CN111812060A - Methane concentration detection system - Google Patents
Methane concentration detection system Download PDFInfo
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- CN111812060A CN111812060A CN202010567355.4A CN202010567355A CN111812060A CN 111812060 A CN111812060 A CN 111812060A CN 202010567355 A CN202010567355 A CN 202010567355A CN 111812060 A CN111812060 A CN 111812060A
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- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 title claims abstract description 152
- 238000001514 detection method Methods 0.000 title claims abstract description 36
- 239000000835 fiber Substances 0.000 claims abstract description 69
- 239000013307 optical fiber Substances 0.000 claims abstract description 44
- 230000003287 optical effect Effects 0.000 claims abstract description 39
- 230000008878 coupling Effects 0.000 claims abstract description 36
- 238000010168 coupling process Methods 0.000 claims abstract description 36
- 238000005859 coupling reaction Methods 0.000 claims abstract description 36
- 238000012360 testing method Methods 0.000 claims description 50
- 238000000034 method Methods 0.000 claims description 12
- 238000007789 sealing Methods 0.000 claims description 10
- 230000007246 mechanism Effects 0.000 claims description 7
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 claims description 6
- 230000035945 sensitivity Effects 0.000 abstract description 11
- 238000005260 corrosion Methods 0.000 abstract description 7
- 230000007797 corrosion Effects 0.000 abstract description 7
- 238000004880 explosion Methods 0.000 abstract description 6
- 230000004044 response Effects 0.000 abstract description 6
- 239000007789 gas Substances 0.000 description 63
- 230000008859 change Effects 0.000 description 10
- 239000003245 coal Substances 0.000 description 5
- 238000005253 cladding Methods 0.000 description 4
- 239000007788 liquid Substances 0.000 description 4
- 239000012535 impurity Substances 0.000 description 3
- 238000005065 mining Methods 0.000 description 3
- 238000012986 modification Methods 0.000 description 3
- 230000004048 modification Effects 0.000 description 3
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000005530 etching Methods 0.000 description 2
- 238000009434 installation Methods 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 239000002121 nanofiber Substances 0.000 description 2
- 230000003044 adaptive effect Effects 0.000 description 1
- 229910002092 carbon dioxide Inorganic materials 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 239000000428 dust Substances 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 238000012544 monitoring process Methods 0.000 description 1
- 230000000149 penetrating effect Effects 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/41—Refractivity; Phase-affecting properties, e.g. optical path length
- G01N21/4133—Refractometers, e.g. differential
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21F—SAFETY DEVICES, TRANSPORT, FILLING-UP, RESCUE, VENTILATION, OR DRAINING IN OR OF MINES OR TUNNELS
- E21F17/00—Methods or devices for use in mines or tunnels, not covered elsewhere
- E21F17/18—Special adaptations of signalling or alarm devices
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- Mining & Mineral Resources (AREA)
- Life Sciences & Earth Sciences (AREA)
- Immunology (AREA)
- Analytical Chemistry (AREA)
- Biochemistry (AREA)
- General Health & Medical Sciences (AREA)
- General Physics & Mathematics (AREA)
- Physics & Mathematics (AREA)
- Pathology (AREA)
- Chemical & Material Sciences (AREA)
- Health & Medical Sciences (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Geochemistry & Mineralogy (AREA)
- Geology (AREA)
- Investigating Or Analysing Materials By Optical Means (AREA)
Abstract
The invention discloses a methane concentration detection system, which comprises: the light source is arranged on the ground and used for generating a light signal; the optical fiber coupling device comprises a plurality of optical fibers arranged under a mine, wherein the optical fibers are connected in parallel to form a first coupling point and a second coupling point, and the first coupling point is coupled with a light source through an optical cable; the fiber gratings are arranged corresponding to the optical fibers and connected with the corresponding optical fibers; a fiber grating demodulator coupled to the second coupling point by an optical cable; the computer is coupled with the fiber bragg grating demodulator and used for calculating the concentration of the methane under the mine according to the received optical signal; the first coupling point and the second coupling point are both provided with optical fiber couplers. The detection system has the advantages of high detection accuracy and sensitivity, quick response, electromagnetic interference resistance, corrosion resistance, explosion resistance, high reliability and remote control.
