JPS63228027A - Flowmeter equipped with rectifier tube - Google Patents

Abstract

PURPOSE:To measure a flow rate in a large-diameter piping by a compact constitution at a low cost with good linearity by arranging a rectifier tube in the piping where conductive fluid flows and inserting an eddy current type current meter into a guide tube arranged in the rectifier tube. CONSTITUTION:The rectifier tube 11 which rectifies the conductive fluid 16 is inserted into the large-diameter piping 10 and fixed to the piping 10 through a support 12. Further, the guide pipe 14 is inserted into the rectifier tube 11 from its downstream side and supported in the rectifier tube 11 by a support 15, and the eddy current type current meter 13 is inserted into the guide tube 13. Thus, the rectifier tube 11, current meter 13, and guide tube 14 are inserted as one set into the piping 10. This rectifier tube 11 is provided so as to a flow velocity distribution suitable to measurement by rectification effect even if the flow state in the piping 10 is not good. Then the flow velocity is found by the current meter 13 and then the flow rate is measured with good linearity because the sectional area of the tube is already known.

Description

[Detailed Description of the Invention] C. Industrial Application Field] The present invention relates to the measurement of the flow rate of conductive fluid used in nuclear power plants and related plants, and is particularly suitable for measuring the fluid flow rate of large-diameter piping. This relates to a flowmeter with a rectifier tube.

[Conventional technology]

Generally, electromagnetic flowmeters are used to measure the flow rate of conductive fluids. Fig. 4 is a diagram for explaining the principle of such an electromagnetic flowmeter. When a conductive fluid moves in a magnetic field with a magnetic flux density B at a speed V perpendicular to the magnetic field, Electric power e is induced.

Since this electromotive force e is proportional to the velocity V, the flow velocity or flow rate of the conductive fluid can be measured by measuring the electromotive force e.

FIG. 5 is a diagram showing the basic configuration of such an electromagnetic flowmeter. In the figure, 1 is a conductive fluid, 2 is piping, 3 is a permanent magnet,
4 is a yoke, 5.6 is a detection electrode, 7 is an output lead wire, 8
is a heat insulating material.

In the figure, a horseshoe-shaped permanent magnet 3 is installed outside a pipe 2 through which a conductive fluid 1 flows, a magnetic field is applied perpendicular to the direction of fluid flow, and the induced electromotive force is measured with a detection electrode 5.6. Measurements can be taken.

[Problems to be solved by the invention]

However, when a conventional electromagnetic flowmeter is scaled up and installed in a large-diameter piping of a large fast reactor main cooling system, the installation space and weight increase due to the increase in the size of the flowmeter itself, and the flowmeter cannot be manufactured due to the increase in size. This will lead to an increase in costs and construction costs, and it will also be necessary to consider earthquake resistance. In addition, straight pipe lengths are required upstream and downstream of the flowmeter, which causes problems such as four turns of piping and uneven magnetic flux distribution.

As shown in Figure 6, the linearity of an electromagnetic flowmeter becomes larger as the diameter becomes larger. As shown in Figure 6, the relationship between flow rate and output becomes more isolated from the proportional relationship as the flow rate increases. Curve B shows the output of a large-diameter electromagnetic flowmeter. Moreover, large diameter 1i
Practical calculation codes for magnetic flowmeters have not been found, and it is necessary to perform actual flow calibration on the same scale as the plant before installation, which increases costs.

The present invention is intended to solve the above problems, and can be installed in large-diameter pipes such as soil cooling systems for large fast reactors.Moreover, the flowmeter manufacturing cost and construction cost can be reduced, and it can be made smaller and lighter. In addition, on-site calibration is possible, and flow rate calibration can be performed on a small scale before plant installation, minimizing the influence of the straight pipe length of the flowmeter and improving linearity. The purpose of this invention is to provide a flowmeter with a rectifier tube.

[Means for solving problems]

To this end, the flowmeter with a rectifier tube of the present invention is characterized in that a rectifier tube is disposed within a pipe through which a conductive fluid flows, and an eddy current type current meter is inserted into a tube directly facing the rectifier tube.

[Effect]

The flowmeter with a rectifier tube of the present invention arranges a rectifier tube in the piping,
By measuring the rectified fluid flow in the rectifier pipe with an eddy current flowmeter, the flow rate of large diameter pipes can be measured with good linearity using a compact and inexpensive flowmeter.

〔Example〕

Examples will be described below with reference to the drawings.

FIG. 1 is a diagram showing an embodiment of a flowmeter with a rectifier tube according to the present invention, in which 10 is a large-diameter pipe, 11 is a rectifier tube, 12 is a support, 13 is an eddy current flow meter, 14 is a guide tube, and 15 is a support tube. The support, 16 is a conductive fluid, and 17 is a lead wire.

In the figure, a rectifier pipe 11 for rectifying a conductive fluid is inserted into a large-diameter pipe 10 in an earth cooling system for a large fast reactor, etc.
The rectifier tube 11 is fixed to the piping 10 via a support 12. Then, the main tube 14 is inserted from the downstream side of the rectifier tube 11 and supported within the rectifier tube by the support 15, and the eddy current type current meter 13 is further inserted therein. In this way, large diameter piping l
A rectifier tube 11, a current meter 13, and a current meter guide tube 14 are inserted as a set into the inside. The current meter 13 detects the speed of the rectified flow in the rectifier tube 11 based on the principle explained below. The rectifying pipe 11 is used to obtain a flow velocity distribution suitable for measurement by a rectifying effect even if the flow condition in the large-diameter pipe is poor. If the flow velocity is determined by the eddy current type current meter 13, the flow rate can be measured since the cross-sectional area of the pipe is known.

