CN103047540A - Natural gas pipe leakage monitoring optical path system based on optical fiber sensing - Google Patents
Natural gas pipe leakage monitoring optical path system based on optical fiber sensing Download PDFInfo
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Abstract
The invention provides a natural gas pipe leakage monitoring optical path system based on optical fiber sensing and relates to the technical field of mechanical vibration measurement, impact measurement and a pipe system. The natural gas pipe leakage monitoring optical path system based on the optical fiber sensing is formed by a light source, optical path adapters, a transmission optical cable and optical fiber sensing units. Each optical path adapter is composed of an optical beam splitter and an optical beam combiner, the optical fiber sensing units are adhered onto a natural gas pipe at a certain distance, every 2-10 adjacent sensing units are of a group, each group of the sensing units adopt two transmission optical fibers, a transmitting optical fiber and a returning optical fiber for transmitting laser light and interference signals; the two transmission optical fibers are sequentially connected with corresponding optical path adapters in series according to setting positions of the sensing units, each optical path adapter is respectively communicated with the corresponding optical fiber sensing units through the two optical fibers, and finally the returning optical fiber in the transmission optical fibers enables the interference signal to be returned to a main machine of the system. The natural gas pipe leakage monitoring optical path system based on the optical fiber sensing is high in sensitivity and accuracy, low in false alarm rate and not prone to be influenced by environment.
Description
Technical field
The present invention is a kind of optical path system for monitoring leakage of natural gas based on Fibre Optical Sensor.Relate to the measurement of mechanical vibration, measurement and the pipe-line system technical field of impact.
Background technique
At present, the pipeline overall length of building up in the world reaches 2,500,000 kilometers, and having surpassed the railway total kilometrage becomes the main means of transportation of world energy sources, and the oil product of developed country and oil-producing area, the Middle East transports all realizes channelization.China's pipeline has also obtained very fast development in recent years, overall length is also above 70,000 kilometers, begun to take shape across thing, stretch from the north to the south, cover the whole nation, be communicated with the overseas large general layout of energy pipe network, pipeline transport becomes the major way of the allotment conveying of the strategic energy such as oil gas.
Pipeline is subjected to the reasons such as natural disaster, third party's breakage in installation owing to cross-regional wide, has caused more pipe leakage accident to occur.External pipe safety situation also allows of no optimist very much, and the natural gas line big bang occurs in U.S. San Bruno city on September 9th, 2010, and blast causes long 51 meters, wide 9 a meters hollow place on the road surface.The pipeline of about 8 meters of one segment length, 76 centimetres of diameters is exploded the Heaven, flies out about 30 meters far away, and causes large-range fire disaster, causes 4 people dead, and 3 people are missing, and at least 52 people are injured, 4 hectares of burnt areas, and tens of houses are burnt.People's safety, environmental consciousness significantly promote in recent years, are also more and more paid attention to as the pipeline transportation safety problem of high risk industries.
Only have the sound wave monitoring method comparatively effective for natural gas line leakage in the ripe technology at present, but in order to improve the real-time of leakage monitoring and the accuracy of leak source location, the layout density that must add at pipeline large sensor, increase simultaneously corresponding power supply, communications equipment, cause system cost and installation and maintenance costly.
Along with the development of sensory technique has been carried out the research of SCADA leakage monitoring system such as companies such as U.S. CSI, ATMOSI, European TER abroad, Sensornet company has also developed the leakage monitoring system based on distributed optical fiber temperature sensor, and portioned product has also been applied for patent protection at home; The units such as domestic University Of Tianjin, Tsing-Hua University, China Renmin People's Liberation Army Office Support Engineering Academy also further investigate the leakage monitoring method of pipeline.
Patent CN200410020046.6 discloses a kind of distribution type fiber-optic method for monitoring leak from oil gas pipe and monitoring device based on principle of interference.This monitoring system requires to lay side by side an optical cable at Near Pipelines along pipeline, utilizes the optical fiber in the optical cable to form a Fiber optic micro-vibration sensor.Patent CN200620119429, CN200610113044.0 are the pipeline leakage monitor based on the Sagnac fibre optic interferometer, and patent CN200610072879.6 is a kind of pipeline leakage monitor based on distributed optical fiber acoustic sensing technology and method.
" sensor and micro-system " the 7th phase of the 26th volume " based on the gas pipeline leakage detection method of distributed fiberoptic sensor " discloses a kind of gas pipeline leak detecting device and method based on distributed fiberoptic sensor, it is to have installing optical fibres sensor on the pipeline body of certain intervals, the vibration wave signal that continuous real-time monitoring is propagated along pipeline body, the vibration wave signal that gathers is carried out analysing and processing, comprise type identification and vibration source location, wherein whether type identification is for to belong to leak type by the extraction and analysis of vibration wave feature being differentiated it, the time lag that simultaneously propagates into adjacent several optical fiber transducers according to vibration wave determines that in conjunction with the velocity of propagation of vibration wave on pipeline body the position at vibration wave source place, the light intensity signal of sensor output realize position definite of leakage point after photoelectric conversion.
