Complex flow multi-channel distributed measurement device and method based on microwave domain demodulation

Abstract

The present invention relates to a complex flow multi-path distributed measurement device based on microwave domain demodulation, 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 fiber amplifier (5), an optical circulator (6), a 1×n fiber coupler (7), n transmission optical fibers (8), n distributed sensing optical fibers (9), a photodetector (10), and a second radio frequency amplifier (11). 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; and a continuous reflector is processed in the core of the n distributed sensing optical fibers (9) using a femtosecond laser. The present invention also provides a complex flow multi-path distributed measurement method implemented by using such a device.

Description

Technical Field

[0001] The present invention belongs to the field of complex flow detection, and in particular relates to a complex flow multi-channel distributed measurement device and method based on microwave domain demodulation. Background Art

[0002] The flow patterns of complex flows such as two-phase and multi-phase flows are complex and changeable. In many industries using two-phase and multi-phase flows as media, in order to ensure the safety, stability and reliability of the production operation process, as well as to design, improve and improve production equipment and processes, it is necessary to accurately measure multiple flow characteristic parameter information of complex flows, as well as flow characteristic distribution information within a certain distance or even the entire domain along the flow direction of the fluid. For this reason, it is often necessary to realize spatially continuous distributed measurement of complex flow characteristic parameters at different circumferential positions along the flow direction in the same pipeline and different pipelines. Therefore, multi-channel spatially continuous distributed simultaneous measurement of flow characteristic parameters of complex flows such as two-phase and multi-phase flows is of great significance.

[0003] The existing distributed detection technology for complex flows such as two-phase and multi-phase flows is mainly based on fiber optic sensing technology based on fiber Bragg gratings. Complex flow detection technology based on fiber Bragg gratings mainly uses multiple fiber Bragg grating sensing units processed in the sensing optical fiber for measurement. There are measurement blind spots and it belongs to quasi-distributed measurement. This technology cannot realize the spatial continuous distributed measurement of flow characteristic parameters of complex flows along the optical fiber. With the development of laser and fiber optic sensing technology, it has been widely studied and applied due to its advantages such as electrical insulation, anti-electromagnetic interference, corrosion resistance, long distance, large range and high sensitivity. Currently, the commonly used distributed fiber optic sensing technologies mainly include optical time domain reflectometry technology based on Rayleigh scattering, distributed measurement technology based on Raman scattering, optical time domain reflectometry technology based on Brillouin scattering, optical time domain analysis technology, optical coherence domain analysis technology, and optical coherence domain reflectometry technology. Among them, the distributed measurement technology based on Raman scattering is only sensitive to temperature and is mainly used for temperature measurement; the reflection technology based on spontaneous Brillouin scattering has a weak signal, resulting in a low signal-to-noise ratio; the optical time domain technology based on pulsed light sources is limited by the phonon lifetime and has a low spatial resolution; and the optical coherence domain measurement technology based on low coherence light sources requires scanning the sensing positions one by one to achieve distributed measurement. These have severely limited the application of existing distributed fiber optic sensing technology in the distributed measurement of flow characteristic parameters of two-phase and multi-phase flows.

[0004] Based on this, it is necessary to invent a new complex flow testing technology to solve the existing problem of spatially continuous distributed simultaneous measurement along the flow direction at multiple locations in the same pipeline and different pipelines. Summary of the invention

[0005] In order to overcome the above-mentioned shortcomings of the prior art, the present invention proposes a complex flow multi-channel distributed measurement device and method based on microwave domain demodulation. The system and method can realize spatially continuous multi-channel distributed measurement of flow parameters of complex flow fields.

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

[0007] A complex flow multi-channel distributed measurement device based on microwave domain demodulation, 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 fiber amplifier (5), an optical circulator (6), a 1×n fiber coupler (7), n transmission optical fibers (8), n distributed sensing optical fibers (9), a photoelectric detector (10), a second radio frequency amplifier (11), and a computer (12), wherein:

[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) 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 1×n optical fiber coupler ( 7), the n output ends of the 1×n optical fiber coupler (7) are respectively connected to n transmission optical fibers (8); the n transmission optical fibers (8) are connected to n distributed sensing optical fibers (9); the signal output end of the optical circulator (6) is connected to the input end of the high-speed photodetector (10) through an optical fiber jumper; the output end of the high-speed photodetector (10) is connected to the signal input end of the second radio frequency amplifier (11) through a high-frequency cable; the signal output end of the second radio frequency amplifier (11) 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 the high-frequency cable;

[0009] Continuous reflectors are processed in the cores of n distributed sensing optical fibers (9) using femtosecond lasers, and the optical path difference corresponding to the spacing between adjacent reflectors is greater than the coherence length of the broadband light source and less than the coherence length of the microwave signal generated by the vector network analyzer; the length of the nth transmission optical fiber is greater than the length of the n-1th transmission optical fiber plus the length of the n-1th sensing optical fiber, wherein N≥n≥2, and N is the maximum value of n.

