CN118223953A - Coal mine explosion monitoring and early warning method and device based on multi-core optical fibers - Google Patents

Abstract

The invention provides a coal mine explosion monitoring and early warning method and device based on multi-core optical fibers, which are characterized in that a plurality of multi-core optical fibers are sequentially connected in series, a gas sensing module is arranged between two adjacent multi-core optical fibers, the multi-core optical fiber at the tail end is divided into a plurality of single-core optical fibers through a coupler, each single-core optical fiber is respectively connected with a demodulator, the demodulator is connected with an upper computer, the gas concentration is sensed by the gas sensing module, the demodulator emits and receives and withdraws reflection light, measurement data of the gas concentration, the temperature, distributed strain and vibration state are obtained according to received optical signals, and the upper computer processes and analyzes the measurement data and makes corresponding early warning; the method and the device realize the simultaneous monitoring of a plurality of external factors in the coal mine tunnel, thereby improving the accuracy of explosion early warning in the coal mine tunnel.

Description

A coal mine explosion monitoring and early warning method and device based on multi-core optical fiber

Technical Field

The present invention relates to the technical field of coal mine safety monitoring, and in particular to a coal mine explosion monitoring and early warning method and device based on multi-core optical fiber.

Background technique

Coal mines often contain a certain concentration of gas. The main components of gas include hydrocarbon compounds such as carbon monoxide, hydrogen sulfide and methane. Gas explosions are often related to environmental factors in mine pipelines. Due to poor air circulation, gas is easy to accumulate; at the same time, temperature, humidity, air pressure, etc. will also affect the accumulation of gas. Once the concentration of gas exceeds the standard, it will cause a gas explosion accident, which will produce great destructive power. It will not only destroy the tunnels and equipment facilities in the coal mine area, but also bring huge economic losses. Even after the explosion, toxic and harmful gases will be produced, causing casualties. Gas outbursts can be divided into two forms: ordinary outbursts and special outbursts. Ordinary outbursts refer to the slow, uniform and persistent outburst of gas from very fine cracks on the surface of coal seams or rock formations. Its outburst area is wide and the time is long, which is the main form of gas outburst. Special outbursts, such as gas eruption and coal or rock and gas outbursts. Gas eruption refers to the phenomenon of a large amount of gas suddenly erupting, which can be long or short (several days or years), and the amount of gas erupted every day and night can reach hundreds of cubic meters; coal or rock and gas outburst, can suddenly erupt a large amount of gas and coal in a moment (a few seconds or minutes), and can even erupt tens of thousands of tons of coal and rock and millions of cubic meters of gas in 1 minute, accompanied by strong sounds and strong impact. When high-concentration gas encounters a high-temperature heat source, a gas explosion will occur. Therefore, for gas explosions in coal mines, it is necessary not only to monitor the gas concentration, but also to monitor and warn of special eruptions. The phenomenon of special eruptions can be judged based on the distributed strain and vibration conditions of the roof of the coal mine tunnel, so it is also necessary to monitor the stress and vibration of the roof. In addition, comprehensive monitoring of the ambient temperature is also required.

At present, the main method for preventing and controlling mine explosion accidents is to monitor the gas concentration underground. The gas concentration monitoring sensors currently mainly include safety lamp type, catalytic combustion type, thermal conductivity type, electrochemical type, gas sensitive semiconductor, optical interference type, non-dispersive infrared absorption type, sound velocity difference type, ionization type, gas chromatography type, pressure type and volumetric type sensors; with the advancement of semiconductor laser technology, methane sensors based on laser technology have achieved rapid development in recent years and gradually entered the industrial field.

However, excessive gas concentration is only one of the necessary conditions for causing mine explosions. If other conditions for mine explosions, such as high-temperature fire sources, are not met, even if the gas concentration exceeds the limit, it will not cause an explosion. Moreover, since the methane sensor is installed near the explosive site, it is easy to cause direct damage when an explosion occurs, and data cannot be collected. Therefore, the traditional gas monitoring and alarm method cannot accurately warn before the mine explosion occurs, nor can it accurately alarm after the explosion occurs. In addition to the gas monitoring method, mine explosion monitoring methods based on smoke, temperature, vibration and other characteristics have also been applied. However, since the current monitoring data and methods are still relatively simple, it is impossible to detect multiple environmental factors at the same time, and mine explosions are often affected by multiple different external factors, the alarm accuracy of the existing monitoring methods is not very ideal.

In view of this, overcoming the defects of the preset technology is an urgent problem to be solved in the field of this technology.

Summary of the invention

The technical problem to be solved by the present invention is how to monitor multiple external factors in a coal mine tunnel at the same time, thereby improving the accuracy of explosion warning in the coal mine tunnel.

In the first aspect, a coal mine explosion monitoring and early warning device based on a multi-core optical fiber is provided, comprising: a plurality of multi-core optical fibers 1, a first coupler 2, a gas sensor module 3, a demodulator 4 and a host computer 5, wherein:

The plurality of multi-core optical fibers 1 are connected in series in sequence, and the gas sensing module 3 is arranged between two adjacent multi-core optical fibers 1;

The multi-core optical fiber 1 at the tail end is divided into a plurality of single-core optical fibers 11 by the first coupler 2, all of the single-core optical fibers 11 are connected to the demodulator 4, the demodulator 4 is connected to the host computer 5, and a plurality of scattering units are arranged in the multi-core optical fiber 1 along the axial direction;

The demodulator 4 is used to send optical signals to the multiple multi-core optical fibers 1 connected in series. The scattering unit in the multi-core optical fiber 1 reflects the optical signal back to the demodulator 4. The gas sensor module 3 is used to change the wavelength of the optical signal according to the change of gas concentration. The demodulator 4 is used to obtain measurement data of gas concentration, temperature, distributed strain and vibration state according to the received optical signal. The host computer 5 is used to process and analyze the measurement data and make corresponding warnings.

