CN1837674A - Apparatus and method for monitoring pipeline leakage based on distributed optical fiber acoustic sensing technology - Google Patents

Abstract

The invention relates to a channel leakage detector and method based on distributed optical fiber acoustic sensing technique, which comprises an optical system (1), a distributed optical fiber sensing system (2), and a detecting system (3). Wherein, the optical system comprises a board band continuous light resource A1, and an optical circulator A2; the distributed optical sensing system comprises the first coupler A3, the delay coil B4, and a reflective mirror A5l; the detecting system comprises an optical-electric converter A6, a demodulate system A7, a A/D converter A8, and a computer A9; the board band continuous light resource via the optical circulator is connected to the Port1 interface of the first coupler A3, whose Port2 and Port3 are connected with delay coil; the Port4 of first coupler via sensing optical fiber is connected to the reflective mirror; and the optical circulator is connected to the optical-electric converter of detecting system, while said system can detect any leakage signal at any time.

Description

Pipeline leakage monitor and method based on distributed optical fiber acoustic sensing technology

Technical field

The present invention is a kind of device and method that adopts the interference type distributed optical fiber acoustic sensing technology to carry out line leakage, belongs to the line leakage field.

Background technique

Pipeline is one of five existing big means of transportation, have cost at aspects such as transporting liquid, gas, slurries low, save the energy, safe and supply with stable advantage, in industries such as oil, chemical industry, rock gas and town water supply, irreplaceable effect is arranged.Along with the continuous development of pipeline industry, for the safe operation of service conduit, pipeline operational monitoring technology is also in continuous development.

In recent years, along with the development of optical fiber sensing technology, the long-distance distributed optical fiber sensory technique also begins to be applied to pipeline leakage testing.Chinese invention patent application number 02145502.3 adopts optical time domain reflection technology to carry out the oil-gas pipeline Leak testtion, it is the fault point of judging optical fiber by Rayleigh scattering that produces in the detection fiber and Fresnel reflection signal, is mainly used in detections such as the loss of fault, fiber lengths, optical fiber of optical cable and opticalfiber splicing loss.

Chinese invention patent application 200410020046.6 adopts the interference type distributed optical fiber vibrative sensor to carry out pipeline leakage testing, as shown in Figure 1.This sensor is to be made of one three core single mode fiber cable and the corresponding optical element laid side by side along pipeline near pipeline, wherein the second sensor fibre B10 and the 3rd sensor fibre B11 form the interference-type optical fiber vibrative sensor, and transmission fiber B12 is used for transmission signal.Its principle is that the light that sends of light source is after the Coupler beam split, wherein a branch of light propagates into the second Coupler A10 through the second guiding fiber B8, and after the second Coupler A10 place is by power beam split in 1: 1, enter the second sensor fibre B10 and the 3rd sensor fibre B11 respectively, another Shu Guangjing the 3rd guiding fiber B9, transmission fiber B12 propagates into the 3rd Coupler A11, and after the 3rd Coupler A11 place is by power beam split in 1: 1, enter the second sensor fibre B10 and the 3rd sensor fibre B11 respectively, the light of the reverse transmission of two bundles converges at the 3rd Coupler A11 of transmission terminal separately and the second Coupler A10 place respectively and interferes, so has in fact formed two interferometers.When pipeline takes place to leak, the leakage noise that produces makes the photophase that transmits in the optical fiber modulated, so interference signal can change, detects the variation of interference light signal in real time, can detect the micro-vibration signal of optical fiber vibrative sensor institute's generation incident generation on the way, realize line leakage.Its positioning principle is that two bundles that transmit in distributed sensing fiber are after reverse light is subjected to same events affecting, since the reverse light of two bundles from the incident nidus propagate into respectively the second Coupler A10 and the 3rd Coupler A11 the light path of process different, therefore it is poor to produce the regular hour, detect the time difference that the caused interference light signal of same incident changes according to the sensor two ends, just can determine the leak position.The deficiency of this technology is: because two sensor fibre close together of this technology, at this moment the phase delay unanimity that pipeline vibration on the way may make two sensor fibres produce does not interfere, and promptly produces the reciprocity effect, and when leakage hole deviates from the optical cable direction, be difficult to detect leak and take place.Localization method also has deficiency, and the zero-time that only captures the pipe leakage incident could be located, and after leakage had taken place, such detection technique no longer had the leakage point stationkeeping ability.

