JP2016038264A - External ultrasonic flowmeter for gas and gas flow rate measuring method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an external ultrasonic flowmeter for gas, which can measure a flow rate of a gas flowing in a pipe even in a state to be externally mounted on the pipe.SOLUTION: An external ultrasonic flowmeter 1 for gas, which is externally mounted on a pipe 40 so as to measure a flow rate of a gas flowing in the pipe 40 by using an ultrasonic wave, includes: a transmission section 11 which is arranged on the external of the pipe 40 and to which voltage is applied so as to generate the ultrasonic wave corresponding to the magnitude of the voltage toward the interior of the pipe 40; a reception section 22 which is arranged on the external of the pipe 40 and which receives the ultrasonic wave which has been generated by the transmission section 11; and an application section 31 for applying the sine-wave voltage to the transmission section 11.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an external ultrasonic flowmeter for gas and a gas flow measurement method for measuring the flow rate of a gas externally attached to a pipe and flowing in the pipe using ultrasonic waves.

  2. Description of the Related Art Conventionally, an ultrasonic flowmeter that measures the flow rate of a liquid or gas flowing in a pipe using ultrasonic waves is known (see, for example, Patent Documents 1 and 2). Patent Document 1 discloses an ultrasonic flowmeter that is externally attached to a pipe and measures the flow rate of a liquid flowing through the pipe using ultrasonic waves. Patent Document 2 discloses an ultrasonic flowmeter that is attached in a pipe and measures the flow rate of the gas flowing in the pipe using ultrasonic waves.

JP 2011-232297 A Japanese Patent Laid-Open No. 9-43017

  Here, when it is desired to measure the flow rate of the fluid flowing in the pipe after laying the pipe, the ultrasonic flowmeter is not installed in the pipe by cutting or processing the pipe. There is a desire to externally attach a sonic flow meter to the pipe and measure the flow rate of the fluid. And when the said fluid is a liquid, an ultrasonic flowmeter can be attached externally to piping, and the flow volume of the liquid which flows through the said piping can be measured.

  However, the conventional ultrasonic flowmeter has a problem that it is difficult to measure the flow rate of the gas flowing in the pipe while being externally attached to the pipe.

  In other words, the difference in acoustic impedance between a pipe (for example, metal) and a liquid (for example, water) is not so large, but a gas (for example, air) has a very small acoustic impedance compared to the pipe or liquid, so that an ultrasonic wave Difficult to communicate. Specifically, the difference in acoustic impedance between metal and water is about one digit, whereas the difference between acoustic impedance in metal and air is as much as four digits. Then, between two substances having greatly different acoustic impedance values, the ultrasonic waves are reflected at the interface between the substances, and the ultrasonic waves are not easily transmitted.

  For this reason, when measuring the flow rate of the liquid flowing in the pipe as in Patent Document 1, even if an ultrasonic flow meter is externally attached to the pipe, the liquid is not obstructed by the pipe. The flow rate can be measured. However, even if an ultrasonic flowmeter is attached to a pipe to measure the gas flowing in the pipe, most of the ultrasonic waves generated from the ultrasonic flowmeter are reflected by the inner surface of the pipe and propagate through the pipe. However, it does not propagate in the gas. For this reason, when measuring the flow rate of the gas flowing in the pipe as in Patent Document 2, the ultrasonic wave generated from the ultrasonic flowmeter is propagated through the gas without being disturbed by the pipe. It is necessary to install an ultrasonic flow meter in the pipe.

  As described above, in the conventional ultrasonic flowmeter, even if an attempt is made to measure the gas flowing in the pipe while being externally attached to the pipe, the ultrasonic wave does not propagate into the gas. There is a problem that it is difficult to measure.

  The present invention has been made to solve the above problems, and an external gas ultrasonic flowmeter capable of measuring the flow rate of the gas flowing in the pipe even when the pipe is externally attached, and An object is to provide a gas flow rate measuring method.

  To achieve the above object, an external ultrasonic flowmeter for gas according to one aspect of the present invention is for a gas that is externally attached to a pipe and measures the flow rate of the gas flowing in the pipe using ultrasonic waves. An external ultrasonic flowmeter, which is disposed outside the pipe and generates an ultrasonic wave corresponding to the magnitude of the voltage toward the inside of the pipe when a voltage is applied And a receiving unit that is disposed outside the pipe and that receives ultrasonic waves generated by the transmitting unit, and an application unit that applies a sinusoidal voltage to the transmitting unit.

  According to this, in the external ultrasonic flow meter for gas, a sine wave voltage is applied to the transmitter disposed outside the pipe to generate ultrasonic waves toward the inside of the pipe, The flow rate of the gas flowing through the pipe is measured by receiving the ultrasonic waves at the receiving unit arranged outside. Here, as a result of diligent research and experiments, the inventors of the present application have found that the ultrasonic wave generated by applying the voltage of the sine wave is compared with the ultrasonic wave generated by applying the voltage of the conventional pulse wave. It was found that it propagates well in the gas flowing inside. For this reason, in an external ultrasonic flowmeter for gas, by applying a sine wave voltage and generating ultrasonic waves, the flow rate of the gas flowing in the pipe is measured even when externally attached to the pipe. be able to.

  The transmitter may generate the ultrasonic waves such that an integral multiple of a half wavelength is equal to the thickness of the pipe.

  Here, as a result of diligent research and experiments, the inventors of the present application propagated better in the gas flowing in the pipe by using an ultrasonic wave whose wavelength is adjusted so that an integral multiple of a half wavelength is equal to the thickness of the pipe. I found out. For this reason, in the external ultrasonic flowmeter for gas, by generating an ultrasonic wave in which an integral multiple of a half wavelength is equal to the thickness of the pipe, the inside of the pipe can be The flow rate of the flowing gas can be measured.

  In addition, the transmission unit may generate the ultrasonic wave in a direction perpendicular to the inner surface of the pipe as viewed from the direction in which the gas flows.

  Here, as a result of intensive studies and experiments, the inventors of the present application have found that the ultrasonic waves are well propagated in the gas flowing in the pipe when the ultrasonic waves are input perpendicularly to the inner surface of the pipe. For this reason, in the external ultrasonic flowmeter for gas, the ultrasonic wave is generated in the direction perpendicular to the inner surface of the pipe when viewed from the direction of gas flow, so that even in the state of being externally attached to the pipe, The flow rate of the gas flowing in the pipe can be measured.

