JP5282955B2 - Ultrasonic flow meter correction method and ultrasonic flow meter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultrasonic flowmeter capable of accurately correcting a flow rate even when the kind or concentration of a measuring fluid changes. <P>SOLUTION: The ultrasonic flowmeter 1 includes: a pipe having two straight portions 2 and 3; first ultrasonic transducers 5a and 5b provided in the first straight portion 2; second ultrasonic transducers 6a and 6b provided in the second straight portion 3; and a control apparatus 7 connected to the individual ultrasonic transducers 5a, 5b, 6a, and 6b. The control apparatus 7 measures flow rates in the individual straight portions 2 and 3, by performing transmission and reception of ultrasonic waves So by the use of the individual ultrasonic transducers 5a, 5b, 6a, and 6b, and flow-rate correction is performed on the basis of the difference between those measurement values. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a method for correcting an ultrasonic flowmeter that measures a flow rate of a fluid based on a difference in propagation time of ultrasonic waves, and an ultrasonic flowmeter.

  In the conventional ultrasonic flowmeter, ultrasonic transmitters / receivers are provided on the upstream side and downstream side of the pipe through which the measurement fluid flows, and ultrasonic waves are transmitted / received using the ultrasonic transmitter / receiver, and are transmitted from the upstream side to the downstream side. The flow rate of the measurement fluid is obtained based on the time difference between the propagation time of the sound wave and the propagation time of the ultrasonic wave propagating from the downstream side to the upstream side. In this type of ultrasonic flowmeter, when the temperature or concentration of the measurement fluid changes, the kinematic viscosity of the fluid changes with the change, which causes a flow measurement error. As a countermeasure, a technique for correcting the flow rate based on the kinematic viscosity corresponding to the temperature change has been proposed (for example, see Patent Document 1).

In the correction method disclosed in Patent Document 1, the flow velocity and sound velocity are measured by an ultrasonic flowmeter, and the temperature of the fluid is obtained using a temperature table using the sound velocity as a parameter. And kinematic viscosity is calculated | required using the kinematic viscosity table which made temperature the parameter, and the flow volume is correct | amended by the ratio according to the kinematic viscosity.
JP 2007-51913 A

  However, in the correction method of Patent Document 1 described above, when measuring a fluid of a type different from a predetermined measurement fluid or a measurement fluid whose concentration has changed, the table data used corresponds to the measurement fluid. As a result, incorrect correction is performed, resulting in a large measurement error. Further, depending on the type of fluid, there may be a maximum point P1 in the relationship between the speed of sound and temperature (see FIG. 7). In this case, since the temperature cannot be uniquely obtained from the measured sound speed, there is a problem that the measurable temperature range is limited.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an ultrasonic flowmeter correction method capable of accurately performing flow rate correction even when the type and concentration of a measurement fluid change, and a super To provide a sonic flow meter.

In order to solve the above-mentioned problem, the invention described in the means 1 transmits / receives ultrasonic waves using ultrasonic transmitters / receivers provided on the upstream side and downstream side of a pipe through which the measurement fluid flows, and from the upstream side to the downstream side An ultrasonic flowmeter correction method for obtaining a flow rate of the measurement fluid based on a time difference between a propagation time of an ultrasonic wave propagating to the upstream side and a propagation time of an ultrasonic wave propagating from a downstream side to an upstream side, the pipe The measurement fluid is measured by transmitting and receiving ultrasonic waves using a plurality of ultrasonic transmitters / receivers provided in measurement sites having different flow path cross-sectional areas or measurement sites having different inner surface roughnesses in the pipe. correction step of correcting a measurement step, the flow rate of the measurement fluid based on a ratio or a difference of the measurement value by the plurality of ultrasonic transducers for measuring respectively the flow velocity or flow rate at the plurality of ultrasonic transducers Correction method of the ultrasonic flowmeter which comprises a as its gist the.

  Therefore, according to the invention described in the means 1, a plurality of ultrasonic transmitters / receivers are provided in measurement parts having different flow characteristics of the measurement fluid in the pipe through which the measurement fluid flows, and in the measurement step, the ultrasonic transmission / reception is performed. The ultrasonic wave propagation time difference is obtained by the measuring device, and the flow velocity or flow rate of the measurement fluid corresponding to the propagation time difference is measured. In the correction step, the flow rate of the measurement fluid is corrected based on the difference between the measurement values obtained by the sound wave transmitters / receivers. In this way, even when the type and concentration of the measurement fluid change, the flow rate can be corrected accurately without using other sensors such as a thermometer and a viscometer.

In the above means 1, a plurality of ultrasonic transmitters / receivers are provided in measurement sites having different flow path cross-sectional areas in piping or measurement sites having different inner surface roughnesses . In this case, since the Reynolds number representing the flow state of the measurement fluid is different at each measurement site, the flow rate measured using each ultrasonic transceiver becomes a different measurement value when the kinematic viscosity of the measurement fluid changes. . Therefore, by correcting using the difference between the measurement values, the flow rate of the measurement fluid can be accurately obtained even when the temperature or concentration of the measurement fluid changes.

