CN110658218B - Gas-liquid two-phase flow phase content detection device and method based on coaxial line phase method - Google Patents
Gas-liquid two-phase flow phase content detection device and method based on coaxial line phase method Download PDFInfo
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Abstract
The invention provides a gas-liquid two-phase flow phase content detection device and method based on a coaxial line phase method. The detection device comprises a signal source, a power divider, a coaxial line sensor mechanism, a phase discriminator and a digital multi-purpose meter. The coaxial line sensor mechanism is designed according to the structure of the coaxial cable, the inner electrode and the outer electrode are coaxial, the inner electrode and the outer electrode form an electric field with the middle fluid, the fluid flows in from one side and flows out from the other side, the state change of the fluid can cause the dielectric constant to change, and the phase change is caused between the inflow end and the outflow end. The dielectric constants of the gas phase and the liquid phase are different, and the phase difference output signals obtained under the condition of different phase contents are also different, so that the phase contents of the corresponding gas-liquid two-phase flow can be obtained through the phase difference output signals. The invention realizes the measurement of the two-phase flow by utilizing the related principle that the propagation characteristics of electromagnetic waves pass through different transmission media, and can realize on-line monitoring.
Description
Technical Field
The invention relates to the technical field of multiphase flow detection, in particular to a gas-liquid two-phase flow phase content detection device and method based on a coaxial line phase method.
Background
The gas-liquid two-phase flow phase content detection method is related to a quick-closing valve method, a capacitance method, a conductivity method, a microwave method, a PIV (PARTICLEIMAGE VELOCIMETER, particle image velocimetry) method and the like.
The quick closing valve method is a common gas content calibration means. And two quick-closing valves are respectively arranged on two sides of the test pipe section, so that when the gas-liquid two-phase fluid flows, the gas-liquid two-phase fluid is quickly intercepted, and the liquid phase volume can be obtained after the gas-liquid two-phase fluid is separated, so that the gas-containing rate can be obtained. However, cutting off the fluid system can interfere with the fluid flowing in the pipeline, which is detrimental to gas-liquid two-phase flow gas void fraction measurements at high flow rates and pressures. Meanwhile, the selected gas-liquid two-phase flow structure and the quick-closing valve spacing have great influence on the measurement accuracy.
The capacitance method can realize the measurement of the water content of crude oil by utilizing the dielectric constant change of a fluid medium in a pipeline. The dielectric constants of the oil and water are greatly different, and when the oil and water content changes, the capacitance also changes. The capacitance method has the advantages of simple structure, convenient installation and low cost. However, the capacitance of the capacitive sensor is small, so that the measurement range is limited and is susceptible to parasitic capacitance.
The conductivity method is to obtain effective parameters such as water content of the oil-gas-water mixed solution according to the different relation between the voltage between the measuring electrodes and the conductivity of each phase in the measuring interval of the sensor. The conductivity method has the advantages of relatively simple structure, high response speed and good measurement of high water content. However, the sensitivity of the sensor is easily affected by the uneven electric field between the electrodes, and the mineral substances contained in the oil field are complex, which is unfavorable for field application.
The microwave method belongs to a non-contact crude oil water content measuring method, and when a microwave signal passes through different fluids, the change of the amplitude, the phase and the propagation speed of the microwave signal is caused in view of the different dielectric constants of different mixed phases. The water content of the crude oil can be detected by detecting various non-electric quantity changes through the microwave measuring sensor. The microwave method has a large measurement range, can well solve the problem of crude oil flow pattern change, and has no bad radiation to human body compared with a ray method with great harm to human body. However, the fluid flow system is very complex, and the specific relationship between microwaves and oil, gas, and water media has yet to be studied. Meanwhile, the sensor transmitting and receiving system is easy to be interfered by external environment, and the electromagnetic interference of the oilfield site is large and can reduce the measurement accuracy of the instrument.
The PIV method is a new flow measurement technology, and the positions of the particles in the flow field at given different moments are obtained through a multi-exposure method, so that the displacement of the corresponding positions of the particles in the flow field at the corresponding moments is measured, and the average speed of the adjacent exposure intervals is obtained. The method can realize the rapid measurement of the whole flow field, has small interference, but needs to be carried out under a transparent pipeline, has high cost and is difficult to be applied on site.
