Smoke methane complex detector and method

Abstract

The application discloses a smoke and methane composite detector and method, and relates to the technical field of gas detectors, and the method is applied to a smoke and methane composite detector with a single-wavelength laser light source. The method comprises the following steps: acquiring an extinction signal background value and a scattering signal background value under the condition of no smoke and methane; acquiring an extinction signal and a scattering signal in real time during the detection process, determining the methane concentration in a detection area based on the extinction signal; constructing a characteristic parameter reflecting the interference degree of aerosol in the detection area based on the extinction signal and the extinction signal background value, and the scattering signal and the scattering signal background value; determining the aerosol type in the detection area according to the characteristic parameter, and executing a corresponding alarm strategy based on the aerosol type. The method can realize the composite detection of smoke and methane under a single light source, effectively suppress the interference of non-fire aerosol on the detection of methane and smoke, and improve the detection precision and reliability.

Description

Technical Field

[0001] This invention relates to the field of gas detector technology, and in particular to a smoke-methane composite detector and method. Background Technology

[0002] With the widespread use of natural gas in cities, methane leaks have become a significant safety hazard, especially in industrial, commercial, and residential settings. Methane leaks not only pose a risk of fire and explosion but can also endanger public safety. Therefore, early warning and detection systems for methane leaks and fires have become crucial safety measures. Currently, a common technical solution for combined detection of methane leaks and fire smoke is to stack and integrate existing methane and smoke detectors to achieve combined detection of both on a single detector. However, this integrated design increases the detector size and cost, and also increases system complexity, making debugging and maintenance more difficult. Alternatively, some solutions use multiple independent detectors to detect methane and smoke separately and process the signals centrally. While this approach allows for independent detection of the two substances, it also results in high alarm system construction costs, complex correlations, and significant issues with false alarms and missed alarms.

[0003] Currently, methane and smoke detection based on photoelectric technology is gaining increasing attention. Among these, Tunable Diode Laser Absorption Spectroscopy (TDLAS) is widely used in methane detection, offering significant advantages in methane gas concentration detection due to its excellent selectivity, fast response, and high sensitivity. However, this technology is susceptible to interference from aerosols (especially water vapor), which can affect detection accuracy. To avoid this interference, filters and waterproof / breathable meshes are often installed in the equipment to block the influence of smoke, dust, and other aerosols on the detection signal.

[0004] In smoke detection, LED light sources are primarily used. While these sources are relatively inexpensive, they suffer from significant wavelength fluctuations and wide emission angles, which can lead to signal power fluctuations and affect the accurate measurement of smoke concentration. Furthermore, LED light sources are susceptible to interference from aerosols such as dust and water vapor in fire smoke detection, resulting in false alarms. Therefore, it is necessary to use multiple LED light sources with different wavelengths and multiple photoelectric converters to receive scattered light from different angles, thereby reducing false alarms. While this approach improves smoke detection performance, it also increases the system's complexity and cost. Summary of the Invention

[0005] This invention aims to at least partially address one of the technical problems in related technologies. Therefore, the objective of this invention is to propose a smoke and methane composite detector and method to simplify the complex design and high cost of the detector, while improving the detection accuracy and reliability of methane leaks and fire smoke in complex environments.

[0006] To achieve the above objectives, a first aspect of the present invention provides a method for detecting smoke-methane recombination, applied to a smoke-methane recombination detector with a single-wavelength laser light source. The smoke-methane recombination detector includes a first photoelectric converter disposed along the laser emission direction and a second photoelectric converter disposed at an acute angle to the laser emission direction. The method includes:

[0007] Under conditions of no smoke and no methane, the background values ​​of extinction signal and scattering signal were obtained respectively.

[0008] During the detection process, extinction and scattering signals are acquired in real time, and the methane concentration in the detection area is determined based on the extinction signal.

[0009] Based on the extinction signal and the background value of the extinction signal, as well as the scattering signal and the background value of the scattering signal, characteristic parameters reflecting the degree of aerosol interference in the detection area are constructed; the characteristic parameters include: scattering signal change, attenuation rate, and scattering extinction ratio;

[0010] Determining the aerosol type within the detection area based on the characteristic parameters includes: determining whether the detection area contains aerosol particles based on the relationship between the change in the scattering signal and a preset scattering threshold; if aerosol particles are determined to be present in the detection area, determining the aerosol type within the detection area based on the light reduction rate and the scattering extinction ratio; and executing a corresponding alarm strategy based on the aerosol type.

[0011] The alarm strategy includes at least one of the following: directly triggering an alarm based on the methane concentration, triggering an alarm after correcting the methane concentration based on the water vapor concentration, and triggering an alarm based on the smoke concentration.

