JP2009270882A - Ultrasonic flowmeter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultrasonic flowmeter which simplifies attachment of ultrasonic equipment, prevents deterioration of measuring accuracy due to a temperature change and lessens a load of flow rate calculation. <P>SOLUTION: The ultrasonic flowmeter includes a plurality of ultrasonic detection means which are installed on the outer surface of a tube part having a passage through which a fluid flows, being arranged in the axial direction of the tube part, a transmission means which is so installed on the outer surface of the tube part as to be opposite, through the tube part, to a reference ultrasonic detection means out of the ultrasonic detection means in a plurality and transmits an ultrasonic wave in the direction to the reference ultrasonic detection means, and an arithmetic means which specifies a position of reception of the ultrasonic wave shifted in the shifting direction deviating from the direction of transmission by a flow of the fluid, based on outputs of the ultrasonic detection means in a plurality, determines a deviation angle being an angle formed by the direction of transmission and the shifting direction, based on a distance between the position of reception and the reference ultrasonic detection means, determines also the sound velocity inside the tube part, based on the outputs of the ultrasonic detection means, and determines a flow rate of the fluid, based on the sound velocity and the deviation angle. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an ultrasonic flow meter, and more particularly to a clamp-on type ultrasonic flow meter.

  A clamp-on type ultrasonic flowmeter (hereinafter simply referred to as “clamp-on flowmeter”) uses an ultrasonic device installed on the outer surface of a pipe part to control the flow rate and flow rate of the fluid flowing in the pipe part. taking measurement.

  In a conventional clamp-on flow meter, first and second ultrasonic transmitters / receivers (hereinafter simply referred to as “transmitters / receivers”) are formed on the outer surface of the pipe portion so as to be diagonally opposed to the fluid flow direction. Installed.

  The flow rate and flow velocity of the fluid in the pipe section are the propagation time from when the first transmitter / receiver transmits the ultrasonic wave until the second transmitter / receiver receives the ultrasonic wave, and the second transmitter / receiver receives the ultrasonic wave. Is measured based on the difference between the transmission time from when the first transmitter / receiver transmits the ultrasonic wave until the first transmitter / receiver receives the ultrasonic wave. This measurement method is called a propagation time difference method.

  In the clamp-on flow meter, if the installation position of an apparatus (for example, a transmitter / receiver) that transmits / receives ultrasonic waves is inaccurate, sufficient ultrasonic sensitivity cannot be obtained and measurement errors occur.

  For this reason, in a clamp-on flow meter in which each transmitter / receiver must be installed so as to be diagonally opposed to the fluid flow direction, a device for positioning each transmitter / receiver becomes a large-scale device, and the mounting of the transmitter / receiver is simple. There wasn't.

  The first and second transceivers transmit and receive ultrasonic waves in an oblique direction with respect to the fluid flow direction. For this reason, when the refraction angle of the ultrasonic wave changes due to a temperature change, there is a problem that the ultrasonic sensitivity is lowered and the performance as a measuring instrument cannot be obtained sufficiently. In particular, this problem is significant when the fluid is a gas having a low density.

  Furthermore, the propagation time difference method requires time measurement with high accuracy, and uses a sufficiently fast clock with respect to the ultrasonic frequency and a large number of data points to capture the entire ultrasonic signal in order to obtain high time resolution. It is necessary to calculate time, and the calculation load tends to increase.

  An object of the present invention is to provide an ultrasonic flowmeter capable of simplifying the installation of an ultrasonic device, preventing deterioration in measurement accuracy due to a temperature change, and reducing the load of flow rate calculation. It is.

