JP5115927B2 - Optical fiber probe bubble measuring device and method - Google Patents

Description

  The present invention relates to all industrial equipment having a flow phenomenon in which gas and liquid are mixed, such as a nuclear reactor, a bioreactor, a heat exchanger, and a gas-liquid reaction apparatus. The present invention relates to an apparatus and method capable of simultaneously measuring volume ratios and the like with high accuracy.

  2. Description of the Related Art Conventionally, a technique for measuring bubbles by arranging an optical fiber probe in a liquid in a mainstream direction of a gas-liquid two-phase flow and detecting a change in the amount of reflected light in the optical fiber probe is known. However, in the conventional bubble measurement technique, in order to simultaneously measure the bubble interface velocity and the bubble chord length, a plurality of probes must be separated and used at predetermined intervals. However, in such a multipoint probe, there is a limit to the minimum bubble diameter that can be measured due to geometric constraints. In order to solve such a problem, the present inventor has developed a bubble measuring method and apparatus using a single probe as disclosed in Patent Document 1. In this bubble measurement technique, an optical fiber having an end surface inclined with respect to a direction perpendicular to the fiber axis is used as a bubble detection probe, and a bubble as a measurement object is reflected by the end surface when passing through the end surface. Measuring the change in the amount of light, and simultaneously obtaining the translation speed, interface speed, bubble chord length, and / or bubble volume ratio of the bubble based on the measurement results. It was impossible to measure bubbles with high accuracy.

In addition to Patent Document 1, there is Patent Document 2 as a conventional technique. Similarly to Patent Document 1, Patent Document 2 is a prior art by the present inventors. This document describes a bubble detection probe that measures the bubble translation speed, interface velocity, bubble chord length, and bubble volume ratio using a fiber having a tip end inclined.
JP 2000-136962 A JP 2006-226703 A

  Since the bubble approaches the probe from an arbitrary place, the center of the bubble does not necessarily pass through the tip of the probe. However, with the conventional bubble measurement techniques such as Patent Documents 1 and 2, it is difficult to grasp the contact position between the tip of the optical fiber probe for detecting bubbles and the bubbles. When the probe comes into contact with the end of the bubble, the bubble chord length, bubble diameter, interface speed, bubble volume ratio, etc. cannot be determined accurately. Therefore, in order to obtain these accurately, it is necessary to measure the change in the amount of reflected light when the center of the bubble passes through the probe tip after detecting the contact state between the probe tip and the bubble.

  In view of the above problems, in the bubble measurement using the optical fiber probe, the present invention also includes the contact state between the probe tip and the bubble in order to accurately obtain the bubble chord length, bubble diameter, interface velocity, bubble volume ratio, etc. An object of the present invention is to provide an optical fiber probe bubble measuring device and method that can be detected.

In order to achieve the above object, the present invention has the following configuration.
An optical fiber probe comprising an optical fiber having a first end face inclined at least partially with respect to a direction perpendicular to the fiber axis, wherein the first end face is disposed in the liquid;
Light supply means for supplying light from the second end surface opposite to the first end surface of the optical fiber;
Reflected light quantity measuring means for measuring the reflected light quantity, wherein the light supplied by the light supply means is reflected by the first end face and returns to the second end face;
A signal processing means for measuring bubbles in the liquid based on the measurement result of the reflected light amount, and a bubble measuring device comprising:
The signal processing means further includes means for determining a contact state between the first end face and the bubble based on a pre-signal of the reflected light amount generated before the first end face comes into contact with the bubble.
Bubble measuring device.
Using an optical fiber probe comprising an optical fiber having a first end face that is at least partially inclined with respect to a direction perpendicular to the fiber axis, wherein the first end face is disposed in a liquid;
A light supplying step of supplying light from a second end surface opposite to the first end surface of the optical fiber;
A reflected light amount measuring step of measuring a reflected light amount, wherein the light supplied by the light supplying step is reflected by the first end surface and returns to the second end surface;
A contact state determination step of determining a contact state between the first end surface and the bubble based on a pre-signal of the reflected light amount generated before the first end surface contacts the bubble;
A bubble measurement method comprising: a bubble measurement step of measuring bubbles in the liquid based on a determination result of the contact state determination step and a measurement result of the amount of reflected light.

