Variable atmosphere ignition combustion experiment device and method for focusing single particle suspension

Abstract

The invention relates to a solid fuel combustion characteristic test technology, and aims to provide a focusing single particle suspension variable atmosphere ignition combustion experiment device and method. A second microporous plate and a feed hopper are arranged at the top of a combustion chamber main body of the device, and a first microporous plate and a gas buffer cavity are arranged at the bottom; the two laser emitters are arranged in an included angle shape, and the energy of a single laser beam is lower than a fuel particle ignition threshold value; the two paths of laser intersect in the central area of the cavity to form a space energy focus, and the superposed energy of the two beams of laser can be absorbed at the position to reach an ignition threshold value; and light paths of diagnosis equipment in the optical acquisition module are intersected in a focus area. According to the invention, through a strategy of airflow disturbance and microwell plate blocking, particles completely move in airflow; the ignition behavior has spatial selectivity, the success rate is high and controllable, and the research is closer to the actual application scene. Through the design of single-particle fixed-point triggering, the system complexity and the control difficulty can be reduced, and the operation stability and the experiment repeatability can be improved.

Description

Technical Field

[0001] This invention relates to the field of solid fuel combustion characteristic testing technology, specifically to a variable atmosphere ignition and combustion experimental device for focusing single-particle suspension. This invention integrates active laser confinement, controllable atmosphere adjustment, airflow suspension disturbance, and multi-parameter optical diagnostics, belonging to high-precision combustion experimental technology. Background Technology

[0002] Pelletized fuels, including metal powders, coal powders, biomass pellets, and energetic material pellets, have combustion characteristics that are crucial in determining the performance of systems in many fields such as energy, aerospace propulsion, and chemical engineering. To fundamentally reveal the physicochemical mechanisms of pelletized fuel combustion and construct accurate predictive models, it is essential to conduct real-time observations of the entire ignition, combustion, and extinguishing process of individual pellets under controlled laboratory conditions with high spatiotemporal resolution, acquiring multi-dimensional key parameters such as flame morphology, combustion temperature, and characteristic spectra.

[0003] However, current experimental research on the combustion behavior of single particles faces a series of challenges: (1) how to stably and effectively confine a single particle within the observation area and completely avoid its contact with solid supports (such as a stage or filaments) to prevent thermal conduction interference and chemical reaction effects; (2) how to reliably and controllably ignite a single particle in motion, especially for fuels with high ignition thresholds; (3) how to measure and diagnose key parameters such as particle morphology, flame structure, combustion temperature and spectral information from multiple angles without interference during the ignition and combustion process, so as to complete the global mechanism analysis of multi-parameter synergy.

[0004] In existing technologies, devices for observing single-particle combustion mainly rely on two technical approaches: "falling" and "suspended." Falling-type devices, such as settling furnaces, allow particles to pass through a high-temperature zone under gravity for passive heating and ignition. Their core drawback is that the particles are in an accelerated state, resulting in extremely short residence times in the observation field, making high-resolution continuous observation difficult. Furthermore, particle groups are difficult to disperse effectively during the fall, easily leading to multiple particles entering the high-temperature zone simultaneously, making it impossible to ensure independent study of the behavior of a single particle in a strictly defined sense. Suspended devices can be achieved through airflow or acoustic / electric fields, with airflow suspension being the most widely used. By adjusting the drag force of the upward airflow to balance particle gravity, it is currently the method closest to the real flow environment. However, simple vertical laminar flow cannot overcome the Brownian motion of particles and flow field disturbances, causing particles to not remain stably in front of the observation window for extended periods, posing difficulties for diagnostics requiring continuous focusing. Acoustic / electric field suspension is suitable for special environments, but the former has relatively small suspension force, and the latter is only effective for conductive or charged particles, resulting in a serious lack of versatility.

[0005] In terms of ignition methods, laser ignition is widely used due to its advantages such as concentrated energy, ease of control, strong anti-interference ability, and high safety. However, existing technologies mostly rely on single-beam laser irradiation, which has inherent limitations: increasing the single-point power to ensure the ignition of particles with high ignition thresholds can easily cause damage to the viewing window or excessive vaporization of particles; at the same time, it is difficult for a single beam of light to continuously and reliably hit and ignite micron-sized targets that are in dynamic fluctuation.

[0006] Most importantly, existing devices are limited by the unpredictable drift of particle positions and the limited focusing range of diagnostic instruments. They can usually only acquire sporadic parameters such as combustion time or flame morphology through image acquisition, making it difficult to simultaneously capture multi-dimensional information such as combustion temperature and characteristic spectra. This makes it impossible to achieve global analysis with multi-parameter coordination, which seriously restricts the in-depth understanding of the complex physicochemical processes of single-particle combustion.

