1、 The purpose and characteristics of the equipment:

When studying some physical phenomena in High-altitude environments, it is necessary to provide a low-pressure high-altitude environment. Therefore, high-altitude low-pressure test chambers are suitable for experiments in high-altitude environments. Before conducting experiments using high-altitude low-pressure test chambers, all specimens must be tested under standard atmospheric conditions to obtain baseline data.

1. Used for conducting thermal balance tests and thermal vacuum tests on various space equipment.

2. Basic requirements

3. Manufacturers of high-altitude climate testing equipment have high design and manufacturing capabilities;

4. Meet the standards:

QJ 20127 Technical Requirements for Spacecraft Space Thermal Environment Test Equipment;

GJB 1033 Spacecraft Thermal Balance Test Method;

Test requirements for GJB 1027 carrier, upper stage, and spacecraft;

GJB 2209 Specification for Geosynchronous Orbit Satellite Transponder;

GJB 2042 Satellite Power System Specification;

QJ 1446 Satellite Thermal Vacuum Test Method.

5. Excellent after-sales service and quality assurance should be provided, and the entire machine is guaranteed for 3 years from the date of acceptance.

This equipment is mainly used for high and low temperature tests and low-pressure discharge tests under high vacuum conditions, and can also be used as a simulation test equipment for other small components in orbit.

6. This technical solution is developed based on the technical requirements of the central thermal vacuum testing equipment (mechanical refrigeration). This technical solution is one of the basis for designing and manufacturing the equipment. This equipment includes five aspects: thermal vacuum simulation container, vacuum protection system, high and low temperature protection system, thermal vacuum state control and display system, and auxiliary supporting system. The equipment developed based on this technical solution can truly simulate the cold and hot environment of a vacuum space, and can effectively control, monitor, and record the vacuum degree and temperature of the space. The device has the following characteristics.

7. The entire equipment vacuum system adopts a low-temperature pump as the main pump, with a screw dry pump as the front stage and pre pumping pump, which can achieve the required working vacuum degree for oil-free testing; In terms of temperature control, mechanical refrigeration is used to obtain a low-temperature background, and advanced intelligent PID temperature controllers are used to control the heating current of the heating cage, thereby accurately controlling the temperature; The acquisition of low temperature adopts a unique mechanical refrigeration technology, which eliminates the cost of using liquid nitrogen refrigeration. The control system adopts a combination of industrial computer and PLC for joint control. The display interface of the industrial computer is clear and easy to understand, the PLC control is accurate and reliable, and the fault diagnosis is simple. In addition, different temperature curve formulas can be made according to the user's process requirements, stored in the industrial computer, and available for users to choose and call during the experiment, making it easy for users to master when conducting experimental operations. In summary, this equipment has high vacuum degree, easy temperature control and good uniformity, stable and reliable long-term operation, and can work continuously for more than 30 days. It is easy and convenient to operate and use. This device has certain specificity and universality, and is an essential equipment for space environment simulation experiments.

　2、 Components of Equipment Design

1. Vacuum simulation container (vacuum chamber and internal support)

2. Vacuum protection system (vacuum pump, valve, pipeline, and vacuum measurement)

3. Temperature protection system:

Low temperature refrigeration system: (regional temperature control refrigeration unit+liquid nitrogen refrigeration, heat sink, low-temperature valve and connecting pipe)

Heating and temperature control system: (heating cage, heating power supply), heating cage, vacuum sealed heating electrode, transformer, voltage regulating module, temperature control box

4. Control and monitoring system (cabinet, industrial computer, PLC).

5. Auxiliary supporting systems (air pump, cooling circulating water machine, pollution monitoring)

3、 Main technical indicators of equipment system (excerpt)

Vacuum degree parameter

1. Internal dimensions of the main heat sink: φ 2m * 4m (length)

2. Equipment usage environment: temperature 0 ℃~40 ℃, humidity ≤ 60%;

3. The total power consumption of the equipment is expected to be 120kw/380V

Equipment lighting system; The lighting intensity shall not be less than 200LX, and the protection level shall be IP67

