DUCTED COMBUSTION CHAMBER FOR DIRECT INJECTION ENGINES AND METHOD

• US 20120186555A1
• Filed: 01/26/2011
• Published: 07/26/2012
• Est. Priority Date: 01/26/2011
• Status: Active Grant

• Current Assignee: Caterpillar Incorporated
• Original Assignee: Caterpillar Incorporated
• Inventors: MUELLER, CHARLES
• Granted Patent: US 8,967,129 B2
• Time in Patent Office: Days
• US Class Current: 123/294
• CPC Class Codes: F02B 23/0627 having additional bores or grooves machined into the piston for guiding air or charge flow to the piston bowl
• CPC Class Codes: F02B 3/00 Engines characterised by air compression and subsequent fuel addition characterised by both fuel-air mixture compression and air compression, or characterised by both positive ignition and compression ignition F02B11/00
• CPC Class Codes: F02F 3/24 having means for guiding gases in cylinders, e.g. for guiding scavenging charge in two-stroke engines
• CPC Class Codes: F02F 3/28 Other pistons with specially-shaped head
• CPC Class Codes: F02F 3/285 the head being provided with an insert located in or on the combustion-gas-swept surface
• CPC Class Codes: Y02T 10/12 Improving ICE efficiencies

Abstract

An internal combustion engine includes an engine block having a cylinder bore and a cylinder head having a flame deck surface disposed at one end of the cylinder bore. A piston connected to a rotatable crankshaft and configured to reciprocate within the cylinder bore has a piston crown portion facing the flame deck surface such that a combustion chamber is defined within the cylinder bore and between the piston crown and the flame deck surface. A fuel injector having a nozzle tip disposed in fluid communication with the combustion chamber has at least one nozzle opening configured to inject a fuel jet into the combustion chamber along a fuel jet centerline. At least one duct defined in the combustion chamber between the piston crown and the flame deck surface has a generally rectangular cross section and extends in a radial direction relative to the cylinder bore substantially along the fuel jet centerline.

Claims

1. An internal combustion engine, comprising:

an engine block having at least one cylinder bore;

a cylinder head having a flame deck surface disposed at one end of the cylinder bore;

a piston connected to a rotatable crankshaft and configured to reciprocate within the cylinder bore, the piston having a piston crown portion facing the flame deck surface such that a combustion chamber is defined within the cylinder bore and between the piston crown and the flame deck surface;

a fuel injector having a nozzle tip disposed in fluid communication with the combustion chamber, the nozzle tip having at least one nozzle opening configured to inject a fuel jet into the combustion chamber and along a fuel jet centerline;

at least one duct defined in the combustion chamber between the piston crown and the flame deck surface, the at least one duct having a generally rectangular cross section and extending in a radial direction relative to the cylinder bore substantially along a segment of the fuel jet centerline.

2. The internal combustion engine of claim 1, wherein the at least one duct is at least partially defined by a pair of fins having an elongate shape that includes sidewalls extending substantially parallel to a centerline of the cylinder bore, and wherein the at least one duct is at least partially defined between two opposing sidewalls disposed to at least partially enclose the segment of the fuel jet centerline.

3. The internal combustion engine of claim 2, wherein at least one fin of the pair of fins is connected to the piston crown.

4. The internal combustion engine of claim 2, wherein at least one fin of the pair of fins is connected to at least one of the flame deck surface of the cylinder head, an intake valve, and an exhaust valve.

5. The internal combustion engine of claim 2, wherein two fins of the pair of fins are connected to one another to form a U-shaped insert that is connected to the piston crown.

6. The internal combustion engine of claim 5, wherein the piston crown portion further includes a piston bowl having a generally concave shape and wherein the at least one duct has an inlet and an outlet that are radially disposed within the piston bowl.

7. The internal combustion engine of claim 1, wherein the at least one duct is partially formed as a groove in the piston crown portion and at least partially formed between two walls extending parallel to one another around a portion of the fuel jet.