[0012] In addition, the smoke methane composite detection method of the above embodiments of the present invention may also have the following additional technical features:

[0013] According to one embodiment of the present invention, constructing the characteristic parameters reflecting the degree of aerosol interference within the detection area includes:

[0014] The difference between the scattered signal and the background value of the scattered signal is calculated to obtain the change in the scattered signal;

[0015] The ratio of the extinction signal to the background value of the extinction signal is calculated to obtain the light reduction rate;

[0016] The ratio of the change in the scattered signal to the attenuation rate is calculated to obtain the scattering extinction ratio.

[0017] According to an embodiment of the present invention, determining the aerosol type within the detection area based on the characteristic parameters includes:

[0018] If the change in the scattered signal is greater than the preset scattering threshold, it is determined that aerosol particles exist in the detection area; the aerosol types include fire smoke, water vapor, oil fumes, and dust.

[0019] According to an embodiment of the present invention, determining the aerosol type within the detection area based on the attenuation rate and the scattering extinction ratio includes:

[0020] Determine whether the light reduction rate is greater than a preset light reduction rate threshold;

[0021] If the light reduction rate is greater than the light reduction rate threshold, and the scattering extinction ratio is within the range of the first preset threshold... With the second preset threshold If the first preset range is defined, then the aerosol type is determined to be oil fume;

[0022] If the light reduction rate is greater than the light reduction rate threshold, and the scattering extinction ratio is within the range of the second preset threshold... With the third preset threshold If the second preset interval is defined, then the aerosol type is determined to be fire smoke;

[0023] If the light reduction rate is less than the light reduction rate threshold, and the scattering extinction ratio is within the range of the fourth preset threshold... With the fifth preset threshold If the third preset range is defined, the aerosol type is determined to be dust.

[0024] If the light reduction rate is less than the light reduction rate threshold, and the scattering extinction ratio is within the range of the fifth preset threshold... With the sixth preset threshold If the fourth preset interval is defined, then the aerosol type is determined to be water vapor; wherein,

[0025] ,and The first preset interval, the second preset interval, the third preset interval, and the fourth preset interval are non-overlapping intervals divided for the same scattering extinction ratio parameter.

[0026] According to one embodiment of the present invention, the execution of the corresponding alarm strategy based on the aerosol type includes:

[0027] When the aerosol type is determined to be fire smoke, an alarm strategy based on smoke concentration is executed; wherein, the alarm strategy is:

[0028] The smoke concentration within the detection area is calculated based on the change in the scattered signal.

[0029] If the smoke concentration is greater than the preset smoke alarm threshold, a fire alarm will be triggered.

[0030] According to one embodiment of the present invention, the execution of the corresponding alarm strategy based on the aerosol type includes:

[0031] When the aerosol type is determined to be water vapor, an alarm strategy is implemented that corrects the methane concentration based on the water vapor concentration before triggering an alarm; wherein, the alarm strategy is:

[0032] The water vapor concentration is calculated based on the change in the scattering signal. The methane concentration is then corrected using the water vapor concentration and a correction coefficient for the influence of water vapor on the methane absorption characteristics to obtain the corrected methane concentration. The correction coefficient is used to characterize the degree of influence of the change in water vapor concentration on the methane absorption signal.

[0033] If the corrected methane concentration is greater than the preset methane alarm threshold, a methane alarm will be triggered.

[0034] According to one embodiment of the present invention, the execution of the corresponding alarm strategy based on the aerosol type includes:

[0035] When the aerosol type is determined to be oil fume or dust, the fire alarm and methane alarm will not be triggered.

[0036] According to one embodiment of the present invention, the execution of the corresponding alarm strategy based on the aerosol type includes:

[0037] If no aerosol particles are detected within the detection area, and the methane concentration is greater than a preset methane alarm threshold, a methane alarm will be triggered directly.

[0038] To achieve the above objectives, a second aspect of the present invention provides a smoke-methane recombination detector, comprising:

[0039] A laser source used to emit laser light of a single wavelength;

[0040] The optical chamber is equipped with a detection area that allows gases or aerosols to enter;

[0041] The first photoelectric converter is arranged along the emission direction of the laser and is used to receive the extinction signal after passing through the detection area;

[0042] The second photoelectric converter is set at an acute angle to the laser emission direction and is used to receive the scattered signal in the detection area;

[0043] The controller is connected to the laser source, the first photoelectric converter, and the second photoelectric converter, respectively; the controller is configured to perform the smoke methane composite detection method proposed in the first aspect embodiment.