Description
Technical Field
The invention relates to the field of gas concentration detection, in particular to a methane concentration detection system.
Background
With the popularization of intelligence in the mining industry, various works in the mining industry have been intelligentized. The gas is one of five natural disasters in the coal mine, and the gas outburst causes great danger to the safety production of the coal mine, so how to intelligently detect the gas is the problem which needs to be solved urgently in modern mining.
The main component of gas under mine is methane (CH)4) The gas is an important industrial raw material and daily life gas, is extremely easy to explode in the air, is the primary hazard in coal mine accidents, has the lower limit of 5.3 percent and the upper limit of 15 percent in the atmosphere, and is considered to be one of the most main gases of the greenhouse effect. Real-time monitoring of downhole methane concentrations is therefore a significant safety concern. At present, methods for detecting the concentration of methane gas include semiconductor type, contact combustion type, electrochemical type, optical type and the like; these types of detection devices have low detection accuracy, low sensitivity, slow response, susceptibility to electromagnetic interference, poor corrosion resistance, and low reliability.
Disclosure of Invention
The present invention is directed to solve one of the problems of the prior art, and an object of the present invention is to provide a detection system of a methane concentration detection method, which has high detection accuracy, high sensitivity, rapid response, electromagnetic interference resistance, corrosion resistance, explosion resistance, high reliability, and remote control.
In order to achieve the above object, according to a methane concentration detection system of the present invention,
the method comprises the following steps:
the light source is arranged on the ground and used for generating a light signal;
the optical fiber coupling device comprises a plurality of optical fibers arranged under a mine, wherein the optical fibers are connected in parallel to form a first coupling point and a second coupling point, and the first coupling point is coupled with a light source through an optical cable;
the fiber gratings are arranged corresponding to the optical fibers and connected with the corresponding optical fibers;
a fiber grating demodulator coupled to the second coupling point by an optical cable; and
the computer is coupled with the fiber bragg grating demodulator and used for calculating the concentration of the methane under the mine according to the received optical signal;
the first coupling point and the second coupling point are both provided with optical fiber couplers.
Specifically, an optical signal is generated by an optical source, the optical signal propagates to the optical fiber coupler at a first coupling point along an optical cable, the optical signal propagates to the optical fiber coupler at a second coupling point along a plurality of optical fibers, then the optical signal is transmitted to the fiber grating demodulator along the optical cable, and finally the data is transmitted to a computer by the fiber grating demodulator; when the methane gas concentration at the detection position of the underground fiber grating is changed, the refractive index of the fiber grating is changed, the refraction direction of the optical signal is changed, so that a new optical signal is formed, the new optical signal is transmitted into a fiber grating demodulator on the ground through an optical cable, the new optical signal is demodulated by the fiber grating demodulator and transmitted into a computer, and the concentration of the underground methane gas is calculated by the computer through the change of the refractive index; the detection system has the advantages of high detection accuracy and sensitivity, quick response, electromagnetic interference resistance, corrosion resistance, explosion resistance, high reliability and remote control.
In one example of the present invention, the method further comprises:
the test box is internally provided with a test chamber, and the test chamber is sleeved outside the fiber bragg grating;
wherein, be equipped with the first blow vent and the second blow vent that are linked together with the test chamber on the test box, just first blow vent with all install the filter on the second blow vent.
In one example of the present invention,
and filters are arranged at the first vent hole and the second vent hole.
In one example of the present invention,
further comprising:
the test device comprises an air guide pipeline with an air guide chamber and two open ends, wherein the air guide pipeline is positioned in the test chamber, the air guide chamber is sleeved outside the fiber bragg grating, and the two ends of the air guide pipeline are respectively communicated with a filter at a first air vent and a filter at a second air vent.
In one example of the present invention,
the air guide duct includes:
a first half-pipe having a first half-lumen and a first connection aperture;
a second half-tube having a second half-lumen and a second connection hole;
the first half pipe and the second half pipe are connected with each other through a fastener for connecting the first connecting hole and the second connecting hole, so that the first half pipe cavity and the second half pipe cavity correspondingly and jointly form the air guide cavity.
