CN108800643B - Pulse tube type free piston Stirling refrigerator and refrigeration method - Google Patents
Pulse tube type free piston Stirling refrigerator and refrigeration method Download PDFInfo
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- CN108800643B CN108800643B CN201810437352.1A CN201810437352A CN108800643B CN 108800643 B CN108800643 B CN 108800643B CN 201810437352 A CN201810437352 A CN 201810437352A CN 108800643 B CN108800643 B CN 108800643B
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B9/00—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point
- F25B9/14—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point characterised by the cycle used, e.g. Stirling cycle
- F25B9/145—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point characterised by the cycle used, e.g. Stirling cycle pulse-tube cycle
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B2309/00—Gas cycle refrigeration machines
- F25B2309/14—Compression machines, plants or systems characterised by the cycle used
- F25B2309/1412—Pulse-tube cycles characterised by heat exchanger details
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Abstract
According to the pulse tube type free piston Stirling refrigerator and the refrigerating method, the pulse tube type free piston Stirling refrigerator comprises a linear motor, a compression unit, an expansion unit and a frame. The refrigerating method of the pulse tube type free piston Stirling refrigerator comprises the following steps: the expansion piston moves upwards from the bottom dead center to the top dead center; the compression piston moves to a lower dead point; the expansion piston pushes the sound waves in the expansion chamber back into the pulse tube; the working medium gas expands in the pulse tube to absorb heat, so as to generate a refrigeration effect; the lowest refrigeration temperature is reached at the top of the pulse tube near the flow director; the generated cold energy is led out to a cold environment through a cold end heat exchanger; the acoustic wave working medium returns to the heat regenerator along the original path and fully contacts with the filler for heat exchange, and returns to the compression cavity again to wait for the next compression after absorbing the heat in the heat regenerator.
Description
Technical Field
The invention belongs to the field of refrigeration, and particularly relates to a pulse tube type free piston Stirling refrigerator and a refrigeration method.
Background
The low-temperature refrigerator is used for refrigeration as an important method for obtaining low temperature, and is widely applied to the fields of aviation, military, superconductivity, communication, electronics, metallurgy, industrial gas liquefaction, biological medical treatment and the like. In particular, in recent years, the application requirements of the cryogenic refrigerator in aerospace are more and more obvious due to the vigorous development of the aerospace industry in China.
Life science and space material science experiments are important components of space scientific research. According to statistics, experimental tasks related to human medical science and biotechnology in international space station scientific research experiments from 9 months to 3 months in 2000 account for more than half of all research activities, and at the beginning of implementation of manned space missions in China, the requirements for development of space low-temperature storage devices are provided aiming at the requirements of space life science and medical related scientific research work. In the experimental research of space science such as space life science, space material science and the like, experimental samples are required to be stored in a low-temperature environment with controllable temperature in a cabin of a space station at a preparation stage, an intermediate process and after the experiment is finished. It can be said that space cryocoolers have become the standard configuration for space stations. At present, in refrigeration and freezing equipment which is put into use by NASA at International Space Station (ISS), the main refrigeration methods include thermoelectric refrigeration, inverted brayton refrigeration, and stirling cycle refrigeration.
GLACER (general Laboratory Active Cryogenic ISS experimental regenerator) is a first low-temperature storage device developed by NASA (national air terminal for refrigeration) at-80 ℃ and can be simultaneously used for two platforms of a space station and an airship, a free piston Stirling refrigerator is adopted for refrigeration, and the refrigeration temperature of 4 ℃ to-95 ℃ can be realized in an air mode; in the water cooling mode, low-temperature storage of 4 ℃ to-160 ℃ can be realized. To further improve the low temperature storage capacity during on-track and up and down, NASA developed a single module cell size (273x460x522mm) low temperature storage product Polar in cooperation with birmingham university, alabama. The device also adopts the free piston Stirling refrigerator as a cold source, can realize low-temperature storage at minus 80 ℃ and sample transportation, and has the maximum storage volume of 12.7L.
The theoretical refrigeration efficiency of the Stirling refrigerator is equal to the Carnot efficiency, and the efficiency of the Stirling refrigerator in actual operation is the highest efficiency of all the low-temperature refrigerators at present. The free piston Stirling refrigerator structure is proposed by William Beam in the 60 th of the 20 th century, and is mainly characterized in that the technologies of linear compressor driving, flexible spring supporting, gap sealing and gas bearing combination and the like are adopted, so that the free piston Stirling refrigerator structure has the advantages of compact structure, low noise, long service life, high reliability and the like. The highest relative carnot efficiency of commercial free piston Stirling cryocoolers developed by Sunpower corporation in the liquid nitrogen temperature region has broken through 20%, and free piston Stirling cryocoolers developed by Stirling Ultracold corporation (original Global Cooling corporation) are adopted by cryocoolers. 2012, Stirling Ultracold corporation compares a two-stage cascade cryocooler with a Stirling cryocooler, and finds that the cryocooler using a free piston Stirling refrigerator has significant advantages in energy saving, and compared with the conventional cryocooler, the Stirling cryocooler can save more than 50% of energy.
As can be seen from the current application situation of the free piston Stirling refrigerator, the free piston Stirling refrigerator has a good application prospect, is particularly worthy of attention in the aspect of space refrigeration application, and aims at the field of low-temperature refrigerators, the main refrigeration temperature region of the free piston Stirling refrigerator is 120-200K, while the low-temperature Stirling refrigerator researched at home and abroad at present is mainly near the liquid nitrogen temperature region. In particular, the research of small-sized low-temperature mechanical refrigerators for refrigerating medium-temperature regions (120K-200K) by domestic scientific research institutions is relatively insufficient.
