Underground coal mine smoke concentration early warning method and system

Abstract

The invention discloses an underground coal mine smoke concentration early warning method and system, and belongs to the technical field of fire early warning. The first wavelength signal and the second wavelength signal of the underground coal mine are acquired, and the target Sott particle size is calculated by adopting a statistical method, so that the data precision is improved. The method comprises the following steps: setting a first threshold and a second threshold, judging an interval where a target Sott particle size is located, judging whether a roadway where a detection unit is located is normal or not according to the interval, collecting multiple groups of continuous first gas concentrations and second gas concentrations in combination with a gas detector, and calculating a first concentration change rate and a second concentration change rate; therefore, the underground state of the coal mine is determined, and the accuracy of smoke alarm is improved. Furthermore, parameters of the smoke detector are periodically updated in combination with equipment noise, the accuracy of data acquisition of the equipment is improved, and the probability of false alarm is reduced.

Description

Technical Field

[0001] This invention relates to the field of early warning technology for coal mine operations, and in particular to a method and system for early warning of underground smoke concentration in coal mines. Background Technology

[0002] Traditional smoke detectors typically use only infrared light as the incident light, with the scattered light intensity corresponding to the volume concentration of smoke aerosols as a parameter characterizing smoke concentration. However, the volume concentration of other particles corresponding to smoke also produces corresponding scattered light intensities, so false alarms caused by non-smoke aerosols cannot be ruled out. Chinese patent application CN111487171A discloses a dual-wavelength dispersion smoke detector and method combining forward and backward dispersion. The detector includes a detection cavity containing a light receiver and two light transmitters. One transmitter forms an acute angle with the receiver (forward transmitter), while the other forms an angle greater than 120 degrees (backward transmitter). The two transmitters sequentially emit blue and red light signals, which are received by the receiver. The scattered power of the backward transmitter is used to determine the median particle size of the smoke, and the forward transmitter determines whether to issue a smoke alarm based on the median particle size. This method determines whether to issue a smoke alarm based on the median particle size of the smoke, but it cannot eliminate interference from water mist, other dust particles, and other contaminants.

[0003] Chinese patent application CN115482643A discloses a fire smoke detector and its detection method. The fire smoke detector includes: a dual-wavelength light source for emitting dual-wavelength light signals based on a received drive signal; at least one detection component for receiving a first-wavelength scattered signal, a second-wavelength scattered signal, a first-wavelength extinction signal, and a second-wavelength extinction signal generated after the dual-wavelength light signals pass through a particle being measured; and a signal processing component for calculating a scattering coefficient based on the first-wavelength scattered signal and the second-wavelength scattered signal, calculating an extinction coefficient based on the first-wavelength extinction signal and the second-wavelength extinction signal, and calculating a scattering extinction ratio based on the scattering coefficient and the extinction coefficient, to generate a smoke detection result based on the scattering coefficient, extinction coefficient, and / or scattering extinction ratio. Due to the limited accuracy of the detection instrument, the above method generates smoke detection results based on the scattering coefficient, extinction coefficient, and / or scattering extinction ratio, resulting in overly absolute judgment boundaries and a high risk of false alarms. Further improvements to the existing technology are necessary. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention proposes a method and system for early warning of smoke concentration in coal mines. The method calculates the target Sotter particle size based on first and second wavelength signals collected by a smoke detector. Then, it determines the range of the target Sotter particle size using different threshold values ​​and combines this with the rate of change in gas concentration to determine the state of the coal mine roadway, thereby improving the accuracy of smoke alarms. Furthermore, this invention updates the smoke detector parameters based on equipment noise and updates the second threshold based on the air turbulence state of the roadway, further improving the accuracy of data acquisition and processing.

