Smoke methane composite detector and method

Abstract

The invention discloses a smog methane composite detector and method, and relates to the technical field of gas detectors, the method is applied to the smog methane composite detector with a single-wavelength laser light source, and the method comprises the following steps: respectively obtaining a light canceling signal background value and a scattering signal background value under smog-free and methane-free environment conditions; in the detection process, acquiring an extinction signal and a scattering signal in real time, and determining the methane concentration in the detection area based on the extinction signal; on the basis of the extinction signal, the extinction signal background value, the scattering signal and the scattering signal background value, constructing characteristic parameters reflecting the aerosol interference degree in the detection area; and determining the aerosol type in the detection area according to the characteristic parameters, and executing a corresponding alarm strategy based on the aerosol type. By adopting the method, composite detection of smoke and methane can be realized under a single light source, interference of non-fire aerosol on methane and smoke detection is effectively inhibited, and the detection precision and reliability are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of gas detectors, in particular to a smoke and methane composite detector and method. BACKGROUND

[0002] With the popularization of city natural gas, methane leakage has become an important safety hazard, especially in industrial and commercial and household places, methane leakage not only brings the risk of fire and explosion, but also may affect the safety of the public. Therefore, the early warning detection system of methane leakage and fire has become an important safety guarantee. At present, for the composite detection of methane leakage and fire smoke, the common technical solution is to stack and integrate the existing methane detector and smoke detector to realize the composite detection of methane leakage and fire smoke on a single detector. However, this integrated design increases the volume of the detector, and the cost is also increased, and the complexity of the system is high, and the debugging and maintenance are difficult. In addition, some schemes use multiple independent detectors to detect methane and smoke respectively and process the signals. Although this scheme can realize independent detection of the two substances, it also brings the problems of high construction cost of the alarm system, complex correlation, false alarm and missing report.

[0003] At present, methane and smoke detection based on photoelectric technology has gradually attracted attention. Among them, the tunable diode laser absorption spectroscopy (TDLAS, Tunable Diode Laser Absorption Spectroscopy) is widely used in methane detection, and has obvious advantages in methane gas concentration detection due to its excellent selectivity, response speed and high sensitivity. However, this technology is easily disturbed by aerosols (especially water vapor) in the application process, thereby affecting the detection accuracy. In order to avoid these disturbances, it is common to set a filter screen and a waterproof air-permeable screen in the device to block the influence of aerosols such as smoke and dust on the detection signal.

[0004] In the aspect of smoke detection, LED light sources are mainly used. Although such light sources have low cost, they have problems such as large wavelength fluctuation and wide light emitting angle, which can easily lead to signal power fluctuation and affect the accurate measurement of smoke concentration. In addition, LED light sources are easily affected by interference aerosols such as dust and water vapor in fire smoke detection, leading to false alarms. Therefore, multiple LED light sources of different wavelengths and multiple photoelectric converters are needed to receive scattered light of different angles, thereby reducing the occurrence of false alarms. This way can improve the effect of smoke detection, but it also increases the complexity and cost of the system. SUMMARY

[0005] The present application aims to at least partially solve one of the technical problems in the related art. To this end, the present application aims to propose a smoke-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 leakage and fire smoke in complex environments.

[0006] To achieve the above-mentioned object, the first aspect of the present application proposes a smoke-methane composite detection method applied to a smoke-methane composite detector with a single-wavelength laser light source, the smoke-methane composite detector comprising a first photoelectric transducer arranged along the laser emission direction and a second photoelectric transducer arranged at an acute angle to the laser emission direction, the method comprising: In the absence of smoke and methane, the extinction signal background value and the scattering signal background value are obtained respectively; In the detection process, the extinction signal and the scattering signal are obtained in real time, and the methane concentration in the detection area is determined based on the extinction signal; Based on the extinction signal and the extinction signal background value, and the scattering signal and the scattering signal background value, a characteristic parameter reflecting the degree of aerosol interference in the detection area is constructed; the characteristic parameter includes: scattering signal change, light attenuation rate and scattering extinction ratio; According to the characteristic parameter, the aerosol type in the detection area is determined, including: determining whether the detection area contains aerosol particles according to the relationship between the scattering signal change and the preset scattering threshold; in the case of determining that there are aerosol particles in the detection area, determining the aerosol type in the detection area according to the light attenuation 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 directly triggering an alarm according to 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.

