WO2018079269A1

WO2018079269A1 - Fluid measuring device

Info

Publication number: WO2018079269A1
Application number: PCT/JP2017/036900
Authority: WO
Inventors: 木代　雅巳; 泰文森本
Original assignee: 富士電機株式会社
Priority date: 2016-10-25
Filing date: 2017-10-12
Publication date: 2018-05-03

Abstract

The objective of the present invention is to provide a fluid measuring device with which it is possible to measure easily and accurately a physical quantity relating to a fluid with a higher degree of accuracy than in the past, irrespective of whether flow is laminar or turbulent. A fluid measuring device (1) forms a plurality of traverse lines by transmitting and receiving ultrasonic waves, from a plurality of ultrasonic probes installed in a pipeline (100), into and from a fluid (102) inside the pipeline, and obtains a physical quantity relating to the fluid using a control unit (60). The control unit is configured to include: a flow velocity calculating unit (42) which calculates flow velocities of the fluid, measured using the plurality of traverse lines; a flow velocity ratio calculating unit (43) which calculates a flow velocity ratio on the basis of the flow velocities of the fluid; and a physical quantity calculating unit (Reynolds number calculating unit (46), flow volume calculating unit (50), viscosity calculating unit (51)) which calculates the abovementioned physical quantity on the basis of the flow velocity ratio.

Description

Fluid measuring device

The present invention relates to a fluid measuring apparatus that measures a physical quantity such as a flow rate of a fluid in a pipe and a Reynolds number by ultrasonic waves.

Conventionally, a flow rate measuring device using ultrasonic waves is known for measuring the flow rate of a fluid flowing through a pipe (see Patent Document 1). In an ultrasonic flow measurement device, a plurality of ultrasonic transmission / reception units are arranged in a pipe, and ultrasonic transmission / reception is alternately performed, and a flow rate is detected from a difference in propagation time.

JP-A-55-160814

By the way, in the case of flow rate measurement, it is necessary to obtain the flow velocity distribution in the fluid piping. The flow velocity distribution varies depending on the Reynolds number. For this reason, it is necessary to obtain the Reynolds number, but in order to obtain the Reynolds number, the piping dimensions, the flow velocity of the fluid, and the kinematic viscosity of the fluid are necessary. Among these, the flow rate of the fluid can use a measured value based on a signal obtained from the ultrasonic transmission / reception unit, but it is necessary to input representative values in advance for the piping dimensions and kinematic viscosity. In particular, kinematic viscosity varies with fluid temperature. For this reason, the temperature characteristics of kinematic viscosity must be measured in advance and a table or the like must be created and stored. In addition, it is necessary to make complicated corrections such as obtaining the exact kinematic viscosity by measuring the temperature separately, and the flow rate cannot be easily measured. In addition, the flow rate could not be accurately measured due to complicated correction.

Also, when measuring the flow rate of fluid with a conventional flow rate measuring device, since the ultrasonic measurement line is a line, there is a problem that an error occurs with respect to the average flow velocity of the entire pipe cross section.

For example, in Patent Document 1, the Gaussian numerical integration method is applied, and the average flow velocity of the pipe cross section is obtained by weighted addition of the average flow velocity measured at the n-point survey line.

However, the flow velocity distribution includes high-order terms so that it can be approximated by an exponential function known by the 1 / n power law, for example, in a turbulent flow region. For this reason, when the Gaussian numerical integration method is applied to this, an integration error occurs. In particular, when trying to apply widely from a laminar basin with a small Reynolds number to a turbulent region with a large Reynolds number, the flow velocity distribution, which was a parabola in the laminar basin, greatly changes to the shape of an exponential function of 1 / n power in the turbulent region. . For this reason, especially in the turbulent flow region, there is a problem that the error greatly varies depending on the Reynolds number, and the flow rate of the fluid cannot be obtained accurately.

For this reason, conventionally, it has been necessary to limit the accuracy guarantee to the Reynolds number and to use only a turbulent flow region or a laminar flow region. However, if the accuracy guarantee is limited to a turbulent flow region or a laminar flow region, for example, a turbulent flow meter is applied to water having a small kinematic viscosity, and a laminar flow meter is applied to an oil having a large kinematic viscosity, for example. It is necessary to prepare two types of flow meters so that The Reynolds number varies with the flow velocity and kinematic viscosity, so it is laminar when the flow velocity is low, but it becomes turbulent when the flow velocity is high, or it is laminar with a large kinematic viscosity at low temperatures. In the case where becomes smaller and becomes turbulent, there is a problem that accurate measurement cannot be performed from the laminar flow region to the turbulent flow region.

The present invention has been made in view of such problems, and the object of the present invention is to measure the physical quantity of fluid with higher accuracy than conventional methods regardless of laminar flow and turbulent flow. It is to provide a fluid measuring device.

