A method and apparatus for detecting fire smoke

Abstract

The present application relates to a kind of fire smoke detection method and corresponding device, belong to fire detection technical field.The method is arranged ionization charged component in the same measurement space, and particle charge collection component and particle scattering light detection component, by receiving particle charge signal Uc And particle scattering light signal Ps;Parameter Dn is obtained by calculation, then respectively compare Dn With preset ultrafine particle size determination threshold Td1, Uc With preset particle concentration alarm threshold Tp And Dn With preset micron level small particle size determination threshold Td2, then according to the judgment result output early fire alarm signal, fire alarm signal or non-fire disturbance signal.The present application does not need to distinguish different particle size when detecting ultrafine particle, obtains 0.1 micron level ultrafine particle size and concentration by calculation, simplifies charge collection structure and circuit, does not need to accurately control airflow, not only can sense early fire smoke PM0.1 Ultrafine particle, but also can detect ordinary smoke particle, and effectively removes large particle interference, significantly reduces false alarm rate.

Description

Technical Field

[0001] This invention relates to a method for detecting fire smoke, particularly a method for detecting fire smoke that can detect very early pyrolysis particles, and also relates to a corresponding device, belonging to the field of fire detection technology. Background Technology

[0002] Studies have shown that fire smoke is a particulate aerosol composed of particulate matter aerosols formed by the rapid nucleation of gaseous products from the high-temperature pyrolysis of combustibles (usually carbon-containing substances) and the products of chemical oxidation reactions during combustion. Related research on the evolution of combustion smoke indicates that in the very early pyrolysis smoldering stage of a fire, the incomplete combustion of combustibles produces large amounts of gaseous hydrocarbons, carbon monoxide, or volatile metal vapors. These gaseous substances are in a supersaturated state within the high-temperature flame. As the smoke gradually cools after leaving the fire source, it rapidly aggregates to form nanoscale molecular clusters. Furthermore, if the fuel contains metal oxides, these will directly melt into nanoscale particles at high temperatures. Thus, the combustible material first decomposes into a large number of 10-50 nm primary particles. During diffusion, some of these primary particles condense and coalesce through multiple collisions to generate larger secondary particles. Therefore, in the very early stages of a fire, when the burning material heats up and decomposes, the smoke is mainly composed of ultrafine aerosol particles (PM0.1) with a particle diameter (particle size) of less than 100 nm. As the fire continues, the smoke particles gradually condense and expand into fine aerosol particles (PM1) with a diameter of about 0.1-1 μm. To detect smoke in the very early stages of a fire, it is necessary to sense ultrafine PM0.1 particles. On the other hand, fine particles (PM2.5) account for about 40%–70% of the mass concentration in ordinary atmosphere, making them the main component of atmospheric particles. Therefore, current mainstream fire smoke detection technology distinguishes between fire smoke and non-fire aerosols by sensing the particle size characteristics of fire smoke and non-fire aerosols, using 1 µm as the boundary. However, 1 µm is not the absolute particle size boundary for determining fire smoke and non-fire aerosols; particles outside the boundary size still exist for both types of aerosols, meaning there is still a possibility of false alarms. Therefore, relying solely on a 1 µm boundary line does not fundamentally solve the problem of false alarms in fire smoke detection devices. In addition, the mass concentration of ultrafine particles (PM0.1) in the atmosphere is extremely low (usually <5%), mainly from combustion gas nucleation, industrial emissions, etc. Once PM0.1 is detected to suddenly and sharply increase to a certain level, it means that combustion products have appeared, which in indoor environments are smoke particles in the very early stage of a fire.

[0003] However, existing fire smoke detection methods mainly employ photoelectric smoke detection devices based on the principle of Mie scattering in particle optics. Their response to particles is described in [reference needed]. Figure 1According to the Mie scattering theory model of particle optics, when the particle diameter is smaller than half the wavelength of the incident light, the intensity of the scattered light decreases rapidly with the sixth power of the particle size. For example, with blue light incident at a wavelength of 430 nm and a particle size of 400 nm, the scattered light intensity is 1 (au), while with a particle size of 270 nm, the scattered light intensity is only 0.4, and if the particle size is 130 nm, the scattered light intensity is close to 0 (Paul A. Baron, Klaus Willeke, Aerosol Measurement: Principles, Techniques, and Applications, John Wiley & Sons, Inc. Second Edition, 2005, p463). Therefore, existing photoelectric smoke detection devices are limited by factors such as the wavelength of light emission and reception, the emission power, the photosensitivity, and the measurement noise, and cannot directly and effectively detect smoke particles with a particle size of less than 150 nm, that is, they cannot detect ultrafine PM0.1 smoke particles in the very early stages of a fire.