[0007] In summary, existing technical solutions struggle to achieve a balance between simulation realism, ignition reliability, and comprehensive diagnostics. In particular, there is a lack of an integrated experimental device capable of precisely igniting individual particles in a simulated, variable atmosphere and supporting comprehensive, multi-parameter diagnostics. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to overcome the difficulty in simultaneously achieving suspension stability, ignition accuracy and comprehensive diagnostics in existing single-particle combustion experimental devices, and to provide a variable atmosphere ignition combustion experimental device that focuses on single-particle suspension; used to simulate a real flow of variable atmosphere environment to achieve stable, accurate and non-contact ignition of a single fuel particle.

[0009] To solve the technical problem, the solution of the present invention is:

[0010] A variable atmosphere ignition and combustion experimental device for focusing single-particle suspension is provided, characterized in that it comprises:

[0011] The combustion chamber body has a vertically penetrating hollow cavity, and a transparent viewing window is provided on the side wall of the cavity for laser incident and recording of the combustion state;

[0012] The airflow transmission module includes a second microporous plate and a feed hopper located at the top of the combustion chamber body, and a first microporous plate and a gas buffer chamber located at the bottom of the combustion chamber body; the first microporous plate has multiple microporous regions, which are arranged in a circumferential gradient according to the difference in the microporous aperture of each region; an air inlet is provided at the bottom of the gas buffer chamber.

[0013] The laser ignition module includes two laser emitters arranged at an angle with adjustable emission power. After the two lasers enter the main body of the combustion chamber, they intersect in the central region of the cavity to form a spatial energy focus. The energy of a single laser beam is lower than the ignition threshold of the fuel particles. The fuel particles can absorb the superimposed energy of the two laser beams at the focal point and reach the ignition threshold.

[0014] The optical acquisition module includes multiple devices for recording the combustion state of fuel particles. Each device is arranged in a viewport and their optical paths converge at the focal region.

[0015] Description of the invention principle:

[0016] This invention, based on the principle of "particle suspension under controlled disturbance and fixed-point trigger ignition," provides a novel experimental device for ignition and combustion of single suspended particles in a variable atmosphere. Its core design concept is "spatial point-selective passive triggering," meaning that instead of actively confining the particles, a fixed high-energy focusing ignition zone is established, and a single particle passing through the focusing point is selected from a randomly moving particle group to achieve ignition and observation.

[0017] First, trace amounts of fuel particles are introduced into a combustion chamber filled with a controlled atmosphere. A regulated airflow from the bottom is designed to create a controlled, slightly turbulent upward motion. Under the influence of this airflow, the particles exhibit a suspension process approximating Brownian motion, thus simulating the dispersion state of particles in a real turbulent environment.

[0018] In addition to preventing fuel particles from falling into the gas supply line, the first microporous plate can also generate different gas flow velocities through multiple microporous regions with the same number of micropores but different pore sizes. With a constant air intake, smaller pore sizes result in higher flow velocities, creating specific velocity and pressure differences in different regions, leading to a certain degree of fluid swirling. By enhancing the turbulence of the fluid in the region above the first microporous plate, it helps to rapidly disperse combustion particles; the larger pore size in the central microporous region results in a large gas flow rate and slow velocity, ensuring sufficient gas flow to allow trace amounts of fuel particles to float to the surface.

[0019] Installing a small booster fan inside the gas buffer chamber can increase the gas pressure in the gas buffer chamber and achieve efficient gas delivery to the combustion chamber body, providing a stable and controllable airflow to the combustion chamber body.

[0020] Secondly, two laser beams are injected into the combustion chamber from two adjacent corners at a specific angle and precisely calibrated to intersect near the geometric center of the cavity. This intersection point forms a high-energy "optical spark" with an energy density far exceeding that of the surrounding area. Since the power of a single laser beam is set insufficient to ignite a particle individually, both laser beams are simultaneously activated only when a particle happens to move through this intersection focal area, accumulating enough energy in a very short time to instantaneously ignite the particle. This process achieves "spatial selection" ignition of individual particles from a group.

[0021] Finally, after the particle is ignited at the focal point, the transient flame and radiation signals it generates are simultaneously captured by a high-speed camera, spectrometer, and thermometer pre-focused and positioned in the optical quartz glass window on the side of the combustion chamber. By controlling the diagnostic equipment, it is possible to ensure that the complete combustion event of a single particle from the moment of ignition is recorded, thereby extracting key parameters such as combustion duration, flame morphology evolution, characteristic emission spectral signals, and combustion flame temperature.

