You cannot imagine the mechanical engineering without piston rings. Piston is a critical part of an engine that creates a movable boundary. When engine starts and fuel burns within the cylinder, it applies a pressure force over piston that moves it downward and transforms thermal energy into mechanical energy.
The component piston rings is intended with some metal rings that possess certain functionalities. These rings are named as piston rings.
Since piston creates a movable boundary within an engine cylinder, you need to ensure that it is properly fitted. If it is tighter, it doesn’t move freely within the cylinder and if it is very loose, it would leaks the pressure force. For high performance, it is must for a piston to provide a good sealing fit and less friction resistance between cylinder wall and piston.
A piston generally includes three rings-
1. Compression rings
Compression rings are designed with an intention to seal the cylinder and combustion space in order to prevent escaping of the gases within the space until they serve their purpose. Oil carried by compression rings help in lubrication of the cylinder. Most of the time manufacturers make compression rings with gray cast iron.
You can avail these rings in a variety of cross sections.
2. Wiper ring or intermediate ring
Wiper ring or intermediate ring is intended with a tapered face. This ring is placed within the ring groove between the compression ring and the oil ring. A wiper ring is used as a sealant. It seals the combustion chamber and wipes the excess oil of the cylinder wall. Combustion gases that pass by the compression ring are barred by the wipe ring.
3. Oil rings
Oil ring is placed in the ring groove closest to the crankcase. This ring is designed to wipe excess oil from cylinder wall when piston moves. The wiped excess oil is returned through ring openings to the oil reservoir within the engine block.
However, the oil ring is absent in the two-stroke cycle engine because lubrication is supplied by mixing oil with gasoline, and there is no requirement of oil reservoir.
Purpose served by piston rings-
- To offer good sealing between engine cylinder and piston.
- To regulate the lubricant amount inside the engine cylinder.
- To offer proper lubrication
- To minimize friction between engine wall and piston
- To transfer piston heat via engine wall and fins
Engine design is incomplete without piston. You cannot imagine any functioning engine without it.