JPWO2008004560A1 - Flow velocity distribution measuring device and ultrasonic flow meter - Google Patents

Abstract

To accurately measure the flow velocity distribution of the gas fluid flowing in the fluid piping using ultrasonic pulses. An ultrasonic pulse is incident on the fluid to be measured G flowing in the fluid pipe (10) from the transmitting transducer (11) installed on the pipe wall of the fluid pipe (10), and the opposite pipe wall in the fluid pipe (10) The ultrasonic pulses are detected by a plurality of receiving transducers (12) installed in a two-dimensional manner. The displacement amount of the ultrasonic pulse in the tube axis direction is detected from the detection signals of the plurality of receiving transducers arranged in the tube axis direction among the plurality of receiving transducers (12). Two measurement lines 1 and 2 having slightly different opening angles α are set, and the flow velocity at the predetermined position [h1, h2] is obtained from the displacement amount and the flight time difference detected for each measurement line 1 and 2 respectively.

Description

  The present invention relates to a flow velocity distribution measuring apparatus suitable for measuring a flow velocity distribution of a fluid to be measured flowing through a pipe, particularly a gas fluid, using an ultrasonic wave, and an ultrasonic flowmeter using the same.

  Conventionally, a Doppler type ultrasonic flowmeter that measures the flow rate of a fluid to be measured using an ultrasonic Doppler shift has been proposed (for example, see Patent Document 1). The Doppler type ultrasonic flowmeter disclosed in Patent Document 1 moves the ultrasonic transducer 101 in the flow direction of the fluid 103 to be measured by an angle α with respect to the diameter direction of the fluid pipe 102 as shown in FIG. Tilt and place. When an ultrasonic pulse having a required frequency is made incident from the ultrasonic transducer 101, it is reflected by a reflector such as a bubble or a foreign substance uniformly distributed on the fluid 103 to be measured on the measurement line ML, as shown in FIG. The reflected echo a enters the ultrasonic transducer 101. In FIG. 16B, reference symbol b is a multiple reflection echo that is reflected by the tube wall on the ultrasonic pulse incident side, and reference symbol c is a multiple reflection echo that is reflected by the opposite tube wall. The transmission interval of the ultrasonic pulses transmitted from the ultrasonic transducer 101 is 1 / Frpf. When the ultrasonic echo received by the ultrasonic transducer 101 is filtered and the flow velocity distribution is measured along the measurement line ML using the Doppler shift method, the display is as shown in FIG.

  In the Doppler shift method, when an ultrasonic pulse is radiated into the fluid 103 to be measured flowing in the fluid pipe 102, it is reflected by a reflector having a mixed or uniform distribution in the fluid 103 to be an ultrasonic echo. It applies the principle that the frequency of the sound echo shifts by a magnitude proportional to the flow velocity. A change in the flow velocity is measured from the fundamental frequency of the ultrasonic pulse incident on the fluid 103 to be measured and the frequency of the ultrasonic echo subjected to the Doppler shift, and the flow velocity distribution in the measurement region along the measurement line ML is calculated. Furthermore, the flow velocity distribution in the vertical cross section of the fluid pipe 102 can be measured by calibrating the flow velocity distribution in the measurement region with the inclination angle α.

The above Doppler type ultrasonic flow meter can obtain the flow velocity distribution in the measurement region instantaneously in a time-dependent manner, and therefore the flow rate of the fluid 103 to be measured can be obtained accurately and accurately regardless of whether it is in a steady state or an unsteady state. Can do.
JP 2003-130699 A

  However, since the Doppler type ultrasonic flowmeter needs to uniformly distribute (mix) the reflector that reflects the incident ultrasonic pulse in the measured fluid, the measured fluid is a gas fluid. Has a problem that the flow velocity distribution cannot be measured accurately.

  The present invention has been made in view of such a point, and even when the fluid to be measured flowing in the fluid piping is a gaseous fluid, the flow velocity distribution measuring device and the ultrasonic flowmeter capable of accurately measuring the flow velocity distribution. The purpose is to provide.

  The flow velocity distribution measuring apparatus according to the present invention includes a transmitter that is installed on a pipe wall of a fluid pipe, generates an ultrasonic pulse, and enters the fluid to be measured flowing in the fluid pipe, and a pipe that faces the transmitter in the fluid pipe. A plurality of receivers that are two-dimensionally installed on the wall and output detection signals having an amplitude corresponding to the received ultrasonic intensity, and detection signals from a plurality of receivers arranged in the tube axis direction among the receivers. The amount of displacement of the sound wave pulse in the tube axis direction is detected, and an angle formed by a line segment passing through the emission end and the pipe center when viewed from the emission end of the transmitter is defined as an open angle, and the transmitter is used to transmit a predetermined receiver. A flow velocity for obtaining a flow velocity at a predetermined position determined by a perpendicular line from the center of the pipe with respect to the two measurement lines, based on a displacement amount detected for each of the two measurement lines having slightly different opening angles, with the measurement area up to the measurement line With distribution measuring means Characterized in that was.

  According to this configuration, the flow velocity at a predetermined position determined by the perpendicular from the center of the pipe to the two measurement lines is obtained from the displacements detected for the two measurement lines having slightly different opening angles. Even in the case of a gas fluid, the flow velocity distribution can be accurately measured without uniformly distributing (mixing) the reflector in the fluid to be measured.

  The flow velocity distribution measuring device of the present invention is installed in a line along the pipe axis direction on the pipe wall of the fluid pipe, generates ultrasonic pulses, and flows into the fluid to be measured from different positions in the pipe axis direction. A plurality of incident transmitters, a plurality of receivers that are installed in a line along a tube circumferential direction on a tube wall facing the transmitter, and that output detection signals having amplitudes according to received ultrasonic intensity, respectively, The maximum peak value of the detection signal is detected for the receiver, and the amount of displacement of the ultrasonic pulse in the tube axis direction is determined from the relative relationship between the receiver showing the maximum peak value and the transmitter position where the ultrasonic pulse was emitted at that time. Detected, the angle formed by the line segment passing through the emission end and the pipe center as seen from the emission end of the transmitter as an open angle, the measurement area from the transmitter to a predetermined receiver as a measurement line, Two measuring lines with slightly different opening angles Characterized by comprising a flow velocity distribution measuring means for determining the flow rate of the predetermined position determined by the perpendicular from the center of the piping from the displacement amount of each detected for the two measurement lines Te.