[0005] The technical solution of this invention is implemented as follows: A method for early warning of smoke concentration in underground coal mines includes the following steps: Step 1: The coal mine operating area has multiple sets of shafts, and fans are installed in the shafts. At least two sets of shafts are connected by roadways. Multiple sets of detection units are arranged in the roadways. The detection units have smoke detectors and gas detectors. Step 2: The smoke detector continuously acquires the first wavelength signal and the second wavelength signal, and the gas detector continuously acquires the first gas concentration and the second gas concentration; Step 3: Calculate the volume concentration and surface area concentration based on the first and second wavelength signals of the smoke detector, and calculate the Sotter particle size and target Sotter particle size based on the volume concentration and surface area concentration. Step 4: If the target Soter particle size is greater than the first threshold, proceed to step 9; otherwise, update the parameters of the smoke detector and proceed to step 5. Step 5: Extract multiple sets of shafts connected to the detection unit, extract the static pressure and air flow of the fan in each shaft, calculate the natural wind pressure of each shaft, and then predict the turbulence coefficient of the detection unit. Step 6: Update the second threshold of the detection unit based on the turbulence coefficient. If the target Soter particle size is smaller than the second threshold, return to step 2; otherwise, proceed to step 7. Step 7: Extract multiple sets of continuous first gas concentration and second gas concentration for the gas detector corresponding to the detection unit, and calculate the rate of change of the first concentration and the rate of change of the second concentration. Step 8: Predict whether the roadway where the detection unit is located is in an abnormal state based on the first concentration change rate and the second concentration change rate. If it is in an abnormal state, proceed to step 9; otherwise, return to step 2. Step 9: Extract the location data of the detection unit and output the location data and alarm signal.

[0006] In this invention, in step 2, the wavelength of the first wavelength signal is 850 nm, the wavelength of the second wavelength signal is 468 nm, the first gas concentration is oxygen concentration, and the second gas concentration is carbon monoxide concentration.

[0007] In this invention, in step 3, the red light intensity I1 and blue light intensity I2 are obtained based on the first wavelength signal and the second wavelength signal. The red light extinction coefficient b1 and the blue light extinction coefficient b2 are calculated. Then, the extinction ratio R is calculated. The average particle size D is obtained by searching the first database based on the extinction ratio. The red light extinction efficiency factor η1 and the blue light extinction efficiency factor η2 are obtained by searching the second database based on the average particle size D, the wavelength j1 of the first wavelength signal, and the wavelength j2 of the second wavelength signal. Thus, the volume concentration V and the surface area concentration S are calculated, where V = 2b1D / (3η1), S = 4b2 / η2, and b1 = [ln(I1 / I2)]. 01 / I1)] / L1, b2=[ln(I 02 / I2)] / L2,R=b1 / b2,I 01 I is the initial red light intensity. 02 L1 represents the initial blue light intensity, L2 represents the red light path length, and L3 represents the blue light path length. The Soter particle size is D1 = 6 V / S.

[0008] In this invention, in step 3, a Soter size set D0 is generated based on multiple continuously acquired first wavelength signals and second wavelength signals, where D0 = {D 11 D 12 ,…,D 1j ,…,D 1J}, D 1j Let J be the j-th Sott size in the Sott size set, where J is the number of samplings. The Sott sizes in the set are sorted in ascending order of absolute value. The target Sott size is calculated as follows: calculate the test statistic for each Sott size. The test statistic r for the j-th Sott size... j =(D 1j -D 1(j-1) ) / (D 1J -D 11 When the test statistic is greater than the test threshold, the corresponding Sotter size in the Sotter size set is deleted. The above steps are repeated until the test statistic of each Sotter size is less than the test threshold. Then the average value of all Sotter sizes in the Sotter size set is calculated and stored as the target Sotter size.

[0009] In this invention, in step 4, noise data G(f, d, I) of the smoke detector is collected, where f is the switching frequency, d is the modulation depth, and I is the bias current. The initial parameter set x0 of the smoke detector is obtained. The total noise energy function E0(x) and the peak energy function E1(x) are fitted according to the noise data and the initial parameter set. The objective function is constructed according to the total noise energy function and the peak energy function, and the objective parameter set is obtained. The parameters of the smoke detector are updated according to the objective parameter set.

[0010] In this invention, in step 5, the air flow rate Q of shaft n is... n and drag coefficient Rn Calculate the flow ventilation pressure R of shaft n n Q n 2 Turbulence coefficient of the detection unit H n F is the static pressure of the blower in shaft n. n Let N be the natural wind pressure of shaft n, and N be the number of shafts connected to this detection unit.

[0011] In this invention, in step 6, the second threshold λ2 = λ1ln(μ+1), and λ1 is the first threshold.

