Classifications

• • 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
• • 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
  • F25B2309/006—Gas cycle refrigeration machines using a distributing valve of the rotary type

Definitions

• Refrigerators are low-temperature chillers in which a thermodynamic cycle takes place.
• a one-stage refractor comprises a work space in which a displacer moves back and forth between two dead centers OT and UT.
• a regenerator is assigned to the displacer, through which a working gas also flows back and forth in accordance with the displacement movement.
• heat is constantly withdrawn from the refrigerator housing in the area of one of the two dead centers.
• temperatures of up to approximately 30 K can be generated.
• Refrigerators are often designed in two stages (see, for example, DE-A-38 36 884). Temperatures of below 10 K can be generated with two- or three-stage refrigerators.
• a gas drive serves to generate the reciprocating movement of the displacer.
• a cylinder-piston device is assigned to the warm side of the displacer, which is to be supplied with a drive gas.
• Refrigerators of the type concerned here must also be equipped with control devices with the aid of which both the supply of the working gas into the working cylinder and the supply of the gas drive are regulated. It is common to use helium both as the working gas and as the driving gas. In versions of this type, it is sufficient if the Refrigerator is equipped with two connections, one of which is supplied with high pressure (eg 20 bar) and the second with low pressure (eg 5 bar) helium.
• high pressure eg 20 bar
• low pressure eg 5 bar
• the object of the present invention is to operate a refrigerator with a gas drive in such a way that an effective reduction of the vibrations can be achieved with relatively simple measures.
• the invention is based on the knowledge that the gas drive in known refrigerators is active during the entire time of the respective movement phases of the displacer, that is to say that the displacer experiences a not inconsiderable acceleration during the entire time of its movement phases. This leads to relatively strong stops at the dead centers, which are responsible for the vibrations. However, if the displacer corresponds to the Invention accelerated only temporarily or only at the beginning of its movement phases, then its top speeds in the dead centers are lower and thus its stops on the housing are less hard. By controlling the amount of gas with which the gas drive is supplied in both directions of movement, the drive energy can be controlled and the desired goal can thus be achieved. With the measures according to the invention, the vibrations that occur can be reduced by more than a factor of 4 without significantly impairing the effectiveness of the refrigerator.
• the two-stage refrigerator 1 shown in the figure has a housing which consists of the two parts 2 and 3.
• the housing part 2 In the housing part 2, the cylindrical work spaces 4 and 5 for the two displacement stages 6 and 7 are accommodated.
• the upper displacement stage 6 is equipped on its warm side with a drive piston 8, the associated cylinder 9 of which is accommodated in a guide bush 10 which closes the working space 4 towards the housing part 3.
• the guide bush 10 is equipped with the bores 11, 12 and 13.
• the bore 11 opens into the working space 4 and serves to supply this space with working gas.
• the bore 13 opens into a transverse bore 14 which is connected to an annular groove 15 in the outer wall of the guide bush 10.
• the bore 12 is indicated by a dash-dotted line and serves to supply the drive cylinder 9 with drive gas.
• the different bores lie in different planes, so that they do not cross each other, which is indicated by the dashed line or dash-dot line.
• a fixed valve disk 16 In the housing part 3, a motor 17 is accommodated, which actuates a rotating valve disk 19 via the shaft 18.
• the fixed valve disk 16 and the rotating valve disk 19 which is under the action of the compression spring 20 form a control valve which, in a manner known per se, serves to supply the various bores with gas under high pressure and under low pressure.
• the working gas and the drive gas are identical. Helium is expediently used.
• the connections for high pressure and low pressure gas are designated 21 and 22, respectively.
• the parting plane 23 between the housing parts 2 and 3 lies at the level of the control valve 16, 19. It is chosen so that after removal of the upper housing part 3 with motor 17 and rotating valve disk 19 above the stationary valve disk 16, a flat cup-shaped space 24 is available. At the level of this space 24, a bore 25 is provided through the wall of the housing part 2 and connects the space 24 to the high-pressure connection 21.
• the low-pressure connection 22 is connected to the bore 26 in the housing part 3, which opens at the level of the annular groove 15 of the guide bush 10.
• the high-pressure working gas flows via the connection 21 into the chamber 24. From there, the various bores are supplied with the aid of the control valve 16, 19. After its expansion in the refrigerator stages 4, 5, the working gas reaches the bores 13, 14 and flows out via the annular groove 15 and the low pressure connection 22.
• the pressure of the working gas at the high-pressure connection 21 is usually about 20 to 22 bar, while the working gas pressure at the low-pressure connection 22 is about 5 to 7 bar.
• FIGS. 2 and 3 show configurations of the valve disks 16 and 19 with which the gas control desired in the sense of the invention is possible.
• the fixed valve disk 16 shown in view (FIG. 3) shows the orifices 27, 28, 29 of the bores 11, 12 and 13, respectively.
