A multi-stage traveling wave thermoacoustic engine is disclosed. A plurality of heat engine stages are formed as a toroidal spiral cascade of N stages inside a pressure vessel. Each stage feeds into the next stage such that all of the thermoacoustic power cycles past a common set of thermal interfaces multiple times with the single domed pressure vessel. The inventive thermoacoustic engine is simpler and cheaper to manufacture and more reliable due to the minimization of hot joints.

A multi-stage traveling wave thermoacoustic engine is disclosed. A plurality of heat engine stages are formed as a toroidal spiral cascade of N stages inside a pressure vessel. Each stage feeds into the next stage such that all of the thermoacoustic power cycles past a common set of thermal interfaces multiple times with the single domed pressure vessel. The inventive thermoacoustic engine is simpler and cheaper to manufacture and more reliable due to the minimization of hot joints.

A method for increasing working gas flow rate through gas bearings of a free piston, gamma configured Stirling heat pump to avoid failure of the gas bearings while maintaining thermal cooling power. The Stirling heat pump lifts heat from a storage chamber and has pistons that are driven in reciprocation at an operating frequency by linear electric motors. A temperature control maintains a steady state storage chamber temperature by sensing storage chamber temperature and modulating piston amplitude. The invention comprises (a) driving the pistons with linear electric motors that are driven by a variable frequency, AC power source; (b) sensing the pistons' amplitude of reciprocation; and (c) if the sensed piston amplitude is less than a selected piston activation amplitude, increasing the frequency of the AC power source to increase the Stirling heat pump's operating frequency. That decreases thermal cooling power which causes the temperature control to increase piston amplitude.

free-piston engine power plant incorporating a first combustion cylinder having a first combustion piston, a fluid expander having an expansion cylinder with an expander piston therein, the expander piston reciprocating in unison with the first combustion piston, a bottoming cycle having a working fluid and a heat exchanger.

A hybrid power or thrust generator including at least one thermodynamic turbine engine and at least one electric power generator. An electric power generator is electrically connected to at least one electric motor, mechanically and rotatably coupled to one or more rotating portions of the thermodynamic turbine engine, and the electric power generator operates simultaneously with the thermodynamic engine so as to supply the electric motor(s) to reduce the power drawn from the turbines of the thermodynamic turbine engine in operation. The electric power generator may comprise a thermoacoustic engine driving a linear electric alternator. The generator is advantageously implemented in a vehicle, such as an aircraft.

A single-acting (two pistons) or double-acting (four pistons) alpha configuration Stirling engine has increased thermal exchange between a hot piston crown and a hot head and between a cold piston crown and a cold head of each piston cylinder assembly, increasing conversion of thermal energy to mechanical motion. The thermal exchange is provided by presenting corresponding transverse peaks and valley that create increased surface area and increased convective fluid flow rate for a working gas sealed in the Stirling engine.

A Stirling engine comprising a first cylinder comprising a piston configured to separate at least two expansion or compression chambers of the first cylinder, and a second cylinder comprising a piston configured to separate at least two expansion or compression chambers of the second cylinder. The pistons of the first and second cylinders are connected, such that the first and second cylinders form a first piston assembly. Each chamber of the first cylinder is fluidly connected to a chamber of a first cylinder of a second piston assembly such that a working fluid to be compressed/expanded can flow between the fluidly connected chambers of the first and second piston assemblies. Each chamber of the second cylinder is fluidly connected to a chamber of a second cylinder of a third piston assembly such that a working fluid to be compressed/expanded can flow between the fluidly connected chambers of the first and third piston assemblies. The first cylinder and the second cylinder of the first piston assembly are each configured as an expansion cylinder or a compression cylinder.

A novel engine for producing power from a temperature differential with additional benefits of low cost, high efficiency, quiet operation minimal wear of components, and the ability to produce power or cooling from low grade heat sources.

An improvement to a free-piston Stirling machine having a cylinder mounted within a housing. The cylinder has a flange for mounting the cylinder within the housing to a transition plate with a central opening for receiving the cylinder. An elastic rim bounds and surrounds the opening and extends in an axial direction from the plate to a crest of the rim. The crest of the rim is in contact against a first axially facing side of the cylinder flange. The interior side of the rim is outwardly spaced from the exterior side of the cylinder. A compliant clamp is attached to the transition plate and is positioned on the opposite, axially facing side of the cylinder flange. The compliant clamp has an elastic spring extending against the cylinder flange which applies a force urging the cylinder flange in an axial direction against the crest of the elastic rim.

A four-process cycle is disclosed for a Vuilleumier heat pump that has mechatronically-controlled displacers. Vuilleumier heat pumps that use a crank to drive the displacers have been previously developed. However, mechatronic controls provides a greater degree of freedom to control the displacers. The four-process cycle provides a higher coefficient of performance than prior cycles in the crank-driven Vuilleumier heat pump and those previously disclosed for a mechatronically-driven Vuilleumier heat pump. The four-process cycle can be drawn out to provide a low demand condition by causing both displacers to remain stationary for a period of time. The four processes in which one of the displacers is commanded to move are separated by periods of inactivity in which both displacers remain stationary.