Double-ring microwave sensor combination and inclined oil-water two-phase flow related flow velocity measurement method

Abstract

The invention provides a double-ring microwave sensor combination which is composed of two microwave annular sensors which are located on the upstream and the downstream of a measuring pipeline respectively and are the same in structure, each microwave annular sensor comprises a coaxial feeder terminal, an annular pole plate and a shielding layer, and the annular pole plate is tightly attached to the outer wall of the measuring pipeline. The coaxial feeder terminal is electrically connected with the annular polar plate; the shielding layer is longer than the annular polar plate and is grounded; the coaxial feeder terminals of the two microwave annular sensors are both used as the access ends of microwave excitation signals and the receiving ends of microwave response signals. The invention also provides a structure optimization method of the double-ring microwave sensor combination and a method for measuring the related flow velocity of the inclined oil-water two-phase flow by using the double-ring microwave sensor combination. According to the invention, related flow velocity measurement of inclined oil-water two-phase flow under a complex flow pattern can be realized.

Description

Technical Field

[0001] This invention relates to the optimized design of a microwave sensor for measuring the correlation velocity of oil-water two-phase flow in the field of industrial fluid measurement technology. Background Technology

[0002] In the oil well industry, accurate measurement of the velocity of oil-water two-phase flows is crucial for oilfield extraction and pipeline transportation. Influenced by the inherent physical properties of each phase, the angle of the measuring pipe, and the pipe diameter, the dispersed phases in oil-water two-phase flows are not uniformly distributed, and the interphase slippage effect is severe, ultimately leading to uneven velocity and concentration distribution across the measuring pipe cross-section. This poses challenges to the measurement of oil-water related velocities. Researchers are continuously developing new velocity measurement devices, and traditional single-phase flowmeters are gradually being adapted for multiphase fluid measurement. Based on measurement principles, velocity measurement methods mainly include: Venturi flowmeters, turbine flowmeters, electromagnetic flowmeters, differential pressure flowmeters, conductivity-related velocimetry, and fiber optic-related velocimetry. Among these, differential pressure flowmeters, which measure the velocity based on the proportionality between fluid pressure difference and flow velocity, offer advantages such as simple structure, low cost, long lifespan, and less susceptibility to fluid medium influences. However, they require standard throttling devices, which are structurally complex, have high installation and positioning requirements, and are susceptible to external temperature and pressure variations. Turbine flow meters are used to measure the average flow rate of fluids. When the turbine rotates under force, its rotational speed is proportional to the average velocity of the fluid flowing through the measuring pipe. They offer advantages such as high measurement accuracy and a wide range. However, turbine flow meters require instrument coefficient calibration, are significantly affected by water content, and are limited in measuring low-velocity fluids. Electromagnetic flow meters measure flow velocity based on Faraday's law of electromagnetic induction. They are only suitable for measuring the velocity of continuous conductive media. When a conductive fluid flows through an electromagnetic flow meter, an induced electromotive force proportional to the flow velocity and perpendicular to the magnetic field direction is generated. Since the introduction of cross-correlation theory, correlation velocity measurement has been widely used for fluid velocity measurement, and has expanded from single-phase fluid velocity measurement to multi-phase fluid measurement. In global measurements, conductivity correlation flow meters are the primary method. Their measurement principle is based on the internal noise signal reflected by the motion wave of the mixed fluid detected by the sensor. By acquiring the transit time of the fluid at different locations across the measuring pipe cross-section, the correlation velocity is measured. By establishing the relationship between the correlation velocity and the mixed velocity, the mixing velocity is ultimately measured. Correlation flow meters offer advantages such as simple measurement, continuous measurement capability, and applicability in industrial settings. However, traditional conductivity-correlated flowmeters are only suitable for measuring the correlation velocity of water as a continuous phase. For multiphase flows with oil as a continuous phase, the measurement fails. Therefore, there is an urgent need to find a correlation velocity measurement technology that can achieve full-range measurement. Using microwave cross-correlation method to measure multiphase flow velocity is an effective approach, but the correlation velocity measurement of multiphase flows with complex flow patterns is currently in the exploratory stage. Summary of the Invention

[0003] The application designs a double-loop microwave sensor combination for measuring the relative flow velocity of inclined oil-water two-phase flow, and realizes the relative flow velocity measurement of inclined oil-water two-phase flow under complex flow patterns by optimizing the sensor structure and the cross-correlation velocity measurement algorithm. The double-loop microwave sensor combination is arranged on the outer periphery of a measurement pipeline and is composed of two microwave loop sensors with the same structure located upstream and downstream of the measurement pipeline respectively. When the microwave excitation signal enters the sensor measurement area through the coaxial feed terminal and the oil-water mixed fluid flows in the measurement pipeline, the relative mixed dielectric constant of the oil-water mixed fluid with different proportions is different, so that the reflection coefficient S 11 of the microwave loop sensor is different in phase shift.

