A gas-liquid two-phase flow gas holdup detection method and system based on conductivity measurement

Abstract

The present application belongs to the technical field of gas-liquid two-phase flow parameter detection, and relates to a gas-liquid two-phase flow gas holdup detection method and system based on conductivity measurement, comprising: a pure liquid phase conductivity reference value, and a conductivity of the gas-liquid two-phase flow; determining a dimensionless equivalent conductivity parameter; determining a gas holdup interval corresponding to the dimensionless equivalent conductivity parameter; and determining the gas holdup of the gas-liquid two-phase flow. Through the conductivity measurement method, the present application can realize undisturbed online measurement of the gas holdup of the gas-liquid two-phase flow in an industrial closed system. By comparing the dimensionless equivalent conductivity parameter with the boundary values of the low gas holdup interval, the medium gas holdup interval and the high gas holdup interval in sequence, the gas holdup interval is determined, and the gas holdup is calculated by substituting into the corresponding gas holdup model, thereby improving the application range and accuracy of the gas holdup calculation, and keeping high measurement accuracy and stability in the range of low, medium and high gas holdups.

Description

Technical Field

[0001] This invention belongs to the field of gas-liquid two-phase flow parameter detection technology, and relates to a method and system for detecting gas content in gas-liquid two-phase flow based on conductivity measurement. Background Technology

[0002] Alkaline water electrolysis for hydrogen production is currently the core pathway for industrial green hydrogen production. With its advantages of high equipment maturity, good operational stability, and low system cost, it has been widely applied in the substitution of hydrogen from chemical byproducts, wind-solar coupled hydrogen production demonstration stations, and large-scale hydrogen production bases. The alkaline water electrolysis hydrogen production system mainly includes a diaphragm-type alkaline electrolyzer. Driven by direct current, hydrogen is evolved at the cathode and oxygen at the anode. A large number of bubbles are continuously generated from the electrode surface and rise to the surface, forming a typical vertically rising gas-liquid two-phase flow together with the electrolyte.

[0003] Currently, in the research and engineering applications of alkaline water electrolysis for hydrogen production, the gas content of gas-liquid two-phase flow is a key parameter characterizing bubble distribution density and two-phase flow structure. Optical measurement, capacitance measurement, and image recognition are commonly used to measure the gas content of gas-liquid two-phase flow. Among them, optical measurement obtains gas content information through the principle of spectral absorption or transmission, capacitance measurement uses the difference in dielectric constants between gas and liquid to reflect the gas content through changes in plate capacitance, and image recognition uses a high-speed camera to acquire flow images and calculates the gas content through bubble identification and statistics.

[0004] However, all of the above measurement methods share common problems such as demanding measurement environment requirements and easy interference with the original flow structure. Among them, optical measurement is easily affected by bubble scattering and ambient light disturbance, making it difficult to guarantee measurement stability. Capacitance measurement relies on a relatively stable liquid surface structure, and its accuracy drops significantly under strong disturbance conditions. Image recognition requires transparent pipe sections and stable lighting conditions. These measurement methods make it difficult to achieve stable and accurate online measurement of gas content in industrial closed systems, thus failing to provide reliable data support for the study of gas-liquid two-phase flow processes and the analysis of the operating status of alkaline water electrolysis hydrogen production systems. Summary of the Invention

[0005] The purpose of this invention is to provide a method and system for detecting the gas content of gas-liquid two-phase flow based on conductivity measurement. This method enables high-precision online calculation and dynamic monitoring of the gas content of gas-liquid two-phase flow, providing reliable data support for the study of gas-liquid two-phase flow processes and the analysis of the operating status of industrial systems.