  The ultrasonic flowmeter according to the present invention includes a plurality of ultrasonic detection means arranged on the outer surface of a pipe portion having a flow path through which fluid flows and arranged in the axial direction of the pipe portion, and the plurality of ultrasonic detection means. Is installed on the outer surface of the pipe part so as to face the reference ultrasonic wave detection means via the pipe part, and transmits the ultrasonic wave with the direction to the reference ultrasonic wave detection means as the transmission direction. And a reception position of the ultrasonic wave traveling in a traveling direction shifted from the transmission direction by the flow of the fluid based on outputs from the plurality of ultrasonic detection means, and the reception position and the reference A deviation angle, which is an angle formed between the transmission direction and the traveling direction, is obtained based on the distance between the ultrasonic detection means, and the tube is obtained based on outputs from the plurality of ultrasonic detection means. The sound speed in the club is calculated and the sound speed and the bias Based on the angular includes, calculating means for determining the flow rate of the fluid.

  According to the above invention, it is not necessary to install the plurality of ultrasonic detection means and the transmission means so as to be diagonally opposed to the fluid flow direction. For this reason, it is possible to simplify the attachment of the plurality of ultrasonic detection means and the transmission means, and it is possible to prevent deterioration in measurement accuracy due to temperature changes.

  The computing means obtains the deviation angle and the sound velocity in the tube section based on the outputs from the plurality of ultrasonic detecting means, and obtains the fluid flow rate based on the sound speed and the deviation angle. For this reason, it is possible to eliminate the need for highly accurate time measurement, which is necessary in the propagation time difference method.

  In addition, it is preferable that the calculation unit obtains the deviation angle based on a distance between the reception position and the reference ultrasonic wave detection unit and a diameter of the flow path.

  Further, the calculation means obtains an amplitude distribution of the ultrasonic waves on a receiving surface constituted by the plurality of ultrasonic detection means based on outputs from the plurality of ultrasonic detection means, and based on the amplitude distribution It is desirable to specify the reception position of the ultrasonic wave.

  Further, the calculation means obtains a point coefficient indicating the degree of sharpness of the amplitude distribution based on outputs from the plurality of ultrasonic detection means, and obtains a sound velocity in the pipe portion based on the point coefficient. Is desirable.

  The arithmetic means preferably obtains a distortion coefficient indicating a degree of distortion of the amplitude distribution based on outputs from the plurality of ultrasonic detection means, and performs pass / fail judgment of the amplitude distribution based on the distortion coefficient. .

  According to the present invention, it is possible to simplify the installation of an ultrasonic device, to prevent deterioration in measurement accuracy due to a temperature change, and to reduce the load of flow rate calculation.

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

  FIG. 1 is a block diagram showing an ultrasonic flowmeter according to an embodiment of the present invention.

  In FIG. 1, the ultrasonic flowmeter includes a plurality of reception sensors 11 to 1n (n is an integer equal to or greater than 2), a transmission sensor 2, and an arithmetic control unit 3. The arithmetic control unit 3 includes a transmission / reception control device (hereinafter simply referred to as “control device”) 31, an ultrasonic transmission device (hereinafter simply referred to as “transmission device”) 32, and an ultrasonic reception device (hereinafter referred to as “control device”). (Hereinafter simply referred to as “receiving device”) 33 and a signal processing device 34.

  The reception sensors 11 to 1n are an example of a plurality of ultrasonic detection means. As the receiving sensors 11 to 1n, for example, ultrasonic transducers are used.

  The receiving sensors 11 to 1n are arranged and arranged in the axial direction of the tube portion 10c on the outer surface 10d of the tube portion 10c having the flow path 10b through which the fluid 10a flows.

  When receiving each ultrasonic wave (ultrasonic beam), each of the reception sensors 11 to 1n outputs a weak signal (hereinafter referred to as a “detection signal”) whose amplitude changes according to the intensity of the ultrasonic wave.

  In the present embodiment, among the reception sensors 11 to 1n, a reception sensor located at the center of the array or in the vicinity of the center is referred to as a center reception sensor 1c. The center reception sensor 1c is an example of a reference ultrasonic wave detection unit.

  The transmission sensor 2 is an example of a transmission unit. For example, an ultrasonic transducer is used as the transmission sensor 2.

