Compact ported cylinder construction for an opposed-piston engine
View Patent ↗A compact construction for an opposed-piston engine includes a cylinder liner with longitudinally-spaced exhaust and intake ports in which the exhaust port has inner and outer edges presenting a port height that causes the exhaust port to be fully open before a piston associated with the exhaust port reaches bottom dead center during an expansion stroke and the end surface of the associated piston to be spaced outwardly of the outer edge when the piston is at bottom dead center.
1. A piston and cylinder combination for a two-stroke, opposed-piston engine, comprising:
a cylinder that provides a bore with a longitudinal axis, the cylinder including an exhaust port and an intake port that are spaced-apart and disposed on respective sides of a central portion of the cylinder, the exhaust port having an annular configuration that is orthogonal to the longitudinal axis and that includes an inner edge and an outer edge, the inner edge and the outer edge presenting a port height therebetween, the exhaust port including a plurality of port openings disposed in an annular array along a first respective circumference of the cylinder, and the intake port including a plurality of port openings disposed in an annular array along a second respective circumference of the cylinder; and,
first and second pistons placed in opposition in the bore, the first piston disposed for controlling the exhaust port and the second piston disposed for controlling the intake port, each of the first and second pistons including a peripheral edge, an upper ring pack, and a lower ring pack, the upper ring pack and the lower ring pack presenting a separation distance therebetween, the upper ring pack comprising at least a compression ring and the lower ring pack comprises at least an oil scraper ring, each of the first and second pistons being operable to reciprocate between top dead center (TDC) and bottom dead center (BDC) locations in the bore; wherein,
when the first piston reaches its TDC location, the exhaust port is between the upper ring pack and the lower ring pack of the first piston, with the lower ring pack adjacent the outer edge of the exhaust port; and,
the exhaust port is fully open so as not to be obstructed by the first piston before the first piston reaches its BDC location,
wherein during an expansion stroke, the peripheral edge of the first piston reaches the outer edge of the exhaust port before the first piston reaches its BDC location,
further wherein:
movement of the first piston from its TDC location to its BDC location presents an expansion stroke comprising 0°-180° of a first engine crankshaft rotation and movement of the first piston from its BDC location to its TDC location following an expansion stroke presents a compression stroke comprising 180°-360° of the first engine crankshaft rotation; and,
the exhaust port height causes the exhaust port to remain fully open in a range of about 135° to about 225° of the first crankshaft rotation.
2. The piston and cylinder combination of claim 1 , in which the upper and lower ring packs each comprise at least two piston rings.
3. A two-stroke, opposed-piston engine comprising at least one piston and cylinder combination according to any preceding claim.