JP2001083170A - Ultrasonic flow velocity-measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an ultrasonic flow velocity-measuring device for equally maintaining the temperature of an ultrasonic vibrator and accurately measuring the flow velocity of fluid for a temperature change around a connection member. SOLUTION: Ultrasonic vibrators 2 and 3 are arranged at the upstream and downstream sides of measurement fluid flowing in the ultrasonic flow velocity-measuring device and are connected by a connection part 7 being formed by a substance with high thermal conductivity, thus efficiently conducting heat entirely through the connection member 7 even if temperature around the connection member 7 differs in the longitudinal direction. Therefore, regardless of the temperature distribution around the connection member 7, the temperature of entire part of the connection member 7 becomes nearly equal, and the temperature of both the ultrasonic vibrators 2 and 3 being connected to the connection member 7 can be maintained nearly equally.

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 continuously or periodically measured, 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.

FIG. 4 shows the principle of such an ultrasonic flow velocity measuring method.
The following is a description of the conventional device shown in FIG. In FIG. 4, reference numeral (31) denotes 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 (31) has a straight tubular connecting member (32).
It has been done. Further, on both sides of the connecting member (32), there are provided a fluid inflow pipe (33) for allowing a fluid to flow into the connecting member (32) and a fluid outflow pipe for allowing the fluid to flow out of the connecting member (34). .

In the ultrasonic flow velocity measuring tube (1), ultrasonic vibrators (2) and (3) are arranged at a predetermined distance from each other on the upstream side and the downstream side 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 vibrators (2) and (3) vibrate are output as electric signals from the amplifier circuit (5).

[0005] The propagation time of the ultrasonic wave until the ultrasonic wave transmitted in the forward direction from the upstream ultrasonic oscillator (2) with respect to the flow is received by the downstream ultrasonic oscillator (3). And the propagation time of the ultrasonic wave until the ultrasonic wave transmitted in the opposite direction to the flow from the downstream ultrasonic oscillator (3) is received by the upstream ultrasonic oscillator (2). Since this is related to the flow velocity, the flow velocity of the fluid is measured by calculating the propagation time difference. In FIG. 4, reference numeral (6) denotes a switching circuit for switching the connection between each of the ultrasonic transducers (2) and (3), the pulse generation circuit (4), and the amplification circuit (5). And the upstream ultrasonic vibrator (2), the downstream ultrasonic vibrator (3) and the amplifier circuit (5) are connected, and the propagation time from the upstream side to the downstream side is measured. According to (6), the pulse generator circuit (4) and the downstream ultrasonic oscillator (3) are switched so that the upstream ultrasonic oscillator (2) and the amplifier circuit (5) are connected to each other, and the downstream ultrasonic oscillator (2) and the amplifier circuit (5) are connected. It measures the propagation time from the upstream side to the upstream side.

[0006] The propagation time of the ultrasonic wave is obtained based on the received wave output from the amplifier circuit (5).
The period of the received wave is affected by the resonance frequency of the ultrasonic transducers (2) and (3). The resonance frequencies of these ultrasonic vibrators are affected by the spring constants of the components of the ultrasonic vibrator, and the spring constants change under the influence of temperature changes. That is, when the temperature changes, the spring constant changes, and the resonance frequency of the ultrasonic transducers (2) and (3) changes accordingly.
Therefore, in order to prevent deviation of the resonance frequency between the ultrasonic vibrators (2) and (3), it is necessary to keep the temperature of the ultrasonic vibrators (2) and (3) the same when measuring the flow velocity. In particular, when the fluid has a small flow rate, the propagation time difference of the ultrasonic waves is small, and the influence of the resonance frequency of the ultrasonic vibrators (2) and (3) is large.
It is important to keep the temperature of the ultrasonic transducers (2) and (3) the same.

However, in the conventional ultrasonic flow velocity measuring device, the connecting member (32) connecting the ultrasonic vibrators (2) and (3) has not been devised with respect to the temperature change. For this reason, if the temperature around the connecting member (32) is different in the longitudinal direction of the connecting member, a temperature difference occurs between the ultrasonic vibrators (2) and (3), and as a result, the ultrasonic vibrators (2) and (3) There is a problem in that a deviation occurs in the resonance frequency between 3) and it is difficult to accurately measure the flow velocity of the fluid.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and can keep the temperature of an ultrasonic vibrator the same with respect to a change in temperature around a connecting member, and can reduce the flow velocity of a fluid. It is an object of the present invention to provide an ultrasonic flow velocity measuring device capable of measuring with high accuracy.

