Apparatus for recirculating a fluid within a turbomachine and method for operating the same

Abstract

A turbomachine for use with a high-temperature and high-pressure working fluid is provided. The turbomachine includes a rotatable shaft and a casing enclosing the rotatable shaft, which defines at least a first and second compartment fluidly coupled together. The first compartment at least partially encloses one of a compressor and an expander. The second compartment at least partially encloses a generator. Attached to opposite ends of the rotatable shaft is a compressor for compressing the working fluid and an expansion turbine for expanding the working fluid. A motor-generator is attached to the rotatable shaft between the compressor and expansion turbine. The turbomachine includes at least one sealing system positioned between the first and second compartments that includes a number of seals for regulating the flow rate of the working fluid between the first and second compartments and for suppressing the heat and pressure transfer between the first and second compartments.

What is claimed is: 
     
         1 . A turbomachine for use with a high-temperature and high-pressure working fluid comprising:
 a rotatable shaft defining an axis of rotation, said rotatable shaft having a first end portion and a second end portion;   a casing enclosing said rotatable shaft, said casing defining at least a first compartment at least partially enclosing one of a compressor apparatus and an expander apparatus, and a second compartment in flow communication with said first compartment and at least partially enclosing a generator apparatus;   a compressor coupled to the first end portion of said rotatable shaft for rotation therewith, said compressor configured to compress the working fluid;   an expansion turbine coupled to the second end portion of said rotatable shaft for rotation therewith, said expansion turbine configured to expand the working fluid;   a motor-generator coupled to said rotatable shaft between the first end portion and a second end portion; and   at least one sealing system positioned between said first compartment and said second compartment, said sealing system comprising a plurality of seals for regulating a predetermined flow rate of the working fluid between said first compartment containing the working fluid at a first pressure and a first temperature, and said second compartment containing the working fluid at a second pressure and a second temperature, wherein the first pressure is greater than the second pressure and the first temperature is greater than the second temperature.   
     
     
         2 . A turbomachine in accordance with  claim 1 , wherein said plurality of seals comprises:
 a first sealing device at least partially defining said first compartment; and   a second sealing device at least partially defining said second compartment.   
     
     
         3 . The turbomachine in accordance with  claim 2 , wherein said first sealing device is a labyrinth seal configured to maintain a temperature gradient across said first sealing device. 
     
     
         4 . The turbomachine in accordance with  claim 2 , wherein said second sealing device is a dry-gas seal configured to induce a pressure gradient across said second sealing device. 
     
     
         5 . The turbomachine in accordance with  claim 2 , wherein said sealing system defines an intermediate sealing cavity in flow communication with said first sealing device and said second sealing device. 
     
     
         6 . The turbomachine in accordance with  claim 5 , further comprising a sealing system cooling circuit in thermal communication with said intermediate sealing cavity. 
     
     
         7 . The turbomachine in accordance with  claim 6 , wherein said sealing system cooling circuit comprises at least one conduit coupled in flow communication with said intermediate sealing cavity, said at least one conduit configured to introduce a cooling fluid into said intermediate sealing cavity. 
     
     
         8 . The turbomachine in accordance with  claim 7 , wherein the cooling fluid is at a third temperature that is less than the second temperature. 
     
     
         9 . The turbomachine in accordance with  claim 7 , wherein said at least one conduit is coupled in flow communication with said casing, said at least one conduit configured to introduce the working fluid into said intermediate sealing cavity. 
     
     
         10 . The turbomachine in accordance with  claim 5 , further comprising at least one heat exchanger positioned within said intermediate sealing cavity, said at least one heat exchanger coupled in flow communication with an external heat transfer source. 
     
     
         11 . A sealing system for a turbomachine that includes a first compartment containing a working fluid at a first pressure and a first temperature, and a second compartment coupled in flow communication with said first compartment, the second compartment containing the working fluid at a second pressure and a second temperature, said sealing system comprising:
 a first sealing device extending about a rotatable shaft and at least partially defining the first compartment; said first sealing device configured to maintain a temperature gradient across said first sealing device; and   a second sealing device extending about the rotatable shaft and at least partially defining the second compartment; said second sealing device configured to induce a pressure gradient across said second sealing device.   
     
     
         12 . The sealing system in accordance with  claim 11 , wherein said first sealing device and said second sealing device are disposed at an axial distance from each other, wherein said first sealing device and said second sealing device define an intermediate sealing cavity in flow communication with said first compartment and said second compartment. 
     
     
         13 . The sealing system in accordance with  claim 11 , further comprising a sealing system cooling circuit in thermal communication with said intermediate sealing cavity. 
     
     
         14 . The sealing system in accordance with  claim 13 , wherein said sealing system cooling circuit comprises at least one conduit coupled in flow communication with said intermediate sealing cavity, said at least one conduit configured to introduce a cooling fluid into said intermediate sealing cavity. 
     
     
         15 . The sealing system in accordance with  claim 14 , wherein said at least one conduit is in flow communication with said first compartment, said at least one conduit configured to introduce the working fluid into said intermediate sealing cavity. 
     
     
         16 . The sealing system in accordance with  claim 11 , further comprising at least one heat exchanger positioned within said intermediate sealing cavity, said at least one heat exchanger in flow communication with an external heat transfer source. 
     
     
         17 . A method of recirculating a high-temperature and high-pressure working fluid within a turbomachine that includes a casing enclosing a rotatable shaft, said method comprising:
 pressurizing a first compartment with a working fluid at a first temperature and a first pressure;   rotating the rotatable shaft;   regulating a predetermined flow rate of the working fluid from the first compartment to a second compartment;   decreasing the first temperature and the first pressure to a second temperature and a second pressure, including;
 suppressing heat and mass transfer from the first compartment to the second compartment with a first sealing device at least partially defining the first compartment and configured to maintain a temperature gradient across the first sealing device; and 
 generating a decrease in pressure from the first compartment to the second compartment with a second sealing device at least partially defining the second compartment and configured to induce a pressure gradient across the second sealing device; and 
   pressurizing the second compartment with the working fluid at the second temperature and the second pressure.   
     
     
         18 . A method in accordance with  claim 17 , wherein decreasing the first temperature and the first pressure to a second temperature and a second pressure further includes introducing a cooling fluid at a third temperature into an intermediate sealing cavity through a sealing system cooling circuit that includes at least one conduit coupled in flow communication with the intermediate sealing cavity, wherein the third temperature is lower than the second temperature. 
     
     
         19 . A method in accordance with  claim 17 , wherein decreasing the first temperature and the first pressure to a second temperature and a second pressure further includes introducing a portion of the working fluid into the intermediate sealing cavity using a flow metering device, wherein the portion of working fluid is channeled through a sealing system cooling circuit that includes at least one conduit coupled in flow communication with the casing and the flow metering device. 
     
     
         20 . A method in accordance with  claim 17 , wherein decreasing the first temperature and the first pressure to a second temperature and a second pressure further includes channeling a cooling fluid through at least one heat exchanger positioned within and intermediate sealing cavity.