Air-fuel control system

• US 6,340,005 B1
• Filed: 04/18/2000
• Issued: 01/22/2002
• Est. Priority Date: 04/18/2000
• Status: Expired due to Term

• Current Assignee: REM Technology Inc.
• Original Assignee: REM Technology Inc.
• Inventors: Malm, Howard Leigh, Keast, Leslie Allan
• Primary Examiner(s): Kwon, John
• Assistant Examiner(s): Vo, Hieu T.
• Application Number:
  US09/551,748
• Time in Patent Office: 644 Days
• Field of Search: 123/352, 123/27.GE, 123/527, 123/478, 123/480, 701/102, 701/103, 701/105
• US Class Current: 123/27.0GE
• CPC Class Codes: F02B 3/06 with compression ignition compression ignition engines using air or gas for blowing fuel into compressed air in cylinder F02B13/02
• CPC Class Codes: F02B 43/02 Engines characterised by means for increasing operating efficiency
• CPC Class Codes: F02D 19/023 to adjust the fuel mass or volume flow
• CPC Class Codes: F02D 31/009 for maximum speed control
• CPC Class Codes: F02D 41/0007 for control of turbo-charged or super-charged engines control of the pumps per se F02B37/12
• CPC Class Codes: F02D 41/0027 the fuel being gaseous non-electrical control F02D19/02
• CPC Class Codes: F02M 21/0215 Mixtures of gaseous fuels; Natural gas; Biogas; Mine gas; Landfill gas
• CPC Class Codes: Y02T 10/12 Improving ICE efficiencies
• CPC Class Codes: Y02T 10/30 Use of alternative fuels, e.g. biofuels

Abstract

A method for controlling the air-fuel ratio in a natural gas engine having an air-fuel mixing device, comprises: determining a speed set-point and an actual engine speed, determining a fuel command based on said speed set-point and said engine speed and controlling the fuel flow to the air-fuel mixing device in response to said fuel command. An air-fuel control system for natural gas engines, comprises: means to determine a speed set-point and an actual engine speed, a governor control unit for generating a fuel command based on said speed set-point and said actual engine speed and a fuel flow regulator coupled to said governor control unit for regulating the flow of fuel to an air-fuel mixing device in response to said fuel command.

Claims

1. An air-fuel control system for a natural gas engine provided with an air-fuel mixing device, comprising:

means for establishing a speed set point;

means for determining an actual engine speed;

a governor control unit for generating a fuel command based on said speed set-point and said actual engine speed;

a fuel flow regulator coupled to said governor control unit for regulating the flow of fuel to the air-fuel mixing device in response to said fuel command to produce an air-fuel mixture; and

air-fuel flow control means for regulating the flow of said air-fuel mixture from said air-fuel mixing device to an intake manifold of said engine.

2. The system in claim 1, wherein said air-fuel flow control means comprises:

a pressure sensor for measuring the pressure value in said engine;

a temperature sensor for measuring the temperature value of said engine;

air-fuel control for receiving said pressure and temperature values and controlling said throttle accordingly.

3. The system in claim 2, further comprising oxygen sensor.

4. A method for controlling the air-fuel ratio in a natural gas engine having an air-fuel mixing device, comprising:

generating a fuel command based on a speed set point and an actual engine speed;

controlling the fuel flow to said air-fuel mixing device in response to said fuel command; and

controlling the air-fuel flow through a throttle valve for regulating the air-fuel flow from the air-fuel mixing device into an intake manifold of the engine.

5. The method in claim 4, wherein the air-fuel mixing device is a carburetor.

6. The method in claim 4, wherein the step of controlling the fuel flow further comprises controlling a fuel pressure regulator located upstream of the air-fuel mixing device.

7. The method in claim 4, further comprising:

calculating an air-fuel set-point;

determining an air-fuel command based on said air-fuel set-point; and

controlling the flow of an air-fuel mixture from the air-fuel mixing device into an intake manifold of the natural gas engine.

8. The method in claim 7, wherein the air-fuel set-point calculation step further comprises calculating the air-fuel set-point based on the actual engine speed.

9. The method of claim 7, wherein the air-fuel set-point calculation further comprises determining the pressure and temperature in the intake manifold;

calculating the air-fuel set-point based on the actual engine speed, the inlet pressure and temperature.

10. The method in claim 7 wherein the calculated air-fuel set-point is derived from a parameter related to at least one of the amount of oxygen and the unused fuel in the combustion products in an exhaust manifold, and a parameter related to the engine speed.