In one example of the present invention,
still include positioning mechanism, positioning mechanism includes:
a positioning block formed on the first half pipe;
and the positioning groove is formed on the second half pipeline and is matched on the positioning block.
In one example of the invention, the first vent and the second vent are disposed on opposite sides of the test chamber and on sides remote from each other.
In one example of the invention, the optical fiber is arranged in the test chamber of the test box in a penetrating way and is connected with the test box in a sealing way through a sealing ring.
In one example of the present invention, the method further comprises:
and the plurality of alarms correspond to the plurality of optical fibers one by one and are coupled between the fiber bragg grating and the second coupling point.
In one example of the present invention, the fiber grating is fabricated by etching a surface thereof with hydrofluoric acid.
The following description of the preferred embodiments for carrying out the present invention will be made in detail with reference to the accompanying drawings so that the features and advantages of the present invention can be easily understood.
Drawings
FIG. 1 is a schematic diagram of a methane gas concentration detection system according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a test cassette coupled to an optical fiber according to an embodiment of the present invention;
FIG. 3 is a schematic structural view of an air guide channel according to an embodiment of the present invention;
fig. 4 is a flow chart of a methane gas concentration detection method according to an embodiment of the invention.
Reference numerals:
a detection system 100;
a light source 10;
an optical fiber 20;
a fiber grating 30;
a fiber grating demodulator 40;
a computer 50;
a fiber coupler 60;
a test cartridge 70;
the first air vent 71;
a second vent 72;
an air guide duct 73;
the air guide chamber 73A;
a first half-pipe 731;
a positioning block 7311;
a first half bore 7312;
a first lumen half 731A;
a first connection hole 731B;
the first connection end face 731C;
second half-pipe 732;
a positioning groove 7321;
a second half bore 7322;
a second lumen half 732A;
second connection holes 732B;
a second connection end surface 732C;
a fastener 733;
a test chamber 70A;
a filter 80;
an alarm 90;
an optical cable 110;
a first coupling point A;
a second coupling point B.
Detailed Description
The invention will be further explained with reference to the drawings.
The following description is provided with reference to the accompanying drawings to assist in a comprehensive understanding of various embodiments of the invention as defined by the claims. It includes various specific details to assist in this understanding, but these details should be construed as merely exemplary. Accordingly, those of ordinary skill in the art will recognize that changes and modifications of the various embodiments described herein can be made without departing from the scope of the invention, which is defined by the appended claims. Moreover, descriptions of well-known functions and constructions may be omitted for clarity and conciseness.
It will be apparent to those skilled in the art that the following descriptions of the various embodiments of the present invention are provided for illustration only and not for the purpose of limiting the invention as defined by the appended claims.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. Singular references include plural references unless there is a significant difference in context, scheme or the like between them.
Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and the present specification and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
In order to achieve the above object, a methane concentration detection system 100 according to the present invention, as shown in fig. 1 to 3,
the method comprises the following steps:
a light source 10 disposed on the ground for generating a light signal;
a plurality of optical fibers 20 arranged in the underground of the mine, wherein the plurality of optical fibers 20 are connected in parallel with each other and form a first coupling point A and a second coupling point B, and the first coupling point A is coupled with the light source 10 through an optical cable 110;
a plurality of fiber gratings 30 disposed corresponding to the optical fibers 20 and connected to the corresponding optical fibers 20;
a fiber grating demodulator 40 coupled to the second coupling point B through an optical cable 110; and
the computer 50 is coupled with the fiber grating demodulator 40 and used for calculating the concentration of the methane in the mine according to the received optical signals;
the first coupling point a and the second coupling point B are both provided with the fiber coupler 60.