[0004] To overcome the aforementioned problems of photoelectric smoke detection, Chinese patent document application number 202010514919.8 discloses a method of treating particles using a water- or compressed gas condensation cloud chamber. This method surrounds both nanoparticles and dust particles generated by pyrolysis with water droplets or compressed gas condensation nuclei, effectively amplifying PM0.1 particles. However, this technical solution also amplifies interfering particles. While it can distinguish between combustion particles and dust in terms of quantity, it cannot differentiate particle size or identify water vapor particles themselves. Therefore, these methods still cannot effectively solve the false alarm problem and require the use of water, ultrasonic equipment, or compressed air pumps and solenoid valves, resulting in complex operation, low accuracy, and high detection equipment costs.

[0005] In fact, mature technologies and equipment for detecting ultrafine particles in atmospheric particulate matter measurement already exist. For example, scanning electromobility particle size spectrometers (SMPS) separate charged particles using an electric field. Particles entering the electric field become charged, and based on the principle that small particles migrate faster than large particles under certain airflow conditions, precise classification is achieved by adjusting the voltage to obtain different particle size concentrations. Chinese patent application number 202010116032.3 discloses a technical solution based on SMPS technology, using a particle charging method to determine fire smoke information by classifying charged particles of different sizes in an air sample and determining the corresponding charge amount of each particle size. This solution can detect 20-100 nanometer ultrafine particles in combustion smoke. However, directly using this method can also detect large particles that interfere with non-fire smoke. As a result, in order to collect small particles and remove large interfering particles, this method must employ complex structures such as jet ducts, negative pressure fluid fields, and narrow jet nozzles, so that charged particles of different sizes have different kinetic energies when ejected from the nozzle. After passing through a long collection electrode, charged particles of different sizes fall onto different sub-collection electrodes. Alternatively, a condenser can be used to detect tiny particles through two-stage charging of bipolar and unipolar charges. This method has a complex structure, is difficult to regulate airflow, and has a large volume. Summary of the Invention

[0006] The purpose of this invention is to address the problems existing in the prior art by proposing a fire smoke detection method that combines ionization charge and light scattering, which can not only sense PM0.1 ultrafine particles in the very early stages of fire smoke, but also effectively remove interference from large particles and significantly reduce the false alarm rate; and based on this, a corresponding device is provided.

[0007] To achieve the above objectives, the basic technical solution of the fire smoke detection method of the present invention is as follows: a corona ionization component, a particle charge collection component, and a particle scattering light detection component are arranged in the same measurement space; the corona ionization component is controlled by a control circuit MCU, and the particle charge collection component and the particle scattering light detection component transmit signals to the control circuit MCU; the control circuit MCU realizes fire alarm through the following steps: Step 1: Control the discharge / ionization of the corona ionization component to form a cloud of free electrons, so that all particles entering the measurement space are charged; Step 2: The receiving particle charge collection component obtains a particle charge signal Uc that is proportional to the particle concentration in the measurement space; and the scattering light detection component collects particle scattering light signals Ps above 150nm by measuring the particle scattering light. Step 3: Calculate the particle size parameter Dn using the following formula. Dn=Ps / Uc; Step 4: Compare Dn with the preset 0.1 micrometer-level ultrafine particle size (usually 100-200nm, especially 150nm) to determine the threshold Td1. If Dn≤Td1, proceed to the next step; otherwise, proceed to step 6. Step 5: Compare Uc with the preset particle concentration alarm threshold Tp. If Uc > Tp, output the very early fire alarm signal; otherwise, return to step 1. Step 6: Compare Dn with the preset micron-scale fine particle size (usually 0.5-1μm, especially 1μm) to determine the threshold Td2. If Dn≤Td2, proceed to the next step; otherwise, proceed to step 8. Step 7: Compare Uc with the preset particle concentration alarm threshold Tp. If Uc > Tp, output a fire alarm signal; otherwise, return to step 1. Step 8: Compare Uc with the preset particle concentration alarm threshold Tp. When Uc > Tp, output a non-fire interference signal; otherwise, return to step 1.

[0008] This invention eliminates the need for different electrodes to distinguish particles of different sizes when detecting ultrafine particles. Instead, it uses a single electrode to receive the sum of particle responses, including those of ultrafine particles, and simultaneously uses scattered light to obtain the responses of particles other than ultrafine particles. Through calculation, the ultrafine particle size and concentration at the 0.1 micrometer level are obtained, simplifying the charge collection structure and circuit. It also eliminates the need for precise airflow control. Therefore, it can not only sense PM0.1 ultrafine particles in the very early stages of fire smoke, but also detect ordinary smoke particles, effectively removing interference from large particles and significantly reducing the false alarm rate.