  The receiving unit may receive the ultrasonic wave propagated through the pipe and the ultrasonic wave propagated through the gas at different times among the ultrasonic waves generated by the transmitting unit.

  According to this, in the external ultrasonic flow meter for gas, the ultrasonic noise propagated through the pipe is received temporally by receiving the ultrasonic wave propagated through the pipe and the ultrasonic wave propagated through the gas at different times. Can be separated.

  In addition, the receiving unit directly receives the ultrasonic wave propagated through the pipe and then receives the ultrasonic wave propagated through the pipe, and then propagates through the pipe to discontinuous part of the pipe. It may be arranged at a position where it can receive the ultrasonic waves reflected by.

  According to this, in the external ultrasonic flowmeter for gas, after receiving the ultrasonic wave propagated through the pipe directly, the ultrasonic wave propagated through the gas is received, and then propagated through the pipe to discontinuous part of the pipe By disposing the receiving unit at a position where the ultrasonic waves reflected at can be received, the ultrasonic noise propagated or reflected on the pipe can be temporally separated.

  Furthermore, you may decide to provide the control part which measures the flow volume of the said gas by isolate | separating the ultrasonic noise which flows through the said piping from the waveform signal of the ultrasonic wave which the said receiving part received.

  According to this, in the external ultrasonic flowmeter for gas, by providing the control unit, the ultrasonic noise flowing in the pipe is separated even in the state of being externally attached to the pipe, and the gas flowing in the pipe is separated. The flow rate can be measured.

  In addition, a gas flow rate measurement method according to an aspect of the present invention is a gas flow rate measurement using an external ultrasonic flow meter for gas that is externally attached to a pipe and measures the flow rate of the gas flowing through the pipe using ultrasonic waves. An ultrasonic generation step of applying a sinusoidal voltage to a transmitter disposed outside the pipe to generate an ultrasonic wave according to the magnitude of the voltage, and an outer side of the pipe And an ultrasonic wave receiving step of receiving an ultrasonic wave generated by the transmitter.

  According to this, by applying a sinusoidal voltage to the transmitting unit arranged outside the pipe to generate an ultrasonic wave, and receiving the ultrasonic wave at the receiving unit arranged outside the pipe Measure the flow rate of the gas flowing in the pipe. Here, as a result of diligent research and experiments, the inventors of the present application have found that the ultrasonic wave generated by applying the voltage of the sine wave is compared with the ultrasonic wave generated by applying the voltage of the conventional pulse wave. It was found that it propagates well in the gas flowing inside. For this reason, even when the external ultrasonic flowmeter for gas is externally attached to the pipe, the flow rate of the gas flowing through the pipe is measured by applying a sine wave voltage and generating ultrasonic waves. Can do.

  Further, in the ultrasonic wave receiving step, the ultrasonic wave propagated through the pipe after directly receiving the ultrasonic wave propagated through the pipe among the ultrasonic waves generated by the transmitter in the receiving part. You may decide to receive the ultrasonic wave, and to receive the ultrasonic wave which propagated through the said piping and reflected by the discontinuous part of the said piping after that.

  According to this, after directly receiving the ultrasonic wave propagated through the pipe, it receives the ultrasonic wave propagated through the gas, and then receives the ultrasonic wave propagated through the pipe and reflected by the discontinuous part of the pipe. It is possible to temporally separate the ultrasonic noise that has propagated or reflected on the pipe.

  Furthermore, the method further includes a gas flow rate measuring step of measuring the gas flow rate by separating ultrasonic noise flowing through the pipe from the ultrasonic waveform signal received by the receiving unit in the ultrasonic wave receiving step. It may be.

  According to this, even when the gas external ultrasonic flowmeter is externally attached to the pipe, the ultrasonic noise flowing through the pipe can be separated and the flow rate of the gas flowing through the pipe can be measured.

  According to the external ultrasonic flowmeter for gas in the present invention, the flow rate of the gas flowing through the pipe can be measured even in a state of being externally attached to the pipe.

It is a block diagram which shows the function structure of the external ultrasonic flowmeter for gas which concerns on embodiment of this invention. It is a schematic diagram which shows the structure at the time of seeing the state by which the 1st probe and 2nd probe which concern on embodiment of this invention were installed in piping. It is a schematic diagram which shows the structure at the time of seeing the state by which the 1st probe and 2nd probe which concern on embodiment of this invention were installed in piping. It is a perspective view which shows typically the external appearance of the 1st probe and 2nd probe which concern on embodiment of this invention. It is a schematic diagram which shows the internal structure of the 1st probe which concerns on embodiment of this invention. It is a figure which shows the state which the 1st probe which concerns on embodiment of this invention oscillates an ultrasonic wave toward the 2nd probe. It is a flowchart which shows the operation | movement which the gas external type ultrasonic flowmeter which concerns on embodiment of this invention measures the flow volume of gas. It is a figure which shows the voltage of the sine wave which the application part which concerns on embodiment of this invention applies. It is a figure explaining the wavelength of the ultrasonic wave oscillated by the voltage application by the application part which concerns on embodiment of this invention. It is a figure explaining the wavelength of the ultrasonic wave oscillated by the voltage application by the application part which concerns on embodiment of this invention. It is a figure which shows that the receiving part of a 2nd probe receives the ultrasonic wave which the transmission part of the 1st probe which concerns on embodiment of this invention generated. It is a figure which shows that the receiving part of the 2nd probe which concerns on embodiment of this invention receives the ultrasonic wave which propagated piping, and the ultrasonic wave which propagated gas at different time. It is a schematic diagram which shows the structure at the time of seeing the state by which the 1st probe and 2nd probe which concern on the modification 1 of embodiment of this invention were installed in piping from the front. It is a schematic diagram which shows the structure at the time of seeing the state by which the 1st probe and 2nd probe which concern on the modification 2 of embodiment of this invention were installed in piping. It is a schematic diagram which shows the structure at the time of seeing the state by which the 1st probe and 2nd probe which concern on the modification 3 of embodiment of this invention were installed in piping from the side.

  Hereinafter, an external ultrasonic flowmeter for gas according to an embodiment of the present invention will be described with reference to the drawings. Each of the embodiments described below shows a preferred specific example of the present invention. The numerical values, shapes, materials, constituent elements, arrangement positions and connecting forms of the constituent elements, steps, order of steps, and the like shown in the following embodiments are merely examples, and are not intended to limit the present invention. In addition, among the constituent elements in the following embodiments, constituent elements that are not described in the independent claims indicating the highest concept are described as optional constituent elements.

