A microwave sensor based on coplanar waveguide excited spiral structure

Abstract

The application relates to a coplanar waveguide excitation type spiral microwave sensor, which comprises a measuring electrode, a coplanar waveguide port, a shielding layer and a test pipeline, the measuring electrode comprises spiral-shaped emitter plates and receiver plates which are identical in structure and size, the spiral-shaped emitter plates and receiver plates are spirally wound along the outer wall of the test pipeline respectively, and the parameter optimization method comprises the following steps: determining the structure parameters to be optimized as a spiral angle, a plate opening angle and a pitch ratio; designing a total sensitivity calculation method; calculating the response of the coplanar waveguide excitation type spiral microwave sensor under the conditions of different dielectric constants, different structure parameters and working frequencies, determining the optimal spiral angle and working frequency; and based on the determined optimal spiral angle and working frequency, the plate opening angle and the pitch ratio of the two structure parameters are simulated and optimized by taking different flow patterns as the optimization objects. The application improves the adaptability of the sensor to non-uniform flow patterns by optimizing the spiral structure, and realizes high-precision and wide-range moisture content measurement.

Description

Technical Field

[0001] Specifically, this invention relates to a microwave sensor based on a coplanar waveguide-excited helical structure, used to measure the water holdup of oil-water two-phase flow in a horizontal pipe. Background Technology

[0002] Horizontal oil-water two-phase flow is widely present in oil extraction and transportation processes. Its flow characteristics are affected by the density difference between oil and water, interfacial tension, and gravity stratification effects, resulting in complex and variable flow patterns, posing a significant challenge to water holdup measurement. Traditional water holdup measurement methods, such as conductivity and capacitance methods, have the following limitations: conductivity methods are only applicable to high water-cut conditions where water is a continuous phase, capacitance methods have insufficient resolution at high water cuts, and both are susceptible to salinity. Furthermore, the significant oil-water phase slippage effect in horizontal pipelines and the non-uniform local concentration distribution further increase the measurement difficulty.

[0003] Microwave methods have gradually become a research hotspot due to their advantages such as non-contact operation, strong anti-interference ability, and sensitivity to changes in dielectric constant. Existing microwave sensors are mostly designed for single or uniform flow patterns, making it difficult to adapt to complex flow patterns such as stratified flow and bidispersed flow in horizontal pipes. For example, traditional resonant cavity sensors have poor adaptability to non-uniform dielectric constant distributions, while transmission antenna sensors lack sensitivity in low-velocity stratified flow. Therefore, there is an urgent need to develop a high-resolution water-holding capacity sensor suitable for all flow patterns and with a wide measurement range in horizontal oil-water two-phase flow. Summary of the Invention

[0004] The purpose of this invention is to provide a coplanar waveguide-excited spiral microwave sensor suitable for measuring the water holdup of horizontal oil-water two-phase flow. By optimizing the spiral structure, the sensor's adaptability to non-uniform flow patterns is improved, achieving high-precision, wide-range water holdup measurement. The technical solution is as follows: A microwave sensor based on a coplanar waveguide-excited helical structure includes a measuring electrode, a coplanar waveguide port, a shielding layer, and a test pipe. The measuring electrode includes a helical emitting electrode and a receiving electrode with identical structure and size, which are spirally wound along the outer wall of the test pipe. The coplanar waveguide port is attached to the outer wall of the pipe and includes a rectangular ground plane, a central rectangular electrode of the coplanar waveguide excitation port electrically connected to the emitting electrode, and a central rectangular electrode of the coplanar waveguide receiving port electrically connected to the receiving electrode.

[0005] Furthermore, its structural parameters include helix angle, electrode opening angle, and pitch ratio. The optimal combination of structural parameters is: helix angle 360°, pitch ratio 94 mm / 30 mm, and electrode opening angle 110°.

[0006] Furthermore, the following method is used for parameter optimization: The overall sensitivity calculation method is as follows: The measured values ​​of the coplanar waveguide-excited helical microwave sensor include amplitude attenuation and phase shift. The comprehensive sensitivity of amplitude attenuation and the comprehensive sensitivity of phase shift are calculated separately. The comprehensive sensitivity of amplitude attenuation and the comprehensive sensitivity of phase shift are multiplied to obtain the overall sensitivity. Based on the overall sensitivity, the response of the coplanar waveguide-excited helical microwave sensor under different dielectric constants, structural parameters and operating frequencies is calculated to determine the optimal helical angle and operating frequency. Based on the determined optimal helix angle and operating frequency, the two structural parameters, plate opening angle and pitch ratio, are optimized through simulation of different flow patterns.

[0007] Furthermore, the comprehensive sensitivity of amplitude attenuation is the sum or weighted sum of the following three items: the mean of the linearly normalized change in amplitude attenuation reflecting the average response of the sensor to changes in dielectric constant, the normalized mean of the maximum amplitude attenuation reflecting the normalized average response, and the reciprocal of the standard deviation of amplitude attenuation reflecting the consistency and stability of the response.

