Sealing in helical trochoidal rotary machines
Sealing in rotary positive displacement machines based on trochoidal geometry that comprise a helical rotor that undergoes planetary motion within a helical stator is described. Seals can be mounted on the rotor, the stator, or both. The rotor can have a hypotrochoidal cross-section, with the corresponding stator cavity profile being the outer envelope of the rotor as it undergoes planetary motion, or the stator cavity can have an epitrochoidal cross-section with the corresponding rotor profile being the inner envelope of the trochoid as it undergoes planetary motion. In some embodiments, the geometry is offset in a manner that provides advantages with respect to sealing in the rotary machine. In multi-stage embodiments, the rotor-stator geometry remains substantially constant or varies along the axis of the rotary machine.
1. A rotary machine comprising a stator having a stator length and a stator axis, and a rotor having a rotor length and a rotor axis, said rotor disposed within said stator,
said rotor, along at least a portion of said rotor length, having a rotor helical profile, and a hypotrochoidal shape at any cross-section transverse to said rotor axis, said rotor configured to undergo planetary motion within said stator,
said stator, along at least a portion of said stator length, having a stator helical profile, and a stator shape at any cross-section transverse to said stator axis that is an outer envelope formed when said hypotrochoidal shape of said rotor undergoes planetary motion,
wherein said rotary machine further comprises at least one helical rotor seal mounted on said rotor and/or at least one helical stator seal mounted on said stator.
2. The rotary machine of claim 1 wherein:
said hypotrochoidal shape of said rotor has n lobes, where n is an integer;
said stator shape has (n−1) lobes;
said rotor has a rotor pitch and a rotor lead, and said stator has a stator pitch and a stator lead;
said rotor pitch is the same said stator pitch; and
a ratio said rotor lead to said stator lead is n:(n 1).
3. The rotary machine of claim 2 wherein said hypotrochoidal shape of said rotor is an ellipse, and n=2, wherein said rotor pitch is the same as said stator pitch, and the ratio of said rotor lead to said stator lead is 2:1.
4. The rotary machine of claim 3 wherein said rotary machine is a multi-stage machine and a plurality of chambers are formed between cooperating surfaces of said rotor and said stator.
5. The rotary machine of claim 4 wherein each of said plurality of chambers has approximately the same volume.
6. The rotary machine of claim 4 wherein at least one of said plurality of chambers has a volume that is different from another of said plurality of chambers.
7. The rotary machine of claim 1 wherein said rotor has a double-start helical profile having a first rotor thread and a second rotor thread, said stator has a single-start helical profile, and said at least one helical seal comprises two rotor seals mounted on said rotor and/or a stator seal mounted on said stator.
8. The rotary machine of claim 1 wherein said rotor has a double-start helical profile having a first rotor thread defining a first rotor thread crest and a second rotor thread defining a second rotor thread crest, and wherein said stator has a single-start helical profile, and said at least one helical seal comprises:
a first helical rotor seal mounted in a first groove extending along said first rotor thread crest; and
a second helical rotor seal mounted in a second groove extending along said second rotor thread crest.
9. The rotary machine of claim 1 wherein said rotor has a double-start helical profile, and said stator has a single-start helical profile having a first stator thread defining a first stator thread crest, and wherein said at least one helical seal comprises:
a helical stator seal mounted in a first groove extending along said first stator thread crest.
10. The rotary machine of claim 1 wherein said rotor has a double-start helical profile having a first rotor thread defining a first rotor thread crest and a second rotor thread defining a second rotor thread crest, and wherein said stator has a single-start helical profile having a first stator thread defining a first stator thread crest, and said at least one helical seal comprises:
a first helical rotor seal mounted in a first rotor groove extending along said first rotor thread crest;
a second helical rotor seal mounted in a second rotor groove extending along said second rotor thread crest; and
a helical stator seal mounted in a first stator groove extending along said first stator thread crest.