[0009]

In order to achieve the above-mentioned object, the present invention provides an ultrasonic transducer in which ultrasonic transducers are arranged on an upstream side and a downstream side of a measurement fluid flowing in an ultrasonic flow velocity measuring device, respectively. In the ultrasonic flow velocity measuring device that generates and transmits ultrasonic waves mutually from the ultrasonic transducers, mutually receives the transmitted ultrasonic waves, and measures the flow velocity based on the difference in the propagation time of the ultrasonic waves, A connecting member for connecting the ultrasonic transducers on the upstream side and the downstream side is provided, and the connecting member is formed of a material having high thermal conductivity.

According to this, since the connecting member is formed of a material having high thermal conductivity, even when the temperature around the connecting member changes in the longitudinal direction, the entire connecting member can be efficiently used. Heat conducts. Therefore, regardless of the temperature distribution around the connecting member, the entire connecting member has substantially the same temperature, and the temperatures of the two ultrasonic transducers connected to the connecting member can be kept substantially the same.

Preferably, the connecting member comprises a flow rate measuring tube or a casing in which the upstream and downstream ultrasonic vibrators are provided in thermal contact. According to this, since there is no need to separately provide a connecting member, the temperature of the ultrasonic vibrator can be easily and reliably maintained at substantially the same temperature.

In addition, a fluid inflow pipe through which a measurement fluid flows and a fluid outflow pipe through which a measurement fluid flows out are provided via the flow velocity measurement pipe or the casing. It is desirable that a part or the whole is formed of a thermal insulator. According to this, even if the temperature of the portion opposite to the connecting member with respect to the thermal insulator of the fluid inflow pipe or the fluid outflow pipe changes due to a temperature change outside the fluid inflow pipe or the fluid outflow pipe, the temperature on the opposite side is changed. Since heat conduction from the portion to the connecting member is limited by the thermal insulator, a change in the temperature of the connecting member due to a change in the temperature of the fluid inflow pipe or the fluid outflow pipe can be prevented.

It is desirable that a heat shield is provided around the connecting member. According to this, even if the temperature outside the heat shield changes, the heat transfer from the outside of the heat shield to the connecting member inside the heat shield is restricted by the heat shield. This can prevent the temperature change of the connecting member due to the above.

[0014]

[First Embodiment] FIGS. 1 and 2
FIG. 1 is a diagram showing a state in which an ultrasonic flow velocity 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 measuring tube (1) has a straight tubular connecting member (7). ). A fluid inflow pipe (9) through which fluid flows into the coupling member (7) and a fluid outflow pipe (10) through which fluid flows out from the coupling member (7) are provided at both longitudinal sides of the coupling member (7). ) Are provided perpendicular to the connecting member (7).

(2) and (3) are ultrasonic vibrators for transmitting and transmitting ultrasonic waves, and are disposed opposite to both longitudinal sides of the connecting member (7). (4) is an ultrasonic transducer (2)
(3) a generating circuit for generating a pulse for driving
(5) is an amplifier circuit for outputting a received wave received by the ultrasonic transducers (2) and (3), and (6) is an ultrasonic transducer (2) (3)
And a switching circuit for switching the connection between the pulse generator circuit (4) and the amplifier circuit (5). The connecting member (7) is formed of a material having high thermal conductivity, for example, copper or aluminum. Therefore, even when the temperature around the connecting member (7) changes in the longitudinal direction, heat is efficiently transmitted to the entire connecting member (7), and as a result, the entire connecting member (7) is the same. Alternatively, the temperature becomes substantially the same, and the ultrasonic vibrators (2) and (3) provided on the connecting member (7)
Can be kept the same.

