CN101799408A - Optical fiber multi-parameter detector for gas power generation - Google Patents
Optical fiber multi-parameter detector for gas power generationDownload PDFInfo
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- CN101799408A CN101799408ACN201010147900ACN201010147900ACN101799408ACN 101799408 ACN101799408 ACN 101799408ACN 201010147900 ACN201010147900 ACN 201010147900ACN 201010147900 ACN201010147900 ACN 201010147900ACN 101799408 ACN101799408 ACN 101799408A
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Abstract
Translated fromChinese
Description
Technical field
Patent of the present invention relates to a kind of multiparameter detection system of using methane electrical generation, uses wavelength-division multiplex technique to realize that safety on line detects simultaneously to multiparameters such as gas density, oxygen concentration, humidity, temperature.
Background technology
China is coal production big country, and the outstanding mine of gas accounts for half of coal mine.Gas is the biggest threat of mine safety, and national colliery serious accident is all relevant with gas explosion more than 70%.Methane content in the gas is very high, and the share of the greenhouse effect of methane in global warming is 15%, is only second to carbon dioxide; And the greenhouse effect that equivalent methane causes are 21 times of carbon dioxide.The data presentation that National Development and Reform Committee announces, national gas utilization rate is 23% only, this means most coal-seam gas just towards the sky discharging, its greenhouse effect can not be ignored.
No matter from mining safety, economic benefit angle, or from the environmental protection aspect, the meaning of the methane drainage and utilization project of gas is all very huge.The important method means that at present gas effectively utilized are mainly methane electrical generation.Methane electrical generation can be divided into high gas conventional power generation usage and present low gas generating two big classes according to source of the gas (methane concentration).In the conventional methane electrical generation technology, the coal-seam gas methane content of extraction is more than 25%; Adopt the present low gas coal-seam gas to carry out the direct generation of electricity and be called the present low gas generating.
According to existing " safety regulations in coal mine ", routine can should not be lower than 25% for the coal-seam gas concentration of carrying.To conventional coal-seam gas distributing system, should the coal-seam gas concentration detection apparatus be set at the extraction pump discharge, when the coal-seam gas concentration of down-hole extraction less than 25% the time, should close the transmission ﹠ distribution valve, open the emptying valve,, prevent that low-concentration methane gas from entering system the direct emptying of low concentration gas.
In the methane electrical generation process, must implement monitoring, also will detect with the degree of oxidation of determining gas and guarantee security problems simultaneously information such as oxygen, humidity to gas density information.No matter high methane electrical generation still is the present low gas generating, the detection technique that adopts often all is traditional electronic sensor or infrared detection technology at present, because the coal-seam gas that is used to generate electricity has characteristics such as high dust, high humility, concentration variation fluctuation are bigger, it is very difficult to make traditional detection technique use, often need constantly to proofread and correct, often change detector and problems such as error is big, range is not enough can occur detecting.For example: the safety that guarantee methane electrical generation, do not cause accidents such as producing blast, just must detect real-time coal-seam gas gas density and temperature, but the conditional electronic pick-up unit under high humidity environment, often can't work, and the charged work of electronic detector has more increased danger; Existing watt inspection instrument (black-and-white component formula, light watt etc.) all needs frequent correction can guarantee to detect accurately.
In addition, the scheme of the employing near-infrared laser measure gas concentrations that proposes in existing patent and the domestic and foreign literature adopts the principle of absorption of gas to laser, still in this scheme, in actual applications, particularly in the inconstant environment of temperature testing result error has appearred.As Figure 11, the gas of same concentration has produced different absorption coefficients under different temperatures, thereby different detection errors all will appear in above-mentioned existing near infrared gas detection scheme, the test data figure of Figure 12 darker curve for arriving with actual detected according to the detection of above scheme, lighter curve is the test data figure after the temperature correction, and effect is very obvious.Be not gas, oxygen, humidity etc. all has this problem to exist.As seen, temperature can not be ignored for the influence that methane gas detects, but the detecting instrument of all present optics does not all have to proofread and correct according to the temperature of gas.
Summary of the invention
Fundamental purpose of the present invention is to design and develop a kind of system that detects simultaneously based on the multiple parameter of optical fiber sensing technology.The present invention be a kind of can be not charged, need not to proofread and correct, instrument that multiparameter detects reliably and with long-term, can also also proofread and correct the error of gas detecting instrument when having detected environment temperature in real time, will be one and the huge great innovative technology of economic and social benefit for methane electrical generation.
