JP2002257614A - Pressure fluctuation alleviating device for gas meter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas meter capable of accurately measuring flow rate even in the case that a pressure fluctuation has occurred in a gas pipe. SOLUTION: The pressure fluctuation alleviating device 3 for gas meter, which is installed in series with a gas pipe on the upstream side, downstream side or both sides of a gas flow rate measuring section 1, includes a space section 5 through which the gas flows in from the gas pipe 2 and flows out to the gas pipe 2, a volume varying mechanism 4 that allows the space section 5 to vary the volume, and a rectifying mechanism 6, 7 that rectifies the gas flow at a gas input aperture and a gas output aperture in the space section 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure fluctuation mitigation device for a gas meter provided with a mechanism for attenuating a pressure fluctuation generated on the upstream side of a flow rate measuring portion.

[0002]

2. Description of the Related Art Generally, a gas meter is installed to measure a gas flow rate. However, when a gas meter that measures the flow rate of a gas is used, there are several factors that cause an error. Exists.

For example, when a plurality of gas meters such as a large flow rate meter, a middle flow rate meter, and a small flow rate meter are used in combination to measure a wide flow rate range, any one of the meters may be used to measure a gas pipe. Pressure fluctuations may occur inside. At this time, if a fluidic meter of a type that measures the frequency of vibration generated by the fluid is used, there is a problem that the frequency due to the above-described pressure fluctuation is detected instead of the frequency due to the original gas flow. appear. In addition, since the flow velocity of the fluid fluctuates due to the pressure fluctuation, there is a problem that an error increases in a gas meter such as an ultrasonic flow measuring apparatus that measures the flow velocity from the flow velocity.

[0004] In order to solve these problems, Japanese Patent Laid-Open No.
A valve mechanism for shutting off a flow path is provided upstream of a gas meter as disclosed in Japanese Patent Application Publication No. 184476, and a valve is opened and closed by a differential pressure between an upstream side and a downstream side of the valve mechanism so that a fluid flows and Pressure fluctuation absorbing devices which attempt to absorb pressure fluctuations generated upstream of the pressure fluctuations have been proposed. Or,
It has been practiced to simply provide one or a plurality of flow regulating plates in the flow path.

[0005]

However, the above-described pressure fluctuation absorbing device requires the provision of a complicated valve mechanism, and further has the problem that the pressure loss of the gas flow is large due to mechanical reasons in the valve mechanism. is there. In addition, since the flow path is blocked by the valve mechanism, when the flow rate is small, the flow velocity of the gas flow reaching the flow rate measurement unit installed on the downstream side is further reduced, and the measurement accuracy is reduced. There is a problem. Even when the flow rate is large, the pressure fluctuation can be absorbed by operating the valve mechanism, but operating the structure called the valve mechanism in the closed space inside the gas pipe is as described above. Since another pressure fluctuation occurs in the gas pipe, it can be said that it has not solved the fundamental problem. Thus, it does not provide a solution to the problem of making accurate flow measurements.

[0006] Further, the pressure fluctuation generated in a closed space such as a gas pipe cannot be completely relieved by merely providing one flow straightening plate or a plurality of flow straightening plates at intervals in the flow path. Alternatively, even if a certain degree of pressure fluctuation can be reduced, there is a problem that the pressure loss due to the moderating action increases.

Alternatively, since various gas appliances are connected to the downstream side of the gas meter, pressure fluctuation (pulsation) occurs in the gas pipe due to on / off of gas use by those gas appliances, and an error caused by the fluctuation occurs. There is also the problem of increase in Similarly, in rotating gas equipment such as gas heat pumps, there is also a problem that not only the ON / OFF timing but also the pulsation during operation is continuously transmitted to the gas meter through the gas pipe, and accurate flow measurement cannot be performed. No solution has been proposed for such a problem.

The present invention has been made in view of the above problems, and has as its object to provide a gas meter capable of performing accurate flow measurement even when a pressure fluctuation occurs inside a gas pipe. To provide.

