Air-fuel ratio control in a multi-fuel internal combustion engine

Patent metadata

Field	Value
Publication number	US-9546615-B2
Application number	US-201514738835-A
Country	US
Kind code	B2
Filing date	Jun 13, 2015
Priority date	Dec 22, 2012
Publication date	Jan 17, 2017
Grant date	Jan 17, 2017

Abstract

A technique for controlling air-fuel ratio in an internal combustion engine consuming more than one fuel type includes determining a target air-fuel ratio as a function of engine operating conditions; determining an actual air-fuel ratio from the engine operating conditions; determining a first fuel quantity of a first fuel to introduce into a combustion chamber as a function of the engine operating conditions; determining a second fuel quantity of a second fuel such that the actual air-fuel ratio equals the target air-fuel ratio to within a predetermined range of tolerance when the first fuel quantity and the second fuel quantity are introduced into the combustion chamber, the second fuel quantity being determined as a function of the engine operating conditions, the target air-fuel ratio, the actual air-fuel ratio and the first fuel quantity; and introducing the first fuel quantity and the second fuel quantity into the combustion chamber.

First claim

What is claimed is:

1. A method for controlling air-fuel ratio in an internal combustion engine consuming more than one fuel type comprising:
(a) determining a target air-fuel ratio as a function of engine operating conditions;
(b) determining an actual air-fuel ratio from said engine operating conditions;
(c) determining a first fuel quantity of a first fuel to introduce into a combustion chamber of said internal combustion engine as a function of said engine operating conditions;
(d) determining a second fuel quantity of a second fuel such that said actual air-fuel ratio equals said target air-fuel ratio to within a predetermined range of tolerance when said first fuel quantity and said second fuel quantity are introduced into said combustion chamber, said second fuel quantity determined as a function of said engine operating conditions, said target air-fuel ratio, said actual air-fuel ratio and said first fuel quantity; and
(e) introducing said first fuel quantity and said second fuel quantity into said combustion chamber.

2. The method of claim 1 , further comprising:
(f) repeating steps (b) and (e) when said engine operating conditions remain unchanged within a predetermined range of tolerance; and
(g) for each repetition of step (b), at least repeating step (d) when said actual air-fuel ratio determined in step (b) is not equal to said target air-fuel ratio to within a predetermined range of tolerance.

3. The method of claim 1 , wherein said first fuel is a liquid fuel and said second fuel is a gaseous fuel.

4. The method of claim 1 , wherein said first fuel is diesel.

5. The method of claim 1 , wherein said second fuel is natural gas.

6. The method of claim 1 , wherein said second fuel is selected from the group consisting of ethane, methane, propane, biogas, landfill gas, hydrogen and mixtures thereof.

7. The method of claim 1 , wherein said first fuel is a pilot fuel and said second fuel is a main fuel.

8. The method of claim 1 , wherein said first fuel is directly introduced into said combustion chamber and said second fuel is introduced into a suction pipe upstream of an intake valve of said combustion chamber.

9. The method of claim 1 , wherein said target air-fuel ratio corresponds to an excess air-fuel ratio of one to within a predetermined range of tolerance.

10. The method of claim 1 , wherein said internal combustion engine is throttled.

11. The method of claim 1 , further comprising:
(f) calculating an air-fuel ratio error as the difference between said target air-fuel ratio and said actual air-fuel ratio; and
(g) in step (d), determining said second fuel quantity as a function of said engine operating conditions, said target air-fuel ratio, said air-fuel ratio error and said first fuel quantity.

12. The method of claim 11 , wherein said second fuel quantity equals a first amount of said second fuel plus a second amount of said second fuel, said first amount equal to a function of said engine operating conditions, said target air-fuel ratio and said first fuel quantity, said second amount equal to a function of said air-fuel ratio error.

13. The method of claim 12 , wherein said function of said air-fuel ratio error corresponds to at least one of a proportional control module, an integral control module and a derivative control module, each of said control modules responsive to said air-fuel ratio error.

14. The method of claim 12 , wherein said function of said air-fuel ratio error corresponds to a control module responsive to said air-fuel ratio error and operable to adjust said second fuel quantity to reduce said air-fuel ratio error to zero within said predetermined range of tolerance.

15. The method of claim 1 , wherein said function for determining said second fuel quantity comprises a gain that is one of a function of a percentage of total fuel of said first fuel quantity and a function of a percentage of total fuel of said second fuel quantity.

16. The method of claim 1 , wherein in step (c) said first fuel quantity is determined as a function of at least one of said engine operating conditions, said target air-fuel ratio, said actual air-fuel ratio and said second fuel quantity.

17. The method of claim 16 , wherein when said target air-fuel ratio is not equal to said actual air-fuel ratio to within a predetermined range of tolerance said first fuel quantity and said second fuel quantity are adjusted by at least one of an equal percentage and an equal amount within a range of tolerance.

18. The method of claim 16 , wherein when said target air-fuel ratio is not equal to said actual air-fuel ratio to within a predetermined range of tolerance said first fuel quantity and said second fuel quantity are adjusted by at least one of a different percentage and a different amount.

19. The method of claim 1 , wherein said second quantity of said second fuel is determined according to the formula:

F

ngb
∼
s

⁡

(

-
1

+

%
⁢
NG

100

)

+

F

ngb
∼
s

λ
target

+

F

ngb
∼
s

⁡

(

I
+
P

)

where:
F ngb˜s is a base quantity of natural gas, determined from a base map indexed by engine operating conditions or from a base function of engine operating conditions, employed for an internal combustion engine operating with said second fuel only at stoichiometry;
% NG is a percentage of total fuel that is said second fuel;
λ target is said target air-fuel ratio;
I is an integral control term; and
P is a proportional control term.

20. An apparatus for controlling air-fuel ratio in an internal combustion engine consuming more than one fuel type comprising:
(a) a direct fuel injector introducing a first fuel into a combustion chamber of said internal combustion engine;
(b) a second fuel injector introducing a second fuel into said combustion chamber;
(c) an electronic control programmed to:
(i) determine a target air-fuel ratio as a function of engine operating conditions;
(ii) determine an actual air-fuel ratio from said engine operating conditions;
(iii) determine a first fuel quantity of said first fuel to introduce through said direct fuel injector as a function of said engine operating conditions;
(iv) dete

Assignees

• Westport Power Inc

Inventors

• Melnyk Borys J

Classifications

• F02D41/38

  of the high pressure type · CPC title

• F02D41/0027

  the fuel being gaseous (non-electrical control F02D19/02) · CPC title

• F02D41/0025

  Controlling engines characterised by use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures · CPC title

• Y02T10/36

  Cross-Sectional Technologies · mapped topic

• F02D41/3094

  the fuel injection being effected by at least two different injectors, e.g. one in the intake manifold and one in the cylinder · CPC title