CN1837674A discloses a kind of pipeline leakage testing device and method based on distributed optical fiber acoustic sensing technology.
US2006/0225507A1 discloses a kind of pipeline leakage testing device and method based on distributed fiberoptic sensor.
Above-mentioned technology all belongs to the distributed optical fiber sensing monitoring method.But such technical monitoring is subject to the impact of the interference incident that pipeline occurs when leaking, have very high system's false alarm rate, and antijamming capability is relatively poor.
Make a general survey of the various line leakage technology of internal and overseas, the negative pressure wave method that generally uses at present, flow equilibrium method, the Pipeline Leak detection techniques such as pressure gradient, can't effectively solve the Leak testtion problem of gas pipeline, especially to identification and the location of minute leakage.And based on the good sensing characteristics of optical fiber, optical fiber sensing technology is able to fast development, wherein using more is to utilize an optical cable with the pipeline laying in one ditch as the Leakage Gas sensing unit, although sensitivity is higher than conventional art, but its locating effect is poor, can not satisfy the application demand of natural gas line leakage fully.Another kind of quasi-distributed optical fiber sensory technique based on fiber multiplex, identification and the location that can effectively solve the pipeline gas minute leakage.But the installation specification of its Fibre Optical Sensor unit is complicated, and design difficulty is large, mainly is to guarantee that the sensitivity of Fibre Optical Sensor unit inspection is enough high, and noise isolation will be got well.
Summary of the invention
The objective of the invention is to invent the optical path system for monitoring leakage of natural gas based on Fibre Optical Sensor that a kind of sensitivity and degree of accuracy are high, false alarm rate is low, be not subject to such environmental effects.
This natural gas pipeline leakage optical fiber monitoring system adopts a kind of highly sensitive quasi-distributed optical fiber sensing leakage vibration monitoring method that has, it is at the pipeline body with certain intervals high sensitivity optical fiber interference type leak optical fiber sensor to be installed, the vibration wave signal that continuous real-time monitoring is propagated along pipeline body, the vibration wave signal that gathers is carried out analysing and processing, comprise type identification and vibration source location, wherein whether type identification is for to belong to leak type by the extraction and analysis of vibration wave feature being differentiated it, the time lag that simultaneously propagates into adjacent several optical fiber transducers according to vibration wave realizes the determining of vibration wave source position in conjunction with the velocity of propagation of vibration wave on pipeline body, and realizing above-mentioned provides the position information of leakage point simultaneously to after the vibration wave signal analysis and processing incident of leakage being reported to the police.The present invention has suitably increased the quantity of optical fiber transducer on employing high sensitivity optical fiber sensor improves the basis of incident of leakage monitoring sensitivity, expanded the frequency range that to pick up monitor signal, and estimated that in conjunction with the time delay that a plurality of optical fiber transducers carry out localization method has guaranteed the accuracy of system location.
In natural gas pipeline leakage optical fiber monitoring system, sensing unit is the key that realizes line leakage, and when pipeline occurs to leak, leaking the vibration wave that excites will propagate to the leakage point both sides along pipeline.A sensing unit is installed on pipeline body at a certain distance, is used for monitoring the leakage vibration wave on the pipeline.Sensing unit adopts the fibre optic interferometer structure, can detect sensing unit as leaking vibration wave for optical fiber Michelson interferometer or fiber Mach-Zehnder interferometer, for the induction sensitivity that increases leaking vibration can be by increasing the mode of sensor fibre length, the light intensity signal of its output can be write as after photoelectric conversion:
V
0∝1+Vcos(φ
s+φ
n+φ
0)+V
n(1)
Wherein, V
0Be the voltage signal of output, V is the visibility of interferometer, V
nThe circuit additional noise, φ
sServe as reasons and leak the phase difference signal that vibration wave causes, be the leakage vibration wave signal that to survey, φ
0Being the initial phase of interferometer, is a constant, φ
nBeing the low frequency wonder of phase difference, is a Uncertainty, changes with temperature and external environment impact.Can realize leaking the vibration wave signal psi by the demultiplexing technology that is complementary with the modulation of source mode
sObtain, and to this signal psi
sThe time lag that arrives corresponding sensing unit estimates, realized that along the speed v of pipe transmmision to the vibration wave source be determining of leakage point position in conjunction with vibration wave.
