JP3401613B2 - Flow measurement method for fluid machinery - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flow rate measuring method of a fluid machine, and more particularly to measuring a fluid flow rate of various fluid machines such as a discharge rate of a pump used in waterworks, sewers, rainwater drainage, agricultural water and the like. The present invention relates to a method for measuring a flow rate of a fluid machine, which is suitable for

[0002]

2. Description of the Related Art As a first conventional example of a pump flow rate measuring method using ultrasonic waves, there is a pump discharge flow rate measuring apparatus and measuring method using ultrasonic waves described in Japanese Patent Laid-Open No. 4-249716. In this first conventional example, the flow velocity in the elbow is measured by an ultrasonic velocity meter installed on the side wall of the discharge elbow of the pump, and the data showing the relation between this flow velocity and the flow velocity previously measured versus the pump discharge amount. Calculate the flow rate from

As a second conventional example of the pump flow rate measuring method, as shown in FIG. 15, there is an example in which an ultrasonic wave velocity meter is applied to the flow rate measurement of the pump. In the second conventional example, a pair of ultrasonic sensors are installed on the outer wall of the pump pipe at predetermined intervals in the pipe axis direction, and ultrasonic waves are transmitted in the forward direction and the reverse direction of the flow, and the flow velocity is determined from the difference in the propagation velocity. This is a method of obtaining and multiplying the flow velocity by the cross-sectional area of the measurement cross section to calculate the flow rate. An ultrasonic propagation type velocity meter is described, for example, on page 131 of the technical data “Fluid Measurement” (published in April 1985) published by the Japan Society of Mechanical Engineers.

[0004]

In the first conventional example described above,
The relationship between the flow rate of the elbow and the flow rate of the pump must be found by actual measurement. Therefore, there is a problem that a pump test for the measurement must be performed at a pump factory or a local pump station, which requires a lot of time and cost. Further, in the actual measurement test in the factory, it is difficult to perform the test with the suction channel and the discharge channel of the local pump being completely the same, and an error may occur in the measurement accuracy.

On the other hand, in the second conventional example, as shown in FIG. 15, the outlet cross section of the discharge elbow 8 of the pump in which the ultrasonic sensors 11a and 11b are to be installed has a large radial velocity distribution. In this type of velocity meter, since only the average value of the flow velocity on the measurement lines 15a and 15b through which the ultrasonic waves pass is obtained, the flow rate calculated by multiplying the average velocity by the cross-sectional area has an error with the actual flow rate. It becomes large and the measurement accuracy deteriorates. In order to solve this problem, it is necessary to measure the length of the upstream straight pipe part 9 of the ultrasonic velocity meter to about 10 times the diameter of the flow passage pipe and measure it when the flow is rectified.

However, at a drainage pump station where an actual pump is installed, the discharge elbow 8 of the pump is provided downstream of the outlet.
Such long straight sections are usually absent. If a straightening device is provided at the pump outlet to straighten the flow, it is possible to improve the measurement accuracy even with a short straight pipe section.
It is necessary to newly install a rectifying device in the existing pump pipe, which requires a great deal of expense.

Further, as shown in FIG. 16, if not only one section of the horizontal section A of the measurement section IX-IX in FIG. 15 but also a plurality of sections such as the sections B and C are measured, improvement of the measurement accuracy is expected. To be done. However, since the measurement accuracy itself of the average flow velocity on each line is not improved, the overall measurement accuracy is not significantly improved.

An object of the present invention is to provide a fluid machine capable of highly accurately performing flow rate measurement of a fluid machine such as an existing pump, which has a low measurement accuracy in the conventional ultrasonic measurement method, without requiring a great expense. It is to provide a flow rate measuring method.

[0009]

In order to achieve the above object, the present invention provides a flow rate measuring method for measuring a flow rate in at least one cross section of a fluid machine and the front and rear flow paths, wherein a velocity distribution in the cross section is pulsed. The flow rate is measured from the Doppler ultrasonic velocity meter and the flow rate is calculated from the velocity distribution and the cross-sectional area. In this measurement method, the flow velocity distribution in the traveling direction of the ultrasonic wave is obtained by the pulse Doppler ultrasonic velocity meter, and the flow velocity distribution on the measurement line in the flow path direction is accurately obtained from the flow velocity distribution, so the flow velocity distribution and the cross-sectional area are Therefore, the flow rate can be calculated with high accuracy. Further, the length required in the flow path direction of the ultrasonic measurement line is about the flow path diameter, and a long straight pipe section is not required in the measurement section. Therefore, compared with the conventional ultrasonic flowmeter,
Highly accurate flow rate measurement is possible in a short distance.