[0006] To achieve the above objectives, the technical solution provided by the present invention is as follows: A method for detecting the gas content in a gas-liquid two-phase flow based on conductivity measurement, comprising: The conductivity of the pure liquid phase under pure liquid phase flow conditions is obtained, and the conductivity of the pure liquid phase is used as the reference value of the pure liquid phase conductivity. The conductivity of the gas-liquid two-phase flow is also obtained in real time. Based on the conductivity of gas-liquid two-phase flow and the benchmark values ​​of conductivity of pure liquid phase, the dimensionless equivalent conductivity parameter is determined. The dimensionless equivalent conductivity parameter is compared with the boundary values ​​of the preset low gas content range, medium gas content range and high gas content range in turn to determine the gas content range corresponding to the dimensionless equivalent conductivity parameter. The dimensionless equivalent conductivity parameter is substituted into the gas content model corresponding to the gas content range to determine the gas content of the gas-liquid two-phase flow.

[0007] The invention is further characterized by: The dimensionless equivalent conductivity parameter is the ratio of the conductivity of the gas-liquid two-phase flow to the baseline value of the conductivity of the pure liquid phase.

[0008] The gas content model for the low gas content range is as follows: , In the formula, α The gas content is the gas-liquid two-phase flow rate. The conductivity of the gas-liquid two-phase flow is given by [value]. This is the baseline value for the conductivity of pure liquid phase.

[0009] The gas content model for the middle gas content range is as follows: , In the formula, α The gas content is the gas-liquid two-phase flow rate. The conductivity of the gas-liquid two-phase flow is given by [value]. This is the baseline value for the conductivity of pure liquid phase.

[0010] The gas content model for the high gas content range is as follows: , In the formula, α The gas content is the gas-liquid two-phase flow rate. Let be the electrical conductivity of the gas-liquid two-phase flow. This is the baseline value for the conductivity of pure liquid phase.

[0011] The low gas content range is (0, 5%).

[0012] The gas content range is (5%, 20%).

[0013] The high gas content range is (20%, 50%).

[0014] A gas-liquid two-phase flow gas-holding detection system based on conductivity measurement, comprising: The conductivity acquisition module is used to acquire the conductivity of pure liquid phase under pure liquid phase flow conditions, use the pure liquid phase conductivity as the reference value of pure liquid phase conductivity, and acquire the conductivity of gas-liquid two-phase flow in real time. The first data processing module is used to determine the dimensionless equivalent conductivity parameters based on the conductivity of the gas-liquid two-phase flow and the reference value of the conductivity of the pure liquid phase. The judgment module is used to compare the dimensionless equivalent conductivity parameter with the boundary values ​​of the preset low gas content range, medium gas content range and high gas content range in sequence to determine the gas content range corresponding to the dimensionless equivalent conductivity parameter. The second data processing module is used to substitute the dimensionless equivalent conductivity parameter into the gas content model corresponding to the gas content range to determine the gas content of the gas-liquid two-phase flow.

[0015] The gas content detection method and system for gas-liquid two-phase flow based on conductivity measurement of the present invention has the following advantages: This invention enables undisturbed online measurement of gas content in gas-liquid two-phase flow within industrial closed systems through conductivity measurement. A dimensionless equivalent conductivity parameter is determined based on a pure liquid phase conductivity benchmark and the real-time acquired gas-liquid two-phase flow conductivity. By comparing this dimensionless equivalent conductivity parameter sequentially with the boundary values ​​of low, medium, and high gas content ranges, the gas content range is determined. This parameter is then substituted into the corresponding gas content model to calculate the gas content, thereby improving the applicability and accuracy of gas content calculation. This ensures high measurement accuracy and stability across low, medium, and high gas content ranges, providing reliable and continuous data support for the study of gas-liquid two-phase flow processes and the operational status analysis of alkaline water electrolysis hydrogen production systems. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the overall process of the present invention.

[0017] Figure 2 This is a schematic diagram of the overall structure of the present invention.

[0018] Figure label: 1. Conductivity acquisition module; 2. First data processing module; 3. Low gas content calculation unit; 4. Medium gas content calculation unit; 5. High gas content calculation unit; 6. Result output module. Detailed Implementation

[0019] The technical solutions of the present invention will now be described clearly and in detail with reference to the accompanying drawings. In the description of the embodiments of the present invention, unless otherwise stated, " / " indicates "or," for example, A / B can mean A or B. "And / or" in the text is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, and B alone. Furthermore, in the description of the embodiments of the present invention, "multiple" refers to two or more. The terms "first" and "second" are used for descriptive purposes only and should not be construed as implying or suggesting relative importance or implicitly indicating the number of indicated technical features. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature.

