Inside Knowledge about Diesel Engines

Inside Knowledge about Diesel Engines

One of the most reliable internal combustion engines around

is the diesel engine. In many industrial installations, diesel

engines are used as prime movers for the generation of

electricity and for emergency air compressors.

It’s true that they are rugged, but one of the most important

advantages of these engines is the fact that they can be

started by manual cranking. In remote areas, diesel engines

can be counted upon for starting up from scratch.

Once a small diesel engine is started, it can be used to drive

a small electrical generator that can then be used to produce

electrical supply for driving other machines like pumps,

compressors, and for lighting.

How does a diesel engine work?

First there must be combustion of fuel. As we have discussed

in our previous articles, combustion or burning of fuel occurs

whenever there is sufficient heat, fuel and oxygen. When

conditions are just right, combustion can be very rapid. Rapid

combustion causes an explosion in an enclosed area. This is

because of the rapid built-up of hot gases during the process.

In an internal combustion engine like a diesel engine, this

rapid combustion, and built-up of hot gas pressure is used to

push a piston away from the enclosed combustion space.

The piston is attached to a crankshaft through a connecting rod.

Because of this, the engine is able to convert the linear

movement of a piston to a rotating movement of a crankshaft.

The outward movement of the piston turns the crankshaft. However,

the momentum of the turning crankshaft forces the piston back

again towards the engine combustion space in a reciprocating


Once the piston moves away from the combustion space, the

pressure drops. The next stage of operation depends on the

design of the engine. These can be either 2-stroke or 4-stroke


Regardless of the type of design, the spent exhaust gas is

first driven out, and then new fresh air is drawn back into

the combustion chamber.

After this, the rotating crankshaft drives the piston to

compress the fresh air inside the combustion chamber. The

piston acts as a reciprocating compressor at this stage.

The compression of the air causes the latter to become hot – hot

enough to ignite finely distributed fuel particles.

At this moment, fuel is sprayed in at high pressure. The tiny

sprayed fuel particles form a mist inside the combustion chamber.

What do think will happen when you have heat, fuel and oxygen?

A fire! Each tiny particle of the fuel burns rapidly, and an

explosion occurs.

The cycle starts again, and the crankshaft turns continuously,

the pistons move continuously, and the engine runs.

How does the engine know when to spray fuel, let in air, compress

the air, and exhaust the spent combustion product?

Well folks, start your engines.

Until next time…

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