Automotive Systems course (Module 01) - Internal Combustion Engine (ICE) basics

29 de setembro de 2016 | 1

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Internal Combustion Engine (ICE) basics

Mário Alves ([email protected])

mailto:[email protected]


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Outline

• ICE definition and operating principle

• ICE classification examples

• ICE types according to the combustion method

• Phases of the combustion cycle

• Camshaft and valve actuation

• ICE types according to the ignition principle

• Phases versus strokes (4-stroke and 2-stroke engines)

• Fuel types

• Mixture formation (direct and indirect injection)

• Cylinders configuration

• Engine cooling

• Engine lubrication


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ICE definition and operating principle

• An ICE is a heat engine based on the combustion of a

fuel with air

• inside a combustion chamber

• The combustion triggers an expansion of the high-

temperature and high-pressure gases

• forcing some components of the engine (e.g. pistons, turbine

blades) to move

• All this process converts chemical into mechanical

energy

• very low efficiency ( 30%) even today


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ICE classification - examples

Classification according to

Ignition principle

Compression Ignition (CI)

Heterogeneous Charge (conventional)

Homogeneous Charge (HCCI)

Spark Ignition

Electromechanical

Distributor-less (Direct Ignition)

http://web.iitd.ac.in/~ravimr/courses/mel345/classification.pdf




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Combustion principle

Intermittent Linear pistons with alternating movement

Rotary pistons (Wankel)

Continuous Turbine engine

Jet engine





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Cylinders number and configuration

Single

Multiple In-line

Horizontally opposed

V-shaped

W-shaped

Radial





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Classification according to the

Working Cycle

2-stroke

4-stroke

Classification according to the

Number of valves

2 per cylinder

3 per cylinder

4 per cylinder

…





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ICE types according to how combustion is performed

• ICEs engines can be classified according to the way

combustion is performed:

• Intermittent combustion

• linear piston (alternating/reciprocating movement)

• rotary piston (Wankel)

https://www.citelighter.com/technology/technology/knowled

gecards/rotary-engine-vs-four-stroke-engine

https://www.citelighter.com/technology/technology/knowledgecards/rotary-engine-vs-four-stroke-engine














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ICE types according to how combustion is performed

• ICEs engines can be classified according to the way

combustion is performed (cont.):

• Continuous combustion

• Turbine engine (e.g. jet engine)

http://www.navyaircrew.com/blog/2009/07/18/suck-squeeze-bang-

and-blow/

http://www.navyaircrew.com/blog/2009/07/18/suck-squeeze-bang-and-blow/











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ICE main components (linear pistons)

• Piston

• transmits movement to the rod

• Connecting Rod

• transmits the movement to the crankshaft

• Crankshaft

• transforms reciprocating into circular movement

http://direns.mines-paristech.fr/Sites/Thopt/en/co/maci.html






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Phases of the combustion cycle (strokes)

• In ICEs, combustion is composed of four phases:

• Admission (or Intake, or Induction) Stroke

• Air (direct injection) or air/fuel mixture (indirect injection) is

admitted into the combustion chamber, by opening the admission

valves

• Air comes from the intake manifold: atmosphere air filter

(throttle body) (turbo-compressor) admission pipes

• Compression Stroke

• the air/fuel mixture is compressed

• the piston moves upwards from the Bottom Dead Center (BDC) to

the Top Dead Center (TDC)

http://www.chevelle.fr/chevelle.fr/articles.php?lng=fr&pg=423




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Phases of the combustion cycle (strokes)

• In ICEs, combustion is composed of four phases (cont.):

• Power (or Expansion) Stroke

• Air/fuel mixture ignites, triggering the combustion

• The piston is forced to move downwards

• Exhaust Stroke

• burned gases are expel from the combustion chamber

• Air goes out through the exhaust valves exhaust pipes turbo-

compressor …





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Camshaft and valve actuation

• Objective

• Open/close intake and exhaust valves

• Operation

• synchronization (aka timing) belt (or chain) drives camshaft

• camshaft lobes (called cams) push (intake and/or exhaust) valves to

open/close as the camshaft rotates

• springs return valves to closed position

• Valve (open/close) timings can be

• fixed (conventional)

• variable, to optimize ICE operation

https://xorl.wordpress.com/2011/03/27/valve-timing-and-variable-valve-timing/














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Camshaft and valve actuation

• The most common camshaft arrangements are:

• OHV (Over-Head Valve) – left

• SOHC (Single Over-Head Cam) – middle

• DOHC (Double Over-Head Cam) – right

http://www.samarins.com/glossary/dohc.html




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ICE types according to ignition principle