[0020] like Figure 1 As shown, this invention provides a method for detecting the gas content in a gas-liquid two-phase flow based on conductivity measurement, comprising: The conductivity of the pure liquid phase was measured under pure liquid phase flow conditions. The conductivity of the pure liquid phase was used as the reference value of the pure liquid phase conductivity, and the conductivity of the gas-liquid two-phase flow was acquired in real time.

[0021] Based on the conductivity of gas-liquid two-phase flow and the baseline values ​​of conductivity of pure liquid phase, the dimensionless equivalent conductivity parameter is determined.

[0022] The dimensionless equivalent conductivity parameter is compared sequentially with the boundary values ​​of the preset low gas content range, medium gas content range, and high gas content range to determine the gas content range corresponding to the dimensionless equivalent conductivity parameter.

[0023] The dimensionless equivalent conductivity parameter is substituted into the gas content model corresponding to the gas content range to determine the gas content of the gas-liquid two-phase flow.

[0024] In summary, this invention first obtains the conductivity of the pure liquid phase under pure liquid phase flow conditions, uses the pure liquid phase conductivity as the reference value, and then obtains the conductivity of the gas-liquid two-phase flow in real time. Based on the conductivity of the gas-liquid two-phase flow and the reference value of the pure liquid phase conductivity, a dimensionless equivalent conductivity parameter is determined. Then, the dimensionless equivalent conductivity parameter is compared with the boundary values ​​of the preset low gas content range, medium gas content range, and high gas content range in sequence to determine the gas content range corresponding to the dimensionless equivalent conductivity parameter. Finally, the dimensionless equivalent conductivity parameter is substituted into the gas content model corresponding to the gas content range to determine the gas content of the gas-liquid two-phase flow. This invention enables undisturbed online measurement of gas content in gas-liquid two-phase flow within industrial closed systems through conductivity measurement. A dimensionless equivalent conductivity parameter is determined based on a pure liquid phase conductivity benchmark and the real-time acquired gas-liquid two-phase flow conductivity. By comparing this dimensionless equivalent conductivity parameter sequentially with the boundary values ​​of low, medium, and high gas content ranges, the gas content range is determined. This parameter is then substituted into the corresponding gas content model to calculate the gas content, thereby improving the applicability and accuracy of gas content calculation. This ensures high measurement accuracy and stability across low, medium, and high gas content ranges, providing reliable and continuous data support for the study of gas-liquid two-phase flow processes and the operational status analysis of alkaline water electrolysis hydrogen production systems.

[0025] Among them, the dimensionless equivalent conductivity parameter is the ratio of the conductivity of the gas-liquid two-phase flow to the reference value of the conductivity of the pure liquid phase. By using the ratio, the influence of the difference in absolute values ​​of different conductivity can be normalized, so that the calculation of gas content depends only on the relative change, thereby enhancing the universality and comparability of the measurement results under different electrolyte systems and operating conditions.

[0026] When the gas holdup in the gas-liquid two-phase flow is low, the bubbles are sparsely distributed in the liquid phase, and the interaction between the bubbles is weak. In this case, the gas holdup model for the low gas holdup range is used. The gas holdup model for the low gas holdup range uses a linear approximation model to calculate the gas holdup. The gas holdup model for the low gas holdup range is as follows: , In the formula, α The gas content is the gas-liquid two-phase flow rate. Let be the electrical conductivity of the gas-liquid two-phase flow. This is the baseline value for the conductivity of pure liquid phase.

[0027] When the gas content is in the medium range, the interaction between bubbles gradually increases, and the liquid phase conductive channel is significantly disturbed. At this time, the gas content model for the medium gas content range is called. The gas content model for the medium gas content range is calculated based on the Bruggemann effective medium model. The gas content model for the medium gas content range is as follows: , In the formula, α The gas content is the gas-liquid two-phase flow rate. Let be the electrical conductivity of the gas-liquid two-phase flow. This is the baseline value for the conductivity of pure liquid phase.

