JP2006226703A - Measuring method and device of multiphase flowing state of optically transparent fluid having different refractive index utilizing optical fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a measuring method and a device therefor capable of grasping highly accurately information on the multiphase flowing state of optically transparent fluids having different refractive indexes from a measured signal acquired from an optical fiber probe. <P>SOLUTION: This device is equipped with an optical fiber having an end face inclined with respect to the axial core direction; a light source for allowing light to enter the optical fiber from the end face on the opposite side to the inclined end face; a photodetector for detecting light reflected by the inclined end face in the light, and converting the light into an electric signal; and an operation device capable of performing at least each processing for dividing the electric signal according to a prescribed time, determining a histogram relative to a detection output in each division, extracting detection outputs corresponding to the maximum frequency and the quasi-maximum frequency, deriving a threshold from the extracted detection outputs, comparing the threshold with a detection output value at each point of time, and thereby determining which of two phases is in contact with the inclined end. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a measuring device that measures a multiphase flow state of light-transmitting fluids having different refractive indexes.

  Ultra-light transmission fluid with different refractive index (hereinafter referred to as “two-phase”), for example, an industrial device having a flow phenomenon in which gas and liquid and / or micro solids are mixed Sound wave type bubble detector, neutron radiography, electrode probe method, PIV method, etc. are known, but all of them are difficult to measure the bubble or droplet diameter, movement speed, and hold-up at the same time, and the measurement cost is low. There is a problem that it is expensive. Hereinafter, for simplification of description, one of the two phases will be described as gas and the other as liquid.

As a method for solving such a problem and measuring a two-phase flow state, Patent Document 1 and Non-Patent Document 1 disclose a bubble measuring method using an optical fiber probe and an apparatus therefor.
JP 2000-136962 A CHEN W, TSUTSUMI A, OTAWARA K, SHIGAKI Y, Can J Chem Eng, VOL. 81 NO. 6; PAGE. 1139-1148; (2003/12) `` Local bubble dynamics and macroscopicity in bubble towers of different scales Flow structure "

  However, according to the method and apparatus disclosed in Non-Patent Document 1, when a bubble hits the tip of an optical fiber, there is a problem that the movement speed of the bubble is reduced and accurate measurement is difficult. . Patent Document 1 solves this problem by forming an inclination at the tip of the optical fiber, but there is no disclosure as to how the detected signal is processed to obtain accurate measurement data.

  Accordingly, the present invention provides a measurement method and apparatus capable of accurately grasping information regarding bubble group or droplet group and / or gas-liquid interface motion from a measurement signal obtained by an optical fiber probe. Let it be an issue.

  The present inventors extract the maximum value and the minimum value within a predetermined time of the measurement signal obtained by the optical fiber probe, derive a predetermined threshold value from these maximum value / minimum value, and this threshold value and each time point By comparing the measured values, it has been found that information on gas-liquid interface motion can be obtained with high accuracy. In addition, when spiked large noise enters the measurement signal, a histogram of the measurement value is created, and a predetermined threshold value is derived from the measurement value corresponding to the maximum frequency and the quasi-maximum frequency. It was found that the information about the gas-liquid interface motion can be grasped with high accuracy by comparing the measured values at the time.

  The present invention will be described below. In order to facilitate understanding of the present invention, reference numerals in the accompanying drawings are appended in parentheses, but the present invention is not limited to the illustrated embodiment.

  According to the first aspect of the present invention, there are two phases having optical transparency and different refractive indexes, the interphase interface moving speed, the diameter of one phase, and the volume between one phase and the other phase. A method of measuring the rate at the same time, the step of disposing an optical fiber having an end face inclined with respect to the axial direction toward the upstream side in the direction in which the two phases move; and an inclined end face; Includes a step of entering light into the optical fiber from the opposite end surface, a step of detecting light reflected from the inclined end surface of the light from the opposite end surface, converting it to an electrical signal, and storing the electrical signal. The maximum and minimum values are extracted every predetermined time, and a threshold value is derived from the maximum value and the minimum value, and the threshold value is compared with the detected output value at each time point, thereby inclining end portions. Determining which of the two phases is in contact with It is a measurement method.