4. Temperature control platform: Thermal oil process;

5. Temperature range of the inner surface of the heat sink: ≥- 150~+160℃

6. Working vacuum degree: ≤ 1.3X10-3 Pa; (at room temperature, with load);

7. Empty load limit vacuum degree: ≤ 2X10-5 Pa; (Low temperature, no load);

8. High temperature no-load vacuum degree: ≤ 5X10-4Pa(100℃，3～4h)

9. Vacuum degree time< 4h

10. The total leakage rate of helium mass spectrometry leak detection for hot vacuum tank body is ≤ 1e-9Pa * m& sup3;/ s;

11. When the heat sink is at room temperature, the pressure inside the vacuum tank can reach 1.33X10-4Pa within 4 hours after the high vacuum pump starts pumping

12. The pressure can be maintained at a constant value within the range of 1000Pa~1.0Pa, and it should be pumped from atmospheric pressure to 1Pa for no more than 20 minutes

Test piece temperature

13. Controllable temperature range for heat sink: -150 ℃~160 ℃; Liquid nitrogen refrigeration+infrared heating cage, or mechanical refrigeration can also be used

It is recommended to use mechanical refrigeration, which can save a lot of operating costs.

14. Temperature display accuracy: 0.1 ℃;

15. Temperature fluctuation: ≤ ±1℃;

16. Temperature uniformity: High temperature constant temperature for 2 hours, temperature uniformity ± 3 ℃

Low temperature constant temperature for 2 hours, temperature uniformity ± 5 ℃;

Heat sink index (bottom plate index)

1. Gas nitrogen process (external heat flow):

Heat sink heating and cooling rate ≥ 1 ℃/min

Temperature range of the inner surface of the heat sink:- 150~+160℃

Uniformity of heat sink temperature: ± 2 ℃

Temperature control precision of temperature control base plate: ± 0.5 ℃

2. Liquid nitrogen process:

Heat sink temperature rate: ≥ 1 ℃/min (-150 ℃~+160 ℃).

Temperature controlled base plate

1. Temperature control process of thermal oil:

Effective temperature control zone: 1.0X1.2m2 x 2

Temperature range of temperature control base plate:- 75℃～+130℃;

Temperature uniformity of temperature control base plate: ± 2 ℃;

Temperature control precision of temperature control base plate: ± 0.5 ℃

Heating and cooling rate: The average temperature change rate of the heat sink and bottom plate (within the range of -45 ℃ to+85 ℃) is ≥ 3 ℃/min;

After the equipment reaches the end temperature during temperature rise and fall operation, the temperature overshoot is less than 2 ℃, and the temperature stabilization time is less than or equal to; 30min;

The bottom plate is easy to disassemble and has a load-bearing capacity of not less than 200kg.

2. Liquid nitrogen process:

Heat sink temperature rate: ≥ 3 ℃/min (-75 ℃~+130 ℃).

Configure the track inside the tank, with a load capacity of ≥ 1000kg (calculated based on a net weight of 500kg for the satellite), and hang a set of tracks inside the tank with a load capacity of ≥ 700kg;

4、 Structure section

1. The test chamber container is designed as a vacuum container and has a horizontal circular cylindrical structure. It is supported by a support frame at the bottom, which directly lands on the ground

2. The vacuum chamber adopts a horizontal stainless steel vacuum container (made of SUS304 stainless steel, with a thickness of 16mm), and the inner side is

Mirror polishing, white spray coating on the outside; The vacuum chamber is equipped with low-pressure lighting, with a brightness of not less than 200 lumens. Vacuum chamber with built-in cargo platform

The platform.

Configure the track inside the tank, and set two parallel guide rails inside the heat sink. The top height of the guide rails is about 60cm below the centerline of the heat sink (safe installation will be carried out in the later stage of development, and the guide rail design will be confirmed by the demand side). The guide rail can bear a load of ≥ 3 tons.