[0004] Further, the inner diameter of the measurement pipeline is 20 mm, the length of the loop plate of the microwave loop sensor is 20 mm, and the center distance between the upstream and downstream microwave loop sensors is 27 mm. L

[0005] Further, the thickness of the microwave loop sensor is 0.2 mm, the length of the copper shielding layer is 40 mm, the thickness of the copper shielding layer is 0.2 mm, and the outer diameter of the measurement pipeline is 30 mm.

[0006] The structure optimization method of the double-loop microwave sensor combination comprises the following steps: S1, select the ultra-high frequency band UHF of the microwave for frequency scanning, the scanning interval is 300 MHz~1 GHz, measure the phase output of the reflection coefficient S 11 under different working conditions, select the frequency point with linear change of the phase output with water content from the interval as the fixed working frequency, and select the working frequency as 450 MHz. S ; and S2, optimize the size of the microwave loop sensor under the working frequency, and define the response sensitivity as the ratio of the phase change ​​​S2, a layered flow simulation model is established, and microwave annular sensor output response characteristic analysis is performed; the length of the annular electrode plate is set to vary in the range of 2 mm-26 mm and the step length, the microwave annular sensor response to the change of the water phase height is simulated and analyzed under different sensor structure sizes, and the length of the annular electrode plate is preliminarily selected according to the layered flow response; S3, an oil-water uniform distribution simulation model is established, and microwave annular sensor output response characteristic analysis is performed when oil-water is uniformly distributed; the mixed dielectric constant of the oil-water two-phase flow in the measurement pipeline is changed, the phase output of the microwave annular sensor is obtained under different annular electrode plate lengths, and the length of the annular electrode plate is selected in combination with the simulation results in (2); S4, a double-ring microwave sensor combination sensor simulation model is established after the length of the annular electrode plate is determined, the upstream coaxial feed line terminal is used as the microwave excitation signal access end, the coaxial feed line terminal of the downstream microwave annular sensor is used as the microwave signal receiving end, the transmission coefficient S 21 response characteristic and electric field distribution are analyzed, and according to the criterion that the amplitude response between the upstream and downstream microwave annular sensors is less than-30 dB, the center distance between the upstream and downstream microwave annular sensors is finally determined. S 21

[0007] Further, in step S3, the length of the annular electrode plate is selected to be 20 mm; in step S4, the center distance between the upstream and downstream microwave annular sensors is determined to be 27 mm.

[0008] The inclined oil-water two-phase flow correlation flow velocity measurement method realized by the above double-ring microwave sensor combination is characterized in that it comprises the following steps: S1, a double-ring microwave sensor combination measurement system for measuring the correlation flow velocity of inclined pipeline oil-water two-phase flow is built, and the phase shift output signal of the microwave excitation signal after passing through the mixed fluid is obtained by each microwave annular sensor; S2, the phase shift output signals obtained by the upstream and downstream microwave annular sensors are used to obtain the transit time by using the cross-correlation function, and the correlation flow velocity of the mixed fluid can be obtained by dividing the center distance between the upstream and downstream microwave annular sensors by the transit time.

[0009] ​Further, two microwave loop sensors are independently measured, and two microwave phase measurement circuits are used respectively, the microwave phase measurement circuit of each microwave loop sensor includes a signal source, a power divider, a cavity coupler, a microwave sensor, a phase detection circuit and a signal acquisition unit, the microwave signal generated by the signal source is divided into two through the power divider, one of which is used as a microwave loop sensor measurement connected to the input end of the three-port cavity coupler, and the other is used as a reference signal connected to one end of the phase detection circuit; the output end of the cavity coupler is connected with the coaxial feed terminal of the microwave loop sensor, the microwave excitation signal is injected into the mixed fluid, and the reflected microwave response signal is connected with the phase detection circuit through the cavity coupler; the phase detection circuit provides accurate phase measurement; the phase detection circuit compares the phase of the reference signal with the phase of the sensor microwave response signal to obtain the phase shift output signal of the microwave excitation signal through the mixed fluid.

[0010] The present application has the following measurement advantages due to the above technical scheme: (1) The double-loop microwave sensor combination of the present application is installed outside the measurement pipeline, and the non-contact design avoids direct contact with the measured fluid, thereby avoiding the influence of particle fouling and oil droplet adhesion in the measurement pipeline on the measurement.

[0011] (2) By optimizing the working frequency, the distance between the two microwave loop sensors and the length of the electrode plate are simulated and optimized, so that the full-range fluid related flow rate measurement under complex flow pattern can be realized while ensuring the independence of the electromagnetic field. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1 is a double-loop microwave sensor combination structure diagram.

