A system including a closed cycle engine having a piston body defining a hot side and a cold side and having a piston assembly movable within the piston body. An electric machine is operatively coupled with the piston assembly. A control system includes one or more sensors operable to detect a piston movement characteristic of the piston assembly movable within the piston body. A controller is communicatively coupled with the one or more sensors and a controllable device. The controller is configured to determine a control command based at least in part on data received from the one or more sensors. The control command is selected based at least in part to cause the electric machine operatively coupled with the piston assembly to generate a preselected electrical power output. The controller provides the determined control command to the controllable device. The controllable device is operable to control an input to an engine working fluid disposed within the piston body.

A monolithic engine assembly may include an engine body that includes a regenerator body. The engine body and the regenerator body may respectively define at least a portion of a monolithic body, or the engine body may define at least a portion of a first monolithic body-segment and the regenerator body may define at least a portion of a second monolithic body-segment operably coupled or operably couplable to the first monolithic body-segment. The regenerator body may include a regenerator conduit, and a plurality of fin arrays adjacently disposed within the regenerator conduit and respectively supported by the regenerator conduit in spaced relation to one another. The spaced relation of the plurality of fin arrays may define a gap longitudinally separating adjacent ones of the plurality of fin arrays.

A monolithic heater body includes a combustor body and an eductor body. The combustor body has an annulus with an outward annular wall and an inward annular wall. The annulus defines a conditioning conduit between the outward annular wall and the inward annular wall, and a combustion chamber circumferentially surrounded by the inward annular wall. A distal portion of the conditioning conduit fluidly communicates with a distal portion of the combustion chamber. The eductor body defines a plurality of eductive pathway couplets circumferentially spaced about a perimeter of the annulus. Respective ones of the eductive pathway couplets have a motive pathway and an eduction pathway respectively oriented oblique to the annulus and fluidly communicating with the conditioning conduit. Respective ones of the plurality of motive pathways are configured to provide a jet of intake air from a corresponding plurality of intake air pathways to the conditioning conduit.

A monolithic combustor body may provide multi-stage combustion. A combustor body may include a combustion chamber body and a plurality of heating walls that include a heat sink. The combustion chamber body may be disposed annularly about a longitudinal axis and defining a combustion chamber. The plurality of heating walls may include heat sink. The plurality of heating walls may occupy a radially or concentrically outward position relative to the combustion chamber and may define a corresponding plurality of combustion-gas pathways fluidly communicating with at least a proximal portion of the combustion chamber. During operation, the combustor body may exhibit multi-stage combustion that includes a first combustion zone occupying a distal or medial position of the combustion chamber relative to the longitudinal axis, and a second combustion zone occupying a proximal position relative to the first combustion zone and a radially or concentrically outward position of the combustion chamber and/or a radially or concentrically inward position of the plurality of combustion-gas pathways.

A monolithic heater body may include a combustor body, a hot-side heat exchanger body, and an eductor body. The combustor body may define a combustion chamber and a conditioning conduit circumferentially surrounding the combustion chamber. The conditioning conduit may fluidly communicate with the combustion chamber at a distal portion of the combustion chamber. The hot-side heat exchanger body may define a hot-side heat exchanger that includes a heating fluid pathway fluidly communicating with a proximal portion of the combustion chamber. The eductor body may define an eduction pathway fluidly communicating with a downstream portion of the heating fluid pathway and a proximal portion of the conditioning conduit.

A monolithic heat exchanger body includes a plurality of heating walls and a plurality of combustion fins. The plurality of heating walls are configured and arranged in an array of spirals or spiral arcs relative to a longitudinal axis. Adjacent portions of the plurality of heating walls respectively define a corresponding plurality of heating fluid pathways therebetween. The plurality of combustion fins are circumferentially spaced about a perimeter of an inlet plenum. The inlet plenum includes or fluidly communicates with a combustion chamber. The plurality of heating fluid pathways fluidly communicate with the inlet plenum. The plurality of combustion fins occupy a radially or concentrically inward portion of the monolithic heat exchanger body. The plurality of heating fluid pathways have a heat transfer relationship with a heat sink disposed about a radially or concentrically outward portion of the monolithic heat exchanger body. A plurality of conduction breaks disposed radially or concentrically outward relative to the plurality of combustion fins at least partially inhibit heat conduction from the plurality of combustion fins to the plurality of heating walls.

A monolithic heat exchanger body includes a plurality of heating walls and a plurality of combustion fins. The plurality of heating walls are configured and arranged in an array of spirals or spiral arcs relative to a longitudinal axis. Adjacent portions of the plurality of heating walls respectively define a corresponding plurality of heating fluid pathways therebetween. The plurality of combustion fins are circumferentially spaced about a perimeter of an inlet plenum. The inlet plenum includes or fluidly communicates with a combustion chamber. The plurality of heating fluid pathways fluidly communicate with the inlet plenum. The plurality of combustion fins occupy a radially or concentrically inward portion of the monolithic heat exchanger body. The plurality of heating fluid pathways have a heat transfer relationship with a heat sink disposed about a radially or concentrically outward portion of the monolithic heat exchanger body. A plurality of conduction breaks disposed radially or concentrically outward relative to the plurality of combustion fins at least partially inhibit heat conduction from the plurality of combustion fins to the plurality of heating walls.

A monolithic heat exchanger body for inputting heat to a closed-cycle engine includes heating walls and heat sink, such as heat transfer regions. The heating walls are configured and arranged in an array of spirals or spiral arcs relative to a longitudinal axis of an inlet plenum. Adjacent portions of the heating walls respectively define corresponding heating fluid pathways fluidly communicating with the inlet plenum. At least a portion of the heat sink is disposed about at least a portion of the monolithic heat exchanger body. The heat sink includes working-fluid bodies including working-fluid pathways that have a heat transfer relationship with the heating fluid pathways. Respective ones of the heat transfer regions have a heat transfer relationship with a corresponding semiannular portion of the heating fluid pathways. Respective ones of the heat transfer regions include working-fluid pathways fluidly communicating between a heat input region and a heat extraction region.

A constant density heat exchanger and method of operating are provided. The constant density heat exchanger includes a housing extending between a first end and a second end and defining a chamber having an inlet and an outlet. A first plate is positioned at the first end of the housing and rotatable about an axis of rotation such that the first plate selectively allows a working fluid to flow into the inlet of the chamber. A second plate is positioned at the second end of the housing and rotatable about the axis of rotation such that the second plate selectively allows the working fluid to flow out of the outlet of the chamber. The first plate and the second plate are rotatable about the axis of rotation so as to hold a volume of the working fluid at constant density as a heat source imparts thermal energy thereto.

A Stirling engine with internal regenerator and integral geometry for heat transfer and fluid flow has a displacer piston with a plurality of cavities traversing through the displacer piston and arranged in a specific cross sectional geometry. A heater head has heater fin protrusions that are arranged in the specific geometry, and a cooling bridge has cooler fin protrusions that are in the specific geometry. The displacer piston alternates between the heater head and the cooling bridge, with the cavities of the piston alternately enveloping the heater protrusions and the cooling protrusions, providing more efficient heat transfer to and from the working fluid. Each cavity in the displacer also contains a regenerator core, further improving heat transfer efficiency. The heater fin protrusions may also contain thermally conductive cores. A bellows assembly may also be used to seal the displacer piston from the heater head in order to reduce unswept volume.