JP2017181214A - Adjusted gas flowmeter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas dispenser which can accurately measure a gas flow rate over a wide range (wide pressure range and a wide flow rate range).SOLUTION: An adjusted gas dispenser according to the present invention is corrected and priced by a standard gas flowmeter 1 having at least two critical flow nozzles 4 with different throat diameters and on-off valves 7 corresponding to the critical flow nozzles 4.SELECTED DRAWING: Figure 5

Description

  The present invention relates to an adjusted gas flow meter.

In recent years, automobiles (fuel cell automobiles, etc.) using hydrogen gas as a power source instead of fossil fuels such as gasoline have attracted attention. In order to supply hydrogen gas to such an automobile, installation of a hydrogen station capable of supplying hydrogen gas is required. The hydrogen station includes a dispenser that supplies hydrogen gas, and hydrogen gas is supplied to the automobile using the dispenser. Specifically, hydrogen gas supplied from a dispenser is filled in a high-pressure hydrogen tank provided in an automobile. The dispenser includes a gas flow meter that measures the flow rate of hydrogen gas supplied to the automobile.
By the way, if there is an error between the flow rate of the hydrogen gas actually supplied from the dispenser and the flow rate of the hydrogen gas measured by the gas flow meter, the amount of the hydrogen gas supplied to the automobile is excessive or insufficient. Therefore, there is a need for a gas flow meter that can accurately measure the flow rate of hydrogen gas supplied from a dispenser. In particular, the hydrogen gas supplied from the dispenser is compressed to a high pressure, and the pressure is wide. For example, hydrogen gas is compressed to 10 MPa to 120 MPa. In addition, the dispenser is expected to be able to supply 5 kg of hydrogen by filling for 3 minutes, although the supply amount of hydrogen required at the beginning and end of filling varies. For example, the supply amount of hydrogen gas supplied from the dispenser is 0.1 kg / min to 3.6 kg / min.
Therefore, there is a need for a gas flow meter that can accurately measure the flow rate of compressed hydrogen gas over a wide range (wide pressure range and wide flow range), that is, a wide measurement range.

Conventionally, as a gas flow meter capable of measuring the flow rate of compressed gas over a wide range, for example, a Coriolis gas flow meter is known (Patent Document 1).
However, although the conventional gas flowmeter can measure the flow rate of compressed gas in a wide range, it is not calibrated and priced using a wide range of gas, so there is a problem that accuracy is poor, and more accurate gas flow rate It is necessary to perform calibration and pricing using a meter (standard gas flow meter).

JP 2012-026776 A

  An object of the present invention is to provide a gas flow meter capable of measuring a gas flow rate with high accuracy over a wide range (wide pressure range and wide flow range).

  The present inventors paid attention to a critical nozzle type gas flow meter as a standard gas flow meter capable of pricing the flow rate of the compressed gas over a wide range (wide pressure range and wide flow range). The critical nozzle type gas flow meter is a gas flow meter equipped with a critical nozzle, and the critical nozzle is a device capable of generating a constant gas flow rate (reference flow rate) for a specific gas under a constant pressure condition. .

  The adjusted gas flow meter of the present invention is calibrated and priced with reference to a standard gas flow meter, and the standard gas flow meter corresponds to at least two critical nozzles having different throat diameters and each critical nozzle. And an on-off valve provided.

  Preferably, the adjusted gas flow meter of the present invention is a Coriolis gas flow meter. Also preferably, the adjusted gas flow meter of the present invention is calibrated and priced with hydrogen gas.

  Since the adjusted gas flowmeter of the present invention is priced by a standard gas flowmeter having at least two critical nozzles having different throat diameters, a wide range of gas flow rates (wide pressure range and wide flow range) Can be measured with high accuracy.

The schematic diagram which shows the critical nozzle type gas flowmeter (1st critical nozzle type gas flowmeter) which has one critical nozzle. The graph which shows the calibration curve obtained using a 1st critical nozzle type gas flowmeter. The schematic diagram which shows the critical nozzle type gas flow meter (2nd critical nozzle type gas flow meter) which has two critical nozzles which have the same throat diameter. The graph which shows the calibration curve obtained using the 2nd critical nozzle type gas flowmeter. The schematic diagram which shows the standard gas flowmeter used in 1st Embodiment of this invention, and the enlarged view of a critical nozzle. The graph which shows the calibration curve obtained using the critical nozzle type gas flow meter concerning a 1st embodiment. The VII-VII line enlarged end elevation in the enlarged view of FIG. The schematic diagram which shows the standard gas flowmeter used in 2nd Embodiment of this invention. The schematic diagram which shows the standard gas flowmeter used in 3rd Embodiment of this invention. The schematic diagram which shows the standard gas flowmeter used in 4th Embodiment of this invention. The schematic diagram which shows the state which connected the standard gas flowmeter and the test gas flowmeter, and formed the gas flow path. The schematic plan view which shows the Coriolis type | mold gas flowmeter which is a kind of test gas flowmeter. FIG. 13 is a schematic side view of the Coriolis gas flow meter of FIG. 12.

  In this specification, although the adjusted gas flowmeter is demonstrated, the term used in this specification and the code | symbol used in drawing are annotated beforehand as follows.

<Terminology>
A “gas flow meter” is a device capable of measuring a gas flow rate.
The “critical nozzle type gas flow meter” is a gas flow meter provided with a critical nozzle. The critical nozzle type gas flow meter can be used not only as a flow meter itself, but also as a standard gas flow meter serving as a reference for calibration and pricing of the test gas flow meter.
The “test gas flow meter” is a gas flow meter to be calibrated and priced by a standard gas flow meter. The test gas flow meter may be a critical nozzle gas flow meter, or may be another gas flow meter (for example, a thermal gas flow meter or a Coriolis gas flow meter).
The “adjusted gas flow meter” is a test gas flow meter that has been calibrated and priced by a standard gas flow meter.
“Calibration” is to derive an error between the gas flow rate measurement value of the standard gas flow meter and the gas flow rate measurement value of the test gas flow meter.
“Pricing” is to correct the gas flow measurement value of the test gas flow meter so that the error between the gas flow measurement value of the standard gas flow meter and the gas flow measurement value of the test gas flow meter is reduced. .
The numerical range represented by “AA to BB” means AA or more and BB or less.

