초록 ▼

A dual cycle system for generating shaft power using a supercritical fluid and a fossil fuel. The first cycle is an open, air breathing Brayton cycle. The second cycle is a closed, supercritical fluid Brayton cycle. After compression of air in the first cycle, the compressed air flows through a firs

A dual cycle system for generating shaft power using a supercritical fluid and a fossil fuel. The first cycle is an open, air breathing Brayton cycle. The second cycle is a closed, supercritical fluid Brayton cycle. After compression of air in the first cycle, the compressed air flows through a first cross cycle heat exchanger through which the supercritical fluid from the second cycle flows after it has been compressed and then expanded in a turbine. In the first cross cycle heat exchanger, the compressed air is heated and the expanded supercritical fluid is cooled. Prior to expansion in a turbine, the compressed supercritical fluid flows through a second cross cycle heat exchanger through which also flows combustion gas, produced by burning a fossil fuel in the compressed air in the first cycle. In the second cross cycle heat exchanger, the combustion gas is cooled and the compressed supercritical fluid is heated.

대표청구항 ▼

1. A method of generating shaft power in a system comprising an air cycle and supercritical fluid cycle, comprising the steps of: a) burning a fossil fuel in air so as to produce a combustion gas;b) compressing a supercritical fluid in a first compressor;c) flowing at least a portion of said compres

1. A method of generating shaft power in a system comprising an air cycle and supercritical fluid cycle, comprising the steps of: a) burning a fossil fuel in air so as to produce a combustion gas;b) compressing a supercritical fluid in a first compressor;c) flowing at least a portion of said compressed supercritical fluid through a first cross cycle heat exchanger, and flowing said combustion gas through said first cross cycle heat exchanger so as to transfer heat from said combustion gas to said compressed supercritical fluid so as to produce a heated compressed supercritical fluid;d) after step (c), expanding said combustion gas in at least a first turbine so as to produce an expanded combustion gas, said expansion of said combustion gas generating a first turbine shaft power;e) expanding at least a portion of said heated compressed supercritical fluid in a second turbine so as to produce an expanded supercritical fluid, said expansion of said supercritical fluid generating a second turbine shaft power; andf) flowing at least a portion of said expanded supercritical fluid through a second cross cycle heat exchanger, and flowing said air through said second cross cycle heat exchanger prior to burning said fossil fuel in said air so as to transfer heat from said expanded supercritical fluid to said air. 2. The method according to claim 1, further comprising the step of compressing said air in a second compressor so as to produce compressed air prior to burning said fossil fuel in said air, wherein said fossil fuel is burned in said compressed air, and wherein at least a portion of said first turbine shaft power is used to drive said second compressor, and wherein the step of flowing said air through said second cross cycle heat exchanger comprises flowing said compressed air through said second cross cycle heat exchanger so as to transfer heat from said expanded supercritical fluid to said compressed air. 3. The method according to claim 1, further comprising the step of compressing said air in a second compressor so as to produce compressed air prior to burning said fossil fuel in said air, and wherein said second compressor is operated at a pressure ratio of no more than about 2.0. 4. The method according to claim 1, wherein said supercritical fluid comprises supercritical carbon dioxide. 5. The method according to claim 1, further comprising the step of further expanding at least a first portion of said expanded supercritical fluid in a third turbine so as to produce a further expanded supercritical fluid, said further expansion of said supercritical fluid generating a third turbine shaft power. 6. The method according to claim 5, wherein said step of further expanding at least said first portion of said expanded supercritical fluid in said third turbine is performed on said supercritical fluid prior to said supercritical fluid flowing through said second cross cycle heat exchanger. 7. The method according to claim 5, further comprising the step of expanding a second portion of said expanded supercritical fluid in a nozzle, said second portion of said expanded supercritical fluid bypassing said third turbine. 8. The method according to claim 1, further comprising steps of (i) further expanding at least a first portion of said expanded supercritical fluid in a third turbine so as to produce a further expanded supercritical fluid, and (ii) reheating said at least a portion of supercritical fluid prior to said step of further expanding said supercritical fluid in said third turbine. 9. The method according to claim 8, wherein the step of reheating at least said portion of said supercritical fluid comprises flowing said portion of said supercritical fluid through said first cross cycle heat exchanger a second time, so as to transfer heat from said combustion gas to said portion of said compressed supercritical fluid thereby reheating said supercritical fluid. 10. The method according to claim 1, further comprising a step of reheating at least a portion of said combustion gas after flowing said combustion gas through said first cross cycle heat exchanger. 