JP6207428B2 - Ultrasonic sound velocity measuring device and ultrasonic sound velocity measuring method - Google Patents

Description

  The present invention relates to an ultrasonic sound velocity measuring device and an ultrasonic sound velocity measuring method for measuring the sound velocity of a fluid in a pipe.

  In such an ultrasonic sound velocity measuring device, an ultrasonic wave is incident on the fluid in the pipe in each of a direction along the flow and a direction opposite to the flow to calculate both propagation times of the ultrasonic waves. A configuration is disclosed in which the sound speed of the fluid in the pipe is calculated from the reciprocal sum of the propagation time, and the gas speed of the fluid in the pipe is determined by comparing the speed of sound with the sound speed of various fluids measured in advance. (For example, refer to Patent Document 1).

  In addition, there is an ultrasonic flowmeter that is a technique related to the ultrasonic sound velocity measuring device in terms of calculating both the propagation times (see, for example, Patent Document 2). In such an ultrasonic flow meter, ultrasonic waves are obliquely incident on the fluid in the pipe in a direction along the flow and in a direction reverse to the flow, and both propagation times of the ultrasonic waves in the respective directions are calculated. A configuration is disclosed in which the flow velocity of the fluid is obtained from the difference between the two propagation times, and the flow rate is obtained from the flow velocity and the pipe cross-sectional area. At that time, a clamp-on type ultrasonic flowmeter that transmits and receives ultrasonic waves from the surface of the tube is used for measuring the flow rate of the fluid flowing through the tube.

JP 2007-17157 A JP 2002-250644 A

  In both cases of the ultrasonic sound velocity measuring device and the ultrasonic flowmeter, if a clamp-on method that transmits and receives ultrasonic waves from the surface of the tube is adopted, the received ultrasonic reception signal includes an ultrasonic wave to the surface of the tube. Surface waves and plate waves generated when sound waves are incident, and reflected waves that repeatedly reflect between the surface and the inner surface of the tube, such as a circulating wave (noise wave) that propagates through the tube itself, and the fluid from the inner surface of the tube And transmitted waves that pass (transmit) through the fluid and enter the inner surface of the opposite tube.

Here, when calculating both the propagation times, it is necessary to use a transmitted wave that has passed (transmitted) through the fluid in the tube. However, the material of the tube is a metal or a resin tube, and the fluid in the tube (especially gas) ) Is large, a large sound pressure loss occurs when passing through the interface between the pipe and the fluid, and the intensity of the ultrasonic wave reception signal of the transmitted wave cannot be sufficiently ensured. In this case, it may be possible to simply transmit a strong ultrasonic wave, but the intensity of the ultrasonic wave reception signal of the transmitted wave can be increased, but at the same time the intensity of the ultrasonic wave reception signal of the circulating wave (noise wave) also increases. Become.
For this reason, conventionally, in order to increase the intensity of the ultrasonic reception signal of the transmitted wave, it has been proposed to transmit ultrasonic waves at the resonance frequency of the tube wall of the tube calculated from the wall thickness of the tube. .

  However, even when the frequency of the ultrasonic wave to be transmitted is set to the resonance frequency, the intensity of the transmitted wave is not sufficiently amplified by the resonance in the received ultrasonic wave reception signal, and the S / N ratio is not sufficient. There was a thing. In such a case, since the circulating wave (noise wave) and the transmitted wave are mixed, it is difficult to distinguish the circulating wave (noise wave) and the transmitted wave. In some cases, it was difficult to calculate a proper propagation time.

  The present invention has been made in view of such a situation, and an object of the present invention is to improve the S / N ratio of a transmitted wave in an ultrasonic reception signal so that the transmitted wave can be easily discriminated, and the transmitted signal is transmitted. An object of the present invention is to provide an ultrasonic sound velocity measuring apparatus and an ultrasonic sound velocity measuring method capable of accurately calculating the wave propagation time and the sound velocity of a fluid.

In order to achieve the above object, an ultrasonic sound velocity measuring apparatus according to the present invention includes a transmission transducer that obliquely injects ultrasonic waves from the surface of a tube through which fluid in the tube flows,
A receiving transducer for receiving the ultrasonic wave transmitted by the transmitting transducer at the surface of the tube;
An ultrasonic reception signal in the first measurement mode in which the receiving transducer is arranged downstream from the transmission transducer, and an ultrasonic reception signal in the second measurement mode in which the receiving transducer is arranged upstream from the transmission transducer; A sound speed calculation unit that calculates the sound speed of the fluid in the pipe from both propagation times, and the characteristic configuration thereof is:
The transmission transducer has a specific transmission frequency shifted by a predetermined frequency with respect to the resonance frequency of the tube wall of the tube calculated from the thickness of the tube in each of the first measurement mode and the second measurement mode. The specific ultrasonic wave is obliquely incident from the surface of the tube,
The receiving transducer receives an ultrasonic wave reaching the receiving transducer in each of the first measurement mode and the second measurement mode;
The sound velocity calculation unit extracts a reception signal corresponding to the resonance frequency from the ultrasonic reception signal of the ultrasonic wave received by the reception transducer in each of the first measurement mode and the second measurement mode, The sound velocity of the fluid in the pipe is calculated from the propagation time of the received signal.