<About drawings>
1 and 3 show not a standard gas flow meter used in the present invention but a standard gas flow meter (critical nozzle type gas flow meter) studied in the formation process of the present invention. The same reference numerals as those in FIGS. 5 and 8 to 10 showing the standard gas flowmeter used are used in FIGS.
3, 5, and 8 to 10, in order to distinguish a plurality of members (a plurality of critical nozzles and a plurality of on-off valves), lower-case alphabets (“a” and “ b ").
Moreover, the black arrow attached | subjected to FIG.1, FIG.3, FIG.5 and FIG. 8 thru | or FIG. 12 means the flow direction of gas. The white arrows attached to FIG. 13 mean the order of the vibration cycle of the flow tube (the process in which the vibration of the flow tube changes).
Furthermore, in FIG. 2, FIG. 4, and FIG. 6, the area surrounded by the broken lines located in the vicinity of the calibration curves S1 to S6 represents the 95% confidence interval of the calibration curves S1 to S6.

<About the formation process of the present invention>
The adjusted gas flow meter of the present invention is priced by a critical nozzle type gas flow meter which is a standard gas flow meter. The critical nozzle type gas flow meter is a gas flow meter having a critical nozzle. The critical nozzle is a device capable of generating a constant reference flow rate under a constant pressure condition, and a calibration curve can be obtained based on the reference flow rate generated using the critical nozzle. This calibration curve serves as a reference for calibration and pricing of the gas flow meter to be detected.
Hereinafter, the principle of the critical nozzle type gas flow meter will be described with reference to the drawings, and then the two types of critical nozzle type gas flow meters studied in the formation process of the present invention will be described. A critical nozzle type gas flow meter used as a meter will be described.

(About the principle of the critical nozzle type gas flow meter)
As shown in FIG. 1, the critical nozzle type gas flow meter 1 generally includes an upstream gas passage (also referred to as a rectifying pipe) 2 having a constant inner diameter and a downstream gas having the same inner diameter as the upstream gas passage 2. The flow path 3, one critical nozzle 4 provided between the upstream gas flow path 2 and the downstream gas flow path 3, the gas sensor 5 connected to the upstream gas flow path 2, and the gas sensor 5 A flow rate calculation unit 6.
The critical nozzle 4 includes a throttle portion 41 whose inner diameter decreases from the upstream gas channel 2 side to the downstream gas channel 3 side, and a diffuser unit whose inner diameter increases from the upstream gas channel 2 side to the downstream gas channel 3 side. 42 and a throat portion 43 which is a boundary portion between the throttle portion 41 and the diffuser portion 42 and has the smallest inner diameter.
The maximum inner diameter of the throttle portion 41 is equal to or smaller than the inner diameter of the upstream gas flow path 2, and the maximum inner diameter of the diffuser portion 42 is equal to or smaller than the inner diameter of the downstream gas flow path 3. The maximum inner diameter of the throttle part 41 means the inner diameter of the part of the throttle part 41 facing the upstream gas flow path 2, and the maximum inner diameter of the diffuser part 42 faces the downstream gas flow path 3 of the diffuser part 42. This means the inner diameter of the part.
In the critical nozzle type gas flow meter 1 of FIG. 1, the maximum inner diameter of the throttle part 41 and the inner diameter of the upstream gas flow path 2 are the same length, and the maximum inner diameter of the diffuser part 42 and the inner diameter of the downstream gas flow path 3 are the same length. It is comprised so that it may become.

  Although not shown, a pressure reducing means such as a vacuum pump is connected downstream of the downstream gas flow path 3, and by operating this vacuum pump, a gas flowing in the upstream gas flow path 2 (hereinafter referred to as "upstream gas"). Is at a higher pressure than the gas flowing through the downstream gas flow path 3 (hereinafter referred to as “downstream gas”). That is, a pressure difference is generated between the upstream gas and the downstream gas. As the pressure difference between the upstream gas and the downstream gas increases, the flow velocity of the gas flowing through the throat portion 43 of the critical nozzle 4 increases. When the ratio of the upstream gas pressure and the downstream gas pressure reaches the critical pressure ratio, the gas flow velocity reaches the critical velocity (sound velocity), and the gas flow velocity does not increase any more. When the gas flow velocity reaches the critical velocity, a gas having a constant mass determined by the upstream gas pressure, temperature, and the inner diameter (throat diameter) of the throat portion 43 flows regardless of the downstream gas flow.

The gas sensor 5 includes at least a pressure gauge capable of measuring the upstream gas pressure, and preferably includes not only the pressure gauge but also a thermometer capable of measuring the temperature of the upstream gas. Based on parameters such as the pressure and temperature of the upstream gas measured by the gas sensor 5, the throat diameter of the critical nozzle 4 and the cross-sectional area of the throat portion 43, the mass flow rate of the gas flowing through the throat portion 43 (that is, the reference flow rate) is 5 is calculated by the flow rate calculation unit 6 connected to 5.
A calibration curve is created using a reference flow rate generated by a critical nozzle provided in the critical nozzle type gas flow meter, and the test gas flow meter can be calibrated and priced based on the calibration curve.

(First critical nozzle type gas flow meter)
In order to obtain a standard gas flow meter capable of calibrating and pricing gas flow measurement values of a test gas flow meter over a wide pressure range and a wide flow range, first, as shown in FIG. Attention was focused on the critical nozzle type gas flow meter 1 (the first critical nozzle type gas flow meter 1) having only one critical nozzle.
A reference gas, for example, high-pressure hydrogen gas, is supplied to the first critical nozzle type gas flow meter 1 a plurality of times while changing the pressure condition, and a flow rate value (reference flow rate) in a critical state is measured a plurality of times. A standard curve S1 as shown in FIG. 2 is obtained by plotting the reference flow rate thus obtained on the coordinates. In FIG. 2, “gas flow rate” means the mass flow rate of the gas flowing through the throat portion 43.
However, since the first critical nozzle type gas flow meter 1 has only one critical nozzle, there is necessarily only one pattern of the throat diameter. Therefore, theoretically, only one reference flow rate is generated under a certain pressure condition, and as a result, only one calibration curve can be obtained. Therefore, even if the adjusted gas flow meter is produced by calibrating and pricing the test gas flow meter based on the first critical nozzle type gas flow meter 1 (calibration curve S1 only), this adjusted gas flow rate is obtained. The meter cannot accurately measure a wide range of gas flow rates under a wide range of pressure conditions.

