Ultrasonic flow measurement device for rectangular pipe section

Abstract

To provide: an ultrasonic flow rate measurement device for a rectangular tube portion that can relax installation conditions, eliminate the need for calibration and verification, simplify maintenance, and perform highly accurate instantaneous flow rate measurement conforming to the definition of the flow rate.SOLUTION: An ultrasonic processing unit 4 causes each of the ultrasonic wave emission units 2 to emit ultrasonic pulses at different frequencies, determines whether an ultrasonic pulse received by an ultrasonic wave reception units 3 is the ultrasonic pulse that has been emitted from the opposing ultrasonic wave emission unit 2 on the basis of the frequency of the ultrasonic pulse, and transmits the reception result to a flow rate calculation unit 5 when the received ultrasonic pulse is determined to be the ultrasonic pulse that has been emitted from the opposing ultrasonic wave emission unit 2. The flow rate calculation unit 5 calculates the local average flow velocity for each of the ultrasonic wave emission units 2 on the basis of the reception result of the ultrasonic pulse transmitted from the ultrasonic processing unit 4 for each of ultrasonic wave reception units 3, and calculates the intra-tube flow rate by a sum of local flow rates obtained by multiplying the local average flow velocity by the local area for each of the ultrasonic wave emission units 2.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to an ultrasonic flow measurement device that measures the flow rate of a fluid to be measured flowing in a pipe by ultrasonic waves, and particularly to an ultrasonic flow measurement device for a rectangular pipe section used in a rectangular pipe section formed in a pipe in a rectangular shape.

Background Art

[0002] Pipes (pipelines) are excellent for transporting fluids such as liquids and gases without leaking them to the outside, and are widely used not only in factories but also in familiar places such as water pipes. Also, grasping the amount of the transported fluid is very important in quality control and the like.

[0003] Therefore, various devices for measuring the flow rate inside pipes have been developed so far. In particular, ultrasonic flow meters utilize ultrasonic waves that can penetrate the pipe wall and have advantages such as being able to measure without directly contacting the fluid, and thus are used in many scenarios.

[0004] A general ultrasonic flow meter emits (incides) an ultrasonic pulse into the fluid to be measured inside the pipe. When the ultrasonic pulse travels at the speed of sound, it travels at a speed obtained by adding or subtracting the average flow velocity of the fluid to be measured. Therefore, the average flow velocity is calculated from the flight time, and the average flow rate is calculated by multiplying the average flow velocity by the cross-sectional area of the pipe. As such an ultrasonic flow meter, in Japanese Unexamined Patent Application Publication No. 2023-35287, a clamp-on type ultrasonic flow sensor that can be attached to an existing pipe has been proposed (Patent Document 1).

[0005] Further, the inventor of the present application has proposed, in Japanese Patent No. 6321316, an ultrasonic flow measurement device capable of calculating the flow rate of the fluid to be measured in the pipe from the shift amount, which is the difference between the reference sound pressure distribution waveform based on the ultrasonic pulse emitted from the transmitter and incident on the receiver in a state where the flow velocity is zero, and the fluctuating sound pressure distribution waveform based on the ultrasonic pulse emitted from the transmitter and incident on the receiver in a state where the flow velocity is non-zero, and has obtained a patent right (Patent Document 2).

[0006] Furthermore, in Japanese Patent Application Laid-Open No. 5-223608, in an ultrasonic flowmeter that measures the flow rate of fluid in a pipe using a plurality of transmit-receive transducers that transmit and receive ultrasonic waves, a measurement pipe section is defined between the upstream and downstream of the pipe. The measurement pipe section is formed to have a rectangular cross-section, and the transmit-receive transducers are attached to the outer walls of the parallel planes of the measurement pipe section. An ultrasonic flowmeter characterized by this is proposed.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0008] However, in a general ultrasonic flowmeter including the invention described in Patent Document 1, the flow rate is calculated using the average flow velocity obtained by integrating the flow velocity distribution on one path (measurement line) passing through the pipe center. Therefore, it is a measurement condition that the flow velocity distribution is axisymmetric (the same average flow velocity even when passing through other paths), and there is a problem that the installation location is greatly restricted. For example, in the pipe immediately after a bent pipe, vortices are generated, etc., so that the flow velocity distribution is not axisymmetric, and the average flow velocity is different for different paths, so it cannot be installed. That is, strict setting conditions (such as ensuring the rectification positions upstream and downstream) are imposed for use. If it is installed in a non-axisymmetric location, special calibration and verification under conditions where the measurement conditions are made to match are required.

[0009] In addition, the inventions described in Patent Document 1 and Patent Document 2 measure the flow rate inside a circular pipe used in general piping. There is a problem that the circular pipe that can be installed is limited by curvature due to the limitation of miniaturization of ultrasonic elements. That is, while the ultrasonic elements that emit and receive ultrasonic waves are formed in a planar shape, the pipe wall of the circular pipe is formed of a curved surface, so it becomes a contact between a surface and a line. When the curvature of the circular pipe is large (the diameter of the circular pipe is small) with respect to the size of the ultrasonic element, the emitted ultrasonic wave is reflected by the wall surface and cannot penetrate into the pipe, making measurement difficult.