Because space refrigeration has strict requirements on energy consumption, the improvement of the efficiency of the refrigerator is always the mainstream research direction of the space refrigerator, the mainstream space refrigerator at present is mainly a Stirling refrigerator and a pulse tube refrigerator, the theoretical refrigeration efficiency of the Stirling refrigerator and the pulse tube refrigerator is compared, and the efficiency of the pulse tube refrigerator working at the same temperature limit is always lower than that of the Stirling refrigerator from the thermodynamic perspective.
The pulse tube refrigerator has lower efficiency than the Stirling refrigerator mainly because the pulse tube refrigerator 'feeds back' the expansion work of gas to the compression cavity unlike the structure that the Stirling refrigerator has an expansion piston, and the expansion work at the hot end of the pulse tube is mainly dissipated to the environment in the form of heat through a phase modulation mechanism such as an inertia tube, a small hole and the like, so that the pulse tube refrigerator has lower efficiency.
Disclosure of Invention
In order to improve the refrigeration efficiency of the pulse tube refrigerator while ensuring the advantages of the pulse tube refrigerator, the sound-power recovery type pulse tube refrigerator is produced. For the occasion with small cold quantity requirement, the sound power dissipated by the pulse tube refrigerator in the phase modulation mechanism is very small, the significance of sound power recovery is not very obvious, for the high-power pulse tube refrigerator refrigerated in a medium-high temperature area, the sound power dissipated by the hot end is very considerable, and the effective recovery of the part of sound power is hopeful to greatly improve the refrigeration efficiency. Therefore, the sound power recovery type pulse tube refrigerator has higher research value in the aspect of large cooling capacity in the middle temperature region.
The invention aims to provide a pulse tube type free piston Stirling refrigerator and a refrigerating method.
The invention provides a pulse tube type free piston Stirling refrigerator, which is characterized by comprising a linear motor, a compression unit, an expander unit and a frame, wherein the frame comprises a flange, a piston tube arranged in the flange and a base, the flange is in a disc shape, one side of the flange is also provided with a concentric small disc, the base is in a cylindrical shape, one end of the base is connected with the other side of the flange, the other end of the base is a free end, the central line of the base is superposed with the central line of the flange, the piston tube is a straight tube, one end of the outer side of the piston tube is opened and positioned at the outer side of the small disc, one end of the inner side of the piston tube is opened and positioned in the base, the piston tube is internally provided with a piston cavity, the piston cavity is provided with a plurality of through holes which are vertical to the axis of the piston tube and penetrate through the wall of the piston tube, the linear motor comprises an outer yoke, the rotor is arranged in the gap, the compression unit is provided with a compression piston and a compression piston spring, the compression piston spring is fixedly connected with the frame through a connecting piece, the compression piston is arranged in the piston tube, one end of the compression piston is connected with the rotor and is connected with the compression piston spring, the other end of the compression piston is a free end, the expander unit comprises an expansion piston, an expansion piston spring, an expansion piston rod, a first-stage hot end heat exchanger, a second-stage hot end heat exchanger, a heat regenerator, a pulse tube, a cold end heat exchanger and a fluid director, the first-stage hot end heat exchanger is cylindrical and is sleeved on the outer wall of the piston tube and arranged on the end surface of the small disc, one end of the pulse tube is connected with one end outside the piston tube, the other end of the pulse tube is connected with the cold end heat exchanger, the heat regenerator is cylindrical and is arranged, the fluid director is arranged at the top end of the pulse tube and is positioned in the pulse tube, the expansion piston is arranged in the piston tube, the expansion piston spring is fixedly connected with the rack through a connecting piece, one end of the expansion piston rod is connected with the expansion piston, the other end of the expansion piston rod penetrates through the compression piston and the compression piston spring and then is connected with the expansion piston spring, the compression piston, the expansion piston and the piston cavity form a compression cavity, and the compression piston, the secondary hot end heat exchanger and the piston cavity form an expansion cavity.
The invention provides a refrigeration method of a pulse tube type free piston Stirling refrigerator, which is characterized by comprising the following steps of: the expansion piston moves upwards from the bottom dead center to the top dead center; the compression piston moves to a lower dead point; the expansion piston pushes the sound waves in the expansion chamber back into the pulse tube; the working medium gas expands in the pulse tube to absorb heat, so as to generate a refrigeration effect; the lowest refrigeration temperature is reached at the top of the pulse tube near the flow director; the generated cold energy is led out to a cold environment through a cold end heat exchanger; the acoustic wave working medium returns to the heat regenerator along the original path and fully contacts with the filler for heat exchange, and returns to the compression cavity again to wait for the next compression after absorbing the heat in the heat regenerator.
In addition, the refrigeration method of the pulse tube type free piston stirling cryocooler provided by the invention can also be characterized in that the regenerator is cylindrical and is made of a polyester film.
In addition, the refrigerating method of the pulse tube type free piston Stirling refrigerator provided by the invention can also be characterized in that the cold end heat exchanger and the heat regenerator are also provided with first filter layers which are cylindrical and made of stainless steel wire meshes.
In addition, the refrigeration method of the pulse tube type free piston Stirling refrigerator provided by the invention can also have the characteristic that the hot end heat exchanger and the cold end heat exchanger are also provided with second filter layers, and the second filter layers are cylindrical and are made of degreased wool.