[0010] Furthermore, the n sensing optical fibers (9) are selected from different types of optical fibers according to actual needs, and reflectors with different numbers and adjacent spacings are designed and processed.

[0011] Furthermore, n sensing optical fibers (9) are arranged inside a single pipe; or are arranged on the inner walls of different pipes respectively, and the number of sensing optical fibers arranged on the inner wall of each pipe is determined according to actual conditions.

[0012] The present invention also provides a complex flow multi-path distributed measurement method based on microwave domain demodulation. The method is implemented in the complex flow multi-path distributed measurement device based on microwave domain demodulation described in the present invention. The method is implemented by the following steps:

[0013] The optical signal output by the polarization-maintaining broadband light source enters the electro-optic modulator; the microwave signal output by the vector network analyzer is amplified by the first radio frequency 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 optical signal modulated by the microwave signal is output from the electro-optic modulator and then enters the erbium-doped fiber amplifier, and then amplified by the erbium-doped fiber amplifier and then input into the optical circulator; the optical signal is output from the reflection end of the optical circulator and then enters the 1×n fiber coupler, and then divided into n paths by the 1×n fiber coupler; the n optical signals enter the n sensing optical fibers through n transmission optical fibers respectively; and are reflected at the reflector in the sensing optical fiber, and the microwave envelopes of the reflected optical signals interfere at the intersection; the interference signal is output from the output end of the optical circulator and then enters the high-speed photodetector; it is converted into an electrical signal by the high-speed photodetector and then enters the second radio frequency amplifier; it is amplified by the second radio frequency amplifier and then collected by the vector network analyzer, and the vector network analyzer inputs the collected interference information into the computer. By sweeping the microwave signal output by the vector network analyzer, the interference spectrum of the microwave signal can be obtained. The sensing optical fiber is affected by the pressure, temperature and other factors of complex flows such as two-phase and multi-phase flows. The length and refractive index of the optical fiber at the corresponding position will change, which will cause 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. There is a corresponding relationship between the pressure, temperature and other parameters of complex flows such as two-phase and multi-phase flows 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. Then, the flow parameters to be measured can be inverted through the frequency shift of the microwave interference spectrum.

[0014] 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; then the reflection signal interval corresponding to each sensing fiber reflector is distinguished according to the actual length of the n sensing fibers and the transmission fibers connected thereto; the two required reflection signals are selected by a rectangular window function and the remaining reflection signals are removed, and the microwave interference spectrum of the selected two reflection signals is reconstructed by Fourier transform; the microwave interference spectra corresponding to the adjacent reflectors of the n distributed sensing fibers are reconstructed respectively, and then the complex flow parameters such as two-phase and multi-phase flow at the corresponding positions can be demodulated, thereby realizing multi-path spatially continuous distributed simultaneous measurement of complex flow characteristic parameters.

[0015] Compared with the existing two-phase and multi-phase flow testing technologies, the complex flow multi-channel distributed measurement device and method based on microwave domain demodulation has the following advantages:

[0016] 1. Compared with the existing multiphase flow detection technology, the complex flow multi-channel distributed measurement device and method based on microwave domain demodulation described in the present invention can use only a single sensor system to achieve spatially continuous long-distance distributed simultaneous measurement of multiphase flow characteristic parameters along the flow direction at multiple positions in the same pipeline and different pipelines.

[0017] 2. The complex flow multi-channel distributed measurement device and method based on microwave domain demodulation described in the present invention is based on microwave photonic technology and uses optical signals as carriers of microwave signals. It has the advantages of being insensitive to optical fiber types, having high signal quality, and having low requirements on the processing quality of reflectors in sensing optical fibers.

[0018] 3. The complex flow multi-channel distributed measurement device and method based on microwave domain demodulation described in the present invention can, during measurement, enable each sensing optical fiber to use the same or different type of waveguide and process the same or different number and spacing of reflectors according to actual needs, and has the characteristics of high flexibility and strong adaptability.

[0019] The present invention effectively solves the problem that existing complex flow testing technologies cannot achieve spatially continuous distributed measurement along the flow direction at different circumferential positions in the same pipeline or different pipelines. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the structure of the complex flow multi-channel distributed measurement device based on microwave domain demodulation described in the present invention.