[0010] Therefore, it is necessary that the curvature of the circular pipe is sufficiently small (the diameter of the circular pipe is large) with respect to the size of the ultrasonic element. For example, a diameter of the circular pipe of 1 or more is required with respect to a diameter of 1 of the ultrasonic element. Furthermore, when a plurality of ultrasonic elements are installed in the circular pipe, it is a condition that the diameter of the circular pipe is larger.

[0011] In addition, there is also a problem that when the incident angle with respect to the circular pipe exceeds the critical angle, the ultrasonic pulse is reflected and cannot enter the circular pipe. For this reason, in order to calculate the flow rate from the average flow velocity on a plurality of parallel measurement lines (three sets of transmission and reception units in Patent Document 2), it is necessary to increase the diameter of the circular pipe so as not to exceed the critical angle, or to arrange the ultrasonic elements so as to be in direct contact with the fluid as disclosed in Patent Document 2.

[0012] Incidentally, the definition of the flow rate is represented by the product of the cross-sectional area and the average flow velocity orthogonal to this cross-sectional area, and the average flow velocity can be calculated by integrating the flow velocity over the entire cross-section. When the flow inside the pipe is set as an xyz orthogonal coordinate with the flow direction as the z coordinate, in a conventional ultrasonic flow rate measuring device as described in Patent Document 3, although integration can be performed in the ultrasonic emission direction (for example, the x direction), the ultrasonic emission positions are different in the z direction, and the integration range in the y direction is different for each measurement line, so there is also a problem that the double integration is not performed accurately.

[0013] Furthermore, in the invention described in Patent Document 3, when the distance between the transmitting and receiving transducers arranged to improve accuracy is reduced, there is a problem that ultrasonic pulses emitted from other than the opposing transmitting and receiving transducers on the receiving side interfere, and the integrated value of the flow velocity in the ultrasonic emission direction cannot be accurately measured.

[0014] The present invention has been made to solve the above problems, and while relaxing the installation conditions, calibration and verification are unnecessary, maintenance can be simplified, and it is possible to perform highly accurate instantaneous flow rate measurement in accordance with the definition of the flow rate. An object of the present invention is to provide an ultrasonic flow rate measuring device for a rectangular pipe section.

Means for Solving the Problems

[0015] The ultrasonic flow measurement device for a rectangular pipe section according to the present invention is installed on one side surface of the rectangular pipe section in order to solve the problem of performing highly accurate flow measurement in accordance with the definition of flow rate without being restricted by the flow velocity distribution in the pipe. It includes an ultrasonic transmitter that emits ultrasonic pulses toward the fluid to be measured in the rectangular pipe section, an ultrasonic receiver that receives the ultrasonic pulses that have passed through the fluid to be measured in the rectangular pipe section, an ultrasonic processing unit that executes the emission process of the ultrasonic pulses in the ultrasonic transmitter and the reception process of the ultrasonic pulses in the ultrasonic receiver, and a flow rate calculation unit that calculates the average flow velocity of the fluid to be measured flowing in the rectangular pipe section based on the reception result of the ultrasonic pulses received by the ultrasonic receiver, and calculates the in-pipe flow rate by multiplying the average flow velocity by the cross-sectional area of the rectangular pipe section. In the ultrasonic flow measurement device for a rectangular pipe section, a plurality of the ultrasonic transmitters are arranged on the same straight line perpendicular to the flow direction on the one side surface and are installed at the same angle with respect to the one side surface, and a plurality of the ultrasonic receivers are installed at positions facing each of the plurality of ultrasonic transmitters on the opposite side surface facing the one side surface. The ultrasonic processing unit emits ultrasonic pulses of different frequencies from each of the ultrasonic transmitters, discriminates whether the ultrasonic pulses received by the ultrasonic receiver are the ultrasonic pulses emitted from the ultrasonic transmitter they face based on the frequencies of these ultrasonic pulses, and when the ultrasonic pulses are emitted from the ultrasonic transmitter they face, transmits the reception result to the flow rate calculation unit. The flow rate calculation unit calculates the local average flow velocity for each ultrasonic transmitter based on the reception result of the ultrasonic pulses for each ultrasonic receiver transmitted from the ultrasonic processing unit, and calculates the in-pipe flow rate by the sum of the local flow rates obtained by multiplying the local average flow velocity by the local area for each ultrasonic transmitter.

[0016] Also, as one aspect of the present invention, in order to solve the problem of further improving the measurement accuracy of the flow rate, the one side surface where the plurality of ultrasonic wave transmitting portions are installed is defined as the first side surface, and the opposing side surface where the plurality of ultrasonic wave receiving portions are installed is defined as the first opposing side surface. Further, a side surface different by 90 degrees from the first side surface is defined as the second side surface, and the side surface opposing the second side surface is defined as the second opposing side surface. Another plurality of the ultrasonic wave transmitting portions are arranged on the same straight line perpendicular to the flow direction on the second side surface and are installed at the same angle with respect to the second side surface. Another plurality of the ultrasonic wave receiving portions are installed at positions opposing the other plurality of the ultrasonic wave transmitting portions on the second opposing side surface. The flow rate calculation unit may calculate the average value of the first in-pipe flow rate calculated based on the local average flow velocity for each of the plurality of the ultrasonic wave transmitting portions on the first side surface and the second in-pipe flow rate calculated based on the local average flow velocity for each of the other plurality of the ultrasonic wave transmitting portions on the second side surface as the in-pipe flow rate.