[0013] Figure 2 is a microwave loop sensor simulation model under stratified flow.

[0014] Figure 3 is the microwave loop sensor response corresponding to different ring lengths of oil-water stratified flow. L

[0015] Figure 4 is a microwave loop sensor simulation model when oil and water are uniformly distributed.

[0016] Figure 5 is the output response of the microwave loop sensor with different micro-ring lengths when the mixed dielectric constant in the measurement pipeline changes when oil and water are uniformly distributed.

[0017] Figure 6 is the electric field distribution corresponding to different water holdup: (a) oil-water two-phase flow stratified flow; (b) uniform oil-water mixture.

[0018] Figure 7 ​is the microwave annular sensor tube longitudinal section electromagnetic field vector distribution, the left picture is electric field distribution, the right picture is magnetic field distribution.

[0019] Figure 8 is the microwave annular sensor response under stratified flow, the left picture is the sweep frequency curve of output phase change with water phase height, the right picture is the microwave annular sensor phase response corresponding to frequency 450MHz.

[0020] Figure 9 is the microwave annular sensor response when oil and water are uniformly distributed, the left picture is the sweep frequency curve of output phase change with water phase height, the right picture is the microwave annular sensor phase response corresponding to frequency 450MHz.

[0021] Figure 10 is the double-ring microwave sensor combination upstream and downstream spacing optimization result.

[0022] Figure 11 is the double-ring microwave sensor combination measurement system principle schematic diagram.

[0023] Figure 12 is the double-ring microwave sensor combination output signal corresponding to different flow patterns: (a) VFD O / W; (b) D O / W CC; (c) D O / W CT; (d) D O / W PS; (e) TF.

[0024] Figure 13 is the double-ring microwave sensor combination related speed basic principle schematic diagram.

[0025] Figure 14 is the double-ring microwave sensor combination correlation function calculation result.

[0026] Figure 15 is the double-ring microwave sensor combination related flow velocity calculation result of inclined oil-water two-phase flow.

[0027] BRIEF DESCRIPTION OF DRAWINGS 1, coaxial feed line terminal; 2, copper annular plate; 3, copper shielding layer; 4, acrylic glass measuring pipe. DETAILED DESCRIPTION

[0028] The present application aims to design a double-ring microwave sensor combination for measuring the related flow velocity of inclined oil-water two-phase flow, by detecting the phase information of upstream and downstream microwave annular sensors, and by using cross-correlation method to obtain the related flow velocity under different working conditions. The specific implementation process is described below in combination with the drawings: (1) The double-ring microwave sensor combination structure is as shown in Figure 1The double-loop microwave sensor combination is close to the outer wall of the measuring pipeline, and the measuring pipeline is an acrylic glass measuring pipeline 4. The double-loop microwave sensor combination is composed of two microwave loop sensors with the same structure located upstream and downstream of the measuring pipeline, and each microwave loop sensor comprises a coaxial feed terminal 1, a copper loop plate 2 and a copper shielding layer 3. L The length of the loop plate is 20 mm, the thickness is 0.2 mm, the length of the shielding layer is 40 mm, and the thickness is 0.2 mm. The addition of the shielding layer can effectively isolate the interference of external electromagnetic waves and prevent internal electromagnetic waves from spreading outward. The non-contact design avoids direct contact with the measured fluid, thereby avoiding the influence of particle fouling and oil droplet adhesion in the measuring pipeline on the measurement. The inner diameter of the measuring pipeline is 20 mm, and the outer diameter is 30 mm, which is also a common well type size of an industrial collection well.

[0029] When the microwave signal enters the sensor measurement area through the coaxial feed terminal and the mixed fluid flows in the measuring pipeline, the relative mixed dielectric constant of the oil-water mixed fluid with different proportions is different, which makes the S 11 coefficient phase of the microwave loop sensor different. Therefore, the microwave signal is obtained by building a microwave phase measurement circuit, and the cross-correlation calculation of the upstream and downstream signals is performed to obtain the related flow rate. Generally, the phase output of the microwave sensor is affected by the mixed dielectric constant and the working frequency. In the research of the microwave sensor, it is found that increasing the working frequency can improve the measurement sensitivity of the microwave sensor, and at the same time, the mixed dielectric constant measurement range will be sacrificed. Therefore, it is extremely important to select a suitable working frequency to make the double-loop microwave sensor combination of the present application respond under dynamic experimental conditions, so as to ensure that the microwave output phase signal fluctuation is good.

