Skip-Fire Fuel Injection System and Method

• US 20160017824A1
• Filed: 06/13/2015
• Published: 01/21/2016
• Est. Priority Date: 12/14/2012
• Status: Active Grant

• Current Assignee: Westport Fuel Systems Canada Inc. (Westport Fuel Systems, Inc.)
• Original Assignee: Westport Power Inc. (Westport Fuel Systems, Inc.)
• Inventors: Touchette, Alain M.J., Thompson, Jeffrey J.
• Granted Patent: US 10,450,975 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: F02B 2075/1824 six
• CPC Class Codes: F02D 17/02 Cutting-out cutting-out engines in multiple engine arrangements F02D25/04
• CPC Class Codes: F02D 41/0027 the fuel being gaseous non-electrical control F02D19/02
• CPC Class Codes: F02D 41/0087 Selective cylinder activation, i.e. partial cylinder operation deceleration cut-off F02D41/123
• CPC Class Codes: F02D 41/3058 the engine working with a variable number of cycles
• CPC Class Codes: F02D 41/403 with pilot injections
• CPC Class Codes: F02D 41/406 Electrically controlling a diesel injection pump F02D41/401 takes precedence
• CPC Class Codes: Y02T 10/30 Use of alternative fuels, e.g. biofuels
• CPC Class Codes: Y02T 10/40 Engine management systems

Abstract

A cycle-by-cycle skip-fire fuel-injection technique for pilot-ignited engines involve skip-firing selected combustion chambers when a low load condition is determined and modulating the fuel delivery to maintain the requisite engine power, while reducing pilot fuel quantity to a predetermined minimum. Overall pilot fuel consumption is thereby reduced.

Claims

1. A method of skip-firing an engine system wherein said engine system has a plurality of combustion chambers and a fuel-injection system and said engine system is configured to use a main fuel and a pilot fuel, said steps of said method comprising:

(a) detecting when said engine system is experiencing a predetermined low load condition for applying a skip-fire injection mode;

(b) determining and selecting at least one combustion chamber of said plurality of combustion chambers designated for skip-firing during a next cycle;

(c) skip-firing said selected at least one combustion chamber for a given duration;

(d) determining whether said engine system continues experiencing said low load condition during said given duration.

2. The method of claim 1, wherein when said engine system is not experiencing said low load condition during said given duration the method further comprises;

(e) returning said plurality of combustion chambers to a normal injection mode.

3. The method of claim 1, further comprising:

(e) delivering at least some of said main fuel and said pilot fuel into said combustion chamber after closing of an associated intake valve, whereby timing for delivery of said at least some of said main fuel is configured to prevent premature ignition.

4. The method of claim 1, further comprising

(e) separately delivering at least some of said main fuel and said pilot fuel into said combustion chamber after closing of an associated intake valve through one body of a fuel injection assembly, whereby timing for delivery of said at least some of said main fuel is selected to prevent premature ignition.

5. The method of claim 1, wherein said selecting at least one combustion chamber of said plurality of combustion chambers designated for skip-firing involves following a predetermined cycle-by-cycle skip-firing pattern that reduces undesirable vibrations in said engine system.

6. The method of claim 1, wherein said main fuel comprises a gaseous fuel and said pilot fuel comprises diesel fuel.

7. The method of claim 1, wherein said given duration comprises a switching period having sufficient time for facilitating detecting and selecting said at least one combustion chamber for skip-fire during the next cycle.

8. The method of claim 1, wherein said engine system is operable using a lower ratio of said pilot fuel to a total fuel quantity measured on an energy basis at said predetermined low load condition compared to said same engine system when operated without skip-firing.

9. The method of claim 1, wherein, under certain predetermined load conditions, said engine system is operable in a mode when said pilot fuel is the only fuel consumed by said engine system;

and further comprising reducing an amount of time that said engine system is fuelled only with said pilot fuel by applying said skip-fire injection mode.

