HYBRID DOUBLE-INLET VALVE FOR PULSE TUBE CRYOCOOLER

Abstract

A double-inlet valve for a Gifford-McMahon (GM) type double-inlet pulse tube cryocooler system for providing cooling at cryogenic temperatures includes a fixed restrictor and a needle valve coupled to the fixed restrictor in parallel. The needle valve produces asymmetric flow. The combination of the fixed restrictor and the needle valve having an asymmetric flow provides improved alternating current (AC) flow characteristics and adjustability of direct current (DC) flow to increase the available cooling.

Claims

1. A double-inlet valve for a Gifford-McMahon (GM) type double-inlet pulse tube cryocooler system for providing cooling at cryogenic temperatures, comprising: a fixed restrictor; and a needle valve coupled to the fixed restrictor in parallel, wherein a flow through the needle valve is asymmetric.

2. The double-inlet valve of claim 1 wherein a flow through the fixed restrictor is symmetric.

3. The double-inlet valve of claim 1 wherein a flow through the fixed restrictor is asymmetric.

4. The double-inlet valve of claim 1 wherein the needle valve defines a cavity having a needle end port and a stem port, and wherein the needle valve comprises: a base that seals the cavity; and a needle extending from the base toward the needle end port, wherein a flow in a direction from the needle end port to the stem port has higher flow resistance than a flow in a direction from the stem port to the needle end port.

5. The double-inlet valve of claim 4 wherein the needle valve is adjustable for regulating an amount of the flow between the needle end port and the stem port.

6. A Gifford-McMahon (GM) type double-inlet pulse tube cryocooler system for providing cooling at cryogenic temperatures, comprising; a compressor supplying gas at a supply pressure through a supply line and receiving gas at a return pressure through a return line; a valve assembly connected to the supply and return lines; and a pulse tube cold head connected to the valve assembly, wherein the valve assembly cycles gas between the supply pressure and the return pressure to the pulse tube cold head through a connecting line, the pulse tube cold head comprising: at least one regenerator having a warm end and a cold end; at least one pulse tube having a warm end and a cold end; at least one double-inlet valve comprising: a fixed restrictor; and a needle valve coupled to the fixed restrictor in parallel, wherein a flow through the needle valve is asymmetric; a buffer volume connected to the warm end of the pulse tube; a first line extending from the connecting line to the warm end of the regenerator, wherein the double-inlet valve is connected to the first line; a second line connecting the cold end of the regenerator to the cold end of the pulse tube; and a third line from the warm end of the pulse tube to the double-inlet valve and to the buffer volume through a single-inlet valve.

7. The GM type double-inlet pulse tube cryocooler system of claim 6 wherein a flow through the fixed restrictor is symmetric.

8. The GM type double-inlet pulse tube cryocooler system of claim 6 wherein a flow through the fixed restrictor is asymmetric

9. The GM type double-inlet pulse tube cryocooler system of claim 6 wherein the needle valve defines a cavity having a needle end port and a stem port, and wherein the needle valve comprises: a base that seals the cavity; and a needle extending from the base toward the needle end port, wherein a flow in a direction from the needle end port to the stem port has higher flow resistance than a flow in a direction from the stem port to the needle end port.

10. The GM type double-inlet pulse tube cryocooler system of claim 9 wherein the needle valve is adjustable for regulating an amount of the flow between the needle end port and the stem port.

11. The GM type double-inlet pulse tube cryocooler system of claim 9 wherein the needle end port is connected to the first line and the stem port is connected to the third line.

12. The GM type double-inlet pulse tube cryocooler system of claim 11 wherein the fixed restrictor has lower flow resistance in a flow from the first line to the third line than in a flow from the third line to the first line.

13. The GM type double-inlet pulse tube cryocooler system of claim 9 wherein the needle end port is connected to the third line and the stem port is connected to the first line.

