Method of operating an internal combustion engine which uses a low energy gaseous fuel

• US 6,176,224 B1
• Filed: 03/30/1998
• Issued: 01/23/2001
• Est. Priority Date: 03/30/1998
• Status: Expired due to Fees

• Current Assignee: Caterpillar Incorporated
• Original Assignee: Caterpillar Incorporated
• Inventors: Wu, Min, Bernardi, John J., Walling, Dennis, Staab, Richard P.
• Primary Examiner(s): Moulis, Thomas N.
• Application Number:
  US09/050,589
• Time in Patent Office: 1,030 Days
• Field of Search: 123/525, 123/527, 123/27.GE, 123/179.16, 123/672, 123/681, 123/682, 123/683, 123/698, 123/700, 606/74, 606/76
• US Class Current: 123/527
• CPC Class Codes: F02D 19/023 to adjust the fuel mass or volume flow
• CPC Class Codes: Y02T 10/30 Use of alternative fuels, e.g. biofuels

Abstract

A method of controlling a internal combustion engine assembly is disclosed. The internal combustion engine assembly includes (i) a internal combustion engine having an engine inlet and an engine outlet, (ii) a mixing chamber having an air inlet, a gaseous fuel inlet, and a fuel-air mixture outlet, (iii) a fuel valve which controls a ratio of air-to-gaseous fuel in a fuel-air mixture advanced through the fuel-air mixture outlet of the mixing chamber, and (iv) a throttle operable to control flow rate of the fuel-air mixture which is advanced from the fuel-air mixture outlet to the engine inlet. The method includes the step of determining oxygen content of exhaust gases advanced through the engine outlet and generating a oxygen content signal in response thereto. The method further includes the step of determining a load on the internal combustion engine and generating a load signal in response thereto. The method still further includes the step of adjusting the fuel valve to alter the ratio of air-to-gaseous fuel in the fuel-air mixture advanced through the fuel-air mixture outlet of the mixing chamber based on the oxygen content signal and the load signal. The internal combustion engine assembly further includes an exhaust conduit positioned in fluid communication with the engine outlet, and an oxygen sensor positioned in the exhaust conduit for generating the oxygen content signal. The internal combustion engine assembly further includes a pressure sensor positioned in a fuel-air mixture conduit for generating the load signal. An internal combustion engine assembly is also disclosed.

Claims

1. A method of controlling an internal combustion engine assembly which includes (i) an internal combustion engine having an engine inlet and an engine outlet, (ii) a mixing chamber having an air inlet, a fuel inlet, and a fuel-air mixture outlet, (iii) a fuel valve which controls the ratio of air-to-gaseous fuel in a fuel-air mixture advanced from the fuel-air mixture outlet of the mixing chamber, and (iv) a throttle operable to control flow rate of the fuel-air mixture which is advanced from the fuel-air mixture outlet to the engine inlet, comprising the steps of:

operating the internal combustion engine assembly at a substantially constant predetermined speed;

determining oxygen content of exhaust gases advanced through the engine outlet and generating an oxygen content signal in response thereto;

measuring a parameter related to load on the internal combustion engine and generating a signal in response thereto;

calculating the internal combustion engine assembly load based upon the substantially constant predetermined speed and the signal; and

adjusting the fuel valve to alter the ratio of air-to-gaseous fuel of the fuel-air mixture advanced through the fuel-air outlet of the mixing chamber based on the oxygen content signal and the calculated load.

2. The method of claim 1, wherein the internal combustion engine assembly further includes (i) an exhaust conduit positioned in fluid communication with the engine outlet, and (ii) an oxygen sensor positioned in the exhaust conduit for generating the oxygen content signal.

3. The method of claim 1, wherein the internal combustion engine assembly further includes (i) a fuel-air mixture conduit which couples the fuel-air mixture outlet to the engine inlet, and (ii) a pressure sensor positioned in the fuel-air mixture conduit for generating the signal.

4. The method of claim 1, wherein:

the internal combustion engine assembly further includes (i) a memory device, and (ii) a data table stored in the memory device,

the data table includes a plurality of target oxygen values which correspond to a respective plurality of measured load values, and

the adjusting step includes (i) retrieving a first target oxygen value from said plurality of target oxygen values which corresponds to said calculated load, (ii) comparing said first target oxygen value to said oxygen content signal and generating a fuel valve adjustment signal in response thereto, and (iii) adjusting the fuel valve to alter the ratio of air-to-gaseous fuel of the fuel air mixture advanced through the fuel-air mixture outlet of the mixing chamber based on the fuel valve adjustment signal.