[0009] Another basic technical solution of the present invention is as follows: a corona ionization component, a particle charge collection component, and a particle scattering light detection component are arranged in the same measurement space; the scattering light detection component contains a pair of dual-wavelength emitting devices; the corona ionization component is controlled by a control circuit MCU, and the particle charge collection component and the particle scattering light detection component transmit signals to the control circuit MCU. The control circuit MCU realizes fire alarm through the following steps: Step 1: Control the discharge / ionization of the corona ionization component to form a cloud of free electrons, so that all particles of different sizes entering the measurement space are charged; Step 2: The particle charge collection component obtains a particle charge signal Uc that is proportional to the concentration of particles of different sizes in the measurement space; and the scattered light detection component collects particle scattered light signals P corresponding to short and long wavelengths, respectively, by measuring the scattered light collected by the particles. BL and P IR ; Step 3: Determine the particle size Dmed based on the ratio of short-wavelength to long-wavelength light scattering power, and calculate the corresponding particle size parameter Dn using the following formula. Dn=P IR / Uc; Step 4: Determine whether Dn is less than or equal to the preset ultra-fine particle size judgment threshold Td1 of 0.1 μm. If so, proceed to the next step; otherwise, proceed to Step 6. Step 5: Determine whether Uc is greater than the preset particle concentration alarm threshold Tp and P BL is less than PBLth; if so, output an ultra-early fire alarm signal; if not, return to Step 2. Step 6: Determine whether Dmed is less than or equal to 1 μm; if so, proceed to the next step; if not, proceed to Step 8. Step 7: Determine whether Uc is greater than the preset particle concentration alarm threshold Tp and P BL is greater than the short-wavelength light scattering power alarm threshold PBLth; if so, output a conventional fire alarm signal; if not, return to Step 2. Step 8: Determine whether P IR is greater than the long-wavelength light scattering power alarm threshold PIRth; if so, output a non-fire interference signal; if not, return to Step 2.

[0010] Since the scattered light part uses dual-wavelength detection (see Patent 201410748629.4), by obtaining the short-wavelength light scattering power P BL and the long-wavelength light scattering power P IR of the corresponding scattered signals, calculate the ratio of the short-wavelength to long-wavelength light scattering power; determine the median particle size Dmed based on the relationship between the ratio and the aerosol median particle size Dmed, and then combine Dn and Uc to issue the corresponding ultra-early fire alarm signal, fire alarm signal or interference prompt signal: Dn < Td, Uc > Tp and P BL is approximately 0 or P BL < PBLth (PBLth is the short-wavelength light scattering power alarm threshold) is an ultra-early fire smoke alarm; Dn > Td, Uc > Tp, Dmed < 1 μm and P BL > PBLth is a conventional fire smoke alarm signal; Dmed ≥ 1 μm and P IR > PIRth (PIRth is the long-wavelength light scattering power threshold), regardless of the magnitudes of Dn and Uc, is a non-fire interference signal.

[0011] It should be noted that the detection device for the ultrafine particle sensing method in the very early stage of a fire, as described in this invention, is composed of three parts: a charge corona ionization component (corona discharge chamber), a particle charge collection component (particle charge collection chamber), and a particle scattering light detection component (scattering light chamber). The device can be configured in series, with the corona discharge chamber, particle charge collection chamber, and scattering light chamber connected in series. An air sample from the monitored space is drawn into the detection device by an intake fan, and after detection, the sample is discharged. In this series configuration, the scattering light chamber can be located before or after the corona discharge chamber and particle charge collection chamber. Alternatively, the device can be configured in parallel, with the air sample entering through a single inlet and then branching out: one path enters the corona discharge chamber and particle charge collection chamber, while the other path enters the scattering light chamber for detection, and the samples are then combined and discharged.

[0012] The corona ionization component is used to ionize air to generate charged ions. Ionization can be achieved through high-voltage corona discharge, radioactive ionization, or dielectric discharge. The charged ions generated by ionization combine with particles in the sampled air to form charged particles, a process known as particle charging. If corona discharge is used, positive unipolar ionization is achieved by applying a positive high voltage to the discharge needle; alternatively, negative unipolar charging can be achieved by applying a negative high voltage. After being charged, the particles enter the particle charge collection chamber, which contains flat or cylindrical electrodes. An appropriate voltage is applied to the electrodes to create an electric field within the chamber. Charged particles, under the influence of this electric field, combine with the corresponding electrodes, releasing their charge. An amplification circuit connected to the electrodes generates a voltage signal Uc proportional to the particle charge. If positive ionization is used, a negative voltage electric field can be used for the collection electrode. If negative ionization is used, a positive voltage electric field can be used for the collection electrode.

