CN114812852A - Multi-sensor fusion optical fiber measuring system and method for complex flow - Google Patents

Abstract

The invention relates to a multi-sensor fusion optical fiber measuring system for complex flow, which comprises: the device comprises a polarization-maintaining output broadband light source, an electro-optical modulator, a vector network analyzer, a first radio frequency amplifier, an erbium-doped fiber amplifier, an optical circulator, a first 1 x 2 fiber coupler, a second 1 x 2 fiber coupler, a third 1 x 2 fiber coupler, a first transmission fiber, a distributed sensing fiber, a second transmission fiber, a temperature probe, a third transmission fiber, an optical collimator, an optical coupler, a fourth transmission fiber, a 2 x 1 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

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

technical field

The invention belongs to the field of complex flow testing, in particular to a multi-sensor fusion optical fiber measurement system and method for complex flow.

Background technique

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

At present, researchers at home and abroad have studied a variety of detection methods for complex flows, including electrical methods, which measure the conductivity changes of two-phase and multi-phase flows through electrode probes; ray methods, which use rays to pass through the fluid. The detection is realized by the absorption and scattering effects during the time; the differential pressure method is measured by the correspondence between the pressure difference generated by the fluid flowing through the throttling device and the fluid flow; the ultrasonic method is used to detect the ultrasonic wave in two-phase and multi-phase flow. The propagation time and the intensity of its scattered signal are measured; the high-speed photography method uses a high-speed camera to directly take the image of the fluid through the transparent pipe section or window, and then extracts the image features through image processing technology, and then obtains the gas-liquid two-phase according to the image features. Various parameters of the flow; fiber probe method, which uses the difference in refractive index between the fiber probe and the fluid to study the change information of the gas-liquid two-phase flow field by detecting the returned light intensity information; the fiber Bragg grating method, when the fiber Bragg When the external conditions such as the ambient temperature and strain of the grating change, the Bragg wavelength of the fiber Bragg grating will drift accordingly. By measuring the Bragg wavelength, the corresponding characteristic parameters can be measured.

However, the above detection technologies have problems such as single measurable characteristic parameters, easy to be affected by external environmental factors, harsh use conditions, low security, and inability to achieve long-distance spatial continuous distributed measurement. However, in practical engineering applications, it is often necessary to measure the spatiotemporal distribution information of multiple complex flow characteristic parameters with high precision to obtain more comprehensive flow field information. However, the existing complex flow detection technologies such as two-phase and multi-phase flow are mainly point-type and quasi-distributed single physical quantity measurement sensors, and the characteristic parameters of two-phase and multi-phase flow that can be demodulated by acquiring physical quantities are relatively limited, which cannot be realized. The comprehensive detection of complex flow field information seriously restricts its practical application in the field of complex flow detection such as two-phase and multi-phase flow. Therefore, a multi-sensor fusion measurement technology suitable for complex flow testing fields such as two-phase and multi-phase flow is required to achieve high-precision simultaneous measurement of spatiotemporal information of different characteristic parameters of the flow field.

SUMMARY OF THE INVENTION

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

The present invention adopts following technical scheme to realize:

A multi-sensor fusion optical fiber measurement system for complex flow: including polarization-maintaining output broadband light source, electro-optic modulator, vector network analyzer, first radio frequency amplifier, erbium-doped fiber amplifier, optical circulator, first 1×2 fiber coupling device, second 1×2 fiber optic coupler, third 1×2 fiber optic coupler, first transmission fiber, distributed sensing fiber, second transmission fiber, temperature probe, third transmission fiber, optical collimator, optical Coupler, fourth transmission fiber, 2×1 fiber coupler, photodetector, second RF amplifier, computer. The temperature probe is composed of a sensing fiber, a reflector, and a capillary stainless steel tube.

