A piston for a diesel engine, includes a piston body having a generally planar crown and a skirt extending from the crown. A stepped combustion bowl is recessed in the crown and includes an outer bowl recessed relative to the crown and an inner bowl recessed relative to the outer bowl.

An internal combustion engine comprises a fuel injector 31, a spark plug 16, a piston 14 having a cavity 91, a swirl control device 95, and a control system 70. The cavity is formed so as to change in distance from the fuel injector to a side wall surface of the cavity, in the circumferential direction. The system performs ignition assist control for successively performing injections of main fuel and ignition assist fuel, makes an air-fuel mixture formed by the ignition assist fuel burn by flame propagation by the spark plug, and makes the remaining fuel burn by pre-mix compression self-ignition. The system controls the swirl control device during the ignition assist control so that when the engine load is high, the fuel sprayed heads toward parts of the side wall surface which are short in distances from the fuel injector.

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.

A piston has a piston crown portion forming at least one arcuate indent in aligned fashion with a fuel jet discharged into a combustion chamber. Each arcuate event forms lobes, which separate the fuel jet into portions, or is tiered, to accommodate fuel jet portions being discharged into the combustion chamber at different times. Each lobe or tier includes an entry surface, a recirculation surface and a wall to separate it from adjacent lobes or tiers, respectively.

The disclosure describes multipoint ignition systems for an engine and methods of operation of the same. The systems and methods can include an engine, including an engine block having at least one cylinder bore, a piston having a piston crown facing a flame deck surface such that a combustion main chamber is defined within a cylinder bore and located between the piston crown and the flame deck surface, the piston crown further including a piston bowl having a generally concave shape, and a combustion pre-chamber having a nozzle tip disposed in fluid communication with the combustion main chamber, the nozzle tip having at least one nozzle opening configured to inject a fuel jet into the combustion main chamber, wherein the piston includes a piston wall located around a circumference of the piston bowl, the piston wall including at least one cavity.

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.

An internal combustion engine includes a combustion chamber having a piston, the piston having at least one arcuate indent of a first type formed in the top surface, and at least one arcuate indent of a second type, wherein the first type includes a first recirculation surface having a concave shape at a first radius and extending along a spiral direction adjacent the entry surface, and wherein the second type includes a second recirculation surface having a concave shape at a second radius that is smaller than the first radius. During operation, a fuel jet provided into the first type occupies a radially outward portion of the combustion chamber, and a fuel jet provided into the second type occupies a central portion of the combustion chamber.

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.

The disclosure describes multipoint ignition systems for an engine and methods of operation of the same. The systems and methods can include an engine, including an engine block having at least one cylinder bore, a piston having a piston crown facing a flame deck surface such that a combustion main chamber is defined within a cylinder bore and located between the piston crown and the flame deck surface, the piston crown further including a piston bowl having a generally concave shape, and a combustion pre-chamber having a nozzle tip disposed in fluid communication with the combustion main chamber, the nozzle tip having at least one nozzle opening configured to inject a fuel jet into the combustion main chamber, wherein the piston includes a piston wall located around a circumference of the piston bowl, the piston wall including at least one cavity.

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.