JP2000171478A - Ultrasonic flow velocity-measuring apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultrasonic flow velocity-measuring apparatus which cannot only increase a gain of a receiving wave to a maximum, but secure a sufficient measurement accuracy. SOLUTION: A flow velocity-measuring part 7 is set to a lower horizontal part of an ultrasonic flow velocity measurement pipe 1 in the ultrasonic flow velocity-measuring apparatus. Inner faces of reflecting parts 7a of the flow velocity-measuring part 7 are formed to parabolic inner faces having an agreeing focal position and arranged symmetrically on the same axis. The inner face of a central part of the flow velocity-measuring part 7 is formed as a connecting part 7b of the parabolic inner faces to a cylindrical face of a small inner diameter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[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 velocity measuring methods, a method utilizing ultrasonic waves is known.

The principle of such an ultrasonic flow velocity measuring method is shown in FIG.
The following is a description of the conventional device 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 generating circuit (4) to vibrate, generate and transmit ultrasonic waves, and receive transmitted ultrasonic waves. The received wave when the ultrasonic vibrators (2) and (3) vibrate is output as an electric signal from the amplifier circuit (5).

[0005] The propagation time until the ultrasonic wave transmitted from the upstream ultrasonic oscillator (2) in the forward direction with respect to the flow is received by the downstream ultrasonic oscillator (3); The difference between the ultrasonic wave transmitted from the downstream ultrasonic vibrator (3) in the opposite direction to the flow and the propagation time until the ultrasonic wave is received by the upstream ultrasonic vibrator (2) depends on the flow velocity. For this reason, the flow velocity of the fluid is measured by calculating the difference between the propagation times. 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),
After connecting the ultrasonic transducer (3) on the downstream side and the amplifier circuit (5) and measuring the propagation time from the upstream side to the downstream side, the pulse generation circuit (4) is operated by the operation of the switching circuit (6). And the ultrasonic transducer (3) on the downstream side, and the ultrasonic transducer (2) on the upstream side and the amplifier circuit (5) are connected so that the propagation time from the downstream side to the upstream side is measured. It has been done.

When the fluid flowing through the ultrasonic flow velocity measuring pipe (1) has a small flow rate, the ultrasonic flow velocity measuring pipe (1)
If the flow velocity measuring section (1a) has a large inner diameter and a large cross-sectional area as shown in FIG. 3, the flow velocity of the fluid becomes slow and sufficient measurement accuracy cannot be obtained. Therefore, conventionally, when a fluid has a small flow rate, as shown in FIG. 4, an ultrasonic flow velocity measuring tube (1) provided with a flow velocity measuring portion (1b) having a small inside diameter is used, and a small flow rate of the fluid is measured. It was intended to maintain the flow rate.

However, the flow velocity measuring unit (1)
When b) is formed with a small inner diameter, the ultrasonic transducers (2) and (3)
Of the ultrasonic waves transmitted in parallel to the fluid to be measured, only those that pass through the flow velocity measuring section (1a) reach the opposed ultrasonic transducers (3) and (2), and the other ultrasonic waves are irregularly reflected. Therefore, only a part of the ultrasonic wave transmitted in parallel with the measurement fluid could be used for the flow velocity measurement. For this reason, there is a drawback that the gain of the received wave cannot be maximized, and that sufficient measurement accuracy for determining the flow velocity cannot be ensured.

[0008] The present invention has been made in view of the above technical background, and maximizes the gain of a received wave.
Further, it is an object of the present invention to provide an ultrasonic flow velocity measuring device capable of securing sufficient measurement accuracy.

[0009]

In order to achieve the above object, the present invention focuses on the fact that ultrasonic waves incident parallel to a paraboloid are focused at the focal point of the paraboloid, and utilizes this. This is a device in which the inner surface structure of the flow velocity measuring unit in the ultrasonic flow velocity measuring device is devised.

That is, according to the present invention, ultrasonic transducers are arranged on the upstream side and the downstream side of the measurement fluid flowing through the ultrasonic flow velocity measuring section, respectively. In an ultrasonic flow velocity measuring device that receives the transmitted ultrasonic waves mutually and measures the flow velocity based on the difference in the propagation time of the ultrasonic waves, the flow direction of the fluid in the ultrasonic flow velocity measuring unit The inner surfaces of both side portions are characterized by being formed as parabolic inner surfaces whose focal positions coincide with each other and are symmetrically arranged on the same axis.

According to this, most of the ultrasonic waves transmitted from the ultrasonic transducer on the transmitting side in parallel with the flow of the measurement fluid,
After being reflected only once on the inner surface of the parabola on the transmitting side of the flow velocity measuring unit,
It passes through the focal position on the inner surface of the parabola. Then, the ultrasonic wave that has passed through the focal position is reflected once only on the inner surface of the parabola on the receiving side of the flow velocity measuring unit, becomes parallel to the flow of the measurement fluid, and is received by the ultrasonic transducer on the receiving side. Is done. For this reason, most of the ultrasonic waves transmitted in parallel to the measurement fluid are used for the flow velocity measurement, and the gain of the received wave can be maximized.

Further, since the intermediate portion of the flow velocity measuring portion is formed as a connecting portion of the paraboloid and has a small inner diameter, the flow velocity of the fluid is increased, and the propagation time difference of the ultrasonic wave can be obtained more reliably. .

The flow velocity measuring section may be formed directly on the inner surface of the ultrasonic flow velocity measuring pipe, or may be provided separately from the ultrasonic flow velocity measuring pipe.