Also adopted optical fiber transducer multiplex/demultiplex method in this system.The method of the comprehensive frequency division multiplexing of the method and space division multiplexing, employing produces leak detection light to the method that tunable laser carries out the optical frequency modulation, use Michelson interferometer as leak sensor, the laying structure of sensor is that a leak sensor is installed on the natural gas tube pipeline outer wall at a certain distance, a plurality of sensors consist of a sensor group, and the optical signal of each sensor group uses an optical fiber to pass system host back.Wherein each sensor is made into the poor different Michelson interferometer of light arm, the sense light signal frequency that each leak sensor is produced is all not identical, utilizes thus the frequency division multiplexing principle optical multiplexed signal of a plurality of sensor different frequencies of every group can be used in the receiving terminal of passing system in the optical fiber back; And employing space division multiplexing mode difference connecting system main frame between a plurality of sensor groups.The optical signal of each the sensor group that receives uses independent photoelectric conversion passage to realize that optical signal is to the conversion of electrical signal, transducing signal after the conversion uses the frequency division mode to realize the demultiplexing of each sensor in the sensor group, and adopt the phase carrier technology to demodulate the original acoustic signals of pipe leakage, pass through again identification and the positioning analysis of leakage signal, but final Obtaining Accurate pipe leakage dot information.The phase carrier demodulation method that leaks acoustic signals is the interference signal that will receive, and carries out first bandpass filtering, one tunnel output and cos (ω
0T) carry out lower pass-filter and differential after multiplying each other and process another road and sin (ω
0T) carrying out lower pass-filter and differential after multiplying each other processes; Behind the output of the differential on last road and rear one tunnel the lower pass-filter output multiplication, subtract each other with rear one tunnel the differential output result with last lower pass-filter output multiplication again, process through integration, high-pass filtering successively afterwards, finally export original leakage vibration wave signal.
Simultaneously, the common communications optical fibre in optical cable of utilization and oil and gas pipes laying in one ditch is respectively as the sending and receiving transmission fiber, the pipe leakage optical fiber sensing probe is connected between the transmitting-receiving transmission fiber by Optical multiplexing technology is parallel with one another, form light circuit, it is along the line that the pipe leakage optical fiber sensing probe evenly is laid in pipeline, and formation can be monitored the optical fiber sensing system of pipe leakage vibration.Utilize light source to each pipe leakage Fibre Optical Sensor unit scan, based on the faraday rotation mirror method, realize the anti-polarization decay of the interference signal of a sensor in sensor group and the group, improve and stablized visibility and the signal to noise ratio of sensor and sensor group interference signal, use photoelectric conversion module that the interference light signal of each sensing unit group is converted to electrical signal, the corresponding photoelectric conversion passage independently of each sensing unit group, the interference signal that is gathered each sensing unit group by signals collecting and puocessing module is digital signal, and the carrier signal of each sensing unit is thoroughly separated in can will organizing by the method for bandpass filtering, by the phase generated carrier modulation and demodulation technology, demodulate original leakage vibration wave signal; Analyze the delay inequality of the leakage vibration wave signal that adjacent several sensing unit detects, in conjunction with vibration wave transmission speed in pipeline, the location that can realize leakage point.Thereby use the multiplexing quantity that the multiplexing modulation-demodulation technique of many sensing units has improved sensor group inner sensor greatly, reduced the usage quantity of optical fiber, detect in keeping system under the prerequisite of effect, reduced system complex degree and cost.
Position for the accurate locating leaks in pipes of energy, this system has adopted a kind of many sensing units localization method based on quasi-distributed optical fiber sensory technique gas pipeline leakage event, when the pipe leakage event occurs, leak the excited vibrational ripple and propagates to two opposite directions along pipeline, system propagates into the delay inequality realization of adjacent several sensing units to the location of leakage point according to leakage signal.When leak occuring, leak and excite pipeline to produce vibration wave, along pipe transmmision, wherein two adjacent sensing units are spaced apart setting value L to vibration wave with speed V, and establishing the time that signal is transmitted to sensing unit n is t
n, the time that is transmitted to sensing unit n+1 is t
N+1, the time that signal is transmitted to sensing unit n-1 is t
N-1, the time that is transmitted to sensing unit n+2 is t
N+2, have following formula (2) to set up:
(2)
Unknown parameter (t wherein
N+1-t
n), (t
N-1-t
N+1), (t
N+2-t
n) and (t
N+2-t
N-1) can carry out relevant treatment by the signal that the several sensing units of correspondence are received and obtain, so just formed the repeatedly observation to the same unknown quantity of event occurrence positions X, it is poor that a plurality of sensing units of combined continuous receive signal time, compares the time difference measurements mode that only adopts two sensing units and have more accurately locating effect.This localization method can be monitored burst or given vent to leakage signal, has the advantages such as accurate positioning is good, stable performance.
The formation of natural gas pipeline leakage optical fiber monitoring system is seen Fig. 1, a Fibre Optical Sensor unit is installed on pipeline body at a certain distance, optical fiber transducer group of a plurality of Fibre Optical Sensor cell formations, each optical fiber transducer group is received light source and the photodetector of receiving terminal with an optical fiber, photodetector output connects signals collecting and the puocessing module that comprises leakage signal identification and state event location function, and described signals collecting and puocessing module comprise that signal condition, signals collecting, processing unit, terminal show and external interface; The signal condition that connects photodetector output is exported successively serial connection, signals collecting and processing unit, and processing unit output has terminal to show and external interface.Signals collecting and puocessing module output connect microcomputer.Through the processing of signals collecting and puocessing module, the sensor group signal that mixes based on the frequency division multiplexing mode has been realized the demultiplexing of each sensor in the sensor group, obtains original leakage vibration wave signal.
