An arc heater pneumatic vacuum assembly

Abstract

This invention discloses a pneumatic vacuum assembly for an arc heater, comprising a plug, a housing, a seal, a spring, a connecting rod, a ejector pin, and a piston. Both the plug and the housing are cylindrical structures connected by coaxial threads. The seal is placed between the plug and the housing. The spring is positioned between the plug and the connecting rod, with the plug determining the upper limit of the spring's horizontal position. Changing the spring tension pushes the connecting rod and ejector pin, causing the piston to move vertically up and down. When the spring is in a relaxed state, the space enclosed by the housing, connecting rod, ejector pin, and piston forms a vacuum channel. When the spring is in a compressed state, the space enclosed by the housing and piston forms a vacuum-stopping channel. The bottom of the vacuum channel is connected to the inner cavity channel of the arc heater. An external vacuum pump is connected to the vacuum channel through a radial hole on the left side of the housing. This invention can be applied to arc heaters in aerospace aerodynamic thermal protection ground simulation tests.

Description

Technical Field

[0001] This invention relates to an aerodynamic vacuum assembly for an electric arc heater, belonging to the field of aerodynamic thermal ground simulation test devices for aerospace vehicles. Background Technology

[0002] Arc heaters are core equipment in ground simulation tests of thermal protection for spacecraft both domestically and internationally. They are a crucial means of addressing ground-based thermal protection assessments for hypersonic vehicles such as missiles, recoverable satellites, and manned spacecraft return capsules. Currently, the development of various spacecraft models in my country places increasing demands on the performance of arc heaters, necessitating further exploration of potential performance enhancements. Among these, the arc ignition performance of the heater directly affects its actual operational capabilities and application range, making it a fundamental and key focus of related research.

[0003] Currently, to achieve high-frequency, high-current, and repeatable arc initiation, arc heaters typically employ a vacuum environment for arc initiation. In a vacuum, the free path of the working fluid molecules increases, and the acceleration time of electrons in the electric field lengthens, resulting in higher energy for individual electrons upon impact, thus enhancing the arc initiation capability of the heater. However, achieving a vacuum environment for the heater currently requires extensive supporting equipment, such as test observation chambers, diffusers, heat exchange chambers, vacuum pumps, and vacuum tanks. These facilities occupy a large area, are difficult to maintain, and involve long vacuum extraction and release times, resulting in a huge and complex workload and limiting the number of tests. In view of these problems, it is necessary to develop a novel vacuum assembly for arc heaters to improve the arc initiation efficiency, simplify the testing process, reduce the cost of supporting equipment, and enhance the reliability of the heater's arc initiation operation. Summary of the Invention

[0004] The technical problem solved by this invention is to overcome the shortcomings of the prior art and provide a pneumatic vacuum assembly for an electric arc heater, which reduces the need for large supporting equipment in the vacuum environment of the electric arc heater, solves the problems of high operation and maintenance costs and free switching of vacuum degree in the inner cavity of the electric arc heater, and improves the arc ignition efficiency and reliability of the electric arc heater.

[0005] The technical solution of this invention: A pneumatic vacuum assembly for an electric arc heater, comprising a plug, a housing, a seal, a spring, a connecting rod, a ejector pin, and a piston; both the plug and the housing are cylindrical structures, connected by a coaxial thread; the seal is placed between the plug and the housing; the spring is placed between the plug and the connecting rod, the upper limit of the spring's horizontal position is determined by the plug, and the spring tension is changed to push the connecting rod and the ejector pin, thereby driving the piston to move up and down in the vertical direction; when the spring is in the relaxed state, the space enclosed by the housing, the connecting rod, the ejector pin, and the piston forms a vacuum passage; when the spring is in the compressed state, the space enclosed by the housing and the piston forms a vacuum stop passage; the bottom of the vacuum passage is connected to the inner cavity passage of the electric arc heater; an external vacuum pump is connected to the vacuum passage through a radial hole on the left side of the housing.