  The transmission sensor 2 is installed on the outer surface 10d of the tube portion 10c so as to face the center reception sensor 1c via the tube portion 10c. In the present embodiment, the transmission sensor 2 is disposed so as to face the center reception sensor 1c perpendicularly to the axial direction of the tube portion 10c. In addition, the transmission sensor 2 may be arrange | positioned so that the center reception sensor 1c may be opposed substantially perpendicularly with respect to the axial direction of the pipe part 10c.

  When the transmission sensor 2 receives a transmission signal from the transmission device 32, an ultrasonic wave (direction indicated by an arrow A shown in FIG. 1) from the transmission sensor 2 to the center reception sensor 1c via the tube portion 10c is used as a transmission direction. Transmit ultrasonic beam).

  Arithmetic controller 3 can generally be referred to as computing means. The calculation control unit 3 calculates the flow rate of the fluid 10a based on detection signals (outputs) from the reception sensors 11 to 1n.

  Specifically, the arithmetic control unit 3 moves in the traveling direction (arrow shown in FIG. 1) shifted from the transmission direction (arrow A direction shown in FIG. 1) by the flow of the fluid 10a (arrow B shown in FIG. 1). The reception positions X of the ultrasonic waves (ultrasonic beams) traveling in the (C direction) on the reception sensors 11 to 1n are specified based on the detection signals from the reception sensors 11 to 1n.

  For example, the arithmetic control unit 3 obtains the amplitude distribution of the ultrasonic wave on the reception surface constituted by the reception sensors 11 to 1n based on the detection signals from the respective reception sensors 11 to 1n, and receives based on the amplitude distribution. The position X is specified.

  Note that the arithmetic control unit 3 obtains a distortion coefficient indicating the degree of distortion of the amplitude distribution based on the detection signals from the reception sensors 11 to 1n, and determines whether the amplitude distribution is acceptable based on the distortion coefficient. Good.

  The arithmetic control unit 3 obtains a distance (δs shown in FIG. 1) between the reception position X and the center reception sensor 1c, and based on the distance δs, a deviation angle that is an angle formed between the transmission direction and the traveling direction. (An angle θ shown in FIG. 1) is obtained.

  Moreover, the calculation control part 3 calculates | requires the sound speed in the pipe part 10c based on the detection signal from each receiving sensor 11-1n.

  For example, the arithmetic control unit 3 obtains a point coefficient indicating the degree of sharpness of the amplitude distribution based on the detection signals from the respective reception sensors 11 to 1n, and obtains the sound speed in the tube unit 10c based on the point coefficient. May be.

  The arithmetic control unit 3 obtains the flow rate of the fluid 10a based on the sound speed and the deviation angle.

  The control device 31 provides a transmission trigger signal to the transmission device 32 and the signal processing device 34. In addition, the control device 31 provides a switch switching signal to the reception device 33.

  When receiving a transmission trigger signal from the control device 31, the transmission device 32 provides a transmission signal to the transmission sensor 2.

  The reception device 33 includes a switch 33a that can be individually connected to each of the reception sensors 11 to 1n, an amplifier (amplifier) 33b, and a filter 33c.

  Each time the reception device 33 receives a switch switching signal from the control device 31, the reception device 33 sequentially switches the connection of the switch 33a, scans the individual detection signals of the reception sensors 11 to 1n, and amplifies the individual detection signals by the amplifier 33b. Then, it is filtered by the filter 33 c and provided to the control device 31. Note that the control device 31 provides each signal detected from the receiving device 33 to the signal processing device 34.

  The signal processing device 34 measures the amplitude peak (peak voltage) of each detection signal based on the detection signals from the individual reception sensors 11 to 1n.

  Based on the measurement result of the peak, the signal processing device 34 obtains the amplitude distribution of the ultrasonic wave (ultrasonic beam) on the reception surface constituted by the reception sensors 11 to 1n, and based on the amplitude distribution, the ultrasonic wave ( The deviation angle of the ultrasonic beam), the speed of sound in the tube 10c, the flow rate of the fluid 10a, and the like are calculated.

  Next, the operation will be described.

  The control device 31 provides a transmission trigger signal to the transmission device 32 and the signal processing device 34 when an operation instruction is received from a user or a management device (not shown) or when a predetermined operation time is reached, for example. The switch switching signal is sequentially provided to the receiving device 33 at predetermined time intervals.

