JP2019090777A - Ultrasonic flow rate measurement device and ultrasonic flow rate measurement method - Google Patents

Abstract

To obtain an ultrasonic flow rate measurement device and an ultrasonic flow rate measurement method each of which enables a flow rate of a measurement object fluid to be correctly measured with simple configuration.SOLUTION: A reference sound pressure distribution waveform holding unit (60) holds a reference sound pressure distribution waveform that is on the basis of an ultrasonic sound wave pulse which a transmission slave (10) emits and is incident on at least three reception slaves (20) while a flow velocity of a measurement object fluid (G) in piping (5) is zero. A fluctuation sound pressure waveform acquisition unit (70) acquire a fluctuation sound pressure distribution waveform that is on the basis of the ultrasonic sound wave which the transmission slave (10) emits and is incident on at least the three reception slaves (20) while the flow velocity of the measurement object fluid (G) in the piping (5) is other than zero. A flow rate calculation unit (80) obtains an amount of shift (S) being a differential between the reference sound pressure distribution waveform and the fluctuation sound pressure distribution waveform, integrates the amount of the shift (S), thereby calculating a flow rate of the measurement object fluid (G) in the piping (5).SELECTED DRAWING: Figure 3

Description

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

  In the conventional general ultrasonic flowmeter, an ultrasonic pulse is made to be incident in the flow direction of the fluid in the pipe, and the ultrasonic pulse travels in the pipe at the speed obtained by adding the speed of sound and the flow velocity. The flow velocity is determined, and the average flow velocity is multiplied by the cross-sectional area of the pipe to obtain an average flow rate. However, the above-mentioned ultrasonic flowmeter only obtains an average flow velocity and an average flow rate 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 piping assumes an ideal flow field (assumed), and it is necessary to prepare a measurement environment in line with the assumption, and various setting conditions (constraints) are imposed. Will be In addition, 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 the calibration and the like. Furthermore, in small diameter tubes, measurement is very difficult, and since the axial symmetry of the flow field is assumed, the stability and reliability of the measured values can not be guaranteed in the wake of a bent tube or the like.

  On the other hand, Patent Document 1 discloses a flow velocity distribution measuring device that measures the flow velocity distribution of a gaseous fluid flowing in a fluid piping using ultrasonic pulses. In this flow velocity distribution measuring device, ultrasonic pulses are emitted from the transmission transducer installed on the pipe wall of the fluid pipe to the fluid to be measured flowing in the fluid pipe, and are two-dimensionally installed on the opposing pipe wall in the fluid pipe. Ultrasonic pulses are detected by a plurality of receiving transducers. The displacement amount of the ultrasonic pulse in the tube axis direction is detected from detection signals of a plurality of receiving transducers arranged in the tube axis direction. More specifically, two measurement lines slightly different in opening angle are set, and the flow velocity at a predetermined position is determined from the difference between the displacement amount detected for each measurement line and the flight time.

WO 2008/004560 pamphlet

  However, according to Patent Document 1, after a plurality of receiving transducers detect an ultrasonic pulse, the flow velocity distribution in the direction orthogonal to the flow direction (the axis of the fluid pipe) based on the displacement of the ultrasonic pulse in the tube axis direction. The flow velocity distribution of the orthogonal cross section is calculated, and the flow rate of the gaseous fluid flowing in the fluid piping is calculated based on the flow velocity distribution. Therefore, the calculation becomes complicated and the capacity is increased, and 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 Flow rate may not be accurately measured.

  The present invention is made based on the above-mentioned problem awareness, and an object of the present invention is to obtain an ultrasonic flow measurement device and an ultrasonic flow measurement method capable of accurately measuring the flow of a fluid to be measured with a simple configuration. I assume.