Summary of the invention

The objective of the invention is to overcome the above defective, a kind of pipeline leakage monitor and method based on distributed optical fiber acoustic sensing technology proposed, the advantage of this device and method is all to have the leakage point stationkeeping ability in the whole leakage process, and detection sensitivity height, rate of failing to report low, can realize little Leak testtion of pipe long-distance and location.

The technical solution adopted in the present invention, concrete structure is referring to Fig. 2, this device mainly includes light path system 1, distributed optical fiber sensing system 2, detection system 3, it is characterized in that: the light path system 1 of this device mainly includes broadband continuous light source A1, optical circulator A2, distributed optical fiber sensing system 2 mainly includes the first Coupler A3, delay winding B4, reflector A5; Wherein, broadband continuous light source A1 is connected with optical circulator A2 by the first Single Mode Fiber B1, optical circulator A2 is connected with the Port1 port of the first Coupler A3 by the first guiding fiber B2 again, the Port2 port of the first Coupler A3 is connected with delay winding B4 by the second Single Mode Fiber B3, delay winding B4 is connected with the Port3 port of the first Coupler A3 by the 3rd Single Mode Fiber B5, the Port4 port of the first Coupler A3 is connected with reflector A5 by the first sensor fibre B6, and the optical circulator A2 of light path system is connected with detection system 3 by the 4th Single Mode Fiber B7 again.

Described detection system 3 mainly includes photoelectric converter A6, demodulating system A7, A/D converter A8, computer A 9; The 4th Single Mode Fiber B7 is connected with photoelectric converter A6, and photoelectric converter A6 is connected with computer A 9 by demodulating system A7, A/D converter A8.

Described distributed optical fiber sensing system 2 has linear structure.

The light that is sent by broadband continuous light source A1 is in the propagation process of this device, specifically referring to Fig. 2, the light that is sent by broadband continuous light source A1 enters optical circulator A2 through the first Single Mode Fiber B1, the light of optical circulator A2 output enters the Port1 port of the first Coupler A3 and is divided into two-beam at 1: 1 by power through the first guiding fiber B2, wherein the first bundle light directly is coupled into the Port4 port from the Port1 port of the first Coupler A3, and enter the first sensor fibre B6, arrive behind the first sensor fibre B6 end again through the reflector A5 reflected back first sensor fibre B6, return the Port4 port of the first Coupler A3 again through the first sensor fibre B6, in this port, to transmit light at 1: 1 by power is divided into two bundles equally, a branch of Port1 port that directly is coupled into is also exported, this road light does not produce with other light path interferes, therefore monitoring system is not had influence, do not consider.Another Shu Guangcong Port4 port cross-over connection is coupled into the Port2 port, enter the Port3 port of the first Coupler A3 through the second Single Mode Fiber B3, delay winding B4, the 3rd Single Mode Fiber B5, the light of this port is pressed power beam split in 1: 1 equally, but the light that has only cross-over connection to be coupled into the first Coupler Port1 port can interfere with the second bundle light, and another Shu Guang does not have interference phenomenon, does not therefore consider here.