The light path system of this natural gas pipeline leakage optical fiber monitoring system (seeing Fig. 2) mainly is based on the frequency division multiplexing principle and designs, and is made of light source, light path ABAP Adapter, transmission cable and Fibre Optical Sensor unit three parts; The light path ABAP Adapter is comprised of beam splitter and combiner device; Mount at a certain distance a Fibre Optical Sensor unit on natural gas line, every 2-10 adjacent sensing unit is divided into one group, and every group of sensing unit adopts two transmission fiber to be used for the transmission (being launching fiber and passback optical fiber) of laser and interference signal; Installation position according to each sensing unit on these two transmission fiber is connected in series corresponding light path ABAP Adapter successively, each light path ABAP Adapter is communicated with corresponding Fibre Optical Sensor unit by two optical fiber respectively, finally passes interference signal back system host by the passback optical fiber in the transmission fiber.
The flow process of whole light path system is: the launching fiber of light source in transmission cable sends exploring laser light, after arriving first light path ABAP Adapter, be divided into two bundle laser by the beam splitter of this light path ABAP Adapter: a branch ofly enter first Fibre Optical Sensor unit through launching fiber, light beam passes to next light path ABAP Adapter through time delay optical fiber in addition, be divided into two bundle laser by the beam splitter in the next light path ABAP Adapter again, a branch ofly enter second Fibre Optical Sensor unit, another Shu Zaijing optical fibre transmission is to next light path ABAP Adapter, by that analogy, until laser arrives last Fibre Optical Sensor unit; In last Fibre Optical Sensor unit of sensing unit group, laser no longer by the light path ABAP Adapter, directly enters the Fibre Optical Sensor unit; And through the optical signal behind each Fibre Optical Sensor unit, the combiner device by in the corresponding light path ABAP Adapter separately passes the optical signal of coming with the back and closes bundle, is back to the signal receiving end of monitoring system finally by the passback optical fiber transmission of corresponding sensing unit group.Wherein said light path ABAP Adapter has been gathered beam splitter and combiner device; Launching fiber and passback optical fiber use is two different fibre cores in the same transmission cable; Transmission cable is together in series all light path ABAP Adapter; The length of the launching fiber on the pipeline between adjacent two sensing units and passback optical fiber all is greater than 1/2 of laser coherent length, to reach the purpose that prevents from occuring between the sensing unit signal cross-talk.
The semiconductor laser that described light source adopts optical frequency to modulate, modulation signal acts on the laser Injection Current, realizes the modulation of optical frequency; Laser optical power 10-20mW, coherent length 400-500m can satisfy the requirement that postpones optical fiber between poor and adjacent two the sensor interferometer instrument of sensor interferometer instrument arm.
The semiconductor laser that wherein said optical frequency can be modulated is to be received on the laser by the output of modulation signal generation module, selects unlike signal amplitude, direct current biasing and the sawtooth wave of frequency or the signal of falling the saw wave modulator by parameter configuration; Modulation signal generation module adopts digital form to realize, namely calculate the modulation signal segment that obtains one-period by digital form according to wave mode, signal amplitude, frequency parameter, then export by digital-to-analog conversion (D/A) mode, the modulated-analog signal of output is connected on the laser, wherein can select such as sawtooth wave or the signal type of falling the saw wave modulator capable of regulating signalization amplitude, direct current biasing and frequency by parameter configuration; Sawtooth wave or the requirement of falling the sawtooth signal amplitude of the output of modulation signal generation module are to the maximum ± 5V, and frequency is 200KHz to the maximum; Laser after modulation output optical frequency is input in the sensing light path with the laser that the modulation signal synchronous waveform changes, and can realize multiplexing, the signal carrier that forms a plurality of sensing units of sensing unit.
The modulation of source circuit as shown in Figure 6, it is mainly by operational amplifier U7, Distributed Feedback Laser U8, operational amplifier U9 and 2 triode Q4, Q5 groups; The 7 termination VDC of U7, connect again with the circuit of capacitor C 38 parallel connections after connecting with diode D8, capacitor C 41 behind the 6 terminating resistor R18, meet VDC behind the 6 terminating resistor R19, connect again simultaneously the ground that is connected in series to of diode D4, D5, D6, D7,4,7,8,9,10 end ground connection, 3 ends are ground connection after resistance R 17,2 ends and the end that meets U8; 1, the 14 end ground connection of U8,12 ends are through capacitor C 34 ground connection, 5,11 termination VDC, 4 termination PDne, 6 termination TEC+, 3 ends are through choke coil L 3 and the collector electrode that meets triode Q4 after resistance R 20 is connected, and 3 ends are through choke coil L 3 and the collector electrode that meets triode Q5 after resistance R 21 is connected simultaneously; Between 1,2 ends of U9 after shunt resistor R22 and the capacitor C 39 by 1 terminating resistor R25 to 6 ends, Pdne connecting resistance R30 again series resistors R27 connects 3 ends of U9, the ground connection of connecting after the resistance R 30 that meets simultaneously Pdne and potentiometer resistance R31, resistance R 32, the capacitor C 43 three's parallel connections, 5 ends meet VREF through resistance R 24, and 7 ends connect capacitor C 45 to ground through resistance R 28 and 8 ends altogether through resistance R 26; Pick out the base stage through diode D11, D12 to Q4 from the upper end of capacitor C 45, base stage connects capacitor C 44 to ground simultaneously, connects with resistance R 29 through diode D10 simultaneously and also arrives ground, and the base stage of Q4 connects the base stage of Q5, and the grounded-emitter connection of Q4, Q5.