  The ultrasonic flow rate measuring apparatus according to the present embodiment includes a transmitter which is installed in a pipe through which a fluid to be measured flows and which emits an ultrasonic pulse, and which is installed in the pipe so as to face the transmitter. And a reference sound based on the ultrasonic pulse emitted from the transmitter and entering the at least three receivers when the flow velocity of the fluid to be measured in the pipe is zero. A reference sound pressure distribution waveform holding unit that holds a pressure distribution waveform, and the ultrasonic waves emitted by the transmitter and entering the at least three receivers in a state where the flow velocity of the fluid to be measured in the pipe is other than zero. A variation sound pressure distribution waveform acquisition unit that obtains a variation sound pressure distribution waveform based on pulses, and a shift amount that is a difference between the reference sound pressure distribution waveform and the variation sound pressure distribution waveform, and the shift amount By integrating, it is characterized by having a flow rate calculation unit for calculating the flow rate of the measurement target fluid in the pipe.

  The (2 n + 1) (n is a natural number of 2 or more) receivers are installed in the receiver, and the fluctuation sound pressure distribution waveform acquiring unit selects three receivers from the (2 n + 1) receivers. The variation sound pressure is generated based on the ultrasonic pulse emitted from the transmitter and incident on the three receivers in a state where the flow velocity of the fluid to be measured in the piping is other than zero for every combination for all the combinations. A distribution waveform can be obtained, and the fluctuating sound pressure distribution waveform for every combination can be averaged.

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

  In the ultrasonic flow rate measurement method of the present embodiment, a transmitter that is installed in a pipe through which a fluid to be measured flows and that emits ultrasonic pulses, and is installed on the pipe so as to face the transmitter, and the ultrasonic pulse An ultrasonic flow rate measuring method using an ultrasonic flow rate measuring device having at least three receivers on which the light is incident, wherein the transmitter is emitted with the flow velocity of the fluid to be measured in the pipe being zero. A reference sound pressure distribution waveform holding step of holding a reference sound pressure distribution waveform based on the ultrasonic pulse incident on at least three receivers; and the transmitter in a state where the flow velocity of the fluid to be measured in the pipe is other than zero. A variable sound pressure distribution waveform acquiring step of acquiring a variable sound pressure distribution waveform based on the ultrasonic pulse emitted and incident on the at least three receivers; the reference sound pressure Calculating a shift amount which is a difference between the cloth waveform and the fluctuating sound pressure distribution waveform, and integrating the shift amount to calculate a flow rate of the fluid to be measured in the pipe; And

  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 a fluid to be measured with a simple configuration.

It is a figure which shows the state which installed the transmission side transducer and receiving side transducer of the ultrasonic flow measurement apparatus of this embodiment in piping. It is a figure which shows a mode that the transmission side transducer radiate | emits an ultrasonic pulse in FIG. 1, and an ultrasonic pulse injects into a receiving side transducer. It is a functional block diagram which shows the internal structure of an ultrasonic flow rate measurement apparatus. It is a figure which shows an example of the measurement method of a reference | standard sound pressure distribution waveform and a fluctuation | variation sound pressure distribution waveform. It is a figure which shows the method of estimating sound pressure distribution by approximating (fitting) three sound pressure measurement values to a quadratic function. It is a figure which shows a mode that a flow volume calculating part calculates the flow volume of the measurement object fluid in piping by integrating the shift amount which is a difference of a reference sound pressure distribution waveform and a fluctuation sound pressure distribution waveform. It is a figure which shows distribution of the shift amount on xy plane in the pipe-axis orthogonal cross section of piping. It is a figure which shows the structure arrange | positioned so that the transmission side transducer and the receiving side transducer could be spread on the inner surface of piping. It is a figure which shows an example of the shift amount obtained by three sets of transmitting side transducers and receiving side transducers which varied the circumferential direction position and were provided in the same tube axial direction position.

