JP2011122831A - Ultrasonic flow rate measurement method and ultrasonic flow rate measurement device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultrasonic flow rate measurement method and device, precisely measuring the flow rate of the entire water channel and simplifying a calculation processing of the flow rate. <P>SOLUTION: A plurality of metering positions are set on a cross-sectional surface substantially perpendicular to the flow through the water channel. A plurality of measurement points are set in a surface including the normal line of the cross-sectional surface about the plurality of metering positions. A sensor unit 110 which has a measurement line in a surface including the normal line and includes two ultrasonic sensors 112b, 112b having different angles relative to the normal line of the measurement line is disposed in the metering positions. Velocity vectors U1, U2 are measured about the plurality of measurement points on each measurement line by the two ultrasonic sensors. A flow velocity vector U3 is calculated by combining the velocity vectors on each measurement line about the plurality of measurement points. A normal line vector U4 indicating the flow velocity in the normal line direction is calculated about the plurality of measurement points. A flow velocity distribution in the normal line direction is obtained from the normal line vector about the entire water channel, and the flow rate of the entire water channel is calculated. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an ultrasonic flow measurement method and an ultrasonic flow measurement device that transmit and receive ultrasonic waves to measure the flow rate of a water channel.

  A hydroelectric power station generates electricity by rotating a water turbine for power generation using flowing water pressure. The turbine efficiency of a power generation turbine is the efficiency at the time of converting hydraulic power into mechanical energy. In order to measure the turbine efficiency, it is necessary to measure the flow rate of water used for power generation. Measuring the turbine efficiency is indispensable for grasping the generator performance, and high accuracy is required for measuring the flow rate of water in a hydroelectric power plant.

  The water used for hydroelectric power generation may be taken by installing a dam or intake weir in a large hydroelectric power plant, but may be taken from a natural river in a small hydroelectric power plant. A waterway branched from a natural river and opened upward is called an open waterway or open channel, and there are various ones having a width of several meters to several tens of meters. Such measurement of the flow rate of the water channel is performed by measuring the flow velocity distribution of the cross section of the water channel.

  Large turbulence and drift are likely to occur in the water channel immediately after branching from the natural river, and it is not easy to accurately acquire the flow velocity distribution. Therefore, conventionally, when measuring the flow rate of a water channel, it is desirable to secure an equal cross-section straight water channel about 5 to 10 times the river width upstream of the flow rate measurement position in order to prevent turbulence and drift. However, in reality, the distance from the branch point of the waterway to the water intake is short, and it is not always possible to secure the installation area of the flow rate measurement facility at a position that meets the above conditions.

  According to the JEC standard of the Institute of Electrical Engineers of Japan, a large-scale rectifier, wave plate, and guiding wall are installed to stabilize the flow as a countermeasure when sufficient equal section straight water channels cannot be secured upstream and downstream. The method of making it become recommended is recommended. As the rectifier, a lattice-shaped device provided in the water channel is illustrated. For example, by providing measurement points on each grid of this rectifier, it is possible to accurately acquire the flow velocity distribution of the cross section of the water channel. In JEC, a recommended value is also set for the number of measurement points for the channel cross section when measuring the flow rate of the channel. For example, in a water channel having a 4 m × 4 m cross section, the number of measurement points is 50 or more, and a very large number of measurement points are obtained. As described above, in the flow rate measurement of the water channel, it is said that the measurement accuracy can be improved by providing a large number of measurement points of the flow velocity regardless of whether turbulent flow and drift flow are involved.

  Conventional flow velocity measurement is basically point measurement, and in order to provide a large number of measurement points, the number of measurement devices proportional to the number of measurement points is required. For example, as a measuring device for point measurement, there are a propeller-type velocimeter and an electromagnetic velocimeter that can measure a unidirectional flow velocity. However, the installation of a large number of these devices may be difficult to implement from the standpoints of equipment cost and transportation labor. In addition, there is a method of obtaining a flow velocity distribution by moving (traversing) the position of the measuring device one by one, but labor and time are required to repeat the movement and measurement. Furthermore, these propeller-type velocimeters and electromagnetic velocimeters have a problem that strong unsteadiness such as immediately after the branch of a river is strong, and appropriate measurement cannot be performed when the flow rate changes with time.

  As other measurement devices, a linear measurement flow rate measurement device using ultrasonic waves and its method are known. This ultrasonic flow measurement device measures the flow velocity by receiving the reflected wave that is reflected by the ultrasonic wave oscillated in the water and returned to the suspended matter or bubbles in the water. It is possible to provide a large number of measurement points. The Doppler method and the cross-correlation method are mainly used for the ultrasonic flow measurement device. In the market, a flow measuring device (ADCP: Acoustic Doppler Current Profiler) using the Doppler method is widely provided and used.

  As an example of the flow velocity measurement by ADCP, for example, Patent Document 1 discloses an ADCP (acoustic Doppler velocimeter) that measures the flow velocity of a river using a first beam upstream of the river flow and a second beam downstream of the flow. ) Is disclosed. According to Patent Document 1, it is said that the river flow rate can be automatically and accurately observed by simultaneous observation of the water level, the flow velocity distribution, and the river bed level.

  As another form of ADCP, for example, Patent Document 2 discloses ADCP (broadband acoustic Doppler flow velocity profiler) that emits an acoustic beam in three or more directions. According to Patent Document 2, it is supposed that a flow velocity profile (flow velocity distribution) can be measured together with a wave direction and a wave height.