Described sensing unit adopts Michelson interferometer or Mach-Zehnder interferometer.Each Fibre Optical Sensor unit is according to equidistantly being installed in pipe surface; Every 2-10 adjacent sensing unit forms a sensing unit group, each sensing unit adopts parallel way to be connected to transmission fiber (being launching fiber and passback optical fiber) in every group, the place that each sensing unit is connected with transmission fiber is used the 1*2 Coupler to realize the beam splitting of light and is closed bundle (being the light path ABAP Adapter), and the transmission fiber length between adjacent two sensing units is greater than 1/2 of laser coherent length; The corresponding photoelectric conversion passage that independently interference light signal of each sensing unit group is converted to electrical signal of each sensing unit group.
The I type structure of described optical fiber transducer is seen Fig. 4, and I type structure is test tube road radial vibration signal, and each sensing unit comprises: elastic cylinder, fibre optic interferometer and tail fiber coiling box; Wherein, the interference arm of uniform sequential winding optical fiber interferometer on the elastic cylinder periphery, and with tackiness agent optical fiber and cylindrical body are bonded together, remaining fibre optic interferometer and related device thereof are with neat being coiled in the tail fiber coiling box after twining; The tail fiber coiling box is fixed on the elastic cylinder top by tackiness agent.Described elastic cylinder bottom indent, and radian is consistent with pipeline external surface.The radial vibration that produces during gas pipeline leakage allows elastic cylinder generation deformation, drives the fibre optic interferometer that the elastic cylinder periphery twines deformation also occurs, and changes thus the state of the light of transmission in the optical fiber, so that is arrived by the leakage monitoring Equipment Inspection.
The another kind of Fibre Optical Sensor unit II type structure that is used for natural gas line leakage axial vibration signal is seen Fig. 5, and this Fibre Optical Sensor unit is comprised of rectangular spring sheet, fibre optic interferometer and tail fiber coiling box; Concrete structure is on the rectangular spring sheet, the fiber optic interferometric arm of fibre optic interferometer is evenly laid with the shape of sine wave, and with tackiness agent optical fiber is close on the rectangular spring sheet, remaining fibre optic interferometer and related device thereof are with neat being coiled in the tail fiber coiling box; The tail fiber coiling box is fixed on above the rectangular spring sheet by tackiness agent.Described rectangular spring sheet is a bottom indent and the radian steel sheet consistent with pipeline external surface; The axial vibration that produces during gas pipeline leakage allows rectangular spring sheet generation deformation, drives the fibre optic interferometer that the rectangular spring sheet coils above deformation also occurs, and changes thus the state of the light of transmission in the optical fiber, so that is detected by rear end equipment.
In addition, use photoelectric conversion module that the interference light signal of each sensing unit group is converted to electrical signal at leakage monitoring equipment receiving terminal, the corresponding photoelectric conversion passage independently of each sensing unit group.
This invention aims at based on the quasi-distributed natural gas line leakage system of fiber multiplex and designs, and when guaranteeing that the natural gas line leakage system is normal and using, has realized simple in structurely, and construction is easy to light path system.
Effect of the present invention and advantage are, quasi-distributed optical path system for monitoring leakage of natural gas based on fiber multiplex, use less fiber number, can realize the natural gas line leakage completely without the source, have the advantage of simple in structure, highly sensitive, anti-riot, the accurate positioning of essence, saving fiber resource, can be natural gas line leakage effective monitoring means is provided.
Description of drawings
Fig. 1 monitoring system of fiber optical sensing natural gas pipeline schematic diagram
The light path system structural drawing of Fig. 2 monitoring system of fiber optical sensing natural gas pipeline
Fig. 3 Fibre Optical Sensor optical path system for monitoring leakage of natural gas schematic diagram
Fig. 4 optical fiber transducer I type structural drawing
Fig. 5 optical fiber transducer II type structural drawing
Fig. 6 modulation of source circuit diagram
Wherein 1-tail fiber coiling box 2-input, output optical fibre 3-elastic cylinder
4-fibre optic interferometer 5-rectangular spring sheet 1n-beam splitter
2n-sensing unit 3n-combiner device
Embodiment
Embodiment. this example mainly is for the designed embodiment of natural gas pipeline leakage optical fiber monitoring system, so need to carry out on this monitoring system embodiment's basis.This monitoring system consists of as shown in Figure 1, on pipeline body, every 1.5km a Fibre Optical Sensor unit is installed, 10 sensors are installed altogether, front 5 sensors and rear 5 sensors consist of respectively a sensor group, an optical fiber in all optical fiber transducer group common transmitted optical cables is connected with system source, as launching fiber, simultaneously each optical fiber transducer group uses alone again optical fiber in the transmission cable to be connected with the system photodetector, as returning optical fiber; Photodetector output termination comprises signals collecting and the puocessing module of leakage signal identification and state event location function, and described signals collecting and puocessing module comprise that signal conditioner, signal picker, processing unit, terminal show and external interface; What wherein connect the photodetector output terminal is signal conditioner, signal picker and processing unit successively, and processing unit output has terminal to show and external interface.Signal picker and processing unit output connect microcomputer.Through the processing of signal picker and processing unit, the sensor group signal that mixes based on the frequency division multiplexing mode has been realized the demultiplexing of each sensor in the sensor group, obtains original leakage vibration wave signal.