The fluid measuring device of the present invention forms a plurality of measurement lines by transmitting and receiving ultrasonic waves from a plurality of ultrasonic transmission / reception units installed in a pipe to the fluid in the pipe, and the control unit obtains a physical quantity of the fluid. In the fluid measurement device, the control unit calculates a flow rate of the fluid measured along the plurality of survey lines, a flow rate ratio calculation unit that calculates a flow rate ratio based on the flow rate of the fluid, and the flow rate A physical quantity computing unit that computes the physical quantity based on the ratio.

This configuration makes it possible to measure the physical quantity of fluid with high accuracy regardless of laminar or turbulent flow.

According to the fluid measuring device of the present invention, the flow rate ratio of the fluid is obtained, and the physical quantity of the fluid is calculated based on the flow rate ratio. Thereby, the physical quantity of fluid can be measured with high accuracy regardless of laminar flow or turbulent flow.

It is a front view which shows arrangement | positioning to piping of the ultrasonic probe which comprises the fluid measuring device of this Embodiment. FIG. 2 is a block diagram of the fluid measuring device according to the first embodiment (including a pipe cut along the line AA shown in FIG. 1 and viewed from the arrow direction, and a partial cross-sectional view of the ultrasonic probe). It is a graph showing the correlation between the flow rate ratio of fluid and the Reynolds (Re) number. It is a graph showing the correlation between the Reynolds (Re) number and the error ε. FIG. 5 is a block diagram of a fluid measuring device according to a second embodiment (including a pipe cut along line AA shown in FIG. 1 and viewed from the direction of an arrow, and a partial sectional view of an ultrasonic probe). It is a graph showing the correlation between the flow rate ratio and the error ε. FIG. 7 is a graph showing a correlation between a flow rate ratio and an error ε after correcting the error of FIG. 6.

Hereinafter, the fluid measuring apparatus according to the present embodiment will be described in detail. In the following description, the same components are denoted by the same reference symbols in all the drawings, and the description thereof is omitted as appropriate.

FIG. 1 is a front view showing an arrangement of ultrasonic probes constituting the fluid measuring device of the present embodiment on a pipe.

In the embodiment shown in FIG. 1, the pipe 100 has a cylindrical shape, and three sets of ultrasonic probes (ultrasonic wave transmission / reception units) are arranged in the pipe 100. That is, the ultrasonic probe 10a and the ultrasonic probe 10b shown in FIG. 1 are combined, the ultrasonic probe 13a and the ultrasonic probe 13b are combined, and the ultrasonic probe 14a and the ultrasonic probe 14b are combined. It is a pair.

The three measurement lines α, the measurement line β, and the measurement line γ of the ultrasonic waves transmitted and received between each set of ultrasonic probes are parallel to each other. Among these, the measurement line α crosses the pipe 100 through the center of the pipe 100, and the measurement line β and the measurement line γ are in symmetrical positions with the measurement line α in between. R represents the inner radius of the pipe 100, and r represents the distance between the measurement line α and the measurement line β, and the distance between the measurement line α and the measurement line γ. The survey line position r / R can be appropriately determined based on a numerical integration method such as a Gaussian numerical integration method.

The pipe 100 is not limited to a cylindrical shape, and may not be three survey lines if the number of survey lines is plural. Further, the measurement line α may not pass through the center of the pipe 100, and the measurement line β and the measurement line γ are not limited to being symmetrical with respect to the measurement line α. Each of the survey lines α, β, γ is not limited to being parallel, but by making each of the survey lines α, β, γ parallel, the accuracy of numerical integration for obtaining the average flow velocity is improved. Can be improved.

FIG. 2 is a block diagram of the fluid measuring apparatus 1 according to the first embodiment. 2 also includes a partial cross-sectional view of the pipe 100 and the

ultrasonic probes

10a and 10b cut along the line AA shown in FIG. 1 and viewed from the arrow direction.

As shown in FIG. 2, the fluid measuring apparatus 1 according to the present embodiment includes a plurality of

ultrasonic probes

10a, 10b, 13a, 13b, 14a, 14b installed in a pipe 100 (however, in FIG. 2, the ultrasonic probe 10a). 10b only) and a control unit 60 for calculating the physical quantity of the fluid 102.

2,

ultrasonic probes

10a and 10b are arranged on the

outer surfaces

101a and 101b of the pipe 100 as shown in the partial cross-sectional view of FIG. In FIG. 2, the

ultrasonic probes

13a, 13b, 14a, and 14b that are not shown are the same as those described below except for the arrangement of the

ultrasonic probes

10a and 10b.

