Fire smoke detector based on the combined characteristics of particle size, shape and refractive index

Abstract

The present invention discloses a fire smoke detector based on the combined characteristics of particle size, shape and refractive index, belonging to the field of fire smoke detection. The detector includes an optical darkroom, a four-way light source, a photodiode, a processing module and an alarm module, which can accurately classify fire smoke and interfering aerosols, reduce the false alarm rate and missed alarm rate of traditional smoke fire detectors, and improve the detection accuracy of photoelectric smoke fire detectors. Fire smoke and three interfering aerosols of oil smoke, dust and water vapor can be accurately identified according to the multi-physical parameters of aerosols, reducing the false alarm rate and missed alarm rate of smoke fire detectors.

Description

Technical Field

[0001] The present invention belongs to the field of fire smoke detection, and more specifically, relates to a fire smoke detector based on the combined characteristics of particle size, shape and refractive index. Background Art

[0002] Accurate detection at the early stage of a fire is critical to fire control. Accurate detection of fire smoke and interfering aerosols can trigger an alarm at the beginning of a fire, so that the fire can be extinguished before it spreads. At the same time, accurate identification of various types of fire smoke can provide guidance for the fire department to judge the fire situation. Fire detectors are an important part of the fire protection system. Photoelectric smoke detectors have the advantages of high sensitivity, low cost, and long life, and are the mainstream choice of current fire monitoring sensors. However, photoelectric smoke detectors still have problems such as false alarms and missed alarms.

[0003] Photoelectric smoke detectors mainly use the optical scattering principle of aerosols for detection. When fire smoke enters the detection area, due to the scattering effect of particulate matter on light, the scattered light power signal collected by the photodiode will increase, and gradually increase with the increase of smoke concentration. When the signal increases to exceed a certain threshold, the detector will determine that a fire has occurred and send out an alarm signal. However, interfering aerosols (oil smoke, dust, water vapor) also have a scattering effect. When such aerosols enter the detector, they will also trigger the detector alarm. Therefore, traditional smoke fire detectors will be interfered by interfering aerosols such as oil smoke, dust, and water vapor, causing the fire detector to falsely alarm.

[0004] Generally, the particle size of fire smoke produced by burning substances is less than 1um, and the particle size of non-fire aerosols such as water vapor and dust is greater than 1um. Patent No. 201410748629.4 discloses an aerosol particle size sensing method based on dual-wavelength scattering signals and its application in fire smoke detection. The method constructs a detector of a light-emitting device and a photoelectric conversion device that can emit infrared light and blue light, and determines the median particle size d of the aerosol according to the ratio R of the scattered light power signal of blue light to the scattered light power signal of infrared light. med , d med and the set threshold value d medth For comparison, if d med Less than d medth However, the particle size of interfering aerosols such as oil smoke and industrial fine dust is usually less than 1um. Therefore, the method of identifying fire smoke and interfering aerosols based only on the median particle size will also cause the smoke detector to falsely alarm when the particle size of the interfering aerosol is close to that of the fire smoke. Summary of the invention

[0005] In view of the above defects or improvement needs of the prior art, the present invention provides a fire smoke detector based on the combined characteristics of particle size, shape and refractive index, thereby solving the problems of false alarm and missed alarm of the existing fire detectors.

[0006] To achieve the above-mentioned object, according to a first aspect of the present invention, there is provided a fire smoke detector based on the combined characteristics of particle size, shape and refractive index, comprising: an optical darkroom, a light source module, a photodiode, a processing module, and an alarm module;

[0007] The optical darkroom is provided with a plurality of through holes for introducing the aerosol to be detected;

[0008] The photodiode is arranged on the inner wall of the optical darkroom;

[0009] The light source module includes first to fourth light sources, which are sequentially arranged around the inner wall of the optical darkroom, the wavelengths of the first and third light sources are both λ1, the wavelengths of the second and fourth light sources are both λ2, and λ1<λ2; and the angles between the emitted light rays of the first and second light sources at the convergence point and the scattered light rays scattered to the photodiode are the same and are both acute angles, and the angles between the emitted light rays of the third and fourth light sources at the convergence point and the scattered light rays scattered to the photodiode are the same and are both obtuse angles; wherein the convergence point is the common convergence point of the first to fourth light sources;