[0008] Furthermore, the phase-shift comprehensive sensitivity is the sum or weighted sum of the following three items: the mean of the linearly normalized change in phase shift reflecting the average response of the sensor to changes in dielectric constant, the normalized mean of the maximum phase shift reflecting the normalized average response, and the reciprocal of the standard deviation of phase shift reflecting the consistency and stability of the response.

[0009] Furthermore, before calculating the response of the coplanar waveguide-excited helical microwave sensor under different dielectric constants, structural parameters, and operating frequencies, and determining the optimal helical angle and operating frequency, the process also includes a step of screening for combinations of structural parameters and operating frequencies that satisfy monotonically changing conditions.

[0010] Furthermore, the method for calculating the response of the coplanar waveguide-excited helical microwave sensor under different dielectric constants, structural parameters, and operating frequencies, and determining the optimal helical angle and operating frequency, is as follows: Considering the influence of the change in helical angle on the selection of operating frequency, for different helical angles, calculate the total sensitivity of each electrode angle and pitch ratio combination at different operating frequencies, and then determine the optimal helical angle and operating frequency.

[0011] Furthermore, based on the determined optimal helix angle and operating frequency, the following method is used to optimize the two structural parameters, plate opening angle and pitch ratio, through simulation of different flow patterns: Different flow patterns were modeled using simulation software. Under each flow pattern, the response characteristics of different structural parameters to water holding capacity were evaluated by changing two structural parameters, plate angle and pitch ratio, and water holding capacity. Calculate the total sensitivity of the coplanar waveguide-excited helical microwave sensor under different structural parameters, and further calculate the mean and standard deviation of the total sensitivity of each set of structural parameters under different flow patterns; The ratio of the mean to the standard deviation of the total sensitivity was used as the final optimization index to determine the optimal combination of structural parameters, including the helix angle, electrode opening angle, and pitch ratio.

[0012] The advantages of this invention are: (1) The spiral electrode design enables the electric field to uniformly cover the pipe cross section, effectively capturing the dielectric constant changes of stratified flow and dispersed flow, and improving the adaptability to non-uniform flow patterns.

[0013] (2) Electromagnetic waves are fed in using a coplanar waveguide feeding method to reduce signal reflection and ensure the stability of high-frequency microwave transmission.

[0014] (3) Experiments show that the sensor has an absolute average relative error (AAPD) of 7.24% in the water holding capacity range of 5% to 95%, and maintains high resolution in all six flow patterns. Attached Figure Description

[0015] Figure 1 This is a structural diagram of a coplanar waveguide-excited spiral microwave sensor.

[0016] Figure 2 Is with Figure 1 The overall structural diagram of the coplanar waveguide-excited helical microwave sensor in different views: (a) is the left view, (b) is the front view, and (c) is the top view.

[0017] Figure 3 This is a schematic diagram of a coplanar waveguide-excited spiral microwave sensor measurement system.

[0018] Figure 4 The simulation model and parameter optimization diagram of the coplanar waveguide-excited helical microwave sensor are shown in (a), (b), and (c), which are respectively the optimized diagrams of the helix angle, electrode opening angle, and pitch of the sensor structure parameters.

[0019] Figure 5 The following are the sensitivity distributions of a coplanar waveguide-excited helical microwave sensor for different helix angles: (a), (b), and (c) are the sensitivity distributions at helix angles of 180°, 270°, and 360°, respectively.

[0020] Figure 6 These are simulation models of a coplanar waveguide-excited helical microwave sensor under different flow patterns: (a), (b), (c), (d), (e), and (f) are simulation structure diagrams of flow patterns ST, ST&MI, DW / O&DO O / W, DO / W&W, DO / W, and DW / O, respectively.

[0021] Figure 7 These are the total sensitivity values ​​corresponding to different combinations of size parameters under different flow patterns of the coplanar waveguide-excited helical microwave sensor: (a), (b), (c), (d), (e), and (f) are the total sensitivities of flow patterns ST, ST&MI, DW / O&DO O / W, DO / W&W, DO / W, and DW / O, respectively.

[0022] Figure 8 These are the sensitivity indices corresponding to different combinations of size parameters of the coplanar waveguide-excited helical microwave sensor: (a) is the mean and standard deviation of the total sensitivity of each group of structural parameters under different flow patterns, and (b) is the ratio of the mean to the standard deviation of the total sensitivity.

[0023] Figure 9 This describes the response characteristics of a coplanar waveguide-excited spiral microwave sensor to water holding capacity under ST flow pattern in a simulation experiment.