Disclosure of Invention
The invention aims to provide a device and a method for detecting the phase content of a gas-liquid two-phase flow based on a coaxial line phase method, and provides a novel method for measuring the phase content of the gas-liquid two-phase flow.
The invention is realized in the following way: a gas-liquid two-phase flow phase content detection device based on a coaxial line phase method comprises a signal source, a power divider, a coaxial line sensor mechanism, a phase discriminator and a digital multi-purpose meter;
The coaxial line sensor mechanism comprises transparent pipe sections on the left side and the right side and a coaxial line sensor measuring pipe section in the middle; the left transparent pipe section comprises a transparent acrylic pipe and first flanges arranged at two ends of the transparent acrylic pipe and used for fixing the transparent acrylic pipe, and the two first flanges at two ends of the transparent acrylic pipe are fixedly connected through a flange fixing rod; the structure of the right transparent pipe section is the same as that of the left transparent pipe section;
The coaxial line sensor measuring tube section comprises a metal round tube and second flanges which are arranged at two ends of the metal round tube and used for fixing the metal round tube, and the second flanges are fixedly connected with the adjacent first flanges through bolts and nuts; a solid metal rod is arranged on the axis of the metal round tube, and two ends of the metal rod are fixed at the center of the second flange through a coaxial bracket; an insulating layer is sleeved outside the metal rod; the metal rod and the metal round tube are respectively used as an inner electrode and an outer electrode and are connected with an external power supply;
The signal source is used for generating electromagnetic wave signals with specific frequencies; the electromagnetic wave signals generated by the signal source form two paths of electromagnetic wave signals with the same frequency and phase after passing through the power divider, the two paths of electromagnetic wave signals are respectively transmitted to the coaxial line sensor mechanism and the phase discriminator, and the electromagnetic wave signals are deviated in phase after passing through the gas-liquid two-phase flow in the coaxial line sensor mechanism; the phase discriminator receives and compares signals output by the coaxial line sensor mechanism and the power divider, converts the phase signals into voltage signals, and then sends the converted voltage signals to the digital multimeter; the digital multimeter processes and displays the received voltage signals, so that the phase contents of the gas-liquid two-phase flow can be obtained.
The signal source adopts an AD9959 DDS signal generator.
The phase detector comprises an AD8302 chip.
A rubber pad is arranged between the adjacent first flange and second flange, a wire guide hole is formed in the rubber pad, and the metal rod is connected with an external power supply through a wire penetrating through the wire guide hole.
The two ends of the metal round tube are fixed with the second flange in a welding mode.
The invention also provides a gas-liquid two-phase flow phase content detection method based on the coaxial line phase method, which specifically comprises the following steps:
a. Setting up the gas-liquid two-phase flow phase content detection device;
b. Introducing a gas-liquid two-phase flow to be detected into the coaxial line sensor mechanism;
c. The signal source generates electromagnetic wave signals with specific frequency and transmits the electromagnetic wave signals to the power divider, and the power divider outputs two paths of electromagnetic wave signals with the same frequency and phase;
d. The two paths of electromagnetic wave signals output by the power divider are respectively transmitted to the coaxial line sensor mechanism and the phase discriminator, the phase of the electromagnetic wave signals in the coaxial line sensor mechanism is deviated after passing through the gas-liquid two-phase flow, and the electromagnetic wave signals after passing through the coaxial line sensor mechanism are also transmitted to the phase discriminator;
e. The phase discriminator receives and compares signals output by the coaxial line sensor mechanism and the power divider, processes the signals, converts the phase signals into voltage signals, and then sends the converted voltage signals to the digital multimeter;
f. the digital multimeter processes and displays the received voltage signals, so that the phase contents of the gas-liquid two-phase flow can be obtained.