[0010] The processing module is used to perform the following operations: A1, turn on the first to fourth light sources in sequence at preset time intervals, and record the scattered light power P received by the photodiode after each light source emits light B1 , P I1 , P B2 , P I2 , and are respectively compared with the scattered light power received by the photodiode when no aerosol is introduced into the optical darkroom Subtract to get ΔP B1 , ΔP I1 , ΔP B2 , ΔP I2 ; A2, if ΔP B1 , ΔP I1 , ΔP B2 , ΔP I2 No more than the threshold △P TH Then return to A1, otherwise according to ΔP B1 , ΔP I1 , ΔP B2 , ΔP I2 Calculate the particle size d, refractive index m and ellipsoidality η of the aerosol to be detected, and TH And η is greater than the ellipsoid threshold η TH , or d is less than the particle size threshold and m is greater than the refractive index threshold mTH When a fire alarm signal is sent out through the alarm module;

[0011] Among them, ΔP B1 , ΔP I1 , ΔP B2 , ΔP I2 Satisfies the relationship between d, m, and η: k1 to k4 are conversion coefficients, σ1(m), σ2(m), σ3(m,d), and σ4(m,d) are deviation functions.

[0012] According to a second aspect of the present invention, there is provided a fire smoke accurate sensing method based on the combined characteristics of particle size, shape and refractive index, which is applied to the fire smoke detector as described in the first aspect, comprising:

[0013] S1, every preset time, turn on the first to fourth light sources in sequence, and record the scattered light power P received by the photodiode after each light source emits light B1 , P I1 , P B2 , P I2 , and are respectively compared with the scattered light power received by the photodiode when no aerosol is introduced into the optical darkroom Subtract to get ΔP B1 , ΔP I1 , ΔP B2 , ΔP I2 ;

[0014] S2, if ΔP B1 , ΔP I1 , ΔP B2 , ΔP I2 No more than the threshold △P TH Then return to S1, otherwise according to ΔP B1 , ΔP I1 , ΔP B2 , ΔP I2 Calculate the particle size d, refractive index m and ellipsoidality η of the aerosol to be detected, and TH And η is greater than the ellipsoid threshold η TH , or d is less than the particle size threshold and m is greater than the refractive index threshold m TH A fire alarm signal is issued.

[0015] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects compared with the prior art:

[0016] Taking into account that the physical properties of fire smoke are mainly related to the physical properties of the burning material itself and the combustion state, the parameters such as the refractive index, particle size, particle shape, component and concentration of the generated combustion products are all different, and the scattering and attenuation characteristics of the incident light are also different. The present invention provides a fire smoke detector based on the combined characteristics of particle size, shape and refractive index, which can accurately identify fire smoke (white smoke produced by the smoldering of cotton rope and beech wood, and black smoke produced by the open flame of polyurethane and n-heptane as specified in the national standard GB4715) and three interfering aerosols of oil smoke, dust and water vapor according to the multiple physical parameters of the aerosol, thereby reducing the false alarm rate and missed alarm rate of the smoke fire detector.

[0017] The detector provided by the present invention can accurately identify the specific type of fire smoke, thereby issuing different types of alarm signals. By accurately identifying various types of fire smoke, it can provide guidance for the fire department to judge the fire situation, so that the fire department can take targeted and reasonable fire-fighting measures. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 A partial structural top view of a fire smoke detector provided in an embodiment of the present invention.

[0019] Figure 2 A three-dimensional schematic diagram of a partial structure of a fire smoke detector provided in an embodiment of the present invention.

[0020] Figure 3 A schematic diagram of the angle between the outgoing light of the light source in the fire smoke detector provided by the embodiment of the present invention at the convergence point and the scattered light scattered to the photodiode at the convergence point.