[0044] According to one embodiment of the present invention, the smoke methane composite detector further includes a folded optical path structure, wherein the laser emitted by the laser source is reflected by at least one mirror and then incident on the first photoelectric converter.

[0045] The smoke and methane composite detector and method of this invention achieve composite detection of methane and smoke by employing a single-wavelength laser light source, avoiding the high cost and complexity issues associated with traditional multi-wavelength detectors and stacked designs. Simultaneously, by utilizing two photoelectric converters to receive extinction signals and forward angular scattering signals, and through signal processing, the interference of aerosols on methane concentration measurement can be minimized. This method not only enables accurate measurement of methane concentration but also reduces the false alarm rate caused by interfering aerosols, improving the stability and reliability of the system. Attached Figure Description

[0046] Figure 1 This is a schematic flowchart of the smoke methane composite detection method in the embodiment;

[0047] Figure 2 This is a schematic diagram of the gas flow process for the sol type in the embodiment;

[0048] Figure 3 This is a schematic diagram of the smoke-methane composite detector in the embodiment;

[0049] Figure 4 This is a schematic diagram of the structure of the smoke and methane composite detector with the optical path increased to 2 times in the embodiment;

[0050] Figure 5 This is a schematic diagram of the data processing flow of the smoke and methane composite detector in the embodiment.

[0051] Figure reference numerals: 1. Laser source; 2. First photoelectric converter; 3. Second photoelectric converter; 4. Optical chamber; 5. Controller; 6. First reflector; 7. Second reflector. Detailed Implementation

[0052] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0053] To facilitate understanding and implementation of the method of this invention by those skilled in the art, the following will first introduce a smoke-methane recombination detector carrying the method of this invention, and then elaborate on the method steps in detail. The structure of the smoke-methane recombination detector is as follows: Figure 3 As shown, the system includes a laser source 1, an optical chamber 4, a first photoelectric converter 2, a second photoelectric converter 3, and a controller 5. Specifically, the laser source 1 emits a single-wavelength laser signal, typically 1653.7 nm, suitable for the characteristic absorption band of methane gas, thus enabling effective detection of methane concentration. The optical chamber 4 has a detection area that allows gas or aerosol to enter, ensuring sufficient interaction between the laser and the target gas or aerosol, thereby inducing extinction and scattering effects. The first photoelectric converter 2 is located directly opposite the laser source and receives the extinction signal after passing through the detection area. The second photoelectric converter 3 is positioned at an acute angle to the laser emission direction and receives the scattered signal within the detection area. The controller 5 is connected to the laser source 1, the first photoelectric converter 2, and the second photoelectric converter 3, and is responsible for processing signals and executing the smoke-methane composite detection method.

[0054] The folded optical path structure of the smoke-methane composite detector effectively guides the laser beam to the first photoelectric converter 2 after reflection by at least one mirror. By folding the optical path, the optical path length of the laser beam within the detection area is increased, thereby enhancing the interaction between the laser and methane gas within the detection area. This design causes the laser beam to undergo multiple reflections within the detection area, amplifying the absorption effect of the methane gas on the laser, thus improving the measurement accuracy of the methane concentration. Figure 4 As shown, the folded optical path consists of a first reflector 6 and a second reflector 7. In this structure, the optical path is doubled after two reflections, thereby improving the detection sensitivity and ensuring more accurate measurement of methane gas concentration.

[0055] After understanding the basic structure and working principle of the smoke and methane combined detector, the following section will detail how to use this detector to detect the combined smoke and methane. In one embodiment, such as... Figure 1 The diagram shows a flowchart of a method for detecting methane in smoke, which may include the following steps:

[0056] Step S101: Under the conditions of no smoke and no methane, the background values ​​of the extinction signal and the background values ​​of the scattering signal are obtained respectively.

[0057] Before detection begins, ensure the detection area is free of smoke and methane interference. Under these conditions, control the laser signal emitted by the laser source to pass through the detection area and interact with gas molecules in the environment. The extinction signal after passing through the detection area is received by the first photoelectric converter 2. And recorded as the background value of the extinction signal. Since there is no methane gas in the environment, the extinction signal at this time is mainly affected by the absorption of the gas itself and aerosols, serving as the reference value for subsequent detection signals.

[0058] At the same time, the scattered signal in the detection area is received by the second photoelectric converter 3. And recorded as the background value of the scattered signal. The signal primarily originates from the scattering of laser light by molecules and tiny particles in the air. Under conditions free of smoke and methane, these signals merely reflect the scattering characteristics under normal environmental conditions and are used as a benchmark for subsequent signal comparisons.