The second bundle light is coupled into the Port3 port from the Port1 port cross-over connection of the first Coupler A3, behind the 3rd Single Mode Fiber B5, delay winding B4, the second Single Mode Fiber B3, enter the Port2 port of the first Coupler A3, after power beam split in 1: 1 is pressed in this port, the Port3 port that wherein a branch of light enters the first Coupler A3 continues along the 3rd Single Mode Fiber B5 by original route, delay winding B4, second Single Mode Fiber B3 transmission, but because the coherent length of light source is shorter, therefore this Shu Guang can not produce interference, does not therefore consider.And the Port2 port cross-over connection of another Shu Guangjing first Coupler A3 is coupled into the Port4 port and the first sensor fibre B6, arrive the first sensor fibre B6 end again by reflector A5 with its reflected back first sensor fibre B6, turn back to the Port4 port of the first Coupler A3 by former road.Equally, this Shu Guang presses power beam split in 1: 1 in this port, and a branch of light directly is coupled into the Port1 port, converges with the first bundle light, because the first bundle light has identical light path with the second bundle light, therefore interferes.(and another Shu Guang does not interfere with other light, and monitoring system is not had influence, does not consider.) this interference light enters photoelectric converter A6 through the first guiding fiber B2, optical circulator A2 and the 4th Single Mode Fiber B7, photoelectric converter A6 is converted to electrical signal with optical signal, and demodulate the phase place of interference signal by demodulating system A7, the signal of demodulation is converted to digital signal and is input to computer A 9 through A/D converter A8, in computer A 9, carry out the FFT conversion at last to gathering signal, by the analytic signal frequency spectrum, can realize leakage alarm and location.

The line leakage principle of this system is: when there is the generation of leakage in the pipeline somewhere, leak fluid produces friction with the leakage hole wall, on tube wall, inspire stress wave (promptly leaking acoustic emission signal), this stress wave activity is modulated to sensor fibre and to the first bundle light, the second bundle photophase that transmit in the sensor fibre, owing to there is delay winding, make the asynchronism(-nization) of the first bundle light and the second bundle light through leakage point D, it is also different to the phase modulation of two-beam to leak acoustic emission signal, produce phase difference between two-beam, so two-beam interferes.(do not have and leak when taking place, two-beam phase place unanimity does not produce interference) can realize line leakage therefore by detecting the variation of interference light signal in real time.Based on same principle, there are around the pipeline construction, artificial or natural causes etc. may cause when the incident of pipeline damage takes place, optical fiber is disturbed, and the photophase that transmits in the optical fiber is modulated, so this system also can realize causing that the incident that pipeline is damaged monitors around the pipeline.

The invention provides the localization method of a kind of pipe leakage position, it is characterized in that: the light that sends from the broadband continuous light source, behind light path system and distributed optical fiber sensing system, produce first bundle light, the second bundle light of two bundles through same paths, this two-beam converges at the first Coupler A3 place and produces interference.When pipeline had leakage point, leaking acoustic emission signal 1. can be represented by formula

Aφsinω _st ①

Δ φ is the amplitude of leakage signal, ω _sFrequency for leakage signal;

The first bundle light is τ through the time of leakage point D for the first time ₁, the first bundle light is τ through the time of leakage point D after mirror reflects for the second time ₂, the second bundle light is τ through the time of leakage point D for the first time ₃, the second bundle light is τ through the time of leakage point D after mirror reflects for the second time ₄, because this two-beam through the asynchronism(-nization) of leakage point D, therefore leaks the phase modulation difference of acoustic emission signal to two-way light.Phase transformation after two-beam is modulated is:

Phase change after the first bundle optical modulation is

Δφ[sinω _s(t-τ ₁)+sinω _s(t-τ ₂)]

Phase change after the second bundle optical modulation is

Δφ[sinω _s(t-τ ₃)+sinω _s(t-τ ₄)]

Therefore produce phase difference between the two-beam

${\mathrm{\φ}}_s\left(t\right)=4\mathrm{\Δ\φ}\cos {\mathrm{\ω}}_s(t-\frac{{\mathrm{\τ}}_T}{2})\sin {\mathrm{\ω}}_s\left(\frac{{\mathrm{\τ}}_d}{2}\right)\cos \left({\mathrm{\ω}}_s{\mathrm{\τ}}_s\right)$ ②

This phase difference has comprised temporal information and has leaked the frequency information of acoustic emission signal, wherein ω _sBe the frequency of leakage acoustic emission signal, ${\mathrm{\τ}}_d=\frac{{\mathrm{\τ}}_3-{\mathrm{\τ}}_2+{\mathrm{\τ}}_4-{\mathrm{\τ}}_1}{2}$ Be the light process delay winding time, ${\mathrm{\τ}}_s=\frac{{\mathrm{\τ}}_4-{\mathrm{\τ}}_3+{\mathrm{\τ}}_2-{\mathrm{\τ}}_1}{4}$ For light from the leak position to reflector needed time, τ _T=τ ₂+ τ ₃For light from the port4 port transmission of first Coupler (A3) to reflector and through mirror reflects, turn back to the port4 port along original route, again through port2 port, delay winding cumulative time to the port3 port;

