Energy conversion apparatus

1. A monolithic engine assembly, comprising:

an engine body comprising a regenerator body, wherein the engine body and the regenerator body respectively define at least a portion of a monolithic body, or wherein the engine body defines at least a portion of a first monolithic body-segment and the regenerator body defines at least a portion of a second monolithic body-segment operably coupled or operably couplable to the first monolithic body-segment;

a piston body, wherein the piston body defines at least a portion of the engine body, or wherein the piston body defines a third monolithic body-segment operably coupled or operably couplable to the engine body; and

a working-fluid heat exchanger body, wherein the working-fluid heat exchanger body defines a portion of the monolithic body, or wherein the working-fluid heat exchanger body defines a fourth monolithic body-segment operably coupled or operably couplable to the first monolithic body-segment or to the second monolithic body-segment;

wherein the working-fluid heat exchanger body comprises a plurality of working-fluid pathways, the plurality of working-fluid pathways respectively fluidly communicating between respective ones of a plurality of piston chamber apertures of a piston chamber defined by the piston body and respective ones of a plurality of regenerator apertures of a regenerator conduit defined by the regenerator body.

2. The monolithic engine assembly of claim 1 , comprising:

wherein the regenerator body defines a portion of the piston body, or wherein the regenerator body is operably coupled or operably couplable to the piston body.

3. The monolithic engine assembly of claim 2 , comprising:

wherein the working-fluid heat exchanger body defines a portion of the monolithic body, or wherein the working-fluid heat exchanger body defines a fourth monolithic body-segment operably coupled or operably couplable to the first monolithic body-segment or to the second monolithic body-segment.

4. The monolithic engine assembly of claim 3 , wherein the regenerator body comprises:

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 defining a gap longitudinally separating adjacent ones of the plurality of fin arrays.

5. The monolithic engine assembly of claim 2 , comprising:

a combustor body, wherein the combustor body defines at least a portion of the monolithic body, or wherein the combustor body defines a fourth monolithic body-segment;

wherein the combustor body defines a combustion chamber, a hot-side heat exchanger body, and a recirculation pathway fluidly communicating with the combustion chamber and the hot-side heat exchanger body, the recirculation pathway configured to recirculate combustion gas through the combustion chamber and the hot-side heat exchanger body;

wherein the hot-side heat exchanger body comprises a plurality of heating fluid pathways and a heat transfer region having a thermally conductive relationship with the plurality of heating fluid pathways; and

wherein the heat transfer region comprises a portion of the plurality of working-fluid pathways.

6. The monolithic engine assembly of claim 1 , wherein the working-fluid heat exchanger body comprises a plurality of heat transfer regions, respective ones of the plurality of heat transfer regions comprising a portion of the plurality of working-fluid pathways;

wherein the piston body defines a portion of the working-fluid heat exchanger body, or wherein the piston body is operably coupled or operably couplable to the working-fluid heat exchanger body;

wherein the regenerator body defines a portion of the working-fluid heat exchanger body, or wherein the regenerator body is operably coupled or operably couplable to the working-fluid heat exchanger body and/or the piston body; and

wherein the regenerator body comprises a regenerator conduit and a heat storage medium disposed within the regenerator conduit.

7. The monolithic engine assembly of claim 1 , wherein the regenerator body comprises:

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 defining a gap longitudinally separating adjacent ones of the plurality of fin arrays.

8. The monolithic engine assembly of claim 7 , wherein adjacent ones of the plurality of fin arrays comprise a proximal fin array having a distal surface and a distal fin array having a proximal surface, the distal surface and the proximal surface defining the gap longitudinally separating the adjacent ones of the plurality of fin arrays, the distal surface facing the proximal surface.

9. The monolithic engine assembly of claim 8 , wherein the gap longitudinally separates the adjacent ones of the plurality of fin arrays by a longitudinal distance of from about 10 microns to about 1 millimeter.

10. The monolithic engine assembly of claim 7 , comprising:

the regenerator conduit disposed about a longitudinal axis and the plurality of fin arrays supported by the regenerator conduit at least in part at an oblique angle relative to the longitudinal axis.

11. The monolithic engine assembly of claim 10 , comprising:

the plurality of fin arrays supported by the regenerator conduit at least in part at a perpendicular angle relative to the longitudinal axis.

12. The monolithic engine assembly of claim 7 , wherein respective ones of the plurality of fin arrays comprise a plurality of fins defining a lattice, the lattice comprising a plurality of lattice walls defining polyhedral passages therebetween.

13. The monolithic engine assembly of claim 7 , wherein the plurality of fin arrays are monolithically integrated with the regenerator conduit.

14. The monolithic engine assembly of claim 7 , wherein the regenerator conduit comprises a ceramic.

15. The monolithic engine assembly of claim 7 , wherein the plurality of fin arrays and/or the regenerator conduit comprises a metal or a metal alloy.

16. The monolithic engine assembly of claim 7 , wherein the regenerator body defines a module insertable into, or operably couplable with, the first monolithic body-segment.

17. The monolithic engine assembly of claim 7 , wherein respective ones of the plurality of fin arrays comprise a plurality of fin supports and a plurality of fins together defining an array of interconnected fins and fin supports, wherein the array of interconnected fins and fin supports define a monolithic structure.

18. The monolithic engine assembly of claim 1 , wherein the regenerator body comprises:

a hot-side portion comprising a hot-side plurality of fin arrays; and

a cold-side portion comprising a cold-side plurality of fin arrays;

wherein the hot-side plurality of fin arrays and the cold-side plurality of fin arrays are adjacently disposed within the regenerator conduit in a spaced relation to one another that defines a hot-to-cold gap longitudinally separating the hot-side plurality of fin arrays from the cold-side plurality of fin arrays.

