KR20100115562A - Non-intrusive ultrasonic flowmeter - Google Patents

Abstract

PURPOSE: A non-intrusive ultrasonic flowmeter is provided to accurately calculate the flow rate of the fluid even if the temperatures of the fluid, a fluid pipe and a housing are changed. CONSTITUTION: A non-intrusive ultrasonic flowmeter(100) comprises housings(10), ultrasonic oscillators(20), an auxiliary housing(30), an ultrasonic sensor(40), and a controller. The housings are connected to the outer wall of a fluid pipe, in which the fluid flows, to be spaced in a direction in which the fluid flows. The ultrasonic oscillators are connected to the housing, receive and send the ultrasonic wave in a direction interacting with the flow direction of the fluid. The auxiliary housing is connected to the outer wall of the fluid pipe. The ultrasonic sensor is connected to the auxiliary housing, receives and sends the ultrasonic wave in a direction orthogonal to the fluid pipe. The controller is electrically connected to a pair of ultrasonic oscillators and the ultrasonic sensor.

Description

Non-intrusive ultrasonic flowmeter

The present invention relates to a dry ultrasonic flow meter attached to an outer wall of an oil pipe to measure the flow rate of the milk pipe.

The method of measuring the flow rate of the fluid flowing along the duct using an ultrasonic vibrator is classified into a wet adhesive method and a dry adhesive method according to the installation method of the ultrasonic vibrator. The wet attachment method forms a through hole in the milk pipe and inserts an ultrasonic vibrator into the through hole. However, in the case of a wet-attachment type, there is a need to cut a milk pipe in order to form a through hole in the milk pipe, or to connect a flow measuring tube having an ultrasonic vibrator to the milk pipe.

Dry-attach is a method of coupling an ultrasonic vibrator to the outer wall of the milk pipe, an example of such a dry ultrasonic flowmeter is shown in FIG. Referring to FIG. 1, a dry ultrasonic flowmeter includes a pair of ultrasonic vibrators 1, which are coupled to each other at an upstream side and a downstream side of an oil pipe 2. In the case of such a dry-type flow meter, since it can be installed without forming a through hole or cutting the oil pipe, there is an advantage that it can be installed very effectively and simply. However, in the case of the conventional dry flow meter, there is a problem that an error occurs when the temperature of the fluid changes. Hereinafter, it demonstrates in detail.

First, as shown in Figure 1, the ultrasonic wave transmitted at the incident angle θ ₁ in the upstream ultrasonic vibrator is incident to the pipe. At this time, some of the ultrasonic waves on the outer wall of the duct 2 are reflected and exhausted, and the remaining ultrasonic waves are refracted at the refraction angle θ ₂ and transmitted to the inside of the duct. Thereafter, the ultrasonic waves incident on the canal ₂ are refracted at the refraction angle θ ₃ in the fluid inside the canal to form a path through which the ultrasonic waves are delivered.

However, when the temperature of the fluid and the tube is changed, the refractive indexes of the fluid and the tube are changed. As a result, the angle of refraction is changed as shown by the virtual line i in FIG. Of course, since the ultrasonic wave transmitted from the ultrasonic vibrator propagates with a predetermined direction angle, the ultrasonic wave is received from the opposite ultrasonic vibrator even when the traveling path of the ultrasonic wave is slightly changed.

However, as described above, when ultrasonic waves are received in a non-optimal state (i.e., transmitted by a direction angle), the wavefront of the ultrasonic beam reached does not coincide with the ultrasonic wave transmitting surface of the opposite (downstream) ultrasonic vibrator. There is a phase difference of, resulting in an error in the delay time. Here, the delay time means a difference between the time taken for the ultrasonic wave transmitted from the upstream ultrasonic vibrator to be received by the downstream ultrasonic vibrator and the time taken for the ultrasonic wave transmitted from the downstream ultrasonic vibrator to be received from the upstream ultrasonic vibrator. .

In the case of the conventional dry ultrasonic flowmeter, as described above, there is no method for efficiently correcting the error of the delay time according to the temperature change, and as a result, there is a problem that the measured flow rate is inaccurate. According to the research results, theoretically, when the temperature of the medium (water) changes by 10 ℃, there is a flow error of about 4%. According to the actual water pipe experiments, about 3.5% when the temperature of water changes by 10 ℃ A flow rate error of occurred. Therefore, there is a need for the development of a dry ultrasonic flowmeter of a new method that can compensate for the above error.

The present invention has been made to solve the above problems, it is an object of the present invention to provide a dry ultrasonic flow meter with improved structure to accurately calculate the flow rate of the fluid even if the temperature of the fluid changes.