JP 2000-111375 A Japanese translation of PCT publication No. 2002-526783

  However, in Patent Document 1, the ADCP is disposed near the side surface of the river and radiates each beam direction toward the width direction and the horizontal direction of the river. Therefore, the emitted beam is propagated in a direction crossing the river flow. However, in this configuration, when the flow of the river is fast, or where turbulent flow and drift are occurring, such as after a branch of the river, the ultrasonic wave is scattered and attenuated, and it is easy to cause an error in the flow velocity measurement. As a result, the measurement accuracy of the flow rate may be reduced.

  On the other hand, the ADCP of Patent Document 2 emits an acoustic beam in three or more directions and measures the flow velocity three-dimensionally, so that even if the flow is fast, turbulent or uneven, the flow velocity Can be measured accurately. However, when the flow velocity is measured three-dimensionally, a huge amount of flow velocity measurement data is acquired, so that the process of calculating the flow rate from there is more complicated than necessary.

  Further, in the conventional ADCP that measures the flow velocity three-dimensionally, since three or more ultrasonic waves are transmitted radially, the ultrasonic waves spread as they move away from the ultrasonic sensor, and the measurable distance becomes shorter. There is concern. In addition, since the three-dimensional flow velocity is measured at the center of the radial ultrasonic wave, for example, when measuring a location such as the vicinity of the wall surface of a water channel from above, it is separated from the wall surface to some extent so that the ultrasonic wave does not hit the wall surface. A measuring point must be provided at the position. However, the vicinity of the wall surface of the water channel is a portion where the change in flow velocity due to friction or the like is large, and unless the flow velocity near the wall surface is measured, the measurement accuracy of the flow rate of the entire water channel calculated therefrom is lowered.

  In view of such problems, the present invention provides an ultrasonic flow measurement method and an ultrasonic flow measurement device capable of accurately measuring the flow rate of the entire water channel and simplifying the flow rate calculation process. For the purpose.

  In order to solve the above problems, a typical configuration of the ultrasonic flow rate measuring method according to the present invention is to set a plurality of measurement positions on a cross section substantially orthogonal to the flow of the water channel, and to cross the plurality of measurement positions. A plurality of measurement points are set in a plane including the normal of the plane, and a sensor unit having two ultrasonic sensors whose measurement lines are in the plane including the normal and have different angles with respect to the normal of the measurement line is set as the measurement position. Place and measure the velocity vector at a plurality of measurement points on each survey line by two ultrasonic sensors, calculate the flow velocity vector by synthesizing the velocity vectors on each survey line at the plurality of measurement points, and perform a plurality of measurements A normal vector indicating the normal flow velocity for a point is calculated, the normal flow velocity distribution is obtained for the entire channel from the normal vector, and the flow rate of the entire channel is calculated from the flow velocity distribution. .

  According to the above configuration, the flow velocity in the flow direction can be acquired for each of a plurality of measurement points with a simple configuration using only two ultrasonic sensors. Even in locations where turbulent flow or drift occurs, the flow rate in the flow direction is obtained, and the flow rate in the entire water channel is calculated with sufficiently high accuracy without measuring the flow rate in the three-dimensional direction. It becomes possible.

  The ultrasonic flow measurement method uses the Gauss quadrature method, the position determined by the Gauss quadrature method from the width of the water channel and the number of sensor units, and the normal position in the normal direction from the flow velocity distribution in the normal direction. And calculating the flow rate of the entire water channel by multiplying the cross-sectional average flow velocity by the cross-sectional area of the water channel.

  According to the above configuration, even if flow measurement is performed on a channel where friction with the wall surface or viscosity of the fluid affects the flow velocity distribution, the entire channel can be measured even if the measurement position is set to a small number by using the Gauss quadrature method. The cross-sectional average flow velocity can be accurately calculated. Therefore, it is possible to reduce the man-hours for installing the measuring apparatus and simplify the flow rate calculation process.

  In the ultrasonic flow measurement method, the sensor unit may be sequentially moved to a plurality of measurement positions to acquire a normal direction flow velocity. According to this, it becomes possible to measure the flow volume of a water channel, without increasing a sensor unit or making a sensor unit permanently installed in a water channel.

  In order to solve the above-described problems, a typical configuration of an ultrasonic flow measuring device according to the present invention includes two superpositions having different measurement line angles in a plane including a normal line of a cross section substantially perpendicular to the flow of a water channel. At least one sensor unit that has an acoustic wave sensor and transmits ultrasonic waves into the fluid at a plurality of measurement points on the respective measurement lines of the two ultrasonic sensors and measures the reflected waves; and the reflection measured by the sensor unit From the wave, measure the velocity vector at multiple measurement points, calculate the normal vector indicating the normal flow velocity at the multiple measurement points from the velocity vector, and calculate the normal flow velocity distribution for the entire channel from the normal vector. A flow rate calculation unit to be acquired, and a flow rate calculation unit that calculates the flow rate of the entire water channel from the flow velocity distribution and the cross-sectional area of the water channel are provided.

  The invention constituent elements corresponding to the technical idea in the ultrasonic flow measurement method described above and the description thereof can also be applied to the ultrasonic flow measurement device.

  According to the present invention, it is possible to provide an ultrasonic flow measuring method and an ultrasonic flow measuring device capable of accurately measuring the flow rate of the entire water channel and simplifying the flow rate calculation process. .