Action and Effect of the invention
The coaxial pulse tube type free piston Stirling refrigerator comprises a driving unit, a compression unit and an expander unit.
The coaxial pulse tube type free piston Stirling refrigerator cancels the longer low-temperature expansion piston of the traditional free piston Stirling refrigerator and is replaced by the work recovery expansion piston working in a shorter room temperature area. The expansion cylinder of the free piston Stirling refrigerator becomes a pulse tube of a pulse tube cold finger, a laminar flow guider is arranged at the cold end of the pulse tube, and a secondary hot end heat exchanger is arranged at the hot end of the pulse tube. The change combines the advantages of the free piston Stirling refrigerator and the pulse tube refrigerator, and eliminates pumping loss, shuttle loss and axial heat conduction loss caused by the low-temperature expansion piston by eliminating the expansion piston which moves at a high frequency at a cold end and a hot end. The problem of sound power recovery of the pulse tube refrigerator is solved by arranging the shorter room-temperature expansion piston at the hot end, and therefore when the sound power of the cold end is completely recovered, the theoretical efficiency of the novel pulse tube type free piston Stirling refrigerator is Carnot cycle efficiency. Meanwhile, the low-temperature expansion piston is eliminated, so that the manufacturing difficulty of the refrigerating machine is reduced, and the quality of the whole machine is reduced.
Drawings
FIG. 1 is a schematic cross-sectional view of a pulse tube type free piston Stirling cryocooler according to an embodiment of the present invention;
FIG. 2 is a perspective view of a frame in an embodiment of the invention;
FIG. 3 is a view from the direction A of FIG. 2;
FIG. 4 is a cross-sectional view C-C of FIG. 3;
FIG. 5 is a schematic cross-sectional perspective view of a frame in an embodiment of the invention;
FIG. 6 is a schematic cross-sectional perspective view of one embodiment of a gantry of the present invention;
FIG. 7 is a schematic cross-sectional view of a pulse tube type free piston Stirling cooler according to a second embodiment of the present invention;
FIG. 8 is a perspective view of a second embodiment of the present invention;
FIG. 9 is a view from the direction B of FIG. 8;
FIG. 10 is a cross-sectional view taken along line D-D of FIG. 9;
FIG. 11 is a schematic cross-sectional view of an integrated airframe according to a sixth embodiment; and
FIG. 12 is a schematic cross-sectional view of an integrated airframe in accordance with an embodiment seven.
Detailed Description
In order to make the technical means, the creation characteristics, the achievement purposes and the effects of the invention easy to understand, the following embodiments are specifically described in the following embodiments of the free piston stirling cryocooler of the coaxial pulse tube type with reference to the attached drawings.
Example one
As shown in fig. 1, the coaxial pulse tube type free piston stirling cooler includes a linear motor 1, a compression unit, an expander unit, an undamped dynamic vibration absorbing unit 4, a frame 50, and a housing 60.
As shown in fig. 2, 3, 4 and 5, the frame 50 includes a flange 52, a piston tube 51 provided in the flange 52 and a base 53,
the flange 52 is in a disc shape, one side of the flange is also provided with a concentric small disc 521, and the flange 52 is uniformly provided with a plurality of connecting through holes.
The base 53 is cylindrical, one end of the base is connected with one side of the flange 52, the other end of the base is a free end, the center line of the base 53 is overlapped with the center line of the flange 52, a plurality of connecting screw holes are formed in the free end of the base 53, and in the embodiment, the base 53 is four support legs which are wound into a cylindrical shape.
The piston tube 51 is a straight tube, the opening at one end of the outer side is positioned at the outer side of the small disc 521, the opening at one end of the inner side is positioned in the base 53, a piston cavity is arranged in the piston tube 51, a plurality of through holes 511 which are perpendicular to the axis of the piston tube and penetrate through the wall of the piston tube are arranged on the piston cavity, and in the embodiment, the cross sections of the through holes 511 are arc grooves, and the number of the through holes is 3.
As a modification, as shown in fig. 6, the frame 50A has a plurality of through holes 511A therein, and the cross section of the through hole 511A is an elongated hole having a length direction parallel to the axis of the piston tube 51.
The linear motor 1 comprises an outer yoke 11, an inner yoke 14 and a rotor, wherein the outer yoke 11 and the inner yoke 14 are respectively arranged on the frame, a gap is formed between the outer yoke and the inner yoke, the rotor is arranged in the gap, and the rotor comprises a permanent magnet 13 and a permanent magnet support 15.
As shown in fig. 1, the linear motor 1 mainly includes an outer yoke 11, a coil 12, a permanent magnet 13, an inner yoke 14, and a permanent magnet support 15, the mover includes a permanent magnet 13, a permanent magnet support 15, a connecting member 16, a fixing nut 18, a compression piston 19, and a compression piston plate spring 17 (1/3, which only takes the plate spring mass when calculating the mover mass), and the permanent magnet support 15 is connected to the permanent magnet 13, and is connected to the compression piston 19 and the connecting member 16 through a screw thread. The outer yoke iron 11 and the inner yoke iron 14 are made of soft magnetic materials, such as electrically pure iron and silicon steel sheets, and the permanent magnet 13 is made of permanent magnetic materials, such as Ru Fe B and Al Ni Co permanent magnetic materials. The outer yoke 11, the coil 12, the permanent magnet 13, and the inner yoke 14 are all annular and are arranged coaxially. The outer yoke 11 and the inner yoke 14 are respectively disposed on the frame 50, and a gap is formed between the outer yoke and the inner yoke, and the mover is disposed in the gap.