The signal output end of the polarization-maintaining output broadband light source is connected to the input end of the electro-optical modulator through a polarization-maintaining fiber jumper; the signal output end of the vector network analyzer is connected to the signal input end of the first radio frequency amplifier through a high-frequency cable; the first radio frequency The signal output end of the amplifier is connected with the signal input end of the electro-optical modulator through a high-frequency cable; the output end of the electro-optical modulator is connected with the input end of the erbium-doped fiber amplifier through a fiber jumper; the output end of the erbium-doped fiber amplifier is connected by a fiber jumper Connect with the signal incident end of the optical circulator; connect the reflection end of the optical circulator with the incident end of the first 1×2 fiber coupler; connect the signal output end of the optical circulator with the first incident end of the 2×1 fiber coupler ; The first outgoing end of the first 1×2 fiber coupler is connected to the incoming end of the second 1×2 fiber coupler, and the second outgoing end of the first 1×2 fiber coupler is connected to the third 1×2 fiber coupler The incident end of the second 1×2 fiber optic coupler is connected to the first transmission fiber, and the first transmission fiber is connected to the distributed sensing fiber; the second output end of the second 1×2 fiber optic coupler is connected It is connected with the second transmission fiber, and the second transmission fiber is connected with the temperature probe; the first output end of the third 1×2 fiber coupler is connected with the third transmission fiber; the second output end of the third 1×2 fiber coupler is connected with The optical collimator is connected; the optical coupler is connected with the fourth transmission fiber; the fourth transmission fiber is connected with the second incident end of the 2×1 fiber coupler; the output end of the fourth fiber coupler is connected to the high-speed photoelectric detection through the fiber jumper The incident end of the high-speed photodetector is connected to the signal input end of the second RF amplifier through a high-frequency cable; the signal output end of the second RF amplifier is connected to the signal input end of the vector network analyzer through a high-frequency cable. , the vector network analyzer is connected to the computer through a high-frequency cable.

The core of the distributed sensing fiber is fabricated with a continuous reflector 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. The distributed sensing optical fiber is axially arranged inside the pipeline along the pipeline 25 under test.

The sensing fiber of the temperature probe is placed in a capillary stainless steel tube, a reflector is processed in the core of the sensing fiber by femtosecond laser, and the end of the sensing fiber is flush with the end of the capillary stainless steel tube. The optical path difference corresponding to the distance between the reflector and the end face of the sensing fiber 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. The temperature probe is embedded in the inner wall of the pipe under test, and the end face of the probe is flush with the inner wall of the pipe.

From the first output end of the third 1×2 fiber coupler, to the end of the third transmission fiber, and then back through the third transmission fiber, the third 1×2 fiber coupler, the first 1×2 fiber coupler, and the optical ring The distance from the runner to the first incident end of the 2×1 fiber coupler and from the second output end of the third 1×2 fiber coupler through the optical collimator, the two-phase/multi-phase flow pipeline under test, the optical coupler, the first The optical path difference corresponding to the distance from the four transmission fibers to the second incident end of the 2×1 fiber coupler is greater than the coherence length of the polarization-maintaining output broadband light source, but less than the coherence length of the microwave signal generated by the vector network analyzer.

The length of the first transmission fiber is greater than the sum of the lengths of the second transmission fiber and the sensing fiber of the temperature probe; the length of the second transmission fiber is greater than the length of the third transmission fiber; the length of the second transmission fiber is greater than that from the third 1×2 fiber The distance from the second outgoing end of the coupler to the second incoming end of the 2×1 fiber coupler through the optical collimator, the pipe under test, the optical coupler, and the fourth transmission fiber.