[0012] In this invention, in step 7, a first concentration set C1 is generated based on the continuously collected first gas concentration, C1={c 11 ,c 12 ,…,c 1k ,…,c 1K}, based on the continuously collected second gas concentrations, a second concentration set C2 is generated, C2={c 21 ,c 22 ,…,c 2k ,…,c 2K}, c 1k Let c be the concentration of the k-th first gas in the first concentration set. 2k The k-th second gas concentration in the second concentration set, and the rate of change of the first concentration. Second concentration change rate .

[0013] In this invention, in step 8, if g1>0 and g2>0 and g2 / g1>λ3, where λ3 is a proportional threshold, then the roadway where the detection unit is located is in an abnormal state.

[0014] An early warning system for implementing the aforementioned method for early warning of underground smoke concentration in coal mines includes: multiple sets of detection units, a shaft monitoring unit, a control center, and a display unit. The detection unit is installed in the tunnel and has a smoke detector for acquiring a first wavelength signal and a second wavelength signal, a gas detector for acquiring a first gas concentration and a second gas concentration, and a signal calibrator for updating the parameters of the smoke detector. The smoke detector has a first transmitter, a second transmitter, a first detector, and a second detector. The well monitoring unit is installed in the well and has a pressure detector for collecting the static pressure of the fan and a gas flow meter for collecting the air flow rate. The control center has a first processing unit, a second processing unit, and a third processing unit. The first processing unit is used to calculate the Soter particle size and the target Soter particle size. The second processing unit is used to predict the turbulence coefficient of the shaft. The third processing unit is used to predict whether the roadway where the detection unit is located is in an abnormal state. The display unit is used to output the location data and alarm signals of the detection unit.

[0015] The coal mine underground smoke concentration early warning method and system of this invention has the following beneficial effects: This invention acquires a first wavelength signal and a second wavelength signal, then calculates the target Sotter particle size in the roadway, and then determines the range of the target Sotter particle size using different thresholds. Furthermore, it predicts whether the roadway where the detection unit is located is in an abnormal state based on the first and second concentration change rates. Compared to existing technologies that determine abnormal states solely through scattering and extinction coefficients, this invention improves the accuracy of smoke alarms and avoids false alarms caused by aerosol particle size. Furthermore, since the equipment operates in an underground roadway, this invention periodically updates the parameters of the smoke detector in conjunction with equipment noise, improving the accuracy of the collected data. Because air turbulence reduces the predictability of particle size and gas flow, to avoid false alarms, the second threshold is adjusted based on the airflow status, improving the accuracy of smoke judgment and reducing the probability of false alarms. Attached Figure Description

[0016] Figure 1 This is a flowchart of the coal mine underground smoke concentration early warning method of the present invention; Figure 2 A plan view of the installation of the detection unit in this invention; Figure 3 A three-dimensional schematic diagram of the detection unit installed in this invention; Figure 4 This is the optical path diagram of the smoke detector of the present invention; Figure 5 This is a line graph showing the preferred second gas concentration according to the present invention; Figure 6 This is a schematic diagram of the gas flow path in the tunnel and shaft of the present invention; Figure 7 This is a block diagram of the early warning system for implementing the coal mine underground smoke concentration early warning method of the present invention. Detailed Implementation

[0017] To better understand the purpose, technical solution, and advantages of this application, the application is described and illustrated below in conjunction with the accompanying drawings and embodiments.

[0018] The median particle size of most common fire smoke particles is less than 1 micrometer, while the median particle size of dust, coal dust, and water mist aerosols is greater than 1 micrometer. When incident light shines on smoke, the scattered light from smoke particles or aerosols can be used to characterize the volume concentration and surface area concentration of smoke or aerosols. Volume concentration is mainly affected by large-diameter particles, while surface area concentration is mainly affected by small-diameter particles. Therefore, a larger wavelength of incident light is used to irradiate the air, and the scattered light is received to measure the volume concentration of particulate matter in the air in coal mines. A smaller wavelength of incident light is used to irradiate the air, and the scattered light is received to measure the surface area concentration of particulate matter in the air in coal mines. The target Sotter particle size is calculated by using volume concentration and surface area concentration to avoid false alarms from aerosols. At the same time, the accuracy of fire alarms is improved by combining changes in oxygen concentration and carbon monoxide concentration, realizing real-time fire monitoring in coal mines. Example 1

[0019] like Figures 1 to 5 As shown, the coal mine underground smoke concentration early warning method of the present invention includes the following steps.

