Piston having combustion bowl shaped to balance combustion efficiency and emission properties

Patent metadata

Field	Value
Publication number	US-9234451-B2
Application number	US-201313892612-A
Country	US
Kind code	B2
Filing date	May 13, 2013
Priority date	Apr 20, 2010
Publication date	Jan 12, 2016
Grant date	Jan 12, 2016

Abstract

A piston for a compression ignition internal combustion engine includes a piston body having a combustion face defining a combustion bowl, and the combustion face including a compound bowl surface and a compound rim surface. The combustion face is profiled to balance a combustion efficiency property of the piston with emissions properties of the piston. A ratio of a diameter of the combustion bowl to a diameter of the cylinder bowl bore is from 0.68 to 0.74. Other dimensional and proportional features of the piston support low smoke and NOx production during operation.

First claim

What is claimed is:

1. A piston for balancing combustion efficiency with NOx generation and smoke generation in a direct injection compression ignition internal combustion engine having a compression ratio of 15:1 to 16:1, where the engine has a swirl ratio of 1 or less, a combustion bowl diameter to cylinder bore diameter ratio of 0.68 to 0.74, and where a fuel injection spray angle is larger than a cone angle defined by a conical projection of the piston within the combustion bowl, the piston comprising:
a piston body having an outer cylindrical surface defining a longitudinal piston axis, an axial piston end which includes a combustion face defining a compound combustion bowl, and a compound rim located on the axial piston end and extending radially outwardly from the combustion bowl to the outer cylindrical surface;
the compound combustion bowl including a convex inner bowl surface located on the conical projection, and a concave outer bowl surface, and the compound rim including a flat outer rim surface adjoining the outer cylindrical surface and a convex inner rim surface adjoining the compound combustion bowl;
wherein the cone angle is equal to about 135° or less, the concave outer bowl surface defines a first radius of curvature which is from 13 mm to 16 mm, and the convex inner bowl surface continuously transitions with the concave outer bowl surface; and
wherein the convex inner rim surface abruptly transitions with the concave outer bowl surface at an edge of the compound combustion bowl, and the convex inner rim surface defines a second radius of curvature which is from 40 mm to 70 mm, whereby the edge of the combustion bowl is axially recessed from a plane defined by the flat outer rim surface, such that gases are squished from a crevice having an outwardly narrowing taper and being defined in part by the cylinder head and in part by the compound rim when the piston is at a top dead center position in the engine.

2. The piston of claim 1 wherein the compound combustion bowl defines a bowl diameter from 94 mm to 106 mm, and a bowl volume from 98 cm 3 to 137 cm 3 .

3. The piston of claim 2 wherein the concave outer bowl surface defines a bowl depth from the plane which is from 17 mm to 20 mm.

4. The piston of claim 3 wherein the concave outer bowl surface forms a straight vertical wall adjoining the edge of the compound combustion bowl and has a uniform curvature from the continuous transition with the convex inner bowl surface to the straight vertical wall.

5. The piston of claim 4 wherein the first radius of curvature is from 15 mm to 16 mm, the bowl diameter is from 103 mm to 104 mm, and the bowl depth is from 18 mm to 19 mm.

6. The piston of claim 5 wherein the bowl volume is from 120 cm 3 to 130 cm 3 .

7. The piston of claim 6 wherein the first radius of curvature is 15 mm, the bowl diameter is 104 mm, the bowl depth is 19 mm, and the second radius of curvature is 50 mm.

