JP2000171277A - Flow rate measuring apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flow rate measuring apparatus which can measure the flow rate over a wide range from a micro flow rate to a large flow rate while ensuring a sufficient accuracy. SOLUTION: The reflective part 7a of a current velocity measuring section 7 is formed to have parabolic inner surfaces arranged symmetrically on a same axis while matching the focal point and the central coupling part 7b of the current velocity measuring section 7 is formed to have a tubular surface of small inside diameter. Ultrasonic oscillators are disposed on the upstream side and the downstream side of fluid flowing through the current velocity measuring section 7 in order to measure the flow rate of fluid from an intermediate flow rate to a large flow rate. Furthermore, a flowmeter 9 measuring micro flow rate is disposed at the coupling part 7b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flow rate measuring device for measuring a flow rate of a gas or other fluid.

[0002]

2. Description of the Related Art In determining the flow rate of a gas or other fluid, the flow rate of the fluid is first measured continuously or periodically, and the flow rate is calculated based on the measured flow rate. I have. As one of such fluid flow measuring methods, a method using ultrasonic waves is known.

The principle of such a method using ultrasonic waves will be described below with reference to a conventional apparatus shown in FIG. In FIG. 3, (1) is an ultrasonic flow velocity measuring tube through which a fluid such as a gas flows. In the ultrasonic flow velocity measuring tube (1), ultrasonic vibrators (2) and (3) are arranged at a predetermined distance upstream and downstream in the flow direction. The ultrasonic vibrators (2) and (3) are driven by a driving pulse from a pulse generation circuit (4) to vibrate, generate and transmit ultrasonic waves, and receive transmitted ultrasonic waves. Received waves when the ultrasonic transducers (2) and (3) vibrate are output as electric signals from the amplifier circuit (5).

Then, the propagation time until the ultrasonic wave transmitted from the upstream ultrasonic oscillator (2) in the forward direction to the flow is received by the downstream ultrasonic oscillator (3), The difference between the ultrasonic wave transmitted from the downstream ultrasonic oscillator (3) in the opposite direction to the flow and the propagation time until the ultrasonic wave is received by the upstream ultrasonic oscillator (2) is related to the flow velocity. Therefore, in the arithmetic circuit (10), the flow velocity is measured based on the propagation time difference, and the flow rate is further determined based on the flow velocity. In FIG. 3, reference numeral (6) denotes a switching circuit for switching the connection between each of the ultrasonic transducers (2) and (3) and the pulse generation circuit (4) and the amplification circuit (5). And the upstream ultrasonic transducer (2), the downstream ultrasonic transducer (3) and the amplifier circuit (5) are connected, and the propagation time from the upstream to the downstream is measured. By the operation of (6), the pulse generator circuit (4) and the downstream ultrasonic oscillator (3), and the upstream ultrasonic oscillator (2) and the amplifier circuit (5) are switched so as to be connected. It measures the propagation time from the downstream side to the upstream side.

The applicant of the present invention has paid attention to the fact that, in the above-described flow rate measuring device utilizing ultrasonic waves, the ultrasonic waves incident parallel to the paraboloid are focused on the focal point of the paraboloid, and FIG. A flow measurement device as shown in Fig. 1 was proposed. In this flow rate measuring device, the inner surfaces of both side portions (7a) and (7a) excluding the intermediate portion (7b) of the flow velocity measuring portion (7) have the same focal position and are symmetrically arranged on the same axis. It is formed on the inner surface of the parabola. According to this, the fluid can flow smoothly in the flow rate measuring unit (7), and most of the ultrasonic waves transmitted in parallel to the flow of the measurement fluid from the ultrasonic transducer (2) on the transmission side Due to the parabolic nature of reception by the ultrasonic transducer (3) on the receiving side, the flow velocity of the fluid, and thus the flow rate, can be efficiently obtained.

However, in the above-described method of obtaining the flow rate using the ultrasonic waves, the flow rate of the medium flow rate or the large flow rate can be determined accurately, but it is difficult to determine the minute flow rate accurately.

The present invention has been made in view of the above-mentioned technical background, and is capable of accurately obtaining a fluid having a wide flow rate from a very small flow rate to a large flow rate, and thus ensuring a sufficient flow rate measurement accuracy. It is intended to provide a device.

