JP6876643B2 - Ultrasonic flow measuring device and ultrasonic flow measuring method - Google Patents

Description

The present invention relates to an ultrasonic flow rate measuring device and an ultrasonic flow rate measuring method.

Conventional general ultrasonic flowmeters make an average by injecting an ultrasonic pulse in the flow direction of the fluid in the pipe and flying the ultrasonic pulse in the pipe at a speed obtained by adding the sound velocity and the flow velocity. The flow velocity is obtained, and the average flow velocity is multiplied by the cross-sectional area of the pipe to obtain the average flow velocity. However, the above-mentioned ultrasonic flowmeter only obtains the average flow velocity and the average flow velocity in the flow direction, and does not consider the flow state (flow velocity distribution in the direction orthogonal to the flow direction). For this reason, the flow velocity distribution in the pipe assumes an ideal flow field (assuming), and it is necessary to prepare a measurement environment that meets that assumption, and various setting conditions (constraints) are imposed. Will be. Further, it is necessary to use a so-called profile factor for correcting the deviation of the flow velocity distribution, and it is difficult to guarantee the accuracy from the viewpoint of calibration or the like. Furthermore, it is very difficult to measure with a small-diameter pipe, and since it is premised on the axial symmetry of the flow field, the stability and reliability of the measured value cannot be guaranteed in the wake of a bent pipe.

On the other hand, Patent Document 1 discloses a flow velocity distribution measuring device that measures the flow velocity distribution of a gas fluid flowing in a fluid pipe by using an ultrasonic pulse. In this flow velocity distribution measuring device, an ultrasonic pulse is emitted from a transmitting transducer installed on the pipe wall of the fluid pipe to the fluid to be measured flowing through the fluid pipe, and the ultrasonic pulse is emitted in a two-dimensional manner on the opposite pipe wall of the fluid pipe. The ultrasonic pulse is detected by a plurality of receiving transducers. The amount of displacement of the ultrasonic pulse in the tube axis direction is detected from the detection signals of a plurality of receiving transducers arranged in the tube axis direction. More specifically, two measurement lines having slightly different opening angles are set, and the flow velocity at a predetermined position is obtained from the difference between the displacement amount and the flight time detected for each measurement line.

International Publication No. 2008/004560 Pamphlet

However, in Patent Document 1, after a plurality of receiving transducers detect an ultrasonic pulse, a flow velocity distribution in a direction orthogonal to the flow direction (axis of a fluid pipe) is based on the amount of displacement of the ultrasonic pulse in the tube axis direction. The flow velocity distribution of the orthogonal cross section) is calculated, and the flow velocity of the gas fluid flowing in the fluid pipe is calculated based on the flow velocity distribution. Therefore, the calculation becomes complicated and the capacity increases, and if a calculation error or a disturbance factor is added in the process of calculating the flow velocity distribution from the displacement amount of the ultrasonic pulse and the process of calculating the flow rate of the gas fluid from the flow velocity distribution, the gas fluid The flow rate of the gas may not be measured accurately.

The present invention has been made based on the above awareness of the problem, and an object of the present invention is to obtain an ultrasonic flow rate measuring device and an ultrasonic flow rate measuring method capable of accurately measuring the flow rate of the fluid to be measured with a simple configuration. And.

The ultrasonic flow measuring device of the present embodiment is installed in a pipe through which the fluid to be measured flows and emits an ultrasonic pulse, and is installed in the pipe facing the transmitter and the ultrasonic pulse. (2n + 1) (n is a natural number of 2 or more) in which is incident, and the transmitter emits to the (2n + 1) receivers in a state where the flow velocity of the fluid to be measured in the pipe is zero. The transmitter emits a reference sound pressure distribution waveform holding portion that holds the reference sound pressure distribution waveform based on the incident ultrasonic pulse, and the flow velocity of the fluid to be measured in the pipe is other than zero, and the above (2n + 1). ) A shift amount that is the difference between the variable sound pressure distribution waveform acquisition unit that acquires the variable sound pressure distribution waveform based on the ultrasonic pulse incident on the receivers, the reference sound pressure distribution waveform, and the variable sound pressure distribution waveform. the seeking, by integrating the shift amount, the have a, a flow rate calculation unit for calculating the flow rate of the measurement target fluid in the pipe, the reference sound pressure distribution waveform holding unit, the (2n + 1) pieces of For every combination for selecting three receivers from the receivers, the transmitter was emitted and incident on the three receivers in a state where the flow velocity of the fluid to be measured in the pipe was zero. It is characterized in that the reference sound pressure distribution waveform is acquired based on an ultrasonic pulse, and the reference sound pressure distribution waveform for all the combinations is averaged.