[0017] Furthermore, as one aspect of the present invention, in order to solve the problem of being able to connect in the middle of the pipe without depending on the shape and pipe diameter of the pipe and to facilitate setting, a rectangular pipe having the rectangular pipe portion formed in a rectangular shape and connecting portions at both ends of the rectangular pipe portion that can be connected to other pipes, and the rectangular pipe portion and each of the ultrasonic wave transmitting portions in the rectangular pipe are integrally installed, and the rectangular pipe portion and each of the ultrasonic wave receiving portions may be integrally installed.

Effects of the Invention

[0018] According to the present invention, the installation conditions can be relaxed, calibration and verification are unnecessary, maintenance can be simplified, and highly accurate instantaneous flow rate measurement conforming to the definition of the flow rate can be performed.

Brief Description of the Drawings

[0019]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0020] Hereinafter, a first embodiment of an ultrasonic flow measurement device for a rectangular pipe section according to the present invention will be described with reference to the drawings.

[0021] An ultrasonic flow measurement device 1 for a rectangular pipe section is a device that measures the flow rate of a fluid to be measured flowing in a rectangular pipe section 10 configured as a part of a pipe (pipeline) in a factory or the like. In this first embodiment, as shown in FIG. 1, an ultrasonic transmitting section 2 that emits an ultrasonic pulse toward the fluid to be measured in the rectangular pipe section 10, an ultrasonic receiving section 3 that receives the ultrasonic pulse, an ultrasonic processing section 4 that executes the emission processing and reception processing of the ultrasonic pulse, and a flow rate calculation section 5 that calculates the in-pipe flow rate based on the reception result of the ultrasonic pulse received by the ultrasonic receiving section 3. Hereinafter, each configuration will be described in detail.

[0022] The ultrasonic transmitting section 2 is for emitting an ultrasonic pulse (a sound wave with a high frequency that cannot be heard by the human ear and is intermittently emitted with a predetermined pulse width), and is configured by a cylindrical ultrasonic transducer having a vibration element that vibrates in response to a voltage fluctuation at its tip.

[0023] In addition, in this first embodiment, a plurality of ultrasonic transmitting units 2 are installed on one side surface 101 of the rectangular pipe section 10. Specifically, as shown in FIG. 2, the plurality of ultrasonic transmitting units 2 are arranged in parallel at predetermined intervals on the same straight line perpendicular to the flow direction on the side surface 101 of the rectangular pipe section 10. Since the side surface 101 is formed in a planar shape, different from the outer peripheral surface of a curved circular pipe, each ultrasonic transmitting unit 2 can be installed at any position on the same straight line without being restricted by the critical angle. Therefore, by installing the ultrasonic transmitting units 2 close to each other, many measurement lines can be set, and it is also possible to measure near the upper and lower walls, which is difficult in a circular pipe due to the limitation of the critical angle, and the measurement accuracy of the flow rate can be improved. Further, each ultrasonic transmitting unit 2 in this first embodiment is installed at the same angle with respect to the side surface 101. Each ultrasonic transmitting unit 2 is installed (clamped on) the outside of the side surface 101 by a transducer holder (not shown) that can hold each ultrasonic transducer at a predetermined angle.

[0024] By arranging a plurality of ultrasonic transmitting units 2 in this way at the same angle and on the same straight line with respect to the side surface 101 of the rectangular pipe section 10, as shown in FIG. 2, it is configured to emit ultrasonic pulses on a plurality of parallel measurement lines ML along a predetermined rectangular cross-section C in the rectangular pipe section 10.

[0025] Note that the installation of each ultrasonic transmitting unit 2 is not limited to the outside of the side surface 101 of the rectangular pipe section 10, and holes may be made in the side surface 101 so that the tip of the ultrasonic transducer directly touches the fluid to be measured.

[0026] The ultrasonic receiving unit 3 receives ultrasonic pulses that have passed through the fluid to be measured in the rectangular pipe section 10, and is composed of a cylindrical ultrasonic transducer having a vibration element at its tip that generates a voltage corresponding to the vibration by vibrating upon receiving the ultrasonic waves. In this first embodiment, the same ultrasonic transducer as the ultrasonic transmitting unit is used.

[0027] Also, in the first embodiment, as shown in FIG. 2, a plurality of ultrasonic receiving units 3 are installed on the opposing side surface 102 facing the side surface 101 where the ultrasonic transmitting unit 2 is installed, and are installed (clamped on) at positions facing each of the plurality of ultrasonic transmitting units 2 by a transducer holder (not shown). Since the opposing side surface 102 is formed in a planar shape similar to the side surface 101, each ultrasonic receiving unit 3 can be installed at the opposing position of the ultrasonic transmitting unit 2 without being restricted by the critical angle.