It is a figure which shows the installation position of the ultrasonic type flow measuring device concerning 1st Embodiment. It is a figure showing a schematic structure of an ultrasonic flow measurement device concerning a 1st embodiment. It is a figure explaining a some measurement position and a test | inspection surface. It is AA sectional drawing of FIG. It is a block diagram which shows the function structure of the ultrasonic type flow measuring device concerning 1st Embodiment. It is a figure explaining flow measurement using a gauss quadrature method. It is a flowchart explaining the ultrasonic flow measurement method using the Gauss quadrature method in 1st Embodiment. It is a flowchart explaining the ultrasonic flow measurement method using the integration method in 1st Embodiment. It is a figure which shows schematic structure of the ultrasonic flow measuring device concerning 2nd Embodiment. It is a figure explaining the ultrasonic sensor of the sensor unit of FIG. It is a flowchart explaining the ultrasonic flow measurement method using the Gauss quadrature method in 2nd Embodiment. It is a figure which shows the outline | summary of other embodiment of the ultrasonic flow measurement method. It is a figure which shows the result of the flow measurement experiment conducted using the Gauss quadrature method. It is a figure which shows the result of the flow measurement experiment conducted using the Gauss quadrature method. It is a figure which shows the result of the comparison experiment of the ultrasonic flow measurement method using the Gauss quadrature method concerning 1st Embodiment, and the flow measurement method by a three-dimensional electromagnetic velocimeter.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The dimensions, materials, and other specific numerical values shown in the embodiments are merely examples for facilitating understanding of the invention, and do not limit the present invention unless otherwise specified. In the present specification and drawings, elements having substantially the same function and configuration are denoted by the same reference numerals, and redundant description is omitted, and elements not directly related to the present invention are not illustrated. To do.

[First Embodiment]
An ultrasonic flow measurement method and an ultrasonic flow measurement device according to the present invention measure the flow rate of a fluid in a water channel, and measure the flow rate in a water channel for intake of hydroelectric power as a representative example. In the following description of the first embodiment, in order to facilitate understanding, the ultrasonic flow rate measuring apparatus according to the first embodiment is described in detail, and then an ultrasonic flow rate using the ultrasonic flow rate measuring apparatus is described. The measurement method will be described in detail.

(Ultrasonic flow measuring device)
FIG. 1 is a diagram illustrating an installation position of an ultrasonic flow measurement device (hereinafter referred to as “measurement device 100”) according to the first embodiment. As shown in FIG. 1, the measuring device 100 can be installed in a water channel 102 for intake of a hydroelectric power plant. The water channel 102 is an open water channel branched from the natural river 104, and the fluid 106 (water) flowing through the water channel 102 is guided from the natural river 104 toward the hydroelectric power station in the direction of the white arrow.

  The measuring apparatus 100 measures the flow rate of the fluid 106 by transmitting an ultrasonic wave toward the fluid 106 flowing through the water channel 102 and receiving a reflected wave reflected by the bubbles 109 (see FIG. 4) included in the fluid 106. When the fluid 106 does not include the bubbles 109, for example, the bubbles 109 can be generated by disposing the bubble generator 108 in the water channel on the upstream side of the measuring device 100.

  FIG. 2 is a diagram illustrating a schematic configuration of the ultrasonic flow rate measuring apparatus according to the first embodiment. The measuring apparatus 100 according to the present embodiment includes a sensor unit 110 and a measurement terminal 120. The sensor unit 110 and the measurement terminal 120 are connected by wire via a cable 144.

  The sensor unit 110 is arranged side by side at a plurality of measurement positions. In the present embodiment, the three sensor units 110 are arranged substantially vertically in the water channel. The sensor unit 110 has two ultrasonic sensors 112 a and 112 b, and each ultrasonic sensor is fixed to a fixing jig 114 and submerged in the fluid 106. The upper part of the fixing jig 114 is fixed to a scaffold 116 that extends over the water channel.

  FIG. 3 is a diagram for explaining a plurality of measurement positions and inspection surfaces. In FIG. 3, in order to clearly indicate the measurement position and the inspection surface S, the water channel 102 is illustrated as a frame line, and the sensor unit 110 includes only the ultrasonic sensors 112 a and 112 b in one of the three sensor units 110. The illustration is omitted.

  As shown in FIG. 3, the plurality of measurement positions are set side by side on a cross section substantially orthogonal to the flow of the water channel 102. The ultrasonic sensors 112 a and 112 b of the sensor unit 110 have an inspection surface S that includes a normal to the transverse section of the water channel 102. In the inspection surface S, a plurality of measurement points are set. The measurement points are a plurality of positions set in the water depth direction as measurement targets of the ultrasonic sensors 112a and 112b.

  In the present embodiment, the inspection surface S is substantially vertical. The ultrasonic sensor 112a and the ultrasonic sensor 112b are disposed in the inspection surface S so that the angles of the measurement lines L1 and L2 with respect to the normal line are different from each other. In FIG. 3, the ultrasonic sensors 112a and 112b are arranged vertically, and the measurement lines L1 and L2 of the ultrasonic sensors 112a and 112b intersect each other. However, the present invention is not limited to this, and both of the ultrasonic sensors 112a and 112b may be arranged above or below, as long as the angles of the measurement lines L1 and L2 with respect to the normal line are different.

  The ultrasonic sensors 112a and 112b will be described in detail with reference to FIG. 4 is a cross-sectional view taken along line AA in FIG. In FIG. 4, the x axis represents the horizontal axis (substantially parallel to the normal line), and the y axis represents the vertical axis (substantially parallel to the cross section).