[0008]

In order to achieve the above object, the present invention provides a method for measuring a flow rate in a predetermined portion of a flow velocity measuring section capable of flowing a fluid over a wide range from a small flow rate to a large flow rate.
It is equipped with a micro flow meter which is most suitable for measuring a micro flow area.

That is, according to the present invention, the inner surfaces of both sides except for the intermediate portion in the fluid flow direction gradually decrease in inner diameter from one end to the intermediate portion, and the inner surface of the intermediate portion has a small inner diameter. An ultrasonic flow velocity measuring unit, comprising an ultrasonic vibrator arranged on the upstream side and the downstream side of the fluid flowing through the flow velocity measuring unit, mutually generating and transmitting ultrasonic waves from each of the ultrasonic vibrators, and transmitted. Flow rate measuring device for receiving the ultrasonic waves mutually, measuring the flow velocity based on the propagation time difference of the ultrasonic waves, and further measuring the flow rate of the fluid, wherein the micro flow meter is provided at the intermediate part of the ultrasonic flow velocity measuring section. Are arranged.

In this way, the fluid smoothly flows in the flow velocity measuring section by gently inclining so that the cross-sectional area decreases from the opening of the flow velocity measuring section to the central section, and the inner surface of the intermediate section has a small inner diameter. This increases the flow velocity of the fluid.

For this reason, while the flow rate of the medium flow rate or the large flow rate fluid can be accurately determined by using the ultrasonic wave, the flow rate is increased by flowing through the intermediate portion using the micro flow meter. The flow rate of the minute flow rate fluid can be accurately determined.

In addition, the inner surfaces of both sides of the flow rate measuring unit except for the intermediate portion are formed as parabolic inner surfaces whose focal positions coincide with each other and are symmetrically arranged on the same axis.
When the inner surface of the intermediate portion is formed on a cylindrical inner surface having a small inner diameter, most of the ultrasonic waves transmitted in parallel with the flow of the measurement fluid from the ultrasonic transducer on the transmission side due to the properties of the paraboloid. Since the ultrasonic wave is received by the ultrasonic transducer on the receiving side, the flow rate of the medium flow rate or the large flow rate fluid can be obtained more efficiently using the ultrasonic waves.

Further, when the micro flow meter is a thermal flow meter, the flow rate of a micro flow rate fluid can be determined with higher accuracy. In addition, as this thermal type flow meter, there is a type in which a microbridge is to be used.

[0014]

1 and 2 show a state in which a flow rate measuring device according to the present invention is applied to a device for measuring a gas flow rate.

In FIG. 1, (1) is a U-shaped ultrasonic flow velocity measuring tube which is open upward and through which gas flows, and a lower horizontal portion of the ultrasonic flow velocity measuring tube (1) has a straight tubular flow velocity measuring section. (7). (2) and (3) are ultrasonic transducers for transmitting and transmitting ultrasonic waves, which are disposed opposite to the inner wall of the ultrasonic flow velocity measuring tube (1) on the center line of the flow velocity measuring section (7). (4) is a generation circuit for generating pulses for driving the ultrasonic transducers (2) and (3), and (5) is an amplifier circuit for outputting a reception wave received by the ultrasonic transducers (2) and (3). , (6) is a switching circuit for switching the connection between the ultrasonic transducers (2) and (3) and the pulse generating circuit (4) and the amplifying circuit (5), and (10) is the flow velocity of the fluid based on the propagation time difference of the ultrasonic waves. And an arithmetic circuit for determining the flow rate.

The flow rate measuring section (7) is connected to the connecting section (7).
Reflecting portions (7a) and (7a) are formed on both left and right sides of b), and the inner diameter of one end opening of the reflecting portions (7a) and (7a) is formed to be substantially the same as the outer diameter of the ultrasonic transducer. ing.

Each of the reflecting portions (7a) has a parabolic inner surface whose diameter gradually decreases from the one end opening to the connecting and connecting portion (7b). The positions coincide and are arranged on the same axis. For this reason, when the flow rate of a medium flow rate gas or a large flow rate gas is determined using ultrasonic waves, the ultrasonic waves transmitted from the ultrasonic transducers (2) and (3) on the transmission side in parallel to the flow of the measurement fluid are measured. Most of the light is reflected only once on the inner surface of the paraboloid of the reflecting section (7a) on the transmitting side, and then passes through the focal point (8) of the inner surface of the paraboloid. And the ultrasonic wave that passed through the focal point (8)
The light is reflected only once on the inner surface of the paraboloid of the reflector (7a) on the receiving side, becomes parallel to the flow of the measurement fluid, and is received by the ultrasonic transducers (3) and (2) on the receiving side. Therefore, most of the ultrasonic waves transmitted in parallel to the measurement fluid are used for measuring the flow velocity, and the gain of the received wave can be maximized.

