CN102352964A - Thermal fluid leak detecting and positioning system based on integrated fiber grating cluster - Google Patents

Abstract

The invention provides a thermal fluid leak detecting and positioning system based on integrated fiber grating cluster and belongs to the technical field of thermal fluid pipeline leak detection. The system comprises a C-waveband continuous broadband light source, an integrated fiber grating cluster, a microcontroller and the like, and is characterized in that an optical modulator is arranged behind the C-waveband continuous broadband light source, the port a of a circulator is connected with the rear of the optical modulator, the port b of the circulator is connected with the input end of an optical switch, the output end of the optical switch is connected with the integrated fiber grating cluster; the port c of the circulator is connected with a photoelectric detector, the photoelectric detector is connected to the input end of a filtering and shaping circuit, the output end of the filtering and shaping circuit is connected to an amplifying circuit, the output end of the amplifying circuit is connected to the input end of an analog-to-digital conversion circuit, the output end of the analog-to-digital conversion circuit is connected with the microcontroller through the IO (input output) port of the microcontroller so as to realize the processing on a obtained digital signal; and the optical modulator and the optical switch are respectively connected with the microcontroller through the IO port of the microcontroller so as to realize the synchronous control on the microcontroller. The system provided by the invention has the advantages of low cost and high detection accuracy.

Description

Thermal Fluid Leak Detection and Locating System Based on Integrated Fiber Bragg Grating Cluster

technical field

The invention relates to a thermal fluid leak detection and positioning system based on an integrated optical fiber grating cluster, and belongs to the technical field of thermal fluid pipeline leak detection. the

Background technique

Generally speaking, there are three main types of leak detection methods for oil pipelines: inspection, direct leak detection methods and software analysis methods.

(1) Inspection method

This is a traditional leak detection method, which mainly uses people or trained animals (dogs) to walk along the pipeline to check the abnormal conditions of the pipeline accessories, smell the smell released from the pipeline, listen to the sound, etc. This method is direct and accurate, but The real-time performance is poor and consumes a lot of manpower. the

(2) Direct leak detection method

Use acoustic sensors, gas detection instruments, etc., such as using temperature sensors to measure the temperature change at the leak, and use multi-sensor cables laid along the pipeline. The acoustic sensor is that when the fluid flows out of the pipeline, it will make a sound. The sound wave propagates at the speed determined by the physical properties of the fluid in the pipeline. The acoustic sensor detects the sound of the wave and finds the leak. For example, the acoustic leak detection system (wavealert) developed by American Houston Acoustic Systems Corporation (ASI) based on this principle is composed of multiple sets of sensors, decoders, wireless transmitters, etc., and the antenna extends out of the ground to communicate with the control center. Limitation of detection range Many acoustic sensors must be installed along the pipeline. The gas detector needs to use a portable gas sampler to walk along the pipeline to detect the leaked gas. the

(3) Software analysis method

It uses the flow, pressure, temperature and other data provided by the SCADA system to detect leaks through the methods of flow or pressure change, mass or volume balance, dynamic model and pressure point analysis software. Foreign companies attach great importance to the safe operation of oil pipelines. The pipeline leakage monitoring technology is relatively mature and has been widely used. For example, after long-term research and development, Shell has produced a new type of pipeline leak detection system with the brand name ATMOS Pine. The overall behavior of pipeline inlet and outlet flow and pressure changes to detect leaks, and it also has advanced graphic recognition functions. The system is able to detect a leak of 1.6kg/s without false alarms. the

Contents of the invention

In order to overcome the defects and deficiencies in the prior art, the present invention proposes a thermal fluid (especially crude oil) leak detection and positioning system based on an integrated fiber grating cluster, aiming at providing a stable, convenient and low-cost leak detection and positioning system. the

Technical scheme of the present invention is realized in the following manner:

A thermal fluid leak detection and positioning system based on an integrated fiber grating cluster, including a C-band continuous broadband light source, an optical modulator, an optical switch, a circulator, a photodetector, a filter shaping circuit, an amplifier circuit, an analog-to-digital conversion circuit, and an integrated optical fiber The grating cluster and single-chip microcomputer are characterized in that an optical modulator is placed behind the C-band continuous broadband light source, the optical modulator is connected to the a port of the circulator, the b port of the circulator is connected to the input end of the optical switch, and the output end of the optical switch is connected to the integrated optical fiber grating cluster; the c port of the circulator is connected to the photodetector, the photodetector is connected to the input end of the filter shaping circuit, the output end of the filter shaping circuit is connected to the amplifying circuit, and the output end of the amplifying circuit is connected to the input end of the analog-to-digital conversion circuit, The output end of the analog-to-digital conversion circuit is connected to the single-chip microcomputer through the IO port of the single-chip microcomputer to process the obtained digital signal; the optical modulator and the optical switch are respectively connected to the single-chip microcomputer through the IO port of the single-chip microcomputer to realize the synchronous control of the single-chip microcomputer . the