Preferably, the coal mine explosion monitoring and early warning device based on multi-core optical fiber further includes: a second coupler 6 and a flange 7, wherein:

In two adjacent multi-core optical fibers 1, one end of the two adjacent multi-core optical fibers 1 for butt connection is divided into a plurality of single-core optical fibers 11 by the second coupler 6;

In two adjacent multi-core optical fibers 1, one end of the gas sensing module 3 is connected to one of the single-core optical fibers 11 of one of the multi-core optical fibers 1 through a flange 7, and the other end of the gas sensing module 3 is connected to one of the single-core optical fibers 11 of the other multi-core optical fiber 1 through a flange 7; the remaining single-core optical fibers 11 of one of the multi-core optical fibers 1 and the remaining single-core optical fibers 11 of the other multi-core optical fiber 1 are connected one-to-one through the flange 7.

Preferably, the multi-core optical fiber 1 includes an intermediate fiber core 12 and a plurality of outer ring fiber cores 13, wherein:

The plurality of outer ring fiber cores 13 are distributed around the circumference of the middle fiber core 12 .

Preferably, the demodulator 4 includes a temperature demodulation module 41, a gas concentration demodulation module 42, a strain demodulation module 43 and a vibration demodulation module 44, wherein:

The intermediate fiber core 12 is connected to the temperature demodulation module 41, and the temperature demodulation module 41 is used to obtain temperature measurement data according to the received optical signal;

At least one outer ring fiber core 13 is connected to the gas concentration demodulation module 42, and the gas concentration demodulation module 42 is used to obtain measurement data of gas concentration according to the received optical signal;

At least one outer ring fiber core 13 is connected to the strain demodulation module 43, and the strain demodulation module 43 is used to obtain measurement data of distributed strain according to the received optical signal;

At least one outer ring fiber core 13 is connected to the vibration demodulation module 44, and the vibration demodulation module 44 is used to obtain measurement data of the vibration state according to the received optical signal.

Preferably, the coal mine explosion monitoring and early warning device based on multi-core optical fiber further includes a protective shell 8, wherein:

The coal mine explosion monitoring and early warning device based on multi-core optical fiber is used to be arranged on the roof 9 of the coal mine tunnel;

The protective shell 8 is used to be arranged on the top plate 9 and cover the serial connection of two adjacent multi-core optical fibers 1;

The protective shell 8 is provided with a leak hole 83 to ensure that the serial connection point of the two multi-core optical fibers 1 is in contact with the outside air.

Preferably, the host computer 5 includes a data receiving module 51, a data processing module 52 and a data early warning module 53, wherein:

The data receiving module 51, the data processing module 52 and the data early warning module 53 are connected in sequence;

The data receiving module 51 is used to receive the measurement data from the demodulator 4 and store the measurement data;

The data processing module 52 is used to process and analyze the measurement data, and send the processed and analyzed measurement data to the data early warning module 53;

The data warning module 53 is used to compare the processed and analyzed measurement data with the corresponding threshold value and issue a corresponding warning.

In a second aspect, a coal mine explosion monitoring and early warning method based on a multi-core optical fiber is used for application in the coal mine explosion monitoring and early warning device based on a multi-core optical fiber, comprising:

The demodulator 4 sends an optical signal to the multiple multi-core optical fibers 1 connected in series, and the scattering unit in the multi-core optical fiber 1 reflects the optical signal back to the demodulator 4. The gas sensor module 3 is used to change the wavelength of the optical signal according to the change of gas concentration;

The demodulator 4 obtains the measurement data of gas concentration, temperature, distributed strain and vibration state according to the received optical signal, and sends the measurement data to the host computer 5;

The host computer 5 processes and analyzes the measurement data and makes corresponding warnings.

Preferably, the corresponding calculation formula for temperature is:

Wherein, T is the current temperature, T ₀ is the initial temperature, h is Planck's constant, k is the coefficient, Δv is the frequency shift, R(T) is the anti-Stokes to Stokes intensity ratio of Raman scattered light at the current temperature, and R(T ₀ ) is the anti-Stokes to Stokes intensity ratio of Raman scattered light at the initial temperature;

The distributed strain is compensated by temperature to obtain the change of distributed strain. The corresponding calculation formula is:

Where Δε is the strain difference, _CT is the temperature sensitivity coefficient, and _Cε is the strain sensitivity coefficient.

Preferably, the host computer 5 processes and analyzes the measurement data and makes corresponding warnings, specifically including:

Determining whether the gas is a special outflow according to the gas concentration, distributed strain and vibration state;

When it is determined that the gas is gushing out specially, it is determined whether the temperature is greater than or equal to the temperature threshold; when the temperature is greater than or equal to the temperature threshold, the host computer 5 issues an explosion warning; when the temperature is less than the temperature threshold, the host computer 5 issues a special gas gushing warning;

When it is determined that the gas is not a special outflow, it is determined whether the gas concentration is greater than or equal to the concentration threshold; when the gas concentration is less than the concentration threshold, the host computer 5 does not issue an early warning; when the gas concentration is greater than or equal to the concentration threshold, it is determined whether the temperature is greater than or equal to the temperature threshold; when the temperature is less than the temperature threshold, the host computer 5 issues a gas extraction prompt; when the temperature is greater than or equal to the temperature threshold, the host computer 5 issues an explosion early warning.

Preferably, judging whether the gas is a special outflow according to the gas concentration, distributed strain and vibration state specifically includes:

Obtaining a correlation coefficient between the gas concentration and the distributed strain and the vibration state, and determining whether the correlation coefficient is greater than or equal to a coefficient threshold;

When the correlation coefficient is less than the coefficient threshold, it is determined that the gas is not a special outflow;

When the correlation coefficient is greater than or equal to the coefficient threshold, it is determined whether the measurement data of the distributed strain is greater than or equal to the strain threshold, and whether the measurement data of the vibration state is greater than or equal to the vibration threshold; when the measurement data of the distributed strain is greater than or equal to the strain threshold, and the measurement data of the vibration state is greater than or equal to the vibration threshold, the gas is determined to be a special outflow, otherwise, the gas is determined not to be a special outflow.