When a plurality of ultrasonic sensors are installed around the outer wall surface of the flow path and the flow velocity distribution on a plurality of measurement lines is measured,
The flow velocity distribution of the measurement cross section is grasped in more detail, and the flow rate can be measured with higher accuracy.

When an array type ultrasonic sensor is installed at a fixed position on the outer wall of the flow channel and the flow velocity distributions on a plurality of lines radially extending in the cross section of the measurement flow channel are simultaneously measured from the ultrasonic sensor, the flow velocity on the entire measurement surface is measured. Since the distribution can be obtained, if the flow velocity at each point is multiplied by a small area and the flow rate at each part is obtained and integrated,
The flow rate across the cross section is accurately measured.

When the flow velocity distribution on a plurality of lines extending from the inlet side cross section of the discharge elbow of the fluid machine to the upstream side is measured, and there is an object whose flow path shape in the ultrasonic emission direction changes immediately after the discharge elbow outlet. However, since the shape of the flow path does not change on the inlet side of the discharge elbow, it is possible to measure the flow rate with high accuracy.

A turbulent flow analysis of the flow channel including the flow velocity measurement cross section is performed, the flow velocity distribution on the flow velocity measurement line is obtained from the analysis, the flow rate Qa is calculated from the flow velocity distribution and the flow channel cross-sectional area, and the inlet is used during the turbulent flow analysis. Ratio α with flow rate Qb preset as boundary condition
= Qb / Qa is obtained, and the corrected flow rate is obtained by multiplying the flow rate Qc calculated from the ultrasonic velocity meter using this α as a correction coefficient. In this case, since the correction coefficient α is obtained in advance by turbulent flow analysis, highly accurate flow rate measurement can be easily performed.

In order to measure the swirl flow as well, the sensor is set at a position such that the ultrasonic wave transmission direction of the ultrasonic sensor is basically parallel to the flow direction. By doing so, the flow direction in the pump flow path is the same as the traveling direction of the ultrasonic waves, so that the measurement accuracy is improved. In addition, since the main flow direction of the swirl flow can be measured even for swirl flow that occurs in the low flow rate range of the pump, this flow rate measurement method that obtains the flow rate from the flow velocity distribution in the axial direction of the flow path provides highly accurate measurement. Is possible.

An ultrasonic sensor is installed on the suction flow path wall or the discharge flow path wall surface of the fluid machine, and the direction of the ultrasonic wave sent from the sensor or the ultrasonic wave received by the sensor is the main flow direction of the discharge flow path. Since the ultrasonic sensors are installed so as to be parallel to each other, it is easy to detect the frequency change of the ultrasonic waves due to the Doppler effect, and the measurement accuracy becomes high. In addition, even in the flow having a swirl component generated in the small flow rate range of the pump, the main flow direction component always exists, so the measurement accuracy of the flow velocity improves.
As a result, the flow rate measurement accuracy is improved.

In the suction or discharge passage of the fluid machine,
Since the ultrasonic sensor is installed on the wall surface where the flow direction is bent by 30 degrees or more, with the axis of the ultrasonic sensor transmitting and receiving ultrasonic waves facing the mainstream direction upstream or downstream of the flow path, It is convenient for mounting the sound wave sensor.

A bar-shaped measuring jig having an ultrasonic sensor is inserted into a hand hole for maintenance and inspection installed in the discharge elbow so as to be orthogonal to the flowing water direction, and the jig is moved in the axial direction of the jig. And measure the flow rate. At that time, if the measurement jig is moved in the axial direction as well as in the circumferential direction, the number of measurement positions in the measurement cross section can be extremely increased, so that highly accurate flow rate measurement can be performed.

Also in this case, if the array type ultrasonic sensor is installed on the measuring jig, the measuring time can be shortened, and the measuring jig can be housed in a compact shape to reduce the size of the measuring jig.

Since the ultrasonic sensor constituting the pulse Doppler ultrasonic velocity meter is provided at the bottom of the suction tank facing the suction flow passage of the fluid machine, the surface on which the ultrasonic sensor is attached becomes a flat surface. Easy installation of the sound wave sensor,
Moreover, there is an advantage that the accuracy of mounting can be improved. The bellmouth contracts and accelerates the flow, creating a uniform, rectified and stable flow. Therefore, the measurement accuracy of the ultrasonic flowmeter is improved and stable measurement is possible. In particular, in the aeration-type preceding standby operation method, if intake is made on the downstream side, the flow rate can be measured in the single-phase state with only water, and in the vicinity of the pump discharge elbow where a large amount of air is mixed, a large amount can be measured. Since the air bubbles of No. 2 become a source of noise, it is possible to prevent the measurement accuracy of the flow rate measuring method using ultrasonic waves from being significantly lowered or becoming impossible to measure.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Next, referring to FIGS.
An embodiment of a method and an apparatus for measuring a flow rate of a fluid machine according to the present invention will be described.

