CN114151988A

CN114151988A - Refrigerator system suitable for 20K temperature zone of infrared camera of space astronomical telescope

Info

Publication number: CN114151988A
Application number: CN202111449214.3A
Authority: CN
Inventors: 周吉; 植晓琴; 倪竹青; 王波; 曹溶菲; 贺瑞聪; 刘志敏; 罗高乔; 王海洋; 李国良
Original assignee: China Electronics Technology Group Corp No 16 Institute; Zhejiang University ZJU; Beijing Institute of Space Research Mechanical and Electricity
Current assignee: China Electronics Technology Group Corp No 16 Institute; Zhejiang University ZJU; Beijing Institute of Space Research Mechanical and Electricity
Priority date: 2021-11-30
Filing date: 2021-11-30
Publication date: 2022-03-08
Anticipated expiration: 2041-11-30
Also published as: CN114151988B

Abstract

The invention discloses a refrigerator system suitable for a 20K temperature area of an infrared camera of a space astronomical telescope, which belongs to the field of space 20K temperature refrigeration based on a gas bearing pulse tube technology, wherein the refrigerator comprises a gas bearing compressor, a secondary pulse tube cold finger and a connecting pipeline; the compressor is driven by a moving magnet linear motor and is arranged oppositely. The cold finger is divided into two stages, a U-shaped structure is adopted, the interstage adopts a thermal coupling mode, and the phase of pressure wave and mass flow is adjusted in a low-temperature inertia tube mode. The invention can realize the light weight, high efficiency and large cooling capacity of the refrigerator, simultaneously realize the long-life operation, and can realize the light weight, high efficiency, easy implementation and high reliability of the space refrigerating system.

Description

Refrigerator system suitable for 20K temperature zone of infrared camera of space astronomical telescope

Technical Field

The invention relates to a refrigerator system.

Background

The gas bearing Stirling pulse tube refrigerator technology has the advantages of both a gas bearing compressor and a low-temperature inertial pulse tube cold finger, and has the advantages of compact structure, light weight, high refrigeration efficiency and reliability, 20K direct cooling of a single compressor and the like, wherein the compressor is a Stirling cycle refrigerator adopting the gas bearing to support a piston and an ejector. The abrasion between the piston and the cylinder is theoretically eliminated, and the reliability can reach 20 ten thousand hours. In addition, the gas bearing replaces the traditional plate spring supporting structure, and is small in size and weight. The general working temperature range suitable for the compressor is far larger than that of an oxford compressor. The cold finger adopts a secondary low-temperature inertia pulse tube to realize phase modulation, the phase modulation reliability is high, the inertia pulse tube realizes the asynchronism of pressure wave and mass flow change based on the airflow high-frequency oscillation effect, the phenomenon of unstable performance of a refrigeration system caused by direct current can be eliminated, and the system can be more compact.

The development of the gas bearing pulse tube refrigerator belongs to a new technology at home and abroad. NASA has years of successful research and development experience in the field of gas bearing Stirling type refrigerators, and a plurality of sets of gas bearing refrigerator Stirling refrigerators are applied to spaceflight, but the research on the gas bearing pulse tube refrigerator is not reported in related technical publications. In view of the fact that the related technology belongs to the advanced deep low temperature refrigeration technology and is strictly sealed off in China abroad, the invention aims to solve a series of key technical problems in the development of the gas bearing pulse tube refrigerator through independent research and development.

Disclosure of Invention

The technical problem to be solved by the invention is as follows: the invention provides a refrigerator system suitable for a 20K temperature zone of an infrared camera of a space astronomical telescope, which adopts a scheme of comprehensively driving a secondary low-temperature inertia pulse tube by an opposed gas bearing compressor to realize refrigeration, solves the problems of large volume and heavy weight and easy failure of a plate spring of an oxford compressor, also solves the problem of overlarge vibration of an integrated gas bearing refrigerator, and simultaneously avoids the problems of DC direct current and hot end instability caused by bidirectional air inlet phase modulation. Therefore, the temperature stability of the detector is well ensured, the imaging quality is ensured, the volume and the weight of the refrigeration assembly are reduced while the energy consumption of the whole satellite is reduced, the service life of a refrigeration system is prolonged, and the improvement of the overall reliability of the infrared camera is facilitated.

The design scheme adopted by the invention is as follows: a refrigerator system suitable for a 20K temperature zone of an infrared camera of a space astronomical telescope comprises a compressor, a compressor bracket, a compressor supporting plate, a compressor heat insulation pad, a compressor vibration reduction pad, a primary cold head, a hot end heat dissipation surface, a secondary cold head, a flexible cold chain and a cold head supporting rod;

the compressor is fixed on the compressor support, the lower plate of the compressor support is connected with the compressor support plate through the compressor heat insulation pad, and the bottom of the compressor support plate is provided with the compressor vibration damping pad; the compressor is connected with a hot end heat exchanger through a three-way transmission pipe, and the hot end heat exchanger is respectively connected with a first-stage cold head and a second-stage cold head; the press and the cold finger connecting pipe adopt argon arc welding, and the flexible cold chain is connected with the secondary cold head; the heat radiating surface at the hot end transfers or radiates the heat generated in the refrigeration process to the outside; the cold head supporting rod is used for supporting the first-stage cold head and the second-stage cold head.

The primary cold head comprises a primary room temperature heat exchanger, a primary pulse tube hot end heat exchanger, a primary heat regenerator, a primary pulse tube, a primary cold end heat exchanger, a primary air reservoir and a primary inertia tube, wherein the primary air reservoir is arranged on the normal temperature area or the hot end heat exchanger and is fixed on a compressor support plate or the hot end heat exchanger; the primary hot end heat exchanger comprises two paths, namely a primary room temperature heat exchanger and a primary pulse tube hot end heat exchanger, wherein the primary room temperature heat regenerator is connected with one side of the primary cold end heat exchanger through the primary heat regenerator, the primary pulse tube hot end heat exchanger is connected with the other side of the primary cold end heat exchanger through the primary pulse tube, and a U-shaped gas flow passage is arranged in the primary cold end heat exchanger to communicate the two sides; the primary inertia tube is used for connecting the primary gas reservoir and the primary pulse tube.

