Spherical diffusion flame experimental device for simulating microgravity environment on ground

Abstract

The invention discloses a spherical diffusion flame experimental device for simulating a microgravity environment on the ground, which comprises a combustion chamber (1), a spherical combustor (11) connected to a port of a fuel pipe (12) in the combustion chamber (1), and a flame combustion area (17) arranged on the periphery of the spherical combustor (11), and further comprises a gas density regulator (2) arranged on the outer wall of the combustion chamber (1), the combustion chamber (1) is used for increasing the gas density of a flame combustion area and reducing the gas density of an inner chamber of the combustion chamber (1), and the measuring mechanism (3) is connected into the inner chamber of the combustion chamber (1) and used for measuring physical parameters of flames and gas pressure in the combustion chamber. The device has the technical effects that the flame microgravity level is realized under the condition of balanced density by reducing the density difference between the gas in the flame combustion area and the cold medium around the flame, the effective experiment time under the microgravity condition is much longer than that of a tower falling experiment device, the cost is low, and equipment accidents or faults caused by electrifying for generating an electric field are avoided.

Description

Technical Field

[0001] The invention belongs to the technical field of microgravity combustion experiments, and specifically relates to a spherical diffusion flame experimental device for simulating a microgravity environment on the ground, which uses gas dilution to reduce the density difference of combustion gas to eliminate flame buoyancy and form a spherical flame. Background Art

[0002] The spherical diffusion flame configuration is widely used in the field of basic research and technical research on combustion. Compared with other flame configurations (such as laminar counterflow flame, droplet flame, zero-dimensional reactor, etc.), the spherical diffusion flame has many advantages: 1. The spherical diffusion flame physical model has a clearer boundary definition, which can well simulate and replace the droplet flame and candle flame, thereby facilitating the research on spray combustion or candle flame. 1. In a droplet flame, the heat conduction and heat feedback from the flame front to the droplet surface will change the fuel evaporation rate on the droplet surface, which will lead to uncontrollable combustion conditions; while in a spherical diffusion flame, fuel is supplied to the surrounding oxidizing atmosphere at a constant mass flow rate from the spherical burner surface, making the boundary conditions of the droplet diffusion combustion research adjustable and controllable; 2. The spherical diffusion flame structure has a one-dimensional spherical symmetry feature, which greatly reduces the dimension and calculation amount of the numerical model, making it convenient to adopt detailed reaction mechanism and component transport models to focus on important physical and chemical processes; 3. Under microgravity conditions, the influence of buoyancy-driven flow on the flow field and the combustion process is eliminated, greatly reducing the complexity of the combustion process analysis; 4. The spherical diffusion flame has a free boundary condition at infinity, which enhances the intensity of the spontaneous oscillation of the flame, making it convenient to carry out oscillation-induced flameout mechanism research.

[0003] At present, there are two main technical paths to establish microgravity experiments: one is to conduct microgravity experiments on the space station; the other is to conduct microgravity experiments on the ground drop tower. The first technical path is limited by the actual conditions such as experimental cost, experimental cycle, experimental risk and funding, and it is difficult to carry out large-scale application; for the second technical path, the domestic drop tower device is limited by the drop height, and its effective microgravity experiment lasts only 3.6 seconds, which cannot meet the requirements of long-term experiments (such as transient oscillation flameout experiments, which last up to 60 seconds or more). Therefore, many current microgravity-related studies are mainly based on numerical simulation.

[0004] In order to carry out microgravity experiments on the ground, create a microgravity environment and meet the requirements of long-term experiments, Chinese patent document CN118425407A discloses an experimental system for simulating the combustion of fuel droplets in a microgravity environment. The system generates an electric field by a conductive part, and the direction of the electric field is opposite to the flow direction of positive ions in the flame of the droplets. The electric field force exerted on the free ions in the flame is used to balance the buoyancy formed by the natural convection exerted on the flame when the droplets burn, and constrain the flame of the droplets to a spherical shape that approximates combustion under microgravity. The system is suitable for low-pressure liquefiable gas fuels, such as liquid ammonia, liquid hydrogen, and dimethyl ether. However, the defects of the patent are: the balance force of the flame is established by the energized electric field, and on the one hand, accidents are prone to occur in the conductors of the high-temperature combustion chamber; on the other hand, a power supply device is required, which increases the cost of the experimental system. Summary of the invention

[0005] In view of the problems existing in the prior art, the technical problem to be solved by the present invention is to provide a spherical diffusion flame experimental device for simulating a microgravity environment on the ground, which can conduct long-term experimental observation and research on spherical diffusion flames, and is safe to use and low in cost.