  When receiving the transmission trigger signal, the transmission device 32 provides the transmission signal to the transmission sensor 2. FIG. 2 is an explanatory diagram showing an example of a transmission signal.

  When the transmission sensor 2 receives the transmission signal, it transmits ultrasonic waves (ultrasonic waves) in a direction perpendicular to the axial direction of the tube 10c, specifically toward the center reception sensor 1c (in the direction of arrow A shown in FIG. 1). Sound wave).

  When each of the reception sensors 11 to 1n receives the ultrasonic wave (ultrasonic beam) transmitted from the transmission sensor 2, it outputs a detection signal.

  Note that the ultrasonic wave (ultrasonic beam) transmitted from the transmission sensor 2 is shifted under the influence of the flow of the fluid 10a in the tube 10c (see arrow C shown in FIG. 1).

  Therefore, when the fluid 10a is not flowing, the amplitude of the detection signal from the center reception sensor 1c is larger than the amplitude of the detection signals from other reception sensors.

  FIG. 3A is an explanatory diagram showing an example of a detection signal (ultrasonic reception signal) output from the center reception sensor 1c in a state where the fluid 10a is not flowing. FIG. 3B is an explanatory diagram showing an example of detection signals (ultrasonic reception signals) output from the reception sensors 11 and 1n at both ends in a state where the fluid 10a is not flowing.

  On the other hand, when the fluid 10a is flowing, there is a high possibility that the amplitude of the detection signal from one receiving sensor different from the center receiving sensor 1c is larger than the amplitude of the detection signal from another receiving sensor.

  In the receiving device 33, each time a switch switching signal is received, the switch 33a sequentially switches the connections in a predetermined order to scan the individual detection signals of the reception sensors 11 to 1n, and the amplifier 33b performs the individual detection signal. The filter 33c filters the individual detection signals, and the individual detection signals are provided to the control device 31.

  FIG. 4A illustrates an example of a signal (amplified and filtered detection signal) that is output when the reception device 33 receives a detection signal output from the center reception sensor 1c in a state where the fluid 10a is not flowing. It is explanatory drawing shown.

  FIG. 4B shows a signal (amplified and filtered detection signal) that is output when the reception device 33 receives detection signals output from the both-end reception sensors 11 and 1n in a state where the fluid 10a is not flowing. It is explanatory drawing which showed an example.

  The control device 31 provides each detection signal received from the receiving device 33 to the signal processing device 34.

  Upon receiving individual detection signals, the signal processing device 34 first calculates a beam (ultrasonic wave) deviation angle (angle θ shown in FIG. 1) based on the detection signals.

  Specifically, the signal processing device 34 first sets the position of the center receiving sensor 1c to 0, and the distance from the center receiving sensor 1c to another receiving sensor (that is, the position of the center receiving sensor 1c is set to 0). The peak voltage of the detection signal from each of the reception sensors 11 to 1n is plotted on a graph in which the horizontal axis is the position of each reception sensor 11 to 1n and the vertical axis is the peak voltage (amplitude peak value) of the detection signal. Obtain the amplitude distribution.

  Note that the positions of the reception sensors 11 to 1n are registered in the signal processing device 34 in advance. In addition, since the connection order of the switch 33a is determined in advance, the signal processing device 34 can recognize from which reception sensor the received detection signal is output.

  FIG. 5 is an explanatory diagram showing an example of the amplitude distribution. In FIG. 5, an amplitude distribution 5a is an example of an amplitude distribution when there is no flow of the fluid 10a, and an amplitude distribution 5b is an example of an amplitude distribution when the fluid 10a flows in the direction of arrow B shown in FIG. It is.

  Subsequently, the signal processing device 34 specifies a position (position on the horizontal axis) δs indicating the peak of the amplitude distribution. Note that δs is a coordinate indicating the reception position X and also represents a distance between the reception position X and the center reception sensor 1c.

