Void rate acquisition method, void rate acquisition device, and program

Abstract

This void ratio acquisition method includes: a measurement results acquisition step of acquiring measurement results by measuring, over a predetermined time period, the voltage in a gas-liquid two-phase flow by using a probe; a frequency distribution creation step of creating a frequency distribution indicating the frequency of voltage values; a phase discrimination step of determining, as a liquid phase level voltage, the value of the voltage of a first peak which is the most frequent; a noise acquisition step of acquiring, as noise, the frequency of the value of the voltage having a small absolute value with respect to the liquid phase level voltage; and a void ratio acquisition step of taking the difference of noise from the frequency of the value of a voltage having a large absolute value with respect to the liquid phase level voltage, acquiring a frequency, from which the noise was removed, as a frequency ratio of the gas phase in the gas-liquid two-phase flow, and acquiring a frequency ratio of the gas phase as a void ratio.

Description

VOID RATIO ACQUISITION METHOD, VOID RATIO ACQUISITION DEVICE, AND PROGRAM

[0001] This application claims priority to Japanese Patent Application No. 2024-092554, filed on June 6, 2024, the contents of which are incorporated herein by reference.

[0002] In boilers and condensers used in chemical plants, the flow of refrigerant or working fluid in the pipes is a gas-liquid two-phase flow, where gas and liquid are mixed. In such equipment, it is necessary to understand the characteristics of the gas-liquid two-phase flow in the pipes for control or performance evaluation.

[0003] A method for obtaining the characteristics of a gas-liquid two-phase flow is described, for example, in Patent Document 1. In the method described in Patent Document 1, a measuring device using a probe distinguishes between the gas phase and the liquid phase, and obtains the characteristics of the gas-liquid two-phase flow.

[0004] JP 2013-238490 A

[0005] However, when trying to obtain the void fraction in a gas-liquid two-phase flow, there is a problem in that it is difficult to properly evaluate small bubbles. This is due to a phenomenon in which bubbles are repelled by the tip of the probe when the bubble diameter is similar to the probe diameter or is smaller than the probe diameter. This results in an extremely short time for the probe tip to be exposed to the gas phase, resulting in a small signal. Therefore, it is difficult to properly distinguish the signal corresponding to the gas phase, making it difficult to obtain an appropriate void fraction.

[0006] The present disclosure provides a void fraction acquisition method, a void fraction acquisition device, and a program that can obtain the void fraction in a gas-liquid two-phase flow with a smaller error range.

[0007] The void fraction acquisition method according to the present disclosure includes a measurement result acquisition step of measuring a voltage in a gas-liquid two-phase flow for a predetermined time using a probe to acquire measurement results; a frequency distribution creation step of creating a frequency distribution indicating the frequency of the voltage values ​​based on the measurement results acquired in the measurement result acquisition step; a phase discrimination step of determining the voltage value of the most frequent first peak as a liquid phase level voltage based on the frequency distribution acquired in the frequency distribution creation step; a noise acquisition step of acquiring, as noise, the frequency of the voltage values ​​in the frequency distribution that have smaller absolute values ​​than the liquid phase level voltage; and a void fraction acquisition step of subtracting the noise acquired in the noise acquisition step from the frequency of the voltage values ​​in the frequency distribution that have larger absolute values ​​than the liquid phase level voltage, acquiring the frequency with the noise removed from the frequency distribution as a frequency proportion of the gas phase in the gas-liquid two-phase flow, and acquiring the frequency proportion of the gas phase as a void fraction.

[0008] A void fraction acquisition device according to the present disclosure includes a probe that measures a voltage in a gas-liquid two-phase flow for a predetermined period of time, and a control unit that processes measurement results obtained by the probe. The control unit includes a measurement result acquisition unit that acquires the measurement results obtained by the probe, a frequency distribution creation unit that creates a frequency distribution indicating the frequency of the voltage values ​​based on the measurement results obtained by the measurement result acquisition unit, a phase discrimination unit that determines the voltage value of the most frequent first peak as a liquid phase level voltage based on the frequency distribution obtained by the frequency distribution creation unit, a noise acquisition unit that acquires, as noise, the frequency of the voltage values ​​that have smaller absolute values ​​than the liquid phase level voltage in the frequency distribution, and a void fraction acquisition unit that takes the difference between the noise acquired by the noise acquisition unit and the frequency of the voltage values ​​that have larger absolute values ​​than the liquid phase level voltage in the frequency distribution, acquires the frequency with the noise removed from the frequency distribution as a frequency proportion of the gas phase in the gas-liquid two-phase flow, and acquires the frequency proportion of the gas phase as a void fraction.

[0009] The program according to the present disclosure causes a computer to execute the following steps: acquiring measurement results obtained from a probe that measures voltage in a gas-liquid two-phase flow for a predetermined period of time; creating a frequency distribution indicating the frequency of the voltage values ​​based on the measurement results; determining the voltage value of the most frequent first peak as the liquid phase level voltage based on the frequency distribution; acquiring the frequency of the voltage values ​​in the frequency distribution that have smaller absolute values ​​than the liquid phase level voltage as noise; calculating the difference between the noise and the frequency of the voltage values ​​in the frequency distribution that have larger absolute values ​​than the liquid phase level voltage, acquiring the frequency with the noise removed from the frequency distribution as the frequency proportion of the gas phase in the gas-liquid two-phase flow, and acquiring the frequency proportion of the gas phase as a void fraction.

[0010] According to the void fraction acquisition method, void fraction acquisition device, and program of the present disclosure, the void fraction in a gas-liquid two-phase flow can be obtained with a smaller error range.

