Four Stroke Petrol Engine.

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Four Stroke Petrol Engine

Four stroke petrol engine is an internal combustion engine in which the piston completes four separate stroke while turning the crank shaft. The four stroke cycle refers to its use in petrol engine, gas engine,light,oil engine and heavy engines in which the mixture of air fuel is drown in the engine cylinder. Since ignition in these engine is due to spark. thus this type of engine is called spark ignition engine. 
Four stroke engine is based on Otto cycle. The Otto cycle describes how heat engine turns gasoline into motion. this cycle converted chemical energy into thermal energy and then into motion. the Otto cycle describes how internal combustion engine works with the use of gasoline.
The Otto cycle provides the energy for most transportation and was essential for the modern time. the vast majority of automobiles seen on the road today use an Otto cycle to convert gasoline into motion.

 Applications of four stroke Petrol Engine:
Petrol engines have many applications, including-
Automobiles
Motorcycles
Aircraft.
Motorboats.
And in some small engines, such as lawn mowers, chainsaws and portable engine generators.

History :

In 1860, Lenoir was created a double acting engine successfully that run on illuminating gas at 4% of efficiency. The 18 L engine produced only 2 horse power(HP). The Lenoir engine run on illuminating gas made from the coal

Nikolaus August Otto and Eugen Langen founded the first internal combustion engine production company, NA Otto and Cie in 1864.
In 1876, Otto and Langen got success in creating the first internal combustion engine that compressed the fuel mixture prior to combustion for higher efficiency than an engine created to this modern time.

Various Scientists and engineers contributed to the development of internal combustion engine. Nikolaus august Otto the German engineer was created 4 stroke petrol engine successfully in 1876.
Although there had been earlier attempts by Etienne Lenoir, Sigfried Marcus,Julius Hock and George Brayton.

Components of Four Stroke Petrol Engine





1. Cylinder
It is a cylindrical vessel in which piston reciprocates. It is made up of cast iron or alloy steel.

2. Piston  
On Combustion inside the cylinder, gasses exert pressure on it.

3.  Wrist or Gudgeon Pin 
It form the link between the small end of the connecting rod and the Piston.

4. Connecting Rod
 Connecting road is connected the piston and crank shaft, and transmitted the forces from piston to the crank shaft.

5. Crank Shaft 
Crank shaft converted the reciprocating motion of Piston into useful rotary motion of the output shaft. It is the enclosed in the crank case. The crank shaft made up of alloy steel.

6. Valves 
 Valves are provided either on cylinder head or on  the side of cylinder for regulating the charge coming into the cylinder and thus discharge the product of combustion from the cylinder.

7. Spark plug 
  It is a electric device that fit into the cylinder head of the internal combustion engine and ignites compressed the gasoline by means of electric spark.


Working

In Four Stroke cycle engine, cycle is completed in two revolutions of crank shaft or four stroke of the piston. Each stroke consists of 1800 of crank shaft rotation. Therefore the cycle consists of 7200 of crank shaft of rotation.
Cycle consists of following four strokes-
Suction Stroke
Compression stroke
Expansion Stroke 
Exhaust Stroke




Suction Stroke-
In this stroke the inlet valve opens and proportionate air and fuel( Petrol or Gasoline) mixture is sucked in the engine cylinder. Thus the piston moves from top dead center (T.D.C.) to bottom dead center (B.D.C.). The exhaust valve remain closed through out of the stroke.

Compression Stroke:
In this stroke both inlet and outlet valve are remain closed during the stroke. The piston moves top dead center (T.D.C.) and compressed then closed fuel(Petrol or Gasoline) and air mixture drawn. Just before the end of this stroke the operating. Plug  initiates a spark which ignites the mixture and the combustion take place at constant pressure.

Expansion Stroke or Power Stroke :
In this stroke both the valve are remain closed during the start of this stroke but when the piston just reaches at bottom dead center (B.D.C.) the exhaust valve opens, when the mixture is ignited by the spark plug then hot gases are produced which drive or throw the piston from T.D.C. to B.D.C. and thus the work is obtained in the stroke.

Exhaust Stroke 
This the last stroke of the cycle.Here the gasses from which the work has been controlled become useless after the completion of the expansion stroke and are made to escape through valve to the atmosphere. thus this removal of gas is accomplished during this stroke. The piston moves from bottom dead center (B.D.C.) to top dead center (T.D.C.) and the exhaust gases are driven out of the engine cylinder. thus this is called scavenging.















Click the bellow link for know about four stroke diesel engine.



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