The document discusses heat engines and internal combustion engines. It defines a heat engine as any engine that converts heat energy from fuel combustion into mechanical work. Internal combustion engines combust fuel within the engine cylinder. The main types are petrol (spark ignition) and diesel (compression ignition) engines. Key parts of internal combustion engines are described like the cylinder, piston, connecting rod and crankshaft. The four-stroke operating cycle and energy balance of internal combustion engines are also summarized.

1. Extracted by:
DEBOLINA MUKHERJEE
From:
IC Engine by
R K RAJPUT

2. HEAT ENGINES
 Any type of ENGINE or MACHINE which derives heat
energy from the combustion of fuel or any other source
and converts this energy into mechanical work is termed
as HEAT ENGINE.
 HEAT ENGINE is classified into:
 External CombustionEngine.
 Internal Combustion Engine.

3. INTERNAL COMBUSTION ENGINE
 In Internal Combustion engine, combustion of the
fuel with oxygen of the air occurs within the cylinder of
the engine.
 The internal Combustionengine is grouped into:
❑ Petrol Engine ( Spark Ignition Engine)
❑ Diesel Engine ( Compression Ignition Engine)

4. ADVANTAGES OF RECIPROCATING
INTERNAL COMBUSTION ENGINE
 Overall efficiency is high.
 Greater mechanical simplicity.
 Weight to power ratio is generally low.
 Generallylow initial cost.
 Easy starting from cold condition.
 This units are compact and thus require less space.

5. CLASSIFICATION OF I.C. ENGINE
According to cycleof operation:
❑ Two Stroke Cycle Engine
❑ Four Stroke Cycle Engine
According to the cycle of combustion:
❑ Otto cycle engine ( Combustion at Constant Volume)
❑ Diesel cycle engine ( Combustion at Constant Pressure)
❑ Duel combustion or Semi- Diesel cycle

6. APPLICATION OF IC ENGINE
❑ Road Vehicles
❑ Aircraft
❑ Locomotives
❑ Construction in civil engineering equipments such as
bull-doser,scraper, power shovels, etc.
❑ Plumbing sets
❑ Cinemas
❑ Hospitals
❑ Several Industrial Applications
IC Engine can be generally used for :

7. ENERGY CYCLE – ENERGY BALANCE OF
IC ENGINE
❑ In an I.C. Engine fuel is fed to the combustion chamber where it burns
in the presence of air and its chemical energy is converted into heat.
❑All this energy is not available for driving the piston, a portion of
energy is lost through exhaust, coolant and radiation.
❑The remaining energy is converted into power and is called Indicated
Energy or Indicated Power (I.P.).
❑The ratio of Indicated Energy to the Fuel energy is called Indicated
Thermal Efficiency.

8. ❑ The Energy available at the piston
passes through the connecting rod
to the crankshaft.
❑ In this transmission of energy or
power, there are losses due to
friction, pumping, etc.
❑ The sum of all those losses, termed
as power is known as frictional
power (F.P.)
❑ The remaining energy is the useful
mechanical energy known as shaft
energy or brake power (B.P.).
❑ The ratio of energy at the shaft to
fuel input energy is called Brake
Thermal Efficiency.
❑ The Ratio of Shaft energy to the
energy available at the piston is
known as Mechanical Efficiency.
ENERGY CYCLE – ENERGY BALANCE OF IC
ENGINE

9. WORKING OF IC ENGINE
❑ The cylinder which is closed at one end is
filledwith a mixture of fuel and air.
❑ As the crankshaft turns, it pushes the
connecting rod.
❑ The piston is forced up and compresses the
mixture in the topof the cylinder.
❑ The air fuel mixture is ignited and as it
burns it creates a gas pressure on the piston,
forcing it down the cylinder. The motion is
shown by arrow 1,
❑ The piston pushes on the rod which pushes
the crank.
❑ The Crank is given rotary or turning motion
as shown by the arrow.

