THERMODYNAMIC REGENERATOR
Various embodiments are directed to a regenerator for use with a regenerative engine. The regenerator may comprise a plurality of regenerator disks. Each of the plurality of regenerator disks may comprises a plurality of concentric ribs defining a plurality of concentric gaps therebetween. Further, the plurality regenerator disks may be arranged within the regenerator longitudinally, such that the plurality of concentric gaps defined by adjacent regenerator disks are substantially aligned.
Latest The Aerospace Corporation Patents:
Regenerative engines are used in many contexts to translate energy between heat and motion. To accomplish this transformation, regenerative engines typically utilize a thermodynamic cycle. Mechanical energy (often involving the compression and expansion of a fluid) is used to shift heat energy, creating a hot source and a cold source. Regenerative engines in this configuration are often utilized as mechanical coolers. Mechanical coolers are used for many purposes including, for example, to cool certain sensor elements, to cool materials during semiconductor fabrication, and to cool superconducting materials such as in Magnetic Resonance Imaging (MRI) systems. Cryocoolers are a class of mechanical coolers that can achieve cold temperatures in the cryogenic range (e.g., <˜123 K). Regenerative engines are also operated in a configuration opposite that described above to translate heat energy to motion. A concentration of heat energy causes compression and expansion of the fluid, which may be used to for various mechanical purposes. Different types of regenerative engines may comprise various valves, thermal compressors, mechanical compressors, displacers, etc., to bring about expansion and compression of the working fluid.
One type of regenerative engine is a pulse tube engine. A pulse tube engine includes a stationary regenerator connected to a pulse tube. A reservoir or buffer volume may be connected to the opposite end of the pulse tube via a phase control device such as a sharp-edged orifice or an inertance tube. The reservoir, pulse tube, and regenerator may be filled with a working fluid (e.g., a gas such as helium). A compressor (e.g., a piston) may compress and warm the working fluid. The compressed working fluid is forced through the regenerator, where part of the heat from the compression is removed at ambient temperature. As the working fluid is passed through the regenerator, it exchanges heat with the regenerator matrix, causing the working fluid to cool down and the regenerator to heat up. The working fluid is then expanded through the pulse tube and the phase control device into the reservoir. This expansion provides further cooling that takes place at a cold temperature. Additional heat is rejected at the end of the pulse tube farthest from the regenerator. Cooling occurs at a cold end of the pulse tube nearest the regenerator. A hot end of the pulse tube farthest from the regenerator collects heat. In an alternate configuration, the pulse tube engine operates in reverse with heat provided at the hot end of the pulse tube bringing about expansion of the working fluid and motion of the piston. Other types of regenerative engines utilize various other means for forcing the working fluid through the regenerator. For example, a Stirling engine utilizes a compressor/piston on both ends of the regenerator. Other types of regenerative engines include Gifford-McMahon engines, Solvay engines, Vulleumier engines, etc.
The performance of regenerative engines depends largely upon the performance of the regenerator. An ideal regenerator will achieve a maximum heat transfer to and/or from the working fluid and a minimum pressure drop in the working fluid across the regenerator. One existing regenerator design involves packing screen material made of a high heat capacity material into a cylindrical package. Working fluid flowing through the regenerator deposits heat to and/or absorbs heat from the screen materials. Screen material regenerators, however, suffer from several problems. With many screen materials, small bits of screen can come apart, clogging openings in the screen and an increasing pressure drops. Also, the pressure drop across a screen regenerator is highly dependent on the manner in which the screen material is packed. If screen material is packed too tightly, unacceptably high pressure drops may occur. Another existing regenerator type is often referred to as a “jelly roll” regenerator. A jelly roll regenerator is formed from a flat piece of high heat capacity material. Spacers are placed on the material and it is rolled upon itself. The spacers create interior channels. In use, working fluid is made to flow through the channels, where the fluid may deposit heat to and receive heat from the regenerator material. The effectiveness of jelly roll regenerators, however, is highly dependant on the manufacturing and mechanical integrity of the interior channels. If the channels are not all of the same width, then working fluid will primarily flow through the channel offering the least resistance, compromising the effectiveness of the regenerator.
SUMMARYVarious embodiments are directed to a regenerator for use with a regenerative engine. The regenerator may comprise a plurality of regenerator disks. Each of the plurality of regenerator disks may comprises a plurality of ribs defining gaps therebetween. In some embodiments, the gaps may be concentric. Further, the plurality regenerator disks may be arranged within the regenerator longitudinally, such that the plurality of concentric gaps defined by adjacent regenerator disks are substantially aligned.