  With this configuration, the opening angle is slightly different from the relative relationship between the transmitters arranged in a line along the pipe axis direction and the receivers arranged in a line along the pipe circumferential direction on the opposite side of the pipe. Since the displacement amount is obtained for the book measurement line, the total number of transmitters and receivers can be reduced.

  The flow velocity distribution measuring apparatus according to the present invention includes a transmitter that is installed on a pipe wall of a fluid pipe, generates an ultrasonic pulse, and enters the fluid to be measured flowing in the fluid pipe, and a pipe wall that faces the transmitter. A plurality of receivers arranged in a line along the tube circumferential direction at a predetermined position in the tube axis direction, each outputting a detection signal having an amplitude corresponding to the received ultrasonic intensity, and the transmitter from the detection signal of each receiver The flight time until the ultrasonic pulse emitted from the transmitter reaches each receiver is detected, and an angle formed by a line segment passing through the output end and the pipe center when viewed from the output end of the transmitter is defined as an opening angle. The measurement region from the transmitter to the predetermined receiver is defined as a measurement line, and a predetermined value determined by a perpendicular to the two measurement lines from the time of flight detected for each of the two measurement lines having slightly different opening angles. Find the velocity of the position Characterized by comprising a speed distribution measurement unit.

  With this configuration, the flow velocity at a predetermined position determined by the perpendicular to the two measurement lines can be obtained from the flight time of the ultrasonic pulse detected for each of the two measurement lines having slightly different opening angles. Even in the case of a gas fluid, the flow velocity distribution can be accurately measured without uniformly distributing (mixing) the reflector in the fluid to be measured. In addition, since the time of flight of the ultrasonic pulse can be detected with one transmitter and the receivers installed in a line along the pipe circumferential direction, the total number of transmitters and receivers installed can be greatly reduced. .

  The ultrasonic flowmeter of the present invention includes the flow velocity distribution measuring device, and measures the flow rate of the fluid to be measured flowing in the pipe based on the flow velocity distribution measured by the flow velocity distribution measuring device.

  ADVANTAGE OF THE INVENTION According to this invention, even if the to-be-measured fluid which flows through the fluid piping is a gaseous fluid, flow velocity distribution can be measured correctly using an ultrasonic wave.

The figure which shows the state which irradiated the ultrasonic pulse with a divergence angle The figure which shows the state where the ultrasonic pulse was displaced The figure which shows the state which inclined the beam axis by an angle (θ) in the tube axis direction The figure which shows the state which emitted the ultrasonic beam in the state opened only the angle α from the diameter Diagram showing two measurement lines with different opening angles Diagram showing that the velocity distribution is a function of radial position only Overall configuration diagram of ultrasonic flowmeter according to Embodiment 1 The figure which shows the arrangement | positioning state of the receiving transducer in Embodiment 1 (A) Vertical sectional view of the pipe in the first embodiment, (b) Cross section in the pipe axis direction of the pipe in the first embodiment. Diagram for explaining the intensity distribution of ultrasonic pulses Overall configuration diagram of ultrasonic flowmeter according to Embodiment 2 Overall configuration diagram of ultrasonic flowmeter according to Embodiment 3 The figure which shows the arrangement | positioning state of the transducer for transmission in Embodiment 3, and the transducer for reception (A) Vertical sectional view of the pipe in the third embodiment, (b) Cross sectional view in the pipe axis direction of the pipe in the third embodiment. (A) Vertical sectional view of a pipe showing a receiving transducer in the pipe circumferential direction in the second measurement principle, (b) Cross sectional view in a pipe axis direction of the pipe showing a receiving transducer in the pipe axis direction in the second measuring principle Diagram for explaining the measurement principle of a conventional Doppler type ultrasonic flowmeter

  Before describing an ultrasonic flowmeter according to an embodiment of the present invention, a first measurement principle for directly obtaining a flow velocity distribution shape will be described. It is assumed that the fluid flowing in the pipe is axisymmetric.

種々の設置拘束条件の緩和や精度の向上には、この数式に基づいた測定を行うのが最善であり、それは管内流速の瞬時空間分布を求めることであると言える。管内流速の瞬時空間分布を求めることができれば、精度の向上、較正の不要、助走区間を考慮する必要がない、などの抜本的改良を加えることが可能となる。ここでは、気体流体を念頭において説明するが、本発明は液体流体であっても適用可能である。(First measurement principle)
In the case of an axisymmetric flow, the relationship between the flow rate (Q) in the pipe and the flow velocity distribution (ν (r)) of the fluid is expressed by the following equation (r is the radial coordinate, R is the radius of the tube).

In order to alleviate various installation constraints and improve accuracy, it is best to perform measurement based on this mathematical formula, and it can be said that the instantaneous spatial distribution of the flow velocity in the pipe is obtained. If the instantaneous spatial distribution of the pipe flow velocity can be obtained, drastic improvements such as improved accuracy, no need for calibration, and no need to consider the run-up section can be added. Here, the description will be made with the gas fluid in mind, but the present invention is also applicable to a liquid fluid.

  As shown in FIG. 1, an ultrasonic pulse is emitted toward an opposing tube wall from an ultrasonic transducer 11 serving as a transmitter installed on the tube wall of a pipe 10 made of a circular tube. The ultrasonic pulse is fired with an appropriate divergence angle with respect to the transducer axis.

  First, the movement (displacement) of the ultrasonic pulse in the cross section in the tube axis direction will be described. As shown in FIG. 2, when the gas in the pipe 10 is stationary, the emitted ultrasonic pulse goes straight in the firing direction (hereinafter referred to as “beam axis”), and the opposite pipe wall of the pipe 10. To reach. If the gaseous fluid in the pipe 10 is flowing in the direction of the arrow, the emitted ultrasonic pulse is displaced in the downstream direction as indicated by W1 in the figure due to the flow of the gaseous fluid. The displacement amount at this time includes flow velocity information.

