Fire early-stage pyrolysis gas laser-induced breakdown spectroscopy measurement device

Abstract

The utility model discloses a fire early-stage pyrolysis gas laser-induced breakdown spectroscopy measuring device which comprises a laser, a focusing lens, a radiation source, an imaging lens, a spectrograph, a combustible material, a combustible material sample box, an electronic balance, a computer and a control module, the radiation source uses electric heating to generate heat flow radiation, the temperature of the combustible material rises in the heating process, and the temperature of the combustible material rises in the imaging lens. The method comprises the following steps of: performing pyrolysis and releasing pyrolysis volatile component gas, generating ultrashort pulse laser by a pulse laser to excite the pyrolysis gas to form plasma, measuring a plasma emission spectrum by a spectrograph, and analyzing the spectrum by a computer to determine the material composition and content of the gas. The laser-induced breakdown spectroscopy measurement device is used for measuring the pyrolysis gas, has the characteristic of measuring the reaction process on line, and provides a data basis for accurately analyzing the components of the pyrolysis gas and deeply researching the pyrolysis process.

Description

Technical Field

[0001] This utility model belongs to the field of testing and measurement technology, and relates to a laser-induced breakdown spectrum measurement device for pyrolysis gas in the early stage of a fire. Background Technology

[0002] In the early stages of a fire, combustibles are heated by radiation and convection. When the temperature reaches a certain threshold, pyrolysis volatile gases are released. Combustion occurs when the concentration and temperature of the pyrolysis gases meet the ignition conditions. Pyrolysis of combustibles is a key link in the occurrence and spread of fires. In-depth analysis of pyrolysis and understanding of the ignition mechanism are important steps in establishing fire spread models and formulating disaster prevention strategies.

[0003] Currently, cone calorimeters are generally used to simulate the real combustion environment of fire materials and to conduct experimental research on the pyrolysis process of combustibles. With optional modules, it is possible to measure smoke density and gases such as O2, CO, and CO2. However, it lacks devices for analyzing other elements and cannot perform comprehensive online analysis of gas composition. Summary of the Invention

[0004] To address the aforementioned problems, this invention discloses a laser-induced breakdown spectroscopy measurement device for pyrolysis gases in the early stages of a fire, enabling online measurement of pyrolysis gases.

[0005] To achieve the above objectives, this utility model provides the following technical solution:

[0006] The fire early stage platform pyrolysis gas laser-induced breakdown spectroscopy measurement device includes a laser, focusing lens, radiation source, imaging lens, spectrometer, combustible material, combustible material sample box, electronic balance, computer and control module. The radiation source uses electric heating to generate heat flow radiation. The temperature of the combustible material increases during heating, pyrolysis occurs and pyrolysis volatile gases are released. The pulsed laser generates ultrashort pulse laser to excite the pyrolysis gas to form plasma. The spectrometer measures the plasma emission spectrum. The computer analyzes the spectrum to determine the material composition and content of the gas.

[0007] Furthermore, the radiation source uses a carbon rod as a heating medium, which is electrically heated to a maximum of 1500°C. The temperature can be designed through a control module.

[0008] Furthermore, the radiation source generates a heat flow that radiates to the surface of the combustible material. The combustible material is placed in the combustible material sample box, and its surface is subjected to approximately uniform heat flow radiation. After heating, pyrolysis volatile gases are released and diffuse outward.

[0009] Furthermore, the laser emits pulsed laser light with a pulse width of less than nanoseconds;

[0010] Furthermore, the focusing lens focuses the pulsed laser at a point approximately 10 mm from the surface of the combustible sample;

[0011] Furthermore, the imaging lens focuses the beam of light emitted by the pyrolysis gas plasma into the spectrometer.

[0012] Furthermore, computer-controlled automated continuous acquisition of plasma spectra is performed, which are then compared with a material spectral database to obtain the elemental composition corresponding to characteristic wavelengths, enabling online measurement of pyrolysis gases.

[0013] Furthermore, the control module is electrically connected to the radiation source.