The invention described in the means 2 further includes a kinematic viscosity calculating step of calculating a kinematic viscosity of the measurement fluid based on a difference between measured values by the plurality of ultrasonic transceivers in the means 1 , and in the correcting step, The gist is to correct the flow rate by the kinematic viscosity.

The ratio of each flow rate before correction measured by the plurality of ultrasonic transceivers varies depending on the kinematic viscosity of the measurement fluid. Therefore, as in the invention described in the means 2 , in the kinematic viscosity calculation step, the kinematic viscosity of the measurement fluid is calculated based on the difference between the measurement values obtained by the plurality of ultrasonic transceivers. In the correction step, the flow rate is corrected by the kinematic viscosity. In this way, even when the temperature or concentration of the measurement fluid changes, the flow rate of the measurement fluid can be accurately obtained.

The gist of the invention described in the means 3 is that, in the means 1 or 2 , the plurality of measurement parts provided with the plurality of ultrasonic transmitters / receivers are positioned on a flow path connected in series.

Therefore, according to the invention described in the means 3 , since the plurality of measurement sites provided with the plurality of ultrasonic transceivers are located on the channels connected in series, the actual flow rates flowing through the respective channels are equal. . Therefore, an accurate flow rate can be obtained by correcting the measurement value measured by each ultrasonic transceiver using the relationship between the flow rates.

The gist of the invention described in the means 4 is that, in the means 1 or 2 , the plurality of measurement sites provided with the plurality of ultrasonic transceivers are located on the flow paths connected in parallel.

Therefore, according to the invention described in the means 4 , since the plurality of measurement parts provided with the plurality of ultrasonic transceivers are located on the flow paths connected in parallel, the actual flow velocities flowing through the respective flow paths are equal. . Therefore, an accurate flow rate can be obtained by correcting the measurement value measured by each ultrasonic transceiver using the relationship between the flow rates.

The invention described in the means 5 includes ultrasonic transmitters / receivers provided on the upstream side and the downstream side of the pipe through which the measurement fluid flows, and transmits / receives ultrasonic waves using the ultrasonic transmitter / receiver. from the propagation time and the downstream side of the ultrasonic wave propagating on the basis of the time difference between the propagation time of the ultrasonic wave propagating on the upstream side, an ultrasonic flow meter for determining the flow rate of the measurement fluid in the flow path in the pipe The flow rate or flow rate of the measurement fluid is measured by transmitting and receiving ultrasonic waves using a plurality of ultrasonic transmitters / receivers provided at measurement sites with different cross-sectional areas or measurement surfaces with different inner surface roughness in the pipe. And an ultrasonic flowmeter comprising a calculation means for correcting the flow rate of the measurement fluid based on a ratio or difference between the measurement values. To do.

Therefore, according to the invention described in the means 5 , in the piping through which the measurement fluid flows, a plurality of ultrasonic transmitters / receivers are provided at measurement sites having different flow characteristics of the measurement fluid. Then, the calculation means calculates the ultrasonic propagation time difference using the ultrasonic transmitter / receiver, and measures the flow velocity or flow rate of the measurement fluid according to the propagation time difference. Thereafter, the flow rate of the measurement fluid is corrected by the calculation means based on the difference between the measurement values obtained by the respective sound wave transceivers. In this way, even when the type or concentration of the measurement fluid changes, flow rate correction can be performed accurately.

As described above in detail, according to the first to fifth aspects of the invention, the flow rate can be accurately corrected even when the type and concentration of the measurement fluid change.

[First Embodiment]

  DESCRIPTION OF EMBODIMENTS A first embodiment embodying the present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic configuration diagram showing an ultrasonic flow meter 1 of the present embodiment. The ultrasonic flowmeter 1 is a measuring instrument that measures the flow rate of the measurement fluid W1 (specifically, for example, a chemical solution for semiconductor cleaning) by an ultrasonic propagation time difference method, and is used to supply the measurement fluid W1. It is provided in the middle of the supply piping.

  The ultrasonic flowmeter 1 includes a pipe 4 having two straight pipe portions 2 and 3, first ultrasonic transceivers 5 a and 5 b provided on the upstream side and the downstream side of the first straight pipe portion 2, Second ultrasonic transmitters / receivers 6a, 6b provided on the upstream and downstream sides of the straight pipe section 3 of the second control unit 7 and a control device 7 (calculation means) connected to the ultrasonic transmitters / receivers 5a, 5b, 6a, 6b. With.