  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 measurement device 1 is mounted on, for example, a muffler of a vehicle and used to measure the flow rate of exhaust gas in the muffler. In addition, the ultrasonic flow measurement device 1 may be mounted on a pipeline of a factory and used to measure the flow rate of gas in the pipeline, or liquefied from a LNG (Liquefied Natural Gas) tanker to a base or the like. When flowing natural gas, it may be used to measure the flow rate of the liquefied natural gas. Furthermore, the ultrasonic flow rate measuring device 1 may be mounted on a marine engine and used to measure the flow rate of exhaust gas in the marine engine. Moreover, the ultrasonic flow measurement apparatus 1 can also be applied to flow measurement of not only gas such as gas but also liquid. That is, the measuring object of the ultrasonic flow rate measuring apparatus 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 apparatus 1 is a transmission side transducer (transmitter) installed on an inner surface of a pipe 5 (for example, a muffler of a vehicle) through which a fluid to be measured G (for example, exhaust gas) flows. It has ten. The transmission side transducer 10 emits an ultrasonic pulse having a spread angle to a certain extent centered on the direction orthogonal to the tube axis, in a direction (right direction in the drawing) orthogonal to the direction of the tube axis of the pipe 5.

  As shown in FIGS. 1 and 2, the ultrasonic flow measurement device 1 has a receiving transducer (receiver) 20 disposed on the inner surface of the pipe 5 so as to face the transmitting transducer 10. The receiving-side transducer 20 is a first receiving-side transducer 21 facing the transmitting-side transducer 10 in a direction perpendicular to the tube axis (left-right direction in the figure), a second receiving-side located upstream of the first receiving-side transducer 21 A side transducer 22 and a third receiving transducer 23, and a fourth receiving transducer 24 and a fifth receiving transducer 25 located downstream of the first receiving transducer 21 are included. The ultrasonic pulse emitted from the transmitting transducer 10 is incident on the first receiving transducer 21 to the fifth receiving transducer 25.

  The transmitting transducer 10 and the first receiving transducer 21 to the fifth receiving transducer 25 can be composed of compatible transducers of the same standard. The transducer has a function of emitting and receiving an ultrasonic pulse.

  Although the case where five of the first reception transducer 21 to the fifth reception transducer 25 are installed as the reception transducer 20 has been described as an example here, the number of reception transducers 20 is limited to this. It is not necessary to make various design changes. That is, at least three receiving transducers 20 may be provided, and preferably, (2n + 1) (n is a natural number of 2 or more) may be provided. Also, the number of receiving transducers disposed upstream and downstream of the first receiving transducer 21 may be different (for example, the former may be smaller than the latter).

  As shown in FIG. 3, the ultrasonic flow rate measuring apparatus 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 calculating unit 80.

  The signal oscillator 30 outputs an oscillation signal supplied to the transmission 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 may be a sharp triangular pulse signal, and the repetition cycle of the pulse signal may 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 transducer 20 as a synchronization signal.

  The detection circuit 40 is connected to the output ends of the first reception transducer 21 to the fifth reception transducer 25. Although not shown, the detection circuit 40 is a signal amplifier for amplifying a detection signal having a magnitude corresponding to the intensity of incident ultrasonic waves output from the first reception transducer 21 to the fifth reception transducer 25. And a peak detection circuit for reading the peak value of the output of the signal amplifier. The detection circuit 40 simultaneously detects the outputs of the first reception transducer 21 to the fifth reception transducer 25 in order to obtain the flow rate at a high sampling rate. The detection circuit 40 sets pulse reception timing in accordance with the timing signal supplied from the signal oscillator 30.

  The data acquisition circuit 50 is configured by, for example, a digital multiplexer that collects all the outputs (peak values) of the first reception transducer 21 to the fifth reception transducer 25 read by the detection circuit 40.