[0024] Figure 10 This describes the response characteristics of a coplanar waveguide-excited helical microwave sensor to water holding capacity under the ST&MI flow pattern in a simulation experiment.

[0025] Figure 11 This describes the response characteristics of a coplanar waveguide-excited spiral microwave sensor to water holding capacity under DW / O&D O / W flow patterns in a simulation experiment.

[0026] Figure 12 This describes the response characteristics of a coplanar waveguide-excited spiral microwave sensor to water holding capacity under DO / W&W flow patterns in a simulation experiment.

[0027] Figure 13 This describes the response characteristics of a coplanar waveguide-excited helical microwave sensor to water holding capacity under DO / W flow patterns in a simulation experiment.

[0028] Figure 14 This describes the response characteristics of a coplanar waveguide-excited spiral microwave sensor to water holding capacity under the DW / O flow pattern in a simulation experiment.

[0029] Figure 15 The following are the signal fluctuations of a coplanar waveguide-excited spiral microwave sensor under different flow patterns in a dynamic experiment: (a), (b), (c), (d), (e), and (f) are the signal fluctuation diagrams of the coplanar waveguide-excited spiral microwave sensor under different flow patterns ST, ST&MI, DW / O&DO O / W, DO / W&W, DO / W, and DW / O, respectively.

[0030] Figure 16 This is the relationship between the phase output of the coplanar waveguide-excited helical microwave sensor and the total flow rate and water content (with flow pattern information).

[0031] Figure 17 The results are the water holding capacity predictions from a coplanar waveguide-excited spiral microwave sensor.

[0032] Explanation of icon numbers: 1. Coaxial feed line; 2. Coplanar waveguide port; 3. Transmitting electrode; 4. Receiving electrode; 5. Shielding layer; 6. Test conduit; 7. Fluid flow area; 8. Rectangular ground plane; 9. Center rectangular electrode of coplanar waveguide excitation port; 10. Center rectangular electrode of coplanar waveguide receiving port. Detailed Implementation

[0033] This invention aims to design a coplanar waveguide-excited helical microwave sensor to measure the water holdup of horizontal oil-water two-phase flow. The water holdup is obtained by detecting the phase information of the microwaves. The specific implementation process is described below with reference to the accompanying drawings: I. Coplanar waveguide-excited helical microwave sensor and microwave measurement system The structure of the coplanar waveguide-excited helical microwave sensor is as follows: Figure 1 and Figure 2 As shown, the sensor consists of a test pipe 6, measuring electrodes, a coplanar waveguide port 2, and a shielding layer 5. The measuring electrodes include a transmitting electrode 3 for signal transmission and a receiving electrode 4 for signal reception. The transmitting electrode 3 and receiving electrode 4 are identical in shape, both being spiral electrodes. The coplanar waveguide port 2, along with the transmitting electrode 3 and receiving electrode 4, encloses the test pipe. A shielding layer 5, 0.2 mm thick, is located 7 mm from the outer wall of the pipe to prevent external interference to the sensor. The measuring electrodes, coplanar waveguide port 2, and shielding layer 5 are all made of copper. The coplanar waveguide port 2 includes a coplanar waveguide excitation port and a receiving port with identical structures. It consists of two rectangular ground planes 8, a central rectangular electrode 9 for the coplanar waveguide excitation port, and a central rectangular electrode 10 for the coplanar waveguide receiving port, all tightly attached to the outer wall of the pipe. The central rectangular electrode 9 for the coplanar waveguide excitation port and the central rectangular electrode 10 for the coplanar waveguide receiving port are respectively connected to the corresponding measuring electrodes.

[0034] Test pipe 6 is an acrylic tube with an inner radius of... r It is 10 mm, outer radius R The sensor is 15 mm in diameter. It is placed close to the outer pipe wall and does not come into contact with the fluid being measured, so the measurement of water holding capacity is no longer affected by particulate scale, oil droplets, and ambient temperature in the pipe.

[0035] The microwave measurement system for detecting water holdup in oil-water two-phase flow established in this invention is as follows: Figure 3 As shown, the microwave signal is fed into the transmitting electrode through a coplanar waveguide port, passes through the oil-water mixture in the test pipe, and is captured by the receiving electrode. It is then connected to the microwave measurement system through the coplanar waveguide port. The dielectric constant of the oil-water mixture varies with the water-holding capacity, resulting in variations in the transmitted signal, i.e., S. 21The amplitude attenuation and phase shift of the parameters; the S-wave at a fixed operating frequency (650 MHz) is detected using an amplitude and phase detection circuit. 21 Parameters; the water holding capacity is calculated based on a mixed dielectric constant model.

