Saturday 11 August 2012
Piston Rings
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Piston rings are fitted into the grooves of the piston to maintain good seal between the piston and the cylinder wall. There are three functions of the piston rings.
- To provide a pressure seal to prevent blow-by of burnt gases. Blow-by is the name that describes the escape of burnt gases from the combustion chamber, past the piston, and into the crankcase.
- To form the main path for conduction of heat from the piston crown to the cylinder walls.
- To control the flow of oil to the skirt and rings themselves in adequate quantity while preventing an excessive amount reaching the combustion chamber with consequent waste and carbonization.
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| Piston rings (Image credit: b2b-piston.com) |
Piston rings material:
Piston rings are usually made of fine grained alloy cast iron. This material possesses excellent heat and wear resisting qualities inherent in its graphitic structure. The elasticity of this material is also sufficient to impart radial expansion and compression which is necessary for assembly and removal of the ring, and particularly to enable it to exercise flexible pressure on the cylinder valves.
Types of rings:
- Compression rings
- Oil control rings
Compression rings seal in the air-fuel mixture as it is compressed, and also the combustion pressure as the mixture burns. There are two or three compression rings fitted into the top grooves. The number of compression rings tend to increase the compression ratio and oil control ring is fitted into the lower groove of the piston. Generally the second and third compression rings are taper-faced and supplied to improve oil sealing. Taper-sided compression rings are used to overcome ring-sticking problems in high output engines.
This post was written by: Sanjay Verma
Sanjay Verma is an experienced mechanical engineer and a lecturer. In this blog he shares his knowledge about various subjects of mechanical engineering. Follow him on Google+