  The invention according to claim 2 is a light-transmitting and two-phase interfacial moving speed, a diameter of one phase, and a volume between one phase and the other phase having different refractive indexes. A method of measuring the rate at the same time, the step of disposing an optical fiber having an end face inclined with respect to the axial direction toward the upstream side in the direction in which the two phases move; and an inclined end face; Includes a step of entering light into the optical fiber from the opposite end surface, a step of detecting light reflected from the inclined end surface of the light from the opposite end surface, converting it to an electrical signal, and storing the electrical signal; Dividing into predetermined times, obtaining a histogram relating to the detection output in the division, extracting detection outputs corresponding to the maximum frequency and sub-maximum frequency, and deriving a threshold value from these detection outputs, Compare with the detected output value at each time point A step of determining whether an end portion inclined is in contact with any of the two phases by that the measurement method comprising.

  According to a third aspect of the present invention, in the measurement method according to the first or second aspect, the two phases are a gas phase and a liquid phase.

  The invention according to claim 4 is a measuring device that can simultaneously measure the interphase interface moving speed formed by the liquid phase and the gas phase, the diameter of one phase, and the volume ratio of one phase and the other phase. An optical fiber having an end surface inclined with respect to the axial direction, a light source that enters light into the optical fiber from an end surface opposite to the inclined end surface, and light reflected by the inclined end surface of the light are opposite to each other. A detector that detects from the end face on the side and converts it into an electrical signal, and divides the electrical signal into predetermined times, obtains a histogram related to the detection output in that category, and detects corresponding to the maximum frequency and sub-maximum frequency Extracting the output and deriving a threshold value from the extracted detection output, and comparing the threshold value with the detection output value at each time point, it is determined which of the two phases is in contact with the inclined end. At least line processing An arithmetic unit for obtaining a measurement device provided with.

  According to the present invention, it is possible to grasp information regarding bubble group or droplet group and / or gas-liquid interface motion with high accuracy from a measurement signal obtained by an optical fiber probe. Such an operation and gain of the present invention will be made clear from the best mode for carrying out the invention described below.

  Hereinafter, the present invention will be described based on embodiments shown in the drawings.

  A basic configuration of a two-phase flow state measuring apparatus provided by the present invention is shown in FIG. The two-phase flow state measuring device 20 includes an optical fiber 1, a detection end 2 formed on one end face side of the optical fiber 1, a spectroscopic end 3 disposed on the other end side of the detection end 2, and a spectroscopic end 3 side in the optical fiber 1. The light source 4 that enters the light from the light source, the light detector 5 that detects the light that has entered the optical fiber 1 and is reflected by the detection end 2 and reaches the spectroscopic end 3, and the data detected by the light detector 5 A data acquisition device 6 to be acquired and a data calculation device 7 for calculating the data and determining whether the detection end 2 is in a gas phase or a liquid phase are included. Part or all of the components are housed in a single or a plurality of cases, and each component is connected directly or indirectly by optical or electrical means. Measurement is performed by inserting the detection end 2 into the measurement target. Below, the case where a liquid phase is an aqueous phase is demonstrated.

  As shown in FIG. 1, the detection end 2 of the optical fiber (hereinafter sometimes simply referred to as “fiber”) 1 has an inclination with respect to the axis of the fiber.

  The light introduced from the light source 4 into the fiber reaches the detection end 2. At the detection end 2, according to Snell's law, a part of the light is emitted to the outside of the fiber, and the remaining light is totally reflected at the detection end 2 and returns to the inside of the fiber to reach the spectral end 3. The amount of returned light is measured by the photodetector 5.

  When the detection end 2 is in the aqueous phase (liquid phase), most of the light is radiated to the aqueous phase because the refractive indices of the fiber and water are almost equal, and the light reflected back into the fiber is small. On the other hand, when the detection end 2 is in the gas phase, the refractive index of the fiber and water are greatly different, so that most of the light is reflected in the fiber and the amount of return light increases. By measuring the change in the amount of light with the light detector 5 in time series, the gas phase / liquid phase state of the measurement point where the detection end 2 is inserted can be known.

