JPH0584850B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an ultrasonic flow velocity measurement method and an apparatus therefor, and particularly relates to an ultrasonic flow velocity measurement method and an apparatus for measuring the flow velocity inside a pipe by attaching an ultrasonic transducer to the outer surface of the pipe. The present invention relates to a method and device for measuring a sound wave velocity.

[Conventional technology]

A conventional example is shown in FIG. In the conventional example shown in FIG. 9, the ultrasonic waves output toward the downstream side from the ultrasonic transducer 51 of one ultrasonic transducer 50 are as follows:
It reaches the ultrasonic transducer 61 of the other ultrasonic transducer 60 via propagation paths l ₁ , l ₂ , l ₃ , l ₄ , and l ₅ . Then, let t _d be the propagation time required in this case.

Further, the ultrasonic waves outputted toward the upstream side from the ultrasonic transducer 61 of the other ultrasonic transducer 60 are as follows:
It reaches the ultrasonic transducer 51 of one ultrasonic transducer 50 via propagation paths l ₅ , l ₄ , l ₃ , l ₂ , and l ₁ . In this case, let the propagation time be t _u .

In this case, the flow velocity in the pipe 3 is determined by the following equation.

V=(C ² /2Dtanθ)·(t _u −t _d ) Here, D is the inner diameter of the pipe 3, θ is the refraction angle in the fluid, and C is the sound speed of the fluid.

As a result, if the sound velocity of the fluid is determined in advance, the flow velocity of the fluid in the pipe 3 can be measured relatively easily based on the above equation, and at the same time, the inner diameter of the pipe 3 can be determined. Therefore, the flow rate of the fluid in the pipe 3 can be determined very easily.

[Problem that the invention seeks to solve]

However, in such conventional examples, if the sound velocity of the fluid in the pipe 3 is unknown, especially if a sample for measuring the sound velocity cannot be collected, the flow velocity and flow rate of the fluid cannot be measured at all. It has always had this essential flaw.

[Purpose of the invention]

The present invention improves the disadvantages of the conventional example and makes it possible to measure the sound velocity of the fluid in the pipe with high accuracy without temperature error even if the sound velocity of the fluid in the pipe is completely unknown. The object of the present invention is to provide an ultrasonic flow velocity measuring method and an apparatus therefor.

[Means for solving problems]

Therefore, in the present invention, ultrasonic transducers are fixedly installed on the upstream and downstream sides of the piping along the ultrasonic propagation line, and then ultrasonic waves are alternately obliquely incident from the outer wall of the piping during measurement. Measure the phase velocity V _p and group velocity V _g due to the ultrasonic waves in the tube wall portion at . Before and after these measurements, the time it takes for the ultrasonic waves oscillated from the upstream side to the downstream side or from the downstream side to the upstream side to propagate within the pipe wall or the fluid in the pipe and to be received, Then, the difference Δt _u and Δt _d from the time taken until the signal is received after passing through the fluid in the pipe for N strokes (N=2, 4, 6, . . . ) are measured, respectively. Based on these measured values, a predetermined function specified in advance, ie, f ₁ (V _p , V _g , Δt _u , Δt _d , C)=0, is calculated to calculate the sound speed C of the fluid in the pipe. Next, based on the real-time sound speed C specified by this calculation and the measured values V _p , V _g , Δt _u , Δt _d , another function, namely, V=f ₂ (V _p , V _g , Δt The configuration is such that the flow velocity of the fluid in the pipe is calculated by calculating _u , Δt _d , C).

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, 1 indicates one ultrasonic transducer installed on the upstream side of piping 3, and 2 indicates the other ultrasonic transducer similarly installed on the downstream side of piping 3. Among these, the one ultrasonic transducer 1
As shown in the figure, the apparatus includes a wedge member 1A and a vibrator 1B for obliquely injecting ultrasonic waves into the piping 3. Further, the other ultrasonic transducer 2 also includes a wedge member 2A and a vibrator 2B that are formed in the same manner.

Each of these ultrasonic transducers 1 and 2 is separately connected to a transmitting circuit section 11 and a receiving circuit section 12 via a transmitting/receiving switching section 10. In FIG. 1, a case is shown in which the liquid in the pipe 3 flows from the left to the right in the figure.

In each of the ultrasonic transducers 1 and 2,
Depending on the flow velocity in the pipe 3, a repeating signal as shown in FIG. 2 is received.