[0030] (2) The present application selects the ultra-high frequency band UHF of microwave for frequency scanning, and the scanning interval is 300 MHz~1GHz. S 11 The phase output of the present application is selected as the fixed working frequency, and the working frequency is finally selected as 450 MHz. Subsequently, the size optimization of the sensor is carried out under this working frequency. The parameters of the size optimization of the present application are mainly the length of the loop plate of the microwave loop sensor LAnd the upstream and downstream spacing. First, the sensor structure's dimensions were optimized. The sensor's response sensitivity to changes in water holdup was then optimized. Since the two microwave ring sensors are identical, the upstream microwave ring sensor was selected, and a simulation model was built using HFSS for simulation optimization. Because the inclined oil-water two-phase flow pattern is between laminar and uniform flow patterns, simulations were performed on both uniformly distributed and laminar oil-water two-phase flows. For the microwave ring sensor, its response sensitivity is defined as the phase change. and corresponding change in water holding capacity ratio S， The following formulas are commonly used for calculation: (1) (3) Establish a laminar flow simulation model and analyze the output response characteristics of the microwave ring sensor with oil-water laminar distribution. Simulate two flow patterns. First, laminar flow: since the oil phase density is less than the water phase, the oil phase is distributed in the upper layer of the measuring pipe, and the water phase is distributed in the lower layer. Change the height of the water layer. h That is, by changing the water holding capacity, a laminar flow simulation model is established, such as... Figure 2 As shown in the figure. The length of the annular electrode was set to vary from 2 mm to 26 mm in 2 mm increments. The response of the microwave annular sensor with varying water phase height under different sensor structure dimensions was simulated and analyzed. The results are as follows. Figure 3 As shown. By Figure 3 It can be seen that in each L Below, the absolute value of the sensor phase output increases linearly with the increase of water phase height. L When the diameter is 2 mm to 4 mm, the sensor phase output is related to the rate of change of water phase height, and the higher the water holding capacity, the smaller the rate of change. With a fixed water phase height, the phase output changes with the length of the annular electrode. L As the phase increases, the phase output gradually increases. L When the water level exceeds 22 mm, the phase output flips after the water phase height exceeds 17 mm, and the sensor response is no longer within the linear range. Therefore, [the following is chosen:] L Sensitivity analysis was performed within a range of 6 mm to 22 mm. Additionally, Figure 3 The scatter distribution also indicates that changes in sensor size will affect the phase output. However, in actual measurement, the focus is on the rate of change of measurement. The phase change caused by the change in water phase height is calculated according to formula (1), which is the response sensitivity.

[0031] The corresponding microwave ring sensor response changes are shown in Table 1, where the table contains... h The corresponding 8 columns of data represent the water phase height. hThe difference in phase output corresponding to the change range of 1 mm to 17 mm with a change step of 2 mm. As can be seen from the table, as the length of the annular electrode plate increases, the response sensitivity also gradually increases, and when the length of the annular electrode plate is greater than 20 mm, the response sensitivity is greater than 2.8 deg / mm. It can also be observed that the size of the change in phase output in each interval with the water phase height is not consistent. In order to achieve the best sensitivity, the average value, standard deviation and uniformity error of each interval of the water phase height change in Table 1 are calculated, and the results are shown in Table 2. As can be seen from Table 1 and Table 2, when the length of the annular electrode plate is greater than 22 mm, the average value of the sensitivity is the largest, and when the length of the annular electrode plate is greater than 20 mm, the average value of the sensitivity is close to the maximum value, and at this time, the standard deviation and the uniformity error are the lowest relative to other sizes. Therefore, according to the response of the stratified flow, the length of the annular electrode plate is selected to be 20 mm. L L L

[0032] Table 1

[0033] Table 2

[0034] (4) A simulation model of uniform oil-water distribution is established to analyze the output response characteristics of the microwave annular sensor in the case of uniform oil-water distribution. The simulation model is shown in Figure 4 . Since the oil used in the experiment is No. 3 industrial white oil, the mixed dielectric constant is 3.2, and the water used is tap water at room temperature, the mixed dielectric constant is 78, so the mixed dielectric constant of the oil-water mixture ε m changes in the range of 3.2 to 78. In the uniform fluid, the sensitivity of the phase output of the microwave annular sensor to the change in the mixed dielectric constant is investigated. Further, the response sensitivity of the uniformly mixed oil-water two-phase flow is simulated, the mixed dielectric constant of the oil-water two-phase flow in the measuring pipeline is changed, and the response of the phase output of the microwave annular sensor to the change in the mixed dielectric constant under different lengths of the annular electrode plate is obtained as shown in Figure 5 . Since the length of the annular electrode plate is initially selected to be 20 mm in the case of the stratified flow, the phase output sensitivity response of the annular electrode plate in the range of 16 mm to 26 mm is investigated in the case of the uniformly mixed oil-water model. As can be seen from Figure 5 , similar to the stratified oil-water flow, as the mixed dielectric constant (water holding rate) increases, the absolute value of the phase output increases, as the length of the electrode plate increases, the phase response increases, and when the length of the annular electrode plate is greater than 24 mm, the phase output is reversed. L