In order to achieve the above object, an ultrasonic sound velocity measuring method according to the present invention includes a tube wall of the tube calculated from the thickness of the tube from a transmitting transducer disposed on the surface of the tube through which the fluid in the tube flows. A specific ultrasonic wave having a specific transmission frequency that is shifted by a predetermined frequency with respect to the resonance frequency is obliquely incident from the surface of the tube;
Receiving ultrasonic waves reaching the receiving transducer with a receiving transducer disposed on the surface of the tube;
A reception signal corresponding to the resonance frequency is extracted from the ultrasonic reception signal in the first measurement mode in which the reception transducer is arranged downstream from the transmission transducer, and the reception transducer is located upstream from the transmission transducer. Extracting a reception signal corresponding to the resonance frequency from the ultrasonic reception signal in the second measurement mode arranged in
And calculating the sound velocity of the fluid in the tube from the propagation times of the extracted received signals.

According to both the above configurations, in each of the first measurement mode and the second measurement mode, the transmitting transducer is identified by a predetermined frequency with respect to the resonance frequency of the tube wall of the tube calculated from the wall thickness of the tube. A specific ultrasonic wave having a transmission frequency is incident at an oblique angle from the surface of the tube, and the receiving transducer receives the ultrasonic wave reaching the receiving transducer.
The ultrasonic reception signal of the ultrasonic wave that has arrived and received by the reception transducer mainly includes the reception signals of the specific transmission frequency component and the resonance frequency component.

The specific transmission frequency component is mainly transmitted from the transmitting transducer and generated when the ultrasonic wave is incident on the surface of the tube, and the reflected wave that repeats reflection between the surface and the inner surface of the tube The resonance frequency component is incident on the fluid mainly from the inner surface of the tube and passes (transmits) through the fluid, while it is a circular wave (noise wave) propagating through the tube itself. The transmitted wave is incident on the inner surface of the tube.
That is, when the transmitting transducer makes a specific ultrasonic wave having a specific transmission frequency shifted from the resonance frequency by a predetermined frequency from the surface of the tube, the circulating wave (noise wave) propagating through the tube itself is approximately the specific transmission frequency. The specific transmission frequency is set in a frequency range that is relatively close to the resonance frequency of the tube wall of the tube, whereas the transmission that passes through (transmits) the fluid inside the tube is achieved. The wave reaches the receiving transducer at a resonance frequency in a state where the wave is amplified by resonance by the tube wall of the tube. Furthermore, since the propagation speed differs between the circulating wave (noise wave) propagating through the tube itself and the transmitted wave, a difference occurs in the arrival time (propagation time) to the receiving transducer.

  Therefore, in the ultrasonic wave reception signal received by the receiving transducer, the intensity of the transmitted wave in the resonance frequency component is amplified by resonance, and the S / N ratio is improved. Then, by extracting only the resonance frequency component including the transmitted wave from the ultrasonic reception signal, the transmitted wave can be easily discriminated from the circulating wave (noise wave) in the specific transmission frequency component and the noise wave in the resonance frequency component. Can do. Accordingly, the propagation time of the transmitted wave can be accurately calculated from the transmitted wave in the resonance frequency component, and the sound speed of the fluid can be accurately calculated based on such an accurate propagation time.

  Therefore, the ultrasonic wave capable of improving the S / N ratio of the transmitted wave in the ultrasonic reception signal and easily determining the transmitted wave, and accurately calculating the propagation time of the transmitted wave and the sound speed of the fluid. Type sound speed measuring apparatus and ultrasonic sound speed measuring method can be provided.

  A further characteristic configuration of the ultrasonic sound velocity measuring device according to the present invention is that the specific transmission frequency of the specific ultrasonic wave transmitted by the transmitting transducer is ± 5% or more and ± 50% or less with respect to the resonance frequency. The frequency is set within a shifted range.

  A further characteristic configuration of the ultrasonic sound velocity measuring method according to the present invention is that the specific transmission frequency of the specific ultrasonic wave transmitted by the transmission transducer is ± 5% or more and ± 50% or less with respect to the resonance frequency. The method includes the step of setting the frequency within the shifted range.