  In the pipe 4, the first straight pipe portion 2 and the second straight pipe portion 3 have different pipe diameters, and the cross-sectional areas of the flow paths 10 and 11 formed in the straight pipe portions 2 and 3 are different. . Specifically, the flow path 10 in the first straight pipe portion 2 is formed to be larger than the cross-sectional area of the flow path 11 of the second straight pipe portion 3. The first straight pipe portion 2 and the second straight pipe portion 3 are connected to each other through a connecting portion 12 that has a parallel flow path direction and perpendicularly intersects with the straight pipe portions 2 and 3. That is, in the pipe 4 of the ultrasonic flowmeter 1, the flow path 10 of the first straight pipe portion 2 and the flow path 11 of the second straight pipe portion 3 are connected in series. Then, the measurement fluid W1 flows in the order from the flow path 10 of the first straight pipe portion 2 having a large flow path cross-sectional area to the flow path 11 of the second straight pipe portion 3 having a small flow cross-section area. Yes.

  The first ultrasonic transmitters / receivers 5a and 5b are respectively provided at the upstream and downstream ends of the first straight pipe part 2, and the sensor surface for transmitting / receiving ultrasonic waves is the first straight pipe. It arrange | positions through the flow path 10 in the part 2 so that it may oppose. These first ultrasonic transmitters / receivers 5 a and 5 b transmit ultrasonic waves to each other and receive ultrasonic waves propagated through the measurement fluid W <b> 1 in the flow path 10. The second ultrasonic transmitters / receivers 6a and 6b are provided at the upstream and downstream ends of the second straight pipe portion 3, respectively, and the sensor surface for transmitting / receiving ultrasonic waves is the second. It arrange | positions so that it may oppose through the flow path 11 in the straight pipe part 3. FIG. These second ultrasonic transmitters / receivers 6a and 6b transmit ultrasonic waves to each other and receive ultrasonic waves propagated through the measurement fluid W1 in the flow path 11.

  The control device 7 includes a CPU 20, signal processing circuits 21, 22, a memory 23, a display device 24, and the like. The signal processing circuits 21 and 22 are circuits that output drive signals for driving the ultrasonic transceivers 5a, 5b, 6a, and 6b, and detect ultrasonic propagation time. The CPU 20 executes a control program using the memory 23 and controls the entire apparatus in an integrated manner. The control program includes a program for calculating the flow rate of the measurement fluid W1, a program for displaying the measurement value of the flow rate on the display device 24, and the like. The program executed by the CPU 20 may be a program stored in a storage medium such as a memory card or a program downloaded via a communication medium, and is read into the memory 23 and used at the time of execution.

  In the ultrasonic flowmeter 1 according to the present embodiment, each of the superfluous components is measured at two measurement sites (the first straight pipe part 2 and the second straight pipe part 3 in the second straight pipe part 3) having different flow path cross-sectional areas. Ultrasonic waves are transmitted and received using the sound wave transmitters / receivers 5a, 5b, 6a and 6b, and the flow rates are simultaneously measured based on the propagation time difference of the ultrasonic waves.

Here, the flow rate measured by the first straight pipe portion 2 and the flow rate measured by the second straight pipe portion 3 are the actual flow rate in a state where a calibration fluid having a predetermined kinematic viscosity is flowed. Calibration is performed in advance so that there is no deviation. In this case, when the dynamic viscosity of the measurement fluid W1 is the same as that of the calibration fluid, the flow rate measured by the first straight pipe portion 2 and the flow rate measured by the second straight pipe portion 3 are the same. Will be. However, when the kinematic viscosity of the measurement fluid W1 is different from that of the calibration fluid, there is a measurement difference between the flow rate measured by the first straight pipe portion 2 and the flow rate measured by the second straight pipe portion 3. This is because the Reynolds number Re defined by the following equation (1) differs depending on the inner diameter of the flow path.

  Here, V is the flow velocity, d is the inner diameter of the flow path, and v is the kinematic viscosity.

Further, the flow rate Q is represented by the following equation (2).

Here, π is the circumference ratio. When the above equation (1) is changed using the above equation (2), the Reynolds number Re is expressed as the following equation (3).

  Accordingly, when the same flow rate is measured on the channels arranged in series, the Reynolds number Re is inversely proportional to the inner diameter d of the channel. This Reynolds number Re is an index representing the flow state, and when measured at measurement sites (the first straight tube portion 2 and the second straight tube portion 3) having different inner diameters d of the flow paths, Measurement differences occur depending on the flow conditions. And the ratio of the flow rate measured by each straight pipe part 2 and 3 will change depending on the kinematic viscosity v of the fluid W1 for measurement.

  In the ultrasonic flowmeter 1 of the present embodiment, the relationship between the measurement differences of the flow rates measured by the straight pipe portions 2 and 3 is examined in advance depending on the flow rate and kinematic viscosity of the fluid flowing in the pipe 4. The correction formulas and correction table data created in accordance with the relationship are stored in the memory 23. Then, the kinematic viscosity of the measurement fluid W1 is obtained using the flow rate measured by the straight pipe portions 2 and 3 and the data in the memory 23, and the flow rate is corrected according to the kinematic viscosity.