[0006] During vacuuming, the spring is in a naturally relaxed state, and the piston is pushed to the bottom of the tank under the action of gravity and the elastic force of the spring. The vacuum channel inside the component connects the inner cavity of the arc heater with the external vacuum pump, and the gas in the inner cavity of the arc heater is extracted by the external vacuum pump through the vacuum channel. During the test phase of the arc heater, the vacuuming is stopped, and high-pressure air is continuously introduced into the vacuum stop channel. Under the action of air pressure, the piston moves upward against gravity and elastic force, and the spring is compressed and deformed until the seal contacts the inner wall of the outer shell, thus completely disconnecting the vacuum channel. After the test is completed, the air supply is stopped, and the piston returns to its original state under the action of gravity and the elastic force of the spring.

[0007] The plug consists of two parts, upper and lower, which are connected to both ends of the outer shell using a coaxial threaded connection. The lower plug is welded to the nozzle and connected to the arc heater.

[0008] The radial fit tolerances between the plug and connecting rod, and between the housing and piston, shall not exceed 0.2 mm and shall not be less than 0.1 mm.

[0009] The seal is made of rubber or aramid.

[0010] The spring is a cylindrical helical compression spring with a Poisson's ratio not higher than 0.32 and an elastic modulus not lower than 206 GPa.

[0011] The effective elastic compression of the spring is not less than the maximum working stroke of the connecting rod and piston.

[0012] The connecting rod and the ejector pin are coaxially connected by a pin, and the ejector pin and the piston are coaxially connected by a thread, with the coaxiality between the connecting rod, ejector pin and piston not exceeding 0.02mm.

[0013] The surface pressure of the piston movement is provided by a radial air inlet that communicates with the vacuum stop air passage, and the number of air inlets is greater than or equal to one, with an equivalent diameter of not less than 2 mm.

[0014] The working pressure of the vacuum passage shall not exceed 2 kPa, and the working pressure of the vacuum stop passage shall not be lower than 2 MPa.

[0015] The beneficial effects of this invention are:

[0016] 1) By using pneumatic vacuum components, the demand for large supporting equipment for the vacuum environment of the electric arc heater is reduced, thus compressing the test costs such as procurement, use, management, and maintenance. On the other hand, with the simplification of supporting equipment, the test operation process is further simplified.

[0017] 2) By using a pneumatic vacuum assembly, with its springs, pins, connecting rods, pistons and other structures, and a specially designed pneumatic channel, the basic requirements of the heater for a vacuum environment can be met. After the test, the system can be restored to its original state, realizing free switching between vacuum and stop. It is particularly suitable for completing high-frequency, repeatable arc ignition actions, expanding the test application range of the arc heater and improving the arc ignition efficiency and reliability of the arc heater. Attached Figure Description

[0018] Figure 1 This is a schematic cross-sectional view of a pneumatic vacuum assembly.

[0019] Figure 2 A schematic diagram of the vacuuming operation of the pneumatic vacuum assembly.

[0020] Figure 3 A schematic diagram illustrating the vacuum stop operation of a pneumatic vacuum assembly. Detailed Implementation

[0021] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0022] This invention provides a pneumatic vacuum assembly for an arc heater, such as... Figure 1 As shown, it includes a plug 1, a housing 2, a seal 3, a spring 4, a connecting rod 5, a pin 6, and a piston 7, wherein:

[0023] Both the plug 1 and the outer shell 2 are cylindrical structures connected by coaxial threads, with multiple sealing elements 3 placed between them to meet gas sealing requirements. The spring 4 is placed between the plug 1 and the connecting rod 5. The upper limit of the horizontal position of the spring 4 is set by the plug 1. By changing the tension of the spring 4, the connecting rod 5 and the ejector pin 6 can be pushed, and the piston 7 can be moved up and down in the vertical direction. When the spring 4 is in the relaxed state, the space enclosed by the outer shell 2, the connecting rod 5, the ejector pin 6, and the piston 7 is the vacuum passage 8. When the spring 4 is in the compressed state, the space enclosed by the outer shell 2 and the piston 7 is the vacuum stop passage 9. The pneumatic vacuum assembly is connected to the arc heater by welding a nozzle to the plug 1. The bottom of the vacuum passage 8 is connected to the inner cavity passage of the arc heater. The external vacuum pump is connected to the vacuum passage 8 through the radial hole on the left side of the outer shell 2.

