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.

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.

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.

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.

A fluid-driven linear motor comprises a cylinder, a piston, and a piston rod connected to the piston. Two sides of the piston in the cylinder are alternately supplied with fluid from a slide valve arrangement. The slide valve arrangement includes a slide and a pilot rod adapted to alternately set a through-bore of a slide in fluid connection with the ends of the slide when the piston is located in its end positions. The pilot rod is provided with an extension rod adapted to move inside a bore of the piston and the piston rod, so that the stroke length of the linear motor can be extended. A pressure chamber is provided at the distal end of the pilot rod. The pressure chamber is adapted to hold the pilot rod with a holding force when in its end positions until mechanical forces from the piston overcome said holding force.

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 air motor assembly includes an exhaust block with an exhaust port that conveys exhaust air into an exhaust manifold. The exhaust port includes an expansion chamber that creates a pressure drop in the exhaust gas, thereby decreasing the temperature of the exhaust gas. The expansion chamber is defined between a first wall that is tangential to the air motor cylinder and a second wall that is transverse to an axis of the exhaust port. Poppet valves control actuation of a shuttle. The poppet valves are disposed on the exterior of the air motor assembly and are thermally insulated from the air motor assembly.

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 therein. The piston may be configured to move in a first stroke that includes an expansion stroke portion and a non-expansion stroke portion. The engine may further include first and second piston rod portions extending from opposite faces of the piston. A recess in the piston rod portions may be configured to communicate gases between a combustion chamber and locations outside the cylinder. There may also be a chamber surrounding the first or second piston rod portion, the chamber configured to be supplied with gas and the chamber being isolated from the first combustion chamber and the second combustion chamber.

In one embodiment, a power generation system includes a pulse detonation engine including a combustion chamber, a linear power generator including a working chamber, and a nozzle positioned between the combustion chamber and the working chamber that expands exhaust gas expelled from the combustion chamber, wherein the nozzle increases thermodynamic efficiency of the system.