In order to achieve the above object, a dry ultrasonic flowmeter according to the present invention is a pair of housings which are coupled to each other in the direction of flow of the fluid to the outer wall of the oil pipe through which the fluid flows therein, respectively coupled to the housing, the fluid A pair of ultrasonic vibrators for transmitting and receiving ultrasonic waves in a direction intersecting with the flow direction of the secondary oscillator, an auxiliary housing coupled to the outer wall of the duct, and coupled to the auxiliary housing, and transmitting ultrasonic waves in a direction orthogonal to the duct; And an ultrasonic sensor for receiving and the controller electrically connected to the pair of ultrasonic vibrators and the ultrasonic sensor, wherein the controller is a time point at which ultrasonic waves are transmitted from the ultrasonic vibrator upstream of the fluid in the pair of ultrasonic vibrators. From when the ultrasonic wave passes through the canal and is received by the downstream ultrasonic vibrator. The first time required, and the time when the ultrasonic wave is transmitted from the downstream ultrasonic vibrator and the ultrasonic wave is received by the upstream ultrasonic vibrator through the same path as the traveling path of the ultrasonic wave transmitted from the upstream ultrasonic vibrator. And a second time required for measuring the second time required, and from the time when the ultrasonic wave is transmitted from the ultrasonic sensor, the third time required for the ultrasonic wave to pass through the auxiliary housing to reach the outer wall of the milk pipe, and The fourth time required for the ultrasonic wave reaching the outer wall to pass through the milk duct, and from the time when the ultrasonic wave is transmitted from the ultrasonic sensor, the ultrasonic wave passes through the milk duct and enters into the fluid and then is reflected from the inner surface of the milk duct. To measure the fifth time required until the time received by the ultrasonic sensor, the measured first time And the is characterized in that using the second difference of the travel time and the third time, the fourth time and the fifth time required for calculating the flow rate of the fluid.

According to the present invention, the third and fourth time requirements are preferably measured using a surface wave transmitted along the outer wall of the milk pipe after reaching the outer wall of the milk pipe.

According to the present invention of the above-described configuration, even if the temperature of the fluid, the oil pipe and the housing changes, it is possible to accurately calculate the flow rate of the fluid.

FIG. 2 is a schematic cross-sectional view of a dry ultrasonic flowmeter according to an exemplary embodiment of the present invention, FIG. 3 is a cross-sectional view of the III-III line of FIG. 2, and FIG. 4 is a diagram for explaining the superposition of ultrasonic waves.

2 to 4, the dry ultrasonic flowmeter 100 according to the present embodiment includes a housing 10, an ultrasonic vibrator 20, an auxiliary housing 30, an ultrasonic sensor 40, and a controller ( Not shown).

The housing 10 is for coupling the ultrasonic vibrator 20 to the outer wall of the duct 2 and is provided with a pair. The pair of housings 10 are coupled to the outer wall of the duct 2 and are spaced apart from each other in the flow direction of the fluid flowing in the duct. Each housing 10 is formed with an inclined surface 11 to which an ultrasonic vibrator is attached.

The ultrasonic vibrator 20 is provided in pairs, one attached to the inclined surface 11 of each housing. The pair of ultrasonic vibrators 20 are electrically connected to a controller (not shown), and receive and transmit ultrasonic waves to each other. In this case, as shown in FIG. 2, the ultrasonic wave is incident to the housing at an angle of α, and when the passing medium is changed, the ultrasonic wave is refracted according to the refractive index of each medium to proceed in a direction intersecting with the flow direction of the fluid.

The auxiliary housing 30 is for coupling the ultrasonic sensor 40 to the outer wall of the duct 2. The auxiliary housing 30 is made of the same material as the housing 10 and is coupled to the outer wall of the oil pipe 2.

The ultrasonic sensor 40 is substantially the same as the ultrasonic vibrator described above (however, the term ultrasonic sensor is used to distinguish names). The ultrasonic sensor 40 is coupled to the auxiliary housing 30 and electrically connected to the controller. As shown in FIG. 2, the ultrasonic sensor 40 transmits ultrasonic waves in a direction orthogonal to the longitudinal direction of the cannula 2, and receives ultrasonic waves reflected from the interface of the medium as described below.