14. The GM type double-inlet pulse tube cryocooler system of claim 6 wherein the pulse tube cold head further comprises: a second stage regenerator connected to the cold end of the regenerator; a second stage pulse tube having a warm end and a cold end; a second stage double-inlet valve connected to the first line; a second stage buffer volume connected to the warm end of the second stage pulse tube; a fourth line connecting the cold end of the second stage pulse tube to a cold end of the second stage regenerator; and a fifth line from the warm end of the second stage pulse tube to the second stage double-inlet valve and to the second stage buffer volume through a single-inlet valve.

15. The GM type double-inlet pulse tube cryocooler system of claim 6 wherein the connecting line between the valve assembly and the pulse tube cold head is a single flexible hose.

16. The GM type double-inlet pulse tube cryocooler system of claim 6 wherein the connecting line between the valve assembly and the pulse tube cold head is at least 0.5 meter long.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The drawing figures depict one or more implementations in accord with the present concepts, by way of example only, not by way of limitations. In the figures, like reference numerals refer to the same or similar elements.

[0016] FIG. 1 shows a schematic of a single stage GM type double-inlet pulse tube cryocooler system having a first embodiment of the double-inlet valve of the disclosed invention.

[0017] FIG. 2 shows a schematic of a single stage GM type double-inlet pulse tube cryocooler system having a second embodiment of the double-inlet valve of the disclosed invention.

[0018] FIG. 3 shows a schematic of a single stage GM type double-inlet pulse tube cryocooler system having a third embodiment of the double-inlet valve of the disclosed invention.

[0019] FIG. 4 shows a schematic of a two stage GM type double-inlet pulse tube cryocooler system having an embodiment of the double-inlet valve of the disclosed invention.

[0020] FIGS. 5A-5C show schematics of first, second and third embodiments of the double-inlet valves.

DETAILED DESCRIPTIONS

[0021] In this section, some embodiments of the invention will be described more fully with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention, however, may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout, and prime notation is used to indicate similar elements in alternative embodiments. Parts that are the same or similar in the drawings have the same numbers and descriptions are usually not repeated.

[0022] With reference to FIG. 1, shown is a schematic of a single stage GM type double-inlet pulse tube cryocooler system 100 having a first embodiment of the double-inlet valve 1a of the disclosed invention. With reference to FIG. 5A, shown is a schematic of the first embodiment of the double-inlet valve 1a. Double-inlet valve 1a is shown in context of the entire system. Referring to FIGS. 1 and 5A, the single stage GM type double-inlet pulse tube cryocooler system 100 includes a compressor 10, a valve assembly 12 including valves 12a and 12b, and a pulse tube cold head 101. Compressor 10 is connected to supply valve 12a, V1, through supply line 11a, and return valve 12b, V2, through return line 11b. Lines 11a and 11b are typically flexible metal hoses 5 to 20 meters long, and valves 12a and 12b are typically slots in a motor driven rotary valve rotating over ports in a stationary seat. Gas, usually helium, cycles in pressure between the supply and return pressures, typically 2.2 MPa and 0.6 MPa, as it flows through connecting line 13 to the warm end 16a of the regenerator 16 and the warm end of the pulse tube 17 through the double-inlet valve 1a. The compressor 10 supplies gas at a supply pressure through a supply line 11a and receives gas at a return pressure through a return line 11b. The valves 12a and 12b are respectively connected to the supply line 11a and return line 11b that cycles gas between the supply pressure and the return pressure, through a connecting line 13, to a pulse tube cold head 101. Connecting line 13 can be a few millimeters long if valves 12a and 12b are integral to the pulse tube cold head 101 or it can be up to a meter long if the valves are remote.