According to both the above configurations, the specific transmission frequency of the specific ultrasonic wave transmitted by the transmission transducer is set to a frequency within a relatively small range of ± 5% to ± 50% with respect to the resonance frequency. Therefore, it is possible to reliably amplify the transmitted wave mainly composed of the resonance frequency component in the ultrasonic reception signal received by the receiving transducer and sufficiently improve the S / N ratio of the transmitted wave. However, in addition, by extracting only the resonant frequency component including the transmitted wave from the ultrasonic reception signal, it is easier to transmit the transmitted wave from the circulating wave (noise wave) in the specific transmission frequency component and the noise wave in the resonant frequency component. Can be determined.
In addition, when the deviation width of the specific transmission frequency with respect to the resonance frequency is smaller than ± 5%, it may be difficult to discriminate between the circulating wave (noise wave) and the transmitted wave. When the deviation width is larger than ± 50%, amplification by resonance of the transmitted wave is not sufficient, so the deviation width of the specific transmission frequency with respect to the resonance frequency is set within a frequency range of ± 5% to ± 50%. Has been.

  In a further characteristic configuration of the ultrasonic sound velocity measuring device according to the present invention, the sound velocity calculator sets the propagation time to the time until the intensity peak value of the received signal extracted corresponding to the resonance frequency appears. In addition, the sound velocity of the fluid in the pipe is calculated based on the reciprocal sum of the two propagation times.

  According to the above configuration, the sound velocity calculation unit sets the propagation time to the time until the intensity peak value of the received signal extracted corresponding to the resonance frequency appears, so that the received signal (the transmission in the resonance frequency component) The intensity of the (wave) is amplified by resonance, the intensity peak value can be easily specified, and the intensity peak value has sufficient intensity. Thereby, propagation time can be specified more correctly and easily using an intensity peak value.

Schematic diagram illustrating the basic configuration of an ultrasonic sound velocity measuring apparatus and ultrasonic sound velocity measuring method Cross-sectional schematic diagram with the section connecting the transmitting transducer and the receiving transducer cut. Schematic diagram showing the schematic configuration of an ultrasonic sound velocity measuring device Outline flow chart of ultrasonic sound velocity measurement method Waveform diagram showing an example of ultrasonic reception signal Waveform diagram showing an example of a received signal corresponding to the resonance frequency extracted from the ultrasonic received signal Waveform diagram showing an example of an ultrasonic reception signal and a reception signal corresponding to a resonance frequency extracted from the ultrasonic reception signal

  An ultrasonic sound velocity measuring apparatus and an ultrasonic sound velocity measuring method according to an embodiment of the present invention will be described with reference to FIGS. First, the basic principle of measuring the speed of sound of a fluid flowing through the inside of the tube 1 (an example of a fluid in the tube) will be described with reference to the schematic diagram of FIG.

As shown in FIG. 1, a fluid such as city gas, air, LPG, water flows in the pipe 1. This fluid may be a gas or a liquid.
The ultrasonic sound velocity measuring device is a clamp-on type in which a pair of ultrasonic transducers capable of transmitting and receiving ultrasonic waves is arranged on the surface of the tube 1, one ultrasonic transducer functions as the transmitting transducer 2, and the other side The ultrasonic transducer functions as the receiving transducer 3. An ultrasonic wave transmitted to the surface (outer peripheral surface) 11 of the tube 1 by the transmitting transducer 2 and passed through the fluid is received from the surface (outer peripheral surface) 11 of the tube 1 by the receiving transducer 3 and this received signal is evaluated. The sound velocity of the fluid flowing inside the tube 1 is measured.

The ultrasonic propagation time is used for the sound velocity measurement.
Specifically, a pair of ultrasonic transducers capable of transmitting and receiving ultrasonic waves are arranged on the upstream side and the downstream side. Propagation time from transmission of ultrasonic waves from the upstream ultrasonic transducer (transmission transducer 2) to reception by the downstream ultrasonic transducer (reception transducer 3), and downstream ultrasonic transducer (transmission transducer) 2) From the reciprocal sum of the propagation time from transmission of ultrasonic waves to reception by the upstream ultrasonic transducer (receiving transducer 3), the sound velocity of the fluid flowing in the tube 1 (propagating through the fluid) Ultrasonic speed of sound) is required. Here, the measurement in the former arrangement configuration is referred to as a first measurement mode, and the measurement in the latter arrangement configuration is referred to as a second measurement mode. That is, in the first measurement mode and the second measurement mode, the functions of the transmission transducer 2 and the reception transducer 3 are reversed in the two ultrasonic transducers.