ここで、m(r)は局所マッハ数であり、速度分布ν（ｒ）を音速ｃで除したものである。軸対称性の仮定から半径位置のみの関数である。Ｄは配管の直径、座標ｘは超音波トランスデューサ１１の先頭位置を原点としたビーム軸上の位置を表す（この場合は配管１０の直径上の位置）。At this time, when the beam axis is perpendicular to the tube wall (θ = 0) and passes over the diameter of the pipe 10 (case 1), the displacement amount (Z) of the ultrasonic pulse in the downstream direction (tube axis direction) is It is expressed by the following formula.

Here, m (r) is a local Mach number, and is obtained by dividing the velocity distribution ν (r) by the sound velocity c. It is a function of only the radial position from the assumption of axial symmetry. D represents the diameter of the pipe, and coordinate x represents the position on the beam axis with the head position of the ultrasonic transducer 11 as the origin (in this case, the position on the diameter of the pipe 10).

（式２）において第一項（D tanθ）はビーム軸が傾斜したことによる変移量、第二項（Mo secθ）は流速分布による変移量である。Next, as shown in FIG. 3, when the beam axis is inclined by an angle (θ) passing through the diameter of the pipe 10 and in the pipe axis direction (case 2), the pipe facing the pipe 10 of the ultrasonic pulse is opposed. Consider the amount of change at the wall. The displacement amount of the ultrasonic pulse in case 2 is expressed by the following equation.

In (Expression 2), the first term (D tan θ) is the amount of change due to the tilt of the beam axis, and the second term (Mo sec θ) is the amount of change due to the flow velocity distribution.

ここで、ξはビーム軸方向にとった座標軸であり、Ｌは配管１０内の経路長である。経路長Ｌは、次式で求まる。
Ｌ＝Ｄcosα （式４）Next, as shown in FIG. 4, consider a case (case 3) in which an ultrasonic beam is launched with an angle α opened from the diameter on a vertical cross section perpendicular to the pipe axis direction of the pipe 10. The angle formed with respect to the line segment (diameter) passing through the center of the pipe from the emission end of the ultrasonic transducer 11 is referred to as an opening angle (α). In this case 3, the amount of displacement of the ultrasonic beam on the opposite tube wall is expressed by the following equation.

Here, ξ is a coordinate axis taken in the beam axis direction, and L is a path length in the pipe 10. The path length L is obtained by the following equation.
L = Dcosα (Formula 4)

Next, let us consider the amount of displacement when the ultrasonic beam is opened by an angle α (opening angle α) from the diameter on the vertical cross section of the tube axis and inclined by the angle θ in the tube axis direction (case 4). In the case 4, the amount of displacement of the ultrasonic beam at the opposite tube wall is expressed by the following equation.

(式６)において、符号Mはビーム軸に沿った積分であるから、二本の測定線１，２について異なっている。この二本の測定線１，２に対する変移量の差は、次式のように表せる。

（式７）において、第一項は任意に設定した測定線１，２の位置によって決まり一定である。（式７）における第二項の積分差について検討する。
図６に示すように、流速分布は半径方向位置のみの関数であることから、ビーム軸上の積分は、管半径方向の積分で、積分範囲が位置hから半径Ｒまでとしたものの２倍と等しい。
すなわち、次式のようになる。

したがって、（式７）における第二項に含まれる変移量の差の積分項（M_１−M₂）については、次式のように表せる。

すなわち、変移量の差は、二本の測定線１，２と中心の距離h1とh2の間で流速分布を積分したものと等しい。距離h1とh2は、配管中心から二本の測定線１，２に引いた垂線との交点までの距離である。なお、軸対称を仮定しているので、距離と位置は同義となる。
今、二本の測定線１，２間の角度を小さくとれば、その間での流速分布は一定値m₁₂と仮定することができるから、（式７）は次式のように変換できる。

したがって、二本の測定線１，２について変移量Ｚ_１，Ｚ₂を測定することで、その位置[h1，h2]での流速が以下のように求まることになる。

そこで、測定領域となる多数の測定線を設置して、各位置での変移量（Ｚ）を測定することで、配管１０内の流速分布v(r)を求めることができる。FIG. 5 shows two measurement lines (1, 2) having different opening angles α. The amount of displacement of the ultrasonic beam at each of the measurement lines 1 and 2 is as follows.

In (Equation 6), since the symbol M is an integral along the beam axis, the two measurement lines 1 and 2 are different. The difference of the displacement amount with respect to the two measurement lines 1 and 2 can be expressed as the following equation.

In (Expression 7), the first term is determined by the position of the measurement lines 1 and 2 set arbitrarily and is constant. Consider the integral difference of the second term in (Equation 7).
As shown in FIG. 6, since the flow velocity distribution is a function of only the radial position, the integration on the beam axis is the integral in the tube radial direction, which is twice the integration range from the position h to the radius R. equal.
That is, the following equation is obtained.

Therefore, the integral term (M ₁ −M ₂ ) of the difference between the shift amounts included in the second term in (Expression 7) can be expressed as the following expression.

That is, the difference in the amount of displacement is equal to that obtained by integrating the flow velocity distribution between the two measurement lines 1 and 2 and the center distances h1 and h2. The distances h1 and h2 are distances from the center of the pipe to the intersection with the perpendicular drawn to the two measurement lines 1 and 2. Since it is assumed to be axially symmetric, distance and position are synonymous.
Now, if the angle between the two measurement lines 1 and 2 is made small, the flow velocity distribution between them can be assumed to be a constant value m ₁₂ , so (Equation 7) can be converted as the following equation.

Therefore, by measuring the displacements Z _{1 and} Z ₂ with respect to the two measurement lines 1 and 2, the flow velocity at the position [h1, h2] is obtained as follows.

Therefore, the flow velocity distribution v (r) in the pipe 10 can be obtained by installing a large number of measurement lines as the measurement region and measuring the amount of displacement (Z) at each position.