[0011] FIG. 1 is a diagram illustrating an example of the configuration of a void fraction acquisition device according to an embodiment of the present disclosure. FIG. 2 is a diagram illustrating an example of voltage data obtained in the first embodiment of the present disclosure. FIG. 3 is a diagram illustrating another example of voltage data obtained in the first embodiment of the present disclosure. FIG. 4 is a diagram illustrating an example of a frequency distribution obtained in the first embodiment of the present disclosure. FIG. 5 is a flowchart illustrating an example of a void fraction acquisition method according to an embodiment of the present disclosure. FIG. 6 is a diagram illustrating an example of voltage data obtained in the second embodiment of the present disclosure. FIG. 7 is a diagram illustrating an example of a frequency distribution obtained in the second embodiment of the present disclosure. FIG. 8 is a diagram illustrating an example of the hardware configuration of a void fraction acquisition device according to an embodiment of the present disclosure.

[0012] First Embodiment A first embodiment according to the present disclosure will be described below with reference to Fig. 1 to Fig. 5. First, a void fraction acquisition method S0 according to the first embodiment will be described. The void fraction acquisition method S0 is a method for acquiring the void fraction in a gas-liquid two-phase flow 1 using a void fraction acquisition device 10. Note that, hereinafter, the void fraction of a gas-liquid two-phase flow will be abbreviated to void fraction for simplicity.

[0013] <Configuration of Void Fraction Acquisition Device> FIG. 1 shows an example of the configuration of a void fraction acquisition device 10 according to an embodiment. The void fraction acquisition device 10 according to the first embodiment includes a probe 11 and a control unit 20. The probe 11 is capable of acquiring a signal that distinguishes between a liquid phase 2 and a gas phase 3 in a gas-liquid two-phase flow 1. The probe 11 has a pointed tip 12. The probe 11 in this embodiment is a laser type. Specifically, a laser can be introduced into the probe 11 up to the tip 12 through the interior of the probe 11. When measurement is performed, at least the tip 12 of the probe 11 is disposed within the gas-liquid two-phase flow 1. The probe 11 in this embodiment is capable of obtaining measurement results at any position on a flow channel cross section perpendicular to the flow direction of the gas-liquid two-phase flow 1. The probe 11 is controlled by a control unit 20 (described later) and is capable of performing measurement for a predetermined period of time.

[0014] Measurement of a gas-liquid two-phase flow 1 using the probe 11 is performed as follows: A laser is introduced into the probe 11 toward its tip 12. The introduced laser is reflected by the tip 12. The reflected laser is converted into a voltage signal and detected. At this time, due to the difference in refractive index between the gas phase 3 and the liquid phase 2, the reflection intensity of the laser differs between when the tip 12 is in the gas phase 3 and when it is in the liquid phase 2. Because the refractive index of the gas phase 3 is smaller than that of the liquid phase 2, the reflection intensity of the laser is stronger when the tip 12 is in contact with the gas phase 3 than when the tip 12 is in contact with the liquid phase 2. In other words, a higher voltage is obtained when the tip 12 is in contact with bubbles rather than with the liquid. This difference in voltage makes it possible to distinguish between the gas phase 3 and the liquid phase 2.

[0015] The control unit 20 controls the probe 11 and is capable of processing the measurement results obtained by the probe 11. The control unit 20 is capable of issuing instructions to the probe 11 to perform measurements within a certain time interval. The control unit 20 of this embodiment includes a measurement result acquisition unit 21, a frequency distribution creation unit 22, a phase discrimination unit 23, an implementation determination unit 24, a noise acquisition unit 25, a void fraction acquisition unit 26, and an output unit 27.

[0016] The measurement result acquisition unit 21 is capable of acquiring the measurement results obtained by the probe 11. By acquiring the measurement results, the measurement result acquisition unit 21 can obtain a graph such as that shown in Fig. 2, for example.

[0017] FIG. 2 shows the measurement results, showing voltage values ​​at a certain time. FIG. 2 is also a graph for a system in which the gas phase 3 is a small bubble. It shows that the probe 11 is in the gas phase 3 at a time corresponding to a voltage peak (a value at a point of locally large amplitude in a waveform showing a voltage) showing a voltage value greater than the liquid-phase level voltage VL described below. When the gas phase 3 is a small bubble, the probe 11 is exposed to the gas phase 3 for a shorter period of time, resulting in a smaller response of the voltage signal even at the voltage peak. Therefore, the voltage drops before it rises sufficiently. On the other hand, when the gas phase 3 is a large bubble, the probe 11 is exposed to the gas phase 3 for a longer period of time, resulting in a larger response of the electrical signal at the voltage peak. Therefore, the voltage rises to a value that fully reflects the gas phase 3, and then drops. In other words, when the gas phase 3 is a large bubble, a graph can be obtained in which the voltage value and time width at the voltage peak are larger than those in the graph of FIG. 2.

[0018] The frequency distribution creating unit 22 is capable of creating a frequency distribution indicating the frequency of voltage values ​​based on the measurement results obtained by the measurement result acquiring unit 21. The frequency distribution creating unit 22 can generate graphs such as those shown in FIGS. 3 and 4. FIG. 3 shows how a voltage value at a certain time differs from the liquid-phase level voltage VL (described in detail below), where a certain voltage value is a liquid-phase level voltage VL. FIG. 4 is a frequency distribution showing how frequently a certain voltage value appears over a certain time span, i.e., a predetermined time period during which measurement by the probe 11 is performed.

[0019] The phase determination unit 23 is capable of determining the liquid phase level voltage VL based on the frequency distribution obtained by the frequency distribution creation unit 22. The frequency distribution has two frequency peaks corresponding to the liquid phase 2 and the gas phase 3. Of the two frequency peaks, the peak with the lower voltage value (the value of a point with a locally large amplitude in a waveform indicating the frequency) indicating the liquid phase 2 is designated as the first peak. The other frequency peak with the higher voltage value indicating the gas phase 3 is designated as the second peak. The second peak indicates the gas phase 3 in the frequency distribution and is located away from the first peak. In other words, the voltage values ​​of the second peak and the first peak are different, and the second peak is a peak separate from the first peak in the frequency distribution where the frequency increases again.