The secondary cold head comprises a secondary heat regenerator precooling section, a precooling heat exchanger, a secondary inertia tube, a secondary heat regenerator low-temperature section, a secondary pulse tube, a secondary cold end heat exchanger, a secondary room temperature heat exchanger, a secondary pulse tube hot end heat exchanger and a secondary air reservoir; the secondary cold end heat exchanger directly outputs cold energy outwards, one end of the secondary cold end heat exchanger is connected with the low-temperature section of the secondary heat regenerator, the other end of the secondary cold end heat exchanger is connected with one end of the secondary pulse tube, and a U-shaped flow passage for helium to flow and exchange heat is arranged in the secondary cold end heat exchanger; the other side of the secondary pulse tube is connected with a secondary gas reservoir through a secondary inertia tube, the secondary gas reservoir is fixed on the primary cold end heat exchanger, and precooling is provided by the primary cold end heat exchanger; the primary cold end heat exchanger transfers a cold chain to the secondary precooling heat exchanger and the secondary pulse tube hot end heat exchanger through thermal bridge connection, so as to provide precooling for the secondary stage; and dividing the secondary heat regenerator into a secondary heat regenerator precooling section and a secondary heat regenerator low-temperature section according to the lap joint position of the thermal bridge, wherein the hot end heat exchanger is connected with the secondary heat regenerator precooling section.

The first-stage vessel and the second-stage vessel are filled with rectifying wire meshes.

And the wire mesh is filled in the primary heat regenerator, the secondary heat regenerator pre-cooling section and the secondary heat regenerator low-temperature section, and the filled wire mesh is prepared by combining a wire mesh formed by drawing, weaving and foam molding of an ErPr material, a pressed stainless steel wire mesh and a brass rectifying wire mesh.

The flexible cold chain is the flexible cold chain of 5N aluminium, including multilayer aluminium foil, cold junction punch holder, cold junction lower plate, hot junction punch holder, hot junction lower plate, cut into special shape with the 5N aluminium foil through electron discharge machining technology, the cutting foil after rinsing and 140 ℃ vacuum baking through isopropyl alcohol bath is placed on the frock, and use the face milling process to get rid of the extra length of 5N aluminium foil, assemble 5N aluminium foil and cold junction punch holder, cold junction lower plate, hot junction punch holder, hot junction lower plate adoption mounting fixture, and through high vacuum electron beam welding.

The cold head support rod is a Bipod support rod and comprises a titanium alloy base, invar steel nests and a hollow glass reinforced plastic rod; the glass fiber reinforced plastic rod is arranged on the outer side, the invar steel nests are respectively located at the upper end and the lower end of the glass fiber reinforced plastic rod and are bonded with the glass fiber reinforced plastic rod through structural adhesive to locally reinforce the glass fiber reinforced plastic rod, and the two ends of the glass fiber reinforced plastic rod are connected with the titanium alloy base through bolts.

The compressor is an opposed gas bearing compressor and comprises a magnetic steel framework, a piston cylinder, a split pipe, magnetic steel, a coil, an outer stator, an inner stator, a compression cavity and an expansion cavity, wherein the split pipe is used for connecting a driven refrigerator, and the magnetic steel is bonded on the magnetic steel framework and then connected with the piston to form a rotor assembly; the coil is wound firstly and then arranged in the outer stator; the outer stator and the inner stator are used as stator parts of the motor, generate a magnetic field after being electrified, and drive the rotor assembly to move after interacting with the magnetic steel; the piston moves in the piston cylinder and compresses a gas working medium in the compression cavity; the working medium gas is helium, and the inflation pressure is 2.5-2.7 Mpa.

The compressor heat insulation pad is a polyimide heat insulation pad.

The compressor vibration damping pad is a titanium alloy damping vibration isolation gasket provided with an unloading groove, and four through holes are reserved on the periphery of the compressor vibration damping gasket so as to be connected with a compressor supporting plate in a threaded manner; the middle of the compressor damping pad is of a hollow structure, and the compressor damping pad main body is provided with at least 3 circles of unloading grooves; and filling damping glue in the unloading groove.

Compared with the prior art, the invention has the advantages that:

the gas bearing compressor is adopted for driving, the total weight of the system can be ensured to be lighter, meanwhile, the service life of the refrigerator is longer, the space application requirement is met, secondary cooling can be realized only by adopting a single compressor, the U-shaped pulse tube has higher efficiency than a coaxial type, and compared with low-temperature bidirectional air inlet phase modulation, pure low-temperature inertia tube phase modulation cannot enable the inside of the system to form a closed loop, DC direct current is generated and periodic fluctuation of the refrigeration temperature is caused, the stability of the refrigeration temperature can be well ensured, and long-term stable operation of the refrigerator is realized. In contrast, the GM type refrigerator has a large size and weight, and the cooling system has moving parts such as an electronic gas distribution valve, and the reliability of the GM type refrigerator is inferior to that of the stirling type pulse tube refrigerator when the GM type refrigerator is operated for a long time. The JT refrigerating machine adopts an irreversible throttling process for refrigeration, has a large working pressure ratio and adopts a dividing wall type heat exchanger for heat exchange, so that the JT refrigerating machine has the defects of low efficiency, large power consumption, large air consumption and large system volume and weight, and cannot realize continuous refrigeration from room temperature to low temperature. Compared with the international mainstream 20K refrigeration system for the space, the refrigeration efficiency is improved from 4 percent to 6 percent, and the weight ratio of the refrigeration capacity is improved from the prior 1W/kg to more than 2.5W/kg. The application of the fourth generation refrigerator technology in the aerospace low-temperature engineering and the aerospace remote sensing field is promoted.

Drawings

Fig. 1 is a diagram of the overall configuration of a 20K gas bearing pulse tube refrigerator system.

Wherein 1 is the opposed gas bearing compressor, 2 is the compressor support, 3 is the compressor backup pad, 4 is the compressor heat insulating mattress, 5 is the compressor damping pad, 6 is the first grade cold head, 7 is the hot junction cooling surface, 8 is the second grade cold head, 9 is the flexible cold chain, 10 is the bipod bracing piece.

FIG. 2 is a diagram of a gas bearing compressor-pulse tube coupling scheme;

6-1 is a primary air reservoir, 6-2 is a primary inertia tube, 6-3 is a 1-stage heat regenerator, 6-4 is a primary pulse tube, 6-5 is a primary cold end heat exchanger, 6-6 is a hot end heat exchanger, 8-1 is a secondary heat regenerator precooling section, 8-2 is a secondary inertia tube, 8-3 is a secondary heat regenerator low temperature section, 8-4 is a secondary pulse tube, 8-5 is a secondary cold end heat exchanger, 8-6 is a secondary air reservoir, 11 is a thermal bridge, and 12 is an 80K radiation screen.