10. PARTS OF IC ENGINE
❑ Cylinder
❑ Cylinder
Head
❑ Piston
❑ Piston Rings
❑ Gudgeon Pin
❑ Connecting
rod
❑ Crankshaft
❑ Crank
❑ Crank case
❑ Engine
bearing
❑ Flywheel
❑ Governor
❑ Valves and
valve
operating
mechanism
PARTS OF PETROL ENGINE
ONLY:
❑ SPARK PLUGS
❑ CARBURETOR
❑ FUEL PUMP
PARTS OF DIESEL ENGINE ONLY:
❑ FUEL PUMP
❑INJECTOR

11. CYLINDER
❑Cylinder contains gas under pressure and guides the Piston.
❑Cylinder is in direct contact with the product of combustion.
❑ The ideal type of Piston consists of plain cylindrical barrel in
which the Piston slides.
❑The upper end of the Cylinder is considered as Combustion or
clearance space in which the combustion of fuel takes place.
❑The Cylinder is made up of a hard grade Cast Iron and cast in
one piece.

12. CYLINDER HEAD
❑ Oneend of the
cylinder isclosed by a
CylinderHead or
CylinderCover.
❑Two types of cylinder
head are:
o Air Cooledcylinder
o WaterCooledcylinder
❑ CylinderHead usually
contains, Inletvalue
and Exhaustvalve.

13. PISTON
❑ Pistonis fittedto each cylinderas a face to receive gas pressure and
transmitthe thrust to the connecting rod.
❑ Pistonmoves up and down withinPistonCylinder. Thisup and down
motion is called the reciprocating motion.
❑ Functionsof Piston:
o To givean gas tightseal to thecylinderthrough bore.
o To slide freely.
o To be light.
o To be strong.
❑ Pistonaremade of Cast Iron and Aluminum alloyfor lightness.

14. PISTON RINGS
❑ The Piston must be a fairly loose fit
in the Cylinder.
❑ If the Piston have a tight fit then it
might expand due to high
temperature and might stick to the
walls of the Cylinder. On the other
hand if there is too much clearance
between the piston and Cylinder
walls, much of the hot gases of
combustion will leak past the Piston.
❑ To provide a good sealing fit
between the Piston and the Cylinder,
Piston are equipped with Piston
Rings.
❑Piston rings are usually made of
Cast Iron. Some Piston rings are made
of alloyspring steel.

15. WORKING OF PISTON RINGS
❑ The outer surface of the cylindrical Piston have Grooves for fitting the
Piston Rings.
❑ The design of the Piston Rings are such that they are spitted at one
end. The Piston Rings are fitted into the grooves of the Piston .
❑ Piston Ring form a good seal between Piston and Cylinder wall.
❑ When the Piston is installed within the cylinder, the rings are
compressed into the ring grooves of the cylinder, so that the Piston Ring
grooves almost come together and fit into the groove between Piston
and cylinder wall.
❑ The Piston Rings can expand and contract within the grooves of the
cylinder as they get heated and cooled and can form a seal between the
Piston and Cylinder wall.

16. WORKING OF PISTON RINGS
❑ The diagram shows how the Piston ring
works to hold the compression and
combustion pressure.
❑ The arrows shows the pressure above the
Piston and the Cylinder wall.
❑ The Piston rings ensure good seal
between the Piston and the Cylinder even at
high pressure.

17. CONNECTING ROD
❑ ConnectingRod connects the Pistontothe Crank.
❑Connecting Rod transmitsthe Pistonload to the
Crank causing the Crank to turn.
❑ The loweror “ big end” of the Connectingrod turns on
“ Crank Pin”.
❑The Pistonendof theconnecting rod is called “small
end” and the Crankend of the Connecting Rod is called
“big end”.
❑ Connecting Rod is made up of nickel, chromeand
chrome vanadium steel.
❑ Forsmall enginesthe materialsmay be aluminum.

18. CRANK
❑ The Piston moves up and down
withinthe enginecylinder.
❑ The reciprocating motion of the
Piston is converted to rotary motion
with the help of Crank and
ConnectingRod.
❑ This rotary motion is required to
make wheels turn.