[0028] When the gas content increases further, bubbles may aggregate. In this case, the gas content model for the high gas content range is used. The gas content model for the high gas content range is calculated based on the Maxwell-Garnett model. The gas content model for the high gas content range is as follows: , In the formula, α The gas content is the gas-liquid two-phase flow rate. Let be the electrical conductivity of the gas-liquid two-phase flow. This is the baseline value for the conductivity of pure liquid phase.

[0029] The low gas content range is (0, 5%), which can accurately define the critical range where bubbles are sparsely distributed and the interaction between bubbles is negligible. This allows for the use of a linear approximation model to simplify calculations and ensure measurement accuracy and computational efficiency under low gas content conditions.

[0030] The gas content range is (5%, 20%), which can accurately cover the typical transition range where the interaction between bubbles gradually increases and the liquid phase conductive channel is significantly disturbed. Therefore, the Bruggemann effective medium model can be used to accurately describe the conductivity characteristics of the gas-liquid two-phase mixture system.

[0031] The high gas content range is (20%, 50%), which can effectively cover the typical range of high gas content where bubbles may form agglomeration structures and the gas-liquid two-phase distribution tends to be complex. Therefore, the Maxwell-Garnett model can be used to accurately describe the conductivity response characteristics of discrete bubbles in the continuous liquid phase.

[0032] like Figure 2 As shown, the present invention also provides a gas-liquid two-phase flow gas content detection system based on conductivity measurement, comprising: The conductivity acquisition module 1 is used to acquire the conductivity of pure liquid phase under pure liquid phase flow conditions, use the conductivity of pure liquid phase as the reference value of pure liquid phase conductivity, and acquire the conductivity of gas-liquid two-phase flow in real time. The first data processing module 2 is used to determine the dimensionless equivalent conductivity parameters based on the conductivity of the gas-liquid two-phase flow and the reference value of the conductivity of the pure liquid phase. The judgment module is used to compare the dimensionless equivalent conductivity parameter with the boundary values ​​of the preset low gas content range, medium gas content range and high gas content range in sequence to determine the gas content range corresponding to the dimensionless equivalent conductivity parameter. The second data processing module is used to substitute the dimensionless equivalent conductivity parameter into the gas content model corresponding to the gas content range to determine the gas content of the gas-liquid two-phase flow.

[0033] like Figure 2 As shown, the second data processing module includes a low gas content calculation unit 3, a medium gas content calculation unit 4, and a high gas content calculation unit 5. The low gas content calculation unit 3 is used to input the dimensionless equivalent conductivity parameter into the gas content model of the low gas content range when the dimensionless equivalent conductivity parameter is in the low gas content range, and calculate the gas content of the gas-liquid two-phase flow. The medium gas content calculation unit 4 is used to input the dimensionless equivalent conductivity parameter into the gas content model of the medium gas content range when the dimensionless equivalent conductivity parameter is in the medium gas content range, and calculate the gas content of the gas-liquid two-phase flow. The high gas content calculation unit 5 is used to input the dimensionless equivalent conductivity parameter into the gas content model of the high gas content range when the dimensionless equivalent conductivity parameter is in the high gas content range, and calculate the gas content of the gas-liquid two-phase flow.

[0034] like Figure 2 As shown, the present invention also provides a gas-liquid two-phase flow gas content detection system based on conductivity measurement, and further includes a result output module 6, which is used to output the gas content of the gas-liquid two-phase flow calculated by the second data processing module.

[0035] Example 1 like Figure 2 As shown, taking an alkaline water electrolysis hydrogen production system as the research object, the gas content of the gas-liquid two-phase flow at the liquid phase outlet of the gas-liquid separator is measured and calculated online to verify the effectiveness of the method of the present invention.

[0036] This alkaline water electrolysis hydrogen production system mainly includes an electrolyzer, a gas-liquid separator, an electrolyte circulation pipeline, and a gas collection system. During operation, hydrogen is generated at the cathode and oxygen at the anode. The generated gases enter the electrolyte circulation pipeline in the form of bubbles and undergo gas-liquid separation in the gas-liquid separator. Due to the migration of bubbles in the liquid phase and incomplete separation, a certain proportion of bubbles may still exist at the liquid phase outlet of the gas-liquid separator, thus forming a two-phase flow state.