<< First Embodiment >> FIG. 1 is a sectional view showing a first embodiment of a flow rate measuring method for a fluid machine according to the present invention.
In the first embodiment, the fluid machine whose flow rate is to be measured is a vertical shaft drainage pump, and its impeller 1 is attached to a pump shaft 2 connected to a shaft of a prime mover (not shown here). . When the pump shaft 2 rotates and the drainage pump operates, the rainwater 4 in the suction tank 3 is discharged to the discharge pipe 9 via the suction bell mouth 5, the impeller 1, the guide blades 6, the discharge column 7, and the discharge elbow 8. To be done. A flow rate control valve 10 is installed downstream of the discharge pipe 9.

An ultrasonic sensor 11 of a pulse Doppler ultrasonic velocity meter 13 is set at the outlet end of the discharge elbow 8. The pulse Doppler ultrasonic velocity meter 13 includes an ultrasonic oscillator, a pulse oscillator, a transmitter, a frequency tracking circuit, a double modulator,
It consists of an indicator. The wave transmission / reception surface of the ultrasonic sensor 11 of the first embodiment is inclined by an angle θ with respect to the flow path wall 9a. The wedge-shaped fixture 12 makes the ultrasonic sensor 11 contact the flow path wall 9a without any gap.

From the ultrasonic sensor 11, the ultrasonic pulse 1
4 are fired at time intervals T. The emitted ultrasonic pulse 14 is scattered and reflected by particles 16 in the fluid on the flow velocity measurement line 15. The reflected wave is received by the ultrasonic sensor 11 that operates as a receiver only for a certain period of time. The received ultrasonic waves are subjected to signal processing in the pulse Doppler ultrasonic velocity meter 13 to obtain the Doppler shift frequency and the flow velocity V.

FIG. 2 is a diagram for explaining the relationship between the transmitted signal, the received signal and the Doppler signal of the pulse Doppler ultrasonic velocity meter according to the present invention. From the ultrasonic sensor 11, a transmission signal including an ultrasonic pulse train, that is, an ultrasonic pulse 1
4 are fired at time intervals T. On the flow velocity measurement line 15,
The scattered reflected wave 17 that is scattered and reflected by the particles at the distance X shown in Formula 1 from the ultrasonic sensor 11 is received by the ultrasonic sensor 11 at the time interval T and becomes a received signal. From the difference between the frequency of the transmitted signal and the frequency of the received signal, a Doppler signal is obtained and converted into a flow velocity V. Therefore, the flow velocity at the position of the ΔX interval on the flow velocity measurement line 15 where the ultrasonic wave advances is measured, and the velocity distribution on that line is obtained. In Equation 1, C is the speed of sound in water, T
Is the time interval of the ultrasonic pulse train, and n is an integer.

[0025]

[Equation 1]

FIG. 3 is a sectional view showing the velocity vector of the flow velocity V at the measurement position P. The flow velocity V measured by the Doppler ultrasonic velocity meter 13 is a component Vx in the traveling direction of the ultrasonic waves. Therefore, the velocity V parallel to the flow path is
The distribution of the flow velocity in the flow channel direction on the flow velocity measurement line 15 is obtained by Expression 2.

[0027]

[Equation 2]

The flow rate in the measurement cross section is obtained by multiplying the flow velocity in each direction of the flow path at each point by a small area and integrating it over the entire cross section of the flow path. In Equation 3, B (r)
Is the channel width shown in FIG.

[0029]

[Equation 3]

The length required for the flow velocity measuring line of the ultrasonic wave emitted from the ultrasonic sensor 11 in the flow passage direction is about the diameter of the flow passage, and a long straight pipe portion is not required for the measurement portion. . Therefore, even at a shorter distance than the conventional ultrasonic flowmeter,
The flow rate can be measured with high accuracy.