(Embodiment)
First, the configuration of the gas external ultrasonic flowmeter 1 will be described.

  FIG. 1 is a block diagram showing a functional configuration of an external gas ultrasonic flowmeter 1 according to an embodiment of the present invention. FIG. 2 shows the state in which the first probe 10 and the second probe 20 according to the embodiment of the present invention are installed in the pipe 40 as viewed from the side (the Y axis direction minus side in the figure). It is a schematic diagram which shows the structure in the case of. FIG. 3 shows a state in which the first probe 10 and the second probe 20 according to the embodiment of the present invention are installed in the pipe 40 as viewed from the front (X-axis direction minus side in FIG. 3). It is a schematic diagram which shows the structure in the case.

  The gas external ultrasonic flowmeter 1 is an ultrasonic flowmeter that is externally attached to a pipe and measures the flow rate of the gas flowing through the pipe using ultrasonic waves. That is, the external ultrasonic flowmeter 1 for gas measures the flow rate of the gas flowing through the pipe without providing a hole in the pipe or disposing the pipe inside the pipe by cutting or processing. This is an ultrasonic flow meter with an external pipe (non-penetrating pipe). That is, the gas external ultrasonic flow meter 1 is a so-called clamp-on ultrasonic flow meter capable of measuring a gas flow rate.

  Note that the gas to be measured is a concept including various gases such as air, steam, natural gas, and high-pressure nitrogen, and any gas other than liquid and solid may be used.

  First, as shown in FIG. 1, the gas external ultrasonic flowmeter 1 includes a first probe 10, a second probe 20, and a control device 30.

  The first probe 10 includes a transmission unit 11 and a reception unit 12. The second probe 20 includes a transmission unit 21 and a reception unit 22. That is, the first probe 10 and the second probe 20 have the same configuration.

  As shown in FIGS. 2 and 3, the first probe 10 and the second probe 20 are disposed outside the pipe 40. That is, the transmission unit 11 and the reception unit 12, and the transmission unit 21 and the reception unit 22 are disposed outside the pipe 40. Note that the pipe 40 is a pipe extending in the X-axis direction, but in these drawings, a part of the pipe 40 is shown and the other parts are omitted.

  The transmitter 11 generates an ultrasonic wave corresponding to the magnitude of the voltage toward the inside of the pipe 40 by applying a voltage. The receiving unit 22 receives the ultrasonic waves generated by the transmitting unit 11.

  Similarly, the transmission unit 21 generates an ultrasonic wave corresponding to the magnitude of the voltage toward the inside of the pipe 40 when a voltage is applied. The receiving unit 12 receives the ultrasonic waves generated by the transmitting unit 21.

  More specifically, as shown in FIGS. 2 and 3, the first probe 10 and the second probe 20 are disposed outside the pipe 40 at positions facing each other with the pipe 40 interposed therebetween. And at different positions in the gas flow direction (gas flow direction G in FIG. 2).

  That is, the transmission unit 11 and the reception unit 12, and the transmission unit 21 and the reception unit 22 are disposed at positions facing each other with the pipe 40 interposed therebetween, and are disposed at different positions in the gas flow direction. And the transmission part 11 and the transmission part 21 generate | occur | produce an ultrasonic wave (ultrasonic wave U1 and U2 in FIG.2 and FIG.3) toward the diagonal direction with respect to the direction through which gas flows. The receiving unit 22 and the receiving unit 12 receive the ultrasonic waves U1 and U2 generated by the transmitting unit 11 and the transmitting unit 21, respectively.

  Here, the transmission unit 11 of the first probe 10 (or the transmission unit 21 of the second probe 20) generates an ultrasonic wave, and the reception unit 22 of the second probe 20 (or the first probe). A specific configuration for the ten receiving units 12) to receive the ultrasonic waves will be described.

  FIG. 4 is a perspective view schematically showing the external appearance of the first probe 10 and the second probe 20 according to the embodiment of the present invention. FIG. 5 is a schematic diagram showing an internal configuration of the first probe 10 according to the embodiment of the present invention. FIG. 6 is a diagram showing a state in which the first probe 10 according to the embodiment of the present invention oscillates the ultrasonic wave U1 toward the second probe 20.

  First, as shown in FIG. 4, the first probe 10 and the second probe 20 are substantially rectangular probes in which surfaces 13 a and 23 a facing the pipe 40 have a curved shape along the outer surface of the pipe 40. It is a tentacle. That is, the first probe 10 and the second probe 20 have the same shape.

  Further, the first probe 10 and the second probe 20 have a shape in which the circumferential width of the pipe 40 is wide so that the areas of the surfaces 13 a and 23 a facing the pipe 40 are large. That is, the first probe 10 and the second probe 20 are formed such that the circumferential width L1 of the pipe 40 is larger than the normal width L2 of the pipe 40. Thereby, the intensity | strength of the ultrasonic wave output from the 1st probe 10 and the 2nd probe 20 can be improved.

  Here, the components of the first probe 10 will be described in detail with reference to FIG. Although the configuration of the first probe 10 is shown in the figure, the second probe 20 has the same configuration as the first probe 10, and therefore the second probe 20. The illustration and description of the configuration of are omitted.

  As shown in the figure, the first probe 10 includes a matching layer 13 formed with the curved surface 13a, a wiring 14, a connector 15, a lead wire 16, an electrode 17, and a piezoelectric element. 18 and a sound absorbing material 19. Further, the wiring 14 is connected to the control device 30.

  With this configuration, a voltage is applied to the electrode 17 by the control device 30 via the wiring 14, the connector 15, and the lead wire 16, and the piezoelectric element 18 is expanded and contracted depending on the magnitude of the applied voltage. Ultrasound is generated. The generated ultrasonic wave oscillates outward through the matching layer 13. Note that the side of the piezoelectric element 18 opposite to the matching layer 13 is absorbed by the sound absorbing material 19.

  As described above, in the first probe 10, the function of generating an ultrasonic wave when a voltage is applied corresponds to the transmission unit 11. That is, the function of generating ultrasonic waves included in the matching layer 13, the wiring 14, the connector 15, the lead wire 16, the electrode 17, the piezoelectric element 18, and the sound absorbing material 19 constitutes the transmission unit 11.

  Further, when ultrasonic waves from the outside are transmitted to the piezoelectric element 18 through the matching layer 13, the piezoelectric element 18 expands and contracts to generate a voltage at the electrode 17. The generated voltage is input to the control device 30 via the lead wire 16, the connector 15, and the wiring 14.

