Supercharging

The principle of supercharging is in supplying more air to the combustion chamber than the atmospheric pressure permits.

When more air and fuel burn in the cylinder, more power is received from the engine.

By fitting a special device the necessary amount of air is supplied into the cylinder. This device is called a supercharger. A supercharger is an air pump that takes air out of the surrounding atmosphere, compresses it to a higher pressure and delivers it to the inlet valve or port of an engine.

Thus, we get an engine of greater power for the same dimensions and almost the same weight.

Experiments show that by supercharging a diesel the power output is increased from 20 to 80 per cent over the normal rating. In order to increase the air pressure in a four-stroke engine, the air charge is pushed in by higher pressure, produced by a separate air pump or a supercharger. When a supercharger is applied to a four-stroke engine, the main change required in the engine design, is a change in the timing of the intake and exhaust valves. The two valves are designed to be opened simultaneously from about 80 to 160 degrees. The selection depends upon the normal engine speed.

A two-stroke engine usually has a blower to obtain scavenge air and its supercharging is obtained by increasing the amount and pressure of scavenging air. In addition, a slight change of the exhaust and scavenge timing is made in order to retain more scavenge air at the beginning of the compression stroke.

supercharger, n нагнетатель, воздуходувка,

компрессор

supercharging продувка

combustion chamber камера сгорания

permit, v разрешать, допускать

power output выходная мощность

rating мощность

fit, v устанавливать

device, n устройство, прибор

dimension, n размер

weight, n вес

change, v, n изменять; изменение

retain, v удерживать

timing регулировка

slight, adj небольшой, незначительный

in addition в добавление, кроме того

supply, v подавать, обеспечивать

surround, v окружать

require, v требовать

apply, v применять

selection, n выбор (зд. переключение)

simultaneously, adv одновременно

obtain, v получать

depend on, v зависеть от

in order to для того, чтобы

normal, adj нормальный, обычный

same, adj одинаковый

design, v, n конструировать,

предназначать; проект,

конструкция

Fuel Injection

The function of the fuel injection mechanism is to put the correct amount of fuel into the cylinder of the engine at the proper time under the right pressure and to ensure good mixing the air and the fuel for complete burning.

At present there are three principal methods of mechanical injection:

1. Direct injection or open combustion chamber method.

2. Pre-combustion chamber method.

3. Air turbulence method.

1. During the direct injection method the fuel is injected directly into the combustion chamber through a spray nozzle and under sufficient pressure. It is done in order to carry the fuel particles into the mass of the compressed air, the injector being fitted into the cylinder head.

The loss of heat during the compression is a minimum, the delay combustion period being short. This method of fuel injection gives better starting from the cold.

2. With a pre-combustion chamber method the cylinder head has a smaller combustion chamber communicating with the cylinder head through a neck.

The compressed air circulates in this chamber, at a certain moment the fuel being injected into the chamber. The fuel immediately begins to ignite. The mixture of burning and unburnt fuel passes from the pre-combustion chamber into the cylinder through the communicating neck.

3. The air turbulence method is used in several types of engines.

This method provides efficient atomizing and mixing the fuel particles with the air at the end of the compression stroke. As the volume of the injected fuel is very small in comparison with the volume of compressed air, the holes in the nozzle must be very fine and numerous. The pressure required to obtain the necessary penetration of the fuel must be very high and the sprays must have a sufficient depth of penetration to reach all the compressed air in the cylinder head.

direct injection method метод прямого впрыска

pre-combustion chamber method метод предкамерного

смесеобразования

air turbulence method вихрекамерный метод

смесеобразования

sufficient, adj достаточный

particle, n частица

amount, n количество

loss, n потеря

delay combustion period период задержки

воспламенения

smooth, adj плавный

neck, n канал

mixture, n смесь

обеспечивать

provide, v

insure, v

atomizing распыление

in comparison with в сравнении с

numerous, adj многочисленный

penetration, n проникновение

depth, n глубина

pass, v проходить