<< Second Embodiment >> FIG. 4 is a sectional view showing a second embodiment of the flow rate measuring method for a fluid machine according to the present invention.
At the outlet of the discharge elbow 8, a plurality of ultrasonic sensors 11a, 11b, 11 of the pulse Doppler ultrasonic velocity meter 13 are provided.
, c, 11d, ... are installed, the flow velocity distribution on each line is obtained, and the flow rate is calculated by Equation 4. In Equation 4,
R is the radius of the measurement cross section, Vax, Vbx, ..., VNx are flow velocity components in the measurement line direction measured by the ultrasonic sensors a, b, ..., N, r is the radius from the center of the flow path at the measurement position, and N is N. Is the number of measurement lines.

[0032]

[Equation 4]

It is desirable to install the ultrasonic sensor on each flow velocity measuring line 15, but when measuring a steady flow rate, the installation position of one ultrasonic sensor may be sequentially changed and measured. By doing so, the flow velocity distribution in the measurement cross section can be grasped in more detail, and the flow rate can be measured with higher accuracy.

<< Third Embodiment >> FIG. 5 is a sectional view showing a third embodiment of the flow rate measuring method for a fluid machine according to the present invention.
As the ultrasonic sensor 11, an array type ultrasonic sensor in which a plurality of small ultrasonic sensors are arranged is adopted. From the ultrasonic sensor of each element, pulsed ultrasonic waves are emitted in the direction of a specific flow velocity measurement line, and many measurement lines are set on the measurement cross section. Similar to the first embodiment, the flow velocity distribution on each measurement line is obtained, and the flow velocity distribution on the entire measurement surface is obtained. Similar to each of the above-described embodiments, the flow rate at each point is obtained by multiplying the flow velocity at each point by a small area, and the flow rate is obtained by integrating over the entire cross section.

<Fourth Embodiment> FIG. 6 is a sectional view showing a fourth embodiment of the flow rate measuring method for a fluid machine according to the present invention.
The fourth embodiment is basically the same as the first embodiment,
Set the measurement position as the inlet of the discharge elbow 8 of the vertical pump,
The ultrasonic wave emitting direction, that is, the flow velocity measuring line is directed upstream. Immediately after the outlet of the discharge elbow 8, the flow control valve 1
0 is set. When there is an object whose flow path shape changes in the ultrasonic wave emission direction, it is difficult to measure the flow rate with high accuracy at the outlet of the discharge elbow 8. However, since the shape of the flow passage on the inlet side of the discharge elbow 8 does not change, the ultrasonic sensor 11 is provided at the inlet of the discharge elbow 8 as in the fourth embodiment.
If installed, the flow rate can be measured with high accuracy.

<< Fifth Embodiment >> FIG. 7 is a flow chart showing a processing procedure of a fifth embodiment of the flow rate measuring method for a fluid machine according to the present invention. In the fifth embodiment, turbulent flow analysis is performed over the entire pump flow channel system for which the flow rate is to be measured, the flow velocity distribution on the flow velocity measurement line is obtained from the turbulent flow analysis, and the flow velocity distribution and the flow passage cross-sectional area are used. The flow rate Qa is calculated, and the ratio α = Qb / Qa with the flow rate Qb preset as the inlet boundary condition at the time of turbulent flow analysis is obtained, and the flow rate Qc calculated from the ultrasonic velocity meter is used as the correction coefficient α. It multiplies and corrects the measured flow rate to realize highly accurate flow rate measurement. Fifth
According to the embodiment, since the correction coefficient α is obtained in advance by the turbulent flow analysis, it is possible to easily measure the flow rate with high accuracy.

In the above description, the vertical drainage pump is described, but the flow rate measuring method of the present invention is not limited to this, and if the fluid flows through the flow path, the horizontal axis of the drainage pump can be used. It can be widely applied to pumps, turbines other than pumps, and blowers.

According to the above-described embodiment of the present invention, it is possible to accurately measure the flow rate of the existing pump, which does not require a great expense and has a low measurement accuracy in the conventional ultrasonic measurement method.

FIG. 17 is a diagram for explaining the problems that could not be solved by the first to fourth embodiments of the present invention. In the pulse Doppler ultrasonic flowmeter described in the first to fourth embodiments, the flow velocity distribution on the measurement line of the pump channel can be obtained, and the ultrasonic sensor can be installed on the outer wall of the pump channel for measurement. The advantage is that it is extremely easy to use.

However, in the measuring methods of the first to fourth embodiments,
It was necessary to set the direction of transmitting ultrasonic waves so as to form an angle with the main flow direction of the flow path. Although there is no problem in measurement near the rated point of the pump, in the low flow rate region where the flow rate is considerably smaller than the rated point, as shown in Fig. 17, the swirling spiral flow 26 remains at the pump outlet, and the direction of the measurement line The flow direction to be measured may be orthogonal. In the pulse Doppler method, since only the component in the direction of transmitting the ultrasonic wave of the flow can be measured in principle, it cannot be measured for the flow in which there is no velocity component in that direction. It suffices to change the transmitting direction variously and set it to a measurable direction, but to realize this, the mechanism becomes complicated.