[0020] Here, the voltage value at the first peak is defined as the liquid-phase level voltage VL. The voltage value at the second peak is defined as the vapor-phase level voltage VG. The phase determination unit 23 is capable of determining the liquid-phase level voltage VL. The frequency peak refers to each maximum point in the frequency distribution where the frequency is high. In the first embodiment, the first peak is larger than the second peak. That is, the most frequent part of the frequency distribution is the first peak. In other words, the frequency at the first peak is the frequency FL of the liquid-phase level voltage, and the frequency at the second peak is the frequency FG of the vapor-phase level voltage.

[0021] The execution determination unit 24 is capable of determining whether or not the subsequent processing is to be executed. The execution determination unit 24 is capable of determining the vapor phase level voltage VG.

[0022] The implementation determination unit 24 can determine whether or not to implement the noise acquisition unit 25 and subsequent steps described below in the following manner. The frequency of the minimum point between the liquid-phase level voltage VL and the gas-phase level voltage VG in the frequency distribution, where the voltage value appears the least, is defined as the minimum point voltage frequency FM. If the minimum point voltage frequency FM is equal to or greater than 1 / 10 of the gas-phase level voltage frequency FG, it is estimated that the system contains many small-diameter bubbles. In this case, the implementation determination unit 24 determines to implement the noise acquisition unit 25 and subsequent steps. Furthermore, if the minimum point voltage frequency FM is less than 1 / 10 of the gas-phase level voltage frequency FG, it is estimated that the system contains many large-diameter bubbles. In this case, the implementation determination unit 24 determines not to implement the noise acquisition unit 25 and subsequent steps. If the noise acquisition unit 25 and subsequent steps are not implemented, the void fraction can be acquired using existing means.

[0023] The execution determination unit 24 may not be provided. For example, the process may proceed without determining whether or not to execute the subsequent processes. Specifically, for example, when it is difficult to identify the region corresponding to the gas phase 3 in the frequency distribution, the process may proceed without determining whether or not to execute the subsequent processes.

[0024] The noise acquisition unit 25 is capable of acquiring noise in the frequency distribution. The noise acquisition unit 25 determines that a portion of the frequency distribution that indicates a voltage lower than the liquid phase level voltage VL is noise. In other words, the noise acquisition unit 25 acquires, as noise, the frequency of voltage values ​​that have an absolute value smaller than the liquid phase level voltage VL in the frequency distribution. This is because it is estimated that voltages lower than the liquid phase level voltage VL in the frequency distribution are due to noise in the liquid phase 2. Note that the noise occurs so as to be mixed with the rising voltage caused by the bubbles.

[0025] The void fraction acquisition unit 26 is capable of acquiring the void fraction. The void fraction acquisition unit 26 processes the noise acquired by the noise acquisition unit 25 as follows. It is estimated that the liquid phase 2 noise also occurs at voltages higher than the liquid phase level voltage VL. Therefore, it is assumed that noise equivalent to the noise at voltages lower than the liquid phase level voltage VL also occurs at voltages higher than the liquid phase level voltage VL. Therefore, by doubling the integrated value of the frequency in the portion of the frequency distribution showing voltages lower than the liquid phase level voltage VL, noise in the portion showing voltages higher than the liquid phase level voltage VL is reflected in addition to the portion showing voltages lower than the liquid phase level voltage VL. In other words, the area of ​​the region corresponding to the noise in the frequency distribution in FIG. 4 is acquired. Note that, since the range is set lower than the reference liquid phase level voltage frequency FL (frequency at the first peak), the acquired value does not include the liquid phase level voltage frequency FL. Therefore, the liquid phase level voltage frequency FL itself is also reflected. Specifically, the frequency FL of the liquid phase level voltage is added to twice the integrated value of the acquired frequency. The value obtained in this way is treated as noise due to the liquid phase 2 in the gas-liquid two-phase flow 1.

[0026] The void fraction acquiring unit 26 acquires the frequency fraction of the gas phase 3 in the gas-liquid two-phase flow 1 by subtracting the noise due to the liquid phase 2 from the integrated value of the frequency over the entire frequency distribution. In other words, the area corresponding to the noise is subtracted from the area of ​​the region surrounded by the frequency distribution in Fig. 4. The frequency fraction of the gas phase 3 indicates the void fraction, so in this way the void fraction acquiring unit 26 can acquire the void fraction.

[0027] The processing by the void fraction acquisition unit 26 can be rephrased as follows: The void fraction acquisition unit 26 calculates the difference between the frequency of voltage values ​​having a larger absolute value than the liquid-phase level voltage VL in the frequency distribution and the noise acquired by the noise acquisition unit 25. The frequency distribution from which the noise has been removed is acquired as the frequency ratio of the gas phase 3 in the gas-liquid two-phase flow 1, and this is acquired as the void fraction.

[0028] The output unit 27 outputs the input information on the void ratio to an external device such as a display device or storage device (not shown). At this time, information other than the void ratio may also be output.

[0029] 5 is a flowchart showing an example of a void fraction acquisition method S0 for a gas-liquid two-phase flow 1 according to an embodiment. This flowchart is merely an example, and the order of steps may be changed, or steps may be added or omitted as appropriate. The void fraction acquisition method S0 according to the first embodiment includes a preparation step S1, a measurement result acquisition step S2, a frequency distribution creation step S3, a phase discrimination step S4, an implementation determination step S5, a noise acquisition step S6, and a void fraction acquisition step S7.

[0030] First, a preparation step S1 is performed in which the void fraction acquisition device 10 described above is prepared.