Further, the connecting member (7) is provided at an intermediate portion (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 one end opening to the intermediate portion (7b), and both paraboloid inner surfaces have the same focal position at the center of the connecting member. And they are arranged on the same axis. For this reason, all the ultrasonic waves transmitted in parallel to the flow of the measurement fluid from the ultrasonic transducers (2) and (3) on the transmission side are reflected only once on the inner surface of the paraboloid of the reflection section (7a) on the transmission side. Thereafter, 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 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. Vibrators (3) and (2) receive the signals. 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 portion (7b) is formed on the inner surface of the cylinder having a small inner diameter, the flow velocity of the fluid becomes large, 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 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). , While the propagation time until the ultrasonic wave transmitted in the opposite direction to the flow from the downstream ultrasonic oscillator (3) is received by the upstream ultrasonic oscillator (2) increases. Therefore, the propagation time difference of the ultrasonic wave can be reliably obtained,
In particular, the effect is exhibited 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 connecting member (7) to the connecting member (7). And flows through the reflection part (7a), the middle part (7b) and the right reflection part (7a) on the left side of the connecting member (7) in this order, and then flows out from the right end part of the connecting member (7). . At this time, since the intermediate 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 with the flow of the measurement fluid is transmitted in the same manner as described above. Are received by the upstream ultrasonic transducer (3).

Thus, 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), and The difference from the propagation time until the ultrasonic wave transmitted in the opposite direction to the flow from the ultrasonic transducer (3) on the upstream side is received by the ultrasonic transducer (2) on the upstream side is derived. Measure the flow rate. When measuring the flow velocity of the fluid, the temperature around the connecting member (7) may be different in the longitudinal direction. However, since the connecting member is formed of a substance having high thermal conductivity, the connecting member is formed. (7) The heat is efficiently conducted to the whole, and as a result, the whole connecting member (7) has the same or almost the same temperature,
The ultrasonic vibrator (2) provided on the connecting member (7)
The temperature of (3) can be kept the same. Accordingly, it is possible to prevent the occurrence of deviation in the resonance frequency of the ultrasonic transducers (2) and (3), and to accurately measure the flow velocity of the fluid.

[Embodiment 2] In this embodiment, as shown in FIG. 2, the fluid inflow pipe (11) and the fluid outflow pipe (12) are partially formed of a thermal insulator (13) in the longitudinal direction. Have been. According to this, the thermal insulator (1) of the fluid inflow pipe (11) or the fluid outflow pipe (12) is changed by the temperature change around the fluid inflow pipe (11) or the fluid outflow pipe (13).
Even if the temperature of the portion opposite to the connecting member (7) changes with respect to (3), the heat conduction from the opposite portion to the connecting member (7) is restricted by the thermal insulator, so that the fluid inflow pipe ( 11)
Alternatively, it is possible to prevent a change in the temperature of the connecting member (7) due to a change in the temperature of the fluid outlet pipe (12). The fluid inflow pipe (11) and the fluid outflow pipe (12) may be formed entirely of a heat insulator.

A heat shield (14) is provided around the connecting member (7). According to this, even if the temperature around the connecting member (7) changes, the heat shut-off unit (1)
Since the connecting member (7) is protected by 4), it is possible to prevent a change in the temperature of the connecting member (7) due to a change in the temperature around the connecting member (7).

The other components that are the same as those shown in FIG. 1 are given the same reference numerals and description thereof is omitted.

[Embodiment 3] In this embodiment, the casing (16) is a connecting member having high thermal conductivity, and the ultrasonic vibrators (2) ( 3) are provided so as to face each other. The interior of the casing (16) is partitioned by a partition wall (17) into an inflow chamber (18) and an outflow chamber (19), and the inflow chamber (17) and the outflow chamber (19) are connected to the inflow pipe (2).
0) and the outflow pipe (21) are connected. A measuring pipe (22) is provided on the partition wall (17).
And the inflow chamber (18) and the outflow chamber (19) are communicated with each other.

The fluid flowing through the inflow pipe (20) flows into the inflow chamber (18) in a direction intersecting with the length direction of the measurement pipe (22) as shown by the white arrow in FIG. Then, the flow force is reduced in the inflow chamber (18). Then, the fluid in the inflow chamber (18) whose flow momentum has been alleviated flows to the opening of the measurement pipe (22) on the inflow chamber (18) side, and flows into the measurement pipe (22) from the opening. . The fluid flowing into the measuring pipe (22) is directly used as the measuring pipe (22).
After flowing through the inside from the inflow chamber (18) side to the outflow chamber (19) side and flowing out of the opening of the measurement pipe (22) on the outflow chamber (19) side to the outflow chamber (19), the outflow pipe (21) remains as it is. Leaks to Then, the flow velocity of the fluid flowing in the measurement pipe (22) is measured by the method using the above-described ultrasonic waves, and the flow rate is obtained based on the flow velocity.

