Method and apparatus for converting thermal energy to mechanical energy

• US 7,284,372 B2
• Filed: 11/04/2004
• Issued: 10/23/2007
• Est. Priority Date: 11/04/2004
• Status: Expired due to Fees

• Current Assignee: Darby Crow
• Original Assignee: Darby Crow
• Inventors: Crow, Darby
• Primary Examiner(s): NGUYEN, HOANG M
• Application Number:
  US10/982,167
• Publication Number:
  US 20060090467A1
• Time in Patent Office: 1,083 Days
• Field of Search: 605/17, 605/18, 605/19, 605/20, 605/21, 605/25
• US Class Current: 60/519
• CPC Class Codes: F02G 1/043 the engine being operated by expansion and contraction of a mass of working gas which is heated and cooled in one of a plurality of constantly communicating expansible chambers, e.g. Stirling cycle type engines
• CPC Class Codes: F02G 2242/44 having two pistons and reverse flow regenerators
• CPC Class Codes: F02G 2244/12 having opposed pistons
• CPC Class Codes: F28D 17/02 using rigid bodies, e.g. of porous material
• CPC Class Codes: F28D 21/00 Heat-exchange apparatus not covered by any of the groups F28D1/00 - F28D20/00

Abstract

A method and apparatus for converting thermal energy to mechanical energy which can use a wide range of fuels and perform with a high efficiency. Operating on a little utilized thermodynamic cycle of isentropic compression, isothermal expansion, isentropic expansion and finally constant pressure cooling and contraction. The external heat engine utilizes a heat exchanger carrying heat from the external energy source to the working parts of the engine. Pistons and cylinders are activated by appropriate means to adiabatically compress the working fluid, for example ambient air, to transfer the entire mass of the air through the heat exchanger to accomplish isothermal expansion followed by adiabatic expansion and, finally, exhaust the air to ambient to allow for constant pressure cooling and contraction. Valve pistons in conjunction with the cylinders form valves that allow for the exchange of working fluid with ambient. Energy is added to the engine during isothermal expansion, whereby the energy of compression is added by a flywheel or other appropriate energy storage means, said flywheel stores energy recovered during adiabatic expansion. The thermodynamic cycle described and the engine embodiments disclosed, when run in reverse, perform as a heat pump or refrigeration device.

Claims

1. A method for converting thermal energy to mechanical energy, comprising the steps of:

providing a unit mass of working fluid;

isentropically compressing the unit mass of working fluid to a higher temperature and a higher pressure;

adding thermal energy from a source external to the working fluid to the unit mass while isothermally expanding the unit mass to a first subsequent volume;

moving at least one driving member by isentropically expanding the unit mass to a second subsequent volume; and

exhausting at least a portion of the unit mass of working fluid to ambient environment.

2. A method according to claim 1 wherein the step of providing a unit mass of working fluid comprises drawing working fluid at an ambient temperature and an ambient pressure into a compression chamber.

3. A method according to claim 2 wherein providing a unit mass of working fluid further comprises drawing working fluid at an ambient temperature and an ambient pressure into a transfer chamber.

4. A method according to claim 2 wherein the step of drawing working fluid comprises withdrawing a compression piston within a compression cylinder.

5. A method according to claim 3 wherein the step of drawing working fluid comprises withdrawing a transfer piston within a transfer cylinder.

6. A method according to claim 2 wherein the step of drawing working fluid further comprises drawing ambient air through an open intake valve.

7. A method according to claim 1 wherein the step of isentropically compressing the unit mass comprises reducing the volume of a compression chamber.

8. A method according to claim 7 wherein the step of isentropically compressing the unit mass comprises moving a compression piston within a compression cylinder defining the compression chamber.

9. A method according to claim 1 wherein the step of isentropically compressing the unit mass comprises reducing the volume of a compression chamber while reducing the volume of a transfer chamber in fluid communication with the compression chamber.

10. A method according to claim 9 wherein reducing the volume of a compression chamber while reducing the volume of a transfer chamber comprises moving a compression piston in a compression cylinder while moving a transfer piston in a transfer cylinder.