[0020] Step 1: The coal mine operating area has multiple sets of shafts, with fans installed in each shaft. At least two sets of shafts are connected by roadways, and multiple detection units, including smoke detectors and gas detectors, are arranged in the roadways. For example... Figure 2 As shown, a coal mine operating area includes goaf, unmined area, roadways, and shafts. The goaf represents the area where coal mining operations have ended, the unmined area represents the area where operations have not yet begun, roadways are the transport channels connecting the coal mining faces, and shafts refer to vertical or steeply inclined passages (such as vertical shafts and blind shafts) used for hoisting ore, equipment, or ventilation. Detection units are installed in the roadways to monitor the smoke conditions within them. Figure 3 As shown, a fan is installed on the shaft to circulate gas, and multiple shafts are connected in the tunnel to form a gas loop. Detection units are installed in the tunnel, including smoke detectors and gas detectors.

[0021] Step 2: The smoke detector continuously acquires the first wavelength signal and the second wavelength signal, and the gas detector continuously acquires the first gas concentration and the second gas concentration. For example... Figure 4 As shown, the smoke detector includes a first transmitter, a second transmitter, a first detector, and a second detector. The first and second detectors are housed in a dark chamber to avoid interference from ambient light. A dust collection plate reflects and refracts a first wavelength signal emitted by the first transmitter to the first detector, and reflects and refracts a second wavelength signal emitted by the second transmitter to the second detector. The wavelength of the first wavelength signal is 850 nm, and the wavelength of the second wavelength signal is 468 nm. The first gas concentration is oxygen concentration, and the second gas concentration is carbon monoxide concentration.

[0022] Step 3: Calculate the volume concentration and surface area concentration based on the first and second wavelength signals from the smoke detector. Then, calculate the Sotter size and target Sotter size based on the volume concentration and surface area concentration. Since the particle sizes of smoke particles and other aerosol particles differ significantly, the volume concentration is mainly affected by large-diameter particles, while the surface area concentration is mainly affected by small-diameter particles. The Sotter size is related to both volume concentration and surface area concentration; therefore, the Sotter size can be used as a basis for fire identification. The calculation steps for the Sotter size and target Sotter size are explained in detail in Example 2.

[0023] Step 4: If the target soter particle size is greater than the first threshold, proceed to step 9; otherwise, update the smoke detector parameters and proceed to step 5. The first threshold is related to the dust environment in the coal mine and the smoke particles generated by the fire, and is set according to the specific environment and historical data, usually 1 micrometer. Update the smoke detector parameters: Collect the noise data G(f, d, I) of the smoke detector, where f is the switching frequency, d is the modulation depth, and I is the bias current. Obtain the initial parameter set x0 of the smoke detector. Fit the total noise energy function E0(x) and the peak energy function E1(x) based on the noise data and the initial parameter set. Construct the objective function based on the total noise energy function and the peak energy function and obtain the objective parameter set. Update the smoke detector parameters based on the objective parameter set.

[0024] Step 5: Extract multiple sets of shafts connected to the detection unit, extract the fan static pressure and airflow of each shaft, calculate the natural wind pressure of each shaft, and then predict the turbulence coefficient of the detection unit. Based on the airflow Q of shaft n... n and drag coefficient R n Calculate the flow ventilation pressure R of shaft n n Q n 2 Turbulence coefficient of the detection unit H n F is the static pressure of the blower in shaft n. n Let N be the natural wind pressure of shaft n, and N be the number of shafts connected to the detection unit. The specific steps for calculating the turbulence coefficient of the detection unit are explained in detail in Example 3.

[0025] Step 6: Update the second threshold of the detection unit based on the turbulence coefficient. If the target Souter particle size is smaller than the second threshold, return to step 2; otherwise, proceed to step 7. The second threshold λ2 = λ1ln(μ+1), where λ1 is the first threshold. Setting the first and second thresholds improves the accuracy of fire detection and reduces the probability of false fire alarms. When the target Souter particle size is between the first and second thresholds, due to measurement errors, it is impossible to determine the occurrence of a fire based solely on the target Souter particle size. It is necessary to combine this with changes in the oxygen and carbon monoxide concentrations in the air to make a judgment, thereby reducing the probability of false fire alarms.