FIG. 2 is a diagram showing the measurement principle of the eddy current type current meter 13 shown in FIG. 1, where 20 is a detector, 21 is an exciting coil, 22.23 is a detection coil, and 24.25 is a magnetic flux distribution.

In the figure, a detector 20 placed in a conductive fluid consists of an excitation coil 21 and two detection coils 22, 23.

When the fluid F is stationary, the alternating current magnetic field created by the excitation coil 21 has a magnetic flux φ that is distributed symmetrically in the axial direction, as shown by the solid line 24 in the figure. When the fluid moves in the direction of the arrow, the magnetic flux φ is distorted in the direction of flow and becomes like the broken line 25.

Therefore, the voltage S induced in the upstream detection coil 22
, and the voltage St induced in the downstream detection coil 23, a signal eF dependent on the flow velocity is obtained. Note that the present invention is not limited to the three-coil type shown in the figure, but may also be a five-coil type in which excitation coils are arranged at both ends of the detection coil.

Figures 3 (a), (b), and (c) are diagrams showing an embodiment in which a plurality of flowmeters shown in Figure 1 are installed in a pipe, and depending on the purpose of use, (a), (b), and (c) are By arranging three, four, five, etc. in combination as shown in ) and (c), it is possible to perform more accurate measurements that take into account the flow velocity distribution in the large-diameter pipe.

By the way, when an eddy current flowmeter is installed in a large-diameter pipe such as a large fast reactor main cooling system, it is necessary to periodically check subsequent changes in the characteristics of the flowmeter and calibrate the flowmeter. Therefore, the flow fluctuation correlation method, which calculates the flow rate from the interaction of turbulence caused by turbulent flow in piping, that is, the flow fluctuation, is applied to the eddy current type current meter, and the on-site calibration of the current meter (flowmeter) is carried out as follows. will be considered.

Flow fluctuations are caused by minute temporally irregular signals (
If the fluctuation signal is observed at two observation points along the flow and the cross-correlation between the two is determined, the time taken for the flow fluctuation to move between the two points along the flow can be obtained. The moving speed of the flow fluctuation matches the fluid speed,
Alternatively, if there is a proportional relationship, the transition time of the observed flow fluctuation is inversely proportional to the flow rate, and if the effective distance between observation points is given, the transition speed of the flow fluctuation can be found by dividing this by the transition time.

In the flow fluctuation correlation method, two detectors are required along the flow, but if two detectors of the 3-coil type shown in Fig. 2 are installed along the flow inside the rectifier tube, the first detector and Since the flow velocity can be determined by the second sensor,
This allows for on-site calibration of current meters (flow meters). In this case, it is not limited to a 3-coil type, but a plurality of 5-coil types, or a combination of a 3-coil type and a 5-coil type may be used.

Furthermore, if multiple current meters are installed along the current flow in the current meter guide pipe and output is obtained independently from each one, when applied to the main cooling system of a large fast reactor, independent safety protection of the main cooling system can be achieved. Multiple, mutually independent flowmeter measurement circuits can be provided that are compatible with system multiplexing.

〔Effect of the invention〕

As described above, according to the present invention, a rectifying pipe is provided in a large-diameter pipe, and an eddy current flowmeter is arranged therein, so that the manufacturing cost of a large-diameter flowmeter can be significantly reduced. In addition, the manufacturing cost does not increase even if the pipe diameter increases.

Furthermore, since the weight of the flowmeter can be reduced, the amount of piping required can be reduced, and the length of straight pipes can also be reduced, so construction costs can be reduced. In addition, calibration of the flowmeter before plant installation only needs to be carried out on the currentmeter alone, and there is no need for a large-scale calibration device comparable to the actual scale. Since it is easy to remove, maintainability is improved. In addition, since it passes through a rectifier pipe, there is little effect on the current meter output signal due to fluctuations in the flow in the pipe, and a stable output can be obtained. By having multiple current meters inserted into the current meter guide pipe, on-site calibration is possible. Multiple, mutually independent flow measurement circuits compatible with multiplexing of safety protection systems can be provided.

[Brief explanation of drawings]

Fig. 1 is a diagram showing an embodiment of the flowmeter with rectifier tube according to the present invention, Fig. 2 is a diagram for explaining the measurement principle of the flowmeter shown in Fig. 1, and Fig. 3 is a diagram showing the rectifier of Fig. 1. Figure 4 is a diagram illustrating the measurement principle of an electromagnetic flowmeter. Figure 5 is a diagram showing the configuration of a conventional electromagnetic flowmeter. FIG. 6 is a diagram showing the output characteristics of a large-diameter electromagnetic flowmeter. 10... Large diameter pipe, 11... Rectifier pipe, 12...
Support, 13... Eddy current type current meter, 14... Guide tube, 15... Support, 16... Conductive fluid, 17
...Lead wire, 20...Detector, 21...Excitation coil, 22.23...Detection coil, 24.25...
Magnetic flux distribution. Applicant Masanobu Hirugawa (2 others, patent attorney representing the Power Reactor and Nuclear Fuel Development Corporation) Figure 1 Figure 3 Figure 4 Figure 5 Figure 6 Flow rate

Claims (3)

[Claims] (1) A flowmeter with a rectifier tube, characterized in that a rectifier tube is arranged in a pipe through which a conductive fluid flows, and an eddy current type current meter is inserted into a guide tube arranged in the rectifier tube. (2) A flowmeter with a rectifier tube according to claim 1, wherein a plurality of combinations of a rectifier tube and an eddy current type current meter are arranged in the pipe. (3) The eddy current type current meter inserted into the guide tube is 3
The rectifier tube according to claim 1 or 2, characterized in that the rectifier tube is composed of a single coil, a 5-coil type, a plurality of coils, or a combination of 3-coil and 5-coil types. Flowmeter.