This programme is realized by following technical measures: it comprises light source driving circuit and the dfb semiconductor laser instrument of the corresponding gas centre wavelength at least one road that is electrically connected with it, light path between described dfb semiconductor laser instrument and the probe is provided with photoswitch, be equipped with photodetector with described probe, all adopt optical cable to connect between dfb semiconductor laser instrument, photoswitch, probe and the photodetector, photodetector is electrically connected with single-chip microcomputer, and photoswitch is electrically connected by the photoswitch control line with single-chip microcomputer.
The concrete characteristics of this programme also have: described dfb semiconductor laser instrument is 2, sends the laser of the centre wavelength of corresponding gas of difference and oxygen.
Described dfb semiconductor laser instrument is 3, sends the laser of corresponding gas, oxygen and steam centre wavelength respectively.By steam the absorption and the laser scanning methods of laser are realized Humidity Detection, make Humidity Detection convenient and reliable.
Described probe comprises a holder, on holder, be relatively set with incident end optical fiber collimator and receiving end optical fiber collimator, between incident end optical fiber collimator and receiving end optical fiber collimator, be formed with air absorbing cavity, incident end optical fiber collimator is connected with optical cable, and the exit end optical fiber collimator is connected with outgoing optical fiber.
Series connection is provided with fiber grating on the light path between receiving end optical fiber collimator and the outgoing optical fiber, near the fiber grating centre wavelength choice of location scope that Distributed Feedback Laser can scan the gas absorption peak.Fiber grating of air absorbing cavity series connection is used for the thermometric degree, temperature and gas synchronous detection, and temperature information can be proofreaied and correct the measuring error that causes because of absorption coefficient difference under the different temperatures.One cover detector can detect multiple gases concentration, humidity and temperature information simultaneously, and is highly integrated.
The invention has the beneficial effects as follows: the light in the optical fiber is coupled to the space transmission by optical fiber collimator, again be coupled back into optical fibers after the gas absorption, light by air absorbing cavity and fiber grating by the single-chip microcomputer collection line data analyzing and processing of going forward side by side, draws gas concentration, humidity through opto-electronic conversion; Single-chip microcomputer switches by photoswitch control line control photoswitch passage, realizes that a probe detects multiple gases simultaneously; Serviceability temperature information is proofreaied and correct gas detection, has avoided the measuring error that gas detection is caused because of environment temperature; Realized the multiparameter detection, the parameter of main monitoring is: gas density, temperature, oxygen content, humidity etc.; The design of employing all optical fibre structure, probe segment are that optical component is formed, and do not use electron device in case cause unsafe factor; Native system is brought into play its not advantage of charged work, has improved the security performance of methane electrical generation checkout equipment.Adopt photoswitch to select the project organization of a plurality of LASER Light Source, make that subsequent optical path and circuit can be shared, saving simplifies the structure, and also makes a probe detect multiple gases.By laser scanning methods, scanning fiber bragg grating and gas absorption peak have realized that temperature gas detects simultaneously simultaneously.Air absorbing cavity is connected with fiber grating, has simplified the detection light path, and an optical fiber can be realized.
Description of drawings
Fig. 1 system construction drawing; Fig. 2 drive signal and opto-electronic conversion signal output waveform figure; Opto-electronic conversion output signal diagram under Fig. 3 different temperatures; Fig. 4 gas abosrption spectrogram; Fig. 5 water vapor absorption spectrogram; Fig. 6 oxygen absorption spectrogram; Opto-electronic conversion output signal under the different vapour concentrations of Fig. 7; The corresponding nominal data figure of Fig. 8 grating wavelength and temperature; Fig. 9 gas concentration and output signal calibration maps; Figure 10 cut-away view of popping one's head in; Methane gas absorption coefficient figure under Figure 11 different temperatures; Detect Error Graph under the different temperatures before and after Figure 12 temperature correction;
Among the figure: 1-light source driving circuit, 2-1653nmDFB laser instrument, 3-761nmDFB laser instrument, the 4-1364nmDFB laser instrument, 5-photoswitch, 6-optical cable, the 7-probe, 8-photodetector, 9-optical cable, the 10-single-chip microcomputer, 11-photoswitch control line, 12-incident end optical fiber collimator, 13-receiving end optical fiber collimator, the 14-fiber grating, 15-holder, 16-outgoing optical fiber.
