CN114812851A - Microwave domain demodulation-based complex flow multi-path distributed measuring device and method - Google Patents

Abstract

The invention relates to a complex flow multi-path distributed measuring device based on microwave domain demodulation, which 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 optical fiber amplifier (5), an optical circulator (6), a 1 x n optical fiber coupler (7), n transmission optical fibers (8), n distributed sensing optical fibers (9), a photoelectric detector (10) and a second radio-frequency amplifier (11). 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; and continuous reflectors are processed in fiber cores of the n distributed sensing optical fibers (9) by adopting femtosecond lasers. The invention also provides a complex flow multi-path distributed measuring method realized by adopting the device.

Description

Multi-channel distributed measurement device and method for complex flow based on microwave domain demodulation

technical field

The invention belongs to the field of complex flow detection, in particular to a complex flow multi-path distributed measurement device and method based on microwave domain demodulation.

Background technique

Two-phase and multi-phase flow and other complex flow patterns are complex and changeable. In many industries that use two-phase and multi-phase flow as media, in order to ensure the safety, stability and reliability of the production and operation process, and to design, improve and improve production The device and process need to accurately measure multiple flow characteristic parameter information of complex flow, as well as flow characteristic distribution information along the fluid flow direction at a certain distance or even in the whole area. The complex flow characteristic parameters in the flow direction enable spatially continuous distributed measurements. Therefore, it is of great significance to measure the flow characteristic parameters of complex flows such as two-phase and multi-phase flows in a multi-channel spatially continuous and distributed manner.

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

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 in different pipelines.

SUMMARY OF THE INVENTION

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

The present invention adopts following technical scheme to realize:

A complex flow multi-channel distributed measurement device based on microwave domain demodulation, characterized in that it comprises a polarization-maintaining output broadband light source (1), an electro-optical modulator (2), a vector network analyzer (3), and a first radio frequency amplifier. (4), erbium-doped fiber amplifier (5), optical circulator (6), 1×n fiber coupler (7), n transmission fibers (8), n distributed sensing fibers (9), photoelectric detection a device (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-optical modulator (2) through a polarization-maintaining optical fiber jumper; the signal output end of the vector network analyzer (3) is connected to the first radio frequency amplifier through a high-frequency cable The signal input end of (4) is connected; 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 by an optical fiber jumper is connected with the input end of the erbium-doped fiber amplifier (5); the output end of the erbium-doped fiber amplifier (5) is connected with 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 1 The incident end of the ×n fiber coupler (7) is connected, and the n output ends of the 1×n fiber coupler (7) are respectively connected with n transmission fibers (8); n transmission fibers (8) are connected with n distributed fibers (8). The sensing fiber (9) is connected; the signal output end of the optical circulator (6) is connected with 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 with the high-frequency cable through a high-frequency cable. The signal input end of the second radio frequency amplifier (11) is connected; 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) passes through The high frequency cable is connected with the computer (12);

The cores of the n distributed sensing fibers (9) are processed by femtosecond laser to have continuous reflectors, 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 that of the vector network analyzer. The coherence length of the generated microwave signal; the length of the nth transmission fiber is greater than the length of the n-1th transmission fiber plus the n-1th sensing fiber, where N≥n≥2, and N is the maximum value of n.

Further: according to actual requirements, the n sensing fibers (9) are selected from different types of fibers, and reflectors with different numbers and adjacent spacings are designed and processed.

Further: n sensing fibers (9) are arranged inside a single pipe; or are respectively arranged on the inner walls of different pipes, and the number of the inner walls of each pipe is determined according to the actual situation.

