Multi-sensor fusion optical fiber measurement system and method for complex flow

Abstract

The present invention relates to a multi-sensor fusion optical fiber measurement system for complex flow, comprising a polarization-maintaining output broadband light source, an electro-optic modulator, a vector network analyzer, a first radio frequency amplifier, an erbium-doped optical fiber amplifier, an optical circulator, a first 1×2 optical fiber coupler, a second 1×2 optical fiber coupler, a third 1×2 optical fiber coupler, a first transmission optical fiber, a distributed sensing optical fiber, a second transmission optical fiber, a temperature probe, a third transmission optical fiber, an optical collimator, an optical coupler, a fourth transmission optical fiber, a 2×1 optical fiber coupler, a photoelectric detector, a second radio frequency amplifier, and a computer. The temperature probe is composed of a sensing optical fiber, a reflector, and a capillary stainless steel tube.

Description

Technical Field

[0001] The present invention belongs to the field of complex flow testing, and in particular relates to a multi-sensor fusion optical fiber measurement system and method for complex flows. Background Art

[0002] Complex flows such as two-phase and multiphase flows are widely present in industrial processes such as nuclear energy, refrigeration, petroleum, and chemical industry. The detection of complex flow characteristic parameters is of great significance to the development of these industries. With the rapid development of industry and the continuous improvement of its automation level, the demand for simultaneous and accurate measurement of multiple parameters of complex flows is also increasing. It can not only be used for the analysis and prediction of complex flow characteristics, but also provide new research methods for in-depth understanding of complex flow characteristics and mechanisms in scientific research and engineering applications. Therefore, the study of the flow mechanism and measurement of complex flows such as two-phase and multiphase flows plays a very important role in industrial production and scientific research.

[0003] At present, researchers at home and abroad have studied a variety of detection methods for complex flows, including electrical methods, which use electrode probes to measure the conductivity changes of two-phase and multi-phase flows; ray methods, which use the absorption and scattering effects of rays when passing through fluids to achieve detection; differential pressure methods, which use the corresponding relationship between the pressure difference generated by the fluid flowing through the throttling device and the fluid flow rate for measurement; ultrasonic methods, which use the propagation time of ultrasonic waves in two-phase and multi-phase flows and the intensity of their scattered signals for measurement; high-speed photography methods, which use high-speed cameras to directly capture images of the fluid through transparent pipe sections or windows, and then use image processing technology to extract image features, and then obtain various parameters of the gas-liquid two-phase flow based on the image features; fiber optic probe methods, which use the difference in refractive index between the fiber optic probe and the fluid to detect the returned light intensity information to study the change information at a certain point in the gas-liquid two-phase flow field; fiber Bragg grating method, when the external conditions such as the ambient temperature and strain of the fiber Bragg grating change, the Bragg wavelength of the fiber Bragg grating will drift accordingly, and the measurement of the corresponding characteristic parameters can be achieved by measuring the Bragg wavelength.

[0004] However, the above detection technology has the problems of single measurable characteristic parameter, easy to be affected by external environmental factors, harsh use conditions, low safety, and inability to achieve long-distance spatial continuous distributed measurement. However, in actual engineering applications, it is often necessary to simultaneously measure the spatiotemporal distribution information of multiple complex flow characteristic parameters with high precision in order to obtain more comprehensive flow field information. The existing detection technology for complex flows such as two-phase and multi-phase flow is mainly point-type and quasi-distributed single physical quantity measurement sensors. The two-phase and multi-phase flow characteristic parameters that can be demodulated by the obtained physical quantity are relatively limited, and it is impossible to achieve a more comprehensive detection of complex flow field information. All these have seriously restricted its practical application in the field of complex flow detection such as two-phase and multi-phase flow. For this reason, a multi-sensor fusion measurement technology suitable for complex flow testing fields such as two-phase and multi-phase flow is needed to achieve high-precision simultaneous measurement of spatiotemporal information of different characteristic parameters of the flow field. Summary of the invention

[0005] In order to overcome the above-mentioned shortcomings of the prior art, the present invention proposes a multi-sensor fusion fiber optic measurement system and method for complex flows, which can realize the simultaneous measurement of flow information such as pressure, temperature, liquid film thickness, etc. of complex flows such as two-phase and multi-phase flows.

[0006] The present invention is achieved by adopting the following technical solutions:

[0007] A multi-sensor fusion optical fiber measurement system for complex flow, characterized by comprising: a polarization-maintaining output broadband light source (1), an electro-optic modulator (2), a vector network analyzer (3), a first radio frequency amplifier (4), an erbium-doped optical fiber amplifier (5), an optical circulator (6), a first 1×2 optical fiber coupler (7), a second 1×2 optical fiber coupler (8), a third 1×2 optical fiber coupler (9), a first transmission optical fiber (10), a distributed sensing optical fiber (11), a second transmission optical fiber (12), a temperature probe (13), a third transmission optical fiber (14), an optical collimator (15), an optical coupler (16), a fourth transmission optical fiber (17), a 2×1 optical fiber coupler (18), a photodetector (19), a second radio frequency amplifier (20), and a computer (21); the temperature probe comprises a sensing optical fiber (22), a reflector (23), and a capillary stainless steel tube (24);

