JPH052249B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for measuring the speed of sound, and particularly to a method for measuring the speed of sound in a liquid in a pipe.

[Conventional technology]

In general, the speed of sound in a liquid is very easily measured by taking a sample liquid, placing it in a predetermined container, and measuring the round-trip propagation time of the ultrasonic wave or the propagation time of the ultrasonic wave from one side to the other. .

For this reason, the sound velocity has been measured and determined as a physical constant for most existing liquids. It is also generally known that the sound velocity of a liquid is highly temperature dependent.

On the other hand, when measuring the flow velocity and flow rate of a liquid flowing in a pipe, the flow velocity and flow rate cannot be measured unless the sound velocity of the fluid to be measured is determined.

For this reason, when measuring the flow rate and flow rate of water in a pipe, first measure the temperature of the water near the pipe, determine the temperature of the water flowing in the pipe from the measured temperature, and tentatively determine the speed of sound. After that, a method is adopted in which the flow rate and flow rate of water inside the pipe are measured from the outside.

[Problem that the invention seeks to solve]

However, the piping is not always equipped with a thermometer at the relevant location. For this reason, at locations where samples of the liquid in the piping cannot be collected, there has been a problem in that the flow velocity, flow rate, etc. of the liquid in the piping cannot be accurately measured because the sound velocity of the liquid is unknown.

[Purpose of the invention]

The purpose of the present invention is to provide a sound velocity measuring method that can improve the disadvantages of the conventional example and accurately measure the sound velocity of a liquid flowing in a pipe in real time without coming into contact with the liquid. shall be.

[Means for solving problems]

Therefore, in the present invention, one and the other ultrasonic transducer having wedge members formed to allow oblique incidence of ultrasonic waves are installed on the upstream and downstream outer wall portions of the piping along the ultrasonic propagation line. The ultrasonic transducers are fixedly equipped with their transmitting and receiving directions facing each other, and the phase velocity V _p of the ultrasonic wave at the part of the tube wall that comes into contact with the wedge member is determined based on the sound speed of the ultrasonic wave propagating inside the wedge member of one or the other ultrasonic transducer. At the same time, based on the propagation time of the ultrasonic wave propagating from one ultrasonic transducer to the other ultrasonic transducer via this tube wall section, the group velocity V _g of the ultrasonic wave in the tube wall section is calculated. Calculate. Then, before and after calculating the phase velocity V _p and group velocity V _g of the ultrasonic waves in the pipe wall portion, the ultrasonic waves transmitted from the upstream side to the downstream side and from the downstream side to the upstream side of the pipe are calculated. The time it takes to propagate through the pipe wall section or the fluid inside the pipe until it is received, and
From there, N strokes (N=2, 4,
6,...) Measure the differences Δt _{d and} Δt u from the time it takes to propagate a lot and receive the signal, respectively, and calculate these measured values Δt _d , _{Δt u and} the calculated phase velocity V _p and group velocity V _{a predetermined} ^function _{specified in advance based on} ^_ _{_ _ _} ^_ _{_} ² ) A configuration in which the sound speed C of the fluid in the pipe is determined by calculating C ² +V _p ² V _g ² = 0 α = (Δt _u + Δt _d ) ² /4M ² D ² or an equivalent function. are being taken. This aims to achieve the above-mentioned purpose.

[Embodiments of the invention]

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

In FIG. 1, reference numeral 1 indicates one ultrasonic transducer installed on the upstream side of the pipe 3, and reference numeral 2 indicates the other ultrasonic transducer installed on the downstream side of the pipe 3. Among them, one of the ultrasonic transducers 1 includes a wedge member 1A and a vibrator 1B for obliquely injecting ultrasonic waves into the piping 3, as shown in the figure. 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, a signal as shown in FIG. 2 is repeatedly received depending on the flow velocity in the pipe 3.

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.
The light enters the lower pipe wall portion of the piping section 3, propagates through the same pipe wall portion, leaks and propagates again into the fluid 4, enters the upper pipe wall portion of the piping section 3, and then passes through the upper pipe wall portion. 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 (N = 2 in the case of reciprocation) V _g : Group velocity of ultrasonic waves propagating through the piping section V _p : Group velocity of the ultrasonic wave propagating through the piping section Phase velocity of the propagating ultrasound θ: Leakage propagation angle of the ultrasound shown in Figure 1 τ ₁ , τ ₂ : Time required for the ultrasound to pass through the ultrasound transducer On the other hand, the ultrasound transmission and reception on the downstream side When an ultrasonic wave is emitted from the transducer 2 toward the upstream side, the total propagation time t _u of the received wave received by the ultrasonic transducer 1 on the upstream side
(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.