[0007] In addition, the smoke-methane composite detection method of the above-mentioned embodiments of the present application can also have the following additional technical features: According to one embodiment of the present application, the characteristic parameter reflecting the degree of aerosol interference in the detection area is constructed, including: The difference between the scattering signal and the scattering signal background value is calculated to obtain the scattering signal change; The ratio of the extinction signal to the extinction signal background value is calculated to obtain the light attenuation rate; The ratio of the scattering signal change to the light attenuation rate is calculated to obtain the scattering extinction ratio.

[0008] According to one embodiment of the present application, the aerosol type in the detection area is determined according to the characteristic parameter, including: In a case that the scattering signal variation is greater than the preset scattering threshold, it is determined that the aerosol particles exist in the detection area; and the aerosol type includes fire smoke, water vapor, oil fume and dust.

[0009] According to an embodiment of the present application, the determining the aerosol type in the detection area according to the light attenuation rate and the scattering extinction ratio comprises: judging whether the light attenuation rate is greater than a preset light attenuation threshold; if the light attenuation rate is greater than the light attenuation threshold and the scattering extinction ratio is in a first preset interval defined by a first preset threshold and a second preset threshold, then it is determined that the aerosol type is oil fume; if the light attenuation rate is greater than the light attenuation threshold and the scattering extinction ratio is in a second preset interval defined by a second preset threshold and a third preset threshold, then it is determined that the aerosol type is fire smoke; if the light attenuation rate is less than the light attenuation threshold and the scattering extinction ratio is in a third preset interval defined by a fourth preset threshold and a fifth preset threshold, then it is determined that the aerosol type is dust; and if the light attenuation rate is less than the light attenuation threshold and the scattering extinction ratio is in a fourth preset interval defined by a fifth preset threshold and a sixth preset threshold, then it is determined that the aerosol type is water vapor. The first preset interval, the second preset interval, the third preset interval and the fourth preset interval are mutually non-overlapping intervals divided for the same scattering extinction ratio parameter.

[0010] According to an embodiment of the present application, the executing the corresponding alarm strategy based on the aerosol type comprises: when it is determined that the aerosol type is fire smoke, a smoke concentration triggered alarm based alarm strategy is executed; wherein the alarm strategy comprises: calculating the smoke concentration in the detection area according to the scattering signal variation; if the smoke concentration is greater than a preset smoke alarm threshold, then fire alarm is triggered.

[0011] According to an embodiment of the present application, the executing the corresponding alarm strategy based on the aerosol type comprises: ​​​​​​​​​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.

[0012] According to one embodiment of the present invention, 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.

[0013] According to one embodiment of the present invention, 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.

[0014] To achieve the above objectives, a second aspect of the present invention provides a smoke-methane recombination detector, comprising: 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; 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.

[0015] 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.

[0016] The smoke-methane composite detector and method of the embodiment of the present application realizes composite detection of methane and smoke by adopting a single-wavelength laser light source, avoids the problems of high cost and complexity in the traditional multi-wavelength detector and stacking design. At the same time, the extinction signal and the forward angle scattering signal are received by two photoelectric converters, and through processing of the signals, the interference of aerosol on the measurement of methane concentration can be minimized. By this method, not only the methane concentration can be accurately measured, but also the false positive rate caused by interfering aerosol can be reduced, and the stability and reliability of the system are improved. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 A flowchart of the smoke-methane composite detection method in the embodiment is shown in FIG. 1. Figure 2 A flowchart of the gas identification process of the sol type in the embodiment is shown in FIG. 2. Figure 3 A structural diagram of the smoke-methane composite detector in the embodiment is shown in FIG. 3. Figure 4 A structural diagram of the smoke-methane composite detector in the embodiment is shown in FIG. 4. Figure 5 A data processing flowchart of the smoke-methane composite detector in the embodiment is shown in FIG. 5.