The present invention provides a coal mine explosion monitoring and early warning method and device based on multi-core optical fiber. The method and device are characterized by connecting a plurality of multi-core optical fibers in series in sequence, arranging a gas sensing module between two adjacent multi-core optical fibers, and dividing the multi-core optical fiber at the tail end into a plurality of single-core optical fibers through a coupler. All the single-core optical fibers are connected to the demodulator, and the demodulator is connected to the host computer. The gas concentration is sensed by the gas sensing module, and the demodulator transmits and receives reflected light. According to the received optical signal, the measurement data of gas concentration, temperature, distributed strain and vibration state are obtained. The measurement data is processed and analyzed by the host computer and a corresponding early warning is issued. The method realizes the simultaneous monitoring of a plurality of external factors in the coal mine tunnel, thereby improving the accuracy of explosion early warning in the coal mine tunnel.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments of the present invention. Obviously, the drawings described below are only some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

FIG1 is a schematic structural diagram of a coal mine explosion monitoring and early warning device based on a multi-core optical fiber provided in an embodiment of the present invention;

FIG2 is a schematic structural diagram of another coal mine explosion monitoring and early warning device based on multi-core optical fiber provided in an embodiment of the present invention;

3 is a schematic diagram of the connection of a flange of a coal mine explosion monitoring and early warning device based on a multi-core optical fiber provided by an embodiment of the present invention;

4 is a schematic structural diagram of a gas sensor module of a coal mine explosion monitoring and early warning device based on a multi-core optical fiber provided in an embodiment of the present invention;

5 is a cross-sectional view of a multi-core optical fiber of a coal mine explosion monitoring and early warning device based on a multi-core optical fiber provided by an embodiment of the present invention;

6 is a partial structural schematic diagram of a coal mine explosion monitoring and early warning device based on a multi-core optical fiber provided in an embodiment of the present invention;

7 is a bonding arrangement diagram of a coal mine explosion monitoring and early warning device based on a multi-core optical fiber provided in an embodiment of the present invention;

8 is a schematic structural diagram of a protective shell of a coal mine explosion monitoring and early warning device based on a multi-core optical fiber provided by an embodiment of the present invention;

9 is a schematic diagram of the installation of a coal mine explosion monitoring and early warning device based on a multi-core optical fiber in a tunnel according to an embodiment of the present invention;

10 is a schematic structural diagram of another coal mine explosion monitoring and early warning device based on multi-core optical fiber provided in an embodiment of the present invention;

11 is a method flow chart of a coal mine explosion monitoring and early warning method based on multi-core optical fiber provided in an embodiment of the present invention;

12 is a flow chart of a method for processing and analyzing measurement data of a coal mine explosion monitoring and early warning method based on a multi-core optical fiber according to an embodiment of the present invention;

13 is a flow chart of a method for determining a special outburst of a coal mine explosion monitoring and early warning method based on a multi-core optical fiber according to an embodiment of the present invention;

The diagram numbers are as follows:

Multi-core optical fiber 1; single-core optical fiber 11; intermediate fiber core 12; outer ring fiber core 13; first coupler 2; gas sensor module 3; demodulator 4; temperature demodulation module 41; gas concentration demodulation module 42; strain demodulation module 43; vibration demodulation module 44; host computer 5; data receiving module 51; data processing module 52; data early warning module 53; second coupler 6; flange 7; protective shell 8; abutment surface 81; receiving groove 82; leak hole 83; top plate 9; coil 10.

Detailed ways

In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

In the description of the present invention, the terms "inside", "outside", "longitudinal", "lateral", "upper", "lower", "top", "bottom" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and do not require that the present invention must be constructed and operated in a specific orientation. Therefore, they should not be understood as limitations on the present invention.

The terms "first", "second", etc. in the present invention are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "plurality" means two or more.

In the present invention, unless otherwise clearly specified and limited, the term "connection" should be understood in a broad sense. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection or an indirect connection through an intermediate medium. In addition, the term "coupling" can be a way of achieving electrical connection for signal transmission.

In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

Embodiment 1:

This embodiment 1 provides a coal mine explosion monitoring and early warning device based on multi-core optical fiber, as shown in FIG1 , comprising: a plurality of multi-core optical fibers 1, a first coupler 2, a gas sensor module 3, a demodulator 4 and a host computer 5, wherein:

The plurality of multi-core optical fibers 1 are connected in series, and the gas sensing module 3 is arranged between two adjacent multi-core optical fibers 1. The multi-core optical fiber 1 at the tail end is divided into a plurality of single-core optical fibers 11 by the first coupler 2, and all the single-core optical fibers 11 are connected to the demodulator 4, and the demodulator 4 is connected to the host computer 5. A plurality of scattering units are arranged in the multi-core optical fiber 1 along the axial direction.

In this embodiment, the scattering units are distributed in the axial direction of the multi-core optical fiber 1, that is, there is at least one scattering unit at a certain distance on the multi-core optical fiber 1, ensuring that most positions on the multi-core optical fiber 1 can reflect the optical signal at any time, thereby obtaining the environmental conditions corresponding to most positions on the multi-core optical fiber 1. Since the scattering unit is a tiny unit inside the multi-core optical fiber 1 and is not arranged outside the multi-core optical fiber, it is not drawn in the drawings of the specification.

In this embodiment, the coal mine explosion monitoring and early warning device based on multi-core optical fiber can be used in coal mine tunnels to measure the temperature, distributed strain, gas concentration and vibration state environmental parameters in the coal mine tunnels, and analyze and process the environmental parameters obtained by the measurement to provide explosion early warning; in actual application, the coal mine explosion monitoring and early warning device based on multi-core optical fiber can be set at the top of the coal mine tunnel.