  The ultrasonic sensors 112a and 112b transmit ultrasonic waves on the respective measurement lines, and measure the reflected waves from the bubbles 109 at a plurality of measurement points. A signal related to the reflected wave measured by the ultrasonic sensors 112 a and 112 b is transmitted to the measurement terminal 120 via the cable 144. Note that FIG. 4 is schematic, and the two ultrasonic sensors 112a and 112b do not measure only the same bubble 109 as a measurement target.

  FIG. 5 is a block diagram illustrating a functional configuration of the ultrasonic flow rate measuring device 100 according to the first embodiment. The measurement terminal 120 shown in FIG. 5 includes a control unit 122, a storage unit 134, an operation unit 136, and a display unit 138, controls transmission of ultrasonic waves by the ultrasonic sensors 112a and 112b, and The reflected waves received by the ultrasonic sensors 112a and 112b are calculated.

  The control unit 122 manages and controls the entire measurement apparatus 100 using a semiconductor integrated circuit including a central processing unit (CPU). In the present embodiment, the control unit 122 also functions as a pulsar 124, a receiver 126, an A / D conversion unit 128, a flow velocity calculation unit 130, and a flow rate calculation unit 132.

  The pulsar 124 transmits an electrical signal (current) corresponding to the waveform of the ultrasonic wave to the ultrasonic sensors 112a and 112b of the sensor unit 110. The electric signal is transmitted at a predetermined frequency and interval for driving the ultrasonic transmission unit 140. The receiver 126 amplifies an analog signal generated when the reflected wave receiving unit 142 receives an ultrasonic reflected wave. The A / D converter 128 converts the analog signal amplified by the receiver 126 into a digital signal.

  The flow velocity calculation unit 130 acquires the flow velocity and the flow velocity distribution at a plurality of measurement points from the reflected wave measured by the sensor unit 110. For example, as shown in FIG. 4, the flow velocity calculation unit 130 measures velocity vectors U1 and U2 from reflected waves measured by the two ultrasonic sensors 112a and 112b at a certain measurement point, respectively. Next, the flow velocity vector U3 (flow velocity in the inspection surface S) is calculated by combining the velocity vectors U1 and U2. Then, the normal vector U4 indicating the flow velocity in the normal direction is calculated by projecting the flow velocity vector U3 in the normal direction. As described above, the flow velocity calculation unit 130 can obtain a normal velocity distribution for the entire water channel by calculating a normal vector for each measurement point.

  The flow rate calculation unit 132 calculates the flow rate of the entire water channel from the flow velocity distribution calculated by the flow rate calculation unit 130 and the cross-sectional area of the water channel 102.

  The storage unit 134 includes a ROM, a RAM, an EEPROM, a nonvolatile RAM, a flash memory, an HDD (Hard Disk Drive), and the like, and stores a program processed by the control unit 122.

  The operation unit 136 includes a plurality of keys (switches) such as a keyboard, a cross key, and a joystick, a mouse, and the like, and receives a user operation input. For example, a plurality of measurement points can be set for each sensor unit 110 by the operation unit 136.

  The display unit 138 includes a liquid crystal display, EL (Electro Luminescence), PDP (Plasma Display Panel), and the like, and can display a GUI (Graphical User Interface) of an application stored in the storage unit 134.

  The ultrasonic transmission unit 140 is configured by a piezoelectric element or the like, and transmits ultrasonic waves into the water channel. The reflected wave receiving unit 142 receives the reflected wave reflected by the bubble 109.

(Setting the measurement position of the sensor unit)
Next, the setting of the measurement position of the sensor unit 110 will be described. The measurement apparatus 100 according to the present embodiment can perform simple and accurate flow rate measurement by setting the measurement position and calculating the flow rate using the Gauss quadrature method. Gauss quadrature is a kind of numerical integration in numerical analysis. The Gaussian quadrature method can obtain a highly accurate result even with a small number of steps by changing the step width according to the shape of the integrand.

  FIG. 6 is a diagram for explaining flow rate measurement using the Gauss quadrature method. FIG. 6A is a formula showing flow rate calculation using the Gauss quadrature method, FIG. 6B is a table showing low-order sampling positions and weights related to the Gauss-Legendre quadrature method, and FIG. It is a figure which shows the sampling position in the case of = 4.

  First, by using the Gaussian quadrature method, the sensor unit 110 is arranged on the cross section of the water channel 102 from the width of the water channel 102 and the number of sensor units 110 used for flow rate measurement (or the number of measurement positions). The optimal measurement position can be set. For example, when the number of sensor units 110 to be used is four, the sampling number N in the table of FIG. 6B is 4, and the sampling position Wi is a value shown in the row of the sampling number N = 4. As shown in FIG. 6C, the sampling position Wi represents the measurement position when the center of the water channel 102 is 0 and the distance from the center to the left and right side walls is 0.5. For example, by substituting the actual measurement value of the width of the water channel 102 into W in the diagram of FIG. 6C, the four sensor units 110 from the center of the water channel can be obtained from the actual measurement value of the width of the water channel 102 and each sampling position Wi. The measurement position can be obtained. Then, from the flow velocity distribution in the normal direction at each measurement position measured by each sensor unit 110, average flow velocity V1 to V4 (average flow velocity in the inspection surface S) in the water depth direction at each measurement position is calculated, and FIG. Substitute into equation (a). Thereby, the average cross-sectional flow velocity in the normal direction is calculated from the average flow velocity V1 to V4 at each measurement position, and the cross-sectional average flow velocity is multiplied by the cross-sectional area of the water channel 102 (water channel width × water level) to calculate the flow rate Q of the entire water channel. can do.