[0026] Step 7: Extract multiple sets of continuous first and second gas concentrations from the gas detector corresponding to the detection unit, and calculate the rate of change of the first and second concentrations. Generate a first concentration set C1 based on the continuously collected first gas concentrations, C1 = {c 11 ,c 12 ,…,c 1k ,…,c 1K}, based on the continuously collected second gas concentrations, a second concentration set C2 is generated, C2={c 21 ,c 22 ,…,c 2k ,…,c 2K}. c 1k Let c be the concentration of the k-th first gas in the first concentration set. 2k Let be the concentration of the k-th second gas in the second concentration set. The rate of change of the first concentration. Second concentration change rate The units for the first and second gas concentrations are m³. 3 / m 3 The gas detector can be a combination of various gas detectors.

[0027] Step 8: Predict whether the roadway where the detection unit is located is in an abnormal state based on the first and second concentration change rates. If it is in an abnormal state, proceed to step 9; otherwise, return to step 2. If g1>0 and g2>0 and g2 / g1>λ3, where λ3 is the proportional threshold, then the roadway where the detection unit is located is in an abnormal state, indicating a fire in the coal mine. The proportional threshold is typically 0.18, which is related to the initial gas concentration and combustion conditions in the coal mine. Coal mines are typically oxygen-deficient. When the combustion conditions are slightly oxygen-deficient, the proportional threshold is generally 0.02 to 0.1; when the combustion conditions are moderately oxygen-deficient, the proportional threshold is generally 0.1 to 0.4; and when the combustion conditions are severely oxygen-deficient, the proportional threshold is generally 0.4 to 1.0. By calculating the first and second concentration change rates to reflect the changes in gas concentration in the coal mine, further judgment can be made as to whether a fire has occurred, thus improving the accuracy of fire early warning. Figure 5 As shown, the horizontal axis represents time and the vertical axis represents carbon monoxide concentration. The two curves in the figure represent the data measured by the gas detectors in different roadways. From day 14 to day 18, the carbon monoxide concentration fluctuated abnormally, and the roadway where the detection unit was located was in an abnormal state.

[0028] Step 9: Extract the location data of the detection unit and output the location data and alarm signal. If the target Soter particle size is greater than the first threshold, it indicates that a fire has occurred in the coal mine. The specific location of the fire is obtained through the location data, and the alarm signal is used to notify the crowd to evacuate and begin fire rescue. Example 2

[0029] This embodiment further discloses a preferred method for calculating the Sotter size and the target Sotter size according to the present invention.

[0030] First, the red light intensity I1 and blue light intensity I2 are obtained based on the first and second wavelength signals. The red light extinction coefficient b1 and the blue light extinction coefficient b2 are calculated, then the extinction ratio R is calculated. The average particle size D is obtained by searching the first database based on the extinction ratio. The red light extinction efficiency factor η1 and the blue light extinction efficiency factor η2 are obtained by searching the second database based on the average particle size D, the wavelength j1 of the first wavelength signal, and the wavelength j2 of the second wavelength signal. Thus, the volume concentration V and surface area concentration S are calculated. V = 2b1D / (3η1), S = 4b2 / η2, b1 = [ln(I1 / 3η1) / ( ... 01 / I1)] / L1, b2=[ln(I 02 / I2)] / L2,R=b1 / b2,I 01 I is the initial red light intensity. 02 L1 represents the initial blue light intensity, L2 represents the red light path length, and L3 represents the blue light path length. The Soter particle size is D1 = 6 V / S.

[0031] The first database is a particle size lookup table for Mie scattering, storing the average particle size under different extinction ratios, enabling rapid particle size inversion based on the extinction ratio. The second database is an extinction efficiency lookup table for Mie scattering, storing extinction efficiency factors for different particle sizes, wavelengths, and refractive indices, supporting rapid lookup of extinction efficiency factors. The units for red and blue light intensity are W / m², and the units for red and blue extinction coefficients are m². -1 The red light extinction efficiency factor and the blue light extinction efficiency factor are dimensionless, and the unit of volume concentration V is m³. 3 / m 3 The unit of surface area concentration S is m. 2 / m 3 The units for average particle size D and soter size are micrometers.