[0031] After the preparation step S1 is performed, a measurement result acquisition step S2 is performed. In the measurement result acquisition step S2, at least the tip 12 of the probe 11 is placed inside the gas-liquid two-phase flow 1 to be measured. The measurement result acquisition step S2 of this embodiment is performed by the measurement result acquisition unit 21. Specifically, the probe 11 performs measurements for a predetermined period of time. The measurement results are obtained as voltages over a certain period of time. From the obtained measurement results, a graph such as that shown in FIG. 2 can be obtained.

[0032] After the measurement result acquisition step S2 is performed, a frequency distribution creation step S3 is performed. In the frequency distribution creation step S3, a frequency distribution indicating the frequency of voltage values ​​is created based on the measurement results obtained in the measurement result acquisition step S2. The frequency distribution creation step S3 of this embodiment is performed by the frequency distribution creation unit 22. In the frequency distribution creation step S3, graphs such as those shown in FIGS. 3 and 4 are obtained.

[0033] After the frequency distribution creation step S3 is performed, the phase determination step S4 is performed. In the phase determination step S4, the liquid phase level voltage VL is determined based on the frequency distribution obtained in the frequency distribution creation step S3. The frequency distribution creation step S3 in this embodiment is performed by the frequency distribution creation unit 22.

[0034] After the phase determination step S4 is performed, an implementation determination step S5 is performed. In the implementation determination step S5, if the frequency FM of the minimum point voltage is equal to or greater than 1 / 10 of the frequency FG of the vapor phase level voltage, it is determined that the noise acquisition step S6 and subsequent steps should be performed. The implementation determination step S5 of this embodiment is performed by the implementation determination unit 24.

[0035] The execution determination step S5 may be omitted. For example, the process may proceed without determining whether or not to execute the subsequent processes. Specifically, for example, when it is difficult to identify the region corresponding to the gas phase 3 in the frequency distribution, the process may proceed without determining whether or not to execute the subsequent processes.

[0036] After the execution determination step S5 is executed, the noise acquisition step S6 is executed. In the noise acquisition step S6, a portion of the frequency distribution that indicates a voltage lower than the liquid phase level voltage VL is determined to be noise. In other words, in the noise acquisition step S6, the frequency of voltage values ​​that have an absolute value smaller than the liquid phase level voltage VL in the frequency distribution is acquired as noise. The noise acquisition step S6 of this embodiment is executed by the noise acquisition unit 25.

[0037] After the noise acquisition step S6 is performed, the void fraction acquisition step S7 is performed. The void fraction acquisition step S7 of this embodiment is performed by the void fraction acquisition unit 26. In the void fraction acquisition step S7, the noise acquired in the noise acquisition step S6 is processed as follows. By doubling the integrated value of the frequency in the portion of the frequency distribution that shows a voltage lower than the liquid phase level voltage VL, the noise in the portion that shows a voltage higher than the liquid phase level voltage VL is reflected. By taking the difference of the noise due to the liquid phase 2 from the integrated value of the frequency in the entire frequency distribution, the frequency ratio of the gas phase 3 in the gas-liquid two-phase flow 1 is acquired. In this manner, the void fraction is acquired.

[0038] The processing in the void fraction acquisition step S7 can be rephrased as follows: In the void fraction acquisition step S7, the difference of the noise acquired by the noise acquisition unit 25 is calculated from the frequency of voltage values ​​having a larger absolute value than the liquid-phase level voltage VL in the frequency distribution. The frequency distribution from which the noise has been removed is acquired as the frequency ratio of the gas phase 3 in the gas-liquid two-phase flow 1, and this is acquired as the void fraction.

[0039] In the present disclosure, small-diameter bubbles refer to bubbles having a diameter of approximately 100 μm to 150 μm. Therefore, the void fraction acquisition device 10 and void fraction acquisition method S0 according to the present disclosure are preferably applied to a system containing many bubbles having a diameter of 150 μm or less, and more preferably to a system containing many bubbles having a diameter of 100 μm or less.

[0040] <Effects> According to the void fraction acquisition device 10 and void fraction acquisition method S0 described above, the frequency of voltage values ​​with a small absolute value relative to the liquid-phase level voltage VL is evaluated as noise due to the liquid phase 2. In the frequency distribution, the difference in noise due to the liquid phase 2 is calculated from the frequency of voltage values ​​with a large absolute value relative to the liquid-phase level voltage VL. This is because noise due to the liquid phase 2 is evaluated to occur not only in areas with a small absolute value relative to the liquid-phase level voltage VL but also in areas with a large absolute value relative to the liquid-phase level voltage VL. It is estimated that noise in areas with a large absolute value relative to the liquid-phase level voltage VL is equivalent to noise in areas with a small absolute value relative to the liquid-phase level voltage VL. This allows noise near the liquid-phase level voltage VL to be removed with high accuracy, thereby accurately obtaining the frequency ratio of the gas phase 3, which indicates the void fraction. This process eliminates the problem of being unable to individually distinguish between noise due to the liquid phase 2 and signals due to bubbles by statistically evaluating the noise due to the liquid phase 2. Therefore, the void fraction in the gas-liquid two-phase flow 1, which is a system in which the bubble diameter is small, can be obtained with a smaller error range.

[0041] Furthermore, the execution determination unit 24 and the execution determination step S5 determine whether or not to execute subsequent processing, which makes it possible to estimate whether or not the void fraction acquisition device 10 and the void fraction acquisition method S0 of the present embodiment are suitably applicable to the system.

[0042] Furthermore, the probe 11 according to the first embodiment is capable of introducing a laser. By using the probe 11 to measure the reflected laser intensity as a voltage, a measurement result can be obtained that distinguishes between the gas phase 3 and the liquid phase 2 of the gas-liquid two-phase flow 1. The measurement result can be obtained by setting the pulse and time for emitting the laser. Furthermore, by using the laser-type probe 11, measurements can be easily performed.

[0043] Second Embodiment Next, a second embodiment will be described with reference to Figures 6 and 7. In the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0044] The void fraction acquisition device 10 and the void fraction acquisition method S0 according to the second embodiment differ from those of the first embodiment in the measurement principle using the probe 11A, and also in the measurement results obtained and the method of processing the results.