In this embodiment, since it is necessary to measure multiple parameters in the coal mine tunnel at the same time, it is necessary to set up multiple different measuring devices for measurement, and each measuring device requires one or more corresponding single-core optical fibers 11 to be connected. Therefore, this embodiment adopts multi-core optical fiber 1 for optical signal transmission. Each fiber core in the multi-core optical fiber 1 is divided into multiple single-core optical fibers 11 through a coupler, and each single-core optical fiber 11 is connected to the corresponding measuring device, thereby meeting the hardware requirements of multiple measuring devices.

At least four fiber cores are used in the multi-core optical fiber 1 , one of which is a middle fiber core 12 , and the other fiber cores are outer ring fiber cores 13 , which are distributed around the middle fiber core 12 .

In this embodiment, the multi-core optical fiber 1 at the head end is provided with a coil 10 , and the coil 10 can be separated from the multi-core optical fiber 1 by a coupler to form a plurality of single-core optical fibers 11 , and the plurality of single-core optical fibers 11 are wound together into the coil 10 .

In addition, in this embodiment, the gas concentration measurement of gas through optical fiber requires engraving corresponding gratings on the optical fiber and coating the corresponding gas-sensitive material on the surface of the optical fiber grating. When the gas concentration of the external gas changes, it will cause a corresponding impact on the wavelength of the optical signal in the optical fiber engraved with the grating. According to the change of the wavelength of the optical signal, the gas concentration of the gas can be obtained. Therefore, the gas sensor module 3 in this embodiment can select one path in the outer ring fiber core 13 in the multi-core optical fiber, set the corresponding fiber core engraved with the grating on this optical path, and coat the corresponding gas-sensitive material, so as to realize the measurement of the gas concentration in the lane.

It is worth mentioning that this embodiment takes into account the length of the tunnel itself. When the tunnel itself is long, it may be necessary to monitor the gas concentration at multiple locations in the tunnel in real time. Therefore, in this embodiment, multiple multi-core optical fibers 1 are connected in series, and the gas sensor module 3 is set between each adjacent two multi-core optical fibers 1, so as to ensure that the entire coal mine explosion monitoring and early warning device based on multi-core optical fibers is provided with a corresponding gas sensor module 3 at every length, thereby improving the accuracy of gas concentration measurement. In addition, the use of multiple multi-core optical fibers 1 can also increase the overall length of the device, allowing the demodulator 4 and the host computer 5 to be away from the area that needs to be monitored, so as to avoid being directly destroyed when an explosion occurs and being unable to issue an early warning, thereby improving the effectiveness and accuracy of the early warning.

The demodulator 4 is used to send optical signals to the multiple multi-core optical fibers 1 connected in series. The scattering units in the multi-core optical fibers 1 reflect the optical signals back to the demodulator 4. The gas sensor module 3 is used to change the wavelength of the optical signal according to the change in gas concentration. The demodulator 4 is used to obtain measurement data of gas concentration, temperature, distributed strain and vibration state according to the received optical signals. The host computer 5 is used to process and analyze the measurement data and make corresponding warnings.

In this embodiment, after the demodulator 4 sends an optical signal to the multi-core optical fiber 1, the optical signal is transmitted in each fiber core of the multi-core optical fiber 1. During the transmission process, the optical signal will change due to the external temperature, distributed strain and vibration state, and the gas sensor module 3 will have a corresponding impact on the optical signal due to the change in the external gas concentration. After the optical signal is received by the corresponding measuring device in the demodulator 4, the corresponding measuring device can obtain the corresponding measurement data based on the optical signal, and then send the measurement data to the host computer 5. The host computer 5 will perform corresponding analysis and processing on the measurement data, and compare it with the corresponding threshold value, so as to obtain a corresponding warning.

In this embodiment, the warning may be: no warning, special outburst warning and explosion warning; in this embodiment, when the gas concentration is higher than a preset threshold and the temperature is also higher than the preset threshold, an explosion warning is issued; when a special outburst is determined to occur and the temperature is higher than the preset threshold, an explosion warning is also issued; when only a special outburst is determined to occur and the temperature is not higher than the preset threshold, a special outburst warning is issued; wherein, special outburst may refer to: a large amount of gas is suddenly outburst, the outburst time may be long or short, and may last for several days or years, and the outburst volume may reach hundreds of cubic meters per day and night; it may also refer to the coal (rock) and gas outburst phenomenon, which is sufficient to cause a sudden explosion in a few seconds or A large amount of gas, coal or rock may suddenly gush out within a few minutes, and even tens of thousands of tons of coal and rock may gush out within 1 minute, or millions of cubic meters of gas may gush out within 1 minute, accompanied by strong noise and powerful impact dynamic phenomenon. When millions of cubic meters of gas or high-concentration gas encounters a high-temperature heat source, a gas explosion will occur. Therefore, in this embodiment, when it is judged that the gas concentration and temperature exceed the threshold, a corresponding explosion warning is required. When it is judged that there is a special gushing phenomenon and the temperature exceeds the threshold, a corresponding explosion warning is also required. When only a special gushing phenomenon is judged to exist, a corresponding special gushing warning is required. When none of the above phenomena occur, it means it is normal and no warning is issued.

In this embodiment, considering that a multi-core optical fiber 1 is used, but a single-core optical fiber 11 engraved with a grating is required to measure the gas concentration, and the corresponding gas-sensitive material needs to be coated on the optical fiber grating, in this embodiment, coating the gas-sensitive material at the optical fiber grating position will cause the refractive index of the multi-core optical fiber at this position to change, resulting in problems with the optical signals in other fiber cores, and ultimately leading to inaccurate measurement results. Therefore, in this embodiment, the multi-core optical fiber 1 needs to be divided into multiple single-core optical fibers 11 by a coupler in the part where the gas sensor module 3 is installed, and the gas sensor module 3 is installed separately on one of the single-core optical fibers 11 to avoid affecting other single-core optical fibers 11. Therefore, this embodiment also involves the following designs:

As shown in FIG2 , the coal mine explosion monitoring and early warning device based on multi-core optical fiber further includes: a second coupler 6 and a flange 7, wherein:

As shown in Figures 2 and 3, in two adjacent multi-core optical fibers 1, one end of the two adjacent multi-core optical fibers 1 for docking is divided into multiple single-core optical fibers 11 by the second coupler 6; in two adjacent multi-core optical fibers 1, one end of the gas sensing module 3 and one of the single-core optical fibers 11 of one of the multi-core optical fibers 1 are connected through a flange 7, and the other end of the gas sensing module 3 and one of the single-core optical fibers 11 of the other multi-core optical fiber 1 are connected through a flange 7; the remaining single-core optical fibers 11 of one multi-core optical fiber 1 and the remaining single-core optical fibers 11 of the other multi-core optical fiber 1 are connected one by one through the flange 7.