11. A method according to claim 1 wherein the step of adding thermal energy to the unit mass while isothermally expanding the unit mass comprises moving the unit mass past a heat exchanger.

12. A method according to claim 11 wherein the step of adding thermal energy to the unit mass further comprises pushing with a compression piston at least a portion of the unit mass toward a transfer chamber in fluid communication with a compression chamber.

13. A method according to claim 12 further comprising expanding a volume defined by the compression and transfer chambers to allow isothermal heat addition.

14. A method according to claim 13 comprising the further step of moving at least one driving member by the isothermal expansion of the unit mass to a first subsequent volume.

15. A method according to claim 14 wherein moving at least one driving member comprises allowing the working fluid to push a transfer piston within the transfer chamber during an early period of the isothermal expansion.

16. A method according to claim 15 wherein moving at least one driving member comprises allowing the working fluid to push the compression piston within the compression chamber during a later period of the isothermal expansion.

17. A method according to claim 12 comprising the further step, after pushing with a compression piston at least a portion of the unit mass toward a transfer chamber, of pushing with a transfer piston at least a portion of the unit mass back toward the compression chamber.

18. A method for converting thermal energy to mechanical energy, comprising the steps of:

providing a unit mass of working fluid at an ambient temperature and an ambient pressure;

isentropically compressing the unit mass of working fluid to a higher temperature and a higher pressure;

heating the unit mass by moving the unit mass past a heat exchanger while isothermally expanding the unit mass to a first subsequent volume;

isentropically expanding the unit mass to a second subsequent volume, thereby moving a first driving member and a second driving member; and

exhausting to ambient environment at least a portion the unit mass of working fluid.

19. A method according to claim 18 wherein the step of providing a unit mass of working fluid comprises drawing the working fluid into a compression chamber.

20. A method according to claim 19 wherein the step of providing a unit mass further comprises drawing the working fluid into a transfer chamber.

21. A method according to claim 19 wherein the step of drawing a working fluid comprises withdrawing a compression piston within a compression cylinder.

22. A method according to claim 21 wherein the step of drawing a working fluid comprises drawing ambient air through an open intake valve.

23. A method according to claim 19 wherein the step of isentropically compressing the unit mass comprises decreasing the combined volumes of the compression chamber and the transfer chamber.

24. A method according to claim 23 wherein the step of decreasing the combined volumes comprises moving a compression piston within a compression cylinder defining the compression chamber, the compression chamber being in fluid communication with the transfer chamber.

25. A method according to claim 19 wherein the step of heating the unit mass further comprises:

pushing with a compression piston at least a portion of the unit mass through the heat exchanger; and

then

pushing with a transfer piston at least a portion of the unit mass through the heat exchanger and toward the compression chamber.

26. A method according to claim 18 wherein isothermally expanding the unit mass comprises permitting the combined volume enclosed by a compression chamber and a transfer chamber to expand to allow isothermal heat addition to the unit mass.

27. A method according to claim 26 wherein permitting the combined volume to expand comprises maintaining the working fluid at a constant temperature.

28. A method according to claim 27 wherein moving a first driving member and a second driving member comprises allowing expanding working fluid to push a compression piston within a compression cylinder and to push a transfer piston within a transfer cylinder.

29. A method according to claim 25 wherein the step of exhausting at least a portion of the unit mass comprises pushing the working fluid with the compression piston and with the transfer piston.

30. An apparatus for converting thermal energy to mechanical energy, comprising:

means for drawing a unit mass of working fluid into a compression chamber at an ambient temperature and an ambient pressure, said means for drawing comprising;

a compression piston slidably movable within a compression cylinder; and

a transfer piston slidably moveable within a transfer cylinder, said transfer cylinder in fluid communication with said compression cylinder;

means for isentropically compressing said unit mass of working fluid to a higher temperature and a higher pressure;

means, external to the working fluid, for heating said unit mass while isothermally expanding the unit mass to a first subsequent volume;

means for isentropically expanding said unit mass to a second subsequent volume; and

means for exhausting at least a portion of said unit mass of working fluid.