[0035] The corresponding microwave sensor response changes are shown in Table 3, where in the table ε ​​​​m The corresponding columns represent phase differences for a mixed dielectric constant variation range of 3.2 to 78 with a variation step size of 2.5. Table 3 shows that the magnitude of phase output change varies across different intervals as the length of the annular electrode increases. To achieve optimal sensitivity, the average value, standard deviation, and uniformity error were calculated for each interval of the mixed dielectric constant variation in the table above, and the results are shown in Table 4. When the annular electrode length is 20 mm, the average sensitivity is close to the maximum value, and the standard deviation and uniformity error are the lowest. Therefore, a annular electrode length of 20 mm was ultimately selected.

[0036] Table 3

[0037] Table 4

[0038] (5) Electromagnetic field distribution of the microwave ring sensor. A stronger electric field indicates better sensor detectability and is more conducive to capturing mixed fluids. After determining the optimal ring electrode length, the electric field distribution corresponding to different water holding capacities in both laminar and uniform oil-water two-phase flows was examined. Figure 6 As shown. By Figure 6 It can be seen that for layered oil-water two-phase flow, the increase in water phase height has a significant impact on the electric field inside the measuring pipe. The electric field strength is strongest when the measuring pipe contains oil, gradually weakening with increasing water phase height, and weakest when the measuring pipe contains water. A clear stratification of the electric field also occurs between the water and oil phases. The magnetic field strength also weakens with increasing water phase height, but the intensity changes from strong to weak from the outer wall of the measuring pipe towards the central axis. There is no obvious barrier layer at the oil-water stratification point. For a uniformly distributed oil-water mixture, the electric field strength gradually weakens from the outer wall of the measuring pipe towards the center, and decreases further with increasing dielectric constant (increased water holding capacity). The magnetic field distribution is similar to that of the oil-water stratification state, indicating that the oil-water distribution has a smaller impact on the magnetic field but a larger impact on the electric field distribution.

[0039] When the mixed dielectric constant inside the pipe is measured to be 3.2, the corresponding cross-sectional electromagnetic field distribution is as follows: Figure 7As shown in the figure, the electric field distribution is parallel to the cross section of the measuring pipe, and the magnetic field is perpendicular to the cross section of the measuring pipe. It is worth noting that the field intensity distribution in the measuring pipe shows a trend of gradually weakening from the electrode plate to the center of the measuring pipe, which is caused by the ring structure of the microwave loop sensor. The sensor adopts a ring electrode plate design. When the microwave is injected into the ring electrode plate through the coaxial feeder, a relatively strong electric field is formed near the electrode plate. Subsequently, the field transmission to the center of the measuring pipe is farthest from the ring electrode plate position, which shows a relatively weak performance. In actual measurement, this field distribution will have a certain impact on the moisture content measurement sensitivity based on the mixed dielectric constant principle, but in the double-ring speed measurement, the use of the fluctuation of the upstream and downstream microwave loop sensor signals is based on the relevant principle to solve, so the influence is small.

[0040] (6) After the length of the ring electrode plate is determined, the simulation model of the microwave loop sensor is established to investigate the phase output of the microwave loop sensor under different mixed dielectric constant conditions. When the oil and water are distributed in layers, the phase output of the microwave loop sensor changes with the water phase height curve as shown in Figure 8 The left figure is the frequency range of 400 MHz~500 MHz, and the microwave loop sensor output phase response can be known. In the frequency range of 400 MHz~460 MHz, the absolute value of the phase output of the microwave loop sensor increases with the increase of the water phase height. Extract the microwave loop sensor phase output corresponding to 450 MHz, and draw the right figure. It can be known that the phase output and the moisture content are almost linearly related.

[0041] When the oil and water are uniformly distributed, the change curve of the microwave loop sensor output corresponding to the change of the mixed dielectric constant is as shown in Figure 9 The change law is consistent with the layered distribution. With the increase of the mixed dielectric constant, the phase output gradually increases, that is, after the sensor structure and working mode are determined, the phase output is positively correlated with the mixed dielectric constant. Extract the phase output corresponding to each mixed dielectric constant at the frequency of 450 MHz, and obtain the change curve of the phase output and the mixed dielectric constant as shown in Figure 9 The right figure shows that the phase output and the moisture content have a monotonically increasing relationship, and the change rate decreases with the increase of the mixed dielectric constant.

[0042] The simulation results show that in the full range of moisture content (0%-100%), the phase output of the microwave loop sensor has good resolution for the two flow patterns.