The following sixth to eleventh embodiments propose a flow rate measuring method for a fluid machine which fundamentally eliminates the problem that could not be solved by the first to fourth embodiments, that is, the measurement line and the flow direction are orthogonal to each other. To do.

<< Sixth Embodiment >> FIG. 8 is a sectional view showing a sixth embodiment of the method for measuring the flow rate of a fluid machine according to the present invention.
8A is a plan view of the sixth embodiment seen from above, FIG. 8B is a vertical cross-sectional view of the sixth embodiment, and FIG. 8C is a measurement plane AA of the flow velocity in the pump. FIG. Also in the sixth embodiment, as in the first embodiment, the fluid machine that is the target of the flow rate measurement is
It is a vertical shaft drainage pump, and its impeller 1 is attached to a pump shaft 2 connected to a shaft of a prime mover (not shown here). When the pump shaft 2 rotates, the rainwater 4 in the suction tank 3 sucks the bell bellmouth 5, the impeller 1, the guide blades 6,
It is discharged to the discharge pipe 9 through the discharge column 7 and the discharge elbow 8. A flow rate control valve 10 is installed downstream of the discharge pipe 9.

In the sixth embodiment, the ultrasonic sensor 11 of the pulse Doppler ultrasonic velocity meter 13 is installed on the outer diameter side wall of the discharge elbow 8. On the wave transmission / reception surface of the ultrasonic sensor 11, the direction of the ultrasonic waves transmitted from the wave transmission / reception surface is parallel to the pump rotation axis 2. Wedge-shaped fitting 12a
Makes the ultrasonic sensor 11a contact the outer wall of the curved discharge elbow 8 without any gap.

From the ultrasonic sensor 11, the ultrasonic pulse 1
4 are fired at time intervals T. The emitted ultrasonic pulse 14 is scattered and reflected by particles 16 in the fluid on the flow velocity measurement line 15. The reflected wave is received by the ultrasonic sensor 11 that operates as a receiver only for a certain period of time. The received ultrasonic waves are subjected to signal processing in the pulse Doppler ultrasonic velocity meter 13 to obtain the Doppler shift frequency and the flow velocity V.

That is, as in the case of FIG. 2, the ultrasonic sensor 11 emits a transmission signal composed of a pulse train of ultrasonic waves, that is, ultrasonic pulses 14 at time intervals T. On the flow velocity measurement line 15, the scattered reflected wave 17 that is scattered and reflected from the ultrasonic sensor 11 at the particle at the distance X shown in the above mathematical expression 1 is received by the ultrasonic sensor 11 at the time interval T and becomes a received signal. . From the difference between the frequency of the transmitted signal and the frequency of the received signal, a Doppler signal is obtained and converted into a flow velocity V. Therefore, the flow velocity measurement line 15 through which the ultrasonic wave advances
The flow velocity at the upper ΔX interval is measured, and the velocity distribution on the line is obtained.

More specifically, FIG. 8 (a) and FIG. 8 (b)
In, first, the flow velocity at the point Aa of the cross section AA at the distance L1 from the ultrasonic sensor 11a is obtained. Next, for the ultrasonic sensor 11b installed at a position rotated by 45 degrees from the ultrasonic sensor 11a around the pump axis, the flow velocity at the point Ab in the cross section A is obtained by the same procedure as above. Circumferential measurement positions 11c, 11d, ..., 11h
Is measured, the flow velocity distribution in the circumferential direction in the pump channel cross section shown in FIG. 8C is obtained.

Once the flow velocity distribution has been obtained, the flow velocity Q flowing through the flow path can be obtained by integrating the flow velocity with respect to the cross section AA according to the equation (5). d ₂ is the inner diameter of the pump discharge column 7,
d ₁ is the outer diameter of the pump shaft 2.

[0048]

[Equation 5]

In the case of the sixth embodiment, the ultrasonic sensor 11
Since the direction of the ultrasonic waves emitted from, that is, the flow velocity measurement line coincides with the main flow direction (pump axis direction) of the flow, it is easy to catch the frequency change of the ultrasonic waves due to the Doppler effect, and the measurement accuracy becomes high. Therefore, even in the flow having a swirl component generated in the small flow rate range of the pump, the main flow direction component always exists, so the measurement accuracy of the flow velocity is improved, and as a result,
The accuracy of flow rate measurement is also high.