[0018] The figure legend: laser light source 1, first photoelectric converter 2, second photoelectric converter 3, light chamber 4, controller 5, first mirror 6, second mirror 7. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical scheme and advantages of the present application clearer, the present application will be further described in detail below in combination with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and do not limit the present application.

[0020] In order to facilitate those skilled in the art to understand and implement the method of the present application, the smoke-methane composite detector carrying the method of the present application will be introduced first, and then the method steps will be described in detail. The structure of the smoke-methane composite detector is shown in FIG. 3. Figure 3As shown, it includes a laser light source 1, a light chamber 4, a first photoelectric converter 2, a second photoelectric converter 3 and a controller 5. Specifically, the laser light source 1 is used to emit a single-wavelength laser signal, which is usually 1653.7 nm, suitable for the characteristic absorption band of methane gas, so as to effectively detect the concentration of methane. The light chamber 4 is provided with a detection area allowing the gas or aerosol to enter, which ensures that the laser interacts with the target gas or aerosol sufficiently, thereby inducing extinction and scattering effects. The first photoelectric converter 2 is located opposite to the laser light source, used to receive the extinction signal after passing through the detection area, and the second photoelectric converter 3 is arranged at an acute angle with the emission direction of the laser, used to receive the scattering signal in the detection area. The controller 5 is connected with the laser light source 1, the first photoelectric converter 2 and the second photoelectric converter 3, responsible for processing signals and performing the smoke-methane composite detection method.

[0021] In the smoke-methane composite detector, the folding light path structure design effectively guides the laser reflected by at least one mirror to the first photoelectric converter 2. Through the folding light path, the optical path of the laser in the detection area is increased, so that the interaction between the laser and the methane gas in the detection area is enhanced. This design makes the laser beam reflect multiple times in the detection area, expands the absorption effect of the methane gas on the laser, and thus improves the measurement accuracy of the methane concentration. As shown, the folding light path is composed of a first mirror 6 and a second mirror 7, in which the optical path is increased to 2 times after two reflections, thereby improving the detection sensitivity and ensuring more accurate measurement of the methane gas concentration. Figure 4

[0022] After understanding the basic structure and working principle of the smoke-methane composite detector, the following will introduce in detail how to realize the composite detection of smoke and methane by the detector. In one embodiment, as shown, a flowchart of a smoke-methane composite detection method is provided, which can include the following steps: Figure 1 Step S101, in the environment without smoke and methane, the extinction signal background value and the scattering signal background value are obtained respectively.

[0023] Before detection, it is ensured that there is no interference of smoke and methane in the detection area. Under this condition, the laser signal emitted by the laser light source passes through the detection area and interacts with the 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 extinction signal background value . 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 the aerosol, which is the reference value for the subsequent detection signal.

[0024] ​​At the same time, the scattered signal in the detection area is received by the second photoelectric converter 3 , and recorded as the scattered signal background value . This signal is mainly from the scattering of laser by molecules and small particles in the air. In the absence of smoke and methane, these signals only reflect the scattering characteristics in normal environment, and are used as a reference for subsequent signal comparison.

[0025] Step S102, during the detection process, the extinction signal and the scattered signal are obtained in real time, and the methane concentration in the detection area is determined based on the extinction signal.

[0026] After the detection starts, the laser source is controlled to continuously emit laser signals with a wavelength of 1653.7 nm, which pass through the detection area and interact with gas molecules (such as methane) and aerosol particles, so that the extinction signal after passing through the detection area can be obtained by the first photoelectric converter 2 , and the scattered signal can be obtained by the second photoelectric converter 3 .

[0027] Among them, the change of the extinction signal reflects the change of gas (especially methane) absorption, and by demodulating the extinction signal , the absorption peak of methane can be identified, and the methane concentration value can be calculated according to the depth and shape of the absorption peak. The calculation of the methane concentration value is based on the standard absorption spectrum analysis method combined with the known absorption coefficient, which can accurately measure the methane concentration.