Configure the lifting and unloading vehicle to complete the installation and docking between the test piece (about 3 tons) and the guide rail,

Install separate guide rails and a temperature control platform for each zone. The temperature control platform can be removed or does not affect the entry and exit of the 3-ton test piece.

Reserve at least 100 temperature measurement terminals for backup by the purchaser, and the selection and length of the temperature measurement terminals shall be confirmed by the purchaser

Reserve at least 100 temperature measurement terminals for backup by the purchaser, and the selection and length of the temperature measurement terminals shall be confirmed by the purchaser

Observation window size: φ300mm， Install one at the center position of the front head of the vacuum container (or according to customer requirements), and install one on one side of the tank perpendicular to the axis direction of the tank to facilitate observation of the situation inside the container during the test

Special aerospace black paint is sprayed on the surface, with a solar absorption coefficient of ≥ 0.90 and a hemispherical emissivity of ≥ 0.90, and it does not peel off within the temperature range of 100K to 150 ℃.

Through holes should be reserved on the cold plate; The loading platform has a pull-out function and can be used for assembling test pieces outside of cabin 54. The vacuum container is a horizontal cylindrical shape;

The vacuum container and internal structural materials are made of 0Gr18Ni9 stainless steel, the external structural components are made of carbon steel, and the outside of the container is treated with spray paint;

The inner wall of the vacuum container is polished (0.8um), and 8 necessary flange holes are opened on the wall (4 on each side), including the inlet and outlet interfaces of the nitrogen packaging system, vacuum pumping interface, vacuum gauge interface, temperature measurement and control interface, inflation interface, and other flanges.

　　5、 Equipment configuration parameter requirements (excerpt)

1. Overall equipment configuration: All necessary peripherals (circulating water machine, air source, various flanges, etc.) need to be fully equipped

2. Extraction system:

A main molecular pump: A molecular pump with a pumping speed of 8000L/S is used, and the molecular pump is started when the vacuum degree reaches 10pa.

Pre stage pump B: TRP-36 mechanical pump, with a pumping speed of 2000L/S, capable of pumping up to 2000pa.

C-stage pump: Roots pump with a pumping speed of 180L/S, capable of pumping up to 10pa, requires one unit.

Based on years of experience using vacuum pumps, it is recommended to use domestically produced vacuum pumps because the technology of domestically produced vacuum pumps is already very mature and has a long warranty period. Imported vacuum pumps do not have warranty as long as they are used. I think there is no need to spend money unnecessarily. Sincere suggestion!

Respect customer feedback in the end.

3. Vacuum measurement system: Choose high-quality Pirani, ionization gauge, and digital vacuum gauge from China

4. Heating and cooling system: Adopting imported refrigeration water-cooled compressor units with PID temperature control regulation, using stable and reliable temperature control methods, namely mechanical refrigeration+thermal cage temperature control. All other refrigeration system components are of good quality.

5. Heat sink structure: The liquid nitrogen tube adopts a grouped structure (using a whole copper tube), with bottom inlet and top outlet, divided into zones on the circumference of the tank body. The gate and bottom heat sink are divided into upper and lower zones respectively, so the entire heat sink zone is temperature controlled and regulated, and asymmetric heating and temperature control can also be used according to the situation. The liquid nitrogen tube has no welded joints in the vacuum chamber. Add a layer of shielding on the outside of the liquid nitrogen tube, and install a leak detection port on the liquid nitrogen inlet pipeline for easy leak detection;

6. The heat sink is fixed on stainless steel with polytetrafluoroethylene insulation pads and equipped with self-aligning bearings as rollers. When loading and unloading the heat sink, simply disconnect the high and low temperature joints of the heat sink, align it with the track in the container, and move it in or out of the container. The method is simple and easy to install and maintain. The heat sink of the gate is made into a flat straight pipe welded to a circular plate, and connected to a metal hose (wrapped in stainless steel wire) for the liquid nitrogen external process;

6. Vacuum chamber: Stainless steel 1Cr18Ni9Ti or other better performing stainless steel should be used, with a suitable thickness of 20mm.