[0024] Specifically, when the arc heater is in a vacuum operating state, such as Figure 2 As shown, spring 4 is in a naturally relaxed state, and piston 7 is pushed to the bottom of the groove under the action of gravity and the elastic force of spring 4. The vacuum channel 8 inside the assembly connects the inner cavity of the arc heater to the external vacuum pump. The gas in the inner cavity of the arc heater is extracted by the external vacuum pump through the vacuum channel 8. The basic requirements of the heater for the vacuum environment are achieved through a simple and clear structural combination, which reduces the cost of vacuum supporting equipment and simplifies the test operation process.

[0025] Specifically, when the arc heater enters the testing phase, high-pressure air is continuously supplied to the vacuum shut-off passage 9. Under the action of air pressure, the piston 7 moves upward against gravity and elastic force, and the spring 4 is compressed and deformed until the seal 3 contacts the inner wall of the outer casing 2, thereby completely disconnecting the vacuum passage 8. Figure 3 As shown, maintaining the vacuum assembly in a vacuum-stopped state prevents hot gas from flowing back into the internal cavity and improves the service life of the vacuum pump.

[0026] Specifically, after the test is completed and the air supply is stopped, the piston 7 returns to its original shape under the action of gravity and the elastic force of the spring 4, giving the system a strong self-recovery capability and enabling free switching between vacuum and stop. It is particularly suitable for completing high-frequency, repeatable arc initiation actions, expanding the test application range of the arc heater and improving the arc initiation efficiency and reliability of the heater.

[0027] The plug 1 consists of two parts, upper and lower, which are coaxially threaded and connected to both ends of the outer shell. The lower plug is welded to a nozzle and docks with the arc heater. The wall thickness of the plug 1 and the outer shell 2 is not less than 5mm to ensure that the pneumatic vacuum assembly has good mechanical strength to withstand the high-frequency, high-pressure pneumatic working environment.

[0028] The radial fit tolerance between the plug 1 and the connecting rod 5, and between the housing 2 and the piston 7, is no greater than 0.2 mm and no less than 0.1 mm, to ensure that the connecting rod 5 and the piston 7 have sufficient axial movement capability without causing sudden changes in radial movement.

[0029] The sealing element 3 may be made of rubber or aramid material, and should be resistant to high temperature, vacuum, and impermeability, and have good sealing resilience to ensure the normal operation of the vacuum passage 8 and the vacuum stopping passage 9, and to prevent cross-flow and leakage.

[0030] The spring 4 has a Poisson's ratio of not more than 0.32 and an elastic modulus of not less than 206 GPa to ensure that its effective elastic compression meets the working stroke of the connecting rod 5 and the piston 7, and does not undergo plastic deformation under working pressure.

[0031] The connecting rod 5, the ejector pin 6, and the piston 7 are coaxially connected by pins and threads, with a coaxiality of no more than 0.02 mm between them, to ensure that the assembly has sufficient accuracy and stability during operation.

[0032] The number of radial air inlets in the cross section of the vacuum stop air passage 9 is not limited to one, and when the number of air inlets is greater than one, they should be evenly distributed along the circumference of the outer shell 2, and the sum of the cross-sectional areas should not be less than 2 mm.

[0033] The working pressure of the vacuum channel 8 is not higher than 2 kPa, so as to ensure that the arc heater can complete the arc ignition action in a suitable vacuum environment.

[0034] The working pressure of the vacuum stop air passage 9 is not less than 2MPa, so as to ensure that the surface pressure of the piston 7 is sufficient to quickly seal the vacuum passage, prevent the high-pressure hot gas in the inner cavity of the arc heater from flowing back into the low-pressure area, and protect the pneumatic vacuum components and external vacuum pump.

[0035] The description of the constituent devices and experimental verification of the present invention have demonstrated the characteristics of the present invention, which can have stronger arc initiation performance, better operability, wider experimental application environment and simpler experimental operation process than traditional electric arc heater vacuum equipment.