Said light modulator is a shutter or a chopper. the

The C-band continuous broadband light source is a light source whose operating wavelength is in the C-band region and emits light continuously, such as a C-band ASE (amplified spontaneous emission) light source. the

The photodetector is a photodiode with a short response time. the

The structure of the integrated fiber grating cluster is as follows: it is composed of multiple fiber grating groups, wherein each fiber grating group is formed by connecting fiber gratings with different central reflection wavelengths in series through connecting optical fibers, and each fiber grating and connection The length of the optical fiber is equal; every two fiber grating groups form a fiber grating group pair, and the fiber gratings and connecting fibers of the two fiber grating groups in the fiber grating group pair are interlaced; the fiber grating group pairs are arranged in a bundle, and each fiber The grating groups are arranged end to end, so that the fiber gratings in each fiber grating group and the fiber gratings in other fiber grating groups are staggered from each other and do not overlap each other, forming an integrated fiber grating cluster. the

There are 5-600 pairs of fiber gratings in the integrated fiber grating cluster. the

When the system of the present invention is in use, the integrated fiber grating cluster is laid in advance along the pipeline for transporting thermal fluid, and pasted on the outside of the pipeline heat insulation layer. The continuous broadband light emitted by the C-band continuous broadband light source is modulated by the light modulator to obtain pulsed light, so that it can repeat The frequency is the same as the switching frequency of the optical switch. It enters the circulator from the a port of the circulator, and enters the optical switch and the integrated fiber grating cluster through the b port output. The light reflected by the grating in the integrated fiber grating cluster returns to the b port of the circulator through the optical switch and is transmitted to the c port, enters the photodetector, and converts the optical signal into an electrical signal (pulse electrical signal) through photoelectric conversion. The pulse electric signal is processed by the filter shaping circuit and the amplification circuit, and then converted by the analog-to-digital conversion circuit, and then the data is sent to the single-chip microcomputer, and then the data is processed according to the noise threshold and other restrictions obtained by the single-chip microcomputer, and it is judged whether there is heat Fluid leaks and location of leaks. The processing result can be sent to the man-machine interface by the single-chip microcomputer to realize the alarm and display the position. the

The concrete operating principle of the system of the present invention is as follows:

Under the control of the single-chip microcomputer, the optical modulator and the optical switch are kept synchronous, so as to ensure that the optical pulse is sequentially input into each fiber grating group of the integrated optical fiber grating. The gratings in each fiber grating group will reflect back the light of the corresponding wavelength to form a pulse sequence that enters the photodetector through the circulator. When the pipeline leaks, the integrated fiber grating is affected by the temperature of the heated fluid, which changes the sequence of light pulses it reflects back. The light pulse sequence is converted into an electrical signal by the photodetector, and the electrical signal is filtered, shaped and amplified, and then the data is processed by the analog-to-digital conversion circuit and the single-chip microcomputer. The preset parameters provided by the single-chip microcomputer are used to judge whether the leakage of the thermal fluid has occurred. If a leak occurs, the distance difference between the leak and the light incident end face can be calculated according to the return time difference of the corresponding pulse, and the position of the light incident end face can be determined to determine the specific position of the temperature change. In this way, the detection of the temperature change is realized, that is, the leak detection and location of the thermal fluid are realized. the

The operating principle of a single fiber grating group in the system of the present invention is:

When thermal fluid leaks, the temperature at the leak point is several degrees or even tens of degrees higher than the temperature in other places. The temperature change will change the period constant of the fiber grating, and then change its central wavelength. Select a suitable wavelength band of light to be incident on a fiber grating with a long length (assumed to be 10m) and a center wavelength of λ. Light of other wavelength components continues to propagate. When the temperature of a subsequent point of the fiber grating changes (corresponding to the situation when the fluid leaks), the central wavelength of the fiber grating at this point becomes λ', and the light with a wavelength of λ' will be reflected, and a new reflected pulse (such as The pulse signal at the corresponding λ' in Fig. 4). the

Assuming that each fiber grating group has 8 fiber gratings with different central reflection wavelengths, that is, the working part of the fiber grating is 10m, and the length of the connecting fiber between each fiber grating is 10m, then when no leakage occurs, return 8 pulses at the same time interval, otherwise, it can be concluded that a leak has occurred. the

