A two-stroke engine is a type of internal combustion engine that completes a power cycle with two strokes of the piston within a single rotation of the crankshaft.

Unlike a four-stroke engine that has separate intake, compression, power, and exhaust strokes, a two-stroke engine combines these functions into two strokes: the compression/exhaust stroke and the power/intake stroke.

Strokes involved are:

  1.  Compression stroke (scavenge / compression): in this stroke, the piston goes from BDC (Bottom Dead Centre) to TDC (Top Dead Centre) and scavenging takes place. Air comes inside the cylinder through scavenge ports when the piston is at BDC and exhaust gases go out, fresh air takes the place of the exhaust gases so that it can get compressed and mixed with fuel.
  2. Power stroke (expansion / exhaust): in this stroke, compressed fuel is ignited and the expansion takes place, giving the power cycle. When the piston goes down at a certain point the exhaust valve opens and the exhaust gases go out. 

Parts of a two-stroke engine:

A piston is one of the most important parts of the combustion chamber. It transmits the expanding gas forces to the connecting rod. Therefore, mechanical power can be generated because of reciprocating motion of the piston. The function is the same for two-stroke and four-stroke engines. It seals the combustion chamber, transmits gas load to the connecting rod.

  1. piston crown: top part of the piston exposed to very high pressure and temperature.
  2. piston skirt: lower part of the piston, which allows to keep the alignment with the piston rod and crosshead.
  3. piston rod: connects piston to crosshead.                           

Materials:

  1. Crown - cast chrome nickel molybdenum alloy steel
  2. Skirt -  cast iron or SI aluminium alloy
  3. Rod -  forged steel

Ultima modificare: joi, 12 septembrie 2024, 10:48