A Polygon Oscillating Piston Engine having multiple pistons on one of two oscillating disks. Each piston moves in a straight line along one of the sides of a polygon within a cylindrical chamber, while the oscillating disks move in an arc about a central shaft. The difference in the straight motion of the piston and angular motion of the oscillating disk is accommodated by a slip sleeve within the piston that slides on a peg or bar mounted to each disk. The engine can be configured to operate as an internal combustion engine that uses diesel fuel, gasoline, or natural gas, or it can be configured as an expander to convert high pressure high temperature gas to rotary power. This engines compact design results in a high power-to-weight ratio.

An internal combustion engine is provided using parts that can be produced simply and inexpensively, in which internal combustion engine the fuel is burned optimally by adjustments of compression ratio and valve control times and thus the least possible harmful exhaust gases are emitted while maximum effective power is achieved. Furthermore, all liquid and gaseous fuels can be used.

A Rankine Expander System that converts low quality heat (heat usually at temperatures below 400 degrees Celsius) to electricity by using the properties of trans-critical CO.sub.2. The system is comprised of a compressor, an expander, three heat exchangers, and a permanent magnet alternator (PMA). It operates at pressures and temperatures that hold the CO.sub.2 above its critical point for the full cycle, and as such, attains high efficiencies even at low power. Under some conditions the efficiency can exceed 50%.

The fixed or variable displacement hydraulic motor-pump (1) includes a motor-pump central rotor (3) in which a hydraulic cylinder (14) is arranged, the rotor (3) being in sealed contact with an input-output spool valve (43) connecting the cylinder (14) with a motor-pump frame (2) while a hydraulic piston (13) moves in the cylinder (14) to push, using a hydraulic piston guided plunger (18), a tangential arm (22) articulated in the central rotor (3), and a tangential arm antifriction roller (28) on a motor-pump peripheral rotor (29) synchronized in rotation with the motor-pump central rotor (3).

The fixed or variable displacement hydraulic motor-pump (1) includes a motor-pump central rotor (3) in which a hydraulic cylinder (14) is arranged, the rotor (3) being in sealed contact with an input-output spool valve (43) connecting the cylinder (14) with a motor-pump frame (2) while a hydraulic piston (13) moves in the cylinder (14) to push, using a hydraulic piston guided plunger (18), a tangential arm (22) articulated in the central rotor (3), and a tangential arm antifriction roller (28) on a motor-pump peripheral rotor (29) synchronized in rotation with the motor-pump central rotor (3).

A five-spindle engine system having a stable center of gravity that operates without oil lubrication. an opposed-piston four-cylinder, two-stroke combustion engine, a double-acting opposed-piston pressure-gradient drive, a multi-rotor/multi-stator/multi-phase disk generator/disk motor including windings printed on printed circuit boards, and/or a heat pump may be integrated in the systemt and housed in a common sealed housing.

A rotational engine system comprises a rotational engine and a propulsion system. The rotational engine includes an outer ring enclosure, an inner ring component, and a drive gear. The inner ring component includes a piston and a drive gear engagement portion. The piston is configured to travel within the outer ring enclosure along a circumference of the outer ring enclosure. The drive gear engagement portion is configured to rotate as the piston travels along the circumference of the circular shape of the outer ring enclosure. The drive gear is coupled to the drive gear engagement portion of the inner ring component such that rotation of the drive gear engagement portion rotationally drives the drive gear. The propulsion system is configured to deliver propulsive energy to propel the piston along the circumference of the outer ring enclosure.

An internal combustion engine with two arced cylinders, with movement of the pistons in first and second cylinders takes place in the same direction. An arcing connecting rod on each of the sides of the pistons are averted from the combustion chambers. A freewheel is associated with each cylinder. An axis of the shaft represents the center of the arced shape of the cylinders and connecting rods. A side of the connecting rod opposite the piston connects to the outer side of a freewheel, and inner sides of the freewheels each connect to the shaft. Movement produced by the combustion is transmitted by the connecting rod to the outer side of the freewheel and the shaft. Outer sides of the freewheels are coupled to move in opposite directions, so the pistons in the first and the second cylinder run oppositely. A method operates such an internal combustion engine.