[0028] In the first embodiment, as will be described later, in order to calculate the average flow velocity based on the flight time of the ultrasonic pulse, one ultrasonic receiving unit 3 is installed for one ultrasonic transmitting unit 2. However, the present invention is not limited to this. When calculating the average flow velocity based on the shift amount of the pressure waveform of the ultrasonic pulse with the same configuration as the ultrasonic flow measurement device disclosed in Japanese Patent No. 6321316 invented by the inventor of the present application, (2n + 1) ultrasonic receiving units 3 (n is a natural number of 2 or more) may be installed for one ultrasonic transmitting unit 2.

[0029] The ultrasonic processing unit 4 executes the emission process of the ultrasonic pulse in the ultrasonic transmitting unit 2 and the reception process of the ultrasonic pulse in the ultrasonic receiving unit 3. In the first embodiment, it has a transmission circuit 41 that applies a voltage of a predetermined frequency and number of cycles to the ultrasonic transmitting unit 2, and a reception circuit 42 that transmits the voltage generated by the vibration element vibrated by the ultrasonic pulse received by the ultrasonic receiving unit 3 to the flow rate calculation unit 5.

[0030] The transmission circuit 41 is a circuit for applying a voltage to the ultrasonic transmitting unit 2 to emit an ultrasonic pulse. In the first embodiment, voltages of different frequencies are applied from each ultrasonic transmitting unit 2, and the time when the voltage is applied to the ultrasonic transmitting unit 2 is transmitted to the flow rate calculation unit 5 as the emission time of the ultrasonic pulse.

[0031] The receiving circuit 42 is a circuit for transmitting to the flow rate calculation unit 5 the voltage generated when the ultrasonic receiving unit 3 receives an ultrasonic pulse. In the present first embodiment, based on the voltage generated by the received ultrasonic pulse, it discriminates whether the ultrasonic pulse has the frequency emitted from the opposing ultrasonic transmitting unit 2, and when the ultrasonic pulse has the frequency sent from the opposing ultrasonic receiving unit 3, it transmits the reception time to the flow rate calculation unit 5 as the arrival time when the ultrasonic pulse reaches the ultrasonic receiving unit 3. The discrimination by the receiving circuit 43 in the present first embodiment is performed by performing frequency analysis of the ultrasonic pulse received by the ultrasonic receiving unit 3, and when the analysis result includes the frequency of the ultrasonic pulse emitted from the opposing ultrasonic transmitting unit 2, it is discriminated that the ultrasonic pulse emitted from the opposing ultrasonic transmitting unit 2 has been received.

[0032] The flow rate calculation unit 5 calculates the flow rate in accordance with the definition of the flow rate based on the reception result of the ultrasonic receiving unit 3. In the present first embodiment, it calculates the average flow velocity based on the reception result of the ultrasonic pulse received by the ultrasonic receiving unit 3, and calculates the in-pipe flow rate by multiplying the average flow velocity by the cross-sectional area C of the rectangular cross-section of the rectangular pipe portion 10.

[0033] Here, the definition of the flow rate Q is described. As shown in the following formula, it is represented by the product of the cross-sectional area A and the velocity u(x) orthogonal to this cross-sectional area A. TIFF0007702178000001.tif29150 The pipe in the present invention is the rectangular pipe portion 10. As shown in FIG. 3, when the width direction of the rectangular pipe portion 10 is x and the height direction is y, the formula can be rewritten in the following orthogonal coordinates. TIFF0007702178000002.tif24150 Also, when the measurement line ML between the ultrasonic transmitting unit 2 and the ultrasonic receiving unit 3 is taken parallel to the x-axis, it can be rewritten as follows. TIFF0007702178000003.tif33150 And when integrating in the y-axis direction using the average flow velocity u(y) on one measurement line ML, the flow rate Q is represented by the following formula. TIFF0007702178000004.tif33150 That is, the flow rate Q of the fluid to be measured flowing through the rectangular pipe portion 10 can be calculated by multiplying the average flow velocity u(y) on the measurement line ML by the area L·dy and integrating in the y-axis direction. Here, the average flow velocity u(y) in actual measurement is the local average flow velocity u measured by the ultrasonic transmitting section 2 and the ultrasonic receiving section 3 installed at the position of y. y It is expressed as such. Also, although the ultrasonic transmitting section 2 and the ultrasonic receiving section 3 are installed at predetermined intervals, if the interval is δ, the above formula can be rewritten as a difference formula. The local area dA is represented by the product of L and δ. In the first embodiment of the present invention, since many measurement lines including the vicinity of the wall can be set as described above, the interval δ can be narrowed to improve the measurement accuracy of the flow rate. TIFF0007702178000005.tif45150 Incidentally, the interval δ may be a constant value with the ultrasonic transmitting section 2 and the ultrasonic receiving section 3 arranged at equal intervals in the y direction, or may be different intervals for each position in the y direction.