• The ignition of the fuel mixture is either

• natural/gradual (Diesel)

• requires high pressure&temp. Compression Ignition (CI)

• Homogeneous Charge technology (HCCI) requires lower

temperatures and results in lower NOx emissions

• forced/artificial (gasoline, LPG, alcohol, natural gas, hydrogen)

• requires an ignition system Spark Ignition (SI)

http://www.ni.com/white-paper/13516/en/






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ICE phases versus piston movements

• The four phases of the ICE cycle can be performed in 2

or 4 piston movements

• 2 stroke engines

• 2 phases per piston movement

• 4-stroke engines

• 1 phase per piston movement


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• Phases • Admission (Intake)

• Compression

• Power (Expansion)

• Exhaust

4-stroke CI engine (Diesel cycle)

Rudolf Diesel (1858 - 1913)

https://www.uclm.es/profesorado/porrasysoriano/




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4-stroke CI engine

• Admission (Intake) stroke

• the piston starts moving down, from the Top

Dead Center (TDC) downwards

• the intake valve opens (forced by the

camshaft), letting fresh air enter the

combustion chamber

• the piston moves down and reaches the

Bottom Dead Center (BDC)

• the combustion chamber is now full of air,

ready to be compressed (next stroke)

http://beamerguide.blogspot.pt/2010/10/how-diesel-engine-work.html










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• Compression

• the intake valve closes (forced by the

camshaft)

• the piston starts moving up, from the BDC

upwards, to the TDC

• the piston moves up, compressing the air, until

reaching the TDC

• at TDC, air temperature and pressure are

maximized, enabling optimized ignition (upon

fuel injection)

4-stroke CI engine











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4-stroke CI engine

• Power (Expansion)

• Fuel is injected into the combustion chamber

(at very high pressure)

• air-fuel mixture inflames (ignites) and

combustion is spread all over the combustion

chamber

• combustion triggers volume expansion,

pushing the piston downwards











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• Exhaust

• at the end of expansion, once the piston hits

the BDC, the exhaust valve opens

• piston moves upwards (forced by the

mechanical inertial movement)

• the burned gases are gradually expel from the

cylinder, through the exhaust valve and pipes

4-stroke CI engine











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• 4 stroke Otto cycle • Admission (Intake)

• Compression

• Ignition + Expansion

• Exhaust

4-stroke SI engine (Otto cycle)

Nicolaus Otto (1852 - 1891)





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• Admission (Intake)

• the piston starts moving down, from the Top

Dead Center (TDC) downwards

• the intake valve opens (forced by the intake

camshaft), letting fresh air enter the

combustion chamber

• (in Indirect Injection fuel is already mixed with air

outside the cylinder)

• the piston moves down and reaches the

bottom dead center (BDC)

• the combustion chamber is now full of air,

ready to be compressed (next stroke)

4-stroke SI engine

http://www.indycarz.com/threads/tech-basics-part-2-the-four-stroke-cycle.141585/


















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• Compression

• the intake valve closes (forced by the

camshaft)

• the piston starts moving up, from the BDC

upwards, to the TDC

• (in Direct Injection, fuel is injected into

the combustion chamber during

Compression)

• the piston reaches TDC, where air

temperature and pressure are maximized,

enabling optimized combustion

4-stroke SI engine



















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• Power (Ignition + Expansion)

• when the piston reaches the TDC

(actually a few miliseconds before), the

spark plug ignites the air-fuel mixture

• air-fuel mixture inflames (ignites) and

combustion is spread all over the

combustion chamber

• combustion triggers volume expansion,

pushing the piston downwards

4-stroke SI engine



















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• Exhaust

• at the end of expansion, once the

piston hits the BDC, the exhaust

valve opens (forced by the exhaust

camshaft)

• piston moves upwards (forced by the

mechanical inertial movement)

• the burned gases are gradually expel

from the cylinder, through the

exhaust valve and pipes

4-stroke SI engine



















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2 stroke gasoline engine

2-stroke SI engine

• 2 stroke SI cycle:

• Compression stroke

• Combustion stroke





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2-stroke SI engine

• Sparks fire

• the fuel-air-oil mixture has been fully compressed

and the spark plug fires, igniting the mixture in the

combustion chamber (red area at the top)

• the piston is driven downwards, compressing the

air-fuel-oil mixture in the crankcase (blue area at

the bottom)

• when reaching the BDC, the exhaust port is left

opened

• the pressure in the cylinder drives most of the

exhaust gases out of it





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2-stroke SI engine

• Fuel intake

• when the piston reaches the BDC, the intake port is

left opened (pipe/port on the lefthand of the

combustion chamber)