(Embodiment 1)
A first embodiment in which the first measurement principle is applied to an ultrasonic flowmeter will be described.
FIG. 7 is an overall configuration diagram of the ultrasonic flowmeter according to the first embodiment. One transmitting transducer 11 serving as a transmitter for transmitting an ultrasonic pulse is installed on one side of the tube wall of the pipe 10 that forms a circular tube through which the fluid G to be measured flows, and the ultrasonic pulse is received by the opposite tube wall of the pipe 10. A receiving transducer array including a plurality of receiving transducers 12 serving as receivers is installed. The transmitting transducer 11 is installed perpendicularly to the pipe wall outside or inside the pipe, and the installation angle is set so that the center of the ultrasonic beam passes through the pipe center and enters the opposite pipe wall perpendicularly. The effective diameter of the transmitting transducer 11 is determined in consideration of the spread of the ultrasonic beam, but in this example, it is desirable to reduce the effective diameter so that the directivity is as wide as possible. FIG. 8, FIG. 9A and FIG. 9B are diagrams showing the arrangement state of the receiving transducer array. The receiving transducer array is composed of a plurality of receiving transducers 12 arranged in a two-dimensional manner (plane) with reference to a position correctly facing the transmitting transducer 11. In FIG. 8, the receiving transducers 12 on both sides in the tube axis direction of the receiving transducer array are partially omitted. Further, as shown in FIG. 9A, j = in the circumferential direction in one direction (counterclockwise in the figure) from the receiving transducer 12 (j = 0) installed at the position facing the transmitting transducer 11 correctly. N are installed at predetermined intervals up to N. The installation intervals of the receiving transducers 12 constituting these receiving transducer arrays are selected so that the opening angle α of the beam axis of the ultrasonic beam is as small as possible. The arrangement range of the receiving transducer in the tube axis direction is equal to or larger than the radius of the pipe 10.

The signal oscillator 13 outputs a transmission signal S1 to be supplied to the transmission transducer 11. The fundamental frequency of the transmission signal in the signal oscillator 13 is determined in consideration of the characteristics of the pipe wall material, the fluid to be measured, the spread of the ultrasonic pulse, and the like. The signal waveform of the transmission signal is a sharp triangular wave pulse signal, which is the same as the waveform used in the normal time difference method. The repetition period f _prf of the pulse signal is determined from the gas sound velocity, the pipe diameter, the average flow velocity, and the like. A timing signal S2 for emitting a pulse signal is sent to the receiving side as a synchronization signal.

  A detection circuit 14 is connected to the output terminal of each receiving transducer 12. The detection circuit 14 includes a signal amplifier that amplifies a detection signal having a magnitude corresponding to the incident ultrasonic wave intensity output from the connected receiving transducer 12, and a peak detection circuit that reads a peak value of the signal amplifier output. . These detection circuits 14 simultaneously detect the outputs of the receiving transducers 12 in order to obtain the flow velocity at a fast sampling rate. Each detection circuit 14 has a pulse reception timing set by a timing signal S <b> 2 supplied from the signal oscillator 13.

  The data acquisition circuit 15 includes a digital multiplexer that collects all peak values read by the detection circuits 14. The data acquisition circuit 15 determines from which detection circuit 14 the information is obtained. The installation position of each detection circuit 14 can be converted into the opening angle (α) of the measurement line and the position in the tube axis direction from the relationship with the corresponding receiving transducer 12. Information on the installation position of the detection circuit 14 (or the installation position of the reception transducer 12) in which the maximum peak value is detected among the plurality of reception transducers 12 arranged in the tube axis direction is output as a displacement detection signal.

The data processing device 20 includes a flow velocity distribution measurement circuit 21 that measures a flow velocity distribution from the displacement detection signal output from the data acquisition circuit 15, and a measurement target that flows in the pipe 10 from the flow velocity distribution data measured by the flow velocity distribution measurement circuit 21. A flow rate measurement circuit 22 that calculates the flow rate of the fluid and a display unit 23 that displays and outputs the measurement result are provided. The flow velocity distribution measurement circuit 21 calculates the average flow velocity m ₁₂ by performing data calculation based on the above-described (Equation 11) from the displacement amounts of two measurement lines slightly different in the opening angle α. The flow velocity distribution data or the flow rate measurement data may be recorded on a recording medium or transmitted to another device.

Next, the operation of the present embodiment configured as described above will be described.
A measurement trigger is given to instruct the signal oscillator 13 to start measurement. The signal oscillator 13 applies a transmission signal S1 having a fundamental frequency to the transmission transducer 11 in response to a measurement trigger, and supplies a timing signal S2 to each detection circuit 14.

  The transmission transducer 11 converts the transmission signal S1 into an ultrasonic pulse and enters the fluid G to be measured in the pipe 10. As shown in FIGS. 1 and 7, the ultrasonic pulse incident on the fluid G to be measured becomes an ultrasonic beam having a predetermined spread around the beam axis, and a receiving transducer array installed on the opposing tube wall. Is incident on. Each receiving transducer 12 constituting the receiving transducer array outputs a detection signal having an amplitude corresponding to the incident ultrasonic intensity.

  All the detection circuits 14 detect the peak value of the detection signal output from each receiving transducer 12 that has received the first arrival wave, using the timing signal S2 synchronized with the ultrasonic pulse emission time as a trigger. The data acquisition circuit 15 takes in the peak value at each position (i, j) from all the detection circuits 14.

  Here, the spatial characteristics of the ultrasonic pulse incident on the receiving transducer array will be described. As shown in FIG. 10, the spatial characteristic of the emitted ultrasonic pulse has a Gaussian distribution with the beam axis as the center. Also in the detection signals output from the receiving transducers 12, the distribution in the tube axis direction has a substantially similar Gaussian distribution at the opening angle (α).

Now, as shown in FIG. 9A, when the opening angle of the beam axis of the ultrasonic beam is α _n , the receiving transducer array in the tube axis direction where the ultrasonic beam having the opening angle (α _n ) is incident is illustrated. 9 (b). As shown in the figure, assuming that Zn is displaced from the original beam axis position by the flow velocity of the fluid to be measured, the peak value of the detection signal output from the receiving transducer 12 installed at a distance Zn from the beam axis position. However, the maximum value is shown in the transducer array for reception shown in FIG. This distance Zn corresponds to the displacement amount Zi (θ) in (Expression 5) or (Expression 6).