<< Seventh Embodiment >> FIG. 9 is a sectional view showing a seventh embodiment of the method for measuring the flow rate of a fluid machine according to the present invention.
The ultrasonic sensors 11a, 11b, 11c, 11d, ...
On the outer diameter surface of the discharge elbow 8, ultrasonic waves to be transmitted are installed so as to be directed to the downstream section B-B and to be parallel to the axial center of the discharge pipe 9. The measurement principle and the procedure for obtaining the flow rate from the flow velocity are the same as in the sixth embodiment.

In the seventh embodiment, as is apparent from FIG. 9B, the space on the left side of the discharge elbow 8 can be utilized, so that the work of attaching the ultrasonic sensor to the discharge elbow 8 and the measurement work are It becomes easy as compared with the sixth embodiment. However, since the pump shaft 2 exists in parallel to the measurement cross section BB, and the ultrasonic waves do not reach the region shaded by the pump shaft 2, the measurement cannot be performed.

<Eighth Embodiment> FIG. 10 is an external view showing an eighth embodiment of the flow rate measuring method for a fluid machine according to the present invention. In the eighth embodiment, on the curved surface of the outer wall of the discharge elbow 8,
For example, measuring seats 18a, 18b, 18c, etc., on which the ultrasonic sensor 11 can be installed without a gap are provided in a layered manner by an adhesive, and the upper surface of each measuring seat 18 is a plane parallel to the measurement cross section AA. Has become. A plurality of ultrasonic sensors 11a, 11b, 11c, 11d and the like are mounted on each measuring seat 18. With this configuration, since the surface on which the ultrasonic sensor is mounted becomes a flat surface, there is an advantage that the mounting of the ultrasonic sensor is easy and the mounting accuracy can be improved.

<< Ninth Embodiment >> FIG. 11 is a sectional view showing a ninth embodiment of the flow rate measuring method for a fluid machine according to the present invention. This is a flow rate measuring method in which an ultrasonic sensor is provided on the bottom surface of the pump suction tank 3 immediately below the pump. 3 which is a part of the bottom
a is made of a steel plate or the like, and a space 19 is formed below the plate.
Is provided and a plurality of ultrasonic sensors are attached to the lower surface of the plate. The signal cable to the ultrasonic sensor is the cable duct 20 provided on the concrete wall of the suction tank 3.
After that, it is guided to the floor surface where the pump is installed and connected to the ultrasonic flowmeter main body 12. The flow rate measurement cross section C-C is set at a position of a distance L from the suction tank bottom surface 3a between the end surface 5a of the bell mouth 5 and the inlet end surface 1a of the impeller 1. The flow velocity distribution in the CC cross section is obtained by the same principle as in the above-described first embodiment, and the flow rate is obtained by integrating these with Equation 2.

In the CC cross section of the measurement cross section, the flow is contracted / accelerated by the bellmouth to be uniform, rectified and stable. Therefore, the measurement accuracy of the ultrasonic flowmeter is improved and stable measurement is possible. In particular, in the aeration-type preceding standby operation method, if the intake is made downstream (upper position) from the C-C cross section, the flow rate in a single-phase state of water alone can be measured, and a large amount of air is generated. In the vicinity of the mixed pump discharge elbow, a large amount of bubbles become a source of noise, so that it is possible to prevent the measurement accuracy of the flow rate measurement method using ultrasonic waves from being significantly reduced or from becoming impossible to measure.

If the signal cable may be hung along the concrete wall surface of the suction tank 3, it is not necessary to provide the cable duct 20.

<< Tenth Embodiment >> FIG. 12 is a sectional view showing a tenth embodiment of a flow rate measuring method for a fluid machine according to the present invention. A plurality of ultrasonic sensors 11a, 11b, 11 are provided on the outer wall surface of the outer diameter of the second discharge elbow 21 of the pump discharge passage.
c, ... are installed. A space 22 is formed in the concrete wall for convenience of mounting the ultrasonic sensor. The installation condition of the ultrasonic sensor is basically the same as that of the sixth embodiment. The flow velocity in the DD cross section, which is the measurement cross section at the distance La from the ultrasonic sensor 11a, is measured, and the flow velocity distribution in the DD cross section is obtained from the measurement result from each ultrasonic sensor. Integrating it in the same manner as Equation 2 gives the measured flow rate.

