Piston crown for an internal combustion engine
A piston crown is provided for a piston in an internal combustion engine arrangement that includes a cylinder, the piston crown having a piston bowl surface adapted for facing a combustion chamber in the cylinder, wherein the piston bowl surface including a circumferential rim portion, a floor portion connected to and surrounded by the circumferential rim portion, a plurality of circumferentially spaced protrusions in the circumferential rim portion, at least one spray impingement portion, located between two adjacent protrusions. The spray impingement portion includes a reflection surface, being defined by that each possible normal to the reflection surface is directed towards a central axis of the piston, and forming an angle being within a range of a constant angle ±10° with the central axis, wherein the constant angle is at least 50°.
1. An internal combustion engine comprising an engine cylinder and a piston positioned for reciprocal movement in the engine cylinder along a central axis between a bottom dead center position and a top dead center position, wherein the piston comprises a piston crown having a piston bowl surface adapted for facing a combustion chamber in the cylinder, wherein the piston crown is arranged in relation to an injector of the combustion engine arrangement, the injector comprising at least one orifice, the orifice being arranged to inject fuel along a fuel spray vector towards a spray impingement portion, wherein the piston bowl surface comprising: a circumferential rim portion, a floor portion connected to and surrounded by the circumferential rim portion a plurality of circumferentially spaced protrusions in the circumferential rim portion, at least one spray impingement portion, located between two adjacent protrusions, wherein the spray impingement portion comprises a reflection surface that substantially has a shape of a portion of an envelope surface of an imaginary cone, being defined by that each possible normal to the reflection surface is directed towards a central axis of the piston, and forming an angle being a constant angle ±2° with the central axis wherein the constant angle is at least 50°, wherein the rim portion defines a maximum level of the piston bowl surface along the central axis, and the floor portion defining a minimum level of the piston bowl surface along the central axis, the piston bowl having a piston bowl extension along the central axis being the difference between the maximum level and the minimum level, and wherein the reflection surface has a reflection surface extension along the central axis, the reflection surface extension being at least 10% of the piston bowl extension, the fuel spray vector forms a spray angle (β) with the central axis, the constant angle being at least 2° smaller than the spray angle (β).
2. The internal combustion engine according to claim 1 , wherein the imaginary cone is a right circular cone.
3. The internal combustion engine according to claim 2 , wherein the imaginary cone has a cone apex and a cone base, the cone apex and the cone base being located on opposite sides of the floor portion, the floor portion facing the cone base.
4. The internal combustion engine according to claim 1 , wherein the reflection surface extension is between 15 and 30% of the piston bowl extension.
5. The internal combustion engine according to claim 1 , wherein the reflection surface extension is extending at a first distance from the minimum level of the piston bowl surface along the central axis, the first distance being at least 15% of the piston bowl extension.
6. The internal combustion engine according to claim 1 , wherein the constant angle is at least 60°.
7. The internal combustion engine according to any one of the preceding claims, wherein the constant angle is less than 85°.
8. The internal combustion engine according to claim 1 , wherein the reflection surface has an extension along the circumferential direction of the rim portion corresponding to an angle of at least 5°, about the central axis, in a plane perpendicular to the central axis.
9. The internal combustion engine in accordance with claim 1 , wherein the rim portion comprises at least two reflection surfaces.
10. The internal combustion engine in accordance with claim 1 , wherein the reflection surfaces are located at regular angular intervals about the central axis.
11. The internal combustion engine in accordance with claim 1 , wherein all reflection surfaces of the piston crown are uniform.
12. The internal combustion engine in accordance with claim 1 , wherein at least some of the protrusions are uniform, preferably all of the protrusions of the piston crown are uniform.
13. The internal combustion engine in accordance with claim 1 , wherein at least the portion that is located closest to the central axis of at least one of the protrusions forms a surface, for which each possible normal forms the same angle as the reflection surface.
14. The internal combustion engine in accordance with claim 1 , wherein the piston bowl surface comprises a concave surface, positioned between the floor portion and the reflection surface, and a convex surface, positioned between the reflection surface and the circumferential rim portion.
15. A vehicle comprising an internal combustion engine in accordance with claim 1 .