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Petrol's and Diesel Engines
By : Asad Ali ArshadPetrol’s and Diesel Engines:
What is Engine?
An engine is a machine that is
designed to convert one form of energy into mechanical form.
The main
parts of Engines:
Cam Shaft takes up and down motion of piston and converts it
into rotating motion. Valves there
are two types of value intake and exhaust as from the name intake value are
used to transfer fuel inside the cylinders and exhaust value is used to exhaust
the burning fuel outside to the environment. Engine head is the head of engine on which the spark plug in
mounted. Spark plug is used to
provide the spark in each cycle to burn the petrol (in petrol engine). Injector
it sprays the fuel (used in diesel engine). Cylinders combustion is take place in cylinder. Piston oil control ring. Connecting Rod connects the piston and
crankshaft. Crankshaft is used when
the multiple pistons are used in an engine in order to convert the each piston
up and down movement into rotation. Flywheel
is attached with the gear train and delivers the power. Gear Train is used to increase or decrease the speed.
Important Terminologies we learn.
Internal Combustion Engine? is an engine in which the combustion of a fuel
occurs in a combustion chamber. External
Combustion Engine? Is an engine in which the combustion takes place in an
external source it is also known as heat engine. Top dead Center the furthest point of a piston's travel, at
which it changes from an upward to a downward stroke. Bottom dead
center the furthest point of a piston's near to crankshaft, at which
it changes from downward to upward stroke. Stroke a stroke refers to the full travel of along the cylinder. Intake Stroke this stroke of the piston
begins at top dead center. The piston descends from the top of the cylinder to
the bottom of the cylinder. A mixture of fuel and air is forced by atmosphere
pressure into the cylinder through the intake port. Compression Stroke when both the intake and exhaust valves are
closed, the piston returns to the top of the cylinder compressing the air or
air-fuel mixture. Power Stroke while
the piston is close to top death center, the compressed air-fuel mixture in a
gasoline engine is ignited, by a spark plug. The resulting pressure from the
combustion of the compressed fuel-air mixture forces the piston back down
toward the bottom dead center. Exhaust during
the exhaust stroke piston once again returns to top dead center while the
exhaust valve is open.
Four
functions known as intake, compression,
combustion and exhaust these
four functions are required to produce a final power stroke. Without these
function no internal combustion engine in the world can work whether it is a
two strokes, four strokes or Wankel engine.
2 Stroke Engines is a type of internal combustion engine which
completes a power cycle in only one crankshaft revolution and with two stroke,
or up and down movements, in short it complete the above four functions intake,
compression, combustion and exhaust in two stroke. Intake and compression in
one stroke and combustion and exhaust in second stroke.
4 Stroke Engine is a type of internal combustion engine in which the
piston completes four separate strokes which comprise a single thermodynamics
cycle.
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Two Stroke Engines
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Four Stroke Engines
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It completes power
cycle within two strokes.
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It completes power
cycle within four strokes.
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In two strokes the end of the
combustion stroke and beginning of the compression stroke take place
simultaneously.
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In four strokes the end of the
combustion stroke occurs separately and beginning of the compression stroke
occurs separately.
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Two stroke engines have high power to
weight ratio.
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Four stroke engines have low power to
weight ratio.
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Two stroke engines have a greatly
reduced number of moving parts and so can be more compact.
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It has more parts.
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Don’t have valve. It has
ports.
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Don’t have ports. It has
valve.
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Cheaper to construct.
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Expensive to construct.
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It is not fuel
efficient.
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It is fuel efficient as
compared to two stroke.
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Low life.
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High life.
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Which one is better?
At
the end of the day the winner is probably going to be the one that has had more
money and technology spent on it. In these days of quick and cheap
international production schedules you can’t take it for granted that the 4
stroke will be better. So for a particular application, we should try to line
up the options and make a decision based on what’s available, not based on
lists that miss the key points of difference.
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Petrol Engines
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Diesel Engines
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It works on Otto Cycle.
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It works on diesel
cycle.
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§ In
petrol engine the air and petrol are mixed in carburetor and it enters into
the cylinder.
§
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In diesel engine the fuel is first fed
into the cylinder by a fuel injector and then gets mixed with air inside the
cylinder.
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In petrol engine first the compression
of air and petrol is done and then it is ignited by an electric spark.
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In diesel engine only the charge of
air is compressed and ignition is done by the heat of compressed air.
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Its compression is low.
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Its compression ratio
is high.
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In petrol engine we use
spark plug for ignition.
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In diesel engine we use
injector for ignition.
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Power developed is low due to low
compression ratio.
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Power developed is high due to high
compression ratio.
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The fuel that burns has
high volatility.
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The fuel that burns has
low volatility.
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It used in light weight vehicles like
in cars, motorcycles, scooters etc.
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It used in heavy weight vehicles like
in cars, motorcycles, scooters etc.
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