In this figure 2, the wave of N=0 in figure 1 is
1 shows received waves that propagate in the order of paths l ₁ , l ₂ , l ₇ , l ₅ and l ₆ shown in FIG. 1 and reach the other ultrasonic transducer 2 without passing through the fluid. On the other hand, Figure 2
The wave of N=0 is the ultrasonic wave emitted from the ultrasonic transducer 2 along the paths l ₆ , l ₅ , l ₇ , l ₂ and l ₁ shown in FIG.
This shows a received wave that propagates in the order of , and reaches one of the ultrasonic transducers 1 without passing through the fluid, that is, an ultrasonic signal wave that propagates in the opposite direction through the same passage area.

In addition, the wave of N=2 in FIG.
It leaks once into the fluid 4 from the upper pipe wall portion of the pipe 3 in the figure, propagates through the fluid 4, and then leaks into the pipe section 3.
It enters the lower pipe wall part of the pipe, propagates through the same pipe wall part, leaks and propagates again into the fluid 4, enters the upper pipe wall part of the piping part 3, and then passes through the upper pipe wall part. A wave propagating and reaching the ultrasonic transducer 2 is shown. That is, a wave with N=2 indicates a received wave whose propagation path in the fluid is two. On the other hand, Figure 2
The wave of N=2 in FIG.
Shows the received waves of the journey.

Similarly, a wave with N=4 indicates a received wave whose path through the fluid is four strokes.

Among these, when ultrasonic waves are emitted from the upstream ultrasonic transducer 1 toward the downstream side, the propagation time t _d of each received wave received by the downstream ultrasonic transducer 2
(d=1, 2, 4, . . . ) is expressed by the following equation in FIG.

t _d = [(L-ND・tanθ)/V _g ]+ [(ND/cosθ)/(C+V・sinθ)] +τ ₁ +τ ₂ ... θ=sin ^-1 (C/V _p ) ... However, L: Distance between ultrasonic transducers N: Number of propagation strokes in the fluid (for round trip, N =
2) V _g : Group velocity of the ultrasonic wave propagating in the piping section V _p : Phase velocity of the ultrasonic wave propagating in the piping section θ : Leakage propagation angle of the ultrasonic wave shown in Fig. 1 τ ₁ , τ ₂ : Ultrasonic wave velocity Time required for sound waves to pass through the ultrasonic transducer 1 On the other hand, when ultrasonic waves are emitted from the downstream ultrasonic transducer 2 toward the upstream side, The total propagation time t _u of the received wave
(u=1, 3, 5, . . . ) is expressed by the following equation similarly to the equation.

t _u = [(L-ND・tanθ)/V _g ]+ [(ND/cosθ)/(C-V・sinθ)] +τ ₁ +τ ₂ ... However, L, N, V _g , V _p , θ and τ ₁ and τ ₂ are the same as in Eq.

These received waves are clocked in the order of N=0, N=2, N=4 by the clocking means 13 via the receiving circuit section 12 and the signal selection means 13A, and then the information regarding the propagation time is 1 memory 14.

Next, the propagation time difference Δt _d and Δt _u of the two received waves whose paths in the fluid differ by M distances is Δt _d = (−MD・tanθ/V _g )+ [(MD/cosθ)/(C+V・sinθ)] ... Δt _u = (-MD・tanθ/V _g ]+ [(MD/cosθ)/(CV・sinθ)] ... Here, if M=2, the relationship with Fig. 2 Then, Δt _d =2t _d =t ₂ −t ₁ =t ₄ −t ₂ Δt _u =2t _u =t ₃ −t ₁ =t ₅ −t ₃ .

The calculation of this equation is performed by the time difference calculation means 15, and the result is stored in the second memory 16. From this equation, the sound speed C of the fluid can be calculated as the root of the following equation.

f ₁ (V _p , V _g , Δt _u , Δt _d , C) = (1+αV _g ² )C ⁴ −(2V _p V _g + αV _p ² V _g ² )C ² +V _p ² V _g ² =0… ...α=(Δt _u +Δt _d ) ² /4M ² D ² The calculation of this formula is performed in the first calculation unit 17, and the result is sent to the second memory 16 and displayed on the display means 18 at the same time. It's becoming like that.

This second memory 16 immediately inputs all other stored data, namely the phase velocity V _{p and group velocity V g of} the ultrasonic wave of the pipe 3.
Then, data on the speed of sound C is sent to the second calculation unit 17 again along with two data Δt _d and Δt _u related to the propagation time difference. In this case, the second calculation unit 17 performs the following calculation.

