TWO STROKE ENGINE

Two stroke engine working Principle:

First, the combustion cycle is completed within a single piston stroke as oppose to two piston strokes, and second, the lubricating oil for the engine is mixed in with the petrol or fuel. ... As the piston (red) reaches the top of its stroke, the spark plug ignites the fuel-air-oil mixture 

Two-stroke cycle engine differs from four-stroke cycle engine in the following ways:

* The cycle is completed in two strokes instead of four.

*The fire every time the piston reaches the top of the stroke.

*It has no valves.

*It crankcase is sealed.

Two stroke cycle engine employs the same sequence of operation of the four-stroke cycle but the cycle is completed as given below in one revolution of the crankshaft so that a power stroke occurs every 360°.

First stroke (Piston move upwards): 

Piston move from B.T.C to T.D.C. Vacuum is created under the piston on clearing the intel port, fresh fuel-air mixture admitted into the crankcase(suction).  Pre-combustion mixture rushes above the piston into the combustion chamber via the transfer port. Burnt gases are pushed out via the exhaust port. Compression starts when the ports are closed.

Second stroke(Piston moves downwards):

Itmixture above the piston is ignited and burnt. High pressure and expansion of gases perform work till exhaust port clears. Below the piston the fuel-air mixture is pre-compressed after covering of the Inlet port. When the transfer port opens, the mixture rushes over into the combustion chamber.

    In compression to four-stroke engine, a two-stroke engine has the following advantages and dis advantages.

Advantages of two-stroke engine:

👉 Doesn't have valves, which simplifies the design.

👉 High power to weight ratio.

👉 It is lighter.

👉 It is less expensive because of simpler design.

👉 Less number of moving parts.

👉 Low service and overhaul cost due to less number of parts.

Disadvantages of two-stroke engine

👉 Faster wear.

👉 Shorter engine life.

👉 Requires special two-stroke oil("premix")

👉 Is fuel less efficient.

👉 Produce more noise.