  As described above, in the first probe 10, the function of receiving an ultrasonic wave from the outside, converting it into a voltage and outputting it corresponds to the receiving unit 12. That is, the function of receiving the ultrasonic waves of the matching layer 13, the wiring 14, the connector 15, the lead wire 16, the electrode 17, the piezoelectric element 18 and the sound absorbing material 19 constitutes the receiving unit 12.

  As described above, the functions of both the transmitter 11 and the receiver 12 can be realized by the matching layer 13, the wiring 14, the connector 15, the lead wire 16, the electrode 17, the piezoelectric element 18, and the sound absorbing material 19. In other words, it can be said that the first probe 10 includes a transmission / reception unit having the functions of both the transmission unit 11 and the reception unit 12. Note that the first probe 10 may include a configuration having the function of the transmission unit 11 and a configuration having the function of the reception unit 12 separately.

  The matching layer 13 has a curved surface 13a along the outer surface 42 of the pipe 40, and as shown in FIG. 6, the pipe 40 is seen from the direction in which the gas in the pipe 40 flows (X-axis direction). The ultrasonic wave U <b> 1 is generated in a direction perpendicular to the inner surface 41. That is, the transmitter 11 generates ultrasonic waves in a direction perpendicular to the inner surface 41 of the pipe 40 as viewed from the direction in which the gas flows.

  Specifically, the matching layer 13 generates the ultrasonic wave U1 in a direction perpendicular to the inner surface 41 and the outer surface 42 of the pipe 40 when viewed from the direction in which the gas flows. That is, the transmitter 11 generates ultrasonic waves in a direction perpendicular to the inner surface 41 and the outer surface 42 of the pipe 40 as viewed from the direction in which the gas flows.

  Thereby, since the ultrasonic wave oscillated from the first probe 10 is propagated toward the second probe 20 so as to intersect at the central portion of the pipe 40, the supersonic wave that reaches the second probe 20 is transmitted. The spread of the sound beam can be suppressed. That is, the ultrasonic beam reaches the second probe 20 with the same width as that generated when oscillated from the first probe 10. In this way, diffusion of the ultrasonic beam can be prevented and focusing can be realized.

  In addition, the ultrasonic wave oscillated from the first probe 10 and propagated through the gas passes through the pipe 40 perpendicular to the inner surface 41 and the outer surface 42 of the pipe 40 when viewed from the direction in which the gas flows (X-axis direction). Then, the second probe 20 is reached. And the receiving part 22 of the 2nd probe 20 receives the said ultrasonic wave.

  The details of the materials and the like of the constituent elements of the first probe 10 and the second probe 20 are the same as those of the constituent elements of the conventional probe, and a detailed description thereof will be omitted.

  Returning to FIG. 1, the control device 30 includes an application unit 31, a control unit 32, and a storage unit 33.

  The application unit 31 applies a sine wave voltage to the transmission unit 11 of the first probe 10 and the transmission unit 21 of the second probe 20. Specifically, the application unit 31 is configured such that an integral multiple of a half wavelength of the ultrasonic wave oscillated from the transmission unit 11 of the first probe 10 or the transmission unit 21 of the second probe 20 is the thickness of the pipe 40. The voltage of the sine wave is applied so as to be equal. A detailed description of the voltage of the sine wave applied by the applying unit 31 will be described later.

  The control unit 32 separates ultrasonic noise flowing through the pipe 40 from the ultrasonic waveform signals received by the receiving unit 12 of the first probe 10 and the receiving unit 22 of the second probe 20, thereby The flow rate of the gas flowing through 40 is measured. Specifically, the control unit 32 determines the difference between the propagation time of the ultrasonic wave U1 propagated from the transmission unit 11 to the reception unit 22 and the propagation time of the ultrasonic wave U2 propagated from the transmission unit 21 to the reception unit 12. The flow rate of the gas is measured. A detailed description of the control unit 32 separating ultrasonic noise will be described later.

  The storage unit 33 is a memory that stores data necessary for the gas external ultrasonic flowmeter 1 to measure the flow rate of the gas flowing through the pipe 40. For example, the storage unit 33 stores in advance the value of the voltage applied by the application unit 31, the frequency of the sine wave, and the like, or the reception unit 12 of the first probe 10 and the reception unit of the second probe 20. The waveform signal of the ultrasonic wave which 22 received is memorize | stored.

  Next, a method (gas flow measurement method) in which the gas external ultrasonic flowmeter 1 measures the flow rate of the gas flowing in the pipe 40 will be described.

  FIG. 7 is a flowchart showing an operation in which the gas external ultrasonic flowmeter 1 according to the embodiment of the present invention measures the gas flow rate.

  As shown in the figure, first, as an ultrasonic wave generation step, the application unit 31 applies a sinusoidal voltage to the transmission unit 11 of the first probe 10 and depends on the magnitude of the voltage. Is generated (S102). Similarly, the application unit 31 applies a sinusoidal voltage to the transmission unit 21 of the second probe 20 to generate an ultrasonic wave depending on the magnitude of the voltage. The sinusoidal voltage applied by the application unit 31 will be described in detail below.

  FIG. 8 is a diagram illustrating a sinusoidal voltage applied by the application unit 31 according to the embodiment of the present invention. Specifically, the figure shows a graph with the vertical axis representing the value of the applied voltage and the horizontal axis representing the elapsed time, as an example of a sine wave voltage applied by the application unit 31 of the control device 30.

  As shown in the figure, the application unit 31 applies, for example, a sinusoidal voltage having a frequency of about 800 kHz to the transmission unit 11 of the first probe 10 or the transmission unit 21 of the second probe 20. That is, for example, in the case of the first probe 10, the application unit 31 applies the sine wave voltage to the piezoelectric element 18 via the electrode 17 to generate an ultrasonic wave.

  Further, the application unit 31 is configured so that an integral multiple of a half wavelength of the ultrasonic wave oscillated from the transmission unit 11 of the first probe 10 or the transmission unit 21 of the second probe 20 is equal to the thickness of the pipe 40. Then, the voltage of the sine wave is applied. This will be specifically described with reference to FIGS. 9 and 10.

