DIESEL ENGINE

1.1 WHAT IS A DIESEL ENGINE
The best way to describe a diesel engine is to look at the following characteristics of the engine:
· RECIPROCATING ENGINE
· INTERNEL COMBUSTION ENGINE
· COMPRESSION IGNITION ENGINE
· TWO OR FOUR STROKE ENGINE

a) Reciprocating Engine (piston)
Reciprocating engines are engines with pistons moving forward and backwards to produce power as opposed to rotary engines. Diesel, engines . petrol and steam engines are examples of reciprocating engines where as turbines are rotary engines,

b) Internal Combustion Engine

Internal Combustion Engines are engines where the fuel is burnt inside the engine rather
outside the engine. In the case of diesel engines the fuel is burnt inside the engine cylinder.

C) Compression Ignition Engine
There are two main types of internal combustion engines -

1. Spark ignition engines and
2. Compression ignition engine.

Petrol engines are spark ignition engines. In petrol engines control amount of petrol and air mixture are drawn into the engine cylinder, compressed and ignited by means of spark through the spark plug.
Diesel engines are compression ignition engines. Maximum amount of air is drawn into the engine, compressed to a temperature sufficient to ignite diesel. Diesel fuel is then injected into the compressed air inside the cylinder and is ignited by the compressed air.

d) Two or Four Stroke Engine
Diesel engines can be four stroke or two stroke engines just like petrol engines. In the
four stroke engines it takes four stroke to complete one cycle namely the intake stroke, compression stroke, power stroke and exhaust stroke.

Fig 1.1 shows the four stroke of a diesel engine.

The difference between the diesel and petrol engine in the intakes is

air/fuel mixture is drawn into the petrol engine whereas

only air is drawn into the diesel engine.


a) INTAKE STROKE
b) COMPRESSION STROKE
c) POWER STROKE
d) EXHAUST STROKE