It is understood that the optical signal is generated by the optical source 10, the optical signal propagates along the optical fiber cable 110 to the fiber coupler 60 at the first coupling point, the optical signal propagates along the plurality of optical fibers 20 to the fiber coupler 60 at the second coupling point, then propagates along the optical fiber cable 110 to the fiber grating demodulator 40, and finally propagates the data to the computer 50 by the fiber grating demodulator 40; when the methane gas concentration at the detection position of the underground fiber grating 30 changes, the refractive index of the fiber grating 30 changes and the refraction direction of the optical signal is changed so as to form a new optical signal, the new optical signal is transmitted into the fiber grating demodulator 40 on the ground through the optical cable 110, the new optical signal is demodulated by the fiber grating demodulator 40 and transmitted into the computer 50, and the concentration of the underground methane gas is calculated by the computer 50 through the change of the refractive index; the detection system has the advantages of high detection accuracy and sensitivity, quick response, electromagnetic interference resistance, corrosion resistance, explosion resistance, high reliability and remote control. It is noted that the above-ground methane gas concentration is a known quantity and is stored in advance in the computer.
In one example of the present invention, the method further comprises:
the test box 70, the test box 70 defines a test chamber 70A therein, and the test chamber 70A is sleeved outside the fiber grating 30;
the test box 70 is provided with a first vent 71 and a second vent 72 which are communicated with the test chamber 70A;
the fiber bragg grating 30 is arranged in the test box 70, so that the fiber bragg grating 30 can more accurately detect methane gas under a mine, the fiber bragg grating 30 can be protected, and the underground detection place is improved for the fiber bragg grating 30.
In one example of the present invention,
a filter 80 is arranged at each of the first vent 71 and the second vent 72;
the filter 80 can filter out impurities such as carbon dioxide and dust in the gas under the mine, so that the influence of the impurities on the measurement precision of the fiber bragg grating 30 is avoided.
In one example of the present invention,
further comprising:
the air guide pipeline 73 is provided with an air guide chamber 73A, two ends of the air guide pipeline 73 are opened, the air guide pipeline 73 is positioned in the test chamber, the air guide chamber 73A is sleeved on the outer side of the fiber bragg grating, and two ends of the air guide pipeline 73 are respectively communicated with the filter at the first air vent and the filter at the second air vent;
through setting up the gas guide pipeline 73 can make the mixed gas of mine underground air and methane get into in the gas guide pipeline 73 by first gas vent or second gas vent to detect the mixed gas by the fiber grating that is located in the gas guide pipeline 73, can be convenient for the flow of mixed gas through setting up the gas guide pipeline 73, can reduce fiber grating's detection space moreover, make fiber grating detect more accurately.
In one example of the present invention,
the air guide duct 73 includes:
a first half-channel 731, the first half-channel 731 having a first half-lumen 731A and a first connection aperture 731B;
a second half-duct 732, said second half-duct 732 having a second half-lumen 732A and a second connection hole 732B;
the first half-duct 731 and the second half-duct 732 are connected to each other by a fastener 733 connecting the first connecting hole 731B and the second connecting hole 732B, such that the first half-lumen 731A and the second half-lumen 732A correspond to form the airway cavity 73A together;
specifically, the first half pipe 731 has a first connecting end surface 731C, the second half pipe 732 has a second connecting end surface 732C, and the first connecting end surface 731C and the second connecting end surface 732C are both planar, and the first connecting end surface 731C and the second connecting end surface 732C can be attached to each other by a fastener 733; the fastener 733 may be a bolt, a screw, a rivet, or the like here.
More specifically, a first half-hole 7312 is provided on both sides of the first half-pipe 731, a second half-hole 7322 is provided at a position opposite to the second half-pipe 732 and the first half-hole 7312 of the first half-pipe 731, and a through-hole is formed by the first half-hole 7312 and the second half-hole 7322 together, the through-hole being adapted to cooperate with the optical fiber 20; in order to improve the sealing property of the air guide chamber 73A, a sealing ring is further interposed between the through hole and the optical fiber 20.
In one example of the present invention,
still include positioning mechanism, positioning mechanism includes:
a positioning block 7311, the positioning block 7311 being formed on the first half pipe 731;
a positioning groove 7321, the positioning groove 7321 being formed on the second half pipe 732 and fitted on the positioning block 7311;
specifically, the first connecting end surface 731C of the first half pipe 731 is provided with recesses at an outer circumference, the recesses are circumferentially spaced along the first half pipe 731, and two adjacent recesses form the positioning block 7311; protrusions are provided on the outer periphery of second connection end face 732C of second half pipe 732, and the protrusions are provided at intervals in the circumferential direction of second half pipe 732, and two adjacent protrusions form positioning grooves 7321.