Before SL varies sound pressure distribution waveform acquiring unit, the (2n + 1) pieces of all for each combination for selecting three receiving terminal from the receiving terminal, the flow velocity of the measurement object fluid in the pipe is non-zero state The variable sound pressure distribution waveform is acquired based on the ultrasonic pulse emitted from the transmitter and incident on the three receivers, and the variable sound pressure distribution waveform for each combination is averaged. be able to.

The transmitter and the receiver can be installed on the inner surface of the pipe.

The ultrasonic flow rate measuring method of the present embodiment is installed in a pipe through which the fluid to be measured flows and emits an ultrasonic pulse, and is installed in the pipe facing the transmitter and the ultrasonic pulse. This is an ultrasonic flow measurement method using an ultrasonic flow measurement device having (2n + 1) receivers (n is a natural number of 2 or more) in which is incident, and the flow velocity of the measurement target fluid in the pipe is zero. The reference sound pressure distribution waveform holding step for holding the reference sound pressure distribution waveform based on the ultrasonic pulse emitted from the transmitter and incident on the (2n + 1) receivers, and the measurement target fluid in the piping. A variable sound pressure distribution waveform acquisition step for acquiring a variable sound pressure distribution waveform based on the ultrasonic pulse emitted from the transmitter in a state where the flow velocity is other than zero and incident on the (2n + 1) receivers, and the reference. seeking a shift amount which is the difference of the sound pressure distribution waveform and the variation sound pressure distribution waveform, by integrating the shift amount, have a, a flow rate calculation step of calculating the flow rate of the measurement target fluid in the pipe In the reference sound pressure distribution waveform holding step, the flow velocity of the measurement target fluid in the pipe is zero for each combination for selecting three receivers from the (2n + 1) receivers. The reference sound pressure distribution waveform is acquired based on the ultrasonic pulse emitted from the transmitter and incident on the three receivers, and the reference sound pressure distribution waveform for all the combinations is averaged. It is characterized by that.

According to the present invention, it is possible to obtain an ultrasonic flow rate measuring device and an ultrasonic flow rate measuring method capable of accurately measuring the flow rate of the fluid to be measured with a simple configuration.

It is a figure which shows the state which installed the transmitting side transducer and the receiving side transducer of the ultrasonic flow rate measuring apparatus of this embodiment in a pipe. FIG. 1 is a diagram showing a state in which a transmitting side transducer emits an ultrasonic pulse and an ultrasonic pulse is incident on the receiving side transducer. It is a functional block diagram which shows the internal structure of an ultrasonic flow rate measuring apparatus. It is a figure which shows an example of the measurement method of the reference sound pressure distribution waveform and the fluctuation sound pressure distribution waveform. It is a figure which shows the method of estimating the sound pressure distribution by approximating (fitting) three sound pressure measurement values to a quadratic function. It is a figure which shows how the flow rate calculation part calculates the flow rate of the fluid to be measured in a pipe by integrating the shift amount which is the difference between the reference sound pressure distribution waveform and the fluctuation sound pressure distribution waveform. It is a figure which shows the distribution of the shift amount on the xy plane in the pipe axis orthogonal cross section of a pipe. It is a figure which shows the structure which arranged so that the transmitting side transducer and the receiving side transducer are spread on the inner surface of a pipe. It is a figure which shows an example of the shift amount obtained by 3 sets of transmission side transducers and reception side transducers provided in the same tube axis direction position with different circumferential positions.

The ultrasonic flow rate measuring device 1 of the present embodiment will be described with reference to FIGS. 1 to 9. The ultrasonic flow rate measuring device 1 is mounted on a muffler of a vehicle and is used for measuring the flow rate of exhaust gas in the muffler, for example. Further, the ultrasonic flow rate measuring device 1 may be mounted on a pipeline of a factory and used to measure the flow rate of gas in the pipeline, or may be liquefied from an LNG (Liquefied Natural Gas) tanker to a base or the like. It may be used to measure the flow rate of the liquefied natural gas when flowing the natural gas. Further, the ultrasonic flow rate measuring device 1 may be mounted on a ship engine and used to measure the flow rate of exhaust gas in the ship engine. Further, the ultrasonic flow rate measuring device 1 can be applied to measure the flow rate of not only a gas such as a gas but also a liquid. That is, the measurement target of the ultrasonic flow rate measuring device 1 is not limited (there is a degree of freedom), and various design changes are possible.