• The piston's downwards movement has pressurized

the mixture in the crankcase, so when the intake

port is opened, the air-fuel-oil mixture rushes into

the combustion chamber, expelling the remaining

exhaust gases





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2-stroke SI engine

• Compression Stroke

• The momentum in the crankshaft starts driving the

piston upwards (compression stroke)

• as the air-fuel-oil mixture in the piston is

compressed, vacuum is created in the crankcase;

this vacuum forces the reed valve to open and lets

the air-fuel-oil mixture enter the cylinder

• once the piston gets to the TDC, the spark plug fires

again…





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2-stroke CI engine

• Intake + Compression

• As the piston reaches BDC, it uncovers the air intake ports, filling the

combustion chamber of fresh air and forcing out the remaining exhaust gases

• the exhaust valves close

• the piston starts moving upwards, covering the intake ports and compressing

the air inside the combustion chamber

http://railmotorsociety.org.au/images/diesel_page_00.gif




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2-stroke CI engine

• Injection + Expansion

• when the piston gets to the TDC, the combustion chamber contains a charge

of highly compressed air.

• Diesel fuel is sprayed into the cylinder by the injector and immediately

ignites due to the heat and pressure inside the cylinder

• The pressure created by the combustion of the air-fuel mixture drives the

piston downward





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2-stroke CI engine

• Exhaust

• as the piston moves downwards (towards BDC),

the exhaust valves open and exhaust gases rush

out of the cylinder, relieving the pressure





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• 4-stroke Wankel engine:

• Intake

• Compression

• Combustion

• Exhaust

4 stroke Wankel engine

4-stroke Wankel engine

http://auto.howstuffworks.com/rotary-engine4.htm






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• Intake

• intake starts when the tip of the rotor passes the

intake port (clockwise movement)

• the intake port is exposed to the chamber, when the

volume of the chamber is close to its minimum

• as the rotor moves past the intake port, the volume

of the chamber expands, drawing air/fuel mixture

into the chamber


Intake







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• Compression

• as the rotor continues its motion around the

housing, the volume of the chamber gets smaller

and the air/fuel mixture gets compressed

• when it reaches the spark plugs, the volume of the

chamber is close to its minimum (maximum

compression)

• this is when sparks ignite the air-fuel mixture and

combustion starts


Compression







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• Combustion

• most rotary engines have two spark plugs; as the

combustion chamber is very long, the flame would

propagate too slowly if there was just one plug

• when the spark plugs ignite the air/fuel mixture,

pressure quickly builds, forcing the rotor to move

(clockwise)


Combustion







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• Exhaust

• once the peak of the rotor passes the exhaust port,

the high-pressure combustion gases are free to flow

out, through the exhaust port

• as the rotor continues to move (clockwise), the

chamber shrinks, forcing the remaining exhaust

gases out


Exhaust







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Fuel types

• ICEs can run on several types of fuels:

• Gasoline*

• Diesel*

• Liquefied petroleum gas (LPG)*

• Alcohol

• Natural gas*

• Hydrogen

• Biodiesel**

* Most common in Europe

** Commonly mixed with Diesel, in a low percentage


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Fuel types – gasoline vs. Diesel

• Advantages of Diesel engines:

• Higher energy efficiency lower fuel consumption

• No spark ignition system (no spark plugs, no igniters, …)

• Longer lifetime (several hundreds of thousands km)

• Advantages of gasoline engines:

• Less acoustic noise and mechanical vibrations

• More elasticity (allows higher RPM)

• Lighter/smaller engine (less CC) for the same power

• No combustion chamber pre-heating system (no glow plugs, no

relays,…)


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Mixture formation

• ICEs can be distinguished according to where the air/fuel

mixture is formed

• Indirect Injection (IDI) aka external injection

• Inside the combustion chamber

• Direct Injection (DI) aka Internal Injection

• Outside the combustion chamber

• This applies to both Compression Ignition (CI) and Spark

Ignition (SI) Engines


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Mixture formation – CI engine

• In Compression Ignition engines

• Indirect Injection

• Injector sprays into a pre-chamber (aka swirl chamber)

• Glow-plug heats pre-chamber

• Direct Injection

• Injector sprays directly into combustion chamber

• Glow-plug heats combustion chamber

http://www.jensales.com/blog/indirect-injection-vs-

direct-injection-diesels/

http://www.jensales.com/blog/indirect-injection-vs-direct-injection-diesels/













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Mixture formation – SI engine

• In Spark Ignition engines

• Indirect Injection

• Injector sprays into the intake pipe (before intake valve)

• Before Throttle Single-Point Injection – Figure a)

• After Throttle Multi-Point Injection – Figure b)