FIG. 3 is a schematic view of an opposed gas bearing compressor;

wherein, 1-1 is a magnetic steel framework, 1-2 is a piston, 1-3 is a piston cylinder, 1-4 is a separate pipe, 1-5 is magnetic steel, 1-6 is a coil, 1-7 is an outer stator, 1-8 is an inner stator, 1-9 is a compression cavity, 1-10 is an expansion cavity

FIG. 4 is a diagram of a 20K gas bearing pulse tube refrigerator cold head configuration;

FIG. 5(a) is a structural diagram of a first stage pulse tube refrigerator, and FIG. 5(b) is a structural diagram of a second stage pulse tube refrigerator;

6-6-1 is a first-stage room temperature heat exchanger, 6-6-2 is a first-stage pulse tube hot end heat exchanger, and 8-2 is a second-stage inertia tube; 13 is a precooling heat exchanger, 6-6-3 is a secondary room temperature heat exchanger, and 6-6-4 is a secondary pulse tube hot end heat exchanger.

FIG. 6-1 is a diagram of a cold finger heat insulation support structure.

14 is a titanium alloy base, 15 is an invar steel nest, 16 is a middle hole glass steel rod which is connected with a main bearing plate.

FIG. 6-2 is a structural view of a flexible 5N aluminum cold chain;

9-1 is a multilayer 5N aluminum foil, and 9-2 and 9-3 are respectively an upper clamping plate and a lower clamping plate at the hot end. 9-4 and 9-5 are respectively a cold end upper splint and a cold end lower splint.

Fig. 7 is a view showing the structure of the compressor fixing and supporting.

1 is compressor main body, 2 is compressor support, 17 is the fixing bolt, 4 is the compressor heat insulating mattress, 5 is the compressor damping vibration-damping mattress.

Fig. 8 is a view showing the structure of a damping shim.

FIG. 9 is a graph of pV work versus transport tube length;

FIG. 10 is a graph of the effect of piston displacement on cooling capacity, output acoustic work and required thrust;

FIG. 11 is a graph of input PV work, precooling and cooling capacity versus charge pressure.

Detailed Description

The invention is further described below with reference to the accompanying drawings.

In order to realize high-precision remote sensing observation of the star bodies of more than fifteen equines, the space astronomical telescope needs to cool a focal plane to 20K and provide refrigerating capacity of not less than 0.3W. In order to ensure the imaging quality, the disturbance vibration force of the end part of the cold finger is required to be less than or equal to 0.1N, the micro-vibration disturbance vibration force of the compressor is required to be not more than 1N, the acceleration of the compressor is less than or equal to 20mg, and the weight of the whole machine is better than 13 kg. The scheme that the opposed gas bearing compressor drives the low-temperature inertia pulse tube (U-shaped) to realize refrigeration is adopted, the characteristics of light weight, high efficiency, U-shaped pulse tube heat regeneration efficiency and high temperature stability of the low-temperature inertia pulse tube of the gas bearing compressor are comprehensively utilized, the structural characteristics determine that the refrigerator realizes the refrigeration of a 20K temperature region at higher frequency above 50Hz, and the high requirements on cold finger coupling matching of the compressor, heat regeneration filler design, pressure wave-mass flow phase regulation and the like are met. If no relevant measures are taken, the refrigerator can not realize the performance, and the application requirement of a new generation of space telescope on the deep space precise remote sensing detection can not be met. For this purpose, the above-mentioned refrigerating machines need to be specially designed to adapt them to the requirements of aerospace applications.

The refrigerator system adopts a highly reliable phase modulation structure (figures 2 and 4) comprising an opposed gas bearing compressor, a multistage pulse tube high-efficiency coupling structure (figure 1), a 20K room temperature inertia tube and a precooling pulse tube, a consistency control method (tables 1, 2 and 3) of an opposed gas bearing press, a high-frequency and high-porosity low-temperature heat regenerator structure (figures 5(a) and 5(b)), a low-cold-loss structure (figures 6-1 and 6-2) combining a flexible cold chain and high-efficiency heat insulation, and a compressor vibration isolation and vibration reduction supporting structure (figure 7) to realize vibration reduction and high-efficiency refrigeration of the 20K space refrigerator and meet the requirement of aerospace application.

As shown in fig. 1, the whole refrigerating machine system comprises an opposed gas bearing compressor 1, a compressor bracket 2, a compressor support plate 3, a compressor heat insulation pad 4, a compressor vibration reduction pad 5, a primary cold head 6, a hot end heat dissipation surface 7, a secondary cold head 8, a flexible cold chain 9 and a cold head support rod 10.

The compressor 1 is fixed on the compressor bracket 2, the screws are symmetrically screwed between the upper plate and the lower plate of the compressor bracket to realize fastening and installation, and the distance between the screws is controlled to be 4cm-6 cm. The lower plate of the compressor bracket 2 is provided with through holes, 12M 3 screws pass through the compressor heat insulation pad 4 to be connected with screw holes on the compressor support plate 3, a large through hole and four small screw holes are respectively reserved on the periphery of the compressor support plate 3, the main body of the compressor vibration damping pad 5 passes through the support plate through holes, and the four small through holes on the periphery of the compressor vibration damping pad 5 correspond to the four small screw holes and are fastened and connected through the screws. The compressor 1 is connected with a hot end heat exchanger 6-6 through a three-way transmission pipe and is respectively connected with a first-stage cold head 6 and a second-stage cold head 8. The compressor 1 is connected with the bottom of the three-way transmission pipe by argon arc welding, the flexible cold chain 9 is connected with the secondary cold head 8 by a screw, and indium foil is filled in the interface. The shell of the compressor 1 and the uppermost end of the secondary cold head 8 are packaged by laser welding, so that air leakage is avoided. The heat end radiating surface 7 transfers or radiates heat generated in the refrigeration process to the outside; the cold head support rod 10 is used for supporting the first-stage cold head 6 and the second-stage cold head 8.