A complex flow-oriented multi-sensor fusion optical fiber measurement method is implemented in the complex flow-oriented multi-sensor fusion optical fiber measurement system of the present invention, and the method is implemented by the following steps:

The optical signal output by the polarization-maintaining output broadband light source enters the electro-optic modulator; the microwave signal output by the vector network analyzer is amplified by the first RF amplifier and then enters the electro-optic modulator; the microwave signal is modulated by the electro-optic modulator and then loaded onto the optical signal; The modulated optical signal is output from the electro-optic modulator and then enters the erbium-doped fiber amplifier, which is amplified by the erbium-doped fiber amplifier and then input to the optical circulator; the optical signal is output through the reflection end of the optical circulator and then enters the first 1×2 fiber coupling It is divided into two paths after passing through the first 1×2 fiber coupler; the optical signal output from the first output end enters the second 1×2 fiber coupler, and the optical signal output from the second output end enters the third 1×2 fiber optic coupler. Optical fiber coupler; the optical signal output from the first output end of the second 1×2 optical fiber coupler enters the distributed sensing fiber through the first transmission fiber, and is reflected at the reflector in the sensing fiber. The microwave envelope interferes at the meeting point, and the interference signal returns to the optical circulator through the first transmission fiber, the second 1×2 fiber coupler, and the first 1×2 fiber coupler in turn, and is output from the output end of the optical circulator Then enter the 2×1 fiber coupler; the optical signal output from the second output end of the second 1×2 fiber coupler enters the temperature probe through the second transmission fiber, and is reflected at the reflector in the sensing fiber and its end face , the microwave envelope of the reflected optical signal interferes at the meeting point, and the interference signal returns to the optical circulator through the second transmission fiber, the second 1×2 fiber coupler, and the first 1×2 fiber coupler in turn, and is transmitted from the optical ring. The optical signal output from the output end of the traveler enters the 2×1 fiber coupler; the optical signal output from the first output end of the third 1×2 fiber coupler enters the third transmission fiber and is reflected at its end face, and the reflected signal passes through the third transmission fiber in turn. The three transmission fibers, the third 1×2 fiber coupler, and the first 1×2 fiber coupler return to the optical circulator, and are output from the output end of the optical circulator and then enter the 2×1 fiber coupler; the third 1×2 fiber coupler The optical signal output from the second output end of the optical fiber coupler enters the optical collimator, and then enters the measured pipeline after passing through the optical collimator. The optical signal enters the optical coupler after passing through the measured pipeline, and enters the 2×1 through the sensing fiber The optical fiber coupler interferes with the microwave envelope of the optical signal reflected by the end face of the third transmission fiber; the microwave interference signal is output from the output end of the 2×1 fiber coupler and then enters the high-speed photodetector; after the high-speed photodetector After being converted into an electrical signal, it enters the second radio frequency amplifier; after being amplified by the second radio frequency amplifier, it is collected by a vector network analyzer, and the vector network analyzer inputs the collected interference information to the computer. By sweeping the microwave signal output by the vector network analyzer, the interference spectrum of the microwave signal can be obtained.

The distributed sensing fiber is affected by the complex flow regime of two-phase/multi-phase flow, and the length of the fiber at the corresponding position will change with the change of the fluid pressure, which will lead to the change of the optical path of the optical signal reflected by the reflector. , and then the interference spectrum of the microwave envelope signal will shift in frequency; due to the thermo-optic effect and thermal expansion effect, the temperature change will cause the length and refractive index of the sensing fiber of the temperature probe to change, so that the end face of the sensing fiber and the reflector will change. The cavity length of the formed Fabry-Perot cavity changes, so the optical path difference corresponding to the reflected optical 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 causes The optical path of the optical signal of this path changes, so that the microwave interference spectrum generated by the interference of the optical signal of this path and the microwave envelope of the optical signal reflected back by the end face of the third transmission fiber is frequency shifted. There is a corresponding relationship between the pressure, temperature, liquid film thickness and other flow field change information of complex flows such as two-phase/multiphase flow and the optical path change. There is a corresponding relationship between the optical path change and the frequency shift of the microwave interference spectrum. Therefore, according to the microwave interference The spectral frequency shift can measure the pressure distribution information through the distributed sensing fiber, measure the temperature information through the temperature probe, and measure the liquid film thickness information through the interference system formed by the two output optical paths of the third 1×2 optical fiber coupler.