Light path in this system (seeing Fig. 2) is based on the frequency division multiplexing principle and designs, and each optical fiber transducer connects the light path ABAP Adapter by two optical fiber, and all light path ABAP Adapter are connected in series successively with transmission cable, by the nearest light path ABAP Adapter welding system main frame of distance receiving terminal; Concrete optical routing light path ABAP Adapter, transmission cable and optical fiber transducer three parts consist of; The light path ABAP Adapter is comprised of beam splitter and combiner device; Optical fiber transducer adopts the interferometer of Michelson-structure.
Wherein the concrete contact between each optical member as shown in Figure 3, the detection light process transmission fiber I5 that light source sends enters the beam splitting apparatus 11 in the light path ABAP Adapter, it is 9: 1 that this beam splitting apparatus 11 adopts splitting ratio, wherein ratio is that 9 output light continues to propagate along time delay optical fiber 4, until light path ABAP Adapter 2, and being 1 output light, export ratio enters first sensor 21, sensor 21 adopts the Michelson's interferometer structure, arm is poor to be 5m, 3m long optic fiber on arm of this interferometer is wound on the elastomer of rubber material, elastomer is close to tube wall, adopts protective housing to fix; Beam splitting apparatus 12 in the light path ABAP Adapter 2 adopts 8: 1 splitting ratio, wherein ratio is that 8 output light continues to be transmitted to next light path ABAP Adapter along time delay optical fiber, and being 1 output light, export ratio enters second sensor 22, it is poor at 7.5m that this sensor adopts equally the Michelson's interferometer structure and controls interferometer arm, the optical fiber that 3m on the arm is long is wound on the elastomer of rubber material, and elastomer is close to tube wall and is fixed; By that analogy, all the other sensor brachium difference Wei 10m, 12.5m, 15m, beam splitting apparatus splitting ratio in the corresponding ABAP Adapter was respectively 7: 1,6: 1,5: 1,4: 1,3: 1,2: 1,1: 1, and during to last sensor, laser directly enters sensor after time delay optical fiber; The output of sensor 21-24 in first sensor group respectively with front four ABAP Adapter in bundle-mixer return optical fiber and be connected with one, the splitting ratio of 4 bundle-mixers is respectively 4: 1,3: 1,2: 1,1: 1, each sensor is that 1 input end is connected with the bundle-mixer ratio all, sensor 25 outputs connect passback optical fiber, and then connect the bundle-mixer in the 4th ABAP Adapter; Similarly, the arm length difference of five sensors in second sensor group is respectively 5m, 7.5m, 10m, 12.5m, 15m, same bundle-mixer and another root passback optical fiber that passes through in the ABAP Adapter is connected, and the bundle-mixer splitting ratio is respectively 4: 1,3: 1,2: 1,1: 1; Two sensor groups use two passback optical fiber to be connected with two ALT-CH alternate channels of photoelectric conversion module respectively altogether;
Between each sensor apart from Accurate Measurement, according to the output of light propagation time control light source; When the pipeline between first sensor and second sensor occurs to leak, leaking the vibration wave that causes is picked up by two sensors respectively through the regular hour along pipe transmmision, import system's photoelectric conversion module into by passback optical fiber, final system receives the time difference of leakage signal and the location that can realize leakage point in conjunction with vibration wave in ducted velocity of propagation according to sensor.
System source is made of optical frequency adjustable laser and dedicated modulation signal generating module in the present embodiment; Modulation signal that light source adds is the sawtooth signal of frequency 10kHz, amplitude ± 1.4V, and the interference signal frequency spectrum of first sensor group output mainly is made of 40kHz, 60kHz, 80kHz, 100kHz, five spectral lines of 120kHz; Use respectively CF center frequency to be 40kHz, 60kHz, 80kHz, 100kHz, 120kHz, the band-pass filter that bandwidth is 4.5kHz carries out filtering to interference signal, obtain the carrier signal of five sensors, corresponding main frequency is respectively 40kHz, 60kHz, 80kHz, 100kHz, 120kHz; Five carrier signals uses are carried out demodulation with cosine and sinusoidal signal frequently, obtain the leakage vibration wave signal of five sensors.
