JP2001281031A - Multifunctional type ultrasonic gas meter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a multifunctional type ultrasonic gas meter by utilizing respective parameters used to calculate a flow rate in an ultrasonic flowmeter, using a propagation velocity different method. SOLUTION: The ultrasonic gas meter 1 comprises a gas passage 2, ultrasonic transducers 5, 6 for detecting a propagation velocities of ultrasonic waves propagating in two different directions in a gas flow flowing through the passage 2, and a controller 10 for calculating a gas flow rate Q which through the passage 2, based on these detected results. The controller 10 discriminates the type of the gas, based on outputs of the transducers and a temperature T, and a pressure P of the gas flowing through the passage 2. For example, the controller discriminates whether the gas is city gas or LP gas.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic gas meter for measuring a gas flow rate by a propagation velocity difference method.
The present invention relates to a multifunctional ultrasonic gas meter capable of discriminating a gas type and calculating a calorific value using various parameters used in a measurement process.

[0002]

2. Description of the Related Art In general, a membrane gas meter is used to measure a gas flow rate. Since the measuring principle of a membrane gas meter is a volume meter, the gas flow volume per unit time (L) is detected, and the flow rate (L / unit time) is determined based on this.
Need to ask. On the other hand, if the ultrasonic flow meter is adopted as a gas meter, the instantaneous flow rate can be easily obtained since the measurement principle is a flow meter. Ultrasonic flowmeters use a transmission velocity difference method that utilizes the fact that when ultrasonic waves propagate in different directions with respect to flowing fluid, a transmission velocity difference occurs due to the fluid flow velocity. It is known to use the Doppler method that utilizes the difference between the ultrasonic frequencies of the transmitting side and the receiving side that propagates the fluid using the Doppler method.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to measure the flow rate of a gas flow, identify a gas type, and calculate a calorific value, etc., by using an ultrasonic flowmeter based on a propagation velocity difference method. It is to propose a multifunctional ultrasonic gas meter.

[0004]

SUMMARY OF THE INVENTION The present invention provides a gas passage,
A detecting unit that detects a propagation speed or a propagation time of an ultrasonic wave propagating in two different directions in a gas flow flowing through the gas passage, and the gas passage based on a difference between the propagation speed or the propagation time detected by the detection unit. In an ultrasonic gas meter having a flow rate calculation unit for calculating a flowing gas flow rate, a type of the gas is determined based on the transmission speed detected by the detection unit and a temperature and a pressure of the gas flowing through the gas passage. It is characterized by having a gas type determination unit.

If the gas type can be determined in this manner, for example, a gas meter commonly used for city gas and LP gas can be easily realized.

The gas meter according to the present invention further comprises a calorific value calculating unit for calculating the calorific value of the gas passing through the gas passage based on the type of the gas and the volume, temperature and pressure of the gas flowing through the gas passage. It can be. According to this configuration, for example, charging for gas usage is
This is convenient because it can be performed based only on the amount of heat regardless of the gas pressure and volume.

Here, it is desirable to have a shut-off mechanism for shutting off the gas passage, and a gas flow shut-off control unit for controlling the drive of the shut-off mechanism based on the heat quantity obtained by the heat quantity calculation unit. If the gas flow can be cut off based on the amount of heat, its security performance can be improved.

Further, the gas flow cutoff control section controls the drive of the cutoff mechanism based on the gas type obtained by the gas type determination section, so that the gas meter having a security function corresponding to the gas used. Can be easily realized.

Next, the gas meter according to the present invention is characterized in that it has a flow direction discriminator for discriminating a flow direction of the gas flowing through the gas passage based on a detection result of the detector.

In this case, it is convenient to have a designating section for designating the flow direction of the gas flowing through the gas passage, since the gas inlet and outlet of the gas meter can be freely changed.

In this case, a backflow detecting unit for detecting that the gas is flowing backward is provided based on the result of the determination by the flow direction determining unit and the flow direction specified by the specifying unit. If it is, the backflow state of the gas can be easily detected.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an ultrasonic gas meter to which the present invention is applied will be described below with reference to the drawings.

FIG. 1 is a schematic block diagram showing an ultrasonic gas meter of this embodiment. Explaining with reference to this figure, the ultrasonic gas meter 1 of the present example is required for calculating a gas passage 2 through which a gas to be measured flows and a gas flow rate flowing through the gas passage 2 by a propagation velocity difference method. A detection unit (5, 6, 7, 8) for detecting a parameter, and a control device 10 for calculating a gas flow rate and performing other control operations are provided.
In this example, a transmission / reception unit 24 for transmitting / receiving data to / from the management unit 30 via the input unit 21, the display unit 22, and the public telephone line 23 is further provided. In addition, a gas shutoff valve 40 for forcibly shutting off gas in an emergency or the like is connected to the output side of the control device 10 via a valve driver 41.