8. A piston for balancing combustion efficiency with NOx generation and smoke generation in a direct injection compression ignition internal combustion engine comprising:
a piston body having an outer cylindrical surface defining a longitudinal piston axis, an axial piston end which includes a combustion face defining a compound combustion bowl, and a compound rim located on the axial piston end and extending radially outwardly from the combustion bowl to the outer cylindrical surface;
the compound combustion bowl including a convex inner bowl surface located on the conical projection and defining a cone angle, and a concave outer bowl surface extending radially outwardly from the inner bowl surface and defining a first radius of curvature;
the compound rim including a flat outer rim surface adjoining the outer cylindrical surface, and a convex inner rim surface adjoining the compound combustion bowl and defining a second radius of curvature;
the convex inner bowl surface continuously transitioning with the concave outer bowl surface, and the convex inner rim surface abruptly transitioning with the concave outer bowl surface at an edge of the compound combustion bowl;
the compound combustion bowl defining a bowl diameter, and the piston body defining a piston body diameter which is about 33% larger than the bowl diameter; and
the cone angle is about 135° or less, the first radius of curvature being from 13 mm to 16 mm, and the second radius of curvature being from 40 mm to 70 mm.

9. The piston of claim 8 wherein the concave outer bowl surface forms a straight vertical wall adjoining the edge of the compound combustion bowl and has a uniform curvature from the continuous transition with the convex inner bowl surface to the straight vertical wall.

10. The piston of claim 9 wherein the flat outer rim surface defines a plane, and the concave outer bowl surface defines a bowl depth from the plane which is about 18% of the bowl diameter.

11. The piston of claim 10 wherein the first radius of curvature has a value R 3 and the second radius of curvature has a value R 1 , as specified for one of Engines 5 , 6 A, 6 B, and 7 in FIG. 4 .

12. The piston of claim 11 wherein the combustion bowl has a bowl volume, and the bowl diameter has a value D 6 , as specified for one of Engines 5 , 6 A, 6 B, and 7 .

13. The piston of claim 12 wherein the piston has all the piston features specified for Engine 7 .

14. A direct injection compression ignition internal combustion engine comprising:
an engine housing defining a cylinder bore having a cylinder bore diameter from 138 mm to 146 mm, and including an intake passage and an exhaust passage each being in fluid communication with the cylinder bore;
a cylinder head coupled with the engine housing;
a fuel injector mounted in the cylinder head and configured to directly inject a fuel into the cylinder bore, the fuel injector having a plurality of spray orifices defining a spray angle;
a piston for balancing combustion efficiency with NOx generation and smoke generation during combusting a mixture of the fuel and air in the cylinder bore, the piston including a piston body having an outer cylindrical surface defining a longitudinal piston axis, and an axial piston end which includes a combustion face defining a compound combustion bowl, and wherein a ratio of a diameter of the combustion bowl to the cylinder bore diameter is from 0.68 to 0.74;
the piston further including a conical projection within the combustion bowl, and a compound rim extending in a radially outward direction from the combustion bowl to the outer cylindrical surface;
the combustion bowl including a convex inner bowl surface located on the conical projection, and a concave outer bowl surface, and the compound rim including a flat outer rim surface adjoining the outer cylindrical surface and a convex inner rim surface adjoining the combustion bowl;
wherein the conical projection defines a cone angle which is smaller than the spray angle and is about 135° or less, the concave outer bowl surface defines a first radius of curvature from 13 mm to 16 mm, and the convex inner bowl surface continuously transitions with the concave outer bowl surface;
wherein the convex inner rim surface abruptly transitions with the concave outer bowl surface at an edge of the combustion bowl, and the convex inner rim surface defines a second radius of curvature which is from 40 mm to 70 mm, such that a crevice having a narrowing taper in the radially outward direction is defined in part by the cylinder head and in part by the compound rim when the piston is at a top dead center position.

15. The engine of claim 14 wherein the combus

Assignees

• Caterpillar Inc

Inventors

• Karch Aaron
• Pierpont David A
• Lang Daniel
• Subatch James A

Classifications

• F02B23/0693

  the combustion space consisting of step-wise widened multiple zones of different depth · CPC title

• F02M25/0727

  Mechanical Engineering · mapped topic

• F02B23/0621

  Squish flow · CPC title

• F02B2275/14

  Direct injection into combustion chamber · CPC title

• F02B23/06 Primary

  the combustion space being arranged in working piston (F02B23/04 takes precedence) · CPC title