  Subsequently, the signal processing device 34 uses a previously registered inner diameter (diameter of the flow path 10b) D of the tube 10c and a value (distance between the reception position X and the central reception sensor 1c) δs, The deviation angle θ is calculated according to the equation shown in Equation 1.

  Subsequently, the signal processing device 34 obtains a point coefficient based on detection signals from the reception sensors 11 to 1n.

  The pointed coefficient is a coefficient indicating how sharp the amplitude distribution is when the amplitude distribution is plotted, and is calculated according to the equation shown in Equation 2.

  Note that n is the number of data (in this case, the number of reception sensors), σ is the standard deviation, xi is the data (in this case, the peak value of the detection signal from the reception sensor 1i),

Is an average value of data (in this case, an average value of peak values of detection signals from the reception sensors 11 to 1i).

  The signal processing device 34 calculates the point coefficient according to the equation shown in Equation 2.

  FIG. 6 is an explanatory diagram showing the relationship between the point coefficient and the amplitude distribution.

  It is known that the point coefficient indicates the spread of the ultrasonic beam and depends on the speed of sound in the tube 10c. For this reason, the signal processing device 34 obtains the speed of sound in the tube 10c based on the point coefficient.

  Subsequently, the signal processing device 34 obtains a distortion coefficient based on the detection signals from the reception sensors 11 to 1n.

  The distortion coefficient is a coefficient indicating how much the amplitude distribution is distorted when the amplitude distribution is plotted, and is calculated according to the equation shown in Equation 4.

  The signal processing device 34 calculates a distortion coefficient according to the equation shown in Equation 4.

  FIG. 7 is an explanatory diagram showing the relationship between the distortion coefficient and the amplitude distribution.

  The signal processing device 34 can estimate the degree of fluid turbulence and drift by obtaining the distortion coefficient.

  For example, the signal processing device 34 uses the degree of fluid turbulence and drift for monitoring the state of the fluid 10a. Further, since the distortion of the amplitude distribution causes an error of the deviation angle θ, the signal processing device 34 uses the degree of fluid turbulence and the degree of drift obtained from the distortion coefficient for determining the quality of the amplitude distribution.

  Since the distortion coefficient, the fluid turbulence degree, and the drift degree are not directly used for the flow rate measurement, the signal processing device 34 may not calculate the distortion coefficient, the fluid turbulence degree, and the drift degree.

  Subsequently, the signal processing device 34 calculates the velocity component V in the flow direction B of the fluid 10a using the sound velocity C and the deviation angle θ according to the mathematical formula shown in Equation 5.

  Subsequently, the signal processing device 34 includes a velocity component V in the flow direction B of the fluid 10a, a pre-registered cross-sectional area in the pipeline (area of the surface defined by the inner periphery of the pipe portion 10c) A, Is used to calculate the flow rate Q of the fluid 10a according to the equation shown in Equation 6.

  According to the present embodiment, it is not necessary to install the reception sensors 11 to 1n and the transmission sensor 2 so as to be diagonally opposed to the flow direction B of the fluid 10a. For this reason, it becomes possible to simplify the attachment of the reception sensors 11 to 1n and the transmission sensor 2, and it is possible to prevent deterioration in measurement accuracy due to temperature changes.

  In particular, when the transmission sensor 2 is disposed so as to face the central reception sensor 1c perpendicularly to the axial direction of the tube portion 10c, the installation space can be made simpler and smaller than the conventional inclined mounting structure. it can.

  In this case, the transmission sensor 2 is disposed so as to face the central reception sensor 1c perpendicularly to the axial direction of the tube portion 10c, and an ultrasonic wave (ultrasonic beam) is also directed to the axial direction of the tube portion 10c. Because it propagates almost vertically, it is less susceptible to changes in temperature.

  In addition, the arithmetic control unit 3 obtains the deviation angle and the sound velocity in the pipe portion 10c based on the outputs from the receiving sensors 11 to 1n, and based on the sound velocity and the deviation angle, the flow rate of the fluid Ask for. For this reason, it is possible to eliminate the need for highly accurate time measurement, which is necessary in the propagation time difference method.