The present invention also provides a complex flow multi-channel distributed measurement method based on microwave domain demodulation. The method is implemented in the microwave domain demodulation-based complex flow multi-channel distributed measurement device of the present invention. The following steps are implemented:

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 by the reflection end of the optical circulator and then enters the 1×n fiber coupler. After passing through a 1×n fiber coupler, it is divided into n paths; n optical signals enter n sensing fibers through n transmission fibers respectively; and reflection occurs at the reflector in the sensing fiber, and the microwave envelope of the reflected optical signal is Interference occurs at the meeting point; the interference signal is output from the output end of the optical circulator and then enters the high-speed photodetector; after being converted into an electrical signal by the high-speed photodetector, it enters the second RF amplifier; after being amplified by the second RF amplifier, it is analyzed by the vector network 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 sensing fiber is affected by the pressure, temperature and other factors of complex flow such as two-phase and multi-phase flow, and the length and refractive index of the fiber at the corresponding position will change, which will cause the optical path of the optical signal reflected by the reflector to change. Then the interference spectrum of the microwave envelope signal will be frequency shifted. Two-phase and multi-phase flow and other complex flow parameters such as pressure and temperature have a corresponding relationship with the optical path variation, and there is a corresponding relationship between the optical path variation and the frequency shift of the microwave interference spectrum, and then the frequency shift of the microwave interference spectrum can be obtained by inversion Flow parameter to be measured.

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 reflection corresponding to each sensing fiber reflector is distinguished according to the actual length of the n sensing fibers and the transmission fibers connected to them. Signal interval; use the rectangular window function to select the required two reflected signals and remove the remaining reflected signals, and reconstruct the microwave interference spectrum of the selected two reflected signals through Fourier transform; The microwave interference spectrum corresponding to the adjacent reflector is reconstructed, and then complex flow parameters such as two-phase and multi-phase flow at the corresponding position can be demodulated, so as to realize the multi-channel spatial continuous distributed simultaneous measurement of complex flow characteristic parameters.

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

1. Compared with the existing multiphase flow detection technology, the complex flow multi-channel distributed measurement device and method based on microwave domain demodulation according to the present invention can only use a single sensing system to realize the measurement of the same pipeline and different pipelines. Long-distance distributed simultaneous measurements of spatial continuity of multiphase flow characteristic parameters at multiple locations along the flow direction.

2. The complex flow multi-channel distributed measurement device and method based on microwave domain demodulation according to the present invention is based on microwave photonic technology, uses optical signal as the carrier of microwave signal, is insensitive to optical fiber type, has high signal quality, and is suitable for The processing quality of the internal reflector in the sensing fiber has the advantages of low processing quality.

3. The multi-channel distributed measurement device and method for complex flow based on microwave domain demodulation according to the present invention, during measurement, according to actual requirements, each channel of sensing fibers can be made of the same or different types of waveguides respectively, and the processing is the same. Or reflectors of different numbers and spacings, with a high degree of flexibility and adaptability.

The invention effectively solves the problem that the existing complex flow testing technology cannot realize the spatial continuous distributed measurement along the flow direction at different circumferential positions in the same pipeline or in different pipelines.

Description of drawings

FIG. 1 is a schematic structural diagram of a complex flow multi-path distributed measurement device based on microwave domain demodulation according to the present invention.

FIG. 2 is an exemplary diagram of the arrangement of multiple distributed sensing fibers in a single pipe in the device according to the present invention.

FIG. 3 is an example diagram of multiple distributed sensing fibers arranged in multiple pipes in the device according to the present invention (taking three pipes and three sensing fibers as an example).

FIG. 4 is a schematic diagram of extracting reflected signals of adjacent reflectors by using a rectangular window function in the method of the present invention.

FIG. 5 is a schematic diagram of the reconstructed microwave interference spectrum in the method of the present invention.

In the figure: 1- Polarization-maintaining output broadband light source; 2- Electro-optic modulator; 3- Vector network analyzer; 4- The first RF amplifier; 5- Erbium-doped fiber amplifier; 6- Optical circulator; 7-1×n fiber coupler; 8-n transmission fibers; 9-n distributed sensing fibers; 10-photodetector; 11-second RF amplifier; 12-computer; 13-pipe; 14-horizontal pipe; 15-inclined pipe ; 16 - Vertical pipe.