[0006] The technical problem to be solved by the present invention is achieved through such a technical solution, which includes a combustion chamber, a spherical burner is connected to the fuel pipe port in the combustion chamber, the periphery of the spherical burner is a flame combustion zone, and also includes: a gas density regulator, arranged on the outer wall of the combustion chamber, used to increase the gas density in the flame combustion zone and reduce the gas density in the combustion chamber, and The measuring mechanism is connected to the inner chamber of the combustion chamber and is used to measure the physical parameters of the flame and the gas pressure in the combustion chamber.

[0007] The technical effects of the present invention are: The present invention reduces the density difference between the gas in the flame combustion zone and the cold medium around the flame, and realizes the flame microgravity level under the condition of density balance. The effective experimental time under microgravity conditions is much longer than that of the drop tower experimental device, the cost is low, and equipment accidents or failures caused by powering on to generate an electric field are avoided. The present invention can carry out experiments for a long time, can collect data more carefully and comprehensively, and is more conducive to carrying out combustion experimental research under microgravity conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The accompanying drawings of the present invention are as follows: Figure 1 It is a structural schematic diagram of the present invention; Figure 2 It is a structural diagram of the combination of a spherical burner and a fuel pipe; Figure 3 The optical path diagram of the spherical diffusion flame observed by the optical measuring device installed in the present invention; Figure 4 This is the flame morphology diagram obtained from the experiment; Figure 5 This is a diagram of the flame shape under natural conditions.

[0009] In the figure, 1, combustion chamber; 11, spherical burner, 12, fuel pipe, 13, rotary drive motor; 14, air inlet filter element, 15, air outlet filter element, 16, observation window; 17, flame combustion area; 2. Gas density regulator; 21. O2 / He mixed gas channel; 22. Fuel / heavy inert gas mixed gas channel; 23. Gas flow control valve; 24. Vacuum pump; 25. Controller; 3. Measuring mechanism; 31. Data acquisition instrument; 32. Radiation heat flow meter; 33. Thermocouple; 34. Barometer; 4. Optical measuring equipment, 41. Point light source, 42. First convex lens, 43. Second convex lens, 44. CCD camera; 45. Reflecting prism; 46. Narrow-band filter; 47. Third convex lens, 48. Enhanced ICCD camera. DETAILED DESCRIPTION

[0010] The present invention will be further described below in conjunction with the accompanying drawings and embodiments: In order to clearly describe the content of the invention, this patent application uses the directional words "upper", "lower", "left" and "right" for distinction. The "upper", "lower", "left" and "right" are determined according to the layout orientation of the above drawings. When the actual use direction of the present invention changes, the directional designation changes accordingly, which cannot be regarded as limiting the scope of patent protection.

[0011] The concept of the present invention is that the flame releases heat energy during the combustion process, which significantly increases the temperature of the gas in the flame combustion zone. Under constant pressure, the increase in temperature causes the volume of the gas to increase, thereby producing a thermal expansion effect, which reduces the gas density in the flame combustion zone and causes a density difference with the surrounding gas. That is, the gas density in the flame combustion zone is usually lower than the density of the gas in the flame surrounding environment, and this density difference is the main driving force of the flame buoyancy. Therefore, as long as the density difference between the flame combustion zone and the cold air zone is eliminated, the influence of the flame buoyancy can be reduced and a spherical flame can be formed.

[0012] like Figure 1 As shown, the present invention includes a combustion chamber 1 for simulating a microgravity environment, a spherical burner 11 is connected to a fuel pipe 12 in the combustion chamber 1, and the periphery of the spherical burner 11 is a flame combustion zone 17, and further includes: A gas density regulator 2 is arranged on the outer wall of the combustion chamber 1 and is used to increase the gas density in the flame combustion zone and reduce the gas density in the inner chamber of the combustion chamber 1 to keep the upward buoyancy generated between the flame gas and the surrounding gas balanced; and The measuring mechanism 3 is connected to the inner chamber of the combustion chamber 1 and is used to measure the physical parameters of the flame and the gas pressure in the combustion chamber.

