Apparatus and method for operating internal combustion engines from variable mixtures of gaseous fuels

• US 6,612,269 B2
• Filed: 08/08/2001
• Issued: 09/02/2003
• Est. Priority Date: 08/11/2000
• Status: Expired

• Current Assignee: Regents of the University of California (University of California)
• Original Assignee: Regents of the University of California (University of California)
• Inventors: Scott, Paul B., Heffel, James W.
• Primary Examiner(s): Yuen, Henry C.
• Assistant Examiner(s): Ali, Hyder
• Application Number:
  US09/925,281
• Publication Number:
  US 20020029770A1
• Time in Patent Office: 755 Days
• Field of Search: 123/527, 123/575, 123/494, 123/1.A, 123/3, 123/DIG.12, 123/27.GE, 123/431
• US Class Current: 123/1.00A
• CPC Class Codes: F02B 43/00 Engines characterised by operating on gaseous fuels; Plants including such engines engines characterised by the gas-air charge being ignited by compression ignition of an additional fuel F02B7/06; engines convertible from gas to other fuel consumption F02B69/04
• CPC Class Codes: F02B 43/10 Engines or plants characterised by use of other specific gases, e.g. acetylene, oxyhydrogen
• CPC Class Codes: F02B 51/00 Other methods of operating engines involving pretreating of, or adding substances to, combustion air, fuel, or fuel-air mixture of the engines
• CPC Class Codes: F02D 19/024 by controlling fuel injectors
• CPC Class Codes: F02D 19/029 Determining density, viscosity, concentration or composition
• CPC Class Codes: F02D 19/0644 the gaseous fuel being hydrogen, ammonia or carbon monoxide
• CPC Class Codes: F02D 19/087 with determination of densities, viscosities, composition, concentration or mixture ratios of fuels
• 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 2254/11 Catalytic burners
• CPC Class Codes: F02M 21/0215 Mixtures of gaseous fuels; Natural gas; Biogas; Mine gas; Landfill gas
• CPC Class Codes: G01N 25/18 by investigating thermal conductivity by calorimetry G01N25/20; by measuring change of resistance of an electrically-heated body G01N27/18
• CPC Class Codes: Y02T 10/30 Use of alternative fuels, e.g. biofuels

Abstract

An apparatus and method for utilizing any arbitrary mixture ratio of multiple fuel gases having differing combustion characteristics, such as natural gas and hydrogen gas, within an internal combustion engine. The gaseous fuel composition ratio is first sensed, such as by thermal conductivity, infrared signature, sound propagation speed, or equivalent mixture differentiation mechanisms and combinations thereof which are utilized as input(s) to a “multiple map” engine control module which modulates selected operating parameters of the engine, such as fuel injection and ignition timing, in response to the proportions of fuel gases available so that the engine operates correctly and at high efficiency irrespective of the gas mixture ratio being utilized. As a result, an engine configured according to the teachings of the present invention may be fueled from at least two different fuel sources without admixing constraints.

Claims

1. A variable gaseous fuels engine, comprising:

an internal combustion engine having a combustion chamber;

said combustion chamber adapted to receive a mixture of a first gaseous fuel and a second gaseous fuel for combustion therein;

means for detecting the ratio of said first and second gaseous fuels in said mixture and generating a fuel composition signal in response to said detected ratio; and

an engine control module;

said engine control module adapted to modulate the quantity of said gaseous fuel mixture received within said combustion chamber in response to said fuel composition signal;

wherein said engine is thereby capable of operating from any arbitrary mixture of said first and second gaseous fuels.

2. A variable gaseous fuels engine as recited in claim 1, wherein said gaseous fuel composition detecting means comprises:

an electronic sensor;

said electronic sensor adapted to differentiate one or more characteristics of hydrogen from one or more characteristics of natural gas.

3. A variable gaseous fuels engine as recited in claim 2, wherein said electronic sensor comprises a thermal conductivity sensor.

4. A variable gaseous fuels engine as recited in claim 3, wherein said thermal conductivity sensor comprises:

a housing having a passageway through which said gaseous fuel can flow; and

a thermal conductivity sensor element positioned within said passageway;

said thermal conductivity sensor element adapted to make fluidic contact with said gaseous fuel.

