Piston, Engine And Operating Method For Reduced Production Of Particulate Matter

An internal combustion engine comprising:

• an engine housing having formed therein a cylinder bore including an inner wall defining a cylinder bore diameter of about 265 mm;
• a fuel injector positioned at least partially within the cylinder bore and configured to directly inject a fuel therein;
• a piston positioned within the cylinder bore and movable from a bottom dead center position to a top dead center position such that a fluid pressure within the cylinder bore is increased by a factor of about fifteen or greater to autoignite the directly injected fuel with air;
• the piston including a combustion face having a convex inner bowl surface and a concave outer bowl surface together forming a combustion bowl, and an outer rim surface and an inner rim surface together forming an annular piston rim extending circumferentially around the combustion bowl and defining a plane extending through an intersection of the outer and inner rim surfaces and oriented normal to the longitudinal axis;
• the combustion bowl having a horizontal diameter, and a vertical depth from the plane such that a ratio of the bowl diameter to the bowl depth is about 7:1, and the concave outer bowl surface defining a radius of curvature fitting the concave outer bowl surface to the depth and diameter and forming a non-reentrant profile of the combustion bowl;
• and
• the inner and outer rim surfaces together comprising a horizontal width of the annular rim in a ratio of inner rim surface width to outer rim surface width from about 1:1 to about 2:1, and the inner rim surface including a chamfer sloping vertically downward from the plane at a chamfer angle from about 9° to about 11° and forming a relieved profile of the annular rim.

A method of operating an internal combustion engine comprising the steps of:

• rotating a crankshaft of the internal combustion engine in an engine cycle such that a piston coupled with the crankshaft is moved between a bottom dead center position and a top dead center position within a cylinder bore having a cylinder bore diameter of about 265 mm;
• injecting a fuel directly into the cylinder bore such that at least some of the fuel is injected after the piston has passed the top dead center position in the engine cycle;
• positioning the piston via the rotation of the crankshaft such that a chamfered inner rim surface of the piston sloping at a chamfer angle from about 9° to about 11° is within a spray path of fuel injected after the piston has passed the top dead center position;
• directing fuel injected after the piston has passed the top dead center position into a combustion bowl of the piston having a bowl diameter to bowl depth ratio of about 7:1 at least in part via impingement upon the chamfered inner rim surface, such that deflection of the injected fuel by the piston toward a wall of the cylinder bore is limited;
• and
• autoigniting a mixture containing the injected fuel and air within the cylinder bore.