As shown in FIGS. 1 and 2, the ultrasonic flow rate measuring device 1 is a transmitting side transducer (transmitter) installed on the inner surface of a pipe 5 (for example, a vehicle muffler) through which a fluid G to be measured (for example, exhaust gas) flows. Has 10. The transmitting side transducer 10 emits an ultrasonic pulse having a certain spread angle around the direction orthogonal to the pipe axis in a direction orthogonal to the pipe axis direction (right side in the drawing) of the pipe 5.

As shown in FIGS. 1 and 2, the ultrasonic flow rate measuring device 1 has a receiving side transducer (receiver) 20 installed on the inner surface of the pipe 5 so as to face the transmitting side transducer 10. The receiving side transducer 20 is a first receiving side transducer 21 facing the transmitting side transducer 10 in the direction orthogonal to the tube axis (left-right direction in the drawing), and a second receiving side located upstream of the first receiving side transducer 21. It has a side transducer 22 and a third receiving side transducer 23, and a fourth receiving side transducer 24 and a fifth receiving side transducer 25 located downstream of the first receiving side transducer 21. The ultrasonic pulse emitted by the transmitting side transducer 10 is incident on the first receiving side transducers 21 to 5 and the fifth receiving side transducer 25.

The transmitting side transducer 10 and the first receiving side transducers 21 to 5 can be configured by compatible transducers of the same standard. The transducer has both an ultrasonic pulse emitting function and an incident function.

Here, a case where five first receiving side transducers 21 to 5th receiving side transducers 25 are installed as the receiving side transducer 20 has been described as an example, but the number of receiving side transducers 20 is limited to this. There is no such thing, and various design changes are possible. That is, at least three receiving side transducers 20 may be installed, preferably (2n + 1) (n is a natural number of 2 or more). Further, the number of receiving side transducers arranged on the upstream side and the downstream side of the first receiving side transducer 21 may be different (for example, the former may be smaller than the latter).

As shown in FIG. 3, the ultrasonic flow measuring device 1 includes a signal oscillator 30, a detection circuit 40, a data acquisition circuit 50, a reference sound pressure distribution waveform holding unit 60, and a fluctuating sound pressure distribution waveform acquisition unit 70. , And a flow rate calculation unit 80.

The signal oscillator 30 outputs an oscillation signal to be supplied to the transmitting side transducer 10. The fundamental frequency of the oscillation signal in the signal oscillator 30 is determined in consideration of the material of the pipe 5, the characteristics of the fluid G to be measured, the spread of the ultrasonic pulse, and the like. The signal waveform of the oscillation signal can be a sharp triangular pulse signal, and the repetition period of the pulse signal can be determined from the gas sound velocity, the pipe diameter, the average flow velocity, and the like. The timing signal for outputting the oscillation signal (pulse signal) is sent to the receiving side transducer 20 as a synchronization signal.

The detection circuit 40 is connected to each output end of the first receiving side transducer 21 to the fifth receiving side transducer 25. Although not shown, the detection circuit 40 includes a signal amplifier that amplifies a detection signal having a magnitude corresponding to the incident ultrasonic intensity output from the first receiving side transducers 21 to 5 and the fifth receiving side transducer 25. It has a peak detection circuit that reads the peak value of the output of the signal amplifier. The detection circuit 40 simultaneously detects the outputs of the first receiving side transducers 21 to 5 in order to obtain the flow rate at a high sampling rate. The detection circuit 40 sets the pulse reception timing according to the timing signal supplied from the signal oscillator 30.

The data acquisition circuit 50 is composed of, for example, a digital multiplexer that collects all the outputs (peak values) of the first receiving side transducers 21 to 5 read by the detection circuit 40.