[0009]

Means for Solving the Problems A first characteristic configuration of a pressure fluctuation mitigation device for a gas meter according to the present invention for solving the above problems is as described in claim 1 of the claims. A pressure fluctuation mitigation device for a gas meter used in series with an upstream or downstream side of a gas flow measurement unit or both gas pipes, and flows in from the gas pipe and flows out to the gas pipe. A space through which the gas flow passes;
The present invention is characterized in that a volume change mechanism that allows a volume change of the space and a rectification mechanism that rectifies a gas flow at a gas inlet and a gas outlet of the space are provided.

[0010] A second characteristic configuration of the pressure fluctuation mitigation apparatus for a gas meter according to the present invention for solving the above-mentioned problem is as described in claim 2 of the claims. In addition, the volume variation mechanism is a mechanism that operates so as to increase the volume of the space when the internal pressure of the space becomes equal to or higher than a predetermined pressure, and has a restoring force.

A third feature of the gas pressure reducing apparatus for a gas meter according to the present invention for solving the above-mentioned problems is as described in claim 3 of the claims. In addition to the characteristic configuration described above, the rectifying mechanism comprises at least one capillary tube.

A fourth characteristic configuration of the gas meter pressure fluctuation alleviating apparatus according to the present invention for solving the above-mentioned problems is as described in the fourth aspect of the present invention. In addition to the above, when the rectifying mechanism includes a plurality of capillaries, an interval between adjacent capillaries is at least twice as long as a diameter of each of the capillaries.

The operation and effect will be described below. According to the first characteristic configuration of the pressure fluctuation mitigation device for a gas meter according to the present invention, even when the pressure fluctuation occurs on the upstream side of the gas flow measurement unit, the rectification provided on the upstream side of the space portion. If the gas flow is decelerated by the mechanism, and the pressure of the gas flow that subsequently flows into the space is large, the volume fluctuation mechanism changes the volume of the space to mitigate the sudden rise in pressure, and the downstream side of the space The gas flow can be made to flow further through the rectification mechanism from the gas flow measuring unit to the gas flow measuring unit. As described above, it is possible to provide a device that does not cause the pressure fluctuation generated on the upstream side of the gas flow measurement unit to act on the gas flow measurement unit. Therefore, it is possible to stabilize the velocity of the gas flow reaching the gas flow measuring unit and to make the velocity distribution of the gas inside the gas pipe uniform, thereby performing gas flow measurement with high measurement accuracy. Can be. Similarly, even when a pressure fluctuation occurs on the downstream side of the gas flow measurement unit, the pressure fluctuation can be prevented from being transmitted to the gas flow measurement unit, and a gas flow measurement with high measurement accuracy can be performed. Can be implemented.

Further, since a space provided with a volume fluctuation mechanism capable of alleviating pressure fluctuation is provided between the rectification mechanisms, it is not necessary to completely alleviate the pressure fluctuation by the rectification mechanism. Can be designed to reduce the pressure loss at Accordingly, it is possible to increase the gas flow rate flowing into the gas flow rate measurement unit until the pressure loss does not matter, that is, to expand the measurable range of the gas flow rate in the gas flow rate measurement unit.

According to the second characteristic configuration of the pressure fluctuation alleviating device for a gas meter according to the present invention, the pressure in the space is abruptly increased by changing the volume of the space by the telescopic mechanism having a restoring force. Even if the pressure rises or the pressure fluctuates continuously like a pulsation, the pressure fluctuation is reduced by increasing the volume of the space, and the gas flow flowing into the space is almost constant. At the gas flow rate measurement unit.

According to the third feature of the pressure fluctuation mitigation device for a gas meter according to the present invention, since the rectifying mechanism comprises at least one capillary tube, the gas flow has a periodic pressure fluctuation. Even so, pressure fluctuations are absorbed by frictional resistance between the gas flow and the inner wall surface of the capillary,
The pressure fluctuation can be reduced with a small pressure loss. The diameter, length, number, cross-sectional shape, etc. of the capillary can be set to various values depending on the pressure fluctuation in question.

According to the fourth characteristic configuration of the pressure fluctuation reducing device for a gas meter according to the present invention, the interval between adjacent capillaries is at least twice as long as the diameter of the capillaries.
The gas flows flowing through the respective capillaries do not pull each other, so that the influence of the pressure loss caused by the pulling can be eliminated.

