An engine system includes a combustion chamber including a cylinder formed in an engine and a piston configured to reciprocate inside the cylinder, a spark plug disposed in a ceiling part of the combustion chamber, and a water injection device configured to inject water into the combustion chamber through a plurality of nozzle holes facing the inside of the combustion chamber. The piston has a cavity in an upper surface thereof. The water injection device injects water into the cavity in a compression stroke at a timing when an extension of axes of at least some of the nozzle holes intersects the cavity. The cavity has a bottom part where the water injected by the water injection device collides, and a raising part configured to raise the water spreading along the bottom part toward the water injection device.

An engine system includes a combustion chamber including a cylinder formed in an engine and a piston configured to reciprocate inside the cylinder, a spark plug disposed in a ceiling part of the combustion chamber, and a water injection device configured to inject water into the combustion chamber through a plurality of nozzle holes facing the inside of the combustion chamber. The piston has a cavity in an upper surface thereof. The water injection device injects water into the cavity in a compression stroke at a timing when an extension of axes of at least some of the nozzle holes intersects the cavity. The cavity has a bottom part where the water injected by the water injection device collides, and a raising part configured to raise the water spreading along the bottom part toward the water injection device.

The present application provides a piston assembly. The piston assembly may include a cylinder bore extending from a thrust side to an antithrust side and a piston positioned within the cylinder bore. The piston may include a top land, a second land, and a skirt with an axis extending therethrough. The piston may include a tight land profile with an offset about the axis of the skirt.

A piston with an improved bowl geometry includes a piston body having a generally planar crown and a skirt extending from the crown. An oval or multi-lobed bowl rim of a combustion bowl that is recessed in the crown so that the sides of the bowl rim are provided with increased material to resist fatigue along the pin plane, optionally along the thrust/antithrust plane and generally optionally along other planes between the pin plane and the thrust/antithrust plane.

The present application provides a piston assembly. The piston assembly may include a cylinder bore extending from a thrust side to an antithrust side and a piston positioned within the cylinder bore. The piston may include a top land, a second land, and a skirt with an axis extending therethrough. The piston may include a tight land profile with an offset about the axis of the skirt.

A piston with an improved bowl geometry includes a piston body having a generally planar crown and a skirt extending from the crown. An oval or multi-lobed bowl rim of a combustion bowl that is recessed in the crown so that the sides of the bowl rim are provided with increased material to resist fatigue along the pin plane, optionally along the thrust/antithrust plane and generally optionally along other planes between the pin plane and the thrust/antithrust plane.

A piston may include an outer peripheral surface and a crown. The outer peripheral surface may include first and second openings spaced about and extending through the outer peripheral surface. The crown may include a recess at least partially defined by a first lobe in fluid communication with the first opening and a second lobe in fluid communication with the second opening. Each of the first and second lobes may be recessed relative to an adjacent portion of the recess of the crown.

A combustion chamber structure for an internal combustion engine includes, in a piston top part, a concave portion formed eccentrically with respect to a cylinder center axis, and a tapered portion that connects an upper end face of the piston top part and a side face of the concave portion. The tapered portion is formed so that a tapered portion volume (volume of a space formed between the tapered portion and an upper wall surface of the combustion chamber) in a first portion of the piston top part is greater than a tapered portion volume in a second portion that is nearer than the first portion to an eccentric direction of the concave portion from the cylinder center axis.

A combustion chamber for an opposed-piston engine has an elongated asymmetrical shape in longitudinal section that runs along a chamber centerline, between diametrically-opposed openings of the combustion chamber through which fuel is injected. The asymmetry apportions combustion chamber volume to provide additional clearance on a side of the chamber centerline toward which swirl is directed, thereby giving a fuel plume space to swing without hindrance in response to swirl.

On a piston top surface, a cavity and two valve recesses are formed. On the piston top surface, a first heat insulating film is formed. However, on edge portions, a second heat insulating film different from the first heat insulating film is formed. The second heat insulating film is formed along the edge portions. The first heat insulating film is composed of porous alumina and a sealer. The second heat insulating film is composed of only porous alumina.