Internal Combustion Engine

Engines operate on cycles. There are four strokes of the piston in one cycle of engine operation. There are two outward strokes toward the crankshaft and two inward strokes away from ¹ the crankshaft.

When the piston is at the end ² of the stroke away from the crankshaft (inward stroke) this is top dead centre (TDC). When the piston is at the end of the out ward stroke (toward the crankshaft) this is bottom dead centre (BDC). The piston movement from TDC to BDC is an engine stroke.

The four strokes in a cycle of the internal combustion engine are: intake, compression, power and exhaust.

Intake. During the intake stroke the piston moves to BDC and the intake valve opens. This movement of the piston draws a mixture of air and fuel into the cylinder (in a diesel this movement of the piston draws in air only)³.

Compression. When the piston reaches⁴ BDC it moves toward the cylinder head (inward motion). The valves do not open and the piston compresses the fuel mixture between the piston and the cylinder head (in a diesel the pis­ton compresses air only).

Power stroke. When the piston reaches TDC, an electric spark ignites the fuel mixture in the combustion chamber of the gasoline engine (in a diesel engine the heat of the highly compressed air ignites the fuel).

When the air-fuel mixture burns it moves the piston with great force.

Exhaust. The exhaust stroke takes place when the pis­ton moves up. The exhaust valve opens and the piston forces out⁵ the gases. The new cycle will begin in the cy­linder.

Because of the four strokes we call this engine a four-stroke-cycle engine. The four-stroke-cycle engine with spark ignition is the most common type of the internal combustion engine.

NOTES

¹away from − у бік від

²end − кінець

³only − лише, тільки

⁴ reach − досягати

⁵force out − виштовху­вати

FOUR-STROKE CYCLE

cylinder head

cylinder block

exhaust valve

air-fuel mixture

piston

intake valve

intake stroke	compression stroke
move open draw in	BDC	reach do not open compress	toward inward

camshaft

burnt gases

spark plug

crankshaft

combustion chamber

connecting rod

power stroke	exhaust stroke
reach ignite burn	TDC electric spark	take place open force out	burnt gases

Дата добавления: 2015-11-16