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 rectangular window function is used to analyze the microwave corresponding to each sensor. The interference spectrum can be reconstructed, and then the flow field flow information such as the pressure distribution, temperature, liquid film thickness and other complex flows of the two-phase and multi-phase flows to be measured can be demodulated.

The temperature information measured by the temperature probe is used to perform temperature compensation for the cross-sensitivity problem of pressure and temperature in the distributed sensing optical fiber measurement.

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

Compared with the existing complex flow measurement 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 is based on the advantages of microwave photonic technology, and combines optical fiber sensing technology with microwave. The combination of interferometric technology has the characteristics of high signal-to-noise ratio, high measurement resolution, low waveguide dependence and strong adaptability. Only one set of signal generating and receiving devices can be used to integrate a variety of optical fiber sensors into a single system to achieve simultaneous measurement of flow parameters such as pressure distribution, temperature, and liquid film thickness in an equivalent complex flow.

Description of drawings

FIG. 1 is a schematic structural diagram of the complex flow-oriented multi-sensor fusion optical fiber measurement system according to the present invention.

FIG. 2 is a schematic structural diagram of a temperature probe in the system according to the present invention.

In the figure: 1- polarization maintaining output broadband light source; 2- electro-optic modulator; 3- vector network analyzer; 4- first RF 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-photodetector; 20-second RF amplifier; 21-computer; 22-sensing fiber; 23-reflector; 24-capillary stainless steel tube; 25-tested pipe.

Detailed ways

Multi-sensor fusion optical fiber measurement system for complex flow, including polarization-maintaining output broadband light source 1, electro-optic modulator 2, vector network analyzer 3, first RF amplifier 4, erbium-doped fiber amplifier 5, optical circulator 6, first 1 ×2 fiber optic coupler 7, second 1×2 fiber optic coupler 8, third 1×2 fiber optic coupler 9, first transmission fiber 10, distributed sensing fiber 11, second transmission fiber 12, temperature probe 13, The third transmission optical fiber 14 , the optical collimator 15 , the optical coupler 16 , the fourth transmission optical fiber 17 , the 2×1 optical fiber coupler 18 , the photodetector 19 , the second radio frequency amplifier 20 , and the computer 21 . The temperature probe is composed of 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-optical modulator 2 through a polarization-maintaining 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 with the signal input end of the electro-optical modulator 2 through a high-frequency cable; the output end of the electro-optical modulator 2 is connected with the input end of the erbium-doped fiber amplifier 5 through a fiber jumper; the erbium-doped fiber The output end of the amplifier 5 is connected to the signal incident end of the optical circulator 6 through a fiber jumper; the reflection end of the optical circulator 6 is connected to the incident end of the first 1×2 fiber coupler 7; the signal output end of the optical circulator 6 is connected to the The first incident end of the 2×1 fiber coupler 18 is connected; the first output end of the first 1×2 fiber coupler 7 is connected to the incident end of the second 1×2 fiber coupler 8, and the first 1×2 fiber is coupled The second outgoing end of the coupler 7 is connected to the incoming end of the third 1×2 fiber coupler 9; the first outgoing end of the second 1×2 fiber coupler 8 is connected to the first transmission fiber 10, and the first transmission fiber 10 is connected to the first transmission fiber 10. The distributed sensing fiber 11 is connected; the second output end of the second 1×2 fiber optic coupler 8 is connected with the second transmission fiber 12 , and the second transmission fiber 12 is connected with the temperature probe 13 ; the third 1×2 fiber optic coupler 9 The first output end of the optical fiber is connected to the third transmission fiber 14; the second output end of the third 1×2 fiber coupler 9 is connected to the optical collimator 15; the optical coupler 16 is connected to the fourth transmission fiber 17; the fourth transmission fiber The optical fiber 17 is connected to the second incident end of the 2×1 optical fiber coupler 18; the outgoing end of the 2×1 optical fiber coupler 18 is connected to the incident end of the high-speed photodetector 19 through a fiber jumper; the outgoing end of the high-speed photodetector 19 Connect 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 the high frequency cable, and the vector network analyzer 3 passes through the high frequency cable. Connect to computer 12 .