[0008] The signal output end of the polarization-maintaining output broadband light source (1) is connected to the input end of the electro-optic modulator (2) via a polarization-maintaining optical fiber jumper; the signal output end of the vector network analyzer (3) is connected to the signal input end of the first radio frequency amplifier (4) via a high-frequency cable; the signal output end of the first radio frequency amplifier (4) is connected to the signal input end of the electro-optic modulator (2) via a high-frequency cable; the output end of the electro-optic modulator (2) is connected to the input end of the erbium-doped optical fiber amplifier (5) via an optical fiber jumper; the output end of the erbium-doped optical fiber amplifier (5) is connected to the optical ring via the optical fiber jumper The optical circulator (6) is connected to the signal input end of the optical circulator (6); the reflection end of the optical circulator (6) is connected to the input end of the first 1×2 optical fiber coupler (7); the signal output end of the optical circulator (6) is connected to the first input end of the 2×1 optical fiber coupler (18); the first output end of the first 1×2 optical fiber coupler (7) is connected to the input end of the second 1×2 optical fiber coupler (8), and the second output end of the first 1×2 optical fiber coupler (7) is connected to the input end of the third 1×2 optical fiber coupler (9); the first output end of the second 1×2 optical fiber coupler (8) is connected to the input end of the third 1×2 optical fiber coupler (9); the second output end of the second 1×2 optical fiber coupler (8) is connected to the input end of the 2×1 optical fiber coupler (18); the first output end of the first 1×2 optical fiber coupler (7) is connected to the input end of the third 1×2 optical fiber coupler (9); the second output end of the second 1×2 optical fiber coupler (8) is connected to the input end of the 2×1 optical fiber coupler (18); the second output end of the first 1×2 optical fiber coupler (7) is connected to the input end of the third 1×2 optical fiber coupler (9); the second output end of the second 1×2 optical fiber coupler (8) is connected to the input end of the 2×1 optical fiber coupler (18); the first output end of the second 1×2 optical fiber coupler (8) is connected to the input end of the 2×1 optical fiber coupler (18); the second output end of the first 1×2 optical fiber coupler (7) is connected to the input end of the third 1×2 optical fiber coupler (9); the first output end of the second 1×2 optical fiber coupler (8) is connected to the input end of the 2×1 optical fiber coupler (18); the first The first transmission optical fiber (10) is connected to a distributed sensing optical fiber (11); the second output end of the second 1×2 optical fiber coupler (8) is connected to the second transmission optical fiber (12), and the second transmission optical fiber (12) is connected to a temperature probe (13); the first output end of the third 1×2 optical fiber coupler (9) is connected to the third transmission optical fiber (14); the second output end of the third 1×2 optical fiber coupler (9) is connected to the optical collimator (15); the optical coupler (16) is connected to the fourth transmission optical fiber (17); the fourth transmission optical fiber (18) is connected to the optical collimator (15); the optical collimator ... The transmission optical fiber (17) is connected to the second incident end of the 2×1 optical fiber coupler (18); the output end of the 2×1 optical fiber coupler (18) is connected to the incident end of the high-speed photodetector (19) via an optical fiber jumper; the output end of the high-speed photodetector (19) is connected to the signal input end of the second radio frequency amplifier (20) via a high-frequency cable; the signal output end of the second radio frequency amplifier (20) is connected to the signal input end of the vector network analyzer (3) via a high-frequency cable, and the vector network analyzer (3) is connected to the computer (12) via the high-frequency cable;

[0009] A core of the distributed sensing optical fiber (11) is provided with continuous reflectors processed by femtosecond laser; wherein the optical path difference corresponding to the spacing between adjacent reflectors is greater than the coherence length of the polarization-maintaining output broadband light source (1) and less than the coherence length of the microwave signal generated by the vector network analyzer (3); the distributed sensing optical fiber (11) is arranged on the inner side of the measured pipeline (25) along the axial direction of the pipeline;

[0010] The sensing optical fiber (22) of the temperature probe (13) is placed in a capillary stainless steel tube (24); a reflector (23) is processed in the core of the sensing optical fiber (22) using a femtosecond laser, and the end of the sensing optical fiber (22) is flush with the end of the capillary stainless steel tube (24); the optical path difference corresponding to the distance between the end faces of the reflector (23) and the end of the sensing optical fiber (22) is greater than the coherence length of the polarization-maintaining output broadband light source (1) and less than the coherence length of the microwave signal generated by the vector network analyzer (3); the temperature probe (13) is embedded in the inner wall of the measured pipeline (25), and the end face of the probe is flush with the inner wall of the pipeline.

[0011] Furthermore, the optical path difference between the distance from the first output end of the third 1×2 optical fiber coupler (9) to the end of the third transmission optical fiber (14) and then back through the third transmission optical fiber (14), the third 1×2 optical fiber coupler (9), the first 1×2 optical fiber coupler (7), the optical circulator (6) to the first input end of the 2×1 optical fiber coupler (18) and the distance from the second output end of the third 1×2 optical fiber coupler (9) through the optical collimator (15), the measured pipeline (25), the optical coupler (16), the fourth transmission optical fiber (17) to the second input end of the 2×1 optical fiber coupler (18) is greater than the coherence length of the polarization-maintaining output broadband light source (1), but less than the coherence length of the microwave signal generated by the vector network analyzer (3).