[0045] The probe 11A of the second embodiment is a point electrode type. Specifically, the probe 11A is capable of conducting electricity between the tip 12 and the base. The probe 11A is energized while disposed inside the gas-liquid two-phase flow 1. A voltage signal obtained when energized is the measurement result. The magnitude of the voltage differs between the state where the tip 12 is in the gas phase 3 and the state where it is in the liquid phase 2. When the tip 12 is in the gas phase 3, current flows through the gas phase 3, resulting in high electrical resistance and a high voltage. When the tip 12 is in the liquid phase 2, current flows through the liquid phase 2, resulting in low electrical resistance and a low voltage. The difference in voltage signals makes it possible to distinguish between the gas phase 3 and the liquid phase 2.

[0046] The frequency distribution creation unit 22 of the second embodiment can obtain graphs such as those shown in Figures 6 and 7. The same processing as in Figures 3 and 4 of the first embodiment is performed, but in the second embodiment, the liquid phase level voltage VL and the gas phase level voltage VG are reversed in voltage order. Therefore, in the second embodiment, the first peak and the second peak are defined as follows: The peak with the higher voltage value of the two frequency peaks in the frequency distribution, which indicates liquid phase 2, is defined as the first peak. The other peak with the lower voltage value, which indicates gas phase 3, is defined as the second peak.

[0047] In the second embodiment, the point at which the voltage value becomes zero is as follows: Referring to Figures 6 and 7, the point at which the voltage value becomes zero is on the opposite side of the voltage axis from the liquid phase level voltage VL as the reference voltage to the gas phase level voltage VG.

[0048] The noise acquiring unit 25 of the second embodiment determines that a portion of the frequency distribution that indicates a voltage higher than the liquid phase level voltage VL is noise. In other words, the noise acquiring unit 25 acquires, as noise, the frequency of voltage values ​​that have an absolute value smaller than the liquid phase level voltage VL in the frequency distribution. This is because it is estimated that a voltage higher than the liquid phase level voltage VL in the frequency distribution is due to noise in the liquid phase 2.

[0049] The void fraction acquisition unit 26 of the second embodiment performs the following processing. It is estimated that noise in the liquid phase 2 also occurs at voltages lower than the liquid-phase level voltage VL. It is assumed that noise equivalent to that at voltages higher than the liquid-phase level voltage VL also occurs at voltages lower than the liquid-phase level voltage VL. Therefore, by doubling the integrated value of the frequency in the portion of the frequency distribution showing voltages higher than the liquid-phase level voltage VL, noise in the portion showing voltages lower than the liquid-phase level voltage VL is reflected in addition to the portion showing voltages higher than the liquid-phase level voltage VL. In other words, the area of ​​the region corresponding to the noise in the frequency distribution of FIG. 7 is acquired. Note that, since the range is set lower than the reference liquid-phase level voltage frequency FL (frequency at the first peak), the acquired value does not include the liquid-phase level voltage frequency FL. Therefore, the liquid-phase level voltage frequency FL itself is also reflected. Specifically, the liquid-phase level voltage frequency FL is added to a value double the integrated value of the acquired frequency. The value thus obtained is treated as noise due to the liquid phase 2 in the gas-liquid two-phase flow 1.

[0050] The void fraction acquiring unit 26 acquires the frequency fraction of the gas phase 3 in the gas-liquid two-phase flow 1 by subtracting the noise due to the liquid phase 2 from the integrated value of the frequency over the entire frequency distribution. In other words, the area corresponding to the noise is subtracted from the area of ​​the region surrounded by the frequency distribution in Fig. 7. The frequency fraction of the gas phase 3 indicates the void fraction, and thus the void fraction acquiring unit 26 can acquire the void fraction in this manner.

[0051] The processing by the void fraction acquisition unit 26 can be rephrased as follows: The void fraction acquisition unit 26 calculates the difference between the frequency of voltage values ​​having a larger absolute value than the liquid-phase level voltage VL in the frequency distribution and the noise acquired by the noise acquisition unit 25. The frequency distribution from which the noise has been removed is acquired as the frequency ratio of the gas phase 3 in the gas-liquid two-phase flow 1, and this is acquired as the void fraction.

[0052] <Void fraction acquisition method> The void fraction acquisition method S0 according to the second embodiment is performed according to the flowchart shown in Fig. 5. That is, it is performed in the same manner as in the first embodiment. However, it is performed while reflecting the above-mentioned differences due to the difference in the measurement principle using the probe 11A.

[0053] <Effects> According to the void fraction acquisition device 10 and void fraction acquisition method S0 described above, the void fraction in the gas-liquid two-phase flow 1, which is a system in which the diameter of the bubbles is small, can be obtained with a smaller error range, as in the first embodiment. In other words, if a measurement result in which the liquid phase 2 and the gas phase 3 can be distinguished can be obtained, the void fraction acquisition method S0 of the present disclosure can be applied.

[0054] Furthermore, the probe 11A according to the second embodiment is configured to allow electricity to pass between the tip 12 and the base. By measuring the voltage when electricity is passed through, a measurement result can be obtained that distinguishes between the gas phase 3 and the liquid phase 2 of the gas-liquid two-phase flow 1. The measurement result can be obtained by setting the time for applying the current. Furthermore, by using the point-electrode type probe 11A, measurements can be easily performed.

[0055] <Hardware Configuration> The void fraction acquisition device 10 of the first and second embodiments described above is implemented in a computer 90 shown in Fig. 8. Fig. 8 is a diagram showing an example of the hardware configuration of the void fraction acquisition device 10 according to each embodiment. The third embodiment can be combined with either the first or second embodiment. The computer 90 includes a processor 91, a main memory 92, a storage 93, and an interface 94.

