| 主权项 |
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. |