<< Eleventh Embodiment >> FIG. 13 is a sectional view showing an eleventh embodiment of a flow rate measuring method for a fluid machine according to the present invention. The discharge elbow may be provided with an inspection hole or hand hole inside the pump that is perpendicular to the pump axis and parallel to the outlet flange surface. The eleventh embodiment is a preferred embodiment for such a pump. Hand hole 24
A rod-shaped measuring jig 25 penetrates through a and 24b. As shown in FIG. 14, the ultrasonic jig 11 is embedded in the measuring jig 25, and the surface center 1 of the ultrasonic sensor 1 is embedded.
No. 1a does not project from the surface 25a of the measuring jig 25. The measuring jig 25 is movable in the axis Y direction of FIG. 13 and the circumferential θ direction of FIG.

FIG. 14 is a sectional view showing details around the measuring jig 25 of the eleventh embodiment. In such a configuration, the flow velocity distribution of the EE cross section at the distance L from the surface center 11a of the ultrasonic sensor is measured. As shown in FIG. 14A, if the measuring jig 25 is traversed in the Y-axis direction, E
The velocity distribution in the Y direction of the -E cross section is measured. Also, Y
At each position in the direction, as shown in FIG. 14B, the measurement jig 25 is rotated in the θ direction around the axis of the measurement jig, and measurement is performed at each θ angular position. The velocity distribution of is measured. When the velocity distribution in the EE cross section is obtained in this way, the flow rate is obtained by integrating the velocity distribution over the cross section by Formula 2. In the case of the present embodiment, the number of measurement positions in the measurement cross section can be extremely increased, so that highly accurate flow rate measurement can be performed.

As an extension of the present embodiment, if not only one ultrasonic sensor but also a plurality of small ultrasonic sensors are arranged in the measuring jig 25 in the axis Y direction and the circumferential θ direction, the measuring time can be shortened. In particular, if an array type ultrasonic sensor is used,
It can be stored in a compact shape, and the measuring jig 25 can be downsized.

In the above description, an example in which the present invention is applied to a vertical shaft drainage pump has been described, but the present invention can also be applied to a fluid machine such as a horizontal shaft pump or a water wheel, a blower, or the like other than the pump.

[0061]

According to the present invention, the fluid flow rate of various fluid machines can be measured with high accuracy. Especially, the discharge amount of a pump used for water supply, sewer, rainwater drainage, agricultural water, etc. can be measured at low cost and with high accuracy.

Further, the fluid flow rate can be measured with high accuracy only by installing a pulse Doppler ultrasonic velocity meter at a small cost for an existing pump, which was only able to obtain a low flow rate measurement accuracy by the conventional ultrasonic measurement method.

[Brief description of drawings]

FIG. 1 is a sectional view showing a first embodiment of a flow rate measuring method for a fluid machine according to the present invention.

FIG. 2 is a diagram for explaining the relationship among a transmission signal, a reception signal, and a Doppler signal of the pulse Doppler ultrasonic velocity meter according to the present invention.

FIG. 3 is a cross-sectional view showing a flow velocity vector at a measurement position.

FIG. 4 is a sectional view showing a second embodiment of the flow rate measuring method for a fluid machine according to the present invention.

FIG. 5 is a sectional view showing a third embodiment of the flow rate measuring method for a fluid machine according to the present invention.

FIG. 6 is a sectional view showing a fourth embodiment of the method for measuring the flow rate of a fluid machine according to the present invention.

FIG. 7 is a flowchart showing a processing procedure of a fifth embodiment of a flow rate measuring method for a fluid machine according to the present invention.

FIG. 8 is a sectional view showing a sixth embodiment of the flow rate measuring method for a fluid machine according to the present invention.

FIG. 9 is a sectional view showing a seventh embodiment of the method for measuring the flow rate of a fluid machine according to the present invention.

FIG. 10 is an eighth flow measuring method for a fluid machine according to the present invention.
It is an external view which shows an Example.

FIG. 11 is a ninth flow measuring method for a fluid machine according to the present invention.
It is sectional drawing which shows an Example.

FIG. 12 is a first flow measuring method for a fluid machine according to the present invention.
It is sectional drawing which shows 0 Example.

FIG. 13 is a first flow measuring method for a fluid machine according to the present invention.
It is sectional drawing which shows 1 Example.

FIG. 14 is a sectional view showing details around a measuring jig in an eleventh embodiment.

FIG. 15 is a cross-sectional view illustrating a flow rate measuring method of a conventional fluid machine.

16 is a view showing a cross section taken along line IX-IX of FIG.

FIG. 17 is a diagram illustrating a problem that cannot be solved by the first to fourth embodiments of the present invention.

