Thursday, March 24, 2011

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 
movement.
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 
designs.
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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Thomas Yoon's skill in illustration/writing has enabled him to produce numerous ebooks on engineering subjects that can be downloaded at Engineering E-books. He has also produced an ebook on "50 Secrets of Truth and Life" that is fully illustrated with cartoons in a humorous way. Subscribe to facworld ezine More information at Marine Engineer andM & E Engineer

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