As shown in FIG. 1, an ultrasonic wave that enters the tube 1 from the surface 11 of the tube 1 at an inclination angle θ1 from the transmitting transducer 2 propagates in the tube wall at an inclination angle θ2 as a transverse wave ultrasonic wave. The transverse wave ultrasonic wave that has reached the inner surface 12 of the tube 1 enters the fluid at an incident angle θ2, but propagates obliquely in the fluid at a refraction angle θ3 as a longitudinal wave ultrasonic wave by mode conversion that occurs at that time. Longitudinal ultrasonic waves crossing the fluid obliquely and reaching the inner surface 12 of the tube 1 enter the tube wall as transverse wave ultrasonic waves again through mode conversion, and exit from the surface 11 of the tube 1 and are received by the receiving transducer 3.
Here, the propagation path length of longitudinal ultrasonic waves obliquely traversing the fluid is L, the sound velocity of the gas flowing through the tube 1 is C, the fluid velocity is V, and the propagation time in the first measurement mode is T1. Assuming that the propagation time in the second measurement mode is T2, the sound velocity C of the fluid can be expressed by the following equation.
C = ((1 / T1) + (1 / T2)). (L / 2) (Formula 1)
Therefore, the sound velocity C of the fluid can be obtained from T1, T2, and L.

Next, a specific configuration of the ultrasonic sound velocity measuring device will be described.
The ultrasonic-type sound velocity measuring apparatus implements the basic principle described with reference to FIG. 1, and includes a transmitting (receiving) transducer 2 (3) and a receiving ( A transmission) transducer 3 (2) and an ultrasonic processing unit 5 are provided. The positional relationship between the transmitting transducer 2 and the receiving transducer 3 is such that the transverse wave ultrasonic wave incident at an oblique angle from the surface 11 of the tube 1 is converted into a longitudinal wave ultrasonic wave by mode conversion at the inner surface 12 of the tube 1 and crosses the fluid. It is set so that the longitudinal wave ultrasonic wave that has propagated is mode-converted again by the inner surface 12 of the gas tube 1 and the transverse wave ultrasonic wave generated by the surface 11 of the tube 1 is received.
On the ultrasonic excitation surfaces of the transmitting transducer 2 and the receiving transducer 3, a shoe member 31 for performing matching with the curved surface of the tube 1 and oblique incidence is mounted.

The transmitting transducer 2 and the receiving transducer 3 are disposed opposite to the axis of the tube 1. The signal received by the receiving transducer 3 contains effective ultrasonic waves necessary for measurement and other noise waves.
Effective ultrasonic waves (hereinafter sometimes referred to as transmitted waves) are ultrasonic waves (longitudinal ultrasonic waves, indicated by reference numeral Wp1 in FIG. 2) that pass from the surface 11 of the tube 1 toward the inner surface 12, and the tube. 1 is an ultrasonic wave (transverse wave ultrasonic wave, which is indicated by reference sign Ws in FIG. 2) that propagates across (transmits) the fluid inherent in the fluid 1 and an ultrasonic wave that passes from the inner surface 12 of the tube 1 toward the surface 11 ( It reaches the receiving transducer 3 through a form such as longitudinal wave ultrasonic waves (denoted by reference numeral Wp2 in FIG. 2).
A noise wave (hereinafter sometimes referred to as a round wave, which is indicated by a symbol Wn in FIG. 2) is an ultrasonic wave transmitted from the transmitting transducer 2 and is decomposed into a plate wave or a surface wave. The ultrasonic wave thus diffused along the tube wall reaches the receiving transducer 3 and is received.

Below, the example in case the city gas which is gas (an example of a fluid) is flowing in the pipe | tube 1 is demonstrated.
As shown in FIG. 3, the ultrasonic processing unit 5 evaluates the ultrasonic reception signal transmitted from the transmission transducer 2 and reaching the reception transducer 3. As a result, in the first measurement mode and the second measurement mode, the propagation times T1 and T2 of the ultrasonic waves propagating obliquely through the gas are calculated, the sound velocity C of the gas is calculated, and as a result, the gas type of the gas is determined. Is done.
Therefore, the ultrasonic processing unit 5 is transmitted from the changeover switch 50a, the mode switching unit 50, the transmission circuit 51, the reception circuit 52, the signal evaluation unit 53, the parameter setting unit 54, the display unit 55, and the transmission transducer 2. A transmission frequency setting unit 56 is provided for setting the frequency of the transmission frequency.

The transmission circuit 51 generates a high-pressure pulse to excite the piezoelectric element of the transmission transducer 2 to generate an ultrasonic pulse. The frequency of this ultrasonic pulse (specific transmission frequency of specific ultrasonic waves) is set by a transmission frequency setting unit 56 as will be described later.
The receiving circuit 52 performs preprocessing such as amplification on the ultrasonic reception signal received by the receiving transducer 3. The reception circuit 52 can also transmit the waveform of the ultrasonic reception signal to the display unit 55 and cause the display unit 55 to display the waveform.
The display unit 55 is a display such as a liquid crystal display that displays information such as the waveform of the ultrasonic reception signal, the calculated sound velocity C of the gas, and the determined gas type.