[0022] Compared with the prior art, the beneficial effects of the present invention are:

[0023] 1. This invention achieves true wall-free single-particle combustion research: through the strategy of "airflow disturbance + microporous plate isolation", the particles move completely in the airflow without contacting any solid support, thus completely eliminating wall heat conduction and catalytic effects, and the data obtained can better reflect the intrinsic combustion characteristics of the particles.

[0024] 2. This invention proposes a novel, highly reliable, and low-risk method for precise ignition: employing a diagonally crossed laser design, the high energy density is strictly confined to the high-energy focal region where the two laser beams intersect. This avoids potential thermal damage to the viewing window and ensures that ignition occurs only when a single particle enters this tiny region. The ignition behavior exhibits spatial selectivity, resulting in a high success rate and controllability.

[0025] 3. This invention creates excellent transient multi-parameter collaborative diagnostic conditions: the four-sided symmetrical window layout allows multiple diagnostic technologies such as high-speed imaging, spectral analysis and radiation thermometry to observe the same combustion event simultaneously without interference, enabling the acquisition of multi-dimensional complete information on the particulate combustion process at one time, with strong data correlation.

[0026] 4. This invention achieves a flexible and realistic variable atmosphere simulation environment: by integrating a multi-channel flow controller, it can accurately prepare and introduce various single or mixed atmospheres, including oxygen, nitrogen, carbon dioxide, argon, etc. The bottom air inlet design can simulate different flow states from laminar flow to turbulent flow, making the research closer to actual application scenarios.

[0027] 5. The device of the present invention has a compact structure. Through the design of "single particle fixed-point triggering", the system complexity and control difficulty are reduced, and the operation stability and experimental repeatability of the device are improved.

[0028] 6. This invention achieves strong turbulence of the fluid inside the combustion chamber through the micro-perforated plate opening and partitioning design. While ensuring the gas flow rate, it can quickly disperse the trace fuel particles inside the combustion chamber, making it easier for them to reach the intersection focal area of ​​the two laser beams, effectively shortening the time from device start-up to particle ignition. Attached Figure Description

[0029] Figure 1 This is an overall structural assembly diagram of the ignition and combustion device of the present invention.

[0030] Figure 2 This is a structural diagram of the combustion chamber in the ignition and combustion device of the present invention.

[0031] Figure 3 This is a top view of the combustion chamber.

[0032] Figure 4 This is a schematic diagram of the first microplate structure.

[0033] Figure 5 This is a schematic diagram of the second microplate structure.

[0034] Figure 6 This is a cross-sectional view of the ignition and combustion device of the present invention.

[0035] Figure 7 This is a schematic diagram of ignition using cross-arranged lasers.

[0036] Figure 8 This is a combustion state diagram of a single aluminum particle in an air atmosphere obtained using the apparatus described in this invention.

[0037] The reference numerals in the figure are as follows: 1. Combustion chamber body; 2. First microporous plate; 3. Second microporous plate; 4. Spectral window; 5. Supplemental lighting window; 6. Laser incident window; 7. Camera window; 8. Temperature measurement window; 9. Combustion chamber chamfer; 10. Combustion chamber fillet; 11. Feed hopper; 12. Gas buffer chamber; 13. Sealing gasket; 14. Spring hinge; 15. Quick clamp; 16. (Small) booster fan; 17. Bolt; 18. Countersunk hole; 19. First microporous area; 20. Second microporous area; 21. Third microporous area; 22. Fourth microporous area; 23. Central microporous area; 24. Micropores of the second microporous plate; 25. Feed port; 26. High-speed high-resolution camera; 27. Fiber optic spectrometer; 28. High-speed infrared thermometer; 29. ​​Supplemental lighting lamp; 30. Spatial energy focus. Detailed Implementation

[0038] Part One: Implementation Scheme of the Invention

[0039] 1. Structure of the experimental apparatus

[0040] The present invention provides a variable atmosphere ignition and combustion experimental device for focusing single-particle suspension, comprising the following functional units: a combustion chamber body, a laser ignition module, an airflow transmission module, and an optical acquisition module. Among them,

[0041] (1) The combustion chamber body has a vertically penetrating hollow cavity, and a transparent viewing window is provided on the side wall of the cavity for laser incident and recording the combustion state of fuel particles.

[0042] The combustion chamber body is a vertical cavity with a rectangular or cylindrical shape; each viewing window is connected to the combustion chamber body by a flange structure, and the center of the viewing window is on the same horizontal plane as the focal area. The inner wall of the combustion chamber body is coated with a silicon carbide coating; the viewing window for laser incident is made of zinc selenide, and the viewing window for recording the combustion state is made of quartz glass; the first microporous plate and the second microporous plate are both high-temperature resistant metal sintered plates.