31. An apparatus according to claim 30 wherein said means for drawing a working fluid further comprises an intake valve means, in fluid communication with said compression chamber, movable between an open condition for allowing ambient air into said compression chamber and a closed condition.

32. An apparatus according to claim 30 wherein said means for isentropically compressing the unit mass comprises a compression piston slidably movable within a compression cylinder.

33. An apparatus according to claim 32 wherein said means for isentropically compressing the unit mass further comprises a transfer piston slidably moveable within a transfer cylinder in fluid communication with said compression cylinder.

34. An apparatus according to claim 30 wherein said means for heating said unit mass comprises a heat exchanger.

35. An apparatus according to claim 33 wherein said means for heating said unit mass comprises a heat exchanger, and said compression piston is slidably movable in said compression cylinder to push at least a portion of said unit mass past said heat exchanger.

36. An apparatus according to claim 35 wherein said transfer piston is slidably movable in said transfer cylinder to push at least a portion of said unit mass past said heat exchanger.

37. An apparatus according to claim 36 wherein said compression chamber is substantially enclosed by said compression piston and said compression cylinder, said transfer chamber is substantially enclosed by said transfer piston and said transfer cylinder, and wherein further said means for isentropically expanding said unit mass to a second subsequent volume comprises said compression piston moving within said compression cylinder.

38. An apparatus according to claim 37 wherein said means for isentropically expanding said unit mass further comprises said transfer piston moving within said transfer cylinder.

39. An apparatus according to claim 30 wherein said means for exhausting at least a portion of said unit mass comprises an exhaust valve means, in fluid communication with a compression chamber, movable between an open condition for allowing working fluid to exhaust from said compression chamber and a closed condition.

40. An apparatus according to claim 33 wherein said heat exchanger is disposed between said compression cylinder and said transfer cylinder, and said compression piston pushes at least a portion of said unit mass from said compression chamber into said transfer chamber.

41. An apparatus according to claim 30 wherein said unit mass is exhausted to ambient air exterior to said compression chamber at a second higher temperature greater than ambient temperature.

42. An engine using a unit mass of working fluid to convert thermal energy into mechanical energy, comprising:

a compression chamber into which said unit mass of working fluid may be drawn, said compression chamber defined in part by a compression cylinder;

a compression piston slidable for reciprocating motion within said compression cylinder to draw said unit mass into said compression chamber and to isentropically compress said unit mass to a higher temperature and a higher pressure;

a transfer chamber into which at least a portion of said unit mass may be pushed, said transfer chamber defined at least in part by a transfer cylinder;

a transfer piston slidable for reciprocating motion within said transfer cylinder; and

a heat exchanger disposed operatively between said compression chamber and said transfer chamber, wherein said heat exchanger imparts thermal energy to said working fluid while at least a portion of said unit mass is moving past said heat exchanger under the urging of said compression piston, whereby at least a portion of said unit mass isothermally expands to a first subsequent volume;

wherein said transfer piston and said compression piston are responsive to isentropic expansion of said unit mass to a second subsequent volume within said transfer chamber.

43. An engine according to claim 42 further including an intake valve in communication with said compression chamber, and movable between an open condition for allowing working fluid to be drawn into said engine and a closed condition to prevent working fluid from exhausting from said engine.

44. An engine according to claim 42 wherein said compression piston is movable in said compression cylinder to push at least a portion of said unit mass from said compression chamber, past said heat exchanger, and toward said transfer chamber.

45. An engine according to claim 42 further comprising an exhaust valve in communication with said compression chamber, and movable between an open condition for allowing working fluid to exhaust from said engine and a closed condition to prevent working fluid from being drawn into said engine.

