Unit 2

1. Read and remember the words. Mind the pronunciation.

   single-acting	–	простого действия
   double-acting	–	двойного действия
   trunk-piston type	–	тронковый тип
   crosshead type	–	крейцкопфный тип
   opposed-piston	–	с противоположно двигающи­мися поршнями
   exhaust stroke	–	выхлопной ХОД
   suction (intake) stroke	–	ход всасывания (впускной)
   to draw	–	втягивать
   to reach	–	достигать
   compression stroke	–	ход сжатия
   sufficiently	–	достаточно
   to cause	–	вызывать
   spontaneous ignition	–	самовоспламенение
   combustion and expansion stroke	–	ход горения и расширения
   immediately	–	мгновенно
   to atomize	–	распылять
   to commence	–	начинать
   working stroke	–	рабочий ход
   to expel	–	удалять
   remainder	–	остаток
   to complete	–	заканчивать
   revolution	–	оборот
   travel	–	ход
   scavenging air	–	продувочный воздух
   to introduce	–	вводить
   series	–	ряд
   port	–	отверстие, окно
   to uncover	–	открывать
   dead centre	–	мертвая точка
   pure	–	чистый
   to require	–	требовать

2. Read and translate the text.

Cycles of a Diesel Engine

Any internal combustion engine, regardless of principle it operates on, is said to have a four stroke cycle or a two stroke cycle. The engines of either type may be single or double acting, trunk-piston type, crosshead type or opposed- piston.

The four-stroke cycle consists of the suction or intake stroke, compression stroke, combustion and expansion stroke and exhaust stroke.

On the suction or intake stroke the piston moves down, the inlet valve is open and air is drawn from the atmosphere into the cylinder through a me­chanically operated inlet valve. At the end of the stroke the cylinder is filled with air. As the piston reaches the end of the intake stroke the inlet valve closes and the piston rises on the second or compression stroke.

On the compression stroke the air is compressed within the cylinder. As a result of this compression the temperature of the air rises. It is sufficiently high to cause spontaneous ignition of the fuel.

On the combustion and expansion stroke the fuel is injected into the cylin­der. Combustion immediately takes place when the fuel in a highly atomized form mixes with the compressed air. Expansion occurs throughout the remain­der of the stroke, this being the working stroke.

On the exhaust stroke the products of combustion in the cylinder are ex­pelled through the mechanically operated exhaust valve and the cycle of opera­tions recommences.

One complete cycle requires four strokes of the piston; the four strokes comprise two complete revolutions of the crankshaft.

In engines operating on the two-stroke principle the cycle of opera­tions is completed in two strokes of the piston or one revolution of the crankshaft.

The two-stroke cycle comprises the compression stroke and the working stroke when combustion and expansion take place.

On the compression stroke the air in the cylinder is compressed with the same resulting rise in temperature as in a four-stroke single-acting engine.

On the working stroke combustion occurs and expansion follows until the piston has moved about 85 per cent of its travel. Scavenging air is then introduced through a series of ports formed in the cylinder walls and uncovered by the piston. This air discharges the exhaust products through the exhaust ports also uncovered by the piston. The piston passes over the dead centre and commences its upward stroke, closing the exhaust ports when the cylinder is filled with pure air.