[0014] The working principle of this utility model is as follows:

[0015] By using nanosecond pulsed lasers to heat pyrolysis gases to form plasma, spectra related to gas elements are generated. By measuring the plasma spectrum with a spectrometer, the elemental composition of pyrolysis gases in the early stages of a fire can be analyzed.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] This invention employs laser-induced breakdown spectroscopy (LASPS) technology, using a pulsed laser and spectrometer to measure the elemental composition of pyrolysis gases online. It features high measurement freedom and a simple measurement device, enabling the acquisition of elemental concentration changes throughout the pyrolysis process of combustible materials, thus providing a solid data foundation for in-depth analysis of the pyrolysis mechanism. Attached Figure Description

[0018] Figure 1 A schematic diagram of a laser-induced breakdown spectroscopy measurement device for pyrolysis gas in the early stage of a fire, provided by this utility model.

[0019] Figure 2 This is a flowchart of the experimental measurement process according to an embodiment of the present invention.

[0020] List of reference numerals in the attached diagram:

[0021] 1-Laser, 2-Focusing lens, 3-Radiation source, 4-Imaging lens, 5-Spectrometer, 6-Combustible material, 7-Combustible material sample box, 8-Electronic balance, 9-Computer, 10-Control module. Detailed Implementation

[0022] The present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. It should be noted that the terms "front," "rear," "left," "right," "up," and "down" used in the following description refer to directions in the accompanying drawings, and the terms "inner" and "outer" refer to directions toward or away from the geometric center of a specific component, respectively.

[0023] like Figure 1As shown, the present invention provides a structure for a laser-induced breakdown spectroscopy measurement device for pyrolysis gas in the early stage of a fire, comprising a laser 1, a focusing lens 2, a radiation source 3, an imaging lens 4, a spectrometer 5, a combustible material 6, a combustible material sample box 7, an electronic balance 8, a computer 9, and a control module 10. The laser and the spectrometer are located on opposite sides of the combustible material, and the focusing lens and the imaging lens form a confocal relationship.

[0024] Specifically, laser 1 is a pulsed laser with a pulse width in the nanosecond range, a working wavelength of 1064nm, a pulse energy of over 1mJ, and a repetition frequency of over 100Hz. It can use a portable compact Nd:YAG laser.

[0025] The focusing lens 2 has a transmittance of over 90% in the 1064nm band and a focal length of 150mm. It focuses a pulsed laser between the radiation source 3 and the combustible material 6. The focused laser heats the pyrolysis volatile gas released from the combustible material to form plasma. The plasma emits radiation light, and the spectrum is closely related to the gas elements.

[0026] Radiation source 3 consists of 7 carbon rods, which can be heated by providing current through control module 10. The carbon rods are 250mm long and 40mm apart. They can be heated up to 1500℃ and form an approximately uniform heat source within a 100mm distance.

[0027] Imaging lens 4 has a transmittance of over 90% in the 1064nm band and a focal length of 100mm. The focusing laser and spectrometer 5 are located in the conjugate position of the imaging lens, ensuring that the spectrometer can effectively detect the spectrum emitted by the plasma.

[0028] The spectrometer 5 is used to obtain spectral data. The measurement range is 200-1100nm, the wavelength resolution reaches 0.11nm, the dynamic range reaches 2000:1, and the signal-to-noise ratio is higher than 250:1. When the spectral characteristic wavelength is in other ranges, the corresponding spectrometer parameters can be selected according to the specific wavelength value.

[0029] Combustible material 6 is the object to be studied, and its size after cutting is 50×50×20mm.

[0030] The mounting hole for the combustible sample box 7 measures 60×60×20mm, slightly larger than the size of the combustible material. The combustible material is wrapped in insulating materials such as asbestos and placed inside the mounting hole. Since the radiation source is much larger than the combustible material, and considering the adiabatic boundary conditions, a one-dimensional model can be used during modeling, reducing model complexity.

[0031] The electronic balance 8 has a mass resolution of 0.1g and is used to measure the rate of weight loss of combustibles during pyrolysis.

[0032] The computer 9 is connected to the spectrometer via a USB interface, which can read and analyze spectral data in real time. It is also connected to the electronic balance 8 and the control module 10 via a serial port to read weightlessness data in real time and send commands to the control module to change the heating current value.

