Part of a reciprocating engine
Two piston rings mounted on a two-stroke engine piston. The ring gap for the bottom ring is visible in the centre of the image.
A piston ring is a metallic split ring that is attached to the outer diameter of a piston in an internal combustion engine or steam engine.
The main functions of piston rings in engines are:
- Sealing the combustion chamber so that there is minimal loss of gases to the crank case.
- Improving heat transfer from the piston to the cylinder wall.
- Maintaining the proper quantity of the oil between the piston and the cylinder wall
- Regulating engine oil consumption by scraping oil from the cylinder walls back to the sump.[1]
Most piston rings are made from cast iron or steel.