[0021] Figure 2 This is an example diagram of the arrangement of multiple distributed sensing optical fibers in a single pipe in the device described in the present invention.

[0022] Figure 3 This is an example diagram of multiple distributed sensing optical fibers in the device of the present invention being arranged in multiple pipelines respectively (taking three pipelines and three sensing optical fibers as an example).

[0023] Figure 4 It is a schematic diagram of using a rectangular window function to extract reflection signals of adjacent reflectors in the method of the present invention.

[0024] Figure 5 It is a schematic diagram of the microwave interference spectrum reconstructed in the method of the present invention.

[0025] 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; 7-1×n fiber coupler; 8-n transmission optical fibers; 9-n distributed sensing optical fibers; 10-photodetector; 11-second radio frequency amplifier; 12-computer; 13-pipeline; 14-horizontal pipeline; 15-inclined pipeline; 16-vertical pipeline. DETAILED DESCRIPTION

[0026] A complex flow multi-channel distributed measurement device based on microwave domain demodulation includes 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 1×n fiber coupler 7, n transmission optical fibers 8, n distributed sensing optical fibers 9, a photodetector 10, a second radio frequency amplifier 11, and a computer 12.

[0027] 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 incident end of the optical circulator 6 through an optical fiber jumper; the reflection end of the optical circulator 6 is coupled to the 1×n optical fiber The incident end of the optical circulator 6 is connected to the incident end of the high-speed photodetector 10 through an optical fiber jumper; the output end of the high-speed photodetector 10 is connected to the signal input end of the second radio frequency amplifier 11 through a high-frequency cable; the signal output end of the second radio frequency amplifier 11 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.

[0028] Among them, continuous reflectors are engraved in the cores of the n distributed sensing optical fibers 9 by femtosecond laser processing, and the optical path difference corresponding to the spacing between adjacent reflectors is greater than the coherence length of the broadband light source and less than the coherence length of the microwave signal generated by the vector network analyzer.

[0029] In a specific implementation, the length of the nth transmission optical fiber is greater than the length of the n-1th transmission optical fiber plus the length of the n-1th sensing optical fiber, wherein N≥n≥2, and N is the maximum value of n.

[0030] During specific implementation, the n sensing optical fibers 9 can be selected from different types of optical fibers according to actual needs, and reflectors with different numbers and adjacent spacings can be designed and processed.

[0031] In specific implementation, n sensing optical fibers 9 can be arranged inside a single pipeline at the same time, such as Figure 2 As shown; or arranged on the inner wall of different pipes, such as Figure 3 As shown, the number of arrangements on the inner wall of each pipeline can be determined according to actual conditions.

[0032] A complex flow multi-path distributed measurement method based on microwave domain demodulation is implemented in a complex flow multi-path distributed measurement device based on microwave domain demodulation described in the present invention. The method is implemented by the following steps:

[0033] 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 to the optical circulator 6; the optical signal is output from the reflection end of the optical circulator 6 and then enters the 1×n optical fiber coupler 7, and then is split by the 1×n optical fiber coupler 7. The n optical signals are respectively transmitted through n transmission optical fibers 8 and enter n sensing optical fibers 9; and are reflected at the reflectors in the sensing optical fibers, and the microwave envelopes of the reflected optical signals interfere at the intersections; the interference signal is output from the output end of the optical circulator 6 and enters the high-speed photodetector 10; it is converted into an electrical signal by the high-speed photodetector 10 and enters the second radio frequency amplifier 11; it is amplified by the second radio frequency amplifier 11 and collected by the vector network analyzer 3, and the vector network analyzer 3 inputs the collected interference information into the computer 12. By sweeping the microwave signal output by the vector network analyzer 3, the interference spectrum of the microwave signal can be obtained. The sensing optical fiber is affected by the pressure, temperature and other factors of complex flows such as two-phase and multi-phase flows, and the length and refractive index of the optical fiber at the corresponding position will change, resulting in a change in 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. There is a corresponding relationship between the pressure, temperature and other parameters of complex flows such as two-phase and multiphase flows and the change in optical path length. There is a corresponding relationship between the change in optical path length and the frequency shift of the microwave interference spectrum. The flow parameters to be measured can be inverted through the frequency shift of the microwave interference spectrum.

[0034] 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; then the reflection signal interval corresponding to the reflector of each sensing fiber is distinguished according to the actual length of the n sensing fibers and the transmission fibers connected to them; the two required reflection signals are selected by using a rectangular window function and the remaining reflection signals are removed, and the microwave interference spectrum of the selected two reflection signals is reconstructed by Fourier transform; the microwave interference spectra corresponding to the adjacent reflectors of the n distributed sensing fibers are reconstructed respectively, as shown in Figures (4) and (5), and then the complex flow parameters such as two-phase and multi-phase flow at the corresponding positions can be demodulated, thereby realizing multi-path spatially continuous distributed simultaneous measurement of complex flow characteristic parameters.