• Direct Injection

• Injector sprays into the combustion chamber – Figure c)

http://www.intechopen.com/books/advances-in-internal-combustion-engines-and-fuel-

technologies/combustion-process-in-the-spark-ignition-engine-with-dual-injection-system

http://www.intechopen.com/books/advances-in-internal-combustion-engines-and-fuel-technologies/combustion-process-in-the-spark-ignition-engine-with-dual-injection-system





































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Mixture formation

• Direct versus indirect injection

Direct Injection Indirect Injection

Losses Lower thermal losses High thermal losses

(between chambers)

Performance Higher Lower

Speed Lower engine speed Higher engine speed

Fuel type Demands higher quality

fuels

Works with lower quality

fuels

Injection Multi-jet

(higher injection pressure)

Single-jet

(lower injection pressures)

Efficiency More efficient

(lower fuel consumption)

Less efficient

(higher fuel consumption)

Emissions Less pollutant More Pollutant


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Cylinders configuration

• ICEs can be classified by their cylinders configuration

In-line V-shape

W-shape Radial

Opposed Horizontal

Wankel

http://auto.howstuffworks.com/




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• In-line configuration

• most used, simple and inexpensive

• single engine block where cylinders are aligned

• main disadvantage (against other configurations) is requiring a

longer crankshaft





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• V-shape configuration

• cylinders are disposed in two blocks, in a V shape

• the two blocks share a common crankshaft

• main advantage is having a shorter crankshaft for the same

number of cylinders (comparing to the in-line configuration)

• most used when the number of cylinders is ≥ 6





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• W-shape configuration

• similar to V-shape but has 3 blocks of cylinders

• This allows to have more cylinders with the same space

(comparing to other configurations), i.e. shorter crankshaft

• mostly used for 12-cylinder engines





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• Opposed-Horizontal configuration (aka boxer or flat)

• more balanced, because the movement of one piston is

compensated by the movement of the other moving in the

opposite direction

• allows a lower center of gravity for, improving driveability

• pistons movement is not affected by gravity (like in other

configurations)





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• Radial configuration

• pistons arranged in circle (around the crankshaft)

• typically 3-9 cylinders

• mostly used in airplanes





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• Wankel configuration

• Piston rotates (instead of linear movement, as in traditional

ICEs)

• Rarely used, due to inherent technical limitations (e.g. cooling,

lubricating)





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Cylinders volume vs number

• Two approaches (for the same volume – CC):

• More cylinders of smaller capacity

• Less cylinders of larger capacity

• Pros of having more cylinders

• Better thermal efficiency

• Larger specific power (relation between the engine capacity and power) augmenting the engine´s maximum regime

• Greater uniformity of engine torque

• Better balance of mass in motion, which results in lower engine vibrations

• Cons of having more cylinders

• Larger crankshaft length, resulting in torsional vibration problems

• Increase in engine volume and weight

• Decrease in mechanical efficiency and thus in engine power


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Cooling System

• Objectives

• Guarantee a suitable engine operating temperature

• cooling it down (after reaching a stationary regime)

• helping to warm it up (keep fluid inside engine, while cold)

• keep the physical and chemical proprieties of the lubricating oil

• can deteriorate upon overheating

• supply heat to acclimatize the interior of the vehicle

• Facts

• Most of the heat is dissipated through the exhaust

• leading to wasted energy, thus low energy efficiency

• Some heat is dissipated via lubricating oil (and oil cooler)

• fixed engine parts (e.g. block, head) are cooled by the main cooling system

• moving parts (e.g. pistons, crankshaft, rods) are mostly cooled by the lubricating oil


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Cooling System

• Liquid-cooled engine

• dedicated cooling circuit (pump, thermostat, radiator, fan,…)

https://tyeschenbach.files.wordpress.com/2013/06/cooling.jpg




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Cooling System

• Air-cooled engine

• air circulates over hot parts; extended cylinders radiation area

http://www.vdubxs.com/vintage-speed-vw-split-screen-rear-end-

transformation/air_cooled_engine/#sthash.k3hPi7nw.dpbs

http://www.vdubxs.com/vintage-speed-vw-split-screen-rear-end-transformation/air_cooled_engine/sthash.k3hPi7nw.dpbs

















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Lubricating System

• Objective

• Mitigate friction and overheating of moving parts

http://www.britannica.com/technology/lubrication




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Glossary (English Portuguese)


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Bibliography

[1] Ricardo Marques (1030379), André Soares (1021069), class project under the

SIAUT course, ISEP, 2011.

Engineering

Automotive Systems course (Module 01) - Internal Combustion Engine (ICE) basics