Closed Cycle Brayton Cycle System and Method

Abstract

Method and unit for generating energy with improved efficiency. A Brayton cycle unit includes a multistage compressor configured to compress a flowing medium; a first heat exchanger fluidly connected to the multistage compressor and configured to transfer heat from a working medium passing the first heat exchanger to the compressed flowing medium; an expander fluidly connected to the first heat exchanger and configured to expand the heated compressed flowing medium for producing a rotation of a shaft of the expander; and a second heat exchanger fluidly connected between the expander and the compressor and configured to remove heat from the expanded flowing medium. A path of the flowing medium through the unit is closed. At least one inter-cooler mechanism between first and second stages of the multistage compressor is configured to cool the flowing medium to a predetermined temperature.

What is claimed is: 
     
         1 . A Brayton cycle unit, the unit comprising:
 a multistage compressor configured to compress a flowing medium;   a first heat exchanger fluidly connected to the multistage compressor and configured to transfer heat from a working medium passing the first heat exchanger to the compressed flowing medium;   an expander fluidly connected to the first heat exchanger and configured to expand the heated compressed flowing medium for producing a rotation of a shaft of the expander; and   a second heat exchanger fluidly connected between the expander and the compressor and configured to remove heat from the expanded flowing medium,   wherein a path of the flowing medium through the multistage compressor, the first heat exchanger, the expander and the second heat exchanger is closed, and   wherein there is at least one inter-cooler mechanism between first and second stages of the multistage compressor configured to cool the flowing medium between the first and second stages to a predetermined temperature.   
     
     
         2 . The unit of  claim 1 , wherein the multistage compressor has four stages and three inter-cooler mechanisms between each pair of adjacent stages. 
     
     
         3 . The unit of  claim 1 , further comprising:
 a recuperator having a first path that fluidly connects the multistage compressor to the first heat exchanger and a second path that fluidly connects the expander to the second heat exchanger and is configured to transfer heat from the expanded flowing medium to the compressed flowing medium.   
     
     
         4 . The unit of  claim 1 , further comprising:
 an external source circuit including
 a compressor configured to compress air and provide it to an external combustion chamber that is configured to receive the air and fuel and burn the mix and provided the exhaust gases to a path through the first heat exchanger, and 
 a heat exchanger configured to cool the exhaust gases coming from the first heat exchanger, 
   wherein the first heat exchanger is divided such that the air, the fuel and the exhaust gases are separated from the flowing medium.   
     
     
         5 . The unit of  claim 1 , wherein the flowing medium is carbon dioxide. 
     
     
         6 . The unit of  claim 5 , wherein the carbon dioxide is in a gas phase throughout the multistage compressor, the first heat exchanger, the expander, and the second heat exchanger. 
     
     
         7 . The unit of  claim 1 , wherein the flowing medium is in a gas phase when being compressed through the multistage compressor, heated in the first heat exchanger, expanded in the expander, and cooled in the second heat exchanger. 
     
     
         8 . The unit of  claim 1 , wherein the at least one inter-cooler mechanism is configured to cool the flowing medium at substantially constant pressure and at a decreasing enthalpy. 
     
     
         9 . The unit of  claim 1 , wherein the flowing medium is carbon dioxide, the carbon dioxide is in a gas phase and remains in the gas phase through the multistage compressor, the first heat exchanger, the expander, and the second heat exchanger, the multistage compressor has four stages and a bull gear with four pinions, each pinion activating an impeller for one of the stages, and the expander is a two stage expander. 
     
     
         10 . The unit of  claim 1 , wherein a compression process through the multistage compressor when plotted in a pressure versus enthalpy state space has a see-saw shape. 
     
     
         11 . A Brayton cycle system, the system comprising:
 a closed cycle Brayton unit;   an external source circuit configured to provide heat to the closed cycle Brayton unit; and   a cooling circuit configured to remove heat from the closed cycle Brayton unit,   wherein the closed cycle Brayton unit includes a multistage compressor configured to cool a flowing medium between the stages to a predetermined temperature.   
     
     
         12 . The system of  claim 11 , wherein the closed cycle Brayton unit further comprises:
 a first heat exchanger fluidly connected to the multistage compressor and configured to transfer heat from a working medium passing the first heat exchanger to the compressed flowing medium;   an expander fluidly connected to the first heat exchanger and configured to expand the heated compressed flowing medium for producing a rotation of a shaft of the expander; and   a second heat exchanger fluidly connected between the expander and the compressor and configured to remove heat from the expanded flowing medium,   wherein a path of the flowing medium through the multistage compressor, the first heat exchanger, the expander and the second heat exchanger is closed, and   wherein there is at least one inter-cooler mechanism between first and second stages of the multistage compressor configured to cool the flowing medium between the first and second stages to a predetermined temperature.   
     
     
         13 . The system of  claim 11 , wherein the multistage compressor has four stages and three inter-cooler mechanisms between each pair of adjacent stages. 
     
     
         14 . The system of  claim 11 , further comprising:
 a recuperator having a first path that fluidly connects the multistage compressor to the first heat exchanger and a second path that fluidly connects the expander to the second heat exchanger and is configured to transfer heat from the expanded flowing medium to the compressed flowing medium.   
     
     
         15 . The system of  claim 11 , wherein the external source circuit comprises:
 a compressor configured to compress air and provide it to an external combustion chamber that is configured to receive the air and fuel and burn the mix and to provide the exhaust gases to a path through the first heat exchanger, and   a heat exchanger configured to cool the exhaust gases coming from the first heat exchanger,   wherein the first heat exchanger is divided such that the air, the fuel and the exhaust gases are separated from the flowing medium.   
     
     
         16 . The system of  claim 11 , wherein the flowing medium is carbon dioxide and the carbon dioxide is in a gas phase throughout the multistage compressor, the first heat exchanger, the expander, and the second heat exchanger. 
     
     
         17 . The system of  claim 11 , wherein the flowing medium is in a gas phase when being compressed through the multistage compressor, heated in the first heat exchanger, expanded in the expander, and cooled in the second heat exchanger. 
     
     
         18 . The system of  claim 11 , wherein the at least one inter-cooler mechanism is configured to cool the flowing medium at substantially constant pressure and at a decreasing enthalpy. 
     
     
         19 . The system of  claim 1 , wherein the flowing medium is carbon dioxide, the carbon dioxide is in a gas phase and remains in the gas phase through the multistage compressor, the first heat exchanger, the expander, and the second heat exchanger, the multistage compressor has four stages and a bull gear with four pinions, each pinion activating an impeller for one of the stages, and the expander is a two stage expander. 
     
     
         20 . A method for rotating a shaft of an expander that is part of a closed cycle Brayton system, the method comprising:
 compressing a flowing medium with a multistage compressor;   cooling the flowing medium with at least one inter-cooler mechanism between first and second stages of the multistage compressor to a predetermined temperature;   circulating the compressed flowing medium to a first heat exchanger fluidly connected to the multistage compressor;   transferring heat from a working medium passing the first heat exchanger to the compressed flowing medium;   circulating the heated flowing medium to an expander that is fluidly connected to the first heat exchanger;   expanding the heated flowing medium in the expander for rotating a shaft of the expander;   circulating the expanded flowing medium to a second heat exchanger that is fluidly connected between the expander and the multistage compressor;   removing heat from the expanded flowing medium in the second heat exchanger; and   circulating the cooled flowing medium back to the multistage compressor.