Various embodiments of the present invention are described here by way of example in conjunction with the following figures, wherein:
Various embodiments may be directed to regenerators for use with regenerative engines. The regenerators may comprise a plurality of disks. Each disk may define a plurality of concentric gaps. The disks may be arranged longitudinally within the regenerator such that the gaps are substantially aligned. In this way, the gaps may form longitudinal channels through the regenerator. When the regenerator is used with a regenerative engine, working fluid may be passed through the longitudinal channels to transfer heat energy to and from the disks. The width of each longitudinal channel may be related to the width of the respective gaps in each disk. According to various embodiments, concentric gap disk regenerators may enjoy several advantages. For example, manufacturing techniques for repeatedly manufacturing concentric gap disks to within acceptable tolerances may be more practical and less expensive than those used with existing regenerators. Also, variations in gap width from disk to disk may be roughly cancelled out over the longitudinal distance of the regenerator. In this way, the fluid resistance of the various longitudinal channels may be relatively equal, leading to greater regenerator performance and, in some cases, less stringent tolerances.
According to various embodiments, the disks 110 may be held in place within the regenerator 100 via an exterior frame or other material. For example,
In some embodiments, a shrink tube may be utilized to secure the disks 110 within the regenerator 100. For example,
As illustrated, the gaps 402 may be defined by a plurality of ribs 404 formed in the face of the disk 110. The gaps 402 and the ribs 404 may be concentric (e.g., around a common center 406). The common center 406 may be at the center of the disk 110. It will be appreciated that although the disk 110 shown in
As illustrated in
According to various embodiments, it may be desirable for the thermal conductivity between adjacent disks 110 to be minimized. For example, materials that have a high heat capacity, such as stainless steel and other metals, may also have a high thermal conductivity. Excessive thermal conductivity within the regenerator 100 may lead to heat loss, reducing the effectiveness of the regenerator 100. Thermal conductivity within the regenerator 100 may be reduced in any of a number of methods. For example, alternating disks 110 in the regenerator may be made from and/or coated (e.g., completely or partially) with a thermally insulating material (e.g., plastic, rubber, etc.).
It will be appreciated that the regenerator 100 and the disks 110 may be of any suitable dimensions. For example, length of the regenerator 110 along the longitudinal axis 106 may be determined based on the thickness of each disk 110 and the number of disks present. In various embodiments, the length of the regenerator 110 may exceed its width (e.g., the width of the regenerator may be the same as the diameter of the disks 110. Also, in various embodiments, the thickness of the disks may be about 130 μm. Similarly, the width of the ribs 404 and gaps 402 may vary in various embodiments and may be selected to optimize performance. For example, in various embodiments, the width of the gaps 402 may vary between about 20 μm and about 30 μm. Also, in various embodiments, the width of the ribs 404 may vary from between about 30 μm and about 130 μm.
The regenerator disks 110 described herein may be manufactured according to any suitable manufacturing method. For example, the disks 110 may be manufactured utilizing a machining technique. Disk blanks may be provided to a machining device, which may cut out the gaps 402 and/or to cut-down around features such as ridges 604, 1004, pegs 804, etc. to form a finished product. Any suitable machining technique may be used. For example, in some embodiments, electric discharge machining (EDM) may be utilized. EDM methods utilize electrical discharges to ablate unwanted material. Also, in some embodiments, the disks 110 may be machined according to a laser direct write method. An example of such a method is disclosed in U.S. Pat. No. 6,783,920 to Livingston, et al., entitled “Photosensitive Glass Variable Exposure Patterning Method,” which is incorporated herein by reference in its entirety. Other example machining methods that may be used include, diamond tool machining, water jet machining, etc.
Also, in various embodiments, the disks 110 may be formed from additive manufacturing methods. For example, the disks 110 may be formed utilizing a powder, which may be formed into the desired shape and then baked. In some embodiments, a laser sintering technique may be used. For example, a laser may be used to heat and/or bind a powder or other loosely bound material into the desired shape. Also, in various embodiments, the disks 110 may be formed by embedding a desired disk material into a polymeric binder. The binder may ultimately be removed (e.g., by melting, etc.), leaving the disk material. Still other example methods that could be used to manufacture the disk 110 may include, using a punch, chemical etch lithography, etc.