In the reference sound pressure distribution waveform holding unit 60, the transmitting side transducer 10 was emitted in a state where the flow velocity of the fluid G to be measured in the pipe 5 was zero, and was incident on the first receiving side transducers 21 to 5 and the fifth receiving side transducer 25. Holds the reference sound pressure distribution waveform based on the ultrasonic pulse. The reference sound pressure distribution waveform, which is set by default at the time of manufacturing the ultrasonic flow measuring device 1, may be held in advance in the reference sound pressure distribution waveform holding unit 60, or may be measured at the time of maintenance of the ultrasonic flow measuring device 1. The reference sound pressure distribution waveform holding unit 60 may hold the sound pressure distribution waveform holding unit 60. Alternatively, the reference sound pressure distribution waveform may be measured every time the pipe 5 or the fluid G to be measured changes, and the reference sound pressure distribution waveform held by the reference sound pressure distribution waveform holding unit 60 may be updated.

When measuring (updating) the reference sound pressure distribution waveform held by the reference sound pressure distribution waveform holding unit 60, in order to select three receiving side transducers from the first receiving side transducers 21 to 5 and the fifth receiving side transducers 25. For each combination of, the transmission side transducer 10 is emitted in a state where the flow velocity of the measurement target fluid G in the pipe 5 is other than zero, and the reference sound pressure distribution is based on the ultrasonic pulses incident on the above three receiving side transducers. The waveform may be acquired and the reference sound pressure distribution waveform for all the combinations may be averaged. There are the following 10 combinations of three receiving side transducers.
(1) First receiving side transducer 21, second receiving side transducer 22, third receiving side transducer 23
(2) First receiving side transducer 21, second receiving side transducer 22, fourth receiving side transducer 24
(3) First receiving side transducer 21, second receiving side transducer 22, fifth receiving side transducer 25
(4) First receiving side transducer 21, third receiving side transducer 23, fourth receiving side transducer 24
(5) First receiving side transducer 21, third receiving side transducer 23, fifth receiving side transducer 25
(6) First receiving side transducer 21, fourth receiving side transducer 24, fifth receiving side transducer 25
(7) Second receiving side transducer 22, third receiving side transducer 23, fourth receiving side transducer 24
(8) Second receiving side transducer 22, third receiving side transducer 23, fifth receiving side transducer 25
(9) Second receiving side transducer 22, fourth receiving side transducer 24, fifth receiving side transducer 25
(10) Third receiving side transducer 23, fourth receiving side transducer 24, fifth receiving side transducer 25

Depending on the combination of selections of the three receiving transducers, it may not be possible to obtain the output of some or all receiving transducers. In that case, assuming that there is no reference sound pressure distribution waveform of the combination, the average of the reference sound pressure distribution waveforms of other combinations may be taken.

The fluctuating sound pressure distribution waveform acquisition unit 70 emits the transmitting side transducer 10 in a state where the flow velocity of the fluid G to be measured in the pipe 5 is other than zero, and is incident on the first receiving side transducers 21 to the fifth receiving side transducer 25. Acquire the fluctuating sound pressure distribution waveform based on the ultrasonic pulse. The fluctuating sound pressure distribution waveform acquisition unit 70 constantly monitors the flow of the fluid G to be measured in the pipe 5, and continues to acquire the fluctuating sound pressure distribution waveform that changes from moment to moment.

The fluctuating sound pressure distribution waveform acquisition unit 70 determines the measurement target fluid G in the pipe 5 for each combination for selecting three receiving side transducers from the first receiving side transducers 21 to 5 and the fifth receiving side transducers 25. The transmitting side transducer 10 emits light in a state where the flow velocity is other than zero, and a fluctuating sound pressure distribution waveform is acquired based on the ultrasonic pulses incident on the above three receiving side transducers, and the fluctuating sound pressure for each combination is obtained. The distributed waveform may be averaged. The combination of the three receiving transducers is as described above.

Depending on the combination of selections of the three receiving transducers, it may not be possible to obtain the output of some or all receiving transducers. In that case, assuming that there is no fluctuating sound pressure distribution waveform of the combination, the average of the fluctuating sound pressure distribution waveforms of other combinations may be taken.

FIG. 4 shows an example of a method for measuring a reference sound pressure distribution waveform and a fluctuating sound pressure distribution waveform. In FIG. 4, the ultrasonic burst wave (Transmitted signal) emitted by the transmitting side transducer 10 and the reception acquired by three receiving side transducers selected from the first receiving side transducers 21 to 5 and the fifth receiving side transducer 25 are shown. Waveforms (Received signal, ch1 to ch3) are drawn. That is, the ultrasonic burst wave shows the voltage waveform applied to the transmitting side transducer 10, and the three receiving waveforms show the voltage waveforms of the three receiving side transducers that reached the opposite side of the transmitting side transducer 10 with a time delay. Shown. In FIG. 4, V1 to V3 show the amplitudes of the three received waveforms (ch1 to ch3) (in this example, V2> V1> V3).