The phase detector comprises an AD8302 chip; in the step e, the phase discriminator compares and processes the received two paths of signals to obtain the phase difference of the two paths of signals, and the voltage corresponding to the phase difference has the following relation with the mixed dielectric constant of the gas-liquid two-phase flow to be detected:
In the formula (1), V PHS is a voltage value corresponding to a phase difference of two paths of signals received by the phase detector, V Φ is a gain ramp voltage, Φ (V INA) is a phase of an output signal of the coaxial line sensor mechanism received by the phase detector, and Φ (V INB) is a phase of an output signal of the power divider received by the phase detector; ΔΦ INA0 is the phase change amount of the signal before the power divider output signal is transmitted to the coaxial line sensor to measure the pipe section, ΔΦ INA is the phase change amount of the signal after the signal passes through the coaxial line sensor to measure the pipe section, and ΔΦ INB is the phase change amount of the signal before the power divider output signal is transmitted to the phase discriminator; omega is the angular frequency of an electromagnetic wave signal generated by a signal source, f is the frequency of the electromagnetic wave signal generated by the signal source, mu 0 is vacuum magnetic permeability, epsilon 0 is vacuum dielectric constant, epsilon gl is gas-liquid mixed dielectric constant, L is the length of a measuring tube section of a coaxial line sensor, and k 0 and k 1 are constants;
The phase content of each phase is calculated according to the dielectric constant epsilon gl of the gas-liquid mixture, and the calculation formula is as follows:
εglmε1β1+nεgβg (2)
βl+βg＝1 (3)
In the formulas (2) and (3), β l is the liquid phase content, β g is the gas phase content, ε l is the dielectric constant of the fluid when it is pure liquid, ε g is the dielectric constant of the fluid when it is pure gas, and m and n are coefficients; m and n can be obtained by experimental fitting.
When the electromagnetic wave signal frequency f=35 MHz and the coaxial line sensor measures the pipe segment l=0.25m, the formula (1) is specifically:
The coaxial line sensor mechanism is designed according to the structure of the coaxial cable, the inner electrode and the outer electrode are coaxial, the inner electrode and the outer electrode form an electric field with the middle fluid, the fluid flows in from one side and flows out from the other side, the state change of the fluid can cause the dielectric constant to change, and the phase change is caused between the inflow end and the outflow end. The dielectric constants of the gas phase and the liquid phase are different, and the phase difference output signals obtained under the condition of different phase contents are also different, so that the phase contents of the corresponding gas-liquid two-phase flow can be obtained through the phase difference output signals.
The invention realizes the measurement of the two-phase flow by utilizing the related principle that the propagation characteristics of electromagnetic waves pass through different transmission media, and can realize on-line monitoring. The electromagnetic wave transmission characteristics can be changed by using the intermediate fluid through the inner electrode and the outer electrode, in addition, the dielectric constants of the gas phase and the liquid phase are different, different phase difference output signals are obtained by using the dielectric constant difference, the phase content of the two-phase flow can be obtained by using the correlation operation, and a new thought is provided for measuring the phase content of the gas phase and the liquid phase flow.
Drawings
Fig. 1 is a block diagram of the structure of the device of the present invention.
Fig. 2 is a schematic structural view of the coaxial line sensor mechanism in the present invention.
Fig. 3 is an axial cross-sectional view of the coaxial line sensor mechanism of the present invention.
Fig. 4 is a partial schematic view of the invention where the rubber pad is notched.
Fig. 5 is a schematic diagram of an AD9959 DDS signal generator in accordance with the present invention.
Fig. 6 is a diagram of an AD8302 chip and its peripheral circuits according to the present invention.
In the figure: 1. a first flange; 2. a second flange; 3. a rubber pad; 4. a transparent sub-gram force tube; 5. a metal round tube; 6. a flange fixing rod; 7. screw holes; 8. a notch; 9. a wire pressing hole; 10. a wire guide; 11. a wire groove; 12. a coaxial support; 13. an outer clamping edge; 14. an inner clamping edge; 15. a radial support plate; 16. a metal rod.
Detailed Description
Embodiment 1, a gas-liquid two-phase flow phase content detection device based on a coaxial line phase method.
As shown in fig. 1, the gas-liquid two-phase flow phase content detection device based on the coaxial line phase method provided by the invention comprises a signal source, a power divider, a coaxial line sensor mechanism, a phase discriminator and a digital multimeter.