[0043] For microwave correlation speed measurement, attention should be paid to the crosstalk between the two microwave loop sensors. In this setting, the coaxial feeder terminal of the upstream microwave loop sensor is input, and the coaxial feeder terminal of the downstream microwave loop sensor is output. The transmission coefficient S 21Response characteristics and electric field distribution, by Figure 10 It is known that when the center distance between the upstream and downstream microwave loop sensors is 27 mm, the difference in electric field distribution between the two sensors is obvious, and the amplitude attenuation response is within -30 dB, and the cross-talk between the electric fields is small. S 21 The amplitude attenuation response is within -30 dB, and the cross-talk between the electric fields is small. Based on this simulation research, the center distance between the upstream and downstream microwave loop sensors is finally determined to be 27 mm.

[0044] Experimental verification and results: The double-loop microwave sensor combination is applied to the dynamic experiment of oil-water two-phase flow at an inclination of 45 degrees. The dynamic measurement performance is investigated in the measurement pipeline (inner diameter 20 mm) of the inclined rising collector. The oil-water two-phase flow experiment is carried out in the multiphase flow sensing system and fluid flow laboratory of Tianjin University. The dynamic experiment is carried out at room temperature, and the environmental temperature is about 25 degrees, which basically belongs to constant temperature measurement. The two-phase medium is tap water and No. 3 industrial white oil (density 801 kg / m 3 , viscosity 2.8 ). The experimental conditions are as follows: total flow rate Q m The measurement range is 5 m 3 / d-15 m 3 / d, corresponding to the total flow rate U m : 0.1472 m / s-0.552 m / s, and the water cut K w The measurement range is 50%-98%.

[0045] In the experiment, the S 11 phase information of the upstream and downstream microwave loop sensors needs to be collected, so the measurement system of the double-loop microwave sensor combination is built as Figure 11As shown, two microwave ring sensors are used for independent measurements, with two identical measurement circuits constructed. Each microwave ring sensor's measurement circuit includes an ADF4351-based signal source, a power divider, a cavity coupler, a microwave sensor, a phase detection circuit, and a signal acquisition unit. The sensor signal source uses an ADF4351, a broadband frequency synthesizer with an output frequency of 35 MHz to 4400 MHz. The excitation signal can be set using the official ADF435x software, with the excitation frequency set to 450 MHz. The microwave signal generated by the signal source is split into two by the power divider. One path is used for microwave ring sensor measurement and connected to the input of a three-port cavity coupler. The other path serves as a reference signal and is connected to one end of the phase detection circuit. The output of the cavity coupler is connected to the coaxial feed terminal of the dual-ring microwave sensor assembly. The microwave excitation signal is injected into the mixed fluid, and the reflected microwave response signal is connected to the phase detection circuit via the cavity coupler. The phase detection circuit uses the AD8302 chip, capable of measuring input signals from -60 dBm to 0 dBm, up to 2.7 GHz, and providing accurate phase measurement for signals within a range of ±30 dB and 0°–180°. The phase detection circuit compares a reference signal with a microwave ring sensor. Response signal The phase shift of the microwave signal after passing through the mixed fluid is obtained. This phase shift is output as a DC voltage signal. The analog signal is input to a PXI-4472 for signal acquisition and uploaded to a host computer for data storage and further processing. The downstream and upstream microwave ring sensor measurement systems are consistent, with the acquisition frequency set to 20 kHz and the acquisition time set to 25 seconds to fully display the flow pattern information.

[0046] The output signals of the dual-ring microwave sensor combination corresponding to five typical flow patterns at a tilt angle of 45° are presented and analyzed. The sensor phase response time series for different flow patterns are shown below. Figure 12 As shown. The five typical flow patterns are: (a) uniformly dispersed oil droplet flow (VFD O / W); (b) oil-in-water dispersed flow with water layers in the same direction. (DO / W CC); (c) Water-in-oil dispersion flow with localized countercurrent in the water layer (DO / W CT); (d) Water-in-oil dispersion flow with pseudo-slug flow in the water layer (DO / W PS); (e) Intermittent transitional flow (TF) between oil-in-water and water-in-oil. The characteristics of each flow pattern are analyzed based on microwave phase signals. First, for... Figure 12 The overall signal analysis shown reveals that the output voltage gradually decreases as the moisture content decreases. The VFD O / W flow pattern exhibits the highest average signal voltage, while the TF flow pattern shows the lowest. From a fluctuation perspective, the more uniform the flow structure, the smaller the signal fluctuation amplitude. Next, the output signals of the dual-ring microwave sensor combination corresponding to each flow pattern are analyzed. Figure 12(a) shows the output signal of the double-loop microwave sensor combination under VFD O / W flow pattern, as the oil phase is uniformly distributed in the continuous water phase in the form of dispersed oil droplets, the signal shows a small fluctuation amplitude with a high voltage as the base value. When the flow pattern is D O / W CC( Figure 12 (b)), the voltage amplitude decreases and the signal fluctuation amplitude increases due to the decrease in water phase flow, which is related to the non-uniform distribution of oil bubbles on the upper layer of the measuring pipeline. When the flow pattern is D O / W CT( Figure 12 (c)), the output signal fluctuation amplitude further increases, and the signal shows a certain periodicity due to the intermittent existence of the reverse flow, and the oil phase depends on the existence of oil droplets, so that the signal fluctuation frequency is fast. When the flow pattern is D O / W PS( Figure 12 (d)), the further increase of the oil phase content leads to a further decrease of the signal voltage value, and the quasi-periodic oil plug makes the signal show a quasi-periodic fluctuation feature, and the signal fluctuation amplitude is large and the fluctuation frequency is low. When the flow pattern is TF( Figure 12 (e)), as the total flow is large and the oil content increases, the voltage value is small, and the signal fluctuation amplitude of the TF flow pattern is smaller than that of the DO / W PS flow pattern, which is a manifestation of the stability of the flow structure. This is because there is continuous oil on the upper layer of the measuring pipeline, continuous water on the lower layer, and uneven distribution of oil droplets in the middle region of the measuring pipeline, and the oil and water change little in the entire measuring pipeline section under the influence of microwave average measurement.