In specific implementation, the core of the distributed sensing fiber 9 is processed with a continuous reflector 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 optical fiber of the distributed sensing 9 is axially arranged inside the pipeline along the pipeline 25 under test.

In specific implementation, the sensing 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 fiber 22 by femtosecond laser, and the end of the sensing fiber 22 is connected to the capillary stainless steel tube 24 . The ends are flush. The optical path difference corresponding to the distance between the reflector 23 and the end face of the sensing 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 pipeline 25 under test, and the end face of the probe is flush with the inner wall of the pipeline.

In the specific implementation, from the first output end of the third 1×2 fiber coupler 9 to the end of the third transmission fiber 14 , and then back through the third transmission fiber 14 , the third 1×2 fiber coupler 9 , the first The distance between the 1×2 fiber coupler 7 and 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 and the measured The optical path difference corresponding to the distance between the two-phase/multi-phase flow pipeline 25, the optical coupler 16, the fourth transmission fiber 17 and 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, and less than The coherence length of the microwave signal generated by the vector network analyzer 3.

In specific implementation, the length of the first transmission fiber 10 is greater than the length sum of the second transmission fiber 12 and the sensing fiber 22 of the temperature probe; the length of the second transmission fiber 12 is greater than the length of the third transmission fiber 14; the second transmission fiber 12 The second output end of the third 1×2 fiber coupler 9 with a length greater than the third 1×2 fiber coupler 9 passes through the optical collimator 15 , the pipe under test 25 , the optical coupler 16 , and the fourth transmission fiber 17 to the 2×1 fiber coupler 18 The second incident distance from the end.

The present invention also provides a complex flow-oriented multi-sensor fusion optical fiber measurement method, which is implemented in the complex flow-oriented multi-sensor fusion optical fiber measurement system of the present invention, 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 into the electro-optic modulator 2. On 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 is amplified by the erbium-doped fiber amplifier 5 and then input to the optical circulator 6; the optical signal is reflected by the optical circulator 6. After the output end, it enters the first 1×2 fiber coupler 7, and is divided into two paths after passing through the first 1×2 fiber coupler 7; the optical signal output from the first output end enters the second 1×2 fiber coupler 8, and is composed of The optical signal output from the second output end enters the third 1×2 fiber coupler 9 ; the optical signal output from the first output end of the second 1×2 fiber coupler 8 enters the distributed sensing fiber 11 through the first transmission fiber 10 , And reflection occurs at the reflector in the sensing fiber 11, the microwave envelope of the reflected optical signal interferes at the meeting point, and the interference signal passes through the first transmission fiber 10, the second 1×2 fiber coupler 8, the first transmission fiber The 1×2 fiber coupler 7 returns to the optical circulator 6, and is output from the output end of the optical circulator 6 and then enters the 2×1 fiber coupler 18; the light output from the second output end of the second 1×2 fiber coupler 8 The signal enters the temperature probe 13 through the second transmission fiber 12, and is reflected at the reflector in the sensing fiber 22 and its end face. The microwave envelope of the reflected optical signal interferes at the meeting point, and the interference signal passes through the second transmission fiber in turn. The transmission fiber 12 , the second 1×2 fiber coupler 8 , and the first 1×2 fiber coupler 7 return to the optical circulator 6 , and are output from the output end of the optical circulator 6 and then enter the 2×1 fiber coupler 18 ; The optical signal output from the first output end of the third 1×2 fiber coupler 9 enters the third transmission fiber 14 and is reflected at its end face, and the reflected signal passes through the third transmission fiber 14 and the third 1×2 fiber coupler in sequence. 9. The first 1×2 fiber coupler 7 returns to the optical circulator 6, and is output from the output end of the optical circulator 6 and then enters the 2×1 fiber coupler 18; the third 1×2 fiber coupler 9 exits the second The optical signal output from the terminal enters the optical collimator 15, and then enters the two-phase/multiphase flow pipeline 25 under test after passing through the optical collimator. 17 enters the 2×1 fiber coupler 18, and interferes with the microwave envelope of the optical signal reflected by the end face of the third transmission fiber 14; the microwave interference signal is output from the output end of the 2×1 fiber coupler 18 and then enters the high-speed optoelectronics The detector 19 is converted into an electrical signal by the high-speed photodetector 19 and then 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 to computer 21. By sweeping the microwave signal output by the vector network analyzer 3, the interference spectrum of the microwave signal can be obtained.