V=f ₂ (V _p , V _g , Δt _u , Δt _d , C) = [V _p −(C ² /V _g )]・(Δt _u −Δt _d )/(Δt _u +Δt _d )...' As a result, the flow velocity of the fluid 4 in the pipe 3 is immediately calculated, and the result is sent to the display means 18. The display means 18 is adapted to convert and display this flow rate data as well as the flow rate data based on the flow rate data.

That is, the arrival time of each reception wave of N=0, 2 or N=2, 4 received by the ultrasonic transducers 1 and 2 is measured, and the difference (for example, the time difference between N=0 and N=2) is calculated. By calculating, if the phase velocity V _p and group velocity V _g of the pipe wall of the pipe 3 are known, the sound velocity C of the fluid 4 in the pipe 3, as well as the flow velocity and flow rate can be immediately determined in real time. In addition, calculations can be displayed with high accuracy.

Here, the operating principle when determining the phase velocity V _p and group velocity V _g of the ultrasonic waves propagating through the pipe wall portion of the pipe 3 will be explained.

First, FIG. 3 shows the wedge member 1A and the ultrasonic transducer 1B of the ultrasonic transducer 1. This wedge member 1A has a trapezoidal cross section, and an ultrasonic transducer 1B is fixed to one slope 1a. Further, the other slope 1C constitutes a surface perpendicular to the propagation path when the ultrasonic waves emitted from the ultrasonic transducer 1B are reflected by the incident surface 1b and propagated within the wedge member 1A. There is. Therefore, the internally reflected waves propagating within the wedge member 1A return to the ultrasonic transducer 1B. l ₁ , l ₁ ′ are
The propagation route and distance in that case are shown.

Therefore, by measuring the propagation time T ₀ of the ultrasonic wave within the wedge member 1A at this time, the sound speed C _p within the wedge member 1A can be calculated by the following equation.

C _p = 2 (l ₁ + l ₁ ′) / T ₀ ... In addition, the relationship between the sound velocity C _p of the wedge member 1A and the phase velocity V _p of the ultrasonic wave propagating through the piping section 3 is expressed by the following equation. be.

V _p = C _p /sin θ _i ... However, θ _i : Incident angle (see Figure 3) Furthermore, as shown in Figure 1, the distance between the ultrasound incident points of the two ultrasound transducers 1 and 2 is If the distance is L and the propagation time is T when the ultrasonic wave emitted from the ultrasonic transducer 1B propagates through the pipe wall of the pipe 3 and reaches the ultrasonic transducer 2B, then the pipe wall of the pipe 3 is The group velocity V _g of the propagating ultrasonic wave is expressed by the following equation.

V _g =L/[T- _T0 ( _l1 /( _l1 + _l1 '))...]. Here, since L, l ₁ and l ₁ ' are numerical values determined geometrically, by measuring the propagation times T and T ₀ in the formula and calculating the formula, the required amount of piping 3 can be calculated. The group velocity of the tube wall can be calculated very easily. This calculation of the group velocity and phase velocity is performed by the first calculation section 13B of the signal processing section 20.

The signal received by the receiving circuit section 12 is sent to the clock means 13 via the signal selection means 13A,
After the propagation time is measured here, the signal processing section 20 performs predetermined signal processing. This signal processing section 20 has a first memory 14, a time difference calculation means 15, a second memory 16, and a second calculation section 17 for calculating sound velocity and flow velocity, and further includes the time measurement means 13 and a second calculation section 17 for calculating sound velocity and flow velocity. The configuration includes a first calculation section 13B between the second memory 16 and the second memory 16. In this signal processing section 20, the phase velocity V _p of the piping section 3, the group velocity V _g ,
The sound velocity C of the fluid in the pipe 3, the flow velocity V of the fluid, etc. are calculated as described later. The calculation results in the signal processing section 20 are displayed on the display means 18.

This signal processing section 20 and the above-mentioned time measurement means 13
Each of the electrical systems, etc., is driven and controlled by the main control section 30, respectively.

This main control unit 30 outputs an overall drive control signal for synchronizing the operation timing of the entire circuit, and also has a first control function to determine the ultrasonic phase velocity in the pipe during measurement, and It has a second control function for determining the ultrasonic group velocity and a third control function for determining the sound velocity of the fluid in the pipe. In this embodiment, these control functions of the main control section 30 can be switched by an external command by an operator using a measurement condition setting section 30A.

Next, the overall operation of the above embodiment will be explained.