The recess is integrally formed with the first half pipe 731, and the recess is formed by following a portion of the outer circumference of the first half pipe 731; the boss is integrally formed with second half-pipe 732.
More specifically, the positioning grooves 7321 are circumferentially spaced along the first connecting end surface 731C, the positioning blocks 7311 are circumferentially spaced along the second connecting end surface 732C, and the positioning blocks 7311 are in one-to-one correspondence with the positioning grooves 7321, so that the installation and connection of the air guide duct 73 can be facilitated by providing the positioning mechanism.
It is understood that since the test cassette 70 is disposed outside the air guide 73, the fiber grating 30 and the air guide 73 can be protected, and the structure of the test cassette 73 can be similar to that of the air guide 73 for easy installation and removal, and will not be described again when the optical fiber 20 passes through the air guide 73.
In one example of the present invention, the method further comprises:
a plurality of alarm devices 90, corresponding to the plurality of optical fibers 20 one by one, and coupled between the fiber bragg grating 30 and the second coupling point B;
that is, one alarm 90 is disposed in each of the optical fibers 20, so that when one of the optical fiber gratings 30 connected in parallel detects that the methane gas concentration at the detection point is greater than the preset methane gas concentration, the alarm 90 connected in series with the optical fiber grating 30 gives an alarm;
specifically, when the methane gas concentration at the detection position of the fiber grating 30 under the mine is changed, the refractive index of the fiber grating 30 is changed to change the refraction direction of the optical signal so as to form a new optical signal, the new optical signal is transmitted into the fiber grating demodulator 40 on the ground through the optical cable 110, the fiber grating demodulator 40 transmits the methane gas concentration signal with the changed refractive index under the mine into the computer 50, and the computer 50 feeds the methane gas concentration signal back to the alarm 90, wherein when the methane gas concentration is greater than the preset methane gas concentration, the alarm 90 gives an alarm. The detection system has the advantages of high detection accuracy and sensitivity, quick response, electromagnetic interference resistance, corrosion resistance, explosion resistance, high reliability and remote control.
In one example of the present invention, the optical fiber 20 is inserted into the testing chamber 70A of the testing box 70, and is hermetically connected to the testing box 70 through a sealing ring;
specifically, be equipped with first through hole and the second through hole on a straight line on test box 70, all be equipped with the sealing washer in first through hole and second through hole, optic fibre 20 passes in proper order the sealing washer of first through hole and second through hole, can prevent through setting up the sealing washer that the gas under the mine from getting into test chamber 70A by the junction of optic fibre 20 with test box 70 in, prevent promptly that impurity from getting into test chamber 70A by first through hole and second through hole to influence the measuring accuracy nature of fiber grating 30.
In one example of the present invention, the first vent 71 and the second vent 72 are disposed on opposite sides of the testing chamber 70A and away from each other, that is, the first vent 71 and the second vent 72 are disposed on opposite sides of the testing chamber 70A and offset from each other, so that the air under the mine must pass through the fiber grating 30 after entering the testing chamber 70A from the first vent 71 and then be discharged from the second vent 72, or enter the testing chamber 70A from the second vent 72 and then be discharged from the first vent 71; the methane gas concentration in the test chamber 70A formed by the test cartridge 70 is thus highly consistent with the methane gas concentration under the mine.
In an example of the present invention, the fiber grating 30 is manufactured by etching the surface of the fiber grating 30 with hydrofluoric acid, for example, the sensitivity of the manufactured micro-nano fiber grating 30 with the diameter of 800nm can reach 993nm/RIU, which is increased by 10 times compared with the fiber grating 30 with the etched cladding. Compared with the method before processing, the method has the characteristics of high sensitivity, corrosion resistance, explosion resistance, easiness in remote control and the like.
A method for detecting methane concentration according to the present invention, as shown in fig. 4, includes the following steps:
s10: obtaining the refractive index of the mixture of air and methane gas on the ground;
s20: detecting the refractive index of the fiber grating 30 mixed with the methane gas in the air under the mine through the fiber grating 30;
s30: and calculating the concentration of the methane gas under the mine according to the change of the mixed refractive index of the air and the methane gas under the mine and the change of the mixed refractive index of the air and the methane gas on the ground.