11. The method according to claim 10, wherein the step of reheating said combustion gas comprises burning additional fossil fuel in said combustion gas. 12. The method according to claim 1, further comprising steps of providing a supply of water and transferring heat from said expanded combustion gas from said first turbine to said water so as to generate steam. 13. The method according to claim 12, further comprising a step of transferring heat from said supercritical fluid to said steam so as to superheat said steam. 14. The method according to claim 12, further comprising a step of introducing said steam into said combustion gas. 15. The method according to claim 1, further comprising the step of flowing said supercritical fluid to said first compressor for entry and compression therein in step (b). 16. The method according to claim 15, further comprising the step of controlling said temperature of said supercritical fluid entering said first compressor. 17. The method according to claim 16, wherein the step of controlling said temperature of said supercritical fluid entering said first compressor comprises controlling said temperature to within ±2° K of the critical temperature of said supercritical fluid entering said first compressor. 18. The method according to claim 16, wherein the step of controlling said temperature of said supercritical fluid entering said first compressor comprises the step of controlling the temperature of said air flowing to said second cross cycle heat exchanger. 19. The method according to claim 18, wherein the step of controlling the temperature of said air flowing to said second cross cycle heat exchanger comprises the step of flowing said air through a cooler. 20. The method according to claim 15, wherein said first compressor has an inlet for receiving said supercritical fluid, and further comprising the step of measuring the temperature of said flow of supercritical fluid proximate the inlet of said first compressor. 21. The method according to claim 20, wherein the step of measuring the temperature of said flow of supercritical fluid comprises the step of determining the speed of sound of said supercritical fluid. 22. The method according to claim 20, wherein the step of measuring the temperature of said flow of supercritical fluid comprises the step of determining the specific heat of said supercritical fluid. 23. The method according to claim 1, wherein at least a portion of said second turbine shaft power is used to drive said first compressor. 24. The method according to claim 1, wherein the step of expanding said combustion gas in said first turbine comprises expanding said combustion gas to a pressure below atmospheric pressure. 25. The method according to claim 24, further comprising the step of compressing said expanded combustion gas to above atmospheric pressure. 26. The method according to claim 1, wherein the step of flowing said air through said second cross cycle heat exchanger comprises flowing air at ambient temperature and pressure through said second cross cycle heat exchanger. 27. A method of generating shaft power in a system comprising an air cycle and supercritical fluid cycle, comprising the steps of: a) burning a fossil fuel in air so as to produce a combustion gas including a first portion of said combustion gas and a second portion of said combustion gas;b) expanding said combustion gas in at least a first turbine so as to produce an expanded combustion gas, said expansion of said combustion gas generating a first turbine shaft power;c) compressing a supercritical fluid in a first compressor;d) flowing at least a portion of said compressed supercritical fluid through a first cross cycle heat exchanger, and flowing said combustion gas through said first cross cycle heat exchanger so as to transfer heat from said combustion gas to said compressed supercritical fluid so as to produce a heated compressed supercritical fluid, wherein said first portion of said combustion gas flows through said first cross cycle heat exchanger before the step of expanding said combustion gas in said first turbine and said second portion of said combustion gas flows through said first cross cycle heat exchanger after the step of expanding said combustion gas in said first turbine;e) expanding at least a portion of said heated compressed supercritical fluid in a second turbine so as to produce an expanded supercritical fluid, said expansion of said supercritical fluid generating a second turbine shaft power; andf) flowing at least a portion of said expanded supercritical fluid through a second cross cycle heat exchanger, and flowing said air through said second cross cycle heat exchanger prior to burning said fossil fuel in said air so as to transfer heat from said expanded supercritical fluid to said air. 28. The method according to claim 27, wherein said supercritical fluid comprises supercritical carbon dioxide. 29. The method according to claim 27, further comprising the step of further expanding at least a first portion of said expanded supercritical fluid in a third turbine so as to produce a further expanded supercritical fluid, said further expansion of said supercritical fluid generating a third turbine shaft power. 30. The method according to claim 27, further comprising the step of flowing said supercritical fluid to said first compressor for entry and compression therein in step (c). 31. The method according to claim 30, further comprising the step of controlling said temperature of said supercritical fluid entering said first compressor. 32. The method according to claim 31, wherein the step of controlling said temperature of said supercritical fluid entering said first compressor comprises controlling said temperature to within ±2° K of the critical temperature of said supercritical fluid entering said first compressor. 