First, ultrasonic transmitter/receivers 1 and 2 are fixedly installed on the outer surface of the pipe 3 on the upstream side and the downstream side of the pipe 3, respectively, along the center line of the pipe. Next, the first control function of the main control unit 30 is activated, and the entire circuit is set to a measurement state of the phase velocity V _p in the pipe wall portion of the pipe 3 (phase velocity measurement mode). When the entire circuit is set to this phase velocity measurement mode, the other ultrasonic transducer 2 is electrically disconnected from the transmission/reception switching section 10, so that only one ultrasonic transducer 1 is able to transmit. It is set to perform operation and reception operation (note that the other ultrasonic transducer 2 may be used instead of one ultrasonic transducer 1).
FIG. 4 shows the transmission state of the transmitted and received signals in this case.
TR ₁ is simultaneously sent to the ultrasonic transducer 1 and the receiving circuit section 12 , and the internally reflected wave RE ₁ from the ultrasonic transducer 1 is also sent to the receiving circuit section 12 . These signals TR ₁ and RE ₁ pass through the signal selection means 13A and are sent to the clock means 13, where the time difference T ₀
is measured, and the time data is sent to the first calculation unit 13B.
sent to. In the first calculation unit 13B, the measurement time
Formulas and calculations are performed based on T ₀ , and the results are stored in the second memory 16 and displayed on the display means 18 .

Next, when the second control function of the main control section 30 is activated by the operator, the entire circuit is set to the group velocity measurement mode of the pipe 3.

In this case, one ultrasonic transducer 1 performs a transmitting operation, and the other ultrasonic transducer 2 performs a receiving operation. That is, the transmission signal TR ₁ and the reception signal RE ₂ are transmitted as shown in FIG. Each of these signals TR ₁ , RE ₂
passes through the signal selection means 13A and enters the timekeeping means 13.
Here, the time difference between the waves TR ₁ and RE ₁ is measured, and the time data is sent to the first calculation unit 13B. In the first calculation unit 13B, the equation is calculated based on the measurement time _T0 , and the group velocity V _g obtained as a result is stored in the second memory 16 in the same way as the phase velocity V _p . It is adapted to be displayed on the display means 18.

Subsequently, when the third control function of the main control section 30 is activated in response to an input command from the operator, the entire circuit is set to a mode for measuring the sound velocity of the liquid flowing inside the piping section 3. In this internal fluid sound velocity measurement mode, the above equations and equations are
t _d and t _u are specifically measured over time at t ₁ , t ₂ , t ₃ , . . . in FIG. 2. In the case of Figure 6 1, t _d
is measured. Specifically, for example, each received signal in the case of N=0, N=2, N=4 with TR ₁ as a reference
The reception times t ₁ , t ₂ , and t ₄ of RE ₂ are measured, amplified by the reception circuit section 12, and then sent to the signal selection means 13A. In this signal selection means 13A, among the input signals, for example, N=
0 and N=2 received signals are selected and sent to the clock means 13. In the timing means 13,
The times t ₁ and t ₂ of the two input signals are measured and the time data is output to the time difference calculating means 15 . This time difference calculation means 15 immediately calculates the time difference Δt _d between t ₁ and t ₂ .
is calculated and stored in the second memory 16.

When the calculation and storage operation of this Δt _d (formula) is completed, the transmission/reception switching unit 10 immediately sets the other ultrasonic transducer 2 as a transmitter and one ultrasonic transducer 1 as a transmitter, as shown in FIG. Set it on the receiver and perform the same measurement as in the case of Δt _d described above, find the difference Δt _u between the propagation times of the two received waves (for example, t ₁ and t ₃ ), and similarly calculate this as the second It is stored in the memory 16.

In the second memory 16, when these Δt _d and Δt _u are input, data related to the phase velocity V _p and group velocity V _g of the ultrasonic waves of the piping 3 stored in advance together with them are transferred to the second calculation unit 17 . Output to. This second
The calculation unit 17 calculates the equation based on these input data, outputs the sound velocity C of the fluid in the pipe 3 obtained as a result to the display means 18 in real time, and immediately calculates the equation ' as described above. After calculating the flow velocity, the flow velocity data is output to the display means 18.

In addition, in the above embodiment, when calculating Δt _d and Δt _u , N=0 and N=2 of the received waves in FIG.
Although the case where N=2 and N=4 are adopted is illustrated, the case is completely equivalent. In addition, in the above embodiment, the case where the phase velocity V _p and group velocity V _g of the ultrasonic wave in the piping section 3 are determined prior to Δt _d and Δt _u was illustrated, but these are obtained in the reverse order. Good too. Further, in the above embodiment, the first, second, and third control functions of the main control unit 30 are operated in response to an input command from the operator, but these control functions are automatically operated in sequence. It may be something that works. Furthermore, since the present invention enables the measurement of the sound velocity of the liquid in the pipe 3 with high precision, it is possible to measure the sound velocity of the liquid in the pipe 3 with high accuracy. It can also be applied to devices that measure temperature changes in corresponding liquids with high precision.