  Next, an example of processing performed by the ultrasonic flowmeter 1 of the present embodiment will be described with reference to the block diagram of FIG. 2 is realized by using an arithmetic processing function of the CPU 20.

  More specifically, first, ultrasonic So is transmitted / received by the first ultrasonic transmitters / receivers 5a, 5b arranged in the first straight pipe part 2, and arranged in the second straight pipe part 3. The ultrasonic wave So is transmitted and received by the second ultrasonic wave transmitters 6a and 6b. At this time, the first signal processing circuit 21 propagates the ultrasonic wave So that propagates from the upstream side to the downstream side of the first straight pipe portion 2 and propagates from the downstream side to the upstream side of the first straight pipe portion 2. The propagation time of the ultrasonic wave So is detected, and the propagation time difference between the ultrasonic waves So is obtained. Further, the propagation time of the ultrasonic wave So that propagates from the upstream side to the downstream side of the second straight pipe portion 3 and the propagation time from the downstream side to the upstream side of the second straight pipe portion 3 by the second signal processing circuit 22. The propagation time of the ultrasonic wave So is detected, and the propagation time difference between the ultrasonic waves So is obtained.

  The first flow rate calculation means 20a acquires the propagation time difference of the ultrasonic wave So in the first straight pipe section 2 from the first signal processing circuit 21, and obtains the flow velocity of the measurement fluid W1 based on the propagation time difference. And the flow volume of the measurement fluid W1 is calculated | required based on the flow velocity of the measurement fluid W1, and the flow-path cross-sectional area in the 1st straight pipe part 2 (measurement step). The flow rate obtained by the first flow rate calculation means 20a is a pre-correction flow rate including a measurement error according to the kinematic viscosity of the measurement fluid W1.

  The second flow rate calculation means 20b obtains the propagation time difference of the ultrasonic wave So in the second straight pipe section 3 from the second signal processing circuit 22, and obtains the flow velocity of the measurement fluid W1 based on the propagation time difference. And the flow volume of the measurement fluid W1 is calculated | required based on the flow velocity of the measurement fluid W1, and the flow-path cross-sectional area in the 2nd straight pipe part 3 (measurement step). The flow rate obtained by the second flow rate calculation means 20b is a pre-correction flow rate including a measurement error corresponding to the kinematic viscosity of the measurement fluid W1.

  The flow rate ratio calculating means 20c is a pre-correction flow rate in the first straight pipe section 2 obtained by the first flow rate calculation means 20a and a pre-correction flow quantity in the second straight pipe portion 3 obtained by the second flow rate calculation means 20b. Based on the above, the flow rate ratio of these uncorrected flow rates is obtained.

  The kinematic viscosity calculating unit 20d performs an operation such as an interpolation operation or a linear approximation based on the flow rate ratio obtained by the flow rate ratio calculating unit 20c and the kinematic viscosity calculation table data 23a stored in the memory 23. Then, kinematic viscosity corresponding to the flow ratio is obtained (kinematic viscosity calculating step).

  The flow rate correction unit 20e corrects the pre-correction flow rate obtained by the second flow rate calculation unit 20b based on the kinematic viscosity obtained by the kinematic viscosity calculation unit 20d (correction step). Here, the flow rate correction means 20e reads the correction formula data 23b for each kinematic viscosity from the memory 23, and calculates the correction formula data and the pre-correction flow rate obtained by the second flow rate calculation means 20b. In this calculation, a correction rate corresponding to the kinematic viscosity and the flow rate before correction is obtained, and the flow rate after correction is obtained by correcting the flow rate before correction based on the correction rate. Thereafter, the flow rate output means 20f transfers the corrected flow rate data to the display device 24 and causes the display device 24 to display the corrected flow rate.

  Therefore, according to the present embodiment, the following effects can be obtained.

  (1) In the ultrasonic flow meter 1 of the present embodiment, when the kinematic viscosity changes with the temperature change or concentration change of the measurement fluid W1, the first straight pipe part 2 and the second straight pipe part 3 are used. The kinematic viscosity of the measurement fluid W1 can be obtained in real time based on the flow rate ratio of the flow rate before correction measured in step (1). Then, by correcting the flow rate based on the kinematic viscosity, the flow rate of the measurement fluid W1 can be accurately measured without using another sensor such as a thermometer or a viscometer.

  (2) In the ultrasonic flowmeter 1 of the present embodiment, since there is no complicated structure such as a protrusion in the pipe 4 and pressure loss in the pipe 4 can be suppressed, the flow rate of the measurement fluid W1 can be further increased. It can be measured accurately.

