22.

The inflow port 5a and the outflow port 5b are formed in a cylindrical shape, for example, for connecting a gas pipe (not shown), and constitute a flow path having a circular cross section. Therefore,
The shielding plates 4a and 4b made of a material that can be flexibly deformed are
It is formed in a disk shape as shown in FIG. 2 according to the inner diameter of the corresponding inlet 5a and outlet 5b.

The shield plates 4a and 4b are cantilevered at the lower ends of the inner walls of the inlets 5a and the outlets 5b communicating with the upstream and downstream chambers 3a and 3b in the case body 2, respectively. It is mounted so that it can be deformed in a direction in which the opening area of the flow path is enlarged by the flow A of the gas in the flow path in the inside 2. Therefore, the shielding plates 4a and 4b
By appropriately selecting the mass, the material, the mounting angle with respect to the gas flow direction, and the pressure receiving area, the deformation amount and the pressure loss can be adjusted. Further, by providing breathing holes in the shielding plates 4a and 4b, the deformation amount and the pressure loss may be adjusted.

The ultrasonic flow meter 100 multiplies the flow rate measured by the flow rate measuring section 8, the cross-sectional area of the gas flow path, and the intermittent time to obtain the flow rate of the gas passing through the gas flow path. And a display means (not shown) for displaying the integrated flow rate obtained by the flow rate measuring means on the outer surface of the case main body 2.

In the case where the gas burner that consumes gas supplied through the ultrasonic flowmeter 100 is a general gas burner, pulsation (pressure fluctuation, flow velocity fluctuation) is caused in the supplied gas during use. Since there is no gas, the gas entering the case body 2 from the inflow port 5a is introduced into the upstream chamber 3a while appropriately deforming the shielding plate 4a, flows smoothly in the measurement duct 22, and flows into the downstream chamber 3b. Through the outlet 5b. Therefore, the flow rate measuring unit 8
Can measure the exact flow rate. Since the shielding plates 4a and 4b can be deformed in a direction in which the opening area of the flow path increases in accordance with an increase in the flow rate of gas, an increase in pressure loss can be suppressed to a minimum.

Next, a combustor that consumes gas supplied through the ultrasonic flowmeter 100 is a combustor such as a gas governor or a gas heat pump (GHP) that performs pulse-like combustion. When these combustors are connected in parallel as in the case of supply or city gas supply,
Since a pulsating flow is generated in the supply gas by the use of the combustor, the pulsation propagating from the upstream side or the downstream side of the ultrasonic flowmeter 100 enters the case body 2 from the inflow port 5a or the outflow port 5b.

At this time, the shielding plate 4a or the shielding plate 4
b absorbs the pulsating energy of the gas by being elastically deformed and vibrated by the pulsation propagated into the case body 2 from the inlet 5a or the outlet 5b. In addition, the shielding plate 4a or the shielding plate 4b, which is deformed by pulsation, affects the flow rate measuring unit 8 by pulsation by changing the opening area of the flow path communicating with the upstream and downstream chambers 3a and 3b. Can be prevented. That is,
When the backflow of gas occurs in the case body 2 due to the pulsation, the pulsation is not transmitted to the flow rate measuring unit 8 because the shielding plate 4a or the shielding plate 4b is deformed in a direction to reduce the opening area of the flow path. When a backflow of gas occurs in the case body 2 due to the pulsation, the shielding plate 4a or the shielding plate 4
b may be configured to block the flow path.

Therefore, since the pulsation propagated from the upstream side or the downstream side of the ultrasonic flow meter 100 is not transmitted to the flow rate measuring section 8 arranged in the case main body 2, the flow rate measuring section 8 is accurate. The flow rate can be measured. Note that the support positions of the shielding plates 4a and 4b are not limited to the embodiment shown in FIG. 1, and the support positions are set to be opposite to each other, for example, as in the ultrasonic flow meter 200 shown in FIG. Is also good. Further, it goes without saying that the shapes of the shielding plates 4a and 4b can be changed as appropriate.

FIG. 4 is a schematic sectional view of an ultrasonic flowmeter 300 having a pulsation absorbing structure according to a second embodiment of the present invention. However, the same components as those of the ultrasonic flowmeter 100 of the first embodiment except for the shielding means are denoted by the same reference numerals, and detailed description thereof will be omitted. The shielding means 11a provided on the inflow port 5a side of the ultrasonic flowmeter 300 is a coil spring which is a stretchable elastic member whose lower end is fixed to a fixing plate 12 provided so as to protrude into the upstream chamber 3a. 14a
And a shielding plate 15 fixed to the upper end of the coil spring 14a.
a and can be displaced so as to change the opening area of the flow path by pulsation propagated from the inflow port 5a.

On the other hand, the shielding means 11b provided on the outflow port 5b side is provided with a partition wall 13 defining the downstream chamber 3b.
A coil spring 14b which is an elastic member whose upper end is fixed to the inner wall of the case 2 opposed to the gas flow filling hole 13a formed in the coil spring 14b, and a shielding plate 15b fixed to the lower end of the coil spring 14b. It can be displaced so as to change the opening area of the flow path by the pulsation propagated from the outlet 5b.

Therefore, the shielding means 11a, 11b
The shape of the shielding plates 15a, 15b and the coil springs 14a, 1
The deformation amount and pressure loss can be adjusted by appropriately selecting the elastic force of 4b, the mounting angle with respect to the gas flow direction, and the like. Further, by providing breathing holes in the shielding plates 15a and 15b, the deformation amount and the pressure loss may be adjusted.