  According to the above configuration, even when the flow rate measurement is performed on the water channel 102 where the friction with the wall surface or the viscosity of the fluid 106 affects the flow velocity distribution, the flow rate of the entire water channel can be accurately measured at a small number of measurement positions by using the Gauss quadrature method. It can be calculated well. Therefore, it is possible to reduce the man-hours for installing the measuring apparatus 100 and simplify the flow rate calculation process.

  If the Gauss quadrature method is not used, the sensor unit 110 is arranged at a plurality of arbitrary measurement positions on the cross section of the water channel 102, and the cross section is divided into meshes at equal intervals and the flow velocity is multiplied. The flow rate may be calculated by integrating the calculated minute flow rate. Even in the case of the integration method, the number of measurement positions may be reduced as in the case of the Gaussian quadrature method, and the flow velocity between the measurement positions may be interpolated. Since this flow rate calculation method is well known to those skilled in the art, a detailed description thereof will be omitted.

(Ultrasonic flow measurement method)
Subsequently, an ultrasonic flow measurement method using the above-described measurement apparatus 100 will be described in detail. FIG. 7 is a flowchart for explaining an ultrasonic flow measurement method using the Gauss quadrature method in the first embodiment.

  In the ultrasonic flow measurement method using the Gauss quadrature method, first, an arbitrary number (or number of measurement positions) of the sensor unit 110 is determined, and substantially orthogonal to the flow of the water channel 102 based on the Gauss quadrature method. A plurality of measurement positions are set on the cross section (S200), and the sensor unit 110 is arranged at each measurement position (S204). At this time, the sensor unit 110 uses the surface including the normal to the cross section of the water channel 102 as the inspection surface S, and the angles of the two ultrasonic sensors 112a and 112b with respect to the normal of the measurement line in the inspection surface S are different from each other. Deploy.

  Next, a plurality of measurement points are set in the inspection surface for each sensor unit 110 arranged at a plurality of measurement positions (S208). Each of the plurality of measurement points is set at a position equidistant from the two survey lines in the horizontal direction.

  Then, the pulsar 124 transmits an electrical signal to the ultrasonic transmission unit 140, so that the ultrasonic transmission unit 140 transmits ultrasonic waves to the fluid 106 in the water channel (S212). The reflected wave receiving unit 142 receives the reflected wave generated when the ultrasonic wave transmitted by the ultrasonic wave transmitting unit 140 is reflected by the bubble 109 (S216).

  The flow velocity calculation unit 130 receives the reflected waves from the reflected wave receiving unit 142 via the receiver 126 and the A / D conversion unit 128 and uses the Doppler method to detect the two ultrasonic sensors 112a and 112b. Two-direction velocity vectors U1 and U2 are measured at a plurality of measurement points on each survey line (S220). Note that the positions at which the velocity vectors U1 and U2 are measured (distances from the ultrasonic sensors 112a and 112b) are the intersections between the horizontal lines including the measurement points and the measurement lines (positions at the same water depth as the measurement points).

  Furthermore, the flow velocity calculation unit 130 combines the two velocity vectors U1 and U2 and calculates the flow velocity vector U3 of the fluid 106 for a plurality of measurement points (S224). Furthermore, the flow velocity calculation unit 130 calculates a normal vector U4 indicating the flow velocity in the normal direction with respect to the transverse section of the water channel 102 at a plurality of measurement points from the calculated flow velocity vector U3 (S228). Thereby, the flow velocity calculation unit 130 can acquire the flow velocity distribution in the normal direction for the entire water channel from the normal vector calculated for each measurement point (S232).

  Next, the flow velocity calculation unit 130 calculates an average flow velocity V on each inspection surface S of the sensor unit 110 at a plurality of measurement positions (S236), and the flow rate calculation unit 132 calculates each inspection surface calculated by the flow velocity calculation unit 130. From the average flow velocity Vi in S and the cross-sectional area of the water channel 102, the flow rate of the entire water channel is calculated by the Gauss quadrature method (S240). Thereby, the processing of the ultrasonic flow measurement method is completed.

  Moreover, the measurement apparatus 100 described above can calculate the flow rate without using the Gauss quadrature method. FIG. 8 is a flowchart for explaining the ultrasonic flow rate measuring method using the integration method in the first embodiment. In addition, about the process similar to FIG. 7, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  In the ultrasonic flow rate measurement method using the normal integration method, first, a plurality of measurement positions (horizontal direction) and a plurality of measurement points at each measurement position are arbitrarily arranged on a cross section substantially orthogonal to the flow of the water channel 102. (Water depth direction) is set (S250). Then, after calculating the flow velocity distribution for each measurement point by the same process as in FIG. 7 (S232), the flow rate is calculated by the integration method (S254), and the process ends.

  According to these configurations, it is possible to acquire the flow velocity (normal vector U4) in the flow direction with a simple configuration of only the two ultrasonic sensors 112a and 112b for each of the plurality of measurement points. Even in locations where turbulent flow or drift occurs, the flow rate in the flow direction is obtained, and the flow rate in the entire water channel is calculated with sufficiently high accuracy without measuring the flow rate in the three-dimensional direction. It becomes possible.

