Aspects of the present invention relate to a valve seat (20) for a poppet valve of an internal combustion engine, wherein the poppet valve comprises a head and a stem behind the head, the valve seat comprising: an aperture (21) configured to form a seal with the head of the poppet valve when the poppet valve is in a closed position; and a peripheral body (22) defining, at least in part, one or more ports (23) shaped like e.g. grooves and sized to enable injection of liquid or gas from a cylinder head of the internal combustion engine into a gas stream behind the head of the poppet valve.

A valve seat insert includes a top convex arcuate blend for improving fluid flow, and a valve seating surface for slowing down valve recession. The valve seating surface includes a radially outer convex arcuate segment defining an outer radius of curvature forming a first wear crown for contacting the valve at an early wear state, a radially inner convex arcuate segment defining an inner radius of curvature forming a second wear crown for contacting the valve at a later wear state, and a linear segment extending between the radially outer convex arcuate segment and the radially inner convex arcuate segment.

A valve seat insert includes a top convex arcuate blend for improving fluid flow, and a valve seating surface for slowing down valve recession. The valve seating surface includes a radially outer convex arcuate segment defining an outer radius of curvature forming a first wear crown for contacting the valve at an early wear state, a radially inner convex arcuate segment defining an inner radius of curvature forming a second wear crown for contacting the valve at a later wear state, and a linear segment extending between the radially outer convex arcuate segment and the radially inner convex arcuate segment.

A valve seat insert includes a top convex arcuate blend for improving fluid flow, and a valve seating surface for slowing down valve recession. The valve seating surface includes a radially outer convex arcuate segment defining an outer radius of curvature forming a first wear crown for contacting the valve at an early wear state, a radially inner convex arcuate segment defining an inner radius of curvature forming a second wear crown for contacting the valve at a later wear state, and a linear segment extending between the radially outer convex arcuate segment and the radially inner convex arcuate segment.

A valve seat insert includes a top convex arcuate blend for improving fluid flow, and a valve seating surface for slowing down valve recession. The valve seating surface includes a radially outer convex arcuate segment defining an outer radius of curvature forming a first wear crown for contacting the valve at an early wear state, a radially inner convex arcuate segment defining an inner radius of curvature forming a second wear crown for contacting the valve at a later wear state, and a linear segment extending between the radially outer convex arcuate segment and the radially inner convex arcuate segment.

Internal combustion piston engine includes a cylinder head partly defining two ducts and a combustion chamber, and poppet valves movably arranged in the cylinder head between positions allowing or preventing flow between the combustion chamber and the ducts. The poppet valve has a stem, a valve head having a hollow interior space, a lower surface facing the combustion chamber, an upper surface including a portion adjacent the stem, and a peripheral edge section that extends from the upper surface of the valve head to the lower surface. The valve head is formed separate from but connected to the valve stem in a manner to enclose the hollow space, for example, by a circumferential welding seam. The peripheral edge section contains an arcuate contact surface that extends from the upper to lower surfaces of the valve head and without any sharp edges between upper and lower surfaces.

Internal combustion piston engine includes a cylinder head partly defining two ducts and a combustion chamber, and poppet valves movably arranged in the cylinder head between positions allowing or preventing flow between the combustion chamber and the ducts. The poppet valve has a stem, a valve head having a hollow interior space, a lower surface facing the combustion chamber, an upper surface including a portion adjacent the stem, and a peripheral edge section that extends from the upper surface of the valve head to the lower surface. The valve head is formed separate from but connected to the valve stem in a manner to enclose the hollow space, for example, by a circumferential welding seam. The peripheral edge section contains an arcuate contact surface that extends from the upper to lower surfaces of the valve head and without any sharp edges between upper and lower surfaces.

An engine valve having a shaft portion and a head portion expanding in diameter like a head at an edge of the shaft portion, and being to open and close a port provided in a cylinder head, wherein the head portion has a head front surface on a bottom side facing a combustion chamber side, a head rear surface on a top side facing the port side, and an outer peripheral surface of the head portion formed between the head front surface and the head rear surface, and the head portion is provided a mirror-finished mirror portion, and the head portion is provided a mirror-finished mirror portion on the entire area of the head front surface exposed to the combustion chamber and the entire area of the outer peripheral surface exposed to the combustion chamber.

Generally, a rotatable valve assembly operative in an internal combustion engine is provided. The rotatable valve assembly may comprise a valve body rotatably supported in the cylinder head. The valve body may have various shapes which may allow to maximize an effective working area of a combustion chamber head and at the same time to decrease an overall space occupied by a cylinder head of the engine. The rotatable valve assembly may directly utilize an engine's camshaft rotational motion to drive the rotational motion of the valve body, thereby eliminating a need in dedicated mechanisms that convert the camshafts rotational motion into linear translational motion typically utilized in current cylinder heads. Finally, rotational motion of the valve body may reduce a time required to reach a maximal effective working area for air-fuel mixture supply and/or gas exhaust and/or may provide a smoother and quitter engine operation.

A scavenger valve and method of directing gas in a two stroke engine are provided involving poppet elements in a scavenger valve with specific multiple, different flow paths from individual poppet heads.