  9 and 10 are diagrams for explaining the wavelength of the ultrasonic wave oscillated by the voltage application by the application unit 31 according to the embodiment of the present invention. Specifically, FIG. 9 is a diagram in which the first probe 10 oscillates the ultrasonic wave U <b> 1 toward the second probe 20. In FIG. 10, two steel plates simulating the piping 40 are arranged between the first probe 10 and the second probe 20, and the wavelength of the ultrasonic wave oscillated by the first probe 10 is set. It is the graph which showed the signal which the 2nd probe 20 at the time of fixing and changing the thickness of a steel plate.

  More specifically, FIG. 10A is a graph in the case where the half-wavelength of the ultrasonic wave is larger than the thickness of the steel plate, and FIG. 10B is a graph in which the half-wavelength of the ultrasonic wave is the thickness of the steel plate. FIG. 10C is a graph when the half wavelength of the ultrasonic wave is smaller than the thickness of the steel plate.

  First, as shown in FIG. 9, when the first probe 10 oscillates an ultrasonic wave, the ultrasonic wave U1 is oscillated toward the second probe 20, but a part of the ultrasonic wave U3 is piped. It is reflected by the inner surface 41 and the outer surface 42 of 40 and propagates through the pipe 40. However, the ultrasonic wave oscillated from the first probe 10 is not reflected by the inner surface 41 and the outer surface 42 of the pipe 40 like the ultrasonic wave U3, but the second probe like the ultrasonic wave U1. It is desirable to oscillate toward 20.

  Here, as shown in FIG. 10A, when the half wavelength of the ultrasonic wave is larger than the thickness of the steel plate, the ultrasonic wave oscillated by the first probe 10 is applied to the second probe 20. As shown in FIG. 10C, when the half wavelength of the ultrasonic wave is smaller than the thickness of the steel plate, the ultrasonic wave oscillated by the first probe 10 is reflected in the steel plate. As a result, it was transmitted to the second probe 20. On the other hand, as shown in FIG. 10B, when the half wavelength of the ultrasonic wave is equal to the thickness of the steel plate, the second probe 20 can receive a relatively clean waveform signal. did it.

  That is, in the graph of FIG. 10B, the waveform signal appeared cleanly within the range surrounded by the dotted line, whereas in the graph of FIG. In the graph of FIG. 10C, the ultrasonic wave was reflected and a plurality of waveform signals appeared.

  For this reason, in order for the ultrasonic wave oscillated from the first probe 10 to be oscillated toward the second probe 20 like the ultrasonic wave U1, an integral multiple of the half wavelength of the ultrasonic wave is the pipe 40. It is preferable to be equal to the wall thickness (wall thickness D of the pipe 40 shown in FIG. 9).

  Thus, the application unit 31 has an integral multiple of the half wavelength of the ultrasonic wave oscillated from the transmission unit 11 of the first probe 10 or the transmission unit 21 of the second probe 20 equal to the thickness of the pipe 40. A sine wave voltage is applied so that Then, the transmission unit 11 and the transmission unit 21 generate ultrasonic waves such that an integral multiple of the half wavelength is equal to the thickness of the pipe 40.

  Returning to FIG. 7, next, as an ultrasonic wave reception step, the ultrasonic wave generated by the transmission unit 11 of the first probe 10 is received by the reception unit 22 of the second probe 20 (S104). Similarly, the reception unit 12 of the first probe 10 receives the ultrasonic waves generated by the transmission unit 21 of the second probe 20.

  Specifically, in the ultrasonic wave reception step, the ultrasonic wave propagated through the pipe 40 among the ultrasonic waves generated by the transmission unit 11 of the first probe 10 at the reception unit 22 of the second probe 20; The ultrasonic waves that have propagated the gas are received at different times. Similarly, among the ultrasonic waves generated by the transmitting unit 21 of the second probe 20 at the receiving unit 12 of the first probe 10, the ultrasonic wave propagating through the pipe 40, the ultrasonic wave propagating through the gas, Are received at different times.

  More specifically, in the ultrasonic wave receiving step, the receiving unit 22 directly receives the ultrasonic wave propagated through the pipe 40 among the ultrasonic waves generated by the transmitting unit 11 and then propagates the gas through the pipe 40. Then, the ultrasonic wave propagated through the pipe 40 and reflected by the discontinuous portion of the pipe 40 is received. This will be specifically described with reference to FIGS. 11 and 12.

  In the following description, the case where the receiving unit 22 of the second probe 20 receives the ultrasonic waves generated by the transmitting unit 11 of the first probe 10 will be described. The same applies to the case where the reception unit 12 of the first probe 10 receives the ultrasonic waves generated by the reference numeral 21, and a description thereof will be omitted.

  FIG. 11 is a diagram illustrating that the reception unit 22 of the second probe 20 receives the ultrasonic waves generated by the transmission unit 11 of the first probe 10 according to the embodiment of the present invention. FIG. 12 shows that the receiving unit 22 of the second probe 20 according to the embodiment of the present invention receives the ultrasonic wave propagated through the pipe 40 and the ultrasonic wave propagated through the gas at different times. FIG.

  First, as illustrated in FIG. 11, the reception unit 22 uses a different route for the ultrasonic wave U1 that has propagated the gas and the ultrasonic waves U3 and U4 that have propagated through the pipe 40 among the ultrasonic waves generated by the transmission unit 11. Receive. Here, the ultrasonic wave U3 is an ultrasonic wave that has directly propagated through the pipe 40 through the shortest route, and the ultrasonic wave U4 is a discontinuous part of the pipe 40 (in this embodiment, the flange 43 at the end of the pipe 40). The ultrasonic waves propagated through the pipe 40 toward the gas flow direction G and reflected by the discontinuous portion (flange 43).

  In addition, the discontinuous part of the piping 40 is a location where the continuity of the piping 40 is lost and ultrasonic waves are reflected. In the present embodiment, the discontinuous portion is the flange 43 at the end of the pipe 40, but is not limited to the flange 43, and ultrasonic waves such as a welded portion, a branch portion of the pipe, or a measuring instrument installation portion are transmitted. Any location may be used as long as it is reflected.

  Further, since the ultrasonic wave propagates in various directions in the pipe 40, the path of the ultrasonic wave U4 shown in the figure is only an example, and the ultrasonic wave U4 follows various paths. The light is reflected at the discontinuous part and reaches the receiving part 22.

  Here, the ultrasonic wave U3 propagating through the pipe 40 has a higher propagation speed than the ultrasonic wave U1 propagating through the gas. In particular, since the first probe 10 and the second probe 20 are arranged at different positions in the gas flow direction G, the propagation distance of the ultrasonic wave becomes long, and the ultrasonic wave U1 and the ultrasonic wave U3 There is a difference in propagation time.