When the coil is energized with a direct current, the outer yoke iron 11 and the inner yoke iron 14 form a magnetic loop, thereby generating magnetic poles on the outer yoke iron 11 and the inner yoke iron 14. When alternating current is supplied to the coil, the permanent magnet 13 is subjected to alternating electromagnetic force to perform reciprocating linear motion. When the permanent magnet 13 makes reciprocating linear motion, the compression piston 19 is driven to make reciprocating linear motion, and the compression piston plate spring 17 provides axial reciprocating elastic force and radial support.
The compression unit comprises a connector 16, a compression piston plate spring 17, a fixing nut 18 and a compression piston 19. The compression piston plate spring 17 is connected with the connecting piece 16 through the fixing nut 18, the compression piston plate spring 17 is fixedly connected with the rack 50 through the connecting piece, the compression piston 19 is arranged in the piston cavity, one end of the compression piston is connected with the rotor and is connected with the compression piston spring 17, and the other end of the compression piston is a free end.
The expander unit comprises an expansion piston 21, an expansion piston plate spring 22, a piston rod 23, a primary hot end heat exchanger 26, a secondary hot end heat exchanger 33, a heat regenerator 25, a pulse tube 31, a cold end heat exchanger 24 and a cold finger shell 35,
the primary hot end heat exchanger 26 is cylindrical, is sleeved on the outer wall of the piston pipe 51 and is arranged on the end face of the small circular disc 521, the primary hot end heat exchanger 26 and the frame 50 are of a split structure, and the primary hot end heat exchanger 26 is in interference fit with the outer wall of the piston pipe 51.
One end of the pulse tube 31 is connected with one end of the outer side of the piston tube 51, the other end is connected with the cold-end heat exchanger 24,
the regenerator 25 is a cylinder with an annular section and is arranged outside the pulse tube 31, one end of the regenerator is connected with the cold-end heat exchanger 24, and the other end of the regenerator is connected with the first-stage hot-end heat exchanger 26. The heat regenerator 25 is made of any one of polyester film, nylon and polytetrafluoroethylene material, and in the embodiment, the heat regenerator 25 is made of polyester film, and the thickness of the polyester film is 20-50 μm.
The secondary hot end heat exchanger 33 is arranged in the pulse tube 31 and located at the joint of the pulse tube 31 and the piston tube 51, the secondary hot end heat exchanger 33 and the frame 50 are of a split structure, and the secondary hot end heat exchanger 33 is in interference fit with the inner wall of the piston tube 51.
The expansion piston 21 is arranged in the piston tube 51, the expansion piston plate spring 22 is fixedly connected with the frame 50 through a connecting piece, one end of the piston rod 23 is connected with the expansion piston 21, the other end of the piston rod passes through the compression piston 19 and the compression piston plate spring 17 and then is connected with the expansion piston plate spring 22,
compression piston 19, expansion piston 21 and piston chamber constitute the compression chamber, and compression piston 19, second grade hot junction heat exchanger 33 and piston chamber constitute the expansion chamber, and the expansion chamber is coaxial arrangement with the compression chamber.
The cold finger shell 35 is arranged outside the primary hot end heat exchanger 26, the heat regenerator 25 and the cold end heat exchanger 24, the shell 60 is arranged outside the frame 50 and the expander unit 30, and the shell 60, the cold finger shell 35 and the frame 50 are connected into a whole through connecting pieces.
The radiator 27 is located outside the first-stage hot-end heat exchanger 26 and is arranged on the cold finger shell 35, and the first-stage hot-end heat exchanger 26 transfers heat to the radiator 27 on the outer side through the cold finger shell 35 and finally releases the heat to the environment.
The undamped dynamic vibration absorbing unit 4 is connected with the housing 60 and is arranged outside the housing 60 for damping the refrigerator.
The motion process of the expansion piston and the compression piston and the gas flow process are as follows:
the expansion piston plate spring 22 is fixed to the piston rod 23, and the expansion piston 21 is connected to the piston rod 23.
The expansion piston 21 is driven by pure air, the refrigeration effect is generated by utilizing the displacement phase difference between the expansion piston 21 and the compression piston 19, the displacement of the expansion piston 21 leads the displacement of the compression piston 19 by 70-100 degrees, and the displacement phase difference is reduced to 50-60 degrees in a low-temperature region (the temperature of a cold head is below minus 100 degrees). Since the linear motor is excited by sine alternating current, the motion of the expansion piston 21 and the compression piston 19 is also continuous motion in a sine curve, but in order to explain the working principle of the linear motor, the expansion piston 21 and the compression piston 19 are assumed to make intermittent jumping motion according to a cycle rule.
And (3) sound wave compression process: the expansion piston 21 stays still at the top dead center, the compression piston 19 moves upwards from the bottom dead center, at the moment, sound waves in the main compression cavity 29 are compressed and flow into the first-stage hot end heat exchanger 26 at the outer side of the cylinder, heat generated in the compression process is released to the first-stage hot end heat exchanger 26, the first-stage hot end heat exchanger 26 transfers the heat to the radiator 27 at the outer side through the outer shell, and finally the heat is released to the environment. Ideally, the cylinder and the outer shell are completely heat-conducting, and meanwhile, the heat exchange area between the primary hot-end heat exchanger 26 and the radiator 27 is infinite, so that the temperature of the working medium is kept unchanged. In practice, however, isothermal compression is not possible and intermittent movement of the expansion piston 21 is not possible, the expansion piston 21 having already begun to move downward as the compression piston 19 moves upward.