[0043] As shown in the figure, the length of the rectangular combustion chamber body can be set to 6-8cm, the width to 4-6cm, and the height to 8-10cm. Two corners on one long side of the rectangular combustion chamber body are rounded, and the corner on the other long side is chamfered at a 45-degree angle. A ring of evenly distributed threaded holes is formed at the bottom of the combustion chamber body, and a step with a depth of 1-2mm is formed at the top of the combustion chamber body.

[0044] Six viewing windows are provided on the wall of the combustion chamber: one camera window, one supplementary lighting window, two laser incident windows, one temperature measurement window, and one spectrum window. Preferably, the camera and supplementary lighting windows are each located on one of the two long sides, the temperature measurement and spectrum windows are each located on one of the two short sides, and the two laser incident windows are located on a 45-degree chamfered surface. The camera window can be rectangular with the largest area; the laser incident window can be circular with the smallest area. The camera, supplementary lighting, temperature measurement, and spectrum windows are made of high-transmittance quartz glass; the laser incident window is made of zinc selenide material with a wide light transmission range. Each window is connected to the combustion chamber body using a flange structure. The centers of the six viewing windows on the combustion chamber wall are on the same horizontal plane, and the center height of the windows is 5-6 cm.

[0045] (2) The airflow transmission module includes a second microporous plate and a feed hopper located at the top of the combustion chamber body, and a first microporous plate and a gas buffer chamber located at the bottom of the combustion chamber body; the first microporous plate has multiple microporous areas, which are arranged in a circumferential gradient according to the difference in the microporous aperture of each area; an air inlet is provided at the bottom of the gas buffer chamber.

[0046] The first microporous plate has a central microporous area in the middle, and multiple peripheral microporous areas are arranged in a circumferential manner around the central microporous area; the number of micropores in the central microporous area is greater than the number of micropores in each peripheral microporous area, and the peripheral microporous areas are arranged in sequence according to the size of the micropore diameter; the second microporous plate has the same micropore diameter as the central microporous area on the first microporous plate, and the micropore diameter is smaller than the minimum particle size of the fuel particles.

[0047] The feed hopper is equipped with a micro-vibration mechanism, with a top cover at the top and a valve at the bottom that communicates with the feed hole in the center of the second micro-perforated plate. Through the coordination of the micro-vibration mechanism and the valve, a micro-feeding of fuel particles is achieved.

[0048] The gas buffer chamber is a box-shaped cavity structure with an open top, installed below the combustion chamber body via side spring hinges and / or quick clamps; the first microporous plate is located between the gas buffer chamber and the combustion chamber body, and a sealing gasket is provided between the first microporous plate and the gas buffer chamber. A booster fan is provided in the gas buffer chamber.

[0049] The bottom of the combustion chamber body has a plurality of screw holes evenly spaced. The first micro-perforated plate has the same external dimensions as the combustion chamber body and is fixed to the bottom of the combustion chamber body by bolts. The top of the combustion chamber body is provided with a recessed step. The second micro-perforated plate has a relatively small external dimension and is installed in the step by a snap-fit ​​method.

[0050] (3) Laser ignition module, including two laser emitters arranged at an angle with adjustable emission power. After the two lasers enter the main body of the combustion chamber, they intersect in the central area of ​​the cavity to form a spatial energy focus. The energy of a single laser beam is lower than the ignition threshold of the fuel particles. The fuel particles can absorb the superimposed energy of the two laser beams at the focal point and reach the ignition threshold.

[0051] (4) Optical acquisition module, including multiple devices for recording the combustion state of fuel particles, each device is arranged with a window corresponding to it, and their optical paths converge at the focal area.

[0052] The device for recording the combustion state includes at least a high-speed, high-resolution camera, a pulse fill light, a fiber optic spectrometer, and an infrared thermometer, with the high-speed, high-resolution camera and the pulse fill light arranged opposite each other on both sides of the combustion chamber body.