Embodiment
Be illustrated in figure 1 as this system construction drawing.Lightsource driving circuit 1 drives 3 dfb semiconductor laser instruments (2,3,4), in the native system, for detecting the special dfb semiconductor laser instrument that adopts respectively corresponding these the three kinds of a certain characteristic absorption of the gas peak positions of centre wavelength of gas density, oxygen concentration and humidity (vapour concentration), the absorption peak of three kinds of gases is respectively as Fig. 4, Fig. 5, shown in Figure 6.The signal ofdriving circuit 1 output is illustrated in figure 2 as a sawtooth wave, makes laser instrument can intactly scan an absorption peak of gas.
Light that laser instrument sends enters intoprobe 7 throughphotoswitch 5,optical cable 6, the absorbing cavity structure that comprises in theprobe 7 as shown in figure 10, by incident end optical fiber collimator 12, exit end optical fiber collimator 13, fiber grating 14 andholder 15 are formed.The pair of alignment device is formed air absorbing cavity, makes light be coupled to from optical fiber in the air, coupled back into optical fibers again after fully being absorbed by gas; Fiber grating 14 is used to measure temperature, and gas detection is compensated correction.Enter intophotodetector 8 by 7 light that see through of popping one's head in throughoptical cable 9 and be converted to electric signal, output signal is shown in Fig. 2 fine rule, and A is the peak that sees through of fiber grating formation among the figure, and B is the gas absorption effect.See through light through signal after the opto-electronic conversion by single-chip microcomputer 10 data acquisitions and carry out demodulation analysis, go out gas concentration value and temperature value according to the calibration formula inverse.
Photoswitch 5 can select three the tunnel to be respectively1653nmDFB laser instrument 2 under the control of single-chip microcomputer 10,761nmDFB laser instrument 3, and its one of1364nmDFB laser instrument 4 directly is connected withoptical cable 6, and other light does not enter optical cable 6.Single-chip microcomputer 10 transmits control signal byphotoswitch control line 11, makes to switchphotoswitch 5 switching channels another road laser instrument and be connected withoptical cable 6, thereby analyze another kind of gas concentration.Three channel cycle are switched, and select the laser instrument of corresponding gas with various absorption peak wavelength can realize that multiple gases detects, and detect successively incessantly and can realize patrolling and examining of three kinds of gas concentrations.Fiber grating is connected in the light path, can be simultaneously to gas and temperature synchronous detection, and the synchronous detection of temperature not only realizes temperature detection, also the accurate detection for gas provides rectification building-out.
Single-chip microcomputer 10 main effects are the collection and the computing of signal.At first be to carry out analog to digital conversion by the signal of A/D after with opto-electronic conversion; The signal that collects carries out digital filtering in single-chip microcomputer, single-chip microcomputer analyzes Current Temperatures information from the signal that collects; In addition, operational analysis from signal goes out gas concentration according to the gas absorption principle, and the formula that calculates by temperature information compensation correction concentration makes the result more accurate.Single-chip microcomputer can adopt 8051 single-chip microcomputers etc. to have A/D and all can be used for this system with the single-chip microcomputer of output control function.
The temperature detection principle:
A position trough minimum value is the centre wavelength position offiber grating 9 among Fig. 2, and the pass of grating and stress and temperature variation is: Δ λB=λB(1-ρ) Δ ε+λB(1+ ξ) Δ T (1)
In the formula, Δ λBIt is the change of the reflected light centre wavelength that causes of stress and temperature variation; Δ ε is the variation of stress; Δ T is the variation of temperature amount; ρ is the strain optical coefficient of optical fiber; ξ is the thermo-optical coeffecient of optical fiber.At the 1.5um wave band, FBG approximately is respectively the sensitivity coefficient of temperature and strain: 12pm/ ℃ and 1pm/ ε.
Fixed grating is not subjected to make under the external force effect fiber grating two ends to fix at fiber grating as shown in Figure 10, and the centre is in free state, is not subjected to the pulling force of device such as external metallization, thereby the influence of STRESS VARIATION in the formula is eliminated, so formula becomes: Δ λB=K+ λBB Δ T (2)
K, B are constant, and as seen, wavelength change is only relevant with Δ T, on the contrary, measure temperature, only need record Δ λBGetting final product, is 25 ℃ of signals as the thin curve of Fig. 3, and bold curve is 30 ℃ of curves, and temperature is high more, and the centre wavelength of grating past more long wavelength move.Only the pattern displacement that need measure in the Wave data can calculate temperature variation, thereby can measure the wind field temperature.