[0034] Therefore, the flow rate calculation section 5 in the first embodiment measures the flight time of the ultrasonic pulse from the ultrasonic transmitting section 2 until it is received by the ultrasonic receiving section 3 for each ultrasonic transmitting section 2. Specifically, the flight time is measured by the difference between the transmission time transmitted from the transmission circuit 41 and the arrival time transmitted from the reception circuit 42.

[0035] Next, based on the flight time, the local average flow velocity u, which is the local average flow velocity between the ultrasonic transmitting section 2 and the ultrasonic receiving section 3, is calculated. y The local average flow velocity u in the first embodiment of the present invention y is calculated by an existing calculation method based on the flight time. The difference between the flight time in the state where the fluid to be measured is not flowing and the flight time in the flowing state is calculated, and the local average flow velocity u is calculated from the time difference and the flight distance from the ultrasonic transmitting section 2 to the ultrasonic receiving section 3. y The local average flow velocity u for each ultrasonic transmitting section 2 in the first embodiment of the present invention y can be calculated as the instantaneous average flow velocity without time difference for each ultrasonic transmitting section 2.

[0036] Incidentally, the method for calculating the local average flow velocity u y is not limited to the method of calculating from the difference between the flight time in the state where the fluid to be measured is not flowing and the flight time in the flowing state. The functions of the ultrasonic transmitting unit 2 and the ultrasonic receiving unit 3 can be interchanged, and it may be calculated from the difference in the respective flight times (one is the flight time when the flow velocity of the fluid to be measured is added, and the other is the flight time when the flow velocity is subtracted, and the difference between them).

[0037] Next, the flow rate calculation unit 5 multiplies the calculated local average flow velocity u y by the local area dA to calculate the local flow rate. The local area dA is the area between the ultrasonic transmitting unit 2 and the corresponding ultrasonic receiving unit 3. In the first embodiment, it is the area calculated by the product of the vertical interval dy between adjacent ultrasonic transmitting units 3 and the width L of the rectangular pipe portion 10. Then, by multiplying this local area dA by the local average flow velocity u y passing through the surface corresponding to the local area dA, the local flow rate is calculated.

[0038] Then, the flow rate calculation unit 5 calculates the in-pipe flow rate by the sum of all the local flow rates calculated for each ultrasonic transmitting unit. This in-pipe flow rate conforms to the definition of the flow rate Q of the fluid to be measured flowing through the rectangular pipe portion 10, which is calculated by multiplying the local average flow velocity u y on the measurement line ML by the local area dA and integrating in the y-axis direction.

[0039] Next, the operation of each component of the ultrasonic flow rate measuring device 1 for a rectangular pipe portion according to the first embodiment will be described.

[0040] First, the transmission circuit 41 simultaneously applies voltages with different frequencies and a predetermined number of cycles to each ultrasonic transmitting unit 2 from each ultrasonic transmitting unit 2. Also, the application time is transmitted to the flow rate calculation unit 5 as the transmission time. At this time, the higher the frequency of the ultrasonic wave, the narrower the beam width of the ultrasonic wave, and in the first embodiment, the spatial resolution in the height direction (y direction) can be increased. Also, the shorter the number of cycles of the ultrasonic wave, the higher the spatial resolution in the width direction (x direction) can be increased.

[0041] The ultrasonic transmitting unit 2 emits ultrasonic pulses when the vibrating element vibrates with the voltage transmitted from the transmitting circuit 41. The emitted ultrasonic pulses pass through the fluid to be measured in the rectangular pipe portion 10 and reach the opposing ultrasonic receiving unit 3.

[0042] The ultrasonic receiving unit 3 causes the vibrating element to vibrate with the reached ultrasonic pulses and generates a voltage. The generated voltage is transmitted to the receiving circuit 41.

[0043] The receiving circuit 41 receives the voltages transmitted from the respective ultrasonic receiving units 3 and determines whether the ultrasonic pulses are of the frequency emitted from the opposing ultrasonic transmitting unit 2 based on the voltages. Here, when the ultrasonic pulses interfere with each other, frequency analysis is performed to determine whether the ultrasonic pulses of the frequency emitted from the opposing ultrasonic transmitting unit 2 are included. When the determination result is that the ultrasonic pulses are those emitted from the opposing ultrasonic receiving unit 3, the time when the ultrasonic pulses of that frequency are received is transmitted to the flow rate calculation unit 5 as the arrival time at each ultrasonic receiving unit 3.

[0044] In this way, since it is possible to make the determination even when the ultrasonic pulses from the opposing ultrasonic transmitting unit 2 interfere with the ultrasonic pulses from other than the opposing ultrasonic transmitting unit 2, even if the interval dy in the height direction between the ultrasonic transmitting units 2 and between the ultrasonic receiving units 3 is narrowed to an interval where the ultrasonic pulses interfere with each other, the accurate arrival time of the ultrasonic pulses emitted from the opposing ultrasonic transmitting unit 2 can be transmitted.

[0045] In addition, when there is a possibility that the ultrasonic pulses interfere even when different frequencies are used, the emission timing is slightly shifted for each ultrasonic transmitting unit 2 for emission.