[0053] 2. Experimental methods using apparatus

[0054] Using the aforementioned apparatus, an experimental method for ignition and combustion of a single suspended particle in a variable atmosphere can be realized, including the following steps:

[0055] (1) Place a sealing gasket between the gas buffer chamber and the first microporous plate, and fix the gas buffer chamber to the bottom of the combustion chamber body by means of spring hinges and / or quick clamps; connect the external gas cylinder to the gas inlet at the bottom of the gas buffer chamber through a hose;

[0056] (2) Confirm that the main body of the combustion chamber is in a vertical position, and arrange the two laser emitters and each device that records the combustion state of fuel particles on the center line of their respective viewing windows;

[0057] (3) Load fuel particles with a diameter of 10 to 100 μm into the feed hopper, and then close the top cover;

[0058] (4) Gas is introduced into the gas buffer chamber. After the pressure is increased by the booster fan, the gas flows through multiple micro-hole areas on the first micro-hole plate to form a difference in flow rate and pressure, which generates a swirling effect in the main cavity of the combustion chamber. The combustion atmosphere is controlled by adjusting the gas flow rate and the speed of the booster fan.

[0059] (5) The micro-feeding of fuel particles is achieved by the coordination of the micro-vibration mechanism and the valve action. The particles exhibit a suspension process of approximately Brownian motion under the action of airflow, simulating the dispersion state of particles in a real turbulent environment.

[0060] (6) If a particle happens to pass through the spatial energy focus at the center of the cavity during random motion, it will be ignited instantaneously because the energy of the two laser beams exceeds the ignition threshold; spatial screening is achieved in this way, and only a single particle is ignited in the particle group.

[0061] (7) Use pre-arranged diagnostic equipment to record the complete combustion process of fuel particles and obtain relevant parameters during the combustion process.

[0062] Part Two: A Specific Example

[0063] 1. The experimental apparatus provided in the embodiments of the present invention mainly includes: a combustion chamber body, a laser ignition module, an airflow transmission module, and an optical acquisition module.

[0064] (1) Combustion chamber body

[0065] The combustion chamber body 1 is a rectangular three-dimensional cavity with internal dimensions of 4cm in length, 6cm in width, and 15cm in height. The cavity is made of high-temperature resistant stainless steel (such as S30408). Circular or elliptical through-holes are located at the center of each of its four side walls, and high-transmittance quartz glass windows are sealed using flange pressing, forming a spectral viewing window 4, a supplementary lighting window 5, a camera window 7, and a temperature measurement window 8. The center line of each window is directly opposite the high-energy spatial focus 30 formed by the intersection and superposition of two laser beams. To prevent the high-energy laser from ablating the inner walls and to improve reflectivity, all inner surfaces of the combustion chamber are coated with a high-temperature resistant silicon carbide coating.

[0066] (2) Laser ignition module

[0067] At approximately 8 cm above the combustion chamber height, a mounting hole is made at the chamfered corner 9 of the combustion chamber. A laser entrance window 6, made of zinc selenide material, with a diameter of approximately 1 cm, is fixedly installed using a flange seal. Typically, the laser is a near-infrared band, continuous or pulsed output semiconductor solid-state laser or fiber laser (power range 0-500W), fixed on both sides of the combustion chamber body. The emitted laser beams, after external collimation and focusing, enter the combustion chamber through the laser entrance windows 6. The paths of the two laser beams are precisely adjusted to ensure they intersect in the central region of the combustion chamber (approximately 8-9 cm above the bottom), forming a spatial energy focus 30 with a diameter of approximately 1-5 mm. The power of each laser is independently adjustable and controlled by a synchronous trigger to ensure simultaneous emission. Different fuel particle compositions have different ignition temperatures, requiring different laser ignition energy thresholds. Depending on the ignition temperature of different samples, the power values ​​of the two lasers are adjusted to ensure that: the energy of a single laser beam cannot ignite the particles, but at the high-energy focal point formed by the intersection of the two lasers, the superimposed energy of the two laser beams can be absorbed, reaching the ignition threshold and effectively igniting the single-particle fuel.

[0068] (3) Airflow transmission module

[0069] The module includes a bottom air intake unit and a top exhaust / feed unit.

[0070] Bottom air intake unit: This includes a gas source (such as a high-pressure gas cylinder providing O2, N2, CO2, Ar, or a mixture thereof), valves, a mass flow meter and flow meter controller, a gas buffer chamber 12, and a first microporous plate 2, connected in sequence. The first microporous plate 2 is a high-temperature resistant sintered metal plate with a maximum pore size of approximately 5 μm. This pore size is smaller than the smallest particle size to be measured (10 μm), effectively preventing particles from backflowing into the gas path. After passing through the first microporous plate 2, the airflow forms a turbulent upward airflow at the bottom of the combustion chamber. The airflow enters the gas buffer chamber 12 from the bottom, passes through the first microporous plate 2, and enters the combustion chamber, forming an upward turbulent airflow field. This causes the trace particles added from the feed hopper 11 to suspend and move within the combustion chamber. The particles are ultimately blocked by the top second microporous plate 3, allowing the airflow to flow out smoothly.

