The invention is provided with an ignition control section and an injection control section. When partial compression ignition combustion is carried out, the ignition control section causes an ignition plug to carry out: main ignition in which a spark is generated in a late period of a compression stroke or an initial period of an expansion stroke to initiate SI combustion; and preceding ignition in which the spark is generated at earlier timing than the main ignition. Also, when the partial compression ignition combustion is carried out, the injection control section causes an injector to inject fuel at such timing that the fuel exists in a cylinder at an earlier time point than the preceding ignition. Timing of the preceding ignition is more advanced when a swirl flow is gentle than when the swirl flow is strong.

A spark-ignition internal combustion engine includes a cylinder head and a piston. A crown surface of the piston includes a central portion, and first outer portions and second outer portions located outside the central portion. The central portion and the first outer portions have a combustion chamber height higher than a predetermined value. The combustion chamber height of the second outer portions is equal to or lower than the predetermined value. The crown surface is composed of a mirror surface region and a rough surface region. The mirror surface region has a surface roughness of less than 0.05 μm. The rough surface region has a surface roughness of 0.05 μm or more and 2.5 μm or less. All of the central portion and the first outer portions are included in the mirror surface region. At least one of the second outer portions is included in the rough surface region.

A spark-ignition internal combustion engine includes a cylinder head and a piston. A crown surface of the piston includes a central portion, and first outer portions and second outer portions located outside the central portion. The central portion and the first outer portions have a combustion chamber height higher than a predetermined value. The combustion chamber height of the second outer portions is equal to or lower than the predetermined value. The crown surface is composed of a mirror surface region and a rough surface region. The mirror surface region has a surface roughness of less than 0.05 μm. The rough surface region has a surface roughness of 0.05 μm or more and 2.5 μm or less. All of the central portion and the first outer portions are included in the mirror surface region. At least one of the second outer portions is included in the rough surface region.

A control apparatus for a compression-ignition type engine is applied to an engine capable of carrying out partial compression ignition combustion in which an air-fuel mixture is subjected to CI combustion by self-ignition. The control apparatus creates a lean A/F environment where an air-fuel ratio as a ratio between air and fuel in a cylinder exceeds 20 and is lower than 35, or a lean G/F environment where a gas air-fuel ratio as a ratio between entire gas and the fuel in the cylinder exceeds 18 and is lower than 50 and the air-fuel ratio substantially matches a stoichiometric air-fuel ratio. Prior to planned timing of the CI combustion, in the lean A/F environment or the lean G/F environment, the control apparatus causes an ignition plug to generate a spark and to generate a high-temperature portion.

To effectively suppress strong knock that occurs in the operating region of high load and high rotation in a specific engine having a pre-chamber in a combustion chamber, the engine includes a piston that defines a combustion chamber together with a cylinder block and a cylinder head. The combustion chamber includes a sub-chamber and a main chamber separated from the sub-chamber by a pre-chamber. The specific ratio obtained by dividing a volume of the sub-chamber by a stroke volume of a cylinder is greater than or equal to 0.00005 and less than or equal to 0.00045.

The subject matter of this specification can be embodied in, among other things, a method of igniting an air/fuel mixture in an internal combustion engine includes receiving an air/fuel mixture into a pre-combustion chamber, the pre-combustion chamber enclosing a portion of an igniter, igniting the air/fuel mixture in in the pre-combustion chamber with the igniter to produce a flame, directing the flame to eject the pre-combustion chamber through a collection of passages in a wall of the pre-combustion chamber, toward a peripheral wall of a main combustion chamber of the internal combustion engine, igniting, by the flame, air/fuel mixture in the main o combustion chamber adjacent the peripheral wall, and then igniting air/fuel mixture in the main combustion chamber in a central region of the main combustion chamber with a propagating flame front of the ignited air/fuel mixture or a portion of the directed flame adjacent the peripheral wall.

The invention relates to an HPDF operation method for an internal combustion engine (100) with internal formation of a mixture and self-ignition, in which, (i) for a combustion cycle of an operation cycle under high pressure, as main fuel (63) at a first time point, the introduction of a nonself-igniting or gasoline engine fuel, and as ignition fuel (64) at a second time point, the introduction of a self-igniting or diesel fuel into a combustion chamber (20) of the internal combustion engine (1) are at least initiated and/or performed, (ii) a self-ignition of the ignition fuel (64) and with the self-ignition a nonself-ignition of the main fuel (63) are effected, and (iii) the self-ignition of the ignition fuel (64) is performed temporally and/or spatially in such a way that the main fuel (63) is ignited at a location (1) and/or in a region of an jet tip (630 and/or a propagation front (630 of a quantity of introduced main fuel (63)—in particular temporally firstly.

An apparatus for cleaning a surface of an optical window includes a first electrode that is provided inside the optical window and is covered with a dielectric material forming the optical window. A second electrode is provided around the optical window and is exposed on at least one surface of the optical window. A power supply is electrically coupled between the first electrode and the second electrode. The apparatus further includes a controller that controls the power supply so as to generate dielectric barrier discharge along the surface of the optical window by applying a high-frequency or pulsed voltage between the first electrode and the second electrode.

The subject matter of this specification can be embodied in, among other things, a method of igniting an air/fuel mixture in an internal combustion engine includes receiving an air/fuel mixture into a pre-combustion chamber, the pre-combustion chamber enclosing a portion of an igniter, igniting the air/fuel mixture in in the pre-combustion chamber with the igniter to produce a flame, directing the flame to eject the pre-combustion chamber through a collection of passages in a wall of the pre-combustion chamber, toward a peripheral wall of a main combustion chamber of the internal combustion engine, igniting, by the flame, air/fuel mixture in the main combustion chamber adjacent the peripheral wall, and then igniting air/fuel mixture in the main combustion chamber in a central region of the main combustion chamber with a propagating flame front of the ignited air/fuel mixture or a portion of the directed flame adjacent the peripheral wall.

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%.