  For this reason, as shown in FIG. 12, the receiving unit 22 receives the ultrasonic wave U3 propagated through the pipe 40 at a time earlier than the ultrasonic wave U1 propagated through the gas. Thereafter, the receiving unit 22 receives the ultrasonic wave U <b> 4 that propagates through the pipe 40 and is reflected by the flange 43 at the end that is a discontinuous part of the pipe 40.

  As described above, the reception unit 22 receives the ultrasonic waves U3 and U4 propagated through the pipe 40 and the ultrasonic wave U1 propagated through the gas among the ultrasonic waves generated by the transmission unit 11 at different times. That is, the receiving unit 22 directly receives the ultrasonic wave U3 propagated through the pipe 40, then receives the ultrasonic wave U1 propagated through the pipe 40, and then propagates through the pipe 40 to discontinue the pipe 40. The ultrasonic wave U4 reflected by the unit is received.

  In other words, the receiving unit 22 directly receives the ultrasonic wave U3 propagated through the pipe 40, then receives the ultrasonic wave U1 propagated through the pipe 40, and then propagates through the pipe 40 to check the pipe 40. It arrange | positions in the position which can receive the ultrasonic wave U4 reflected in the continuous part.

  Returning to FIG. 7, next, as the gas flow rate measurement step, the control unit 32 uses the ultrasonic waveform signals received by the reception unit 12 and the reception unit 22 in the ultrasonic reception step (S <b> 104) and flows through the pipe 40. By separating the noise (S106), the gas flow rate is measured (S108).

  Specifically, for the ultrasonic waves received by the receiving unit 22, the control unit 32 separates the waveform signals of the ultrasonic waves U3 and U4 propagated through the pipe 40 from the ultrasonic waveform signal shown in FIG. Thereby, the ultrasonic wave U1 which propagated gas is extracted. Similarly, the control unit 32 extracts the ultrasonic wave U2 that has propagated the gas from the ultrasonic wave received by the receiving unit 12.

  Then, the control unit 32 calculates the gas from the difference between the propagation time of the ultrasonic wave U1 propagated from the transmission unit 11 to the reception unit 22 and the propagation time of the ultrasonic wave U2 propagated from the transmission unit 21 to the reception unit 12. Measure the flow rate.

  As described above, according to the gas external ultrasonic flowmeter 1 according to the embodiment of the present invention, the voltage of the sine wave is applied to the transmission unit disposed outside the pipe 40 by applying a sine wave voltage. The flow rate of the gas flowing through the pipe 40 is measured by generating an ultrasonic wave inward and receiving the ultrasonic wave at a receiving unit arranged outside the pipe 40. Here, as a result of diligent research and experiments, the inventors of the present application have found that the ultrasonic wave generated by applying the voltage of the sine wave is compared with the ultrasonic wave generated by applying the voltage of the conventional pulse wave. It has been found that it propagates well in the gas flowing through 40.

  This is because the sine wave is larger in energy for causing resonance than the conventional pulse wave, and the pipe 40 is likely to vibrate, so the ultrasonic wave generated by applying the voltage of the sine wave is It is thought that this is because it propagates well in the gas flowing in the pipe 40. That is, a large resonance can be generated by applying a voltage of a sine wave (burst wave) having a predetermined frequency having a plurality of cycles to a piezoelectric element that resonates at the predetermined frequency.

  Therefore, in the external ultrasonic flowmeter 1 for gas, the flow rate of the gas flowing in the pipe 40 even in the state of being externally attached to the pipe 40 by applying a sine wave voltage to generate ultrasonic waves. Can be measured.

  In addition, as a result of intensive studies and experiments, the inventors of the present application are better able to use the ultrasonic wave whose wavelength is adjusted so that an integral multiple of the half wavelength is equal to the thickness of the pipe 40 in the gas flowing in the pipe 40. I found it to propagate. This prevents the ultrasonic wave input from the outside of the pipe 40 from being reflected from the inner surface of the pipe 40 by making the integral multiple of the half wavelength of the ultrasonic wave equal to the thickness of the pipe 40. This is probably because the gas in the pipe 40 can be reached. For this reason, in the external ultrasonic flowmeter 1 for gas, even if it is externally attached to the pipe 40 by generating an ultrasonic wave such that an integral multiple of a half wavelength is equal to the thickness of the pipe 40, the pipe The flow rate of the gas flowing through 40 can be measured.

  In addition, the inventors of the present application have found that, as a result of diligent research and experiments, when ultrasonic waves are input perpendicularly to the inner surface of the pipe 40, the ultrasonic waves propagate well in the gas flowing through the pipe 40. . This is because ultrasonic waves are input perpendicularly to the inner surface of the pipe 40, so that the ultrasonic waves input from the outside of the pipe 40 are prevented from being reflected by the inner surface of the pipe 40 and reach the gas in the pipe 40. It is thought that it is possible to do. For this reason, in the external ultrasonic flowmeter 1 for gas, the state externally attached to the pipe 40 by generating ultrasonic waves in a direction perpendicular to the inner surface of the pipe 40 as seen from the direction in which the gas flows. However, the flow rate of the gas flowing through the pipe 40 can be measured.

  Further, in the external ultrasonic flowmeter 1 for gas, by generating an ultrasonic wave in an oblique direction with respect to the direction in which the gas flows, the distance that the ultrasonic wave propagates in the pipe 40 or the gas is increased. Further, it is possible to easily separate the ultrasonic wave propagated through the pipe 40 and the ultrasonic wave propagated through the gas.

  In addition, in the gas external ultrasonic flowmeter 1, the ultrasonic noise propagated through the pipe 40 is temporally received by receiving the ultrasonic wave propagated through the pipe 40 and the ultrasonic wave propagated through the gas at different times. Can be separated.

  Further, in the gas external ultrasonic flowmeter 1, after directly receiving the ultrasonic wave propagated through the pipe 40, the ultrasonic wave propagated through the gas is received, and then propagated through the pipe 40 and discontinuous of the pipe 40. By arranging the receiving unit at a position where the ultrasonic wave reflected by the unit can be received, the ultrasonic noise propagated or reflected by the pipe 40 can be temporally separated.

  In addition, in the gas external ultrasonic flowmeter 1, by providing the control unit 32, gas that flows through the pipe 40 by separating ultrasonic noise flowing through the pipe 40 even in a state of being externally attached to the pipe 40. Can be measured.