[0012] Furthermore: the length of the first transmission optical fiber (10) is greater than the sum of the lengths of the second transmission optical fiber (12) and the sensing optical fiber (22) of the temperature probe; the length of the second transmission optical fiber (12) is greater than the length of the third transmission optical fiber (14); the length of the second transmission optical fiber (12) is greater than the distance from the second output end of the third 1×2 optical fiber coupler (9) through the optical collimator (15), the measured pipeline (25), the optical coupler (16), the fourth transmission optical fiber (17) to the second input end of the 2×1 optical fiber coupler (18).

[0013] The present invention also provides a multi-sensor fusion optical fiber measurement method for complex flow, which is implemented in the multi-sensor fusion optical fiber measurement system for complex flow. The method is implemented by the following steps:

[0014] The optical signal output by the polarization-maintaining output broadband light source (1) enters the electro-optic modulator (2); the microwave signal output by the vector network analyzer (3) is amplified by the first radio frequency amplifier (4) and then enters the electro-optic modulator (2); the microwave signal is modulated by the electro-optic modulator (2) and then loaded onto the optical signal; the optical signal modulated by the microwave signal is output from the electro-optic modulator (2) and then enters the erbium-doped fiber amplifier (5), and then amplified by the erbium-doped fiber amplifier (5) and then input into the optical circulator (6); the optical signal is output from the reflection end of the optical circulator (6) and then enters the first 1×2 optical fiber coupler (7), and then is divided into two paths after passing through the first 1×2 optical fiber coupler (7); the optical signal output from the first output end enters the second 1×2 optical fiber coupler (8), and is then output from the second output end. The optical signal output from the emission end enters the third 1×2 optical fiber coupler (9); the optical signal output from the first emission end of the second 1×2 optical fiber coupler (8) enters the distributed sensing optical fiber (11) through the first transmission optical fiber (10), and is reflected at the reflector in the sensing optical fiber (11). The microwave envelopes of the reflected optical signals interfere at the intersection. The interference signal passes through the first transmission optical fiber (10), the second 1×2 optical fiber coupler (8), and the first 1×2 optical fiber coupler (7) in sequence and then returns to the optical circulator (6). After being output from the emission end of the optical circulator (6), it enters the 2×1 optical fiber coupler (18); the optical signal output from the second emission end of the second 1×2 optical fiber coupler (8) enters the temperature sensor through the second transmission optical fiber (12). The probe (13) is provided with a reflector in the sensing optical fiber (22) and at its end face. The microwave envelopes of the reflected optical signals interfere at the intersection. The interference signal passes through the second transmission optical fiber (12), the second 1×2 optical fiber coupler (8), and the first 1×2 optical fiber coupler (7) in sequence and then returns to the optical circulator (6). The interference signal is output from the output end of the optical circulator (6) and then enters the 2×1 optical fiber coupler (18). The optical signal output from the first output end of the third 1×2 optical fiber coupler (9) enters the third transmission optical fiber (14) and is reflected at its end face. The reflected signal passes through the third transmission optical fiber (14), the third 1×2 optical fiber coupler (9), and the first 1×2 optical fiber coupler (7) in sequence and then returns to the optical circulator. (6), and is output from the output end of the optical circulator (6) and enters the 2×1 optical fiber coupler (18); the optical signal output from the second output end of the third 1×2 optical fiber coupler (9) enters the optical collimator (15), enters the measured pipe (25) after passing through the optical collimator, and enters the optical coupler (16) after passing through the measured pipe (25), and enters the 2×1 optical fiber coupler (18) through the sensing optical fiber (17), and interferes with the microwave envelope of the optical signal reflected back from the end face of the third transmission optical fiber (14); the microwave interference signal is output from the output end of the 2×1 optical fiber coupler (18) and enters the high-speed photodetector (19); after being converted into an electrical signal by the high-speed photodetector (19), it enters the second radio frequency amplifier (20);After being amplified by the second radio frequency amplifier (20), the interference information is collected by the vector network analyzer (3), and the vector network analyzer (3) inputs the collected interference information into the computer (21); by performing a frequency sweep on the microwave signal output by the vector network analyzer (3), the interference spectrum of the microwave signal can be obtained;

[0015] The distributed sensing optical fiber (11) is affected by the complex flow pattern of the two-phase / multi-phase flow, and the length of the optical fiber at the corresponding position thereof will change with the change of the fluid pressure, thereby causing the optical path of the light signal reflected by the reflector to change, and then the interference spectrum of the microwave envelope signal will shift in frequency; due to the thermo-optical effect and the thermal expansion effect, the temperature change will cause the length and refractive index of the sensing optical fiber (22) of the temperature probe (13) to change, thereby causing the cavity length of the Fabry-Perot cavity formed by the end face of the sensing optical fiber (22) and the reflector (23) to change, so that the optical path difference corresponding to the reflected light signal changes, causing the corresponding microwave interference spectrum to shift in frequency; the measured pipeline (25) The change in the thickness of the liquid film causes the optical path of the optical signal to change, thereby causing the microwave interference spectrum generated by the interference between the optical signal and the microwave envelope of the optical signal reflected back from the end face of the third transmission optical fiber (14) to shift in frequency; there is a corresponding relationship between the pressure, temperature, and liquid film thickness flow field change information of the complex flow of two-phase / multi-phase flow and the change in the optical path, and there is a corresponding relationship between the change in the optical path and the frequency shift of the microwave interference spectrum. Therefore, based on the frequency shift of the microwave interference spectrum, the pressure distribution information can be measured through the distributed sensing optical fiber (11), the temperature information can be measured through the temperature probe (13), and the liquid film thickness information can be measured through the interference system composed of the two output optical paths of the third 1×2 optical fiber coupler (9).