  The changeover switch 50 a is a switch for selectively connecting one of the two ultrasonic transducers to the transmission circuit 51 and selectively connecting the other to the reception circuit 52. In the first measurement mode, the mode switching unit 50 connects the ultrasonic transducer located on the upstream side to the transmission circuit 51 as the transmission transducer 2 and connects the ultrasonic transducer located on the downstream side to the reception circuit 52. Then, a control signal is given to the changeover switch 50a so that the receiving side transducer 3 is obtained. On the other hand, in the second measurement mode, the mode switching unit 50 connects the ultrasonic transducer located on the downstream side to the transmission circuit 51 to be the transmission transducer 2 and the ultrasonic transducer located on the upstream side is the reception circuit. A control signal is given to the changeover switch 50a so that it is connected to 52 and becomes the receiving side transducer 3.

  In the parameter setting unit 54, various parameters used in the signal evaluation unit 53 and the transmission frequency setting unit 56 are recorded, and necessary parameters are selected or set directly through an input operation device (not shown) at the time of measurement. The parameters to be set include the material of the tube 1 through which the gas to be measured flows, the wall thickness and the sound velocity of the tube 1 itself (wall portion), the sound velocity of a known gas measured in advance, the transmission transducer 2 to be used, and The frequency of the receiving transducer 3, the angle of incidence on the tube 1, the distance between the transmitting transducer 2 and the receiving transducer 3 are included.

The parameter setting unit 54 selects or directly inputs the parameters recorded in the parameter setting unit 54, and from the information such as the material and thickness of the tube 1 and the sound velocity of the tube 1 itself, the parameter setting unit 54 Set the resonance frequency.
Since the following equation 2 is established for the resonance frequency in relation to the material and thickness of the tube 1 and the sound velocity of the tube 1 itself, by recording this equation 2 in the parameter setting unit 54 in advance, The resonance frequency can be set according to the material, the wall thickness, and the sound speed of the tube 1 itself. The set resonance frequency is sent to the transmission frequency setting unit 56 as a control signal.
f _n = (N × W) / 2d (Expression 2)
f _n : resonance frequency, N: integer, W: speed of sound of the tube itself, d: thickness of the tube

The transmission frequency setting unit 56 transmits a specific ultrasonic wave having a specific transmission frequency shifted from the control signal of the resonance frequency transmitted from the parameter setting unit 54 by a predetermined frequency from the transmission transducer 2. A control signal is transmitted to.
The specific transmission frequency of the specific ultrasonic wave is set to a frequency within a range of ± 5% or more and ± 50% or less with respect to the resonance frequency, and more preferably a frequency within a range of ± 8% or more and ± 40% or less. Set to
For example, as will be described later, since the material of the tube 1 is iron, the wall thickness is 3.2 mm, and the sound speed of the tube 1 itself is 3240 m / sec, the resonance frequency is set to 1.1 MHz, and specific transmission of specific ultrasonic waves is performed. The frequency is set to 1.0 MHz.
The set specific transmission frequency of the specific ultrasonic wave is sent to the transmission circuit 51 as a control signal, and the specific ultrasonic wave of the specific transmission frequency is transmitted to the surface 11 of the tube 1 by the transmission transducer 2.

The signal evaluation unit 53 includes a sound speed calculation unit 53a, a gas type determination unit 53b, and a display data generation unit 53c.
The sound speed calculation unit 53a uses the ultrasonic reception signal in the first measurement mode (solid line in FIGS. 1 and 3) and the ultrasonic reception signal in the second measurement mode (broken line in FIGS. 1 and 3) to receive both ultrasonic reception signals. Propagation times T1 and T2 are calculated. Since the two ultrasonic transducers including the shoe member 31 have the same shape, the time for propagation through the tube wall of the tube 1 is the same in the first measurement mode and the second measurement mode. Therefore, the propagation time corresponds to the propagation times T1 and T2 in the fluid propagation path (indicated by the length L in FIG. 1) when obliquely traversing the fluid (here, gas such as city gas).

The sound velocity calculation unit 53a can extract only the resonance frequency component from each ultrasonic reception signal in the first measurement mode and the second measurement mode received by the reception transducer 3 and transmitted from the reception circuit 51 by frequency separation. It is configured. Then, the intensity peak value of the received signal of the extracted resonance frequency component is specified, and the time from when the specific ultrasonic wave is transmitted until the intensity peak value appears is calculated as propagation times T1 and T2.
Thereafter, the sound velocity C of the gas in the tube 1 is calculated from the propagation times T1 and T2 and the propagation path length L using Equation 1. The sound speed calculation unit 53a can transmit the waveform of the received signal of the extracted resonance frequency component, the calculated propagation times T1 and T2, and the sound speed C of the gas to the display unit 55 so that the display unit 55 displays them.