46. An engine according to claim 42 wherein said compression cylinder and said transfer cylinder are attached to opposite sides of said heat exchanger, and further comprising:

a frame upon which said heat exchanger is mounted;

an intake valve lever mounted for pivotal motion on said frame, and operatively connected to said intake valve;

an exhaust valve lever mounted for pivotal motion on said frame, and operatively connected to said exhaust valve;

a transfer lever mounted for pivotal motion on said frame, and operatively connected to said transfer piston; and

a cam drive assembly on said frame, said assembly comprising a plurality of rotatable cams engageable with corresponding ones of said levers to coordinate the timing of the movement of said pistons and said valves.

47. An engine according to claim 46 further comprising:

an intake valve port providing fluid communication between said compression chamber and the interior of an intake valve cylinder;

an exhaust valve port providing fluid communication between said compression chamber and the interior of an exhaust valve cylinder;

an intake valve piston within said intake valve cylinder, said intake valve piston slidable within said intake valve cylinder between an open position wherein said intake valve piston is removed from said intake valve port, and a closed position wherein said intake valve piston covers said intake valve port;

an exhaust valve piston within said exhaust valve cylinder, said exhaust valve piston slidable within said exhaust valve cylinder between an open position wherein said exhaust valve piston is removed from said exhaust valve port, and a closed position wherein said exhaust valve piston covers said exhaust valve port.

48. An engine according to claim 47 wherein said intake valve port is defined at least in part by an intake aperture in said intake valve cylinder, said intake aperture is aligned with an aperture in said compression cylinder, and said intake valve cylinder is disposed exterior to said compression cylinder.

49. An engine according to claim 47 wherein said exhaust valve port is defined at least in part by an exhaust aperture in said exhaust valve cylinder, said exhaust aperture is aligned with an aperture in said compression cylinder, and said exhaust valve cylinder is disposed exterior to said compression cylinder.

50. An engine according to claim 46 further comprising:

an intake valve port providing fluid communication between said compression chamber and the interior of an intake valve cylinder;

an exhaust valve port providing fluid communication between said compression chamber and the interior of an exhaust valve cylinder;

a hollow intake valve piston coaxial with said intake valve cylinder and having an intake aperture therein, said intake valve piston rotatable within said intake valve cylinder between an open position wherein said intake aperture is aligned with said intake valve port, and a closed position wherein said intake aperture is out of alignment with said intake valve port;

a hollow exhaust valve piston coaxial with said exhaust valve cylinder and having an exhaust aperture therein, said exhaust valve piston rotatable within said exhaust valve cylinder between an open position wherein said exhaust aperture is aligned with said exhaust valve port, and a closed position wherein said exhaust aperture is out of alignment with said exhaust valve port.

51. An engine according to claim 50 wherein said intake valve port is defined at least in part by an intake aperture in said intake valve cylinder, said intake aperture is aligned with an aperture in said compression cylinder, and said intake valve cylinder is disposed exterior to said compression cylinder.

52. An engine according to claim 50 wherein said exhaust valve port is defined at least in part by an exhaust aperture in said exhaust valve cylinder, said exhaust aperture is aligned with an aperture in said compression cylinder, and said exhaust valve cylinder is disposed exterior to said compression cylinder.

53. An engine according to claim 50 wherein:

said intake valve port is defined at least in part by an intake aperture in said intake valve cylinder, said intake aperture is aligned with an aperture in said compression piston;

said exhaust valve port is defined at least in part by an exhaust aperture in said exhaust valve cylinder, said exhaust aperture is aligned with an aperture in said compression piston whereby working fluid may flow through said compression piston; and

said intake valve cylinder and said exhaust valve cylinder are disposed on said compression piston.

54. An engine according to claim 50 wherein said cam drive assembly further comprises a drive axle about which said cams rotate, and further comprising:

an intake valve axle in operative connection with said intake valve piston and said drive axle, wherein rotation of said drive axle imparts rotary motion to said intake valve axle to open and close said import valve; and

an exhaust valve axle in operative connection with said exhaust valve piston and said drive axle, wherein rotation of said drive axle imparts rotary motion to said exhaust valve axle to open and close said exhaust valve.

55. An engine according to claim 54 further comprising a power lever mounted for pivotal motion on said frame, and operatively connected to said compression piston.