11. The rotary machine of claim 1 wherein said rotor has a double-start helical profile having a first rotor thread and a second rotor thread, said stator has a single-start helical profile, and said at least one helical seal comprises:
a first helical rotor seal mounted on said first rotor thread by cooperation of a first mating feature on said first rotor thread with a second mating feature on said first helical rotor seal; and
a second helical rotor seal mounted on said second rotor thread by cooperation of a third mating feature on said second rotor thread with a fourth mating feature on said first helical rotor seal.
12. A rotary machine comprising a stator having a stator length and a stator axis, and a rotor having a rotor length and a rotor axis, said rotor disposed within said stator,
said rotor, along at least a portion of said rotor length, having a rotor helical profile, and a rotor shape at any cross-section transverse to said rotor axis, wherein said rotor shape is inwardly offset from a hypotrochoidal shape, said rotor configured to undergo planetary motion within said stator, and
said stator, along at least a portion of said stator length, having a stator helical profile, and a stator shape at any cross-section transverse to said stator axis wherein said stator shape is an outer envelope formed when said rotor shape undergoes planetary motion,
wherein said rotary machine further comprises at least one helical rotor seal mounted to said rotor and/or at least one helical stator seal mounted to said stator.
13. The rotary machine of claim 12 wherein:
said rotor shape has n lobes, where n is an integer;
said stator shape has (n−1) lobes;
said rotor has a rotor pitch and a rotor lead, and said stator has a stator pitch and a stator lead;
said rotor pitch is the same said stator pitch; and
a ratio said rotor lead to said stator lead is n:(n 1).
14. The rotary machine of claim 13 wherein said rotor shape is an ellipse, and n=2, wherein said rotor pitch is the same as said stator pitch, and the ratio of said rotor lead to said stator lead is 2:1.
15. The rotary machine of claim 12 wherein said rotor has a double-start helical profile having a first rotor thread and a second rotor thread, said stator has a single-start helical profile, and said at least one helical seal comprises two rotor seals mounted on said rotor and/or a stator seal mounted on said stator.
16. The rotary machine of claim 12 wherein said rotor has a double-start helical profile having a first rotor thread defining a first rotor thread crest, and a second rotor thread defining a second rotor thread crest, and wherein said stator has a single-start helical profile, and said at least one helical seal comprises:
a first helical rotor seal mounted in a first groove extending along said first rotor thread crest; and
a second helical rotor seal mounted in a second groove extending along said second rotor thread crest.
17. The rotary machine of claim 12 wherein said rotor has a double-start helical profile, and said stator has a single-start helical profile having a first stator thread defining a first stator thread crest, and wherein said at least one helical seal comprises:
a helical stator seal mounted in a first groove extending along said first stator thread crest.
18. The rotary machine of claim 12 wherein said rotor has a double-start helical profile having a first rotor thread defining a first rotor thread crest, and a second rotor thread defining a second rotor thread crest, and wherein said stator has a single-start helical profile having a first stator thread defining a first stator thread crest, and said at least one helical seal comprises:
a first helical rotor seal mounted in a first groove extending along said first rotor thread crest;
a second helical rotor seal mounted in a second groove extending said second rotor thread crest; and
a helical stator seal mounted in a third groove extending along said first stator thread crest.
19. The rotary machine of claim 12 wherein said rotor has a double-start helical profile having a first rotor thread and a second rotor thread, said stator has a single-start helical profile, and said at least one helical seal comprises:
a first helical rotor seal mounted on said first rotor thread by cooperation of a first mating feature on said first rotor thread with a second mating feature on said first helical rotor seal; and
a second helical rotor seal mounted on said second rotor thread by cooperation of a third mating feature on said second rotor thread with a fourth mating feature on said first helical rotor seal.
20. The rotary machine of claim 12 wherein said rotary machine is a multi-stage machine and a plurality of chambers are formed between cooperating surfaces of said rotor and said stator.