The high-reliability phase modulation is realized by the inertia tube and the precooling pulse tube, as shown in fig. 2 and fig. 4. The refrigerating machine is divided into two stages, the temperature of the cold end of the first-stage cold head 6 is reduced to 80-100K through first-stage refrigeration, and the temperature of the cold end of the second-stage cold head 8 is reduced to below 20K through second-stage refrigeration on the basis. The primary cold head mainly comprises a primary room temperature heat exchanger 6-6-1, a primary pulse tube hot end heat exchanger 6-6-2, a primary heat regenerator 6-3, a primary pulse tube 6-4, a primary cold end heat exchanger 6-5, a primary air reservoir 6-1 and a primary inertia tube 6-2, wherein the primary air reservoir 6-1 can be arranged in a room temperature area or a hot end heat exchanger 6-6 and is usually fixed on a compressor support plate or a hot end heat exchanger 6-6 in a direct threaded manner, the primary hot end heat exchanger comprises two paths, namely a primary room temperature heat exchanger 6-6-1 and a primary pulse tube hot end heat exchanger 6-6-2, the primary room temperature heat regenerator 6-6-1 is connected with one side of the primary cold end heat regenerator 6-5 through the primary heat regenerator 6-3, the first-stage pulse tube hot end heat exchanger 6-6-2 is connected with the other side of the first-stage cold end heat exchanger 6-5 through a first-stage pulse tube 6-4. A U-shaped gas micro-channel is arranged in the first-stage cold-end heat exchanger to communicate the two sides. The first-level inertia pipe 6-2 is used for connecting the first-level gas reservoir and the first-level pulse tube, and under the condition of maintaining the volume of the gas reservoir unchanged, the inertia pipe can be wound on the outer side of the gas reservoir or buried on the inner side of the gas reservoir.

The secondary cold head mainly comprises a secondary heat regenerator pre-cooling section 8-1, a pre-cooling heat exchanger 13, a secondary inertia tube 8-2, a secondary heat regenerator low-temperature section 8-3, a secondary pulse tube 8-4, a secondary cold end heat exchanger 8-5, a secondary room temperature heat exchanger 6-6-3, a secondary pulse tube hot end heat exchanger 6-6-4 and a secondary air reservoir 8-6. As shown in fig. 5. The secondary cold end heat exchanger 8-5 is the lowest temperature area of the whole refrigerator and directly outputs cold energy outwards, one end of the secondary cold end heat exchanger is connected with the low temperature end 8-3 of the secondary heat regenerator, and the other end of the secondary cold end heat exchanger is connected with the secondary pulse tube 8-4. And a U-shaped micro-channel for helium to flow and exchange heat is also arranged in the secondary cold-end heat exchanger. The other side of the secondary pulse tube 8-4 is connected with a secondary gas reservoir 8-6 through a secondary inertia tube 8-2, the secondary gas reservoir 8-6 is fixed on a primary cold end heat exchanger 6-5 in a screw joint or welding mode, and precooling is provided by the primary cold end heat exchanger 6-5. The primary cold end heat exchanger 6-5 is connected through a thermal bridge 11 to transmit a cold chain to a secondary precooling heat exchanger 13 and a secondary pulse tube hot end heat exchanger 6-6-4, so as to provide precooling for the secondary stage. The secondary heat regenerator is divided into a secondary heat regenerator precooling section 8-1 and a secondary heat regenerator low-temperature section 8-3 according to the lap joint position of the thermal bridge, and the hot end heat exchanger 6-6 is directly connected with the secondary heat regenerator precooling end 8-1. The gas temperature is reduced to be below 100K through the pre-cooling end 8-1 of the secondary heat regenerator, and then the working medium gas passes through the low-temperature section 8-3 of the secondary heat regenerator to further reduce the gas temperature from 100K to be below 20K.

A certain amount of rectification wire nets are filled in the first-stage pulse tube 6-4 and the second-stage pulse tube 8-4 to ensure that gas enters the pulse tubes and can keep a better layered flow state, so that a jet flow phenomenon is avoided, the first stage adopts a room-temperature inertia tube 6-2 and an air reservoir 6-1 for phase modulation, the second stage adopts a low-temperature (80K temperature region) inertia tube 8-2 and an air reservoir 8-6 for phase modulation, and the first-stage cold head 6 is connected with the second-stage cold head through a heat exchanger. The inertia tube is a red copper tube and is wound outside the gas reservoir, and the structural characteristic dimension of the inertia tube/vessel is shown in table 1.

The high-frequency and high-porosity low-temperature regenerator structure and the filler adopt the following methods: aiming at different application temperature zones of the first stage and the second stage, a wire mesh is filled in the first-stage heat regenerator 6-3, the second-stage heat regenerator pre-cooling section 8-1 and the second-stage heat regenerator low-temperature section 8-3, the wire mesh is organically combined with a pressed stainless steel wire mesh and a brass rectifying wire mesh through wire drawing weaving and foam molding of an ErPr material, and the problems of high gas viscosity, serious pressure ratio loss and low sound power utilization rate of the high-temperature section heat regenerator (the first-stage heat regenerator 6-3 and the second-stage heat regenerator pre-cooling section 8-1 in the graph 5 (a)) are effectively solved through increasing the porosity. In the low-temperature section (the low-temperature section 8-3 of the secondary heat regenerator in fig. 5(b)), the total heat capacity of the filler is effectively increased by reducing the porosity of the wire mesh, so that the total heat capacity of the gas working medium is reduced, the heat penetration depth and the permeability of the gas in one period are further increased, and the heat exchange efficiency is improved.

Aiming at the working requirement of a 20K temperature zone, a 5N aluminum flexible cold chain (shown in figure 6-2) is formed by integrally welding a 5N aluminum high-purity aluminum foil and an aluminum cold and hot end, the aluminum is subjected to surface treatment by chemical plating, electroplating, ion implantation and magnetron sputtering methods before welding, a reaction layer is prefabricated on the surface of the aluminum alloy, and the influence of compact aluminum oxide on the surface of the aluminum alloy on the wetting of brazing filler metal is eliminated. The 5N aluminum cold chain comprises 9-1 parts of multilayer aluminum foils, 9-2 parts of cold end upper clamping plates, 9-3 parts of cold end lower clamping plates, 9-4 parts of hot end upper clamping plates and 9-5 parts of hot end lower clamping plates, and the 5N aluminum foils are firstly cut into special shapes through an electronic discharge machining process. The cut foils after washing with isopropanol alcohol bath and vacuum baking at 140 ℃ were placed on a special tool, and stacking was secured by a special bolt assembly. And removing the extra length of the 5N aluminum foil by using a high-speed end face milling process, assembling the extra length of the 5N aluminum foil with a cold end upper clamp plate 9-2, a cold end lower clamp plate 9-3, a hot end upper clamp plate 9-4 and a hot end lower clamp plate 9-5 which are machined in advance by adopting a fixed clamp, and welding by using a high-vacuum electron beam to form a whole.