When measuring the reference sound pressure distribution waveform and the fluctuating sound pressure distribution waveform, for example, the received waveform as shown in FIG. 4 is repeatedly acquired at a frequency of about several tens of Hz to 1 kHz. The voltage waveform of the received wave is observed with a delay of a certain time from the transmission of the ultrasonic burst wave. This time difference simply corresponds to the inner diameter of the pipe / the speed of sound, but since the distance is slightly longer for a wave traveling diagonally, a time difference corresponding to that is added. In signal processing, for example, a mode in which the sound pressure at the time obtained by adding the rise time of the received sensor waveform (primary delay of the sensor) to the time difference or the time difference is determined by the envelope detection by the Hilbert transform, and further, the envelope The instantaneous shift amount is determined depending on the mode in which the maximum value of the line is used. By repeating the above operation and taking the time average (smoothing) of the shift amount, the reference sound pressure distribution waveform and the fluctuating sound pressure distribution waveform are measured.

Further, the reference sound pressure distribution waveform held by the reference sound pressure distribution waveform holding unit 60 and the fluctuating sound pressure distribution waveform acquired by the fluctuating sound pressure distribution waveform acquisition unit 70 can be measured, for example, as follows. That is, the sound pressure distribution is represented by a Gaussian distribution, but since it is possible to approximate a quadratic function in the vicinity of the peak, the sound pressure distribution including the peak center position from at least three sound pressure measurement values. The waveform can be estimated. FIG. 5 shows a method of estimating the sound pressure distribution waveform by approximating (fitting) the three sound pressure measured values to a quadratic function.

The Gaussian distribution is expressed as follows when polynomial expansion is performed near the center value.

Therefore, the Gaussian distribution can be approximated by a parabola (quadratic function) near the center value. Since the quadratic function has three unknown coefficients (a ₁ + a ₂ x + a ₃ x ² ), the sound pressure distribution waveform is estimated by approximating (fitting) the three sound pressure measurement values to the quadratic function. Can be done.

On the other hand, if the asymmetry of the flow velocity distribution or the flight position spreads at an angle in the flow direction, the shape deviates from the symmetry shape like a pure parabola. Therefore, in the present embodiment, the portion deviating from the symmetry shape is corrected. Therefore, a higher-order polynomial function is adopted.

If there are more sound pressure measurements, a higher-order approximate solution can be used, so improvement in detection accuracy can be expected. For example, as in the present embodiment, if (2n + 1) n = 2 and 5 receiving side transducers are used, the quartic polynomy enables fitting in consideration of the asymmetry of the sound pressure distribution waveform, and the peak. It becomes possible to estimate the sound pressure distribution waveform including the center position with higher accuracy. The quartic polynomial is expressed, for example, as follows.

_{Further, as in the present embodiment, every combination (2n + 1} C ₃ ) for selecting three receiving side transducers from (2n + 1) (n is a natural number of 2 or more) is measured in the pipe 5. The sound pressure distribution waveform is acquired based on the ultrasonic pulses emitted by the transmitting side transducer 10 and incident on the above three receiving side transducers in a state where the flow velocity of the target fluid G is other than zero, and the sound for all the combinations is obtained. By averaging the pressure distribution waveform, the detection accuracy of the sound pressure distribution waveform can be improved. In particular, when the fluctuation of the moving amount of the ultrasonic pulse in the pipe 5 is large, the sound pressure distribution waveform in a wider range can be detected, so that the dynamic range can be improved.

As shown in FIG. 6, the flow rate calculation unit 80 has the center position of the reference sound pressure distribution waveform held by the reference sound pressure distribution waveform holding unit 60 and the fluctuating sound pressure distribution waveform acquired by the fluctuating sound pressure distribution waveform acquisition unit 70. The flow rate of the fluid G to be measured in the pipe 5 is calculated by obtaining the shift amount S which is the difference between the peak positions and integrating the shift amount S.

Let Q be the flow rate of the fluid G to be measured in the pipe 5, S be the shift amount which is the difference between the reference sound pressure distribution waveform and the fluctuating sound pressure distribution waveform, U be the flow velocity distribution of the fluid G to be measured in the pipe 5, and c be the sound velocity. , The following formulas hold. This assumes a case where the fluid G to be measured in the pipe 5 has a non-axisymmetric flow. In each of the following mathematical formulas, the coordinate system of the pipe 5 in the plane orthogonal to the pipe axis is x and y (the center of the pipe 5 is the origin), and the coordinate system of the pipe 5 in the pipe axis direction is z.