As shown in FIG. 4 , in this embodiment, the gas sensing module 3 includes a separate single-core optical fiber 11, and a grating is engraved on the single-core optical fiber 11, and a gas-sensitive material is coated at the optical fiber grating. The two ends of the single-core optical fiber 11 are connected to the single-core optical fibers 11 separated from the two adjacent multi-core optical fibers 1 through a flange 7.

In this embodiment, the gas-sensitive material can be divided into metal oxides and their doped materials, supramolecular Acryptophane-A, graphene composite materials and carbon nanotube materials. Metal oxide materials are a common type of gas-sensitive materials. For example, metal oxide materials such as nano-tin oxide (SnO2), zinc oxide (ZnO), vanadium dioxide (VO2), indium oxide (In2O3) have excellent response characteristics to methane gas. Compared with single metal oxide materials, nano-metal oxide composite materials and their doped materials are more widely used. By doping precious metals such as Pt and Pb into metal oxide materials, the response characteristics of the sensor to gas are optimized.

In this embodiment, for the gas sensing module 3, a phase mask method is used to engrave multiple sections of gratings on a single-core optical fiber 11, the coating layer of the grating part is peeled off, and then the optical fiber cladding is thinned to a certain extent by etching with a 40% concentration of hydrofluoric acid aqueous solution, and then the corresponding gas-sensitive material is made by selecting relevant nano-metal oxide composite materials and their doping materials, and the gas-sensitive material is coated on the surface of the processed optical fiber grating to make a gas sensing module 3. The gas sensing module 3 is connected to the single-core optical fiber 11 separated from the flange 7 and other multi-core optical fibers 1 at both ends, and the demodulator 4 connected with the multi-core optical fiber 1 is used to achieve synchronous demodulation.

In this embodiment, for the grating optical fiber, the corresponding equation is:

λ _B =2n _eff Λ;

Where n _eff is the effective refractive index of the grating, Λ is the grating period, and λ _B is the wavelength of the optical signal.

When the gas-sensitive material is coated on the surface of the fiber grating, the methane in the lane contacts and reacts with the gas-sensitive material. The adsorption of methane gas by the gas-sensitive material causes the effective refractive index _neff of the core layer to change. Different methane concentrations lead to different changes in the refractive index. The grating period Λ is a constant, and the change in the wavelength of the light signal _λB has a certain change relationship with methane. By comparing the size of the change in _λB and the degree of wavelength deviation, the methane gas concentration in the lane can be inferred.

As shown in FIG5 , the multi-core optical fiber 1 includes an intermediate fiber core 12 and a plurality of outer ring fiber cores 13, wherein:

The plurality of outer ring fiber cores 13 are distributed around the circumference of the middle fiber core 12 .

As shown in FIG6 , the demodulator 4 includes a temperature demodulation module 41, a gas concentration demodulation module 42, a strain demodulation module 43 and a vibration demodulation module 44, wherein:

The intermediate fiber core 12 is connected to the temperature demodulation module 41, and the temperature demodulation module 41 is used to obtain temperature measurement data based on the received optical signal; at least one outer ring fiber core 13 is connected to the gas concentration demodulation module 42, and the gas concentration demodulation module 42 is used to obtain gas concentration measurement data based on the received optical signal; at least one outer ring fiber core 13 is connected to the strain demodulation module 43, and the strain demodulation module 43 is used to obtain strain measurement data based on the received optical signal; at least one outer ring fiber core 13 is connected to the vibration demodulation module 44, and the vibration demodulation module 44 is used to obtain vibration state measurement data based on the received optical signal.

In this embodiment, the temperature demodulation module 41 can be a Raman thermometer, which uses Raman optical time domain reflectometry technology to measure temperature; the strain demodulation module 43 can be a Brillouin demodulator, and when the Brillouin demodulator is used for distributed strain measurement, a pair of single-core optical fibers 11 can also be used for docking; the vibration demodulation module 44 can be connected to a Mach-Zehnder interferometer for measuring high-frequency vibration of the structure, and the vibration demodulation module 44 can also be connected to a phase-sensitive optical time domain reflectometer for measuring structural vibration.

According to the above description, it can be known that in this embodiment, at least four fiber cores need to be arranged in the multi-core optical fiber 1; it is worth noting that, in this embodiment, the distributed strain measurement adopts the distributed stress-strain sensing technology based on Brillouin scattering, but this method will be affected by temperature in the measurement of distributed stress, and the Raman optical time-domain reflectometry technology, which is a method for measuring temperature, is only sensitive to temperature changes, and therefore can accurately measure the temperature changes. In summary, in this embodiment, the temperature measured by the temperature demodulation module 41 is used to compensate for the measurement of distributed strain, and a corresponding set of equations is established to solve the measured value of the compensated distributed strain, thereby solving the cross-sensitivity problem of the distributed stress-strain sensing technology based on Brillouin scattering to temperature and strain, and ensuring the accuracy of the distributed strain measurement.

In this embodiment, the temperature is measured as follows:

According to the Raman scattered light temperature measurement principle, the anti-Stokes and Stokes intensity ratio of Raman scattered light is:

P _AS and P _S are two scattered light intensities. v _As is the anti-Stokes light frequency, vs is the Stokes light frequency, _T is the current temperature, and Δv is the frequency shift. The external temperature can be measured according to the intensity ratio of the two lights, h is the Planck constant, k is the coefficient; T ₀ is the initial temperature, which can be the temperature before being affected by the outside world.