7. Observation window: 300mm for the main door

8. Bearing internal pressure: ≥ 2MPa;

9. Total leakage rate: ≤ 5X10-9Pa*m3/s

10. Internal lighting: not less than 200LX

11. Vacuum flange: Multiple 240mm flanges are opened on both sides of the container. (Subject to specific customer requirements)

12. Measurement location: Pirani and ionization gauge are installed at the front of the container.

13. Container support plate: The size of the support plate should be as large as possible, and the stress point of the support plate should be on the tank body.

14. General control system: This equipment is a fully automatic control system.

15. Equipment features: This equipment is a horizontal high vacuum system.

16. Install a mechanical cold trap at the pumping port of the molecular pump (the molecular pump is only used under special conditions).

The function of the operating vehicle is to transport the product into the tank. The running car is parked outside the tank, and the load running car is placed on the running car. Then, the running car is automatically docked with the track inside the tank, and the load trolley can be pushed from the running car to the guide rail of the vacuum tank truck.

The operating vehicle is made of stainless steel material, with adjustable height and direction, and a load-bearing capacity of not less than 3 tons. The operating vehicle is a truss structure, welded with 60mm x 20mm rectangular stainless steel square tubes as the frame material. There are four limit PTFE rollers below, which can be used with support to achieve positioning and leveling at different positions.

The function of the loading trolley is to transport the test piece to the vacuum tank after completing the preparation work outside the tank. The load trolley is parked outside the tank on a movable vehicle that is the same height as the track inside the tank. During the test, it is moved into a fixed bracket inside the tank. The load trolley is made of stainless steel material with adjustable height and front and rear, and the bracket on the vehicle is designed according to the requirements of the test piece. The car adopts a truss structure with four limit PTFE rollers underneath to achieve positioning and leveling at different positions. The surface of the car bracket is covered with double-sided aluminum coated polyester film to reduce heat leakage.

19. Design of hanging points inside the vacuum container: There are 10 hanging points at the top of the heat sink of the vacuum container, with a single point bearing capacity of not less than 3 tons, used for hanging and moving test specimens, or binding and fixing measuring devices and lines during testing. 10 M24 suspension rods are connected to the top of the heat sink skeleton.

20. Pedestrian pedal design: Pedestrian pedals are installed on both sides of the heat sink, and on both sides of the guide rail. The design takes into account the heat sink effect and requires easy folding and disassembly, with a width of ≥ 400mm and a load-bearing capacity of not less than 500gg/m2.

21. The total power of the power supply shall not be less than 50KW. Imported or domestically produced DC power supplies (with grid ports) of the same quality shall be selected, and the power supply shall be independently controllable according to the test environment.

6、 Vacuum section

To ensure the no-load ultimate vacuum degree: ≤ 2X10-5 Pa; (Low temperature, no load), high temperature, no load vacuum degree: ≤ The requirement is 5X10-4Pa (100 ℃, 3-4 hours) to prevent contamination of the specimen. The system consists of three pumping subsystems: a German Leybold dry vacuum pump and a Roots dry pump (German Leybold, Hanzhong) as the coarse pumping system, a magnetic levitation molecular pump (German Leybold, Sumitomo) as the pre pumping unit, and a low-temperature pump (Leybold) as the main pumping unit. The characteristics are fast pumping, high vacuum degree, no pollution, and no vibration. The pumping speed of low vacuum is related to the pumping speed of the low vacuum pump and the volume of the container being pumped; The pumping time of high vacuum is related to the pumping speed of the high vacuum pump and the exhaust volume of everything inside the vacuum container.

2. According to the requirement of temperature coverage of -150~+160 ° C for the equipment, liquid nitrogen refrigeration and infrared heating cage are selected to provide heating power to achieve temperature control of the equipment. The temperature guarantee system consists of a heat sink, an infrared heating cage, a liquid nitrogen refrigeration system, a heating and temperature control system, connecting pipelines, and low-temperature valves.