[0013] If the corona ionization component uses radioactive ionization, the sampling method of drawing air samples with an intake fan can be eliminated, and a diffusion-type smoke detection device structure can be adopted. Furthermore, the corona discharge chamber and the charge collection chamber can be integrated. In this case, the corona ionization component can use the ionization discharge chamber of a commonly used ionization smoke detection device, using radioactive material as the radiation source to release radiation particles, ionizing the air to generate positive and negative ions. Under the action of an electric field, a stable current is formed. When smoke particles pass through the corona discharge chamber, they adsorb ions, causing a change in current. The amount of this change is proportional to the concentration of smoke particles, thereby obtaining Uc.

[0014] For corona ionization components that use high-voltage corona discharge, the high-voltage needle tip corona discharge method is generally used. In order to protect the discharge needle tip and extend its service life, this invention uses a discharge needle protection structure, that is, the discharge needle is in an independent space, with only the outlet connected to the sampling space, so that the discharge needle is not easily contaminated by particulate matter in the sampled air. For the specific structure, please refer to the corresponding illustrations and descriptions of the embodiments.

[0015] Since the present invention can effectively detect ultrafine particles smaller than 100nm, it can detect overheating or discharge faults in electrical equipment where metal oxides and other materials directly melt into nanoscale particles at high temperatures. This forms an ultra-early particle detection device for detecting overheating or discharge faults in metal connectors of electrical equipment. Its response characteristics are shown in the corresponding illustrations and descriptions of the embodiments. Attached Figure Description

[0016] Figure 1 It is a particle optical scattering response diagram; Figure 2 This is a schematic diagram of the fire detection device according to Embodiment 1 of the present invention; Figure 3 This is a fire alarm flowchart according to Embodiment 1 of the present invention; Figure 4 This is a graph showing the test data of charged and single-wavelength scattered light signals in Embodiment 1 of the present invention; Figure 5 This is a schematic diagram of the fire detection device according to Embodiment 2 of the present invention; Figure 6 This is a fire alarm flowchart according to Embodiment 2 of the present invention; Figure 7 This is a graph of dual-wavelength scattering photoelectric detection data from Embodiment 2 of the present invention; Figure 8 This is a charge response diagram of different particle sizes and concentrations in Embodiment 2 of the present invention. Figure 9 This is a response diagram of charge and photoelectric effect on smoldering cotton rope according to Embodiment 2 of the present invention; Figure 10 This is a diagram showing the initial response of charge and photoelectric effect to the combustion of n-heptane in Embodiment 2 of the present invention. Figure 11 This is a distribution diagram of metal oxide particles generated by overheating of the copper wire in Embodiment 2 of the present invention; Figure 12 This is a response diagram of charged and scattered light to the overheating of copper wires in Embodiment 2 of the present invention, showing the response of ultrafine particles. Figure 13 This is a schematic diagram of the fire detection device according to Embodiment 3 of the present invention. Detailed Implementation

[0017] The technical methods of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] It should be understood that, when used in this specification and the appended claims, the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0019] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. It should also be further understood that the term "and / or" as used in this specification and the appended claims refers to any combination of one or more of the associated listed items, and all possible combinations, and includes such combinations.

[0020] The accompanying drawings illustrate various structural schematic diagrams according to embodiments disclosed in this invention. These drawings are not to scale, and some details have been enlarged for clarity, and some details may have been omitted. The shapes of the various regions and layers shown in the drawings, as well as their relative sizes and positional relationships, are merely exemplary and may deviate from reality due to manufacturing tolerances or technical limitations. Furthermore, those skilled in the art can design regions / layers with different shapes, sizes, and relative positions as needed.

[0021] Example 1 The fire detection device used in this embodiment is as follows: Figure 2 As shown, a scattering light chamber 1 with an inlet 1.1 at one end is connected to a corona discharge chamber 2 through two air inlets 1.2 at the other end. The corona discharge chamber 2 is connected to a charge collection chamber 3 with a narrowed diameter. A fan 4 is installed at the outlet end of the charge collection chamber 3, thus forming the same measurement space.

[0022] The scattering chamber 1 is equipped with an infrared light source 1.3 (i.e., a photoelectric emitting device) and a corresponding light receiving tube 1.4 (i.e., a photoelectric receiving device) on both sides, which can detect the scattered light signal Ps of particles larger than 150nm entering the sample gas, thus forming a particle scattering light detection component; the corona discharge chamber 2 houses a discharge needle 2.1 covered by a protective cover 2.2. The protective cover 2.2 can reduce particle contamination of the discharge needle. The protective cover has an opening 2.3 at the tip of the discharge needle 2.1, thus forming a corona ionization component; the charge collection chamber 3 is equipped with charge collection plates 3.1 on both sides, which can obtain a particle charge signal Uc proportional to the concentration of particles of different sizes—the sum of nano- to submicron- to micron-scale aerosols, that is, the sum of signals including PM0.1 ultrafine particles and other particles, thus forming a particle charge collection component.