  In the reference sound pressure distribution waveform holding unit 60, the transmission side transducer 10 emits light in a state where the flow velocity of the fluid G to be measured in the piping 5 is zero, and enters the first reception side transducer 21 to the fifth reception side transducer 25. The reference sound pressure distribution waveform based on the ultrasonic pulse is held. The reference sound pressure distribution waveform may be previously held in the reference sound pressure distribution waveform holding unit 60 in advance by default when the ultrasonic flow measurement device 1 is manufactured, or may be measured during maintenance of the ultrasonic flow measurement device 1 The reference sound pressure distribution waveform holding unit 60 may be held. 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, to select three reception transducers from the first reception transducer 21 to the fifth reception transducer 25 In all combinations of the above, the reference sound pressure distribution based on the ultrasonic pulses emitted from the transmitting side transducer 10 and incident on the three receiving side transducers in a state where the flow velocity of the fluid G to be measured in the piping 5 is other than zero. A waveform may be acquired, and the reference sound pressure distribution waveform for each of all the combinations may be averaged. There are ten combinations of three receiving transducers:
(1) first receiving transducer 21, second receiving transducer 22, third receiving transducer 23
(2) The first receiving transducer 21, the second receiving transducer 22, the fourth receiving transducer 24
(3) first receiving transducer 21, second receiving transducer 22, fifth receiving transducer 25
(4) The first receiving transducer 21, the third receiving transducer 23, the fourth receiving transducer 24
(5) The first receiving transducer 21, the third receiving transducer 23, the fifth receiving transducer 25
(6) The first receiving transducer 21, the fourth receiving transducer 24, the fifth receiving transducer 25
(7) Second receiving transducer 22, third receiving transducer 23, fourth receiving transducer 24
(8) Second receiving transducer 22, third receiving transducer 23, fifth receiving transducer 25
(9) Second receiving transducer 22, fourth receiving transducer 24, fifth receiving transducer 25
(10) Third receiving transducer 23, fourth receiving transducer 24, fifth receiving transducer 25

  Depending on the combination of the three receiver transducers selected, the output of some or all of the receiver transducers may not be available. In that case, assuming that the reference sound pressure distribution waveform of the combination is not present, the average of the reference sound pressure distribution waveforms of other combinations may be taken.

  In the fluctuating sound pressure distribution waveform acquisition unit 70, the transmission side transducer 10 emits when the flow velocity of the fluid G to be measured in the pipe 5 is other than zero, and enters the first reception side transducer 21 to the fifth reception side transducer 25. The fluctuating sound pressure distribution waveform based on the ultrasonic pulse is acquired. 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 keeps acquiring the fluctuating sound pressure distribution waveform that changes from moment to moment.

  The fluctuating sound pressure distribution waveform acquisition unit 70 measures the fluid G to be measured in the pipe 5 for every combination for selecting three receiving transducers from the first receiving transducer 21 to the fifth receiving transducer 25. The fluctuating sound pressure distribution waveform is acquired based on the ultrasonic pulses emitted from the transmitting transducer 10 and incident to the three receiving transducers in a state where the flow velocity of the fluid is not zero, The distribution waveform may be averaged. The combination of the three receiving transducers is as described above.

  Depending on the combination of the three receiver transducers selected, the output of some or all of the receiver transducers may not be available. In such a case, it is possible to take an average of other combinations of fluctuating sound pressure distribution waveforms, assuming that there is no fluctuating sound pressure distribution waveform of the combination.

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

  In the measurement of the reference sound pressure distribution waveform and the fluctuating sound pressure distribution waveform, for example, a reception waveform as shown in FIG. 4 is repeatedly acquired at a frequency of about several tens Hz to 1 kHz. The voltage waveform of the received wave is observed with a predetermined time delay from the transmission of the ultrasonic burst wave. This time difference simply corresponds to the tube inner diameter / sound velocity, but since the distance is slightly longer for waves traveling obliquely, a time difference corresponding to that is added. In the signal processing, for example, a mode in which three sound pressures at a time obtained by adding the rise time (first delay of the sensor) of the reception sensor waveform to the time difference or the time difference are determined by envelope detection by Hilbert transform, and further The shift amount of the moment is determined by an aspect using the maximum value of the line or the like. The reference sound pressure distribution waveform and the fluctuating sound pressure distribution waveform are measured by repeating the above operation and taking time average (smoothing) of the shift amount.

  Also, 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 acquiring unit 70 can be measured, for example, as follows. That is, although the sound pressure distribution is represented by a Gaussian distribution, since it is possible to approximate to 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 a sound pressure distribution waveform by approximating (fitting) three sound pressure measurement values to a quadratic function.

