Tuesday, May 12, 2015

Diesel Generator working principle; Four and two stroke Diesel Generator

In Diesel generator there is Diesel engine which acts as a primary mover, Diesel engine drives an alternator to produce the electricity. In diesel engine air is compressed to a high ratio ranging from 14:1 to 25:1. During this compression, the air is heated to a temperature of 700–900°C. Depending upon the requirement quantity of diesel fuel is then injected into the cylinder, which ignites spontaneously because of the high temperature.

That is why diesel engine is also known as compression ignition engine.

DG has two types
1.      Two stroke and
2.      Four stroke.

Mostly engines use the four stroke cycle. Here below is the working principle of four stroke engine.

Four Stroke - Diesel Engine

There are 4 stroke as below which takes place in Diesel Engine:
(a)    Induction stroke
(b)   Compression stroke
(c)    Ignition & Power Stroke
(d)   Exhaust stroke.

Induction stroke
Inlet valve is open the descending piston draws in fresh air.

Compression stroke
When the valves are closed the air is compressed to a pressure of up to 25 bar.

Ignition and power stroke
Fuel Injection takes place in this stoke, while the valves are closed the fuel ignites naturally and the piston is forced downwards by the burning gases.
Exhaust stroke
The exhaust valve is open and the rising piston discharges the spent gases from the cylinder.

Diesel generator working; DG four Stroke

From above working we have seen that power is developed only in one stroke so a single cylinder four stroke engine could not serve the purpose. So for Smoother operation multi cylinder engines are used because the cranks are staggered in relation to one another on the crankshaft.

There are many variations of engine configuration e.g.
(i)                  4 or 6 cylinder
(ii)               In-line
(iii)             Horizontally opposed
(iv)             Vee or radial.