[0046] The flow rate calculation unit 5 calculates the flight time for each ultrasonic transmitter 2 from the transmission time for each ultrasonic transmitter 2 transmitted from the ultrasonic processing unit 4 and the arrival time for each ultrasonic receiver 3 facing the ultrasonic transmitter 2. The flight time calculated here is the flight time of the ultrasonic wave passing on the measurement line ML from the ultrasonic transmitter 2 to the opposing ultrasonic receiver 3, and is the time adjusted by the flow velocity distribution on the measurement line ML.

[0047] Therefore, the flow rate calculation unit 5 calculates the difference from the flight time in a state where the fluid to be measured that has been measured in advance is not flowing, and calculates the local average flow velocity u from the time difference and the flight distance from the ultrasonic transmitter 2 to the ultrasonic receiver 3. y That is, the local average flow velocity u y is the average flow velocity between the ultrasonic transmitter 2 and the ultrasonic receiver 3 (on the measurement line ML). Even if the flow velocity distribution is different for each measurement line ML, the average flow velocity for each can be obtained.

[0048] Then, the flow rate calculation unit 5 multiplies the calculated local average flow velocity u y by the local area dA to calculate the local flow rate, and calculates the in-pipe flow rate from the sum of these local flow rates. Since this method of calculating the in-pipe flow rate conforms to the formula rewritten for the rectangular pipe section 10 based on the definition of the flow rate, calibration and verification are not required in principle, and an accurate flow rate can be calculated.

[0049] As described above, the ultrasonic flow rate measuring device 1 for a rectangular pipe section according to the first embodiment can achieve the following operational effects. 1. By adopting a configuration for use in the rectangular pipe section 10, the curvature of the installation surface can be eliminated, and a plurality of ultrasonic transmitters 2 and ultrasonic receivers 3 facing them can be arranged side by side on the same straight line perpendicular to the flow direction, and ultrasonic pulses can be passed through a plurality of measurement lines ML along the rectangular cross-section C. 2. By causing each ultrasonic wave transmitting unit 2 to transmit ultrasonic wave pulses of different frequencies respectively, even if there is interference from ultrasonic wave pulses emitted from sources other than the ultrasonic wave transmitting unit 2 that is opposed to the ultrasonic wave pulses received by the ultrasonic wave receiving unit 3, it is possible to determine whether the ultrasonic wave pulses are emitted from the opposed ultrasonic wave transmitting unit 2, and based on the reception result by the ultrasonic wave pulses emitted from the opposed ultrasonic wave transmitting unit 2, the local average flow velocity u of each ultrasonic wave transmitting unit 2 can be accurately obtained. y can be calculated. 3. When calculating the in-pipe flow rate, the local average flow velocity u on a plurality of measurement lines ML that pass parallel to the rectangular cross-section C in the rectangular pipe section 10 y is calculated, the local flow rate is calculated from each local average flow velocity u y and the in-pipe flow rate is calculated from the sum thereof. Since a flow rate calculation method that conforms to the definition of flow rate is adopted, highly accurate flow rate measurement that does not require calibration or verification can be performed. 4. Since the installation conditions are significantly relaxed by the flow rate calculation method that conforms to the definition of flow rate, it can be installed at any location in the piping, such as immediately after the bent portion, and can also cope with changes in the in-pipe flow due to secular changes, etc., so maintenance can be simplified.

[0050] Next, a second embodiment of the ultrasonic flow rate measuring device 1 for a rectangular pipe section according to the present invention will be described. Among the configurations of this second embodiment, the same reference numerals are given to the configurations that are equivalent or corresponding to the configurations of the above-described first embodiment, and the repeated description will be omitted.

[0051] The ultrasonic flow rate measuring device 1 for a rectangular pipe section of this second embodiment is different from the first embodiment in that the rectangular pipe 100, each ultrasonic wave transmitting unit 2, and each ultrasonic wave receiving unit 3 are integrally formed, and the in-pipe flow rate is measured from two directions. This will be described in detail below.

[0052] The rectangular pipe 100 in this second embodiment has, as shown in FIG. 4, a rectangular pipe section 10 formed in a rectangular shape, and connecting portions 11 that can be connected to other pipes at both ends thereof.

[0053] The rectangular pipe portion 10 is a portion where each ultrasonic transmitting portion 2 and each ultrasonic receiving portion 3 are installed. It is composed of flat plates on all four sides, and both the inner and outer circumferences are formed in a rectangular shape. In the present second embodiment, as shown in FIG. 5, when one side surface is the first side surface 101a and the opposing surface facing the first side surface 101a is the first opposing surface 102a, a side surface different from the first side surface 101a by 90 degrees is the second side surface 101b, and the opposing side surface facing the second side surface 101b is the second opposing side surface 102b.

[0054] The connecting portion 11 is a portion for connecting to other pipes 20 (mainly circular pipes). In the present second embodiment, it is formed in a donut shape, and a plurality of bolt holes are formed for fastening and fixing to the flange portion of the other pipe 20. Since the ultrasonic flow measurement device 1 for a rectangular pipe portion according to the present invention is a calculation method along the definition of the in-pipe flow rate (the product of the average flow velocity and the cross-sectional area passing through the pipe), the pipe shape is different from that of the pipe 20, and even if there is flow disturbance such as drift or reverse flow, a highly accurate flow rate can be measured.