The gas detection principle:
When light passes through gas, can be absorbed selectively by gas, be CH as Fig. 44Gas is in the abosrption spectrogram at different wave length place, and Fig. 5 is the abosrption spectrogram of steam at the different wave length place, and Fig. 6 is the abosrption spectrogram of oxygen at the different wave length place.As seen every kind of different gas has its different absorption peak, and according to the Beer law, the concentration relationship of absorption intensity and gas is: I=I0Exp (aλCL) (3)
In the formula: I-is through the emergent light intensity after the absorption of gas; λ-laser wavelength of incidence; The absorption coefficient of α-unit absorption length, unit concentration; C-gas concentration (ppm); L-is by the path (cm) of air chamber.
Can release by following formula:
Following formula just can calculate the concentration value of gas as can be seen at known input light intensity and absorption coefficient and when detecting output intensity.The signal that obtains when being illustrated in figure 7 as different vapour concentration, fine rule is a high concentration signal, concentration is high more, absorbs by force more, same, can inverse goes out the concentration of gas according to the trough degree of depth of absorption signal, thus the humidity of calculating.Switch by photoswitch, can measure the concentration of other gases such as gas, oxygen etc. with above principle.
Single-chip microcomputer is gathered the electric signal of opto-electronic conversion, calculates temperature, methane gas concentration, oxygen concentration and humidity information by above methods analyst.The native system design has realized that a cover detector detects the function of multiple parameter simultaneously, is convenient to installing and using of detecting instrument; Simultaneously, only beoptical cable 6, fiber grating 14 because be installed in the part at methane electrical generation scene, incident end optical fiber collimator 12 and exit end optical fiber collimator 13 these a few part optical elements, other parts are in Control Room, on-the-spot without any charged components and parts, need not frequent correction, also need not power supply, improved the security performance of methane electrical generation monitoring system.
During use, according to Fig. 1 system construction drawing connected system, at first regulate driving circuit, make its output as Fig. 2 darker curve pattern driving current signal, it is used for driving the Distributed Feedback Laser that three branch center wavelength are respectively 1653nm, 761nm, 1364nm, and laser instrument sends scan laser.Single-chip Controlling photoswitch timesharing (switching once for per 0.7 second in this system) selects laser instrument to enter follow-up light path.Scan laser enters through optical cable and installs and the air absorbing cavity that detects the scene, air absorbing cavity is an a pair of communication ordinary optic fibre collimating apparatus, (operating distance 5cm collimating apparatus commonly used in this system), light is coupled to the air of absorbing cavity environment from optical fiber, gas can fully absorb laser, and then coupled back into optical fibers.Enter fiber grating again through the light after the gas absorption, fiber grating adopts common communication single-mode fiber grating, the position that the centre wavelength of grating must be positioned at the laser scans scope and not overlap with gaseous absorption line, as A point among Fig. 2 is the grating center, apart from gas absorption peak B point certain distance and relatively poor or coincidence.The light that sees through fiber grating is exported in the mode of voltage signal through opto-electronic conversion, output waveform such as Fig. 3, shown in Figure 7 after gas absorption and grating effect, wherein among Fig. 3 two curves be not both since the temperature difference cause, among Fig. 7 two curves be not both since the gas concentration difference cause, can calculate temperature and gas concentration value according to these feature single-chip microcomputers.Single-chip microcomputer is gathered the voltage signal after the opto-electronic conversion, and the analytic signal feature compares with nominal data and to calculate gas concentration and temperature, and for example Fig. 8 is the temperature calibration curve, can draw the computing formula of temperature; Fig. 9 is the gas concentration calibration map, also can draw the concentration computing formula.
When photoswitch switched to another road laser instrument, the gas of detection changed thereupon, and detecting gas concentration when selecting 1653nm is gas density, was oxygen when selecting 761nm, was humidity when selecting 1364nm.
Single Chip Microcomputer (SCM) program needs to analyze the correlation calibration data when calculating output temperature and gas concentration value.When measuring temperature, at first temperature is demarcated in the grating wavelength corresponding relation, be illustrated in figure 8 as the corresponding nominal data figure of a grating wavelength and temperature.Can calculate temperature value according to the temperature wavelength computing formula that calibrates among the figure.When measurement gas, be respectively V as B, C, 3 signal voltage values of D among Fig. 2b, Vc, Vd, note
At first feed multiple standards gas, write down gas concentration and corresponding W value respectively, draw concentration and signal value curve equation, as shown in Figure 9.During detected gas, the data that the single-chip microcomputer analysis collects draw the W value, and the formula that draws by Fig. 9 just can calculate the output gas concentration value again.
