Engine.
Engine.
An engine is
a mechanical device which is design to convert one form of energy into
mechanical energy.
Example.
·
Heat
engine is use to convert heat energy into mechanical energy.
·
Electric
meter is use to convert electrical energy into mechanical energy.
·
Hydraulic
meter is used to convert pressure fluid into some mechanical work.
·
Molecular
motor found in living things use chemical reaction to do useful work.
Part
of engine.
Engine is
used to produce some power, there are many part of an engine bolted together,
they are used to do some work in connection with each other.
Cylinder block or cylinder.
Cylinder
block is main part of an engine in which combustion (burning of fuel) take
place many other parts such as piston, connecting rods, crankshafts are bolted
in it.
Piston.
Piston is
connected with cylinder block. It move freely up and down. It compress air fuel
mixture and convert fuel energy into mechanical energy. It transmit power to
the crankshaft.
Cylinder head.
Cylinder
head is fitted on the top of cylinder block and the function of cylinder head
is to seal the working end of cylinder block and not to permit entry and exit
of gases, valve, cam shaft, and spark plugs are fitted on it.
Connecting rod.
It connects
piston to the crankshaft and transmit motion.
Classification
of I.C engine.
Classification
of I.C engine are defined below.
1.
According to the design of the
engine.
a) Reciprocating engine (petrol engine).
a. in reciprocating engine the pressure
force is generated by combustion is exerted on the piston and it transmit the
pressure force to crankshaft through connecting rods, so the crankshaft start
to rotate the wheel of vehicle.
b) Rotary engine (winkle engine).
a. In rotary engine a rotor is used
which is free to move when pressure force is exerted on the rotor. It start to
rotate and thus rotate the crankshaft.
2.
According to the type of fuel used.
a) Diesel engine (I.C engine). b) Petrol engine (S.I engine).
c) Gas engine (hot spot engine).
3.
According to the stroke.
a) Two stroke engine. b) Four stroke engine.
c) Six stroke engine.
4.
According to number of cylinder.
a) Single cylinder engine. b) Multi cylinder engine.
5.
According to arrangement of cylinder.
a) Inline cylinder. b) V type cylinder.
c) Opposed type cylinder.
d) W type cylinder.
e) Radial engine.
Spark
ignition (S.I) engine.
Spark
ignition engine generally known as petrol/gasoline engine in an I.C engine,
where the combustion process of air fuel mixture is ignited by spark from spark
plug. S.I engine can run on fuel other than petrol such as auto gas (L.P.G),
compressed natural gas (C.N.G), hydro gas, nitro methane in racing cars.
Ignition
compression (I.C) engine.
I.C engine
are commonly known as diesel engine in an I.C engine in which combustion take
place due to high temperature which the gas (air) achieve when greatly
compressed. Diesel engine work by compressing air, this this increase the air
temperature to such an high extend that it ignite the fuel, diesel engine may be
design either two stroke or four stroke cycle.
Spark ignition (S.I) engine
|
Ignition compression (I.C) engine
|
S.I engine work on Otto cycle or
constant volume heat addition cycle.
|
I.C engine work on diesel cycle or
constant pressure heat addition cycle.
|
S.I engine uses petrol as working
fuel. It is highly volatile fuel.
|
I.C engine uses diesel as working
fuel. It is nonvolatile fuel.
|
In S.I engine a carburetor is used for
air fuel mixture.
|
In I.C engine fuel is injected
directly into combustion chamber with a high pressure thus it consist of fuel
pump and injector.
|
In S.I engine ignition is carried out
with the help of spark plug.
|
In I.C engine ignition is carried out
due to high compression of air.
|
In S.I engine compression ratio varies
from 6 to 10.
|
In I.C engine compression ratio varies
from 16 to 20.
|
Due to the lower compression ratio its
thermal efficiency is lower
|
Due to higher compression its thermal
efficiency is higher.
|
Two
stroke cycle engine.
In a two
stroke cycle engine the working cycle is completed in two stroke of a piston or
one revolution of crankshaft. This is archive by carrying out suction,
compression process in one stroke, expansion and exhaust process in second
stroke.
Four
stroke cycle engine.
In four
stroke cycle engine, the working cycle is completed in four strokes of piston
or two revolution of crankshaft, this is achieved by carrying out suction, compression,
power and exhaust in each stroke.
two stroke cycle petrol engine.
Advantages.
·
A
two stroke cycle engine gives twice the no. of power stroke than four stroke
cycle engine at the same engine speed. Theoretically two stroke cycle engine
should develop twice the power as that of four stroke.
·
For
the same power developed, a two stroke is lighter, less bulky and occupy less
floor area.
·
A
two stroke cycle engine has lighter flywheel, thus it lead to higher mechanical
efficiency as compare to four stroke cycle engine.
·
Initial
cost of two stroke cycle engine is less than four stroke cycle engine.
·
The
mechanism of two stroke cycle engine is much simpler than four stroke cycle
engine.
·
The
two stroke cycle engine are easier to start.
Disadvantages.
·
Thermal
efficiency of two stroke cycle engine is less than four stroke cycle engine
because of less compression ratio as compare to four stroke cycle engine.
·
Overall
efficiency of two stroke cycle is less than four stroke cycle engine because in
a two stroke inlet and exhaust ports remain open, at the time small quantity of
charge lost from engine cylinder.
·
The
consumption of lubricating oil is large in two stroke cycle engine as compare
to four stroke cycle engine.
·
The
exhaust gas in two stroke cycle engine create noise because of short time
available for exhaust.
Four
stroke cycle petrol engine.
It is also
known as Otto cycle, it require four stroke of a piston to complete a cycle.
The four stroke of petrol engine are described below.
1. Suction stroke.
In this stroke, the inlet valve opens and charge is sucked into the
cylinder as the piston move downward from TDC (top dead center) it continues
till the position reaches BDC (bottom dead center)
2. Compression stroke.
In this stroke both inlet and exhaust valve are closed and the charge is
compressed as the piston moves from BDC (bottom dead center) to TDC (top dead
center). As a result the pressure and temperature increased, this complete one
revolution of crankshaft.
3. Expansion or power stroke.
In this stroke shortly before the piston reaches TDC (top dead center)
(during compression) the charge is ignited with the help of spark plug, it
suddenly increases the pressure and temperature of product of combustion, due
to rise in pressure the piston is pushed down with the great force. Hot burnt
gases expend due to high speed piston, during this stroke both valves are
closed and the piston moves from TDC (top dead center) to BDC (bottom dead
center).
4. Exhaust stroke.
In this stroke, exhaust valve is open as piston moves from BDC (bottom
dead center) to TDC (top dead center). This movement of piston pushes burnt
gases out from the engine cylinder. This compile the cycle and engine cylinder
is ready to suck new charge again.
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