As shown in fig. 2 and 3, the coaxial line sensor mechanism includes left and right transparent tube sections and a central coaxial line sensor measurement tube section. The transparent pipe sections on the left side and the right side have the same structure. The left transparent pipe section structure is described as an example: the left transparent pipe section comprises a transparent acrylic pipe 4 and first flanges 1 arranged at two ends of the transparent acrylic pipe 4 and used for fixing the transparent acrylic pipe 4, and the two first flanges 1 at two ends of the transparent acrylic pipe 4 are fixedly connected through flange fixing rods 6. The two ends of the transparent sub-gram force pipe 4 are embedded in the center holes (circular through holes) of the two first flanges 1, and specifically: the clamping edges can be arranged in the central holes of the two first flanges 1 opposite to each other, so that the two ends of the transparent acrylic tube 4 are clamped on the clamping edges of the central holes of the first flanges 1, and then the flange fixing rods 6 are used for fixing the relative positions of the two first flanges 1, so that the transparent acrylic tube 4 can be fixed. The flange fixing rod 6 and the first flange 1 can be fixedly connected by pins. In this embodiment, four flange fixing rods 6 are uniformly distributed between the two first flanges 1. Both the first flange 1 and the flange fixing rod 6 are made of a metal material.
The coaxial line sensor measuring tube section comprises a metal circular tube 5 and second flanges 2 which are arranged at two ends of the metal circular tube 5 and used for fixing the metal circular tube 5. When the coaxial line sensor measuring tube section is connected with the transparent tube sections on the left side and the right side, the coaxial line sensor measuring tube section is connected with the first flange 1 adjacent to the coaxial line sensor measuring tube section through the second flange 2. Four screw holes 7 are uniformly distributed on the first flange 1 at a distance from the center of the first flange, screw holes corresponding to the screw holes 7 on the first flange 1 one by one are formed in the second flange 2, and the first flange 1 and the second flange 2 can be fixed by screwing nuts on the exposed end parts of the bolts through bolts penetrating through the screw holes on the first flange 1 and the second flange 2.
In the invention, a waterproof rubber gasket 3 is also arranged between the first flange 1 and the second flange 2 which are connected, and in order to ensure that the rubber gasket 3 is tightly and fixedly connected with the first flange 1 and the second flange 2, screw holes which are in one-to-one correspondence with the screw holes 7 on the first flange 1 are also arranged on the rubber gasket 3. The center hole of the first flange 1, the center hole of the second flange 2 and the center hole of the rubber pad 3 are all corresponding and have the same size.
Opposite inner clamping edges 14 are arranged in the center holes of the two opposite second flanges 2, and two ends of the metal round tube 5 are respectively clamped on the inner clamping edges 14 of the two second flanges 2. The second flange 2 and the metal round tube 5 are both made of metal materials and are fixed together by welding.
A solid metal rod 16 is arranged on the axis of the metal round tube 5, and two ends of the metal rod 16 are fixed in the central hole of the second flange 2 through a coaxial bracket 12. The coaxial mount 12 is formed by an outer cylinder and a radial support plate 15 within the cylinder. The coaxial mount 12 is made of nylon material. An outer clamping edge 13 is arranged on the back surface of the inner clamping edge 14 in the central hole of the second flange 2, and the coaxial bracket 12 is clamped on the outer clamping edge 13 of the central hole of the second flange 2 through a cylinder at the outer side of the coaxial bracket. A through hole is formed in the center of the radial supporting plate 15 of the coaxial bracket 12, and two ends of the metal rod 16 are connected in the central through hole of the radial supporting plate 15 in a penetrating way. An insulating layer is provided on the outside of the metal rod 16 to avoid conduction between it and the outer metal tube 5, while avoiding interference with the fluid in the pipe or the like.
The metal round tube 5 and the metal rod 16 respectively form an outer electrode and an inner electrode, which are coaxial, the length of the inner electrode is slightly longer than that of the outer electrode, and the inner electrode and the outer electrode can be roughly considered to be equal in length. The inner and outer electrodes and the middle fluid form an electric field, the fluid flows in from one side and flows out from the other side, the state change of the fluid can cause the dielectric constant to change, and the phase change of the inflow end and the outflow end is caused.