[0013] The measuring mechanism 3 includes a data acquisition instrument 31, a radiation heat flux meter 32, a thermocouple 33 and a barometer 34. The thermocouple 33 is arranged in the flame combustion zone, the radiation heat flux meter 32 is arranged outside the flame combustion zone, and the barometer 34 is on the combustion chamber wall. The signal line of the data acquisition instrument 31 placed outside the combustion chamber 1 connects the radiation heat flux meter 32, the thermocouple 33 and the barometer 34. A highly sensitive radiation heat flux meter 32 is arranged at a certain distance outside the flame combustion zone and connected to a computer via the data acquisition instrument 31 to record the change of the radiation heat flux density to reflect the instantaneous change of temperature.

[0014] The steady-state experiment measures the thermochemical structure of a strong flame with stable combustion. Several K-graded thermocouples 33 are arranged at equal intervals in the flame combustion zone to measure the radial distribution of temperature. The flue gas sample is extracted using a water-cooled sampling tube (the water-cooled sampling tube is installed in the middle of the combustion chamber or in an area close to the combustion zone. This position allows the sample to contain various gas components produced during the combustion process, ensuring that a representative flue gas sample can be extracted.) and sent to a gas chromatograph to obtain the radial distribution of the concentrations of O2, CO2, CO, CH4, C2H6, C2H4 and H2. The transient experiment measures the oscillation of the flame under near-extinguishing limit conditions. On the basis of a steady-state flame, the oscillating extinguishing condition is obtained by slowly reducing the proportion of O2 in the oxidant. During the transient experiment, the thermocouple is removed to avoid its interference with the flame oscillation. At the same time, a highly sensitive radiation heat flux meter 32 (data acquisition frequency 200 Hz) is arranged at a certain distance from the periphery of the flame; the barometer 34 is used to measure the pressure change during the combustion process.

[0015] like Figure 2 As shown, the spherical burner 11 is a spherical shell with fine holes on the surface, and the spherical shell is a copper spherical shell. The fuel pipe 12 is connected to the spherical burner 11 from the bottom. The fuel introduced into the fuel pipe 12 is a fuel / heavy inert gas mixture. The heavy inert gas can be a gas with a heavier density such as Kr (krypton), Ar (argon) or CO2, and the fuel is methane. The heavy inert gas helps to balance the buoyancy of the flame; the spherical burner 11 can help the flame to form a spherical shape.

[0016] The lower part of the fuel pipe 12 is equipped with a rotary drive motor 13, which is specifically installed as follows: the rotary drive motor 13 is fixed with a motor bracket, and the motor bracket can bear the weight of the motor and the vibration generated during operation, and the fuel pipe 12 is firmly connected to the rotating shaft of the motor with a connecting piece such as a flange, a joint or a clamp. The rotating shaft is designed to be hollow so that the fuel can flow into the fuel pipe through the rotating shaft and then supply the combustion chamber. The fuel pipe 12 is flange-connected to the motor rotating shaft, and the flange is fastened together with bolts, and the sealing and stability of the connection part are ensured. The port of the fuel / heavy inert gas mixed gas channel 22 is connected to the rotating shaft of the rotary drive motor through a rotary joint, so that the continuous supply of fuel can be achieved while maintaining rotation. The upper end of the fuel pipe 12 is connected to the spherical burner, and the rotary drive motor drives the fuel pipe 12 to rotate, thereby driving the spherical burner 11 to rotate, generating a swirl field around the spherical burner, and the controller 3 is connected to the rotary drive motor 13. The size of the swirl field can be continuously adjusted by the controller 3 controlling the speed of the rotary drive motor 13.

[0017] A cyclone field is constructed for a combustion test. A cyclone field refers to a flow state in which fluid particles rotate around a certain axis or center point during the flow of a fluid. In a cyclone field, the motion trajectory of the fluid is annular or spiral, and its flow characteristics are significantly different from linear flows (such as laminar or turbulent flows). The cyclone field can significantly enhance the mixing efficiency of the fluid, promote the full mixing of different components, and increase the reaction rate and product uniformity. At the same time, the cyclone field improves the heat exchange efficiency and makes the heat distribution in the fluid more uniform, thereby enhancing the performance of the heat exchanger and cooling system.

[0018] The fuel pipe 12 is a copper thin pipe with a sufficiently large flow resistance to ensure a stable fuel flow. An electric spark igniter is used for ignition, and the igniter is quickly withdrawn after ignition to avoid affecting the flame.