The relationship between the Raman intensity of the optical fiber and the temperature can be calculated:

The temperature is calculated as:

The Brillouin frequency shift has a linear relationship with temperature and strain:

Δv＝C _T ΔT+C _ε Δε；

Δv is the frequency shift, ΔT is the temperature difference (TT ₀ ), Δε is the strain difference, C _T and C _ε are the temperature sensitivity coefficient and the strain sensitivity coefficient respectively. Substituting the above measured temperature T into the temperature difference ΔT, the external strain can be obtained:

In this embodiment, the current distributed strain can be obtained by adding the strain difference to the original distributed strain.

As shown in FIG. 7 , the plurality of multi-core optical fibers 1 connected in series make a turn every preset distance; and the gas sensing module 3 is located at the turning point.

By arranging the multiple multi-core optical fibers 1 connected in series with multiple turns on the top plate 9, the density of distribution of the multiple multi-core optical fibers 1 connected in series on the top plate 9 is ensured, the measurement of temperature and gas concentration at the top plate 9 is more accurate, and it is ensured that strain occurring at various locations on the top plate 9 is more easily sensed by the multi-core optical fibers 1.

As shown in FIG. 7 , in this embodiment, the plurality of multi-core optical fibers 1 are connected in series and bonded to the tunnel top plate 9 in an S-shaped or Z-shaped arrangement. In this embodiment, epoxy resin adhesive may be used for bonding to achieve monitoring of specific areas in the tunnel.

Considering that during the actual installation and bonding, after the multi-core optical fiber 1 is divided into multiple single-core optical fibers 11 by the coupler, the single-core optical fibers 11 are also butted together through the flange 7. There is a difference in the cross-sectional diameters of the flange 7 and the single-core optical fiber 11, resulting in that the part of the area where the single-core optical fiber 11 and the flange 7 are butted together cannot fit with the tunnel top plate 9 during bonding, resulting in the possibility of insufficient bonding strength of this part. In order to prevent this part from falling off later, this embodiment also involves the following designs:

As shown in FIG8 and FIG9 , the coal mine explosion monitoring and early warning device based on multi-core optical fiber further includes a protective shell 8, wherein:

The coal mine explosion monitoring and early warning device based on multi-core optical fiber is used to be installed on the roof 9 of the coal mine tunnel; the protective shell 8 is used to be installed on the roof 9 and cover the serial connection of two adjacent multi-core optical fibers 1; the protective shell 8 is provided with a leakage hole 83 to ensure that the serial connection of the two multi-core optical fibers 1 is in contact with the outside air.

In this embodiment, as shown in Figure 8, abutment surfaces 81 are provided on both sides of the protective shell 8 for fitting with the tunnel roof 9, and through holes are also provided on the abutment surfaces 81 for screws to pass through, thereby fixing the protective shell 8 on the tunnel roof 9; the middle part of the protective shell 8 is a receiving groove 82 for accommodating the series connection of two adjacent multi-core optical fibers 1, and the protective shell 8 should avoid contact with the multi-core optical fiber 1 as much as possible.

As shown in FIG10 , the host computer 5 includes a data receiving module 51, a data processing module 52 and a data early warning module 53, wherein:

The data receiving module 51, the data processing module 52 and the data early warning module 53 are connected in sequence; the data receiving module 51 is used to receive the measurement data from the demodulator 4 and store the measurement data; the data processing module 52 is used to process and analyze the measurement data, and send the processed and analyzed measurement data to the data early warning module 53; the data early warning module 53 is used to compare the processed and analyzed measurement data with the corresponding threshold value, and issue a corresponding early warning.

Embodiment 2:

This embodiment 2 provides a coal mine explosion monitoring and early warning method based on multi-core optical fiber on the basis of embodiment 1, which is used for applying to the coal mine explosion monitoring and early warning device based on multi-core optical fiber described in embodiment 1. As shown in FIG11 , the method flow includes:

In step 101, the demodulator 4 sends an optical signal to the plurality of multi-core optical fibers 1 connected in series, and the scattering unit in the multi-core optical fiber 1 is used to reflect the optical signal back to the demodulator 4, and the gas sensor module 3 senses the gas concentration.

In step 102 , the demodulator 4 obtains measurement data of gas concentration, temperature, distributed strain and vibration state according to the received optical signal, and sends the measurement data to the host computer 5 .

In step 103, the host computer 5 processes and analyzes the measurement data and makes corresponding warnings.

In this embodiment, the measurement and calculation method of temperature and distributed strain has been described in Embodiment 1, and will not be elaborated here.

The host computer 5 processes and analyzes the measurement data and makes corresponding warnings. As shown in FIG12 , the method flow includes:

In step 201, it is determined whether the gas is a special outflow according to the gas concentration, distributed strain and vibration state.

In step 202, when it is determined that the gas is specially gushing out, it is determined whether the temperature is greater than or equal to the temperature threshold; when the temperature is greater than or equal to the temperature threshold, the host computer 5 issues an explosion warning; when the temperature is less than the temperature threshold, the host computer 5 issues a special gas gushing out warning.

In step 203, when it is determined that the gas is not a special outflow, it is determined whether the gas concentration is greater than or equal to the concentration threshold; when the gas concentration is less than the concentration threshold, the host computer 5 does not issue an early warning; when the gas concentration is greater than or equal to the concentration threshold, it is determined whether the temperature is greater than or equal to the temperature threshold; when the temperature is less than the temperature threshold, the host computer 5 issues a gas extraction prompt; when the temperature is greater than or equal to the temperature threshold, the host computer 5 issues an explosion early warning.

In this embodiment, the temperature threshold and the concentration threshold can be set by those skilled in the art according to actual conditions. The gas extraction prompt indicates that the gas concentration at the current detection position is high. Although the temperature is not high enough to cause an explosion, it is necessary to remind those skilled in the art to discharge the gas at the detection position to avoid the risk of subsequent explosion.