  That is, the flow rate calculation process can be simplified by reducing the number of measurement data to be acquired as compared to the case of using a three-dimensional velocimeter or the like. Further, since the measurement is performed on the inspection surface S including the normal line of the cross section, the sensor unit 110 can be brought closer to the wall surface. Therefore, the velocity vector in the vicinity of the wall surface where the flow velocity change is large can be measured. By these, it becomes possible to measure the flow volume of the whole water channel accurately.

[Second Embodiment]
(Ultrasonic flow measuring device)
FIG. 9 is a diagram showing a schematic configuration of an ultrasonic flow rate measuring apparatus (hereinafter referred to as “measuring apparatus 300”) according to the second embodiment. The measurement apparatus 300 according to the second embodiment is capable of acquiring the flow velocity in the normal direction of the water channel 102 by sequentially moving the sensor unit 310 to a plurality of measurement positions. And different. In the sensor unit 310, the two ultrasonic sensors 312a and 312b both transmit ultrasonic waves from above to below. Hereinafter, the same operation and configuration elements as those of the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

  The measurement apparatus 300 includes one sensor unit 310 having two ultrasonic sensors 312a and 312b. In this embodiment, the sensor unit 310 is movably attached to a guide 320 that extends over the water channel. The guide 320 is laid substantially parallel to a cross section that is substantially orthogonal to the flow of the water channel 102, and the sensor unit 310 moves on the guide 320 so as to be substantially parallel to the cross section, thereby performing a plurality of measurements on the cross section. The position can be moved sequentially. The guide 320 is exemplified as a support member of the sensor unit 310, and the support member is not limited to this. For example, the scaffold 116 may be a supporting member, and the sensor unit 310 may be simply detachable from the scaffold 116 at a plurality of locations.

  FIG. 10 is a diagram for explaining the ultrasonic sensors 312a and 312b of the sensor unit 310 of FIG. Similar to the sensor unit 110 according to the first embodiment, the sensor unit 310 according to the present embodiment uses a surface including a normal line to the cross section of the water channel 102 as an inspection surface S. The inspection surface S is substantially vertical. The ultrasonic sensor 312a and the ultrasonic sensor 312b are arranged in the inspection surface S so that the angles of the measurement lines L3 and L4 with respect to the normal line (substantially parallel to the x axis) are different from each other.

  The ultrasonic sensors 312a and 312b measure the reflected waves from the transmitted ultrasonic bubbles 109 at a plurality of measurement points on each measurement line. A signal related to the reflected wave measured by the ultrasonic sensors 312 a and 312 b is transmitted to the measurement terminal 120 via the cable 144. In the measurement terminal 120, the velocity vectors U5 and U6 are measured by the flow velocity calculation unit 130 from the signal relating to the reflected wave, and the velocity vectors U5 and U6 are further combined to calculate the flow velocity vector U7. Next, a normal vector U8 indicating the flow velocity in the normal direction is calculated from the flow velocity vector U7, and the flow velocity distribution of the entire water channel is acquired by calculating the normal vector of each measurement point. Then, the flow rate calculation unit 132 measures the flow rate of the entire water channel from the flow velocity distribution calculated by the flow rate calculation unit 130 and the cross-sectional area of the water channel 102.

(Ultrasonic flow measurement method)
Subsequently, an ultrasonic flow measurement method using the above-described measurement apparatus 300 will be described in detail. FIG. 11 is a flowchart for explaining an ultrasonic flow measurement method using the Gauss quadrature method in the second embodiment. In addition, about the process similar to FIG. 7, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  In the ultrasonic flow measurement method using the Gauss quadrature method by the measurement device 300, first, the number of arbitrary measurement positions where the sensor unit 310 performs measurement is changed to the flow of the cross section of the water channel 102 based on the Gauss quadrature method. A plurality of measurement positions are set on a substantially orthogonal cross section (S200), and the sensor unit 310 is arranged at one of the measurement positions (S350). At this time, by arranging the measurement position at the measurement position closest to the wall surface of the water channel 102 among the plurality of measurement positions, the measurement position can be sequentially moved toward the wall surface on the opposite side to smoothly acquire the flow velocity. The sensor unit 310 is arranged so that the surface including the normal to the cross section of the water channel 102 is the inspection surface S, and the angles of the two ultrasonic sensors 312a and 312b with respect to the normal of the measurement line are different in the inspection surface S. To do.

  Next, the normal vector U8 at the measurement position is calculated by the same processing as in FIG. 7 (S228). Thereby, the flow velocity calculation unit 130 can acquire the normal velocity flow velocity distribution from the normal vector calculated up to that point (S232).

  Then, the sensor unit 310 moves to the next measurement position (YES in S354), and acquires the flow velocity distribution at the next measurement position.

  When the sensor unit 310 finishes acquiring the flow velocity distribution at all measurement positions, the movement ends (NO in S354), and the flow rate is calculated by the flow velocity calculation unit 130 and the flow rate calculation unit 132 in the same process as in FIG. .

  According to the above configuration, it is possible to measure the flow rate of the water channel 102 without increasing the number of sensor units or permanently installing the sensor unit in the water channel 102. That is, the flow rate can be measured by providing at least one sensor unit 310.

  In the measuring apparatus 300 according to the present embodiment, it is also possible to calculate the flow rate using the integration method without using the Gauss quadrature method.