[0019] The gas density regulator 2 includes an O2 / He mixed gas passage 21, a fuel / heavy inert gas mixed gas passage 22, a vacuum pump 24 and a controller 25. The fuel / heavy inert gas mixed gas passage 22 is connected to the fuel pipe 12, and the O2 / He mixed gas passage 21 leads to the inner chamber of the combustion chamber 1. Since the density of He is relatively small, the density of the oxygen mixed gas in the inner chamber of the combustion chamber 1 is reduced. A vacuum pump 24 is installed at the outlet of the outer wall of the combustion chamber opposite to the O2 / He mixed gas passage 21. The vacuum pump 24 keeps the inner chamber of the combustion chamber 1 at a negative pressure, which can further reduce the gas density inside the combustion chamber and control the buoyancy of the flame. The O2 / He mixed gas passage 21 and the fuel / heavy inert gas mixed gas passage 22 are both equipped with a flow control valve 23. The controller 25 connects the gas flow control valve 23 and the vacuum pump 24 to control the intake and exhaust volume of the combustion chamber 1.

[0020] An inlet filter 14 is installed at the gas inlet of the O2 / He mixed gas channel 21, and an outlet filter 15 is installed at the air inlet of the vacuum pump 23. The filter is used to reduce the disturbance of the local gas flow to the flame. The inlet filter 14 and the outlet filter 15 are copper filter elements.

[0021] like Figure 3 As shown, there are observation windows 16 in three directions on the wall of the combustion chamber 1. The observation windows 16 face the flame combustion zone 17. The optical axes of the left observation window and the right observation window are consistent. The optical axis of the third observation window is deflected by a certain angle, usually 90° along the line connecting the optical axes of the left and right observation windows. An optical measuring device 4 is installed corresponding to the observation window 16, and the changes in the flame morphology during the flameout process are recorded through the observation window 16. The light formed by the point light source 41 passes through the first convex lens 42, enters the combustion chamber 1 from the left observation window, and is emitted from the right observation window through the flame combustion zone 17. It passes through the second convex lens 43 and is focused on a knife edge to obtain a flame schlieren image, which is recorded by an industrial CCD camera 44 equipped with an optical zoom lens.

[0022] The function of the point light source is: the light emitted by the point light source enters the combustion chamber after passing through the first convex lens 42, and passes through the flame combustion zone. These light rays undergo refraction, scattering and other effects in the flame, so that the texture changes of the flame can be captured. Finally, the second convex lens 43 focuses on the blade to form a schlieren image of the flame. This schlieren imaging technology uses the changes of light when it propagates in the flame to effectively show the shape and dynamic characteristics of the flame. The CCD camera 44 captures the flame image, in which the point light source 41 plays multiple important roles in lighting, enhancing visibility, forming schlieren images, improving contrast, and providing reference light in capturing the flame image during the combustion process. By optimizing the use of point light sources, the quality of the flame image can be effectively improved, making the observation and analysis of the combustion process more accurate.

[0023] Considering that the combustion process is greatly affected by the intensity of free radicals, and OH concentration is a typical free radical in the combustion process, the OH* autofluorescence signal is recorded to reflect the combustion process. A reflecting prism 45 is installed outside the third position observation window. The flame light is reflected by the reflecting prism 45, filtered by the narrow band filter 46, and focused by the third convex lens 47 to form an image. It is recorded by an image intensified ICCD camera 48 with a UV aperture. The filtering wavelength of the narrow band filter is 310±10 nm.

[0024] Experiment 1: The mass ratio of CH4 / 80%Ar is 20% in the fuel pipe 12; the mass ratio of O2 / He mixed gas passage 21 is 20%O2 / 80%He. Kr in the fuel and He in the oxygen mixed gas account for the vast majority of the shares, so the fuel / Kr mixed gas has a larger density, while the O2 / He mixed gas has a smaller density, and the concentration of Kr decreases rapidly outside the flame surface. At the same time, the flame temperature after dilution decreases significantly, which makes the density of the smoke in the flame combustion zone and the density of the oxygen mixed gas very small. In addition, the combustion chamber is negative pressure, which further reduces the buoyancy of the smoke in the flame combustion zone. Figure 4 As shown, the flame shape is spherical, and the flame horizontal diameter / vertical diameter = 0.98. Under natural conditions, the flame shape is Figure 5 shown.

[0025] The present invention has the advantages of compact structure, simple experimental operation, high microgravity level, long effective combustion time, consideration of flow field swirl effect, and measurement in combination with visual measurement equipment, etc. It has broad application potential in scientific research and industrial applications.

