A combustion-chamber structure of an engine comprises a combustion chamber which is partitioned by a cylinder block, a cylinder head, and a piston. The piston includes a piston body having an upper surface facing the combustion chamber, a heat-insulation layer provided at least in a central area, in a radial direction, of the upper surface and having smaller heat conductivity than the piston body, a heat-barrier layer provided to cover the upper surface and having smaller heat conductivity than the piston body and the heat-insulation layer, and a heat-diffusion layer provided between the heat-insulation layer and the heat-barrier layer and having larger heat conductivity than the heat-insulation layer and the heat-barrier layer. The heat-diffusion layer comprises a side end edge and an extension portion which contact with the piston body.

A reciprocating engine includes a crankshaft and a connecting rod rotatably coupled to the crankshaft. The connecting rod defines a fluid passage extending along a length thereof. The reciprocating engine also includes a piston dome coupled to the connecting rod, the piston dome defining an inlet in fluid communication with the fluid passage of the connecting rod for receiving a fluid from the fluid passage of the connecting rod, a cooling passage in fluid communication with the inlet for circulating the fluid through the piston dome, and an exit in fluid communication with the cooling passage.

A compressor comprises a first compressor piston assembly including a first compressor piston head having a bottom side and a longitudinal central axis. The compressor also comprises a first nozzle arranged to direct a first oil stream towards the bottom side of the first compressor piston head to cool the piston assembly. The compressor further comprises a second nozzle arranged to direct a second oil stream towards the bottom side of the first compressor piston head to cool the piston assembly. Each of the oil streams is substantially parallel to each other and to the longitudinal central axis to provide a flow of oil to cool the piston assembly and to reduce an oil carryover by the first compressor piston assembly by up to about fifty percent as compared to a compressor having no nozzles directing oil streams towards the bottom side of the first compressor piston head.

Pistons and piston assemblies for an internal combustion engine is provided. The piston assembly includes a piston coupled to a connecting rod with a piston pin. The piston pin includes a non-circular outer cross-sectional shape.

A piston for an internal combustion engine includes a piston crown having a combustion bowl formed therein, a piston rim extending circumferentially around the combustion bowl and a heat-dissipating chamfer between the combustion bowl and the piston rim. The chamfer is structured by way of at least one of size, angle, or material thickness to an oil gallery to balance heat dissipation with combustion properties. Related methodology is disclosed.

A steel piston achieving increased thermal brake efficiency in an internal combustion engine is provided. The piston includes a crown presenting a combustion surface, an outer side wall depending from the combustion surface, an outer cooling gallery, and an undercrown cooling gallery. The outer cooling gallery extends circumferentially along the outer side wall beneath the combustion surface. According to one embodiment, the outer cooling gallery is sealed and filled with air, argon, helium, xenon, or carbon dioxide as a cooling media. In this embodiment, the undercrown cooling gallery is filled with air as a cooling media and includes an open inlet hole having a diameter being from 2% to 4% of an outer diameter of the piston. Alternatively, the undercrown cooling gallery is filled with air, argon, helium, xenon, or carbon dioxide as a cooling media, and the inlet hole is sealed.

A steel piston achieving increased thermal brake efficiency in an internal combustion engine is provided. The piston includes a crown presenting a combustion surface, an outer side wall depending from the combustion surface, an outer cooling gallery, and an undercrown cooling gallery. The outer cooling gallery extends circumferentially along the outer side wall beneath the combustion surface. According to one embodiment, the outer cooling gallery is sealed and filled with air, argon, helium, xenon, or carbon dioxide as a cooling media. In this embodiment, the undercrown cooling gallery is filled with air as a cooling media and includes an open inlet hole having a diameter being from 2% to 4% of an outer diameter of the piston. Alternatively, the undercrown cooling gallery is filled with air, argon, helium, xenon, or carbon dioxide as a cooling media, and the inlet hole is sealed.

A piston for an internal combustion engine is formed from an upper part connected to a lower part. The upper part has a combustion bowl, a top land, and a ring belt extending circumferentially around the piston upper part. The lower part contains pin bosses and a piston skirt. A circumferential cooling channel is formed by joining the upper and lower parts. There is an oil inlet formed in one piece with the piston lower part. The inlet has a lower extremity and an upper extremity that terminates at the floor of the cooling channel. A bore extends through the oil inlet from the lower extremity up though the floor of the cooling channel. The circumference of the bore increases from the upper extremity to the lower extremity, so the oil inlet forms a funnel shape.

Pressurized lubricating oil is accumulated in the bearings of opposed pistons and accumulated oil is dispensed therefrom for bearing lubrication and also for cooling the undercrowns of the pistons by jets of oil emitted from the bearings.

An opposed-piston engine includes pistons, each piston having an annular cavity in the piston's sidewall and positioned between its crown and ring grooves to block transfer of heat from the crown to the piston body.