The heat release process of the heat regenerator is as follows: the compression piston 19 does not move after moving to the top dead center, the expansion piston 21 moves downwards, at the moment, sound waves pass through the heat regenerator 25 and are fully contacted with the filler in the heat regenerator 25 for heat exchange, heat is released into the heat regenerator 25, at the moment, the temperature of the heat regenerator 25 is increased, and the temperature and the pressure of the sound waves are reduced. However, in the actual heat exchange process, the heat exchange process of the regenerator 25 is not constant volume, and complete heat exchange between the sound wave and the filler of the regenerator 25 is not possible.
The sound wave laminar flow process: after passing through the cold side heat exchanger 24, the gas passes through the flow director 32 and enters the pulse tube 31 in a laminar flow to push the gas in the pulse tube 31 towards the expansion chamber 28. After the gas is compressed, the pressure and temperature rise. The generated heat is transferred radially through the secondary hot side heat exchanger 33 to the primary hot side heat exchanger 26 and ultimately to the radiator 27 and released to the environment. The gas in the expansion cavity 28 expands to do work, and assists in pushing the expansion piston to a lower dead center, and the work recovery compression cavity 34B becomes small, so that the effect of recovering acoustic work is achieved. In practice, the compression piston 19 does not remain at top dead centre but moves downwards with the expansion piston 21, but it is noted that the two do not move in the same direction but that the expansion piston leads the compression piston by a certain phase angle.
The sound wave refrigeration process: the expansion piston 21 starts to move upwards from the bottom dead center to the top dead center, the compression piston 19 moves to the bottom dead center, the expansion piston 21 pushes sound waves in the expansion cavity 28 back to the pulse tube 31, gas expands in the pulse tube to absorb heat, a refrigeration effect is generated, and the lowest refrigeration temperature is reached at the top of the pulse tube 31 close to the fluid director 32. The generated cold is led out to the cold environment through the cold end heat exchanger 24. The acoustic wave working medium returns to the heat regenerator 25 along the original path and fully contacts with the filler for heat exchange, and returns to the main compression cavity 29 again to wait for the next compression after absorbing the heat in the heat regenerator 25. The temperature and pressure of the acoustic wave increase and the temperature of regenerator 25 decreases. In practice, the expansion piston 21 does not reach the top dead center when the compression piston 19 reaches the bottom dead center, but during the return to the top dead center, but it still leads the compression piston 19 in the phase of the displacement wave.
The embodiment is suitable for the refrigerating temperature above 220K (-53 ℃), and can provide the refrigerating capacity of 50W-200W.
Example two
As shown in fig. 7, the coaxial pulse tube type free piston stirling cooler includes a linear motor 1, a compression unit, an expander unit, an undamped dynamic vibration absorbing unit 4, a frame 50B, and a housing 60.
As shown in fig. 8, 9 and 10, the frame 50B includes a flange 52B, an expansion piston tube 51B, a compression piston tube 54B and a base 53B,
the flange 52B is in a disc shape, one side surface of the flange 52B is provided with a concentric disc 521B, the other side surface is connected with the base 53B, and the flange 52B is uniformly provided with a plurality of connecting through holes.
The base 53B is cylindrical, one end of the base is connected to the flange 52B, the other end of the base is a free end, the center line of the base 53B is overlapped with the center line of the flange 52B, the free end of the base 53B is provided with a plurality of connecting screw holes, and in the embodiment, the base 53B is four support legs surrounding the center line of the base 53B.
The expansion piston tube 51B is a straight tube having one end connected to the disc 521B and the other end being a free end for connection to a pulse tube of a refrigerator, the expansion piston tube 51B having a cylindrical expansion piston chamber 511B therein,
the compression piston tube 54B is a straight tube and is disposed in the base 53B, one end of the compression piston tube 54B is connected to the flange 52B, the other end is a free end, a cylindrical compression piston cavity 541B is disposed in the compression piston tube 54B, and the compression piston cavity 541B and the expansion piston cavity 511B are coaxial and communicated.
Parallel to the axis of the compression piston chamber 541B, the disk 521B is provided with a plurality of through holes communicating the compression piston chamber 541B with the outside, the number of the through holes being between 3 and 9. In the embodiment, the cross section of the through hole 522B is an arc groove, and the number of the through holes is 4.
The compression piston chamber 541B has a larger inner diameter than the expansion piston chamber 511B, and the expansion piston chamber 511B has the same inner diameter as the pulse tube.
The linear motor 1 comprises an outer yoke 11, an inner yoke 14 and a rotor, wherein the outer yoke 11 and the inner yoke 14 are respectively arranged on the frame, a gap is formed between the outer yoke and the inner yoke, the rotor is arranged in the gap, and the rotor comprises a permanent magnet 13 and a permanent magnet support 15.