56. An engine according to claim 55 further comprising:

an intake valve roller rotatably disposed on said intake valve lever;

an exhaust valve roller rotatably disposed on said intake valve lever;

a transfer roller rotatably disposed on said transfer lever;

a power push roller rotatably disposed on said power lever; and

a power retract roller rotatably disposed on said power lever.

57. An engine according to claim 56 wherein said plurality of cams comprises:

an intake valve cam in rolling contact with said intake valve roller;

an exhaust valve cam in rolling contact with said exhaust valve roller;

a transfer cam in rolling contact with said transfer roller;

a compression push cam in rolling contact with said power push roller; and

a compression retract cam in rolling contact with said power retract roller;

wherein each of said cams comprises an eccentric profile, and further wherein the rotation of any one of said cams induces pivotal movement in a corresponding one of said levers.

58. An engine according to claim 54 wherein said plurality of cams are mounted on said cam drive axle for rotation at a uniform angular velocity, and further comprising a flywheel disposed on said cam drive axle.

59. An engine according to claim 54 further comprising a compression push rod mounted for reciprocating linear translation in relation to said frame, and operatively connected to said compression piston.

60. An engine according to claim 59 further comprising means for mounting said push rod for reciprocating translational movement, said mounting means comprising:

a transverse shaft;

at least two pairs of connection arms pivotally connected to said transverse shaft; and

at least two pairs of crank arms, each said crank arm pivotally connected to a corresponding connection arm, and each said connection arm pivotally connected to said frame;

wherein said push rod is connected to said transverse shaft, and wherein at least two of said crank arms are drivable in opposite directions by the rotation of one of said plurality of cams, thereby to induce translation of said push rod along the axis of said rod.

61. An engine according to claim 45 wherein said compression chamber is further defined by a supplemental compression cylinder, and further comprising:

a supplemental compression piston slidable for reciprocating motion within said supplemental compression cylinder cooperatively with the sliding of said compression piston; and

a passageway for fluid communication between said compression cylinder and said supplemental compression cylinder.

62. An engine according to claim 61 further comprising a supplemental valve in operative connection with said supplemental cylinder for permitting working fluid to be drawn into and exhausted from said supplemental compression chamber.

63. An engine according to claim 42 further comprising:

a second compression chamber into which a second unit mass of working fluid may be drawn, said second compression chamber defined at least in part by a second compression cylinder;

a second compression piston slidable for reciprocating motion within said second compression cylinder, non-cooperatively with said compression piston, to draw said second unit mass into said second compression chamber and to isentropically compress said second unit mass to said higher temperature and said higher pressure;

passage means for fluid communication between said heat exchanger and said first compression chamber, and between said heat exchanger and said second compression chamber, respectively; and

valve means for controlling flow of working fluid through said passage means;

wherein;

said heat exchanger is disposed operatively between said second compression chamber and said transfer chamber;

said heat exchanger imparts thermal energy to said working fluid while at least a portion of said second unit mass is moving past said heat exchanger under the urging of said second compression piston, whereby said at least a portion of said second unit mass isothermally expands to a first subsequent volume; and

said compression pistons reciprocate out of phase in relation to each other.

64. An engine according to claim 63 further comprising:

intake valves in communication with corresponding ones of said compression chambers, and movable between an open condition for allowing working fluid to be drawn into said engine and a closed condition to prevent working fluid from exhausting from said engine; and

exhaust valves in communication with corresponding ones of said compression chambers, and movable between an open condition for allowing working fluid to exit said engine and a closed condition to prevent working fluid from being drawn into said engine.

65. An engine according to claim 64 wherein:

said compression piston is movable in said compression cylinder to push at least a portion of said unit mass from said compression chamber, past said heat exchanger, and toward said transfer chamber;

said second compression piston is movable in said second compression cylinder to push at least a portion of said second unit mass from said second compression chamber, past said heat exchanger, and toward said transfer chamber;

wherein when said compression piston is isothermally compressing said unit mass, said second compression piston is moving to perform at least one function selected from the group consisting of isentropically expanding working fluid, exhausting working fluid, intaking working fluid, and isentropically compressing working fluid.