5. A variable gaseous fuels engine as recited in claim 4, wherein said housing is maintained at a substantially constant temperature.

6. A variable gaseous fuels engine as recited in claim 4, wherein said thermal conductivity sensor element comprises a filament through which a first electrical current is passed for the registration of thermal conductivity for said gaseous fuel with which it is in contact.

7. A variable gaseous fuels engine as recited in claim 5:

wherein said first electrical current is of sufficient amperage to heat said filament to a temperature exceeding the temperature of said gaseous fuel; and

wherein the thermal conductivity of said gaseous fuel is determined from analyzing the conductive heat dissipation which occurs to moderate the elevation of filament temperature.

8. A variable gaseous fuels engine as recited in claim 7, wherein said first electrical current is in excess of one milliampere.

9. A variable gaseous fuels engine as recited in claim 7, wherein said first electrical current is less than approximately two hundred milliamperes.

10. A variable gaseous fuels engine as recited in claim 7:

wherein the amount of said filament heating is detected by registering electrical resistance of said filament;

said resistance comprising the quotient of filament voltage divided by said first current induced in said filament.

11. A variable gaseous fuels engine as recited in claim 10, wherein conductivity of the gaseous mixture is determined from the amount of filament temperature moderation which occurs in response to conductive energy losses.

12. A variable gaseous fuels engine as recited in claim 6, wherein said filament comprises a metallic material.

13. A variable gaseous fuels engine as recited in claim 12, wherein said metallic material substantially comprises tungsten.

14. A variable gaseous fuels engine as recited in claim 13, wherein said filament contains an operable quantity of Rhenium.

15. A variable gaseous fuels engine as recited in claim 14, wherein said quantity of said Rhenium is up to approximately ten percent.

16. A variable gaseous fuels engine as recited in claim 14, wherein said quantity of Rhenium is greater than approximately two percent.

17. A variable gaseous fuels engine as recited in claim 4, wherein said filament is positioned in a chamber that is in fluid communication with said passageway.

18. A variable gaseous fuels engine as recited in claim 17, wherein said filament is positioned within said chamber a predetermined offset distance from the center of said passageway.

19. A variable gaseous fuels engine as recited in claim 18, wherein said predetermined offset distance is in relation to the diameter of said chamber.

20. A variable gaseous fuels engine as recited in claim 19, wherein said offset distance is given by a distance approximately equivalent to four times the diameter of said chamber.

21. A variable gaseous fuels engine as recited in claim 18:

wherein the diameter of said chamber is approximately one-half centimeter; and

wherein the distance from the center of said passageway to said filament is approximately 2.3 centimeters.

22. A variable gaseous fuels engine as recited in claim 1, further comprising:

a pressure regulator;

said pressure regulator adapted to regulate pressure of said gaseous fuel flowing to said combustion chamber.

23. A variable gaseous fuels engine as recited in claim 22:

wherein said pressure regulator is adapted to reduce the gaseous fuel pressure to a predetermined value; and

wherein the predetermined value of fuel pressure is consistent with proper modulation of gaseous fuel quantity by said engine control module.

24. A variable gaseous fuels engine as recited in claim 23, wherein said predetermined value is approximately one hundred forty-five pounds per square inch.

25. A variable gaseous fuels engine as recited in claim 4, further comprising means for registering the temperature of said gaseous fuel whose conductivity is being registered by said thermal conductivity sensor.

26. A variable gaseous fuels engine as recited in claim 25:

wherein the temperature of said gaseous fuel is measured by passing a second current through said filament;

wherein said second current is substantially less than said first current; and

wherein the voltage expressed across said filament by said second current is substantially indicative of the temperature of said filament in substantial thermal equilibrium with said surrounding gaseous fuel.

27. A variable gaseous fuels engine as recited in claim 26, wherein said second current is less than approximately ten milliamperes.

28. A variable gaseous fuels engine as recited in claim 27, wherein said second current is approximately one milliampere.

29. A variable gaseous fuels engine as recited in claim 1, wherein said engine control module is adapted to control ignition timing within said combustion chamber in response to said fuel composition signal.