[0056] The operation of the void fraction acquisition device 10 described above is stored in the form of a program in the storage 93. The processor 91 reads the program from the storage 93, loads it into the main memory 92, and executes various processes such as the process shown in Fig. 5 described above in accordance with the program. The processor 91 also allocates a storage area in the main memory 92 corresponding to the storage area inside the void fraction acquisition device 10 described above in accordance with the program. A control line is connected to the interface 94, and, for example, receives values ​​output by the output unit 27 and the like and transmits command values ​​to the probe 11, which is the object of control.

[0057] The program may be for realizing some of the functions to be performed by the computer 90. For example, the program may be combined with other programs already stored in the storage 93 or other programs implemented in other devices to perform the functions. In other embodiments, the computer 90 may include a custom LSI (Large Scale Integrated Circuit) such as a PLD (Programmable Logic Device) in addition to or instead of the above configuration. Examples of PLDs include PAL (Programmable Array Logic), GAL (Generic Array Logic), CPLD (Complex Programmable Logic Device), and FPGA (Field Programmable Gate Array). In this case, some or all of the functions realized by the processor 91 may be realized by the integrated circuit.

[0058] Examples of the storage 93 include a hard disk drive (HDD), a solid state drive (SSD), a magnetic disk, a magneto-optical disk, a compact disc read-only memory (CD-ROM), a digital versatile disc read-only memory (DVD-ROM), and a semiconductor memory. The storage 93 may be an internal medium directly connected to the bus of the computer 90, or an external medium connected to the computer 90 via the interface 94 or a communication line. Furthermore, when the program is distributed to the computer 90 via a communication line, the computer 90 that receives the program may load the program into the main memory 92 and execute various processes such as the process shown in FIG. 5 described above. In the above embodiment and at least one of the other embodiments, the storage 93 is a non-transitory tangible storage medium.

[0059] <Other Embodiments> Although the embodiments of the present disclosure have been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment, and design changes and the like are also included within the scope that does not deviate from the gist of the present disclosure.

[0060] For example, the control unit 20 according to one embodiment may be configured such that each component is provided separately, or may be integrated as appropriate.

[0061] Furthermore, the control unit 20 according to an embodiment may not include the output unit 27 .

[0062] Furthermore, the probes 11 and 11A according to an embodiment may be probes of other types.

[0063] Furthermore, the void fraction acquisition method S0 according to the embodiment is not limited to being performed using the void fraction, and may be performed by an operator without using the control unit 20, for example.

[0064] <Additional Notes> The void fraction acquisition method S0, the void fraction acquisition device 10, and the program described in each embodiment can be understood, for example, as follows.

[0065] (1) A void fraction acquisition method S0 according to a first aspect includes a measurement result acquisition step S2 of measuring a voltage in a gas-liquid two-phase flow 1 for a predetermined time using probes 11 and 11A to acquire a measurement result; a frequency distribution creation step S3 of creating a frequency distribution indicating the frequency of the voltage values ​​based on the measurement result acquired in the measurement result acquisition step S2; and a phase determination step S4 of determining the voltage value of the most frequent first peak as a liquid phase level voltage VL based on the frequency distribution acquired in the frequency distribution creation step S3. The method includes a noise acquisition process S6 for acquiring, as noise, the frequency of voltage values ​​whose absolute values ​​are smaller than the liquid phase level voltage VL in the frequency distribution, and a void fraction acquisition process S7 for calculating the difference between the noise acquired in the noise acquisition process S6 and the frequency of voltage values ​​whose absolute values ​​are larger than the liquid phase level voltage VL in the frequency distribution, acquiring the frequency from which the noise has been removed from the frequency distribution as the frequency proportion of the gas phase 3 in the gas-liquid two-phase flow 1, and acquiring the frequency proportion of the gas phase 3 as the void fraction.

[0066] According to the above configuration, in the noise acquisition step S6, the frequency of voltage values ​​whose absolute values ​​are smaller than the liquid-phase level voltage VL is evaluated as noise due to the liquid phase 2. Furthermore, noise due to the liquid phase 2 is evaluated to occur not only in areas where the absolute values ​​are small relative to the liquid-phase level voltage VL, but also in areas where the absolute values ​​are large. Therefore, noise near the liquid-phase level voltage VL can be removed with high accuracy, and the frequency rate of the gas phase 3, which indicates the void fraction, can be accurately obtained. Therefore, the void fraction in the gas-liquid two-phase flow 1 can be obtained with a smaller error range.

[0067] (2) The void fraction acquisition method S0 according to the second aspect is the void fraction acquisition method S0 of (1), in which the measurement result acquisition step S2 acquires the measurement result by measuring the reflection intensity of the laser introduced into the probe 11 as a voltage signal.

[0068] According to the above configuration, by measuring the reflected laser intensity as a voltage, it is possible to obtain a measurement result that distinguishes between the gas phase 3 and the liquid phase 2 of the gas-liquid two-phase flow 1. The measurement result can be obtained by setting the pulse and time for emitting the laser. Furthermore, the measurement can be easily performed.

[0069] (3) The void fraction acquisition method S0 according to the third aspect is the void fraction acquisition method S0 of (1), in which the measurement result acquisition step S2 acquires the measurement result by measuring the voltage required to pass a current between the tip and base ends of the probe 11A.

[0070] According to the above configuration, the probe 11A is capable of conducting electricity between the tip 12 and the base. By measuring the voltage when the current is conducted, a measurement result that distinguishes between the gas phase 3 and the liquid phase 2 of the gas-liquid two-phase flow 1 can be obtained. The measurement result can be obtained by setting the time for applying the current. Furthermore, the measurement can be easily performed.