First, the flow rate Q is represented by the surface integral of the flow velocity distribution U.

Next, the shift amount S is represented by the line integral of the measured linear flow velocity, and the distribution of the shift amount S is integrated as follows.

Then, the flow rate Q is obtained by the line integral of the distribution of the shift amount S.

On the other hand, when the fluid G to be measured in the pipe 5 has an axisymmetric flow, in addition to the above, when the average flow velocity of the fluid G to be measured in the pipe 5 is v and the inner diameter of the pipe 5 is D, the following items are obtained. The formula holds.

First, the shift amount S is obtained by integrating the flow velocity distribution U in the pipe 5.

Next, the average flow velocity v is expressed by the following equation.

Then, the flow rate Q is expressed by the following equation.
^{Q = v · (πD 2/} 4)

FIG. 7 shows the distribution of the shift amount S on the xy plane in the pipe axis orthogonal cross section of the pipe 5. As shown in FIG. 7, since the shift amount S varies on the xy plane in the pipe axis orthogonal cross section of the pipe 5, for example, the above-mentioned averaging method is considered to be useful.

FIG. 8 shows a configuration in which the transmitting side transducer 10 and the receiving side transducer 20 are arranged so as to be spread on the inner surface of the pipe 5. That is, the shift amount S and thus the flow rate obtained by a plurality of sets of the transmitting side transducer and the receiving side transducer provided at the same tube axial position with different circumferential positions may be averaged. FIG. 9 shows an example (numerical calculation result and experimental result) of the shift amount S obtained by three sets of the transmitting side transducer and the receiving side transducer provided at the same tube axis direction position with different circumferential positions. ing.

As described above, according to the present embodiment, the reference sound pressure distribution waveform holding unit 60 emits the transmitting side transducer 10 in a state where the flow velocity of the measurement target fluid G in the pipe 5 is zero, and the first receiving side transducer 21 The reference sound pressure distribution waveform based on the ultrasonic pulse incident on the fifth receiving side transducer 25 is held, and the variable sound pressure distribution waveform acquisition unit 70 is in a state where the flow velocity of the measurement target fluid G in the pipe 5 is other than zero. The transmitting side transducer 10 emits and acquires the fluctuating sound pressure distribution waveform based on the ultrasonic pulse incident on the first receiving side transducers 21 to 5 and the fifth receiving side transducer 25, and the flow rate calculation unit 80 acquires the reference sound pressure distribution. The flow rate of the measurement target fluid G in the pipe 5 is calculated by obtaining the shift amount S which is the difference between the waveform and the fluctuating sound pressure distribution waveform and integrating the shift amount S. This makes it possible to accurately measure the flow rate of the fluid G to be measured with a simple configuration.

In the above embodiment, the case where the transmitting side transducer 10 and the receiving side transducer 20 are installed on the inner surface of the pipe 5 has been described as an example, but the so-called so-called that the transmitting side transducer 10 and the receiving side transducer 20 are installed on the outer surface of the pipe 5 A clamp-on method is also applicable. However, the amount of movement of the ultrasonic pulse in the pipe 5 depends on the size (diameter) of the pipe 5, but is usually very small (for example, 0.1 mm to several mm). It is better to install it on the inner surface of the pipe 5. This is because when the receiving side transducer 20 is installed on the outer surface of the pipe 5 by the clamp-on method, the amount of refraction of the beam due to the presence of the wall surface of the pipe 5 becomes about the same as the amount of movement of the ultrasonic pulse, and the receiving side transducer 20 This is because the detection accuracy of is lowered. Further, since the distance between the adjacent first receiving side transducers 21 to 5 is very small, for example, another receiving side transducer adjacent to the receiving side transducer detects an ultrasonic pulse to be detected by one receiving side transducer. This is because an error such as "doing" is likely to occur. From the above, when the diameter of the pipe 5 is large and the wall surface is thin, the receiving side transducer 20 can be installed on the outer surface of the pipe 5 by the clamp-on method, but in other cases, the receiving side transducer 20 is piped. It is preferable to install it on the inner surface of 5.

