ULTRA HIGH PRESSURE TURBOMACHINE FOR WASTE HEAT RECOVERY

• US 20120306206A1
• Filed: 05/31/2012
• Published: 12/06/2012
• Est. Priority Date: 06/01/2011
• Status: Active Grant

• Current Assignee: R&D Dynamics Corporation
• Original Assignee: R&D Dynamics Corporation
• Inventors: Agrawal, Giridhari L., Buckley, Charles W., Shakil, Ali, Coward, Andrew Hamilton
• Granted Patent: US 9,476,428 B2
• Time in Patent Office: Days
• US Class Current: 290/52
• CPC Class Codes: F01D 15/10 Adaptations for driving, or combinations with, electric generators
• CPC Class Codes: F01D 25/125 of bearings
• CPC Class Codes: F01D 25/168 for axial load mainly
• CPC Class Codes: F04D 25/024 the driving means being assisted by a power recovery turbine
• CPC Class Codes: F04D 25/0606 the electric motor being specially adapted for integration in the pump
• CPC Class Codes: F04D 29/0513 hydrostatic; hydrodynamic thrust bearings
• CPC Class Codes: F04D 29/054 Arrangements for joining or assembling shafts
• CPC Class Codes: H02K 1/32 with channels or ducts for flow of cooling medium

Abstract

A turbine-driven alternator (i.e., a turbomachine) suitable for generating electrical power from process gas waste energy. In particular suitable for very high density process gases such as super critical CO2, R134a, R245fa, etc. The turboalternator comprises two separate machines, specifically, a turbine device and an alternator device operatively connected together by a coupling shaft. The rotating shaft assemblies for each machines on the turbine side and the alternator side are supported by hydrodynamic foil gas bearings. The foil gas bearings use process gas at the turbine side, enabling high-pressure operation (˜3000 psia) and thrust load balancing. At the alternator side, cooling fluid is used in the foil gas bearings, enabling high-speed (˜40,000 rpm), low-windage, oil-free operation with closed-loop shaft cooling.

Claims

1. A turbomachine for processing a high pressure process gas, said turbomachine comprising:

a turbine impeller rotatably housed in a turbine housing for processing process gas flowing between an inlet and an outlet of the turbine housing, said turbine impeller being mounted to a rotating shaft disposed within the turbine housing for rotation about a central longitudinal axis;

an electric machine housed in a machine housing, said electric machine including a stator assembly mounted in the machine housing and a rotor assembly mounted for rotation in the machine housing relative to the stator assembly;

an adapter housing connected between the turbine housing and the machine housing; and

a coupling housed in the adapter housing and joining the rotating shaft associated with the turbine impeller to the rotor assembly of the electric machine.

2. The turbomachine as claimed in claim 1, further comprising a cooling and thrust balancing system configured to use the process gas for supplying gas flow to least one hydrodynamic foil gas bearing assembly contained within the turbomachine, said cooling and thrust balancing system including:

a supply manifold for distributing process gas to at least one injection port in the turbine housing;

a plurality of seals configured to maintain pre-determined leakage from the turbine housing into the adapter housing for maintaining a pressure difference between the turbine housing and the adapter housing, said pressure in the turbine housing being higher than the pressure in the adapter housing; and

a cooling fan mounted in the machine housing and having an inlet operatively connected to the adapter housing so as to draw process gas from the adapter housing for maintaining a pressure difference between the machine housing and the adapter housing, said pressure in the machine housing being higher than the pressure in the adapter housing but lower than the pressure in the turbine housing.

3. A turbomachine comprising:

a turbine including;

a turbine housing having an inlet for receiving a process gas at a first pressure and having an outlet for discharging the process gas at a second pressure, wherein said second pressure is lower than said first pressure;

a rotating shaft mounted within the turbine housing for rotation about a central longitudinal axis, said rotating shaft being radially supported by at least one journal bearing assembly and axially supported by a thrust bearing assembly mounted within the turbine housing;

an impeller rigidly attached to the rotating shaft for rotation therewith for processing the process gas from the first pressure to the second pressure, said impeller being housed in a collector portion of the turbine housing and discharging the process gas to the outlet of the turbine housing; and

a cooling and thrust balancing system including a supply manifold connected from the inlet of the turbine housing to at least one gas injection port within the turbine housing and an exhaust manifold connected to the outlet of the turbine housing via at least one vent port within the turbine housing.

4. The turbomachine as claimed in claim 3, wherein the thrust bearing assembly includes a thrust runner operatively connected to the rotating shaft for rotation therewith, said thrust runner including a plurality of axial throughholes extending therethrough for thrust balancing.

5. The turbomachine as claimed in claim 3, further comprising:

an alternator including;

an alternator housing;

a rotor assembly rotatably mounted for rotation within the alternator housing an comprising a rotating shaft;

a stator assembly mounted in stationary relationship in the alternator housing relative to the rotor assembly; and

a cooling fan rigidly attached to the rotating shaft of the rotor assembly for rotation therewith for driving gas flow through the alternator housing and the rotor assembly; and

a coupling connecting the rotating shaft of the turbine and the rotating shaft of the alternator.

6. The turboalternator as claimed in claim 5, further comprising:

an adapter housing mounted between the turbine housing and the alternator housing;

wherein the coupling is mounted within the adapter housing.

7. The turbomachine as claimed in claim 6, wherein an inlet the cooling fan of the alternator is operatively connected to the adapter housing so as to draw gas from the adapter through a heat exchanger.

8. The turbomachine as claimed in claim 6, wherein the cooling and thrust balancing system of the turbine is configured to supply process gas to the adapter housing via controlled shaft seal leakage from the turbine housing.