[0059] Step S102: During the detection process, extinction signal and scattering signal are acquired in real time, and the methane concentration in the detection area is determined based on the extinction signal.

[0060] After detection begins, the laser source continuously emits a laser signal with a wavelength of 1653.7 nm. This signal passes through the detection area and interacts with gas molecules (such as methane) and aerosol particles. The first photoelectric converter 2 then acquires the extinction signal after the signal has passed through the detection area. and the scattered signal is obtained through the second photoelectric converter 3. .

[0061] Among them, extinction signal The changes reflect changes in gas (especially methane) absorption, as indicated by the extinction signal. The demodulation can identify the absorption peak of methane, and calculate the methane concentration based on the depth and shape of the absorption peak. Methane concentration value The calculation is based on standard absorption spectroscopy analysis and, combined with known absorption coefficients, can accurately measure methane concentration.

[0062] Step S103: Based on the extinction signal and the extinction signal background value, as well as the scattering signal and the scattering signal background value, construct characteristic parameters that reflect the degree of aerosol interference in the detection area.

[0063] By comprehensively analyzing the variation characteristics of extinction and scattering signals relative to the corresponding background values, the influence of aerosols on the propagation of light signals within the detection area is quantitatively characterized, thereby forming characteristic parameters that reflect the degree of aerosol interference.

[0064] Aerosol interference refers to the combined effect of aerosol particles (such as fire smoke, water vapor, and dust) on the laser signal propagation path after entering the detection area, causing changes in the extinction and scattered signals. This interference not only affects the intensity of the extinction and scattered signals but may also impact the accurate measurement of methane concentration. To accurately quantify this effect, characteristic parameters are constructed to characterize the degree of aerosol interference.

[0065] By constructing characteristic parameters, we can assess the impact of different aerosol types on the detection signal. This is a key step in achieving accurate detection and reducing false alarms, thereby enabling more accurate responses in various complex environments.

[0066] In one embodiment, when constructing characteristic parameters reflecting the degree of aerosol interference, the change in the scattered signal is first obtained by subtracting the real-time scattered signal from its background value. This change reflects the degree of scattering enhancement caused by aerosol particles within the detection area. The change in the scattered signal... It can be represented as:

[0067]

[0068] Simultaneously, the attenuation rate is obtained by calculating the ratio of the real-time extinction signal to the background value of the extinction signal. This attenuation rate characterizes the degree of transmission attenuation caused by aerosol and gas absorption during laser propagation within the detection area. The attenuation rate is... It can be represented as:

[0069]

[0070] Based on this, the ratio of the change in scattered signal to the attenuation rate is further calculated to obtain the scattering extinction ratio. The scattering extinction ratio is used to comprehensively characterize the relative relationship between scattering and extinction effects, thereby improving the ability to distinguish aerosol interference characteristics. Specifically, the scattering extinction ratio... It can be represented as:

[0071]

[0072] By calculating the above parameters, the interference characteristics of aerosols on the propagation of optical signals can be characterized from multiple dimensions, providing a reliable quantitative basis for subsequent aerosol type identification and alarm strategy selection based on feature parameters.

[0073] Step S104: Determine the aerosol type in the detection area based on the characteristic parameters, and execute the corresponding alarm strategy based on the aerosol type.

[0074] By comprehensively analyzing the characteristic parameters reflecting the degree of aerosol interference, the influence of aerosols on the propagation of optical signals within the detection area can be determined. Because different types of aerosols exhibit significant differences in their absorption and scattering behaviors due to variations in particle size distribution, refractive index, and other physical properties, their characteristic parameters for extinction and scattered signals also differ. Based on these differences, the types of aerosols within the detection area can be distinguished.

[0075] Among them, such as Figure 2 As shown, the process for determining the type of aerosol may include the following steps:

[0076] Step S201: Based on the relationship between the change in the scattering signal and the preset scattering threshold, determine whether aerosol particles are present in the detection area.

[0077] Step S202: If it is determined that there are aerosol particles in the detection area, the type of aerosol in the detection area is determined according to the light reduction rate and the scattering extinction ratio.

[0078] Specifically, the presence of aerosol particles in the detection area is determined based on the relationship between the change in the scattered signal and a preset scattering threshold. The change in the scattered signal reflects the degree of scattering enhancement caused by suspended particles during the propagation of the detection beam. This is achieved by comparing the change in the scattered signal with a preset scattering threshold. By comparing the samples, it can be confirmed whether aerosol particles are present in the detection area.

[0079] Given the presence of aerosol particles within the detection area, the interference properties of aerosols are analyzed based on attenuation rate and scattering extinction ratio. Different types of aerosols exhibit significant differences in particle size distribution, composition, and refractive index, resulting in varying overall performance in absorption and scattering behavior. Consequently, they display distinguishable differences in the combined characteristics of attenuation rate and scattering extinction ratio.