The cold head support rod 10 is a Bipod support rod, the cold head of the refrigerator is connected with the support force plate through the Bipod support rod, and the Bipod support rod mainly comprises a titanium alloy base 14, an invar steel nest 15 and a hollow glass fiber reinforced plastic rod 16. The outer side is a glass fiber reinforced plastic rod 16, the invar steel nests 15 are positioned at the upper end and the lower end of the glass fiber reinforced plastic rod 16, are bonded with the glass fiber reinforced plastic rod 16 through structural adhesive, locally reinforce the glass fiber reinforced plastic rod 16, and are connected with the titanium alloy base 14 through bolts at two ends of the glass fiber reinforced plastic rod 16. The design of the Bipod supporting rod 10 not only meets the heat insulation requirement between the refrigerator and the main bearing plate, but also effectively unloads the thermal stress caused by the use from normal temperature installation and adjustment to low temperature through the design of the invar steel nesting and the flexible unloading groove on the titanium alloy base.

In order to meet the requirement of the satellite on micro-vibration, the compressors 1 are arranged oppositely, and the linear driving gas bearing compressors which are symmetrically arranged mainly comprise a rotor, a gas spring, a driving motor and the like. As shown in fig. 3, the refrigerating machine mainly comprises a magnetic steel framework 1-1, a piston 1-2, a piston cylinder 1-3, a split pipe 1-4, magnetic steel 1-5, a coil 1-6, an outer stator 1-7, an inner stator 1-8, a compression cavity 1-9 and an expansion cavity 1-10, wherein the split pipe 1-4 is used for being connected with a driven refrigerating machine. The magnetic steel 1-5 is adhered to the magnetic steel framework 1-1 and then connected with the piston 1-2 through a screw to form a rotor assembly, the coil 1-6 is wound firstly and then is not known to be in the outer stator 1-7, the outer stator 1-7 and the inner stator 1-8 are used as stator components of a motor, a magnetic field is generated after the coil is electrified, and the rotor assembly (comprising the piston 1-2) is driven to move after the coil interacts with the magnetic steel 1-5. The piston 1-2 moves in the piston cylinder 1-3 and compresses the gas working medium in the compression cavity 1-9. The working medium gas is helium, and the inflation pressure is 2.5-2.7 Mpa. The compressor operating parameters are shown in table 2. In order to ensure that the micro-vibration output of the opposed linear compressor meets the design index, a consistency control strategy needs to be carried out on various parameters of the opposed linear compressor, and the indexes of the various parameters are shown in a table 3.

On the basis, the supporting mode of the compressor is improved, the compressor 1 is connected with the camera bottom plate through secondary support, firstly, the compressor is connected with the transition substrate through a mode that the compressor bracket 2 is mechanically and fixedly supported, a polyimide heat insulation pad 4 is filled between the compressor and the transition substrate, and a screw 17 penetrates through the compressor positioning tool and the heat insulation pad and is screwed on the transition substrate. A specially-made titanium alloy damping vibration isolation gasket 5 with unloading grooves is adopted between the transition substrate and the camera bottom plate, and four through holes are reserved around the titanium alloy damping vibration isolation gasket to be connected with the compressor support plate in a threaded mode as shown in fig. 8. The middle of the vibration isolation gasket is of a hollow structure so as to be connected with a threaded hole which is screwed with the camera bottom plate from the upper end of the vibration isolation gasket. The main body of the vibration isolator is provided with at least 3 circles of unloading grooves, and the clearance of each unloading groove is larger than 0.5mm and smaller than 1 mm. The unloading groove is filled with damping glue, and the damping glue and the unloading groove generate damping dissipation when being subjected to external vibration input, so that the micro-vibration output by the compressor is further reduced, and the micro-vibration is restrained at a reasonable magnitude.

The gas bearing Stirling pulse tube refrigerator is compatible with the advantages of a gas bearing compressor and a pulse tube refrigerator, has the characteristics of compact structure, light weight, wear resistance, high reliability and high temperature stability, and can realize refrigeration in a 20K temperature region through a single compressor. However, to achieve the above performance, precise model selection and coupling optimization design are required, so that the compressor and the cold head are optimally matched, and the optimal performance of the refrigerator is exerted.

The opposed gas bearing compressor and the multistage pulse tube high-efficiency coupling structure realize the high-efficiency cooling of the 20K temperature area space. When the compressor-pulse tube coupling is optimized, firstly, a relation curve of the electric power of the compressor and the output PV power under different frequencies/different inflation pressures is obtained based on an RC load method, primary design is carried out on each stage of the pulse tube refrigerator based on a peak point, a linear compressor driving two-stage pulse tube refrigerator model of the whole machine is established based on Sage software, input parameters of the pulse tube refrigerator are changed, efficiency curves of the pulse tube under different frequencies, piston displacement, pressure ratio, PV power and inflation pressures are obtained, optimal parameters of pulse tube work are obtained, on the basis, pulse tube structures and fillers are optimized, real objects are put into production, a joint test is carried out based on the real objects and the compressor, input-output performance curves of the whole machine under different power inflation pressures and different frequencies are obtained, and multiple iteration optimization is carried out aiming at a single variable. The parameters resulting from the final optimization are shown in table 1.

TABLE 1.20K REFRIGERATOR-RELATED PARAMETERS

According to the phase modulation requirement, the first stage adopts room temperature phase modulation, the second stage adopts 80K low-temperature inertia tube phase modulation, and the first stage provides cold quantity. Considering that the gas bearing refrigerator has better performance when the frequency is higher than 50Hz and belongs to high frequency above 50Hz in the 20K temperature region, the inertia tube is adopted to replace a bidirectional air inlet structure for phase modulation, and further the phenomenon of unstable performance of the refrigerator caused by direct current is eliminated. The first stage of the refrigerator adopts a low-temperature inertia tube and an air reservoir for phase modulation, the heat dissipation temperature is 220K-normal temperature, the refrigeration temperature is 80K-130K, and a certain pre-refrigeration amount is provided for the heat regenerator and the inertia tube in the second season; the second-stage heat regenerator dissipates heat at 80-130K, the phase modulation device is a low-temperature inertia tube plus an air reservoir for phase modulation, the refrigeration temperature is 20K, and the first-stage cold head cools through a heat bridge.