[0047] Figure 13 The principle diagram of the related speed measurement using the double-loop microwave sensor combination in the application is shown. The upstream and downstream spacing is L 1. The output signals of the two pairs of microwave loop sensors are and , according to the "flow solidification" assumption of the fluid, the corresponding motion waves of the fluid flowing through the upstream and downstream microwave loop sensor pairs have similarity within a certain time, so that the sensor output signals and have similarity, but there is a time delay of transit time between them. At this time , satisfy: (2) According to the related speed measurement theory, the cross-correlation function of , is: (3) Substituting equation (2) into equation (3) gives: (4) Reflects the correlation between upstream and downstream signals. When , The maximum value is obtained. The time corresponding to the peak That is .

[0048] In a short time, it can be assumed that the flow velocity of each point of the fluid is the same, at this time, the transit time and the distance between the upstream and downstream microwave loop sensors L 1, the fluid correlation flow rate U cc : (5) Figure 14 The combination of measurement signals and cross-correlation calculation results of the double-loop microwave sensor for 45-degree inclined oil-water two-phase flow are shown. As can be seen from the figure, the measurement signals of the upstream and downstream microwave sensors have good correlation under five flow patterns, and the peak value of the cross-correlation function is obvious, which shows that the oil-water two-phase flow keeps a similar flow structure when flowing through the upstream and downstream microwave sensors. With the increase of the total flow rate, the transit time gradually decreases, and the correlation flow rate increases. According to formula (5), the correlation flow rate under the experimental conditions is obtained, Figure 15 The combination of measurement signals and cross-correlation calculation results of the double-loop microwave sensor for 45-degree inclined oil-water two-phase flow are shown. As can be seen from the figure, the measurement signals of the upstream and downstream microwave sensors have good correlation under five flow patterns, and the peak value of the cross-correlation function is obvious, which shows that the oil-water two-phase flow keeps a similar flow structure when flowing through the upstream and downstream microwave sensors. With the increase of the total flow rate, the transit time gradually decreases, and the correlation flow rate increases. According to formula (5), the correlation flow rate under the experimental conditions is obtained, K w When the water cut U cc increases, the correlation flow rate measured by the sensor U m increases, and this trend does not change with the change of the flow pattern. For each water cut value, the corresponding correlation flow rate and the mixing speed show a clear linear relationship. It shows that the double-loop microwave sensor combination designed by the invention can effectively measure the correlation flow rate of the fluid in the inclined oil-water two-phase flow with complex flow pattern.

Claims

1. A dual-ring microwave sensor assembly, arranged on the outer periphery of a measuring pipe, comprising two identical microwave ring sensors located upstream and downstream of the measuring pipe, characterized in that, Each microwave ring sensor includes a coaxial feed terminal, a ring electrode plate, and a shielding layer. The ring electrode plate is in close contact with the outer wall of the measuring pipe, and the coaxial feed terminal is electrically connected to the ring electrode plate. The shielding layer is longer than the ring electrode plate and is grounded. The coaxial feed terminals of the two microwave ring sensors serve as the input terminals for microwave excitation signals and also as the receiving terminals for microwave response signals. When the microwave excitation signal enters the sensor measurement area through the coaxial feed terminal, and an oil-water mixture flows through the measuring pipe, the relative mixing dielectric constants of oil-water mixtures with different proportions are different, causing the reflection coefficient S of the microwave ring sensor to increase. 11 Since the phase shifts are different, the two microwave ring sensors are connected to two identical microwave phase measurement circuits respectively. The microwave phase response signals are simultaneously acquired and obtained through the microwave phase measurement circuits, and then the cross-correlation calculations of the upstream and downstream signals are performed to obtain the relevant flow velocities.