• the bore 13 and its orifice 29 lie in the center, while the radial distance of the orifices 27, 28 of the orifices 11 and 12 is no longer the same as in the prior art - from the axis of rotation of the valve disk 19 ( Circles 31, 32).
• the mouth 28 of the bore 12 has a significantly smaller diameter than the mouth 27 of the bore 11.
• the rotating valve disk 19, rotates according to the arrow 33 on the fixed valve disk 16 assigned to a relatively large cross section.
• the recess 35 associated with the circle 32 is designed as a relatively narrow slot.
• the valve disc 19 is equipped with a relatively large recess 36 which extends from the center to the circle 31. From this recess 36 a slot-shaped recess 37 extends to the circle 32.
• the control openings 34 to 37 of the valve disk 19 and the control openings 27 to 29 of the valve disk 16 pass over one another.
• the slot 35 lying on the circle 32 reaches the mouth 28 of the bore 12.
• the drive cylinder 9 is connected to the high-pressure space 24 for a relatively short time and the displacer 6 is accelerated towards the cold side of the work space.
• the bore 34 of the rotating valve disk lying on the circle 31 reaches the mouth 27 of the bore 11 in the fixed valve disk 16.
• the working space 14 also becomes High pressure gas supplied.
• FIGS. 4 and 5 show an exemplary embodiment in which two bores 11, 11 ', 12, 12' and 34, 34 'with their associated openings are provided in the valve disks 16, 19, each offset by 180 °.
• the elongated recess 36 extends on both sides of the center to the circle 31.
• Two slots 37, 37 'extending to the circle 32 are present.
• the displacer 6 makes twice the number of strokes per revolution of the valve disk 19.
• the orifices 27, 28 (27 ', 28') of the bores 11 (11'9 and 12 (12 ') in the fixed valve disk 17 lie on circles 31, 32 with different radii.
• the bores 34 (34 ') or recesses 35 (35'), 36 (36 '), 37 (37') in the rotating valve disk 19 also lie on circles with corresponding different radii. This makes it possible to set great differences with regard to the sweep times.
• the supply holes for the gas drive open on the circle 32 with the larger diameter. Short sweep times are not achieved through small holes or recesses, but also through the higher peripheral speed.
• the sweeping times for the gas drive which depend on the speed of the rotating valve disk 19, on the position and on the design of the orifices 27 to 29, recesses 35 to 37 and bore 34, are expediently to be selected as follows:
• the drive cylinder 9 is connected to the high-pressure connection 21 only for a first fraction of its total movement time.
• This fraction is to be chosen - expediently empirically - in such a way that the vibrations caused by stops of the displacer on the housing are considerably reduced, but there is still no significant impairment of the effectiveness of the refractor.
• the order of the fraction is about a third of the time of the total movement time.
• the sweep time should be chosen so short that the connection between the drive cylinder 9 and the low-pressure connection 22 is already closed again before the displacer reaches its dead center.
• the pressure increase in the residual gas is expediently chosen such that a pressure which is somewhat higher than the high pressure level is reached in the drive cylinder shortly before the dead center.
• FIGS. 6 and 7 show embodiments of the stationary or rotating valve disk, with the aid of which the displacer 6, 7 is accelerated several times for short times.
• either the bore 28 of the fixed valve disk 16 in (for example) three bores 41, 42, 43 or the cutouts 35, 37 in the rotating valve disk 19 in each (for example) three cutouts 44 to 46 or 47 to 49 have been divided.
• Figures 8 and 9 show the effect of these measures.
• the path s of the displacer against the time t is plotted in the upper coordinate system in each case.
• the respective lower coordinate system shows the times ti, t 2 and t 3 at which the drive cylinder 9 is subjected to high pressure (FIG. 8) or low pressure (FIG. 9).
• Figure 8 shows the course of movement of the displacer from the warm to the cold side.
• the drive cylinder is acted upon for the time t (for example 5% of the time of the entire movement phase) with high pressure gas.
• the displacer experiences three brief thrusts that move it towards the cold side, with an alternately accelerated and decelerated movement (movement curve 51).
• the impact of the displacer 6, 7 on the housing 2 (dashed line 52), which is decisive for the vibration, is relatively small.
• the movement of the displacer 6, 7 from the cold to the warm side runs accordingly (cf. movement curve 53 in FIG. 9 with stop line 54).
• the time segments t are chosen so short that a damping gas cushion is created in each case.
• FIGS. 6 to 9 enable controlled control of the movement sequence of the displacer 6, 7 with the aid of short pressure pulses. Compared to continuously accelerated displacers, the displacer 6, 7 moved according to the invention reaches its dead center at a later point in time; however, this does not significantly affect the effectiveness of the refrigerator.

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Publications (1)

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Cited By (2)

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Citations (9)

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• 1993
  • 1993-06-03 DE DE4318406A patent/DE4318406A1/de not_active Withdrawn
• 1994
  • 1994-03-31 DE DE59408146T patent/DE59408146D1/de not_active Expired - Lifetime
  • 1994-03-31 EP EP94912556A patent/EP0700502B1/de not_active Expired - Lifetime
  • 1994-03-31 JP JP50122095A patent/JP3299970B2/ja not_active Expired - Fee Related
  • 1994-03-31 WO PCT/EP1994/001012 patent/WO1994029653A1/de active IP Right Grant

Patent Citations (9)

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