[0018]

FIG. 1 shows a gas meter 1 and a gas pipe 2.
The positional relationship between the pressure fluctuation reducing device 3 and the pressure fluctuation reducing device 3 is shown. Another gas meter or the like is connected to the upstream side of the gas meter (gas flow measuring unit) 1, and there is a possibility that pressure fluctuations may occur in the gas pipe due to the measurement mechanism of those gas meters. For example,
A structure (for example, such as a valve mechanism) that generates a pressure fluctuation upstream of the gas meter 1 may cause a pressure fluctuation upstream of the gas meter 1. In addition, various gas appliances are connected downstream of the gas meter, and continuous pressure fluctuations (pulsations) may occur in the gas pipe between the gas meter and the gas appliance depending on the operating state of the gas appliance. In particular, pressure fluctuation may occur inside the gas pipe due to turning on / off of gas equipment.

As the gas meter 1, a general ultrasonic flow meter, fluidic meter, hot wire flow meter or the like can be applied. On the upstream side of the gas meter 1, a pressure fluctuation mitigation device 3 for mitigating pressure fluctuation generated inside the gas pipe 2
Is installed. The pressure fluctuation mitigation device 3 includes a space portion 5 having a volume fluctuation mechanism 4 and rectification mechanisms 6 and 7 connecting the space portion 5 to the gas pipe 2. Is supplied to the gas meter 1 only through the gas flow path, but there is no place where the gas flow path is shut off, and the gas flow flowing from the gas pipe 2 via the gas inlet (rectifying mechanism 6) passes through the space 5. Thereafter, the gas flows out to the gas pipe 2 via the gas outlet (rectifying mechanism 7). Here, the volume change mechanism 4 operates to increase the volume of the space 5 when the internal pressure of the space 5 becomes equal to or higher than a predetermined pressure, and reduces the internal pressure of the space by increasing the volume. The pressure fluctuation is reduced by adjusting the pressure to a predetermined value. In addition, since the volume changing mechanism 4 is made of a mechanism having a restoring force, the restoring force for reducing the volume by the amount of the volume increased first is always applied to the space 5.

For example, when the gas flow is in a steady state, since the internal pressure of the space 5 is also in a steady state at a predetermined pressure, the volume fluctuation mechanism 4 does not operate, and its restoring force is zero. When the pressure fluctuation flows into the space 5, the internal pressure of the space 5 also fluctuates, and the volume fluctuation mechanism 4 operates so that the volume increases according to the magnitude of the fluctuated internal pressure. As the volume increases, the internal pressure of the space portion 5 becomes the same pressure as in the steady state, but since the volume fluctuation mechanism 4 has a restoring force of the same magnitude as the pressure fluctuation,
Operates in the direction of decreasing volume. Accordingly, the volume of the space 5 starts to decrease at the same time as the pressure to flow into the space 5 decreases due to the pressure fluctuation, and the volume is reduced until the restoring force becomes zero. In this way, the gas flow that has flowed into the space 5 flows smoothly to the gas meter 1 side without including a sudden pressure change.

FIG. 2 shows an example of the configuration of the pressure fluctuation reducing device 3. In the pressure fluctuation mitigation device 3 shown in FIG.
One surface of the space portion 5 is formed of an elastic rubber plate 8 and functions as a volume change mechanism 4a (4). In a state where gas normally flows into the space 5 via the rectification mechanism 6, the force for pushing the rubber plate 8 out by the pressure inside the space 5 and the rubber plate 8 return to the original shape. The resilience to return is kept in balance. When the internal pressure of the space portion 5 further increases due to the pressure fluctuation included in the gas flow, the rubber plate 8 is further pushed out to increase the volume of the space portion 5. The internal pressure drops,
A gas flow without pressure fluctuation is supplied from the rectifying mechanism 7 to the gas meter 1 via the gas pipe 2. Further, since the rubber plate 8 serving as the volume changing portion 4 has a restoring force for returning to the original shape, if the internal pressure of the space 5 becomes smaller than the restoring force, the volume of the space 5 becomes smaller. It moves in the direction to move to the steady state.