As shown in fig. 3, the opposed compressor of the present invention is supported by the static pressure gas bearing technology, and the piston is supported by the gas bearing, so that not only the wear between the piston and the ejector and the cylinder is theoretically eliminated, but also the plate spring bearing part of the conventional stirling refrigerator is eliminated, thereby simplifying the structure and reducing the weight. The compressor adopts an axisymmetric Redlich linear motor, the motor adopts a moving magnet type drive, a small amount of magnets can provide high magnetic flux, the mass of the compressor can be reduced, the compressor is more efficient and compact, the side end effect of the linear motor is smaller, the corresponding eddy current loss is also small, and the efficiency higher than 92% can be achieved. And no axial force exists during no-load, which is beneficial to the stable operation of the motor. In this example, the design operating parameters of the compressor should meet the following criteria:

TABLE 2 compressor operating parameters

Parameter(s)	Index requirement
		Thrust of motor	≥80N
Specific thrust of motor	≥7N/A
		Compressor efficiency	≥80％
Bearing capacity of gas bearing	≥80％
		Gas bearing stiffness	≥1200N/mm

As shown in fig. 4, the two-stage pulse tube adopts a U-shaped arrangement with a compact structure and high refrigeration performance. A precooling pulse tube and low-temperature inertia tube phase modulation form is adopted to replace bidirectional inlet phase modulation, so that the phenomenon of unstable performance of the refrigerating machine caused by direct current is eliminated. According to the phase modulation requirement, the first stage adopts room temperature phase modulation (more than 220K), the second stage adopts 80K low-temperature inertia tube phase modulation, and the first stage provides the refrigerating capacity. The inertia pipe is made of red copper pipe, the room temperature gas reservoir is made of stainless steel, the low temperature gas reservoir is made of red copper, the inertia pipe and the first-stage cold head are integrally processed, and the inertia pipe is wound outside the gas reservoir to reduce occupied space. The same refrigerating working medium helium-4 is adopted at each stage of the two-stage pulse tube refrigerator.

As shown in fig. 5, the heat exchangers of each stage are all circular slit type heat exchangers, and the heat exchangers are formed by cutting red copper and oxygen-free copper wires with smaller thermal resistance. A screw with a conical head is added into a center hole formed in the process of linear cutting, so that the effect of flow guiding is achieved, and the defects of jet flow and heat exchange caused by the hole are reduced. When the flow passage has reducing diameter, the section of the slit heat exchanger is processed into a cone shape so as to reduce the flow loss caused by the transition of the special-shaped section to the maximum extent.

The pulse tube in the invention is a metal hollow tube. The hot end and the phase modulation structure are in the same temperature zone, the first-stage pulse tube works in the temperature zone of 80K-220K, and the second-stage pulse tube works in the temperature zone of 20K-80K. The wall of the vessel is made of 304 stainless steel, and the wall thickness is 0.3-0.35 mm. In order to ensure that gas can keep a better layered flow state when entering the pulse tube and avoid the jet phenomenon, a certain amount of brass wire mesh is filled at the cold end and the hot end of each stage of pulse tube for rectification.

In the aspect of regenerative filling, a stainless steel wire mesh with a larger porosity is selected for the 80K-220K regenerator, and the mesh number is 350-400, so that smaller resistance is ensured. For the heat regenerator in the temperature range of 20K-80K, the specific heat capacity of the filler must be increased to reduce the total heat capacity of the gas working medium. A screen with a lower porosity is used. Optionally, a screen pressed with a 500 mesh screen size of 25 microns and a 635 mesh screen size of 18 microns, with a porosity of about 0.6, may be used. The brass rectifying wire mesh is arranged at the inlet and the outlet of the flow passage, the thickness is generally not more than 5mm, the wire diameter is 0.05-0.1mm, and the mesh number is 100-200 meshes.

As shown in fig. 6, the refrigerator is connected with the main bearing plate through 3 sets of supporting rods. The supporting rod consists of a glass fiber reinforced plastic hollow tube with low thermal conductivity, an invar steel nest and 2 titanium alloy bases, wherein the glass fiber reinforced plastic rod is glued with the invar steel nest and then is connected with the titanium alloy bases through bolts. The design of the supporting rod meets the heat insulation requirement between the refrigerator and the main bearing plate, and meanwhile, the thermal stress brought by the use from normal temperature installation and adjustment to low temperature is effectively unloaded through the design of the flexible unloading groove on the titanium alloy base. The end part of the cold head is connected with the detector assembly through the 5N aluminum heat conduction band, the characteristic that the 5N aluminum heat conduction band is high in heat transfer efficiency in a 20-40K temperature zone (the heat conductivity is higher than 800W/mK) is fully utilized, and the efficient transfer of cold energy is realized. In the cold chain manufacturing process, the cold ends and the hot ends of the multilayer 5N aluminum foils with enough length allowance are respectively welded together in a pressing mode, the excessive allowance is cut, and then the aluminum foils are welded with the end heads as a whole.

In order to reduce the micro-vibration output of the refrigerator from the source, a consistency control measure is taken for 2 linear compressors of the opposite type compressor. In addition, in order to compensate for the lack of uniformity control (always having a gap) of 2 compressors, the vibration of the compressors can be further reduced by adjusting the phase between the relative movements of the compressors.

The vibration control measures of the compressor are summarized as shown in table 3 below.

TABLE 3 vibration control measures for opposed compressors

Besides, a damping vibration isolator can be arranged between the compressor support seat and the camera bottom plate to inhibit the vibration of the compressor from being output outwards. The compressor damping vibration-damping pad and the arrangement structure thereof are shown in fig. 7. By adopting a unique stress unloading structure, the external micro-vibration output of the compressor can be controlled below 15 mg.

In order to verify the correctness and feasibility of the invention, the development of the 20K gas bearing pulse tube refrigerator is completed based on the principle, a principle prototype is obtained, a probing test is carried out on the principle prototype through refrigeration, and the test result shows that: when the means of the refrigerating machine is not optimized, the refrigerating machine cannot be cooled to 20K and cannot meet the application requirement of aerospace, and after the scheme is adopted, the refrigerating machine can be smoothly cooled to below 20K and can generate refrigerating capacity of not less than 0.3W at 20K. Can meet the requirement of aerospace application.

The relationship between the displacement of the fixed piston, the pV work at the outlet of the compressor and the pV work at the hot end of the pulse tube refrigerator as a function of the length of the transfer tube is shown in FIG. 9. The effect of piston displacement on the electromagnetic force, the output sound function and the refrigerating performance of the compressor is shown in fig. 10, wherein the larger the piston displacement is, the larger the refrigerating capacity is, and the larger the electromagnetic force is. The piston displacement must not exceed 6mm due to the limitation of the compressor output and the electromagnetic force. The relationship graph of the performance and the inflation pressure of the two-stage pulse tube refrigerator driven by the double-piston air bearing linear compressor is shown in FIG. 11.