The connecting portion (7b) is a portion connecting the inner surfaces of the paraboloids of the two reflecting portions (7a) and (7a), and is formed on the inner surface of the cylinder having a small inner diameter. It is getting bigger. For this reason, when the flow rate of the medium flow rate or the large flow rate gas is obtained by using the ultrasonic waves, the ultrasonic waves transmitted in the forward direction from the upstream ultrasonic vibrator (2) with respect to the flow are converted to the ultrasonic waves on the downstream side. While the propagation time until reception by the ultrasonic vibrator (3) is shortened, the ultrasonic wave transmitted from the downstream ultrasonic vibrator (3) in the opposite direction to the flow is the upstream ultrasonic vibrator. Since the propagation time until reception in (2) becomes long, the propagation time difference of the ultrasonic wave can be reliably obtained.

The connecting portion (7b) is provided with a minute flow meter (9), which accurately measures the flow rate of the gas having a small flow rate flowing through the connecting portion (7b) and having a large flow velocity. You can do it. The micro flow meter (9) is configured using a micro bridge, and measures a micro flow rate region with high accuracy using the micro bridge.

Next, the principle of ultrasonic flow velocity measurement using the ultrasonic flow velocity measuring device shown in FIG. 1 will be described.

First, as shown by a white arrow in FIG. 1, when a fluid such as a gas flows through the ultrasonic flow velocity measuring tube (1), the fluid flows from the left end of the flow velocity measuring section (7) to the flow velocity measuring section (1). 7), the reflection part (7a) on the left side of the flow velocity measurement part (7),
After flowing sequentially through the connecting part (7b) and the right reflecting part (7a), it flows out from the right end of the flow velocity measuring part (7). At this time, the left and right portions of the flow velocity measuring section (7) have a parabolic inner surface that is gently inclined from the opening to the center of the flow velocity measuring section (7) so that the cross-sectional area decreases. The gas flows smoothly in the flow rate measuring section (7), and the connecting section (7b) of the flow rate measuring section (7) is formed on a cylindrical surface having a small inner diameter, so that the gas flow rate increases.

When the gas has a medium flow rate or a large flow rate, a pulse for driving the ultrasonic vibrator (2) on the upstream side of the gas is output from the pulse generation circuit (4). Ultrasonic waves are transmitted according to the vibration of 2). Among these, most of the ultrasonic waves transmitted in parallel to the gas flow from the upstream ultrasonic transducer (2) are reflected only once on the parabolic inner surface of the upstream reflecting portion (7a), It passes through the focal point (8) on the inner surface of the parabola. Then, the ultrasonic wave passing through the focal point (8) is reflected once only on the inner surface of the paraboloid of the downstream reflecting portion (7a), becomes parallel to the gas flow, and is then subjected to the downstream ultrasonic vibration. Received by child (3). Next, when the connection is switched by the switching circuit and the ultrasonic waves are transmitted from the ultrasonic transducer (3) on the downstream side of the gas, all the ultrasonic waves transmitted in parallel with the gas flow are transmitted upstream in the same manner as described above. Received by the ultrasonic transducer (2) on the side.

In the arithmetic circuit (10), the ultrasonic wave obtained in the above and transmitted from the upstream ultrasonic oscillator (2) in the forward direction with respect to the flow is applied to the downstream ultrasonic oscillator (2). The ultrasonic wave transmitted in the opposite direction to the flow from the ultrasonic transducer on the downstream side (3) and the propagation time until it is received in 3) is received by the ultrasonic transducer on the upstream side (2). The flow velocity of the gas is measured from the difference with the propagation time until the flow rate of the gas at the medium or large flow rate.

On the other hand, when the gas has a very small flow rate, a very small flow meter provided at the connecting part (7b) of the flow velocity measuring part (7) increases the flow velocity through the connecting part (7b). Find the gas flow rate.