The controller is for calculating the flow rate of the fluid flowing in the duct using the propagation time difference method. First, the controller outputs an outgoing signal to the upstream ultrasonic vibrator 20, and thus ultrasonic waves are transmitted from the upstream ultrasonic vibrator 20. As shown in FIG. 2, the transmitted ultrasonic waves are passed into the fluid through the housing 10 and the canal 2, and then received by the downstream ultrasonic vibrator 10, and the controller transmits ultrasonic waves from the upstream ultrasonic vibrator. From this point of time, the first time required for the ultrasonic wave to be received by the downstream ultrasonic vibrator is measured. In addition, the controller outputs an outgoing signal to the downstream ultrasonic vibrator 20, and thus ultrasonic waves are transmitted from the downstream ultrasonic vibrator 20. The transmitted ultrasonic waves are received along the same path as the traveling path (g) of the ultrasonic waves transmitted from the upstream ultrasonic vibrator (the opposite direction), and then received by the upstream ultrasonic vibrator 20, where the controller is downstream. The second time required for the ultrasound to be received by the upstream ultrasound 20 from the time when the ultrasound is transmitted from the ultrasound vibrator 20 is measured. Then, the delay time Δt which is the difference between the first time required and the second time required is obtained.

On the other hand, the controller outputs an outgoing signal to the ultrasonic sensor 40, accordingly the ultrasonic wave is sent from the ultrasonic sensor 40. As shown in FIG. 3, the transmitted ultrasonic waves travel downward to reach the outer wall of the cannula 2, and three at the outer wall of the canal, namely, reflected waves f ₁ , shear waves f ₂ , and surface waves. (surface wave) (f ₃ ). Of the three waves, the reflected wave f ₁ is received by the ultrasonic sensor 40 again, and the surface wave f ₂ is transmitted at the shortest distance along the surface of the outer wall of the cannula 2 (one revolution) and then again the auxiliary housing ( 30 is received by the ultrasonic sensor 40. Then, the shear wave (f ₃₎ is while going downward, and part (f ₄₎ reflected on the boundary surface of oil pipes and fluids, and the remainder while proceeding downward reflection at the interface of the fluid and the oil pipes (f ₅₎ after the ultrasonic sensor (40 Is received).

From the time point at which the ultrasonic wave is transmitted, the third time t ₃ , the fourth time t ₄ , and the fifth time time are used by using the time point at which the ultrasonic wave is separated during the process and received by the ultrasonic sensor 40 again. Measure t ₅ and sixth time t ₆ .

The third time required is the time required for the ultrasonic wave to pass through the auxiliary housing 30 and reach the outer wall of the cannula 2 from the time when the ultrasonic wave is transmitted from the ultrasonic sensor 40. In addition, the fourth time required is the time required for the ultrasonic waves that reach the outer wall of the milk duct to pass through the milk duct 2. The third time duration can be obtained by measuring the time from the time when the ultrasonic wave is transmitted from the ultrasonic sensor to the time point when the ultrasonic wave is reflected from the outer wall of the canal (f ₁ ) and dividing the time by 2. The time required may be obtained by dividing by 2 the time between the time when the ultrasonic wave f ₁ reflected from the outer wall of the milk duct is received and the time when the ultrasonic wave f ₄ reflected from the inner wall of the milk can is received.

However, since the thickness T ₁ of the auxiliary housing 30 and the thickness T ₂ of the milk pipe are thin, there is a fear that overlap occurs between the received ultrasonic waves. That is, immediately after receiving the ultrasonic wave f ₁ reflected from the outer wall of the milk canal as shown in FIG. 4, the two waves overlap by receiving the ultrasonic wave f ₄ reflected from the inner wall of the milk canal, and thus are received later. It is not possible to accurately determine the point of reception of the ultrasonic wave f ₄ . Therefore, the above described method cannot accurately measure the third time and the fourth time.

In order to solve the above problems, in the present embodiment, the third and fourth time periods are measured using the surface wave f ₂ . That is, the time t ₈ required from the time when the ultrasonic wave is transmitted to the time when the surface wave f ₂ separated from the outer wall of the canal is received by the ultrasonic sensor 40 is measured. since there is no possibility that overlapping) length of the path which the ultrasound is in progress is _{{2T 1 + π (D +} 2T 2)}. In addition, since the materials of the auxiliary housing 30 and the oil pipe 2 are known, the data input in advance of the speed of the ultrasonic wave in the auxiliary housing 30 and the speed of the surface wave in the oil pipe 2 according to the temperature are previously input. This can be seen through. Therefore, using t ₈ = 2T ₁ / C _w + π (D + 2T ₂ ) / C _{p -p,} we can set the traveling speed C _w and the traveling speed C _{p -p} of the related surface wave in the auxiliary housing. have. At this time, since the auxiliary housing 30 and the housing 10 are made of the same material, the traveling speed of the ultrasonic waves in the auxiliary housing 30 becomes the traveling speed of the ultrasonic waves in the housing 10.