[0028] Step S103, based on the extinction signal and the extinction signal background value, and the scattered signal and the scattered signal background value, a characteristic parameter reflecting the interference degree of aerosol in the detection area is constructed.

[0029] By comprehensively analyzing the change characteristics of the extinction signal and the scattered signal relative to the corresponding background values, the influence of aerosol on the propagation of light signals in the detection area is quantitatively characterized, thereby forming a characteristic parameter reflecting the interference degree of aerosol.

[0030] The interference degree of aerosol refers to the comprehensive influence degree of the change of the extinction signal and the scattered signal caused by the absorption and scattering of aerosol (such as fire smoke, water vapor, dust, etc.) in the laser signal propagation path after the aerosol particles enter the detection area. This interference not only affects the intensity of the extinction signal and the scattered signal, but also may affect the accurate measurement of methane concentration. In order to accurately quantify this influence, a characteristic parameter is constructed to characterize the interference degree of aerosol.

[0031] By constructing the characteristic parameters, the influence of different aerosol types on the detection signal can be evaluated, which is a key link to realize accurate detection and reduce false positives, so that more accurate responses can be made in various complex environments.

[0032] In one embodiment, when constructing the characteristic parameters reflecting the degree of aerosol interference, first, the real-time scattering signal is subtracted from the scattering signal background value to obtain the scattering signal change, which is used to reflect the degree of scattering enhancement caused by aerosol particles in the detection area. Among them, the scattering signal change can be expressed as:

[0033] At the same time, by calculating the ratio of the real-time extinction signal and the extinction signal background value, the light attenuation rate is obtained, which is used to represent the degree of transmission attenuation caused by aerosol and gas absorption during the propagation of laser in the detection area. Among them, the light attenuation rate can be expressed as:

[0034] On this basis, the scattering signal change and the light attenuation rate are further calculated by ratio, and the scattering extinction ratio is obtained. The scattering extinction ratio is used to comprehensively represent the relative relationship between scattering effect and extinction effect, so as to improve the distinguishing ability of aerosol interference characteristics. Among them, the scattering extinction ratio can be expressed as:

[0035] Through the calculation of the above parameters, the interference characteristics of aerosol on the propagation of light signal can be described from multiple dimensions, providing reliable quantitative basis for subsequent aerosol type recognition and alarm strategy selection based on characteristic parameters.

[0036] Step S104, determining the aerosol type in the detection area according to the characteristic parameters, and executing the corresponding alarm strategy based on the aerosol type.

[0037] By comprehensively analyzing the characteristic parameters reflecting the degree of aerosol interference, the influence characteristics of aerosol on the propagation of light signal in the detection area can be judged. Because different types of aerosol have significant differences in particle size distribution, refractive index and other physical parameters, which lead to significant differences in their absorption and scattering behaviors of light signal, the characteristic parameters formed by the scattering signal and the extinction signal are also different. Based on the above differences, the aerosol type in the detection area can be distinguished.

[0038] Among them, as Figure 2 shown, the determination process of the aerosol type can include the following steps: Step S201, according to the relationship between the scattering signal change and the preset scattering threshold, it is judged whether the aerosol particles are contained in the detection region.

[0039] Step S202, in the case that the aerosol particles exist in the detection region, and according to the extinction ratio and the scattering extinction ratio, the type of the aerosol in the detection region is determined.

[0040] Specifically, according to the relationship between the scattering signal change and the preset scattering threshold, it is judged whether the aerosol particles exist in the detection region. The scattering signal change reflects the degree of scattering enhancement of the detection light beam in the propagation process due to the suspended particles. By comparing the scattering signal change with the preset scattering threshold, it can be confirmed whether the aerosol particles are contained in the detection region.

[0041] In the case that the aerosol particles exist in the detection region, the interference properties of the aerosol are analyzed based on the extinction ratio and the scattering extinction ratio. Different types of aerosols have significant differences in particle size distribution, composition and refractive index, and their comprehensive performance in light absorption and scattering behavior is also different, so they show distinguishable differences in the combined characteristics of the extinction ratio and the scattering extinction ratio.