[0055] Note that the connecting portion 11 is not limited to a flange shape and may be appropriately selected according to the end shape of the pipe 20. Further, as shown in FIG. 6, a rectifying portion 12 may be formed between the rectangular pipe portion 10 and the connecting portion 11 to suppress the flow disturbance generated by gradually deforming the cross-sectional shape from a circular shape to a rectangular shape or from a rectangular shape to a circular shape.

[0056] The ultrasonic transmitting portion 2 in the present second embodiment is integrally formed with the rectangular pipe portion 10 and emits ultrasonic pulses from two directions, so it is installed on the second side surface 101b together with the first side surface 101a. Specifically, as shown in FIG. 5, a plurality of ultrasonic transmitting portions 2a are arranged in a direction perpendicular to the flow direction on the first side surface 101a and are installed in advance at the same angle with respect to the first side surface 101a, and another plurality of ultrasonic transmitting portions 2b are arranged in a direction perpendicular to the flow direction on the second side surface 101b and are installed in advance at the same angle with respect to the second side surface 101b.

[0057] In addition, the ultrasonic receiving unit 3 in the second embodiment is integrally formed with the rectangular tube portion 10 and is installed on the second opposing side surface 102b together with the first opposing side surface 102a in order to receive ultrasonic pulses emitted from two directions. Specifically, as shown in FIG. 5, a plurality of ultrasonic receiving units 3a are pre-installed in a state of being arranged at positions facing a plurality of ultrasonic transmitting units 2a installed on the first side surface 101a on the first opposing side surface 102a, and another plurality of ultrasonic receiving units 3b are pre-installed in a state of being arranged at positions facing another plurality of ultrasonic transmitting units 2b installed on the second side surface 101b on the second opposing side surface 102b.

[0058] The ultrasonic processing unit 4 in the second embodiment causes ultrasonic pulses of different frequencies to be emitted from each of the ultrasonic transmitting units 2a and each of the ultrasonic transmitting units 2b. Specifically, the frequencies of the ultrasonic pulses emitted from each of the ultrasonic transmitting units 2a installed on the first side surface 101a and the frequencies of the ultrasonic pulses emitted from each of the ultrasonic transmitting units 2b installed on the second side surface 101b are set to different frequencies. By setting all the frequencies to different frequencies in this way, even if the ultrasonic pulses emitted from the ultrasonic transmitting unit 2a and the ultrasonic transmitting unit 2b interfere with the ultrasonic receiving unit 3a and the ultrasonic receiving unit 3b installed on the other opposing side surface due to reflection by the inner wall of the rectangular tube portion 10 or the like, it is possible to determine whether the ultrasonic pulses are emitted from the opposing ultrasonic transmitting unit 2a and the ultrasonic transmitting unit 2b.

[0059] Note that the frequencies of the ultrasonic pulses emitted from each of the ultrasonic transmitting units 2a and each of the ultrasonic transmitting units 2b are not limited to different frequencies. When it is not necessary to consider reflection by the inner wall of the rectangular tube portion 10 or the like, the combination of the frequencies of each of the ultrasonic transmitting units 2a installed on the first side surface 101a and the combination of the frequencies from each of the ultrasonic transmitting units 2b installed on the second side surface 101b may be the same.

[0060] And the flow rate calculation unit 5 in the second embodiment calculates the local average flow velocity u calculated for each of the plurality of ultrasonic transmitting units 2a on the first side surface 101a by a method in accordance with the definition of the in-pipe flow rate in the same manner as in the first embodiment.y Based on this, the flow rate in the first pipe is calculated. Also, for each of the other plurality of ultrasonic transmitting parts 2b installed on the second side surfaces 101b with different directions, the local average flow velocity u calculated y is used to calculate the flow rate in the second pipe. Then, the average value of the flow rate in the first pipe and the flow rate in the second pipe is calculated as the flow rate in the pipe.

[0061] As described above, the ultrasonic flow rate measuring device 1 for the rectangular pipe part of the second embodiment has the same effects as the first embodiment, and can also achieve the effect of being easily connected to other pipes 20. In particular, even if the flow is disturbed due to the shape difference or the like with the pipe 20 to be connected, it is possible to measure the flow rate in the pipe with high accuracy, and the pipe 20 to be connected can be freely selected.

[0062] Also, in the second embodiment, the flow rate in the first pipe and the flow rate in the second pipe are measured from two directions, and the measurement accuracy can be improved by calculating the flow rate in the pipe from the average value thereof.

[0063] That is, the average flow velocity on the measurement line ML can theoretically obtain continuous measurement results, while there are technical limitations in miniaturizing the vibration elements of the ultrasonic transducers used in the ultrasonic receiving part 2 and the like, and the interval dy between the measurement lines ML cannot be made infinitely small. Therefore, by measuring from directions 90 degrees different, continuous measurement results in the y direction can be obtained, compensating for the limitations in miniaturizing the vibration elements of the ultrasonic transducers and improving the measurement accuracy.

