Further reading

I. Learn the following words and word-combinations to comprehend the text.

air	mixture
bottom dead centre	movement
call	new
common	operate
cycle	outward
draw (drew, drawn)	spark
draw in (into)	stroke
exhaust	power stroke
great	top dead centre
heat	because of
heavy	during
high	from
ignite	than
intake	toward
inward

II. Read and translate the text. Principles of engine operations

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 the crankshaft.

When the piston is at the end of the stroke away from the crankshaft (inward stroke) this is top dead centre (TDC). When the piston is at the end of the outward 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).

Compression. When the piston reaches 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 heatl (in a diesel the pis­ton compresses air only). ,

Power. 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.

There are higher pressures in the diesel engines and because of these pressures the diesel engines have heavier piston pins, connecting rods and crankshafts than the ga­soline engines.

Exhaust. The exhaust stroke takes place when the piston moves up. The exhaust valve opens and the piston forces out 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.

away from	у бік від
end	кінець
only	лише, тільки
reach	досягати
pressure	тиск
force out	виштовху­вати

III. Fill in the gapes with the appropriate word-combinations. Translate the sentences into Ukrainian.

1. During the intake stroke the piston moves to the ... and the intake valve opens (top dead centre, bottom dead centre).

2. The piston compresses the fuel mixture during the ... (exhaust stroke, compression stroke).

3. During the ... an electric spark ignites the fuel (power stroke, compression stroke).