[0016] Furthermore: the spatial distribution information of the reflected signal is obtained by transforming the collected microwave interference spectrum from the frequency domain to the time domain, and then the reflected signal corresponding to each sensor is distinguished according to the actual optical path of each optical path; the microwave interference spectrum corresponding to each sensor is reconstructed using a rectangular window function, and then the pressure distribution, temperature and liquid film thickness information of the flow field to be measured can be demodulated, thereby realizing the simultaneous measurement of the complex flow pressure distribution, temperature and liquid film thickness flow parameters of two-phase / multi-phase flow.

[0017] Furthermore, temperature information measured by the temperature probe (13) is used to perform temperature compensation on the pressure and temperature cross-sensitivity problem in the measurement of the distributed sensing optical fiber (11).

[0018] The system and method are used for simultaneous measurement of flow field information such as pressure distribution, temperature, liquid film thickness, etc. of different flow types and flow states under complex flows including two-phase flows such as gas-liquid and liquid-liquid, and multiphase flows including oil-gas-water three-phase flows.

[0019] Compared with the existing complex flow testing technologies such as two-phase and multi-phase flow, the multi-sensor fusion optical fiber measurement system and method for complex flow described in the present invention, based on the advantages of microwave photon technology, combines optical fiber sensing technology with microwave interferometry technology, and has the characteristics of high signal-to-noise ratio, high measurement resolution, low waveguide dependence, and strong adaptability. Only one set of signal generation and receiving devices can be used to integrate multiple optical fiber sensors into a single system to achieve simultaneous measurement of flow parameters such as pressure distribution, temperature, and liquid film thickness of complex flows. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the structure of the multi-sensor fusion optical fiber measurement system for complex flows described in the present invention.

[0021] FIG. 2 is a schematic diagram of the structure of a temperature probe in the system of the present invention.

[0022] In the figure: 1-polarization-maintaining output broadband light source; 2-electro-optic modulator; 3-vector network analyzer; 4-first radio frequency amplifier; 5-erbium-doped fiber amplifier; 6-optical circulator; 7-first 1×2 fiber coupler; 8-second 1×2 fiber coupler; 9-third 1×2 fiber coupler; 10-first transmission fiber; 11-distributed sensing fiber; 12-second transmission fiber; 13-temperature probe; 14-third transmission fiber; 15-optical collimator; 16-optical coupler; 17-fourth transmission fiber; 18-2×1 fiber coupler; 19-photoelectric detector; 20-second radio frequency amplifier; 21-computer; 22-sensing fiber; 23-reflector; 24-capillary stainless steel tube; 25-tested pipeline. DETAILED DESCRIPTION

[0023] The multi-sensor fusion optical fiber measurement system for complex flow includes a polarization-maintaining output broadband light source 1, an electro-optic modulator 2, a vector network analyzer 3, a first radio frequency amplifier 4, an erbium-doped fiber amplifier 5, an optical circulator 6, a first 1×2 optical fiber coupler 7, a second 1×2 optical fiber coupler 8, a third 1×2 optical fiber coupler 9, a first transmission optical fiber 10, a distributed sensing optical fiber 11, a second transmission optical fiber 12, a temperature probe 13, a third transmission optical fiber 14, an optical collimator 15, an optical coupler 16, a fourth transmission optical fiber 17, a 2×1 optical fiber coupler 18, a photodetector 19, a second radio frequency amplifier 20, and a computer 21. The temperature probe is composed of a sensing optical fiber 22, a reflector 23, and a capillary stainless steel tube 24.

[0024] The signal output end of the polarization-maintaining output broadband light source 1 is connected to the input end of the electro-optic modulator 2 through a polarization-maintaining optical fiber jumper; the signal output end of the vector network analyzer 3 is connected to the signal input end of the first radio frequency amplifier 4 through a high-frequency cable; the signal output end of the first radio frequency amplifier 4 is connected to the signal input end of the electro-optic modulator 2 through a high-frequency cable; the output end of the electro-optic modulator 2 is connected to the input end of the erbium-doped fiber amplifier 5 through an optical fiber jumper; the output end of the erbium-doped fiber amplifier 5 is connected to the signal incident end of the optical circulator 6 through an optical fiber jumper; the reflection end of the optical circulator 6 is connected to the incident end of the first 1×2 optical fiber coupler 7; the signal output end of the optical circulator 6 is connected to the first incident end of the 2×1 optical fiber coupler 18; the first output end of the first 1×2 optical fiber coupler 7 is connected to the incident end of the second 1×2 optical fiber coupler 8, and the second output end of the first 1×2 optical fiber coupler 7 is connected to the incident end of the third 1×2 optical fiber coupler 9; the first output end of the second 1×2 optical fiber coupler 8 is connected to the incident end of the third 1×2 optical fiber coupler 9; the second ... The emitting end is connected to the first transmission optical fiber 10, and the first transmission optical fiber 10 is connected to the distributed sensing optical fiber 11; the second emitting end of the second 1×2 optical fiber coupler 8 is connected to the second transmission optical fiber 12, and the second transmission optical fiber 12 is connected to the temperature probe 13; the first emitting end of the third 1×2 optical fiber coupler 9 is connected to the third transmission optical fiber 14; the second emitting end of the third 1×2 optical fiber coupler 9 is connected to the optical collimator 15; the optical coupler 16 is connected to the fourth transmission optical fiber 17; the fourth transmission optical fiber 17 is connected to the second incident end of the 2×1 optical fiber coupler 18; the emitting end of the 2×1 optical fiber coupler 18 is connected to the incident end of the high-speed photodetector 19 through an optical fiber jumper; the emitting end of the high-speed photodetector 19 is connected to the signal input end of the second radio frequency amplifier 20 through a high-frequency cable; the signal output end of the second radio frequency amplifier 20 is connected to the signal input end of the vector network analyzer 3 through a high-frequency cable, and the vector network analyzer 3 is connected to the computer 12 through a high-frequency cable.

