Page 52 - Mechanic Diesel - TT

MECHANIC DIESEL - CITS

Two stroke engine - Petrol is used as fuel in these types of engines and they are used in applications where a
simple and low cost prime mover is required; Like scooter, motorcycle etc. In two stroke petrol engines, usually all
four strokes of the engine operating cycle (suction, compression, power and exhaust) are completed in just two
strokes of the piston.
In these types of engines, the fuel combustion time is short while the fuel consumption per horse power is high.
Principle - In two stroke petrol engines, a working cycle is completed in just two strokes of the piston, that is, the
engine gets power in every revolution of the crank shaft. This power is obtained as a result of combustion of the
mixture of air and petrol in the engine’s crank case. These engines are based on Otto cycle.

Four stroke engine - Spark ignition engine is also called petrol engine. In these engines petrol and air mixture is
compressed in the combustion chamber through the spark plug. Power is generated by igniting. For this reason,
this type of engine is called spark ignition engine. This type of engines is mostly used in the automobile sector. In
this, to burn fuel (petrol), it is necessary to make arrangements like carburetor, ignition coil, spark plug, distributor
and battery etc.
The torque of this engine is low. Therefore, there is no need to make its parts very strong. Generally, all four
strokes of the engine operating cycle (suction, compression, power and exhaust) are completed in just four
strokes of the piston.
In this type of engines, there is only one action in one stroke and one spark is available per cylinder for every
two revolutions and their fuel consumption per horse power is also less. The most important thing is that in these
engines valves are used instead of ports
Principle - In four stroke petrol engine one cycle completed when the piston completes its four strokes.

Therefore, one working cycle is achieved only when the suction, compression, power and exhaust strokes of
the engine are completed, that is, in one working cycle of the engine, the crankshaft completes two cycles. Four
stroke petrol engines are also based on Otto cycle.

Diesel engine - Compression ignition engine is also a type of internal combustion engine. In these, diesel is
used as fuel and it is used as fuel in airless form. In these, fuel ignition occurs due to temperature increase in the
cylinder as a result of combustion of the engine.
Principle - Compression ignition engine is also called diesel engine. In these engines, only air is compressed in
the combustion chamber, due to which the pressure and temperature of the air increases. In this compressed air,
a fine spray of diesel is sprayed through the injector, due to which combustion starts in the combustion chamber
and the engine starts getting power. This engine (compression ignition engine) works on the principle of diesel
cycle.
Two stroke diesel engine - Diesel is used as fuel in this type of engines and these engines are generally used
in ship propulsion. These engines are not very flexible due to their lower governed (ii) speed; Like- ship engine.
Principle - Two stroke based diesel engines are based on diesel cycle. In these, power is obtained as a result
of combustion of diesel vapor and compressed air. In this type of engine, one working cycle is completed in
two strokes of the piston, that is, all four strokes of the engine (suction, compression, ignition and exhaust) are
completed in only two strokes of the piston.
Like a two-stroke petrol engine, in a two-stroke diesel engine, power is obtained in each cycle of the crankshaft.

Four stroke engine - Generally, in these engines, all four strokes of the engine operating cycle (suction,
compression, power and exhaust) are completed in four strokes of the piston. In this type of engines, there is only
one action in one stroke and one spark is available per cylinder for every two revolutions and the fuel consumption
per horse power is less in these engines. The most important thing is that in these engines valves are used
instead of ports. Such engines are often used in petrol and diesel engines like two-stroke engine.
Principle - In a four stroke petrol engine one working cycle is completed in four strokes of the piston. Therefore,
one working cycle is achieved only after the suction, compression, ignition and exhaust strokes of the engine are
completed, that is, in one working cycle of the engine, the crankshaft completes two cycles. Four stroke petrol
engines are based on Otto cycle.

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CITS : Automotive - Mechanic Diesel - Lesson 08 - 10