The metal round tube 5 and the metal rod 16 are connected with an external power supply. Because the metal round tube 5 and the second flange 2 are fixedly welded together and are both made of metal, the connection between the metal round tube 5 and an external power supply is relatively simple. The metal rod 16 needs to be provided with a wire passing through the coaxial bracket 12 and the rubber pad 3, and then the metal rod 16 is connected with an external power supply through the wire. In the invention, two ends of a metal rod 16 are flush with the end of a coaxial bracket 12, a wire groove 11 parallel to the plate surface is formed on a radial supporting plate 15, a wire hole 10 is formed on a rubber pad 3 along the radial direction, and the wire groove 11 and the wire hole 10 are in the same straight line in combination with fig. 4. A notch 8 is formed at the edge of the rubber pad 3, and a wire connected with the metal rod 16 can extend out through the wire groove 11, the wire guide 10 and the notch 8. The position department that corresponds with breach 8 on rubber pad 3 on second flange 2 opens line ball hole 9, and line ball hole 9 is in same circular arc with the screw hole on the second flange 2, and the line ball hole 9 is equal to the distance between the adjacent screw hole, and line ball hole 9 is used for fixed lead wire to play the connection effect with the outer electrode simultaneously, specifically: the connection of the second flange 2 (metal round tube 5) to an external power supply can be achieved by providing a wire in the wire-pressing hole 9 and extending the wire through the notch 8.
The right transparent pipe section and the left transparent pipe section are the same in size and shape and are of symmetrical structures. The coaxial line sensor mechanism is a three-body structure and is of a central symmetrical structure as a whole. The other components of the coaxial line sensor mechanism are made of metal materials except for the transparent acrylic tube 4, the rubber pad 3 and the coaxial line bracket 12 made of nylon materials.
Referring to fig. 1, the signal source is configured to generate an electromagnetic wave signal with a certain frequency, the electromagnetic wave signal is transmitted to the power divider through the DDS channel, and the power divider generates two paths of electromagnetic wave signals with identical transmission parameters such as frequency and phase, and the two paths of electromagnetic wave signals are simultaneously transmitted to the coaxial line sensor mechanism and the phase discriminator. When the phase content of the gas-liquid two-phase flow is measured, fluid enters the right transparent pipe section from the left transparent pipe section through the middle coaxial line sensor measuring pipe section, and when the two-phase fluid passes through a detection electric field formed between the inner electrode and the outer electrode, the equivalent dielectric constant of the two-phase fluid is changed along with the change of the phase content, so that the measured value is directly influenced. The electromagnetic wave signal is shifted in phase after passing through the gas-liquid two-phase flow mixed medium in the coaxial line sensor mechanism; the phase discriminator receives and compares signals output by the coaxial line sensor mechanism and the power divider, converts the phase signals into voltage signals, and then sends the converted voltage signals to the digital multimeter; the digital multimeter processes and displays the received voltage signals, so that the phase contents of the gas-liquid two-phase flow can be obtained.
The signal source in the invention adopts an AD9959 DDS signal generator. As shown in fig. 5, the AD9959 uses a high-level direct digital frequency synthesizer DDS technology, and is formed by four DDS cores to form four channels (500 MSPS), each of which adopts a high-bit proportional multiplier, and integrates a high-speed 10-bit DAC. Four programmable modes of serial I/O can be controlled through four data pins (SDIO_0/SDIO_1/SDIO_2/SDIO_3), and the flexibility is high. Each channel has the function of adjusting frequency and phase, and has 14-phase offset resolution; but also has the advantages of low power consumption and flexibility. In the aspect of board manufacturing, the 56-pin LFCSP is adopted for packaging, so that the space is greatly saved. In the aspect of temperature interference, the heat-resistant ceramic material can normally work at the industrial temperature of-40 ℃ to +85 ℃, and has strong heat resistance. The power supply voltage is 5V, the module bandwidth is 200MHz, the output waveform is a standard sine wave, the maximum output amplitude of the module is about 500mVPP, the frequency can be changed according to actual needs, and the maximum output voltage is reduced along with the increase of the frequency.