[0025] In a specific implementation, a continuous reflector is processed in the core of the distributed sensing optical fiber 11 by using a femtosecond laser. The optical path difference corresponding to the spacing between adjacent reflectors is greater than the coherence length of the polarization-maintaining output broadband light source and less than the coherence length of the microwave signal generated by the vector network analyzer 3. The distributed sensing optical fiber 9 is arranged on the inner side of the pipeline 25 along the axial direction of the pipeline to be measured.

[0026] In specific implementation, the sensing optical fiber 22 of the temperature probe 13 is placed in the capillary stainless steel tube 24, a reflector 23 is processed in the core of the sensing optical fiber 22 by femtosecond laser, and the end of the sensing optical fiber 22 is flush with the end of the capillary stainless steel tube 24. The optical path difference corresponding to the distance between the reflector 23 and the end face of the sensing optical fiber 22 is greater than the coherence length of the polarization-maintaining output broadband light source, and less than the coherence length of the microwave signal generated by the vector network analyzer 3. The temperature probe 13 is embedded in the inner wall of the measured pipeline 25, and the end face of the probe is flush with the inner wall of the pipeline.

[0027] In specific implementation, the optical path difference corresponding to the distance from the first output end of the third 1×2 fiber coupler 9 to the end of the third transmission fiber 14 and then returning through the third transmission fiber 14, the third 1×2 fiber coupler 9, the first 1×2 fiber coupler 7, the optical circulator 6 to the first incident end of the 2×1 fiber coupler 18 and the distance from the second output end of the third 1×2 fiber coupler 9 through the optical collimator 15, the measured two-phase / multi-phase flow pipeline 25, the optical coupler 16, the fourth transmission fiber 17 to the second incident end of the 2×1 fiber coupler 18 is greater than the coherence length of the polarization-maintaining output broadband light source 1, but less than the coherence length of the microwave signal generated by the vector network analyzer 3.

[0028] In a specific implementation, the length of the first transmission optical fiber 10 is greater than the sum of the lengths of the second transmission optical fiber 12 and the sensing optical fiber 22 of the temperature probe; the length of the second transmission optical fiber 12 is greater than the length of the third transmission optical fiber 14; the length of the second transmission optical fiber 12 is greater than the distance from the second output end of the third 1×2 optical fiber coupler 9 through the optical collimator 15, the measured pipeline 25, the optical coupler 16, the fourth transmission optical fiber 17 to the second incident end of the 2×1 optical fiber coupler 18.

[0029] A multi-sensor fusion optical fiber measurement method for complex flow is implemented in the multi-sensor fusion optical fiber measurement system for complex flow described in the present invention. The method is implemented by the following steps:

[0030] The optical signal output by the polarization-maintaining broadband light source 1 enters the electro-optic modulator 2; the microwave signal output by the vector network analyzer 3 enters the electro-optic modulator 2 after being amplified by the first radio frequency amplifier 4; the microwave signal is modulated by the electro-optic modulator 2 and loaded onto the optical signal; the optical signal modulated by the microwave signal is output from the electro-optic modulator 2 and enters the erbium-doped fiber amplifier 5, and is amplified by the erbium-doped fiber amplifier 5 and input to the optical circulator 6; the optical signal enters the first 1×2 optical fiber coupler 7 after being output from the reflection end of the optical circulator 6, and is divided into two paths after passing through the first 1×2 optical fiber coupler 7; the optical signal output from the first output end enters the second 1×2 optical fiber coupler 8, and the optical signal output from the second output end enters the third 1×2 The optical signal output from the first output end of the second 1×2 optical fiber coupler 8 enters the distributed sensing optical fiber 11 through the first transmission optical fiber 10, and is reflected at the reflector in the sensing optical fiber 11. The microwave envelopes of the reflected optical signals interfere at the intersection. The interference signal returns to the optical circulator 6 after passing through the first transmission optical fiber 10, the second 1×2 optical fiber coupler 8, and the first 1×2 optical fiber coupler 7 in sequence, and enters the 2×1 optical fiber coupler 18 after being output from the output end of the optical circulator 6; the optical signal output from the second output end of the second 1×2 optical fiber coupler 8 enters the temperature probe 13 through the second transmission optical fiber 12, and is reflected at the reflector in the sensing optical fiber 22 and its end face. The microwave envelopes of the reflected optical signals interfere at the intersection, and the interference signal returns to the optical circulator 6 after passing through the second transmission optical fiber 12, the second 1×2 optical fiber coupler 8, and the first 1×2 optical fiber coupler 7 in sequence, and enters the 2×1 optical fiber coupler 18 after being output from the output end of the optical circulator 6; the optical signal output from the first output end of the third 1×2 optical fiber coupler 9 enters the third transmission optical fiber 14 and is reflected at the end face thereof, and the reflected signal returns to the optical circulator 6 after passing through the third transmission optical fiber 14, the third 1×2 optical fiber coupler 9, and the first 1×2 optical fiber coupler 7 in sequence, and enters the 2×1 optical fiber coupler 18 after being output from the output end of the optical circulator 6; The optical signal output from the second output end enters the optical collimator 15, and then enters the two-phase / multiphase flow pipeline 25 to be measured after passing through the optical collimator. After passing through the pipeline 25 to be measured, the optical signal enters the optical coupler 16, and then enters the 2×1 optical fiber coupler 18 through the sensing optical fiber 17, and interferes with the microwave envelope of the optical signal reflected back from the end face of the third transmission optical fiber 14; the microwave interference signal is output from the output end of the 2×1 optical fiber coupler 18 and then enters the high-speed photodetector 19; after being converted into an electrical signal by the high-speed photodetector 19, it enters the second radio frequency amplifier 20; after being amplified by the second radio frequency amplifier 20, it is collected by the vector network analyzer 3, and the vector network analyzer 3 inputs the collected interference information into the computer 21. By sweeping the microwave signal output by the vector network analyzer 3, the interference spectrum of the microwave signal can be obtained.