2. The dual-ring microwave sensor assembly according to claim 1, characterized in that, The inner diameter of the pipe being measured is 20 mm, and the length of the annular electrode plate of the microwave ring sensor is... L =20 mm, and the center-to-center distance between the upstream and downstream microwave ring sensors is 27 mm.

3. The dual-ring microwave sensor assembly according to claim 2, characterized in that, The microwave ring sensor has a thickness of 0.2 mm, the copper shielding layer has a length of 40 mm and a thickness of 0.2 mm, the outer diameter of the measuring pipe is 30 mm, and the operating frequency of this dual-ring microwave sensor combination is 450 MHz.

4. The structural optimization method for the dual-ring microwave sensor assembly according to any one of claims 1 to 3, characterized in that, Includes the following steps: S1. Select the UHF band of microwaves for frequency scanning, with a scanning range of 300 MHz to 1 GHz, and measure the reflection coefficient under different operating conditions. S 11 The phase output was determined, and a frequency point within this range where the phase output showed a linear change with water content was selected as the fixed operating frequency, which was set to 450 MHz. The size optimization of the microwave ring sensor was performed at this operating frequency. The response sensitivity was defined as the phase change. and corresponding change in water holding capacity ratio S ; S2. Establish a laminar flow simulation model and analyze the output response characteristics of the microwave ring sensor. Set the ring electrode length variation range to 2 mm to 26 mm and the step size, and simulate and analyze the response of the microwave ring sensor with the water phase height under different sensor structure sizes. Based on the laminar flow response, the ring electrode length is initially selected. S3, establish a simulation model of uniform oil-water distribution, analyze the output response characteristics of microwave ring sensor when oil and water are uniformly distributed, change the mixing dielectric constant of oil and water two-phase flow in the measuring pipeline, obtain the response of microwave ring sensor phase output with the mixing dielectric constant under different ring plate lengths, and select the ring plate length based on the simulation results of (2). S4. Establish a simulation model of the dual-ring microwave sensor combination after determining the length of the annular electrode plate. Use the upstream coaxial feed terminal as the microwave excitation signal input terminal and the downstream coaxial feed terminal of the microwave ring sensor as the microwave signal receiving terminal. Analyze the transmission coefficient. S 21 Response characteristics and electric field distribution, based on the absence of electric field interference between upstream and downstream microwave ring sensors, and S 21 The amplitude response was less than -30dB, and the center distance between the upstream and downstream microwave ring sensors was finally determined based on this criterion.

5. The structural optimization method for the dual-ring microwave sensor assembly according to claim 4, characterized in that, In step S3, the length of the annular electrode plate is selected as 20 mm; in step S4, the center-to-center distance between the upstream and downstream microwave annular sensors is determined to be 27 mm.

6. A method for measuring the correlation velocity of inclined oil-water two-phase flow using the dual-ring microwave sensor combination as described in any one of claims 1 to 3, characterized in that, Includes the following steps: S1, Construct a dual-ring microwave sensor combination measurement system for measuring the correlation velocity of oil-water two-phase flow in an inclined pipeline, and simultaneously acquire the phase shift output signal of each microwave ring sensor after the microwave excitation signal passes through the mixed fluid; S2. Based on the phase shift output signals obtained from the upstream and downstream microwave ring sensors, the transit time is obtained using the cross-correlation function. The relevant flow velocity of the mixed fluid can be obtained by dividing the center distance between the upstream and downstream microwave ring sensors by the transit time.

7. The method for measuring the correlation velocity of inclined oil-water two-phase flow according to claim 6, characterized in that, Two microwave ring sensors are used for independent measurements, each employing a separate microwave phase measurement circuit. Each microwave ring sensor's phase measurement circuit includes a signal source, a power divider, a cavity coupler, a microwave sensor, a phase detection circuit, and a signal acquisition unit. The microwave signal generated by the signal source is split in two by the power divider. One path is used for measurement by the microwave ring sensor and connected to the input of the three-port cavity coupler. The other path serves as a reference signal and is connected to one end of the phase detection circuit. The output of the cavity coupler is connected to the coaxial feed terminal of the microwave ring sensor. The microwave excitation signal is injected into the mixed fluid, and the reflected microwave response signal is connected to the phase detection circuit via the cavity coupler. The phase detection circuit provides accurate phase measurement. By comparing the phase of the reference signal with the phase of the sensor's microwave response signal, the phase shift output signal of the microwave excitation signal after passing through the mixed fluid is obtained.

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