Detailed ways

A complex flow multi-channel distributed measurement device based on microwave domain demodulation, including 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, and an optical circulator 6 , 1×n fiber coupler 7 , n transmission fibers 8 , n distributed sensing fibers 9 , photodetector 10 , second radio frequency amplifier 11 , and computer 12 .

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 the fiber jumper; The ends are respectively connected with n transmission fibers 8; n transmission fibers 8 are connected with n distributed sensing fibers 9; the signal output end of the optical circulator 6 is connected with the incident end of the high-speed photodetector 10 through the fiber jumper; The output end of the 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 The analyzer 3 is connected to the computer 12 through a high frequency cable.

Among them, the cores of the n distributed sensing fibers 9 are engraved with continuous reflectors 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 vector network analysis. The coherence length of the microwave signal generated by the instrument.

In specific implementation, the length of the nth transmission fiber is greater than the length of the n-1th transmission fiber plus the n-1th sensing fiber, where N≥n≥2, and N is the maximum value of n.

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

In specific implementation, n sensing fibers 9 can be arranged inside a single pipe at the same time, as shown in FIG. 2; or respectively arranged on the inner walls of different pipes, as shown in FIG. 3, and the number of the inner walls of each pipe can be arranged according to the actual situation Situation ok.

A complex flow multi-channel distributed measurement method based on microwave domain demodulation, the method is implemented in the complex flow multi-channel distributed measurement device based on microwave domain demodulation according to the present invention, and the method is realized by adopting 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 from 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 end output, it enters the 1×n fiber coupler 7, and is divided into n paths after passing through the 1×n fiber coupler 7; the n paths of optical signals enter n sensing fibers 9 through n transmission fibers 8 respectively; Reflection occurs at the reflector of the optical circulator, and the microwave envelope of the reflected optical signal interferes at the meeting point; the interference signal is output from the output end of the optical circulator 6 and then enters the high-speed photodetector 10; Then enter 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 to 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 fiber is affected by the pressure, temperature and other factors of complex flow such as two-phase and multi-phase flow, and the length and refractive index of the fiber at the corresponding position will change, which will cause the optical path of the optical signal reflected by the reflector to change. Then the interference spectrum of the microwave envelope signal will be frequency shifted. Two-phase and multi-phase flow and other complex flow parameters such as pressure and temperature have a corresponding relationship with the optical path variation, and there is a corresponding relationship between the optical path variation and the frequency shift of the microwave interference spectrum, and then the frequency shift of the microwave interference spectrum can be obtained by inversion Flow parameter to be measured.

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 reflection of each sensing fiber is distinguished according to the actual length of the n sensing fibers and the transmission fibers connected to them. The reflected signal interval corresponding to the detector; use the rectangular window function to select the two required reflected signals and remove the remaining reflected signals, and reconstruct the microwave interference spectrum of the selected two reflected signals through Fourier transform; The microwave interference spectrum corresponding to the adjacent reflectors of the sensing fiber is reconstructed, as shown in Figures (4) and (5), and then complex flow parameters such as two-phase and multi-phase flows at the corresponding positions can be demodulated. Realize multi-channel spatially continuous distributed simultaneous measurement of complex flow characteristic parameters.

Claims (5)