(3) In the ultrasonic flowmeter 1 of the present embodiment, the flow rate calculation process and the flow rate correction process in each straight pipe section 2 and 3 are performed by one CPU 20, so that each process is performed separately. Compared with the case of using this CPU, the configuration can be simplified. Moreover, since the time required for data exchange between CPUs can be reduced, flow rate correction can be performed more quickly.
[Second Embodiment]

  Next, a second embodiment of the present invention will be described with reference to FIG. The ultrasonic flowmeter 1A of the present embodiment differs from the first embodiment in the configuration of the pipe 30 and the arrangement of the ultrasonic transmitters / receivers 5a, 5b, 6a, and 6b. The configuration is the same as that of the first embodiment.

  As shown in FIG. 3, the pipe 30 has a large diameter part 31 having a large pipe diameter and a small diameter part 32 having a smaller pipe diameter than the large diameter part 31, and the large diameter part 31, the small diameter part 32, and the like. Is provided on the coaxial line. In the pipe 30, the measurement fluid W <b> 1 flows in the order from the large diameter portion 31 having a large cross-sectional area of the flow path 33 to the small diameter section 32 having a small cross-sectional area of the flow path 34.

  Further, the first ultrasonic transceivers 5 a and 5 b are provided on the large diameter portion 31 side of the pipe 30, and the second ultrasonic transceivers 6 a and 6 b are provided on the small diameter portion 32 side of the pipe 30. In these ultrasonic transmitters / receivers 5a, 5b, 6a, 6b, one ultrasonic transmitter / receiver 5a, 6a is mounted on the upstream side of the other ultrasonic transmitter / receiver 5b, 6b, and the flow direction of the measuring fluid W1 The ultrasonic wave So propagates at a predetermined angle (for example, an angle of 45 °).

  In this ultrasonic flowmeter 1A, each of the ultrasonic transmitters / receivers 5a, 5b, 6a, and 6b is connected to two measurement parts (the large diameter part 31 and the small diameter part 32 in the small diameter part 32) having different flow path cross sections. The ultrasonic wave So is transmitted and received, and the flow rate is measured based on the propagation time difference of the ultrasonic wave So. As in the first embodiment, the kinematic viscosity of the measurement fluid W1 is obtained based on the measured flow rate ratio of the pre-correction flow rate, and the flow rate of the measurement fluid W1 is calculated based on the kinematic viscosity. to correct.

Also in the ultrasonic flowmeter 1A of the present embodiment, as in the first embodiment, the measurement fluid is based on the flow rate ratio of the flow rate before correction measured at two measurement sites having different channel cross-sectional areas. The kinematic viscosity of W1 can be obtained in real time. Then, by correcting the flow rate based on the kinematic viscosity, the flow rate of the measurement fluid W1 can be accurately measured without using another sensor such as a thermometer or a viscometer.
[Third Embodiment]

  Next, a third embodiment of the present invention will be described with reference to FIG. The ultrasonic flowmeter 1B of the present embodiment is different from the first embodiment in the configuration of the pipe 40, and the other configurations are the same as those in the first embodiment.

  As shown in FIG. 4, the pipe 40 includes a first straight pipe portion 41 having a large pipe diameter and a second straight pipe portion 42 having a small pipe diameter, and the straight pipe portions 41 and 42 are connected portions. It is formed in a crank shape by being connected through 43. Also in the pipe 40, the measurement fluid W1 flows in the order from the first straight pipe portion 41 having a large cross-sectional area of the flow path 44 to the second straight pipe section 42 having a small cross-sectional area of the flow path 45. Yes.

  The first ultrasonic transceivers 5a and 5b are arranged at the upstream and downstream ends of the first straight pipe portion 41 so as to face each other through the flow path 44 in the first straight pipe portion 41. ing. Further, the second ultrasonic transmitters / receivers 6a and 6b are opposed to each other through the flow path 45 in the second straight pipe portion 42 at the upstream and downstream ends of the second straight pipe portion 42. Has been placed.

  In the ultrasonic flowmeter 1B, similarly to the first embodiment, the two measurement sites (the first straight pipe portion 41 and the second straight pipe portion 42 in the second straight pipe portion 42) having different flow path cross-sectional areas are used. , 45), ultrasonic waves are transmitted and received using the respective ultrasonic transmitters / receivers 5a, 5b, 6a and 6b, and the flow rates are measured based on the propagation time difference of the ultrasonic waves. Then, the kinematic viscosity of the measurement fluid W1 is obtained based on the measured flow rate ratio of the pre-correction flow rate, and the flow rate of the measurement fluid W1 is corrected based on the kinematic viscosity.

Also in the ultrasonic flowmeter 1B of the present embodiment, the kinematic viscosity of the measurement fluid W1 can be obtained in real time based on the flow rate ratio of the flow rate before correction measured at two measurement sites having different channel cross-sectional areas. it can. Then, by correcting the flow rate based on the kinematic viscosity, the flow rate of the measurement fluid W1 can be accurately measured without using another sensor such as a thermometer or a viscometer.
[Fourth Embodiment]

  Next, a fourth embodiment embodying the present invention will be described with reference to FIG. The ultrasonic flowmeter 1C of the present embodiment is different from the first embodiment in the configuration of the pipe 50, and the other configurations are the same as those in the first embodiment.