[0032] Based on multiple consecutively acquired first-wavelength and second-wavelength signals, a Soter size set D0 is generated, where D0 = {D... 11 D 12 ,…,D 1j ,…,D 1J}, D 1j Let J be the j-th Sott size in the Sott size set, where J is the number of samplings. The Sott sizes in the set are sorted in ascending order of absolute value. The target Sott size is calculated as follows: Calculate the test statistic for each Sott size. The test statistic r for the j-th Sott size... j =(D 1j -D 1(j-1) ) / (D 1J -D11 When the test statistic exceeds the test threshold, the corresponding Sotter size is deleted from the Sotter size set. This process is repeated until the test statistic for each Sotter size is less than the test threshold. The average value of all Sotter sizes in the Sotter size set is then calculated, which is the target Sotter size. Calculating the target Sotter size eliminates the influence of occasional water droplets and large dust particles in the air on fire detection. A significance level of 0.05 is used, and the test threshold is set based on the Dixon criterion critical value table and the number of samplings. Example 3

[0033] This embodiment further discloses a preferred method for updating the second threshold of the detection unit according to the present invention. Due to changes in the airflow state of the tunnel, the actual particle size may differ from the target Sotter particle size. Especially when turbulence occurs in the tunnel, the disturbance causes ion aggregation and dispersion, reducing the predictability of particle size and gas flow. To further improve the accuracy of the early warning, a second threshold needs to be generated based on the turbulence state of the tunnel, and the second threshold is used to further determine whether the target Sotter particle size exceeds the limit. This embodiment determines whether internal turbulence exists in the tunnel connected to the shaft by using the airflow volume and direction of the shaft.

[0034] First, extract the multiple sets of shafts connected to the detection unit. The detection unit mainly absorbs or expels air through the shafts directly connected to it. A method for locating shafts can be a depth-first search. First, determine the roadway where the detection unit is located. Then, using the detection unit as the center, search for other roadways one by one from both ends of the roadway. When passing a roadway node, continue searching along all the branch roadways of that node until a shaft connecting to the roadway is found, or if the roadway is a tactile paving path and the shaft is connected to the detection unit. End the search for that branch roadway and save its shaft number. Continue searching for other branch roadways until all branch roadways have been searched.

[0035] Then, the static pressure and airflow of the fan in each shaft are extracted, and the flow pressure of each shaft is calculated. Flow pressure refers to the air pressure that ultimately produces airflow; flow pressure = R n Q n 2 Q n Let R be the airflow rate in shaft n, where airflow rate refers to the amount of air passing through the shaft. n Let be the drag coefficient of shaft n. The drag coefficient is used to quantify the amount of air resistance an object experiences when moving in a fluid (such as air). It reflects the aerodynamic performance of the object and is affected by factors such as shaft shape, support method, and roughness. It can be obtained through on-site measurement.

[0036] Simultaneously calculate the natural wind pressure for each shaft. Measure the height difference Z between any location in the shaft and the ground (horizontal elevation). The natural wind pressure can be expressed as... Where g is the acceleration due to gravity. The air density ρ in the mine... Z The relationship between the air density and the height difference Z is complex. For ease of calculation, the average density ρ is usually calculated by measuring the air density at multiple points in the shaft. The natural wind pressure can be expressed as F. n =ρgZ. The air density in the shaft cannot be directly measured; in this embodiment, it is calculated indirectly by measuring temperature. Specifically, the air temperature t, absolute pressure P, and relative humidity β are measured at multiple points in the shaft. According to the gas law, ρ = 0.003484P(1 - 0.378P) t β / P) / (237+t), P t Let be the partial pressure of saturated water vapor at temperature t.

[0037] Then calculate the turbulent air pressure for each shaft. Based on... Figure 6 The actual pressure difference between the static pressure of the fan in the shaft and the natural wind pressure creates airflow. According to the wind pressure balance equation, under ideal conditions, H... n +F n =R n Q n 2 ,Right now H n Let F be the static pressure of the fan in shaft n. The static pressure of the fan refers to the rated air pressure supplied by the fan to the shaft, which can be determined based on the fan's operating parameters. For ease of calculation, this invention defines the direction of airflow in the shaft as the positive direction; when airflow cannot be measured, the outward direction of the shaft is defined as the positive direction. When the fan in shaft n is in exhaust mode, F... n <0, when the fan in shaft n is in the air intake state, F n >0.