Next, another embodiment will be described based on FIGS. 7 and 8.

In the embodiment shown in FIG. 7, the other ultrasonic transducer 2 is mounted on the reflection side of the pipe 3 (relative to the ultrasonic transducer 1) as shown. Figure 8 shows
The received waves obtained in this case are shown.

Even in this case, the group velocity V _g described above can be changed to the first
By measuring in advance using the method shown in the figure,
It is possible to obtain the same effects as in the case of FIG. 1 described above.

〔Effect of the invention〕

Since the present invention is configured and functions as described above,
According to this, the flow velocity of a fluid such as a liquid in a pipe can be measured with high precision without contacting the fluid and even if the sound velocity of the fluid is completely unknown. It is possible to provide an excellent ultrasonic flow velocity measurement method and device.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention;
Fig. 2 1, 2, and 3 are explanatory diagrams showing the received signals etc. received during the sound velocity measurement mode in Fig. 1, Fig. 3 is a detailed explanatory diagram of the ultrasonic transducer shown in Fig. 1, and Figs. Figures 6 1 and 2 are explanatory diagrams of the operation of Figure 1, and Figure 7
8 through 8 are explanatory diagrams showing other embodiments, respectively,
FIG. 9 is an explanatory diagram showing a conventional example. 1, 2... Ultrasonic transducer, 3... Piping section, 4
... Fluid in the pipe, 10 ... Transmission/reception switching section, 1
1... Transmission circuit section, 12... Receiving circuit section, 13A
...Signal selection means, 13...Timekeeping means, 13B...
...First calculation unit, 15... Time difference calculation means, 16...
...Second memory, 17...Second calculation unit, 18...
Display means, 30...main control section, 30A...measurement condition setting section.

Claims (1)

[Claims] 1. Ultrasonic transducers are fixedly installed on the upstream and downstream sides of the piping along the ultrasonic propagation line, and then ultrasonic waves are alternately obliquely incident from the outer wall of the piping for measurement. Measure the phase velocity V _p and group velocity V _g due to the ultrasonic wave on the pipe wall portion at the same time, and before and after these measurements, the oscillation is generated from the upstream side to the downstream side or from the downstream side to the upstream side, respectively. The time it takes for the ultrasonic waves to propagate within the tube wall or the fluid inside the tube until they are received, and the time it takes for the ultrasonic waves to travel through the fluid N more steps (N = 2, 4, 6,...) before being received. Δt _u and Δt _d are respectively measured, and a predetermined function specified in advance, that is, f ₁ (V _p , V _g , Δt _u , Δt _d , C)=0, is calculated based on these measured values. Then, other functions are calculated based on the real-time sound speed C specified by this calculation and the measured values V _p , V _g , Δt _u , Δt _d . That is, an ultrasonic flow velocity measuring method characterized in that the flow velocity V of the fluid in the pipe is calculated by calculating V=f ₂ (V _p , V _g , Δt _u , Δt _d , C). 2 Ultrasonic transducers are installed on the upstream and downstream sides of the piping along the ultrasonic propagation line, and the transmitting circuit and receiving circuit are installed in these two ultrasonic transducers as necessary. and a transmitting/receiving switching unit that is alternately connected to the receiving circuit unit, and the ultrasonic wave transmitted from the upstream side to the downstream side or from the downstream side to the upstream side of the ultrasonic transducer is transmitted to the receiving circuit unit, respectively. The propagation time until it is received after propagating inside the wall or inside the fluid inside the pipe, and the N distance inside the fluid (however, N = 2, 4,
6,...) A clock means for measuring the propagation time of each wave received after a long time, a time difference calculation means for calculating the difference in arrival time of two received waves in the same direction measured by the clock means, A storage means for storing the output of the means is provided, and the storage means measures and stores the phase velocity and group velocity of the ultrasonic wave used at the time of measuring the flow velocity in the pipe wall portion, and the output information of the storage means is sound velocity calculation means for performing a predetermined calculation based on the sound velocity to specify the sound velocity of the fluid in the pipe; and a flow velocity calculation unit for performing a predetermined calculation based on each output information of the sound velocity calculation means and the storage means to specify the flow velocity of the fluid in the pipe. 1. An ultrasonic flow velocity measuring device comprising: means.