[0071] The gas buffer chamber is made of metal and its shape and size are consistent with the main body of the combustion chamber. The gas height is approximately one-fifth to one-sixth of the height of the main body of the combustion chamber. A fixing column is installed inside the gas buffer chamber to secure a small booster fan placed inside. The gas buffer chamber 12 is fixed to the main body of the combustion chamber 1 by one spring hinge 14 and four quick clamps 15. The spring hinge 14 and quick clamps 15 are located on the four outer walls of the main body of the combustion chamber, facilitating maintenance or replacement of the small booster fan 16 and the first micro-perforated plate 2. During installation, the gas buffer chamber 12 is installed at the bottom of the main body of the combustion chamber 1, and a sealing gasket 13 is placed between the first micro-perforated plate 2 and the gas buffer chamber 12 to prevent air leakage and ensure proper air intake. A pipe is located at the bottom of the gas buffer chamber 12, connecting it to an external gas source.

[0072] The first micro-perforated plate has the same shape and dimensions as the main body of the combustion chamber. The second micro-perforated plate has the same shape as the main body of the combustion chamber, but its dimensions are smaller than the external dimensions of the main body and larger than the internal dimensions. During installation, it is fitted into the upper step of the main body of the combustion chamber. The first micro-perforated plate has a ring of countersunk holes along its edge, the positions of which correspond to the threaded holes on the lower part of the main body of the combustion chamber. The first micro-perforated plate is connected to the main body of the combustion chamber by bolts.

[0073] The first microporous plate 2 is a high-temperature resistant metal sintered plate, and the micropore size distribution is divided into five regions: the first micropore region 19, the second micropore region 20, the third micropore region 21, the fourth micropore region 22, and the central micropore region 23; among them, the first micropore region 19, the second micropore region 20, the third micropore region 21, and the fourth micropore region 22 are located at the edge of the first microporous plate 1, and the central micropore region 23 is located in the central region of the first microporous plate 2; the central micropore region 23 has the largest micropore size, the first ... The pore sizes of the first micropore region 19, the second micropore region 20, the third micropore region 21, and the fourth micropore region 22 increase sequentially in a clockwise or counterclockwise order, but none are larger than the pore size of the central micropore region 23. The number of micropores in the first micropore region 19, the second micropore region 20, the third micropore region 21, and the fourth micropore region 22 is the same. The number of micropores in the central micropore region 23 is larger than the number of micropores in the first micropore region 19, and can be set to be 1.3 to 1.8 times the number of micropores in the first micropore region 19. The pore sizes of the first and second micropore plates are smaller than the minimum particle size of the particles to be measured, but gas is allowed to pass through. The thickness of the first and second micropore plates can be set to 3 to 4 mm.

[0074] Top exhaust / feed unit: Includes a second microporous plate 3 and a closable feed hopper 11. The pore diameter 24 of the second microporous plate 3 is consistent with the pore diameter of the central microporous region 23 of the first microporous plate 2, ensuring smooth airflow and maintaining pressure balance within the chamber. A circular hole is opened in the center of the second microporous plate, connected to a closable feed hopper for rapid fuel feeding. The feed port 25 of the feed hopper 11 is located in the center of the second microporous plate 3. Before the experiment, a trace amount (milligram level) of fuel particles (particle size 10-100μm) can be added. After feeding, the valve can be closed to prevent particle escape.

[0075] (4) Optical acquisition module

[0076] In addition to placing a laser emitter in each of the two viewing windows, diagnostic devices are placed in the remaining four viewing windows:

[0077] Morphology recording unit: A high-speed, high-resolution camera 26 is arranged outside the camera window 7, and a high-brightness pulsed fill light 29 is arranged outside the fill light window 5. The two are synchronized by an electrical signal. The fill light is turned on at the moment of camera exposure to provide backlight illumination, which is used to clearly capture the two-dimensional projection morphology and motion trajectory of the original particles and flames.

[0078] Spectral diagnostic unit: A fiber optic spectrometer 27 is arranged outside the spectral window 4. Its collection probe is equipped with a collimating lens, and the optical path is precisely aligned with the laser cross focal region to collect the emission spectrum in the 200-1100μm band during the combustion process.

[0079] Temperature diagnostic unit: A high-speed infrared thermometer 28 is arranged outside the temperature measurement window 8, with its field of view also aligned with the focal area, for non-contact measurement of the surface temperature field of the burning particles and its evolution process.