8. The internal combustion engine of claim 1, further comprising at least one recirculation inhibiting surface defined on a fin disposed between the piston crown and the flame deck surface, the fin having an elongate shape such that the at least one recirculation inhibiting surface is substantially parallel to a centerline of the cylinder bore and disposed between the at least one duct and an additional duct.

9. The internal combustion engine of claim 1, wherein a cross sectional area of an inlet of the at least one duct is between 3 and 10 times a cross sectional area of the fuel jet.

10. The internal combustion engine of claim 1, wherein a length of the at least one duct along the fuel jet centerline is between 1 and 8 times a minimum hydraulic diameter of an inlet cross section of the at least one duct.

11. The internal combustion engine of claim 1, wherein an inlet of the at least one duct is disposed at a radial distance from a centerline of the cylinder bore that is about 0.75 to 3 times a minimum hydraulic diameter of an inlet cross section of the at least one duct.

12. The internal combustion engine of claim 1, wherein a cross sectional area of the at least one duct increases in a radial direction away from a centerline of the cylinder bore at a rate of not more than 100% over a length of the at least one duct along the fuel jet centerline that is about equal to a hydraulic diameter of an inlet cross section of the at least one duct.

13. A ducted combustion system, comprising:

a combustion chamber defined in a machine;

a fuel injector configured to inject a fuel jet into the combustion chamber along a fuel jet centerline;

a duct having a generally rectangular cross section is defined within the combustion chamber and disposed to receive therein the fuel jet, the duct at least partially surrounding the fuel jet centerline.

14. The ducted combustion system of claim 13, wherein the duct is at least partially defined by a pair of fins having an elongate shape, each fin including a sidewall extending substantially parallel to the fuel jet centerline, and wherein the duct is at least partially defined between two opposing sidewalls disposed on each side of the fuel jet centerline.

15. The ducted combustion system of claim 13, wherein the duct is partially formed as a groove in a component, which is disposed around and at least partially defining the combustion chamber, and at least partially formed between two walls extending parallel to one another around the fuel jet centerline.

16. The ducted combustion system of claim 13, wherein a cross sectional area of an inlet of the duct is between 3 and 10 times a cross sectional area of the fuel jet where the fuel jet passes through the inlet, wherein a length of the duct along the fuel jet centerline is between 1 and 8 times a minimum hydraulic diameter of the inlet of the duct, wherein a cross sectional area of the duct increases in a direction along the fuel jet centerline at a rate of not more than 100% over a length of the duct along the fuel jet centerline that is about equal to a hydraulic diameter of an inlet of the duct.

17. A method for operating a combustion system, comprising:

injecting a fuel jet along a fuel jet centerline into a combustion chamber;

directing the fuel jet at least partially into a duct having a generally rectangular cross section such that local velocity gradients around the fuel jet create a substantially uniform mixture of fuel from the fuel jet with air present in the combustion chamber;

preventing entrainment of recirculated combustion products from a downstream region of the fuel jet to an upstream region of the fuel jet by substantially containing a segment of the fuel jet within the duct.

18. The method of claim 17, further comprising maintaining an equivalence ratio of about 2 at a flame lift-off length.

19. The method of claim 17, further comprising decelerating the recirculation of combustion products by creating velocity gradients in the combustion products that are induced by surfaces disposed between adjacent ducts.

20. A piston for use in an internal combustion engine, comprising:

a body portion connectable to a crankshaft of the engine, the body portion having a generally cylindrical shape defining a centerline;

a crown portion connected to the body portion;

at least one pair of elongate fins connected to the crown portion and extending away therefrom in a direction of the centerline, each fin of the at least one pair of elongate fins having a duct surface facing the other fin, the duct surface extending away from the centerline in a generally radial direction relative to the crown portion;

wherein a duct having a generally U-shaped cross section is defined on the crown portion of the piston between two facing duct surfaces of the at least one pair of fins and a bottom surface defined on the crown portion.