Exhaust gas recirculation methods and apparatus for reducing NOx emissions from internal combustion engines

• US 7,302,939 B2
• Filed: 03/29/2005
• Issued: 12/04/2007
• Est. Priority Date: 10/02/2002
• Status: Expired due to Fees

• Current Assignee: Westport Power Inc. (Westport Fuel Systems, Inc.)
• Original Assignee: Westport Power Inc. (Westport Fuel Systems, Inc.)
• Inventors: Munshi, Sandeep, Hill, Philip G., Dunn, Mark E.
• Primary Examiner(s): Gimie; Mahmoud
• Application Number:
  US11/092,094
• Publication Number:
  US 20050224060A1
• Time in Patent Office: 980 Days
• Field of Search: 123/568.2, 123/568.21, 123/568.12, 123/568.11, 123/568.15, 123/559.1, 123/559.2, 123/563
• US Class Current: 123/568.12
• CPC Class Codes: F02B 2075/027 four
• CPC Class Codes: F02B 2275/14 Direct injection into combustion chamber
• CPC Class Codes: F02B 29/0437 Liquid cooled heat exchangers
• CPC Class Codes: F02B 29/0493 Controlling the air charge temperature
• 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 37/00 Engines characterised by provision of pumps driven at least for part of the time by exhaust
• CPC Class Codes: F02B 37/005 Exhaust driven pumps being combined with an exhaust driven auxiliary apparatus, e.g. a ventilator
• CPC Class Codes: F02B 37/18 by bypassing exhaust from the inlet to the outlet of turbine or to the atmosphere
• CPC Class Codes: F02B 37/24 by using pumps or turbines with adjustable guide vanes
• 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 47/08 the substances including exhaust gas
• CPC Class Codes: F02B 7/06 the fuel in the charge being gaseous
• CPC Class Codes: F02B 9/06 with non-timed positive ignition, e.g. with hot-spots
• CPC Class Codes: F02D 19/0628 Determining the fuel pressure, temperature or flow, the fuel tank fill level or a valve position
• CPC Class Codes: F02D 19/0631 by estimation, i.e. without using direct measurements of a corresponding sensor
• CPC Class Codes: F02D 19/0689 for in-cylinder direct injection
• CPC Class Codes: F02D 19/10 peculiar to compression-ignition engines in which the main fuel is gaseous
• CPC Class Codes: F02D 21/08 the other gas being the exhaust gas of engine
• CPC Class Codes: F02M 26/05 High pressure loops, i.e. wherein recirculated exhaust gas is taken out from the exhaust system upstream of the turbine and reintroduced into the intake system downstream of the compressor
• CPC Class Codes: F02M 26/06 Low pressure loops, i.e. wherein recirculated exhaust gas is taken out from the exhaust downstream of the turbocharger turbine and reintroduced into the intake system upstream of the compressor
• CPC Class Codes: F02M 26/07 : Mixed pressure loops, i.e. wherein recirculated exhaust gas is either taken out upstream of the turbine and reintroduced upstream of the compressor, or is taken out downstream of the turbine and reintroduced downstream of the compressor
• CPC Class Codes: F02M 26/08 : for engines having two or more intake charge compressors or exhaust gas turbines, e.g. a turbocharger combined with an additional compressor
• CPC Class Codes: F02M 26/22 : with coolers in the recirculation passage
• 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 of operating an internal combustion engine employs exhaust gas recirculation (EGR) in combination with directly injected gaseous fuels that are burned within the engine in a stratified combustion mode. An engine that employs EGR includes an injector adapted to provide a high pressure quantity of fuel into a combustion chamber within a given pressure range, at a given angle and through a nozzle hole size to help provide for EGR tolerance and, consequently, reduce emissions.

Claims

1. A method of operating a gaseous-fuelled internal combustion engine, said method comprising:

during a cycle of said engine;

(a) directing an intake charge from an intake line into a combustion chamber of said internal combustion engine,

(b) compressing said intake charge within said combustion chamber,

(c) injecting a directly injected gaseous fuel into said compressed intake charge within said combustion chamber at a pressure above 12 MPa,

(d) igniting said directly injected gaseous fuel,

(e) burning said directly injected gaseous fuel,

(f) directing exhaust gas produced during burning of said directly injected gaseous fuel from said combustion chamber into an exhaust line,

wherein a quantity of said exhaust gas from said exhaust line is directed through an EGR line to said intake line and, during a subsequent cycle of said engine, a subsequent intake charge comprises said quantity of said exhaust gas; and

wherein said quantity of said exhaust gas is dependent on at least one of;

(1) a target NOx concentration resulting from burning said directly injected gaseous fuel, and (2) said pressure.

2. The method of claim 1 wherein said pressure is dependent on said quantity of said exhaust gas.

3. The method of claim 1 further comprising injecting said directly injected gaseous fuel for a predetermined duration, said predetermined duration dependent on said quantity of said exhaust gas.

4. The method of claim 1 further comprising injecting said directly injected gaseous fuel for a predetermined timing, said predetermined timing dependent on said quantity of said exhaust gas.

5. The method of claim 1 further comprising commencing injection of said gaseous fuel at between −

20 and 5 degrees ATDC.

