Combustion chamber constructions for opposed-piston engines

• US 20110271932A1
• Filed: 04/18/2011
• Published: 11/10/2011
• Est. Priority Date: 04/27/2010
• Status: Active Grant

• Current Assignee: Achates Power, Inc.
• Original Assignee: Achates Power, Inc.
• Inventors: Fuqua, Kevin B., Redon, Fabien G., Lenski, Brendan M., Shen, Huixian, Wahl, Michael H.
• Granted Patent: US 8,800,528 B2
• Time in Patent Office: Days
• US Class Current: 123/301
• CPC Class Codes: F01B 7/02 with oppositely reciprocating pistons
• CPC Class Codes: F02B 2275/48 Tumble motion in gas movement in cylinder
• CPC Class Codes: F02B 23/0621 Squish flow
• CPC Class Codes: F02B 23/0624 Swirl flow
• CPC Class Codes: F02B 23/0633 the combustion space being almost completely enclosed in the piston, i.e. having a small inlet in comparison to its volume
• CPC Class Codes: F02B 23/0651 the fuel spray impinging on reflecting surfaces or being specially guided throughout the combustion space
• CPC Class Codes: F02B 23/0663 having multiple injectors per combustion chamber
• CPC Class Codes: F02B 23/0675 the combustion space being substantially spherical, hemispherical, ellipsoid or parabolic
• CPC Class Codes: F02B 23/0678 Unconventional, complex or non-rotationally symmetrical shapes of the combustion space, e.g. flower like, having special shapes related to the orientation of the fuel spray jets
• CPC Class Codes: F02B 75/28 Engines with two or more pistons reciprocating within same cylinder or within essentially coaxial cylinders arranged oppositely relative to main shaft F02B75/24
• CPC Class Codes: F02B 75/282 the pistons having equal strokes
• CPC Class Codes: F02F 3/0015 Multi-part pistons
• CPC Class Codes: F02F 3/24 having means for guiding gases in cylinders, e.g. for guiding scavenging charge in two-stroke engines
• CPC Class Codes: Y02T 10/12 Improving ICE efficiencies

Abstract

A combustion chamber for an opposed-piston engine includes a squish zone defined between circumferential peripheral areas of opposing end surfaces of the pistons, a cavity defined by one or more bowls in the end surfaces, and at least one injection port that extends radially through the squish zone into the cavity. The cavity has a cross-sectional shape that imposes a tumbling motion on air flowing from the squish zone into the cavity.

Claims

1. A combustion chamber structure for an internal combustion engine including at least one cylinder with longitudinally-separated exhaust and intake ports and a pair of pistons disposed in opposition to one another in a bore of the cylinder, in which the combustion chamber structure includes a squish zone defined between peripheral areas of opposing end surfaces of the pistons, an elongated cavity defined between the end surfaces, and at least one injection port that extends through the squish zone into the cavity.

2. The combustion chamber structure of claim 1, in which the cavity is defined between a bowl in a first end surface and a flat surface of the second end surface.

3. The combustion chamber structure of claim 2, in which the bowl has a clam shell shape.

4. The combustion chamber structure of claim 1, in which the cavity is defined between a bowl in a first end surface and a bowl in the second end surface.

5. The combustion chamber structure of claim 4, in which the bowl of each piston is a bowl defining a concave surface with a first portion curving inwardly from the end surface toward the interior of the piston and a second portion protruding outwardly from the end surface.

6. The combustion chamber structure of claim 5, in which the cavity has a generally elongated ellipsoidal shape.

7. The combustion chamber structure of claim 1, in which the at least one injection port extends generally radially through the squish zone.

8. An internal combustion engine including at least one cylinder with longitudinally-separated exhaust and intake ports, and a pair of pistons disposed in opposition to one another in a bore of the cylinder, in which a combustion chamber is defined between opposing end surfaces of the pistons, and the end surface of at least one of the pistons has a circumferential area defining a periphery of the end surface and a bowl within the periphery, the bowl defining a concave surface with a first portion curving inwardly from a plane containing the circumferential contact area toward the interior of the piston and a second portion curving outwardly from the interior of the piston through the plane containing the circumferential contact area.

9. The internal combustion engine of claim 8, in which each bowl has a generally semi-ellipsoidal shape.

10. The internal combustion engine of claim 8, in which the opposing pistons are oriented in the bore such that a combustion chamber having an elongated ellipsoidal shape is defined between the bowls when the pistons are near respective top dead center (TDC) positions in the bore.

11. The internal combustion engine of claim 10, in which at least one injector port is provided in the cylinder at a position on a major axis of the combustion chamber.