  As shown in FIG. 5, a first channel 51 and a second channel 52 having different channel cross-sectional areas are provided in parallel in the pipe 50 of the present embodiment. The first ultrasonic transceivers 5 a and 5 b are provided so as to face each other via the first flow path 51, and the second ultrasonic transceivers 6 a and 6 b are disposed via the second flow path 52. It is provided so as to face each other.

  In this ultrasonic flowmeter 1C, ultrasonic transducers 5a, 5b, 6a, and 6b are used at two measurement sites (first flow channel 51 and second flow channel 52) having different flow channel cross-sectional areas. Ultrasonic waves are transmitted and received, and the flow velocity is measured based on the propagation time difference of the ultrasonic waves. Here, when the flow paths 51 and 52 are connected in parallel, the flow velocities of the measurement fluid W1 measured using the ultrasonic transceivers 5a, 5b, 6a, and 6b are substantially equal. Thus, when the same flow velocity is measured in the flow paths 51 and 52 connected in parallel, the Reynolds number Re is proportional to the inner diameter d of the flow path due to the relationship of the above equation (1). A measurement difference will occur between each flow velocity.

  Therefore, in the ultrasonic flowmeter 1C according to the present embodiment, the relationship between the measurement differences of the flow velocity is examined in advance depending on the flow velocity and kinematic viscosity measured by each of the ultrasonic transceivers 5a, 5b, 6a, 6b. The correction formulas and correction table data created in accordance with the relationship are stored in the memory 23. Then, the kinematic viscosity of the measurement fluid W1 is obtained using the measured flow velocity and data in the memory 23, and the flow rate is corrected according to the kinematic viscosity.

In the ultrasonic flowmeter 1C of the present embodiment, the kinematic viscosity of the measurement fluid W1 can be obtained in real time based on the difference in flow velocity measured in each of the flow paths 51 and 52. Then, by correcting the flow rate based on the kinematic viscosity, the flow rate of the measurement fluid W1 can be accurately measured without using another sensor such as a thermometer or a viscometer.
[Fifth Embodiment]

  Next, a fifth embodiment of the present invention will be described with reference to FIG. The ultrasonic flowmeter 1D of the present embodiment differs from the first embodiment in the configuration of the pipe 60, and the other configurations are the same as those in the first embodiment.

  As shown in FIG. 6, the pipe 60 of the present embodiment has a first straight pipe portion 61 and a second straight pipe portion 62. The 1st straight pipe part 61 and the 2nd straight pipe part 62 are formed so that a pipe diameter and a flow-path cross-sectional area may become equal. Further, the first straight pipe portion 61 and the second straight pipe portion 62 are formed using different resin materials, and the flow paths 63 and 64 provided in the straight pipe portions 61 and 62 have inner surfaces. The surface roughness is different. Then, the first ultrasonic transceivers 5a and 5b are opposed to each other through the flow path 63 in the first straight pipe portion 61 at the upstream and downstream ends of the first straight pipe portion 61. Has been placed. In addition, at the upstream and downstream ends of the second straight pipe portion 62, the second ultrasonic transmitters / receivers 6a and 6b are opposed to each other through the flow path 64 in the second straight pipe portion 62. Has been placed.

  In this ultrasonic flowmeter 1D, each ultrasonic transmitter / receiver is installed in a measurement portion (the flow paths 63 and 64 of the first straight pipe portion 61 and the second straight pipe portion 62) having different inner surface roughness in the pipe 60. Ultrasonic waves are transmitted and received using 5a, 5b, 6a, and 6b, and the flow rate is measured based on the propagation time difference of the ultrasonic waves. When the surface roughness of the inner wall surface of each flow path 63, 64 is different as in the present embodiment, the flow characteristics of the measurement fluid W1 in each flow path 63, 64 are different. A measurement difference in flow rate will occur depending on the viscosity. Accordingly, as in the first embodiment, the kinematic viscosity of the measurement fluid W1 is obtained based on the measured flow rate ratio of the pre-correction flow rate, and the flow rate of the measurement fluid W1 is further calculated based on the kinematic viscosity. to correct.

  Also in the ultrasonic flowmeter 1D of the present embodiment, the kinematic viscosity of the measurement fluid W1 is determined based on the flow rate ratio of the pre-correction flow rate measured by the first straight pipe portion 61 and the second straight pipe portion 62. It can be obtained in real time. Then, by correcting the flow rate based on the kinematic viscosity, the flow rate of the measurement fluid W1 can be accurately measured without using another sensor such as a thermometer or a viscometer.

  In addition, you may change embodiment of this invention as follows.