Specifically, when calibration and pricing of the test gas flow meter is performed based on the calibration curve S1, the range of the 95% confidence interval on the calibration curve S1 (for example, point i in FIG. 2) and the calibration curve S1. The inside (for example, point ii) can be calibrated and priced with high accuracy. Therefore, when the flow rate of a gas is measured using a calibrated and priced test gas flow meter (adjusted gas flow meter), the measured gas flow rate is 95% reliable on the calibration curve S1 and the calibration curve S1. When the value is within the range, the reliability of the measured gas flow rate is high.
On the other hand, when the flow rate of a certain gas is measured using the adjusted gas flow meter, if the measured gas flow rate is outside the 95% confidence interval, the reliability of the measured gas flow rate is low. That is, when the flow rate of gas over a wide range (wide pressure range and wide flow range) is measured using the adjusted gas flow meter calibrated and priced by the first critical nozzle type gas flow meter 1 The adjusted gas flow meter showed a high gas flow measurement value under low pressure conditions (see point iii in FIG. 2) or a low gas flow measurement value under high pressure conditions (point iv in FIG. 2) Even if it is shown, the reliability of the measured value is low. Thus, the reliability of the gas flow measurement value of the adjusted gas flow meter decreases as the value deviates from the calibration curve S1.
Therefore, even if the first critical nozzle type gas flow meter 1 is used as a standard gas flow meter, the test gas flow meter cannot be calibrated and priced with high accuracy under a wide range of pressure conditions and a wide range of gas flow rates.

In FIG. 2, for the sake of convenience, the calibration curve S1 (solid line) and the upper and lower limits (broken line) of the 95% confidence interval are shown as straight lines represented by a linear function. The upper and lower limits of the calibration curve S1 and the 95% confidence interval are not limited to those represented by such straight lines, but may be represented by curves (the same applies to FIGS. 4 and 6 described later).
The functions of the calibration curve S1 and the upper and lower limits of the 95% confidence interval may vary depending on the type and temperature of the reference gas, the throat diameter of the critical nozzle, and the like.
However, no matter what gas is used as a reference or whatever critical nozzle is used, there is a relationship in which the gas flow rate increases in proportion to the increase in upstream gas pressure.

(Second critical nozzle type gas flow meter)
In view of the above problems when the first critical nozzle type gas flow meter 1 is used, the present inventors have provided a second critical nozzle type gas flow meter 1 having a plurality of critical nozzles 4 having the same throat diameter. We focused on calibrating and pricing the gas flow meter to be detected using.
FIG. 3 is a schematic diagram showing a second critical nozzle type gas flow meter 1 having a plurality of critical nozzles 4 (two of the first critical nozzle 4a and the second critical nozzle 4b in FIG. 3) having the same throat diameter. is there.
The upstream gas flow path 2 of the second critical nozzle type gas flow meter 1 includes an upstream single path portion 21 and a plurality of upstream branches branched from the upstream single path portion 21 in accordance with the number of critical nozzles 4 from upstream to downstream. And has a path portion 22 (two in FIG. 3). The downstream gas flow path 3 includes, from upstream to downstream, the same number of downstream branch path sections 32 as the number of critical nozzles 4 and a single downstream path section 31 configured by joining the downstream branch path sections 32. Have. The upstream gas flow path 2 and the downstream gas flow path 3 are connected by a plurality of critical nozzles 4 (first critical nozzle 4a and second critical nozzle 4b) provided between the upstream branch path section 22 and the downstream branch path section 32. Has been. In other words, the plurality of critical nozzles 4 are arranged in parallel via the upstream branch path portion 22 of the upstream gas flow path 2 and the downstream branch path section 32 of the downstream gas flow path 3.

  In the second critical nozzle type gas flow meter 1, the number of on-off valves 7 corresponding to the critical nozzle 4 is provided. In FIG. 3, a first on-off valve 7 a corresponding to the first critical nozzle 4 a and a second on-off valve 7 b corresponding to the second critical nozzle 4 b are provided, and the upstream branch passage portion 22 of the upstream gas passage 2 is respectively provided. Each on-off valve 7a, 7b is provided. By operating the on-off valve 7, it is possible to switch between the open state (the state in which the gas flows into the critical nozzle 4) and the closed state (the state in which the gas does not flow into the critical nozzle 4) of the upstream branch path portion 22, From the upstream gas channel 2 to the downstream gas channel 3, the gas can flow through the first critical nozzle 4a or the second critical nozzle 4b, or through the first critical nozzle 4a and the second critical nozzle 4b.

Similarly to the first critical nozzle type gas flow meter 1, a gas sensor 5 is connected to the upstream single path portion 21 of the upstream gas flow path 2, and a flow rate calculation unit 6 is connected to the gas sensor 5. Therefore, two calibration curves S2 and S3 as shown in FIG. 4 are obtained by flowing a reference gas through the second critical nozzle type gas flow meter 1 while changing the pressure condition. That is, when one of the two on-off valves 7a and 7b is opened and the other on-off valve 7 is closed, the gas flows through the first critical nozzle 4a or the second critical nozzle 4b. A calibration curve S2 is obtained (since the first critical nozzle 4a and the second critical nozzle 4b have the same throat diameter, the same calibration curve is theoretically obtained).
On the other hand, when both of the two on-off valves 7a and 7b are in the open state, the calibration curve S3 is obtained because the gas flows through the first critical nozzle 4a and the second critical nozzle 4b. When two critical nozzles 4a and 4b are used, the same flow rate can be obtained under a low gas pressure condition as compared with the case where one critical nozzle 4 is used.

When the second critical nozzle type gas flow meter 1 is used, a plurality of calibration curves are obtained as described above. Since the plurality of critical nozzles 4 included in the second critical nozzle type gas flow meter 1 all have the same throat diameter, the number of calibration curves obtained is the critical nozzle 4 included in the second critical nozzle type gas flow meter 1. Is equal to the number of
That is, as shown in FIG. 4, in the case of the critical nozzle type gas flow meter 1 using two critical nozzles 4, two calibration curves are obtained, and the critical nozzle type using three or more critical nozzles 4 is obtained. In the case of the gas flow meter 1, three or more calibration curves equal to the number of critical nozzles 4 are obtained (not shown).
Then, calibration and pricing of the test gas flow meter is performed based on the calibration curves S2 and S3 to prepare an adjusted gas flow meter, and when the flow rate of a certain gas is measured using the adjusted gas flow meter, The measured gas flow rate is on the calibration curve S2 (for example, point v in FIG. 4), within the 95% confidence interval of the calibration curve S2 (for example, point vi), and on the calibration curve S3 (for example, FIG. 4). If the value is within the range of the 95% confidence interval of the calibration curve S3 (for example, the point viii), the gas flow rate measurement value is highly reliable.
On the other hand, when the flow rate of a gas is measured using an adjusted gas flow meter, if the measured gas flow rate is a value outside the 95% confidence interval (see point ix and point x in FIG. 4), the gas The reliability of the measured flow rate is low.

Thus, even if the second critical nozzle type gas flow meter 1 is used as the standard gas flow meter, only the same number of calibration curves as the number of critical nozzles 4 can be obtained. When trying to price the test gas flowmeter with a wide range of gas flow rates under a wide range of pressure conditions, it is necessary to use a large number of critical nozzles 4.
However, in general, the critical nozzle 4 is large. When measuring the flow rate of the high pressure gas, it is necessary to use a larger critical nozzle 4 in order to provide the critical nozzle 4 with a sufficient pressure-resistant structure. Accordingly, it is extremely impractical and impractical to calibrate and price the test gas flow meter using the second critical nozzle type gas flow meter 1.