[0023] The pulse tube cold head 101 includes a regenerator 16 having a warm end 16a and a cold end 16b, a pulse tube 17 having a warm flow smoother 17a at a warm end and a cold flow smoother 17b at a cold end, a line 18 connecting the regenerator cold end 16b of the regenerator 16 to the cold flow smoother 17b of the pulse tube 17, a line 7 extending from the connecting line 13 to the warm end 16a of the regenerator 16, lines 6a and 9a extending from the line 7 to a double-inlet valve 1a, a line 5 from the warm flow smoother 17a of the pulse tube 17 to a buffer volume 15 through a single-inlet valve 4, and lines 8a and 9b from the double-inlet valve 1a to the line 5 and to the warm flow smoother 17a of the pulse tube 17. Cycling flow continues to the warm end 16a of regenerator 16 through line 7, and continues to line 5 through double-inlet valve 1a. Line 5 connects at one end to the warm end of pulse tube 17 which contains warm flow smoother 17a, and at the other end to single-inlet valve 4 which in turn connects to buffer volume 15. The cold end 16b of regenerator 16 connects through line 18 to the cold end of pulse tube 17 which contains cold flow smoother 17b.

[0024] Referring to FIGS. 1 and 5A, double-inlet valve 1a includes fixed restrictor 3a and needle valve 2a which is adjustable for regulating the amount of the flow from both directions. The needle valve 2a and the fixed restrictor 3a are connected in parallel. The needle valve 2a includes a base 30 and a needle 31 extending from the base 30, both of which are disposed inside the cavity 32 formed in the needle valve 2a. Needle valve 2a includes needle end port 33 that is connected to line 7 through line 6a, and stem port 34 that is connected to the line 5 through line 8a. The needle 31 protrudes toward the needle end port 33 while the base 30 seals the cavity 32 so that a fluid flow path is formed between the needle end port 33 and stem port 34 through the cavity 32. Moving the needle 31 towards or away from the needle port 33 changes the opening of the flow channel, which changes the flow rates in both directions and the degree of asymmetry between the bidirectional flows. It is noted that the size and shape of the needle 31 and needle port 33 can be varied to change the flow rates in both directions and the degree of asymmetry of needle valve 2a, and thus the AC and DC flow characteristics.

[0025] The fixed restrictor 3a has a hole (flow path) 35a that is connected to line 9a, which is connected to the line 7, and line 9b which is connected to the line 5. The hole 35a may have the same cross-sectional area through the length of the hole, and consequently, flow through the restrictor 3a is symmetric. The symmetric flow means that gas flow in a direction has the same flow resistance as gas flow in the opposite direction. An asymmetric flow means that gas flow in a direction has a different flow resistances from gas flow in the opposite direction. In the asymmetric flow, flow resistance for gas flowing in a direction is greater or smaller than flow resistance for gas flowing in the opposite direction. The flow through needle valve 2a is asymmetric. Flow for gas entering the needle port 33 through line 6a is more restricted than flow for gas entering the stem port 34 through line 8a. Consequently, gas flow from the needle port 33 to the stem end port 34 has higher flow resistance than the gas flow from the stem port 34 to the needle port 33. In other words, flow in a direction from the needle 31 to the base 30 has a higher flow resistance than an opposite direction.

[0026] With reference to FIG. 2, shown is a schematic of a single stage GM type double-inlet pulse tube cryocooler system 200, having a second embodiment of the double-inlet valve 1b of the disclosed invention. With reference to FIG. 5B, shown is a schematic of the second embodiment of the double-inlet valve 1b. Double-inlet valve 1b differs from the double-inlet valve 1a in having needle valve 2b turned around so that the needle end port 33 connects to line 5 through line 6b and the stem port 34 connects to line 7 through line 8b. The hole 35a of the fixed restrictor 3a may have the same cross-sectional area through the length of the hole, and consequently, flow through the restrictor 3a is symmetric. The flow through needle valve 2b is asymmetric. Flow for gas entering the needle port 33 through line 6b is more restricted than flow for gas entering the stem port 34 through line 8b. Gas flow from the needle port 33 to the stem port 34 has higher flow resistance than the gas flow from the stem port 34 to the needle port 33.