6. The method of claim 1 wherein said directly injected gaseous fuel is injected at a pressure below 30 MPa.

7. The method of claim 1 wherein said directly injected gaseous fuel burns in a stratified combustion mode.

8. The method of claim 7 further comprising promoting diffusion combustion of said directly injected gaseous fuel.

9. The method of claim 7 wherein said intake charge within said intake line is substantially free of a gaseous fuel.

10. The method of claim 7 wherein said intake charge is substantially free of a gaseous fuel prior to introduction of said directly injected gaseous fuel.

11. The method of claim 1 further comprising cooling said quantity of said exhaust gas prior to directing said quantity of said exhaust gas from said intake line into said combustion chamber.

12. The method of claim 1 further comprising compressing said quantity of said exhaust gas prior to directing said quantity of said exhaust gas from said intake line into said combustion chamber.

13. The method of claim 1 further comprising directing a remaining quantity of said exhaust gas through a turbine of a turbo-charger after said quantity of said exhaust gas is directed into said EGR line.

14. The method of claim 1 further comprising directing said exhaust gas through a turbine of a turbo-charger before said quantity of said exhaust gas is directed into said EGR line.

15. A method of operating a gaseous-fuelled internal combustion engine, said method comprising:

during a cycle of said engine;

(a) directing an intake charge from an intake line into a combustion chamber of said internal combustion engine,

(b) compressing said intake charge within said combustion chamber,

(c) injecting a directly injected gaseous fuel into said compressed intake charge within said combustion chamber at a pressure above 12 MPa,

(d) igniting said directly injected gaseous fuel,

(e) burning said directly injected gaseous fuel,

(f) directing exhaust gas produced during burning of said directly injected gaseous fuel from said combustion chamber into an exhaust line,

(g) determining an emissions concentration within said exhaust gas directed from said combustion chamber, said emissions concentration being the concentration of one of;

(1) carbon monoxide,

(2) hydrocarbons,

(3) combined carbon monoxide and hydrocarbons,

(4) combined carbon monoxide and particulates,

(5) combined hydrocarbons and particulates, or

(6) combined carbon monoxide, hydrocarbons and particulates,

(h) determining an EGR rate set point at which said emissions concentration exceeds a maximum emissions concentration,

(i) adjusting said quantity of said exhaust gas to provide an EGR level below said set point when said emissions concentration exceeds said maximum emissions concentration,

wherein a quantity of said exhaust gas from said exhaust line is directed through an EGR line to said intake line and, during a subsequent cycle of said engine, a subsequent intake charge comprises said quantity of said exhaust gas.

16. A method of operating an internal combustion engine, said method comprising:

during a cycle of said engine;

(a) directing an intake charge from an intake line into a combustion chamber of said internal combustion engine,

(b) compressing said intake charge,

(c) introducing a fuel into said intake charge within said combustion chamber,

(d) igniting said fuel,

(e) burning said fuel,

(f) directing exhaust gas generated by combustion of said fuel from said combustion chamber into an exhaust line;

(g) determining an emissions concentration within said exhaust gas, said emissions concentration being the concentration of one of;

(1) carbon monoxide,

(2) hydrocarbons,

(3) combined carbon monoxide and hydrocarbons,

(4) combined carbon monoxide and particulates,

(5) combined hydrocarbons and particulates, or

(6) combined carbon monoxide, hydrocarbons and particulates,

(h) determining an EGR level set point at which said emissions concentration equals or exceeds a maximum emissions concentration,

(i) determining a predetermined quantity of said exhaust gas to direct through an EGR line, said quantity of said exhaust gas providing an EGR level below said set point,

(j) directing a quantity of said exhaust gas based on said predetermined quantity of said exhaust gas to an EGR line to said intake line, wherein during a subsequent cycle of said engine, a subsequent intake charge comprises said quantity of said exhaust gas.

17. The method of claim 16 wherein said emissions concentration is determined from a look up table based on a set of engine operating parameters.

18. The method of claim 16 wherein said emissions concentration is determined by a mathematical model based on a set of engine operating parameters.

19. The method of claim 16 wherein said emissions concentration is determined by reference to bench tests.

20. The method of claim 16 wherein said emissions concentration is measured directly.

21. The method of claim 16 further comprising injecting said fuel directly into said combustion chamber.

22. The method of claim 21 further comprising injecting said fuel for a predetermined pressure, said predetermined pressure dependent on said quantity of said exhaust gas.

23. The method of claim 21 further comprising injecting said fuel for a predetermined duration, said predetermined duration dependent on said quantity of said exhaust gas.

24. The method of claim 21 further comprising injecting said directly injected gaseous fuel for a predetermined timing, said predetermined timing dependent on said quantity of said exhaust gas.

25. The method of claim 21 further comprising injecting said fuel into said combustion chamber when a piston disposed in a cylinder within said internal combustion engine is at or near top dead center.

26. The method of claim 21 wherein said fuel is a gaseous fuel.

27. The method of claim 16 wherein said fuel bums in a stratified combustion mode.

28. The method of claim 21 wherein said fuel burns in a stratified combustion mode.

29. The method of claim 21 wherein said fuel comprises natural gas.

30. The method of claim 16 wherein said fuel is a gaseous fuel.

31. The method of claim 30 wherein said fuel bums in a stratified combustion mode.

32. The method of claim 30 wherein said fuel comprises natural gas.

33. The method of claim 31 wherein said fuel comprises natural gas.

34. The method of claim 16 wherein said fuel comprises natural gas.