As shown in fig. 7, the linear motor 1 mainly includes an outer yoke 11, a coil 12, a permanent magnet 13, an inner yoke 14, and a permanent magnet support 15, the mover includes a permanent magnet 13, a permanent magnet support 15, a connecting member 16, a fixing nut 18, a compression piston 19, and a compression piston plate spring 17 (1/3, which only takes the plate spring mass when calculating the mover mass), and the permanent magnet support 15 is connected to the permanent magnet 13, and is connected to the compression piston 19 and the connecting member 16 through a screw thread. The outer yoke iron 11 and the inner yoke iron 14 are made of soft magnetic materials, such as electrically pure iron and silicon steel sheets, and the permanent magnet 13 is made of permanent magnetic materials, such as Ru Fe B and Al Ni Co permanent magnetic materials. The outer yoke 11, the coil 12, the permanent magnet 13, and the inner yoke 14 are all annular and are arranged coaxially. The outer yoke 11 and the inner yoke 14 are respectively disposed on the frame 50B with a gap therebetween, and the mover is disposed in the gap.
When the coil is energized with a direct current, the outer yoke iron 11 and the inner yoke iron 14 form a magnetic loop, thereby generating magnetic poles on the outer yoke iron 11 and the inner yoke iron 14. When alternating current is supplied to the coil, the permanent magnet 13 is subjected to alternating electromagnetic force to perform reciprocating linear motion. When the permanent magnet 13 makes reciprocating linear motion, the compression piston 19 is driven to make reciprocating linear motion, and the compression piston plate spring 17 provides axial reciprocating elastic force and radial support.
The compression unit comprises a connector 16, a compression piston plate spring 17, a fixing nut 18 and a compression piston 19. The compression piston plate spring 17 is connected with the connecting piece 16 through the fixing nut 18, the compression piston plate spring 17 is fixedly connected with the rack 50B through the connecting piece, the compression piston 19 is arranged in the compression piston cavity 541B, one end of the compression piston is connected with the rotor and connected with the compression piston spring 17, and the other end of the compression piston is a free end.
The expander unit comprises an expansion piston 21B, an expansion piston plate spring 22B, a piston rod 23B, a primary hot end heat exchanger 26B, a secondary hot end heat exchanger 33B, a heat regenerator 25B, a pulse tube 31B, a cold end heat exchanger 24B and a cold finger shell 35B.
The first-stage hot-end heat exchanger 26 is cylindrical, is sleeved on the outer wall of the expansion piston pipe 51B and is arranged on the end face of the small circular disc 521B, the first-stage hot-end heat exchanger 26B and the frame 50B are of a split structure, and the first-stage hot-end heat exchanger 26B is in interference fit with the outer wall of the piston pipe 51.
Pulse tube 31B has one end connected to one end of expansion piston tube 51B and the other end connected to cold side heat exchanger 24B.
Regenerator 25B is a cylinder with an annular cross section and is disposed outside pulse tube 31B, with one end connected to cold-end heat exchanger 24B and the other end connected to primary hot-end heat exchanger 26B.
The secondary hot end heat exchanger 33B is arranged in the pulse tube 31B and is positioned at the joint of the pulse tube 31B and the expansion piston tube 51B, the secondary hot end heat exchanger 33B and the frame 50 are of a split structure, and the secondary hot end heat exchanger 33B is in interference fit with the inner wall of the expansion piston tube 51B.
The expansion piston 21B is arranged in the expansion piston pipe 51B, the expansion piston plate spring 22B is fixedly connected with the frame 50B through a connecting piece, one end of the piston rod 23B is connected with the expansion piston 21B, the other end of the piston rod passes through the compression piston 19 and the compression piston plate spring 17 and then is connected with the expansion piston plate spring 22B,
the compression piston 19, the expansion piston 21B, the compression piston chamber 541B, and the expansion piston chamber 511B constitute a compression chamber.
Expansion piston 21B, secondary warm end heat exchanger 33B and expansion piston chamber 511B form an expansion chamber. The expansion chamber and the compression chamber are coaxially arranged.
The cold finger shell 35 is arranged outside the primary hot end heat exchanger 26, the heat regenerator 25 and the cold end heat exchanger 24, the shell 60 is arranged outside the frame 50 and the expander unit 30, and the shell 60, the cold finger shell 35 and the frame 50 are connected into a whole through connecting pieces.
The radiator 27 is located outside the first-stage hot-end heat exchanger 26B and is arranged on the cold finger shell 35, and the first-stage hot-end heat exchanger 26B transfers heat to the radiator 27 on the outer side through the cold finger shell 35 and finally releases the heat to the environment.
The undamped dynamic vibration absorbing unit 40 is connected to the housing 60 and disposed outside the housing 60 for damping the refrigerator.
The sound wave laminar flow process: after passing through the cold side heat exchanger 24, the gas passes through the flow director 32 and enters the pulse tube 31 in a laminar flow to push the gas in the pulse tube 31 towards the expansion chamber 28. After the gas is compressed, the pressure and temperature rise. The generated heat is transferred radially through the secondary hot side heat exchanger 33 to the primary hot side heat exchanger 26 and ultimately to the radiator 27 and released to the environment. The gas in the expansion cavity 28 expands to do work, and assists in pushing the expansion piston to a lower dead center, and the work recovery compression cavity 34B becomes small, so that the effect of recovering acoustic work is achieved. In practice, the compression piston 19 does not remain at top dead centre but moves downwards with the expansion piston 21, but it is noted that the two do not move in the same direction but that the expansion piston leads the compression piston by a certain phase angle.
The embodiment is suitable for the refrigerating temperature range of 120K-220K (-153 ℃ to-53 ℃), and can provide 20W-50W of refrigerating capacity.
EXAMPLE III
The other structure of this embodiment is the same as that of the embodiment, except that it further includes a flow director 32B disposed at one end of the pulse tube 31B and located inside the pulse tube 31B, and the flow director 32B is connected to the cold-side heat exchanger 24B.