[0027] The single stage GM type double-inlet pulse tube cryocooler system 200 includes a compressor 10, a valve assembly 12 including valves 12a and 12b, and a pulse tube cold head 201. The compressor 10 supplies gas at a supply pressure through a supply line 11a and receives gas at a return pressure through a return line 11b. The valves 12a and 12b are respectively connected to the supply line 11a and return line 11b that cycles gas between the supply pressure and the return pressure, through a connecting line 13, to a pulse tube cold head 201. The pulse tube cold head 201 includes a regenerator 16 having a warm end 16a and a cold end 16b, a pulse tube 17 having a warm flow smoother 17a at a warm end and a cold flow smoother 17b at a cold end, a line 18 connecting the regenerator cold end 16b to the cold flow smoother 17b of the pulse tube 17, a line 7 extending from the connecting line 13 to the warm end 16a of the regenerator 16, lines 8b and 9a extending from the line 7 to a double-inlet valve 1b, a line 5 from the warm flow smoother 17a of the pulse tube 17 to a buffer volume 15 through a single-inlet valve 4, and lines 6b and 9b from the double-inlet valve 1b to the line 5 and to the warm flow smoother 17a of the pulse tube 17.

[0028] With reference to FIG. 3, shown is a schematic of a single stage GM type double-inlet pulse tube cryocooler system 300, having a third embodiment of the double-inlet valve 1c of the disclosed invention. With reference to FIG. 5C, shown is a schematic of the third embodiment of the double-inlet valve 1c. Double-inlet valve 1c differs from 1a in having fixed restrictor 3b that has a tapered hole 35b which produces an asymmetric flow pattern. In this embodiment, the cross-sectional area of the hole 35b increases while proceeding from the connection point of the line 9a to the connection point of the line 9b. In this configuration, the fixed restrictor 3b has lower flow resistance in flow from the line 9a to the line 9b than flow in the opposite direction. It is understood that asymmetric restrictor 3b can be oriented in either direction in combination with adjustable restrictor 2a or 2b. For example, if the fixed restrictor 3b is combined with the needle valve 2b of the embodiment shown in FIG. 2, the cross-sectional area of the hole 35b may decrease while proceeding from the connection point of the line 9a to the connection point of the line 9b.

[0029] The single stage GM type double-inlet pulse tube cryocooler system 300 includes a compressor 10, a valve assembly 12 including valves 12a and 12b, and a pulse tube cold head 301. The compressor 10 supplies gas at a supply pressure through a supply line 11a and receives gas at a return pressure through a return line 11b. The valves 12a and 12b are respectively connected to the supply line 11a and return line 11b that cycles gas between the supply pressure and the return pressure, through a connecting line 13, to a pulse tube cold head 301. The pulse tube cold head 301 includes a regenerator 16 having a warm end 16a and a cold end 16b, a pulse tube 17 having a warm flow smoother 17a at a warm end and a cold flow smoother 17b at a cold end, a line 18 connecting the regenerator cold end 16b to the cold flow smoother 17b of the pulse tube 17, a line 7 extending from the connecting line 13 to the warm end 16a of the regenerator 16, lines 6a and 9a extending from the line 7 to a double-inlet valve 1c, a line 5 from the warm flow smoother 17a of the pulse tube 17 to a buffer volume 15 through a single-inlet valve 4, and lines 8a and 9b from the double-inlet valve 1c to the line 5 and to the warm flow smoother 17a of the pulse tube 17.