[Other Embodiments]
FIG. 12 is a diagram showing an outline of another embodiment of the ultrasonic flow rate measuring method. In the following description, elements having functions and configurations similar to those of the above-described embodiments are denoted by the same reference numerals and description thereof is omitted.

  In the ultrasonic flow measurement method using the Gauss quadrature method in each embodiment described above, the flow measurement for the water channel 102 having a rectangular cross section has been described. However, it is possible to perform flow rate measurement using the Gauss quadrature method even in a water channel whose cross section is not rectangular. For example, as shown in FIG. 12A, for a water channel 402 having a trapezoidal cross section, the measurement position is determined by the Gauss quadrature method from the width of the water channel 402 and the number of sensor units 110 used on each of the water surface and the bottom of the water. The sensor unit 110 is arranged such that the inclined surfaces connecting the measurement positions of the water surface and the bottom surface are the inspection surfaces S1 to S4. Thereby, even if the cross section is the trapezoidal water channel 402, flow measurement using the Gauss quadrature method is possible.

  Moreover, in each embodiment mentioned above, the sensor unit 110 was arrange | positioned so that an inspection surface might become substantially vertical. However, the inspection surface is not limited to this. For example, as shown in FIG. 12B, even if the sensor unit 110 is arranged so that the inspection surfaces S1 to S4 are substantially horizontal, the flow rate using the Gauss quadrature method is used. Measurement is possible. However, in this case, it is necessary to measure the flow rate in consideration of the temporal change of the water level.

[Evaluation test]
FIG. 13 and FIG. 14 are diagrams showing the results of a flow measurement experiment performed using the Gauss quadrature method. As experimental conditions, a water channel 410 (opening) having a width of 1500 mm and a water level of 1250 mm was used as shown in FIG. The flow rate condition of the water channel 410 was 1.5 m / s, and microbubbles were injected into the water channel from upstream.

  The experiment was conducted with and without obstacles in the channel. The obstacle is for generating turbulence and drift in the water channel. As the obstacle, a pipe 414 is arranged on the right side wall 1.8 m upstream of the Pitot tube 412.

  FIG. 13B shows the flow velocity distribution in the horizontal direction when there is no obstacle, and FIG. 13C shows the flow velocity distribution in the horizontal direction when there is an obstacle. The flow rate in FIGS. 13B and 13C was measured using a Pitot tube 412 (tube diameter: 9 mm), and the measurement was performed at 50 Hz for 30 seconds / point. Moreover, the measurement of the flow velocity was performed at intervals of 10 mm from one side wall surface of the water channel 410 to the opposite side wall surface at a constant water level (0.5 m). Comparing FIG. 13 (b) and FIG. 13 (c), since the flow velocity distribution is disturbed in FIG. 13 (c), turbulence and drift are generated due to the presence of obstacles in the water channel. Can be confirmed.

  The broken line and the alternate long and short dash line in FIG. 13B and FIG. 13C indicate the sampling position (N = 3,4) of the Gauss quadrature method. FIG. 14 is a diagram showing the difference in cross-sectional average flow velocity obtained by the Gaussian quadrature method and the integration method. The average cross-sectional flow velocity by the Gaussian quadrature method was calculated by extracting measurement data at sampling positions (N = 3, 4) indicated by broken lines in FIGS. 13 (b) and 13 (c). Moreover, the cross-sectional average flow velocity by the integration method was obtained by integrating all measured data shown in FIGS. 13 (b) and 13 (c).

  From FIG. 14, it can be seen that the difference in cross-sectional average flow velocity from the integration method is small even in the flow measurement using the Gaussian quadrature method using a small amount of measurement data, compared to the integration method using all measurement data. Recognize. Further, even when turbulent flow and drift are generated by an obstacle, it can be seen that the difference from the integration method is small when the sampling position of the Gauss quadrature method is 3 or more. From these facts, it can be confirmed that by using the Gauss quadrature method, the measurement position can be set to a small number, and the flow rate of the entire water channel can be accurately calculated even when turbulent flow and drift are generated.

  FIG. 15 shows the result of a comparison experiment between the ultrasonic flow measurement method using the Gauss quadrature method according to the first embodiment and the flow measurement method using a three-dimensional electromagnetic velocimeter (hereinafter referred to as “EMC”). FIG. As an experimental condition, as shown in FIG. 15A, a water channel 410 (opening) having a width of 1500 mm and a water level of 1250 mm was used. Moreover, the flow rate conditions of the water channel 410 were 0.5 m / s, 1.0 m / s, and 1.5 m / s, and microbubbles were injected into the water channel from the upstream. Further, a pipe 414 is disposed on the right side wall of the water channel 410 as an obstacle that generates turbulent flow and drift in the water channel 410. The pipe 414 was positioned 2200 mm upstream of the sensor unit 110.

  A total of three sensor units 110 of the measuring apparatus 100 were used and arranged at measurement positions based on the Gauss quadrature method. Each of the ultrasonic sensors 112a and 112b was disposed toward the upstream side of the water channel 410 and inclined by 30 ° from the vertical direction. The ultrasonic frequency transmitted by the ultrasonic sensors 112a and 112b was 200 kHz. An EMC having a sensor diameter of φ20 mm and a measurement range of ± 2.5 m / s (accuracy FS ± 2%) was used. The measurement of the flow velocity by EMC is performed from the water surface to the bottom of the water at a position 1800 mm downstream of the pipe 414 (position 400 mm upstream of the sensor unit 110) and substantially the same inspection surface S1 to S3 as each sensor unit 110 of the measuring device 100. The sample was traversed in a substantially vertical direction and measured at intervals of 10 mm.