  In addition, according to the gas flow rate measuring method according to the embodiment of the present invention, an ultrasonic wave is generated by applying a sinusoidal voltage to the transmitting unit arranged outside the pipe 40, and the outside of the pipe 40. The flow rate of the gas flowing in the pipe 40 is measured by receiving the ultrasonic waves at the receiving unit arranged in the pipe. Therefore, even when the gas external ultrasonic flowmeter 1 is externally attached to the pipe 40, the flow rate of the gas flowing through the pipe 40 is measured by generating ultrasonic waves by applying a sine wave voltage. can do.

  Moreover, according to the gas flow rate measuring method, the ultrasonic noise propagated through the pipe 40 is separated temporally by receiving the ultrasonic wave propagated through the pipe 40 and the ultrasonic wave propagated through the gas at different times. Can do. Specifically, after receiving the ultrasonic wave U3 propagated through the pipe 40 directly, the ultrasonic wave U1 propagated through the gas is received, and then the ultrasonic wave U4 propagated through the pipe 40 and reflected by the discontinuous part of the pipe 40. , The ultrasonic noise propagated or reflected on the pipe 40 can be temporally separated.

  Further, according to the gas flow measurement method, even when the gas external ultrasonic flowmeter 1 is externally attached to the pipe 40, the ultrasonic noise flowing through the pipe 40 is separated and flows through the pipe 40. The gas flow rate can be measured.

(Modification 1)
Next, Modification 1 of the above embodiment will be described. FIG. 13 is a front view of a state in which the first probe 10, 10a and the second probe 20, 20a according to the first modification of the embodiment of the present invention are installed in the pipe 40 (in the X-axis direction in FIG. 13). It is a schematic diagram which shows the structure at the time of seeing from the minus side.

  As shown in the figure, the external ultrasonic flowmeter for gas in the present modification includes the first probe 10 and the second probe included in the external ultrasonic flowmeter 1 for gas in the above embodiment. In addition to the child 20, a first probe 10a and a second probe 20a are provided.

  The first probe 10 a and the second probe 20 a are arranged outside the pipe 40 at positions facing each other with the pipe 40 interposed therebetween, and are arranged at different positions in the gas flow direction G. The first probe 10a and the second probe 20a are located between the first probe 10 and the second probe 20 when viewed from the direction in which the gas flows in the pipe 40 (X-axis direction). The pipes 40 are arranged so as to face each other.

  That is, the first probe 10 a and the second probe 20 a are disposed at positions where the first probe 10 and the second probe 20 are rotated 90 degrees around the pipe 40. Therefore, the first probe 10, the first probe 10a, the second probe 20, and the second probe 20a are arranged so as to be arranged at equal intervals when viewed from the direction in which the gas flows. Yes.

  Since the first probe 10a and the second probe 20a have the same configuration as the first probe 10 and the second probe 20 in the above embodiment, detailed description thereof is omitted.

  As described above, according to the gas external ultrasonic flowmeter according to the first modification of the embodiment of the present invention, the first probe in addition to the first probe 10 and the second probe 20 is used. Since the child 10a and the second probe 20a are also provided, the flow rate of the gas flowing through the pipe 40 can be accurately measured.

(Modification 2)
Next, a second modification of the above embodiment will be described. FIG. 14 is a side view of the state in which the first probe 10b and the second probe 20b according to the second modification of the embodiment of the present invention are installed in the pipe 40 (Y-axis direction minus side in the figure). It is a schematic diagram which shows the structure at the time of seeing from.

  As shown in the figure, the external ultrasonic flowmeter for gas in the present modification includes the first probe 10 and the second probe included in the external ultrasonic flowmeter 1 for gas in the above embodiment. Instead of the child 20, a first probe 10b and a second probe 20b are provided.

  The first probe 10b and the second probe 20b are arranged outside the pipe 40 on the same side of the pipe 40 (in the figure, the Z-axis direction plus side) and differ in the gas flow direction G. Placed in position. That is, the first probe 10b and the second probe 20b are disposed so as to be at the same position when viewed from the gas flow direction G (X-axis direction) in the pipe 40. Since the first probe 10b and the second probe 20b have the same configuration as the first probe 10 and the second probe 20 in the above embodiment, detailed description thereof is omitted.

  With such a configuration, the ultrasonic wave U1a oscillated from the first probe 10b is reflected by the inner surface (the inner surface on the negative side in the Z-axis direction) of the pipe 40, and becomes the ultrasonic wave U1b to be the second probe. 20b. Similarly, the ultrasonic wave U2a oscillated from the second probe 20b is reflected by the inner surface of the pipe 40 (the inner surface on the negative side in the Z-axis direction) and becomes an ultrasonic wave U2b, which is applied to the first probe 10b. Received. That is, the ultrasonic wave oscillated from the transmitter is reflected in a V shape and received by the receiver.

  The ultrasonic wave oscillated from the first probe 10b is reflected by the inner surface of the pipe 40 three times and received by the second probe 20b. Similarly, the ultrasonic wave oscillated from the second probe 20b is used. The sound wave may be reflected by the inner surface of the pipe 40 three times and received by the first probe 10b. That is, the ultrasonic wave oscillated from the transmission unit may be reflected in a W shape and received by the reception unit.

  As described above, according to the external ultrasonic flowmeter for gas according to the second modification of the embodiment of the present invention, the same effects as those of the above embodiment can be obtained.

(Modification 3)
Next, Modification 3 of the above embodiment will be described. FIG. 15 shows the state in which the first probes 10c and 10d and the second probe 20c according to the third modification of the embodiment of the present invention are installed in the pipe 40 laterally (Y-axis direction minus in the figure). It is a schematic diagram which shows the structure at the time of seeing from the side.

  As shown in the figure, the external ultrasonic flowmeter for gas in the present modification includes the first probe 10 and the second probe included in the external ultrasonic flowmeter 1 for gas in the above embodiment. Instead of the child 20, first probes 10c and 10d and a second probe 20c are provided.

  The first probes 10c and 10d and the second probe 20c are arranged outside the pipe 40 at positions facing each other across the pipe 40 and at different positions in the gas flow direction G. The Further, the first probes 10c and 10d are arranged on the same side of the pipe 40 (Z-axis direction plus side in the figure) and are arranged at different positions in the gas flow direction G.

