Open exhaust chamber constructions for opposed-piston engines
View Patent ↗A configuration for a uniflow-scavenged, opposed-piston engine reduces exhaust cross-talk caused by mass flow between cylinders resulting from one cylinder having an open exhaust port during scavenging and/or charging while an adjacent cylinder is undergoing blowdown. Some configurations include a wall or other barrier feature between cylinders that are adjacent to each other and fire one after the other. Additionally, or alternatively, some engine configurations include cylinders with intake and exhaust ports sized so that there is an overlap in crank angle of two or more cylinders having open exhaust ports of about 65 crank angle degrees or less.
1. A uniflow-scavenged, opposed-piston engine comprising:
two or more cylinders, wherein at least two of the two or more cylinders are adjacent and have consecutive blowdown events, each of the two or more cylinders comprising:
a cylinder wall with an interior surface defining a bore centered on a longitudinal axis of the cylinder, the bore having a first diameter relative to the longitudinal axis; and
intake and exhaust ports formed in the cylinder wall near respective opposite ends of the cylinder;
an exhaust chamber, in which the exhaust ports of each of the two or more cylinders are situated and that receives all exhaust from each of the two or more cylinders; and
a wall with ends in the exhaust chamber, between the at least two cylinders of the two or more cylinders that are adjacent and have consecutive blowdown events,
in which the exhaust chamber has an interior floor and an interior ceiling, and further wherein the wall extends from the interior floor to a height at least equal to the height of openings through which exhaust gas pulses emanate, and the wall does not reach the interior ceiling of the exhaust chamber.
2. The opposed-piston engine of claim 1 , further comprising a crankshaft that rotates through 360 crank angle degrees during each cycle of engine operation, wherein at any given time during a cycle of engine operation, any two of the two or more cylinders simultaneously have open exhaust ports, and the simultaneously open exhaust ports are open simultaneously for 65 crank angle degrees or less.
3. The opposed-piston engine of claim 2 , wherein the simultaneously open exhaust ports are open simultaneously for about 40 crank angle degrees or less.
4. The opposed-piston engine of claim 2 , wherein the simultaneously open exhaust ports are open simultaneously for about 38 crank angle degrees or less.
5. A uniflow-scavenged, opposed-piston engine comprising:
two or more cylinders arranged inline in a cylinder block, wherein at least two of the two or more cylinders are adjacent and have consecutive blowdown events, each of the two or more cylinders comprising:
a cylinder wall with an interior surface defining a bore centered on a longitudinal axis of the cylinder, the bore having a first diameter relative to the longitudinal axis; and
intake and exhaust ports formed in the cylinder wall near respective opposite ends of the cylinder;
an exhaust chamber, in which the exhaust ports of each of the two or more cylinders are situated and that receives all exhaust from each of the two or more cylinders; and
a wall with ends in the exhaust chamber, between the at least two of the two or more cylinders that are adjacent and have consecutive blowdown events, in which a length of the wall is terminated by a post on each end of the wall and coolant flows through at least each end of the wall.
6. The opposed-piston engine of claim 5 , further comprising a crankshaft that rotates through 360 crank angle degrees during each cycle of engine operation, wherein at any given time during a cycle of engine operation, any two of the two or more cylinders simultaneously have open exhaust ports, and the simultaneously open exhaust ports are open simultaneously for 65 crank angle degrees or less.
7. The opposed-piston engine of claim 6 , wherein the simultaneously open exhaust ports are open simultaneously for 40 crank angle degrees or less.
8. The opposed-piston engine of claim 6 , wherein the simultaneously open exhaust ports are open simultaneously for 38 crank angle degrees or less.
9. A method of operating a two-stroke, uniflow-scavenged, opposed-piston engine, the engine comprising:
four cylinders in an in-line array, each cylinder in the in-line array of four cylinders comprising an exhaust port;
a pair of pistons in each cylinder in the in-line array of four cylinders, in which each pair of pistons comprises an intake piston and an exhaust piston;
an engine block with an exhaust chest configured to receive all exhaust gas discharged from the four cylinders;
in which the four cylinders in the in-line array are designated cylinder 1 , cylinder 2 , cylinder 3 , and cylinder 4 consecutively from a first end of the in-line array to a second end of the in-line array;
the method comprising firing the four cylinders in a firing sequence in which cylinder 1 is fired first, cylinder 3 is fired second, cylinder 2 is fired third, and cylinder 4 is fired last, such that blowdown event order for the four cylinders is cylinder 1 , cylinder 3 , cylinder 2 , then cylinder 4 , in which the exhaust chest comprises a wall between cylinder 2 and cylinder 3 .
10. The method of claim 9 , wherein the wall between cylinder 2 and cylinder 3 comprises a wall with ends that terminate in spaces through which coolant flows when the engine is in use.
11. The method of claim 10 , further comprising flowing coolant through the ends of the wall between cylinder 2 and cylinder 3 when the engine is in use.
12. The method of claim 9 , wherein an overlap in crank angle between open exhaust ports of cylinder 3 and cylinder 2 is 65 crank angle degrees or less during operation of the engine.