The ultrasonic flow meter 1 of the present embodiment can be used, for example, for mounting on a muffler of a vehicle and measuring the flow rate of exhaust gas in the muffler.

1 Ultrasonic flowmeter 5 Piping 10 Transmitter side transducer (transmitter)
20 Receiving side transducer (receiver)
21 First Receiving Transducer 22 Second Receiving Transducer 23 Third Receiving Transducer 24 Fourth Receiving Transducer 25 Fifth Receiving Transducer 30 Signal Oscillator 40 Detection Circuit 50 Data Acquisition Circuit 60 Reference Sound Pressure Distribution Waveform holding unit 70 Fluctuation sound pressure distribution waveform acquisition unit 80 Flow rate calculation unit G Measurement target fluid S Shift amount

Claims (4)

A transmitter that is installed in the piping through which the fluid to be measured flows and emits ultrasonic pulses,
(2n + 1) receivers (n is a natural number of 2 or more) that are installed in the pipe so as to face the transmitter and that the ultrasonic pulse is incident on, and
A reference sound pressure distribution that holds a reference sound pressure distribution waveform based on the ultrasonic pulses emitted from the transmitter and incident on the (2n + 1) receivers in a state where the flow velocity of the fluid to be measured in the pipe is zero. Waveform holder and
A fluctuating sound pressure that acquires a fluctuating sound pressure distribution waveform based on the ultrasonic pulses that the transmitter emits and is incident on the (2n + 1) receivers when the flow velocity of the fluid to be measured in the pipe is other than zero. Distribution waveform acquisition section and
A flow rate calculation unit that calculates the flow rate of the fluid to be measured in the pipe by obtaining the shift amount that is the difference between the reference sound pressure distribution waveform and the fluctuating sound pressure distribution waveform and integrating the shift amount.
Have a,
The reference sound pressure distribution waveform holding unit is said to be in a state where the flow velocity of the fluid to be measured in the pipe is zero for each combination for selecting three receivers from the (2n + 1) receivers. The reference sound pressure distribution waveform is acquired based on the ultrasonic pulses emitted by the transmitter and incident on the three receivers, and the reference sound pressure distribution waveforms for all the combinations are averaged.
An ultrasonic flow rate measuring device characterized by this. Before SL varies sound pressure distribution waveform acquiring unit, the (2n + 1) pieces of all for each combination for selecting three receiving terminal from the receiving terminal, the flow velocity of the measurement object fluid in the pipe is non-zero state Acquires the fluctuating sound pressure distribution waveform based on the ultrasonic pulses emitted from the transmitter and incident on the three receivers, and averages the fluctuating sound pressure distribution waveform for all the combinations. ,
The ultrasonic flow rate measuring device according to claim 1. The transmitter and the receiver are installed on the inner surface of the pipe.
The ultrasonic flow rate measuring device according to claim 1 or 2, wherein the ultrasonic flow rate measuring device is characterized. A transmitter that is installed in the piping through which the fluid to be measured flows and emits ultrasonic pulses,
(2n + 1) receivers (n is a natural number of 2 or more) that are installed in the pipe so as to face the transmitter and that the ultrasonic pulse is incident on, and
It is an ultrasonic flow rate measuring method by an ultrasonic flow rate measuring device having
A reference sound pressure distribution that holds a reference sound pressure distribution waveform based on the ultrasonic pulses emitted from the transmitter and incident on the (2n + 1) receivers in a state where the flow velocity of the fluid to be measured in the pipe is zero. Waveform retention step and
A fluctuating sound pressure that acquires a fluctuating sound pressure distribution waveform based on the ultrasonic pulses that the transmitter emits and is incident on the (2n + 1) receivers when the flow velocity of the fluid to be measured in the pipe is other than zero. Distribution waveform acquisition step and
A flow rate calculation step for calculating the flow rate of the fluid to be measured in the pipe by obtaining a shift amount which is a difference between the reference sound pressure distribution waveform and the fluctuating sound pressure distribution waveform and integrating the shift amount.
Have a,
In the reference sound pressure distribution waveform holding step, the flow velocity of the fluid to be measured in the pipe is zero for each combination for selecting three receivers from the (2n + 1) receivers. The reference sound pressure distribution waveform is acquired based on the ultrasonic pulses emitted by the transmitter and incident on the three receivers, and the reference sound pressure distribution waveforms for all the combinations are averaged.
An ultrasonic flow rate measuring method characterized by this.

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