  The gas type determination unit 53b compares the sound speed C of the gas calculated by the sound speed calculation unit 53a with the sound speed of a fluid such as gas or liquid recorded in advance in the parameter setting unit 54, and there is an approximate sound speed. Determines the gas type of the gas flowing in the pipe 1. Then, the gas type determination unit 53 b generates display data for displaying the determined gas type and sends the display data to the display unit 55. Even if the display data generation unit 53d generates display data for displaying the sound velocity C, gas type, and the like of the gas transmitted from the sound speed calculation unit 53a, the gas type determination unit 53b, and the like, and sends them to the display unit 55, Good.

  Next, an ultrasonic sound velocity measuring method for determining the sound velocity of the gas in the tube 1 and the gas type of the gas using the ultrasonic sound velocity measuring apparatus having the above configuration will be described.

First, two ultrasonic transducers are mounted on the surface 11 of the tube 1 as described above.
Subsequently, the material and thickness of the tube 1 and the sound speed of the tube 1 are collated with the material and thickness of the tube 1 recorded in the parameter setting unit 54 in advance, and the sound speed of the tube 1 itself. A frequency is set (step # 1). For example, the material of the tube 1 is iron, the thickness is 3.2 mm, the sound speed of the tube 1 itself is 3240 m / sec, and the resonance frequency of the tube 1 is set to 1.1 MHz. The set resonance frequency is sent from the parameter setting unit 54 to the transmission frequency setting unit 56 as a control signal.
The transmission frequency setting unit 56 sets the specific transmission frequency of the specific ultrasonic wave that is shifted by a predetermined frequency with respect to the set resonance frequency. Specifically, the specific transmission frequency is set to 1.0 MHz that is shifted to the negative side by 0.1 MHz from the resonance frequency.

Thereafter, in the first measurement mode, a specific ultrasonic wave having a specific transmission frequency is transmitted from the upstream transmitting transducer 2, and the ultrasonic wave reaching the receiving transducer 3 is received (steps # 2 to # 4).
Further, in the second measurement mode, a specific ultrasonic wave having a specific transmission frequency is transmitted from the downstream transmission transducer 2, and the ultrasonic wave reaching the reception transducer 3 is received (steps # 5 to # 7).

  FIG. 5 shows the waveform of the ultrasonic reception signal received by the receiving transducer 3 when the resonance frequency is 1.1 MHz and the specific ultrasonic transmission frequency is 1.0 MHz. The waveform of this ultrasonic reception signal is a state in which reception signals of mainly a resonance frequency component (1.1 MHz) and a specific transmission frequency component (1.0 MHz) are mixed.

Here, the specific transmission frequency component is mainly transmitted from the transmission transducer 2 and is generated when the ultrasonic wave is incident on the surface 11 of the tube 1, or the surface 11 and the inner surface 12 of the tube 1. The resonance frequency component is mainly incident into the gas from the inner surface 12 of the tube 1, whereas it is a reflected wave (noise wave) that propagates through the tube 1 itself, which is a reflected wave that repeatedly reflects between It is a transmitted wave that passes (transmits) through the gas and enters the inner surface 12 of the opposite tube 1.
That is, when the transmission transducer 2 enters a specific ultrasonic wave having a specific transmission frequency shifted from the resonance frequency by a predetermined frequency from the surface 11 of the tube 1, a circulating wave (noise wave) propagating through the tube 1 itself is While reaching the receiving transducer 3 with the substantially specific transmission frequency, the transmitted wave that passes through (transmits) the gas inside the tube 1 has a specific transmission frequency relatively lower than the resonance frequency of the tube wall of the tube 1. Since the frequency range is set to be close, it reaches the receiving transducer 3 at the resonance frequency in a state of being amplified by resonance by the tube wall of the tube 1. Further, since the propagation speed differs between the circulating wave (noise wave) propagating through the tube 1 itself and the transmitted wave, a difference occurs in the arrival time (propagation time) to the receiving transducer 3.

Next, only the resonance frequency component is extracted from the ultrasonic reception signal by frequency separation (step # 8), the intensity peak value of the reception signal of the extracted resonance frequency component is specified, and the relevant ultrasonic wave is transmitted from the transmission of the specific ultrasonic wave. Times until the intensity peak value appears are calculated as propagation times T1 and T2 (step # 9).
Specifically, in step # 8, as shown in FIG. 6, only the resonance frequency component is extracted from the ultrasonic reception signal (see FIG. 5) by frequency separation. In the extracted resonance frequency component (received signal waveform), the intensity of the transmitted wave is improved by resonance and the S / N ratio is improved, so that the transmitted wave can be easily identified. The intensity peak value of the transmitted wave is clearly shown, and the time (propagation time T1, T2) until the intensity peak value appears in step # 9 can be easily specified.