33. The method according to claim 31, wherein the step of controlling said temperature of said supercritical fluid entering said first compressor comprises the step of controlling the temperature of said air flowing to said second cross cycle heat exchanger. 34. The method according to claim 33, wherein the step of controlling the temperature of said air flowing to said second cross cycle heat exchanger comprises the step of flowing said air through a cooler. 35. A method of generating shaft power in a system comprising an air cycle and supercritical fluid cycle, comprising the steps of: a) burning a fossil fuel in air so as to produce a combustion gas;b) expanding said combustion gas in at least a first turbine so as to produce an expanded combustion gas, said expansion of said combustion gas generating a first turbine shaft power;c) compressing a supercritical fluid in a first compressor;d) flowing at least a portion of said compressed supercritical fluid through a first cross cycle heat exchanger, and flowing said combustion gas through said first cross cycle heat exchanger so as to transfer heat from said combustion gas to said compressed supercritical fluid so as to produce a heated compressed supercritical fluid;e) expanding at least a portion of said heated compressed supercritical fluid in a second turbine so as to produce an expanded supercritical fluid, said expansion of said supercritical fluid generating a second turbine shaft power; andf) flowing at least a portion of said expanded supercritical fluid through a second cross cycle heat exchanger, and flowing said air through said second cross cycle heat exchanger prior to burning said fossil fuel in said air so as to transfer heat from said expanded supercritical fluid to said air, wherein sufficient heat is transferred from said expanded supercritical fluid to said air in said second cross cycle heat exchanger to cool said expanded supercritical fluid to approximately the critical temperature of said supercritical fluid. 36. The method according to claim 35, wherein the step of flowing said combustion gas through said first cross cycle heat exchanger is performed after the step of expanding said combustion gas in said first turbine. 37. The method according to claim 35, wherein the step of flowing said combustion gas through said first cross cycle heat exchanger is performed before the step of expanding said combustion gas in said first turbine. 38. The method according to claim 35, wherein a first portion of said combustion gas flows through said first cross cycle heat exchanger before the step of expanding said combustion gas in said first turbine and a second portion of said combustion gas flows through said first cross cycle heat exchanger after the step of expanding said combustion gas in said first turbine. 39. The method according to claim 35, wherein said supercritical fluid comprises supercritical carbon dioxide. 40. The method according to claim 35, wherein said air is cooled prior to said air flowing through said second cross cycle heat exchanger. 41. The method according to claim 40, wherein the amount of cooling of said air prior to said air flowing through said second cross cycle heat exchanger is adjusted so as to control the amount of heat transferred from said expanded supercritical fluid to said air in said second cross cycle heat exchanger so as to cool said expanded supercritical fluid to approximately the critical temperature of said supercritical fluid. 42. The method according to claim 35, further comprising the step of further expanding at least a first portion of said expanded supercritical fluid in a third turbine so as to produce a further expanded supercritical fluid, said further expansion of said supercritical fluid generating a third turbine shaft power. 43. The method according to claim 35, further comprising the step of flowing said supercritical fluid to said first compressor for entry and compression therein in step (c). 44. The method according to claim 43, further comprising the step of controlling said temperature of said supercritical fluid entering said first compressor. 45. The method according to claim 44, wherein the step of controlling said temperature of said supercritical fluid entering said first compressor comprises controlling said temperature to within ±2° K of the critical temperature of said supercritical fluid entering said first compressor. 46. The method according to claim 44, wherein the step of controlling said temperature of said supercritical fluid entering said first compressor comprises the step of controlling the temperature of said air flowing to said second cross cycle heat exchanger. 47. The method according to claim 46, wherein the step of controlling the temperature of said air flowing to said second cross cycle heat exchanger comprises the step of flowing said air through a cooler. 48. A method of generating shaft power in a system comprising an air cycle and supercritical fluid cycle, comprising the steps of: a) burning a fossil fuel in air so as to produce a combustion gas;b) expanding said combustion gas in at least a first turbine so as to produce an expanded combustion gas, said expansion of said combustion gas generating a first turbine shaft power, wherein the first turbine drives a first turbine shaft;c) compressing a supercritical fluid in a first compressor;d) flowing at least a portion of said compressed supercritical fluid through a first cross cycle heat exchanger, and flowing said combustion gas through said first cross cycle heat exchanger so as to transfer heat from said combustion gas to said compressed supercritical fluid so as to produce a heated compressed supercritical fluid;e) expanding at least a portion of said heated compressed supercritical fluid in a