Moreover, there may exist the following as preferable embodiment.
The optical fiber probe is composed of a plurality of optical fibers arranged close to each other, and the signal processing unit determines a contact state between the first end surface and the bubbles based on a measurement result of the amount of reflected light from the plurality of optical fibers, Bubbles in the liquid are measured.
The optical fiber probe is composed of two optical fibers arranged close to each other, and the two optical fibers are arranged back to back so that the inclined directions of the first end faces are opposite to each other, The signal processing means measures bubbles in the liquid when a pre-signal is detected by both of the amounts of light reflected from the two optical fibers.
The signal processing means simultaneously measures at least two of the bubble chord length, bubble diameter, interface speed, and bubble volume ratio of bubbles in the liquid.

Since the present invention employs the above configuration, in the bubble measurement using the optical fiber probe, in order to accurately obtain the bubble chord length, bubble diameter, interface speed, bubble volume ratio, etc., the contact state between the probe tip and the bubble is also determined. It can also be detected. Since the tip (first end surface) of the optical fiber probe is in the liquid, the difference in refractive index between the probe tip surface and the liquid is small, and light leaks from the probe tip into the liquid. When the bubble approaches, the leaked light is reflected on the bubble surface and is observed as a “pre-signal” before the probe tip contacts the bubble. Since this pre-signal differs depending on the contact state (contact position, contact angle) between the probe tip and the bubble, the contact state between the probe tip and the bubble can be determined by observing this pre-signal. If the contact state between the probe tip and the bubble is known, it can be determined whether the bubble center is in contact with the probe tip. Using the measurement result of the amount of reflected light at this time, the bubble chord length, bubble diameter, interface Speed, bubble volume ratio, etc. can be accurately measured.
Furthermore, if a plurality of optical fibers arranged close to each other are used as optical fiber probes, the inclination directions of the plurality of optical fibers can be made different even if the tip direction of each optical fiber is only one direction. Signal "can be detected. Thereby, the contact state between the probe tip and the bubble can be detected more easily and accurately.

Hereinafter, preferred embodiments of the present invention will be described.
The bubble detection unit (first end surface) of the bubble detection optical fiber probe used in this embodiment is formed by combining optical fibers having end surfaces inclined with respect to a direction perpendicular to the fiber axis back to back as shown in FIG. Has been. Moreover, it is desirable to change the distance between the detection parts of the front-end | tip part with the bubble diameter which is a measuring object. The rear end of the optical fiber, that is, the end face (second end face) in the light input / output unit is preferably formed perpendicular to the fiber axis. A laser light source can be used as a light source for supplying light to the bubble detection portion of the bubble detection optical fiber probe. The light quantity measuring means for measuring the change in the quantity of light reflected from the detection unit can be appropriately used as long as it can measure the reflected light quantity. For example, a photomultiplier tube, a phototransistor, or the like is used. The

  FIG. 1 is a two-point optical fiber probe in which optical fibers having end faces inclined with respect to the fiber axis are combined back to back, and the structure of an optical fiber for detecting bubbles using each tip portion of the optical fiber as a detection unit. It is shown. In FIG. 1, the upper side is a top view and the lower side is a side view. The tip (first end face) of the bubble detection optical fiber 1 is composed of a first bubble detection optical fiber tip (bubble detection unit) 2 and a second bubble detection optical fiber tip (bubble detection unit) 3 at a position about 200 μm apart. Combined. On the other hand, the rear end (second end face) of the bubble detection optical fiber 1, that is, the light input / output end face 6, has an angle of 90 degrees between the light input / output end face 6 and the fiber axis in both of the two bubble detection optical fibers. It is formed as follows. The diameter of the optical fiber for bubble detection 1 of this embodiment is about 230 μm.

  The optical system of the present embodiment will be described with reference to FIG. In the first bubble detection optical fiber, the light emitted from the light source 8 passes through the beam splitter 9, is collected by the lens 10, enters the bubble detection optical fiber 1 from the rear end 6 thereof, and enters the bubble detection unit 2. Reach. The light reaching the bubble detection unit 2 is reflected by the end face, returns through the optical fiber, passes through the lens 10, changes its traveling direction by the beam splitter 9, passes through the polarizer 11 for removing scattered light, and passes through the photomultiplier tube. 12 and the amount of light is measured. The second bubble detection optical fiber is the same except that the bubble detection unit 3 detects bubbles, and each output signal is measured.