[0023] During operation, the fan draws the air (sample gas YQ) from the sampling space into the detection device of this embodiment. First, the sample passes through the scattering light chamber to obtain the aerosol scattering light signal. Then, aerosol particles KL enter the corona discharge chamber through the air inlet between the scattering light chamber and the corona discharge chamber. A high voltage HV1 is applied to the discharge needle, causing the aerosol particles to be ionized at the opening at the tip of the protective cover, forming a charged ion cloud LZ, which enters the charge collection chamber with the airflow. A voltage HV2 is applied to the upper electrode of the charge collection plate in the charge collection chamber, causing charged particles DD to fall to the lower electrode. The collected charge is obtained by the charge collection circuit and neutralized. The decharged particles are then discharged from the detection device by the fan, completing the smoke detection process. In short, after entering the detection device, the sample gas sequentially passes through the scattering light component, the corona ionization component, and the charge collection component, and is finally discharged by the fan. Therefore, from the perspective of sampling the sample gas, this embodiment is a serial operation mode.

[0024] The corona ionization component is controlled by the control circuit MCU. The particle charge collection component and the particle scattering light detection component transmit signals to the control circuit MCU. The configuration of the control circuit can be found in Chinese patent documents with application numbers 201410748629.4, 201580043588.1, and 202010116032.3. It is similar to the prior art and will not be described in detail here.

[0025] See Figure 3 The MCU implements fire alarm through the following steps: Step 1: Control the discharge / ionization of the corona ionization component to form a cloud of free electrons, so that all particles of different sizes entering the measurement space are charged; Step 2: The particle charge collection component obtains a particle charge signal Uc (which is dimensionless and includes the total number of nano- to submicron- to micron-scale aerosols) that is proportional to the particle size concentration in the measurement space; and the particle scattered light signal Ps (which is dimensionless and generally proportional to the particle volume concentration, belonging to the submicron- to micron-scale aerosols) collected by the scattered light detection component through the measurement of particle scattered light. Step 3: Calculate the particle size parameter Dn using the following formula. Dn=Ps / Uc Step 4: Compare Dn with the preset 0.1 micrometer ultrafine particle size judgment threshold Td1. The specific value is calibrated by a particle size analyzer. In this embodiment, an aerosol generator (TSI3480 type) is used to generate nanoscale microspheres with a particle size of about 150 nm and the required concentration. The concentration increases linearly. The center particle size generated by the particle size analyzer (TSI3910 SMPS type) is used as Td1 (it can also be calibrated based on experience). When Dn≤Td1, proceed to the next step; otherwise, proceed to step 6. Step 5: Compare Uc with the preset particle concentration alarm threshold Tp. In this embodiment, an aerosol generator is used to generate nanospheres with a particle size of about 150 nm and a concentration set to exceed the PM0.1 content in polluted air by 5 - 10 times, approximately 50 - 100 μg / m3. The central particle size of the generated particles measured by a particle size analyzer is used as Tp (which can also be calibrated based on experience). When Uc > Tp, an ultra - early fire alarm signal is output; otherwise, return to Step 1. Step 6: Compare Dn with the preset micron - scale fine particle size judgment threshold Td2. In this embodiment, an aerosol generator is used to generate nanospheres with a particle size of about 1 μm and the required concentration. The central particle size of the generated particles measured by a particle size analyzer is used as Td2. When Dn ≤ Td2, proceed to the next step; otherwise, proceed to Step 8. Step 7: Compare Uc with the preset particle concentration alarm threshold Tp. When Uc > Tp, output a fire alarm signal; otherwise, return to Step 1. Step 8: Compare Uc with the preset particle concentration alarm threshold Tp. When Uc > Tp, output a non - fire interference signal; otherwise, return to Step 1.

[0026] Under the condition of the same particle concentration, the value of Ps decreases as the particle size becomes smaller, and gradually drops to 0 after 150 nm. Uc responds to various particle sizes. Therefore, Dn decreases as the particle size becomes smaller and finally approaches 0. On the contrary, if the particle size increases, the value of Ps gradually increases, and Dn approaches a value greater than 0 as the particle size increases. Therefore, Dn is related to the particle size.

[0027] When Dn ≤ Td1 (Td1 is the 0.1 - micron - scale ultra - fine particle size judgment threshold, and in this embodiment, Td1 corresponds to 150 nm), and at the same time Uc > Tp (Tp is the particle concentration alarm threshold), it is determined as an ultra - early fire alarm signal; when Dn < Td2 (in this embodiment, Td2 corresponds to 1 μm), and at the same time Uc > Tp, it can be determined as a conventional fire smoke alarm; when Dn > Td2, and at the same time Uc > Tp, it is determined as non - fire large - particle interference.

