A spherical diffusion flame experimental device for simulating a microgravity environment on the ground

Abstract

The application discloses a kind of spherical diffusion flame experimental device of ground simulation microgravity environment, it includes combustion chamber (1), fuel pipe (12) port connection spherical combustor (11) in combustion chamber (1), spherical combustor (11) periphery is flame combustion zone (17), further include: gas density regulator (2), layout is in the outer wall of combustion chamber (1), for increasing the gas density of flame combustion zone and reducing the gas density in the inner chamber of combustion chamber (1), and measuring mechanism (3), access inner chamber of combustion chamber (1), for measuring the physical parameter of flame and the gas pressure in combustion chamber.The technical effect of the application is: by reducing the density difference of flame combustion zone gas and the cold medium around flame, realize the microgravity level of flame under the condition of density balance, the effective experimental time under the condition of microgravity is much longer than falling tower experimental device, low in cost, and avoid the equipment accident or failure caused by power supply when generating electric field.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of microgravity combustion experiment, and particularly relates to a spherical diffusion flame experimental device for simulating a microgravity environment on the ground. BACKGROUND

[0002] The spherical diffusion flame configuration is widely used in the fields of combustion basic research and technical research. Compared with other flame configurations (such as: laminar opposed flow flame, droplet flame, zero-dimensional reactor, etc.), the spherical diffusion flame has many advantages: 1. The physical model of the spherical diffusion flame has a clearer boundary definition, and can well simulate the liquid droplet flame and the candle flame, and then facilitate the research on spray combustion or candle flame. In the liquid droplet flame, the heat conduction and heat feedback of the flame front to the surface of the liquid droplet will change the fuel evaporation rate of the surface of the liquid droplet, and then cause the combustion condition to be uncontrollable; while in the spherical diffusion flame, the fuel is supplied to the surrounding oxidizing atmosphere at a constant mass flow rate from the surface of the spherical burner, so that the boundary condition of the liquid droplet diffusion combustion research is adjustable and controllable; 2. The spherical diffusion flame structure has one-dimensional spherical symmetry characteristics, and the dimension and calculation amount of the numerical model are greatly reduced, so that a detailed reaction mechanism and a component transport model can be used to focus on important physical and chemical processes; 3. Under the microgravity condition, the influence of the buoyancy-driven flow on the flow field and the combustion process is eliminated, and the complexity of the combustion process analysis is greatly reduced; 4. The free boundary condition at the far field of the spherical diffusion flame enhances the intensity of the spontaneous oscillation of the flame, and facilitates the research on the mechanism of oscillation-induced extinction.

[0003] Now, there are two technical paths to establish a microgravity experiment: one is to carry out a microgravity experiment on a space station; and the other is to carry out a microgravity experiment on a falling tower on the ground. The first technical path is difficult to carry out on a large scale due to the actual situation of experimental cost, experimental period, experimental risk and funds, etc.; for the second technical path, the effective microgravity experiment duration of the domestic falling tower device is only 3.6 seconds due to the limitation of the falling distance, which cannot meet the requirements of long-period experiments (such as transient oscillation extinction experiments with a duration of 60 seconds or even more). Therefore, at present, many microgravity related researches 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 fuel droplet combustion in a microgravity environment. The system generates an electric field by using a conductive part, and the direction of the electric field is opposite to the direction of the positive ion flow in the flame. The electric field force on the free ions in the flame balances the buoyancy formed by the natural convection of the flame during droplet combustion, and the flame of the droplet is restrained to be approximately spherical shape under microgravity combustion. It is suitable for low-pressure liquefiable gas fuels such as liquid ammonia, liquid hydrogen and dimethyl ether. However, the patent has the following defects: the balance force of the flame is established by the electric field, on the one hand, the conductor in the high-temperature combustion chamber is prone to accidents; on the other hand, a power supply device needs to be provided, which increases the cost of the experimental system. SUMMARY

[0005] In view of the problems existing in the prior art, the technical problem to be solved by the present application is to provide a spherical diffusion flame experimental device for simulating a microgravity environment on the ground, which can observe and study the spherical diffusion flame for a long time, and is safe and low in cost.

