COMBUSTION CHAMBER CONSTRUCTIONS FOR OPPOSED-PISTON ENGINES

An internal combustion engine including at least one cylinder (220) with longitudinally separated exhaust (226) and intake (224) ports， and a pair of pistons (280) disposed in opposition to one another in a bore of the cylinder， in which a combustion chamber is defined between opposing end surfaces (282) of the pistons， and the end surface (282) of each of the pistons has a circumferential area (284) defining a periphery of the end surface and a bowl (286) within the periphery， the bowl defining a concave surface (286) with a first portion (290) curving inwardly from a plane containing the circumferential area toward the interior of the piston and a second portion (292) curving outwardly from the interior of the piston through the plane containing the circumferential area. 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.