<Standard gas flowmeter used in the present invention>
As described above, the present invention has been made in view of the problems that occur when the gas flow meter to be measured is calibrated and priced using the first and second critical nozzle gas flow meters. The adjusted gas flow meter of the present invention uses a critical nozzle type gas flow meter according to any one of the first to fourth embodiments described later as a standard gas flow meter to calibrate and price the test gas flow meter. Obtained.
A standard gas flow meter used as a calibration and pricing reference in the present invention is a critical nozzle type having at least two critical nozzles having different throat diameters, and on-off valves provided corresponding to the respective critical nozzles. It is a gas flow meter. Hereinafter, the critical nozzle type gas flowmeter used in the present invention will be described in detail.

(First embodiment)
The configuration of the critical nozzle type gas flow meter according to the first embodiment is basically the same as that of the second critical nozzle type gas flow meter, but at least two critical nozzles among the plurality of critical nozzles have different throat diameters. It differs from the 2nd critical nozzle type gas flowmeter in having.
In the description of the first embodiment, since the configuration other than the throat diameter of the critical nozzle is the same as that of the second critical nozzle type gas flow meter, the description thereof is omitted as appropriate.

As shown in FIG. 5, the critical nozzle type gas flow meter 1 used in the present invention includes a plurality of upstream gas passages 2, downstream gas passages 3, and gas passages 2 and 3 (in FIG. 2) critical nozzles 4. The upstream gas passage 2 has an upstream single passage portion 21 and an upstream branch passage portion 22 branched from the upstream single passage portion 21 in accordance with the number of critical nozzles 4. It has a downstream single path portion 31 and a downstream branch path portion 32.
An on-off valve 7 corresponding to each critical nozzle 4 is provided in the upstream branch section 22 of the upstream gas flow path 2. By operating the on-off valve 7, it is possible to switch between the open state and the closed state of the upstream branch path portion 22, and as a result, gas flows from the upstream gas flow path 2 to the downstream gas flow path 3 through any selected critical nozzle 4. Can flow.
A gas sensor 5 is connected to the upstream single path portion 21 of the upstream gas flow path 2, and a flow rate calculation unit 6 is connected to the gas sensor 5.

  In the critical nozzle type gas flow meter 1 used in the present invention, a plurality of critical nozzles 4 are used, and at least two critical nozzles 4 have different throat diameters. In the example shown in FIG. 5, two critical nozzles 4 (first critical nozzle 4a and second critical nozzle 4b) are provided, and the throat diameter of the first critical nozzle 4a is equal to the throat diameter of the second critical nozzle 4b. It is configured to be doubled.

Three calibration curves S4 to S6 as shown in FIG. 6 are obtained by flowing a reference gas through the critical nozzle type gas flow meter 1 while changing the pressure condition. That is, when the on / off valve 7a corresponding to the first critical nozzle 4a is opened and the on / off valve 7b corresponding to the second critical nozzle 4b is closed among the two on / off valves 7a and 7b, the second throat diameter is large. Since the gas flows only through the one critical nozzle 4a, a calibration curve S4 is obtained. On the other hand, when the on-off valve 7b corresponding to the second critical nozzle 4b is opened and the on-off valve 7a corresponding to the first critical nozzle 4a is closed, the gas flows only through the second critical nozzle 4b having a small throat diameter. Therefore, a calibration curve S5 is obtained. Further, when both of the two on-off valves 7a and 7b are opened, a calibration curve S6 is obtained because gas flows through the first critical nozzle 4a and the second critical nozzle 4b.
Thus, since the critical nozzle type gas flowmeter used in the present invention has at least two critical nozzles 4 having different throat diameters, the number of critical nozzles 4 can be determined by appropriately combining the critical nozzles 4 through which gas passes. Many calibration curves can be obtained.
Therefore, if the critical nozzle type gas flow meter 1 used in the present invention is used as a standard gas flow meter, the test gas flow meter can be priced over a wide range (wide pressure condition and wide flow range). As a result, an adjusted gas flow meter capable of measuring the gas flow rate with high accuracy over a wide range can be obtained.

  The lower limit value of the number of critical nozzles included in the critical nozzle type gas flowmeter used in the present invention is two, preferably three, and more preferably four. The upper limit value of the number of critical nozzles is not particularly limited, but is preferably 7 and more preferably 6. If the number of critical nozzles exceeds seven, the critical nozzle type gas flow meter becomes too large, which may impair practicality.

  In the present invention, it is preferable that all of the plurality of critical nozzles have different throat diameters. If the throat diameters of the critical nozzles are all different, the maximum number of calibration curves represented by the following formula (1) can be obtained.

As described above, in the case of a gas flow meter (second critical nozzle type gas flow meter) provided with critical nozzles having the same throat diameter, only the same number of calibration curves as the number of critical nozzles can be obtained. For example, when the number of critical nozzles is three, only three calibration curves are obtained, and when the number of critical nozzles is four, only four calibration curves are obtained.
On the other hand, in the present invention, when the number of critical nozzles is 3 (n = 3) based on the above formula (1), a maximum of 7 calibration curves can be obtained, and the number of critical nozzles is When there are four (n = 4), a maximum of 15 calibration curves can be obtained.
As described above, in the present invention, as the number of critical nozzles increases, the number of calibration curves obtained by the combination increases. Therefore, the test gas flowmeter is calibrated under a wide range of pressure conditions and a wide range of gas flow rates. And can be priced.

Further, in the critical nozzle type gas flowmeter used in the present invention, the ratio of the throat diameter D _MAX of the critical nozzle having the largest throat diameter to the throat diameter D _MIN of the critical nozzle having the smallest throat diameter is (D _MAX / D _MIN ) Although not particularly limited, the lower limit of the ratio is preferably 1.4, more preferably 2.0, and particularly preferably 2.4.
The upper limit of the throat diameter ratio (D _MAX / D _MIN ) is not particularly limited, but is preferably 5.0, more preferably 4.0, and particularly preferably 3.0.
When the ratio of the throat diameter (D _MAX / D _MIN ) is less than 1.4, the calibration curve obtained by each critical nozzle becomes too close, and the 95% confidence interval of each calibration curve overlaps more than necessary. There is a possibility that calibration and pricing of the detection gas flow meter may become inefficient.
When the throat diameter ratio (D _MAX / D _MIN ) exceeds 5.0, the calibration curve obtained by combining the critical nozzle with the largest throat diameter and the critical nozzle with the smallest throat diameter and the criticality with the largest throat diameter are obtained. The calibration curve obtained with the nozzle alone is too close. As a result, the 95% confidence intervals of both calibration curves overlap more than necessary, which may result in inefficient calibration and pricing of the test gas flowmeter.