The compressor 1102, may drive the thermodynamic cycle of the engine 1100 at various frequencies. For example, in various embodiments, one thermodynamic cycle of the engine 1100 may correspond to one complete cycle of the piston 1102 or other mechanism of the compressor 1102. According to the thermodynamic cycle of the engine 1100, the compressor 1102 may provide work to compress a portion of the working fluid, adding heat and causing the temperature of the working fluid to rise at heat exchanger 1110. The heat of compression may be removed to the ambient. As the compressor 1102 further compresses, warm working fluid is passed through the regenerator 100, where the working fluid is cooled and the energy stored in the regenerator material. Working fluid already present in the pulse tube 1106 may be at a relatively lower pressure than that entering the pulse tube via 1106 via the regenerator 100. Accordingly, the working fluid entering the pulse tube 1106 via the regenerator 100 may expand in the pulse tube 1106, causing cooling at the exchanger 1112. Excess pressure in the pulse tube 1106 from the expansion may be relieved across the phase control device 1116 into the reservoir. As the cycle continues, the compressor 1102 begins to draw the working fluid from the cold end 1199 of the pulse tube 1106 back through the regenerator 100, where the stored heat is reintroduced. Resulting low pressure in the pulse tube 1106 may also cause working fluid from the reservoir 1108 to be drawn across the phase control device 1116 into the pulse tube 1106. This working fluid from the reservoir 1108 may be at a higher pressure than that already in the pulse tube 1106 and, therefore, may enter with heat energy and at a temperature that is relatively warmer than that of the other working fluid in the pulse tube 1106. A new cycle may begin as the compressor 1102 again reverses and begins to compress the working fluid. Examples of the operation of pulse tube engines are provided in the following commonly assigned U.S. Patent Applications: Publication No. 2009/0084114, entitled “Gas Phase-Shifting Inertance Gap Pulse Tube Cryocooler,” filed on Sep. 28, 2007; Publication No. 2009/0084115, entitled “Controlled and Variable Gas Phase Shifting Cryocooler,” filed on Sep. 28, 2007; Publication No. 2009/0084116, entitled “Gas Phase Shifting Multistage Displacer Cryocooler,” filed on Sep. 28, 2007; Ser. No. 12/611,764, entitled “Phase Shift Devices for Pulse Tube Coolers,” filed on Nov. 3, 2009; Ser. No. 12/611,774, entitled “Phase Shift Devices For Pulse Tube Coolers,” filed on Nov. 3, 2009; and Ser. No. 12/611,784, entitled “Multistage Pulse Tube Coolers,” filed on Nov. 3, 2009, all of which are incorporated herein by reference in their entirety.
According to various embodiments, the regenerator 100 may be constructed with disks exhibiting non-concentric patterns. For example, the disks may comprise ribs defining gaps that are linear, zig-zag or any other suitable pattern. In embodiments exhibiting non-concentric patterns, it may be desirable to achieve uniform alignment of the disks about the longitudinal axis of the regenerator 100 (e.g., uniform alignment of the gaps). This may reduce flow resistance (e.g., by creating channels that extend longitudinally through the regenerator 100). Disk alignment may be achieved in any suitable manner. For example, the disks may be constructed with non-continuous alignment grooves 602, as illustrated in
It is to be understood that the figures and descriptions of the present invention have been simplified to illustrate elements that are relevant for a clear understanding of the present invention, while eliminating other elements, for purposes of clarity. Those of ordinary skill in the art will recognize that these and other elements may be desirable. However, because such elements are well known in the art and because they do not facilitate a better understanding of the present invention, a discussion of such elements is not provided herein.
In various embodiments disclosed herein, a single component may be replaced by multiple components and multiple components may be replaced by a single component to perform a given function or functions. Except where such substitution would not be operative, such substitution is within the intended scope of the embodiments.
Any patent, publication, or other disclosure material, in whole or in part, that is said to be incorporated by reference herein is incorporated herein only to the extent that the incorporated materials does not conflict with existing definitions, statements, or other disclosure material set forth in this disclosure. As such, and to the extent necessary, the disclosure as explicitly set forth herein supersedes any conflicting material incorporated herein by reference. Any material, or portion thereof, that is said to be incorporated by reference herein, but which conflicts with existing definitions, statements, or other disclosure material set forth herein will only be incorporated to the extent that no conflict arises between that incorporated material and the existing disclosure material.
While various embodiments have been described herein, it should be apparent that various modifications, alterations, and adaptations to those embodiments may occur to persons skilled in the art with attainment of at least some of the advantages. The disclosed embodiments are therefore intended to include all such modifications, alterations, and adaptations without departing from the scope of the embodiments as set forth herein.
Claims
1. A regenerator for use with a regenerative engine, the regenerator comprising:
- a plurality of regenerator disks;
- wherein each of the plurality of regenerator disks comprises a plurality of ribs defining a plurality of gaps therebetween; and
- wherein the plurality regenerator disks are arranged within the regenerator longitudinally, such that the plurality of concentric gaps defined by adjacent regenerator disks are substantially aligned.
2. The regenerator of claim 1, wherein the plurality of regenerator disks comprise at least one material selected from the group consisting of stainless steel, phosphor bronze, lead, and a rare-earth metal.
3. The regenerator of claim 1, wherein a diameter of the plurality of regenerator disks is between about ¼ inch and one foot.
4. The regenerator of claim 1, wherein a width of the gaps is between about 20 μm and about 30 μm.
5. The regenerator of claim 1, wherein a width of the ribs is between about 30 μm and about 130 μm.
6. The regenerator of claim 1, wherein the plurality of ribs and the plurality of gaps are concentric.
7. The regenerator of claim 6, wherein, for each of the plurality of regenerator disks, a common center of the plurality of concentric ribs and a common center of the plurality concentric gaps are at about a center of the disk.