The working principle of the integrated fiber grating cluster:

When the light is incident on the m-th fiber grating group through the optical switch, it will be reflected back within a small distance from the incident end face of each segment of the grating, thereby obtaining a pulse-time signal as shown in Fig. 3 . If there is a leak somewhere (not the incident end face of the grating), the leaking fluid will cause the fiber grating at the corresponding point to generate a new pulse, as shown in Figure 4; if the leak is just at the incident end face of a certain section of the grating, then at The light pulse that will be reflected back to λ' (the changed wavelength) at the incident end face will be reflected back to the light pulse of λ (the unchanged wavelength) at the unaffected grating at the back, and the reflected pulse situation is also as shown in Figure 4 shown. Therefore, for this special situation, it is necessary to accurately determine the location of the leak point through certain logical reasoning. In the fiber grating group pair in the fiber grating cluster of this system, there are two grating end faces corresponding to the same monitoring point. If a leak occurs on a certain grating end face, the two fiber grating groups should be obtained as shown in Figure 4. pulse, so it can be judged that the leak is located at the end face of the grating; if only one fiber grating group gets the pulse shown in Figure 4, and the other gets the pulse shown in Figure 3, it can be judged that the leak is located in a non- The entrance facet of the grating. In this way, the position of the leakage point can be accurately judged. the

As mentioned above, it can be judged whether a leak occurs through the pulse signal reflected back by the fiber bundle. Since the control circuit synchronizes the incident light and the optical switch, the specific location of the leakage can be determined by comparing the time with the pulse signal obtained by the photodetector. the

The present invention has the following advantages:

The integrated fiber grating cluster is used as the sensor for distributed detection; the temperature difference is used for leak detection, which cleverly removes the interference caused by the change of the ambient temperature, and the signal-to-noise ratio is high; the measurement length can be changed flexibly, when the length of the pipeline to be detected is too long, it can be used Multiple systems; a wide range of applications, suitable for leak detection of various thermal fluid transportation. The system cost of the invention is low, and the detection accuracy is high. the

Description of drawings

Accompanying drawing 1 is the structure diagram of the present invention. the

Among them: 1. C-band continuous broadband light source; 2. Optical modulator; 3. Circulator; 4. Optical switch; 5. Single-chip microcomputer; 6. Analog-to-digital conversion circuit; 7. Photoelectric detector; 9. Filter shaping circuit; 10. Amplifying circuit. the

Figure 2 is a schematic diagram of the structure of the integrated fiber grating cluster of the present invention. the

Among them: 11. Fiber Bragg grating group pair, 12. Fiber Bragg grating group, 13. Integrated fiber Bragg grating cluster access port, 14. Fiber Bragg grating, 15. Connecting optical fiber. It can be seen from the figure that the fiber grating group in the fiber grating cluster of the present invention and the arrangement of gratings on each fiber grating group, wherein the white part in each fiber grating group shows the connecting optical fiber, and the black part shows the optical fiber Grating (that is, the key working part of leak detection and positioning). the

Figure 3 is the pulse signal obtained by scanning the m-th optical fiber when there is no leakage. the

Fig. 4 is the pulse signal obtained by scanning the m-th optical fiber when there is leakage. The pulse signal at λ' corresponds to the leakage of the thermal fluid pipeline. the

Detailed ways

The present invention will be further described below with reference to the drawings and embodiments, but not limited thereto. the

Example 1:

Embodiment 1 of the present invention, as shown in accompanying drawings 1-2, includes a C-band continuous broadband light source 1, an optical modulator 2, an optical switch 4, a circulator 3, a photodetector 7, a filter shaping circuit 9, an amplifier circuit 10, a Digital conversion circuit 6, integrated fiber grating cluster 8 and single-chip microcomputer 5 are characterized in that optical modulator 2 is placed behind C-band continuous broadband light source 1, and optical modulator 2 is connected with port a of circulator 3 behind optical modulator 2, and port b of circulator 3 is connected The input end of the optical switch 4, the output end of the optical switch 4 is connected to the integrated fiber grating cluster 8; the c port of the circulator 3 is connected to the photodetector 7, and the photodetector 7 is connected to the input end of the filter shaping circuit 9, and the input end of the filter shaping circuit 9 The output end is connected to the amplification circuit 10, and the output end of the amplification circuit 10 is connected to the input end of the analog-to-digital conversion circuit 6, and the output end of the analog-to-digital conversion circuit 6 is connected with the single-chip microcomputer 5 through the IO port of the single-chip microcomputer 5, to realize the digital conversion of the gained The signal is processed; the optical modulator 2 and the optical switch 4 are respectively connected to the single-chip microcomputer 5 through the IO port of the single-chip microcomputer 5, so as to realize the synchronous control of the single-chip microcomputer 5 to it. the