  An example of a signal measured by the photodetector 5 when a single bubble collides with the detection end 2 is shown in FIG. The time when the signal level rises sharply is the bubble collision time, and the time when the signal level falls is the bubble separation time. During this time, it is determined that the detection end 2 is exposed to the gas phase. By dividing the total time during which the detection end 2 is exposed to the gas phase by the total measurement time, the volume ratio of the gas phase in the gas-liquid mixed state at the measurement point where the detection end 2 is inserted (hereinafter referred to as “hold”). You can know "up".)

  Furthermore, by using two or more optical fibers 1 including the detection end 2, in addition to the hold-up, the bubble speed and diameter can be measured. As an example, FIG. 3 shows a waveform of a signal measured by the photodetector 5 when two probes are configured with the position of the detection end 2 slightly shifted. Due to the displacement of the detection end position, there is a difference in the rise time of each probe. The gas-liquid interface velocity is determined by dividing the deviation length of the tip position by the time difference. The gas-liquid interface velocity has a strong correlation with the bubble velocity. Further, by multiplying the time difference in which one probe is in a gas phase state by the bubble velocity, the passage chord length of the bubble is determined. The passing chord length has a strong correlation with the bubble diameter. When measuring a droplet, the treatment of peaks and valleys in the signal waveform may be reversed.

  The material of the optical fiber 1 can be arbitrarily selected according to the pressure, density, temperature, flow state, optical characteristics, and chemical characteristics of the measurement target. For example, plastic, glass, sapphire and the like. One or more optical connectors may be included in the middle of the optical fiber 1.

  When the measurement object includes bubbles, the outer diameter of the optical fiber 1 is preferably 0.1 to 2 times, more preferably 0.2 to 1 times the average bubble diameter. The fiber diameter when measuring a gas-liquid two-phase flow that does not include bubbles such as a slag flow is preferably 0.05 to 2.0 mm, more preferably 0.1 to 1.0 mm.

  As described above, the end surface of the detection end 2 has a characteristic that it is formed so as to be inclined to the fiber axis. As a sensor having a shape in which the detection end 2 is cut perpendicularly to the fiber axis, a sensor described in Non-Patent Document 1 or the like is known, but in such a shape, it is easy to reduce the bubble velocity at the time of bubble collision. There is a problem that the measurement error becomes large.

  The angle formed between the end face of the detection end 2 and the fiber axis is preferably 5 to 45 °, more preferably 20 to 30 °. If the angle exceeds 45 °, the effect of decelerating the bubble velocity at the time of bubble collision is increased, so that the measurement accuracy is lowered. If the angle is less than 5 °, the end face is fragile and easily broken.

  As a configuration method of the spectroscopic end 3, a part or all of the light incident from the light source 4 reaches the detection end 2, and a part or all of the return light from the detection end 2 can reach the photodetector 5. If it is a structure, it will not specifically limit. For example, a method disclosed in Patent Document 1, a half mirror method, or the like can be employed.

  As the light source 4, an arbitrary light source can be selected as long as it is a light source sufficiently brighter than the light intensity around the detection end 2. Examples thereof include a halogen lamp and a laser diode.

  The photodetector 5 can select any device as long as it has the ability to measure the change in the amount of reflected light from the detection end 2 with sufficient time resolution. Examples thereof include a photomultiplier tube and a photodiode.

  The data acquisition device 6 can select any device as long as it has the ability to sample the signal data from the photodetector 5 at a sufficient speed. A sampling rate of 1 kHz or more is sufficient. More preferably, it is 10 kHz or more. For example, an A / D conversion card or a general-purpose data logger that can be installed in a personal computer can be used. The data acquisition device 6 does not necessarily have a data storage capability, but may have it.

  The data calculation device 7 can select any device as long as it includes software including an algorithm for estimating the bubble motion state from the signal data acquired by the data acquisition device 6. For example, a personal computer or data processing dedicated hardware can be used. The data arithmetic unit 7 is not necessarily required to have the data storage capability, but it is desirable to have it.

(First embodiment)
Now, an algorithm (hereinafter referred to as “algorithm A”) according to the first embodiment for automatically determining the bubble collision time and the bubble separation time in the data calculation device 7 is shown in FIG. 4 and the following.