Specifically, the invention deduces the change of the refractive index of methane gas from the ground to the underground coal mine according to the variable quantities of the optical fiber grating 30 on the ground and the underground coal mine wavelength respectively, determines whether the underground methane concentration exceeds the standard or not according to the change of the refractive index, and presets different methane concentration alarm values at different underground positions.
The specific calculation principle is as follows:
the center wavelength (bragg wavelength) of the fiber grating 30 of uniform period satisfies:
λB＝2neffΛ(1)
in the formula: lambda [ alpha ]BIs the central wavelength of the optical fiber, neffIs the effective index, Λ grating period.
As shown in the formula (1), the center wavelength is represented by neffAnd Λ is varied. The change of the refractive index of the external medium where the fiber grating 30 is located can result in the effective refractive index n of the fiber core of the fiber grating 30effA change occurs. Amplitude of wavelength drift DeltaLambdaBChange of effective refractive index delta n of coreeffIn a relationship of
ΔλB＝2ΔneffΛ (2)
From equation (2) and the relationship between wavelength and refractive index, one can deduce:
ΔλB＝2Λ·kn·Δn1＝k·Δn1(3)
in the formula,. DELTA.n1Is the refractive index variation of the environmental cladding; and K is the sensitivity of the resonant wavelength of the micro-nano fiber grating 30 changing with the ambient refractive index. k is the grid period Λ and the sensitivity k of the effective index to changes in the index of the surrounding claddingnAs a function of (c). When the concentration of a known liquid or gas to be measured changes, the refractive index of the known liquid or gas changes, and the known liquid or gas changes in a linear manner with the mass concentration C of the known liquid or gas. Let refractive index variable Δ n1K between the concentration and the concentration variable Δ CcThen, then
Δn1＝kC·ΔC (4)
In the formula: k is a radical ofCDepending on the kind of gas, an
Therefore (4) becomes:
according to the difference of methane alarm concentration at each position under a mine, the methane concentration alarm value at each position is accurately set, and according to the mixed refractive index of air and methane:
C1na+C2nb＝nc(6)
C1+C2＝1 (7)
in the formula: n isaIs the refractive index of air, nbIs the refractive index of methane, ncIs the refractive index of the gas after mixing, C1Is the air concentration, C2Is the methane concentration.
When the methane concentration test alarm is placed on the ground, a change base point of methane and air is set, and the methane concentration C20.02% of C199.8%, the concentration of methane and air is the data pre-adjusted during the production process, and the refractive index n of the mixed air at the surface is not entered into the well along with the equipment in order to make the equipment more accurate, and the mixed air has the refractive index n at the surfacec1Comprises the following steps:
0.02％nb+99.98％na＝nc1(8)
the methane concentration test alarm is placed underground, and when the methane concentration is too high, the alarm sounds a whistle, the refractive index nc2Comprises the following steps:
C2nb+C1na＝nc2(9)
the refractive index Δ n of the change1＝nc2-nc1
Δn1＝C2nb+C1na-0.02％nb-99.98％na
Δn1＝(C2-0.02％)(nb-na)
In one example of the invention, the methane gas concentration is calculated downhole in the mine according to the following formula:
in the formula, C2The concentration of methane gas under a mine; delta lambdaBIs the amplitude of the wavelength drift; k is a function of the grid period Λ and the sensitivity kn of the effective refractive index to changes in the refractive index of the ambient cladding; 0.02% is the concentration of methane gas on the ground.
In one example of the present invention, the method further comprises:
when the concentration of the methane gas in the mine is detected to be larger than the preset concentration value of the methane gas, an alarm is generated, namely, the preset concentration value of the methane gas is a mine methane gas safety critical value, and when the calculated concentration of the methane gas is larger than the preset concentration value of the methane gas, the alarm is generated to prompt the safety operation in the mine.
In one example of the present invention, the step S20 includes:
a plurality of detection points under the mine are simultaneously detected through the fiber bragg grating 30, and when the concentration of methane gas at one detection point is greater than the preset concentration of methane gas, an alarm is generated;
specifically, the plurality of detection points are arranged under the mine, so that the concentration of methane gas under the mine can be detected more accurately, and an alarm can be generated as long as the concentration of methane gas at one detection point is greater than a preset value of the concentration of methane gas, so that the alarm under the mine is safer and more reliable.