As shown in FIG. 2, the ultrasonic probe 10 a is arranged on the upstream side with respect to the flow of the fluid 102 in the pipe 100, and the ultrasonic probe 10 b is arranged on the downstream side with respect to the flow of the fluid 102. . The ultrasonic probe 10a is configured to include an ultrasonic transducer 11a and a wedge 12a, and the ultrasonic probe 10b is configured to include an ultrasonic transducer 11b and a wedge 12b. As shown in FIG. 2, the

ultrasonic transducers

11 a and 11 b are disposed obliquely with respect to the flow direction of the fluid 102.

As shown in FIG. 2, each

ultrasonic transducer

11a, 11b is connected to a

switch

33a, 33b, respectively. The

ultrasonic probes

13a and 13b shown in FIG. 1 are electrically connected to the

switches

34a and 34b shown in FIG. 2, and the

ultrasonic probes

14a and 14b shown in FIG. It is electrically connected to 35a, 35b.

Subsequently, the control unit 60 will be described. As shown in FIG. 2, the control unit 60 includes a transmission unit 31, a reception unit 32, a time measurement unit 40, a switch switching unit 41, a flow rate calculation unit 42, a flow rate ratio calculation unit 43, a Reynolds number calculation unit 46, a flow rate ratio − The Reynolds number conversion table 47, the error calculation unit 44, the Reynolds number-error conversion table 48, the flow rate calculation unit 50, and the viscosity calculation unit 51 are configured.

The transmission unit 31 is electrically connected to each

switch

33a, 33b, 34a, 34b, 35a, 35b. The transmission unit 31 transmits an electrical signal to an ultrasonic transducer that is electrically connected to the switch to generate an ultrasonic wave.

The receiving unit 32 is electrically connected to the

switches

33a, 33b, 34a, 34b, 35a, and 35b. The receiving unit 32 receives an electrical signal from an ultrasonic transducer that is electrically connected to the switch.

The time measurement unit 40 is electrically connected to the transmission unit 31 and the reception unit 32. The time measuring unit 40 measures the propagation time from transmission to reception of ultrasonic waves on each of the measurement lines α, β, and γ (see FIG. 1).

The flow velocity calculation unit 42 is electrically connected to the time measurement unit 40. The flow velocity calculation unit 42 calculates the flow velocity of each of the measurement lines α, β, and γ of the fluid 102 based on the propagation time transmitted from the time measurement unit 40. Further, the flow velocity calculation unit 42 calculates the average flow velocity of the entire pipe cross section by weighting and adding to each of the survey lines α, β, γ by, for example, the Gaussian numerical integration method.

The flow rate ratio calculation unit 43 is electrically connected to the flow rate calculation unit 42. The flow rate ratio calculation unit 43 calculates the flow rate ratio based on the flow rates of the respective survey lines α, β, and γ obtained by the flow rate calculation unit 42.

The Reynolds number calculation unit 46 is electrically connected to the flow rate ratio calculation unit 43. The Reynolds number calculator 46 calculates the Reynolds (Re) number based on the flow rate ratio.

The flow rate ratio / Reynolds number conversion table 47 is electrically connected to the Reynolds number calculation unit 46. The flow rate ratio-Reynolds number conversion table 47 is prepared in advance for calculating the Reynolds number and the flow rate. In the flow rate ratio-Reynolds number conversion table 47, the flow rate ratio and the Reynolds number are correlated. The Reynolds number calculation unit 46 calculates the Reynolds number from the flow rate ratio-Reynolds number conversion table 47 based on the flow rate ratio.

The error calculation unit 44 is electrically connected to the Reynolds number calculation unit 46. The error calculation unit 44 obtains an error (integration error) of the average flow velocity obtained by the flow velocity calculation unit 42. In the embodiment shown in FIG. 2, this error is obtained from the relationship between the Reynolds number and the error.

The Reynolds number-error conversion table 48 is electrically connected to the error calculation unit 44. The Reynolds number-error conversion table 48 is prepared in advance for calculating the flow rate. In the Reynolds number-error conversion table 48, the Reynolds number and the error are correlated. Then, the error calculator 44 calculates an error from the Reynolds number-error conversion table 48 based on the Reynolds number acquired from the Reynolds number calculator 46.

The flow rate calculation unit 50 is electrically connected to the flow rate calculation unit 42 and the error calculation unit 44. The flow rate calculation unit 50 calculates the flow rate based on the average flow velocity and the error.

Next, the flow of various calculation processes from time measurement to flow rate calculation will be described using the block diagram shown in FIG.

As shown in FIG. 2, the transmission unit 31 and the switch 33a are electrically connected by a signal from the switch switching unit 41. Thereby, the ultrasonic transducer | vibrator 11a and the transmission part 31 are electrically connected via the switch 33a. Further, the receiving unit 32 and the switch 33b are electrically connected by a signal from the switch switching unit 41. Thereby, the ultrasonic transducer | vibrator 11b and the receiving part 32 are electrically connected via the switch 33b.