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

In the 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 the sensor is reconstructed, and then the pressure distribution, temperature, liquid film thickness and other flow field flow information of complex flows such as two-phase and multi-phase flows to be measured can be demodulated.

In a specific implementation, temperature compensation is performed for the cross-sensitivity problem of pressure and temperature in the measurement of the distributed sensing fiber 11 through the temperature information measured by the temperature probe 13 .

In specific implementation, the system and method are used for the pressure distribution, temperature, pressure, temperature, pressure, etc. of different flow patterns and flow states of complex flows such as two-phase flows including gas-liquid and liquid-liquid and multi-phase flows including oil-gas-water three-phase flow. Simultaneous measurement of flow parameters such as liquid film thickness.

Claims (6)

1. A multi-sensor fusion optical fiber measuring system for complex flow is characterized in that: the device comprises a polarization-maintaining output broadband light source (1), an electro-optical 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 x 2 fiber coupler (7), a second 1 x 2 fiber coupler (8), a third 1 x 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 x 1 fiber coupler (18), an electro-optical detector (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);

the signal output end of the polarization-maintaining output broadband light source (1) is connected with the input end of the electro-optical modulator (2) through a polarization-maintaining optical fiber jumper; the signal output end of the vector network analyzer (3) is connected with 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 with the signal input end of the electro-optical modulator (2) through a high-frequency cable; the output end of the electro-optical modulator (2) is connected with the input end of the erbium-doped fiber amplifier (5) through a fiber jumper; the output end of the erbium-doped optical fiber amplifier (5) is connected with the signal incidence end of the optical circulator (6) through an optical fiber jumper; the reflection end of the optical circulator (6) is connected with the incident end of the first 1 multiplied by 2 optical fiber coupler (7); the signal output end of the optical circulator (6) is connected with the first incident end of the 2 multiplied by 1 optical fiber coupler (18); the first emergent end of the first 1 x 2 optical fiber coupler (7) is connected with the incident end of the second 1 x 2 optical fiber coupler (8), and the second emergent end of the first 1 x 2 optical fiber coupler (7) is connected with the incident end of the third 1 x 2 optical fiber coupler (9); the first emergent end of the second 1 multiplied by 2 optical fiber coupler (8) is connected with a first transmission optical fiber (10), and the first transmission optical fiber (10) is connected with a distributed sensing optical fiber (11); the second emergent end of the second 1 x 2 optical fiber coupler (8) is connected with a second transmission optical fiber (12), and the second transmission optical fiber (12) is connected with a temperature probe (13); the first emergent end of the third 1 x 2 optical fiber coupler (9) is connected with a third transmission optical fiber (14); the second emergent end of the third 1 multiplied by 2 optical fiber coupler (9) is connected with the optical collimator (15); the optical coupler (16) is connected with a fourth transmission optical fiber (17); the fourth transmission optical fiber (17) is connected with the second incident end of the 2 x 1 optical fiber coupler (18); the emergent end of the 2 multiplied by 1 optical fiber coupler (18) is connected with the incident end of the high-speed photoelectric detector (19) through an optical fiber jumper; the emergent end of the high-speed photoelectric detector (19) is connected with the signal input end of a second radio-frequency amplifier (20) through a high-frequency cable; the signal output end of the second radio frequency amplifier (20) is connected with the signal input end of the vector network analyzer (3) through a high-frequency cable, and the vector network analyzer (3) is connected with the computer (12) through the high-frequency cable;

