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.

Various disclosed embodiments include combined heating and power modules and combined heat and power devices. In an illustrative embodiment, a combined heat and power device includes a heating system including: at least one burner; at least one igniter configured to ignite the at least one burner; a fluid motivator assembly including an electrically powered prime mover; and a heat exchanger fluidly couplable to the fluid motivator assembly. At least one alkali metal thermal-to-electricity converter (AMTEC) has a high pressure zone and a low pressure zone, the high pressure zone being thermally couplable to the at least one burner, the low pressure zone being thermally couplable to the heat exchanger.

Various disclosed embodiments include combined heating and power modules and combined heat and power devices. In an illustrative embodiment, a combined heat and power device includes a heating system including: at least one burner; at least one igniter configured to ignite the at least one burner; a fluid motivator assembly including an electrically powered prime mover; and a heat exchanger fluidly couplable to the fluid motivator assembly. At least one alkali metal thermal-to-electricity converter (AMTEC) has a high pressure zone and a low pressure zone, the high pressure zone being thermally couplable to the at least one burner, the low pressure zone being thermally couplable to the heat exchanger.

A two-phase immersion-type heat dissipation structure having fins with different thermal conductivities is provided. The two-phase immersion-type heat dissipation structure includes a heat dissipation substrate, and a plurality of fins. The heat dissipation substrate has a fin surface and a non-fin surface that face away from each other. The non-fin surface is configured to be in contact with a heating element immersed in a two-phase coolant. The fin surface is connected with the plurality of fins. At least one of the plurality of fins is a functional fin that is made of a single metal material and has two or more thermal conductivities. A thermal conductivity of a lower portion of the functional fin that is connected with the heat dissipation substrate is lower than thermal conductivities of other portions of the functional fin.

A two-phase immersion-type heat dissipation structure having fins with different thermal conductivities is provided. The two-phase immersion-type heat dissipation structure includes a heat dissipation substrate, and a plurality of fins. The heat dissipation substrate has a fin surface and a non-fin surface that face away from each other. The non-fin surface is configured to be in contact with a heating element immersed in a two-phase coolant. The fin surface is connected with the plurality of fins. At least one of the plurality of fins is a functional fin that is made of a single metal material and has two or more thermal conductivities. A thermal conductivity of a lower portion of the functional fin that is connected with the heat dissipation substrate is lower than thermal conductivities of other portions of the functional fin.

An energy conversion apparatus may include an engine assembly, such as a monolithic engine assembly. The engine assembly may include a first monolithic body segment and a plurality of second monolithic body segments directly coupled or directly couplable to the first monolithic body segment. The first monolithic body segment may define a combustion chamber and a recirculation pathway in fluid communication with the combustion chamber. The recirculation pathway may be configured to recirculate combustion gas through the combustion chamber. The plurality of second monolithic body segments may respectively define at least a portion of a piston chamber and a plurality of working-fluid pathways fluidly communicating with the piston chamber.

An energy conversion apparatus may include an engine assembly, such as a monolithic engine assembly. The engine assembly may include a first monolithic body segment and a plurality of second monolithic body segments directly coupled or directly couplable to the first monolithic body segment. The first monolithic body segment may define a combustion chamber and a recirculation pathway in fluid communication with the combustion chamber. The recirculation pathway may be configured to recirculate combustion gas through the combustion chamber. The plurality of second monolithic body segments may respectively define at least a portion of a piston chamber and a plurality of working-fluid pathways fluidly communicating with the piston chamber.

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 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.

Disclosed herein are various technologies pertinent to rocket engines, including injector, thrust chamber, and electrical turbopump devices that may be combined to provide a more efficient rocket engine. The thrust chamber may be coupled with an injector having a circular array of support columns supporting a distribution system. Liquid may be flowed from the distribution system, through the support columns, and into a combustion chamber of the thrust chamber.