[0080] Aerosol type is used to characterize the presence of aerosols in the current detection environment that affect methane and smoke detection, as well as the interference properties of these aerosols on the detection results. By introducing the determination of aerosol type, it is possible to avoid misjudging signal changes caused by non-fire-related aerosols or non-methane factors as alarm events.

[0081] After determining the aerosol type, an alarm strategy is selected and executed based on the influence characteristics of different aerosol types on the detection results. The alarm strategy includes at least one of the following:

[0082] (1) The alarm is triggered directly based on the methane concentration determined in step S102, which is suitable for situations where aerosol interference is small or negligible.

[0083] (2) Correcting the methane concentration based on the water vapor concentration before determining whether to trigger an alarm is applicable to situations where aerosols in the detection area affect the methane absorption signal, resulting in inaccurate methane concentration determined based on the extinction signal.

[0084] (3) Alarms are triggered based on smoke concentration, which is applicable to situations where the aerosol type is characterized as fire-related smoke.

[0085] By employing the above methods, timely early warnings of methane leaks and fire risks can be ensured, while effectively reducing the probability of false alarms caused by interfering aerosols in the environment, thereby improving the reliability and environmental adaptability of composite detection.

[0086] In one embodiment, when the change in the scattering signal, representing the degree of scattering enhancement, exceeds a preset scattering threshold... When the time is right, it indicates the presence of aerosol particles in the detection area that are sufficient to significantly affect the propagation of the light signal, thus confirming that the detection area contains aerosol particles.

[0087] In environments with no aerosol particles or extremely low aerosol concentrations, the propagation of the laser within the detection area is relatively stable, and the scattered signal mainly originates from the optical device itself and environmental background noise. Its variation relative to the background value is typically within a small fluctuation range. However, when aerosol particles are present in the detection area, the particles exert additional scattering on the laser, significantly increasing the energy of the scattered light entering the second photoelectric converter. This results in a significant enhancement of the scattered signal relative to the background value.

[0088] Based on the above characteristics, by comparing the change in the scattered signal with a preset scattering threshold, it is possible to effectively distinguish between normal fluctuations caused by system noise or slight environmental disturbances and genuine scattering enhancement introduced by aerosol particles, effectively confirming the presence of aerosol particles in the detection area. Furthermore, by comprehensively analyzing the relationship between attenuation rate and scattering extinction ratio, the type of aerosol interference in the detection area can be determined, thereby classifying aerosols into different types such as fire smoke, water vapor, oil fumes, and dust.

[0089] In one embodiment, aerosol types are further subdivided by combining light reduction rate and scattering extinction ratio. Specifically, when the light reduction rate is greater than a light reduction rate threshold... In this case, it indicates that the aerosols in the detection area have a strong extinction effect on the optical signal. Further analysis based on the scattering extinction ratio is then necessary. Differentiate aerosol types based on scattering extinction ratio The overall value range is pre-divided into multiple non-overlapping intervals, and a portion of these intervals are selected for aerosol type determination under high extinction conditions. When the scattering extinction ratio... Falling into the first preset interval At that time, the aerosol type in the detection area was determined to be oil fume. When the scattering extinction ratio... Falling into the second preset interval At that time, the aerosol type in the detection area is determined to be fire smoke. Since cooking fumes and fire smoke differ in particle composition and scattering characteristics, their corresponding scattering extinction ratio ranges are different, so they can be distinguished using the above method.

[0090] When the light reduction rate is less than the light reduction rate threshold This indicates that the overall extinction effect of aerosols on the optical signal is relatively weak. Under further circumstances, continuing to use the same scattering extinction ratio... In another region of the non-overlapping interval system, the aerosol type under low extinction conditions is determined. When the scattering extinction ratio... Falling into the third preset interval At that time, the aerosol type was determined to be dust. When the scattering extinction ratio... Falling into the fourth preset interval At that time, the aerosol type was determined to be water vapor.

[0091] in, , , , , , , These are the preset threshold values, and ,and This ensures that the interval divisions of different aerosol types in the scattering extinction ratio dimension do not overlap.

[0092] In one embodiment, when the aerosol type in the detection area is determined to be fire smoke based on the aerosol type determination result, an alarm strategy based on smoke concentration is executed to further determine whether the fire alarm conditions have been met.