The data acquisition circuit 15 selects the position of the transducer 12 showing the maximum peak value from the transducer array for reception in the tube axis direction shown in FIG. 9 (b) corresponding to each opening angle α _i of the ultrasonic beam axis, The selected position is transmitted to the data processor 20 as the displacement Z from the original beam axis at the opening angle α _i .

In the flow velocity distribution measurement circuit 21 of the data processing device 20, the displacement amount Z _i at the measurement lines i and i + 1 of the adjacent opening angles [α _i , α _{i + 1} ] from the displacement amount information taken in from the data acquisition circuit 15. , Z _{i + 1} is extracted and substituted into (Equation 11) to obtain the average flow velocity m _{i, i + 1} at [h _i , h _{i + 1} ]. This is to set the measurement line 1 of the opening angle [α _i ] as one measurement line (beam axis) to be measured, and the opening angle as the other measurement line (beam axis) adjacent to the measurement line 1 in the opening angle direction. Set the measurement line 2 of [α _{i + 1} ], the intersection (distance h _i from the pipe center to the measurement line 1) with the perpendicular drawn from the pipe center to the measurement line 1, and the perpendicular drawn from the pipe center to the measurement line 2 The average flow velocity m _{i, i + 1} is obtained from the intersection (distance h _{i + 1} from the pipe center to the measurement line 2).

From the assumption that the angle between the two measurement lines is reduced to such an extent that the flow velocity distribution between the distance h1 and the distance h2 from the pipe center can be assumed to be a constant value, the opening angles [α _i , α _{i + 1} ] Measurement lines 1 and 2 adjacent to each other are used. Thereby, it can be considered that the flow velocity of one place on the circumference of radius h _i centering on the pipe center shown in FIG. 6 was calculated | required.

The flow velocity distribution measuring circuit 21 sets a large number of adjacent measurement line pairs such as the opening angles [α _i , α _{i + 1} ], and sets the average flow velocity m at each position in the pipe diameter direction corresponding to the opening angle αn. Ask. The flow velocity distribution v (r) in the pipe 10 is obtained from the average flow velocity m at each position where the pipe diameter direction is different.

  The flow rate measurement circuit 22 calculates the average flow rate in the pipe 10 based on the flow rate distribution v (r) in the pipe 10 obtained by the flow rate distribution measurement circuit 21 and outputs the average flow rate to the display unit 23.

  As described above, according to the present embodiment, even when the fluid G to be measured is a gas fluid such as a gas in which reflectors are not mixed or nonuniformly included, the flow velocity distribution is measured using ultrasonic waves. It is possible to measure the flow rate with high accuracy.

  In addition, the transducer axis of the transmitting transducer 11 that emits the ultrasonic pulse is set perpendicular to the tube axis direction, and the displacement amount of the ultrasonic pulse is detected by the receiving transducer provided on the opposite tube wall. Since it is the structure which calculates | requires directly the flow velocity in the predetermined position on a vertical cross section, the calibration operation | work of the measured value required with the conventional Doppler type ultrasonic flowmeter can be reduced.

(Embodiment 2)
Next, an ultrasonic flowmeter in which the detection circuit 14 on the reception side is deleted from the ultrasonic flowmeter of the first embodiment and the circuit configuration is simplified will be described as a second embodiment.

  FIG. 11 is an overall configuration diagram of the ultrasonic flowmeter according to the second embodiment. The arrangement of the transmitting transducer 11 and the receiving transducer 12 is the same as in the first embodiment. In the present embodiment, the analog multiplexer 31 is connected to the output terminal of the receiving transducer 12, thereby reducing the number of M × N detection circuits 14 required in the first embodiment. The analog multiplexer 31 operates to selectively input the detection signal from each receiving transducer 12 to the data acquisition circuit 32 at the subsequent stage.

  The data acquisition circuit 32 includes an AD converter. The data acquisition circuit 32 detects the peak value from the detection signal converted into a digital signal by the AD converter, determines which receiving transducer 12 to obtain information from, and displaces the receiving transducer position information of the maximum peak value. Output as a quantity detection signal. The timing signal S2 for emitting the pulse signal is supplied to the data acquisition circuit 32 and used for sampling timing in the AD converter.

In the ultrasonic flowmeter configured as described above, detection signals from the receiving transducer 12 are input to the data acquisition circuit 32 one by one via the analog multiplexer 31, and the peak value is detected. The maximum peak value is detected from each receiving transducer array arranged in the tube axis direction, and position information (i, j) indicating the maximum peak value for each receiving transducer array is output to the flow velocity distribution measuring circuit 21 as displacement amount information. . In the flow velocity distribution measurement circuit 21, by substituting the amount of displacement (11) determining the average flow velocity _{m 12.}

  As described above, according to the present embodiment, the output of the M × N receiving transducers 12 is input to the data acquisition circuit 32 via the analog multiplexer 31, and therefore the detection circuit 14 is reduced and the circuit configuration is reduced. It can be simplified.

  When configured as in the present embodiment, the detection signals of the M × N receiving transducers 12 are processed one by one, so that it takes more time than the first embodiment, but the fluid to be measured has less fluctuation. In case of G, it is effective.

(Embodiment 3)
Next, an ultrasonic flowmeter according to Embodiment 3 of the present invention will be described.
FIG. 12 is an overall configuration diagram of an ultrasonic flowmeter according to Embodiment 3 of the present invention. One pipe wall of the pipe 10 is formed with a transmitting transducer array composed of a plurality of transmitting transducers 40 arranged in a line along the pipe axis direction. A receiving transducer array including a plurality of receiving transducers 41 arranged in a line along the pipe circumferential direction at a predetermined position H is formed.