<Algorithm A>
(A1) The maximum value and the minimum value of the data received from the data acquisition device 6 are extracted and set as V _Max and V _Min , respectively.
(A2) One or two threshold values are set between V _Max and V _Min to be V ₁ and V ₂ , respectively. However, V _Max > V ₁ ≧ V ₂ > V _Min
It is.
(A3) extracting _{V 1} or more signals, and the average value _{V Gas.}
(A4) _{V 2} extracts the following signals, and the average value _{V Liquid.}
(A5) Two threshold values are set between V _Gas and V _Liquid , and are set as V ₃ and V ₄ , respectively. However, V _Gas > V ₃ ≧ V ₄ > V _Liquid
It is.

Determines that when the output value from the light detector exceeds the V ₃ is the detection end 2 is in the gas phase. Determines that when the output value from the light detector falls below the V ₄ is the detection end 2 is in the liquid phase.

As the calculation formulas for V ₁ , V ₂ , V ₃ , and V ₄ , the following formula is used in the first embodiment.
V ₁ = V _Min + α ₁ (V _Max −V _Min ) (1)
V ₂ = V _Min + α ₂ (V _Max −V _Min ) (2)
V ₃ = V _Liquid + α ₃ (V _Gas −V _Liquid ) (3)
V ₄ = V _Liquid + α ₄ (V _Gas −V _Liquid ) (4)

Here, α ₁ , α ₂ , α ₃ , and α ₄ are tuning parameters of the two-phase flow state measuring device.
α ₁ = 0.005 to 0.5,
α ₂ is ₁ to 5 times α ₁ and V ₂ does not exceed V _Max ,
α ₃ = 0.01 to 0.9,
α ₄ is 1 to 5 times α ₃ and V ₄ does not exceed V _Gas .

(Second embodiment)
Although it is necessary to set the parameter group before measurement, the method according to the first embodiment has a problem that it is difficult to determine an appropriate value in advance. In particular, it is difficult to predict the values of α ₁ and α ₂ . The reason for this will be described in detail below.

  For the case where the detection end 2 is inserted into the bubble flow of average bubble diameter = about 4 mm, average bubble rising speed = about 0.8 m / second, holdup = about 10%, from the data stored in the data calculation device 7 An example of the extracted signal waveform is shown in FIG. In addition, since the high frequency noise is cut with the data arithmetic unit 7, it is a smooth curve compared with FIG. 3 and FIG.

  When measuring a bubble group, spike noise as shown in FIG. 5C often occurs. This is because, in the shape of the detection end 2, light tends to concentrate on the acute angle portion due to the refractive index, and the amount of return light increases markedly when the gas-liquid interface shape becomes a lens shape at the tip portion at the time of bubble collision. It is estimated to be.

As an example, threshold values V ₁ and V ₂ when α ₁ = 0.21 and α ₂ = 0.64 are shown in FIG. In this case, since the gas phase signal level V _Gas cannot be determined normally, the subsequent gas-liquid flow state calculation (such as bubble velocity) will fail.

As a method of solving the problem,
(1) The bubble signal including spike noise is removed from the recorded data.
(2) Decrease the values of α ₁ and α ₂ .
Etc. are conceivable. However, with respect to (1), since it takes a very long time to remove while confirming by humans, the number of bubbles to be measured has to be reduced compared to automatic processing by a computer. As a result, there is a problem that measurement accuracy deteriorates. Regarding (2), since the magnitude of spike noise is difficult to predict, it is very difficult to predict appropriate values for α ₁ and α ₂ before measurement.

  In the second embodiment, a measurement error caused by spike noise included in the signal is avoided by using the histogram of the optical fiber sensor signal.

  In this embodiment, although the signal level of spike noise illustrated in FIG. 5 is large, attention is paid to the property that the generation time is very small compared to the whole. That is, when the histogram of the signal level V is created for FIG. 5, FIG. 6 is obtained. Specifically, digital sampling is performed when creating the histogram. For example, when measurement is performed for 10 seconds at a sampling period of 50 kHz, 50 k × 10 = 100,000 pieces of output value data are obtained. A histogram is created by counting the number N of the data for each section of the signal level V.

  In FIG. 6, the maximum frequency is “1”, and other frequencies are expressed as a ratio to this. The maximum frequency in FIG. 6 is approximately equal to the liquid phase signal level, and the quasi-maximum frequency is approximately equal to the gas phase signal level. The spike noise information is hidden in the flat portion on the right side of the quasi-maximum frequency. Using this property, the following algorithm B was derived.