At this time, the transmission unit 31 transmits an electrical signal to the ultrasonic transducer 11a to generate an ultrasonic wave. The generated ultrasonic wave passes through the wedge 12 a and enters the fluid 102 in the pipe 100. The ultrasonic wave incident on the fluid 102 in the pipe 100 propagates in the fluid 102 at an incident angle θ from the upstream side to the downstream side of the fluid 102. The ultrasonic wave propagated to the ultrasonic probe 10b is converted into an electric signal by the ultrasonic transducer 11b. This electrical signal is received by the receiving unit 32 via the switch 33b.

At this time, the time measuring unit 40 measures the propagation time from transmission to reception of ultrasonic waves. The propagation time along the flow of the fluid 102 is Tf.

Subsequently, the switch 33a and the switch 33b are respectively switched by a signal from the switch switching unit 41 (shown by dotted lines in the switch 33a and the switch 33b. The same applies to FIG. 5 described later). Thereby, the ultrasonic transducer | vibrator 11a and the receiving part 32 are electrically connected via the switch 33a, and the ultrasonic transducer | vibrator 11b and the transmission part 31 are connected via the switch 33b. At this time, the ultrasonic waves propagate from the downstream ultrasonic transducer 11b toward the upstream ultrasonic transducer 11a. Then, the ultrasonic wave propagated to the ultrasonic probe 10a is converted into an electric signal by the ultrasonic transducer 11a. This electric signal is received by the receiving unit 32 via the switch 33a.

At this time, the time measuring unit 40 measures the propagation time of the ultrasonic wave against the flow of the fluid 102 as Tr.

Thereby, the propagation times Tf and Tr of the survey line α shown in FIG. 1 can be acquired. Here, the propagation time of the ultrasonic waves is affected by the flow of the fluid 102, so that Tf is short and Tr is long. Since the difference between Tf and Tr changes according to the flow velocity of the fluid 102, the average flow velocity on the measurement line of the fluid 102 can be measured by measuring this difference.

As shown in FIG. 1, in this embodiment, there are three survey lines α, β, and γ. Therefore, each

switch

34a, 34b, 35a, 35b is switched between transmission and reception by a signal from the switch switching unit 41, and the propagation times Tf, Tr of the survey lines β, γ are obtained in the same manner as described above. To do.

The propagation times Tf and Tr of the measurement lines α, β, and γ are transmitted from the time measurement unit 40 to the flow velocity calculation unit 42. Then, the flow velocity calculation unit 42 calculates the flow velocity V of the fluid 102 from the propagation times Tf and Tr. The propagation times Tf and Tr are expressed by the following mathematical formulas (1) and (2).

Tf = L / (C + V cos θ) (1)
Tr = L / (C−Vcos θ) (2)
Here, C is the speed of sound of the fluid 102, θ is the incident angle, and L is the propagation path length through which the ultrasonic wave propagates in the fluid 102.

From each formula (1) and (2), the flow velocity V can be expressed by the following formula (3).
V = L / 2 cos θ × ((1 / Tf) − (1 / Tr)) (3)

Calculating the flow velocity V of each survey line α, β, γ, respectively, and let the obtained flow velocity values be v1, v2, v3, respectively.

Further, the flow velocity calculation unit 42 obtains the average flow velocity of the entire pipe cross section by weighting each of the survey lines α, β, γ, for example, based on the Gaussian numerical integration method. The Gaussian numerical integration method is one of the numerical integration methods in which the integration of the (2n-1) degree polynomial is obtained by weighted addition of n points. That is, the average flow velocity of the entire pipe cross section can be obtained by weighted addition of the average flow velocity measured at the n-point survey line. This average flow velocity can be determined regardless of the Reynolds number.

The average flow velocity can be obtained as an integral value of w1 · v1 + w2 · v2 + w3 · v3. Here, w1, w2, and w3 are weighted addition values for the flow velocity values v1, v2, and v3, respectively, and the weighted addition values w1, w2, and w3 are specified values. For example, in this embodiment, there are 3 survey lines (n = 3). When there are three survey lines, the survey line α passing through the center of the pipe 100 is the survey line position r / R = 0, and the survey lines β and γ are the survey line position r / R = 0.7746 (rounded to the fifth decimal place). It is adjusted to become. Then, according to the Gaussian numerical integration method, the weighted addition value of the survey line α (that is, the flow velocity value v1) is 0.4444444 (rounded to the eighth decimal place). Further, the weighted addition value of the measurement lines β and γ (that is, the flow velocity values v2 and v3) is 0.2777778 (rounded to the eighth decimal place). Such a relationship between the survey line position (minute point) and the weighted addition value is generally known. The relationship between the survey line position (minute point) and the weighted addition value can be determined by a numerical integration method to be applied. In this embodiment, the Gaussian numerical integration method is representatively used. However, as the numerical integration method, a Chebyshev integration method or a Lobat integration method can be used in addition to the Gaussian numerical integration method.