  In the ultrasonic flowmeters 1 and 1A to 1C of the above-described embodiments, flow measurement is performed at measurement sites (channels 10, 11, 33, 34, 44, 45, 51, 52) having different channel cross-sectional areas. However, the flow rate may be measured at a plurality of measurement sites having different cross-sectional shapes. In this case, even if the flow path cross-sectional area is the same, the flow characteristics of the measurement fluid W1 can be varied by changing the cross-sectional shape, so that the flow rate correction is performed in the same manner as in the above embodiment. be able to.

  In the ultrasonic flowmeter 1D of the fifth embodiment, the first straight pipe portion 61 and the second straight pipe portion 62 are formed using different resin materials, so that each straight pipe portion 61, Although the surface roughness of the inner walls of the flow paths 63 and 64 formed in 62 is different, the present invention is not limited to this. For example, the first straight pipe portion 61 and the second straight pipe portion 62 are formed of the same material, and the inner wall surface of one flow path of each of the straight pipe portions 61 and 62 is covered with a predetermined coating material. The surface roughness of the inner walls of the flow paths 63 and 64 may be varied. Further, for example, the first straight pipe portion 61 and the second straight pipe portion 62 are formed of the same material, and the inner wall surface of one flow path of each of the straight pipe portions 61 and 62 is made uneven so that each You may vary the surface roughness of the inner wall of the flow paths 63 and 64.

  In each of the above embodiments, the flow rate is detected at two measurement sites with different flow characteristics of the measurement fluid W1, but the measurement results are obtained by measuring the flow rate at three or more measurement sites. The flow rate correction may be performed based on the above. In this way, when the number of measurement sites is increased to three or more, the kinematic viscosity corresponding to the flow rate difference of the flow rate before correction can be accurately obtained by the approximate curve.

  In the ultrasonic flowmeters 1 and 1A to 1D according to each of the above embodiments, when the flow rate obtained by the flow rate calculation units 20a and 20b is within a predetermined range, the flow rate ratio calculation unit 20c, the kinematic viscosity calculation unit 20d, In addition, each calculation process by the flow rate correction unit 20e may be executed. Here, when the difference between the flow rates measured at a plurality of measurement sites is small, the relationship with the kinematic viscosity is weak, so the flow rate correction accuracy may deteriorate. On the other hand, only when the flow rate calculated by the flow rate calculation units 20a and 20b is within a predetermined range, the calculation processing of the flow rate ratio calculation unit 20c, the kinematic viscosity calculation unit 20d, and the flow rate correction unit 20e is performed. It is possible to improve the reliability of the flow rate correction.

  Further, each calculation process by the flow rate ratio calculating means 20c, the kinematic viscosity calculating means 20d, and the flow rate correcting means 20e is executed based on a correction permission signal input from the outside of the ultrasonic flowmeters 1, 1A to 1D. May be. If it does in this way, in the control system which has ultrasonic flowmeters 1 and 1A-1D, since the timing which performs flow volume correction can be grasped and managed, it becomes a thing practically desirable.

  In each of the above embodiments, the flow rate is corrected using one ultrasonic flow meter 1, 1A to 1D. However, the present invention is not limited to this. The present invention may be embodied in an ultrasonic flow rate correction system including a plurality of ultrasonic flow meters and a correction device. Specifically, for example, the first ultrasonic flowmeter is configured by the first straight pipe portion 2 of the pipe 4 in FIG. 1, the first ultrasonic transmitters / receivers 5a and 5b, and a first arithmetic device (not shown). The second straight pipe portion 3, the second ultrasonic transmitters / receivers 6a and 6b, and the second arithmetic unit (not shown) constitute a second ultrasonic flow meter. Then, the measurement data of each flow rate measured by each ultrasonic flowmeter is taken into the correction device, and the correction device corrects the flow rate of the measurement fluid based on the difference between the measurement data. As described above, even when the ultrasonic flow rate correction system is configured, the movement of the measurement fluid W1 is based on the flow rate ratio of the pre-correction flow rate measured by the first ultrasonic flow meter and the second ultrasonic flow meter. The viscosity can be determined in real time. The correction device corrects the flow rate based on the kinematic viscosity, so that the flow rate of the measuring fluid W1 can be accurately measured without using other sensors such as a thermometer and a viscometer.

  Next, in addition to the technical ideas described in the claims, the technical ideas grasped by the respective embodiments described above are listed below.

  (1) In the above means 2, the plurality of ultrasonic transmitters / receivers are provided at measurement sites having different surface cross-sectional areas in the pipe but having the same surface roughness on the inner surface. Flow meter correction method.

  (2) The ultrasonic flowmeter according to the above means 3, wherein the plurality of ultrasonic transmitters / receivers are provided in measurement sites having different flow path cross-sectional areas while only the surface roughness of the inner surface is different. Correction method.

  (3) In any one of the above means 1 to 6, the correction step is executed when the measurement value measured in the measurement step is within a predetermined range set in advance. Correction method.

  (4) The ultrasonic flowmeter correction method according to any one of the above means 1 to 6, wherein the correction step is executed based on a correction permission signal input from the outside of the ultrasonic flowmeter.