[0031] During specific implementation, the distributed sensing optical fiber 11 is affected by the complex flow pattern of the two-phase / multi-phase flow, and the length of the optical fiber at the corresponding position thereof will change with the change of the fluid pressure, thereby causing the optical path of the light signal reflected by the reflector to change, and then the interference spectrum of the microwave envelope signal will shift in frequency; due to the thermo-optical effect and the thermal expansion effect, the temperature change will cause the length and refractive index of the sensing optical fiber 22 of the temperature probe 13 to change, thereby causing the cavity length of the Fabry-Perot cavity formed by the end face of the sensing optical fiber 22 and the reflector 23 to change, so that the optical path difference corresponding to the reflected light signal changes, causing the corresponding microwave interference spectrum to shift in frequency; the change in the thickness of the liquid film in the measured pipeline 25 causes the optical path of the light signal to change, thereby causing the microwave interference spectrum generated by the interference between the light signal and the microwave envelope of the light signal reflected back from the end face of the third transmission optical fiber 14 to shift in frequency. There is a corresponding relationship between the flow field change information such as pressure, temperature, liquid film thickness and other flow field change information of complex flows such as two-phase / multiphase flow and the change in optical path, and there is a corresponding relationship between the change in optical path and the frequency shift of the microwave interference spectrum. Therefore, according to the frequency shift of the microwave interference spectrum, the pressure distribution information can be measured through the distributed sensing optical fiber 11, the temperature information can be measured through the temperature probe 13, and the liquid film thickness information can be measured through the interference system composed of the two output optical paths of the third 1×2 optical fiber coupler 9.

[0032] In specific implementation, the spatial distribution information of the reflected signal is obtained by transforming the collected microwave interference spectrum from the frequency domain to the time domain, and then the reflected signal corresponding to each sensor is distinguished according to the actual optical path of each optical path; the microwave interference spectrum corresponding to each sensor is reconstructed using a rectangular window function, and then the flow field flow information such as the pressure distribution, temperature, liquid film thickness, etc. of the complex flow such as the two-phase and multi-phase flow to be measured can be demodulated.

[0033] In specific implementation, the temperature information measured by the temperature probe 13 is used to perform temperature compensation on the cross-sensitivity problem of pressure and temperature in the measurement of the distributed sensing optical fiber 11 .

[0034] In specific implementation, the system and method are used to simultaneously measure flow parameters such as pressure distribution, temperature, liquid film thickness, etc. in different flow types and flow states under complex flows including two-phase flows such as gas-liquid and liquid-liquid, and multiphase flows including oil-gas-water three-phase flows.