[0093] Specifically, based on the change in the scattered signal Calculate the smoke concentration value within the detection area. Since fire smoke particles significantly enhance the scattering effect in the light propagation path, the change in the scattering signal can effectively characterize the concentration change of smoke particles. Therefore, the change in the scattering signal can be used as an input parameter for smoke concentration calculation.

[0094] Obtaining smoke concentration values Then, compare it with the preset smoke alarm threshold. The system compares the smoke concentration with the alarm threshold. When the smoke concentration exceeds the alarm threshold, the system determines that the smoke concentration in the detection area has reached the alarm condition and triggers a fire alarm. If the smoke concentration does not exceed the alarm threshold... In such cases, the fire alarm will not be triggered to avoid false alarms caused by low concentrations of smoke.

[0095] By adopting the above method, and given that the aerosol type is clearly fire smoke, introducing a secondary determination mechanism based on smoke concentration can further improve the reliability and accuracy of fire alarms.

[0096] In one embodiment, when the aerosol type in the detection area is determined to be water vapor, an alarm strategy is implemented to trigger an alarm after correcting the methane concentration based on the water vapor concentration, so as to reduce the interference of water vapor on the methane detection results.

[0097] Specifically, based on the change in the scattered signal Calculate the water vapor concentration value within the detection area. Water vapor particles produce a significant scattering effect in the laser propagation path, and there is a corresponding relationship between the change in the scattering signal and the water vapor concentration. Therefore, the water vapor concentration can be calculated based on the change in the scattering signal.

[0098] Since water vapor can affect the intensity of the methane absorption peak and thus interfere with the methane concentration measurement results, a preset correction coefficient is introduced after obtaining the water vapor concentration value. The methane concentration is then corrected to obtain the corrected methane concentration. The correction factor is... It is used to characterize the degree of influence of unit water vapor concentration on methane concentration measurement results. It can be preset according to the characteristics of the detection optical path, the working band, and the interference relationship between water vapor and methane absorption characteristics, so that the correction process can reflect the actual influence of water vapor on methane detection results.

[0099] Corrected methane concentration It can be represented as:

[0100]

[0101] Subsequently, the corrected methane concentration Compared with the preset methane alarm threshold The system compares the results, and when the corrected methane concentration exceeds the methane alarm threshold, it determines that there is a risk of methane leakage in the detection area and triggers a methane alarm.

[0102] By correcting the methane concentration under water vapor conditions, the interference of water vapor on methane detection results can be effectively reduced, thereby improving the accuracy of methane alarms.

[0103] In one embodiment, when the aerosol type in the detection area is determined to be oil fume or dust based on the aerosol type determination result, an alarm strategy that does not trigger fire alarm and methane alarm is implemented.

[0104] Specifically, oil fumes and dust are non-fire, non-gas leakage aerosols that may occur in daily or industrial environments. Within a certain concentration range, they can scatter and extinct light signals, but they do not directly represent fire risk or methane leakage risk.

[0105] Therefore, if the aerosol type is determined to be oil fumes or dust, the fire alarm process based on smoke concentration will not be activated, nor will the methane alarm based on methane concentration be triggered, thereby avoiding false alarms caused by non-hazardous aerosols.

[0106] In one embodiment, when it is determined from the analysis results of the characteristic parameters that there are no aerosol particles in the detection area, it is considered that there is no significant optical interference caused by aerosols such as smoke, water vapor, oil fumes or dust in the current detection environment.

[0107] In this case, the methane absorption characteristics contained in the extinction signal mainly reflect the absorption of the light signal by the methane gas itself, and the influence of aerosols on the methane concentration measurement results can be ignored. Therefore, there is no need to correct for the methane concentration or introduce an additional aerosol discrimination process.

[0108] Based on this, when the change in the scattering signal is less than the preset scattering threshold, it can be determined that there are no aerosol particles in the detection area. Therefore, the methane concentration calculated based on the extinction signal can be directly compared with the preset methane alarm threshold. The comparison is performed, and when the methane concentration is greater than the methane alarm threshold, the methane alarm is triggered directly.

[0109] Understandably, if no aerosol particles are present in the detection area, it is unnecessary to determine the aerosol type, and therefore, there is no need to calculate the attenuation rate and scattering extinction ratio. During the construction of characteristic parameters, when the change in the scattered signal is less than a preset scattering threshold, the calculation of the attenuation rate and scattering extinction ratio can be omitted; only when the change in the scattered signal exceeds the preset scattering threshold is it necessary to calculate the attenuation rate and scattering extinction ratio to further analyze the aerosol type and execute the corresponding alarm strategy.