More specifically, the gas passage 2 has a rectangular cross-section with a constant cross-sectional area S, and its gas inlet 3
Side wall and the gas outlet 4 side wall,
The ultrasonic transducers 5 and 6 are attached, and are set so that ultrasonic waves transmitted from one side can be received on the other side.

The gas passage 2 is provided with a temperature sensor 7 and a pressure sensor 8 for detecting the temperature T and the pressure P of the gas flowing in the gas passage.
A gas shutoff valve 40 is mounted on the upstream side of the gas inlet 3 and is a normally open valve, which is closed in an emergency or the like to forcibly shut off gas supply.

The control device 10 is mainly composed of a microcomputer, and a ROM is controlled under the control of the CPU.
The following functions are realized by executing a control program stored in advance in the CPU. (1) Gas flow rate calculation function and function utilizing the ability to obtain instantaneous values (2) Gas type discrimination function for discriminating the type of the gas based on the propagation speed of the ultrasonic wave and the temperature and pressure of the gas ( 3) A function for calculating the number of moles of the gas passing through the gas passage based on the type of gas and the volume, temperature, and pressure of the gas flowing through the gas passage, and a calorie calculation function for calculating the amount of heat based on the number of moles. (5) Flow direction determination function for determining the flow direction of gas flowing through the gas passage (6) Designated via the input unit 21 Backflow detection function for detecting whether gas is flowing backward based on the gas flow direction and the actual gas flow direction First, a gas flow rate calculation function and a function using an instantaneous value will be described. In this example, the gas flow rate is calculated based on the difference in the propagation speed of the ultrasonic wave propagating in the gas flowing through the gas passage 2, the gas flow velocity flowing through the gas passage 2 is V, the gas passage length is L, the ultrasonic transducer 5 , 6 is denoted by C. The control device 10 calculates the arrival time of the ultrasonic wave transmitted from each of the ultrasonic transducers 5 and 6 based on the detection output of each ultrasonic transducer 5 and 6. In this example, as shown in FIG. 1, the case of traveling in the same direction as the gas flow is represented as a forward sound wave arrival time t1, and the case of the reverse direction is represented as a backward sound wave arrival time t2.

In this case, the gas flow velocity V is obtained by the calculation formula shown in FIG. 2, and the flow velocity V is multiplied by the gas passage sectional area S to obtain the volume flow rate Q per time.

Here, the current membrane gas meter uses 15 to 30 to recognize (determine) the flow rate of the flowing gas.
Since it takes seconds, it takes a long time before a security function, for example, a function of shutting off gas due to an excessive flow rate works. On the other hand, in the ultrasonic gas meter of the present embodiment, the flow rate can be recognized in a few seconds (2 to 4 seconds) because of the integration based on the instantaneous value. Therefore, the security function can be operated quickly.

Next, the gas type determining function will be described. The control device 10 stores a gas type discrimination table, and this table is a correspondence table of the ultrasonic transmission speed, the gas temperature, the gas pressure, and the gas type. For example, a gas type discrimination table for discriminating between city gas and LP gas is stored. The controller 10 determines the type of gas flowing based on the ultrasonic wave transmission speed C (t1) or C (t2) and the detected gas temperature T and gas pressure P.

The calorific value calculation function of the controller 10 is for calculating the calorific value of the gas flowing through the gas passage 2 based on the gas type, gas volume, gas temperature and gas pressure. The amount of heat can be determined as follows.

That is, in the ultrasonic gas meter of this embodiment,
When the type of gas is determined, based on this, the passing volume V of the gas flowing through the gas passage 2, the gas temperature T (absolute temperature) and the gas pressure P (absolute pressure), The number of moles can be calculated.

(Mol number) = R (T / PV) where R: constant P: absolute pressure V: passing volume T: absolute temperature Further, based on the number of moles, the calorific value can be calculated as follows.

Heat amount = (number of moles) × (calorific value per mole) Next, the control device 10 drives and controls the gas shutoff valve 40 based on the calculated heat amount and flow rate. For example, the upper limits of the heat quantity and the flow rate are set in advance. When the upper limits are reached, the control device 10 forcibly shuts off the normally-open gas shutoff valve 40 via the valve driver 41. For example, the upper limit value may be set and changed via the input unit 21.

Here, if the upper limit value is held in the form of a correspondence table with the gas type, when the gas type is determined by the above-mentioned gas type determination function, the corresponding gas type is automatically determined. By selecting an upper limit, the operation of the gas shutoff valve 40 can be controlled based on the upper limit. This configuration is convenient because a gas meter that can be used for city gas and LP gas can be realized as a security function.