[0042] The aerosol type is used to represent whether there is an aerosol in the current detection environment that affects the methane detection and smoke detection, and the interference properties of the aerosol to the detection results. By introducing the judgment of the aerosol type, it can avoid misjudging the signal change caused by non-fire class aerosols or non-methane factors as an alarm event.

[0043] After determining the aerosol type, further according to the influence characteristics of different aerosol types on the detection results, the corresponding alarm strategy is selected and executed. Among them, the alarm strategy includes at least one of the following: (1) According to the methane concentration determined in step S102, the alarm is directly triggered, which is suitable for the case that the aerosol interference is small or negligible.

[0044] (2) Based on the water vapor concentration, the methane concentration is corrected and then it is judged whether to trigger the alarm, which is suitable for the case that the aerosol in the detection region affects the methane absorption signal, resulting in inaccurate methane concentration determined based on the extinction signal.

[0045] (3) Trigger the alarm based on the smoke concentration, which is suitable for the case that the aerosol type represents the characteristics of fire-related smoke.

[0046] In the above manner, while ensuring timely early warning of methane leakage and fire risk, the false alarm probability caused by the interference aerosol in the environment can be effectively reduced, and the reliability and environmental adaptability of the composite detection can be improved.

[0047] ​In one embodiment, when the scattering signal change value represents a scattering enhancement degree exceeding a preset scattering threshold value , it indicates that there are aerosol particles in the detection region which are sufficient to have a significant impact on the propagation of the light signal, and thus it can be confirmed that the detection region contains aerosol particles.

[0048] In the absence of aerosol particles or under extremely low aerosol concentration environmental conditions, the propagation state of the laser in the detection region is relatively stable, and the scattering signal mainly comes from the optical device itself and environmental background noise, and its change value relative to the background value is usually within a small fluctuation range. However, in the presence of aerosol particles in the detection region, the particles produce additional scattering effects on the laser, resulting in a significant increase in the scattering light energy entering the second photoelectric converter, thereby causing the scattering signal to be significantly enhanced relative to the background value.

[0049] Based on the above characteristics, by comparing the scattering signal change value with the preset scattering threshold value, the normal fluctuations caused by system noise or slight environmental disturbances can be effectively distinguished from the real scattering enhancement introduced by aerosol particles, and it can be effectively confirmed that the detection region contains aerosol particles. On this basis, the interference type of the aerosol in the detection region can be determined by comprehensive analysis of the relationship between the light attenuation rate and the scattering extinction ratio, so as to distinguish the aerosol into different types such as fire smoke, water vapor, oil smoke, dust, etc.

[0050] In one embodiment, the light attenuation rate and the scattering extinction ratio are combined to analyze the aerosol type in detail. Specifically, when the light attenuation rate is greater than a light attenuation threshold value , it indicates that the aerosol in the detection region has a strong light extinction effect on the light signal, and at this time the aerosol type is further distinguished according to the scattering extinction ratio . Within the overall value range of the scattering extinction ratio , multiple non-overlapping intervals are pre-divided, and some of the intervals are selected for aerosol type determination under high extinction conditions. When the scattering extinction ratio falls within a first preset interval , it is determined that the aerosol type in the detection region is oil smoke. When the scattering extinction ratio falls within a second preset interval , it is determined that the aerosol type in the detection region is fire smoke. Since oil smoke and fire smoke differ in particle composition and scattering characteristics, their corresponding scattering extinction ratio intervals are different, and thus they can be distinguished by the above method.

[0051] When the light attenuation rate is less than the light attenuation threshold value , it indicates that the overall light extinction effect of the aerosol on the light signal is weak, and in this case the aerosol type is further determined based on 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] Specifically, based on the change in the scattered signal Calculate the water vapor concentration value in the detection area Water vapor particles will produce obvious scattering effects in the laser propagation path, and the scattering signal change amount has a corresponding relationship with the water vapor concentration, so the water vapor concentration can be calculated based on the scattering signal change amount.