[0080] The optical paths of all diagnostic devices converge at the laser ignition focal area. All diagnostic devices can be commercially available products and can be remotely controlled and have their data collected and stored via computer. The raw data obtained by the diagnostic devices is processed using visualization software or functional modules in the computer to acquire flame image sequences, combustion temperature, and spectral radiation intensity changes during the single-particle ignition and combustion process. These can all be achieved using existing technologies, which will not be elaborated upon in this invention.

[0081] 2. The method of using the experimental apparatus provided in this embodiment is described below.

[0082] This embodiment provides some parameters and specifications, but the selection of the actual specific equipment can be determined according to the different materials, sizes and weights of the fuel particles.

[0083] Gas parameters: Dry compressed air was used as the experimental atmosphere. The total flow rate was set to 4.0 L / min by a mass flow controller (MFC, accuracy ±1%FS). The gas was evenly distributed in the buffer chamber and then entered the combustion chamber through the first microporous plate.

[0084] Microplate parameters: The gas flow rate required for aluminum particle suspension is initially calculated based on Stokes' drag formula. In this embodiment, the gas flow rate through the first microplate is approximately 7.4 cm / s, and the microplate aperture distribution is adjusted accordingly to ensure flow field stability.

[0085] Fan specifications: A DC brushless micro booster fan (rated voltage 12 VDC, maximum air volume 8 L / min, static pressure 150 Pa, power 6 W) is installed in the gas buffer chamber to increase the pressure in the gas chamber and stabilize the gas supply.

[0086] Laser parameters: Two continuous output fiber lasers are used (wavelength 1070 nm, maximum output power 300 W, power stability ±2%).

[0087] Optical diagnostic equipment: a high-speed camera with a resolution of 1024×860 and a frame rate of 10000 fps; a 640 nm pulsed illumination source with a pulse width of 10 ns, triggered synchronously with the camera; a fiber optic spectrometer with a wavelength range of 200~1100 nm, a resolution of 0.5 nm, and an integration time of 1 ms; and an infrared thermometer with a temperature range of 500~3200 ℃ and a sampling rate of 1 kHz.

[0088] Close the feed inlet, turn on the gas source, and use the flow meter controller to fill and maintain the experimental atmosphere with the set composition and flow rate into the combustion chamber 1, forming a stable flow field through the bottom airflow; open the top cover of the feed hopper 11 and load 5 mg of spherical aluminum powder particles with a median diameter of 30 μm. Open the bottom valve and, with the assistance of a micro-vibration mechanism, allow the particles to gradually fall into the combustion chamber.

[0089] Under the influence of the turbulent airflow at the bottom, multiple fuel particles are suspended and move randomly in the central space of the combustion chamber. The laser power is set so that the energy of a single laser beam is below the particle's ignition threshold. A synchronous trigger command is activated, causing two lasers to emit light simultaneously, intersecting in the central region of the cavity to form a spatial energy focus 30. Simultaneously, a high-speed, high-resolution camera 26, a fiber optic spectrometer 27, and a high-speed infrared thermometer 28 begin recording. When a fuel particle randomly moves to the spatial energy focus 30, it absorbs the superimposed energy of the two laser beams, reaching the ignition threshold and thus being instantly ignited. Multiple diagnostic devices record simultaneously throughout the experiment, acquiring images, spectra, and temperature signals of the entire single-particle combustion event. After one combustion event ends, the next ignition can be initiated when the next particle randomly enters the spatial energy focus 30.

[0090] By repeatedly conducting experiments, statistical distribution data on the combustion characteristics of fuel particles under a specific atmosphere can be accumulated. All data are synchronized, aligned, and correlated using a LabVIEW or Python integrated processing platform. After the experiment is completed, the laser, intake valve, laser, and diagnostic equipment are turned off sequentially.

[0091] Although embodiments of the present invention have been shown and described above, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the claims and their equivalents.

[0092] In summary, the above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A variable atmosphere ignition and combustion experimental device for focusing single-particle suspension, characterized in that, include: The combustion chamber body has a vertically penetrating hollow cavity, and a transparent viewing window is provided on the side wall of the cavity for laser incident and recording of the combustion state; The airflow transmission module includes a second microporous plate and a feed hopper located at the top of the combustion chamber body, and a first microporous plate and a gas buffer chamber located at the bottom of the combustion chamber body; the first microporous plate has multiple microporous regions, which are arranged in a circumferential gradient according to the difference in the microporous aperture of each region; an air inlet is provided at the bottom of the gas buffer chamber. The laser ignition module includes two laser emitters arranged at an angle with adjustable emission power. After the two lasers enter the main body of the combustion chamber, they intersect in the central region of the cavity to form a spatial energy focus. The energy of a single laser beam is lower than the ignition threshold of the fuel particles. The fuel particles can absorb the superimposed energy of the two laser beams at the focal point and reach the ignition threshold. The optical acquisition module includes multiple diagnostic devices for recording the combustion state of fuel particles. Each device is arranged in a viewport and their optical paths converge at the focal region.