Claims

1. A multi-sensor fusion optical fiber measurement system for complex flows, characterized by: It comprises a polarization-maintaining output broadband light source (1), an electro-optic modulator (2), a vector network analyzer (3), a first radio frequency amplifier (4), an erbium-doped fiber amplifier (5), an optical circulator (6), a first 1×2 fiber coupler (7), a second 1×2 fiber coupler (8), a third 1×2 fiber coupler (9), a first transmission fiber (10), a distributed sensing fiber (11), a second transmission fiber (12), a temperature probe (13), a third transmission fiber (14), an optical collimator (15), an optical coupler (16), a fourth transmission fiber (17), a 2×1 fiber coupler (18), a photodetector (19), a second radio frequency amplifier (20), and a computer (21); the temperature probe comprises a sensing fiber (22), a reflector (23), and a capillary stainless steel tube (24); The signal output end of the polarization-maintaining output broadband light source (1) is connected to the input end of the electro-optic modulator (2) through a polarization-maintaining optical fiber jumper; the signal output end of the vector network analyzer (3) is connected to the signal input end of the first radio frequency amplifier (4) through a high-frequency cable; the signal output end of the first radio frequency amplifier (4) is connected to the signal input end of the electro-optic modulator (2) through a high-frequency cable; the output end of the electro-optic modulator (2) is connected to the input end of the erbium-doped optical fiber amplifier (5) through an optical fiber jumper; the output end of the erbium-doped optical fiber amplifier (5) is connected to the signal input end of the optical circulator (6) through the optical fiber jumper; the reflection end of the optical circulator (6) is connected to the input end of the first 1×2 optical fiber coupler (7); the signal output end of the optical circulator (6) is connected to the first input end of the 2×1 optical fiber coupler (18); the first 1×2 optical fiber coupler (7 ... signal output end of the optical circulator (6); the first 1×2 optical fiber coupler (7) is connected to the signal input end of the erbium-doped optical fiber amplifier (5) through the optical fiber jumper; the output end of the optical circulator (6) is connected to the first input end of the 2×1 optical fiber coupler (18); the first The first output end of the coupler (7) is connected to the input end of the second 1×2 optical fiber coupler (8), and the second output end of the first 1×2 optical fiber coupler (7) is connected to the input end of the third 1×2 optical fiber coupler (9); the first output end of the second 1×2 optical fiber coupler (8) is connected to the first transmission optical fiber (10), and the first transmission optical fiber (10) is connected to the distributed sensing optical fiber (11); the second output end of the second 1×2 optical fiber coupler (8) is connected to the second transmission optical fiber (12), and the second transmission optical fiber (12) is connected to the temperature probe (13); the first output end of the third 1×2 optical fiber coupler (9) is connected to the third transmission optical fiber (14); the second output end of the third 1×2 optical fiber coupler (9) is connected to the optical collimator (15); and the optical coupler (16) is connected to the fourth transmission optical fiber (17); The fourth transmission optical fiber (17) is connected to the second incident end of the 2×1 optical fiber coupler (18); the output end of the 2×1 optical fiber coupler (18) is connected to the incident end of the high-speed photodetector (19) via an optical fiber jumper; the output end of the high-speed photodetector (19) is connected to the signal input end of the second radio frequency amplifier (20) via a high-frequency cable; the signal output end of the second radio frequency amplifier (20) is connected to the signal input end of the vector network analyzer (3) via a high-frequency cable, and the vector network analyzer (3) is connected to the computer (12) via the high-frequency cable; A core of the distributed sensing optical fiber (11) is provided with continuous reflectors processed by femtosecond laser; wherein the optical path difference corresponding to the spacing between adjacent reflectors is greater than the coherence length of the polarization-maintaining output broadband light source (1) and less than the coherence length of the microwave signal generated by the vector network analyzer (3); the distributed sensing optical fiber (11) is arranged on the inner side of the measured pipeline (25) along the axial direction of the pipeline; The sensing optical fiber (22) of the temperature probe (13) is placed in a capillary stainless steel tube (24); a reflector (23) is processed in the core of the sensing optical fiber (22) using a femtosecond laser, and the end of the sensing optical fiber (22) is flush with the end of the capillary stainless steel tube (24); the optical path difference corresponding to the distance between the end faces of the reflector (23) and the end of the sensing optical fiber (22) is greater than the coherence length of the polarization-maintaining output broadband light source (1) and less than the coherence length of the microwave signal generated by the vector network analyzer (3); the temperature probe (13) is embedded in the inner wall of the measured pipeline (25), and the end face of the probe is flush with the inner wall of the pipeline.

2. The multi-sensor fusion optical fiber measurement system for complex flow according to claim 1, characterized in that: The optical path difference between the distance from the first output end of the third 1×2 optical fiber coupler (9) to the end of the third transmission optical fiber (14) and then back through the third transmission optical fiber (14), the third 1×2 optical fiber coupler (9), the first 1×2 optical fiber coupler (7), the optical circulator (6) to the first input end of the 2×1 optical fiber coupler (18) and the distance from the second output end of the third 1×2 optical fiber coupler (9) through the optical collimator (15), the measured pipeline (25), the optical coupler (16), the fourth transmission optical fiber (17) to the second input end of the 2×1 optical fiber coupler (18) is greater than the coherence length of the polarization-maintaining output broadband light source (1) and less than the coherence length of the microwave signal generated by the vector network analyzer (3).

3. The multi-sensor fusion optical fiber measurement system for complex flow according to claim 1, characterized in that: The length of the first transmission optical fiber (10) is greater than the sum of the lengths of the second transmission optical fiber (12) and the sensing optical fiber (22) of the temperature probe; the length of the second transmission optical fiber (12) is greater than the length of the third transmission optical fiber (14); The length of the second transmission optical fiber (12) is greater than the distance from the second output end of the third 1×2 optical fiber coupler (9) through the optical collimator (15), the measured pipeline (25), the optical coupler (16), the fourth transmission optical fiber (17) to the second input end of the 2×1 optical fiber coupler (18).

