A top surface of the piston includes a first region. A heat shielding film is formed on the first area. The top surface further includes a second region. There is no heat shielding film formed on the second region. Instead, the second area is mirror-finished. The top surface includes a central portion. A valve recess portion is formed on an intake side of the central portion. A squish portion is formed the intake side of the valve recess portion. The first area includes at least the central portion. The second area includes at least the squish portion.

Operating an internal combustion engine includes conveying fuel of spray plumes of directly injected fuel out of a swirl pocket in a combustion bowl in a piston, and impinging the fuel upon an anti-sooting ramp transitioning between a radially inner shelf surface of the combustion bowl and a radially outer squish surface of the piston. The shelf surface is spaced an axial distance (FA) from a plane defined by the squish surface that is from 1% to 2% of an outer diameter (OD) dimension of the piston. Impinging the fuel upon the anti-sooting ramp directs the fuel upwardly from the squish surface to limit wall-wetting in the combustion cylinder.

A cavity includes a lower-side cavity, an upper-side cavity, a first lip and a second lip. The upper-side cavity has a guide curved surface which extends along a circumference of a first imaginary circle in a section along a cylinder-axis direction, and the first lip has a curved surface which extends along a circumference of a second imaginary circle in a section along the cylinder-axis direction. An angle X which a cylinder axis makes with a common tangential line of the first imaginary circle and the second imaginary circle is set as 75°<X<80°. The guide curved surface is configured such that an angle Y of this guide curved surface which occupies at the circumference of the first imaginary circle is set as 80°<Y<(180°−X).

An engine system comprising an internal combustion engine and a turbocharger, where a diameter of the at least one intake valve is greater than a diameter of the at least one exhaust valve, the salient angle of the piston bowl is at least 10 degrees, the ratio between the piston bowl opening diameter and the piston bowl depth is approximately 0.5 to 2.0, the intake valve opens before top dead center on an exhaust stroke of the internal combustion engine and closes before bottom dead center of an intake stroke of the internal combustion engine, and the turbocharger has a combined efficiency of more than 50%.

A combustion chamber structure for an engine includes a combustion chamber where SI combustion by spark ignition and CI combustion by self-ignition are conducted. A crown surface includes a cavity recessed to have a bowl-shape, and a pair of raised portions. The cavity includes a bottom portion which is a lower region of the recessed part, the bottom portion having an outer circumferential edge which is circular in a top view. With a height of the raised portion relative to a height position of a deepest portion of the cavity being represented as H1 and a diameter of an outer circumferential edge of the bottom portion of the cavity being represented as D, H1/D as a ratio of the height H1 of the raised portion to the diameter D of the cavity is set to be in a range of 0.05 or more and 0.36 or less.

Methods and systems are provided for a piston. In one example, a system may comprise a plurality of first protrusions and a plurality of second protrusions working in tandem to confine an injection to a radial zone defined by the protrusions.

An engine system comprising an internal combustion engine and a turbocharger, where a diameter of the at least one intake valve is greater than a diameter of the at least one exhaust valve, the salient angle of the piston bowl is at least 10 degrees, the ratio between the piston bowl opening diameter and the piston bowl depth is approximately 0.5 to 2.0, the intake valve opens before top dead center on an exhaust stroke of the internal combustion engine and closes before bottom dead center of an intake stroke of the internal combustion engine, and the turbocharger has a combined efficiency of more than 50%.

A porous alumina layer with a sealer (i.e., a coating layer) is formed on a top surface or a piston (i.e., a second cavity surface and a second squish surface) and a surface of a bottom surface of a cylinder which forms a cavity area CA (i.e., a first cavity surface). The porous alumina layer without the sealer (i.e., an exposed layer) is formed on a surface of the bottom surface which forms a squish area SA (i.e., a first squish surface).

A cavity includes a lower-side cavity, an upper-side cavity, a first lip and a second lip. The upper-side cavity has a guide curved surface which extends along a circumference of a first imaginary circle in a section along a cylinder-axis direction, and the first lip has a curved surface which extends along a circumference of a second imaginary circle in a section along the cylinder-axis direction. An angle X which a cylinder axis makes with a common tangential line of the first imaginary circle and the second imaginary circle is set as 75<X<80. The guide curved surface is configured such that an angle Y of this guide curved surface which occupies at the circumference of the first imaginary circle is set as 80<Y<(180X).

When an amount of a backward tumble flow is smaller than an amount of a forward tumble flow, the intake-side valve recess is used as a first valve recess and the exhaust-side valve recess is used as a second valve recess. When the amount of the backward tumble flow is larger than the amount of the forward tumble flow, the exhaust-side valve recess is used as a first valve recess and the intake-side valve recess is used as a second valve recess. An inclination angle of the first valve recess is larger than an inclination angle of the second valve recess when comparing the inclination angle such that a height of the recess decreases gradually toward an inner side of a cross-section.