  (5) The above means 7 further comprises storage means for storing table data for calculating the kinematic viscosity of the measurement fluid and correction data for obtaining the correction rate of the flow rate, and the calculation means comprises: The data stored in the storage means is used to determine the kinematic viscosity according to the difference between the measured values, and the correction rate of the flow rate according to the kinematic viscosity and the flow rate of the measurement fluid. The ultrasonic flowmeter, wherein the flow rate of the measurement fluid is corrected by the correction rate.

  (6) The ultrasonic flowmeter according to claim 7, further comprising display means for displaying the flow rate corrected by the computing means.

  (7) The ultrasonic flowmeter according to (7), further comprising output means for outputting the flow rate data corrected by the calculation means to an external device.

  (8) Ultrasonic wave transmission / reception using ultrasonic transmitters / receivers provided on the upstream side and downstream side of the pipe through which the measurement fluid flows, and the propagation time of the ultrasonic wave propagating from the upstream side to the downstream side and the upstream side from the downstream side A system including two or more ultrasonic flowmeters for obtaining a flow rate of the measurement fluid based on a time difference with a propagation time of the ultrasonic wave propagating to the side, wherein the flow characteristic of the measurement fluid in the pipe is A correction device is provided that acquires measurement data of the flow rate from two or more ultrasonic flow meters provided at different measurement sites, and corrects the flow rate of the measurement fluid based on a difference between the measurement data. Ultrasonic flow rate correction system.

The schematic block diagram which shows the ultrasonic flowmeter of 1st Embodiment. The block diagram which shows schematic structure of the ultrasonic flowmeter of 1st Embodiment. The schematic block diagram which shows the ultrasonic flowmeter of 2nd implementation. The schematic block diagram which shows the ultrasonic flowmeter of 3rd implementation. The schematic block diagram which shows the ultrasonic flowmeter of 4th implementation. The schematic block diagram which shows the ultrasonic flowmeter of 5th implementation. The graph which shows the relationship between sound speed and temperature.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,1A-1D ... Ultrasonic flowmeter 4,30,40,50,60 ... Piping 5a, 5b, 6a, 6b ... Ultrasonic transmitter / receiver 7 ... Control apparatus 10,11,33,34,44 as a calculation means , 45, 51, 52, 63, 64 ... flow path So ... ultrasonic wave W1 ... fluid for measurement

Claims (5)

Ultrasonic waves are transmitted and received by using ultrasonic transmitters and receivers installed on the upstream and downstream sides of the pipe through which the measurement fluid flows, and the propagation time of the ultrasonic waves propagating from the upstream side to the downstream side and from the downstream side to the upstream side An ultrasonic flowmeter correction method for obtaining a flow rate of the measurement fluid based on a time difference with an ultrasonic propagation time,
By performing transmission and reception of ultrasonic waves using a plurality of ultrasonic transmitters / receivers provided at measurement sites having different flow path cross-sectional areas in the pipe, or measurement sites having different inner surface roughness in the pipe, A measurement step of measuring the flow velocity or flow rate of the fluid with each of the plurality of ultrasonic transceivers;
And a correction step of correcting a flow rate of the measurement fluid based on a ratio or difference between measurement values obtained by the plurality of ultrasonic transceivers. The method further includes a kinematic viscosity calculating step of calculating a kinematic viscosity of the measurement fluid based on a difference between measured values by the plurality of ultrasonic transceivers, and the correction step corrects the flow rate by the kinematic viscosity. The method of correcting an ultrasonic flowmeter according to claim 1 , wherein the ultrasonic flowmeter is corrected. A plurality of measurement sites of the plurality of ultrasonic transducers are provided, the correction method of the ultrasonic flowmeter according to claim 1 or 2, characterized in that located in the flow path leading to series. A plurality of measurement sites of the plurality of ultrasonic transducers are provided, the correction method of the ultrasonic flowmeter according to claim 1 or 2, characterized in that located in the flow path leading to parallel. Propagation time of ultrasonic waves that are equipped with ultrasonic transmitters / receivers provided on the upstream side and downstream side of the pipe through which the measurement fluid flows, transmit and receive ultrasonic waves using the ultrasonic transmitter / receiver, and propagate from the upstream side to the downstream side And an ultrasonic flowmeter for determining the flow rate of the measurement fluid based on the time difference between the propagation time of the ultrasonic wave propagating from the downstream side to the upstream side,
By performing transmission and reception of ultrasonic waves using a plurality of ultrasonic transmitters / receivers provided at measurement sites having different flow path cross-sectional areas in the pipe, or measurement sites having different inner surface roughness in the pipe, Ultrasonic flow rate characterized by comprising a calculation means for measuring the flow velocity or flow rate of a fluid with each of the plurality of ultrasonic transceivers and correcting the flow rate of the measurement fluid based on the ratio or difference of the measured values. Total.

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