[0033] The control module 10 includes two sub-modules: a communication module and a current drive module. The former communicates with the computer, while the latter changes the drive current value and heating temperature according to commands.

[0034] A laser-induced breakdown spectroscopy measurement device for pyrolysis gas in the early stage of a fire, the working process of which is as follows: Figure 2 As shown.

[0035] 1. Place the combustible sample and prepare for the experiment;

[0036] 2. The laser emits pulsed laser light, and the computer collects the spectrometer data as the background spectrum F0(λ); 3. The computer sends a command to the control module to heat the radiation source and generate radiant heat.

[0037] 4. After the combustible material is heated, it begins to pyrolyze. The computer continuously collects the spectrum F1(λ) emitted by the plasma of the pyrolysis volatile gas.

[0038] 5. Remove the background spectrum to obtain the gas plasma spectrum G(λ) = F1(λ) - F0(λ);

[0039] 6. Based on the characteristic wavelength analysis G(λ) from publicly available elemental spectral databases on the internet, and combined with weight loss data, the content of various elements in the pyrolysis gas is obtained.

[0040] The technical means disclosed in this invention are not limited to those disclosed in the above embodiments, but also include technical solutions composed of any combination of the above technical features.

Claims

1. A device for fire early pyrolysis gas laser-induced breakdown spectroscopy measurement, characterized in that: The application relates to a combustible material testing device, which comprises a laser (1), a focusing lens (2), a radiation source (3), an imaging lens (4), a spectrometer (5), combustible material (6), a combustible material sample box (7), an electronic balance (8), a computer (9) and a control module (10); the laser (1) and the spectrometer (5) are respectively arranged on the two sides of the combustible material (6), the focusing lens (2) and the imaging lens (4) form a confocal relationship; the two sides above the combustible material (6) are respectively provided with the laser (1) and the spectrometer (5); the focusing lens (2) and the imaging lens (4) are sequentially arranged between the laser (1) and the spectrometer (5); the combustible material sample box (7) is placed on the electronic balance (8); the combustible material (6) is placed in the combustible material sample box (7); the radiation source (3) is arranged above the combustible material (6); the control module (10) is electrically connected with the radiation source (3); the computer (9) is connected with the spectrometer (5) through a USB interface; the computer (9) is connected with the electronic balance (8) and the control module (10) through a serial port.

2. The device for measuring the early pyrolysis gas of fire by laser-induced breakdown spectroscopy according to claim 1, wherein: The combustible (6) has a size after cutting of mm.

3. The device for measuring the early pyrolysis gas of fire by laser-induced breakdown spectroscopy according to claim 1, wherein: The combustible sample box (7) is installed in the hole with a size of mm, and the combustible (6) is wrapped with heat insulation material and placed in the hole.

4. The device for measuring the early pyrolysis gas of fire by laser-induced breakdown spectroscopy according to claim 1, wherein: The control module (10) comprises a communication module and a current driving module; the communication module is in communication connection with the computer (9); the current driving module changes the driving current value and the heating temperature of the radiation source according to the command sent by the computer.

5. The device for measuring the early pyrolysis gas of fire by laser-induced breakdown spectroscopy according to claim 1, wherein: The laser (1) is a pulse laser, the working wavelength is 1064 nm, the pulse energy is above 1 mJ, and the repetition frequency is above 100 Hz.

6. The device for measuring the early pyrolysis gas of fire by laser-induced breakdown spectroscopy according to claim 1, wherein: The focusing lens (2) has a transmittance higher than 90% at a 1064 nm wave band and a focal length of 150 mm.

7. The device for measuring the early pyrolysis gas of fire by laser-induced breakdown spectroscopy according to claim 1, wherein: The radiation source (3) is composed of seven carbon rods, the interval between every two adjacent carbon rods is 40 mm, the highest heating temperature is 1500 DEG C, and a uniform heat source is formed within a distance of 100 mm.

8. The device for measuring the early pyrolysis gas of fire by laser-induced breakdown spectroscopy according to claim 1, characterized in that: The imaging lens (4) has a transmittance higher than 90% at a 1064 nm wave band and a focal length of 100 mm.

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