30. A variable gaseous fuels engine as recited in claim 1:

wherein said engine control module is adapted for scaling the amount of fuel being metered to said combustion chamber under current operating conditions;

wherein the scaling of the fuel amount to said combustion chamber is based on an estimation of the energy density contained in said gaseous fuel mixture; and

wherein the composition of said gaseous fuel mixture has been communicated by the receipt of said fuel composition signal.

31. A variable gaseous fuels engine capable of operating from a variable mixture of hydrogen gas and natural gas, comprising:

an internal combustion engine having a combustion chamber;

said combustion chamber adapted to receive a mixture of a first gaseous fuel and a second gaseous fuel for combustion therein;

a thermal conductivity sensor;

said thermal conductivity sensor adapted to generate a fuel composition signal indicative of the ratio of said first and second gaseous fuels in said mixture; and

an engine control module;

said engine control module adapted to modulate said quantity of said gaseous fuel mixture received within said combustion chamber in response to said fuel composition signal;

wherein said engine is thereby capable of operating from any arbitrary mixture of said first and second gaseous fuels.

32. A variable gaseous fuels engine as recited in claim 31, wherein said engine control module is adapted to modulate ignition timing in response to changes in gaseous fuel composition as indicated by said fuel composition signal.

33. A variable gaseous fuels engine as recited in claim 31, wherein said thermal conductivity sensor comprises:

a housing having a passageway through which gaseous fuel can flow; and

a thermal conductivity sensor element positioned within said passageway.

34. A variable gaseous fuels engine as recited in claim 33, wherein said housing is maintained at a controlled temperature.

35. A variable gaseous fuels engine as recited in claim 33:

wherein said thermal conductivity sensor element comprises an electrical filament; and

wherein a first electrical current is passed through the filament for sensing the thermal conductivity of said gaseous fuels in contact therewith.

36. A variable gaseous fuels engine as recited in claim 35:

wherein said first electrical current is of sufficient amperage to heat said filament to a temperature which is elevated above that of said gaseous fuel mixture;

whereby the thermal conductivity of said gaseous fuel mixture is determined.

37. A variable gaseous fuels engine as recited in claim 36, wherein said first electrical current exceeds approximately one milliampere.

38. A variable gaseous fuels engine as recited in claim 36, wherein said first electrical current is under approximately two hundred milliamperes.

39. A variable gaseous fuels engine as recited in claim 36:

wherein conductivity of said gaseous mixture is determined from the amount of filament temperature elevation which occurs;

wherein said filament temperature elevation is determined from the resistance of said filament as given by quotient which results from dividing filament voltage by said first filament current.

40. A variable gaseous fuels engine as recited in claim 35, wherein said filament comprises a metallic material.

41. A variable gaseous fuels engine as recited in claim 40, wherein said metallic material substantially comprises Tungsten.

42. A variable gaseous fuels engine as recited in claim 40, wherein said filament comprises less than approximately ten percent Rhenium.

43. A variable gaseous fuels engine as recited in claim 40, wherein said filament comprises greater than approximately two percent Rhenium.

44. A variable gaseous fuels engine as recited in claim 35:

wherein said filament is positioned within a chamber fluidly connected to said passageway; and

wherein said chamber is adapted to partially isolate said filament from changes in convective cooling that may occur in response to variations in the gaseous fuel flow rate.

45. A variable gaseous fuels engine as recited in claim 31, further comprising:

a pressure regulator;

said pressure regulator adapted to regulate pressure of said gaseous fuel flowing to said combustion chamber.

46. A variable gaseous fuels engine as recited in claim 45, wherein said pressure regulator is adapted to limits the pressure enroute to said combustion chamber to a predetermined maximum value.

47. A variable gaseous fuels engine as recited in claim 46, wherein said maximum value of pressure is approximately one hundred forty five pounds per square inch.

48. A variable gaseous fuels engine as recited in claim 31, further comprising means for detecting the temperature of the gaseous fuel whose thermal conductivity is to be registered by said thermal conductivity sensor.

49. A variable gaseous fuels engine as recited in claim 48:

wherein the temperature of said gaseous fuel is measured by passing a second current through said filament within said thermal conductivity sensor;

wherein said second current is substantially less than said first current; and

wherein the voltage induced in the filament by said second current is substantially indicative of the temperature of the filament in substantial thermal equilibrium with the surrounding gaseous fuel.

