Topic –“ Two Stroke Petrol

Engine ”

Presented By : Darshan Harsora (150280116029)

L.D. College of EngineeringSubject : Elements of Mechanical Engineering (2110006)

~ History The First two stroke design was a diesel engine invented by Dugald

Clark in 1878.

He used a similar cylinder head to a four stroke diesel engine and a supercharger.

The petrol two stroke engine with cylinder ports was invented by Joseph Day in 1889.

The two-stroke petrol (gasoline) engine was very popular throughout the 19th-20th century in motorcycles and small-engined devices, such as chainsaws and outboard motors.

The first truly practical two-stroke engine was attributed by Yorkshireman Alfred Angas Scott, who started producing twin-cylinder water-cooled motorcycles in 1908.

~ Function of Two Stroke Petrol EngineThe function of a

two stroke petrol engine is to deliver power to the crank shaft joined with the rotary wheel with the use of working substance as Petrol (Gasoline) entered through inlet port (Carbureter) which is ignited inside the cylinder through the spark plug and remaining substance is released through exhaust port. This whole process is completed in one revolution of flywheel.

Construction of Two Stroke Petrol Engine

Beginning of First Stroke When the piston moves

upward a partial vaccum is created in the crank case until its lowers edge uncovers the inlet port completely as shown in Fig.(A)

The pressure difference set

up between the atmosphere and crankcase will suck the petrol-Air mixture through the carburetor fitted to inlet port into the crank case.

The suction will be continued till the inlet port is covered by the piston during its next downward stroke.

After the inlet port is covered by the piston as shown in the Fig. (B) , its further downward motion will compress the Charge ( Petrol-Air Mixture ) in the crankcase upto the top edge of the piston uncovers the transfer port as shown in fig. (B).

The Compressed charge flows from the crank case to the cylinder through transfer port.

The electric spark ignites the compressed charge . The combustion of charge will release hot gases which increase the pressure and temperature in the cylinder .

The high pressure combustion gases force the piston downwards .The piston performs the power stroke till it uncovers the exhaust port as shown in the figure. (B)

The combustion gases which are at a pressure slightly higher than the atmosphere pressure escape through the exhaust port .

The piston uncovers the transfer port .The fresh charge which enters the cylinder pushes the burnt gases so more amount of exhaust gases comes out .

This sweeping out of exhaust gases by the incoming fresh charge is called scavenging

In this stroke the piston moves from BDC to TDC . It covers the transfer port as shown in the Figure ( c ) .

SECOND STROKE

After the above situation the supply of the charge is stopped and then when it moves further up it covers the exhaust port completely as shown in Fig.(D) stops scavenging.Upward motion of the piston will compress the charge in the cylinder.After the piston reaches TDC the first stroke repeat again.

Thank You