[0021] Figure 4 A flowchart of the fire smoke detector provided by an embodiment of the present invention.

[0022] Figure 5 This is a classification result diagram of fire smoke and interfering aerosol experimental data provided by an embodiment of the present invention; in the figure, the diamond represents white smoke from a fire, the triangle represents black smoke from a fire, and the square represents interfering aerosol. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0024] By observing several representative smoke agglomerates under a scanning electron microscope (SEM), it can be seen that polyurethane and white smoke particle agglomerates have long chain shape characteristics, while white smoke particles are spherical or shorter chain-like. Interference aerosols are generally generated through physical reactions and are generally spherical in shape. Therefore, the method of identifying fire smoke and interference aerosols based only on aerosol shape characteristics will miss white smoke.

[0025] Based on this, the embodiment of the present invention provides a fire smoke detector based on the combined characteristics of particle size, shape and refractive index, such as Figure 1-2 As shown, it includes: an optical darkroom, a light source module, a photodiode, a processing module, and an alarm module;

[0026] The optical darkroom is provided with a plurality of through holes for introducing the aerosol 6 to be detected.

[0027] It is understood that the aerosol can also diffuse out of the optical darkroom through the through holes.

[0028] The photodiode is arranged on the inner wall of the optical darkroom;

[0029] The light source module includes first to fourth light sources, which are arranged in sequence around the inner wall of the optical darkroom, the wavelengths of the first and third light sources are both λ1, the wavelengths of the second and fourth light sources are both λ2, and λ1<λ2; and the angles between the emitted light of the first and second light sources at the convergence point and the scattered light scattered to the photodiode at the convergence point are the same and are both acute angles, and the angles between the emitted light of the third and fourth light sources at the convergence point and the scattered light scattered to the photodiode at the convergence point are the same and are both obtuse angles; wherein the convergence point is the common convergence point of the first to fourth light sources.

[0030] The processing module is used to perform the following operations:

[0031] A1, every preset time, turn on the first to fourth light sources in sequence, and record the scattered light power P received by the photodiode after each light source emits light B1 , P I1 , P B2 , P I2 , and are respectively compared with the scattered light power received by the photodiode when no aerosol is introduced into the optical darkroom Subtract to get ΔP B1 , ΔP I1 , ΔP B2 , ΔP I2 ;

[0032] A2, if ΔP B1 , ΔP I1 , ΔP B2 , ΔP I2No more than the threshold △P TH Then return to A1, thereby continuously updating ΔP B1 , ΔP I1 , ΔP B2 , ΔP I2 , otherwise according to ΔP B1 , ΔP I1 , ΔP B2 , ΔP I2 Calculate the particle size d, refractive index m and ellipsoidality η of the aerosol to be detected, and TH And η is greater than the ellipsoid threshold η TH , or d is less than the particle size threshold and m is greater than the refractive index threshold m TH When a fire alarm signal is sent out through the alarm module;

[0033] Among them, ΔP B1 , ΔP I1 , ΔP B2 , ΔP I2 Satisfies the relationship between d, m, and η: k1 to k4 are conversion coefficients, σ1(m), σ2(m), σ3(m,d), and σ4(m,d) are deviation functions.

[0034] Specifically, in the design of photoelectric smoke detectors, the scattering characteristics of light sources with the same observation angle and different wavelengths can be used to characterize the particle size of aerosols, and the refractive index will introduce deviations in the detection of particle size; the scattering characteristics of light sources with the same wavelength and different observation angles can be used to characterize the shape of aerosols, and the refractive index and particle size will introduce deviations in the detection of shape. So:

[0035] P(θ1,λ1,λ2)=k1[d+σ1(m)] (1)

[0036] P(θ2,λ1,λ2)=k2[d+σ2(m)] (2)

[0037] P(λ1,θ1,θ2)=k3[η+σ3(m,d)] (3)

[0038] P(λ2,θ1,θ2)=k4[η+σ4(m,d)] (4)

[0039] Among them, d is the particle size of the aerosol, m is the refractive index of the aerosol, the shape of the aerosol is approximately an ellipsoid, which can be expressed by the ellipsoidity η, P is the scattering characteristic of the scattered light power signal, k is the conversion coefficient, and σ is the measurement deviation. When detecting the shape characteristics of the aerosol, the deviation σ is related to m and d, and when detecting the particle size characteristics, the deviation σ is related to m. In the above equation, d, m and η are unknown parameters, and the solution can be obtained by combining the equations.