Low temperature process diagram

3. Equipped with stable control measures for vacuum degree, the vacuum degree should be able to stay and maintain at any point within the full pressure range;

During use, the vacuum degree should not be too high or too low. The plan provides a detailed description of the vacuum degree stability control scheme.

4. Vacuum simulation container:

It is mainly used to accommodate test specimens and can create a vacuum and temperature environment that meets the test conditions. There is a platform inside for placing workpieces, which can be installed., The vacuum container is equipped with an exhaust port for connecting vacuum equipment. It also has some electrical interfaces to connect necessary cables, enabling good connection between the test pieces inside the vacuum chamber and the instruments outside the vacuum chamber. Above the vacuum container, there is also a gauge for measuring vacuum degree, and there is a PT100 sensor for measuring temperature inside, in order to measure the main technical parameters of this equipment (vacuum degree and temperature). In addition, there are observation windows and lighting fixtures to observe the condition of the internal test pieces

5. Vacuum protection system:

It is a device that pumps a vacuum container into a vacuum environment, which is divided into two parts: a pre pumping system and a main pumping system. The pre pumping system pumps the vacuum chamber into a low vacuum, and then the main pumping system pumps the vacuum chamber into a high vacuum. It consists of a vacuum pump, a vacuum valve, and a vacuum pipeline.

6. Temperature guarantee system:

It is mainly used to ensure the temperature environment required for the experiment, including positive and negative temperature environments. Both positive and negative temperatures are achieved by setting a cold background and controlling the temperature through a heating cage. Users only need to set the target temperature to achieve temperature control, and can achieve cyclic temperature control according to the temperature cycling test requirements.

7. Thermal vacuum state control monitoring system:

It is used to control the actions of components in the vacuum system and temperature assurance system, display the current control status, and is responsible for saving and recording parameters such as vacuum degree and temperature, drawing specific curves, and facilitating intuitive understanding of parameter changes. It mainly consists of two parts: control cabinet and industrial computer.

The control system adopts a micro programmable controller, and the vacuum system and temperature control system each use a PLC, so that each control system has a certain degree of independence. Once a problem occurs, it can be diagnosed and repaired separately.

This system can also provide corresponding alarms for major faults such as gas and water outages.

8. Auxiliary supporting system:

There are mainly cooling water systems and air circuit systems. The cooling water system provides cooling for the vacuum pump of the vacuum system and the refrigeration unit of the temperature guarantee system, while the air circuit system provides air source power for the vacuum valve.

Pollution monitoring mainly monitors the composition of residual gases inside the vacuum chamber and the molecular deposition on the surface of objects.

9. Working method

This system adopts a self pressurized open boiling working mode, mainly composed of a liquid nitrogen storage tank, low-temperature valves, and pipelines. The supply of liquid nitrogen relies on the pressure of the liquid nitrogen storage tank itself (0.2MPa), which enters the heat sink and undergoes heat exchange through boiling and evaporation of liquid nitrogen in the heat sink, keeping the heat sink at a low temperature below 100K. The gas produced after heat exchange is directly discharged into the atmosphere after passing through the heat sink.

& nbsp; & nbsp;  Entering the heat sink through an electric liquid nitrogen flow control valve, the entire process is automatically controlled, including valve opening, etc; The manual control system is used as a backup system, which is used in emergency situations such as power outages. The supply of liquid nitrogen enters the heat sink through the pressure of the liquid nitrogen storage tank itself (generally ≤ 0.1MPa) through a manual valve switch.

& nbsp;  In order to avoid unreasonable distribution of liquid nitrogen in each branch, an electric low-temperature shut-off valve (dual channel redundant design) is also installed on the branch of the heat sink. The liquid nitrogen shut-off valves in each zone can control the on/off of liquid nitrogen through the heat sink temperature, and can automatically and stably maintain the heat sink temperature below 100K without wasting liquid nitrogen. The liquid outlet adopts a gas-liquid separator to reduce the waste of liquid nitrogen caused by gas flow flushing in the system.