[0006] The technical problem to be solved by the present application is solved by the technical scheme, which comprises a combustion chamber, a spherical combustor connected to a fuel pipe port in the combustion chamber, and a flame combustion zone around the spherical combustor. The application also comprises a gas density regulator arranged on the outer wall of the combustion chamber for increasing the gas density of the flame combustion zone and reducing the gas density in the combustion chamber, and

[0007] A measuring mechanism is connected to the combustion chamber for measuring the physical parameters of the flame and the gas pressure in the combustion chamber.

[0008] The technical effect of the present application is:

[0009] The present application reduces the density difference between the gas in the flame combustion zone and the cold medium around the flame, and realizes microgravity level of the flame under the condition of density balance. The effective experimental time under microgravity condition is much longer than that of the falling tower experimental device, the cost is low, and the equipment accidents or failures caused by power supply for generating electric field are avoided. The present application can carry out long-term experiments, collect data more carefully and comprehensively, and is more conducive to carrying out combustion experiments under microgravity conditions. BRIEF DESCRIPTION OF DRAWINGS

[0010] The brief description of the drawings of the present application is as follows:

[0011] Figure 1 The structure of the present application is shown in the structure diagram;

[0012] Figure 2 The structure diagram of the combination of the spherical combustor and the fuel pipe;

[0013] Figure 3The optical measuring device installed in the present application observes the light path of the spherical diffusion flame;

[0014] Figure 4 The flame shape map obtained in the test;

[0015] Figure 5 The flame shape map in the natural condition.

[0016] In the figure, 1, combustion chamber; 11, spherical burner, 12, fuel pipe, 13, rotary drive motor; 14, air inlet filter core, 15, air outlet filter core, 16, observation window; 17, flame combustion zone;

[0017] 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;

[0018] 3, measuring mechanism; 31, data acquisition instrument; 32, radiation heat flow meter, 33, thermocouple; 34, barometer;

[0019] 4, optical measuring device, 41, point light source, 42, first convex lens, 43, second convex lens, 44, CCD camera; 45, reflecting prism; 46, narrowband filter; 47, third convex lens, 48, enhanced ICCD camera. DETAILED DESCRIPTION

[0020] The present application will be further described below in conjunction with the accompanying drawings and examples:

[0021] In order to clearly describe the invention content, the present patent application uses the orientation words "up", "down", "left", "right" for distinction, and the "up", "down", "left", "right" are determined according to the layout direction of the above drawings, and when the actual use direction of the present application is changed, the orientation will change accordingly, and it cannot be regarded as a limitation on the scope of patent protection.

[0022] The concept of the present application is that the flame releases heat energy in the combustion process, which significantly increases the temperature of the gas in the flame combustion zone. Under constant pressure, the increase in temperature leads to the increase in volume of the gas, thereby producing thermal expansion effect, which reduces the gas density in the flame combustion zone, causing the density difference with the surrounding gas. That is, the gas density in the flame combustion zone is generally lower than that of the gas surrounding the flame, and the difference in density 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 the spherical flame is formed.

[0023] As Figure 1As shown, the present application includes a combustion chamber 1 for simulating microgravity environment, a fuel pipe 12 port connected to a spherical burner 11 in the combustion chamber 1, and a flame combustion zone 17 outside the spherical burner 11, further comprising:

[0024] A gas density regulator 2 is arranged on the outer wall of the combustion chamber 1 for increasing the gas density of the flame combustion zone and reducing the gas density in the inner chamber of the combustion chamber 1 to keep the upward buoyancy between the flame gas and the surrounding gas balanced; and

[0025] A measuring mechanism 3 is connected to the inner chamber of the combustion chamber 1 for measuring the physical parameters of the flame and the gas pressure in the combustion chamber.

[0026] The measuring mechanism 3 includes a data acquisition instrument 31, a radiation heat flow meter 32, a thermocouple 33 and a barometer 34, the thermocouple 33 is arranged in the flame combustion zone, the radiation heat flow meter 32 is arranged outside the flame combustion zone, and the barometer 34 is arranged on the wall of the combustion chamber outside the combustion chamber 1. The signal lines of the data acquisition instrument 31 outside the combustion chamber 1 are connected to the radiation heat flow meter 32, the thermocouple 33 and the barometer 34. A high-sensitivity radiation heat flow meter 32 is arranged at a certain distance outside the flame combustion zone and is connected to a computer through the data acquisition instrument 31 to record the change of the radiation heat flow density to reflect the instantaneous change of the temperature.