[0040] Correspondingly, four LED light sources and a photodiode 5 are arranged in the optical darkroom 7 of the smoke fire detector. The function of the optical darkroom is to allow fire smoke and interfering aerosol (i.e., the aerosol 6 to be detected) to pass in and block the entry of ambient light. Among the four LED light sources, the wavelengths of the first and third light sources are both λ1, and the wavelengths of the second and fourth light sources are both λ2, and λ1<λ2. For example, the first and third light sources are blue light, and the second and fourth light sources are infrared light; or the first and third light sources are red light, and the second and fourth light sources are near-infrared light. The photodiode is a photoelectric conversion device that can convert the received scattered light function signal into an electrical signal.

[0041] Furthermore, the angles between the emitted light rays from the first and second light sources at the convergence point and the scattered light rays scattered to the photodiode at the convergence point are the same and are both acute angles, and the angles between the emitted light rays from the third and fourth light sources at the convergence point and the scattered light rays scattered to the photodiode at the convergence point are the same and are both obtuse angles; wherein the convergence point is the common convergence point of the first to fourth light sources.

[0042] Taking the example that two light sources are blue LED light sources that can emit short wavelength (LED light sources that emit 450nm blue light) and two light sources are infrared LED light sources that can emit long wavelength (LED light sources that emit 950nm infrared light), the spatial angle formed by one blue LED light source (first light source 1) and one infrared LED light source (second light source 2) and the photodiode is an acute angle, and the spatial angle formed by the other blue LED light source (third light source 3) and one infrared LED light source (fourth light source 4) and the photodiode is an obtuse angle.

[0043] Preferably, the angles between the emitted light from the first and second light sources at the convergence points and the scattered light scattered to the photodiode are the same and are both 40 degrees, and the angles between the emitted light from the third and fourth light sources at the convergence points and the scattered light scattered to the photodiode at the convergence points are the same and are both 140 degrees.

[0044] like Figure 3 As shown, taking the first light source 1 as an example, the angle between the emitted light at the common convergence point A of the first to fourth light sources and the scattered light scattered to the photodiode 5 at A is 40 degrees.

[0045] Preferably, the first to fourth light sources and the photodiodes are all arranged on the same plane, so as to integrate them on the same circuit board to achieve device integration.

[0046] like Figure 4 As shown, the detector provided by the present invention implements aerosol multi-parameter joint sensing based on optical scattering according to the following steps:

[0047] The first step is to turn on the first light source, the second light source, the third light source and the fourth light source respectively when the detector is powered on in an environment without fire smoke and interfering aerosols. The four light sources send optical pulse signals in sequence. For example, the period of the optical pulse signal is 1 second, and the pulse width is several milliseconds to tens of milliseconds. After each light source emits light, the scattered light power received by the photodiode is recorded, and the optical power signal is converted into a voltage signal through the photoelectric conversion module in the photodiode. The AD sampling value is the background value of each signal, which is recorded as and It can be understood that this step is the initialization step of the smoke fire detector system. and They can also be stored in the processing module of the detector in advance.