[Explanation of symbols]

1 impeller 2 pump shaft 3 suction tank 4 rainwater 5 suction bell mouth 6 guide vanes 7 Discharge column 8 discharge elbow 9 discharge pipe 10 Flow control valve 11 Ultrasonic sensor 12 wedge mount 13 pulse Doppler ultrasonic velocity meter 14 Ultrasonic pulse transmission wave 15 Flow velocity measurement line 16 particles 17 Scattered reflected wave 18 Ultrasonic sensor mounting seat 19 Suction side measurement space 20 cable ducts 21 Second discharge elbow 22 Discharge side measurement space 23 Discharge tank 24 hand holes 25 Measuring jig 26 Swirling spiral flow

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yuji Kato 2-8-4 Jinritsu Higashi 2-chome, Tsuchiura City, Ibaraki Hiratsuno Engineering Co., Ltd. Tsuchiura Works (56) Reference JP-A-4-249716 (JP, A) JP-A-1-193617 (JP, A) JP-A-54-121770 (JP, A) JP-A-60-262015 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) ) G01F 1/00-9/02

Claims (7)

(57) [Claims] 1. The velocity distribution in at least one cross section of a fluid machine and at least one of the flow passages before and after the fluid machine is measured by pulse Doppler super
Measured with an acoustic velocity meter, and the velocity distribution and the cross-sectional area
In the method for measuring the flow rate of a fluid machine, the flow rate is calculated from
A method for measuring the flow rate of a fluid machine, which comprises measuring the flow velocity distribution on multiple curved lines . 2. The velocity distribution in at least one cross section of the fluid machine and the flow passages before and after the fluid machine is measured by a pulse Doppler method.
Measured with an acoustic velocity meter, and the velocity distribution and the cross-sectional area
In the flow rate measuring method of a fluid machine for calculating the flow rate from, a turbulent flow analysis of a flow channel including the flow velocity measurement cross section is performed, a flow velocity distribution on a flow velocity measurement line is obtained from the analysis result, and the flow velocity distribution and flow channel disconnection are obtained. The flow rate Qa is calculated from the area and the ratio α = Qb / Qa with the flow rate Qb preset as the inlet boundary condition at the time of the turbulent flow analysis is obtained, and the α is used as the correction coefficient from the pulse Doppler ultrasonic velocity meter. A flow rate measuring method of a fluid machine, characterized in that the corrected flow rate is obtained by multiplying the flow rate Qc. 3. An ultrasonic sensor of a pulse Doppler ultrasonic velocity meter is provided on a suction flow passage wall or a discharge flow passage wall surface of a fluid machine such that the direction of transmission and reception of the ultrasonic sensor is parallel to the main flow direction of the discharge flow passage. Installed in the same way as before and after
Pulse velocity distribution in at least one cross section of the flow path
Measured with a Doppler ultrasonic velocity meter,
In a flow rate measuring method for a fluid machine that calculates the flow rate from the cross-sectional area, a rod-shaped measuring jig that is orthogonal to the flowing water direction and has an ultrasonic sensor is installed in a maintenance / inspection handhole installed in the discharge elbow. A flow rate measuring method for a fluid machine, which comprises inserting the jig, moving the jig in an axial direction of the jig, and measuring the flow rate. 4. The flow rate measuring method for a fluid machine according to claim 3 , wherein ultrasonic waves are transmitted and received on a wall surface of the flow path of the suction or discharge path of the fluid machine, which is bent by 30 degrees or more. A flow rate measuring method for a fluid machine, wherein an ultrasonic sensor is installed in a direction in which a sensor axis is opposed to a mainstream direction upstream or downstream of a flow path. 5. The flow rate measuring method for a fluid machine according to claim 3 , wherein the measuring jig is movable in an axial direction and / or a circumferential direction. 6. The flow rate measuring method for a fluid machine according to claim 5 , wherein an array type ultrasonic sensor is installed on a measuring jig. 7.There are few fluid machines and the flow paths before and after
In both cases, the velocity distribution in one section is
Measured with an acoustic velocity meter, and the velocity distribution and the cross-sectional area
Calculate the flow rate fromHow to measure the flow rate of fluid machinery
hand, The ultrasonic sensor that constitutes the pulse Doppler ultrasonic velocity meter
The suction tank bottom facing the suction passage of the fluid machine.To
Provided, From the inlet side section of the discharge elbow of the fluid machine to the upstream side
Measure velocity distribution on multiple lines Flow characterized by
Flow measurement method for body machine.