50. A variable gaseous fuels engine as recited in claim 49, wherein said second current is less than approximately ten milliamperes.

51. A variable gaseous fuels engine as recited in claim 50, wherein said second current is approximately one milliampere.

52. A variable gaseous fuels engine as recited in claim 31, wherein said engine control module is adapted to vary ignition timing of said internal combustion engine in response to the determined fuel composition.

53. A variable gaseous fuels engine as recited in claim 31:

wherein said engine control module is adapted to modulate the amount of fuel being metered to said combustion chamber; and

wherein fuel metering is based on an estimation of the energy density contained in said gaseous fuel mixture whose composition has been determined.

54. In an internal combustion engine configured for generating mechanical energy by the combustion of a gaseous fuel mixture of first and second gaseous fuels, the improvement comprising:

a fuel composition sensor positioned for contacting said gaseous fuel mixture;

said fuel composition sensor adapted to generate a gaseous fuel composition signal indicative of the ratio of said first and second gaseous fuels in said gaseous fuel mixture; and

an engine control module;

said engine control module adapted to modulate said quantity of said gaseous fuel received within said combustion chamber in response to said fuel composition signal;

wherein said engine is thereby capable of operating from any arbitrary mixture of said first and second gaseous fuels.

55. An improved internal combustion engine as recited in claim 54, wherein the gaseous fuel composition substantially comprises hydrogen gas, or natural gas, or any combined mixture of hydrogen and natural gas.

56. An improved internal combustion engine as recited in claim 54:

wherein said fuel composition sensor comprises a sensor capable of registering a differentiable characteristic of the admixed constituents of said gaseous fuel; and

wherein said differentiable characteristic is substantially indicative of fuel composition.

57. An improved internal combustion engine as recited in claim 56, wherein said differentiable characteristic is registered by a thermal conductivity sensor positioned for contact with said gaseous fuel.

58. An improved internal combustion engine as recited in claim 57:

wherein said thermal conductivity sensor comprises a heated filament retained in contact with said gaseous fuel; and

wherein the temperature of said heated filament in relation to the temperature of said gaseous fuel is utilized as an indicator of the thermal conductivity of said gaseous fuel which is in contact with said heated filament.

59. A fuel composition sensor capable of communicating a differentiable characteristic between at least two gaseous fuels within a gaseous fuel mixture, said characteristic being communicated for receipt by an electronic engine control module within an internal combustion engine that operates subject to the receipt of variable mixtures of gaseous fuel, comprising:

a housing having a passageway through which a gaseous fuel mixture passes prior to receipt by the internal combustion engine;

a filament positioned within said passageway and positioned to establish fluidic contact with said gaseous fuel mixture;

a first electrical current source capable of being connected to said filament;

said first electrical current source capable of inducing sufficient current flow within said filament to increase the temperature of said filament above the temperature of the surrounding gaseous fuel composition; and

voltage measurement means configured to register filament voltage and to communicate said filament voltage to an electronic engine control module;

whereby the ratio of a first gaseous fuel and a second gaseous fuel in said gaseous fuel mixture is determined by evaluating the thermal conductivity of said gaseous fuel mixture as a function of filament voltage;

wherein said fuel composition sensor renders said engine capable of operating from any arbitrary mixture of said first and second gaseous fuels.

60. A fuel composition sensor as recited in claim 59, wherein the gaseous fuel comprises a variable gaseous mixture of fuels comprising a first gaseous fuel, or a second gaseous fuel, or an admixed combination of said first gaseous fuel and said second gaseous fuel.

61. A fuel composition sensor as recited in claim 60, wherein said first gaseous fuel comprises hydrogen gas.

62. A fuel composition sensor as recited in claim 60, wherein said second gaseous fuel comprises natural gas.

63. A fuel composition sensor as recited in claim 59, wherein said housing is maintained at a substantially fixed temperature.

64. A fuel composition sensor as recited in claim 59, wherein said first electrical current source is capable of inducing a current in excess of approximately one milliampere within said filament.

65. A fuel composition sensor as recited in claim 59, wherein said first electrical current source is capable of inducing a current less than or equal to approximately two hundred milliamperes within said filament.