1. A complex flow multi-path distributed measurement device based on microwave domain demodulation is characterized in that: comprising a polarization-maintaining output broadband light source (1), an electro-optical modulator (2), a vector network analyzer (3), a first RF amplifier (4), erbium-doped fiber amplifier (5), optical circulator (6), 1×n fiber coupler (7), n transmission fibers (8), n distributed sensing fibers (9), A photodetector (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-optical modulator (2) through a polarization-maintaining optical fiber jumper; the signal output end of the vector network analyzer (3) is connected to the first radio frequency amplifier through a high-frequency cable The signal input end of (4) is connected; 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 by an optical fiber jumper is connected with the input end of the erbium-doped fiber amplifier (5); the output end of the erbium-doped fiber amplifier (5) is connected with 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 1 The incident end of the ×n fiber coupler (7) is connected, and the n output ends of the 1×n fiber coupler (7) are respectively connected with n transmission fibers (8); n transmission fibers (8) are connected with n distributed fibers (8). The sensing fiber (9) is connected; the signal output end of the optical circulator (6) is connected with 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 with the high-frequency cable through a high-frequency cable. The signal input end of the second radio frequency amplifier (11) is connected; 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) passes through The high frequency cable is connected with the computer (12); The cores of the n distributed sensing fibers (9) are processed by femtosecond laser to have continuous reflectors, 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 that of the vector network analyzer. The coherence length of the generated microwave signal; the length of the nth transmission fiber is greater than the length of the n-1th transmission fiber plus the n-1th sensing fiber, where N≥n≥2, and N is the maximum value of n. 2. The complex flow multi-path distributed measurement device based on microwave domain demodulation according to claim 1, is characterized in that: n sensing fibers (9) select different types of fibers according to actual requirements, and design Process reflectors of different numbers, adjacent spacing. 3. The complex flow multi-path distributed measurement device based on microwave domain demodulation according to claim 1, characterized in that: n sensing fibers (9) are arranged inside a single pipe; or are respectively arranged in different pipes The inner wall, and the number of the inner wall of each pipeline is determined according to the actual situation. 4. A complex flow multi-path distributed measurement method based on microwave domain demodulation is characterized in that the method is in the complex flow multi-path distributed measurement based on microwave domain demodulation as described in any one of claims 1-3 The device is implemented, 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 The signal is modulated by the electro-optical modulator (2) and then loaded onto the optical signal; the optical signal modulated by the microwave signal is output from the electro-optical modulator (2) and then enters the erbium-doped fiber amplifier (5), and is passed through the erbium-doped fiber amplifier (5) After being amplified, it is input to the optical circulator (6); the optical signal is output by the reflection end of the optical circulator (6) and then enters the 1×n fiber coupler (7), and is divided into n paths after passing through the 1×n fiber coupler (7) ; n optical signals enter n sensing fibers (9) through n transmission fibers (8) respectively; and reflect at the reflectors in the sensing fibers, and the microwave envelopes of the reflected optical signals interfere at the meeting point The interference signal enters the high-speed photodetector (10) after being output from the output end of the optical circulator (6); after being converted into an electrical signal by the high-speed photodetector (10), it enters the second radio frequency amplifier (11); After being amplified by the amplifier (11), it is collected by the vector network analyzer (3), and the vector network analyzer (3) inputs the collected interference information to the computer (12); Sweep the frequency, that is, the interference spectrum of the microwave signal is obtained; the sensing fiber is affected by the pressure and temperature factors of the complex flow of two-phase and multi-phase flow, and the length and refractive index of the fiber at the corresponding position will change, resulting in reflector reflection. The optical path of the optical signal changes, 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 two-phase and multi-phase flow and the optical path variation, and the optical path variation is related to the microwave interference. There is a corresponding relationship between the spectral frequency shifts, and the flow parameters to be measured are obtained by inversion of the microwave interference spectral frequency shifts. 5. The complex flow multi-path distributed measurement method based on microwave domain demodulation according to claim 4, wherein 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, according to the actual length of the n sensing fibers and the transmission fibers connected to them, distinguish the reflected signal interval corresponding to each sensing fiber reflector; use the rectangular window function to select the required two reflected signals and remove the remaining reflected signals. The microwave interference spectrum of the two selected reflected signals is reconstructed by Fourier transform; the microwave interference spectrum corresponding to the adjacent reflectors of the n distributed sensing fibers is reconstructed, and then the two-phase signals at the corresponding positions are demodulated. And multi-phase flow complex flow parameters, so as to achieve multi-channel spatial continuous distributed simultaneous measurement of complex flow characteristic parameters.

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