Abstract: A loop-scavenged two-stroke internal combustion engines with an intake valve (7) engaging a seat (10) for fresh air intake, and an exhaust valve (8) engaging a seat (13) for combustion gas exhaust, is disclosed. The valves are arranged in such a way that the fresh air intake scavenges a substantial part of the burnt gases. In at least one of the valves, the valve surface (21) located downstream from the valve face (9) and the surface (23) of the downstream extension of the seat (10) are configured in such a way that they form a substantially isentropic diffuser.

Abstract: Internal combustion engines with a cylindrical working chamber (1) in which there slides a piston (3), and which is closed by a cylinder head (4) with a device (5) for injecting atomized liquid fuel under high pressure and operating on the two-stroke cycle with a loop-scavenging system across the cylinder head, with two axisymmetric valves with coincident axes, one of these, an external, inlet valve (7) interacting with a seat (15) in the cylinder head and the other, an exhaust valve (6), exhibiting a tubular shape with a bearing surface applied against a seat (16) formed at the lower part of the inlet valve (7), the inlet valve opening towards the working chamber and the exhaust valve opening in the opposite direction, in order to delimit an exhaust passage (8) between them, the injection device (5) emerging in the working chamber substantially at the centre of a central hub (21) borne by the cylinder head and about which the exhaust valve (6) slides.

Abstract: In a two-stroke internal combustion engine with a compression-ignition of Diesel type, the exhaust valve or valves (10) are so arranged as to allow flow on at least the major part of their periphery; the piston (3) cooperates with the ceiling of the cylinder head (6) in such manner as to leave, in the vicinity of top dead center, only the required operational clearance between the piston (3) and the part of the ceiling of the cylinder head in which the exhaust valve or valves (10) is or are placed; and a cylindrical recess (14) in which is placed the head (13) of the inlet valve or valves (8) and into which a fuel injector discharges, is arranged in such manner as to constitute practically alone the combustion chamber (7) when the piston (3) is in the vicinity of top dead center.

Abstract: The two-stroke cycle engine employing intake and exhaust valves comprises a combustion and scavenging prechamber having substantially a shape of revolution about an axis and provided with an intake valve seat. Deflecting means or vanes are disposed inside the intake pipe as directly as possible on the upstream side of the seat so as to urge the mass of air into the combustion chamber in the manner of a whirl.