In the numerical integration method, as in the normal integration method, when obtaining the area, the area is not divided into strips and all the strip areas are added, but weighted addition is performed at a specific location. When the numerical integration method is applied to the fluid measurement device of the present embodiment, the average flow velocity of the entire pipe cross section can be obtained by weighted addition of the flow velocity of the survey line at a specific location. However, in the numerical integration method, especially in the turbulent region of the fluid 102, the integration error fluctuation becomes large. Thus, in the present embodiment, the relationship between the flow rate ratio or the Reynolds number correlated with the flow rate ratio and the error (integration error) is found, and the error can be estimated from the flow rate ratio and the Reynolds number. A specific method for obtaining the error will be described later.

Next, the flow velocity values v 1, v 2, v 3 of the respective measurement lines α, β, γ obtained by the flow velocity calculation unit 42 are sent to the flow velocity ratio calculation unit 43. The flow rate ratio calculation unit 43 calculates the flow rate ratio Vr from the flow rate values v1, v2, and v3.

In the embodiment shown in FIG. 1, the measurement line α passes through the center of the pipe 100, and the measurement line β and the measurement line γ are located symmetrically with respect to the measurement line α. In such a configuration, for example, the flow rate ratio can be calculated by the following mathematical formula (4).
Vr = 2 × v2 / (v1 + v3) (4)

Subsequently, the Reynolds number calculator 46 calculates the Reynolds (Re) number based on the flow rate ratio obtained from the flow rate ratio calculator 43. In the present embodiment, the relationship between the flow rate ratio Vr and the Reynolds number is derived in advance by simulation or the like. The simulation result is stored in the control unit 60 of the fluid measuring apparatus 1 as a flow rate ratio-Reynolds number conversion table 47. The Reynolds (Re) number can be calculated from the flow rate ratio-Reynolds number conversion table 47 using the flow rate ratio Vr obtained from the flow rate ratio calculation unit 43.

FIG. 3 is a graph showing the correlation between the fluid flow rate ratio and the Reynolds (Re) number. The correlation shown in FIG. 3 is numerically analyzed using a 1 / n power law (specifically, a 1/7 power law) as an approximate expression of the turbulent flow velocity distribution and a parabola as a laminar flow velocity distribution. Can be obtained. According to FIG. 3, the Reynolds (Re) number decreases substantially monotonically with respect to the flow rate ratio Vr. Further, in the turbulent flow region shown by the solid line in FIG. 3, there is only one Reynolds number corresponding to the flow velocity ratio Vr, and the Reynolds number can be uniquely obtained. 4, 6, and 7, similarly, the turbulent flow region is indicated by a solid line. The flow rate ratio Vr in the laminar flow is a constant value. In the laminar basin, the Reynolds number cannot be specified from the flow rate ratio, but the error occurring in the laminar basin is a constant value as will be described later, and therefore the error can be corrected. Moreover, the dotted line shown in FIG. 3 has shown the transition area | region between a laminar flow and a turbulent flow. Similarly, in FIGS. 4, 6, and 7, the laminar flow has a constant value, and the transition region is indicated by a dotted line.

The flow rate ratio-Reynolds number conversion table 47 shown in FIG. 2 constitutes a conversion table based on the graph shown in FIG. Therefore, the Reynolds (Re) number can be calculated from the flow rate ratio-Reynolds number conversion table 47 using the flow rate ratio Vr obtained from the flow rate ratio calculation unit 43.

Subsequently, the error calculation unit 44 shown in FIG. 2 calculates the error ε based on the Reynolds number acquired by the Reynolds number calculation unit 46. Here, the error ε corresponds to an integration error with respect to the average flow velocity obtained by a numerical integration method such as a Gaussian numerical integration method.

As shown in FIG. 2, the correlation between the Reynolds number and the error ε is prepared in advance in the Reynolds number-error conversion table 48. The relationship between the Reynolds number and the error ε is derived by simulation in advance. The simulation result is stored as a Reynolds number-error conversion table 48 in the control unit 60 of the fluid measuring apparatus 1. The error ε can be calculated from the Reynolds number-error conversion table 48 using the Reynolds number obtained from the Reynolds number calculation unit 46.

FIG. 4 is a graph showing the correlation between the Reynolds (Re) number and the error ε. FIG. 4 shows the correlation with the error of the flow rate measurement value obtained by weighted addition using the numerical integration method. As shown in FIG. 4, it can be seen that in the turbulent flow region, the variation of the error ε is large due to the Reynolds number. In the laminar basin, the error ε is a constant value. In FIG. 3, it has been described that the Reynolds number cannot be specified in the laminar basin. However, since it is understood that the laminar basin is present, the error ε can be obtained.