The method of judging whether the gas is a special outflow according to the gas concentration, distributed strain and vibration state, as shown in FIG13 , includes:

In step 301, the correlation coefficient between the gas concentration and the distributed strain and the vibration state is obtained, and it is determined whether the correlation coefficient is greater than or equal to a coefficient threshold.

In step 302, when the correlation coefficient is less than the coefficient threshold, it is determined that the gas is not a special outflow.

In step 303, when the correlation coefficient is greater than or equal to the coefficient threshold, it is determined whether the measurement data of the distributed strain is greater than or equal to the strain threshold, and whether the measurement data of the vibration state is greater than or equal to the vibration threshold; when the measurement data of the distributed strain is greater than or equal to the strain threshold, and the measurement data of the vibration state is greater than or equal to the vibration threshold, it is determined that the gas is a special outflow, otherwise, it is determined that the gas is not a special outflow.

In this embodiment, the sparse threshold, the strain threshold, and the vibration threshold can all be set by those skilled in the art according to actual conditions.

In this embodiment, it is first determined whether the gas concentration is correlated with the distributed strain and the vibration state. A multivariate linear regression model is established through machine learning, and the complex correlation coefficient is calculated for evaluation. A linear model is constructed, and the gas concentration is regarded as the dependent variable y, the distributed strain is regarded as the independent variable x ₁ , and the vibration is regarded as the independent variable x ₂ . The relationship is as follows:

y＝b ₀ +b ₁ x ₁ +b ₂ x ₂ +ε;

Where b ₀ , b ₁ , b ₂ and ε are relationship coefficients.

Perform a linear regression on the relationship to obtain Then for y and /> Perform simple correlation analysis and calculate the complex correlation coefficient/>

In this embodiment, taking the coefficient threshold n=0.5 as an example, and n, to determine whether the gas concentration is correlated with the distributed strain and the vibration state;/> For y and /> The oblique variance of is the square root of the variance of y, /> For/> The square root of the variance.

like When it is greater than 0.5, it indicates that there is a strong correlation. Therefore, first determine whether the measured values of the distributed strain and vibration state of the roadway exceed the set threshold:

If the measurement data of the distributed strain and vibration state exceed the corresponding thresholds, and because the gas concentration at this time has a strong correlation with its change, it is judged that a special outburst may occur, and then the temperature measurement data is used to determine whether the temperature threshold is exceeded. If the temperature threshold is exceeded, it indicates that a high-temperature fire source exists, the explosion conditions are met, and there is a possibility of explosion. At this time, an explosion warning is issued; if the temperature threshold is not exceeded, it indicates that no high-temperature fire source has been found, and the explosion conditions are not met. At this time, no explosion warning is issued, but because a special outburst may occur, a special outburst warning is still required.

If the measurement data of the distributed strain and vibration state do not all exceed the corresponding thresholds, it is determined whether the gas concentration exceeds the corresponding threshold at this time. If not, it indicates that it is normal and no warning is issued. If it exceeds, it is determined whether it exceeds the temperature threshold based on the temperature information. If it exceeds the temperature threshold, it indicates that there is a high-temperature fire source, the explosion conditions are met, and there is a possibility of explosion. At this time, an explosion warning is issued; if it does not exceed the temperature threshold, it indicates that no high-temperature fire source has been found yet, the explosion conditions are not met, the display is normal, and no warning is issued.

when When it is less than 0.5, it indicates that the correlation is weak. Therefore, it is determined whether the gas concentration exceeds the corresponding threshold. If it does not exceed, it indicates that it is normal and no warning is issued. If it exceeds, it indicates that gas is accumulated. Then, it is determined whether it exceeds the temperature threshold based on the temperature information. If it exceeds the temperature threshold, it indicates that there is a high-temperature fire source, which meets the explosion conditions and has the possibility of explosion. At this time, an explosion warning is issued. If it does not exceed the temperature threshold, it indicates that no high-temperature fire source has been found yet, the explosion conditions are not met, and no warning is issued.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims (10)

1. Colliery explosion monitoring early warning device based on multicore optic fibre, its characterized in that includes: the multi-core optical fiber (1), a first coupler (2), a gas sensing module (3), a demodulator (4) and an upper computer (5), wherein:

The multi-core optical fibers (1) are sequentially connected in series, and the gas sensing module (3) is arranged between two adjacent multi-core optical fibers (1);

The multi-core optical fiber (1) at the tail end is divided into a plurality of single-core optical fibers (11) through the first coupler (2), all the single-core optical fibers (11) are connected with the demodulator (4), the demodulator (4) is connected with the upper computer (5), and a plurality of scattering units are axially arranged in the multi-core optical fiber (1);

The demodulator (4) is used for sending optical signals to a plurality of multi-core optical fibers (1) after being connected in series, a scattering unit in the multi-core optical fibers (1) reflects the optical signals back to the demodulator (4), the gas sensing module (3) is used for changing the wavelength of the optical signals according to the change of the gas concentration, the demodulator (4) is used for obtaining measurement data of the gas concentration, the temperature, the distributed strain and the vibration state according to the received optical signals, and the upper computer (5) is used for processing and analyzing the measurement data and making corresponding early warning.

2. The multi-core fiber based coal mine explosion monitoring and early warning device according to claim 1, further comprising: a second coupler (6) and a flange (7), wherein:

in the two adjacent multi-core optical fibers (1), one end of each of the two adjacent multi-core optical fibers (1) for butt joint is divided into a plurality of single-core optical fibers (11) through the second coupler (6);

In two adjacent multi-core optical fibers (1), one end of the gas sensing module (3) is connected with one single-core optical fiber (11) of one multi-core optical fiber (1) through a flange (7), and the other end of the gas sensing module (3) is connected with one single-core optical fiber (11) of the other multi-core optical fiber (1) through the flange (7); the other single-core optical fibers (11) of one multi-core optical fiber (1) are connected with the other single-core optical fibers (11) of the other multi-core optical fiber (1) in a one-to-one correspondence manner through the flange plate (7).