As described above, when the gas has a medium flow rate or a large flow rate, the flow rate can be obtained by using an ultrasonic wave as in the conventional case. On the other hand, when the gas has a small flow rate, the connecting portion (7b) is used. The gas flow rate can be accurately determined using the gas flow meter (9) provided in the apparatus.

In the above embodiment, the flow velocity measuring section (7) is formed directly on the inner surface of the ultrasonic flow velocity measuring pipe (1). However, the present invention is not limited to this. The ultrasonic flow velocity measuring tube (1) may be provided separately.

Further, the reflecting part (7a) of the flow velocity measuring part (7)
Was formed on the inner surface of the parabola, and the inner surface of the connecting portion (7b) at the center of the flow velocity measuring section (7) was formed on the inner surface of the cylinder having a small inner diameter. However, the reflecting portion (7a) was not limited to these inner surface shapes. May be an inner surface that is gently inclined so as to reduce the cross-sectional area from the opening of the flow velocity measuring part (7) to the central part, and the inner surface of the connecting part (7b) may have an inner diameter other than the inner surface of the cylinder. It may be a small inner surface.

[0028]

The present invention is characterized in that a minute flow meter is disposed at the intermediate portion of the ultrasonic flow velocity measuring section, so that a medium flow rate or a large flow rate of a fluid can be measured using ultrasonic waves. While the flow rate can be determined accurately, the flow rate of a fluid having a small flow rate flowing through the intermediate portion and having a large flow rate can be determined accurately using a micro flow meter provided in the intermediate portion. Therefore, it is possible to accurately obtain a fluid having a wide flow rate from a very small flow rate to a large flow rate,
As a result, it is possible to provide an ultrasonic flow velocity measuring device that can ensure sufficient measurement accuracy. In addition, the inner surfaces of both sides except for the intermediate portion of the flow velocity measuring unit are formed on a parabolic inner surface whose focal positions coincide with each other and are arranged symmetrically on the same axis, and the inner surface of the intermediate portion is formed. When formed on the inner surface of a cylinder having a small inner diameter, the flow rate of a medium flow rate or a large flow rate fluid can be obtained more efficiently using ultrasonic waves.

When the flow meter is a thermal type flow meter, the flow rate of a minute flow rate of the fluid can be determined more accurately.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a flow measurement device according to an embodiment of the present invention.

FIG. 2 is a sectional view taken along line II of FIG. 1;

FIG. 3 is a schematic configuration diagram of a conventional flow measuring device having a large inner diameter.

FIG. 4 is a schematic configuration diagram of a conventional flow measurement device having a parabolic inner surface.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Ultrasonic flow velocity measuring tube 2, 3 ... Ultrasonic vibrator 7 ... Flow velocity measuring part 7a ... Reflecting part 7b ... Connecting part 8 ... Focus 9 ... Micro flow meter

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takaomi Raft 4-1-2 Hirano-cho, Chuo-ku, Osaka City Inside Osaka Gas Co., Ltd. Kansai Gas Meter Co., Ltd. (72) Inventor Tetsuya Yasuda 2-10-16 Higashikobashi, Higashinari-ku, Osaka City Kansai Gas Meter Co., Ltd. F-term (reference) 2F035 DA19 DA22 EA04

Claims (3)

[Claims] 1. An ultrasonic flow rate measuring section in which the inner surfaces of both sides except the intermediate portion in the fluid flow direction gradually decrease in inner diameter from one end to the intermediate portion, and the inner surface of the intermediate portion has a smaller inner diameter. And an ultrasonic vibrator disposed on the upstream side and the downstream side of the fluid flowing through the flow velocity measuring unit.The ultrasonic vibrators generate and transmit each other ultrasonic waves, and transmit the transmitted ultrasonic waves. Mutually received, the flow rate is measured based on the propagation time difference of the ultrasonic wave, a flow rate measuring device for further measuring the flow rate of the fluid, in the intermediate portion of the ultrasonic flow rate measuring unit, a micro flow meter is arranged A flow measurement device. 2. An inner surface of both sides of the flow rate measuring unit except for an intermediate portion is formed on a parabolic inner surface whose focal positions coincide with each other and are symmetrically arranged on the same axis, and the intermediate portion is formed. 2. The flow measuring device according to claim 1, wherein an inner surface of the cylinder is formed on a cylindrical inner surface having a small inner diameter. 3. The flow measuring device according to claim 1, wherein the micro flow meter is a thermal flow meter.