The Reynolds number-error conversion table 48 shown in FIG. 2 constitutes a conversion table based on the graph shown in FIG. Therefore, the error ε can be calculated from the Reynolds number-error conversion table 48 using the Reynolds number obtained from the Reynolds number calculation unit 46.

Subsequently, the flow rate calculation unit 50 shown in FIG. 2 calculates the flow rate Q by the following formula (5).

Q = A × (w1 · v1 + w2 · v2 + w3 · v3) × (100 / (100 + ε)) (5)
Here, A is a cross-sectional area of the pipe 100 and is represented by the following formula (6) using the inner diameter D (inner radius R × 2) of the pipe 100.
A = (D / 2) ² × π (6)

The parts of w1, v1 + w2, v2 + w3, and v3 shown in Equation (5) indicate the average flow velocity, and the error ε corresponds to the integration error of the average flow velocity. Therefore, the flow rate Q can be calculated by adding the error ε by the calculation of the equation (5), whereby the flow rate Q can be calculated with high accuracy.

2 calculates the kinematic viscosity ν of the fluid 102 using Equation (8) obtained by modifying the following Equation (7) for obtaining the Reynolds number.
Re = D · v / ν (7)
ν = D · v / Re (8)

In addition, the flow velocity value v1 of the survey line α passing through the center of the pipe 100 shown in FIG. 1 can be used as the flow velocity v shown in the mathematical formulas (7) and (8).

FIG. 5 is a block diagram of the fluid measuring apparatus 1 according to the second embodiment. 5 includes a partial cross-sectional view of the pipe 100 and the

ultrasonic probes

10a and 10b cut along the line AA shown in FIG. 1 and viewed from the arrow direction. In the following, description will be made centering on differences from the block diagram of the first embodiment shown in FIG.

5, the Reynolds number calculation unit 46, the flow rate ratio-Reynolds number conversion table 47, the Reynolds number-error conversion table 48, and the viscosity calculation unit 51 shown in FIG. 2 are not provided. On the other hand, in the second embodiment shown in FIG. 5, the error calculation unit 44 is electrically connected to the flow rate ratio calculation unit 43, and the error calculation unit 44 acquires the flow rate ratio from the flow rate ratio calculation unit 43. Then, the error ε is calculated based on the flow rate ratio.

Also, as shown in FIG. 5, the flow rate ratio-error conversion table 45 is electrically connected to the error calculation unit 44. The flow rate ratio-error conversion table 45 is prepared in advance for calculating the flow rate. In the flow rate ratio-error conversion table 45, the flow rate ratio and the error ε are correlated. Then, the error calculator 44 calculates an error ε from the flow rate ratio-error conversion table 45 based on the flow rate ratio.

As shown in FIG. 5, the flow rate calculation unit 50 is electrically connected to the flow rate calculation unit 42 and the error calculation unit 44. The flow rate calculation unit 50 calculates the flow rate based on the average flow velocity and the error.

FIG. 6 is a graph showing the correlation between the flow rate ratio and the error ε. 3 and 4 described above, the Reynolds number can be obtained from the flow rate ratio, and the error ε can be estimated from the Reynolds number. Therefore, the error ε can be estimated from the flow rate ratio.

In the turbulent flow region shown in FIG. 6, the relationship between the flow velocity ratio and the error ε can be approximated by a quadratic function (least square method) or can be approximated by a broken line.

That is, in the error calculation unit 44 shown in FIG. 5, for example, an equation approximated by a quadratic function is derived from the flow rate ratio-error conversion table 45, and the flow rate ratio acquired from the flow rate ratio calculation unit 43 is approximated by a quadratic function. By applying the above equation, the error ε can be calculated.

In the flow rate calculation unit 50 shown in FIG. 5, the flow rate Q can be calculated by the mathematical formula (5) described above. As described above, in the present embodiment, the error ε of the average flow velocity can be added to the calculation of the flow rate Q, so that the flow rate Q can be calculated with high accuracy.

FIG. 7 shows a flow rate error after correcting the relationship between the flow rate ratio and the error ε in the turbulent flow region of FIG. 6 by estimating the error of FIG. 6 using an equation approximated by a quadratic function. That is, FIG. 6 shows the error before correction, and FIG. 7 shows the error after correction. The error shown in FIG. 7 can be reduced to a maximum of 1/100 times the error ε shown in FIG. 6, and according to the present embodiment, the flow rate error can be extremely reduced.