  FIG. 15B is a diagram for comparing the flow velocity distributions acquired by the measuring apparatus 100 and the EMC. As shown in FIG. 15B, it can be confirmed that the flow velocity distributions of the measuring device 100 and the EMC are relatively coincident with each other on the inspection surface S1 far from the pipe 414 that is an obstacle. Further, there is a difference in the flow velocity distribution between the measuring device 100 and the EMC on the inspection surfaces S2 and S3. This is because the turbulence and the drift are generated by the pipe 414 on the inspection surfaces S2 and S3, and the measuring device 100. It is thought that this is because the measurement position (distance from the pipe 414) is slightly different from that of EMC.

  FIG. 15C is a diagram comparing the cross-sectional average flow velocities of the water channels 410 calculated by the measuring device 100 and the EMC, respectively. In FIG.15 (c), the cross-sectional average flow velocity calculated | required by the Gauss quadrature method from the average flow velocity which the measuring apparatus 100 and EMC measured in each measurement position was compared.

  As shown in FIG. 15 (c), when the flow velocity is 1 m / s or more, the difference in cross-sectional average flow velocity between the measuring apparatus 100 and the EMC is less than 1%. From this result, it is understood that the flow velocity measurement by the ultrasonic flow measurement method using the Gauss quadrature method is highly accurate even in the water channel 410 in which turbulent flow or drift occurs. That is, the ultrasonic flow measurement method using the Gauss quadrature method according to the present invention can calculate the flow rate of the entire water channel with sufficiently high accuracy without measuring the flow velocity in the three-dimensional direction. It can be confirmed that there is.

  Note that the difference is large at a flow velocity of 0.5 m / s or less, but this is presumed to be due to the fact that the measurement accuracy of EMC has dropped under the low flow rate condition of 0.5 m / s.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to the example which concerns. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Understood.

  INDUSTRIAL APPLICABILITY The present invention can be used for an ultrasonic flow measurement method and an ultrasonic flow measurement device that transmit and receive ultrasonic waves and measure the flow rate of a water channel.

S, S1, S2, S3 ... Inspection planes U1, U2, U5, U6 ... Velocity vectors U3, U7 ... Velocity vectors U4, U8 ... Normal vectors 100, 300 ... Measuring devices 102, 402, 410 ... Water channels 104 ... Natural rivers 106 ... Fluid 108 ... Bubble generator 109 ... Bubbles 110 and 310 ... Sensor units 112a, 112b, 312a and 312b ... Ultrasonic sensor 114 ... Fixing jig 116 ... Scaffold 120 ... Measuring terminal 122 ... Control part 124 ... Pulsar 126 ... Receiver 128 ... A / D conversion unit 130 ... flow rate calculation unit 132 ... flow rate calculation unit 134 ... storage unit 136 ... operation unit 138 ... display unit 140 ... ultrasonic wave transmission unit 142 ... reflected wave reception unit 144 ... cable 320 ... guide 412 ... Pitot Pipe 414 ... Pipe

Claims (4)

Set multiple measurement positions on the cross section approximately perpendicular to the flow of the waterway,
Setting a plurality of measurement points in a plane including the normal line of the cross section for the plurality of measurement positions;
A sensor unit having two ultrasonic sensors in which a survey line is in a plane including the normal line and the angles of the survey line to the normal line are different from each other at the measurement position;
The two ultrasonic sensors measure velocity vectors for the plurality of measurement points on the respective survey lines,
A velocity vector is calculated by combining the velocity vectors on each survey line for the plurality of measurement points,
Calculating a normal vector indicating the flow velocity in the normal direction for the plurality of measurement points;
Obtaining a flow velocity distribution in the normal direction for the entire water channel from the normal vector;
An ultrasonic flow rate measuring method, wherein the flow rate of the entire water channel is calculated from the flow velocity distribution. The ultrasonic flow measurement method uses a Gauss quadrature method,
From the width of the water channel and the number of sensor units, the position determined by the Gauss quadrature method is the measurement position,
From the flow velocity distribution in the normal direction, calculate the cross-sectional average flow velocity in the normal direction,
The ultrasonic flow rate measurement method according to claim 1, wherein the flow rate of the entire water channel is calculated by multiplying the cross-sectional average flow velocity by the cross-sectional area of the water channel.   The ultrasonic flow rate measuring method according to claim 1, wherein the sensor unit is sequentially moved to the plurality of measurement positions to acquire the flow velocity in the normal direction. Two ultrasonic sensors having different measurement line angles in a plane including a normal line of a cross section substantially orthogonal to the flow of the water channel are provided, and ultrasonic waves are measured at a plurality of measurement points on the respective measurement lines of the two ultrasonic sensors. At least one sensor unit for transmitting the fluid into the fluid and measuring the reflected wave;
A velocity vector is measured for the plurality of measurement points from the reflected wave measured by the sensor unit, a normal vector indicating a flow velocity in the normal direction is calculated for the plurality of measurement points from the velocity vector, and the normal line is calculated. A flow velocity calculation unit for obtaining a flow velocity distribution in the normal direction for the entire water channel from a vector;
An ultrasonic flow rate measuring apparatus comprising: a flow rate calculation unit that calculates a flow rate of the entire water channel from the flow velocity distribution and a cross-sectional area of the water channel.

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