The phase discriminator in the invention takes an AD8302 chip as a main detection module, and the AD8302 chip can measure the phase difference between two input signals in the frequency range from low frequency to 2.7 GHz. As shown in FIG. 6, in the AD8302 chip and the peripheral circuits thereof, the phase difference and the output voltage are in a linear relation, the phase measurement range of the circuit is 0-180 degrees, and the output voltage range is 30 mV-1.8V. When the input end floats, 0.9V is output and can be used as a parameter for judging whether the circuit operates normally or not. The AD8302 chip and the external wiring terminal of the peripheral circuit comprise two signal input ends, a power interface and a phase difference output part. The power supply selects 5V, the signal input end is used for accessing electromagnetic wave signals transmitted by two routes DDS channels, one route is transmitted by a coaxial cable, and the other route is transmitted by a coaxial cable sensor mechanism. After the connection, the measurement of two parameters is realized through a logarithmic amplifier and a logarithmic detector inside the chip.
Embodiment 2, a method for detecting phase content of a gas-liquid two-phase flow based on a coaxial line phase method.
The embodiment takes a gas-water two-phase flow as an example to introduce a gas-liquid two-phase flow phase content detection method based on a coaxial line phase method, and the specific steps are as follows:
a. The gas-liquid two-phase flow phase content detection device described in example 1 was set up.
B. And introducing a gas-water two-phase flow to be detected into the coaxial line sensor mechanism. The flow state of the fluid can be observed through the transparent pipe sections on the left side and the right side.
C. The signal source generates electromagnetic wave signals with specific frequency and transmits the electromagnetic wave signals to the power divider, and the power divider outputs two paths of electromagnetic wave signals with the same frequency and phase.
D. The two paths of electromagnetic wave signals output by the power divider are respectively transmitted to the coaxial line sensor mechanism and the phase discriminator, the phase of the electromagnetic wave signals in the coaxial line sensor mechanism is deviated after passing through the gas-water two-phase flow, and the electromagnetic wave signals after passing through the coaxial line sensor mechanism are also transmitted to the phase discriminator.
Before the air-water mixed medium to be measured is introduced, a measuring circuit is opened for measurement, namely, the air-water mixed medium is tested in a pipeline without a fluid medium, the change of an upper computer is observed, and the calibration is carried out. And then opening an air valve, enabling air to flow through the coaxial line sensor mechanism at a certain flow rate, and recording the phase difference output value to be 1.033V after the air valve is stabilized. The phase difference output value when the gas is introduced into the pipeline is used as a reference when the gas content is 100%.
Since the dielectric constant and the conductivity change the electromagnetic wave transmission characteristic, the electromagnetic wave signal passing through the coaxial line sensor mechanism is transmitted in the gas-water mixed medium to generate phase difference change, so that the respective contents of the gas phase and the water phase can be judged according to the detected electromagnetic wave transmission characteristic result.
According to maxwell's equation, when the coaxial line sensor measures the transmission of electromagnetic waves in the pipe section as TEM waves, the phase constant β can be expressed as:
In the formula (1):
the sigma-coaxial line sensor measures the equivalent conductivity (S.m -1) of the medium in the pipe section;
Omega-signal angular frequency (rad. S -1);
Epsilon 0 -vacuum absolute dielectric constant, epsilon 0＝8.85×10-12 F/m;
Mu 0 -vacuum permeability, mu 0＝4π×10-7 H/m;
Epsilon gw -coaxial line sensor is used for measuring the relative dielectric constant of the gas-water mixed medium in the pipe section.
When σ/(ωε 0εgw) < 1, the derivation is:
Thus, when the frequency is fixed, the TEM wave passes through the long L coaxial line sensor to measure the phase shift generated by the pipe section as
In formula (3), L refers to the length of the tube section measured by the coaxial line sensor, and specifically refers to the length of the metal round tube.
E. The phase discriminator receives and compares signals output by the coaxial line sensor mechanism and the power divider, processes the signals, converts the phase signals into voltage signals, and then sends the converted voltage signals to the digital multimeter.
The phase detector comprises an AD8302 chip. The AD8302 utilizes the logarithmic compression principle of a logarithmic amplifier and measures the phase of signals of two input channels through two wideband logarithmic detectors which are matched precisely, and the phase difference measurement equation is as follows:
VPHS＝VΦ[Φ(VINA)-Φ(VINB)] (4)
in the formula (4):
V Φ -gain ramp voltage/-10 mV/(o)
Phi (V INA) -phase/(o) of received coaxial line sensor mechanism output signal
Phi (V INB) -phase/(o) of received output signal of power divider
V PHS -output value after phase difference conversion into voltage/(V)
Let the phase change of the signal before the output signal of the power divider is transmitted to the coaxial line sensor measuring tube section be delta phi INA0, the phase change of the signal after the signal passes through the coaxial line sensor measuring tube section be delta phi INA, the phase change of the signal before the output signal of the power divider is transmitted to the phase discriminator be delta phi INB, and the phase difference response value can be obtained along with the dielectric constant change law of medium mixture by combining formulas (1) - (4):
In the formula (5), k 0、k1 is constant.
