Passive alternator depressurization and cooling system

Abstract

A pressure reduction system may include an alternator with a casing and a rotor positioned, at least in part, within a cavity defined by the casing. The pressure reduction system may also include a mass management system that includes a control tank configured to be maintained at a tank pressure lower than a cavity pressure within the cavity of the alternator, thereby forming a pressure differential. A first transfer conduit may transfer a working fluid from the cavity of the alternator to the control tank via the pressure differential. The mass management system may be positioned at an elevation above the alternator, and include a refrigeration loop configured to cool the working fluid contained within the control tank. A second transfer conduit may fluidly couple the alternator and the mass management system, and may transfer the cooled working fluid from the control tank to the cavity via gravitational force.

1 . A pressure reduction system comprising:
 an alternator comprising a casing and a rotor positioned, at least in part, within a cavity defined by the casing;   a mass management system comprising a control tank configured to be maintained at a tank pressure lower than a cavity pressure within the cavity to form a pressure differential therebetween; and   a first transfer conduit configured to transfer a working fluid from the cavity of the alternator to the control tank via the pressure differential.   
     
     
         2 . The pressure reduction system of  claim 1 , further comprising a second transfer conduit configured to transfer the working fluid from the control tank to the cavity. 
     
     
         3 . The pressure reduction system of  claim 1 , wherein the control tank comprises a closed refrigeration loop configured to cool the working fluid. 
     
     
         4 . The pressure reduction system of  claim 1 , further comprising a heat exchanger configured to cool the working fluid prior to the working fluid entering the control tank. 
     
     
         5 . The pressure reduction system of  claim 2 , further comprising:
 a first valve configured to control a flow of the working fluid through the first transfer conduit; and   a second valve configured to control a flow of the working fluid through the second transfer conduit.   
     
     
         6 . The pressure reduction system of  claim 2 , further comprising:
 a return conduit fluidly coupled with the second transfer conduit between the control tank and the alternator; and   a pump fluidly coupled with the return line conduit and configured to transfer the working fluid out of the pressure reduction system.   
     
     
         7 . The pressure reduction system of  claim 1 , wherein the control tank is configured to be maintained at a tank pressure between about 0.5 MPa and about 2 MPa. 
     
     
         8 . The pressure reduction system of  claim 7 , wherein the cavity is configured to maintain a cavity pressure between about 0.5 MPa and about 11 MPa. 
     
     
         9 . A cooling system comprising:
 an alternator comprising a casing and a rotor positioned, at least in part, in a cavity defined by the casing;   a mass management system comprising a control tank configured to be positioned at an elevation above the alternator, the control tank comprising a refrigeration loop configured to cool a working fluid contained within the control tank;   a first transfer conduit fluidly coupling the alternator and the mass management system and configured to transfer the working fluid from the cavity to the control tank; and   a second transfer conduit fluidly coupling the alternator and the mass management system and configured to transfer the cooled working fluid from the control tank to the cavity via gravitational force.   
     
     
         10 . The cooling system of  claim 9 , wherein the refrigeration loop is closed. 
     
     
         11 . The cooling system of  claim 9 , further comprising a heat exchanger fluidly coupled with the first transfer conduit and configured to cool the working fluid prior to the working fluid entering the control tank. 
     
     
         12 . The cooling system of  claim 9 , wherein the control tank is configured to be maintained at a tank pressure substantially lower than a cavity pressure within the cavity of the alternator. 
     
     
         13 . The cooling system of  claim 9 , further comprising:
 a return conduit fluidly coupled with the second transfer conduit between the control tank and the alternator; and   a pump fluidly coupled with the return line conduit and configured to transfer the working fluid out of the pressure reduction system.   
     
     
         14 . The cooling system of  claim 9 , wherein the working fluid comprises carbon dioxide. 
     
     
         15 . A heat engine system, comprising:
 an expansion device in a working fluid circuit, the expansion device configured to receive a working fluid at an expansion device inlet at a high pressure and to output the working fluid at a low pressure, and wherein the expansion device converts a pressure drop in the working fluid to mechanical energy;   an alternator fluidly coupled to the expansion device, the alternator converting the mechanical energy to electrical energy, the alternator comprising a casing and a rotor positioned at least in part in a cavity defined within the casing, the cavity further configured to receive a portion of the working fluid from the expansion device;   a mass management system comprising a control tank configured to be maintained at a tank pressure substantially lower than a cavity pressure within the cavity to form a pressure differential therebetween;   a first transfer conduit configured to transfer the working fluid from the cavity to the control tank via the pressure differential;   a pump fluidly coupled to the expansion device and configured to receive the working fluid at a low pressure and output the working fluid at a high pressure;   a recuperator fluidly coupled to the pump and configured to heat the working fluid exiting the pump; and   a waste heat exchanger fluidly coupled to the recuperator and configured to further heat the working fluid after exiting the recuperator and before entering the expansion device.   
     
     
         16 . The heat engine system of  claim 15 , further comprising a second transfer conduit configured to transfer the working fluid from the control tank to the cavity of the alternator. 
     
     
         17 . The system of  claim 16 , further comprising:
 a return conduit fluidly coupled with the second transfer conduit between the control tank and the alternator; and   a transfer pump configured to transfer the working fluid out of the control tank to a location in the working fluid circuit between the pump and the expansion device.   
     
     
         18 . The system of  claim 17 , wherein the cavity is configured to receive the portion of the working fluid at a leak rate, and the transfer pump is configured to transfer the working fluid to the location in the working fluid circuit between the pump and the expansion device at a rate substantially equal to the leak rate. 
     
     
         19 . The system of  claim 17 , wherein the mass management system comprises:
 a third transfer conduit configured to transfer the working fluid between the control tank and a location upstream of the expansion device; and   a fourth transfer conduit configured to transfer the working fluid between the control tank and a location upstream of the pump.   
     
     
         20 . The system of  claim 17 , further comprising a second mass management system comprising:
 a second control tank;   a third transfer conduit configured to transfer the working fluid between the second control tank and a location upstream of the expansion device; and   a fourth transfer conduit configured to transfer the working fluid between the second control tank and a location upstream of the pump.