  The first probes 10c and 10d have the function of the transmission unit 11 included in the first probe 10 in the above embodiment, but do not have the function of the reception unit 12. The second probe 20c has the function of the receiving unit 22 included in the second probe 20 in the above embodiment, but does not have the function of the transmitting unit 21.

  With such a configuration, the ultrasonic wave U1c oscillated from the first probe 10c and the ultrasonic wave U2c oscillated from the first probe 10d are received by the second probe 20c. As a result, the control unit 32 propagates the ultrasonic wave U1c propagated from the first probe 10c to the second probe 20c and propagates from the first probe 10d to the second probe 20c. From the difference from the propagation time of the ultrasonic wave U2c, the flow rate of the gas can be measured.

  As described above, according to the external ultrasonic flow meter for gas according to the third modification of the embodiment of the present invention, the same effects as those of the above embodiment can be obtained.

  As described above, the external ultrasonic flowmeter for gas according to the embodiment of the present invention and the modified example thereof has been described, but the present invention is not limited to the above-described embodiment and the modified example thereof. In other words, it should be considered that the embodiment and its modification disclosed this time are illustrative and not restrictive in all respects. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  For example, in the above-described embodiment and its modification, the transmission unit generates ultrasonic waves such that an integral multiple of a half wavelength is equal to the thickness of the pipe 40. However, the wavelength of the ultrasonic wave generated by the transmission unit is not limited to the above, and some deviation is allowed. That is, it suffices if the transmission unit is controlled to generate an ultrasonic wave so that an integral multiple of the half wavelength is equal to the wall thickness of the pipe 40, and the ultrasonic wave actually generated by the transmission unit is half the wavelength. The integral multiple of the wavelength and the wall thickness of the pipe 40 do not have to be exactly the same, and deviation within a range of about ± 15% is allowed.

  Moreover, in the said embodiment and its modification, the transmission part decided to generate an ultrasonic wave toward the direction perpendicular | vertical to the inner surface of the piping 40 seeing from the direction through which gas flows. However, the direction in which the transmitter generates ultrasonic waves is not limited to the above, and some deviation is allowed.

  Moreover, in the said embodiment and its modification, the receiving part decided to receive the ultrasonic wave which propagated the piping 40 and was reflected by the discontinuous part of the piping 40. FIG. However, the receiving unit may not receive the ultrasonic wave reflected by the discontinuous part of the pipe 40 because the pipe 40 is very long.

  Moreover, in the said embodiment and its modification, the gas external type ultrasonic flowmeter was provided with the control apparatus 30 which has the application part 31, the control part 32, and the memory | storage part 33. FIG. However, the control apparatus 30 should just have the application part 31 at least. That is, the control device 30 may not include the control unit 32 or / and the storage unit 33, and the control unit 32 or / and the storage unit 33 may be provided in an external device.

  Moreover, the form constructed | assembled combining the said embodiment and the said modification arbitrarily is also contained in the scope of the present invention. For example, a configuration in which the first modification is applied to the second or third modification or a combination of the second and third modifications is also included in the scope of the present invention.

  The present invention can be applied to an external ultrasonic flowmeter for gas that is externally attached to a pipe and measures the flow rate of the gas flowing in the pipe using ultrasonic waves.

DESCRIPTION OF SYMBOLS 1 External-type ultrasonic flowmeter for gas 10, 10a, 10b, 10c, 10d First probe 11, 21 Transmitter 12, 22 Receiver 13 Matching layer 13a, 23a Surface 14 Wiring 15 Connector 16 Lead wire 17 Electrode DESCRIPTION OF SYMBOLS 18 Piezoelectric element 19 Sound absorbing material 20, 20a, 20b, 20c 2nd probe 30 Control apparatus 31 Application part 32 Control part 33 Memory | storage part 40 Piping 41 Inner surface 42 Outer surface 43 Flange

Claims (9)

An external ultrasonic flow meter for gas that is externally attached to a pipe and measures the flow rate of the gas flowing through the pipe using ultrasonic waves,
A transmitter that is arranged outside the pipe and generates an ultrasonic wave corresponding to the magnitude of the voltage toward the inside of the pipe by applying a voltage;
A receiver that is disposed outside the pipe and that receives the ultrasonic waves generated by the transmitter;
An external ultrasonic flow meter for gas, comprising: an application unit that applies a sinusoidal voltage to the transmission unit. The external transmission ultrasonic flowmeter for gas according to claim 1, wherein the transmission unit generates the ultrasonic waves such that an integral multiple of a half wavelength is equal to a thickness of the pipe. The external transmission ultrasonic flowmeter for gas according to claim 1, wherein the transmission unit generates the ultrasonic wave in a direction perpendicular to an inner surface of the pipe as viewed from a direction in which the gas flows. The said receiving part receives the ultrasonic wave which propagated the said piping among the ultrasonic waves which the said transmission part generated, and the ultrasonic wave which propagated the said gas at different time. The external ultrasonic flowmeter for gas described. The receiving unit directly receives the ultrasonic wave propagated through the pipe and then receives the ultrasonic wave propagated through the pipe and then propagates through the pipe and is reflected by a discontinuous part of the pipe. The gas-type external ultrasonic flowmeter according to claim 4, wherein the external ultrasonic flowmeter for gas is disposed at a position where the ultrasonic wave can be received. further,
The control part which measures the flow volume of the said gas is provided by isolate | separating the ultrasonic noise which flows through the said piping from the waveform signal of the ultrasonic wave which the said receiving part received. External flow meter for gas. A gas flow measurement method using an external ultrasonic flowmeter for gas, which is externally attached to a pipe and measures the flow rate of the gas flowing through the pipe using ultrasonic waves,
An ultrasonic wave generating step of applying a sinusoidal voltage to the transmitter disposed outside the pipe and generating an ultrasonic wave according to the magnitude of the voltage; and
An ultrasonic flow receiving method for receiving an ultrasonic wave generated by the transmitting unit at a receiving unit disposed outside the pipe. In the ultrasonic wave receiving step, the ultrasonic wave propagated through the pipe after directly receiving the ultrasonic wave propagated through the pipe among the ultrasonic waves generated by the transmitter in the receiving part. The gas flow rate measuring method according to claim 7, wherein the ultrasonic wave that is received and then propagated through the pipe and reflected by a discontinuous portion of the pipe is received. further,
The gas flow measurement step of measuring the flow rate of the gas by separating ultrasonic noise flowing through the pipe from the ultrasonic waveform signal received by the receiving unit in the ultrasonic reception step. The gas flow measurement method described in 1.

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