[0071] (4) A void fraction acquisition method S0 according to a fourth aspect is the void fraction acquisition method S0 of any one of (1) to (3), and further includes an implementation determination step S5 that is carried out between the phase determination step S4 and the noise acquisition step S6 and determines whether or not to carry out the noise acquisition step S6. In the phase determination step S4, the voltage value of a second peak, which is different from the first peak and which again occurs frequently, is determined to be the gas phase level voltage VG. In the implementation determination step S5, it is determined that the noise acquisition step S6 is to be carried out if the frequency of the minimum point, which is the voltage value having the fewest occurrences between the liquid phase level voltage VL and the gas phase level voltage VG in the frequency distribution, is 1 / 10 or more of the frequency FG of the gas phase level voltage.

[0072] According to the above configuration, the execution determination step S5 determines whether or not to execute the noise acquisition step S6, which makes it possible to estimate whether or not the void fraction acquisition method S0 of this embodiment is suitably applicable to the system.

[0073] (5) A void fraction acquisition device 10 according to a fifth aspect includes probes 11, 11A that measure voltage in a gas-liquid two-phase flow 1 for a predetermined time, and a control unit 20 that processes measurement results obtained by the probes 11, 11A. The control unit 20 includes a measurement result acquisition unit 21 that acquires the measurement results obtained by the probes 11, a frequency distribution creation unit 22 that creates a frequency distribution indicating the frequency of the voltage values ​​based on the measurement results obtained by the measurement result acquisition unit 21, and a frequency distribution creation unit 23 that creates a frequency distribution indicating the frequency of the voltage values ​​based on the frequency distribution obtained by the frequency distribution creation unit 22. The system includes a phase determination unit 23 that determines the value of the voltage to be a liquid phase level voltage VL, a noise acquisition unit 25 that acquires, as noise, the frequency of the voltage value whose absolute value is smaller than the liquid phase level voltage VL in the frequency distribution, and a void fraction acquisition unit 26 that takes the difference of the noise acquired by the noise acquisition unit 25 from the frequency of the voltage value whose absolute value is larger than the liquid phase level voltage VL in the frequency distribution, acquires the frequency from which the noise has been removed from the frequency distribution as the frequency fraction of the gas phase 3 in the gas-liquid two-phase flow 1, and acquires the frequency fraction of the gas phase 3 as a void fraction.

[0074] According to the above configuration, the noise acquisition unit 25 evaluates the frequency of voltage values ​​whose absolute values ​​are smaller than the liquid-phase level voltage VL as noise due to the liquid phase 2. Furthermore, it is also evaluated that noise due to the liquid phase 2 occurs not only in areas where the absolute values ​​are small relative to the liquid-phase level voltage VL, but also in areas where the absolute values ​​are large. Therefore, it is possible to accurately remove noise near the liquid-phase level voltage VL and accurately obtain the frequency rate of the gas phase 3, which indicates the void fraction. Therefore, the void fraction in the gas-liquid two-phase flow 1 can be obtained with a smaller error range.

[0075] (6) The void fraction acquisition device 10 according to the sixth aspect is the void fraction acquisition device 10 of (5), in which the measurement result acquisition unit 21 acquires the measurement result by measuring the reflection intensity of the laser introduced into the probe 11 as a voltage signal.

[0076] According to the above configuration, by measuring the reflected laser intensity as a voltage, it is possible to obtain a measurement result that distinguishes between the gas phase 3 and the liquid phase 2 of the gas-liquid two-phase flow 1. The measurement result can be obtained by setting the pulse and time for emitting the laser. Furthermore, the measurement can be easily performed.

[0077] (7) The void fraction acquisition device 10 according to the seventh aspect is the void fraction acquisition device 10 of (5), in which the measurement result acquisition unit 21 acquires the measurement result by measuring the voltage required to pass a current between the tip and base ends of the probe 11A.

[0078] According to the above configuration, the probe 11A is capable of conducting electricity between the tip 12 and the base. By measuring the voltage when the current is conducted, a measurement result that distinguishes between the gas phase 3 and the liquid phase 2 of the gas-liquid two-phase flow 1 can be obtained. The measurement result can be obtained by setting the time for applying the current. Furthermore, the measurement can be easily performed.

[0079] (8) The void fraction acquisition device 10 according to an eighth aspect is the void fraction acquisition device 10 of any one of (5) to (7), wherein the control unit 20 further includes an implementation determination unit 24 that is implemented between the phase discrimination unit 23 and the noise acquisition unit 25 and determines whether or not to implement the noise acquisition unit 25, wherein the phase discrimination unit 23 determines the voltage value of a second peak, which is different from the first peak and which again becomes more frequent, as the gas phase level voltage VG, and the implementation determination unit 24 determines that the noise acquisition unit 25 should be implemented when the frequency of the minimum point, where the voltage value appears least frequently between the liquid phase level voltage VL and the gas phase level voltage VG in the frequency distribution, is 1 / 10 or more of the frequency FG of the gas phase level voltage.

[0080] According to the above configuration, the implementation determination unit 24 determines whether or not to implement the noise acquisition unit 25. This makes it possible to estimate whether or not the void fraction acquisition device 10 of this embodiment is suitably applicable to the system.

[0081] (9) A program according to a ninth aspect causes a computer 90 to execute the following steps: acquiring measurement results obtained from probes 11, 11A that measure voltage in a gas-liquid two-phase flow 1 over a predetermined time; creating a frequency distribution indicating the frequency of the voltage values ​​based on the measurement results; determining the voltage value of the most frequent first peak as a liquid phase level voltage VL based on the frequency distribution; acquiring, as noise, the frequency of the voltage values ​​in the frequency distribution that have smaller absolute values ​​than the liquid phase level voltage VL; calculating the difference of the noise from the frequency of the voltage values ​​in the frequency distribution that have larger absolute values ​​than the liquid phase level voltage VL, acquiring the frequency with the noise removed from the frequency distribution as the frequency proportion of the gas phase 3 in the gas-liquid two-phase flow 1, and acquiring the frequency proportion of the gas phase 3 as a void fraction.