The Gaussian distribution is expressed as follows when it is subjected to polynomial expansion near the center value.

Therefore, it is possible to approximate a Gaussian distribution with a parabola (quadric function) in the vicinity of the central value. Since the quadratic function has three unknown coefficients (a ₁ + a ₂ x + a ₃ x ² ), estimate the sound pressure distribution waveform by fitting (fitting) the three measured sound pressure values to the quadratic function Can.

  On the other hand, if the asymmetry of the flow velocity distribution or the flight position spreads at an angle in the flow direction, it deviates from a symmetrical shape like a pure parabola, so in this embodiment, the part deviated from the symmetrical shape is corrected. In order to use higher order polynomial functions.

Since higher order approximate solutions can be used if there are more sound pressure measurement values, improvement in detection accuracy can be expected. For example, if five receiving transducers are used as (2n + 1) n = 2 as in the present embodiment, the fourth-order polynomial 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 fourth order polynomial is expressed, for example, as follows.

Furthermore, as in this embodiment, (2n + 1) (n is a natural number of 2 or more) for each of all the combinations to select the three receiving side transducers from the _{(2n + 1 C 3),} measured in the pipe 5 A sound pressure distribution waveform is acquired based on the ultrasonic pulse emitted from the transmitting side transducer 10 and incident on the three receiving side transducers in a state where the flow velocity of the target fluid G is other than zero, and the sound for every combination The detection accuracy of the sound pressure distribution waveform can be improved by averaging the pressure distribution waveform. In particular, when the variation of the movement 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 calculating unit 80 is configured such that the center position of the reference sound pressure distribution waveform held by the reference sound pressure distribution waveform holding unit 60 and the fluctuation sound pressure distribution waveform acquired by the fluctuation sound pressure distribution waveform acquiring unit 70. The flow rate of the fluid G to be measured in the pipe 5 is calculated by calculating the shift amount S which is the difference between peak positions and integrating the shift amount S.

  Assuming that the flow rate of the fluid G to be measured in the pipe 5 is Q, the shift amount that is the difference between the reference sound pressure distribution waveform and the fluctuating sound pressure distribution waveform is S, the flow velocity distribution of the fluid G to be measured in the pipe 5 is U, and the speed of sound is c. , Each following formula holds. This assumes that the fluid G to be measured in the pipe 5 has a non-axisymmetric flow. In the following formulas, the coordinate system in the plane orthogonal to the pipe axis of the pipe 5 is x, 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 area fraction 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 line integration of the distribution of the shift amount S.

  On the other hand, when the fluid G to be measured in the piping 5 has an axisymmetric flow, in addition to the above, when the average flow velocity of the fluid G to be measured in the piping 5 is v and the inside diameter of the piping 5 is D, 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.

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

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

  As described above, according to the present embodiment, the reference sound pressure distribution waveform holding unit 60 emits the transmission side transducer 10 when the flow velocity of the fluid G to be measured in the pipe 5 is zero, and the first reception side transducer 21 The reference sound pressure distribution waveform based on the ultrasonic pulse incident on the fifth reception-side transducer 25 is held, and the fluctuating sound pressure distribution waveform acquisition unit 70 determines that the flow velocity of the fluid G to be measured in the pipe 5 is other than zero. The variation sound pressure distribution waveform based on the ultrasonic pulse emitted from the transmission side transducer 10 and incident on the first reception side transducer 21 to the fifth reception side transducer 25 is acquired, and the flow rate operation unit 80 generates the reference sound pressure distribution. A shift amount S which is a difference between the waveform and the fluctuating sound pressure distribution waveform is determined, and the shift amount S is integrated to calculate the flow rate of the fluid G to be measured in the pipe 5 . This makes it possible to accurately measure the flow rate of the fluid G to be measured with a simple configuration.