  An example of a signal processing system for the measured light quantity is shown in a schematic block diagram in FIG. A light quantity measuring device 17 comprising a photomultiplier tube 12, an output amplifier and high-voltage DC application circuit 13, an amplifier power supply 14, a DC voltage 15, and a photomultiplier tube shield case 16, an A / D converter 18, a personal computer 19 A signal processing system is constituted by the arithmetic unit 20 constituted by

The optical fiber probe of this embodiment is installed and used in parallel with the main flow direction of the gas-liquid two-phase flow. The light incident into the optical fiber probe reaches the bubble detection unit of the optical fiber probe, is reflected by the bubble detection unit, and returns through the optical fiber. When the bubble detection unit is in the liquid, the light in the fiber is emitted into the liquid. Therefore, almost no light is reflected by the bubble detector, and almost no light is detected by the photomultiplier tube. When the bubble that has advanced from the upstream of the optical fiber probe contacts the tip that is the bubble detection unit 2 of the first bubble detection optical fiber probe, the amount of light reflected by the bubble detection unit increases due to the difference in refractive index between the gas and the liquid, The amount of light returning inside the first bubble detection optical fiber probe increases, and the amount of light detected by the photomultiplier tube increases. Furthermore, when the bubble comes into contact with the bubble detection unit 3 of the second bubble detection optical fiber probe, the amount of light reflected by the bubble detection unit increases and the amount of reflected light in the optical fiber increases. Thereafter, the bubble interface passes through and leaves the first bubble detection optical fiber and the second bubble detection optical fiber to come into contact with the liquid, the amount of reflected light decreases, the amount of light returning inside the optical fiber decreases, and the photoelectron increases. The amount of light detected by the double tube decreases. The reflected light amount change pattern measured by the photomultiplier tube depends on the distance between the first bubble detection optical fiber and the second bubble detection optical fiber and the bubble diameter which is a measurement object. When the distance L _P between the tip of the air-bubble detector 3 at the tip of the air-bubble detector 2 of the first bubble detection optical fiber and a second bubble detection optical fiber, the cell diameter that is the measuring object and D _B, L _P> the light amount change pattern for D _B Figure 2 shows it in the case of L _P <D _B in FIG. From the figure, it can be seen that a pre-signal, which is reflected light from the bubble surface, is observed prior to a change in the amount of reflected light accompanying bubble contact.

  The principle of pre-signal generation is shown in FIG. When the bubble detection part of the optical fiber is in the liquid, the reflected light is radiated in the liquid, and when the bubble advances from the upstream of the optical fiber probe, the relationship between the bubble detection part and the bubble contact position causes the liquid to enter the liquid. There is a case where the emitted light returns to the bubble detection unit. In this case, a pre-signal is generated before the bubble detection unit and the bubble contact. In the conventional single optical fiber probe, as shown in FIG. 4, a pre-signal is seen even when it does not contact the center of the bubble. This is only when the bubble is in contact with the center of the bubble, so that the contact position can be determined, and bubble measurement can be performed with higher accuracy than in the past. The relationship between the two-point optical fiber and the bubble contact position is shown in FIG.

となる。さらに、第１気泡検出光ファイバー接触終了時間をt₃とすると、（t₃-t₁）間の気泡移動距離は気泡弦長L_Bに等しい。よって、

となる。即ち、本光ファイバープローブで気泡の中心に接触した気泡のみの気泡界面速度、気泡並進速度及び気泡弦長を計測することができる。また、気泡体積率は光ファイバープローブ検出端面が気泡に覆われていた時間と全計測時間の比により求めることができる。上記の演算は、パーソナルコンピュータ等公知の演算手段を用いて演算させることができる。 The bubble interface velocity can be calculated from the reflected light amount change and the contact start time difference between the first bubble detection optical fiber and the second bubble detection optical fiber. Therefore, if the difference in the distance between the first bubble detection optical fiber and the second bubble detection optical fiber is L _P , the first bubble detection optical fiber contact start time is t ₁ , and the second bubble detection optical fiber contact start time is t ₂ , the bubble interface velocity. U _B

It becomes. Furthermore, if the first bubble detection optical fiber contact end time is t ₃ , the bubble moving distance between (t ₃ -t ₁ ) is equal to the bubble chord length L _B. Therefore,

It becomes. That is, it is possible to measure the bubble interface velocity, bubble translation speed, and bubble chord length of only the bubble that is in contact with the center of the bubble with this optical fiber probe. The bubble volume ratio can be obtained from the ratio of the time during which the detection end face of the optical fiber probe was covered with bubbles to the total measurement time. The above calculation can be performed using known calculation means such as a personal computer.

