PEPM
AEL2501
Automotive Engines
Lecture delivered by:
Prof. Ashok C.Meti
MSRSAS--Bangalore
MSRSAS
M.S Ramaiah School of Advanced Studies - Bangalore
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Session Objectives
• To understand the classification of
automotive engines.
• Study the constructional features and
arrangement of various parts of IC engines.
• Discus the new developments to improve
the low-end performance of an engine
• Understand the lubrication system and
cooling system of an IC engine
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Topics
•
•
•
•
•
Introduction to automotive engines
4S, Petrol and Diesel engines
Main engine components
Cooling system
Lubrication system
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Introduction to Automotive Engines
• An automotive engine is a complex piece
of precision
precision--built machinery.
• It provides power to drive the vehicle’s
wheels.
wheels
• In addition, it is also a source of power to
other sub-systems like– charging,
– a/c unit,
– hydraulic system for power steering,
suspension, etc.
• The engines used in automobiles are also
known as internal combustion engines as
the burning of air and fuel mixture takes
place inside the cylinder
cylinder.
Ex: The mHawk Engine
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Engine classification
Some engine classifications include:
• Cylinder arrangement
– In-line*, V engine, opposed
piston / flat engine
• Type
yp of fuel burned
–
–
–
–
Diesel*
Petrol
CNG / LPG
Dual fuel engine
• Type of ignition
– Compression ignition*
– Spark ignition
• Number of strokes / cycle
– 4 – stroke cycle*
– 2 – stroke cycle
• Cooling system type
– Water cooled engine*
– Air cooled engine
• Type of aspiration
– Naturally aspirated engine
– Turbo* / super charged engine
• Number of valve / cylinder
– 2 valves per cylinder*
– Multi valve engines
• Valve location
– L – head engine
– I – head engine ( OHV)*
• Camshaft location
– Overhead cam engine
– Cam in the block engine*
• Combustion chamber design
– Shapes: Pancake, wedge,
hemispherical, pent roof, precombustion chamber
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In-line Engines
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V- Engines
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Horizontally Opposed
PORSCHE 911 Carrera –flat 6, 3.8 Lt. 283 kW (380bhp), DFI
120bar multiple injection (at high load and speed<3500rpm), CR
12.5:1, 7 speed DCT,2W/4W, 0-100kmph in 4.3s, VarioCam+
Valve system,
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Four Stroke Petrol Engine Operation
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Four-stroke cycle: Diesel Engine
The four strokes of the engine
operation requires 2 rotations of
the crankshaft.
crankshaft
1 IInduction
1.
d ti St
Stroke
k
•
•
•
Starting from TDC, the piston
moves downwards.
The inlet valve also opens at the
same time and air is drawn into
cylinder with out restriction by a
throttle valve.
valve
When the piston reaches the
BDC, the cylinder capacity is the
largest.
largest
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2. Compression stroke
•
•
•
•
•
The inlet and exhaust valves are
closed.
closed
The piston’s upward movement
compresses the air to the degree
d
determined
i d by
b the
h compression
i
ratio (16:1 to 24:1).
The air, in this process, heats up to
9000C.
Near the completion of the
compression stroke, the fuelinjection system injects the fuel at
high pressure (as much as 2000
bar in modern engines) in to hot
compressed air in the CC.
When the cylinder reaches the
TDC, the cylinder capacity is at its
minimum.
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3. Ignition stroke
•
•
•
•
•
After the ignition lag (a few
degrees of C/s rotation) the
ignition stroke begins.
The finely atomized and easily
combustible
b ibl diesel
di l fuel
f l
spontaneously ignites and burns.
As a result, the cylinder charge
heats up even more and pressure
in the cylinder rises.
The mass of the fuel injected
(quality based control) determines
the amount of energy released.
The pressure forces the piston
downwards. The C/s drive
translates the KE of the piston into
torque.
torque
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4. Exhaust stroke
•
•
•
Just before the piston reaches
the BDC,, the exhaust valve
opens.
opens
The hot pressurized gases flow
out of the cylinder.
The upwards movement of the
piston forces the remaining
exhaust gas out of the cylinder.
cylinder
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Piston Assembly
• The piston converts the potential
energy of the combustion gases, into
the kinetic energy that turns the
crankshaft.