[0028] Therefore, appropriately selecting Td1 and Td2 can not only achieve conventional fire smoke alarms, but also enable Dn to remove the particle response above 150 nm from all particles when it is less than a certain Td1, and be only proportional to the PM0.1 ultra - fine particle concentration, so as to effectively detect ultra - early fire smoke particles. At the same time, after Dn is greater than Td2, it can remove the interference of non - fire large particles.

[0029] Figure 4The measured data of the response of Dn, which is the ratio of the particle infrared photoelectric scattering signal Ps to the charged signal Uc, to particles of different particle sizes. Among them, the ratio of the particle size of 144.9 nm is only about 0.003. When the particle size is greater than 600 nm, Dn gradually rises above 1. When the particle size is greater than 1 μm, Dn is greater than 2. If Td1 = 0.009, the detection device signal only responds to particles with a particle size below 170 nm. If Td2 = 2, Dn < Td2 is the response of the detection device to particles below 1 μm, and Dn > Td2 is determined to be interference from large non-fire particles.

[0030] Example Two The fire detection device used in this example is as Figure 5 shown. Different from Example One, the inlet 1.1 of the scattering light chamber 1 is in parallel with the inlet of the corona discharge chamber 2. The corona discharge chamber 2 is connected to the charge collection chamber 3 with a reduced path. The outlet of the scattering light chamber 1 and the outlet of the charge collection chamber 3 are equipped with a fan 4 in parallel, thus forming the same measurement space. In addition, different from using single-wavelength scattered light in the scattering light chamber, a pair of dual-wavelength emitting devices 1.3' and 1.4' and receiving devices 1.2' are used (see the patent documents 201410748629.4 and 201580043588.1. In fact, a structure with more wavelengths can also be used, which will not be elaborated here).

[0031] During operation, the sampled gas is divided into two paths after entering the detection device. One path enters the scattering light chamber, and the other path enters the corona discharge and charge collection chamber, and then they are combined and discharged through the fan, thus actually forming a parallel form. Although the scattering light chamber and the corona discharge and charge collection chamber intake gas separately, the entire detection device still has the same intake and outlet, so it is ensured that the sampled gas for the scattered light and the corona discharge and charge collection chamber is the same.

[0032] See Figure 6 , the MCU of the control circuit in this example realizes fire alarm through the following steps: Step One: Control the corona ionization component to discharge / ionize to form a free electron cloud, so that particles of all sizes entering the measurement space are charged; Step Two: Receive the particle charge signal Uc obtained by the particle charge collection component, which is proportional to the concentration of particles of all sizes in the measurement space; and the particle scattered light signals P corresponding to the short blue wavelength and long red wavelength collected by the scattered light detection component BL and P IR ; Step Three: Determine the particle size Dmed according to the ratio of the scattered light power of the short wavelength to the long wavelength (the determination of the ratio and Dmed can be seen in the patent documents 201410748629.4 and 201580043588.1, which will not be elaborated here), and calculate the particle size corresponding parameter Dn through the following formula Dn = P IR / Uc Step 4: Determine whether Dn is less than or equal to the preset ultra-fine particle size judgment threshold Td1 of 0.1 μm. If so, proceed to the next step; otherwise, proceed to Step 6. Step 5: Determine whether Uc is greater than the preset particle concentration alarm threshold Tp and P BL is less than PBLth (the meaning and determination of PBLth are shown in the patent documents 201410748629.4 and 201580043588.1); if so, output an early fire alarm signal; if not, return to Step 2. Step 6: Determine whether Dmed is less than or equal to 1 μm; if so, proceed to the next step; if not, proceed to Step 8. Step 7: Determine whether Uc is greater than the preset particle concentration alarm threshold Tp and P BL is greater than the short-wavelength light scattering power alarm threshold PBLth (the meaning and determination of PBLth are shown in the patent documents 201410748629.4 and 201580043588.1); if so, output a conventional fire alarm signal; if not, return to Step 2. Step 8: Determine P IR whether it is greater than the long-wavelength light scattering power alarm threshold PIRth (the meaning and determination of PIRth are shown in the patent documents 201410748629.4 and 201580043588.1). If so, output a non-fire interference signal; if not, return to Step 2.