19. CRANK SHAFT
❑ The Crankshaftis a shaft that is
connected to theConnecting Rod
throughthe Crank.
❑ As the Pistonmoves up and down,
the ConnectingRod connectedto it
also moves up and down and the
Crankconnected to the Connecting
Rod startsrotatingthuscausing the
Crankshaftto rotate. Thewheels
connected to theCrankshaftalso
rotatesas the Crankshaftrotates.
❑ Crank shaft is made of forged steel.

20. SPARK PLUG
❑ The Spark Plug is a device that produces
spark in the ignitionchamber for the
combustion of fuel.
❑ The Spark Plug consistsof a metal shell
having two electrodes which are insulatedfrom
each otherthroughan air gap.
❑The high ampcurrent supplied through the
supplyelectrode produce the necessary spark.
❑ Porcelain is used as the insulatingmaterial in
Spark Plug. Mica isalso used as the insulating
material in Spark Plug.

21. ❑ Spark Plug must withstandpressure upto
55 bar.
❑ It must provide suitable insulation
between two electrodes toprevent short
circuiting.
❑ It must withstanda high temperature
upto 2000 ⁰ C and 2500 ⁰ C.
❑ It must possessa high temperature
resistanceso that the electrodedo not
become sufficientlyhot tocause the
preignitionof the charge / fuel withinthe
enginecylinder.
QUALITY REQUIRES IN SPARK PLUG

22. SIMPLE CARBURATOR
❑ The function of Carburetor is to atomizeand
meter the liquid fuel and mix it with the air as it
enters the induction systemof the engine,
maintaining underall conditions of operations the
correct fuel- air proportion.
❑ The diagram showsa Simple Carburetor .
❑ L = float chamber for the storage of fuel.
❑ F= filter.
❑ M= floatvalve
❑ N = Jet from which fuel is sprayed
❑ S = Inlet
❑ R = Throat / Venturi
❑ Q = Induction Manifold
❑ T = Throat Valve

23. SIMPLE CARBURATOR
❑ The diagram showsa Simple Carburetor.
❑ L is the float chamber for the storage of
fuel.
❑ The fuel supplied under gravity action or by
fuel pump enters the float chamber
through the filter F.
❑ The arrangement is such that when the oil
reaches a particular level, the float valve M
blocks the inlet passage and thus cuts off
the fuel oil supply.
❑ On the fall of oil level, the float descends
down consequently intake passage opens
and again the chamber is filled with oil.
❑ Then the float and the float valve
maintains a constant fuel oil level in the
float chamber.
❑ N is the jet from which the fuel is sprayed
into the air stream as it enters the
Carburetor at the inlet S and passes
through the throat / venturi R. The fuel
level is slightly below the outlet of the jet
when the carburetoris inoperative.
❑ As the Piston moves down through the
engine cylinder, vacuum is produced in the
engine cylinder as well as in the induction
manifold Q as a result of which air flows
through the Carburetor. The velocity of air
increases as it passes through the
construction at the venturi R and pressure
decreases due to the conversion of a
portion of pressure head into kinetic
energy.
❑ Due to decreased pressure at the venturi
and by virtue of differenceof pressure
( between the float chamber and venturi )
the jet sprays fuel oil into air stream.
❑ Since the jet has a very fine bore, the oil
flowing from the jet is in form of fine spray,
it vaporizesquicklyand mixes with air.
❑ The air-fuel mixture enters the engine
cylinder, its quantity being controlled by
varying the position of the Throttle valve T.

24. FLYWHEEL
❑ Flywheel is a Steel or Cast Iron disc that is
mountedon the Crankshaft.
❑ Flywheel is the componentof the IC
enginethat is mountedon the Crank Shaft.
❑ Flywheel helps in the following function:
o Startingtheengine.
o Overcomes thefluctuation of load.
o Makes theCrankshaft rotatesmore
uniform.

25. GOVERNOR
 Governor is a device that controls the output of a machine
or engine by regulating the Working fluid supplied i.e
controlling the supplyof fuel.
 Types of GOVERNOR:
❑ Centrifugal Governor
❑ Inertia Governor