• The piston is a cylindrical shaped
hollow part that moves up and down
inside the engine's cylinder.
• It has grooves around its perimeter
near the top where rings are placed.
• The wrist pin connects the piston to
the connecting rod. The connecting
rod comes up through the bottom of
the piston.
• The wrist pin is inserted into a hole
( b
(about
half
h lf way up)) that
h goes through
h
h
the side of the piston, where it is
attached to the connecting rod.
• Pistons are usually made of aluminum
alloy, because it is light and a good
heat conductor.
Diesel Engine Piston
Petrol Engine Piston
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• Pistons perform several functions.
– Transmit the driving force of combustion to
the crankshaft. This causes the crankshaft
to rotate.
– Also acts as a moveable gas-tight plug that
keeps the combustion in the cylinder.
– Acts as a bearing for the small end of the
connecting-rod.
• The piston head or "crown
crown" is the top
surface against which the explosive
force is exerted. It may be flat,
concave, convex or any one off a great
variety of shapes to promote turbulence
or help control combustion.
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Crank Shaft
AEL2501
• The crankshaft converts the reciprocating motion of the pistons into a
turning (rotary) motion.
• The crankshaft is usually either alloy steel or cast iron.
• The crankshaft is connected to the pistons by the connecting-rods.
• Some parts of the shaft do not move up and down; they rotate in the
stationary main bearings. These parts are known as journals.
• There are usually five journals in a four cylinder engine
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Engine Block
Typical Cummins Engine Block
• A metal casting containing the cylinders and cooling ducts of an
engine
engine.
• All other sub-systems are bolted to the block.
• Cast Iron or Aluminum alloys are used to build the blocks.
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Cylinder sleeves or liners
• They are inserts that fit
into the cylinder block
• They
h act as cylinder
li d walls
ll
for the piston to
reciprocate
• Many vehicles use
aluminum or CI cylinder
blocks with cast iron, wet
sleeves
l
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Engine Head
• The cylinder head is the metal part of the
engine that encloses and covers the
cylinders.
• Bolted on to the top of the block, the
cylinder
y
head contains combustion
chambers (petrol engine), water jackets
and valves (in overhead-valve engines).
• The head gasket seals the passages within
the head-block connection, and seals the
cylinders as well.
Typical Diesel Engine Heads
Typical School
Petrol Engine
HeadStudies - Bangalore
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of Advanced
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Diesel combustion chambers
Indirect Injection:
• In indirect injection, the fuel is injected into a separate chamber that is connected to the
main chamber above the piston by a narrow passage-way.
• When the piston rises toward top-dead-center, the air is forced through the connecting
passage att high
hi h velocity
l it into
i t the
th small
ll chamber,
h b called
ll d a swirl
i l chamber.
h b
• The high velocity air rotates at high velocity in the chamber as fuel is injected.
• A glow plug inserted into the chamber helps during cold starting.
• This type of system relies on the high velocity air swirl to mix the air so the fuel
injection system can operate at lower pressures and be less expensive.
• After the fuel ignites, the combusting mixture pushes back out through the passage-way
where the rise in pressure does work on the piston.
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Direct Injection:
• In the direct injection diesel engine, the
fuel is sprayed into the combustion
chamber directly above the piston.
• The ppiston usuallyy has a recess or bowl
that is designed to confine the air into a
region that matches the fuel spray
trajectory.
• This type of system relies primarily on
the momentum of the fuel spray to mix
the fuel and air.
•
•
The indirect injection (IDI) engine is less
efficient than the direct injection (DI)
engine
engine.
This is because the high velocity air
motion in the combustion chamber causes
high heat transfer rates resulting in greater
loss of fuel energy.
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Valve Train
•
•
•
The valve train consists of the valves
and a mechanism that opens and closes
them.
The opening and closing system is
made upp of a camshaft and rocker
arms.
arms
The camshaft has lobes on it that move
the valves up and down.
Diesel Engine Cam shaft
Poppet valves
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Common valve mechanisms
Overhead cam engine with OHV
Valve in block or L-head
Cam-in-block / I –head
(pushrod valve M/sm
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Valve Timing Diagram – Petrol Engine
(Advanced inlet gives more top end power at the expense of low end power, and vice-versa)
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Valve Timing Diagram – Diesel Engine
SOC- start of combustion
IO- Inlet open
IC- Inlet close
IP- Injection point
EO-Exhaust open
EC-Exhaust close
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Flywheels
• A flywheel is bolted to the
crankshaft flange
• The flywheel is also fitted
with a ring
w
g ge
gear to
ow
which
c thee
starter pinion meshes while
cranking the engine using
starter.
• The clutch cover with the
clutch disc are bolted to the
flywheel.
y
• In certain diesel engines used
on light vehicle, the flywheel
will be replaced with a DMF
for smoother, vibration free
operation.
operation
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Engine Cooling System
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Cooling System: Introduction
• In a typical gasoline engine,
about 33% of the total heat
input is lost to the coolant.
• The cooling system is
responsible for dissipating
this heat to the atmosphere
• The cooling system used in
engines can be –
– Liquid cooled system – used
in engines used in cars and
trucks
– Air cooled system – used in
smaller engines like twowheelers
Heat loss in an engine
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Functions of cooling system
•
Cooling system has several functions:
– Removing excess heat from engine
• The combustion of the fuel produces tremendous amount of heat
• Combustion flame temperatures can reach approx 2500 degree Centigrade- enough to melt the metal
parts
• Part of this is removed by the cooling system fluid to protect the metal parts from damage
– Maintaining a constant operating temperature
• Engine operating temperature is the temperature the engine coolant reaches under normal running
conditions
• Typically, an engine’s operating temperature is in the range of 80 – 100 degree Centigrade
• This temperature ensures that all part clearances are correct after expansions.
• Also ensures proper combustion, emission output levels and engine performance
– Increase the temperature of a cold engine quickly
• An engine
g must warm upp rapidly
p y to prevent
p
ppoor combustion,, ppart wear,, oil contamination,, reduced
fuel economy, increased emissions and other problems.
• Too much of clearances
• Oil in a cold engine can be thick- increased wear
• Improper vaporization of fuel – improper combustion
– Provide a means for warming the passenger compartment
• A cooling system commonly circulates coolant to the vehicle’s heater.
• The engine coolant is warm, its heat can be used to warm the passenger compartment.
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Liquid cooling system
• Circulates coolant (a solution of
water and cooling fluid) through
water jackets.
• The coolant then collects excess
heat and carries it out of the
engine
• Liquid cooling:
– more precise control of the engine
temperature
– Less temperature variations in side
the engine
g
– Better temperature control leading
to reduced ehaust emissions
– Improved heater operation for
warming the passenger space
Engine water jackets
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Coolants
• Ethylene glycol based engine coolant concentrate
• 40 to 70 percent concentration in water
• Effective during both winter and summer in
automotive
i vehicle
hi l cooling
li systems to provide
id
protection against freezing, boiling and corrosion.
• A typical coolant fluid used in cooling system
consists essentially of:
–
–
–
–
ethylene glycol
corrosion inhibitors,
a foam
f
suppressor,
sufficient water to dissolve the additives
• Can be poured at temperatures as low as zero
degrees -17.8 degrees C.
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Cooling system components
Conventional coolant flow type
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• Water pump:
– A centrifugal pump forces coolant through
the engine block, cylinder head, intake
manifold, hoses and radiator
– It is often driven by engine crankshaft
through belt
• Radiator
– Transfers coolant heat to the outside air
– Normally mounted in the front of the engine
– Consists:
•
•
•
•
•
Scorpio water pump
Radiator core
Radiator tanks
Radiator filler neck
Transmission oil cooler
Radiator drain cock
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Radiator Types
• Availability of space generally dictates the choice of the radiator.
• Both cross flow and down flow radiators are used
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Radiator Pressure Cap
Closed system
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Thermostat
• Senses engine temperature and
controls the coolant flow through
the radiator.
• It reduces the coolant flow when
engine is cold and increases as the
engines gets warmer
• Wax pellet type is commonly used.
W pellet
Wax
ll t type
t
thermostat
th
t t operation
ti
• When heated, the pellet expands and
pushes the valve open.