[0033] In this embodiment, by obtaining the corresponding scattering signals reflected by the short-wavelength light scattering power P BL and the long-wavelength light scattering power P IR calculate the ratio of the short-wavelength to long-wavelength light scattering power; determine the median particle size Dmed according to the relationship between the ratio and the aerosol median particle size Dmed, and then combine Dn and Uc to issue corresponding early fire alarm signals, fire alarm signals or interference prompt signals: Dn < Td, Uc > Tp and P BL is approximately 0 or P BL < PBLth (PBLth is the short-wavelength light scattering power alarm threshold) is an early fire smoke alarm; Dn > Td, Uc > Tp, Dmed < 1 μm and P BL > PBLth is a conventional fire smoke alarm signal; Dmed ≥ 1 μm, and P IR > PIRth (PIRth is the long-wavelength light scattering power threshold), regardless of the magnitudes of Dn and Uc, is an interference prompt signal.

[0034] Figure 7This data represents the test results of the ratio of blue and infrared light dual-wavelength photoelectric particle scattering signals to the response of particles of different sizes. From... Figure 7 The ratio shows that after the particle size is greater than 250 nm, the ratio is basically proportional to the particle size Dmed, so the particle size can be obtained from the ratio.

[0035] Figure 8 The display shows the response of the charged signal at different particle sizes, and it can be seen that the charged response increases linearly with particle concentration. If the Tp value of Uc is set to 1050, an alarm can be triggered when the concentration of particles with a median particle size of 129.8 nm reaches Uc exceeding Tp, thus effectively detecting ultrafine smoke particles of PM0.1 and completing the very early warning of fire smoke.

[0036] Figure 9 The data shows the charge and scattered light signals during smoldering of cotton rope. Since the particle size distribution of smoldering cotton rope ranges from approximately 200 nm to 400 nm, the scattered light signal, especially the blue light signal, is strong, with the maximum blue light value exceeding 4700. The maximum infrared light value does not exceed 870, and the maximum charge signal value does not exceed 1900. Dn is approximately 0.458 (P). IR / Uc), from Figure 7 The corresponding particle size is approximately 300 nm. Based on the ratio of dual-wavelength scattered light (Dmed < 1 μm), after 350 s, Uc > Tp (1050), and the blue light signal value reaches above 3500, thus triggering a conventional fire smoke alarm signal.

[0037] Figure 10 The results show the response of charged and scattered light to small particles in the early stages of n-heptane combustion. The charged signal value reaches over 3000, while the maximum infrared signal value is only around 12, and the maximum blue signal value is only around 109, far lower than the charged signal. Between 200-300 seconds, Dn < 0.009, Uc > Tp (1050), triggering an early smoke alarm for the fire. Therefore, it can effectively detect the very early smoke signal of a n-heptane fire.

[0038] Figure 11 The distribution of metal oxide particles when a copper conductor is overheated shows a peak particle size of approximately 61.5 nm, with the vast majority of particles having a diameter of less than 100 nm.

[0039] Figure 12 The results show the response of charged and scattered light to the overheating of copper wires, which produces copper oxide particles. The infrared and blue scattered light signals are both 0, while the charged signal value reaches a maximum of 2500. After 250 seconds, Dn remains approximately 0, and Uc > Tp (1050), triggering an early-stage smoke alarm. Therefore, this method can effectively detect the very early smoke signal from the overheating of copper wires.

[0040] Example 3 The fire detection device used in this embodiment is as follows: Figure 13 As shown, unlike the previous embodiment, an independent light-scattering chamber 1 with airflow holes and a radioactive source ionization chamber 2' that combines a corona discharge chamber and a charge collection chamber are arranged within the same outer casing 4', forming a single measurement space. The light-scattering chamber 1 has photoelectric emitting devices (light sources) 1.3 and corresponding photoelectric receiving devices (light receivers) 1.4 mounted on both sides, and contains a conventional photoelectric smoke detector's optical chamber labyrinth structure. The radioactive source ionization chamber 2' houses an Americium-231 radioactive source 2.1' and charge collection plates 3.1 located on either side of the radioactive source. Since a diffused smoke intake is essentially formed, no fan or high-voltage discharge is required.

[0041] In addition to the embodiments described above, the present invention may have other implementations. For example, the scattering chamber may be placed behind the corona discharge chamber and the charge collection chamber, and the fan may be placed at the sample gas inlet. All technical solutions formed by equivalent substitution or equivalent transformation fall within the scope of protection claimed by the present invention.