[0048] Step 2: At each interval Δt, turn on the first light source, the second light source, the third light source and the fourth light source respectively. The four light sources send light pulse signals in sequence. After each light source emits light, the scattered light power received by the photodiode is recorded, which is recorded as P B1 , P I1 , P B2 and P I2 , subtract the corresponding background value from the scattered light power received by the photodiode to obtain the corresponding scattered light power change value ΔP B1 , ΔP I1 , ΔP B2 and ΔP I2 ;

[0049] Step 3: When ΔP B1 ≤P TH , and ΔP I1 ≤P TH , and ΔP B2 ≤P TH , and ΔP I2 ≤P TH When ΔP B1 >P TH , or ΔP I1 >P TH , or ΔP B2 >P TH , or ΔP I2 >P TH Start recording ΔP B1 , ΔP I1 , ΔP B2 and ΔP I2 , and substituting into formulas (1), (2), (3), and (4), we can obtain:

[0050]

[0051] in,

[0052] Step 4. In the above formulas, the parameters on the left side of the equations are all known. By solving equations (5) and (6), d and m can be obtained. Substituting d and m into equations (7) or (8) can obtain η.

[0053] Step 5: If the aerosol particle size d>d TH , the aerosol is determined to be dust or water vapor; otherwise, the aerosol is fire smoke or oil smoke, and the process goes to step 6;

[0054] Step 6: If the shape of the aerosol η>η TH , the aerosol is determined to be black smoke from fire, and the detector sends out a black smoke alarm signal; otherwise, the aerosol is oil smoke or white smoke from fire, and the seventh step is entered;

[0055] Step 7: If the refractive index of the aerosol is m>m TH , the aerosol is determined to be white smoke from a fire, and the detector sends out a white smoke alarm signal; otherwise, the aerosol is oil smoke.

[0056] It can be understood that the above conversion coefficients k1 to k4, deviation functions σ1(m), σ2(m), σ3(m, d), and σ4(m, d) are all obtained in advance in a laboratory environment by introducing fire smoke and interference aerosols with known particle size, refractive index, and ellipsoidality into the optical darkroom. B1 , ΔP I1 , ΔP B2 , ΔP I2 After being substituted into the relationship, numerical analysis methods such as polynomial approximation and Taylor expansion are used to fit the equation. Wherein, fire smoke includes black smoke and white smoke; and the interfering aerosol includes oil smoke, dust and water vapor.

[0057] △P TH Refer to the national standard GB4715 and determine it by calibration of standard instruments. In this embodiment, △P TH =300.

[0058] d TH , η TH and m TH It is obtained based on fire smoke and interference aerosol with known particle size, refractive index and ellipsoidality and measuring instruments.

[0059] Black smoke, white smoke, oil smoke, water vapor and dust are introduced into the fire detector respectively, and the measured particle size, shape and refractive index parameters are plotted in a three-dimensional scatter plot, as shown in the figure. Figure 5 As shown, it can be seen that the fire smoke and interference sources are distinguished.

[0060] The embodiment of the present invention provides a fire smoke accurate sensing method based on the combined characteristics of particle size, shape and refractive index, which is applied to the fire smoke detector as described in the above embodiment, including:

[0061] S1, every preset time, turn on the first to fourth light sources in sequence, and record the scattered light power P received by the photodiode after each light source emits light B1 , P I1 , P B2 , P I2 , and are respectively compared with the scattered light power received by the photodiode when no aerosol is introduced into the optical darkroom Subtract to get ΔP B1 , ΔP I1 , ΔP B2 , ΔP I2 ;

[0062] S2, if ΔP B1 , ΔP I1 , ΔP B2 , ΔP I2 No more than the threshold △P TH Then return to S1, otherwise according to ΔP B1 , ΔP I1 , ΔP B2 , ΔP I2 Calculate the particle size d, refractive index m and ellipsoidality η of the aerosol to be detected, and TH And η is greater than the ellipsoid threshold η TH , or d is less than the particle size threshold and m is greater than the refractive index threshold m TH A fire alarm signal is issued.