As a specific example, the throat diameter (D _MAX ) of the critical nozzle having the largest throat diameter is 1.8 mm to 3.0 mm, preferably 1.8 mm to 2.0 mm. The throat diameter (D _MIN ) of the critical nozzle with the smallest throat diameter is 0.3 mm to 1.0 mm, preferably 0.3 mm to 0.6 mm.
However, the length of the throat diameter is not limited to the above range, and can be appropriately set depending on the type of gas used for calibration and pricing, the gas pressure range, the gas flow rate, and the like.

In this specification, the throat diameter of the critical nozzle is a distance obtained by connecting a first point of the inner edge of the throat part and a second point of the inner edge of the throat part independent of the first point by a straight line. is there. There are an infinite number of such straight lines, but an infinite number of straight lines having the maximum distance corresponds to the throat diameter in the present invention.
Normally, as shown in FIG. 7, since the end surface shape of the throat portion 43 is circular, the throat diameter means the length X of the diameter of the circle.

  The critical nozzle type gas flowmeter used in the present invention has a plurality of critical nozzles, and at least two critical nozzles of the plurality of critical nozzles have different throat diameters. Therefore, a large number of calibration curves can be obtained by combining critical nozzles. Therefore, by using this critical nozzle type gas flow meter as a standard gas flow meter, the test gas flow meter can be calibrated and priced under a wide range of pressure conditions and a wide range of gas flow rates, and highly accurate adjustment is possible. A spent gas flow meter can be obtained.

In the first embodiment, as shown in FIG. 5, the upstream gas passage 2 has an upstream single passage portion 21 and an upstream branch passage portion 22, and a plurality of downstream gas passage portions 22 are disposed downstream of the upstream branch passage portion 22. Although the critical nozzles 4 (the first critical nozzle 4a and the second critical nozzle 4b) are connected, the critical nozzle type gas flowmeter 1 used in the present invention is not limited to the first embodiment.
Hereinafter, the critical nozzle type gas flowmeter 1 according to the second to fourth embodiments used in the present invention will be described, but mainly only the parts different from the critical nozzle type gas flowmeter 1 according to the first embodiment. explain.

(Second Embodiment)
FIG. 8 is a schematic view showing a critical nozzle type gas flow meter 1 according to the second embodiment used in the present invention.
In this embodiment, the upstream gas flow path 2 and the downstream gas flow path 3 are connected via a gas introduction chamber 8, and a plurality of critical nozzles 4 (in FIG. Two nozzles, a nozzle 4a and a second critical nozzle 4b) are provided.
The gas introduction chamber 8 is a closed space. The interior of the gas introduction chamber 8 is partitioned by a partition wall 83 into a first chamber 81 on the upstream gas flow path 2 side and a second chamber 82 on the downstream gas flow path 3 side, and the plurality of critical nozzles 4 are arranged in the first chamber. The partition wall 83 is provided so as to communicate the 81 and the second chamber 82. Specifically, the first critical nozzle 4 a and the second critical nozzle 4 b have their throttle portions 41 a and 42 b exposed to the first chamber 81 of the gas introduction chamber 8 and their diffuser portions 42 a and 42 b of the gas introduction chamber 8. A partition wall 83 is attached so as to be exposed to the second chamber 82.

  The second chamber 82 of the gas introduction chamber 8 is provided with an opening / closing valve 7 corresponding to each critical nozzle 4, and the opening / closing valve 7 is operated to open the critical nozzle 4 (the gas is in the second chamber 82). 82) and a closed state (a state where gas does not flow into the second chamber 82) can be switched. Since the critical nozzle type gas flow meter 1 of FIG. 8 uses two critical nozzles 4 (first critical nozzle 4a and second critical nozzle 4b), the first on-off valve 7a corresponding to the first critical nozzle 4a. A second on-off valve 7b corresponding to the second critical nozzle 4b is provided in the second chamber 82. Therefore, by operating the first on-off valve 7a and the second on-off valve 7b, from the first chamber 81 to the second chamber 82 of the gas introduction chamber 8, through the first critical nozzle 4a or the second critical nozzle 4b, or Gas can flow through the first critical nozzle 4a and the second critical nozzle 4b.

  Although the structure of the on-off valve 7 is not particularly limited, in the example shown in FIG. 8, the first on-off valve 7a corresponding to the first critical nozzle 4a is exposed to the diffuser portion 42a of the first critical nozzle 4a (exposed to the second chamber 82). A plug portion 71a covering the opening) and an elongated rod portion 72a. One end of the rod portion 72 a is connected to the plug portion 71 a, and the other end of the rod portion 72 a is exposed to the outside of the second chamber 82 of the gas introduction chamber 8. Since the position of the plug portion 71a can be operated from the outside of the gas introduction chamber 8 via the rod portion 72a, the first critical nozzle 4a is opened from the outside of the gas introduction chamber 8 (the diffuser portion 42a is first opened and closed). The state where the valve 7a is not covered) and the closed state of the first critical nozzle 4a (the state where the diffuser portion 42a is covered with the first on-off valve 7a) can be switched. Similarly to the first on-off valve 7a, the second on-off valve 7b corresponding to the second critical nozzle 4b also has a plug portion 71b and a rod portion 72b, and the second critical nozzle 4b is opened from the outside of the gas introduction chamber 8. And can be switched between closed states.

In the critical nozzle type gas flow meter 1 according to the first embodiment shown in FIG. 5, the upstream gas flow path 2 has an upstream branch section 22. If gas stays in the upstream branch section 22, there is a possibility that a highly reliable calibration curve cannot be obtained.
On the other hand, in the critical nozzle type gas flow meter 1 according to the second embodiment, the upstream gas flow path 2 and the downstream gas flow path 3 are not branched, so the critical nozzle type gas flow meter 1 according to the first embodiment. A calibration curve with higher reliability than that can be obtained.