[0036] II. Overall Sensitivity Design For the selected structural parameters and operating frequency, the following calculations are performed: Response change Find the maximum value of the sensor's response to each dielectric constant under each structural parameter and frequency condition. and minimum value The sensor response value is linearly normalized: (1) After normalization, calculate the relative response change caused by each change in dielectric constant: (2) In the formula For the first i The change in relative response caused by the change in the secondary dielectric constant ε i For the first i The dielectric constant of the fluid inside the secondary pipe. ε i+1 For the first i +1 Dielectric constant of the fluid in the pipe.

[0037] The mean of the relative response change caused by each change in dielectric constant is defined as the mean of the linearly normalized change. The larger the change in response, the more sensitive the sensor is to changes in dielectric constant. The calculation formula is as follows: (3) Maximum value normalization: Extracting the maximum value of the change in each group of responses. The change in each response group is then normalized by dividing it by the maximum value, and this normalized change in response is defined as the maximum value normalized response change. Calculate the mean of the maximum normalized response change of the sensor under the current structure and frequency. and standard deviation Normalization can eliminate the influence of dimensions, facilitating comparisons under different conditions. (4) To design a reasonable overall sensitivity value, the following three indicators should be considered: mean of linearly normalized change This reflects the sensor's average response to changes in dielectric constant during actual measurements. The larger the average value, the more sensitive the sensor is to changes in dielectric constant at that structure and frequency.

[0038] The mean of the normalized response change at the maximum value This reflects the normalized average response. The larger the normalized mean, the more uniform the sensor's response is at that structure and frequency, indicating better measurement consistency.

[0039] Standard deviation ( std The standard deviation reflects the consistency and stability of the response. The smaller the standard deviation, the more consistent the sensor's response is under that structure and frequency, and the better the measurement stability.

[0040] Therefore, when optimizing the sensor's structural parameters and operating frequency, the appropriate choice should be made. and Large and standard deviation std Small structural parameters and operating frequency. To uniformly describe the three indicators and facilitate the optimization of structural parameters and operating frequency selection, a comprehensive sensitivity is set: (5) As a comprehensive indicator of sensor response sensitivity, the larger this indicator is, the higher the sensor's response sensitivity under that structure and operating frequency, and the better the measurement consistency.

[0041] The sensor's measurements include amplitude attenuation and phase shift. Amplitude attenuation and phase shift play a crucial role in decoupling the salinity of the aqueous phase. To comprehensively consider the sensor's potential future applications, both amplitude and phase information need to be taken into account, and the combined sensitivity of amplitude attenuation for these two measurements needs to be calculated separately. and phase shift overall sensitivity The overall sensitivity. For certain structural parameters and frequencies, the sensor may only be measurable in either amplitude or phase, meaning the sensitivity is not zero. To comprehensively consider the measurement sensitivity levels of both amplitude and phase, the overall sensitivity is set as follows: (6) Multiplying the amplitude sensitivity by the phase sensitivity eliminates structural parameters and frequencies that have only one measurable value. The total sensitivity is maximized only when both amplitude and phase are measurable and both have high sensitivity.

[0042] In summary, the overall sensitivity designed in this invention is as follows: the sensor's measured values ​​include amplitude attenuation and phase shift; the comprehensive sensitivity for amplitude attenuation is calculated separately. and phase shift overall sensitivity The amplitude attenuation is combined with the sensitivity. With phase shift Multiply the combined sensitivities to obtain the total sensitivity. ; Among them, the comprehensive sensitivity of amplitude attenuation It is the sum or weighted sum of the following three items: the mean of the linearly normalized change in amplitude decay of the average response of the sensor to changes in dielectric constant, the normalized mean of the maximum amplitude decay of the normalized average response, and the reciprocal of the standard deviation of amplitude decay, which reflects the consistency and stability of the response. Phase shift overall sensitivity It is the sum or weighted sum of the following three terms: the mean of the linearly normalized change in phase shift reflecting the average response of the sensor to changes in dielectric constant, the normalized mean of the maximum phase shift reflecting the normalized average response, and the reciprocal of the standard deviation of phase shift reflecting the consistency and stability of the response.

[0043] III. Parameter Design for Simulation Optimization of Coplanar Waveguide Excited Helical Microwave Sensor To ensure that the electromagnetic field excited by the sensor in the fluid of the pipeline measurement area is uniform and strong, the key geometric dimensions of the coplanar waveguide-excited helical microwave sensor are optimized using HFSS software.

[0044] To comprehensively verify the dielectric constant detection capability of a coplanar waveguide-excited helical microwave sensor under different structural parameters, operating frequencies, and flow patterns, a detailed simulation scheme and analysis procedure were designed as follows. The simulation model of the sensor is shown in the figure. Figure 4 As shown. The following are the specific parameter settings and sensitivity analysis steps: Dielectric constant Sixteen different dielectric constants were set, ranging from 3 to 78. , ε w The dielectric constant of water is ε o (where is the dielectric constant of the oil phase), with a step size of 5. These dielectric constant values ​​simulate the mixed dielectric constant under different oil-water ratios in the test pipeline, ensuring the adaptability and accuracy of the sensor across the entire range of water holdup in oil-water two-phase flow.