<Algorithm B>
(B1) Create a histogram of the data stored in the signal processor 6,
An output value corresponding to the maximum frequency is V _Liquid-H and an output value corresponding to the quasi-maximum frequency is V _Gas-H . Where V _Gas-H > V _Liquid-H
It is.
_(B2) threshold and one or two sets of between _{V Liquid-H} and _{V Gas-H,} respectively V` <sub>1,</sub> and V` _2. However <sub>V Gas-H> V` 1 ≧</sub> V` 2> V Liquid-H
It is.
(B3) V` extracted <sub>one</sub> or more signals, and the average value <sub>V Gas.</sub>
V` extracted _two following signals, and the average value _{V Liquid.}
(B4) Two threshold values are set between V _Gas and V _Liquid, and are set as V ₃ and V ₄ , respectively.
However, V _Gas > V ₃ ≧ V ₄ > V _Liquid
It is.
(B5) judges that the detection end 2 when the output value from the light detector exceeds a V ₃ is in the gaseous state. On the other hand, it is determined that if the output value from the light detector falls below the V ₄ is the detection end 2 is in the liquid phase.

B4 and B5 in algorithm B are the same as A4 and A5 in algorithm A described above.
V` <sub>1,</sub> as formula for <sub>V` 2, V 3, V 4</sub> , and using the following equation.
<sub>V` 1 = V Liquid-H +</sub> α` 1 (V Gas-H -V Liquid-H) (5)
<sub>V` 2 = V Liquid-H +</sub> α` 2 (V Gas-H -V Liquid-H) (6)
V ₃ = V _Liquid + α ₃ (V _Gas −V _Liquid ) (7)
V ₄ = V _Liquid + α ₄ (V _Gas −V _Liquid ) (8)

  The expression (7) is the same as the expression (3), and the expression (8) is the same as the expression (4).

Here, α ′ ₁ , α ′ ₂ , α ₃ , and α ₄ are tuning parameters of the two-phase flow state measuring device.
α` <sub>1</sub> = 0.005~0.5,
Arufa` ₂ range of 1 to 5 times and V` <sub>2</sub> of Arufa` ₁ does not exceed _{V Gas-H,}
α ₃ = 0.01 to 0.9
α ₄ is 1 to 5 times α ₃ and V ₄ does not exceed V _Gas .
Preferably,
α` <sub>1</sub> = 0.4~0.5
α` ₂ = 0.4 ~ 0.6
α ₃ = 0.1 to 0.5
α ₄ = 0.2 to 0.9
It is.

If the algorithm is configured as described above, the gas phase signal level V _Gas and the liquid phase signal level V _Liquid can be determined without being substantially affected by the magnitude of spike noise included in the signal.

An embodiment of the present invention is shown in FIG.

  The detection end group 8 includes four detection ends, and the tip of each detection end is arranged to be the apex of a downward triangular pyramid. The detection end 11 of the center probe 9 disposed substantially at the center protrudes 1.38 mm from the detection ends 12 of the other surrounding probes 10. The tip of the detection end 12 of the surrounding probe 10 is arranged at substantially the same height, and the radius of a circle passing through the center point is 0.25 mm.

By using a configuration including four detection ends, three-dimensional measurement of the bubble velocity becomes possible. When a bubble collides with the detection end group 8, the difference between the collision time with the center probe detection end 11 and the collision time with the other three surrounding probe detection ends 12 is t ₁ , t ₂ , and t ₃ , respectively. , Bubble velocity vector magnitude

およびファイバー軸に対する相対角度

And relative angle to fiber axis

は次式で計算される。

Is calculated by the following equation.

  The measuring device was installed inside a water-air vertical bubble column having an average bubble diameter of 3.1 mm, an average ascending speed of 0.334 m / sec, and a hold-up of 7.9%. Table 1 shows the tuning parameters of the measuring device.

The measurement result of the bubble rising speed is shown in FIG. The value of tuning parameter alpha ₃ the horizontal axis shows the bubble rising velocity on the vertical axis.

