The various strokes in the operation of a four-stroke cycle petrol engine are described below. And these valves are operated by means of Camshaft. It is rotated at half the speed of a crankshaft. The travel of the piston from one dead center to another is called piston stroke and a four-stroke cycle consists of four strokes :. In this stroke the suction valve opens, exhaust valves remain in close condition.
When the piston reaches the BDC, the inlet valve closes and the flywheel makes a half revolution. In this stroke, the piston moves from the bottom dead center BDC to the top dead center TDC , and both the suction and exhaust valves are in closed condition. The mixture, which was sucked into the cylinder during the suction stroke, is compressed into the combustion chamber. The heat produced during the compression stroke and vaporize the mixture.
As the piston approaches the top dead center, the compression stroke completes, and then the spark plug gives the spark. Again both the inlet and exhaust valves are closed in this stroke.
The compressed charge ignited by the high intensity of the spark and expands adiabatically, therefore, it pushes the piston downward i. During the exhaust stroke, the inlet valve is in a closed condition and the exhaust valve is opened. The stroke is completed when the piston reaches the Top Dead Center. And then again stokes are recycled.
In the exhaust stroke in one situation both the valves are in an open condition for some seconds so that fresh charge entered to engine cylinder and pushes the burnt gases out of the cylinder. This process is called Scavenging. The strokes are:. The suction stroke draws air into the cylinder liner combustion space as the piston moves down towards bottom dead centre BDC.
When the piston reaches BDC , the inlet valves close and the piston travels back upwards towards top dead centre TDC ; this is the compression stroke. As the piston moves towards TDC , the air in the cylinder is compressed volume reduces and its temperature and pressure increases. Shortly before TDC, fuel is injected into the combustion space.
The fuel ignites and a controlled explosion occurs. Once ignition occurs, the power stroke begins. Viertakt-Verbrennungsmotor ohne Ventile.
Vierzylinder Boxermotor. Categories : Animations of engines Four-stroke engines. Namespaces Category Discussion. Views View Edit History. Main page Welcome Community portal Village pump Help center.
Upload file Recent changes Latest files Random file Contact us. What links here Related changes Special pages Permanent link Page information. The four strokes of the cycle are intake, compression, power, and exhaust.
Each corresponds to one full stroke of the piston; therefore, the complete cycle requires two revolutions of the crankshaft to complete. The illustrated engine features a poppet intake valve which is drawn open by the vacuum produced by the intake stroke. The exhaust valve is held shut by a spring not illustrated here. As the piston rises, the poppet valve is forced shut by the increased cylinder pressure.
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