19. The monolithic engine assembly of claim 7 , comprising:

a plurality of hot-side working-fluid pathways fluidly communicating with a hot-side portion of the regenerator conduit; and/or

a plurality of cold-side working-fluid pathways fluidly communicating with a cold-side of the piston chamber.

20. The monolithic engine assembly of claim 1 , wherein the regenerator body comprises:

a sidewall;

a regenerator conduit; and

a heat storage medium disposed within the regenerator conduit;

wherein the sidewall has a gradient in gradient in cross-sectional thickness and/or material thickness oriented along a longitudinal axis of the regenerator conduit, and/or wherein the sidewall has a gradient in surface area, and/or material density or porosity, oriented along a longitudinal axis and/or a radial axis of the regenerator conduit; and/or

wherein the regenerator conduit and/or the heat storage medium has a gradient in cross-sectional thickness or material thickness oriented along a longitudinal axis of the regenerator conduit, and/or wherein the regenerator conduit and/or the heat storage medium has a gradient in surface area, and/or material density or porosity, oriented along a longitudinal axis and/or a radial axis of the regenerator conduit.

21. A monolithic engine assembly, comprising:

an engine body comprising a regenerator body, wherein the engine body and the regenerator body respectively define at least a portion of a monolithic body, or wherein the engine body defines at least a portion of a first monolithic body-segment and the regenerator body defines at least a portion of a second monolithic body-segment operably coupled or operably couplable to the first monolithic body-segment;

a piston body, wherein the piston body defines at least a portion of the engine body, or wherein the piston body defines a third monolithic body-segment operably coupled or operably couplable to the engine body, and wherein the regenerator body defines a portion of the piston body, or wherein the regenerator body is operably coupled or operably couplable to the piston body;

a combustor body, wherein the combustor body defines at least a portion of the monolithic body, or wherein the combustor body defines a fourth monolithic body-segment;

wherein the combustor body defines a combustion chamber, a hot-side heat exchanger body, and a recirculation pathway fluidly communicating with the combustion chamber and the hot-side heat exchanger body, the recirculation pathway configured to recirculate combustion gas through the combustion chamber and the hot-side heat exchanger body;

wherein the hot-side heat exchanger body comprises a plurality of heating fluid pathways and a heat transfer region having a thermally conductive relationship with the plurality of heating fluid pathways; and

wherein the heat transfer region comprises a plurality of working-fluid pathways fluidly communicating with the regenerator body and a piston chamber defined by the piston body.

22. The monolithic engine assembly of claim 21 , wherein the heat transfer region comprises at least a portion of the piston body and/or at least a portion of the regenerator body.

23. The monolithic engine assembly of claim 21 , comprising:

a working-fluid body, wherein the heat transfer region comprises at least a portion of a working-fluid body.

24. The monolithic engine assembly of claim 21 , wherein the plurality of working-fluid pathways have a thermally conductive relationship with at least some of the plurality of heating fluid pathways.

25. The monolithic engine assembly of claim 21 , wherein the hot-side heat exchanger body comprises a plurality of heating walls, and wherein the plurality of working-fluid pathways are respectively defined at least in part within a corresponding one of the plurality of heating walls of the hot-side heat exchanger body.

26. A monolithic engine assembly, comprising:

an engine body comprising a regenerator body, wherein the engine body and the regenerator body respectively define at least a portion of a monolithic body, or wherein the engine body defines at least a portion of a first monolithic body-segment and the regenerator body defines at least a portion of a second monolithic body-segment operably coupled or operably couplable to the first monolithic body-segment;

a working-fluid heat exchanger body comprising a plurality of heat transfer regions, respective ones of the plurality of heat transfer regions comprising a plurality of working-fluid pathways fluidly communicating between a regenerator conduit defined by the regenerator body and a piston chamber defined by a piston body;

wherein the working-fluid heat exchanger body defines a portion of the monolithic body, or wherein the working-fluid heat exchanger body defines a third monolithic body-segment operably coupled or operably couplable to the first monolithic body-segment or to the second monolithic body-segment;

wherein the piston body defines a portion of the working-fluid heat exchanger body, or wherein the piston body defines a fourth monolithic body-segment operably coupled or operably couplable to the working-fluid heat exchanger body;

wherein the regenerator body defines a portion of the working-fluid heat exchanger body, or wherein the regenerator body is operably coupled or operably couplable to the working-fluid heat exchanger body and/or the piston body; and

wherein the regenerator body comprises a regenerator conduit and a heat storage medium disposed within the regenerator conduit.

27. The monolithic engine assembly of claim 26 , wherein the plurality of heat transfer regions comprise at least a portion of the piston body and/or at least a portion of the regenerator body.

28. The monolithic engine assembly of claim 26 , comprising:

a working-fluid body, wherein the plurality of heat transfer regions comprise at least a portion of a working-fluid body.

29. The monolithic engine assembly of claim 26 , comprising:

a hot-side heat exchanger body comprising a plurality of heating fluid pathways, wherein the plurality of working-fluid pathways have a thermally conductive relationship with at least some of the plurality of heating fluid pathways.

30. The monolithic engine assembly of claim 29 , wherein the hot-side heat exchanger body comprises a plurality of heating walls, and wherein the plurality of working-fluid pathways are respectively defined at least in part within a corresponding one of the plurality of heating walls of the hot-side heat exchanger body.