From FIG. 8, it can be said that it is relatively difficult to predict before measurement because the tuning range of α ₃ for ensuring measurement accuracy is narrow in the method of the first embodiment. However, according to the system of the second embodiment, it is generally only necessary to be in the range of α ₃ = 0.2 to 0.45. Therefore, it can be said that the two-phase flow state measuring device provided with the algorithm of the second embodiment can perform measurement more stably.

  While the present invention has been described in connection with embodiments that are presently the most practical and preferred at the present time, the present invention is not limited to the embodiments disclosed herein. Rather, the method and apparatus for measuring a two-phase flow state using an optical fiber can be changed as appropriate without departing from the spirit or concept of the invention that can be read from the claims and the entire specification. It should be understood as being included in the technical scope of the invention.

It is a figure which shows the structure of the two-phase flow state measuring apparatus which concerns on this invention. It is a figure which shows the example of the output value of a photodetector when a single bubble collides with a detection end. It is a figure which shows the example of the output value of a photodetector, when two probes are comprised in the state which shifted the position of the detection end a little. It is explanatory drawing of the algorithm which determines a gaseous-phase signal level and a liquid phase signal level from the data acquired with the data acquisition apparatus. It is a figure which shows the example of the signal at the time of inserting the optical fiber which concerns on this invention in a bubble group. It is a figure which shows the histogram of FIG. It is a figure which shows the Example of this invention. It is a figure which shows the average speed of the bubble group measured by the measuring method of 1st embodiment of this invention, and 2nd embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical fiber 2 Detection end 3 Spectroscopic end 4 Light source 5 Photo detector 6 Data acquisition device 7 Data operation device 8 Detection end group 9 Center probe 10 Surrounding probe 11 Detection end of center probe 12 Detection end of surrounding probe 20 Two-phase flow state measurement apparatus

Claims (4)

A method capable of simultaneously measuring two-phase interfacial interface moving speed, the diameter of one phase, and the volume ratio of the one phase and the other phase having light transmittance and different refractive indexes. Because
Disposing an optical fiber having an end face inclined with respect to the axial direction toward the upstream side in the direction in which the two phases move;
Injecting light into the optical fiber from an end surface opposite to the inclined end surface;
Of the light, the step of detecting the light reflected by the inclined end face from the opposite end face, converting it to an electrical signal and storing it;
By extracting the maximum value and the minimum value of the electrical signal at predetermined time intervals, deriving a threshold value from the maximum value and the minimum value, and comparing the threshold value with the detection output value at each time point, Determining which of the two phases the inclined end is in contact with;
Measuring method including A method capable of simultaneously measuring two-phase interfacial interface moving speed, the diameter of one phase, and the volume ratio of the one phase and the other phase having light transmittance and different refractive indexes. Because
Disposing an optical fiber having an end face inclined with respect to the axial direction toward the upstream side in the direction in which the two phases move;
Injecting light into the optical fiber from an end surface opposite to the inclined end surface;
Of the light, the step of detecting the light reflected by the inclined end face from the opposite end face, converting it to an electrical signal and storing it;
The electrical signal is divided into predetermined times, a histogram relating to the detection output in the division is obtained, detection outputs corresponding to the maximum frequency and sub-maximum frequency are extracted, and a threshold is derived from these detection outputs. Determining which of the two phases the inclining end is in contact with by comparing the threshold value with the detected output value at each time point;
Measuring method including The measurement method according to claim 1, wherein the two phases are a gas phase and a liquid phase. A measuring device capable of simultaneously measuring the interphase transition speed formed by the liquid phase and the gas phase, the diameter of one phase, and the volume ratio of the one phase and the other phase,
An optical fiber having an end face inclined with respect to the axial direction;
A light source for entering light into the optical fiber from an end surface opposite to the inclined end surface;
Among the light, a photodetector that detects light reflected by the inclined end surface from the opposite end surface and converts it into an electrical signal;
The electrical signal is divided into predetermined times, a histogram relating to the detection output in the division is obtained, detection outputs corresponding to the maximum frequency and sub-maximum frequency are extracted, and a threshold value is derived from the extracted detection outputs. And an arithmetic unit capable of at least performing a process of determining which of the two phases is in contact with the inclined end by comparing the threshold value with a detection output value at each time point;
Measuring device equipped with.

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