1. What is an engine ?
An engine is a mechanical system which transforms heat energy into mechanical energy
using fuel.

There are generally two types of engine: internal and external combustion engines.


1. Internal combustion engines are divided based on the following :

1) Type of fuel - diesel, petrol and gas.
2) Stroke – four-stroke and two-stroke.
3) Cylinders - single and multiple cylinders.
4) Cooling system.


2. What is a diesel engine ?

The diesel engine is a type of internal combustion engine, more specifically, a
compression ignition engine, in which the fuel isignited by the high temperature of
compressed gas, rather than a separate source of energy (such as a spark plug).

How diesel engines work - When gas is compressed its temperature rises. A diesel engine exploits this property in
order to ignite the fuel. Air is drawn into the cylinder of a dieselengine, and compressed
by the rising piston. This happens at a much higher compression rate than in a sparkignition
engine. At the top of the piston stroke diesel fuel is injected into the combustion
chamber at high pressure through an atomising nozzle. It mixes with the hot, pressurised
air. The resulting mixture ignites and burns very rapidly. This contained explosion causes
the gas in the chamber to expand, driving the piston down with considerable force, and
creating power in a vertical direction. The connecting rod transmits this motion to the
crankshaft which is forced to turn, delivering rotary power at the output end of the
crankshaft. ‘Scavenging’ - pushing the exhausted gas-charge out of the cylinder and
drawing in a fresh draught of air - is done through ports or valves.
A vital component of any diesel engine system is the governor, which limits the speed of
the engine by controlling the rate of fuel delivery.

Diesel engine working principles
· Suction stroke
· Compression stroke
· Power stroke
· Exhaust stroke

Fuel and fluid characteristics
Diesel fuel is a product of crude oil, although other oils can be burned inside an adapted
engine. Good quality diesel fuel can be synthesized from vegetable fat and alcohol.
Diesel engines can work on thicker, heavier oil, or oil with higher viscosity, as long as it is
heated in order to ease pumping and injection. These fuels are cheaper but dirtier than
clean, refined diesel oil.

Diesel fuel is more difficult to ignite than gasoline because of its higher flash point, but
once burning, a diesel fire can be extremely fierce.
The use of low-grade fuels can lead to serious maintenance problems.


3. Diesel engine supporting systems

A number of systems are in place for proper operation of an engine
· Intake and exhaust system
· Starting system
· Fuel system
· Cooling system
· Lubricating system

3.1 Intake system and exhaust system
· The function of this system is to allow the purified air to the cylinder
Components :
· The system is composed of Air cleaner,
· Intake manifold,
· Intake valve,
· Super charger etc.

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