Claims

1. A method for detecting smoke in a fire, characterized in that: A corona ionization component, a particle charge collection component, and a particle scattering light detection component are arranged in the same measurement space. The corona ionization component is controlled by a control circuit MCU. The particle charge collection component and the particle scattering light detection component transmit signals to the control circuit MCU. The control circuit MCU realizes fire alarm through the following steps: Step 1: Control the discharge / ionization of the corona ionization component to form a cloud of free electrons, so that all particles entering the measurement space are charged; Step 2: The receiving particle charge collection component obtains a particle charge signal Uc that is proportional to the particle concentration in the measurement space; and the scattering light detection component collects particle scattering light signals Ps above 150nm by measuring the particle scattering light. Step 3: Calculate the particle size parameter Dn using the following formula. Dn=Ps / Uc; Step 4: Compare Dn with the preset 0.1 micrometer ultrafine particle size judgment threshold Td1. If Dn≤Td1, proceed to the next step; otherwise, proceed to step 6. Step 5: Compare Uc with the preset particle concentration alarm threshold Tp. If Uc > Tp, output the very early fire alarm signal; otherwise, return to step 1. Step 6: Compare Dn with the preset micron-level fine particle size judgment threshold Td2. If Dn≤Td2, proceed to the next step; otherwise, proceed to step 8. Step 7: Compare Uc with the preset particle concentration alarm threshold Tp. If Uc > Tp, output a fire alarm signal; otherwise, return to step 1. Step 8: Compare Uc with the preset particle concentration alarm threshold Tp. When Uc > Tp, output a non-fire interference signal; otherwise, return to step 1.

2. A method for detecting smoke in a fire, characterized in that: A corona ionization component, a particle charge collection component, and a particle scattering light detection component are arranged in the same measurement space; the scattering light detection component contains a pair of dual-wavelength emitting devices; the corona ionization component is controlled by a control circuit MCU, and the particle charge collection component and the particle scattering light detection component transmit signals to the control circuit MCU. The control circuit MCU realizes fire alarm through the following steps: Step 1: Control the discharge / ionization of the corona ionization component to form a cloud of free electrons, so that all particles of different sizes entering the measurement space are charged; Step 2: The particle charge collection component obtains a particle charge signal Uc that is proportional to the concentration of particles of different sizes in the measurement space; and the scattered light detection component collects particle scattered light signals P corresponding to short and long wavelengths, respectively, by measuring the scattered light collected by the particles. BL and P IR ; Step 3: Determine the particle size Dmed based on the ratio of short-wavelength to long-wavelength light scattering power, and calculate the corresponding particle size parameter Dn using the following formula. Dn=P IR / Uc; Step 4: Determine whether Dn is less than or equal to the preset 0.1 micrometer ultrafine particle size judgment threshold Td1. If yes, proceed to the next step; otherwise, proceed to step 6. Step 5: Determine if Uc is greater than the preset particle concentration alarm threshold Tp, and if P BL If less than PBLth; if so, output the very early fire alarm signal; otherwise, return to step two. Step 6: Determine if Dmed is less than or equal to 1 μm; if so, proceed to the next step; otherwise, proceed to step 8. Step 7: Determine if Uc is greater than the preset particle concentration alarm threshold Tp, and if P BL If the power of the scattered light exceeds the alarm threshold PBLth for short-wavelength light, output a normal fire alarm signal; otherwise, return to step two. Step 8: Determine P IR If the power of the scattered light is greater than the alarm threshold PIRth for long-wavelength light, output a non-fire interference signal; otherwise, return to step two.

3. A fire smoke detection device that implements the method of claim 1 or 2, characterized in that: The scattering light chamber has at least one light source and a corresponding light-collecting tube installed on each side, forming a particle scattering light detection component; the corona discharge chamber has a discharge needle housed in a protective cover, with an opening at the tip of the discharge needle, forming a corona ionization component; the charge collection chamber has charge collection plates installed on each side, forming a particle charge collection component.

4. The fire smoke detection device according to claim 3, characterized in that: The particle scattering light detection component contains multiple light sources of different wavelengths and corresponding light-receiving tubes.

5. The fire smoke detection device according to claim 3, characterized in that: The scattering chamber has an inlet at one end and is connected to the corona discharge chamber through air inlets on both sides at the other end. The corona discharge chamber is connected to the charge collection chamber with a narrowed diameter. The outlet end of the charge collection chamber is equipped with a fan.

6. The fire smoke detection device according to claim 3, characterized in that: The inlet of the light scattering chamber is connected in parallel with the inlet of the corona discharge chamber. The corona discharge chamber is connected to the charge collection chamber with a narrowed aperture. The outlet of the light scattering chamber is connected in parallel with the outlet of the charge collection chamber and is equipped with a fan.

7. A fire smoke detection device that implements the method of claim 1 or 2, characterized in that: An independent scattering light chamber with airflow holes and a radioactive source ionization chamber that combines a corona discharge chamber and a charge collection chamber are installed in the same outer shell, forming a common measurement space; photoelectric emitting devices and corresponding photoelectric receiving devices are installed on both sides of the scattering light chamber, and a radioactive source and charge collection plates are installed in the radioactive source ionization chamber.

8. The fire smoke detection device according to claim 7, characterized in that: The interior of the scattering light chamber is equipped with a light chamber labyrinth structure.

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