12. The internal combustion engine of claim 8, in which the opposing pistons are oriented in the bore such that a combustion chamber having the shape of an elongated, tapered cylinder is defined between the bowls when the pistons are near respective top dead center (TDC) positions and least one injection port is provided in the cylinder on a line transverse to a major axis of the combustion chamber.

13. The internal combustion engine of claim 12, in which the injector port is provided in the cylinder on a line generally perpendicular to the major axis of the combustion chamber.

14. The internal combustion engine of claim 8, in which each end surface further includes a convex surface within the periphery and curving outwardly from the plane containing the circumferential contact area, and the convex surface meets the second portion of the concave surface to form a ridge.

15. The internal combustion engine of claim 14, in which the opposing pistons are oriented in the bore such that the convex surface of each piston end surface defines a squish zone with the second portion of the concave surface of the other piston when the pistons are near respective top dead center (TDC) positions in the bore.

16. The internal combustion engine of claim 15, in which opposing concave and convex surface portions in each squish zone cause squish flow toward a cavity defined between the bowls when the pistons are near respective TDC positions in the bore.

17. The internal combustion engine of claim 16, in which at least one injector port is provided in the cylinder at a position on a major axis of the cavity.

18. The internal combustion engine of claim 16, in which at least one injector port is provided in the cylinder on a line transverse to a longitudinal axis of the cavity.

19. The internal combustion engine of claim 18, in which the injector port is provided in the cylinder on a line generally perpendicular to the longitudinal axis of the cavity.

20. A piston having an end surface for defining a combustion chamber with the end surface of an opposing piston, in which the end surface has a circumferential area centered on the longitudinal axis of the piston to define a periphery of the end surface and a bowl within the periphery, the bowl defining a concave surface with a first portion curving inwardly from a plane containing the circumferential contact area toward the interior of the piston and a second portion curving outwardly from the interior of the piston through the plane.

21. The piston of claim 20, in which the end surface further includes a convex surface within the periphery and curving outwardly from the plane containing the circumferential contact area, and the convex surface meets the second portion of the concave surface to form a ridge.

22. The piston of claim 20, in which the bowl has a semi-ellipsoidal shape.

23. The piston of claim 21, in which at least one notch is provided in the periphery at a position on a major axis of the bowl.

24. The piston of claim 21, in which at least one notch is provided in the periphery on a line transverse to a major axis of the bowl.

25. The piston of claim 24, in which the notch is provided in the periphery on a line generally perpendicular to the longitudinal axis of the generally semi-ellipsoidal shape.

26. A method for operating an internal combustion engine including at least one cylinder with longitudinally-separated exhaust and intake ports, and a pair of pistons disposed in opposition to one another in a bore of the cylinder, by admitting air into the bore through the intake port as the pistons move from respective bottom dead center positions in the bore, causing a tumbling motion in the charge of air between opposing end surfaces of the pistons as the pistons move toward respective top dead center positions in the bore, and injecting a charge of fuel into the combustion chamber.

27. The method of claim 26, including moving the opposing bowls on facing end surfaces of the pistons together to define a combustion chamber having an elongated ellipsoidal shape.

28. The method of claim 26, in which injecting a charge of fuel into the charge of air includes injecting the fuel along a major axis of the combustion chamber.

29. The method of claim 26, in which injecting a charge of fuel into the charge of air includes injecting the fuel across a major axis of the combustion chamber.

30. The piston of claim 29, in which injecting a charge of fuel into the charge of air includes injecting the fuel perpendicularly to the major axis.

31. The method of claim 26, in which a swirling motion is imposed on the air admitted into the bore.

32. The method of claim 31, including moving the opposing bowls on facing end surfaces of the pistons together to define a combustion chamber having an elongated ellipsoidal shape having a major axis.

33. The method of claim 32, in which injecting a charge of fuel into the charge of air includes injecting the fuel along the major axis.

34. A method for operating an internal combustion engine including at least one cylinder with longitudinally-separated exhaust and intake ports, and a pair of pistons disposed in opposition for reciprocating in a bore of the cylinder, by forming a combustion chamber having an elongated ellipsoidal shape between the end surfaces of the pistons as the pistons move toward respective top dead center positions in the bore, providing squish flows of charge air into the combustion chamber in directions that are skewed with respect to a major axis of the elongated ellipsoidal shape, generating at least one tumbling motion of charge air in the combustion chamber in response to the squish flows and swirling charge air, and injecting fuel into the combustion chamber.

35. The method of claim 34, in which injecting a charge of fuel into the combustion chamber includes injecting the fuel along the major axis.

36. The method of claim 34, in which generating at least one tumbling motion includes generating a first tumbling motion about a major axis and generating a second tumbling motion about an axis orthogonal to the major axis.

37. The method of claim 34, in which injecting a charge of fuel into the combustion chamber includes injecting opposing sprays of fuel along the major axis.