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 stator, along at least a portion of said stator length, having a stator helical profile and an epitrochoidal shape at any cross-section transverse to said stator axis,
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 that is an inner envelope formed when said epitrochoidal shape of said stator undergoes planetary motion, said rotor configured to undergo planetary motion within said stator,
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 epitrochoidal shape of said stator has n−1 lobes, where n is an integer; said rotor shape has n 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 as said stator pitch; and
a ratio of said rotor lead to said stator lead is n:(n−1).
3. The rotary machine of claim 2 wherein n=2, said rotor pitch is the same as said stator pitch, and said 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 having a plurality of chambers 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 at least one helical seal comprises at least one rotor seal mounted on said rotor.
8. The rotary machine of claim 1 wherein said at least one helical seal comprises at least one stator seal mounted on said stator.
9. The rotary machine of claim 1 wherein said at least one helical seal comprises at least one rotor seal mounted on said rotor and at least one stator seal mounted on said stator.
10. The rotary machine of claim 1 wherein said at least one helical seal comprises a rotor seal mounted on said rotor by cooperating mating features on said rotor and said rotor seal, and/or a stator seal mounted on said stator by cooperating mating features on said stator and said stator seal.
11. 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 stator, along at least a portion of said stator length, having a stator helical profile and a stator shape that is outwardly offset from an epitrochoidal shape at any cross-section transverse to said stator axis,
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 that is an inner envelope formed when said stator shape undergoes planetary motion, said rotor configured to undergo planetary motion within said stator,
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.
12. The rotary machine of claim 11 wherein:
said stator shape has n−1 lobes, where n is an integer;
said rotor shape has n 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 as said stator pitch; and
a ratio of said rotor lead to said stator lead is n:(n−1).
13. The rotary machine of claim 12 wherein n=2, said rotor pitch is the same as said stator pitch, and said ratio of said rotor lead to said stator lead is 2:1.
14. The rotary machine of claim 13 wherein said rotary machine is a multi-stage machine having a plurality of chambers between cooperating surfaces of said rotor and said stator.
15. The rotary machine of claim 14 wherein at least one of said plurality of chambers has a volume that is different from another of said plurality of chambers.
16. The rotary machine of claim 14 wherein each of said plurality of chambers has approximately the same volume.
17. The rotary machine of claim 11 wherein said at least one helical seal comprises at least one rotor seal mounted on said rotor.
18. The rotary machine of claim 11 wherein said at least one helical seal comprises at least one stator seal mounted on said stator.
19. The rotary machine of claim 11 wherein said at least one helical seal comprises at least one rotor seal mounted on said rotor and at least one stator seal mounted on said stator.
20. The rotary machine of claim 11 wherein said at least one helical seal comprises a rotor seal mounted on said rotor thread by cooperating mating features on said rotor and said rotor seal, and/or a stator seal mounted on said stator by cooperating mating features on said stator and said stator seal.