(Third embodiment)
FIG. 9 is a schematic view showing a critical nozzle type gas flow meter 1 according to the third embodiment used in the present invention.
A critical nozzle type gas flow meter 1 according to the third embodiment has both the configuration of the first embodiment and the configuration of the second embodiment.
Specifically, the critical nozzle type gas flow meter 1 according to the third embodiment includes an upstream gas channel 2, a gas introduction chamber 8 connected to the most downstream side of the upstream gas channel 2, and a gas introduction chamber 8. It has the some critical nozzle 4 provided in the outer wall, and the downstream gas flow path 3 connected to each critical nozzle 4. FIG. In the present embodiment, the upstream gas flow path 2 is composed of only the upstream single path portion 21, and the downstream gas flow path 3 includes the same number of downstream branch path portions 32 as the number of critical nozzles 4 from upstream to downstream, A downstream single path portion 31 formed by joining the downstream branch path portions 32 together.
In the present embodiment, the first on-off valve 7 a corresponding to the first critical nozzle 4 a and the second on-off valve 7 b corresponding to the second critical nozzle 4 b are respectively provided in the branch passage portion 32 of the downstream gas passage 3. .

(Fourth embodiment)
FIG. 10 is a schematic view showing a critical nozzle type gas flow meter 1 according to the fourth embodiment used in the present invention.
Similar to the third embodiment, the critical nozzle gas flow meter 1 according to the fourth embodiment has both the configuration of the first embodiment and the configuration of the second embodiment.
Specifically, the critical nozzle type gas flow meter 1 according to the fourth embodiment includes an upstream gas channel 2, a plurality of critical nozzles 4 connected to the most downstream side of the upstream gas channel 2, and each critical nozzle 4. And a downstream gas passage 3 connected to the gas inlet chamber 8. In the present embodiment, the upstream gas flow path 2 includes an upstream single passage portion 21 and an upstream branch passage portion 22 that branches according to the number of critical nozzles 4, and each critical nozzle 4 has its diffuser. The portion 42 is provided on the outer wall of the gas introduction chamber 8 so as to be positioned inside the gas introduction chamber 8. Further, the downstream gas flow path 3 is composed only of the downstream single path portion 31 communicating with the gas introduction chamber 8.
In the present embodiment, the first on-off valve 7a corresponding to the first critical nozzle 4a and the second on-off valve 7b corresponding to the second critical nozzle 4b are respectively provided in the gas introduction chamber 8 as in the second embodiment. ing.

  Also in the second to fourth embodiments, the critical nozzle type gas flowmeter 1 has a plurality of critical nozzles 4, and at least two critical nozzles 4 among the plurality of critical nozzles 4 are different from each other. Have a diameter. Therefore, as with the critical nozzle type gas flow meter 1 according to the first embodiment, a large number of calibration curves can be obtained by combining the critical nozzles 4. Therefore, it is possible to price the test gas flow meter over a wide range (wide pressure conditions and wide flow range), and as a result, the adjusted gas flow rate that can measure the gas flow rate with high accuracy over a wide range. A total is obtained.

The critical nozzle type gas flowmeter 1 used in the present invention is not limited to the first to fourth embodiments described above as long as it has a plurality of critical nozzles 4 having different throat diameters. Therefore, the critical nozzle type gas flow meter 1 used in the present invention can use the configuration of a conventionally known critical nozzle type gas flow meter as it is, except for the critical nozzle 4.
For example, in the first to fourth embodiments, as shown in FIGS. 5 and 8 to 10, the gas sensor 5 and the flow rate calculation unit 6 are depicted as separate devices, but the gas sensor 5 uses the flow rate calculation unit 6. You may also serve.

<Test gas flow meter>
The adjusted gas flow meter of the present invention can be obtained by calibrating and pricing the test gas flow meter using the critical nozzle type gas flow meter according to the first to fourth embodiments as described above as a standard gas flow meter. . When performing calibration and pricing, it is necessary to connect a critical nozzle type gas flow meter 1 which is a standard gas flow meter and a test gas flow meter 9 in series to form a gas flow path as shown in FIG. . A specific method of calibration and pricing will be described in detail later in the section <Method for adjusting gas flow meter to be detected>.

As the test gas flow meter, a conventionally known gas flow meter capable of measuring the mass flow rate of the gas can be used. For example, positive displacement, area, turbine, differential pressure, electromagnetic, vortex flow, ultrasonic An equation, Coriolis, or thermal gas flow meter can be used.
Preferably, the test gas flow meter is a Coriolis gas flow meter. The Coriolis type gas flow meter is not only a relatively small gas flow meter, but can measure a wide range of gas flow rate under a wide range of pressure conditions. Therefore, a Coriolis gas flow meter is often built in the dispenser installed in the hydrogen station.
An adjusted gas flow meter is produced by calibrating and pricing (adjusting) a Coriolis gas flow meter, which is a gas flow meter to be detected, by the critical nozzle gas flow meter according to the first to fourth embodiments. By incorporating this adjusted gas flow meter in the dispenser, the supply amount of hydrogen gas supplied from the dispenser can be measured under a wide range of pressure conditions and over a wide range of gas flow rates.
Hereinafter, the measurement principle of the Coriolis gas flow meter will be briefly described with reference to FIGS. 12 and 13. Since the Coriolis type gas flow meter is a kind of the test gas flow meter, the same reference numeral “9” as that of the test gas flow meter is attached to the Coriolis type gas flow meter in FIGS. ing.

(Measurement principle of Coriolis gas flow meter)
FIG. 12 is a schematic plan view of the Coriolis gas flow meter 9. As shown in FIG. 12, the Coriolis gas flow meter 9 includes an upstream manifold section 91, a downstream manifold section 92, and a flow tube 93 that connects the upstream manifold section 91 and the downstream manifold section 92.
The upstream manifold portion 91 and the downstream manifold portion 92 are cylindrical members having gas flow paths therein. The end of the flow tube 93 is fixed to the upstream manifold section 91 and the downstream manifold section 92. Since the flow tube 93 has flexibility, it vibrates by Coriolis force when a gas flows in the flow tube 93.
The gas flow path of the upstream manifold section 91 and the gas flow path of the downstream manifold section 92 are not directly connected, but are indirectly connected via the flow tube 93. In FIG. 12, a partition wall 94 is provided between the manifold portions 91 and 92 so that gas does not flow directly from the upstream manifold portion 91 into the downstream manifold portion 92. Accordingly, when a gas is passed through the Coriolis gas flow meter 9, the gas flows in the order of the upstream manifold portion 91, the flow tube 93, and the downstream manifold portion 92.

The flow tube 93 includes a first straight body portion 931 connected to the upstream manifold portion 91 substantially vertically, a second straight body portion 932 connected to the downstream manifold portion 92 substantially vertically, and an end portion of the first straight body portion 931. U connecting the end of the second straight body 932 (the end opposite to the end connected to the downstream manifold 92) and the end of the second straight body 932 (the end opposite to the end connected to the upstream manifold 91). And a character-shaped portion 933.
A first displacement sensor 95 is attached to an end portion of the U-shaped portion 933 connected to the first straight body portion 931 of the flow tube 93, and the U-shaped portion 933 connected to the second straight body portion 932 is attached. A second displacement sensor 96 is attached to the end, and a vibration device 97 is attached to the tip of the U-shaped portion 933. The first displacement sensor 95 and the second displacement sensor 96 are connected to a flow rate calculation unit 98, and the mass flow rate of the gas flowing through the Coriolis type gas flow meter 9 is calculated in the flow rate calculation unit 98.
Hereinafter, a description will be given with reference to FIG. 13 showing a state in which a gas flows through the flow tube 93.