2. The apparatus according to claim 1, characterized in that, The combustion chamber body is a vertical cavity with a rectangular or cylindrical shape; each window is connected to the combustion chamber body by a flange structure, and the center of the window and the focal area are located on the same horizontal plane.

3. The apparatus according to claim 1, characterized in that, The inner wall of the combustion chamber body is coated with a silicon carbide coating; the viewing window for laser incident is made of zinc selenide, and the viewing window for recording the combustion state is made of quartz glass; the first microporous plate and the second microporous plate are both high-temperature resistant metal sintered plates.

4. The apparatus according to claim 1, characterized in that, The first microporous plate has a central microporous area in the middle, and multiple peripheral microporous areas are arranged in a circumferential manner around the central microporous area; the number of micropores in the central microporous area is greater than the number of micropores in each peripheral microporous area, and the peripheral microporous areas are arranged in sequence according to the size of the micropore diameter; the second microporous plate has the same micropore diameter as the central microporous area on the first microporous plate, and the micropore diameter is smaller than the minimum particle size of the fuel particles.

5. The apparatus according to claim 1, characterized in that, The feed hopper is equipped with a micro-vibration mechanism, with a top cover at the top and a valve at the bottom that communicates with the feed hole in the center of the second micro-perforated plate. Through the coordination of the micro-vibration mechanism and the valve, a micro-feeding of fuel particles is achieved.

6. The apparatus according to claim 1, characterized in that, The gas buffer chamber is a box-shaped cavity structure with an open top, and is installed below the combustion chamber body via a side spring hinge and / or quick clamp; the first microporous plate is located between the gas buffer chamber and the combustion chamber body, and a sealing gasket is provided between the first microporous plate and the gas buffer chamber.

7. The apparatus according to claim 1, characterized in that, The bottom of the combustion chamber body has a plurality of screw holes evenly spaced. The first micro-perforated plate has the same external dimensions as the combustion chamber body and is fixed to the bottom of the combustion chamber body by bolts. The top of the combustion chamber body is provided with a recessed step. The second micro-perforated plate has a relatively small external dimension and is installed in the step by a snap-fit ​​method.

8. The apparatus according to claim 1, characterized in that, A booster fan is installed in the gas buffer chamber.

9. The apparatus according to claim 1, characterized in that, The diagnostic equipment for recording the combustion state includes at least a high-speed, high-resolution camera, a pulse fill light, a fiber optic spectrometer, and an infrared thermometer, with the high-speed, high-resolution camera and the pulse fill light arranged opposite each other on both sides of the combustion chamber body.

10. A method for conducting a variable atmosphere ignition and combustion experiment with focused single-particle suspension using the apparatus described in any one of claims 1 to 9, characterized in that, Includes the following steps: (1) Place a sealing gasket between the gas buffer chamber and the first microporous plate, and fix the gas buffer chamber to the bottom of the combustion chamber body by means of spring hinges and / or quick clamps; connect the external gas cylinder to the gas inlet at the bottom of the gas buffer chamber through a hose; (2) Confirm that the main body of the combustion chamber is in a vertical position, and arrange the two laser emitters and each device that records the combustion state of fuel particles on the center line of their respective viewing windows; (3) Load fuel particles with a diameter of 10 to 100 μm into the feed hopper, and then close the top cover; (4) Gas is introduced into the gas buffer chamber. After the pressure is increased by the booster fan, the gas flows through multiple micro-hole areas on the first micro-hole plate to form a difference in flow rate and pressure, which generates a swirling effect in the main cavity of the combustion chamber. The combustion atmosphere is controlled by adjusting the gas flow rate and the speed of the booster fan. (5) The micro-feeding of fuel particles is achieved by the coordination of the micro-vibration mechanism and the valve action. The particles exhibit a suspension process of approximately Brownian motion under the action of airflow, simulating the dispersion state of particles in a real turbulent environment. (6) If a particle happens to pass through the spatial energy focus at the center of the cavity during random motion, it will be ignited instantaneously because the energy of the two laser beams exceeds the ignition threshold; spatial screening is achieved in this way, and only a single particle is ignited in the particle group. (7) Use pre-arranged diagnostic equipment to record the complete combustion process of fuel particles and obtain relevant parameters during the combustion process.

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