Open-faced piston assembly

1. A piston assembly comprising:

a piston, comprising:

a circumferential groove that extends at least partially around an outer surface of the piston, and

a plurality of openings located along the circumferential groove; and

a piston ring assembly arranged within the circumferential groove, wherein the plurality of openings is configured to allow a combustion reaction to propagate into a volume and burn the fuel therein, the volume defined between an inner surface of the piston ring assembly and the piston, the volume comprising an oxidizer and fuel mixture, wherein each of the plurality of openings are larger than a quench distance of the oxidizer and fuel mixture.

2. The piston assembly of claim 1 , wherein each of the plurality of openings is sized and arranged such that a minimum opening along a gas path between each opening and the inner surface of the piston ring assembly is larger than a quench distance of the oxidizer and fuel mixture in the volume.

3. The piston assembly of claim 2 , wherein the quench distance is approximately 1 mm.

4. The piston assembly of claim 1 , wherein a radial distance between the piston and the inner surface of the piston ring assembly is greater than 1 mm.

5. The piston assembly of claim 1 , wherein the piston further comprises:

a front land;

a piston face; and

at least one structural web that attaches the front land to the piston face.

6. The piston assembly of claim 1 , wherein the plurality of openings comprises a plurality of spaced openings along the circumferential groove that are substantially equidistant from each other.

7. The piston assembly of claim 1 , wherein the plurality of openings comprises a plurality of spaced openings along the circumferential groove that are of substantially equivalent geometry to one another.

8. The piston assembly of claim 1 , wherein the plurality of openings is configured to allow at least a majority of the oxidizer and fuel mixture in the volume to react.

9. The piston assembly of claim 1 , wherein the plurality of openings comprises a plurality of spaced openings along the circumferential groove that comprise a majority of a surface area of a bottom of the circumferential groove.

10. The piston assembly of claim 1 , wherein the piston assembly is a free-piston assembly.

11. The piston assembly of claim 1 , wherein the piston assembly is configured for oil-less operation.

12. The piston assembly of claim 1 , wherein the piston ring assembly comprises a solid lubricating material.

13. The piston assembly of claim 1 , wherein the circumferential groove is a first circumferential groove, the piston assembly further comprising a second circumferential groove arranged in parallel to and behind the first circumferential groove.

14. The piston assembly of claim 1 , wherein the combustion reaction propagates from a combustion section of an engine in which the piston assembly is configured to translate.

15. An engine comprising:

at least one cylinder comprising:

a combustion section, and

an inner cylinder surface; and

at least one piston assembly arranged within the cylinder, the at least one piston assembly comprising:

a piston comprising:

a circumferential groove that extends at least partially around an outer surface of the piston, and

a plurality of openings located along the circumferential groove, and

a piston ring assembly arranged within the circumferential groove, wherein the plurality of openings is configured to allow a combustion reaction to propagate from the combustion section into a volume and burn the fuel therein, the volume defined between an inner surface of the piston ring assembly and the piston, the volume comprising an oxidizer and fuel mixture, wherein each of the plurality of openings are larger than a quench distance of the oxidizer and fuel mixture.

16. The engine of claim 15 , wherein the oxidizer and fuel mixture is able to pass from the combustion section into the volume defined between the inner surface of the piston ring assembly and the piston.

17. The engine of claim 15 , wherein each of the plurality of openings is sized and arranged such that a minimum opening along a gas path between each opening and an inner surface of the piston ring assembly is larger than a quench distance of the oxidizer and fuel mixture.

18. The engine of claim 17 , wherein the quench distance is approximately 1 mm.

19. The engine of claim 15 , wherein a radial distance between the piston and the inner surface of the piston ring assembly is greater than 1 mm.

20. The engine of claim 15 , wherein the piston further comprises:

a front land;

a piston face; and

at least one structural web that attaches the front land to the piston face.

21. The engine of claim 15 , wherein the plurality of openings comprises a plurality of spaced openings along the circumferential groove that are substantially equidistant from each other.

22. The engine of claim 15 , wherein the plurality of openings comprises a plurality of spaced openings along the circumferential groove that are of substantially equivalent geometry.

23. The engine of claim 15 , wherein the plurality of openings is configured to allow at least a majority of the oxidizer and fuel mixture in the volume to react.

24. The engine of claim 15 , wherein the piston assembly is a free-piston assembly.

25. The engine of claim 15 , wherein the piston assembly is configured for oil-less operation.

26. The engine of claim 15 , wherein the plurality of openings comprises a plurality of spaced openings that comprise a majority of a surface area of a bottom of the circumferential groove.

27. The engine of claim 15 , wherein the piston ring assembly comprises a solid lubricating material.

28. The engine of claim 15 , wherein the circumferential groove is a first circumferential groove, the piston further comprising a second circumferential groove arranged in parallel to and behind the first circumferential groove.