A combustion chamber for an opposed-piston engine has a rotationally skewed shape in a longitudinal section that is orthogonal to a chamber centerline, between diametrically-opposed openings of the combustion chamber through which fuel is injected. The rotationally skewed shape interacts with swirl to generate a tumble bulk charge air motion structure that increases turbulence.

A combustion chamber for an opposed-piston engine has a rotationally skewed shape in a longitudinal section that is orthogonal to a chamber centerline, between diametrically-opposed openings of the combustion chamber through which fuel is injected. The rotationally skewed shape interacts with swirl to generate a tumble bulk charge air motion structure that increases turbulence.

A piston of a direct injection type diesel engine has a re-entrant type cavity, and a fuel injection nozzle with multiple nozzle holes is arranged on the center line thereof. The cavity has a lip portion, which is the portion thereof having the smallest diameter, positioned below a piston crown surface and a pocket portion formed above the lip portion. The pocket portion is positioned at a height to which a pilot injection injected prior to the top dead center under engine idling is directed, and the position of a wall surface is so set that a leading part of the injection spray does not collide strongly therewith. The fuel from the pilot injection temporarily stays in the pocket portion and moves into the cavity by means of a subsequent squish flow. Accordingly, an increase in unburned hydrocarbons is suppressed.

A self-igniting internal combustion engine includes at least one cylinder and a piston, which can be moved back and forth in the cylinder and which bounds a combustion chamber together with the cylinder and which has a piston recess facing the combustion chamber, said piston recess having flow cross-sections that vary in a circumferential direction of the cylinder and of the piston, and comprising an injector arranged centrally above the piston recess for injecting fuel into the piston recess, wherein the injector has a plurality of injection openings. In order to reduce the emissions and in particular the soot emissions of the internal combustion engine, at least some of the injection openings have different opening cross-sections, wherein the injection openings having the different opening cross-sections are directed at areas of the combustion chamber recess having different flow cross-sections.

A piston for a diesel engine is prepared as a piston for a direct injection engine, a cavity face of the piston is grinded, and a squish face thereof is masked. Next, a high-purity aluminum coating is formed on the cavity face, and the masking of the squish face is removed and the entire area of the piston top face is subjected to an anodizing treatment. Thereafter, the cavity face is masked, and the squish face is subjected to a sealing treatment.

A direct injection diesel engine includes a piston having a reentrant cavity and a multi-hole fuel injection nozzle disposed on a center line of the cavity. The cavity is formed by a lip portion defining a smallest diameter at a position below a piston crown surface and a raised portion formed at a center of the bottom and shaped like a frustum of a cone. A conical surface of the raised portion is formed to have an angle pointing to a spray point of the fuel injection nozzle at a piston top dead center position. The height position of a top surface is substantially equal to the height position of the lip portion. This structure is to promote the oxidation of soot by utilizing the air in the central part of the cavity.

A piston for an internal combustion engine includes a piston body forming a crown portion and a skirt portion. The skirt portion includes a bore that receives a pin for connecting the piston to a connecting rod, and the crown portion forms a bowl surrounded by a flat crown surface having an annular shape and disposed along a plane. The bowl and the flat crown surface meet along a circular edge surrounding a rim of the bowl. The piston further includes an annular protrusion disposed within the bowl adjacent the rim. The annular protrusion has a generally convex shape in cross section created by an upper, inwardly extending surface and a lower, inwardly extending surface that meet along a convex apex. The piston further includes an airfoil surface formed in the flat crown surface. The airfoil surface has a convex shape and extends annularly around the rim of the bowl.

A combustion chamber for an opposed-piston engine includes a squish zone defined between circumferential peripheral areas of opposing end surfaces of the pistons, a cavity defined by one or more bowls in the end surfaces, and at least one injection port that extends radially through the squish zone into the cavity. The cavity has a cross-sectional shape that imposes a tumbling motion on air flowing from the squish zone into the cavity.

A piston may have an annular body including a crown portion defining a longitudinal axis, a radial direction perpendicular to the longitudinal axis, a plane containing the longitudinal axis and the radial direction, and a contoured combustion bowl. In the plane containing the longitudinal axis and the radial direction, the crown portion includes a radially outer squish surface, and a swirl pocket having a reentrant surface that extends axially downwardly and radially outwardly from the squish surface defining a tangent that forms a reentrant angle with the squish surface that ranges from 53.0 degrees to 57.0 degrees.

A combustion chamber for an opposed-piston engine has a rotationally skewed shape in a longitudinal section that is orthogonal to a chamber centerline, between diametrically-opposed openings of the combustion chamber through which fuel is injected. The rotationally skewed shape interacts with swirl to generate a tumble bulk charge air motion structure that increases turbulence.