The volume changing portion 4b (4) shown in FIG. 2B includes a plate 9 and a spring 10. When the internal pressure of the space 5 rises, the plate 9 is pushed in and the spring 10 contracts, and the space 10 is compressed. Expand the volume of 5. The spring 10 than the internal pressure of the space 5
When the restoring force increases, the spring 10 expands and operates in a direction to reduce the volume of the space 5. Therefore, FIG.
As described above with reference to, the gas flow without pressure fluctuation is supplied from the rectifying mechanism 7 to the gas meter 1 side via the gas pipe 2 by operating the volume changing section 4b. The structure of the volume changing mechanism 4 is not limited to the above-described structure including the rubber plate 8, the plate 9 and the spring 10, and may be any structure as long as the structure can change the volume.

Even if the pressure fluctuations generated inside the gas pipe 2 are of the same magnitude, the larger the volume of the space 5 is, the smaller the pressure fluctuation of the internal pressure generated in the space 5 becomes.
It is preferable that the volume of the space 5 is large.

The space 5 and the gas pipe 2 are connected via rectifying mechanisms 6 and 7. The rectifying mechanisms 6 and 7 use the viscosity of the gas to reduce instantaneous pressure fluctuations (flow rate fluctuations). It has the effect of suppressing. The rectifying mechanisms 6 and 7 have a capillary structure, and pressure fluctuation is reduced by utilizing frictional resistance between the inner wall surface of the capillary and the gas.

The rectifying mechanisms 6 and 7 have a typical fluid length of 3 m.
It is provided with one or a plurality of capillary tubes having a circular cross-sectional shape having a diameter of not more than m or other polygonal cross-sectional shapes having the same cross-sectional area. When the flow rate of the flowing gas is large, it is preferable that the diameter of each of the capillaries is large in order to minimize the pressure loss caused by the rectifying mechanisms 6 and 7. When the flow rate of the gas is small, the diameter of the capillary is preferably small. preferable. The length of the capillary is preferably long in order to increase the frictional resistance of the gas flow from the wall. When the rectifying mechanisms 6 and 7 include a plurality of capillaries, it is preferable that the total cross-sectional area of the capillaries is large. Therefore, a rectifying mechanism in which about 1,000 to 2,000 capillary tubes having a diameter of about 1 (mm) and a length of about 2 to 3 (mm) are formed in a predetermined plate-like portion is preferably used.

When the diameter of each capillary is d, the distance between adjacent capillaries is set to 2d or more. The effect of the pressure loss of the resulting gas stream can be eliminated. Therefore,
By adjusting those values in accordance with the magnitude of the pressure fluctuations generated in the gas pipe 2 and in accordance with the gas flow rate, the pressure fluctuations in the rectifying mechanisms 6 and 7 can be suitably reduced. As the configuration of the rectifying mechanisms 6 and 7, in addition to the capillary formed by machining or die-forming the plate portion,
A structure in which slit-shaped gaps are periodically formed in parallel with a predetermined plate-shaped part by machining or die processing, or a slit-shaped gap is formed by overlapping a plurality of plates so that gaps are left Or a structure in which multiple tubes (for example, glass tubes) are bundled and then extended in the longitudinal direction of the tubes so that the capillaries are arranged side by side. The rectification principle is the same as in the case of capillaries. It is intended to eliminate the pressure fluctuation included in the gas flow by using the resistance between the gas flow.

Therefore, the rectifying mechanisms 6 and 7 need only have a structure that gives resistance to the gas flow flowing into or out of the space 5 and comes into contact with the gas like a capillary. A structure having a large area is preferable. FIG.
A rectification mechanism 6 when formed using a plurality of capillaries;
7 illustrates the structure of FIG. For example, if the pressure fluctuation is such that a pressure width of 40 (Pa) periodically fluctuates at 4 (Hz), 1280 capillaries having a diameter of 1 (mm) and a length of 2.5 (mm) are formed. The total cross-sectional area is about 1000
By using perforated plates having a size of (mm ² ) as the rectifying mechanisms 6 and 7, pressure fluctuations can be suitably reduced. The dimensions of the capillary of the rectification mechanism 6 and the dimensions of the capillary of the rectification mechanism 7 may be different from each other. In addition, the cross-sectional shape of the capillary may be various shapes other than a circle, such as a polygon, a shape combining a straight line and a curve.

