JP2002071399A - Flow rate using optical loop interferometer or flow rate measurement method and device thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and device for measuring the flow rate or flow velocity with an inexpensive and simple configuration by eliminating the need for a power supply at a flow rate measurement location, and increasing the distance between a measuring device body and the measurement location. SOLUTION: By using the optical loop interferometer, a loop-like optical fiber in the optical loop interferometer is made to vibrate according to the rotary speed of a vane that is rotated by fluid to generate a change in the intensity of interference light, and the flow rate or the flow velocity of the fluid is measured, based on the generation interval of a signal for indicating the change in the intensity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for measuring a flow rate or a flow rate of a fluid using an optical fiber loop interferometer, and more particularly to an optical fiber loop interference method using an impeller for measuring the flow rate or wind speed of a sewer. The present invention relates to a method and an apparatus for measuring a water amount, a wind speed, and the like by exciting a sensor section of a meter.

[0002]

2. Description of the Related Art As a conventional technique for measuring a flow rate, a method of measuring a flow rate by detecting a rotation speed and a rotation direction of an impeller by utilizing light reflection using one or a pair of optical fibers. An optical fiber is placed in the flow, the frequency-modulated light in the optical fiber passes through, and the force applied to the optical fiber by the vortex of the flow detects the phenomenon in which the width of the light pulse that has passed through the optical fiber decreases, and the flow rate is measured. How to do. A method of measuring flow using a conventional electromagnetic flow meter or ultrasonic flow meter. And the like.

[0003]

The above-mentioned prior art uses weakly reflected light from the impeller and is weak light and has a problem in extending the measurement distance.

[0004] In the above, it is necessary to install a measuring device main body at a measurement (observation) place, and a high level of waterproof measures is required because a power supply is used, which has an effect on cost, maintenance, management and the like. In addition, there is a problem that the measurement unit (sensor unit) cannot be installed at a place away from the apparatus main body.

[0005] The present invention provides a method and an apparatus in which a power source is abolished at a measurement place, the distance between the apparatus main body and the measurement place can be increased, and a flow rate can be measured with an inexpensive and simple configuration. It is.

[0006]

According to the present invention, there is provided a method for measuring a flow rate or a flow velocity using an optical loop interferometer. And the clockwise light and the counterclockwise light propagated through the loop-shaped optical fiber are coupled by the optical branching coupling element, made incident on the light receiving element, and rotated by the fluid. By vibrating the loop-shaped optical fiber according to the rotation of the impeller, a change occurs in the intensity of the interference light due to the phase difference between the clockwise light and the counterclockwise light output by the light receiving element, and this intensity is changed. The flow rate or the flow rate of the fluid is measured based on the change of the fluid.

A flow rate or flow velocity measuring apparatus using an optical loop interferometer according to the present invention comprises at least a light-emitting element, a light-receiving element, a loop-shaped optical fiber, an optical branch connected to the light-emitting element, the light-receiving element, and both ends of the loop-shaped optical fiber. It has a coupling element and a vibrating means for a loop-shaped optical fiber that operates by being transmitted to the rotation of the impeller rotating by a fluid.

Further, a flow rate or flow velocity measuring apparatus using the optical loop interferometer according to the present invention is characterized by having at least a flow rate or flow velocity measuring circuit.

The vibrating means vibrates the loop-shaped optical fiber by the rotational motion of the vibrating rod transmitted to the rotation of the impeller.

Further, the vibration means vibrates the loop-shaped optical fiber by the motion of the vibration rod converted from the rotational motion of the impeller into the vertical motion.

Further, the vibrating means is configured such that a vibrating rod which engages with the rotation of the impeller to follow and urges a spring, and the vibrating force is applied by the spring when the engagement is released. The shaking rod gives a shock to the loop-shaped optical fiber.

With the above configuration, the light output from the light emitting element of the main body is branched clockwise and counterclockwise by the optical branching / coupling element, passes through the same optical path length, and is coupled by the optical branching / coupling element. Is incident on the light receiving element of the main body.
At this time, since the two lights clockwise and counterclockwise have the same optical path length, the light detected by the light receiving element is in a certain interference state. When the vibrating rod impacts the looped optical fiber with the impeller rotated by the air volume and water volume,
As the optical path length changes, the constant interference state changes. The change can be detected by the light receiving element.

When the rotation speed of the impeller changes due to the amount of air or water, the interval between shocks applied to the loop-shaped optical fiber by the vibrating rod also changes, and the light receiving element detects a change in interference according to the rotation speed of the impeller. . Therefore, by measuring the interval of the change of the interference, the air volume and the water volume can be measured.

When the impeller is placed in the middle of the flow of the fluid, the impeller rotates by the velocity energy of the fluid. Since the rotation speed of the impeller at this time is almost proportional to the speed of the fluid, the flow rate can be obtained from the rotation speed of the impeller.