  Although the above embodiment exemplifies the case where the transmitting transducer 10 and the receiving transducer 20 are installed on the inner surface of the pipe 5, the transmitting transducer 10 and the receiving transducer 20 are installed on the outer surface of the pipe 5. The clamp on method is also applicable. However, although the amount of movement of the ultrasonic pulse in the pipe 5 depends on the size (diameter) of the pipe 5, it is usually very small (for example, 0.1 mm to several mm). It is better to install on the inner surface of the pipe 5. This is because, when the receiving transducer 20 is installed on the outer surface of the pipe 5 in the clamp-on method, the amount of refraction of the beam due to the presence of the wall of the pipe 5 becomes approximately the same as the displacement of the ultrasonic pulse. This is because the detection accuracy of Furthermore, since the distance between the adjacent first reception transducers 21 to the fifth reception transducers 25 is very small, for example, another reception transducer adjacent to an ultrasonic pulse to be detected by one reception transducer detects It is because it becomes easy to generate an error such as As described above, when the diameter of the pipe 5 is large and the wall surface is thin, it is possible to install the receiving side transducer 20 on the outer surface of the pipe 5 by clamp-on method, but in other cases, the receiving side transducer 20 is piped It is preferable to install in the inner surface of 5.

  The ultrasonic flowmeter 1 of the present embodiment can be mounted, for example, on a muffler of a vehicle and used to measure the flow rate of exhaust gas in the muffler.

1 Ultrasonic Flowmeter 5 Piping 10 Transmitter Transducer (Transmitter)
20 Receiver 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 60 reference sound pressure distribution Waveform holding unit 70 Fluctuating sound pressure distribution waveform acquiring unit 80 Flow rate calculating unit G Measurement target fluid S Shift amount

Claims (4)

A transmitter which is installed in a pipe through which a fluid to be measured flows and which emits an ultrasonic pulse;
At least three receivers disposed in the pipe opposite to the transmitter and on which the ultrasonic pulse is incident;
Reference sound pressure distribution waveform that holds a reference sound pressure distribution waveform based on the ultrasonic pulses emitted from the transmitter and incident on the at least three receivers when the flow velocity of the fluid to be measured in the pipe is zero A holding unit,
Fluctuating sound pressure distribution for acquiring fluctuating sound pressure distribution waveforms based on the ultrasonic pulses emitted from the transmitter and incident on the at least three receivers in a state where the flow velocity of the fluid to be measured in the piping is other than zero A waveform acquisition unit,
A flow rate calculating unit which calculates a flow rate of the fluid to be measured in the pipe by calculating 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;
An ultrasonic flow measuring device characterized by having. The (2 n + 1) (where n is a natural number of 2 or more) receivers are installed.
The fluctuating sound pressure distribution waveform acquiring unit is configured such that the flow velocity of the fluid to be measured in the pipe is other than zero for every combination for selecting three receivers from the (2n + 1) receivers. Acquiring the fluctuating sound pressure distribution waveform based on the ultrasonic pulse emitted from the transmitter and incident on the three receptive members, and averaging the fluctuating sound pressure distribution waveform for all the combinations;
The ultrasonic flow measurement device according to claim 1, characterized in that: The transmitter and the receiver are disposed on the inner surface of the pipe,
The ultrasonic flow measurement device according to claim 1 or 2, characterized in that: A transmitter which is installed in a pipe through which a fluid to be measured flows and which emits an ultrasonic pulse;
At least three receivers disposed in the pipe opposite to the transmitter and on which the ultrasonic pulse is incident;
A method of ultrasonic flow measurement with an ultrasonic flow measurement device having
Reference sound pressure distribution waveform that holds a reference sound pressure distribution waveform based on the ultrasonic pulses emitted from the transmitter and incident on the at least three receivers when the flow velocity of the fluid to be measured in the pipe is zero Holding step,
Fluctuating sound pressure distribution for acquiring fluctuating sound pressure distribution waveforms based on the ultrasonic pulses emitted from the transmitter and incident on the at least three receivers in a state where the flow velocity of the fluid to be measured in the piping is other than zero Waveform acquisition step,
A flow rate calculating step of calculating a flow rate of the fluid to be measured in the pipe by calculating 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;
An ultrasonic flow rate measuring method characterized by having.

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