  FIGS. 13 and 14A and 14B show the positional relationship between the transmitting transducer 40 and the receiving transducer 41. FIG. FIG. 13 is an external view of the pipe 10, and the receiving transducer 41 indicated by a broken line is installed on the pipe wall opposite to the installation position of the transmitting transducer 40. 14A is a vertical cross-sectional view with respect to the tube axis of the pipe 10, and FIG. 14B is a cross-sectional view along the tube axis direction at the position of the transmitting transducer 40. FIG.

  As shown in FIG. 14A, one end (j = 0) of the receiving transducer array and a predetermined transmitting transducer 40 face each other across the center of the pipe, and from the one end position (j = 0) to the pipe circumferential direction. The receiving transducer 41 is continuously installed. A receiving transducer array is formed in a range of about 90 degrees when viewed from the center of the pipe. Further, as shown in FIG. 14B, a receiving transducer 41 is installed in the tube circumferential direction at a distance H in the tube axis direction from the beam axis B of the center transmitting transducer 40.

  The signal oscillator 42 generates a transmission signal S1 having a desired fundamental frequency for generating an ultrasonic pulse. The transmitting transducer 40 supplies a timing signal S2 to a timing controller 45 described later in synchronization with the output of the transmitting signal S1.

  The transmission multiplexer 43 operates to switch the transmission transducer 40 to which the transmission signal S1 output from the signal oscillator 42 is applied. For example, it is assumed that the transmission multiplexer 43 sequentially selects from the most upstream transmission transducer 40 (i = 0) to the most downstream transmission transducer 40 (i = M).

  Similar to the above embodiment, each transmitting transducer 40 is installed perpendicular to the tube wall outside or inside the pipe, and the center of the ultrasonic beam passes through the pipe center and enters the opposite pipe wall perpendicularly. Set the installation angle as follows. In addition, the effective diameter of the transmitting transducer 40 is reduced so that the directivity is as wide as possible.

  On the receiving side, output terminals of all receiving transducers 41 installed in the pipe circumferential direction are connected to a receiving multiplexer 44. The reception multiplexer 44 sequentially selects the detection signals output from the reception transducers 41 and outputs them to the data acquisition circuit 46. The operation timing of the transmission multiplexer 43 and the reception multiplexer 44 is controlled by a timing controller 45.

  The timing controller 45 controls the switching operation timing of the transmission multiplexer 43 and the reception multiplexer 44 using the timing signal S2 supplied from the signal oscillator 42 as a trigger. Specifically, when one transmission transducer 40 is selected by the transmission multiplexer 43, control is performed so that the transmission transducers 40 to be applied are not switched until the sampling of the detection signals for all the reception transducers 41 is completed. To do. When the sampling of the detection signals for all the reception transducers 41 is completed, the next transmission transducer 40 is selected by the transmission multiplexer 43 until the sampling of the detection signals for all the reception transducers 41 is completed again. Control is performed so that the transmitting transducer 40 is not switched. Such timing control is executed for all the transmission multiplexers 43.

  The data acquisition circuit 46 includes an AD converter. In the data acquisition circuit 46, a peak value is detected from the detection signal converted into a digital signal by the AD converter, and the detected peak value is stored in correspondence with the transmitting transducer 40 selected by the transmitting multiplexer 43 at that time. To do. The switching timing of the transmitting transducer 40 is given from the timing controller 45. When the information (peak value) regarding the ultrasonic reception intensity in the tube circumferential direction is acquired for all the transmitting transducers 40, the transmitting transducer 40 (position information in the tube axis direction) showing the maximum peak value at each opening angle (α). ) And the position information of the transmitting transducer 40 showing the maximum peak value is output as a displacement amount detection signal. Although the displacement amount detection signal is output to the data processing device 20, the configuration and function are the same as those in the first and second embodiments, and thus the description thereof is omitted.

  In the present embodiment configured as described above, the transmission signal S1 is supplied from the signal oscillator 52 to the transmission multiplexer 43, and at the same time, the timing signal S2 is supplied to the timing controller 45. The timing controller 45 controls the transmission multiplexer 43 so as to select the first transmission transducer 40 and also controls the reception multiplexer 44 so as to select detection signals in order from the first reception transducer 41. . Then, each time the reception multiplexer 44 finishes sampling the detection signals for all the reception transducers 41, the timing controller 45 switches the transmission transducer 40 to which the transmission signal S1 is to be applied.

  The data acquisition circuit 46 stores the peak values of all the receiving transducers 41 in correspondence with the respective transmitting transducers 40 (position information). As a result, the data acquisition circuit 46 has a plurality of receiving transducers with different launch angles (α) with respect to each launch position (position in the tube axis direction) of the ultrasonic beam shifted in the tube axis direction and each launch position. The peak value of the ultrasonic reception intensity indicated by 41 is stored in association with each other.

  In the first and second embodiments, the displacement amount in the tube axis direction is obtained by detecting the maximum peak values of a plurality of receiving transducers arranged in the tube axis direction. In the third embodiment, instead of detecting using a plurality of receiving transducers in the tube axis direction, the emission position of the ultrasonic beam (the position of the transmitting transducer 40 in the tube axis direction) is shifted, so that It is intended to obtain information equivalent to the first and second embodiments.

  Therefore, since the peak value at each launch position is stored corresponding to each receiving transducer 41, the data acquisition circuit 46 specifies the launch position having the maximum peak value from among the peak values. If the beam axis B shown in FIG. 12 is a reference position in the tube axis direction, the launch position showing the maximum peak value corresponds to the displacement of the ultrasonic beam. The data acquisition circuit 46 specifies the maximum peak values for all the receiving transducers 41 having different opening angles (α), and converts the firing position indicating the maximum peak value into a displacement amount from the reference position in the tube axis direction. And output to the data processor 20 as a displacement detection signal.

  In the data processing device 20, as in the first and second embodiments, the flow velocity distribution measurement circuit 21 substitutes the displacement amount of the predetermined measurement lines 1 and 2 into (Equation 11) to obtain the average flow velocity at each position. The flow rate measuring circuit 22 calculates the gas flow rate from the flow velocity distribution in the vertical section of the pipe.