[0038] Finally, update the second threshold of the detection unit. The turbulence coefficient of the detection unit. The smaller the turbulence coefficient, the greater the difference between the actual pressure difference and the flow ventilation pressure in the shaft corresponding to the detection unit, and the greater the likelihood of turbulence in the roadway corresponding to that detection unit. An ideal value for the turbulence coefficient and the second threshold is fitted to generate a fitting function. In a preferred embodiment, to adjust the upper limit growth rate of the second threshold, the fitting function can be a logarithmic function, i.e., the second threshold λ2 = λ1ln(μ+1), where λ1 is the first threshold. In other specific embodiments, the turbulence coefficient and the second threshold can be fitted into a linear function by combining experimental parameters. Example 4

[0039] like Figure 7As shown, an early warning system for implementing the aforementioned coal mine underground smoke concentration early warning method includes: multiple detection units, a shaft monitoring unit, a control center, and a display unit. The detection units are installed in the shaft and have smoke detectors for acquiring first and second wavelength signals, gas detectors for acquiring first and second gas concentrations, and signal calibrators for updating smoke detector parameters. Each smoke detector has a first transmitter, a second transmitter, a first detector, and a second detector. The shaft monitoring unit is installed in the shaft and has a pressure detector for acquiring fan static pressure and a gas flow meter for acquiring airflow. The control center has a first processing unit, a second processing unit, and a third processing unit. The first processing unit calculates the Sotter particle size and the target Sotter particle size. The second processing unit predicts the turbulence coefficient of the shaft. The third processing unit predicts whether the shaft where the detection unit is located is in an abnormal state. The display unit outputs the location data and alarm signals of the detection units. The control center also includes a wireless communication interface, a main control unit, and a wired communication interface. The wireless communication interface connects to the detection units and the shaft monitoring unit to accelerate data transmission. The wired communication interface connects to the display unit. The main control unit controls the data processing of the first processing unit, the second processing unit, and the third processing unit, and controls the data transmission of the wired communication interface and the wireless communication interface.

[0040] 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 within the protection scope of the present invention.

Claims

1. A method for early warning of smoke concentration in underground coal mines, characterized in that, Includes the following steps: Step 1: The coal mine operating area has multiple sets of shafts, and fans are installed in the shafts. At least two sets of shafts are connected by roadways. Multiple sets of detection units are arranged in the roadways. The detection units have smoke detectors and gas detectors. Step 2: The smoke detector continuously acquires the first wavelength signal and the second wavelength signal, and the gas detector continuously acquires the first gas concentration and the second gas concentration; Step 3: Calculate the volume concentration and surface area concentration based on the first and second wavelength signals of the smoke detector, and calculate the Sotter particle size and target Sotter particle size based on the volume concentration and surface area concentration. Step 4: If the target Soter particle size is greater than the first threshold, proceed to step 9; otherwise, update the parameters of the smoke detector and proceed to step 5. Step 5: Extract multiple sets of shafts connected to the detection unit, extract the static pressure and air flow of the fan in each shaft, calculate the natural wind pressure of each shaft, and then predict the turbulence coefficient of the detection unit. Step 6: Update the second threshold of the detection unit based on the turbulence coefficient. If the target Soter particle size is smaller than the second threshold, return to step 2; otherwise, proceed to step 7. Step 7: Extract multiple sets of continuous first gas concentration and second gas concentration for the gas detector corresponding to the detection unit, and calculate the rate of change of the first concentration and the rate of change of the second concentration. Step 8: Predict whether the roadway where the detection unit is located is in an abnormal state based on the first concentration change rate and the second concentration change rate. If it is in an abnormal state, proceed to step 9; otherwise, return to step 2. Step 9: Extract the location data of the detection unit and output the location data and alarm signal.

2. The method for early warning of underground smoke concentration in coal mines according to claim 1, characterized in that, In step 2, the wavelength of the first wavelength signal is 850nm, the wavelength of the second wavelength signal is 468nm, the first gas concentration is oxygen concentration, and the second gas concentration is carbon monoxide concentration.

3. The method for early warning of underground smoke concentration in coal mines according to claim 2, characterized in that, In step 3, the red light intensity I1 and blue light intensity I2 are obtained based on the first wavelength signal and the second wavelength signal. The red light extinction coefficient b1 and the blue light extinction coefficient b2 are calculated. Then, the extinction ratio R is calculated. The average particle size D is obtained by searching the first database based on the extinction ratio. The red light extinction efficiency factor η1 and the blue light extinction efficiency factor η2 are obtained by searching the second database based on the average particle size D, the wavelength j1 of the first wavelength signal, and the wavelength j2 of the second wavelength signal. Thus, the volume concentration V and the surface area concentration S are calculated, where V = 2b1D / (3η1), S = 4b2 / η2, and b1 = [ln(I1 / I2)]. 01 / I1)] / L1, b2=[ln(I 02 / I2)] / L2,R=b1 / b2,I 01 I is the initial red light intensity. 02 L1 represents the initial blue light intensity, L2 represents the red light path length, and L3 represents the blue light path length. The Soter particle size is D1 = 6 V / S.