That is, assuming that one impact is given to the optical fiber by one rotation of the impeller, the interval between changes of the interference light is represented by t.
If i (sec), the rotation speed of the impeller becomes 1 / ti ^rps , and the flow velocity v (m / s) of the fluid becomes k / ti. Note that k is a constant determined by the state of the impeller.

Sectional area of pipe through which fluid is flowing = A (m
² ), the flow rate Q (m ³ / s) is: Q = Av = A (m ² ) · k / ti (m / s) = kA / t
i (m ³ / s).

Although the present invention has been described with reference to the measurement of the flow rate of a fluid, it also includes the measurement of the flow rate of a fluid.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a flow rate or flow velocity measuring device using an optical loop interferometer according to a second aspect of the present invention. In the figure, laser light emitted from a light emitting element (laser light source) 1 excited by a drive circuit 10 is:
The light propagates through the optical fiber cable 2 and is incident on the branching / coupling element 3. The branching / coupling element 3 branches the light in the clockwise direction A and the counterclockwise direction B and makes the light enter both ends of the loop-shaped optical fiber 4. The light propagating in the direction A and the light propagating in the direction B reach the respective opposite ends of the loop-shaped optical fiber 4 and are then coupled by the branch coupling element 3 to propagate through the optical fiber cable 2 and receive the light receiving element 5. Is incident on. At this time, the two lights in the clockwise direction A and the counterclockwise direction B propagate on the same optical path, and have a certain phase difference and the branch coupling element 3
Are combined and detected by the light receiving element 5, so that the combined light is in a certain interference state. The impeller 103 rotated by the fluid (air volume, water volume, etc.)
When the exciting rod 6 transmitting to the optical fiber 3 gives an impact to the loop-shaped optical fiber 4, the loop-shaped optical fiber 4 is bent, so that the optical path length changes and the phase of the propagating light changes to be constant. The interference state changes. If there is a difference in the propagation time between the direction A and the direction B of the phase change, the same phase change occurs in the coupled light, and when this change is detected by the light receiving element 5,
An electric signal having an amplitude corresponding to the phase change of the combined light, that is, the magnitude of the shock is output.

When the rotation speed of the impeller 103 changes according to the flow rate of the fluid, the interval of the impact applied by the vibrating rod 6 to the loop-shaped optical fiber 4 also changes, and the light receiving element 5 causes interference light according to the rotation speed of the impeller 103. Is detected.

The flow rate of the fluid is measured by measuring the interval of the change of the interference light (see FIG. 3).

As the device, the light receiving element 5 detects the light as interference light, and the photoelectric conversion is performed by the light receiving element 5, the electric signal is converted into an electric signal corresponding to the light intensity. Output to The flow rate measuring circuit 12 measures the interval of the signal indicating the change of the input interference light, and obtains the flow velocity and the flow rate of the fluid. These are digitally processed by the CPU in the measuring circuit. Reference numeral 101 denotes an apparatus main body, and reference numeral 102 denotes a sensor unit.

FIG. 2 is a block diagram showing a configuration of a flow rate or flow velocity measuring device using a loop interferometer according to another embodiment of the present invention. The difference from FIG. The branch coupling element 3 is accommodated, and the sensor unit 102
Optical fiber 7 provided by extending the loop optical fiber 4 of FIG.
Was connected to the branch coupling element 3. Although the optical delay element 8 is provided in the sensor unit 102, it is not an essential component.

The operation of FIG. 2 is the same as that of FIG. 1 described above, and a description thereof will be omitted. However, the operation of FIG. 2 is applied to a case where no vibration or impact is applied to the optical fiber 7 between the apparatus main body 101 and the sensor 102.

In FIG. 1 or FIG. 2, a configuration is adopted in which a shock is directly applied to the loop optical fiber 4 by the vibrating rod 6, but the present invention is not limited to this configuration. Even if the optical fiber 4 is housed in a cable or a protection pipe or the like, and an impact is applied to the jacket of the cable or the protection pipe with a vibrating rod, an impact is indirectly applied to the loop-shaped optical fiber 4. Good. In this case, all of the loop-shaped optical fibers 4 may be accommodated in the cable or the protection pipe or the like, or at least a part thereof may be accommodated.

Next, embodiments of the impeller and the vibration means according to the present invention will be described.

FIG. 4 shows an example of an impeller used for measuring the flow velocity and flow rate of a gas or liquid. In the figure, the impeller 40 is rotated by the impact of the fluid flowing from the inlet A. Since the rotation speed is proportional to the inflow speed if the flow rate is high to some extent, the rotation speed of the impeller 40 is integrated to measure the volume (flow rate) of the passing fluid. The excitation rod is attached to the rotating shaft 41 of the impeller.