second turbine so as to produce an expanded supercritical fluid, said expansion of said supercritical fluid generating a second turbine shaft power, wherein said second turbine drives a second turbine shaft;f) transmitting torque from said second turbine shaft to an output shaft without contact between said second turbine shaft and said output shaft; andg) flowing at least a portion of said expanded supercritical fluid through a second cross cycle heat exchanger, and flowing said air through said second cross cycle heat exchanger prior to burning said fossil fuel in said air so as to transfer heat from said expanded supercritical fluid to said air. 49. The method according to claim 48, wherein the step of flowing said combustion gas through said first cross cycle heat exchanger is performed after the step of expanding said combustion gas in said first turbine. 50. The method according to claim 48, wherein the step of flowing said combustion gas through said first cross cycle heat exchanger is performed before the step of expanding said combustion gas in said first turbine. 51. The method according to claim 48, wherein a first portion of said combustion gas flows through said first cross cycle heat exchanger before the step of expanding said combustion gas in said first turbine and a second portion of said combustion gas flows through said first cross cycle heat exchanger after the step of expanding said combustion gas in said first turbine. 52. The method according to claim 48, wherein said supercritical fluid comprises supercritical carbon dioxide. 53. The method according to claim 48, wherein sufficient heat is transferred from said expanded supercritical fluid to said air in said second cross cycle heat exchanger to cool said expanded supercritical fluid to approximately the critical temperature of said supercritical fluid. 54. The method according to claim 48, further comprising prior to the step of expanding at least a first portion of said heated expanded supercritical fluid in said second turbine, expanding said supercritical fluid in a third turbine, said expansion of said supercritical fluid in the third turbine generating a third turbine shaft power. 55. The method according to claim 48, wherein the step of transmitting torque from said second turbine shaft to said output shaft comprises transmitting said torque via an eddy current coupling. 56. The method according to claim 55, further comprising the step of flowing a portion of said compressed supercritical fluid to said eddy current coupling so as to cool said coupling and heat said portion of said compressed supercritical fluid. 57. The method according to claim 56, further comprising flowing said portion of said heated compressed supercritical fluid from said eddy current coupling to said first cross cycle heat exchanger. 58. A method of generating shaft power in a system comprising an air cycle and supercritical fluid cycle, comprising the steps of: a) burning a fossil fuel in air so as to produce a combustion gas;b) expanding said combustion gas in at least a first turbine so as to produce an expanded combustion gas, said expansion of said combustion gas generating a first turbine shaft power;c) compressing a supercritical fluid in a first compressor;d) flowing at least a portion of said compressed supercritical fluid through a first cross cycle heat exchanger, and flowing said combustion gas through said first cross cycle heat exchanger so as to transfer heat from said combustion gas to said compressed supercritical fluid so as to produce a heated compressed supercritical fluid and cooled combustion gas;e) transferring heat from said cooled combustion gas to a flow of water so as to heat said flow of water;f) expanding at least a portion of said heated compressed supercritical fluid in a second turbine so as to produce an expanded supercritical fluid, said expansion of said supercritical fluid generating a second turbine shaft power; andg) flowing at least a portion of said expanded supercritical fluid through a second cross cycle heat exchanger, and flowing said air through said second cross cycle heat exchanger prior to burning said fossil fuel in said air so as to transfer heat from said expanded supercritical fluid to said air. 59. The method according to claim 58, wherein the step of flowing said combustion gas through said first cross cycle heat exchanger is performed after the step of expanding said combustion gas in said first turbine. 60. The method according to claim 58, wherein the step of flowing said combustion gas through said first cross cycle heat exchanger is performed before the step of expanding said combustion gas in said first turbine. 61. The method according to claim 58, wherein a first portion of said combustion gas flows through said first cross cycle heat exchanger before the step of expanding said combustion gas in said first turbine and a second portion of said combustion gas flows through said first cross cycle heat exchanger after the step of expanding said combustion gas in said first turbine. 62. The method according to claim 58, wherein said supercritical fluid comprises supercritical carbon dioxide. 63. The method according to claim 58, wherein sufficient heat is transferred from said expanded supercritical fluid to said air in said second cross cycle heat exchanger to cool said expanded supercritical fluid to approximately the critical temperature of said supercritical fluid. 64. The method according to claim 58, further comprising the step of further expanding at least a first portion of said expanded supercritical fluid in a third turbine so as to produce a further expanded supercritical fluid, said further expansion of said supercritical fluid generating a third turbine shaft power.