4. The method for early warning of underground smoke concentration in coal mines according to claim 3, characterized in that, In step 3, a Sotter size set D0 is generated based on multiple consecutively acquired first wavelength signals and second wavelength signals, where D0 = {D 11 D 12 ,…,D 1j ,…,D 1J }, D 1j Let J be the j-th Sott size in the Sott size set, where J is the number of samplings. The Sott sizes in the set are sorted in ascending order of absolute value. The target Sott size is calculated as follows: calculate the test statistic for each Sott size. The test statistic r for the j-th Sott size... j =(D 1j -D 1(j-1) ) / (D 1J -D 11 When the test statistic is greater than the test threshold, the corresponding Sotter size in the Sotter size set is deleted. The above steps are repeated until the test statistic of each Sotter size is less than the test threshold. Then the average value of all Sotter sizes in the Sotter size set is calculated and stored as the target Sotter size.

5. The method for early warning of underground smoke concentration in coal mines according to claim 1, characterized in that, In step 4, noise data G(f, d, I) of the smoke detector is collected, where f is the switching frequency, d is the modulation depth, and I is the bias current. The initial parameter set x0 of the smoke detector is obtained. The total noise energy function E0(x) and the peak energy function E1(x) are fitted based on the noise data and the initial parameter set. The objective function is constructed based on the total noise energy function and the peak energy function, and the objective parameter set is obtained. The parameters of the smoke detector are updated based on the objective parameter set.

6. The method for early warning of underground smoke concentration in coal mines according to claim 4, characterized in that, In step 5, based on the air flow rate Q of shaft n n and drag coefficient R n Calculate the flow ventilation pressure R of shaft n n Q n 2 Turbulence coefficient of the detection unit H n F is the static pressure of the blower in shaft n. n Let N be the natural wind pressure of shaft n, and N be the number of shafts connected to this detection unit.

7. The method for early warning of underground smoke concentration in coal mines according to claim 6, characterized in that, In step 6, the second threshold λ2 = λ1ln(μ+1), where λ1 is the first threshold.

8. The method for early warning of underground smoke concentration in coal mines according to claim 7, characterized in that, In step 7, a first concentration set C1 is generated based on the continuously collected first gas concentrations, C1 = {c 11 ,c 12 ,…,c 1k ,…,c 1K }, based on the continuously collected second gas concentrations, a second concentration set C2 is generated, C2={c 21 ,c 22 ,…,c 2k ,…,c 2K }, c 1k Let c be the concentration of the k-th first gas in the first concentration set. 2k The k-th second gas concentration in the second concentration set, and the rate of change of the first concentration. Second concentration change rate .

9. The method for early warning of underground smoke concentration in coal mines according to claim 8, characterized in that, In step 8, if g1>0 and g2>0 and g2 / g1>λ3, where λ3 is the proportional threshold, then the roadway where the detection unit is located is in an abnormal state.

10. An early warning system for implementing the coal mine underground smoke concentration early warning method of claim 1, characterized in that, include: Multiple detection units, wellbore monitoring units, control center, and display units. The detection unit is installed in the tunnel and has a smoke detector for acquiring a first wavelength signal and a second wavelength signal, a gas detector for acquiring a first gas concentration and a second gas concentration, and a signal calibrator for updating the parameters of the smoke detector. The smoke detector has a first transmitter, a second transmitter, a first detector, and a second detector. The well monitoring unit is installed in the well and has a pressure detector for collecting the static pressure of the fan and a gas flow meter for collecting the air flow rate. The control center has a first processing unit, a second processing unit, and a third processing unit. The first processing unit is used to calculate the Soter particle size and the target Soter particle size. The second processing unit is used to predict the turbulence coefficient of the shaft. The third processing unit is used to predict whether the roadway where the detection unit is located is in an abnormal state. The display unit is used to output the location data and alarm signals of the detection unit.

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