9. The turbomachine as claimed in claim 6, wherein the rotor assembly of the alternator includes:

a hub having axial grooves along its outer surface;

a conductive sleeve covering the axial grooves;

at least one permanent magnet mounted over the conductive sleeve; and

an outer sleeve mounting the at least one permanent magnet to the conductive sleeve;

wherein the axial grooves are configured to receive gas flow directed through the alternator housing by rotation of the cooling fan for cooling the conductive sleeve and the hub of the rotor assembly.

10. The turbomachine as claimed in claim 9, wherein the hub of the rotor assembly is made of a non-conductive material.

11. The turbomachine as claimed in claim 5, wherein the rotor assembly of the alternator is radially supported by at least one journal bearing assembly and axially supported by a thrust bearing assembly mounted within the alternator housing, said thrust bearing assembly includes a thrust runner operatively connected to the rotor assembly for rotation therewith, said thrust runner including a plurality of axial throughholes extending therethrough for thrust balancing.

12. The turbomachine as claimed in claim 3, the cooling and thrust balancing system including:

a gas injection port through the turbine housing into a thrust bearing chamber housing the thrust bearing assembly;

a pressure relief vent port through the turbine housing at a location rearward from the thrust bearing chamber;

first and second axial seals on the rotating shaft respectively forward and rearward of the impeller;

third and fourth axial seals on the rotating shaft rearward of the thrust bearing chamber, said third and fourth axial seals being configured to supply a controlled amount of leakage from the turbine housing;

a flow vent port through the turbine housing between the third and fourth axial seals;

a plurality of pressure equalizing holes axially extending through a thrust runner operatively connected to the rotating shaft for rotation therewith; and

a bleed hole vent port formed in the turbine housing to collect flow from the at least one journal bearing assembly and from the rearward one of the first pair of axial seals.

13. The turbomachine as claimed in claim 12, said gas injection port being oriented to inject gas tangentially to the thrust runner.

14. A turbomachine for extracting energy from a high pressure process gas, said turbomachine comprising:

a turbine having a rotating shaft;

an alternator having a rotating shaft;

an adapter housing connected between static portions of the turbine and the alternator;

a coupling connecting the respective rotating shafts of the turbine and the alternator through the adapter housing;

said alternator comprising;

an alternator housing;

a stator assembly mounted in said alternator housing;

a rotor assembly rotatably housed in said alternator housing and including;

a hub having axial grooves along its outer surface;

a conductive sleeve covering the axial grooves;

at least one permanent magnet mounted over the conductive sleeve; and

an outer sleeve mounting the at least one permanent magnet to the conductive sleeve; and

a cooling fan rotatably housed in said alternator housing and rigidly connected with the rotor assembly for coaxial rotation, said cooling fan configured to drive gas flow through the axial grooves of the hub for cooling said rotor assembly and for maintaining a pressure level within the alternator housing.

15. The turbomachine as claimed in claim 14, wherein the rotor assembly includes first and second journal bearing assemblies disposed at opposing ends of the rotor assembly for radially supporting said rotor assembly within the alternator housing, and

wherein the cooling fan is configured to drive a gas flow through radial clearances through said journal bearing assemblies.

16. The turbomachine as claimed in claim 14, wherein the rotor assembly includes a thrust runner operatively connected thereto for rotation therewith, said thrust runner being associated with thrust bearings for axially supporting the rotor assembly in the alternator housing, and

wherein the cooling fan is configured to drive a gas flow through axial clearances around said thrust runner.

17. The turbomachine as claimed in claim 14, wherein the hub of the rotor assembly is made from a non-conductive material.

18. The turbomachine as claimed in claim 14, wherein the rotor assembly includes forward and rearward rings configured to axially retain the at least one permanent magnet on the conductive sleeve.

19. The turbomachine as claimed in claim 18, wherein the forward ring supports the teeth of a labyrinth seal.

20. The turbomachine as claimed in claim 18, wherein the forward and rearward rings include through holes aligned with the axial grooves of the hub.

21. The turbomachine as claimed in claim 14, wherein the cooling fan has an inlet operatively connected to the adapter housing so as to draw process gas from the adapter housing for maintaining a pressure difference between the alternator housing and the adapter housing, said pressure in the alternator housing being higher than the pressure in the adapter housing.

22. The turbomachine as claimed in claim 21, wherein the cooling fan draws process gas form the adapter housing via a sealed heat exchanger.

23. The turbomachine as claimed in claim 21, wherein the turbine includes a turbine housing and the operating pressure in said turbine housing is higher than the pressure in the alternator housing.

24. The turbomachine as claimed in claim 23, wherein said turbine housing includes an inlet for receiving a process gas at a first temperature and an outlet for discharging the process gas at a second temperature, said second temperature being less than said first temperature;

said turbine further comprising;

a rotating shaft mounted for rotation within the turbine housing, said rotating shaft including at least one journal bearing assembly for radially supporting the rotating shaft and a thrust bearing assembly for axially supporting the rotating assembly;

an impeller rigidly attached to the rotating shaft for processing the process gas from the first pressure to the second pressure, said impeller being housed in a collector portion of the turbine housing and discharging the reduced pressure process gas to the outlet of the housing;

a cooling and thrust balancing system, said system including a supply manifold connected from the inlet of the turbine housing to at least one gas injection port within the turbine housing and an exhaust manifold connected to the outlet of the turbine housing via at least one vent port within the turbine housing, said system further including at least one path for supplying process gas from the supply manifold to the adapter housing; and

a plurality of seals configured to maintain pre-determined leakage from the turbine housing into the adapter housing for maintaining a pressure difference between the turbine housing and the adapter housing, said pressure in the turbine housing being higher than the pressure in the adapter housing.

25. The turbomachine as claimed in claim 24, wherein said turbine housing, said adapter housing, and said alternator housing are hermetically sealed with a process gas loop.