When the speed is set in this way, the third time required t ₃ = T ₁ / C _w . On the other hand, the surface wave velocity C _{p -p} and the transverse wave velocity C _{s -p} in the related art are known as C _{s -p} ≒ 2C _{p -p} . The fourth time is t ₄ = T ₂ / 2C _{p -p} .

A fifth time t ₅ is a from the time when the ultrasonic waves are sent from the ultrasonic sensor 40. The ultrasonic waves are in time is reflected on the inner wall of the post related transferred to a fluid until it is received again, that the ultrasonic wave signal output It can be measured through the time point and the time point at which the ultrasonic reception signal is input.

A sixth time is a time at which ultrasonic waves are required to proceed with the internal fluid, a sixth time t _6, t ₅ = {- 2 (t ₃ + t ₄ )} / 2 Therefore, the traveling speed C _l of the ultrasonic wave in the fluid is D / t ₆ (D is the inner diameter of the canal).

On the other hand, the controller calculates the flow rate Q of the fluid using C _w , C _sp , C _l, and Δt obtained as described above. At this time, the following <mathematical formula> known as a flow measurement formula in a dry ultrasonic flowmeter is used. (Reference: MLSanderson, H. yeung, Guidelines for the use of ultrasonic non-invasive metering techniques, Flow Measurement Instrumentation 13 (2002) p. 125-142)

&Lt; Equation &

Q = k · π · D · C l 2 · Δt / 16 · cotθ

Here, k denotes a correction coefficient that makes the flow velocity of the fluid passing between a pair of ultrasonic vibrators the total average flow velocity in the conduit, and mainly Reynolds number (Re: determined by the conduit's diameter, temperature, viscosity, and velocity). And the flow distribution function. Θ represents the angle of incidence when the ultrasonic wave is incident on the fluid.

On the other hand, since the θ varies depending on the temperature of the housing, the tube and the fluid, if it is changed to a fixed angle of incidence α, the <Equation> is changed as shown in <Equation 1>. Snell's law is used to change θ to α.

<Equation 1>

Q = k · π · C _l · C _w · D · [1-(C _l sinα / C _w ) ² ] ^0.5 · Δt / 16 · sinα

C ₁ , C _w and Substituting Δt can calculate the flow rate Q of the fluid. At this time, since C _l , C _w and Δt are values measured in a state where the temperature of the fluid, the housing, and the pipe are reflected, and the values are substituted into Equation 1, the flow rate value at which the error of the delay time is corrected according to the temperature change is corrected. Will be calculated.

C _l and C _w measured in Equation 1 And Substituting Δt can calculate the flow rate Q of the fluid. At this time, C _l , C _w And Δt is a value measured in a state where the temperature of the fluid, the housing, and the related pipe is reflected, and thus, when the values are substituted into Equation 1, a flow rate value at which an error of a delay time due to a temperature change is corrected is calculated.

As described above, in the dry ultrasonic flowmeter according to the present embodiment, the traveling speed of the ultrasonic wave at the corresponding temperature is measured, and the flow rate of the fluid is calculated using this value. Even if is changed, the flow rate of the fluid can be calculated accurately.

In addition, in the case of measuring the temperature of the fluid or duct using a temperature sensor or the like only the temperature at the portion (local range) where the temperature sensor is located. Therefore, the measured temperature cannot reflect the overall condition (average temperature) of the fluid or pipe, so even if you try to calibrate according to the temperature when calculating the flow rate using the temperature measured by the temperature sensor, the accuracy is limited. It will exist. However, in the present embodiment, since the traveling speed of the ultrasonic wave passing through the actual housing, the oil pipe, and the entire fluid is directly measured and reflected in the flow rate calculation, the correction according to the temperature can be performed more efficiently. You can measure it.

Although the preferred embodiments of the present invention have been shown and described above, the present invention is not limited to the specific preferred embodiments described above, and the present invention belongs to the present invention without departing from the gist of the present invention as claimed in the claims. Various modifications can be made by those skilled in the art, and such changes are within the scope of the claims.

For example, in the above-described embodiment, the ultrasonic wave transmitted from the upstream ultrasonic vibrator is configured to be directly received by the downstream ultrasonic vibrator (so-called Z method), but the ultrasonic wave transmitted from the upstream ultrasonic vibrator as shown in FIG. 5. The invention can be configured such that is reflected by the inner wall of the milk pipe once and then received by the upstream ultrasonic vibrator (so-called V method).