On the other hand, the control device 10 determines the flow direction of the gas flowing through the gas passage 2 based on the difference between the ultrasonic arrival times t1 and t2, and the gas direction specified through the input unit 21. And a backflow detecting function for detecting whether or not the gas is flowing backward based on the flow direction of the gas and the actual gas flow direction. In this example, the input unit 21 is provided with input designation means such as a key for setting a gas flow direction.
For example, as shown in FIG. 1, one is a gas inlet 3 and the other is a gas outlet 4. In this case, the direction of the actual gas flow can be obtained based on the outputs of the ultrasonic transducers 5 and 6. By comparing the determined gas flow direction with the set gas flow direction, the gas backflow state can be detected.

Therefore, the gas meter 1 of the present embodiment has the input unit 2
The gas inlet side and the outlet side can be switched via 1. Therefore, the layout of the gas meter connection and the like can be easily changed, which is convenient.

The gas meter 1 of the present embodiment has a management headquarters 3
Since it has a communication function with 0, for example, an automatic meter reading system that performs automatic meter reading by remote control from the management headquarters 30 can be easily constructed.

Since the display device 22 is provided,
It is possible to display and output the measured gas flow rate, pressure, temperature, calorific value, forced shut-off state, and the like.

[0029]

As described above, since the multifunctional ultrasonic gas meter of the present invention has the gas type discriminating section,
This is extremely convenient because a common meter can be used for city gas and LP gas.

Further, in the present invention, since the calorific value calculation unit for calculating the calorific value of the passing gas is provided, for example, the billing for the gas usage amount can be conveniently performed based only on the calorific value regardless of the gas pressure and volume. It is.

Further, the present invention has a gas flow cutoff control unit for cutting off the gas supply based on the calorific value of the gas. Therefore, for example, if the cutoff control of the gas supply is performed based on the gas type, a gas meter having a security function corresponding to the used gas can be easily realized.

Further, according to the present invention, it is possible to easily determine the flow direction of the gas flowing through the gas passage using the parameters used for calculating the flow rate. As a result, even if the flow direction of the gas flowing through the gas passage is switched,
The security function can be maintained, and the gas inlet / outlet of the gas meter can be easily changed. In addition, the backflow state of the gas can be easily detected.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram showing the overall configuration of an ultrasonic gas meter to which the present invention has been applied.

FIG. 2 is an explanatory diagram for explaining a flow rate calculation principle in the gas meter of FIG. 1;

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 multifunctional ultrasonic gas meter 2 gas passage 3 gas inlet 4 gas outlet 5, 6 ultrasonic transducer 7 temperature sensor 8 pressure sensor 10 control device 21 input unit 22 display device 24 transmission and reception unit 25 public line 30 management headquarters 40 gas shutoff valve 41 valve driver

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kazuhiko Hayashi 3967-10, Wada, Matsumoto-shi, Nagano F-term in Toyo Keiki Co., Ltd. (Reference) 2F030 CC13 CF05 CF11 2F035 DA14 DA22

Claims (8)

[Claims] 1. A gas passage, a detecting unit for detecting a propagation speed or a propagation time of an ultrasonic wave propagating in two different directions in a gas flow flowing through the gas passage, and a propagation speed or a propagation time detected by the detection unit. An ultrasonic gas meter having a flow rate calculation unit that calculates a gas flow rate flowing through the gas passage based on a difference between the transmission speed or the transmission time detected by the detection unit, and a temperature and a pressure of the gas flowing through the gas passage. A multi-function ultrasonic gas meter having a gas type discriminating unit for discriminating the type of the gas based on the above. 2. The multifunctional ultrasonic gas meter according to claim 1, wherein the gas type determination unit determines at least whether the gas is a city gas or an LP gas. 3. The gas according to claim 1, wherein a type of the gas, a volume of the gas flowing through the gas passage,
A multifunctional ultrasonic gas meter, comprising: a calorific value calculating unit that calculates a calorific value of a gas passing through the gas passage based on a temperature and a pressure. 4. The apparatus according to claim 3, further comprising: a shutoff mechanism that shuts off the gas passage; and a gas flow shutoff control unit that drives and controls the shutoff mechanism based on the heat quantity obtained by the heat quantity calculation unit. Multifunctional ultrasonic gas meter characterized by the above-mentioned. 5. The multifunctional ultrasonic gas meter according to claim 4, wherein the gas flow cutoff control unit controls the drive of the cutoff mechanism based on the gas type obtained by the gas type determination unit. . 6. The apparatus according to claim 1, further comprising a flow direction determination unit configured to determine a flow direction of the gas flowing through the gas passage based on a detection result of the detection unit. Multifunctional ultrasonic gas meter characterized by the above-mentioned. 7. The multifunctional ultrasonic gas meter according to claim 6, further comprising a designation unit for designating a flow direction of the gas flowing through the gas passage. 8. The backflow detection unit according to claim 7, further comprising a backflow detection unit that detects that the gas is flowing backward based on a result of the determination by the flow direction determination unit and a flow direction designated by the designation unit. A multifunctional ultrasonic gas meter, characterized in that: