Engine

ENGINE
An engine, or motor, is a machine designed to convert
one form of energy into mechanical energy.

OBJECTIVES
 Explain the basic function of an internal
combustion engine.
 Describe the five events required for internal
combustion engine operation.
 Describe selected individuals and events in the
history of engine development.
 Explain principles of 2 - and 4-stroke cycle engine
operation, both S.I. And C.I.

Types of Engine
Internal Engine
Petrol Engine Diesel Engine
External Engine
Steam Engine Turbines

ENGINE TYPES
External Combustion Engines (ECE)
Internal Combustion Engine (ICE)

 INTERNAL COMBUSTION ENGINE (ICE)
 The internal combustion engine (ICE) is a heat engine
that converts chemical energy in a fuel into mechanical
energy, usually made available on a rotating output shaft.
 Chemical energy of the fuel is first converted to thermal
energy by means of combustion or oxidation with air inside
the engine.
 This thermal energy raises the temperature and pressure of
the gases within the engine, and the high-pressure gas then
expands against the mechanical mechanisms of the engine.
 This expansion is converted by the mechanical linkages of
the engine to a rotating crankshaft, which is the output of the
engine.

The crankshaft, in turn, is connected to a tranmission
and/or power train to transmit the rotating mechanical
energy to the desired final use.

 Function - Converts
potential chemical
energy in fuel into heat
energy then to
mechanical energy to
perform useful work.
Chemical
Heat
Mechanical

 EXTERNAL COMBUSTİON ENGİNES (ECE)
Combustion takes place outside the mechanical engine
(include steam engines and gas turbine engines etc.)

Requirements for
I.C. Engine Operation
 All Internal combustion engines
must carry out five events:
 Air-fuel mixture must be brought
into the combustion chamber.
 Mixture must be compressed.
 Mixture must be ignited.
 Burning mixture must expand into
increasing combustion chamber
volume.
 Exhaust gasses must be removed.

Historical Development
of the I.C. Engine
 1862 - Rochas described the basic principles
essential for efficient engine operation.
 1878 – Otto built the first successful 4-stroke cycle
engine.
 1891 – Day built an improved 2-stroke cycle
engine.
 1892 – Diesel patented the compression-ignition
(diesel) engine.
 To present – emphasis on improved engine
efficiency, through refinement.

CAR ENGINE MAIN
STRUCTURE COMPONENTS
 Engine Block
 Camshaft
 Carburetor
 Catalytic converter
 Combustion chamber
 Connecting rod
 Connecting rod bearing
 Cooling fins

 Crankcase
 Crankshaft
 Cylinders
 Exhaust manifold
 Exhaust system
 Fan
 Flywheel
 Fuel injector
 Fuel pump
 Engine head
 Head gasket

 Intake manifold
 Oil pump
 Piston
 Piston rings
 Push rods
 Rocker arm
 Radiator
 Spark plug
 Supercharger
 Throttle

 Turbocharger
 Valves
 Water jacket
 Water pump
 Wrist pin

ENGINE RELATED TERMS
 TDC (Top Dead Center)- Upper side limit of piston to move.
 BDC (Bottom Dead Center)-Lower side limit of piston to move.
 Stroke- The movement of piston in cylinder to move up and down between TDC & BDC.
 Bore- The diameter of cylinder
 Revolution- related rotation of crankshaft to complete cycle.
 Compression Ratio-The compression ratio of an internal-combustion
engine or external combustion engine is a value that represents the ratio of the volume of
its combustion chamber from its largest capacity to its smallest capacity.
 Displacement – The movement of piston moves from TDC to BDC or BDC to TDC.
 Cycle – The process starting from suction then all process done still exhaust . Again this
process start from suction its means complete 1 cycle. 16

ENGINE CLASSIFICATIONS
Internal combustion engines can be classified in a
number of different ways

TYPES OF IGNİTİON
 Spark Ignition (SI)
 Compression Ignition(CI)

SPARK IGNITION (SI)
An SI engine starts the combustion process in each
cycle by use of a spark plug. The spark plug gives a
high-voltage electrical discharge between two
electrodes which ignites the air-fuel mixture in the
combustion chamber surrounding the plug.

 COMPRESSION IGNITION(CI)
The combustion process in a CI engine starts when the
air-fuel mixtures self-ignites due to high temperature in
the combustion chamber caused by high compression.

ENGİNE CYCLE
 Four-Stroke Cycle
 Two-Stroke Cycle

FOUR-STROKE CYCLE
A four-stroke cycle experiences four piston movements
over two engine revolutions for each cycle.

TWO-STROKE CYCLE
A two-stroke cycle has two piston movements over one
revolution for each cycle.

Piston moves from TDC to BDC..
Air –Fuel Mixture come inside
Intake Valve Open & Exhaust Valve Closed.

Inlet valve
open
INTAKE STROKE
The four-stroke engine
Exhaust
valve
closed

Inlet valve
open
Piston down
INTAKE STROKE
Exhaust
valve closed

Inlet valve
open
Piston down
INTAKE STROKE
Fuel in
Exhaust
valve
closed

Compression stroke consist of the piston travelling
back up.
Both intake and exhaust valves are closed
Air fuel mixture is now being compressed

Inlet valve
closed
COMPRESSION STROKE
Piston up
Exhaust
valve
closed

Inlet valve
closed
COMPRESSION STROKE
Piston up
Exhaust
valve closed

The piston is now at the TDC
Spark plug ignites, creating a spark that ignites the
compressed air fuel mixture.
Explosion is created and the piston is forced back
down.
Hence the Power stroke
Both valves are still closed

Inlet valve
closed
POWER STROKE
BANG
Exhaust
valve
closed

Inlet valve
closed
POWER STROKE
Piston down
powerfully
Exhaust
valve
closed

Inlet valve
closed
POWER STROKE
Exhaust
valve
closed

Exhaust stroke the piston is travelling up
Exhaust valve is open
Intake valve is Closed
Exhaust gases being pushed out by piston

Inlet valve
closed
EXHAUST STROKE
Exhaust
valve closed

Inlet valve
closed
EXHAUST STROKE
Exhaust valve
open
Piston up
Exhaust gases
out

Inlet valve
open
INTAKE STROKE
Exhaust valve
closed

BASIC ENGINE CYCLES
 Four-Stroke SI Engine Cycle
 Four-Stroke CI Engine Cycle
 Two-Stroke SI Engine Cycle
 Two-Stroke CI Engine Cycle

FOUR-STROKE SI
ENGİNE CYCLE
Intake Stroke : The
piston starts at the TDC,
the intake valve opens,
and the piston moves
down to let the engine
take in a cylinder-full of
air and gasoline. Only the
tiniest drop of gasoline
needs to be mixed into
the air for this to work.

Compression Stroke :
Then the piston moves
BDC to compress this
fuel/air mixture.
Compression makes
the explosion more
powerful.

Expansion or Power
Stroke : When the
piston reaches the top
of its stroke, the spark
plug emits a spark to
ignite the gasoline.
The gasoline charge in
the cylinder
explodes, driving the
piston BDC (i.e nearly
constant-volume
combustion).

Exhaust Stroke :
Once the piston hits
the bottom of its
stroke, the exhaust
valve opens and the
exhaust leaves the
cylinder to go out the
tailpipe.

FOUR-STROKE CI ENGİNE CYCLE
Intake Stroke : The same as the intake stroke in an
SI engine with major difference : no fuel is added to
the incoming air.

Compression Stroke : The same as in in an SI engine
except that only air is compressed and compression is
to higher pressures and temperature. Late in the
compression stroke fuel is injected directly into the
combustion chamber, where it mixes with the very
hot air. This causes the fuel to evaporate and self-
ignite, causing combustion to start.

Expansion or Power Stroke : Combustion is fully
developed by TDC and continues at about constant
pressure until fuel injection is complete and the
piston has started towards BDC.

Exhaust Stroke : Same as with an SI engine.

Two-Stroke Cycle
Engine Operation

METHOD OF FUEL INPUT FOR SI
ENGİNES
 Carburetor for taking Air- Fuel mixture
 Proper Air- Fuel mixture Ratio.
 Spark Plug
 Correct Valve Timing.

METHOD OF FUEL INPUT FOR CI
ENGİNES
 Multipoint Port Fuel Injection
 Throttle Body Fuel Injection
 Direct Injection
 Indirect Injection

The throttle body injection (TBI)
system uses one or two injector valves
mounted in a throttle body assembly. The
injectors spray fuel into the top of the
throttle body air horn. The TBI fuel spray
mixes with the air flowing through the air
horn. The mixture is then pulled into the
engine by intake manifold vacuum.

Traditional fuel injection systems pre-mix the
gasoline and air in a chamber just outside
the cylinder called the intake manifold. In a
direct-injection system, the air and
gasoline are not pre-mixed; air comes in via
the intake manifold, while the gasoline is
injected directly into the cylinder.

In Indirect Injection sytem, the fuel is injected
into a small pre-chamber attached to the main
cylinder chamber. The combination of rapidly
swirling air in the prechamber and the jet-like
expansion of combustion gases from the
prechamber into the cylinder enhances the mixing
and combustion of the fuel and air.

BASİC DESİGN
 Reciprocating
 Rotary

RECIPROCATING
Engine has one or more cylinders
in which pistons reciprocating
back and forth. The combustion
chamber is located in the closed
end of each cylinder. Power is
delivered to a rotating shaft
output crankshaft by mechanical
linkage with the pistons.

ROTARY
Engine is made of a block (stator) built around a large
non-concentric rotor and crankshaft.

AIR INTAKE PROCESS
 Naturally Aspirated
 Supercharged
 Turbocharged
 Crankcase Compressed

NATURALLY ASPIRATED
No intake air pressure boost system

SUPERCHARGER
Intake air pressure increased with the compressor
driven off of the engine crankshaft.

TURBOCHARGER
Intake air pressure increased with the turbine-
compressor driven by the engine exhaust gas.

CRANKCASE COMPRESSED
Two-stroke cycle engine which uses the crankcase as
the intake air compressor.

FUEL USED
 Gasoline
 Diesel Oil or Fuel Oil
 Gas, Natural Gas, Methane
 LPG
 Alcohol – Ethyl, Methyl
 Dual Fuel
 Gasohol

POSITION & NUMBER OF CYLINDERS
OF RECIPROCATING ENGINES
 Single Cylinder
 In-Line
 V Engine
 Opposed Cylinder Engine
 Opposed Piston Engine

APPLİCATİON
 Automobile, Truck, Bus
 Locomotive
 Stationary
 Marine
 Aircraft
 Small Portable, Chain Saw, Model Airplane

Engine

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