Example four
The other structures of this embodiment are the same as those of this embodiment, except that a first filter layer is further disposed between the cold-end heat exchanger 24B and the heat regenerator 25B, and the first filter layer is in a cylindrical shape with an annular cross section and is made of a stainless steel wire mesh. The stainless steel wire has a wire diameter of 20 to 50 μm, and in the examples, the stainless steel wire has a wire diameter of 30 μm. The pressure drop of helium passing through the stainless steel wire layer is small, and the stainless steel wire layer has the characteristics of strong cold storage capacity and strong liquidity.
EXAMPLE five
The other structure of this embodiment is the same as that of the fourth embodiment, except that a second filter layer is further disposed between the primary hot-end heat exchanger 26B and the heat regenerator 25B, and the second filter layer is in the shape of a cylinder with an annular cross section and made of degreased wool. The diameter of the wool is 10-30 μm, and in the examples, the diameter of the wool is 20 μm. The wool layer has the characteristics of buffering assembly and adjusting assembly size. The sectional type heat regenerator is divided into three sections, the stainless steel wire mesh, the polyester film and the degreased wool are respectively arranged from top to bottom, the length ratio of the stainless steel wire mesh to the polyester film to the degreased wool is 1:8:1, and the void ratios of the stainless steel wire mesh, the polyester film and the degreased wool are respectively 70%, 50% and 70%.
EXAMPLE six
The other structure of this embodiment is the same as that of the embodiment except that the secondary hot side heat exchanger 33B1 is an integral structure with the frame 50B. In the embodiment shown in fig. 11, the secondary hot side heat exchanger 33B1 is fabricated from aluminum as a whole with the frame 50B as 50B 1.
The integral structure of secondary hot side heat exchanger 33B1 and frame 50B effectively eliminates thermal contact resistance between secondary hot side heat exchanger 33B1 and frame 50B, and secondary hot side heat exchanger 33B1 may also function as a flow director.
EXAMPLE seven
The other construction of this embodiment is the same as that of the sixth embodiment except that the primary hot side heat exchanger 26B2 is of unitary construction with the frame 50B. In the embodiment shown in fig. 12, the primary hot side heat exchanger 26B2, the secondary hot side heat exchanger 33B1, and the frame 50B are integrally formed of aluminum as 50B 2.
The integrated structure of first-stage hot side heat exchanger 26B2, second-stage hot side heat exchanger 33B1 and frame 50B effectively eliminates thermal contact resistance between first-stage hot side heat exchanger 26B2, second-stage hot side heat exchanger 33B1 and frame 50B, and at the same time, second-stage hot side heat exchanger 33B1 can also function as a flow director.
Effects and effects of the embodiments
The pulse tube type free piston Stirling refrigerator of the embodiment cancels the longer low-temperature expansion piston of the traditional free piston Stirling refrigerator and replaces the long low-temperature expansion piston with the work recovery expansion piston working in a shorter room temperature area. The expansion cylinder of the free piston Stirling refrigerator becomes a pulse tube of a pulse tube cold finger, a laminar flow guider is arranged at the cold end of the pulse tube, and a secondary hot end heat exchanger is arranged at the hot end of the pulse tube. The change combines the advantages of the free piston Stirling refrigerator and the pulse tube refrigerator, and eliminates pumping loss, shuttle loss and axial heat conduction loss caused by the low-temperature expansion piston by eliminating the expansion piston which moves at a high frequency at a cold end and a hot end. The problem of sound power recovery of the pulse tube refrigerator is solved by arranging the shorter room-temperature expansion piston at the hot end, and therefore when the sound power of the cold end is completely recovered, the theoretical efficiency of the novel pulse tube type free piston Stirling refrigerator is Carnot cycle efficiency. Meanwhile, the low-temperature expansion piston is eliminated, so that the manufacturing difficulty of the refrigerating machine is reduced, and the quality of the whole machine is reduced.
The above embodiments are preferred examples of the present invention, and are not intended to limit the scope of the present invention.