K 0 is related to the excitation source frequency f, the gain ramp voltage V Φ, and the measurement end length L, which can be determined from the selected frequency. In the case of pure air medium in the measuring section, the relative dielectric constant value is 1, and k 1 can be determined from the determined k 0 value and the reference value. Thus, when f=35 mhz, l=0.25 m, a phase difference output measurement model is obtained:
f. the digital multimeter processes and displays the received voltage signals, so that the phase contents of the gas-liquid two-phase flow can be obtained.
The digital multimeter receives the voltage signal output by the phase discriminator, calculates the mixed dielectric constant epsilon gw of air and water according to the formula (6), then calculates the content of each phase of air and water according to the mixed dielectric constant epsilon gw of air and water, and combines the following formulas:
εgw＝mεwβw+nεgβg (7)
βw+βg＝1 (8)
In the formulas (7) and (8), beta w is the water phase content, beta g is the gas phase content, epsilon w is the dielectric constant of the fluid when pure water is used, epsilon g is the dielectric constant of the fluid when pure air is used, and m and n are coefficients; m and n can be obtained through experimental fitting, and the specific fitting process is as follows: the phase difference of two signals is measured by a phase discriminator, the composite dielectric constant epsilon gw of the fluid is calculated according to a formula (6), the dielectric constant epsilon w of the fluid in pure water is known (measured according to pure water experiments), the dielectric constant epsilon g of the fluid in pure air is also known (measured according to pure gas experiments), the phase contents of the gas phase and the water phase (namely beta g and beta w are known), and the specific values of m and n can be obtained by fitting corresponding calculation formulas through five quantities of the composite dielectric constant epsilon gw of the fluid, the dielectric constant epsilon w of the fluid in pure water, the dielectric constant epsilon g of the fluid in pure gas, the water phase content beta w and the gas phase content beta g.
Claims (7)
1. The gas-liquid two-phase flow phase content detection device based on the coaxial line phase method is characterized by comprising a signal source, a power divider, a coaxial line sensor mechanism, a phase discriminator and a digital multi-purpose meter;
The coaxial line sensor mechanism comprises transparent pipe sections on the left side and the right side and a coaxial line sensor measuring pipe section in the middle; the left transparent pipe section comprises a transparent acrylic pipe and first flanges arranged at two ends of the transparent acrylic pipe and used for fixing the transparent acrylic pipe, and the two first flanges at two ends of the transparent acrylic pipe are fixedly connected through a flange fixing rod; the structure of the right transparent pipe section is the same as that of the left transparent pipe section;
The coaxial line sensor measuring tube section comprises a metal round tube and second flanges which are arranged at two ends of the metal round tube and used for fixing the metal round tube, and the second flanges are fixedly connected with the adjacent first flanges through bolts and nuts; a solid metal rod is arranged on the axis of the metal round tube, and two ends of the metal rod are fixed at the center of the second flange through a coaxial bracket; an insulating layer is sleeved outside the metal rod; the metal rod and the metal round tube are respectively used as an inner electrode and an outer electrode and are connected with an external power supply;
The signal source is used for generating electromagnetic wave signals with specific frequencies; the electromagnetic wave signals generated by the signal source form two paths of electromagnetic wave signals with the same frequency and phase after passing through the power divider, the two paths of electromagnetic wave signals are respectively transmitted to the coaxial line sensor mechanism and the phase discriminator, and the electromagnetic wave signals are deviated in phase after passing through the gas-liquid two-phase flow in the coaxial line sensor mechanism; the phase discriminator receives and compares signals output by the coaxial line sensor mechanism and the power divider, converts the phase signals into voltage signals, and then sends the converted voltage signals to the digital multimeter; the digital multimeter processes and displays the received voltage signals, so that the phase content of each phase of the gas-liquid two-phase flow can be obtained;
The signal source adopts an AD9959 DDS signal generator;
The phase detector comprises an AD8302 chip.