[0030] With reference to FIG. 4, shown is a schematic of a two stage GM type double-inlet pulse tube cryocooler system 400 which includes two pulse tubes 17 and 21. Double-inlet valve 1a is connected to first stage pulse tube system 17 and double-inlet valve 1d is connected to second stage pulse tube 21. The double-inlet valve 1d is equivalent to 1a in structures, but is arranged differently. Specifically, the double-inlet valves 1a and 1d are arranged in a mirror symmetry with respect to the line 7. Cycling flow continues to the warm end 16a′ of first stage regenerator 16′ and to second stage regenerator 20 through line 7, and continues to line 5 through double-inlet valve 1a, and to line 5a through second stage double-inlet valve 1d. Line 5 connects at one end to the warm end of first stage pulse tube 17 which contains warm flow smoother 17a, and at the other end to single-inlet valve 4 which in turn connects to buffer volume 15. Line 5a connects at one end to the warm end of the second stage pulse tube 21 which contains warm flow smoother 21a, and at the other end to single-inlet valve 4a which in turn connects to second stage buffer volume 15a.

[0031] As shown in FIG. 4, the two stage GM type double-inlet pulse tube cryocooler system 400 includes the second stage regenerator 20 as an extension of first stage regenerator 16′. The second stage pulse tube 21 is separated from first stage pulse tube 17, with the warm end at room temperature. The cold end 16b′ of first stage regenerator 16 connects through line 18 to the cold end of the first stage pulse tube 17 which contains cold flow smoother 17b. The cold end 20b of second stage regenerator 20 connects through line 22 to the cold end of the pulse tube 21 which has flow smoother 21b. The warm end of first stage pulse tube 17 has flow smoother 17a and connects to line 5, which connects to first double-inlet valve 1a and buffer volume 15 through single-inlet valve 4. The warm end of second stage pulse tube 21 has flow smoother 21a and connects to line 5a, which connects to double-inlet valve 1d and buffer volume 15a through single-inlet valve 4a.

[0032] The two stage GM type double-inlet pulse tube cryocooler system 400 includes a compressor 10, a valve assembly 12 including valves 12a and 12b, and a pulse tube cold head 401. The compressor 10 supplies gas at a supply pressure through a supply line 11a and receives gas at a return pressure through a return line 11b. The valves 12a and 12b are respectively connected to the supply line 11a and return line 11b that cycles gas between the supply pressure and the return pressure, through a connecting line 13, to a pulse tube cold head 401. The pulse tube cold head 401 includes first stage regenerator 16′ having a warm end 16a′ and a cold end 16b′, second stage regenerator 20 attached to the cold end 16b′ of the first stage regenerator 16′ and having a cold end 20b, first stage pulse tube 17 having a warm flow smoother 17a at a warm end and a cold flow smoother 17b at a cold end, second stage pulse tube 21 having a warm flow smoother 21a at a warm end and a cold flow smoother 21b at a cold end, a line 18 connecting the regenerator cold end 16b′ to the cold flow smoother 17b of the pulse tube 17, a line 22 connecting the regenerator cold end 20b to the cold flow smoother 21b of the pulse tube 21, a line 7 extending from the connecting line 13 to the warm end 16a′ of the regenerator 16, lines 6a and 9a extending from the line 7 to double-inlet valves 1a, lines 6a′ and 9a′ extending from the line 7 to double-inlet valves 1d, a line 5 from the warm flow smoother 17a of the pulse tube 17 to a buffer volume 15 through a single-inlet valve 4, and a line 5a from the warm flow smoother 21a of the pulse tube 21 to a buffer volume 15a through a single-inlet valve 4a, lines 8a and 9b from the double-inlet valve 1a to the line 5 and to the warm flow smoother 17a of the pulse tube 17, and lines 8a′ and 9b′ from the double-inlet valve 1d to the line 5a and to the warm flow smoother 21a of the pulse tube 21.

[0033] Double-inlet valve 1a has been found to give the best results for the present design. For other designs that have different pulse tube and regenerator sizes, double-inlet valves 1b and 1c may be preferred. Double-inlet valve 1a or 1d can be solely used on either the first or the second stage of the two stage GM type double-inlet pulse tube cold head 401, combined with a conventional double-inlet valve 2a on the other stage.

[0034] The terms and descriptions used herein are set forth by way of illustration only and are not meant as limitations. Those skilled in the art will recognize that many variations are possible within the spirit and scope of the invention and the embodiments described herein.