Claims

1. A spherical diffusion flame experimental device for simulating a microgravity environment on the ground, comprising a combustion chamber (1), characterized in that: A spherical burner (11) is connected to a port of a fuel pipe (12) in the combustion chamber (1), and the periphery of the spherical burner (11) is a flame combustion zone (17), which further comprises: A gas density regulator (2) is arranged on the outer wall of the combustion chamber (1) and is used to increase the gas density in the flame combustion zone and reduce the gas density in the inner chamber of the combustion chamber (1); and The measuring mechanism (3) is connected to the inner chamber of the combustion chamber (1) and is used to measure the physical parameters of the flame and the gas pressure in the combustion chamber.

2. The spherical diffusion flame experimental device according to claim 1 is characterized in that: The spherical burner (11) is a spherical shell with a surface covered with fine pores. The fuel pipe (12) is connected to the spherical burner (11) from below. The fuel introduced into the fuel pipe (12) is a fuel / heavy inert gas mixture.

3. The spherical diffusion flame experimental device according to claim 2 is characterized in that: The measuring mechanism (3) comprises a data acquisition instrument (31), a radiation heat flux meter (32), a thermocouple (33) and a barometer (34); the thermocouple (33) is arranged in the flame combustion zone, the radiation heat flux meter (32) is arranged outside the flame combustion zone, and the barometer (34) is on the combustion chamber wall; a signal line of the data acquisition instrument (31) arranged outside the combustion chamber (1) is connected to the radiation heat flux meter (32), the thermocouple (33) and the barometer (34); and the data acquisition instrument (31) is connected to a computer.

4. The spherical diffusion flame experimental device according to claim 3 is characterized in that: The gas density regulator (2) comprises an O2 / He mixed gas passage (21), a fuel / heavy inert gas mixed gas passage (22), a vacuum pump (24) and a controller (25); the fuel / heavy inert gas mixed gas passage (22) is connected to the fuel pipe (12), the O2 / He mixed gas passage (21) leads to the inner chamber of the combustion chamber (1), the outer wall outlet of the combustion chamber opposite to the O2 / He mixed gas passage (21) is equipped with a vacuum pump (24), the O2 / He mixed gas passage (21) and the fuel / heavy inert gas mixed gas passage (22) are both equipped with flow control valves (23), and the controller (25) connects the gas flow control valve (23) and the vacuum pump (24).

5. The spherical diffusion flame experimental device according to claim 4 is characterized in that: An air inlet filter element (14) is installed at the gas inlet of the 2 / He mixed gas channel (21), and an air outlet filter element (15) is installed at the air intake of the vacuum pump (23).

6. The spherical diffusion flame experimental device according to any one of claims 1 to 5, characterized in that: The burner (11) is a copper spherical shell with a surface covered with fine pores, the fuel pipe (12) is a copper thin pipe, and a rotary drive motor (13) is installed at the lower part of the fuel pipe (12).

7. The spherical diffusion flame experimental device according to claim 6 is characterized in that: The combustion chamber (1) has observation windows (16) in three directions on the wall thereof. The observation windows (16) face the flame combustion zone (17). Optical measuring devices (4) are installed corresponding to the observation windows (16). The optical measuring devices (4) include a point light source (41), a first convex lens (42), a second convex lens (43) and a CCD camera (44). Light from the point light source (41) passes through the first convex lens (42), enters the combustion chamber (1) from the left observation window, is emitted from the right observation window through the flame combustion zone (17), passes through the second convex lens (43), and is focused on a knife edge to obtain a flame schlieren image. A CCD camera (44) is placed outside the schlieren image to record the image.

8. The spherical diffusion flame experimental device according to claim 7 is characterized in that: The optical measuring device (4) further comprises a reflecting prism (45), a narrow-band filter (46), a third convex lens (47) and an image-intensified ICCD camera (48); the reflecting prism (45) is arranged outside the third position observation window; the flame light is reflected by the reflecting prism (45), filtered by the narrow-band filter (46) and focused by the third convex lens (47) into an image; and the image-intensified ICCD camera (48) with an ultraviolet aperture is arranged outside the schlieren image to record the image.

9. The spherical diffusion flame experimental device according to claim 8 is characterized in that: The heavy inert gas is krypton, argon or CO2, and the fuel is methane.

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