[0064] Note that the ultrasonic flow rate measuring device for the rectangular pipe part according to the present invention is not limited to the above-described embodiments, and can be appropriately changed. For example, when measuring the flow rate from one direction of the rectangular pipe 10 as in the first embodiment, the ultrasonic flow rate measuring device 1 for the rectangular pipe part may be integrally formed with the rectangular pipe 10, and conversely, when measuring the flow rate from two directions of the rectangular pipe 10 as in the second embodiment, it may be installed (clamped on) from two directions with respect to the existing rectangular pipe.

Description of Reference Numerals

[0065] 1 Ultrasonic Flow Measurement Device for Rectangular Pipe Section 2, 2a, 2b Ultrasonic Transmitting Section 3, 3a, 3b Ultrasonic Receiving Section 4 Ultrasonic Processing Section 5 Flow Rate Calculation Section 10 Rectangular Pipe Section 11 Connecting Section 12 Rectifying Section 41 Transmitting Circuit 42 Receiving Circuit 100 Rectangular Pipe 101 Side Surface 101a First Side Surface 101b Second Side Surface 102 Opposite Side Surface 102a First Opposite Side Surface 102b Second Opposite Side Surface C Rectangular Cross-Section ML Measurement Line dA Local Area

Claims

1. An ultrasonic transmitting unit installed on one side of a rectangular pipe section, which emits ultrasonic pulses toward a fluid to be measured inside the rectangular pipe section; an ultrasonic receiving unit that receives the ultrasonic pulses that have passed through the fluid to be measured inside the rectangular pipe section; an ultrasonic processing unit that executes the emission process of the ultrasonic pulses in the ultrasonic transmitting unit and the reception process of the ultrasonic pulses in the ultrasonic receiving unit; a flow rate calculation unit that calculates the average flow velocity of the fluid to be measured flowing inside the rectangular pipe section based on the reception result of the ultrasonic pulses received by the ultrasonic receiving unit, and calculates the in-pipe flow rate by multiplying the average flow velocity by the cross-sectional area of the rectangular pipe section An ultrasonic flow rate measuring device for a rectangular pipe section, comprising: A plurality of the ultrasonic transmitting units are arranged on the same straight line perpendicular to the flow direction on the one side surface, and are installed at the same angle with respect to the one side surface, and a plurality of the ultrasonic receiving units are installed at positions facing the plurality of the ultrasonic transmitting units on the opposite side surface facing the one side surface, The ultrasonic processing unit emits ultrasonic pulses of different frequencies from each of the ultrasonic transmitting units, transmits the emission time to the flow rate calculation unit, performs frequency analysis of the ultrasonic pulses received by the ultrasonic receiving unit, and determines whether the frequency of the ultrasonic pulses emitted from the opposing ultrasonic transmitting unit is included as an analysis result, and when the frequency of the ultrasonic pulses emitted from the opposing ultrasonic transmitting unit is included, transmits the arrival time when the ultrasonic pulses are received to the flow rate calculation unit, The flow rate calculation unit calculates the flight time for each ultrasonic transmitting unit from the emission time of the ultrasonic pulses for each ultrasonic receiving unit transmitted from the ultrasonic processing unit and the arrival time for each ultrasonic receiving unit facing each ultrasonic transmitting unit, calculates the local average flow velocity for each ultrasonic transmitting unit from the flight time and the flight distance from the ultrasonic transmitting unit to the ultrasonic receiving unit, and calculates the in-pipe flow rate from the sum of the local flow rates obtained by multiplying the local average flow velocity by the local area for each ultrasonic transmitting unit. An ultrasonic flow rate measuring device for a rectangular pipe section.

2. Let the one side surface where a plurality of the ultrasonic transmitting units are installed be the first side surface, the opposite side surface where a plurality of the ultrasonic receiving units are installed be the first opposite side surface, and a side surface different from the first side surface by 90 degrees be the second side surface, and the side surface facing the second side surface be the second opposite side surface. The plurality of other ultrasonic transmitting parts are arranged on the same straight line perpendicular to the flow direction on the second side surface, and are installed at the same angle with respect to the second side surface, and the plurality of other ultrasonic receiving parts are installed at positions facing the plurality of other ultrasonic transmitting parts on the second opposite side surface, The flow rate calculation unit calculates, as the in-pipe flow rate, an average value between a first in-pipe flow rate calculated based on the local average flow velocity for each of the plurality of ultrasonic transmitting parts on the first side surface and a second in-pipe flow rate calculated based on the local average flow velocity for each of the plurality of other ultrasonic transmitting parts on the second side surface. The ultrasonic flow rate measuring device for a rectangular pipe part according to claim 1.

3. A rectangular pipe having the rectangular pipe part formed in a rectangular shape and a connecting part connectable to other pipes at both ends of the rectangular pipe part, wherein the ultrasonic transmitting parts and the ultrasonic receiving parts are installed in the rectangular pipe part. The ultrasonic flow rate measuring device for a rectangular pipe part according to claim 1 or claim 2.

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