66. A fuel composition sensor as recited in claim 59, wherein said filament comprises a metallic material.

67. A fuel composition sensor as recited in claim 66, wherein said metallic material substantially comprises Tungsten.

68. A fuel composition sensor as recited in claim 67, wherein said Tungsten comprises less than approximately ten percent by weight of Rhenium.

69. A fuel composition sensor as recited in claim 67, wherein said Tungsten comprises at least approximately two percent by weight of Rhenium.

70. A fuel composition sensor as recited in claim 59, wherein said filament is positioned within a chamber of said passageway to isolate said filament from the convective influence of said gaseous fuel flow through said passageway.

71. A fuel composition sensor as recited in claim 70, wherein said filament is offset from the center of said passageway by a distance approximately equivalent to four times the diameter of said chamber.

72. A fuel composition sensor as recited in claim 71, wherein the diameter of said chamber is approximately one half centimeter and the distance from the center of the passageway to said filament is approximately two centimeters.

73. A fuel composition sensor as recited in claim 59, further comprising means for registering the temperature of the gaseous fuel surrounding said filament and communicating a signal in response to said temperature for receipt by an electronic engine control module.

74. A fuel composition sensor as recited in claim 73:

wherein said temperature registration means comprises a second electrical current source which is incapable of generating sufficient current to cause substantial filament heating; and

wherein gaseous fuel temperature can be determined from the registered filament voltage.

75. A fuel composition sensor as recited in claim 74, wherein said second current is less than approximately ten milliamperes.

76. A fuel composition sensor as recited in claim 75, wherein said second current is approximately one milliampere.

77. A method of operating an internal combustion engine from a variable mixture of gaseous fuels, comprising:

determining the ratio of a first gaseous fuel and a second gaseous fuel in said mixture;

determining an amount of said gaseous fuel mixture to be metered into said internal combustion engine based on said ratio; and

adjusting fuel metering of said gaseous fuel mixture into said internal combustion engine based on said ratio;

wherein said engine is thereby capable of operating from any arbitrary mixture of first and second gaseous fuels.

78. A method as recited in claim 77, wherein said gaseous fuel comprises a first gaseous fuel, or a second gaseous fuel, or any admixed combination of said first and said second gaseous fuels.

79. A method as recited in claim 78, wherein said first gaseous fuel comprises hydrogen gas.

80. A method as recited in claim 78, wherein said second gaseous fuel comprises natural gas.

81. A method as recited in claim 78, wherein detecting the composition of the gaseous fuel mixture containing said first and said second gaseous fuel comprises finding the mixture ratio of said first gaseous fuel within said second gaseous fuel.

82. A method as recited in claim 78, wherein the detection of the gaseous fuel composition comprises:

detecting the thermal conductivity of said gaseous fuel being received by said internal combustion engine; and

evaluating the relative thermal conductivity contributions of each primary constituent of said gaseous fuel mixture to arrive at a gaseous fuel composition value expressed as a percentage of said first gaseous fuel within said second gaseous fuel.

83. A method as recited in claim 82, wherein detecting thermal conductivity is comprising:

supplying an amount of energy to heat a filament that is retained in contact with said gaseous fuel to a temperature which exceeds the gaseous fuel;

determining the temperature of the heated filament; and

determining thermal conductivity from evaluating filament temperature in relation to the supplied energy.

84. A method as recited in claim 83, wherein supplying the energy to heat the filament comprises inducing a predetermined current to flow through the filament.

85. A method as recited in claim 84, wherein determining the temperature of the filament comprises:

detecting the voltage which exists across said filament;

computing filament resistance from ohm'"'"'s law, R=V/I; and

finding the characteristic filament temperature from the computed filament Lance, wherein empirical filament data is used for correlating filament resistance to filament temperature.

86. A method as recited in claim 77, further comprising maintaining gaseous fuel pressure at a substantially constant pressure, whereby the conditions are simplified under which fuel composition is detected.

87. A method as recited in claim 77, further comprising maintaining gaseous fuel temperature at a substantially constant temperature, whereby the conditions are simplified under which the fuel composition is detected.

88. A method as recited in claim 77, further comprising measuring said gaseous fuel temperature to increase the accuracy of detecting the composition of said gaseous fuel.