FIG. 13 is a schematic side view of the Coriolis gas flow meter 9 in a state where gas is flowed (however, for convenience, the vibration device 97 is omitted). FIG. 13 shows a state in which a gas is passed through the Coriolis type gas flow meter 9 and the flow tube 93 is vibrated using the vibration device 97.
When gas flows through the Coriolis type gas flow meter 9 and the flow tube 93 is vibrated, the flow tube 93 exhibits a certain vibration cycle due to Coriolis force. Specifically, the U-shaped portion 933 of the flow tube 93 continuously and periodically changes to the states of FIGS. 13A to 13D while the gas is flowing. When the flow tube 93 exhibits such a vibration cycle, the first displacement sensor 95 and the second displacement sensor 96 also vibrate (displace). Therefore, the position information measured by the first displacement sensor 95 and the second displacement sensor 96 The measured position information also changes continuously and periodically.
Based on the measurement value of the first displacement sensor 95 and the measurement value of the second displacement sensor 96, the mass flow rate of the gas flowing through the flow tube 93 is calculated by the flow rate calculation unit 98.
As described above, the Coriolis type gas flow meter 9 is a device that measures the mass flow rate of the gas by utilizing the fact that the flexible flow tube 93 exhibits a constant vibration cycle due to the Coriolis force.

<Adjustment method of test gas flow meter>
By using the critical nozzle gas flow meter as the standard gas flow meter, the test gas flow meter can be calibrated and priced (adjusted), and as a result, an adjusted gas flow meter can be obtained. Hereinafter, a method for adjusting a test gas flow meter of the present invention, that is, a method for producing an adjusted gas flow meter will be described.
The adjustment method of the test gas flow meter includes a preparation step of preparing a test gas flow meter to be adjusted and a critical nozzle type gas flow meter, and connecting the test gas flow meter and the critical nozzle type gas flow meter. A gas flow path forming step for forming a gas flow path, a gas introduction process for introducing gas into the gas flow path, a gas flow rate measurement value of the gas flow meter to be tested, and a gas of the critical nozzle type gas flow meter And a pricing step of correcting the gas flow rate measurement value of the test gas flow meter so that the error of the flow rate measurement value is reduced.

(Preparation process)
The preparation step is a step of preparing a critical nozzle type gas flow meter and a test gas flow meter to be adjusted by the critical nozzle type gas flow meter.
As described above, the test gas flowmeter used in the present invention is not particularly limited, but a Coriolis gas flowmeter is preferably used.

(Gas flow path forming process)
The gas flow path forming step is a step of forming a gas flow path by connecting a test gas flow meter and a critical nozzle type gas flow meter. Specifically, as shown in FIG. 11, by connecting a test gas flow meter 9 in series to the upstream gas flow path 2 of the critical nozzle type gas flow meter 1 which is a standard gas flow meter, from upstream to downstream. A gas flow path in which the test gas flow meter 9 and the critical nozzle gas flow meter 1 are connected is formed.
In FIG. 11, the test gas flow meter 9 is connected upstream of the critical nozzle type gas flow meter 1, but the test gas flow meter 9 is located downstream of the critical nozzle type gas flow meter 1. It may be connected. Whether the test gas flow meter 9 is connected upstream or downstream of the critical nozzle type gas flow meter 1 can be appropriately set in consideration of the properties (pressure resistance, etc.) of the test gas flow meter 9. it can.

(Gas introduction process)
The gas introduction step is a step of introducing gas into a gas flow path configured by connecting a test gas flow meter and a critical nozzle type gas flow meter. The introduced gas reaches a critical velocity in the throat portion by operating a decompression means (for example, a vacuum pump) included in the critical nozzle type gas flow meter.
By appropriately changing the pressure of the introduced gas, the reference flow rate is generated under each pressure condition. Therefore, as described above, a plurality of calibration curves can be obtained based on a combination of each critical nozzle and a plurality of critical nozzles by arbitrarily changing the opening / closing state of the on-off valve of the critical nozzle gas flow meter.
The kind of gas to introduce | transduce is not specifically limited, Oxygen gas, nitrogen gas, hydrogen gas, carbon monoxide, methane gas etc. are mentioned. However, in recent years, since fuel cell vehicles using hydrogen as fuel have attracted attention, it is preferable that the gas to be introduced is hydrogen gas.
Moreover, the pressure range of the gas to introduce | transduce is not specifically limited, According to the kind and use of gas, and the pressure resistance of a gas flow path, it can change suitably. For example, when hydrogen gas is used, the lower limit value of the gas pressure range is preferably 0.5 MPa, more preferably 1.0 MPa, considering the pressure range required by the dispenser of the hydrogen station. The pressure is preferably 2.0 MPa, particularly preferably 10 MPa. Further, the upper limit value of the gas pressure range is preferably 120 MPa, more preferably 100 MPa.

(Pricing process)
In the pricing process, the error of the test gas flow meter is corrected so that the error between the gas flow measurement value of the test gas flow meter and the gas flow measurement value of the critical nozzle type gas flow meter becomes small, and the adjusted gas flow meter It is a process of producing.
Specifically, based on a plurality of calibration curves obtained in the gas introduction process, an error between the gas flow measurement value indicated by the gas flow meter to be detected and the gas flow measurement value indicated by the critical nozzle gas flow meter is derived (calibration). Furthermore, the measured gas flow rate of the test gas flow meter is corrected so that this error is reduced. In other words, the gas flow rate measurement value of the test gas flow meter is corrected so that the gas flow rate measurement value indicated by the test gas flow meter and the gas flow rate measurement value indicated by the critical nozzle type gas flow meter become the same value. As a method for correcting the gas flow rate measurement value of the test gas flow meter, for example, a correction coefficient stored in a flow rate calculation unit of the test gas flow meter is changed.
In addition, by using the critical nozzle type gas flowmeter according to the first to fourth embodiments, the maximum number of calibration curves represented by the above formula (1) can be obtained. The flow meter may be calibrated and priced based on all the obtained calibration curves, or may be calibrated and priced based on a plurality of calibration curves selected from the obtained calibration curves. This is because if the number of critical nozzles increases, the number of calibration curves obtained becomes enormous, and it may take too much time to calibrate and price the test gas flowmeter.