[0036] The undisclosed technologies in this invention are common knowledge to those skilled in the art.

Claims

1. A pneumatic vacuum assembly for an electric arc heater, characterized in that: The components include a plug (1), a housing (2), a seal (3), a spring (4), a connecting rod (5), a ejector pin (6), and a piston (7). Both the plug (1) and the housing (2) are cylindrical structures connected by coaxial threads. The seal (3) is placed between the plug (1) and the housing (2). The spring (4) is placed between the plug (1) and the connecting rod (5). The upper limit of the horizontal position of the spring (4) is determined by the plug (1). By changing the tension of the spring (4), the connecting rod (5) and the ejector pin are pushed. (6), and drive the piston (7) to move up and down in the vertical direction; when the spring (4) is in the relaxed state, the space enclosed by the outer shell (2), connecting rod (5), ejector pin (6), and piston (7) forms a vacuum passage (8); when the spring (4) is in the compressed state, the space enclosed by the outer shell (2) and piston (7) forms a vacuum stop passage (9); the bottom of the vacuum passage (8) is connected to the inner cavity passage of the electric arc heater; the external vacuum pump is connected to the vacuum passage (8) through the radial hole opened on one side of the outer shell (2); When vacuuming, the spring (4) is in a naturally relaxed state, and the piston (7) is pushed to the bottom of the tank under the action of gravity and the elastic force of the spring (4). The vacuum channel (8) in the component connects the inner cavity of the arc heater with the external vacuum pump. The gas in the inner cavity of the arc heater is extracted by the external vacuum pump through the vacuum channel (8). During the test phase of the arc heater, the vacuuming is stopped, and high-pressure air is continuously introduced into the vacuum stop channel (9). Under the action of air pressure, the piston (7) moves upward against gravity and elastic force, and the spring (4) is compressed and deformed until the seal (3) contacts the inner wall of the outer shell (2), and then the vacuum channel (8) is completely disconnected. After the test is over, the air supply is stopped, and the piston (7) returns to its original state under the action of gravity and the elastic force of the spring (4). The plug (1) consists of two parts, upper and lower, which are connected to the two ends of the outer shell (2) by coaxial thread. The lower plug is welded to the nozzle and connected to the arc heater.

2. The pneumatic vacuum assembly for an electric arc heater according to claim 1, characterized in that: The radial fit tolerances of the plug (1) and connecting rod (5), and the outer shell (2) and piston (7) are all not higher than 0.2 mm and not lower than 0.1 mm.

3. The pneumatic vacuum assembly for an electric arc heater according to claim 1, characterized in that: The sealing element (3) is made of rubber or aramid.

4. The pneumatic vacuum assembly for an electric arc heater according to claim 1, characterized in that: The spring (4) is a cylindrical helical compression spring with a Poisson's ratio not higher than 0.32 and an elastic modulus not lower than 206 GPa.

5. The pneumatic vacuum assembly for an electric arc heater according to claim 4, characterized in that: The effective elastic compression of the spring (4) is not less than the maximum working stroke of the connecting rod (5) and the piston (7).

6. The pneumatic vacuum assembly for an electric arc heater according to claim 1, characterized in that: The connecting rod (5) and the ejector pin (6) are coaxially connected by a pin, and the ejector pin (6) and the piston (7) are coaxially connected by a thread. The coaxiality between the connecting rod (5), the ejector pin (6) and the piston (7) is no greater than 0.02 mm.

7. The pneumatic vacuum assembly for an electric arc heater according to claim 1, characterized in that: The surface pressure of the piston (7) is provided by a radial air inlet that communicates with the vacuum stop air passage (9), and the number of air inlets is greater than or equal to one, the equivalent diameter of the air inlet is not less than 2 mm, and the air inlets are evenly distributed along the circumference of the outer shell (2).

8. The pneumatic vacuum assembly for an electric arc heater according to claim 1, characterized in that: The working pressure of the vacuum passage (8) is not higher than 2KPa, and the working pressure of the vacuum stop passage (9) is not lower than 2MPa.

Images