Next, an embodiment of the vibrating rod 6 which operates by transmitting the rotation of the impeller 103 will be described. 5 to 7 are image diagrams for explaining the relationship between the windmill and the excitation rod.
FIG. 4 is an explanatory view showing one embodiment. In FIG. 5, a vibrating rod 6 is attached in a direction orthogonal to a rotation shaft 51 of a wind turbine 50. In addition, 6a is a head and 6b is a spring. In this case, one impact is applied to the loop-shaped optical fiber 4 for each rotation of the wind turbine 50.

FIG. 6 is an explanatory view showing another embodiment. In FIG. 6, four projections 62 are radially provided on the rotation shaft 61 of the wind turbine 60 so as to be engaged with the projections 6 c provided on the vibrating rod 6. The vibrating rod 6 is slidably supported by a support member 63 so as to be able to drop vertically to the optical fiber 4. In this case, the impact is applied to the loop-shaped optical fiber 4 four times for each rotation of the wind turbine 60.

FIG. 7 is an explanatory view showing another embodiment. In FIG. 7, four screw-shaped pieces 71 are provided on the outer periphery of the windmill 70, and follow the rotation of the windmill 70 by a rod 72 integrated with the vibrating rod 6 engaged with the screw-shaped piece 71. . The vibrating rod 6 is fixed to the rotating shaft 73, and a spring is provided between the fixed shaft 74 and the rotating shaft 73, and when the rod 72 moves along the screw-shaped piece 71, the spring is biased. When the rod 72 comes off the end of the screw-shaped piece 71, the vibrating rod 6 gives an impact to the loop-shaped optical fiber 4 by the biased spring. In this embodiment, one of the windmills 70
The impact is applied to the loop-shaped optical fiber 4 four times for each rotation.

[0030]

As described above, according to the present invention, there is provided a method and an apparatus for measuring a flow rate or a flow velocity with a simple and inexpensive structure, which can simplify the structure because no power supply is required for the sensor section, does not require waterproofing measures, and is simple. can do.

Further, since the distance between the main body of the apparatus and the sensor section can be increased by an optical fiber cable, the execution range of flow rate or flow velocity measurement using an optical loop interferometer has been greatly expanded.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of one embodiment of a flow rate or flow velocity measuring device using an optical loop interferometer of the present invention.

FIG. 2 is a block diagram showing a configuration of another embodiment of a flow rate or flow velocity measuring device using the optical loop interferometer of the present invention.

FIG. 3 is an explanatory diagram showing a change interval of interference light according to the present invention.

FIG. 4 is an explanatory diagram showing an example of an impeller used for measuring the flow velocity and flow rate of a gas or liquid according to the present invention.

FIG. 5 is an explanatory diagram of one embodiment showing a relationship between a windmill and a vibrating rod according to the present invention.

FIG. 6 is an explanatory diagram of another embodiment showing a relationship between a windmill and a vibrating rod according to the present invention.

FIG. 7 is an explanatory view of another embodiment showing a relationship between a windmill and a vibrating rod according to the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 light emitting element 2 optical fiber cable 3 branch coupling element 4 loop optical fiber 5 light receiving element 6 vibrating rod 7 optical fiber 8 optical delay element 10 drive circuit 11 amplifier circuit 12 flow rate measurement circuit 40, 103 impeller 50, 60, 70 Wind turbine 101 Flow measurement device main body 102 Flow measurement device sensor

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Toru Takashima 1440, Mukurosaki, Sakura-shi, Chiba Prefecture Fujikura Co., Ltd. Sakura Office, Chiba Pref. 2F030 CA02 CC09 CC11 CG01 2F064 AA00 AA11 FF00 GG00 GG02 GG17 HH01

Claims (3)

[Claims] 1. A light output from a light-emitting element is branched into a loop-shaped optical fiber from both ends of an open portion thereof by an optical branching coupling element and propagates clockwise and counterclockwise, and propagates through the loop-shaped optical fiber. The clockwise light and the counterclockwise light are coupled by the light branching / coupling element and made incident on the light receiving element, and the loop-shaped optical fiber is vibrated in accordance with the rotation of the impeller rotated by the fluid, so that the light receiving element Causing a change in the intensity of the interference light due to the phase difference between the clockwise light and the counterclockwise light outputted by the optical loop, and measuring the flow rate or the flow velocity of the fluid based on the change in the intensity. A flow rate or flow velocity measuring method using an interferometer. 2. A light-emitting element, a light-receiving element, a loop-shaped optical fiber, an optical branching / coupling element connecting the light-emitting element, the light-receiving element, and both ends of the loop-shaped optical fiber, and transmission to rotation of an impeller rotated by a fluid. And a vibrating means for the loop-shaped optical fiber operating as follows: a flow rate or flow velocity measuring device using an optical loop interferometer. 3. The flow rate or flow velocity measuring apparatus using an optical loop interferometer according to claim 2, further comprising at least a flow rate or flow velocity measuring circuit.