Combustion chamber constructions for opposed-piston engines

#The field is combustion chambers for internal combustion engines. In particular, the field includes constructions for opposed-piston engines in which a combustion chamber is defined between end surfaces of pistons disposed in opposition in the bore of a ported cylinder. More particularly, the field includes opposed-piston engines with combustion chamber constructions that produce a tumbling motion in charge air admitted into the cylinder between the piston end surfaces.

#Per FIG. 1, an opposed-piston engine includes at least one cylinder 10 with a bore 12 and longitudinally-displaced intake and exhaust ports 14 and 16 machined or formed therein. One or more fuel injectors 17 are secured in injector ports (ports where injectors are positioned) that open through the side surface of the cylinder. Two pistons 20, 22 according to the prior art are disposed in the bore 12 with their end surfaces 20e, 22e in opposition to each other. For convenience, the piston 20 is denominated as the “intake” piston because of its proximity to the intake port 14. Similarly, the piston 22 is denominated as the “exhaust” piston because of its proximity to the exhaust port 16.

#Operation of an opposed-piston engine with one or more ported cylinders (cylinders with one or more of intake and exhaust ports formed therein) such as the cylinder 10 is well understood. In this regard, in response to combustion the opposed pistons move away from respective top dead center (TDC) positions where they are at their innermost positions in the cylinder 10. While moving from TDC, the pistons keep their associated ports closed until they approach respective bottom dead center (BDC) positions where they are at their outermost positions in the cylinder. The pistons may move in phase so that the intake and exhaust ports 14, 16 open and close in unison. Alternatively, one piston may lead the other in phase, in which case the intake and exhaust ports have different opening and closing times.

#FIG. 1 is a side sectional partially schematic drawing of a cylinder of an opposed-piston engine with prior art opposed pistons near respective bottom dead center locations, and is appropriately labeled “Prior Art”.

#FIG. 2 is a side sectional partially schematic drawing of the cylinder of FIG. 1 with the prior art opposed pistons near respective top dead center locations where flat end surfaces of the pistons define a prior art combustion chamber, and is appropriately labeled “Prior Art”.

#FIG. 3 is a side schematic view of a pair of opposed pistons in which the end surfaces of the pistons define a first combustion chamber construction.

#In the combustion chamber constructions to be described, an internal combustion engine includes at least one cylinder with longitudinally-separated exhaust and intake ports; see, for example, the cylinder 10 illustrated in FIGS. 1 and 2. A pair of pistons is disposed in opposition in a bore of the cylinder and a combustion chamber structure is defined between the opposing end surfaces of the pistons as the pistons move toward top dead center positions. A circumferential area defines a periphery on each of the end surfaces. The combustion chamber includes a cavity defined between the end surfaces, and has at least one opening through which fuel is injected (hereinafter an “injection port”) that extends at least generally in radial direction of the cylinder and opens into the cavity.

#During operation of the internal combustion engine, as the pistons approach TDC, one or more squish zones direct flows of compressed air (called “squish flows”) into the combustion chamber in at least one direction that is skewed with respect to a diametrical direction of the bore. This process is referred to as “generating squish”. The portions of the end surfaces that generate squish are referred to as squish surfaces, and channels defined between the squish surfaces are referred to as squish channels. Squish flow is deflected or redirected by one or more curved surfaces in a combustion chamber cavity into at least one tumble motion that circulates in the cavity.

#In the following descriptions, “fuel” is any fuel that can be used in an opposed-piston engine. The fuel may be a relatively homogeneous composition, or a blend. For example, the fuel may be diesel fuel or any other fuel ignitable by compression ignition. Further, the descriptions contemplate ignition resulting from compression of an air/fuel mixture; however it may be desirable to provide additional mechanisms, such as glow plugs, to assist compression ignition. The descriptions contemplate injection of fuel into a compressed gas in a combustion chamber when opposed pistons are at or near TDC locations. The gas is preferably pressurized ambient air; however, it may include other components such as exhaust gases or other diluents. In any such case, the gas is referred to as “charge air.”