Therefore, in the ultrasonic reception signal received by the receiving transducer 3, the intensity of the transmitted wave in the resonance frequency component is amplified by resonance, and the S / N ratio is improved. Then, by extracting only the resonance frequency component including the transmitted wave from the ultrasonic reception signal, the transmitted wave can be easily discriminated from the circulating wave (noise wave) in the specific transmission frequency component and the noise wave in the resonance frequency component. Can do. Accordingly, the propagation time of the transmitted wave can be accurately calculated from the transmitted wave in the resonance frequency component, and the sound speed of the fluid can be accurately calculated based on such an accurate propagation time.
In particular, since the specific transmission frequency is set to a frequency within a relatively small range of ± 5% to ± 50% with respect to the resonance frequency, the ultrasonic reception signal received by the receiving transducer 3 In addition, the transmission wave mainly composed of the resonance frequency component can be surely amplified to sufficiently improve the S / N ratio of the transmission wave, and in addition, the transmission wave is included from the ultrasonic reception signal. By extracting only the resonance frequency component, the transmitted wave can be more easily discriminated from the circulating wave (noise wave) in the specific transmission frequency component and the noise wave in the resonance frequency component.

Then, the speed of sound C of the gas in the tube 1 is calculated from the both propagation times T1 and T2 and the propagation path length L calculated by Equation 1 (step # 10). That is, the sound velocity C of the gas is calculated from the reciprocal sum of both propagation times T1 and T2, and the sound velocity C is displayed on the display unit 55.
Therefore, the transmitted wave in the ultrasonic reception signal can be easily discriminated and the S / N ratio can be improved, and the propagation time of the transmitted wave and the sound velocity C of the gas can be accurately calculated.

Thereafter, the calculated sound velocity C of the gas is compared with the sound velocity of a known gas or liquid recorded in advance in the parameter setting unit 54. If there is an approximate sound velocity, the gas in the tube 1 is the gas of the sound velocity. If so, the gas type is determined (step # 11), and the determined gas type is displayed on the display unit 55.
Therefore, it is possible to determine the gas type using the sound velocity C of the gas calculated more accurately, and it is also possible to accurately determine the gas type.

[Another embodiment]
(1) In the above embodiment, an example has been described in which the resonance frequency of the tube wall of the tube 1 is set to 1.1 MHz and the specific transmission frequency of the specific ultrasonic wave transmitted by the transmission transducer 2 is set to 1.0 MHz. The resonance frequency can be appropriately set according to the material, thickness, etc. of the tube 1, and the specific transmission frequency of the specific ultrasonic wave also improves the S / N ratio of the resonance frequency component and transmits the resonance frequency component. If it is the structure which can discriminate | determine a wave appropriately, it can set to the frequency shifted | deviated only the predetermined frequency with respect to the said resonant frequency.

For example, the material of the tube 1 is iron, the wall thickness is 3.2 mm, the sound speed of the tube 1 itself is 3240 m / sec, the resonance frequency is set to 1.1 MHz, and the specific transmission frequency of the specific ultrasonic wave is set to 800 kHz. You can also.
In this case, as shown in FIG. 7, the waveform of the ultrasonic wave reception signal received by the reception transducer 3 includes mainly reception signals of the resonance frequency component (1.1 MHz) and the specific transmission frequency component (800 kHz). It is in a state of being.
From this ultrasonic wave reception signal, only the resonance frequency component is extracted by frequency separation, the intensity peak value of the extracted reception signal of the resonance frequency component is specified, and the intensity peak value appears from the transmission of the specific ultrasonic wave Are calculated as propagation times T1 and T2.
Therefore, in the ultrasonic reception signal received by the receiving transducer 3, the intensity of the transmitted wave in the resonance frequency component is amplified by resonance, and the S / N ratio is improved. Then, by extracting only the resonance frequency component including the transmitted wave from the ultrasonic reception signal, the transmitted wave can be easily discriminated from the circulating wave (noise wave) in the specific transmission frequency component and the noise wave in the resonance frequency component. Can do. Accordingly, the propagation times T1 and T2 of the transmitted wave can be accurately calculated from the transmitted wave in the resonance frequency component, and the sound velocity C of the fluid can be accurately calculated based on the accurate propagation times T1 and T2. Can be calculated.
As shown in FIG. 7, in the ultrasonic reception signal received by the receiving transducer 3, the extracted resonance frequency component basically has the same intensity fluctuation (of the ultrasonic reception signal as that of the ultrasonic reception signal). It has a waveform with a strength attenuated at a predetermined rate with respect to the strength), but the portion of the resonant frequency component that has passed (transmitted) the gas in the tube 1 (transmitted wave) is amplified by resonance. Therefore, the attenuation ratio with respect to the intensity of the ultrasonic reception signal becomes low. Therefore, a portion of the extracted resonance frequency component having a low attenuation ratio can be identified as a transmitted wave, and the intensity peak value of the transmitted wave can be used for calculating the propagation times T1 and T2.
In addition, since the intensity of the transmitted wave, which is a resonance frequency component, is amplified by resonance, the propagation time of the transmitted wave can be calculated more accurately. Based on such an accurate propagation time, the flow of the fluid can be calculated. The speed of sound can be calculated accurately.