3. The multi-core fiber-based coal mine explosion monitoring and early warning device according to claim 1, wherein the multi-core fiber (1) comprises an intermediate fiber core (12) and a plurality of outer ring fiber cores (13), wherein:

the plurality of outer ring cores (13) are distributed at the circumferential position of the middle core (12).

4. A multi-core optical fiber based coal mine explosion monitoring and early warning device according to claim 3, wherein the demodulator (4) comprises a temperature demodulation module (41), a gas concentration demodulation module (42), a strain demodulation module (43) and a vibration demodulation module (44), wherein:

The intermediate fiber core (12) is connected with the temperature demodulation module (41), and the temperature demodulation module (41) is used for obtaining temperature measurement data according to the received optical signals;

the at least one outer ring fiber core (13) is connected with the gas concentration demodulation module (42), and the gas concentration demodulation module (42) is used for obtaining measurement data of gas concentration according to the received optical signal;

at least one outer ring fiber core (13) is connected with the strain demodulation module (43), and the strain demodulation module (43) is used for obtaining measurement data of distributed strain according to the received optical signals;

At least one outer ring fiber core (13) is connected with the vibration demodulation module (44), and the vibration demodulation module (44) is used for obtaining measurement data of vibration states according to received optical signals.

5. The multi-core fiber based coal mine explosion monitoring and early warning device according to claim 1, further comprising a protective housing (8), wherein:

The coal mine explosion monitoring and early warning device based on the multi-core optical fiber is arranged on a top plate (9) of a coal mine tunnel;

the protective shell (8) is arranged on the top plate (9) and covers the serial connection position of two adjacent multi-core optical fibers (1);

And a leak hole (83) is formed in the protective shell (8) to ensure that the serial connection part of the two multi-core optical fibers (1) is contacted with the outside air.

6. The multi-core fiber-based coal mine explosion monitoring and early warning device according to claim 1, wherein the upper computer (5) comprises a data receiving module (51), a data processing module (52) and a data early warning module (53), wherein:

the data receiving module (51), the data processing module (52) and the data early warning module (53) are connected in sequence;

The data receiving module (51) is used for receiving the measurement data from the demodulator (4) and storing the measurement data;

The data processing module (52) is used for processing and analyzing the measurement data and sending the processed and analyzed measurement data to the data early warning module (53);

the data early warning module (53) is used for comparing the measurement data after processing and analysis with a corresponding threshold value and sending out a corresponding early warning.

7. A coal mine explosion monitoring and early warning method based on a multi-core optical fiber, which is applied to the coal mine explosion monitoring and early warning device based on the multi-core optical fiber according to any one of claims 1 to 6, and is characterized by comprising the following steps:

the demodulator (4) sends optical signals to a plurality of multi-core optical fibers (1) which are connected in series, a scattering unit in the multi-core optical fibers (1) reflects the optical signals back to the demodulator (4), and the gas sensing module (3) is used for changing the wavelength of the optical signals according to the change of the gas concentration;

The demodulator (4) obtains measurement data of gas concentration, temperature, distributed strain and vibration state according to the received optical signals, and sends the measurement data to the upper computer (5);

And the upper computer (5) processes and analyzes the measurement data and gives corresponding early warning.

8. The multi-core fiber based coal mine explosion monitoring and early warning method according to claim 7, wherein the corresponding calculation formula of the temperature is:

Wherein T is the current temperature, T ₀ is the initial temperature, h is the Planckian constant, k is the coefficient, deltav is the frequency shift amount, R (T) is the anti-Stokes to Stokes intensity ratio of the Raman scattered light at the current temperature, and R (T ₀) is the anti-Stokes to Stokes intensity ratio of the Raman scattered light at the initial temperature;

the distributed strain is compensated through temperature, the change of the distributed strain is obtained, and the corresponding calculation formula is as follows:

Where Δε is the strain difference, C _T is the temperature sensitivity coefficient, and C _ε is the strain sensitivity coefficient.

9. The multi-core fiber-based coal mine explosion monitoring and early warning method according to claim 7, wherein the upper computer (5) processes and analyzes the measurement data and makes corresponding early warning, and the method specifically comprises the following steps:

judging whether the gas is special gushes or not according to the gas concentration, the distributed strain and the vibration state;

When judging that the gas is special gushing, judging whether the temperature is greater than or equal to a temperature threshold value; when the temperature is greater than or equal to the temperature threshold, the upper computer (5) sends out explosion early warning; when the temperature is smaller than the temperature threshold, the upper computer (5) gives out a special gas surge early warning;

When judging that the gas is not special gushing, judging whether the gas concentration is greater than or equal to a concentration threshold value; when the gas concentration is smaller than the concentration threshold value, the upper computer (5) does not send out early warning; when the gas concentration is greater than or equal to a concentration threshold, judging whether the temperature is greater than or equal to a temperature threshold; when the temperature is smaller than the temperature threshold, the upper computer (5) sends out a gas pumping prompt; when the temperature is greater than or equal to the temperature threshold, the upper computer (5) sends out explosion early warning.

10. The method for monitoring and early warning coal mine explosion based on the multi-core optical fiber according to claim 9, wherein the judging whether the gas is a special surge according to the gas concentration, the distributed strain and the vibration state comprises the following steps:

acquiring a correlation coefficient between the gas concentration and the distributed strain and vibration state, and judging whether the correlation coefficient is larger than or equal to a coefficient threshold value;

When the correlation coefficient is smaller than the coefficient threshold value, judging that the gas is not special gushing out;

When the correlation coefficient is greater than or equal to a coefficient threshold, judging whether the measurement data of the distributed strain is greater than or equal to a strain threshold, and judging whether the measurement data of the vibration state is greater than or equal to a vibration threshold; when the measurement data of the distributed strain is larger than or equal to the strain threshold value and the measurement data of the vibration state is larger than or equal to the vibration threshold value, judging that the gas is special gush, otherwise, judging that the gas is not special gush.