8. The regenerator of claim 6, wherein, for each of the plurality of regenerator disks, the concentric ribs extend less than 360° about a common center.
9. The regenerator of claim 8, wherein, for each of the plurality of regenerator disks, the concentric ribs extend about 120° about the common center.
10. The regenerator of claim 8, wherein, for each of the plurality of regenerator disks, the angular positions of plurality of concentric ribs about the common center are aligned.
11. The regenerator of claim 8, wherein, for each of the plurality of regenerator disks, the angular positions of plurality of concentric ribs about the common center are offset.
12. The regenerator of claim 1, further comprising an outer cylinder and wherein the regenerator disks are positioned within the outer cylinder.
13. The regenerator of claim 12, further comprising a cap positioned at a first end of the outer cylinder.
14. The regenerator of claim 1, further comprising a shrink tube surrounding the regenerator disks.
15. The regenerator of claim 1, wherein each of the plurality of regenerator disks comprises a ridge on a first surface and defines a corresponding groove on a second opposite surface.
16. The regenerator of claim 15, wherein at least a portion of the ridges are thermally insulating.
17. The regenerator of claim 15, wherein the ridge and the groove extends completely around a common center of the concentric ribs.
18. The regenerator of claim 1, wherein at least a portion of the plurality of regenerator disks are thermally insulating.
19. The regenerator of claim 1, wherein the at least a portion of the plurality of regenerator disks that are thermally insulating are selected from the group consisting of regenerator disks made from a thermally insulating material and regenerator disks having a thermally insulating coating.
20. The regenerator of claim 1, wherein the plurality of ribs and the plurality of gaps are linear.
21. The regenerator of claim 20, wherein the plurality of ribs are parallel to one another.
22. The regenerator of claim 1, wherein each of the plurality of ribs comprises a plurality of alternating portions meeting one another at angles of less than 180°.
23. The regenerator of claim 22, wherein the plurality of ribs are parallel to one another.
24. A regenerative engine comprising:
- a regenerator, the regenerator comprising: a plurality of regenerator disks, wherein each of the plurality of regenerator disks comprises a plurality of concentric ribs defining a plurality of concentric gaps therebetween, and wherein the plurality regenerator disks are arranged within the regenerator longitudinally, such that the plurality of concentric gaps defined by adjacent regenerator disks are substantially aligned;
- a pulse tube comprising a cold end and a hot end, wherein the pulse tube is in fluid communication with and is coupled to the regenerator at the cold end;
- a reservoir, wherein the reservoir is in fluid communication with the pulse tube at the hot end of the pulse tube;
- a working fluid positioned within the regenerator, the pulse tube, and the reservoir; and
- a phase control device positioned in a fluid path between the hot end of the pulse tube and the reservoir.
25. The regenerative engine of claim 24, wherein the pulse tube and the regenerator share a common outer cylinder, and where the plurality of regenerator disks are positioned within the common outer cylinder.
26. The regenerative engine of claim 24, wherein each of the plurality of regenerator disks comprises a ridge on a first surface and defines a corresponding groove on a second opposite surface.
27. The regenerative engine of claim 24, wherein, for each of the plurality of regenerator disks, the concentric ribs extend less than 360° about a common center.
28. A regenerator for use with a regenerative engine, the regenerator comprising:
- a plurality of regenerator disks;
- wherein each of the plurality of regenerator disks comprises a plurality of concentric ribs defining a plurality of concentric gaps therebetween;
- wherein the plurality regenerator disks are arranged within the regenerator longitudinally, such that the plurality of concentric gaps defined by adjacent regenerator disks are substantially aligned;
- wherein a diameter of the plurality of regenerator disks is between about ½ inch and one foot;
- wherein a width of the concentric gaps is between about 20 μm and about 30 μm;
- wherein a width of the concentric ribs is between about 30 μm and about 130 μm;
- wherein, for each of the plurality of regenerator disks, a common center of the plurality of concentric ribs and a common center of the plurality concentric gaps are at about a center of the disk;
- wherein, for each of the plurality of regenerator disks, the concentric ribs extend less than 360° about a common center; and
- wherein each of the plurality of regenerator disks comprises a ridge on a first surface and defines a corresponding groove on a second opposite surface.
Type: Application
Filed: Feb 2, 2011
Publication Date: Aug 2, 2012
Applicant: The Aerospace Corporation (El Segundo, CA)
Inventors: Sidney W. K. Yuan (Los Angeles, CA), Sonny Yi (Huntington Beach, CA), John W. Welch (Torrance, CA)
Application Number: 13/019,863
International Classification: F28D 17/02 (20060101); F25B 9/00 (20060101);