As described above, since the casing (16) is a connecting member having high heat conductivity, the casing (1)
Even when the ambient temperature in 6) changes in the longitudinal direction, heat is efficiently transmitted to the entire casing (16). Accordingly, the entire casing (16) has the same or almost the same temperature regardless of the temperature distribution around the casing (16), and the temperature of the ultrasonic vibrators (2) and (3) provided in the casing (16) is high. Can be kept the same.

In these embodiments, the connecting member is the flow velocity measuring pipe (7) or the casing (14).
The present invention is not limited to this, and a connecting member having high thermal conductivity for connecting the ultrasonic vibrators (2) and (3) may be provided separately from the flow velocity measuring tube (7) or the casing (14).

[0031]

According to the first aspect of the present invention, since the connecting member is formed of a material having high thermal conductivity, even when the temperature around the connecting member is different in the length direction, In addition, heat is efficiently conducted to the entire connecting member. Therefore,
Regardless of the temperature distribution around the connecting member, the entire connecting member has substantially the same temperature, and the temperatures of both ultrasonic transducers connected to the connecting member can be kept substantially the same, and the flow velocity of the fluid can be precisely controlled. It becomes possible to measure well.

According to the second aspect of the present invention, there is no need to separately provide a connecting member, so that the temperature of the ultrasonic vibrator can be easily and reliably maintained at substantially the same temperature.

According to the third aspect of the present invention, the temperature of the portion opposite to the connecting member with respect to the thermal insulator of the fluid inflow pipe or the fluid outflow pipe is changed by the temperature change outside the fluid inflow pipe or the fluid outflow pipe. Even if the temperature changes, the heat transfer from the opposite portion to the connecting member is limited by the thermal insulator, so that the temperature change of the connecting member due to the temperature change of the fluid inflow pipe or the fluid outflow pipe can be prevented.

According to the fourth aspect of the invention, even if the temperature outside the heat shield changes, the heat transfer from the outside of the heat shield to the connecting member inside the heat shield is restricted by the heat shield. In addition, it is possible to prevent a temperature change of the connecting member due to a temperature change outside the heat shield.

[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 schematic configuration diagram showing an ultrasonic flow velocity measuring device according to another embodiment of the present invention.

FIG. 3 is a schematic configuration diagram showing an ultrasonic flow velocity measuring device according to still another embodiment of the present invention.

FIG. 4 is a schematic configuration diagram showing a conventional ultrasonic flow velocity measuring device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Flow velocity measuring tube 2, 3 ... Ultrasonic vibrator 7 ... Connecting member material 8 ... Focus 9 ... Fluid inflow tube 10 ... Fluid outflow tube

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Yama ▲ Saki ▼ Yu 2-10-16 Higashiobashi, Higashinari-ku, Osaka-shi Kansai Gas Meter Co., Ltd. No. 16 Kansai Gas Meter Co., Ltd. F term (reference) 2F035 DA07 DA14 DA22

Claims (4)

[Claims] An ultrasonic transducer is arranged on each of an upstream side and a downstream side of a measurement fluid flowing in an ultrasonic flow velocity measuring device,
Ultrasonic flow velocity measurement, wherein ultrasonic waves are generated and transmitted from each of the ultrasonic transducers, the transmitted ultrasonic waves are mutually received, and the flow velocity is measured based on a difference in propagation time of the ultrasonic waves. In the apparatus, a connection member that connects the upstream and downstream ultrasonic transducers is provided, and the connection member is formed of a material having high thermal conductivity. 2. The ultrasonic flow velocity measuring device according to claim 1, wherein the connecting member comprises a flow velocity measuring tube or a casing in which the upstream and downstream ultrasonic vibrators are provided in thermal contact. 3. A fluid inflow pipe through which a measurement fluid flows and a fluid outflow pipe through which a measurement fluid flows out are provided via the flow velocity measurement pipe or the casing, and a length direction of the fluid inflow pipe and the fluid outflow pipe is provided. 3. The ultrasonic flow velocity measuring device according to claim 2, wherein a part or the whole of is formed of a thermal insulator. 4. The ultrasonic flow velocity measuring device according to claim 1, wherein a heat shield is provided around the connection member.