Wherein the modulation of source circuit as shown in Figure 6, it is mainly by operational amplifier U7, Distributed Feedback Laser U8, operational amplifier U9 and 2 triode Q4, Q5 groups; The 7 termination VDC of U7, connect again with the circuit of capacitor C 38 parallel connections after connecting with diode D8, capacitor C 41 behind the 6 terminating resistor R18, meet VDC behind the 6 terminating resistor R19, connect again simultaneously the ground that is connected in series to of diode D4, D5, D6, D7,4,7,8,9,10 end ground connection, 3 ends are ground connection after resistance R 17,2 ends and the end that meets U8; 1, the 14 end ground connection of U8,12 ends are through capacitor C 34 ground connection, 5,11 termination VDC, 4 termination PDne, 6 termination TEC+, 3 ends are through choke coil L 3 and the collector electrode that meets triode Q4 after resistance R 20 is connected, and 3 ends are through choke coil L3 and the collector electrode that meets triode Q5 after resistance R 21 is connected simultaneously; Between 1,2 ends of U9 after shunt resistor R22 and the capacitor C 39 by 1 terminating resistor R25 to 6 ends, Pdne connecting resistance R30 again series resistors R27 connects 3 ends of U9, the ground connection of connecting after the resistance R 30 that meets simultaneously Pdne and potentiometer resistance R31, resistance R 32, the capacitor C 43 three's parallel connections, 5 ends meet VREF through resistance R 24, and 7 ends connect capacitor C 45 to ground through resistance R 28 and 8 ends altogether through resistance R 26; Pick out the base stage through diode D11, D12 to Q4 from the upper end of capacitor C 45, base stage connects capacitor C 44 to ground simultaneously, connects with resistance R 29 through diode D10 simultaneously and also arrives ground, and the base stage of Q4 connects the base stage of Q5, and the grounded-emitter connection of Q4, Q5.
Wherein: operational amplifier U7 selects AD623; Laser U8 selects the internal modulation semiconductor light sources; Operational amplifier U9 selects AD8572; Triode Q4, Q5 select NPN9014;
This example is through test of many times, can realize the monitoring along any disturbance behavior of pipe transmmision by install to leak vibration sensing interference type sensing unit at tube wall, through realizing signal analysis and processing and intelligent recognition incident of leakage is reported to the police and provided the leakage point position, system sensitivity is high, by the intelligent recognition of leaking has been reduced system's false alarm rate that incident causes largely.
Claims (6)
1. the optical path system for monitoring leakage of natural gas based on Fibre Optical Sensor is characterized in that it is by light source, light path ABAP Adapter, transmission cable and Fibre Optical Sensor cell formation; The light path ABAP Adapter is comprised of beam splitter and combiner device; Mount at a certain distance a Fibre Optical Sensor unit on natural gas line, every 2-10 adjacent sensing unit is divided into one group, and every group of sensing unit adopts two transmission fiber to be used for the transmission of laser and interference signal; Installation position according to each sensing unit on these two transmission fiber is connected in series corresponding light path ABAP Adapter successively, each light path ABAP Adapter is linked to each other with corresponding Fibre Optical Sensor unit by two optical fiber respectively, finally passes interference signal back system host by the passback optical fiber in the transmission fiber;
The launching fiber of light source in transmission cable sends exploring laser light, after arriving first light path ABAP Adapter, be divided into two bundle laser by the beam splitter of this light path ABAP Adapter: a branch ofly enter first Fibre Optical Sensor unit through launching fiber, light beam passes to next light path ABAP Adapter through time delay optical fiber in addition, be divided into two bundle laser by the beam splitter in the next light path ABAP Adapter again, a branch ofly enter second Fibre Optical Sensor unit, another Shu Zaijing optical fibre transmission is to next light path ABAP Adapter, by that analogy, until laser arrives last Fibre Optical Sensor unit; In last Fibre Optical Sensor unit of sensing unit group, laser no longer by the light path ABAP Adapter, directly enters the Fibre Optical Sensor unit; And through the optical signal behind each Fibre Optical Sensor unit, the combiner device by in the corresponding light path ABAP Adapter separately passes the optical signal of coming with the back and closes bundle, is back to the signal receiving end of monitoring system finally by the passback optical fiber transmission of corresponding sensing unit group.
2. the optical path system for monitoring leakage of natural gas based on Fibre Optical Sensor according to claim 1 is characterized in that the semiconductor laser that described light source adopts optical frequency to modulate; Laser optical power 10-20mW, coherent length is 400-500m;
The semiconductor laser that described optical frequency can be modulated is to be received on the laser by the output of modulation signal generation module, selects unlike signal amplitude, direct current biasing and the sawtooth wave of frequency or the signal of falling the saw wave modulator by parameter configuration; Sawtooth wave or the requirement of falling the sawtooth signal amplitude of the output of modulation signal generation module are to the maximum ± 5V, and frequency is 200KHz to the maximum.