  By using the critical nozzle type gas flow meter according to the first to fourth embodiments, a large number of calibration curves can be obtained by a combination of critical nozzles. Therefore, the gas flow measurement value of the test gas flow meter can be calibrated and priced over a wide pressure range and a wide flow range, and as a result, a wide range gas flow rate can be accurately measured under a wide range of pressure conditions. An adjustable gas flow meter that can be measured can be made.

The gas flow meter to be tested becomes an adjusted gas flow meter through the pricing process. Thereafter, the adjusted gas flow meter can be used as an independent gas flow meter by disconnecting from the critical nozzle gas flow meter which is a standard gas flow meter.
From another point of view, it can be said that the adjusted gas flow meter of the present invention has the standard gas flow meter as an accessory until the connection with the standard gas flow meter is released. Specifically, the adjusted gas flow meter of the present invention has a critical nozzle type gas flow meter, and the critical nozzle type gas flow meter is provided corresponding to a plurality of critical nozzles and each critical nozzle. It can be said that at least two of the plurality of critical nozzles have different throat diameters.

  Hereinafter, the present invention will be further described with reference to examples. However, the present invention is not limited only to the following examples. The critical nozzle type gas flowmeter used in the present invention was produced by constructing the following traceability system.

(Calibration and pricing using a primary standard critical nozzle gas flow meter)
(National Institute of Technology) A critical nozzle type gas flow meter (hereinafter referred to as critical nozzle type gas flow meter A) owned by the National Institute of Advanced Industrial Science and Technology was prepared as a primary standard. The critical nozzle type gas flow meter A includes one critical nozzle having a throat diameter of 2.4 mm. The pressure range of the critical nozzle type gas flow meter A that can be priced is 0.6 MPa or less, and the flow rate range that can be priced is 0.1 kg / min or less.
Subsequently, a critical nozzle type gas flow meter (hereinafter referred to as a critical nozzle type gas flow meter B), which is an object of calibration and pricing, was prepared. The critical nozzle type gas flow meter B includes ten critical nozzles having the same throat diameter of 2.4 mm as the critical nozzle type gas flow meter A.
A critical nozzle gas flow meter A, which is a primary reference, was connected downstream of the critical nozzle gas flow meter B, and pricing was performed using hydrogen gas. In this way, the critical nozzle type gas flow meter B was calibrated and priced using the primary standard critical nozzle type gas flow meter A, so that the critical nozzle type gas flow meter B was made the 2.1 order reference.
2. The pressure range that can be calibrated and priced for the critical nozzle type gas flow meter B of the primary standard was 0.6 MPa or less, and the flow rate range that could be calibrated and priced was 1.0 kg / min or less.

(Calibration and pricing using 2.1 standard nozzle critical gas flow meter)
Subsequently, a critical nozzle type gas flow meter (hereinafter referred to as a critical nozzle type gas flow meter C), which is an object of further calibration and pricing, was prepared. The critical nozzle type gas flow meter C includes ten critical nozzles having a throat diameter of 3.6 mm. The critical nozzle of the critical nozzle type gas flow meter C has a pressure resistance and is larger than the critical nozzles provided in the primary standard and 2.1 standard critical nozzle type gas flow meters.
A critical nozzle type gas flow meter B, which is the 2.1st order standard, was connected downstream of the critical nozzle type gas flow meter C, and pricing was performed using hydrogen gas. Thus, by calibrating and pricing the critical nozzle type gas flow meter C using the 2.1 order standard critical nozzle type gas flow meter B, the critical nozzle type gas flow meter C is changed to the 2.2 order standard. did.
The pressure range in which the calibration and pricing of the critical nozzle type gas flow meter C of the second order standard was 0.9 MPa or less, and the flow rate range in which calibration and pricing were possible was 3.6 kg / min or less.

(Calibration and pricing using a critical nozzle type gas flow meter of 2.2 standard)
Subsequently, a critical nozzle type gas flow meter (hereinafter referred to as a critical nozzle type gas flow meter D), which is an object of further calibration and pricing, was prepared. The critical nozzle type gas flow meter D includes five critical nozzles having different throat diameters, and the throat diameters are 1.95 mm, 1.25 mm, 0.94 mm, 0.67 mm, and 0.48 mm in this order. It was. The critical nozzle of the critical nozzle type gas flow meter D has a pressure resistance and is larger than the critical nozzle provided in the 1st to 2.2th order critical nozzle type gas flow meter.
A critical nozzle type gas flow meter C which is a 2.2 order reference or a critical nozzle type gas flow meter B which is a 2.1 order reference is connected downstream of the critical nozzle type gas flow meter D and is calibrated using hydrogen gas. Priced. In this way, by calibrating and pricing the critical nozzle type gas flow meter D using the 2.2 order standard critical nozzle type gas flow meter C and the 2.1 order standard critical nozzle type gas flow meter B, A critical nozzle gas flow meter (2.3th order standard), which is a standard gas flow meter used in the present invention, was produced.
The prepared standard gas flow meter (critical nozzle type gas flow meter) had a pressure range of 87.5 MPa or less, and the flow rate range that could be calibrated and priced was 3.6 kg / min or less.

(2.3 Calibration and pricing using a 3rd order critical nozzle gas flow meter)
Using the fabricated 2.3 standard critical gas flow meter (standard gas flow meter), the Coriolis gas flow meter as the gas flow meter to be tested is calibrated and priced, and the adjusted gas flow meter (3 Next standard) was prepared.
In this embodiment, the standard gas flow meter (critical nozzle type gas flow meter) has five critical nozzles having different throat diameters, so that a maximum of 31 calibration curves can be obtained by combining critical nozzles. it can. Therefore, the Coriolis gas flowmeter could be calibrated and priced under a wide range of pressure conditions and a wide range of gas flow rates.

DESCRIPTION OF SYMBOLS 1 ... Critical nozzle type gas flow meter, 2 ... Upstream gas flow path, 3 ... Downstream gas flow path, 4 ... Critical nozzle, 5 ... Gas sensor, 6 ... Flow-rate calculating part, 7 ... On-off valve, 8 ... Gas introduction chamber, 9 ... Test gas flow meter

Claims (3)

A gas flow meter calibrated and priced with reference to a standard gas flow meter,
The adjusted gas flow meter, wherein the standard gas flow meter has at least two critical nozzles having throat diameters different from each other, and an on-off valve provided corresponding to each critical nozzle.   The adjusted gas flow meter according to claim 1, wherein the gas flow meter calibrated and priced with reference to the standard gas flow meter is a Coriolis gas flow meter.   The adjusted gas flowmeter according to claim 1 or 2, which has been calibrated and priced with hydrogen gas.

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