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Chapter: Mechanical : Advanced IC Engines : Spark Ignition Engines

The operation of the piston engine can best be understood bycomparing it to a simple cannon. In view A of figure 1 on the following page, a cannon barrel, charge of gunpowder, and a cannonball are illustrated.

The operation of the piston engine can best be understood bycomparing it to a simple cannon. In view A of figure 1 on the following page, a cannon barrel, charge of gunpowder, and a cannonball are illustrated. In view B of figure 1, the gunpowder is ignited. The gunpowder burns very rapidly and as it burns there is a rapid expansion of the resulting gases. This rapid expansion causes a tremendous increase in pressure that forces the cannonball from the barrel.

Now the cannon barrel has been replaced by a cylinder and a combustion chamber. The cannonball has been replaced by a piston. A mixture of vaporized fuel and air has replaced the gunpowder. In view B of figure, the gasoline is ignited. This time, the resulting force acts to push the piston downward.

The force of the piston acting in a downward notion is of little immediate value if it is to turn the wheels of a vehicle. In order to use this straight line or reciprocating motion, it must be transformed into rotary motion. This is made possible through the use of a crankshaft. The crankshaft is connected to the driving wheels of a vehicle throughthe drive train on one end. On the other end of the shaft is a crank with acrankpin offset from the shaft's centre. Figure below illustrates how the piston and the crankshaft are connected through the connecting rod and the crankpin. Figure below on the following page illustrates how reciprocating motion of the piston is changed to rotating motion of the crankshaft.

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Mechanical : Advanced IC Engines : Spark Ignition Engines : Introduction about IC Engines |