3. the optical path system for monitoring leakage of natural gas based on Fibre Optical Sensor according to claim 2 is characterized in that described modulation of source main circuit will be by operational amplifier U7, Distributed Feedback Laser U8, operational amplifier U9 and 2 triode Q4, Q5 groups; The 7 termination VDC of U7, connect again with the circuit of capacitor C 38 parallel connections after connecting with diode D8, capacitor C 41 behind the 6 terminating resistor R18, meet VDC behind the 6 terminating resistor R19, connect again simultaneously the ground that is connected in series to of diode D4, D5, D6, D7,4,7,8,9,10 end ground connection, 3 ends are ground connection after resistance R 17,2 ends and the end that meets U8; 1, the 14 end ground connection of U8,12 ends are through capacitor C 34 ground connection, 5,11 termination VDC, 4 termination PDne, 6 termination TEC+, 3 ends are through choke coil L3 and the collector electrode that meets triode Q4 after resistance R 20 is connected, and 3 ends are through choke coil L3 and the collector electrode that meets triode Q5 after resistance R 21 is connected simultaneously; Between 1,2 ends of U9 after shunt resistor R22 and the capacitor C 39 by 1 terminating resistor R25 to 6 ends, Pdne connecting resistance R30 again series resistors R27 connects 3 ends of U9, the ground connection of connecting after the resistance R 30 that meets simultaneously Pdne and potentiometer resistance R31, resistance R 32, the capacitor C 43 three's parallel connections, 5 ends meet VREF through resistance R 24, and 7 ends connect capacitor C 45 to ground through resistance R 28 and 8 ends altogether through resistance R 26; Pick out the base stage through diode D11, D12 to Q4 from the upper end of capacitor C 45, base stage connects capacitor C 44 to ground simultaneously, connects with resistance R 29 through diode D10 simultaneously and also arrives ground, and the base stage of Q4 connects the base stage of Q5, and the grounded-emitter connection of Q4, Q5.
4. the optical path system for monitoring leakage of natural gas based on Fibre Optical Sensor according to claim 1 is characterized in that described sensing unit adopts Michelson interferometer or Mach-Zehnder interferometer; Each Fibre Optical Sensor unit is according to equidistantly being installed in pipe surface; Every 2-10 adjacent sensing unit forms a sensing unit group, each sensing unit employing parallel way is connected to the transmission fiber that comprises launching fiber and passback optical fiber in every group, the place that each sensing unit is connected with transmission fiber connects the light path ABAP Adapter that the 1*2 Coupler consists of, and the transmission fiber length between adjacent two sensing units is greater than 1/2 of laser coherent length; The corresponding photoelectric conversion passage that independently interference light signal of each sensing unit group is converted to electrical signal of each sensing unit group.
5. the optical path system for monitoring leakage of natural gas based on Fibre Optical Sensor according to claim 1 is characterized in that described light path ABAP Adapter gathered beam splitter and combiner device; Launching fiber and passback optical fiber use is two different fibre cores in the same transmission cable; Transmission cable is together in series all light path ABAP Adapter; The length of the launching fiber on the pipeline between adjacent two sensing units and passback optical fiber all is greater than 1/2 of laser coherent length.
6. according to claim 1 or 4 described optical path system for monitoring leakage of natural gas based on Fibre Optical Sensor, it is characterized in that sensing unit comprises two kinds on the II type structure of the optical fiber transducer of the I type structure of optical fiber transducer of test tube road radial vibration signal and test tube road axial vibration signal, the I type structure of optical fiber transducer comprises elastic cylinder, fibre optic interferometer and tail fiber coiling box; Wherein, the interference arm of uniform sequential winding optical fiber interferometer on the elastic cylinder periphery, and with tackiness agent optical fiber and cylindrical body are bonded together, remaining fibre optic interferometer and related device thereof are with neat being coiled in the tail fiber coiling box after twining; The tail fiber coiling box is fixed on the elastic cylinder top by tackiness agent; Described elastic cylinder bottom indent, and radian is consistent with pipeline external surface; Fibre Optical Sensor unit II type structure is comprised of rectangular spring sheet, fibre optic interferometer and tail fiber coiling box; On the rectangular spring sheet, the fiber optic interferometric arm of fibre optic interferometer is evenly laid with the shape of sine wave, and with tackiness agent optical fiber is close on the rectangular spring sheet, remaining fibre optic interferometer and related device thereof are with neat being coiled in the tail fiber coiling box; The tail fiber coiling box is fixed on above the rectangular spring sheet by tackiness agent; Described rectangular spring sheet is a bottom indent and the radian steel sheet consistent with pipeline external surface.
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Effective date of registration: 20170301 Address after: 100007 Dongcheng District, Dongzhimen, China, North Street, No. 9 Oil Mansion, No. Patentee after: China National Petroleum Corporation Patentee after: China Petroleum Pipeline Bureau Engineering Co., Ltd. Address before: 100007 Dongcheng District, Dongzhimen, China, North Street, No. 9 Oil Mansion, No. Patentee before: China National Petroleum Corporation Patentee before: China Petroleum and Natural Gas Pipeline Bureau |