[0027] The steady-state experiment is to measure the thermochemical structure of the stable combustion strong flame, a plurality of K scale thermocouples 33 are arranged at equal intervals in the flame combustion zone to measure the radial distribution of the temperature; and the water-cooled sampling tube (the water-cooled sampling tube is installed in the middle of the combustion chamber or in the area close to the combustion zone, which position can make the sample contain various gas components generated in the combustion process, and ensure that the representative flue gas sample can be extracted.) is used to extract the flue gas sample and send it into the gas chromatograph to obtain the radial distribution of the concentrations of O2, CO2, CO, CH4, C2H6, C2H4 and H2. The transient experiment is to measure the oscillation of the flame under the near-extinction limit condition, and the oscillation extinction condition is obtained by slowly reducing the proportion of O2 in the oxidant on the basis of the steady-state flame. During the transient experiment, the thermocouple is removed to avoid its interference with the flame oscillation, and a high-sensitivity radiation heat flow meter 32 (data acquisition frequency 200 Hz) is arranged at a certain distance outside the flame; the barometer 34 is used to measure the pressure change in the combustion process.

[0028] As shown in Figure 2 The spherical burner 11 is a spherical shell with fine holes on the surface, the spherical shell is a copper spherical shell, the fuel pipe 12 is connected to the spherical burner 11 from below, the fuel introduced into the fuel pipe 12 is fuel / heavy inert gas mixture, the heavy inert gas can be Kr (krypton), Ar (argon) or CO2 and other gases with relatively heavy density, and the fuel is selected as methane. The heavy inert gas helps to balance the flame buoyancy; the spherical burner 11 can assist the flame to form a spherical shape.

[0029] The lower part of the fuel tube 12 is equipped with a rotary drive motor 13, which is fixed by a motor support capable of bearing the weight of the motor and the vibration generated during operation, and is connected to the rotating shaft of the motor by a connecting member such as a flange, joint or clamp. The rotating shaft is designed to be hollow so that fuel can flow into the fuel tube through the rotating shaft and then be supplied to the combustion chamber. The fuel tube 12 is flange-connected to the rotating shaft of the motor, and the flanges are fastened together by bolts to ensure the sealing and stability of the connection. The port of the fuel / heavy inert gas mixing channel 22 is connected to the rotating shaft of the rotary drive motor through a rotary joint, which can realize continuous fuel supply while maintaining rotation. The upper end of the fuel tube 12 is connected to the spherical burner, and the rotary drive motor drives the fuel tube 12 to rotate, thereby driving the spherical burner 11 to rotate and generating a rotational flow field around the spherical burner. The controller 3 is connected to the rotary drive motor 13. The size of the rotational flow field can be continuously adjusted by controlling the rotational speed of the rotary drive motor 13 through the controller 3.

[0030] A rotational flow field is constructed for a combustion test. Rotational flow refers to the flow state of fluid particles rotating around an axis or central point during the flow process. In a rotational flow field, the trajectory of fluid motion presents a ring or spiral shape, which is significantly different from linear flow such as laminar flow or turbulent flow. The rotational flow field can significantly enhance the mixing efficiency of the fluid, promote the thorough mixing of different components, and improve the reaction rate and product uniformity. At the same time, the rotational flow field improves the heat exchange efficiency, making the heat distribution in the fluid more uniform, thereby enhancing the performance of heat exchangers and cooling systems.

[0031] The fuel tube 12 is a copper tube with a large enough flow resistance to ensure stable fuel flow. An electric spark igniter is used for ignition, and the igniter is quickly withdrawn after ignition to avoid affecting the flame.

[0032] The gas density regulator 2 includes an O2 / He mixing channel 21, a fuel / heavy inert gas mixing channel 22, a vacuum pump 24 and a controller 25. The fuel / heavy inert gas mixing channel 22 is connected to the fuel tube 12, and the O2 / He mixing channel 21 is connected to the inner chamber of the combustion chamber 1. Since the density of He is smaller, the oxygen mixing gas density in the inner chamber of the combustion chamber 1 is reduced. The vacuum pump 24 is installed at the outlet of the outer wall of the combustion chamber opposite to the O2 / He mixing channel 21, which maintains the inner chamber of the combustion chamber 1 at a negative pressure, further reducing the gas density in the inner chamber of the combustion chamber and controlling the flame buoyancy. The O2 / He mixing channel 21 and the fuel / heavy inert gas mixing channel 22 are both equipped with flow control valves 23, and the controller 25 is connected to the gas flow control valves 23 and the vacuum pump 24 to control the air intake and exhaust of the combustion chamber 1.