It should be noted that the present invention is not limited to the above embodiment, and can be implemented with various modifications. In the above-described embodiment, the configuration illustrated in the accompanying drawings is not limited to this, and can be appropriately changed within a range in which the effect of the present invention is exhibited. In addition, various modifications can be made without departing from the scope of the object of the present invention.

For example, in the present embodiment, the flow rate, the Reynolds number, and the kinematic viscosity are measured as physical quantities of the fluid. In particular, both FIG. 2 and FIG. 5 have a block configuration for finally determining the flow rate of the fluid 102. However, for example, in FIG. 2, it is possible to calculate only the Reynolds number and the kinematic viscosity, or the Reynolds number without obtaining the flow rate.

Further, in the present embodiment, although not particularly limited, it can be preferably applied to a spool type fluid measuring device.

Finally, the feature points in the above embodiment are organized.

The fluid measuring apparatus 1 of the present embodiment forms a plurality of measurement lines α, β, γ by transmitting and receiving ultrasonic waves from a plurality of ultrasonic probes installed in the pipe 100 to the fluid 102 in the pipe 100, and a control unit 60, in the fluid measuring device 1 for obtaining the physical quantity of the fluid 102, the control unit 60 calculates the flow velocity of the fluid 102 measured by a plurality of measurement lines α, β, γ, and the flow velocity of the fluid 102. The flow rate ratio calculating unit 43 calculates a flow rate ratio based on the flow rate ratio, and the physical quantity calculation unit calculates a physical quantity based on the flow rate ratio. Here, the physical quantity calculation unit corresponds to the Reynolds number calculation unit 46, the flow rate calculation unit 50, and the viscosity calculation unit 51 in the embodiment of FIGS.

As described above, in this embodiment, the physical quantity of the fluid 102 can be obtained based on the ratio of the flow rates of the fluid 102, and in particular, the physical quantity can be measured with high accuracy regardless of the laminar flow / turbulent flow. Therefore, it is not necessary to prepare separate fluid measurement devices for laminar flow and turbulent flow, and it is possible to perform highly accurate measurement with a single fluid measurement device.

In the present embodiment, the physical quantity calculation unit is a flow rate calculation unit 50 that calculates at least the flow rate of the fluid 102, and further includes an error calculation unit 44 that calculates an error in the average flow velocity calculated from the flow velocity by the numerical integration method. The flow rate calculation unit 50 preferably calculates the flow rate of the fluid 102 using the average flow velocity and the error obtained by the error calculation unit 44. The embodiment shown in FIGS. 2 and 5 corresponds to this embodiment. Thereby, an error can be taken into account in the flow rate calculation, and in particular, the flow rate can be calculated with high accuracy in a turbulent flow region where the error fluctuation is large.

In this embodiment, the Reynolds number calculation unit 46 is further provided. The Reynolds number calculation unit 46 calculates the Reynolds number based on the flow rate ratio, and the error calculation unit 44 converts the error into the Reynolds number. It can be set as the structure calculated based on. The embodiment shown in FIG. Thereby, the flow rate can be acquired as the physical quantity together with the Reynolds number. In particular, in the present embodiment, the Reynolds number can be calculated easily and accurately based on the flow rate ratio without requiring piping dimensions and kinematic viscosity that were necessary for the calculation of the Reynolds number. Further, by calculating the Reynolds number, the error calculation unit 44 can calculate an error based on the Reynolds number. The flow rate calculation unit 50 can accurately calculate the flow rate of the fluid 102 using the average flow velocity and the error obtained by the error calculation unit 44.

In the present embodiment, a Reynolds number / error conversion table 48 is further provided, and the error calculation unit 44 uses the Reynolds number obtained from the Reynolds number calculation unit 46 to perform Reynolds number-error conversion. It is preferable to calculate the error based on the table 48. The embodiment shown in FIG. In this way, by providing the Reynolds number-error conversion table 48 in advance, if the Reynolds number is obtained, the error can be calculated quickly, and consequently the flow rate calculation processing time can be shortened.

Further, in the present embodiment, the physical quantity calculation unit is a Reynolds number calculation unit 46 that calculates at least the Reynolds number of the fluid, and the Reynolds number calculation unit 46 preferably calculates the Reynolds number based on the flow rate ratio. The embodiment shown in FIG. 2 and its modifications are applicable. The deformation of FIG. 2 corresponds to a form in which the flow rate of the fluid 102 is calculated in FIG. Thus, in this embodiment, the Reynolds number can be calculated easily and accurately based on the flow rate ratio without requiring the piping dimensions and kinematic viscosity required for the calculation of the Reynolds number.