[0110] The smoke and methane combined detection method of this invention uses a single-wavelength laser light source and combines multi-dimensional analysis of extinction and scattering signals to simultaneously and effectively detect methane and fire smoke under the same optical path. It also suppresses interference from non-fire aerosols on the detection results. By measuring methane concentration based on extinction signals and identifying aerosol interference from scattering signals, it can accurately distinguish between fire smoke, water vapor, dust, and other aerosols. Furthermore, it corrects the methane detection results based on water vapor concentration, reducing the probability of false alarms caused by aerosol interference, thereby improving the overall performance and reliability of the detection system.

[0111] In the aforementioned specific embodiments, a detailed description is provided of how the smoke and methane composite detector identifies aerosols within the detection area through multi-dimensional analysis, thereby effectively reducing false alarms during methane and smoke detection. Based on this, Figure 5 A schematic diagram of the data processing flow for a smoke-methane recombination detector is shown below.

[0112] In the data processing flow, the first photoelectric converter 2 and the second photoelectric converter 3 receive and record the background values ​​of the extinction signal and the background values ​​of the scattering signal under smoke-free and methane-free environments, respectively. Upon entering the real-time detection phase, the smoke-methane composite detector continuously receives the current real-time extinction signal and real-time scattering signal in a loop. In this phase, the smoke-methane composite detector first calculates the current methane concentration based on the demodulated real-time extinction signal. At the same time, the change in the real-time scattered signal relative to the background value is calculated, i.e., the change in the scattered signal.

[0113] Subsequently, the smoke and methane composite detector determines whether the change in the scattered signal exceeds a preset scattering threshold. If the result is negative, it indicates that there are no obvious aerosol particles in the optical path. In this case, the methane concentration is directly compared with the preset methane alarm threshold. The comparison is performed. If the value is greater than the value, a methane alarm is triggered; otherwise, the system returns to continue receiving real-time signals.

[0114] If the change in the scattered signal is determined to be greater than the scattering threshold, it indicates the presence of aerosol particles in the detection area, and the aerosol classification and identification process begins. In this process, the attenuation rate is first calculated, and then the scattering extinction ratio of the change in the scattered signal to the attenuation rate is further calculated. The smoke-methane composite detector classifies aerosols into two processing paths based on the magnitude of the attenuation rate:

[0115] When the light reduction rate is greater than the preset light reduction rate threshold, it is further determined whether the scattering extinction ratio is greater than the second preset threshold. If the scattering extinction ratio is not greater than If the scattering extinction ratio is greater than 1, it is determined to be oil fume interference and no alarm is triggered; If the smoke concentration exceeds the smoke alarm threshold, it is determined to be fire smoke, and the smoke concentration is calculated based on the scattered signal. When the smoke concentration exceeds the smoke alarm threshold, a fire alarm is triggered.

[0116] When the light reduction rate is not greater than the preset light reduction rate threshold, it is further determined whether the scattering extinction ratio is greater than the fifth preset threshold. If the scattering extinction ratio is not greater than If the scattering extinction ratio is greater than 1, it is determined to be dust interference and no alarm is triggered; If the water vapor concentration is too high, it is determined to be a water vapor interference. To address this, the water vapor concentration is calculated, and the initially calculated methane concentration is corrected to obtain the corrected methane concentration. Finally, it is determined whether the corrected methane concentration exceeds the methane alarm threshold. If it does, a methane alarm is triggered; otherwise, the detection cycle returns to the next iteration.

[0117] Through this data processing workflow, the smoke-methane composite detector can achieve accurate methane leak monitoring while effectively avoiding the risk of false alarms caused by aerosol interference. The intelligent analysis and precise identification mechanism of this smoke-methane composite detector greatly improves the accuracy of fire early warning and gas detection, especially under complex environmental conditions, ensuring stable and effective operation.

[0118] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0119] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0120] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for detecting methane in smoke, characterized in that, A method for a smoke-methane recombination detector with a single-wavelength laser source, the smoke-methane recombination detector comprising a first photoelectric converter disposed along the laser emission direction and a second photoelectric converter disposed at an acute angle to the laser emission direction, the method comprising: Under conditions of no smoke and no methane, the background values ​​of extinction signal and scattering signal were obtained respectively. During the detection process, extinction and scattering signals are acquired in real time, and the methane concentration in the detection area is determined based on the extinction signal. Based on the extinction signal and its background value, as well as the scattered signal and its background value, characteristic parameters reflecting the degree of aerosol interference within the detection area are constructed. These characteristic parameters include: calculating the difference between the scattered signal and its background value to obtain the change in the scattered signal; calculating the ratio of the extinction signal to its background value to obtain the attenuation rate; and calculating the ratio of the change in the scattered signal to the attenuation rate to obtain the scattering extinction ratio. Determining the aerosol type within the detection area based on the characteristic parameters includes: determining whether the detection area contains aerosol particles based on the relationship between the change in the scattering signal and a preset scattering threshold; if aerosol particles are determined to be present in the detection area, determining the aerosol type within the detection area based on the light reduction rate and the scattering extinction ratio; and executing a corresponding alarm strategy based on the aerosol type. The alarm strategy includes at least one of the following: directly triggering an alarm based on the methane concentration, triggering an alarm after correcting the methane concentration based on the water vapor concentration, and triggering an alarm based on the smoke concentration.