[0037] In this embodiment, a conductivity acquisition module 1 is installed at the liquid phase outlet pipe of the gas-liquid separator. The conductivity acquisition module includes an online conductivity sensor for real-time measurement of the conductivity of the gas-liquid two-phase fluid. The conductivity sensor is installed inside the liquid phase outlet pipe of the gas-liquid separator and is connected to the first data processing unit 2 via a wireless transmission unit.

[0038] Before system startup, the conductivity measurement system is first calibrated. Under the condition that only pure electrolyte flows in the gas-liquid separator, the conductivity of the pure electrolyte is measured using conductivity acquisition module 1. This value is then sent to the first data processing unit 2 as a reference conductivity parameter. Subsequently, under stable operating conditions of the water electrolysis hydrogen production system, the effective conductivity of the gas-liquid two-phase flow system is acquired in real time through the conductivity acquisition module 1. And transmit it to the first data processing unit 2.

[0039] The first data processing unit 2 processes the acquired conductivity signal and calculates the ratio between the effective conductivity of the gas-liquid two-phase system and the conductivity of the pure liquid phase, thereby obtaining the dimensionless equivalent conductivity parameter. .

[0040] The judgment module compares the dimensionless equivalent conductivity parameter with the boundary values ​​of the preset low gas content range, medium gas content range and high gas content range in sequence to determine the gas content range corresponding to the dimensionless equivalent conductivity parameter.

[0041] When the dimensionless equivalent conductivity parameter is in the low gas content range (0, 5%), the gas content of the gas-liquid two-phase flow is low, the bubbles are sparsely distributed in the liquid phase, and the interaction between the bubbles is weak. The low gas content calculation unit 3 of the second data processing module calls the gas content model of the low gas content range, inputs the dimensionless equivalent conductivity into the gas content model of the low gas content range, calculates the gas content of the gas-liquid two-phase flow, and outputs it through the result output module 6.

[0042] When the dimensionless equivalent conductivity parameter is in the medium gas content range of (5%, 20%), the interaction between bubbles gradually increases, and the liquid phase conductive channel is significantly disturbed. The medium gas content calculation unit 4 calls the gas content model in the medium gas content range, inputs the dimensionless equivalent conductivity into the gas content model in the medium gas content range, calculates the gas content of the gas-liquid two-phase flow, and outputs it through the result output module 6.

[0043] When the dimensionless equivalent conductivity parameter is in the high gas content range (20%, 50%), the gas content increases further, and the bubbles may form agglomeration structures. The high gas content calculation unit 5 calls the gas content model of the high gas content range, inputs the dimensionless equivalent conductivity into the gas content model of the high gas content range, calculates the gas content of the gas-liquid two-phase flow, and outputs it through the result output module 6.

[0044] By continuously monitoring the gas content at the liquid outlet of the gas-liquid separator, the separation efficiency of the gas-liquid separator can be further analyzed, and important data can be provided for the optimization of the gas-liquid separator structure, the adjustment of operating parameters, and the analysis of the operating status of the electrolyzer.

[0045] By combining the above-mentioned different models, a correspondence between conductivity and gas phase volume fraction can be established over a wide range of gas holdup, thereby enabling the calculation of gas holdup in gas-liquid two-phase flow. Finally, based on the measured effective conductivity data and the corresponding model calculation results, the gas holdup parameters of the gas-liquid two-phase flow are obtained, and the measurement results are output through the result output module 6.

[0046] Compared with existing technologies, the gas holdup calculation method for gas-liquid two-phase flow proposed in this invention improves the applicability and accuracy of gas holdup calculation by combining multiple effective medium theoretical models and selecting appropriate calculation methods according to different gas holdup ranges. At the same time, the method is simple to operate, the measurement process is stable, and it can be applied to various gas-liquid two-phase flow conditions, which has important engineering application value for the measurement of multiphase flow parameters in industrial processes.