[0045] helix angle The helix angle is the angle at which the helical electrode plate winds around the pipe. Three angles were chosen: 180°, 270°, and 360°. The helix angle determines the integrity of the helical structure, and different helix angles affect the electromagnetic field distribution and sensitivity of the sensor.

[0046] Plate angle The electrode angle refers to the central angle corresponding to the horizontal cross-section of the helical electrode. The width of the electrode should ideally encompass the area through which the fluid flows within the pipe; therefore, it cannot be too narrow, nor too wide to avoid interference between the two electrodes. Thus, five angles are set: 100°, 110°, 120°, 130°, and 140°. Changes in the electrode angle can affect the sensor's capacitance characteristics and electric field distribution, thereby influencing the sensor's sensitivity.

[0047] pitch L Pitch refers to the axial distance between two adjacent turns of the helical electrode plate. Five lengths are provided: 84 mm, 89 mm, 94 mm, 99 mm, and 104 mm. Variations in pitch affect the inductive characteristics and resonant frequency of the sensor, making it an important parameter for optimizing sensor performance. Furthermore, this invention utilizes the pitch ratio, i.e., the ratio of pitch to the outer diameter of the test pipe, as a structural parameter that substitutes for pitch.

[0048] The emitter plate 3 and the receiver plate 4 have the same shape, i.e., the helix angle is the same. , plate angle pitch L All are identical. The measuring electrode consists of a spiral emitting electrode and a receiving electrode, the electrode material being copper, spirally wound along the outer wall of the pipe.

[0049] With a total of 75 different combinations of structural parameters, this design ensures a wide range of design options, enabling a comprehensive evaluation of the impact of structural parameters on sensor performance.

[0050] frequency f The frequency range is from 0.3 GHz to 1.2 GHz, with a step size of 0.005 GHz, totaling 181 frequency points. Through precise frequency settings, the sensor's response characteristics at different frequencies can be studied in detail, and the optimal operating frequency can be found.

[0051] Exclude structural parameters and frequency combinations whose responses do not monotonically change with dielectric constant to ensure the measurement reliability of the sensor.

[0052] IV. Simulation Optimization of Helix Angle First, calculate the sensor response under the different dielectric constants, structural parameters, and frequencies described above. The specific steps are as follows: 1) Response Calculation: Simulate the sensor's response to each dielectric constant under various structural parameters and frequency conditions using ANSYS. Reveal the sensor's overall sensitivity and response characteristics under different conditions.

[0053] 2) Monotonicity Verification: Check whether the sensor's response changes monotonically with the dielectric constant. A monotonically changing sensor response indicates stable and measurable detection capability. Eliminate structural parameters and frequency combinations whose responses do not change monotonically with the dielectric constant to ensure the sensor's measurement reliability.

[0054] The change in helix angle has a significant impact on frequency selection. After selecting structural parameters and frequencies that satisfy monotonic variation, the average of the total sensitivity of the 25 combinations of electrode angles and pitches corresponding to different helix angles is taken to obtain the total sensitivity at different frequencies when the helix angle is determined.

[0055] like Figure 5 As shown, the sensor exhibits the best overall sensitivity at a helix angle of 360° and an operating frequency of 0.65 GHz. Therefore, the helix angle of 360° and the operating frequency of 0.65 GHz were determined. Subsequent simulations of different flow patterns were used to optimize the two structural parameters: the plate angle and the helix pitch.

[0056] V. Simulation Optimization of Two Structural Parameters: Plate Angle and Pitch There are six basic flow patterns in horizontal oil-water two-phase flow: ST, ST&MI, DW / O&DO O / W, DO / W&W, DO / W, and DW / O. To determine the optimal parameters for the electrode angle and pitch, these six flow patterns were modeled and simulated in ANSYS software. Figure 6 As shown. Under one flow pattern, the response characteristics of different structures to water holding capacity are evaluated by changing structural parameters and water holding capacity.

[0057] For ST flow patterns, set the water holding capacity. The range is 10%-90%, with a step size of 5%; for the ST&MI flow pattern, the water holding capacity is set to 10%-90%. The water holdup is set to 15%-85%, with a step size of 5%; for DW / O & D O / W flow patterns, the water holdup is set to... The range is 21%-77%, with a step size of 4%; for DO / W&W flow patterns, the water holding capacity is set to 21%-77%. The water holding capacity is set at 76%-92%, with a step size of 2%; for DO / W flow patterns, the water holding capacity is set at... The water holdup is set to 75%-95%, with a step size of 5%; for DW / O flow patterns, the water holdup is set to... The range is 5%-25%, with a step size of 5%. After simulation, the overall sensitivity of the sensor under different structural parameters is calculated using the same method. The overall sensitivity of the sensor under different flow patterns is as follows: Figure 7 As shown in Table 1, for ease of representation, the 25 combinations of plate angle and pitch are numbered.