  As described above, according to the present embodiment, a line of transmitting transducers 40 is provided on the transmitting side in the tube axis direction, and a line of receiving transducers 41 is provided on the receiving side in the circumferential direction of the tube. Since the amount can be detected, the number of transducers can be reduced as compared with the first embodiment.

  In the first measurement principle described above, the displacement amount of the ultrasonic beam is used to directly obtain the flow velocity distribution shape, but the flow velocity distribution shape can also be obtained directly using the flight time of the ultrasonic pulse. Next, a second measurement principle for directly obtaining the flow velocity distribution shape using the time of flight of the ultrasonic pulse will be described. It is assumed that the fluid flowing in the pipe is axisymmetric.

(Second measurement principle)
First, a receiving transducer arrangement as shown in FIGS. 15A and 15B is considered. That is, one transmission transducer 50 is installed on one tube wall of the pipe 10 so that the beam axis is perpendicular to the tube wall, and the reception transducer 51 is placed on the other opposite tube wall in a predetermined position in the tube axis direction. It is set as the form which provided in H a line in the pipe circumferential direction. The installation position in the tube axis direction of the receiving transducer 51 provided along the tube circumferential direction is provided at a distance H in the tube axis direction from the beam axis position perpendicular to the tube wall as shown in FIG. It has been.

In such a transducer arrangement, the path length along which the ultrasonic pulse emitted at an inclination angle θ with respect to the tube axis direction flies to the receiving transducer 51 at position H is expressed by the following equation.

ここで、Ｍ_hは流速分布の積分である。
ビーム軸Ｂへの傾斜角θは検出位置に到達するのに必要なビーム発射角度であるから、この段階では未知数である。The relationship with the flight time T is T = P / c.
The integrand of the path length P can be approximated as follows using the fact that the local Mach number is m << 1 in the square root.

Here, M _h is the integral of the flow velocity distribution.
Since the tilt angle θ with respect to the beam axis B is a beam emission angle necessary to reach the detection position, it is unknown at this stage.

（式１４）では、実効傾斜角θ_１２と流速値m_１２が未知数である。
一方、この形態での変移量はHであるが、そこに到達するパルスの発射角は、次式から逆に求めることができる。

上記（式１４）と（式１５）からθ_１２を消去することにより、流速値m_１２を求めることができる。Considering the difference in time of flight between two measurement lines in the immediate vicinity, when the tilt angle is θ ₁ θ ₂ = θ ₁₂ , it can be expressed as:

In (Expression 14), the effective inclination angle θ ₁₂ and the flow velocity value m ₁₂ are unknown.
On the other hand, the amount of shift in this form is H, but the firing angle of the pulse reaching there can be obtained in reverse from the following equation.

By eliminating θ ₁₂ from (Expression 14) and (Expression 15), the flow velocity value m ₁₂ can be obtained.

(Embodiment 4)
Embodiment 4 in which the second measurement principle is applied to an ultrasonic flowmeter will be described.
Since the ultrasonic flowmeter according to the fourth embodiment has substantially the same overall configuration as the ultrasonic flowmeter of the first embodiment (FIG. 7), the parts different from the first embodiment are mainly described with reference to FIG. Explained.

  In the fourth embodiment, the arrangement of receiving transducers is different from that in the first embodiment. As shown in FIGS. 15 (a) and 15 (b), one transmitting transducer 50 is installed on one tube wall of the pipe 10 so that the beam axis is perpendicular to the tube wall, and the other tube wall facing the other. The receiving transducers 51 are provided in a single line in the tube circumferential direction at a position H in the tube axis direction.

  Further, the detection circuit 14 is connected to the output end of each receiving transducer 51 arranged in a line in the tube circumferential direction. Each detection circuit 14 amplifies a detection signal having a magnitude corresponding to the incident ultrasonic wave intensity output from the connected receiving transducer 51, and the flight time T (output of the transmission signal S1) from the signal amplifier output. A delay time detection circuit for detecting a delay time from the timing). The delay time detection circuit detects the flight time T until the ultrasonic pulse emitted from the transmitting transducer 50 reaches each receiving transducer 51 using the timing signal S1 input from the signal transmitter 13 as a reference time.

The flow velocity distribution measurement circuit 21 sets two measurement lines 1 and 2 (FIG. 5) in the vicinity, and the flight time T ₁ obtained from the output of the receiving transducer 51 corresponding to the two measurement lines 1 and 2. , T ₂ is specified, and the flight times T ₁ and T ₂ are substituted into (Expression 14) and (Expression 15) to determine the average flow velocity m ₁₂ at the position [h ₁ , h ₂ ]. Similarly, two measurement lines 1 and 2 (FIG. 5) in the immediate vicinity are sequentially set, and the flight times T ₁ and T ₂ at each measurement line 1 and ₂ are specified, and the vertical cross section is determined. An average flow velocity m ₁₂ at each position is obtained.

  According to the fourth embodiment, the flow velocity distribution shape and the flow rate can be directly obtained using the flight time of the ultrasonic pulse, and the number of receiving transducers that are difficult to install can be reduced. is there.

Note that the second measurement principle can be applied to the ultrasonic flowmeter of the second embodiment. In this case, the flight time T until the sound wave pulse reaches each receiving transducer 51 is detected by the data acquisition circuit 32, and the flight times T ₁ and T ₂ are expressed by (Expression 14) and (Expression 15) in the flow velocity distribution measurement circuit 21. To obtain the average flow velocity m ₁₂ at the position [h ₁ , h ₂ ].

  The present invention is applicable to a flow velocity distribution measuring device and a flow meter for a gaseous fluid flowing in a pipe.