[0082] According to the void fraction acquisition method, void fraction acquisition device, and program of the present disclosure, the void fraction in a gas-liquid two-phase flow can be obtained with a smaller error range.

[0083] 1 Gas-liquid two-phase flow 2 Liquid phase 3 Gas phase 10 Void fraction acquisition device 11, 11A Probe 12 Tip 20 Control unit 21 Measurement result acquisition unit 22 Frequency distribution creation unit 23 Phase discrimination unit 24 Implementation determination unit 25 Noise acquisition unit 26 Void fraction acquisition unit 27 Output unit VL Liquid phase level voltage FL Frequency of liquid phase level voltage VG Gas phase level voltage FG Frequency of gas phase level voltage VM Minimum point voltage FM Frequency of minimum point voltage S0 Void fraction acquisition method S1 Preparation process S2 Measurement result acquisition process S3 Frequency distribution creation process S4 Phase discrimination process S5 Implementation determination process S6 Noise acquisition process S7 Void fraction acquisition process 90 Computer 91 Processor 92 Main memory 93 Storage 94 Interface

Claims

1. A void fraction acquisition method comprising: a measurement result acquisition step of measuring voltage in a gas-liquid two-phase flow for a predetermined time using a probe to acquire measurement results; a frequency distribution creation step of creating a frequency distribution indicating the frequency of the voltage values ​​based on the measurement results acquired in the measurement result acquisition step; a phase discrimination step of determining the voltage value of the most frequent first peak as the liquid phase level voltage based on the frequency distribution acquired in the frequency distribution creation step; a noise acquisition step of acquiring, as noise, the frequency of the voltage values ​​in the frequency distribution that are smaller in absolute value than the liquid phase level voltage; and a void fraction acquisition step of subtracting the noise acquired in the noise acquisition step from the frequency of the voltage values ​​in the frequency distribution that are larger in absolute value than the liquid phase level voltage, acquiring the frequency with the noise removed from the frequency distribution as the frequency proportion of the gas phase in the gas-liquid two-phase flow, and acquiring the frequency proportion of the gas phase as the void fraction.

2. A void fraction acquisition method according to claim 1, wherein the measurement result acquisition step acquires the measurement result by measuring the reflection intensity of a laser introduced into the probe as a voltage signal.

3. A void fraction acquisition method as described in claim 1, wherein the measurement result acquisition process acquires the measurement result by measuring the voltage required to pass a current between the tip and base ends of the probe.

4. The void fraction acquisition method according to claim 1, further comprising an implementation determination step that is carried out between the phase discrimination step and the noise acquisition step and that determines whether or not the noise acquisition step should be carried out, wherein in the phase discrimination step, the voltage value of a second peak that is different from the first peak and that again becomes more frequent is determined to be the gas phase level voltage, and in the implementation determination step, it is determined that the noise acquisition step should be carried out if the frequency of a minimum point between the liquid phase level voltage and the gas phase level voltage in the frequency distribution, where the number of occurrences of the voltage value is the smallest, is 1 / 10 or more of the frequency of the gas phase level voltage.

5. A void fraction acquisition device comprising: a probe that measures voltage in a gas-liquid two-phase flow for a predetermined period of time; and a control unit that processes measurement results obtained by the probe, wherein the control unit has: a measurement result acquisition unit that acquires the measurement results obtained by the probe; a frequency distribution creation unit that creates a frequency distribution indicating the frequency of the voltage values ​​based on the measurement results obtained by the measurement result acquisition unit; a phase discrimination unit that determines the voltage value of the most frequent first peak as a liquid phase level voltage based on the frequency distribution obtained by the frequency distribution creation unit; a noise acquisition unit that acquires, as noise, the frequency of the voltage values ​​in the frequency distribution that have smaller absolute values ​​than the liquid phase level voltage; and a void fraction acquisition unit that takes the difference between the noise acquired by the noise acquisition unit and the frequency of the voltage values ​​in the frequency distribution that have larger absolute values ​​than the liquid phase level voltage, acquires the frequency with the noise removed from the frequency distribution as a frequency proportion of the gas phase in the gas-liquid two-phase flow, and acquires the frequency proportion of the gas phase as a void fraction.

6. A void fraction acquisition device according to claim 5, wherein the measurement result acquisition unit acquires the measurement results by measuring the reflection intensity of a laser introduced into the probe as a voltage signal.

7. A void fraction acquisition device as described in claim 5, wherein the measurement result acquisition unit acquires the measurement result by measuring the voltage required to pass a current between the tip and base ends of the probe.

8. The control unit further has an implementation determination unit that is implemented between the phase discrimination unit and the noise acquisition unit and determines whether or not to implement the noise acquisition unit, wherein the phase discrimination unit determines the voltage value of a second peak that is different from the first peak and that again becomes more frequent as the gas phase level voltage, and the implementation determination unit determines that the noise acquisition unit should be implemented when the frequency of the minimum point between the liquid phase level voltage and the gas phase level voltage in the frequency distribution, where the number of occurrences of the voltage value is the smallest, is 1 / 10 or more of the frequency of the gas phase level voltage.

9. A program that causes a computer to execute the steps of: acquiring measurement results obtained from a probe that measures voltage in a gas-liquid two-phase flow for a predetermined time; creating a frequency distribution indicating the frequency of the voltage values ​​based on the measurement results; determining the voltage value of the most frequent first peak as the liquid phase level voltage based on the frequency distribution; acquiring the frequency of the voltage values ​​in the frequency distribution that have smaller absolute values ​​than the liquid phase level voltage as noise; taking the difference of the noise from the frequency of the voltage values ​​in the frequency distribution that have larger absolute values ​​than the liquid phase level voltage, acquiring the frequency with the noise removed from the frequency distribution as the frequency proportion of the gas phase in the gas-liquid two-phase flow, and acquiring the frequency proportion of the gas phase as a void fraction.

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