• As the pellet and the thermostat cool,
the spring tension overcomes pellet
expansion
i andd the
th valve
l closes
l
• The rating of the thermostat is its
operating temperature which is
normally 82 – 91 degree Centigrade
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Engine Lubrication System
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Lubrication system functions
• Important functions of
lubricating systems. The
system:
– Reduces friction and wear and
tear between moving parts
– Helps transfer heat away from
engine parts
– Cleans the inside of the engine
by removing contaminants
(metal, dirt, plastic, rubber and
other particles)
– Cuts power loss and increases
fuel economy
– Absorbs shocks between
moving parts to quiet engine
operation and increase engine
life
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Engine Oil Classifications:
American Petroleum Institute (API)
• API established a classification system for
the designation of gasoline and diesel engine
oils which reflects the quality,
oils,
quality performance,
performance
and suitability of the oils for various
engines.
• These classifications are arranged into two
different groups,
– For automotive gasoline engine service
– For commercial diesel engine service.
• The former is listed in "S" or "Service"
categories (*presently SA through SM)
• The later is listed in "C" or "Commercial"
categories (*presently CA through CI-4 PLUS).
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# Energy conserving – reduce friction,
Friction modifiers and other additives.
1.5% / 2.7%
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SAE Classification
• A higher viscosity oil is very thick and resists flow and
vise versa
• SAE has established an oil viscosity classification system.
• It is a numeric rating in which higher the number,
number higher
the viscosity.
• Single-viscosity oil:
– Rated and designated for a limited range of operating temperatures.
Its viscosity is not stable as multiviscosity oil
• Multiviscosity oil:
– Will exhibit operating characteristics of a thin oil light oil when
cold and a thicker, heavier oil when hot.
• Although single
single--viscosity oils are available, most engine
oils are multiviscosity oils.Ex:
oils
SAE 10W-30
• To specify engine oil, both the API service designation and
the SAE viscosity grade are required.
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Components of Lubricating Systems
• Main components of a typical
lubricating systems:
–
–
–
–
–
–
–
–
–
Oil pump
Oil pump pick-up
i k
Oil pan or sump
Pressure relief valve
Oil filter
Engine oil passage or galleries
Oil pressure indicator
Dipstick
Oil cooler
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Typical heavy duty diesel engine lubrication circuit
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•
Oil pump:
– Most commonly used oil pumps:
• Rotor type
• Gear type
– Both are positive displacement type
pumps.
– The output volume is proportional to
the speed of the pump.
– Pump is directly or indirectly driven by
the cam shaft or a gear at the front of
the crankshaft.
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• Engine oil galleries:
– The oil galleries consist of interconnecting passages
that have been drilled completely through the engine
block during manufacturing.
– The oil is routed through these passages to various parts
of the engine
engine.
– The crankshaft also contains oil passages to route the
oil from the main bearing to the connecting rod bearing
surfaces.
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• Oil filters
– All the oil that leaves the pump is directed to the oil filter (Full-flow filter).
– This is to ensure that very small particles of dirt and metal carried by the oil
will not reach the close-fitting engine parts.
– From filter, oil flows into engine’s main oil gallery
gallery.
Full-flow filtration system
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Example: Commercial vehicle engine
Specifications
• The combustion technology with 4 valve per
cylinder and optimised fuel injection system
helps in achieving the stringent BS III
emissions without any after treatment and
not even EGR system.
• The superior combustion technology
enables to meet the futuristic emission
norms of BSIV also without any after‐
treatment like SCR or Catalytic convertors.
6.12TCA
6.12TCE
Emissions
Euro III, capability for
Euro IV
Euro III, capability for
Euro IV
Configuration
6, Inline
6, Inline
Valves / Cylinder
4
4
Displacement – Lts
7.2
7.2
Bore x Stroke – mm
105 x 137
105 x 137
Combustion system
Direct Injection
Direct Injection
Injection system
Mechanical
Common Rail
Power Output hp (kW) @ rpm
180 - 210 (132.5 154.5) @ 2200
260 - 315 (190 - 232)
@ 2200
Peak Torque kgf-m (Nm) @ rpm 89.7 (880) @ 1400
97.8 - 112 (960 1100) @ 1250 - 1500
Weight (Dry) – kg
540
570
Length
1100
1100
Width
734
734
Height
985
985
Dimensions – mm
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Summary
• The classification of IC engines based on various
parameters, and engine applications have been
explained.
• The constructional details of the main parts of an
engine like – piston assembly, block, head and
valve mechanisms including the recent
developments have been discussed.
• The lubrication system and cooling systems of an
IC engine has been explained
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