2. The method for detecting combined smoke and methane according to claim 1, characterized in that, Determining the aerosol type within the detection area based on the characteristic parameters includes: If the change in the scattered signal is greater than the preset scattering threshold, it is determined that aerosol particles exist in the detection area; the aerosol types include fire smoke, water vapor, oil fumes, and dust.

3. The method for detecting combined smoke and methane according to claim 2, characterized in that, Determining the aerosol type within the detection area based on the attenuation rate and the scattering extinction ratio includes: Determine whether the light reduction rate is greater than a preset light reduction rate threshold; If the light reduction rate is greater than the light reduction rate threshold, and the scattering extinction ratio is within the range of the first preset threshold... With the second preset threshold If the first preset range is defined, then the aerosol type is determined to be oil fume; If the light reduction rate is greater than the light reduction rate threshold, and the scattering extinction ratio is within the range of the second preset threshold... With the third preset threshold If the second preset interval is defined, then the aerosol type is determined to be fire smoke; If the light reduction rate is less than the light reduction rate threshold, and the scattering extinction ratio is within the range of the fourth preset threshold... With the fifth preset threshold If the third preset range is defined, the aerosol type is determined to be dust. If the light reduction rate is less than the light reduction rate threshold, and the scattering extinction ratio is within the range of the fifth preset threshold... With the sixth preset threshold If the fourth preset interval is defined, then the aerosol type is determined to be water vapor; wherein, ,and The first preset interval, the second preset interval, the third preset interval, and the fourth preset interval are non-overlapping intervals divided for the same scattering extinction ratio parameter.

4. The method for detecting combined smoke and methane according to claim 2, characterized in that, The execution of the corresponding alarm strategy based on the aerosol type includes: When the aerosol type is determined to be fire smoke, an alarm strategy based on smoke concentration is executed; wherein, the alarm strategy is: to calculate the smoke concentration in the detection area based on the change in the scattered signal; If the smoke concentration is greater than the preset smoke alarm threshold, a fire alarm will be triggered.

5. The method for detecting combined smoke and methane according to claim 2, characterized in that, The execution of the corresponding alarm strategy based on the aerosol type includes: When the aerosol type is determined to be water vapor, an alarm strategy is implemented that corrects the methane concentration based on the water vapor concentration before triggering an alarm; wherein, the alarm strategy is: The water vapor concentration is calculated based on the change in the scattering signal. The methane concentration is then corrected using the water vapor concentration and a correction coefficient for the influence of water vapor on the methane absorption characteristics to obtain the corrected methane concentration. The correction coefficient is used to characterize the degree of influence of the change in water vapor concentration on the methane absorption signal. If the corrected methane concentration is greater than the preset methane alarm threshold, a methane alarm will be triggered.

6. The method for detecting combined smoke and methane according to claim 2, characterized in that, The execution of the corresponding alarm strategy based on the aerosol type includes: When the aerosol type is determined to be oil fume or dust, the fire alarm and methane alarm will not be triggered.

7. The method for detecting combined smoke and methane according to claim 2, characterized in that, The execution of the corresponding alarm strategy based on the aerosol type includes: If no aerosol particles are detected within the detection area, and the methane concentration is greater than a preset methane alarm threshold, a methane alarm will be triggered directly.

8. A smoke-methane composite detector, characterized in that, include: A laser source used to emit laser light of a single wavelength; The optical chamber is equipped with a detection area that allows gases or aerosols to enter; The first photoelectric converter is arranged along the emission direction of the laser and is used to receive the extinction signal after passing through the detection area; The second photoelectric converter is set at an acute angle to the laser emission direction and is used to receive the scattered signal in the detection area; A controller is connected to the laser light source, the first photoelectric converter, and the second photoelectric converter, respectively; the controller is configured to perform the smoke methane composite detection method as described in any one of claims 1 to 7.

9. The smoke and methane composite detector according to claim 8, characterized in that, The smoke methane composite detector also includes a folded optical path structure, and the laser emitted by the laser source is reflected by at least one mirror and then incident on the first photoelectric converter.

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