Therefore, the gas bearing pulse tube refrigerator technology can effectively meet the requirement of the space air telescope on a refrigerator system in a 20K temperature region, is beneficial to promoting the application of the gas bearing pulse tube refrigerator technology in China in the fields of aerospace low-temperature engineering and aerospace remote sensing, and provides a feasible way for the weight reduction of the whole machine, high efficiency and long service life and the improvement of reliability.

The working frequency of the compressor is 52Hz-55Hz, the piston stroke of the compressor is 6.5mm-7mm, the inflation pressure is 2.6-2.7Mpa, and the pressure ratio is maintained at 1.10 +/-0.02. The thrust of the motor of the compressor is more than or equal to 80N, the specific thrust of the motor is more than or equal to 7N/A, and the efficiency of the compressor is more than or equal to 80%. The pressure of the air film in the compressor is more than or equal to 5N, and the rigidity of the air film is more than or equal to 1200N/mm. The sound work efficiency of the compressor reaches more than 52 percent.

The secondary pulse tube cold head structure adopts a precooling pulse tube and low-temperature inertia tube phase modulation form to replace bidirectional inlet phase modulation, thereby eliminating the unstable performance of the refrigerating machine caused by direct current. The stainless steel wire mesh with larger porosity is selected for the 80K-220K heat regenerator, and the mesh number is 350-400, so that smaller resistance is ensured. For the heat regenerator in the temperature range of 20K-80K, the specific heat capacity of the filler must be increased to reduce the total heat capacity of the gas working medium. A screen with a lower porosity is used. Optionally, a screen pressed with a 500 mesh screen size of 25 microns and a 635 mesh screen size of 18 microns, with a porosity of about 0.6, may be used.

The pulse tube cold head structure is characterized in that heat exchangers at all levels are round slit type heat exchangers, and the heat exchangers are formed by cutting red copper and oxygen-free copper wires with smaller thermal resistance. A screw with a conical head is added into a center hole formed in the process of linear cutting, so that the effect of flow guiding is achieved, and the defects of jet flow and heat exchange caused by the hole are reduced. When the flow passage has reducing diameter, the section of the slit heat exchanger is processed into a cone shape so as to reduce the flow loss caused by the transition of the special-shaped section to the maximum extent. In order to ensure that gas can keep a better layered flow state when entering the pulse tube and avoid the jet phenomenon, a certain amount of brass wire mesh is filled at the cold end and the hot end of each stage of pulse tube for rectification.

The two-stage cold head structure adopts a Bipod supporting structure to realize low cold loss temperature equalization design, the supporting rod consists of a glass fiber reinforced plastic hollow tube with low thermal conductivity, an invar steel nest and 2 titanium alloy bases, the glass fiber reinforced plastic rod and the invar steel nest are glued and then connected with the titanium alloy bases through bolts, and the support and vibration separation is realized while the support heat leakage is reduced. The cold end of the secondary cold head is connected with the detector substrate through a 5N aluminum heat conduction chain, and the compatibility design of ultrahigh heat conductivity and efficient vibration reduction of a 20K temperature zone is realized.

The compressor supporting and vibration isolating scheme of the present invention has vibration controlling measures for opposite compressor realized mainly in the control of compressor consistency, and the micro vibration of the compressor is further reduced through regulating the phase between the relative motion of the compressor. On the basis, a unique heat insulation and vibration isolation supporting mode is adopted for the compressor and the camera floor, so that the micro-vibration output of the compressor is suppressed to be below 10 mg.

In the process of compressor-pulse tube coupling optimization, parameters such as high-temperature section regenerative filler, low-temperature section regenerative filler (including filler types, filler compositions, filler structures and filling forms), working frequency, inflation pressure, primary pulse tube size, secondary pulse tube size, flow channel structure, compressor heat dissipation structure, compressor piston weight, piston stroke, coil turns and the like are adjusted, and finally an optimized curve of a compressor-cold head is obtained, when the length of a connecting tube is not less than 500mm, 0.05W @20K refrigerating capacity is realized at normal temperature, and 0.33W @20K refrigerating capacity is realized at low temperature (the temperature of the hot end of a primary cold head is 223K).

The present invention has not been described in detail, partly as is known to the person skilled in the art.

Claims

1. A refrigerator system suitable for a 20K temperature zone of an infrared camera of a space astronomical telescope is characterized by comprising a compressor (1), a compressor bracket (2), a compressor supporting plate (3), a compressor heat insulation pad (4), a compressor vibration reduction pad (5), a primary cold head (6), a hot end radiating surface (7), a secondary cold head (8), a flexible cold chain (9) and a cold head supporting rod (10);

the compressor (1) is fixed on the compressor support (2), the lower plate of the compressor support (2) is connected with the compressor support plate (3) through the compressor heat insulation pad (4), and the bottom of the compressor support plate (3) is provided with the compressor vibration reduction pad (5); the compressor (1) is connected with hot end heat exchangers (6-6) through a three-way transmission pipe, and the hot end heat exchangers (6-6) are respectively connected with a primary cold head (6) and a secondary cold head (8); the press and the cold finger connecting pipe adopt argon arc welding, and a flexible cold chain (9) is connected with a secondary cold head (8); the heat radiating surface (7) at the hot end transfers or radiates the heat generated in the refrigeration process to the outside; the cold head support rod (10) is used for supporting the first-stage cold head (6) and the second-stage cold head (8).

2. The refrigerator system suitable for the 20K temperature zone of the infrared camera of the space astronomical telescope according to claim 1, wherein the primary cold head (6) comprises a primary room temperature heat exchanger (6-6-1), a primary pulse tube hot end heat exchanger (6-6-2), a primary heat regenerator (6-3), a primary pulse tube (6-4), a primary cold end heat exchanger (6-5), a primary air reservoir (6-1) and a primary inertia tube (6-2), the primary air reservoir (6-1) is arranged on the normal temperature zone or the hot end heat exchanger (6-6) and fixed on the compressor support plate (3) or the hot end heat exchanger (6-6); the primary hot end heat exchanger comprises two paths, namely a primary room temperature heat exchanger (6-6-1) and a primary pulse tube hot end heat exchanger (6-6-2), wherein the primary room temperature heat regenerator (6-6-1) is connected with one side of the primary cold end heat exchanger (6-5) through a primary heat regenerator (6-3), the primary pulse tube hot end heat exchanger (6-6-2) is connected with the other side of the primary cold end heat exchanger (6-5) through a primary pulse tube (6-4), and a U-shaped gas flow channel is arranged in the primary cold end heat exchanger (6-5) to communicate the two sides; the primary inertia pipe (6-2) is used for connecting the primary gas reservoir (6-1) and the primary pulse tube (6-4).