a continuous reflector is processed in a fiber core of the distributed sensing optical fiber (9) by adopting femtosecond laser; the optical path difference corresponding to the distance between the adjacent reflectors is greater than the coherence length of the polarization-maintaining output broadband light source (1) and less than the coherence length of a microwave signal generated by the vector network analyzer (3); the distributed sensing optical fiber (9) is arranged on the inner side of the pipeline along the axial direction of the tested pipeline (25);

a sensing optical fiber (22) of the temperature probe (13) is arranged in the capillary stainless steel pipe (24), a reflector (23) is machined in a fiber core of the sensing optical fiber (22) by adopting femtosecond laser, and the tail end of the sensing optical fiber (22) is flush with the tail end of the capillary stainless steel pipe (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 (1) and less than the coherence length of a 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 surface of the probe is flush with the inner wall of the pipeline.

2. The complex flow oriented multi-sensor fusion fiber optic measurement system of claim 1, wherein: the optical path difference corresponding to the distance from the first emergent end of the third 1 x 2 optical fiber coupler (9), the first 1 x 2 optical fiber coupler (7) and the optical circulator (6) to the first incident end of the 2 x 1 optical fiber coupler (18) and the distance from the second emergent end of the third 1 x 2 optical fiber coupler (9), the optical collimator (15), the tested pipeline (25), the optical coupler (16) and the fourth transmission optical fiber (17) to the second incident end of the 2 x 1 optical fiber coupler (18) is larger than the coherence length of the polarization maintaining output broadband light source (1) and smaller than the coherence length of the microwave signal generated by the vector network analyzer (3) from the first emergent end of the third 1 x 2 optical fiber coupler (9) to the tail end of the third transmission optical fiber (14).

3. The complex flow oriented multi-sensor fusion fiber optic measurement system of claim 1, wherein: the length of the first transmission optical fiber (10) is greater than the sum of the length of the second transmission optical fiber (12) and the length of the sensing optical fiber (22) of the temperature probe; the length of the second transmission fiber (12) is greater than the length of the third transmission fiber (14); the length of the second transmission fiber (12) is larger than the distance from the second emergent end of the third 1 x 2 fiber coupler (9) to the second incident end of the 2 x 1 fiber coupler (18) through the optical collimator (15), the tested pipeline (25), the optical coupler (16) and the fourth transmission fiber (17).

4. A multi-sensor fusion optical fiber measurement method facing complex flow, which is implemented in the multi-sensor fusion optical fiber measurement system facing complex flow according to claims 1-3, and is implemented by the following steps:

