Tài liệu Lesson 12-Marine Diesel Engines (3) pdf

Lesson 12-Marine Diesel Engines (3)

Indeed, a diesel engine is really a very complex and complicated combination of

thousands and thousands of elements. Apart from its various parts, there are also a few

auxiliary systems in a diesel engine. They are as follows:

1.The Fuel Injection System

The fuel injection system, in delivering the liquid fuel to the combustion chamber, must

fulfill the following assignments:

A: To measure the correct quantity of the fuel to be injected.

B: To time the fuel injection.

C: To control the rate of fuel injection.

D: To atomize or break up, fuel into fine particles.

E: To distribute fuel properly in the combustion chamber.

2. The Combustion System

There are three basic models of combustion chambers, namely, direct injection or

open chamber, swirl chamber and pre-combustion chamber.

Whether the engine is a four-stroke one or a two-stroke one is not of radical

significance, but there is in fact less freedom of choice with two-stroke engines because

with the two-stroke cycle it is necessary to maintain a pattern of scavenge flow as well as

a pattern of combustion air movement in the meanwhile. The trouble is that combustion

chambers that produce a very vigorous air movement may disrupt the scavenge pattern

and so a relatively quiescent chamber is to be preferred for two-stroke engines.

Fig. 12.1

3. The Lubrication System