2. obtain time τ from formula _sJust can obtain the distance of leakage point in optical fiber according to the speed that light is propagated apart from reflector.But can't directly obtain τ 2. from formula _s, 2. formula is done FFT (Fu Liye) conversion, time-domain signal is transformed into frequency domain.Formula 2. in, $4\mathrm{\Δ\φ}{\sin \mathrm{\ω}}_s\left(\frac{{\mathrm{\τ}}_d}{2}\right)\cos \left({\mathrm{\ω}}_s{\mathrm{\τ}}_s\right)$ Proportional with the signal frequency-domain amplitude, after leakage takes place, in the wide frequency range that leaks acoustic emission signal, always there is a frequency to make $4\mathrm{\Δ\φ}\sin {\mathrm{\ω}}_s\left(\frac{{\mathrm{\τ}}_d}{2}\right)\cos \left({\mathrm{\ω}}_s{\mathrm{\τ}}_s\right)=0,$ And

Irrelevant with the leak position, therefore determine delay winding length, guarantee in the wide frequency range of leakage signal

Be not equal to zero, cos (ω is so just arranged _sτ _s)=0, therefore can occur amplitude in frequency domain is zero point, frequency that this point is corresponding is called zero frequency.In order to determine this zero frequency, the form of frequency-region signal with spectrogram is presented on the computer A 9, then the frequency of amplitude minimum point correspondence is exactly a zero frequency on the spectrogram.Basis after finding zero frequency on the spectrogram ${\mathrm{\τ}}_s=\frac{\mathrm{\π}(1+n)}{2{\mathrm{\ω}}_s}$ (n is an even number) calculated bright dipping and propagated into reflector needed time τ from leakage point _sTry to achieve τ _sAfter, according to formula s=v τ _s(v is the velocity of propagation of light in optical fiber) calculate the leak position to reflector apart from s.

2. also can find τ from formula _T, τ _dBe definite value, τ _sIt is the function of leak position, whole signal is irrelevant with the initial time that takes place to leak, only relevant with the frequency of leakage signal, be a continuous signal because of leakage signal again, therefore as long as leak, this sensing device can detect the leakage signal in any moment, finds zero frequency by signal is done frequency analysis, just can determine the leak position, will catch the initial time that leak to take place like that and just can locate and need not patent application 200410020046.6.

The advantage of this system is: native system has adopted the straight line type distributed optical fiber acoustic sensing technology that pipeline is monitored in real time, and whole transducing part is made of an optical fiber, therefore can adapt to the detection of various complicated pipelines.Owing in the sensor delay winding is arranged, make two-beam arrive the asynchronism(-nization) of leak position, therefore can not produce the reciprocity effect, improved detection sensitivity.Monitoring system can detect the leakage signal in any moment, does not therefore exist and fails to report alert phenomenon.Simultaneously because therefore the low-loss of optical fiber and to the hypersensitivity of acoustic signal can realize the little Leak testtion of long-distance pipe.

Description of drawings

The structural drawing of Fig. 1 patent application 200410020046.6

Fig. 2 system construction drawing of the present invention

Among the figure: A1, the broadband continuous light source, A2, optical circulator, A3, first Coupler, A4, pipeline, A5, reflector, A6, photoelectric converter, A7, demodulating system, A8, A/D converter, A9, computer, A10, second Coupler, A11, the 3rd Coupler, B1, first Single Mode Fiber, B2, first guiding fiber, B3, second Single Mode Fiber, B4, delay winding, B5, the 3rd Single Mode Fiber, B6, first sensor fibre, B7, the 4th Single Mode Fiber, B8, second guiding fiber, B9, the 3rd guiding fiber, B10, second sensor fibre, B11, the 3rd sensor fibre, B12, transmission fiber, 1, light path system, 2, distributed optical fiber sensing system, 3, detection system.

