An object of the present invention is to provide a method and a system for implementing the method so as to alleviate the disadvantages of a reciprocating combustion engine and gas turbine when generating power. The invention is based on the idea of arranging a multifunction valve inside a combustion chamber to create more favorable conditions for combustion process. The multifunction valve may act as an output valve, but it can also provide additional final compression to contents of the compression chamber and it may even capture part of energy released in a combustion process.

An object of the present invention is to provide a method and a system for implementing the method so as to alleviate the disadvantages of a reciprocating combustion engine and gas turbine when generating power. The invention is based on the idea of arranging a multifunction valve inside a combustion chamber to create more favorable conditions for combustion process. The multifunction valve may act as an output valve, but it can also provide additional final compression to contents of the compression chamber and it may even capture part of energy released in a combustion process.

A free piston apparatus includes a piston receptacle in which a piston device having a piston is reciprocable along an axis. The piston receptacle includes a combustion chamber delimited by a wall arrangement forming an inlet opening for the supply of fresh gas and an outlet opening for the removal of exhaust gas. The free piston apparatus includes an inflow device, which has the inlet opening and is configured such that fresh gas flowing into the combustion chamber is directed to an incident flow region in the combustion chamber arranged offset axially to the inlet opening, which incident flow region is arranged off-center relative to the axis. A method for operating a free piston apparatus includes operating an inflow device which has an inlet opening configured such that fresh gas is directed to an incident flow region in a combustion chamber offset axially to the inlet opening.

A free piston apparatus includes a piston receptacle in which a piston device having a piston is reciprocable along an axis. The piston receptacle includes a combustion chamber delimited by a wall arrangement forming an inlet opening for the supply of fresh gas and an outlet opening for the removal of exhaust gas. The free piston apparatus includes an inflow device, which has the inlet opening and is configured such that fresh gas flowing into the combustion chamber is directed to an incident flow region in the combustion chamber arranged offset axially to the inlet opening, which incident flow region is arranged off-center relative to the axis. A method for operating a free piston apparatus includes operating an inflow device which has an inlet opening configured such that fresh gas is directed to an incident flow region in a combustion chamber offset axially to the inlet opening.

A free piston apparatus includes a piston receptacle in which a piston device having a piston is linearly reciprocable. The piston receptacle includes or forms a combustion chamber delimited by a wall arrangement forming a first opening and a second opening. The openings include an inlet opening for the supply of fresh gas and an outlet opening for the removal of exhaust gas for a uniflow scavenging of the combustion chamber. Movement of the piston device is controllable by a control device. The bottom dead center of the piston can be adjustable such that when the piston adopts the bottom dead center, the first opening is partially unblocked and partially blocked for adjusting a free cross sectional area of the first opening. An opening duration can also be adjustable. A method for operating a free piston apparatus includes controlling movement of a piston device with a control device.

Disclosed is a thermodynamic cycle process, performing transfer between mechanical and heat energies, by changing a state of a fluid, including: an expansion of the fluid, an energy retrieval from the fluid expansion, a step of powering a liquid pump or a gas compressor with the retrieved energy, using a cyclic free piston expander which alternatively changes direction of the free piston sliding: by alternatively: closing the fluidic communication between the both opposite sides of the free piston, to make different from each other the pressures applied respectively thereon, so the free piston slides in a first direction, opening a fluidic communication between both opposite sides of the free piston, to make equal to each other the pressures applied respectively thereon, so the free piston slides in a second direction opposite to the first direction, the free piston sliding, directly and mechanically, opening and closing, the fluidic communication.

An opposed, free-piston engine includes a pair of adjacent cylinders, each extending from a first cylinder end to a second cylinder end along an elongate axis and having a first cylinder housing a first pair of opposed, free pistons including a first piston housed towards the first cylinder end and a second piston housed towards the second cylinder end; a second cylinder housing a second pair of opposed, free pistons having a third piston and a fourth piston; and a pair of link rods including a first link rod and a second link rod. The first link rod has a first link rod end and a second link rod end, the second link rod having a third link rod end and a fourth link rod end.

An internal combustion may include a cylinder having a first combustion chamber at one end and a second combustion chamber at an opposing end, first and second cylinder heads located at an end of the first and second combustion chambers, respectively, and a double-faced piston slidably mounted within the cylinder. The piston may be configured to move in the cylinder in a work stroke from one end to another. The work stroke may include an expansion stroke portion, a momentum stroke portion, and a compression stroke portion. The engine may further include first and second piston rod portions extending from opposite faces of the piston. Passageways in the piston rod portions may be configured to communicate gases between a combustion chamber and a location outside the cylinder.

An internal combustion may include a cylinder having a first combustion chamber at one end and a second combustion chamber at an opposing end, first and second cylinder heads located at an end of the first and second combustion chambers, respectively, and a double-faced piston slidably mounted within the cylinder. The piston may be configured to move in the cylinder in a work stroke from one end to another. The work stroke may include an expansion stroke portion and a non-expansion stroke portion. The non-expansion stroke portion may include a momentum stroke portion, and a compression stroke portion. The engine may further include first and second piston rod portions extending from opposite faces of the piston. Passageways in the piston rod portions may be configured to communicate gases between a combustion chamber and other locations.

Various embodiments of the present disclosure are directed towards free-piston combustion engines. As described herein, a method and system are provided for displacing a free-piston assembly to achieve a desired engine performance by repeatedly determining position-force trajectories over the course of a propagation path and effecting the displacement of the free-piston assembly based, at least in part, on the position-force trajectory. In a dual-piston assembly free-piston engine, synchronization of the two piston assemblies is provided.