an optical signal output by the polarization-maintaining output broadband light source (1) enters an electro-optical modulator (2); a microwave signal output by the vector network analyzer (3) is amplified by a first radio frequency amplifier (4) and then enters an electro-optical modulator (2); the microwave signal is modulated by the electro-optical modulator (2) and then loaded on the optical signal; the optical signal modulated by the microwave signal is output from the electro-optical modulator (2), enters the erbium-doped optical fiber amplifier (5), is amplified by the erbium-doped optical fiber amplifier (5) and is input into the optical circulator (6); the optical signal enters the first 1 x 2 optical fiber coupler (7) after being output by the reflection end of the optical circulator (6), and is divided into two paths after passing through the first 1 x 2 optical fiber coupler (7); the optical signal output by the first outgoing end enters a second 1 x 2 optical fiber coupler (8), and the optical signal output by the second outgoing end enters a third 1 x 2 optical fiber coupler (9); the optical signal output by the first exit 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 signal interfere at the meeting position, the interference signal sequentially 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), then returns to the optical circulator (6), and is output from the exit end of the optical circulator (6) and then enters the 2 × 1 optical fiber coupler (18); the optical signal output by the second exit 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 the end face of the tail end of the reflector, the microwave envelopes of the reflected optical signal interfere at the meeting position, the interference signal sequentially 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) and then returns to the optical circulator (6), and the interference signal is output from the exit end of the optical circulator (6) and then enters the 2 × 1 optical fiber coupler (18); the optical signal output by the first emergent end of the third 1 x 2 optical fiber coupler (9) enters a third transmission optical fiber (14) and is reflected at the end face of the tail end of the third transmission optical fiber, the reflected signal returns to the optical circulator (6) after sequentially passing through the third transmission optical fiber (14), the third 1 x 2 optical fiber coupler (9) and the first 1 x 2 optical fiber coupler (7), and the reflected signal enters the 2 x 1 optical fiber coupler (18) after being output from the emergent end of the optical circulator (6); an optical signal output by a second emergent end of the third 1 x 2 optical fiber coupler (9) enters an optical collimator (15), enters a detected pipeline (25) after passing through the optical collimator, enters an optical coupler (16) after passing through the detected pipeline (25), enters a 2 x 1 optical fiber coupler (18) through a sensing optical fiber (17), and interferes with microwave envelopes of the optical signal reflected by the end face of the third transmission optical fiber (14); microwave interference signals are output from the exit end of the 2 multiplied by 1 optical fiber coupler (18) and then enter a high-speed photoelectric detector (19); the electric signal is converted into an electric signal by a high-speed photoelectric detector (19) and then enters a second radio frequency amplifier (20); the interference information is amplified by a second radio frequency amplifier (20) and then collected by a vector network analyzer (3), and the collected interference information is input into a computer (21) by the vector network analyzer (3); the interference spectrum of the microwave signal can be obtained by sweeping the frequency of the microwave signal output by the vector network analyzer (3);

the distributed sensing optical fiber (11) is influenced by the complex flow pattern flow state of the two-phase/multiphase flow, the length of the optical fiber at the corresponding position of the distributed sensing optical fiber changes along with the change of fluid pressure, so that the optical path of an optical signal reflected by the reflector changes, and further the interference spectrum of a microwave envelope signal shifts; due to a thermo-optic effect and a thermal expansion effect, the length and the refractive index of a sensing optical fiber (22) of a temperature probe (13) can be changed due to temperature change, so that the cavity length of a Fabry-Perot cavity formed by the end face of the end of the sensing optical fiber (22) and a reflector (23) is changed, the optical path difference corresponding to the reflected optical signal is changed, and the corresponding microwave interference spectrum is subjected to frequency shift; the change of the thickness of the liquid film in the measured pipeline (25) causes the optical path of the optical signal to change, so that the microwave interference spectrum generated by the interference of the optical signal and the microwave envelope of the optical signal reflected back by the end face of the third transmission optical fiber (14) shifts; the flow field change information of the two-phase/multiphase flow complex flow pressure, temperature and liquid film thickness has a corresponding relation with the optical path variable quantity, and the optical path variable quantity has a corresponding relation with the microwave interference spectrum frequency shift quantity, so that the pressure distribution information can be measured through a distributed sensing optical fiber (11) according to the microwave interference spectrum frequency shift quantity, the temperature information can be measured through a temperature probe (13), and the liquid film thickness information can be measured through an interference system formed by two output optical paths of a third 1 x 2 optical fiber coupler (9).

5. The complex flow oriented multi-sensor fusion fiber optic measurement method of claim 4, wherein: transforming the collected microwave interference spectrum from a frequency domain to a time domain to obtain spatial distribution information of the reflected signals, and distinguishing the reflected signals corresponding to each sensor according to the actual optical path of each optical path; the microwave interference spectrum corresponding to each sensor is reconstructed by utilizing the rectangular window function, so that the pressure distribution, the temperature and the liquid film thickness information of the flow field to be measured can be demodulated, and the simultaneous measurement of the flow parameters of the pressure distribution, the temperature and the liquid film thickness of the complex flow of the two-phase/multi-phase flow is realized.

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

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