(2) In the above embodiment, in calculating the sound velocity of the fluid, both propagation times when the longitudinal ultrasonic wave obliquely crosses the fluid only once in the first measurement mode and the second measurement mode are used. However, the sound velocity of the fluid can also be calculated by using both propagation times when the ultrasonic wave crosses the fluid at least twice using the reflected wave that the longitudinal ultrasonic wave repeats on the inner surface 12 of the tube 1. .

(3) In the above embodiment, gas such as city gas has been described as an example of the fluid (in-pipe fluid), but it may be a liquid such as water.

  The present invention improves the S / N ratio of the transmitted wave in the ultrasonic reception signal and can easily determine the transmitted wave, and can accurately calculate the propagation time of the transmitted wave and the sound speed of the fluid. The present invention can be applied to an ultrasonic sound velocity measuring apparatus and an ultrasonic sound velocity measuring method.

1 Tube 2 Transducer for transmission (ultrasonic transducer)
3 Receiving transducer (ultrasonic transducer)
11 Surface 53a Sound velocity calculation unit T1 Propagation time (first measurement mode)
T2 propagation time (second measurement mode)
C Sound velocity of gas (fluid)

Claims (5)

A transducer for transmitting oblique incidence of ultrasonic waves from the surface of the tube through which the fluid in the tube flows;
A receiving transducer for receiving the ultrasonic wave transmitted by the transmitting transducer at the surface of the tube;
An ultrasonic reception signal in the first measurement mode in which the receiving transducer is arranged downstream from the transmission transducer, and an ultrasonic reception signal in the second measurement mode in which the receiving transducer is arranged upstream from the transmission transducer; A sound speed calculation unit that calculates the sound speed of the fluid in the pipe from both propagation times, and an ultrasonic sound speed measurement device comprising:
The transmission transducer has a specific transmission frequency shifted by a predetermined frequency with respect to the resonance frequency of the tube wall of the tube calculated from the thickness of the tube in each of the first measurement mode and the second measurement mode. The specific ultrasonic wave is obliquely incident from the surface of the tube,
The receiving transducer receives an ultrasonic wave reaching the receiving transducer in each of the first measurement mode and the second measurement mode;
The sound velocity calculation unit extracts a reception signal corresponding to the resonance frequency from the ultrasonic reception signal of the ultrasonic wave received by the reception transducer in each of the first measurement mode and the second measurement mode, An ultrasonic sound velocity measuring device that calculates the sound velocity of the fluid in the pipe from the propagation time of the received signal.   The specific transmission frequency of the specific ultrasonic wave transmitted by the transmission transducer is set to a frequency within a range that is shifted by ± 5% or more and ± 50% or less with respect to the resonance frequency. Ultrasonic sound velocity measuring device.   The sound speed calculation unit sets the propagation time to a time until the intensity peak value of the received signal extracted corresponding to the resonance frequency appears, and based on the reciprocal sum of the two propagation times, The ultrasonic sound velocity measuring device according to claim 1, wherein the sound velocity of the fluid is calculated. Specific ultrasonic waves having a specific transmission frequency that is shifted by a predetermined frequency from the resonance frequency of the tube wall of the tube calculated from the wall thickness of the tube from a transmission transducer arranged on the surface of the tube through which the fluid in the tube flows Obliquely incident from the surface of the tube;
Receiving ultrasonic waves reaching the receiving transducer with a receiving transducer disposed on the surface of the tube;
A reception signal corresponding to the resonance frequency is extracted from the ultrasonic reception signal in the first measurement mode in which the reception transducer is arranged downstream from the transmission transducer, and the reception transducer is located upstream from the transmission transducer. Extracting a reception signal corresponding to the resonance frequency from the ultrasonic reception signal in the second measurement mode arranged in
Calculating the sound velocity of the fluid in the pipe from the extracted propagation times of the two received signals.   The step of setting the specific transmission frequency of the specific ultrasonic wave transmitted by the transducer for transmission to a frequency within a range shifted by ± 5% or more and ± 50% with respect to the resonance frequency. Ultrasonic sound speed measurement method.

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