That is, the ultrasonic flowmeter 3 of the second embodiment
00 is similar to the ultrasonic flow meter 100 of the first embodiment, when a pulsating flow is generated in the supply gas by use of a combustor such as a gas governor or a gas heat pump (GHP), the ultrasonic flow meter 100 is used. The pulsation propagated from the upstream side or the downstream side of 300 enters the case body 2 from the inlet 5a or the outlet 5b, and the shielding means 11a or the shielding means 11b is connected to the inlet 5a or the outlet 5b. From the coil spring 1
The pulsating energy of the gas is absorbed by the elastic deformation and vibration of 4a and 14b.

The shielding plate 15a displaced by pulsation.
Alternatively, the shielding plate 15b is connected to the upstream and downstream chambers 3a, 3
By changing the opening area of the flow path communicating with each of b, it is possible to prevent the flow rate measuring unit 8 from being affected by pulsation. That is, when a backflow of gas occurs in the case body 2 due to the pulsation, the shielding plate 15a or the shielding plate 15b is displaced in a direction to reduce the opening area of the flow path, so that the pulsation is transmitted to the flow rate measurement unit 8. Absent. When a backflow of gas occurs in the case body 2 due to the pulsation, the shielding means 1
1a or the shielding means 11b may be configured to block the flow path. Accordingly, the pulsation propagated from the upstream side or the downstream side of the ultrasonic flow meter 300 is not transmitted to the flow rate measuring section 8 disposed in the case main body 2, so that the flow rate measuring section 8 accurately measures the flow velocity. can do.

The mounting position of the shielding means 11a, 11b is not limited to the form shown in FIG. 4, but may be, for example, an ultrasonic flow meter 400 shown in FIG. Alternatively, the shielding means 11a may be provided so as to bend the gas flow path by providing the partition plate 16 and to face the flow hole 16a formed in the partition plate 16. or,
The partitioning plate 17 may be provided in the downstream chamber 3b to bend the gas flow path, and the blocking means 11b may be provided so as to face the flow hole 17a formed in the partitioning plate 17. According to this configuration, the case main body 2 is connected to the inflow port 5a or the outflow port 5b.
The pulsation that has entered the inside is bumped by the partition plates 16 and 17 before being absorbed by the shielding means 11a and 11b, and the pressure fluctuation is attenuated in advance, so that the pulsation can be absorbed more efficiently. .

It should be noted that the configurations of the case body, the measuring means and the shielding means in the present invention are not limited to the configurations of the above embodiments, but can be changed as appropriate based on the gist of the present invention. . For example, in the above embodiment, the pulsation absorbing structure of the ultrasonic flow meter has been described. However, the pulsation absorbing structure of the flow meter of the present invention is not limited to this, and other structures such as a fluidic flow meter may be used. It can be applied to guess type flow meters, and LP can be used as a fluid.
The invention is not limited to gas and city gas, but can be applied to fluids such as water and oil other than gas.

[0030]

As described above, according to the pulsation absorbing structure of the flow meter according to the present invention, the pulsation propagated from the upstream side or the downstream side of the flow meter enters the case body and displaces the shielding means. It is absorbed by letting it go. In addition, the shielding means changes the opening area of the flow path communicating with the upstream and downstream chambers, thereby preventing the measurement means from being affected by pulsation. Therefore, it is possible to provide a good pulsation absorbing structure of a flow meter which can reduce the influence of pulsation in a guess-type flow meter and realize accurate flow measurement easily and at low cost.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of an ultrasonic flowmeter provided with a pulsation absorbing structure according to a first embodiment of the present invention.

FIG. 2 is a partially cutaway perspective view showing a configuration of a main part of the ultrasonic flowmeter shown in FIG.

FIG. 3 is a schematic sectional view showing a modified example of the ultrasonic flow meter shown in FIG.

FIG. 4 is a schematic sectional view of an ultrasonic flow meter provided with a pulsation absorbing structure according to a second embodiment of the present invention.

FIG. 5 is a schematic sectional view showing a modified example of the ultrasonic flow meter shown in FIG.

FIG. 6 is a schematic sectional view showing a basic structure of an ultrasonic flowmeter.

FIG. 7 is a configuration diagram illustrating generation and influence of pulsation.

FIG. 8 is an explanatory diagram of a measurement error caused by pulsation when calculating a flow rate from a measured value of a flow velocity.

[Explanation of symbols]

 2 Case main body 3a Upstream chamber 3b Downstream chamber 4a Shielding plate 4b Shielding plate 5a Inlet 5b Outlet 8 Flow rate measuring unit 22 Measurement duct 100 Ultrasonic flow meter

Claims (4)

[Claims] 1. A case body having a flow path communicating an inflow port and an outflow port, and disposed between an upstream chamber and a downstream chamber in the case body, the flow rate of the fluid in the flow path being reduced. A pulsation absorbing structure of a flow meter comprising a measuring means for intermittently measuring a physical quantity that changes in accordance with the flow rate, wherein at least one of the inflow port and the outflow port communicating with the upstream and downstream chambers includes A pulsation absorbing structure for a flow meter, wherein a shielding means capable of being displaced so as to change an opening area of a flow path by pulsation propagated from an inlet and an outlet is provided. 2. The pulsation absorbing structure for a flow meter according to claim 1, wherein said shielding means is displaced in a direction to increase an opening area of the flow path by a flow of a fluid in the flow path. 3. The pulsation absorbing structure for a flow meter according to claim 1, wherein said shielding means includes a shielding plate that is cantilevered by a case main body and can be flexibly deformed. 4. The shielding means comprises a stretchable elastic member having one end fixed to the case main body, and a shielding plate fixed to the other end of the elastic member. 3. The pulsation absorbing structure of the flow meter according to 1 or 2.