Claims

1. A complex flow multi-channel distributed measurement device based on microwave domain demodulation, characterized by: The invention 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 1×n optical fiber coupler (7), n transmission optical fibers (8), n distributed sensing optical fibers (9), a photoelectric detector (10), a second radio frequency amplifier (11), and a computer (12), wherein: 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 1×n optical fiber coupler ( 7), the n output ends of the 1×n optical fiber coupler (7) are respectively connected to n transmission optical fibers (8); the n transmission optical fibers (8) are connected to n distributed sensing optical fibers (9); the signal output end of the optical circulator (6) is connected to the input end of the high-speed photodetector (10) through an optical fiber jumper; the output end of the high-speed photodetector (10) is connected to the signal input end of the second radio frequency amplifier (11) through a high-frequency cable; the signal output end of the second radio frequency amplifier (11) 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 the high-frequency cable; Continuous reflectors are processed in the cores of n distributed sensing optical fibers (9) using femtosecond lasers, and the optical path difference corresponding to the spacing between adjacent reflectors is greater than the coherence length of the broadband light source and less than the coherence length of the microwave signal generated by the vector network analyzer; the length of the nth transmission optical fiber is greater than the length of the n-1th transmission optical fiber plus the length of the n-1th sensing optical fiber, wherein N≥n≥2, and N is the maximum value of n.

2. The complex flow multi-channel distributed measurement device based on microwave domain demodulation according to claim 1 is characterized in that: The n sensing optical fibers (9) are selected from different types of optical fibers according to actual needs, and reflectors with different numbers and adjacent spacings are designed and processed.

3. The complex flow multi-channel distributed measurement device based on microwave domain demodulation according to claim 1 is characterized in that: The n sensing optical fibers (9) are arranged inside a single pipeline; or respectively arranged on the inner walls of different pipelines, and the number of the sensing optical fibers arranged on the inner wall of each pipeline is determined according to actual conditions.

4. A complex flow multi-path distributed measurement method based on microwave domain demodulation, characterized in that The method is implemented in a complex flow multi-channel distributed measurement device based on microwave domain demodulation as described 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 1×n optical fiber coupler (7), and then is divided into n paths after passing through the 1×n optical fiber coupler (7); the n paths of optical signals respectively enter the n sensing optical fibers (9) through n transmission optical fibers (8); and are reflected at the reflector in the sensing optical fiber, and the microwave envelopes of the reflected optical signals interfere at the intersection; The interference signal is output from the output end of the optical circulator (6) and enters the high-speed photoelectric detector (10); after being converted into an electrical signal by the high-speed photoelectric detector (10), it enters the second radio frequency amplifier (11); after being amplified by the second radio frequency amplifier (11), it is collected by the vector network analyzer (3), and the vector network analyzer (3) inputs the collected interference information into the computer (12); by sweeping the microwave signal output by the vector network analyzer (3), the interference spectrum of the microwave signal is obtained; the sensing optical fiber is affected by the pressure and temperature factors of the complex flow of the two-phase and multi-phase flow, and the length and refractive index of the optical fiber at the corresponding position will change, thereby causing the optical path of the optical signal reflected by the reflector to change, and then the interference spectrum of the microwave envelope signal will shift in frequency; there is a corresponding relationship between the pressure and temperature parameters of the complex flow of the two-phase and multi-phase flow and the optical path change amount, and there is a corresponding relationship between the optical path change amount and the microwave interference spectrum frequency shift amount, and then the flow parameter to be measured is obtained by inverting the microwave interference spectrum frequency shift amount.

5. The complex flow multi-path distributed measurement method based on microwave domain demodulation according to claim 4 is characterized by: 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; then the reflection signal interval corresponding to each sensing fiber reflector is distinguished according to the actual length of the n sensing fibers and the transmission fibers connected thereto; the two required reflection signals are selected by using a rectangular window function and the remaining reflection signals are removed, and the microwave interference spectrum of the selected two reflection signals is reconstructed by Fourier transform; The microwave interference spectra corresponding to the adjacent reflectors of n distributed sensing optical fibers are reconstructed respectively, and then the complex flow parameters of two-phase and multi-phase flows at the corresponding positions are demodulated, thereby realizing multi-path spatially continuous distributed simultaneous measurement of complex flow characteristic parameters.

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