[0058] Table 1

[0059] After calculating the sensitivity of different structural parameters under various flow patterns, in order to determine the optimal combination of structural parameters, the mean total sensitivity of each set of structural parameters under different flow patterns was further calculated. and standard deviation std .

[0060] The mean overall sensitivity reflects the average sensitivity of the structural parameter under different flow patterns. A larger mean indicates higher sensitivity of the sensor under any flow pattern. The standard deviation measures the degree of sensitivity fluctuation between different flow patterns. A smaller standard deviation indicates higher consistency of sensitivity across different flow patterns. Therefore, when optimizing structural parameters, the mean overall sensitivity should be as large as possible, while the standard deviation should be as small as possible to ensure that the sensor maintains stable and sensitive measurement performance under different flow patterns.

[0061] To comprehensively consider the influence of the mean and standard deviation of sensitivity, the ratio of the mean to the standard deviation is used as the final optimization index. After flow pattern simulation, the mean, standard deviation, and ratio of the total sensitivity for all structural parameters are as follows: Figure 8 As shown.

[0062] Depend on Figure 8 It can be seen that the sensor exhibits the best measurement performance when the pitch is 94 mm and the electrode angle is 110°. In this embodiment, the inner radius of pipe 6 is tested. r It is 10 mm, outer radius R The pitch is 15 mm, and the pitch ratio is used instead of the pitch. The pitch ratio refers to the ratio of the pitch to the outer diameter of the pipe. Therefore, a helix angle of 360°, a pitch ratio of 94 mm / 30, and an electrode angle of 110° are the optimal combination of structural parameters for this sensor.

[0063] In oil-water two-phase flow, the distribution of oil and water phases within the pipeline is not uniform due to different flow patterns, and the water holdup measurement of the sensor may be affected by changes in flow pattern. Therefore, it is necessary to investigate the corresponding characteristics of the sensor in terms of water holdup variation under different horizontal oil-water two-phase flow patterns. For these six flow patterns, the following method is still used. Figure 6 The simulation structure shown alters the water holdup of three flow patterns—ST, ST&MI, and DW / O&DO O / W—by changing the oil-water interface height, and alters the water holdup of three other flow patterns—DO / W&W, DO / W, and DW / O—by changing the diameter of the dispersed phase droplets. The sensor's response characteristics to changes in water holdup under these six flow patterns are as follows: Figures 9-14 As shown.

[0064] like Figures 9-14As shown, under all flow patterns, the amplitude attenuation and phase shift of the S21 parameter exhibit a highly linear correlation with the water holdup. This phenomenon indicates that the sensor can achieve accurate linear measurement relationships for any flow pattern in horizontal oil-water two-phase flow, whether stratified or dispersed, and ensures measurement consistency across different flow patterns. This demonstrates that the sensor is not limited by flow pattern and can operate stably in various horizontal oil-water two-phase flow patterns. Traditional conductivity and capacitance methods are often affected by flow pattern, while the microwave sensor of this invention overcomes this problem and enhances measurement stability.

[0065] VI. Experimental Verification and Results A coplanar waveguide-excited helical microwave sensor was applied to a dynamic experiment of oil-water two-phase flow to investigate its dynamic measurement performance. The dynamic experiment was conducted using a multiphase flow loop device and sensor system at Tianjin University. A total of 130 operating conditions were set under different flow rates and water contents. The total flow rate range was 10 m³ / s. 3 / day-55 m 3 / day, set interval 5 m 3 / day; the water content varies in three ranges: 5%-20%, changing in 5% increments; 20%-80%, changing in 10% increments; 80%-95%, changing in 5% increments. In sensor detection, due to the different dielectric constants of the oil and water phases, the output response voltage of the microwave sensor differs when oil-water two-phase flows enter the detection pipe section under different flow conditions. Therefore, the amplitude and phase signal fluctuations and output voltage values ​​acquired by the microwave sensor differ significantly depending on the flow structure. The flow patterns of horizontal oil-water two-phase flows are classified as: ST, ST&MI, DW / O&DO / W, DO / W&W, DO / W, and DW / O. The amplitude and phase fluctuation signals of the coplanar waveguide-excited spiral microwave sensor corresponding to different flow patterns are as follows: Figure 15 As shown.

[0066] Stratified flow (ST) primarily occurs when the flow rate of an oil-water mixture is low. The density difference between the oil and water phases plays a dominant role, causing the lighter oil to distribute in the upper part of the pipe and the heavier water in the lower part, forming a stable stratified interface. Due to the interface stability, the sensor's output signal exhibits small fluctuations and low disturbance characteristics, such as... Figure 15 As shown in (a).