[0047] It is understood that this invention has been described through some embodiments, and those skilled in the art will recognize that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of this invention. Furthermore, under the teachings of this invention, these features and embodiments can be modified to adapt to specific situations and materials without departing from the spirit and scope of this invention. Therefore, this invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this invention are within the protection scope of this invention.

Claims

1. A method for detecting the gas content in a gas-liquid two-phase flow based on conductivity measurement, characterized in that, include: The conductivity of the pure liquid phase under pure liquid phase flow conditions is obtained, and the conductivity of the pure liquid phase is used as the reference value of the pure liquid phase conductivity. The conductivity of the gas-liquid two-phase flow is also obtained in real time. Based on the conductivity of gas-liquid two-phase flow and the benchmark values ​​of conductivity of pure liquid phase, the dimensionless equivalent conductivity parameter is determined. The dimensionless equivalent conductivity parameter is compared with the boundary values ​​of the preset low gas content range, medium gas content range and high gas content range in turn to determine the gas content range corresponding to the dimensionless equivalent conductivity parameter. The dimensionless equivalent conductivity parameter is substituted into the gas content model corresponding to the gas content range to determine the gas content of the gas-liquid two-phase flow.

2. The method for detecting gas content in a gas-liquid two-phase flow based on conductivity measurement according to claim 1, characterized in that, The dimensionless equivalent conductivity parameter is the ratio of the conductivity of the gas-liquid two-phase flow to the baseline value of the conductivity of the pure liquid phase.

3. The method for detecting gas content in a gas-liquid two-phase flow based on conductivity measurement according to claim 1, characterized in that, The gas content model for the low gas content range is as follows: ， In the formula, α The gas content is the gas-liquid two-phase flow rate. Let be the electrical conductivity of the gas-liquid two-phase flow. This is the baseline value for the conductivity of pure liquid phase.

4. The method for detecting gas content in a gas-liquid two-phase flow based on conductivity measurement according to claim 1, characterized in that, The gas content model for the middle gas content range is as follows: ， In the formula, α The gas content is the gas-liquid two-phase flow rate. The conductivity of the gas-liquid two-phase flow is given by [value]. This is the baseline value for the conductivity of pure liquid phase.

5. The method for detecting gas content in a gas-liquid two-phase flow based on conductivity measurement according to claim 1, characterized in that, The gas content model for the high gas content range is as follows: ， In the formula, α The gas content is the gas-liquid two-phase flow rate. Let be the electrical conductivity of the gas-liquid two-phase flow. This is the baseline value for the conductivity of pure liquid phase.

6. The method for detecting gas content in a gas-liquid two-phase flow based on conductivity measurement according to claim 1, characterized in that, The low gas content range is (0, 5%).

7. The method for detecting gas content in a gas-liquid two-phase flow based on conductivity measurement according to claim 1, characterized in that, The gas content range is (5%, 20%).

8. The method for detecting gas content in a gas-liquid two-phase flow based on conductivity measurement according to claim 1, characterized in that, The high gas content range is (20%, 50%).

9. A gas-liquid two-phase flow gas-holding rate detection system based on conductivity measurement, characterized in that, The method described in any one of claims 1 to 8 includes: The conductivity acquisition module is used to acquire the conductivity of pure liquid phase under pure liquid phase flow conditions, use the pure liquid phase conductivity as the reference value of pure liquid phase conductivity, and acquire the conductivity of gas-liquid two-phase flow in real time. The first data processing module is used to determine the dimensionless equivalent conductivity parameters based on the conductivity of the gas-liquid two-phase flow and the reference value of the conductivity of the pure liquid phase. The judgment module is used to compare the dimensionless equivalent conductivity parameter with the boundary values ​​of the preset low gas content range, medium gas content range and high gas content range in sequence to determine the gas content range corresponding to the dimensionless equivalent conductivity parameter. The second data processing module is used to substitute the dimensionless equivalent conductivity parameter into the gas content model corresponding to the gas content range to determine the gas content of the gas-liquid two-phase flow.

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