10. A skip-fire fuel-injection engine system, comprising:

(a) an engine system configured to use a main fuel and a pilot fuel, wherein said engine system comprises;

(i) a plurality of combustion chambers; and

(ii) a fuel injection system,

(b) a feedback and control system in communication with said fuel injection system, said feedback and control system configured to;

(i) detect when said engine system is experiencing a predetermined low load condition associated with a skip-fire injection mode;

(ii) when said predetermined low load is detected, determine and select at least one combustion chamber of said plurality of combustion chambers designated for skip-firing during a next cycle;

(iii) skip-firing said selected at least one combustion chamber for a given duration;

(iv) determine whether said engine system continues experiencing said low load condition.

11. The system of claim 10, wherein said feedback and control system is further adapted to:

(v) deliver at least some of said main fuel into a combustion chamber after closing of an associated intake valve, whereby timing for delivery of said at least some of said main fuel is selected to prevent premature ignition; and

(vi) control timing for delivery of said pilot fuel independently from said timing for delivery of said at least some of said main fuel.

12. The system of claim 10, wherein said pilot fuel on average comprises less than 5% of a total fueling measured on an energy basis.

13. The system of claim 10, wherein said given duration comprises a switching period having sufficient time for facilitating detecting and selecting said at least one combustion chamber for skip-fire during the next cycle.

14. The system of claim 10, wherein said engine system is operable using a lower ratio of said pilot fuel to a total fuel quantity measured on an energy basis at said predetermined low load condition compared to said same engine system when operated without skip-firing.

15. The system of claim 10, wherein, said engine system is operable in a mode when said pilot fuel is the only fuel consumed by said engine system and said feedback and control system is further adapted to reduce an amount of time that said engine system is fuelled only with said pilot fuel by applying said skip-fire injection mode.

16. The system of claim 10, wherein said feedback and control system is further adapted to deliver at least some of said main fuel into a combustion chamber after closing of an associated intake valve through one body of a fuel injection assembly, whereby timing for delivery of said at least some of said main fuel is selected to prevent premature ignition;

and said one body of said fuel injection assembly comprises a first fuel injection valve that is operable to inject said pilot fuel independently from a second fuel injection valve that is operable to inject said main fuel; and

said fuel injection assembly comprises a concentric needle injector, with said first injection valve having a needle concentric with a needle of said second injection valve.

17. The system of claim 10, wherein said fuel injection system comprises nozzles in fluid communication with said combustion chamber whereby said pilot fuel and said main fuel can be introduced into said combustion chamber after an associated air intake valve is closed.

18. A method of fabricating a skip-fire fuel-injection engine system, comprising:

(a) providing an engine system having a plurality of combustion chambers and a fuel injection system, said engine system being operable with a main fuel and a pilot fuel; and

(b) providing a feedback and control system in electronic communication with said fuel injection system, said feedback and control system adapted to;

(i) detect when said engine system is experiencing a predetermined low load condition associated with a skip-fire injection mode;

(ii) when said predetermined low load is detected, determine and select at least one combustion chamber of said plurality of combustion chambers designated for skip-firing during a next cycle;

(iii) skip-fire said selected at least one combustion chamber for a given duration;

(iv) determine whether said engine system continues experiencing said low load condition during said given duration.

19. The method of claim 18, wherein said feedback and control system is further adapted to:

(v) deliver at least some of said main fuel into a combustion chamber after closing of an associated intake valve, and whereby timing for delivery of said at least some of said main fuel is selected to prevent premature ignition; and

control timing for delivery of said pilot fuel independently from said timing for delivery of said at least some of said main fuel.

20. The method of claim 18, wherein said feedback and control system is further adapted to follow a predetermined cycle-by-cycle skip-firing pattern that reduces formation of harmonic frequency vibrations in said engine system when selecting at least one combustion chamber of said plurality of combustion chambers designated for skip-firing.