66. A method for converting thermal energy to mechanical energy, comprising the steps of:

providing a unit mass of working fluid;

isentropically compressing the unit mass of working fluid to a higher temperature and a higher pressure;

isothermally expanding the unit mass to a first subsequent volume while adding thermal energy to the unit mass from a source external to the working fluid, thereby moving at least one driving member;

isentropically expanding the unit mass to a second subsequent volume, thereby moving at least one driving member; and

exhausting to ambient environment at least a portion of the unit mass of working fluid.

67. A method according to claim 66 wherein providing a unit mass of working fluid comprises supplying air.

68. A method according to claim 66 wherein providing a unit mass of working fluid comprises expanding a compression chamber to draw working fluid.

69. A method according to claim 68 wherein expanding a compression chamber comprises moving a compression piston in a compression cylinder.

70. A method according to claim 68 wherein providing a unit mass further comprises the step of expanding a transfer chamber to draw working fluid.

71. A method according to claim 70 wherein expanding a transfer chamber comprises moving a transfer piston in a transfer cylinder.

72. A method according to claim 66 wherein isentropically compressing the unit mass comprises reducing the volume of a compression chamber containing working fluid.

73. A method according to claim 72 wherein reducing the volume of a compression chamber comprises moving a compression piston in a compression cylinder.

74. A method according to claim 72 wherein the volume of the compression chamber is reduced while the volume of a transfer chamber, in fluid communication with the compression chamber, is maintained substantially constant.

75. A method according to claim 72 wherein compressing the unit mass further comprises the step of reducing the volume of a transfer chamber in fluid communication with the compression chamber.

76. A method according to claim 75 wherein the volume of the transfer chamber is reduced while reducing the volume of the compression chamber.

77. A method according to claim 75 wherein reducing the volume of the transfer chamber comprises moving a transfer piston in a transfer cylinder.

78. A method according to claim 66 wherein adding thermal energy to the unit mass comprises moving at least a portion of the unit mass past a heat exchanger.

79. A method according to claim 78 wherein moving at least a portion of the unit mass past a heat exchanger comprises forcing at least a portion of the unit mass from a compression chamber into a transfer chamber in fluid communication with the compression chamber.

80. A method according to claim 79 wherein moving at least a portion of the unit mass comprises moving substantially all the unit mass past a heat exchanger.

81. A method according to claim 79 wherein forcing at least a portion of the unit mass from a compression chamber into a transfer chamber comprises forcing substantially all the unit mass from the compression chamber into the transfer chamber.

82. A method according to claim 66 wherein expanding the unit mass to a first subsequent volume while adding thermal energy to the unit mass, thereby moving at least one driving member, comprises moving a transfer piston within a transfer cylinder.

83. A method according to claim 82 wherein expanding the unit mass to a first subsequent volume while adding thermal energy to the unit mass, thereby moving at least one driving member, comprises the further step of moving a compression piston within a compression cylinder.

84. A method according to claim 83 wherein the moving of the transfer piston begins during an early period of the isothermal expansion, before the moving of the compression piston begins during a later period of the isothermal expansion.

85. A method according to claim 66 wherein isentropically expanding the unit mass to a second subsequent volume, thereby moving at least one driving member, comprises moving a compression piston within a compression cylinder.

86. A method according to claim 66 wherein isentropically expanding the unit mass to a second subsequent volume, thereby moving at least one driving member, comprises the further step of forcing at least a portion of the unit mass from a transfer chamber into a compression cylinder, thereby moving a driving member comprising a piston moveable within a cylinder.

87. A method according to claim 66 wherein exhausting at least a portion of the unit mass of working fluid comprises exhausting the unit mass at a constant pressure.

88. A method according to claim 66 wherein providing a unit mass of working fluid comprises providing a unit mass at an initial temperature, and wherein exhausting at least a portion of the unit mass comprises exhausting the unit mass at a temperature greater than the initial temperature.