By installing the pressure fluctuation mitigation device 3 configured as described above on the upstream side of the gas meter 1, it is possible to prevent the pressure fluctuation from reaching the gas meter 1,
As a result, accurate gas flow measurement can be performed in the gas meter 1.

FIG. 1 shows an embodiment in which the pressure fluctuation mitigation device 3 is installed on the upstream side of the gas meter 1. This is because the pressure fluctuation generated from other meters and devices on the upstream side of the gas meter 1 is reduced. 1 to solve the problem that the gas meter 1 cannot measure the flow rate accurately. In the following, the pressure fluctuation generated by the gas consuming equipment on the downstream side of the gas meter 1, for example, the ON / OFF of the gas in the gas consuming equipment.
A measure for solving the problem that the flow rate cannot be accurately measured in the gas meter 1 due to the pulsation generated by turning off will be described below.

FIG. 4 differs from the device shown in FIG. 1 in that pressure fluctuation reducing devices 3 are provided on both the upstream side and the downstream side of the gas meter 1. The configuration of the pressure fluctuation mitigation device 3 is the same as that described with reference to FIG. However, depending on the magnitude of the pressure fluctuation to be solved as described above, the volume of the space 5, the strength of the restoring force determined by the rubber plate 8 and the spring 10, or the dimensions of the capillaries 6, 7 are also different. Adjusted.

Here, the case where the pressure fluctuation mitigation device 3 is provided in both the upstream portion and the downstream portion of the gas meter 1 has been described. However, the pressure fluctuation mitigation device 3 is provided only in the downstream portion of the gas meter 1, Pressure fluctuations occurring on the downstream side can also be eliminated.

2 and 3, the structure of the pressure fluctuation mitigation device 3 has been described by way of example, but the specific configuration is not limited to the illustrated one. For example, the gas flow path from the gas pipe 2 to the gas pipe 2 via the rectification mechanism 6, the space portion 5, and the rectification mechanism 7 is arranged in a straight line, or as shown in FIG. A configuration in which the channels are arranged so as to be bent is implemented.

Alternatively, it is possible to provide not only one rectifying mechanism 6 and 7 but also a plurality of rectifying mechanisms inside the gas pipe so as to further reduce the pressure fluctuation. Similarly, a plurality of pressure fluctuation mitigation devices 3 may be provided on the upstream side, the downstream side, or both sides of the gas meter 1 so as to further reduce the pressure fluctuation.

[Brief description of the drawings]

FIG. 1 is a diagram showing an arrangement of a pressure fluctuation mitigation device.

FIG. 2 is a diagram showing a configuration of a pressure fluctuation mitigation device.

FIG. 3 is a view showing a structure of a capillary tube.

FIG. 4 is a diagram showing another arrangement of the pressure fluctuation mitigation device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Gas meter 2 Gas pipe 3 Pressure fluctuation alleviation device 4 Volume fluctuation mechanism 5 Space part 6 Rectification mechanism 7 Rectification mechanism 8 Rubber plate 9 Plate 10 Spring

Claims (4)

[The claims] 1. A pressure fluctuation mitigation device for a gas meter, which is used by being interposed in series on a gas pipe upstream or downstream of a gas flow measuring section or both gas pipes, wherein the gas flow rate is reduced by flowing from the gas pipe. A space through which a gas flow flowing to the gas pipe passes; a volume change mechanism that allows a volume change of the space; and a rectification mechanism that rectifies a gas flow at a gas inlet and a gas outlet of the space. A pressure fluctuation reducing device for a gas meter, comprising: 2. The system according to claim 1, wherein the volume variation mechanism is a mechanism that operates so as to increase the volume of the space when the internal pressure of the space exceeds a predetermined pressure and has a restoring force. The pressure fluctuation alleviation device for a gas meter according to claim 1. 3. The pressure fluctuation mitigation device for a gas meter according to claim 1, wherein the rectification mechanism includes at least one capillary. 4. The apparatus according to claim 3, wherein when the rectifying mechanism includes a plurality of capillaries, an interval between adjacent capillaries is at least twice as long as a diameter of each of the capillaries. A pressure fluctuation reducing device for a gas meter as described in the above.