[0067] As the flow rate increases, small-scale fluctuations begin to appear at the oil-water interface, and local disturbances occur at the oil-water phase interface. Simultaneously, a small amount of droplet entrainment may occur on both sides of the interface, such as... Figure 15As shown in (b), at this point, the flow pattern gradually evolves into a mixed-interface stratified flow (ST&MI), with increased fluctuations at the oil-water interface. Simultaneously, some dispersed oil and water droplets can be observed near the interface, but a continuous dispersed flow layer has not yet formed. The signal fluctuation curve of this flow pattern shows low-frequency oscillations, indicating the presence of interfacial fluctuations and droplets, but overall it remains in a relatively stable stratified state.

[0068] The upper oil-in-water and lower water-in-oil flow patterns (DW / O&D O / W) are based on the ST&MI flow pattern. As the apparent flow velocities of oil and water increase, more dispersed water droplets appear in the upper layer (oil as the continuous phase) and more dispersed oil droplets appear in the lower layer (water as the continuous phase), resulting in two flow patterns existing simultaneously: upper oil-in-water and lower water-in-oil flow patterns. This flow pattern exhibits characteristics of a two-layer heterogeneous dispersed flow pattern. Compared to the ST&MI flow pattern, the signal amplitude of the upper oil-in-water and lower water-in-oil flow patterns fluctuates more dramatically, such as... Figure 15 As shown in (c).

[0069] If the water content in the oil-water mixture is high and the mixing velocity is fast, a flow pattern of oil-in-water at the top and laminar water at the bottom (DO / W&W) is likely to occur. Oil droplets, under the influence of buoyancy, accumulate at the top of the pipe and disperse in the continuous water phase, while water forms a continuous phase at the bottom. This flow pattern is said to have the characteristics of a half-space dispersion flow pattern, meaning that the upper part of the pipe is a water-in-oil dispersed phase, such as... Figure 15 As shown in (d).

[0070] When the water content in an oil-water mixture is high, an increase in flow velocity to a certain extent will result in an oil-in-water (DO / W) flow pattern across the entire pipe cross-section. In this flow pattern, the water phase is continuous, and oil droplets are dispersed within the continuous water phase. The oil-in-water flow pattern is a relatively stable dispersion flow pattern. This flow pattern exhibits the characteristics of an oil-in-water dispersion flow pattern throughout the entire space.

[0071] If the oil content in an oil-water mixture is high, a water-in-oil emulsion (DW / O flow pattern) will appear when the flow rate exceeds a certain value. In this flow pattern, the oil is the continuous phase, and the water droplets are completely dispersed within the continuous oil phase. This flow pattern exhibits the characteristics of a full-space water-in-oil dispersion.

[0072] DO / W and DW / O flow patterns occur at higher mixing velocities, indicating higher turbulent kinetic energy. The fluid's energy is sufficient to overcome interfacial tension, maintaining a uniform distribution of dispersed phase droplets within the continuous phase. The signal fluctuation curves under these flow patterns exhibit larger amplitude fluctuations, indicating higher flow turbulence. Figure 15 As shown in (e)(f).

[0073] The relationship between the sensor phase output value and the flow velocity under different moisture contents is as follows: Figure 16As shown in the figure, corresponding flow pattern information is also provided. It can be seen from the figure that the flow pattern distribution and the analysis results of the influence of velocity on the slip effect are highly consistent. When the flow velocity is low, the flow pattern is mainly ST, and the phase output of the sensor tends to be flat, indicating that the flow pattern is stable. As the flow velocity increases, ST&MI and DW / O&DO O / W flow patterns appear, and the slip effect begins to appear, which directly affects the sensor output. At high flow velocities, such as DO / W and DW / O, the slip effect reaches its maximum, and the influence of velocity on slip tends to stabilize. This phenomenon is consistent with the flow instability and phase change law caused by increased velocity, fully verifying the accuracy of the experimental results.

[0074] The measured voltage signal U phs Transformed into phase shift : (7) Mixing dielectric constant of oil-water two-phase flow Phase shift with microwave signal The following relationship must be satisfied: (8) In the formula λ 0 represents the wavelength in free space. p This represents the propagation path between microwave excitation and reception.

[0075] The mixing dielectric constant of horizontal oil-water two-phase flow and its water holdup satisfy the following relationship: (9) In the formula, ε m It is a mixed dielectric constant. ε w The dielectric constant of water is ε o The dielectric constant of the oil phase is... The fitting coefficients of this function are used. Based on the actual water holdup in the experiment, the fitting parameters are solved separately for different flow patterns. After determining the fitting parameters, the water holdup measurement under different flow patterns in the dynamic experiment of horizontal oil-water two-phase flow is finally realized according to Formula 9. The results are as follows: Figure 17 As shown in the figure. The results show that the sensor maintains good measurement stability under different flow conditions. Within the water holding capacity range of 5% to 95%, the absolute mean error (AAD) is 0.0222 and the absolute mean relative error (AAPD) is 7.24%, maintaining high resolution under all six flow conditions.