3. The refrigerator system suitable for the 20K temperature zone of the infrared camera of the space astronomical telescope according to claim 2, wherein the secondary cold head (8) comprises a secondary heat regenerator precooling section (8-1), a precooling heat exchanger (13), a secondary inertia tube (8-2), a secondary heat regenerator low temperature section (8-3), a secondary pulse tube (8-4), a secondary cold end heat exchanger (8-5), a secondary room temperature heat exchanger (6-6-3), a secondary pulse tube hot end heat exchanger (6-6-4) and a secondary air reservoir (8-6); the secondary cold end heat exchanger (8-5) directly outputs cold energy outwards, one end of the secondary cold end heat exchanger (8-5) is connected with the low temperature section (8-3) of the secondary heat regenerator, the other end of the secondary cold end heat exchanger is connected with one end of the secondary pulse tube (8-4), and a U-shaped flow channel for helium to flow and exchange heat is arranged in the secondary cold end heat exchanger (8-5); the other side of the secondary pulse tube (8-4) is connected with a secondary gas reservoir (8-6) through a secondary inertia tube (8-2), the secondary gas reservoir (8-6) is fixed on a primary cold end heat exchanger (6-5), and precooling is provided by the primary cold end heat exchanger (6-5); the primary cold end heat exchanger (6-5) is connected through a thermal bridge (11) to transmit a cold chain to the secondary precooling heat exchanger (13) and the secondary pulse tube hot end heat exchanger (6-6-4) so as to provide precooling for the secondary stage; the secondary heat regenerator is divided into a secondary heat regenerator precooling section (8-1) and a secondary heat regenerator low-temperature section (8-3) according to the lap joint position of the heat bridge (11), and the hot end heat exchanger (6-6) is connected with the secondary heat regenerator precooling section (8-1).

4. The refrigerating machine system suitable for the 20K temperature zone of the infrared camera of the space astronomical telescope as claimed in claim 3, wherein the primary pulse tube (6-4) and the secondary pulse tube (8-4) are filled with rectification wire nets.

5. The refrigerator system suitable for the 20K temperature zone of the infrared camera of the space astronomical telescope as claimed in claim 4, wherein the primary heat regenerator (6-3), the secondary heat regenerator pre-cooling section (8-1) and the secondary heat regenerator low temperature section (8-3) are filled with wire meshes, and the filled wire meshes are made by combining a wire mesh formed by wire drawing weaving and foam molding of ErPr materials with a pressed stainless steel wire mesh and a brass rectifying wire mesh.

6. The refrigerator system suitable for the 20K temperature zone of the infrared camera of the space astronomical telescope according to claim 5, wherein the flexible cold chain (9) is a 5N aluminum flexible cold chain, and comprises a plurality of layers of aluminum foils (9-1), a cold end upper clamp plate (9-2), a cold end lower clamp plate (9-3), a hot end upper clamp plate (9-4) and a hot end lower clamp plate (9-5), the 5N aluminum foils are cut into a set shape by an electronic discharge machining process, the cut foils after cleaning by an isopropanol alcohol bath and vacuum baking at 140 ℃ are placed on a tool, the extra length of the 5N aluminum foils is removed by using an end face milling process, the 5N aluminum foils and the cold end upper clamp plate (9-2), the cold end lower clamp plate (9-3), the hot end upper clamp plate (9-4) and the hot end lower clamp plate (9-5) are assembled by using a fixed clamp, and welded by high vacuum electron beam.

7. The refrigerator system suitable for the 20K warm area of the infrared camera of the space astronomical telescope as claimed in claim 6, wherein the cold head support rod (10) is a Bipod support rod, and comprises a titanium alloy base (14), an invar steel nest (15) and a hollow glass steel rod (16); the outer side of the glass fiber reinforced plastic rod is provided with a glass fiber reinforced plastic rod (16), the invar steel nests (15) are respectively positioned at the upper end and the lower end of the glass fiber reinforced plastic rod (16), are bonded with the glass fiber reinforced plastic rod (16) through structural adhesive, locally reinforce the glass fiber reinforced plastic rod (16), and are connected with the titanium alloy base (14) through bolts.

8. The refrigerating machine system suitable for the 20K temperature zone of the infrared camera of the space astronomical telescope according to claim 7, wherein the compressor (1) is an opposed gas bearing compressor and comprises a magnetic steel framework (1-1), a piston (1-2), a piston cylinder (1-3), a split tube (1-4), magnetic steel (1-5), a coil (1-6), an outer stator (1-7), an inner stator (1-8), a compression cavity (1-9) and an expansion cavity (1-10), the split tube (1-4) is used for connecting a driven refrigerating machine, the magnetic steel (1-5) is bonded on the magnetic steel framework (1-1) and then connected with the piston (1-2) to form a rotor assembly; the coils (1-6) are wound firstly and then arranged in the outer stators (1-7); the outer stators (1-7) and the inner stators (1-8) are used as stator parts of the motor, generate a magnetic field after being electrified, and drive the rotor assembly to move after interacting with the magnetic steel (1-5); the piston (1-2) moves in the piston cylinder (1-3) and compresses a gas working medium in the compression cavity (1-9); the working medium gas is helium, and the inflation pressure is 2.5-2.7 Mpa.

9. The refrigerator system suitable for the 20K temperature zone of the infrared camera of the space astronomical telescope as claimed in claim 8, wherein the compressor heat insulation pad (4) is a polyimide heat insulation pad.

10. The refrigerator system suitable for the 20K temperature zone of the infrared camera of the space astronomical telescope as claimed in claim 9, wherein the compressor vibration damping pad (5) is a titanium alloy damping vibration isolation gasket provided with an unloading groove, and four through holes are reserved on the periphery of the compressor vibration damping vibration isolation gasket so as to be in threaded connection with the compressor support plate; the middle of the compressor damping pad (5) is of a hollow structure, and the compressor damping pad main body is provided with at least 3 circles of unloading grooves; and filling damping glue in the unloading groove.