As Figure 12 after temperature variation, there is error in the concentration computing formula that draws according to Fig. 9, because the absorption coefficient of gas is linear the change with temperature, as Figure 11, so need proofread and correct gas concentration value according to the temperature data that absorption coefficient and the grating of Figure 11 are measured, be the comparison diagram before and after proofreading and correct as thick line among Figure 12 and fine rule, proofread and correct the back effect and obviously change.
Claims (6)
1. optical fiber multi-parameter detector that is used for methane electrical generation, it is characterized in that it comprises light source sawtooth wave driving circuit and the dfb semiconductor laser instrument at the corresponding gas absorption of at least one road centre wavelength peak that is electrically connected with it, light path between described dfb semiconductor laser instrument and the probe is provided with photoswitch, be equipped with photodetector with described probe, all adopt optical cable to connect between dfb semiconductor laser instrument, photoswitch, probe and the photodetector, photodetector is electrically connected with single-chip microcomputer, and photoswitch is electrically connected by the photoswitch control line with single-chip microcomputer.
2. the optical fiber multi-parameter detector that is used for methane electrical generation according to claim 1 is characterized in that described dfb semiconductor laser instrument is 2, sends the laser of the centre wavelength of corresponding gas of difference and oxygen.
3. the optical fiber multi-parameter detector that is used for methane electrical generation according to claim 1 is characterized in that described dfb semiconductor laser instrument is 3, sends the laser of corresponding gas, oxygen and steam centre wavelength respectively.
4. the optical fiber multi-parameter detector that is used for methane electrical generation according to claim 1, it is characterized in that described probe comprises a holder, on holder, be relatively set with incident end optical fiber collimator and receiving end optical fiber collimator, between incident end optical fiber collimator and receiving end optical fiber collimator, be formed with air absorbing cavity, incident end optical fiber collimator is connected with optical cable, and the exit end optical fiber collimator is connected with outgoing optical fiber.
5. the optical fiber multi-parameter detector that is used for methane electrical generation according to claim 1 is characterized in that series connection is provided with fiber grating on the light path between receiving end optical fiber collimator and the outgoing optical fiber.
6. the optical fiber multi-parameter detector that is used for methane electrical generation according to claim 1 is characterized in that described single-chip microcomputer is 8051 single-chip microcomputers.
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| CN105738318A (en)* | 2016-02-18 | 2016-07-06 | 北京航天易联科技发展有限公司 | Environment humidity monitoring method and system for cultural relic preservation |
| CN109406450A (en)* | 2018-10-18 | 2019-03-01 | 山东大学 | Multiple absorption trace gas detection system |
| CN109540840A (en)* | 2019-01-22 | 2019-03-29 | 国网电力科学研究院武汉南瑞有限责任公司 | A kind of sulfur hexafluoride decomposition gas-detecting device |
| CN115420709A (en)* | 2022-07-21 | 2022-12-02 | 华南师范大学 | A Cadmium Ion Optical Fiber Sensor Based on Asymmetric Structure |
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Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN102226759A (en)* | 2011-03-21 | 2011-10-26 | 山东大学 | A micro-water detection system based on scanning method |
| CN105738318A (en)* | 2016-02-18 | 2016-07-06 | 北京航天易联科技发展有限公司 | Environment humidity monitoring method and system for cultural relic preservation |
| CN105738318B (en)* | 2016-02-18 | 2018-11-06 | 北京航天易联科技发展有限公司 | One kind being used for historical relic's protection ambient humidity monitoring method and its system |
| CN109406450A (en)* | 2018-10-18 | 2019-03-01 | 山东大学 | Multiple absorption trace gas detection system |
| CN109540840A (en)* | 2019-01-22 | 2019-03-29 | 国网电力科学研究院武汉南瑞有限责任公司 | A kind of sulfur hexafluoride decomposition gas-detecting device |
| CN115420709A (en)* | 2022-07-21 | 2022-12-02 | 华南师范大学 | A Cadmium Ion Optical Fiber Sensor Based on Asymmetric Structure |
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