[0059] Since water vapor will affect the intensity of the methane absorption peak, thereby interfering with the methane concentration measurement result, after obtaining the water vapor concentration value, a preset correction coefficient is introduced to correct the methane concentration to obtain the corrected methane concentration. The correction coefficient is used to represent the degree of influence of unit water vapor concentration on the methane concentration measurement result, which can be preset according to the detection light path characteristics, the working waveband, and the interference relationship of water vapor on the methane absorption characteristics, so that the correction process can reflect the actual influence of water vapor on the methane detection result.

[0060] The corrected methane concentration can be expressed as:

[0061] Subsequently, the corrected methane concentration is compared with a preset methane alarm threshold When the corrected methane concentration is greater than the methane alarm threshold, it is determined that there is a risk of methane leakage in the detection area, and a methane alarm is triggered.

[0062] By correcting the methane concentration under the condition of water vapor, the interference of water vapor on the methane detection result can be effectively weakened, and the accuracy of the methane alarm can be improved.

[0063] In one embodiment, when the determination result based on the aerosol type determines that the aerosol type in the detection area is cooking fume or dust, an alarm strategy of not triggering a fire alarm and a methane alarm is executed.

[0064] Specifically, cooking fume and dust both belong to non-fire and non-gas leakage aerosols that may occur in daily or industrial environments, which will have scattering and extinction effects on light signals within a certain concentration range, but do not directly represent fire risk or methane leakage risk.

[0065] Therefore, in the case where the aerosol type is determined to be cooking fume or dust, the fire alarm process based on smoke concentration is not started, and the methane alarm based on methane concentration is not triggered, thereby avoiding false alarms caused by non-dangerous aerosols.

[0066] In one embodiment, when it is determined according to the analysis result of the characteristic parameter that there is no aerosol particle in the detection area, it is considered that there is no significant optical interference caused by aerosols such as smoke, water vapor, cooking fume, or dust in the current detection environment.

[0067] In this case, the methane absorption characteristics contained in the extinction signal mainly reflect the absorption of the methane gas itself to the light signal, and the influence of the aerosol on the methane concentration measurement result can be ignored. Therefore, at this time, it is not necessary to correct the methane concentration or introduce an additional aerosol discrimination process.

[0068] Based on this, when the scattering signal change amount is less than the preset scattering threshold, it is determined that there is no aerosol particle in the detection area, and the methane concentration calculated based on the extinction signal is directly compared with the preset methane alarm threshold When the methane concentration is greater than the methane alarm threshold, the methane alarm is directly triggered.

[0069] It can be understood that, in the case that there is no aerosol particle in the detection area, the aerosol type does not need to be determined, and therefore the light attenuation rate and the scattering extinction ratio do not need to be calculated. In the process of constructing the characteristic parameters, when it is judged that the scattering signal change amount is less than the preset scattering threshold, the calculation of the light attenuation rate and the scattering extinction ratio can be omitted; when the scattering signal change amount exceeds the preset scattering threshold, the light attenuation rate and the scattering extinction ratio need to be calculated to further analyze the aerosol type and execute the corresponding alarm strategy.

[0070] The smoke-methane composite detection method of the present application can simultaneously realize effective detection of methane and fire smoke in the same optical path by using a single-wavelength laser light source, combining multi-dimensional analysis of the extinction signal and the scattering signal, and can also suppress the interference of non-fire aerosol on the detection result. Through methane concentration measurement based on the extinction signal and aerosol interference identification based on the scattering signal, fire smoke, water vapor, dust and other aerosols can be accurately distinguished, and the methane detection result can be corrected according to the water vapor concentration to reduce the false alarm probability caused by aerosol interference, thereby improving the overall performance and reliability of the detection system.

[0071] In the foregoing specific embodiments, the smoke-methane composite detector is described in detail for identifying the aerosol in the detection area through multi-dimensional analysis, thereby effectively reducing false alarms in the methane and smoke detection process. Based on this, Figure 5 A data processing flow diagram of the smoke-methane composite detector is shown, and the specific content is as follows: In the data processing flow, the first photoelectric converter 2 and the second photoelectric converter 3 respectively receive and record the extinction signal background value and the scattering signal background value in the smoke-free and methane-free environment. After entering the real-time detection stage, the smoke-methane composite detector will continuously receive the current real-time extinction signal and real-time scattering signal. In this stage, the smoke-methane composite detector first calculates the current methane concentration At the same time, the change amount of the real-time scattering signal relative to the background value, i.e. the scattering signal change amount, is calculated.

