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.

Systems and methods for converting energy are provided. In one aspect, the system includes a closed cycle engine defining a cold side. The system also includes a bottoming-cycle loop. A pump is operable to move a working fluid along the bottoming-cycle loop. A cold side heat exchanger is positioned along the bottoming-cycle loop in a heat exchange relationship with the cold side of the closed cycle engine. A constant density heat exchanger is positioned along the bottoming-cycle loop downstream of the cold side heat exchanger and upstream of an expansion device. The constant density heat exchanger is operable to hold a volume of the working fluid flowing therethrough at constant density while increasing, via a heat source, the temperature and pressure of the working fluid. The expansion device receives the working fluid at elevated temperature and pressure and extracts thermal energy from the working fluid to produce work.

Systems and methods for converting energy are provided. In one aspect, the system includes a closed cycle engine defining a cold side. The system also includes a bottoming-cycle loop. A pump is operable to move a working fluid along the bottoming-cycle loop. A cold side heat exchanger is positioned along the bottoming-cycle loop in a heat exchange relationship with the cold side of the closed cycle engine. A constant density heat exchanger is positioned along the bottoming-cycle loop downstream of the cold side heat exchanger and upstream of an expansion device. The constant density heat exchanger is operable to hold a volume of the working fluid flowing therethrough at constant density while increasing, via a heat source, the temperature and pressure of the working fluid. The expansion device receives the working fluid at elevated temperature and pressure and extracts thermal energy from the working fluid to produce work.

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 method for limiting the amplitude of reciprocation of a piston reciprocating in a cylinder of a free-piston Stirling engine. The method is the combination of both at least partially covering the heat rejecter cylinder port by the piston sidewall during a peak part of the inward reciprocation of the piston and at least partially covering the heat rejecter cylinder port by the displacer sidewall during a peak part of the outward reciprocation of the displacer. The piston and the displacer, at times during their reciprocation, fully cover the effective heat rejecter cylinder port when the piston amplitude of reciprocation is large and approaches the physical limit of the amplitude of reciprocation in order to avoid internal collisions by a reciprocating component.

A method for limiting the amplitude of reciprocation of a piston reciprocating in a cylinder of a free-piston Stirling engine. The method is the combination of both at least partially covering the heat rejecter cylinder port by the piston sidewall during a peak part of the inward reciprocation of the piston and at least partially covering the heat rejecter cylinder port by the displacer sidewall during a peak part of the outward reciprocation of the displacer. The piston and the displacer, at times during their reciprocation, fully cover the effective heat rejecter cylinder port when the piston amplitude of reciprocation is large and approaches the physical limit of the amplitude of reciprocation in order to avoid internal collisions by a reciprocating component.

The articulated plenum (1) forms an intake pipe (3) which is ended with tight ball joint links (16) held by restraining means (17), said plenum (1) connecting a heat source (39) to an expansion cylinder (32) and comprising a plenum inlet orifice (4), a plenum outlet orifice (6) which receives a valve seat (9), and an actuator orifice (8) which receives an intake valve actuator (50) which controls a valve (10), the latter engaging with the valve seat (9) to close the intake pipe (3).