Ducted combustion chamber for direct injection engines and method
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.
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 a plurality of nozzle openings configured to inject a plurality of fuel jets into the combustion chamber, each of the plurality of fuel jets travelling along a respective fuel jet centerline;
a plurality of ducts defined in the combustion chamber between the piston crown and the flame deck surface, each duct having a generally rectangular cross section, and extending in a radial direction relative to the cylinder bore substantially along a segment of a respective fuel jet centerline.
2. The internal combustion engine of claim 1 , wherein each of the plurality of ducts 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 each of the plurality of ducts is at least partially defined between two opposing sidewalls disposed to at least partially enclose the segment of the respective 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 each of the plurality of ducts has an inlet and an outlet that are radially disposed within the piston bowl.
7. The internal combustion engine of claim 1 , wherein each of the plurality of ducts 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 two adjacent ducts.
9. The internal combustion engine of claim 1 , wherein a cross sectional area of an inlet of each of the plurality of ducts 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 each of the plurality of ducts along the fuel jet centerline is between 1 and 8 times a minimum hydraulic diameter of an inlet cross section of each of the plurality of ducts.
11. The internal combustion engine of claim 1 , wherein an inlet of each of the plurality of ducts 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 respective duct.
12. The internal combustion engine of claim 1 , wherein a cross sectional area of each of the plurality of ducts 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 respective duct.
13. 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.