Explain working of 2 stroke petrol engine

Explain working of 2 stroke petrol engine?

WORKING OF TWO STROKE PETROL ENGINE:

Two stroke and four stroke engines are different in the method of filling the cylinder with fresh charge and also in the removal of burnt gases from the cylinder. In a four stroke engine these processes are performed by the movement of piston during suction and exhaust stroke. In four stroke engines these are suction and exhaust valves where as suction (inlet) and exhaust (outlet) ports are cut in the walls of cylinder.

Whole process of has been shown in Figure. The Figure shows a three channel system in which the fresh charge is compressed in the crank case of the engine. This is also called crank are compression system. Figure shows all working of two stroke petrol engine in three stages.

Exhaust and Transference:

Figure shows the exhaust and transfer process. When the piston moves from TDC to BDC, i.e. downwards after expansion of gases, the piston uncovers the exhaust port. The burnt gases start going out of the cylinder. Simultaneously the slightly compressed charge in the crank case is forced into the cylinder through transfer port. The deflector on the piston crown deflects this charge and the fresh charge moves in the upward direction. This fresh charge pushes the burnt gases out of cylinder. During this process, some fresh charge may also leave the cylinder through exhaust port.4mechtech

Compression

When the piston moves upwards from BDC to TDC, transfer port and exhaust ports are closed. Compression of charge, present in the cylinder takes place. During this motion the inlet valve open and fresh charge enters the crank case. When the piston reaches TDC, compression process is completed.

Ignition and Expansion

After compression, spark plug generates spark and ignition of fuel takes place. Rapid rise in pressure and temperature takes place at constant volume. At this stage both transfer port and exhaust port are closed. Expansion of burnt gases takes place at the piston moves downward from TDC to BDC. The gases push the piston with great force and power is obtained during this process. Simultaneously, slight compression of fresh charge, present in crank case takes place.

After this process i.e. exhaust and transfer of charge takes place and cycle is repeated again. Thus, the cycle is completed in two strokes of piston and one revolution of crank shaft. In case of petrol engines, fresh charge consists of air petrol mixture which comes from carburetor after mixing.