Embodiment

The concrete structure of present embodiment, referring to Fig. 2, this device mainly is made up of light path system 1, distributed optical fiber sensing system 2, detection system 3.Light path system 1 is made up of JW-3107 type ASE broadband continuous light source A1, optical circulator A2, the first guiding fiber B2 again; Distributed optical fiber sensing system 2 is made up of the first Coupler A3, delay winding B4, reflector A5; Detection system 3 is made up of 1811 type photoelectric converter A6, demodulating system A7, A/D converter A8, computer A 9.Wherein, the ASE broadband continuous light source A1 of light path system 1 is connected with optical circulator A2 by the first Single Mode Fiber B1, optical circulator A2 is connected with the Port1 port of the first Coupler A3 by the first guiding fiber B2 again, the Port2 port of the first Coupler A3 is connected with delay winding B4 by the second Single Mode Fiber B3, delay winding B4 is connected with the Port3 port of the first Coupler A3 by the 3rd Single Mode Fiber B5, the Port4 port of the first Coupler A3 is connected with the first sensor fibre B6 of distributed optical fiber sensing system 2, the end of the first sensor fibre B6 is provided with reflector A5, the optical circulator A2 of light path system 1 is connected with photoelectric converter A6 by the 4th Single Mode Fiber again, and photoelectric converter A6 is by demodulating system A7, A/D converter A8 is connected with computer A 9.

Light path system 1 is mainly used in distributed optical fiber sensing system 2 launches light wave, and detected signal in the distributed optical fiber sensing system 2 is transferred to detection system 3.And detection system 3 is finished the conversion of optical signal to electrical signal by photoelectric converter A6, carry out signal processing by demodulating system A7 again, be digital signal by A/D converter A8 with analog signal conversion then and send into and carry out Digital Signal Processing and data analysis in the computer A 9.Because light path system 1 and detection system 3 all are installed in the monitoring chamber; distributed optical fiber sensing system 2 then is installed in the pipeline scene; therefore the first guiding fiber B2 that connects light path system 1 and distributed optical fiber sensing system 2 must carry out insulation blocking when mounted, in order to avoid damage.

The first sensor fibre B6 of distributed optical fiber sensing system 2 is healthy and free from worry Single Mode Fiber (SMF-28); imbed underground with pipeline it or pipe alley in; and with epoxy resin glue it is sticked on the tube wall, the reflector A5 of the first sensor fibre B6 end places a protection box.Coupler guarantees that by beam split in 1: 1 two-beam intensity is close, can increase the intensity of interference signal, detects easily.The length of delay winding B4 is 2Km in the distributed optical fiber sensing system 2, because the frequency of leakage acoustic emission signal is less than 50KHz, then

Therefore value in the 0-50KHz frequency range can not influence zero frequency greater than zero.

The location of leakage point is the phase difference that demodulates interference light earlier by the demodulating system in the detection system 3, be digital signal and import computer and carry out Digital Signal Processing by the analog signal conversion of A/D converter then phase difference, restituted signal is done the FFT conversion, and the frequency of amplitude minimum point correspondence is zero frequency ω on the spectrogram _s, cursor is moved on to herein directly read zero dot frequency value.According to ${\mathrm{\τ}}_s=\frac{\mathrm{\π}(1+n)}{2{\mathrm{\ω}}_s}$ (n is an even number, occurs a plurality of zero frequency sometimes in the wide frequency range of leakage signal, only gets the zero frequency of frequency minimum here, and this moment, the n value was zero) calculated bright dipping and propagated into reflector needed time τ from leakage point _s, again according to formula s=v τ _s(v is the velocity of propagation of light in optical fiber) calculates the distance of leak position apart from reflector.