[0063] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A fire smoke detector based on the combined characteristics of particle size, shape and refractive index, characterized in that: include: Optical darkroom, light source module, photodiode, processing module, alarm module; The optical darkroom is provided with a plurality of through holes for introducing the aerosol to be detected; The photodiode is arranged on the inner wall of the optical darkroom; The light source module includes first to fourth light sources, which are sequentially arranged around the inner wall of the optical darkroom, the wavelengths of the first and third light sources are both λ1, the wavelengths of the second and fourth light sources are both λ2, and λ1<λ2; and the angles between the emitted light rays of the first and second light sources at the convergence point and the scattered light rays scattered to the photodiode are the same and are both acute angles, and the angles between the emitted light rays of the third and fourth light sources at the convergence point and the scattered light rays scattered to the photodiode are the same and are both obtuse angles; wherein the convergence point is the common convergence point of the first to fourth light sources; The processing module is used to perform the following operations: A1, turn on the first to fourth light sources in sequence at preset time intervals, and record the scattered light power P received by the photodiode after each light source emits light B1 , P I1 , P B2 , P I2 , and are respectively compared with the scattered light power received by the photodiode when no aerosol is introduced into the optical darkroom Subtract to get ΔP B1 , ΔP I1 , ΔP B2 , ΔP I2 ; A2, if ΔP B1 , ΔP I1 , ΔP B2 , ΔP I2 No more than the threshold △P TH Then return to A1, otherwise according to ΔP B1 , ΔP I1 , ΔP B2 , ΔP I2 Calculate the particle size d, refractive index m and ellipsoidality η of the aerosol to be detected, and TH And η is greater than the ellipsoid threshold η TH , or d is less than the particle size threshold and m is greater than the refractive index threshold m TH When a fire alarm signal is sent out through the alarm module; Where ΔP B1 , ΔP I1 , ΔP B2 , ΔP I2 Satisfies the relationship between d, m, and η: k1 to k4 are conversion coefficients, σ1(m), σ2(m), σ3(m,d), σ4(m,d) are deviation functions; d is less than the particle size threshold d TH And η is greater than the ellipsoid threshold η TH When the fire alarm signal is a fire black smoke alarm signal; d is less than the particle size threshold and m is greater than the refractive index threshold m TH , the fire alarm signal is a fire white smoke alarm signal; k1 to k4, σ1(m), σ2(m), σ3(m, d), and σ4(m, d) are all ΔP obtained by introducing fire smoke and interfering aerosols with known particle size, refractive index, and ellipsoidality into the optical darkroom. B1 , ΔP I1 , ΔP B2 , ΔP I2 And the relationship is solved to obtain; Among them, fire smoke includes fire black smoke and fire white smoke; The interfering aerosol includes oil smoke, dust and water vapor.

2. The fire smoke detector according to claim 1, characterized in that: The first and third light sources are both blue LED light sources, and the second and fourth light sources are both infrared LED light sources.

3. The fire smoke detector according to claim 1, characterized in that: The angles between the emitted light at the convergence point of the first and second light sources and the scattered light scattered to the photodiode are the same and are both 40 degrees. The angles between the emitted light at the convergence point of the third and fourth light sources and the scattered light scattered to the photodiode are the same and are both 140 degrees.

4. The fire smoke detector according to claim 1, characterized in that: The first to fourth light sources and the photodiodes are all arranged on the same plane.

5. A fire smoke precision sensing method based on the combined characteristics of particle size, shape and refractive index, applied to the fire smoke detector according to any one of claims 1 to 4, characterized in that: include: S1, every preset time, turn on the first to fourth light sources in sequence, and record the scattered light power P received by the photodiode after each light source emits light B1 , P I1 , P B2 , P I2 , and are respectively compared with the scattered light power received by the photodiode when no aerosol is introduced into the optical darkroom Subtract to get ΔP B1 , ΔP I1 , ΔP B2 , ΔP I2 ; S2, if ΔP B1 , ΔP I1 , ΔP B2 , ΔP I2 No more than the threshold △P TH Then return to S1, otherwise according to ΔP B1 , ΔP I1 , ΔP B2 , ΔP I2 Calculate the particle size d, refractive index m and ellipsoidality η of the aerosol to be detected, and TH And η is greater than the ellipsoid threshold η TH , or d is less than the particle size threshold and m is greater than the refractive index threshold m TH A fire alarm signal is issued.

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