The above description is intended to be illustrative of the present invention and not to limit the scope of the invention, which is defined by the claims appended hereto.
Those skilled in the art will appreciate that various features of the various embodiments of the invention described hereinabove may be omitted, added to, or combined in any manner, respectively. Moreover, simple modifications and structural modifications that are adaptive and functional to those skilled in the art are within the scope of the present invention.
While the invention has been shown and described with reference to various embodiments, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention as defined by the appended claims.
Claims (10)
1. A methane concentration detection system is characterized in that,
the method comprises the following steps:
a light source (10) disposed on the ground for generating a light signal;
the optical fiber coupling device comprises a plurality of optical fibers (20) arranged under a mine, wherein the optical fibers (20) are connected in parallel with one another to form a first coupling point (A) and a second coupling point (B), and the first coupling point (A) is coupled with the light source (10) through an optical cable (110);
a plurality of fiber gratings (30) provided corresponding to the optical fibers (20) and connected to the corresponding optical fibers (20);
a fiber grating demodulator (40) coupled to the second coupling point (B) by an optical cable (110); and
a computer (50) coupled to the fiber grating demodulator (40) for calculating the concentration of methane in the mine well according to the received optical signal;
wherein, the first coupling point (A) and the second coupling point (B) are both provided with optical fiber couplers (60).
2. The methane concentration detecting system according to claim 1,
further comprising:
the test box (70), the test box (70) defines a test chamber (70A) inside, and the test chamber (70A) is sleeved outside the fiber grating (30);
wherein, the test box (70) is provided with a first vent (71) and a second vent (72) which are communicated with the test chamber (70A).
3. The methane concentration detecting system according to claim 1,
and filters (80) are arranged at the first vent (71) and the second vent (72).
4. The methane concentration detecting system according to claim 1,
further comprising:
have air guide cavity (73A) and both ends open air guide pipeline (73), air guide pipeline (73) are located in test cavity (70A) and air guide cavity (73A) cover establish the outside of fiber grating (30), the both ends of air guide pipeline (73) are linked together with filter (80) of first air vent (71) department and filter (80) of second air vent (72) department respectively.
5. The methane concentration detecting system according to claim 1,
the air guide duct (73) includes:
a first half-channel (731), the first half-channel (731) having a first half-lumen (731A) and a first connection hole (731B);
a second half duct (732), the second half duct (732) having a second half lumen (732A) and a second connection hole (732B);
the first half-duct (731) and the second half-duct (732) are connected to each other by a fastener (733) connecting the first connecting hole (731B) and the second connecting hole (732B) so that the first half-lumen (731A) and the second half-lumen (732A) correspondingly form the air guide chamber (73A) together.
6. The methane concentration detection system according to claim 5,
still include positioning mechanism, positioning mechanism includes:
a locating block (7311), the locating block (7311) being formed on the first half pipe (731);
a positioning groove (7321), the positioning groove (7321) being formed on the second half pipe (732) and being fitted on the positioning block (7311).
7. The methane concentration detecting system according to claim 1,
the first vent (71) and the second vent (72) are disposed on opposite sides of the test chamber (70A) and away from each other.
8. The methane concentration detection system according to claim 2,
the optical fiber (20) penetrates through a testing chamber (70A) of the testing box (70) and is connected with the testing box (70) in a sealing mode through a sealing ring.
9. The methane concentration detecting system according to claim 1,
further comprising:
and the alarms (90) correspond to the optical fibers (20) one by one and are coupled between the fiber bragg grating (30) and the second coupling point (B).
10. The methane concentration detecting system according to claim 1,
the fiber grating (30) is manufactured by corroding the surface of the fiber grating by hydrofluoric acid.
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| CN202010567355.4A CN111812060A (en) | 2020-06-19 | 2020-06-19 | Methane concentration detection system |
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| CN202010567355.4A CN111812060A (en) | 2020-06-19 | 2020-06-19 | Methane concentration detection system |
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Application publication date: 20201023 |