Claims (3)

1, based on the pipeline leakage monitor of distributed optical fiber acoustic sensing technology, this device mainly includes light path system (1), distributed optical fiber sensing system (2), detection system (3), it is characterized in that: the light path system of this device (1) mainly includes broadband continuous light source (A1), optical circulator (A2), distributed optical fiber sensing system (2) mainly includes first Coupler (A3), delay winding (B4), reflector (A5); Wherein, broadband continuous light source (A1) is connected with optical circulator (A2) by first Single Mode Fiber (B1), optical circulator (A2) is connected with the Port1 port of first Coupler (A3) by first guiding fiber (B2) again, the Port2 port of first Coupler (A3) is connected with delay winding (B4) by second Single Mode Fiber (B3), delay winding (B4) is connected with the Port3 port of first Coupler (A3) by the 3rd Single Mode Fiber (B5), the Port4 port of first Coupler (A3) is connected with reflector (A5) by first sensor fibre (B6), and the optical circulator of light path system (A2) is connected with detection system (3) by the 4th Single Mode Fiber (B7) again.

2, the pipeline leakage monitor based on distributed optical fiber acoustic sensing technology according to claim 1 is characterized in that: described detection system (3) mainly includes photoelectric converter (A6), demodulating system (A7), A/D converter (A8), computer (A9); The 4th Single Mode Fiber (B7) is connected with photoelectric converter (A6), and photoelectric converter (A6) is connected with computer (A9) by demodulating system (A7), A/D converter (A8).

3, according to the described pipeline leakage monitor of claim 1 based on distributed optical fiber acoustic sensing technology, a kind of method to the leakage point location is proposed, it is characterized in that this method is to carry out the leakage point location as follows:

1) when pipeline has leakage point, leaks acoustic emission signal and 1. represent by formula

Δφsinω _st ①

Δ φ is the amplitude of leakage signal, ω _sFrequency for leakage signal;

From the light that the broadband continuous light source sends, behind light path system and distributed optical fiber sensing system, the phase difference between the first bundle light that two bundles of generation interfere with each other and the second bundle light is:

${\mathrm{\φ}}_s\left(t\right)=4\mathrm{\Δ\φ}\cos {\mathrm{\ω}}_s(t-\frac{{\mathrm{\τ}}_T}{2})\sin {\mathrm{\ω}}_s\left(\frac{{\mathrm{\τ}}_d}{2}\right)\cos \left({\mathrm{\ω}}_s{\mathrm{\τ}}_s\right)$ ②

Wherein, ω _sBe the frequency of leakage acoustic emission signal, ${\mathrm{\τ}}_d=\frac{{\mathrm{\τ}}_3-{\mathrm{\τ}}_2+{\mathrm{\τ}}_4-{\mathrm{\τ}}_1}{2}$ Be the light process delay winding time, ${\mathrm{\τ}}_s=\frac{{\mathrm{\τ}}_4-{\mathrm{\τ}}_3+{\mathrm{\τ}}_2-{\mathrm{\τ}}_1}{4}$ For light from the leak position to reflector needed time, τ _T=τ ₂+ τ ₃For light from the port4 port transmission of first Coupler (A3) to reflector and through mirror reflects, turn back to the port4 port along original route, again through port2 port, delay winding cumulative time, τ to the port3 port ₁Be the time that the first bundle light passes through leakage point D for the first time, τ ₂Be the first bundle light passes through leakage point D for the second time after mirror reflects time, τ ₃Be the time that the second bundle light passes through leakage point D for the first time, τ ₄It is the second bundle light passes through leakage point D for the second time after mirror reflects time;

2) 2. formula is done the FFT conversion, time-domain signal is transformed into frequency domain, determine delay winding length, guarantee in the wide frequency range of leakage signal Be not equal to zero;

3) amplitude that occurs in frequency domain is that the frequency of zero some correspondence is called zero frequency, and this zero frequency satisfies cos (ω _sτ _s)=0; Determine this zero frequency by the spectrogram that shows on the computer A 9, find basis after the zero frequency ${\mathrm{\τ}}_s=\frac{\mathrm{\π}(1+n)}{2{\mathrm{\ω}}_s}$ (n is an even number) calculated bright dipping and propagated into reflector needed time τ from leakage point _s

5) again according to formula s=v τ _s(v is the velocity of propagation of light in optical fiber) calculate the leak position to reflector apart from s.

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