Claims (8)

A transmitter installed on the pipe wall of the fluid pipe to generate an ultrasonic pulse and to enter the fluid to be measured flowing in the fluid pipe;
A plurality of receivers that are two-dimensionally installed on a pipe wall facing the transmitter in the fluid piping and output a detection signal having an amplitude corresponding to the received ultrasonic intensity;
A displacement amount in the tube axis direction of the ultrasonic pulse is detected from detection signals of a plurality of receivers arranged in the tube axis direction among the receivers, and the emission end and the pipe center as viewed from the emission end of the transmitter. The amount of displacement detected for each of two measurement lines having slightly different opening angles, where the angle formed by the line segment passing through is the opening angle and the measurement area from the transmitter to the predetermined receiver is the measurement line A flow velocity distribution measuring means for obtaining a flow velocity at a predetermined position determined by a perpendicular from the center of the pipe to the two measurement lines;
A flow velocity distribution measuring apparatus comprising: A plurality of transmitters that are installed in a line along the pipe axis direction on the pipe wall of the fluid pipe, generate ultrasonic pulses, and enter the measured fluid flowing in the fluid pipe from different positions in the pipe axis direction, and
A plurality of receivers that are installed in a line along the pipe circumferential direction on the tube wall facing the transmitter and output detection signals having amplitudes according to the received ultrasonic intensity,
The maximum peak value of the detection signal is detected for each of the receivers, and the displacement of the ultrasonic pulse in the tube axis direction from the relative relationship between the receiver showing the maximum peak value and the transmitter position where the ultrasonic pulse was emitted at that time The angle between the outgoing end of the transmitter and the line passing through the center of the pipe as viewed from the outgoing end of the transmitter is defined as an opening angle, and a measurement area from the transmitter to a predetermined receiver is measured as a measurement line. A flow velocity distribution measuring means for obtaining a flow velocity at a predetermined position determined by a perpendicular line from the center of the pipe with respect to the two measurement lines from displacement amounts detected for two measurement lines having slightly different opening angles;
A flow velocity distribution measuring apparatus comprising: 3. The flow velocity distribution measuring device according to claim 1, wherein the flow velocity distribution measuring unit calculates an average flow velocity between the predetermined positions [h ₁ ] and [h ₂ ] based on the following equation. .

However, m ₁₂ is the average flow velocity between the predetermined positions [h ₁ ] and [h ₂ ] Z ₁ is the displacement amount detected for one measurement line Z ₂ is the displacement amount α ₁ detected for the other measurement line Is the opening angle of the one measurement line α ₂ is the opening angle of the other measurement line θ is the inclination of each measurement line in the tube axis direction D is the diameter of the pipe h ₁ is the tube axis direction of the one measurement line Said one measurement from the pipe center at the position
The radial position h ₂ where the perpendicular line dropped to the line intersects is the other measurement from the center of the pipe at the position in the pipe axis direction of the other measurement line.
Radial position where the vertical line intersects the line A transmitter installed on the pipe wall of the fluid pipe to generate an ultrasonic pulse and to enter the fluid to be measured flowing in the fluid pipe;
A plurality of receivers that are installed in a line along the tube circumferential direction at a predetermined position in the tube axis direction on the tube wall facing the transmitter and each output a detection signal having an amplitude corresponding to the received ultrasonic intensity;
From the detection signal of each receiver, the time of flight until the ultrasonic pulse emitted from the transmitter reaches each receiver is detected, and the emission end and the center of the pipe are seen from the emission end of the transmitter. From the flight time detected for each of two measurement lines having slightly different opening angles, the opening angle is the angle formed by the line segment that passes and the measurement area from the transmitter to the predetermined receiver is the measurement line. A flow velocity distribution measuring means for obtaining a flow velocity at a predetermined position determined by a perpendicular to the two measurement lines;
A flow velocity distribution measuring apparatus comprising: 5. The flow velocity distribution measuring apparatus according to claim 4, wherein the flow velocity distribution measuring means calculates an average flow velocity between the predetermined positions [h ₁ ] and [h ₂ ] based on the following formula.

Where m ₁₂ is the average flow velocity between the predetermined positions [h ₁ ] and [h ₂ ], c is the speed of sound, T ₁ is the flight time detected for one measurement line, and T ₂ is the flight detected for the other measurement line. Time α ₁ is the opening angle of the one measurement line α ₂ is the opening angle of the other measurement line θ ₁₂ is the inclination of each measurement line in the tube axis direction D is the diameter of the pipe h ₁ is the angle of the one measurement line One of the measurements from the center of the pipe at the position in the pipe axis direction
The radial position h ₂ where the perpendicular line dropped to the line intersects is the other measurement from the center of the pipe at the position in the pipe axis direction of the other measurement line.
Radial position where the vertical line intersects the line   The flow velocity distribution measuring device according to claim 1 is provided, and the flow rate of the fluid to be measured flowing in the pipe is measured based on the flow velocity distribution measured by the flow velocity distribution measuring device. Ultrasonic flow meter. An ultrasonic pulse is incident on the fluid to be measured flowing from the transmitter installed on the pipe wall of the fluid pipe,
In the fluid piping, the ultrasonic pulse is detected by a plurality of receivers installed two-dimensionally on a tube wall facing the transmitter,
Detecting the displacement amount of the ultrasonic pulse in the tube axis direction from detection signals of a plurality of receivers arranged in the tube axis direction among the receivers,
The angle between the outgoing end of the transmitter and the line segment passing through the center of the pipe is defined as the opening angle, and the measurement area from the transmitter to the predetermined receiver is defined as the measuring line. A flow velocity distribution measuring method characterized in that a flow velocity at a predetermined position determined by a perpendicular line from the center of a pipe with respect to two measurement lines is obtained from a displacement amount detected for two slightly different measurement lines. An ultrasonic pulse is incident on the fluid to be measured flowing from the transmitter installed on the pipe wall of the fluid pipe,
The ultrasonic pulse is detected by a plurality of receivers arranged in a line along the tube circumferential direction at a predetermined position in the tube axis direction on the tube wall facing the transmitter,
Detecting the time of flight from the detection signal of each receiver to the time when the ultrasonic pulse emitted from the transmitter reaches each receiver;
The angle between the outgoing end of the transmitter and the line segment passing through the center of the pipe is defined as the opening angle, and the measurement area from the transmitter to the predetermined receiver is defined as the measuring line. A flow velocity distribution measuring method characterized in that a flow velocity at a predetermined position determined by a perpendicular line from the center of a pipe with respect to two measurement lines is obtained from the time of flight detected for two slightly different measurement lines.

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