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 ^2The calculation of this equation is performed in the first calculation unit 17,
The results are sent to the second memory 16 and displayed on the display means 18 at the same time.

This second memory 16 immediately inputs all other stored data, that is, the phase velocity V _p and group velocity V _g of the ultrasonic wave of the pipe 3, as soon as the data of the sound velocity C is input.
The data on the sound speed C is sent to the second calculation unit 17 again along with the 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 = ₂ (V _p , V _g , Δt _u , Δt _d , C) = [V _p − (C ² /V _g )]・ (Δt _u −Δt _d ) / (Δt _u + Δt _d )...' This 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−T ₀ (l ₁ /(l ₁ +l ₁ ′))] ……. 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 timer means 13 via the signal selection means 13A, where the propagation time is measured, and then the signal is sent to the signal processing section 20.
Predetermined signal processing is performed at . This signal processing section 20 includes a first memory 14 and a time difference calculation means 1.
5, a second memory 16, and a second calculation section 17 for calculating the speed of sound and the flow velocity, and further includes a clock means 13.
The configuration includes a first arithmetic unit 13B between the second memory 16 and the second memory 16. In this signal processing unit 20, the phase velocity V _p of the pipe wall portion of the pipe 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 signal processing systems, etc., is driven and controlled by a main control section 30, respectively.

This main control section 30 outputs an overall drive control signal for synchronizing the operation timing of the entire circuit, and also switches the signal processing section 20 and the entire circuit configuration to the phase velocity calculation mode of the ultrasonic wave used. The first control function to be set and the signal processing unit 20
and a second control function that switches and sets the entire circuit configuration to the group velocity calculation mode of the ultrasonic wave used, and a second control function that switches and sets the entire circuit configuration to the group velocity calculation mode of the ultrasonic wave used, and a A third control function is provided for switching and setting the entire signal processing unit 20 and each circuit configuration to a sound speed calculation mode with the intention of calculating the sound speed of the medium to be measured. 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 transducers 1 and 2 are fixedly installed on the outer surface of the pipe 3 on the upstream and downstream sides 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 unit 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 section 13B. The first calculation unit 13B calculates the equation based on the measurement time _T0 , and the group velocity V _g obtained as a result is stored in the second memory 16 at the same time as the phase velocity V _p , and is similarly displayed. It is adapted to be displayed on 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 accordance with an input command from the operator, but these control functions are automatically operated one after another. 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, an excellent sound velocity measurement method that does not exist in the past allows for highly accurate measurement of the sound velocity of liquids such as fluids in piping in real time without contacting the liquid or without temperature correction. can be provided.

[Brief explanation of the drawing]

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. 1, 2... Ultrasonic transducer, 3... Piping section, 4... Fluid in the piping.

Claims (1)

[Scope of Claims] 1. One and the other ultrasonic transducers having wedge members formed to allow oblique incidence of ultrasonic waves are connected to the outer wall portions of the upstream and downstream sides of the piping along the propagation line of the ultrasonic waves. are fixedly equipped with the transmitting and receiving directions facing each other, and the phase velocity of the ultrasonic wave at the part of the pipe wall that comes into contact with the wedge member is determined based on the sound speed of the ultrasonic wave propagating within the wedge member of the one or the other ultrasonic transducer. In addition to calculating V _p , the group of ultrasonic waves in the tube wall section is calculated based on the propagation time of the ultrasonic waves propagating from the one ultrasonic transducer to the other ultrasonic transducer via the tube wall section. The velocity V _g is calculated, and before and after calculating the phase velocity V _p and group velocity V _g of the ultrasonic waves in the pipe wall portion, the velocity is The time it takes for the emitted ultrasonic waves to propagate through the pipe wall portion or the fluid in the pipe and to be received,
From there, N strokes (N=2, 4,
6,...) Measure the differences Δt _{d and} Δt u from the time it takes to propagate a lot and receive the data, respectively, and calculate these measured values Δt _d and _{Δt u and} the calculated phase velocity V _p and group velocity. A predetermined function specified in advance based on V _g , namely, ₁ (V _p , V _g , Δt _d , Δt _u , 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 or an equivalent function to determine the sound speed C of the fluid in the pipe. Featured sound speed measurement method.