4. A multi-sensor fusion optical fiber measurement method for complex flows, characterized in that The method is implemented in a multi-sensor fusion optical fiber measurement system for complex flow as claimed in any one of claims 1 to 3, and the method is implemented by the following steps: The optical signal output by the polarization-maintaining output broadband light source (1) enters the electro-optic modulator (2); the microwave signal output by the vector network analyzer (3) is amplified by the first radio frequency amplifier (4) and then enters the electro-optic modulator (2); the microwave signal is modulated by the electro-optic modulator (2) and then loaded onto the optical signal; the optical signal modulated by the microwave signal is output from the electro-optic modulator (2) and then enters the erbium-doped fiber amplifier (5), and then amplified by the erbium-doped fiber amplifier (5) and then input into the optical circulator (6); the optical signal is output from the reflection end of the optical circulator (6) and then enters the first 1×2 optical fiber coupler (7), and then is divided into two paths after passing through the first 1×2 optical fiber coupler (7); the optical signal output from the first output end enters the second 1×2 optical fiber coupler (8), and is then output from the second output end. The optical signal output from the emission end enters the third 1×2 optical fiber coupler (9); the optical signal output from the first emission end of the second 1×2 optical fiber coupler (8) enters the distributed sensing optical fiber (11) through the first transmission optical fiber (10), and is reflected at the reflector in the sensing optical fiber (11). The microwave envelopes of the reflected optical signals interfere at the intersection. The interference signal passes through the first transmission optical fiber (10), the second 1×2 optical fiber coupler (8), and the first 1×2 optical fiber coupler (7) in sequence and then returns to the optical circulator (6). After being output from the emission end of the optical circulator (6), it enters the 2×1 optical fiber coupler (18); the optical signal output from the second emission end of the second 1×2 optical fiber coupler (8) enters the temperature sensor through the second transmission optical fiber (12). The probe (13) is provided with a reflector in the sensing optical fiber (22) and at its end face. The microwave envelopes of the reflected optical signals interfere at the intersection. The interference signal passes through the second transmission optical fiber (12), the second 1×2 optical fiber coupler (8), and the first 1×2 optical fiber coupler (7) in sequence and then returns to the optical circulator (6). The interference signal is output from the output end of the optical circulator (6) and then enters the 2×1 optical fiber coupler (18). The optical signal output from the first output end of the third 1×2 optical fiber coupler (9) enters the third transmission optical fiber (14) and is reflected at its end face. The reflected signal passes through the third transmission optical fiber (14), the third 1×2 optical fiber coupler (9), and the first 1×2 optical fiber coupler (7) in sequence and then returns to the optical circulator. (6), and is output from the output end of the optical circulator (6) and enters the 2×1 optical fiber coupler (18); the optical signal output from the second output end of the third 1×2 optical fiber coupler (9) enters the optical collimator (15), enters the measured pipe (25) after passing through the optical collimator, and enters the optical coupler (16) after passing through the measured pipe (25), and enters the 2×1 optical fiber coupler (18) through the sensing optical fiber (17), and interferes with the microwave envelope of the optical signal reflected back from the end face of the third transmission optical fiber (14); the microwave interference signal is output from the output end of the 2×1 optical fiber coupler (18) and enters the high-speed photodetector (19); after being converted into an electrical signal by the high-speed photodetector (19), it enters the second radio frequency amplifier (20);After being amplified by the second radio frequency amplifier (20), the interference information is collected by the vector network analyzer (3), and the vector network analyzer (3) inputs the collected interference information into the computer (21); by performing a frequency sweep on the microwave signal output by the vector network analyzer (3), the interference spectrum of the microwave signal can be obtained; The distributed sensing optical fiber (11) is affected by the complex flow pattern of the two-phase / multi-phase flow, and the length of the optical fiber at the corresponding position thereof changes with the change of the fluid pressure, thereby causing the optical path of the light signal reflected by the reflector to change, and then the interference spectrum of the microwave envelope signal will shift in frequency; due to the thermo-optical effect and the thermal expansion effect, the temperature change will cause the length and refractive index of the sensing optical fiber (22) of the temperature probe (13) to change, thereby causing the cavity length of the Fabry-Perot cavity formed by the end face of the sensing optical fiber (22) and the reflector (23) to change, so that the optical path difference corresponding to the reflected light signal changes, causing the corresponding microwave interference spectrum to shift in frequency; The change in the thickness of the liquid film in the measured pipeline (25) causes the optical path of the optical signal to change, thereby causing the microwave interference spectrum generated by the interference between the optical signal and the microwave envelope of the optical signal reflected back from the end face of the third transmission optical fiber (14) to shift in frequency; there is a corresponding relationship between the flow field change information of the complex flow pressure, temperature, and liquid film thickness of the two-phase / multi-phase flow and the change in the optical path, and there is a corresponding relationship between the change in the optical path and the frequency shift of the microwave interference spectrum. Therefore, according to the frequency shift of the microwave interference spectrum, the pressure distribution information can be measured through the distributed sensing optical fiber (11), the temperature information can be measured through the temperature probe (13), and the liquid film thickness information can be measured through the interference system composed of the two output optical paths of the third 1×2 optical fiber coupler (9).

5. The multi-sensor fusion optical fiber measurement method for complex flow according to claim 4, characterized in that: The spatial distribution information of the reflected signal is obtained by transforming the collected microwave interference spectrum from the frequency domain to the time domain, and then the reflected signal corresponding to each sensor is distinguished according to the actual optical path of each optical path; the microwave interference spectrum corresponding to each sensor is reconstructed using a rectangular window function, and then the pressure distribution, temperature and liquid film thickness information of the flow field to be measured can be demodulated, thereby realizing the simultaneous measurement of the complex flow pressure distribution, temperature and liquid film thickness flow parameters of two-phase / multi-phase flow.

6. The multi-sensor fusion optical fiber measurement method for complex flow according to any one of claims 4 or 5, characterized in that: Temperature information measured by a temperature probe (13) is used to perform temperature compensation for the cross-sensitivity problem of pressure and temperature in the measurement of a distributed sensing optical fiber (11).

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