Claims

1. A method for optimizing the structural parameters of a microwave sensor based on a coplanar waveguide-excited helical structure, wherein the microwave sensor includes a measuring electrode, a coplanar waveguide port, a shielding layer, and a test conduit, characterized in that, The measuring electrode comprises a helical emitting electrode and a receiving electrode with identical structure and dimensions, which are spirally wound along the outer wall of the test pipe. The coplanar waveguide port is tightly attached to the outer wall of the pipe and includes a rectangular ground plane, a central rectangular electrode plate of the coplanar waveguide excitation port electrically connected to the emitting electrode, and a central rectangular electrode plate of the coplanar waveguide receiving port electrically connected to the receiving electrode. Its structural parameters include helix angle, electrode opening angle, and pitch ratio. The helix angle refers to the angle at which the helical electrode winds around the pipe; the electrode opening angle refers to the central angle corresponding to the horizontal cross-section of the helical electrode; the pitch refers to the axial distance between two adjacent turns of the helical electrode; and the pitch ratio refers to the ratio of the pitch to the diameter of the outer wall of the test pipe. The structural parameters are optimized using the following method: The overall sensitivity calculation method is as follows: The measured values ​​of the coplanar waveguide-excited helical microwave sensor include amplitude attenuation and phase shift. The comprehensive sensitivity of amplitude attenuation and the comprehensive sensitivity of phase shift are calculated separately. The comprehensive sensitivity of amplitude attenuation and the comprehensive sensitivity of phase shift are multiplied to obtain the overall sensitivity. The amplitude attenuation comprehensive sensitivity is the sum or weighted sum of the following three items: the mean of the linearly normalized change in amplitude attenuation reflecting the average response of the sensor to changes in dielectric constant, the normalized mean of the maximum amplitude attenuation reflecting the normalized average response, and the reciprocal of the standard deviation of amplitude attenuation reflecting the consistency and stability of the response. The phase shift comprehensive sensitivity is the sum or weighted sum of the following three items: the mean of the linearly normalized change in phase shift reflecting the average response of the sensor to changes in dielectric constant, the normalized mean of the maximum phase shift reflecting the normalized average response, and the reciprocal of the standard deviation of phase shift reflecting the consistency and stability of the response. Based on the overall sensitivity, the response of the coplanar waveguide-excited helical microwave sensor under different dielectric constants, structural parameters and operating frequencies is calculated to determine the optimal helical angle and operating frequency. Based on the determined optimal helix angle and operating frequency, the two structural parameters, plate opening angle and pitch ratio, are optimized through simulation of different flow patterns.

2. The method for optimizing the structural parameters of a microwave sensor according to claim 1, characterized in that, The optimal combination of structural parameters for helix angle, plate angle, and pitch ratio is: helix angle 360°, pitch ratio 94mm / 30mm, and plate angle 110°.

3. The method for optimizing the structural parameters of a microwave sensor according to claim 1, characterized in that, Before calculating the response of the coplanar waveguide-excited helical microwave sensor under different dielectric constants, structural parameters, and operating frequencies, and determining the optimal helical angle and operating frequency, the process also includes a step of screening for combinations of structural parameters and operating frequencies that satisfy monotonically changing conditions.

4. The method for optimizing the structural parameters of a microwave sensor according to claim 1, characterized in that, The method for calculating the response of a coplanar waveguide-excited helical microwave sensor under different dielectric constants, structural parameters, and operating frequencies, and determining the optimal helical angle and operating frequency, is as follows: Considering the influence of the change in helical angle on the selection of operating frequency, for different helical angles, calculate the total sensitivity of each electrode angle and pitch ratio combination at different operating frequencies, and then determine the optimal helical angle and operating frequency.

5. The method for optimizing the structural parameters of a microwave sensor according to claim 4, characterized in that, Based on the determined optimal helix angle and operating frequency, the following method is used to optimize the two structural parameters, plate opening angle and pitch ratio, through simulation of different flow patterns: Different flow patterns were modeled and simulated using simulation software. Under each flow pattern, the response characteristics of different structural parameters to water holding capacity were evaluated by changing two structural parameters, plate angle and pitch ratio, and water holding capacity. Calculate the total sensitivity of the coplanar waveguide-excited helical microwave sensor under different structural parameters, and further calculate the mean and standard deviation of the total sensitivity of each set of structural parameters under different flow patterns; The ratio of the mean to the standard deviation of the total sensitivity was used as the final optimization index to determine the optimal combination of structural parameters, including the helix angle, electrode opening angle, and pitch ratio.

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