In addition, in the above-described embodiment, the housing and the auxiliary housing are configured to be separated, but as shown in FIG. 6, the auxiliary housing is integrally formed with any one of the pair of housings 10a and the ultrasonic sensor 40a is formed therein. May be configured such that In this case, since the process of installing the auxiliary housing does not need to be carried out separately, it is possible to install a dry ultrasonic flowmeter more easily than the previous embodiment.

In addition, in the above-described embodiment, the traveling speed of the ultrasonic wave transmitted from the ultrasonic sensor is carried out in the fluid, and the traveling speed of the ultrasonic wave in the fluid is calculated using the diameter D of the canal. It is set equal to the temperature of the tube (the temperature of the tube is obtained using the fourth time and the ultrasonic handbook) and the diameter of the tube can be determined by using the speed of the ultrasonic wave in the fluid and the time required for the ultrasonic wave to progress in the fluid. Can be. At this time, by measuring the ultrasonic sensor by moving along the circumference of the tube, it is possible to determine the shape of the inner diameter of the tube (whether it is a circle or a crush), and through this, obtain a cross-sectional area in the tube and reflect it when calculating the flow rate to further increase the flow rate of the fluid. It can be measured accurately.

1 is a cross-sectional view of a conventional dry ultrasonic flowmeter.

2 is a cross-sectional view of a dry ultrasonic flowmeter according to an embodiment of the present invention.

3 is a cross-sectional view taken along line III-III of FIG. 2.

4 is a view for explaining the superposition of the ultrasonic waves.

5 is a cross-sectional view of a dry ultrasonic flowmeter according to another embodiment of the present invention.

6 is a cross-sectional view of a dry ultrasonic flowmeter according to another embodiment of the present invention.

<Description of the symbols for the main parts of the drawings>

100 ... Dry Ultrasonic Flowmeter 10 ... Housing

20 ... ultrasonic oscillator 30 ... secondary housing

40 ... ultrasonic sensor

Claims (4)

A pair of housings spaced apart from each other in a flow direction of the fluid on an outer wall of the oil pipe through which the fluid flows; A pair of ultrasonic vibrators, each coupled to the housing, for transmitting and receiving ultrasonic waves in a direction crossing the flow direction of the fluid; An auxiliary housing coupled to an outer wall of the duct; An ultrasonic sensor coupled to the auxiliary housing and configured to transmit and receive ultrasonic waves in a direction orthogonal to the duct; And And a controller electrically connected to the pair of ultrasonic vibrators and ultrasonic sensors. The controller is a first time required from the time when the ultrasonic wave is transmitted from the upstream ultrasonic vibrator in the flow direction of the fluid among the pair of ultrasonic vibrators until the ultrasonic wave passes through the duct and is received from the downstream ultrasonic vibrator And a second time required from the time when the ultrasonic wave is transmitted from the downstream ultrasonic vibrator to the time when the ultrasonic wave passes through the same path as that of the ultrasonic wave transmitted from the upstream ultrasonic vibrator and is received by the upstream ultrasonic vibrator. To measure, The third time required for the ultrasonic wave to pass through the auxiliary housing and reach the outer wall of the duct from the time when the ultrasonic wave is transmitted from the ultrasonic sensor, and the ultrasonic wave reaching the outer wall of the duct passes through the duct. 4th time required, and from the time when the ultrasonic wave is transmitted from the ultrasonic sensor, the ultrasonic wave passes through the tube and enters into the fluid, and is then reflected from the inner surface of the tube to be received by the ultrasonic sensor. Measure the fifth time required, And a flow rate of the fluid is calculated using the measured difference between the first time and the second time and the third time, the fourth time, and the fifth time. The method of claim 1, And the auxiliary housing is integrally formed with any one of the pair of housings. The method of claim 1, And the third and fourth time periods are measured using surface waves transmitted along the outer wall of the milk pipe after reaching the outer wall of the milk pipe. The method of claim 3, The controller is a dry ultrasonic flowmeter, characterized in that for calculating the flow rate of the fluid using the following Equation 1. <Equation 1> Q = k π C _l C _w D D [1-(C _l sin a / C _w ) ² ] ^0.5 t / 16 sin a Where Q is the flow rate of the fluid, k is the correction factor, C _l is the traveling speed of the ultrasonic waves in the fluid, C _w is the traveling speed of the ultrasonic waves in the housing, D is the diameter of the canal, and Δt is the delay time. Is the incident angle of the ultrasonic wave incident on the housing.

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