Although an example of the embodiment of the present invention has been described above, the present invention is not limited to this, and it goes without saying that various modifications can be made within the scope of the technical idea described in the claims. Yes. For example, in the above-described embodiment, an example in which two optical fibers are used as a probe is shown. However, if the shape of the bubble detection unit (first end surface) is devised even with a single optical fiber, contact between the bubble and the bubble detection unit by pre-signaling It is possible to detect the state.

It is a figure which shows the structure of the optical fiber for bubble detection which combined the optical fiber which has an end surface inclined with respect to the direction perpendicular | vertical to an axis | shaft back to back. In the case of L _P > D _B , this is an example of a change in the amount of reflected light detected by the bubble detection optical fiber. In the case of L _P <D _B , this is an example of a change in the amount of reflected light detected by the bubble detection optical fiber. It is an example of pre-signal generation conditions. It is an example of the relationship between the contact position of the bubble by a two-point optical fiber probe, and an output signal. It is the schematic of the Example which introduces the light from a light source into the optical fiber for bubble measurement, and measures the light quantity detected with the same optical fiber. It is a schematic block diagram of the signal processing system of the light quantity detected with the optical fiber for bubble detection.

Explanation of symbols

1: Bubble detecting optical fiber probe 2: Bubble detecting portion (first end face) of the first bubble detecting optical fiber
3: Bubble detection part (first end face) of the second bubble detection optical fiber
4: Clad portion in the optical fiber for detecting bubbles 5: Core portion in the optical fiber for detecting bubbles 6: Light input / output end face (second end face)
8: Light source 9: Beam splitter 10: Lens 11: Polarizer 12: Photomultiplier tube 13: Output amplifier and high-voltage DC application circuit 14: Amplifier power supply 15: DC voltage 16: Photomultiplier tube shield case 17: Light quantity measuring device 18: A / D converter 19: Personal computer 20: Arithmetic unit

Claims (5)

An optical fiber probe comprising an optical fiber having a first end face inclined at least partially with respect to a direction perpendicular to the fiber axis, wherein the first end face is disposed in the liquid;
Light supply means for supplying light from the second end surface opposite to the first end surface of the optical fiber;
Reflected light quantity measuring means for measuring the reflected light quantity, wherein the light supplied by the light supply means is reflected by the first end face and returns to the second end face;
A signal processing means for measuring bubbles in the liquid based on the measurement result of the reflected light amount, and a bubble measuring device comprising:
The signal processing means further includes means for determining a contact state between the first end face and the bubble based on a pre-signal of the reflected light amount generated before the first end face comes into contact with the bubble.
Bubble measuring device. The optical fiber probe is composed of a plurality of optical fibers arranged close to each other,
The signal processing means determines a contact state between the first end surface and the bubbles based on a measurement result of the amount of reflected light from the plurality of optical fibers, and measures bubbles in the liquid.
The bubble measuring device according to claim 1. The optical fiber probe consists of two optical fibers arranged close to each other,
The two optical fibers are arranged back to back such that the inclined directions of the respective first end faces are opposite to each other,
The signal processing means measures bubbles in the liquid when a pre-signal is detected by both reflected light amounts from the two optical fibers.
The bubble measuring device according to claim 2. The signal processing means simultaneously measures at least two of bubble chord length, bubble diameter, interface velocity, bubble volume ratio of bubbles in the liquid,
The bubble measuring device according to claim 1. Using an optical fiber probe comprising an optical fiber having a first end face that is at least partially inclined with respect to a direction perpendicular to the fiber axis, wherein the first end face is disposed in a liquid;
A light supplying step of supplying light from a second end surface opposite to the first end surface of the optical fiber;
A reflected light amount measuring step of measuring a reflected light amount, wherein the light supplied by the light supplying step is reflected by the first end surface and returns to the second end surface;
A contact state determination step of determining a contact state between the first end surface and the bubble based on a pre-signal of the reflected light amount generated before the first end surface contacts the bubble;
A bubble measurement method comprising: a bubble measurement step of measuring bubbles in the liquid based on a determination result of the contact state determination step and a measurement result of the amount of reflected light.

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