[0033] 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 suction port of the vacuum pump 23. The filter cores are used to reduce the disturbance of the flame caused by the local flow of gas. The inlet filter 14 and the outlet filter 15 are made of copper.

[0034] like Figure 3 As shown, three observation windows 16 are opened 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.

[0035] The function of the point light source is as follows: 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, among which the point light source 41 plays multiple important roles in capturing the flame image during the combustion process, such as lighting, enhancing visibility, forming schlieren images, improving contrast, and providing reference light. 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.

[0036] Considering that the combustion process is significantly affected by free radical intensity, 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. Flame light is reflected by the reflecting prism 45, filtered by a narrowband filter 46, and focused by a third convex lens 47. The image is then recorded by an image-intensified ICCD camera 48 with a UV aperture. The narrowband filter has a filtering wavelength of 310 ± 10 nm.

[0037] In experiment 1, the fuel pipe 12 is connected with 20% CH4 / 80% Ar, and the O2 / He mixed gas pipe 21 is connected with 20% O2 / 80% He. Since Kr is in the fuel and He is in the oxygen mixed gas, the fuel / Kr mixed gas has a large density, and the O2 / He mixed gas has a small density. The concentration of Kr decreases rapidly outside the flame surface, and the temperature of the diluted flame decreases significantly, which makes the density difference between the flame combustion zone flue gas and the oxygen mixed gas very small. In addition, the combustion chamber is under negative pressure, which further reduces the buoyancy of the flame combustion zone flue gas. As shown in Figure 4 , the flame shape is spherical, and the horizontal diameter / vertical diameter of the flame = 0.98. Under natural conditions, the flame shape is as shown in Figure 5 .

[0038] The present application has the advantages of compact structure, simple experimental operation, high microgravity level, long effective combustion time, consideration of flow field swirl effect, combination with visual measurement equipment for measurement, etc., and has wide application potential in scientific research and industrial application.

Claims

1. A spherical diffusion flame experimental device for simulating a microgravity environment on the ground, comprising a combustion chamber (1), characterized in that: The fuel pipe (12) in the combustion chamber (1) is connected to the spherical burner (11). The periphery of the spherical burner (11) is a flame combustion zone (17), which also 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 maintain a balance between the upward buoyancy generated between the flame gas and the surrounding gas; and A 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; 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. 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), the O2 / He mixed gas passage (21) is connected to the inner chamber of the combustion chamber (1), and 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) is connected to the gas flow control valve (23) and the vacuum pump (24).

2. The spherical diffusion flame experimental device according to claim 1, characterized in that: The measuring mechanism (3) includes a data acquisition instrument (31), a radiation heat flux meter (32), a thermocouple (33) and a barometer (34), wherein 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.

3. The spherical diffusion flame experimental device according to claim 2, 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 suction port of the vacuum pump (23).

4. The spherical diffusion flame experimental device according to any one of claims 1 to 3, 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 tube, and a rotary drive motor (13) is installed at the lower part of the fuel pipe (12).

5. The spherical diffusion flame experimental device according to claim 4 is characterized in that: Three observation windows (16) are provided on the wall of the combustion chamber (1), and the observation windows (16) face the flame combustion zone (17). Optical measuring equipment (4) is installed corresponding to the observation windows (16), and the optical measuring equipment (4) includes 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.

6. The spherical diffusion flame experimental device according to claim 5, characterized in that: The optical measuring device (4) further comprises a reflecting prism (45), a narrowband filter (46), a third convex lens (47) and an image-intensified ICCD camera (48). The reflecting prism (45) is mounted on the outside of the third position observation window. The flame light is reflected by the reflecting prism (45), filtered by the narrowband filter (46) and focused by the third convex lens (47) to form an image. An image-intensified ICCD camera (48) with an ultraviolet aperture is mounted on the outside of the schlieren image to record the image.

7. The spherical diffusion flame experimental device according to claim 6, characterized in that: The heavy inert gas is krypton, argon or CO2, and the fuel is methane.

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