  Moreover, since the calculation control part 3 can calculate a flow volume only using the maximum amplitude of the detection signal from each receiving sensor 11-1n as a parameter for flow volume calculation, a calculation load becomes very small.

  Further, the calculation control unit 3 can estimate the fluid sound speed by obtaining a point coefficient relating to the amplitude distribution.

  In addition, the arithmetic control unit 3 can determine whether or not the fluid turbulence is measured and the measurement value is good or bad by obtaining a distortion coefficient related to the amplitude distribution.

  In the embodiment described above, the illustrated configuration is merely an example, and the present invention is not limited to the configuration.

  For example, the signal processing device 34 may measure the propagation time from when the ultrasonic wave is transmitted from the transmission sensor 2 until the central reception sensor 1c receives the ultrasonic wave. The signal processing device 34 uses the measurement result for self-diagnosis of the sound speed obtained from the point coefficient. Further, the signal processing device 34 may obtain the sound velocity C in the tube 10c from the measurement result.

It is the block diagram which showed the ultrasonic flowmeter of one Embodiment of this invention. It is explanatory drawing which showed an example of the transmission signal. It is explanatory drawing which showed an example of the detection signal. It is explanatory drawing which showed an example of the signal which the receiver 33 outputs. It is explanatory drawing which showed an example of amplitude distribution. It is explanatory drawing which showed the relationship between a point coefficient and amplitude distribution. It is explanatory drawing which showed the relationship between a distortion coefficient and amplitude distribution.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10a Fluid 10b Flow path 10c Pipe part 10d Outer surface 11-1n Reception sensor 1c Center reception sensor 2 Transmission sensor 3 Arithmetic control part 31 Transmission / reception control apparatus 32 Ultrasonic transmission apparatus 33 Ultrasonic reception apparatus 33a Switch 33b Amplifier 33b Filter 34 Signal processing apparatus

Claims (5)

A plurality of ultrasonic detection means arranged in the axial direction of the pipe part on the outer surface of the pipe part having a flow path through which the fluid flows;
It is installed on the outer surface of the pipe part so as to face the reference ultrasonic detection means among the plurality of ultrasonic detection means via the pipe part, and the direction to the reference ultrasonic detection means is a transmission direction. Transmitting means for transmitting ultrasonic waves;
Based on the outputs from the plurality of ultrasonic detection means, the reception position of the ultrasonic wave traveling in the traveling direction deviated from the transmission direction by the flow of the fluid is specified, and the reception position and the reference ultrasonic wave detection A deviation angle, which is an angle formed by the transmission direction and the traveling direction, is obtained based on a distance between the plurality of means, and based on outputs from the plurality of ultrasonic detection means, An ultrasonic flowmeter comprising: calculating means for obtaining a sound velocity and obtaining the flow rate of the fluid based on the sound velocity and the deviation angle. The ultrasonic flowmeter according to claim 1,
The said calculating means is an ultrasonic flowmeter which calculates | requires the said deviation angle based on the distance between the said receiving position and the said reference | standard ultrasonic detection means, and the diameter of the said flow path. The ultrasonic flowmeter according to claim 1 or 2,
The calculation means obtains an amplitude distribution of the ultrasonic waves on a receiving surface constituted by the plurality of ultrasonic detection means based on outputs from the plurality of ultrasonic detection means, and based on the amplitude distribution, An ultrasonic flowmeter that identifies a reception position of the ultrasonic wave. The ultrasonic flowmeter according to claim 3,
The calculation means obtains a point coefficient indicating the degree of sharpness of the amplitude distribution based on outputs from the plurality of ultrasonic detection means, and obtains a sound velocity in the tube portion based on the point coefficient. Flowmeter. The ultrasonic flowmeter according to claim 3 or 4,
The calculation means obtains a distortion coefficient indicating a degree of distortion of the amplitude distribution based on outputs from the plurality of ultrasonic detection means, and performs pass / fail judgment of the amplitude distribution based on the distortion coefficient. Flowmeter.

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