The optical modulator 2 is a chopper. the

The C-band continuous broadband light source 1 is a light source whose operating wavelength is in the C-band region and emits light continuously, that is, a C-band ASE (amplified spontaneous emission) light source. the

The photodetector 7 is a photodiode with a short response time. the

The structure of the integrated fiber grating cluster 8 is as follows: it is composed of a plurality of fiber grating groups 12, wherein each fiber grating group 12 is formed by connecting fiber gratings 14 with different central reflection wavelengths in series through connecting optical fibers 15, each The lengths of each fiber grating 14 and connecting fiber 15 are equal; every two fiber grating groups 12 form a fiber grating group pair 11, and the fiber grating 14 and connecting fiber 15 of the two fiber grating groups 12 in the fiber grating group pair 11 are interlaced with each other ; Fiber Bragg grating groups 11 are arranged in bundles, and each fiber Bragg grating group is arranged end to end to each other, so that the fiber gratings 14 in each fiber grating group 12 and the fiber gratings in other fiber grating groups 12 are staggered from each other. coincide to form an integrated fiber grating cluster. the

There are 400 pairs of fiber gratings in the integrated fiber grating cluster. the

Example 2:

Embodiment 2 of the present invention is the same as Embodiment 1, except that the optical modulator 2 is a shutter; the number of fiber grating pairs in the integrated fiber grating cluster is 20. the

Claims (6)

1. hot fluid leak detection and navigation system based on an integrated optical fiber grating bunch; Comprise C-band continuous wide band light source, optical modulator, optical switch, circulator, photodetector, filtering shaping circuit, amplification circuit, analog to digital conversion circuit, integrated optical fiber grating bunch and single-chip microcomputer; It is characterized in that C-band continuous wide band light source back placement optical modulator; The optical modulator back connects a mouth of circulator; The b mouth of circulator connects the input end of optical switch, and the optical switch output terminal connects integrated optical fiber grating bunch; The c mouth of circulator connects photodetector; Photodetector is connected to the input end of filtering shaping circuit, the output terminal of filtering shaping circuit is connected to amplification circuit; The output terminal of amplification circuit is connected to the input end of analog to digital conversion circuit; The output terminal of analog to digital conversion circuit is connected with single-chip microcomputer through the IO of single-chip microcomputer mouth, with realization the gained digital signal is handled; Optical modulator is connected with single-chip microcomputer respectively through the IO of single-chip microcomputer mouth with optical switch, to realize that single-chip microcomputer carries out synchronization control to it.

2. a kind of hot fluid leak detection and navigation system based on integrated optical fiber grating bunch as claimed in claim 1 is characterized in that described optical modulator is shutter or chopper.

3. a kind of hot fluid leak detection and navigation system based on integrated optical fiber grating bunch as claimed in claim 1 is characterized in that described C-band continuous wide band light source is that operation wavelength is C-band zone, continuous radiative light source, i.e. the ASE light source of C-band.

4. a kind of hot fluid leak detection and navigation system based on integrated optical fiber grating bunch as claimed in claim 1 is characterized in that described photodetector is short photodiode of response time.

5. a kind of hot fluid leak detection and navigation system as claimed in claim 1 based on integrated optical fiber grating bunch; It is characterized in that described integrated optical fiber grating clustering architecture is following: it is to be made up of multifiber grating group; Wherein every fiber bragg grating group is that fiber bragg grating by different foveal reflex wavelength is in serial connected through connecting optical fiber, and each fiber bragg grating is with to be connected length of fiber equal; It is right that per two fiber bragg grating groups are formed the fiber bragg grating group, and two fiber bragg grating groups fiber bragg grating each other of fiber bragg grating group centering is with to be connected optical fiber interlaced; The fiber bragg grating group is pencil to arrangement; Each fiber bragg grating group is to end-to-end arrangement each other; Make fiber bragg grating in each road fiber bragg grating group be staggered mutually and do not coincide each other, constitute integrated optical fiber grating bunch with fiber bragg grating in other fiber bragg grating groups.

6. a kind of hot fluid leak detection and navigation system as claimed in claim 5 based on integrated optical fiber grating bunch, it is characterized in that in the said integrated optical fiber grating bunch the fiber bragg grating group to for 5-600 right.

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