[0072] Subsequently, the smoke-methane composite detector determines whether the scattering signal change amount is greater than a preset scattering threshold. If the determination result is no, it indicates that there is no obvious aerosol particle in the light path, and at this time, the methane concentration is directly compared with a preset methane alarm threshold . If it is greater, methane alarm is triggered, otherwise, it returns to continue receiving real-time signals.

[0073] If it is determined that the scattering signal change amount is greater than the scattering threshold, it indicates that there is an aerosol particle in the detection area, and then enters the aerosol classification and identification process. In this process, the light attenuation rate is first calculated, and then the scattering extinction ratio of the scattering signal change amount and the light attenuation rate is further calculated. The smoke-methane composite detector divides the aerosol into two processing paths according to the size of the light attenuation rate: When the light attenuation rate is greater than a preset light attenuation rate threshold, it is further determined whether the scattering extinction ratio is greater than a second preset threshold . If the scattering extinction ratio is not greater than , it is determined to be oil smoke interference, and no alarm is performed; if the scattering extinction ratio is greater than , it is determined to be fire smoke, and the smoke concentration is calculated according to the scattering signal, and fire alarm is triggered when the smoke concentration exceeds a smoke alarm threshold.

[0074] When the light attenuation rate is not greater than the preset light attenuation rate threshold, it is further determined whether the scattering extinction ratio is greater than a fifth preset threshold . If the scattering extinction ratio is not greater than , it is determined to be dust interference, and no alarm is performed; if the scattering extinction ratio is greater than , it is determined to be water vapor interference. For water vapor interference, the water vapor concentration is calculated and the preliminary calculated methane concentration is corrected to obtain the corrected methane concentration. Finally, it is determined whether the corrected methane concentration is greater than the methane alarm threshold, and if it is greater, methane alarm is triggered, otherwise, it returns to the next round of detection cycle.

[0075] Through the data processing flow, the smoke-methane composite detector can realize accurate methane leakage monitoring, while effectively avoiding the false alarm risk caused by aerosol interference. The intelligent analysis and accurate identification mechanism of the smoke-methane composite detector greatly improves the accuracy of fire warning and gas detection, especially in complex environmental conditions, it can still stably and effectively operate.

[0076] In the description of the specification, the description of the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the description of the specification, the illustrative description of the above terms does not necessarily mean the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0077] In addition, the terms "first", "second" are only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined with "first", "second" can explicitly or implicitly include at least one of the features. In the description of the present application, the meaning of "a plurality of" is at least two, for example, two, three, etc., unless otherwise specifically limited.

[0078] Although the embodiments of the present application have been shown and described above, it is understood that the above-described embodiments are exemplary and cannot be construed as limiting the present application, and those skilled in the art can make changes, modifications, replacements and variations to the above-described embodiments within the scope of the present application.

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 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; 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, The constructed characteristic parameters reflecting the degree of aerosol interference within the detection area include: The difference between the scattered signal and the background value of the scattered signal is calculated to obtain the change in the scattered signal; The ratio of the extinction signal to the background value of the extinction signal is calculated to obtain the light reduction rate; The ratio of the change in the scattered signal to the attenuation rate is calculated to obtain the scattering extinction ratio.

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 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.

4. The method for detecting combined smoke and methane according to claim 3, 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.

5. The method for detecting combined smoke and methane according to claim 3, 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: The smoke concentration within the detection area is calculated 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.

6. The method for detecting combined smoke and methane according to claim 3, 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.

7. The method for detecting combined smoke and methane according to claim 3, 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.

8. The method for detecting combined smoke and methane according to claim 3, 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.

9. 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 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 8.

10. The smoke and methane composite detector according to claim 9, 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.

Images