2. The gas-liquid two-phase flow phase content detection device based on the coaxial line phase method according to claim 1, wherein a rubber pad is arranged between the adjacent first flange and the second flange, a wire hole is formed in the rubber pad, and the metal rod is connected with an external power supply through a wire penetrating through the wire hole.
3. The gas-liquid two-phase flow phase content detection device based on the coaxial line phase method according to claim 1, wherein two ends of the metal round tube are fixed with the second flange in a welding mode.
4. The gas-liquid two-phase flow phase content detection method based on the coaxial line phase method is characterized by comprising the following steps of:
a. setting up the gas-liquid two-phase flow phase content detection device according to claim 1;
b. Introducing a gas-liquid two-phase flow to be detected into the coaxial line sensor mechanism;
c. The signal source generates electromagnetic wave signals with specific frequency and transmits the electromagnetic wave signals to the power divider, and the power divider outputs two paths of electromagnetic wave signals with the same frequency and phase;
d. The two paths of electromagnetic wave signals output by the power divider are respectively transmitted to the coaxial line sensor mechanism and the phase discriminator, the phase of the electromagnetic wave signals in the coaxial line sensor mechanism is deviated after passing through the gas-liquid two-phase flow, and the electromagnetic wave signals after passing through the coaxial line sensor mechanism are also transmitted to the phase discriminator;
e. The phase discriminator receives and compares signals output by the coaxial line sensor mechanism and the power divider, processes the signals, converts the phase signals into voltage signals, and then sends the converted voltage signals to the digital multimeter;
f. the digital multimeter processes and displays the received voltage signals, so that the phase contents of the gas-liquid two-phase flow can be obtained.
5. The method for detecting the phase content of the gas-liquid two-phase flow based on the coaxial line phase method according to claim 4, wherein in the step e, the phase discriminator compares and processes the received two paths of signals to obtain the phase difference of the two paths of signals, and the following relationship exists between the voltage corresponding to the phase difference and the mixed dielectric constant of the gas-liquid two-phase flow to be detected:
In the formula (1), V PHS is a voltage value corresponding to a phase difference of two paths of signals received by the phase detector, V Φ is a gain ramp voltage, Φ (V INA) is a phase of an output signal of the coaxial line sensor mechanism received by the phase detector, and Φ (V INB) is a phase of an output signal of the power divider received by the phase detector; ΔΦ INA0 is the phase change amount of the signal before the power divider output signal is transmitted to the coaxial line sensor to measure the pipe section, ΔΦ INA is the phase change amount of the signal after the signal passes through the coaxial line sensor to measure the pipe section, and ΔΦ INB is the phase change amount of the signal before the power divider output signal is transmitted to the phase discriminator; omega is the angular frequency of an electromagnetic wave signal generated by a signal source, f is the frequency of the electromagnetic wave signal generated by the signal source, mu 0 is vacuum magnetic permeability, epsilon 0 is vacuum dielectric constant, epsilon gl is gas-liquid mixed dielectric constant, L is the length of a measuring tube section of a coaxial line sensor, and k 0 and k 1 are constants;
The phase content of each phase is calculated according to the dielectric constant epsilon gl of the gas-liquid mixture, and the calculation formula is as follows:
εgl＝mεlβl+nεgβg (2)
In the formulas (2) and (3), β l is the liquid phase content, β g is the gas phase content, ε l is the dielectric constant of the fluid when it is pure liquid, ε g is the dielectric constant of the fluid when it is pure gas, and m and n are coefficients; m and n can be obtained by experimental fitting.
6. The method for detecting the phase content of a gas-liquid two-phase flow based on the coaxial line phase method according to claim 4, wherein when the electromagnetic wave signal frequency f=35 MHz and the coaxial line sensor measuring pipe section l=0.25 m, the formula (1) is specifically:
7. The method for detecting the phase content of the gas-liquid two-phase flow based on the coaxial line phase method according to claim 4, wherein a rubber pad is arranged between the adjacent first flange and the second flange, a wire hole is formed on the rubber pad, and the metal rod is connected with an external power supply through a wire penetrating through the wire hole.
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