In the present embodiment, a conversion table 47 between the flow rate ratio and the Reynolds number is further provided. The Reynolds number calculation unit 46 uses the flow rate ratio acquired from the flow rate ratio calculation unit 43 to use the flow rate ratio − It is preferable to calculate the Reynolds number based on the Reynolds number conversion table 47. The embodiment shown in FIG. Thus, by providing the flow rate ratio-Reynolds number conversion table 47 in advance, the Reynolds number can be calculated quickly and accurately if the flow rate ratio is acquired.

Further, in the present embodiment, a viscosity calculation unit 51 is further provided, and the viscosity calculation unit 51 calculates the kinematic viscosity of the fluid 102 based on the Reynolds number obtained by the Reynolds number calculation unit 46. Is possible. The embodiment shown in FIG. Thus, in this Embodiment, kinematic viscosity can be calculated rapidly and with high precision with Reynolds number.

In this embodiment, the flow rate ratio / error conversion table 45 is further provided. The error calculation unit 44 uses the flow rate ratio acquired from the flow rate ratio calculation unit 43 to convert the flow rate ratio into the error. Based on the table 45, the error can be calculated. The embodiment shown in FIG. Thereby, an error can be taken into account in the flow rate calculation, and in particular, the flow rate can be calculated with high accuracy in a turbulent flow region where the error fluctuation is large. In particular, in the present embodiment, the error calculation unit 44 can calculate an error based on the flow rate ratio by calculating the flow rate ratio. The flow rate calculation unit 50 can calculate the flow rate of the fluid frequently using the average flow velocity and the error obtained by the error calculation unit 44. In the embodiment of FIG. 5, as shown in FIG. 2, it is possible to calculate the flow rate quickly and accurately based on the flow rate ratio without requiring the calculation of the Reynolds number.

Further, in the present embodiment, as shown in FIG. 1, it is possible for the plurality of measurement lines α, β, and γ to be parallel to improve the accuracy of numerical integration in obtaining the average flow velocity, which is preferable. It is.

The present invention described above is useful for a fluid measurement device for measuring a physical quantity of a fluid, specifically, a flow rate, a Reynolds number, a kinematic viscosity, and the like.

This application is based on Japanese Patent Application No. 2016-208860 filed on Oct. 25, 2016. All this content is included here.

Claims

In a fluid measurement device that forms a plurality of measurement lines by transmitting and receiving ultrasonic waves to and from the fluid in the pipe from a plurality of ultrasonic transmission and reception units installed in the pipe, and in the control unit to obtain the physical quantity of the fluid,
The control unit is a flow rate calculation unit that calculates the flow rate of the fluid measured by the plurality of survey lines,
A flow rate ratio calculation unit for calculating a flow rate ratio based on the flow rate of the fluid;
A physical quantity computing unit for computing the physical quantity based on the flow rate ratio;
A fluid measuring device comprising:
The physical quantity calculation unit is a flow rate calculation unit that calculates at least the flow rate of the fluid,
Furthermore, an error calculation unit for obtaining an error of the average flow velocity calculated by the flow velocity calculation unit is provided,
2. The fluid measurement device according to claim 1, wherein the flow rate calculation unit calculates the flow rate of the fluid using the average flow velocity and the error obtained by the error calculation unit.
3. The fluid measuring device according to claim 2, wherein the flow velocity calculation unit calculates an average flow velocity from the flow velocity by a numerical integration method.
A Reynolds number calculation unit,
The Reynolds number calculation unit calculates the Reynolds number based on the flow rate ratio,
The fluid measurement apparatus according to claim 3, wherein the error calculation unit calculates the error based on the Reynolds number.
Further comprising a conversion table between the Reynolds number and the error,
5. The fluid measurement device according to claim 4, wherein the error calculation unit calculates the error based on a Reynolds number-error conversion table using the Reynolds number acquired from the Reynolds number calculation unit. .
The physical quantity computing unit is a Reynolds number computing unit that computes at least the Reynolds number of the fluid,
The fluid measuring apparatus according to claim 1, wherein the Reynolds number calculation unit calculates a Reynolds number based on the flow rate ratio.
A conversion table between the flow rate ratio and the Reynolds number;
7. The Reynolds number calculation unit calculates the Reynolds number based on a flow rate ratio-Reynolds number conversion table using the flow rate ratio acquired from the flow rate ratio calculation unit. The fluid measuring device according to any of the above.
It further includes a viscosity calculation unit,
The fluid according to any one of claims 4 to 7, wherein the viscosity calculating unit calculates a kinematic viscosity of the fluid based on the Reynolds number obtained by the Reynolds number calculating unit. Measuring device.
A conversion table of the flow rate ratio and the error is further provided;
4. The fluid measuring device according to claim 3, wherein the error calculation unit calculates the error based on a flow rate ratio-error conversion table using the flow rate ratio acquired from the flow rate ratio calculation unit.
The fluid measuring device according to any one of claims 1 to 9, wherein the plurality of survey lines are parallel to each other.