Claims (5)
1. A pulse tube type free piston stirling cooler comprising:
a linear motor, a compression unit, an expander unit and a frame,
wherein the frame comprises a flange, an expansion piston pipe, a compression piston pipe, a secondary hot end heat exchanger and a base,
the flange is in a disc shape, one side surface of the flange is provided with concentric discs, the other side surface of the flange is connected with the base,
the expansion piston tube is a straight-through tube, one end of the expansion piston tube is connected with the disc, the other end of the expansion piston tube is a free end and is used for connecting a pulse tube of a refrigerator, a cylindrical expansion piston cavity is arranged in the expansion piston tube,
the compression piston pipe is a straight-through pipe and is arranged in the base, one end of the compression piston pipe is connected with the flange, the other end of the compression piston pipe is a free end, a cylindrical compression piston cavity is arranged in the compression piston pipe, the compression piston cavity and the expansion piston cavity are coaxial and communicated,
the secondary hot end heat exchanger is arranged in the expansion piston pipe,
parallel to the axis of the compression piston cavity, a plurality of through holes which are communicated with the compression piston cavity and the outside are arranged on the disc,
the compression piston chamber has an inner diameter greater than the expansion piston chamber, the expansion piston chamber has an inner diameter that is the same as the pulse tube,
the linear motor comprises an outer yoke iron, an inner yoke iron and a rotor, the outer yoke iron and the inner yoke iron are respectively arranged on the rack, a gap is arranged between the outer yoke iron and the inner yoke iron, the rotor is arranged in the gap,
the compression unit is provided with a compression piston and a compression piston spring, the compression piston spring is fixedly connected with the rack through a connecting piece, the compression piston is arranged in the compression piston pipe, one end of the compression piston is connected with the rotor and the compression piston spring, the other end of the compression piston is a free end,
the expansion unit comprises an expansion piston, an expansion piston spring, an expansion piston rod, a pulse tube, a cold end heat exchanger, a fluid director, a primary hot end heat exchanger and a heat regenerator,
the first-stage hot end heat exchanger is cylindrical, is sleeved on the outer wall of the expansion piston pipe and is arranged on the end surface of the disc,
one end of the pulse tube is connected with the expansion piston tube, the other end of the pulse tube is connected with the cold end heat exchanger, the cold end heat exchanger is positioned at the opening end of the pulse tube,
the fluid director is arranged at one end of the pulse tube and is positioned in the pulse tube,
the heat regenerator is cylindrical and arranged on the outer side of the pulse tube, one end of the heat regenerator is connected with the cold end heat exchanger, the other end of the heat regenerator is connected with the primary hot end heat exchanger,
the expansion piston is arranged in the expansion piston pipe, the expansion piston spring is fixedly connected with the frame through a connecting piece, one end of the expansion piston rod is connected with the expansion piston, the other end of the expansion piston rod penetrates through the compression piston and the compression piston spring and then is connected with the expansion piston spring,
the compression piston, the expansion piston, the compression piston cavity and the expansion piston cavity form a compression cavity,
the expansion piston, the secondary hot end heat exchanger and the expansion piston cavity form an expansion cavity, and the expansion cavity and the compression cavity are coaxially arranged.
2. A method of refrigerating a pulse tube type free piston stirling cooler in accordance with claim 1, comprising the steps of:
the expansion piston moves upwards from the bottom dead center to the top dead center;
the compression piston moves to a lower dead point;
the expansion piston pushes the acoustic waves within the expansion chamber back into the pulse tube;
the working medium gas expands in the pulse tube to absorb heat, so that a refrigeration effect is generated;
reaching a minimum refrigeration temperature at the top of the pulse tube near the flow director;
the generated cold energy is led out to a cold environment through the cold end heat exchanger;
and the sound wave working medium returns to the heat regenerator along the original path and is fully contacted with the filler for heat exchange, and returns to the compression cavity again to wait for the next compression after absorbing the heat in the heat regenerator.
3. The method of claim 2, wherein the method further comprises the steps of:
wherein, the heat regenerator is cylindrical and is made of polyester films.
4. The method of claim 2, wherein the method further comprises the steps of:
and a first filtering layer is also arranged between the cold end heat exchanger and the heat regenerator, is cylindrical and is made of a stainless steel wire mesh.
5. The method of claim 2, wherein the method further comprises the steps of:
and a second filter layer is also arranged between the primary hot end heat exchanger and the heat regenerator, is cylindrical and is made of degreased wool.
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| CN201810437352.1A CN108800643B (en) | 2018-05-09 | 2018-05-09 | Pulse tube type free piston Stirling refrigerator and refrigeration method |
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| Application Number | Priority Date | Filing Date | Title |
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| CN201810437352.1A CN108800643B (en) | 2018-05-09 | 2018-05-09 | Pulse tube type free piston Stirling refrigerator and refrigeration method |
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| CN108800643B true CN108800643B (en) | 2019-12-31 |
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| CN109834240B (en) * | 2019-01-28 | 2024-01-26 | 广东省智能制造研究所 | Temperature self-adjusting injection punch |
| CN111089435A (en) * | 2019-11-18 | 2020-05-01 | 上海厚酷科技有限公司 | Refrigerating machine |
| CN112880226B (en) * | 2021-03-11 | 2024-06-21 | 中国科学院上海技术物理研究所 | Cold accumulation filler filling device for Stirling refrigeration product and operation method |
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| CN1127876A (en) * | 1995-01-24 | 1996-07-31 | 中国科学院低温技术实验中心 | Reversible vessel refrigerator driven by conventional gas refrigerator |
| US5647217A (en) * | 1996-01-11 | 1997-07-15 | Stirling Technology Company | Stirling cycle cryogenic cooler |
| JP2003130480A (en) * | 2001-10-19 | 2003-05-08 | Global Cooling Bv | Casing of free-piston stirling device |
| CN101619687A (en) * | 2009-08-11 | 2010-01-06 | 深圳市中科力函热声技术工程研究中心有限公司 | Piston-free Stirling engine system |
| CN105066500A (en) * | 2015-09-22 | 2015-11-18 | 中国科学院理化技术研究所 | Thermally driven pulse tube refrigerator system |
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Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1127876A (en) * | 1995-01-24 | 1996-07-31 | 中国科学院低温技术实验中心 | Reversible vessel refrigerator driven by conventional gas refrigerator |
| US5647217A (en) * | 1996-01-11 | 1997-07-15 | Stirling Technology Company | Stirling cycle cryogenic cooler |
| JP2003130480A (en) * | 2001-10-19 | 2003-05-08 | Global Cooling Bv | Casing of free-piston stirling device |
| CN101619687A (en) * | 2009-08-11 | 2010-01-06 | 深圳市中科力函热声技术工程研究中心有限公司 | Piston-free Stirling engine system |
| CN105066500A (en) * | 2015-09-22 | 2015-11-18 | 中国科学院理化技术研究所 | Thermally driven pulse tube refrigerator system |
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