[0014]

1 and 2 show a state in which an ultrasonic flow velocity measuring apparatus according to the present invention is applied to an apparatus 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 measuring tube (1) has a straight tubular flow velocity measuring portion ( 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) are switching circuits for switching the connection between the ultrasonic transducers (2) and (3), the pulse generation circuit (4) and the amplification circuit (5).

The flow rate measuring section (7) has reflecting sections (7a) and (7a) formed on both left and right sides of the intermediate connecting section (7b), and one end opening of the reflecting sections (7a) and (7a). Has an inner diameter substantially equal to the outer diameter of the ultrasonic transducer.

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. Therefore, the ultrasonic transducers (2) and (3) on the transmission side
All of the ultrasonic waves transmitted in parallel with the flow of the measurement fluid from the first reflector are reflected only once on the inner surface of the paraboloid of the reflector (7a) on the transmitting side, and then pass through the focal point (8) of the inner surface of the paraboloid. Then, the ultrasonic wave that has passed through the focal point (8) is reflected only once on the inner surface of the paraboloid of the reflection unit (7a) on the receiving side, becomes parallel to the flow of the measurement fluid, and then becomes an ultrasonic wave on the receiving side. Vibrator (3)
Received in (2). Therefore, all the ultrasonic waves transmitted in parallel to the measurement fluid are used for the flow velocity measurement, and the gain of the received wave can be maximized.

Further, since the intermediate connecting portion (7b) is formed on the inner surface of the cylinder having a small inner diameter, the flow velocity of the fluid is increased, and the difference in the propagation time of the ultrasonic wave can be reliably obtained.

That is, when the flow velocity of the fluid increases, 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). , While the propagation time until the ultrasonic wave transmitted in the opposite direction to the flow from the downstream ultrasonic transducer (3) is received by the upstream ultrasonic transducer (2) is reduced. Becomes longer, the difference in the propagation time of the ultrasonic wave can be reliably obtained, and the effect is exhibited particularly when the flow rate of the ultrasonic wave is small and the flow rate is small.

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 through the intermediate connecting part (7b) and the right reflecting part (7a) in order, it flows out from the right end of the flow velocity measuring part (7). At this time, since the intermediate connecting portion (7b) is formed on the inner surface of the cylinder having a small inner diameter as described above, the flow velocity of the fluid is large.

When a pulse for driving the ultrasonic vibrator (2) on the upstream side of the fluid is output from the pulse generating circuit (4), the ultrasonic wave is generated according to the vibration of the ultrasonic vibrator (2). Sent. Of these, all the ultrasonic waves transmitted from the upstream ultrasonic transducer (2) in parallel with the flow of the measurement fluid are reflected only once on the parabolic inner surface of the upstream reflecting portion (7a) and then reflected therefrom. It passes through the focal point (8) on the inner surface of the parabola. Then, the ultrasonic wave that has passed through the focal point (8) is reflected once only on the inner surface of the paraboloid of the downstream reflecting portion (7a), and becomes parallel to the flow of the measurement fluid. Received by the vibrator (3).

Next, when the connection is switched by the switching circuit and the ultrasonic wave is transmitted from the ultrasonic transducer (3) on the downstream side of the fluid, the ultrasonic wave transmitted in parallel to the flow of the measurement fluid is transmitted in the same manner as described above. Are received by the upstream ultrasonic transducer (3).

Thus, until the ultrasonic wave transmitted in the forward direction from the upstream ultrasonic oscillator (2) obtained above in the flow is received by the downstream ultrasonic oscillator (3). And the propagation time from when the ultrasonic wave transmitted in the opposite direction to the flow from the downstream ultrasonic transducer (3) is received by the upstream ultrasonic transducer (2). Is derived and the flow velocity of the fluid is measured.

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 measuring tube may be provided separately.

Further, although the middle connecting portion (7b) at the center of the flow velocity measuring portion (7) is formed on the inner surface of the cylinder having a small inner diameter, it may be formed into another inner surface shape if the inner diameter is small.

[0027]

According to the present invention, the inner surfaces of both sides in the flow direction of the fluid in the ultrasonic flow velocity measuring section are formed on the inner surfaces of the parabolas whose focal positions coincide with each other and are symmetrically arranged on the same axis. Because most of the ultrasonic waves transmitted parallel to the measurement fluid are used for flow velocity measurement, the gain of the received wave can be maximized and the flow velocity of the fluid increases. In addition, it is possible to provide an ultrasonic flow velocity measuring device that can more reliably determine the difference in propagation time of ultrasonic waves, and that can ensure sufficient measurement accuracy.

[Brief description of the drawings]

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

FIG. 2 is a sectional view taken along line II of the ultrasonic flow velocity measuring device shown in FIG.

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

FIG. 4 is a schematic configuration diagram of a conventional ultrasonic flow velocity measuring device having a small inner diameter.

[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 ... Intermediate connecting part

 ──────────────────────────────────────────────────続 き Continued 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

Claims (1)

[Claims] 1. An ultrasonic transducer is disposed on each of an upstream side and a downstream side of a measurement fluid flowing through an ultrasonic flow velocity measuring unit, and ultrasonic waves are generated and transmitted from each of the ultrasonic transducers and transmitted. In an ultrasonic flow velocity measuring device which receives ultrasonic waves mutually and measures a flow velocity based on a difference in propagation time of ultrasonic waves, inner surfaces of both sides in a flow direction of a fluid in the ultrasonic flow velocity measuring section Is an ultrasonic flow velocity measuring device characterized in that the focal positions coincide with each other and are formed on the inner surface of a parabola symmetrically arranged on the same axis.