5. The method of claim 4, wherein the correspondence between the plurality of target oxygen values and the plurality of calculated load values are experimentally determined.

6. The method of claim 4, further comprising the steps of:

determining NO_x content of exhaust gases advanced through the engine outlet and generating a NO_x content signal in response thereto; and

adjusting the plurality of target oxygen values based on the NO_x content signal.

7. The method of claim 6, wherein:

the internal combustion engine assembly further includes a NO_x sensor positioned relative to the exhaust gases which are advanced through the engine outlet for generating the NO_x content signal.

8. The method of claim 1, wherein:

the gaseous fuel contains approximately X% hydrocarbon fuel, and

30<

X<

40.

9. The method of claim 1, further comprising the step of:

adjusting the fuel valve to alter the ratio of air-to-gaseous fuel in the fuel-air mixture advanced from the fuel-air mixture outlet of the mixing chamber until the oxygen content signal reaches a predetermined oxygen value in response to the calculated load being below a predetermined value.

10. The method of claim 1, further comprising the steps of (i) detecting an engine start-up condition, and (ii) performing an engine start-up routine in response to the detecting step, wherein the engine start-up routine includes the steps of:

positioning the fuel valve in a closed position so that none of the gaseous fuel is advanced through the fuel inlet of the mixing chamber;

determining engine speed of the internal combustion engine and generating an engine speed signal in response thereto; and

continuously adjusting the fuel valve to increase the ratio of air-to-gaseous fuel in the fuel-air mixture advanced through the fuel-air mixture outlet of the mixing chamber after the fuel valve positioning step until the engine speed signal reaches a predetermined level.

11. The method of claim 10, wherein the continuously adjusting step includes the step of terminating the engine start-up routine performing step if the engine speed signal does not reach the predetermined level within a predetermined time period.

12. A method of controlling a internal combustion engine assembly which includes (i) an internal combustion engine having an engine inlet and an engine outlet, (ii) a mixing chamber having an air inlet, a gaseous fuel inlet, and a fuel-air mixture outlet, (iii) a fuel valve which controls the ratio of air-to-gaseous fuel in a fuel-air mixture advanced from the fuel-air mixture outlet of the mixing chamber, and (iv) a throttle operable to control flow rate of the fuel-air mixture which is advanced from the fuel-air mixture outlet to the engine inlet, comprising the steps of:

operating the internal combustion engine assembly at a substantially constant predetermined speed;

determining oxygen content of exhaust gases advanced through the engine outlet and generating an oxygen content signal in response thereto;

measuring a parameter related to load on the internal combustion engine and generating a signal in response thereto;

calculating the internal combustion engine assembly load based upon the substantially constant predetermined speed and the signal; and

adjusting the fuel valve to alter the ratio of air-to-gaseous fuel in the fuel-air mixture advanced through the fuel-air mixture outlet of the mixing chamber based on the oxygen content signal and the calculated load,

wherein the internal combustion engine assembly further includes (i) an exhaust conduit positioned in fluid communication with the engine outlet, and (ii) an oxygen sensor positioned in the exhaust conduit for generating the oxygen content signal, and

wherein the internal combustion engine assembly further includes (i) a fuel-air mixture conduit which couples the fuel-air mixture outlet to the engine inlet, and (ii) a pressure sensor positioned in the fuel-air mixture conduit for generating the signal.

13. The method of claim 12, wherein:

the internal combustion engine assembly further includes (i) a memory device, and (ii) a data table stored in the memory device,

the data table includes a plurality of target oxygen values which correspond to a respective plurality of measured load values, and

the adjusting step includes (i) retrieving a first target oxygen value from the plurality of target oxygen values which corresponds to the calculated load (ii) comparing the first target oxygen value to the oxygen content signal and generating a fuel valve adjustment signal in response thereto, and (iii) adjusting the fuel valve to alter the ratio of air-to-gaseous fuel in the fuel-air mixture advanced through the fuel-air mixture outlet of the mixing chamber based on the fuel valve adjustment signal.

14. The method of claim 13, wherein the correspondence between the plurality of target oxygen values and the plurality of calculated load values are experimentally determined.

15. The method of claim 13, further comprising the steps of:

determining NO_x content of exhaust gases advanced through the engine outlet and generating a NO_x content signal in response thereto; and

adjusting the fuel valve to alter the ratio of air-to-gaseous fuel in the fuel-air mixture advanced through the fuel-air mixture outlet of the mixing chamber based on the NO_x content signal and the calculated load.

16. The method of claim 12, wherein:

the gaseous fuel contains approximately X% hydrocarbon fuel, and

30<

X<

40.