INTERNAL COMBUSTION ENGINE

INTRODUCTIONGroup 1

Engine Definition

Historically : Any machine that does work, no matter how it is powered (eg. wind mills, water wheels)

Origin of word "engine" - Latin and Greek roots of invention.

Modern : Prime movers that operate automatically/continuously to convert some form of energy into useful mechanical power.

Heat Engine History (Early 19th)Sadi Carnot (1824) - Essentially stated the first and

second laws of thermodynamics.James Joule (1850) - Measured the fixed ratio

between work and heat; defining the first law.Wm. Rankine (1889) - Wrote the first formalized

thermodynamics textbook; defining the second law - "absolute" temperature scale.

Alternatives to steam engines had been developed in the 19th century (1800s).

Mid 19th CenturyDespite of generally good

recoed of engineering development, steam engine was not satisfactory for all purposes - due to poor efficiency and other disadvantages.

Therefore, search for new engine started.

Opportunity presented by new fuel, "gases" from cooking ovens.

Stanley Steamer

History of IC Engine

1800’s - Nikolaus Otto is considered the inventor of IC engine and founder of the industry.

1876 – Otto developed a 4-stroke engine, which often referred as Spark Ignition as it needs spark to ignite the fuel-air mixture.

1864 – 1878 – Otto and Langen developed the Otto Langen Atmosphere engine.

Limited design, poor power & fuel consumption, noisy

Early Attempts Impacts of IC Engine – almost all transportation powered

by IC engine (Spark ignition).1900’s – IC Engine is replaced with Steam Engine, with

same working principle

1897 – Rudolph Diesel developed the Diesel cycle; also known as compression ignition engine (No spark plug)

Diesel engine - noisy, large, slow, single-cylinder engines, however, it is generally more efficient than spark ignition engines.

1920’s - multicylinder compression ignition engines, used in today automobile and trucks.

Background of IC Engine “IC Engine is a heat engine that converts chemical

energy in a fuel into mechanical energy, usually made available on a rotating output shaft”.

Some basic activities of IC engine includes the following: A working fluid Injecting heat to fluid Recover a great amount of work Return to initial state by removal of some heat

Internal Combustion Engine

Petrol engine Gas engine

Closed system Open system

Background of IC Engine

Basic Process of IC Engine

1) Ingest a mixture of fuel and air

2) Compress it

3) Cause it to react, thus effectively adding heat through converting chemical energy into thermal energy

4) Expand the combustion products

5) Eject the combustion products and replace them with a new charge of fuel and air

Basic Process of IC Engine

1) Type of IgnitionSpark Ignition

Generally homogeneous mixture (air-fuel mixture)

Ignition occurs with the presence of spark plug

Controlled energy released Intake air throttled Limited variation in A/F

ratio Distinct fuel requirements Relatively low cost High efficiency

Compression Ignition Non-homogeneous

mixture Ignition due to high

temperature No throttling of air intake Wide range of A/F ratio Needs high compression

ratio (no knock limitation)

Classification of IC Engine

1) Type of IgnitionSpark Ignition

Generally volatile fuel (gasoline); does not ignite spontaneously at lower temperatures

Lower compression ratio (knock limited)

Lighter construction; higher rpm

High fuel consumption Turbocharger; optional for

high performance engines

Compression Ignition

Generally distillate oil (diesel); must ignite at lower temperatures

Heavier construction; limited rpm

Low fuel consumption Turbocharger is

necessary except for small diesel engines

Four Stroke Engine CycleFour Stroke Spark Ignition

Air-fuel mixture introduced into cylinder through intake valve (Stroke 1)

Air-fuel mixture is compressed (Stroke 2)

Combustion (at constant volume) occurs and product gases expand producing work (Stroke 3)

Product gases pushed out of the cylinder through the exhaust valve (Stroke 4)

Four Stroke Compression Ignition

Air is introduced by intake valve into the cylinder (Stroke 1)

Air is compressed (Stroke 2) Combustion (at constant

pressure) occurs and product gases expand producing work (Stroke 3)

Product gases pushed out of the cylinder through the exhaust valve (Stroke 4)

Four Stroke Spark Ignition

Four Stroke Compression Ignition

Four Stroke Engine Cycle

Two Stroke Cycle

In a two-stroke engine all the processes are the same but the cycle is completed in two strokes of the piston.

Since there is one power stroke per revolution, one would expect the power output of a 2-stroke engine to be twice that of a 4-stroke engine for the same displacement.

* Power delivered to the crankshaft on every revolution

compressed, combustion initiated at the end of the stroke

Stroke 2:Combustion products expand doing work and then exhausted

Stroke 1:Fuel-air mixture is introduced into the cylinder

Advantages of the two stroke engine

Power to weight ratio is higher than the four stroke engine since there is one power stroke per crank shaft revolution.

Simple valve design Most often used for small engine applications such as lawn

mowers, marine outboard engines, motorcycles….

Disadvantages of the two-stroke engine: Incomplete scavenging or to much scavenging Burns oil mixed in with the fuel

Valve Location Valves in Head (overhead valve), also called I Head

Engine. Valve in Block (Flat head), also called L Head Engine or

T Head Engine. One valve in Head and one valve in Block, also called F

Head engine.

F Head Engine T Head Engine OverHead Engine

Basic Design Reciprocating Engines Linear motion of piston in a cylinder and

conversion of linear into rotary motion using crankshaft.

Advantages- better sealing of high pressure gases ease of lubrication lower surface area less wear on rings/seals

Disadvantages- reciprocating mass and force unbalance vibrations lower power density (based on mass) larger physical size

Rotary

Rotary motion of rotor-direct output at the shaft. Advantages:

compact size power plant higher power density smooth vibration-free operation lower height

Disadvantages: sealing of high pressure gases and leakage cost and durability of seals lubrication of seals larger surface area

Wankel Engines

No valves needed Continuous motion less vibration Leaks through seals low compression ratio pollution (high levels of

HC and CO)

Position and Number of Cylinders of Reciprocating Engines

Single Cylinder. In-Line V Engine Opposed Cylinder Engine W Engine Opposed Piston Engine Radial Engine

NUMBER OF CYLINDERSSingle-cylinder engine gives one power stroke per

crank revolution (2 stroke) or two revolutions (4 stroke). The torque pulses are widely spaced, and engine vibration and smoothness are significant problems. Used in small engine applications where engine size is more important

Multi-cylinder engines spread out the displacement volume amongst multiple smaller cylinders. Increased frequency of power strokes produces smoother torque characteristics. Engine balance (inertia forces associated with accelerating and decelerating piston) better than single cylinder.

Cylinder Arrangements Most common :

In-line 4-cylinder

V-6

V-8

Air Intake Process

Naturally Aspirated Supercharged Turbocharged Crankcase Compressed

Super Charger and Turbo Charger

Supercharger and Turbocharger are devices used to increase the power of an IC engine by raising the intake pressure in order to make more fuel to be burned per cycle.

Knock or autoignition phenomenon limits the amount of precompression.

Supercharger An air compressor used for

forced induction of an internal combustion engine.

The greater mass flow-rate for more oxygen to support combustion, which allows more fuel to be burned and more work to be done per cycle, increasing the power output of the engine.

Turbocharger

gas compressor used for forced induction of an internal combustion engine.

turbocharger increases the pressure of air entering the engine to create more power.

It has the compressor powered by a turbine.

Super Charger

They suck engine power simply to produce engine power. They’re run off an engine belt connected to the crankshaft, so superchargers are significantly less efficient

For lag this is where the supercharger has its biggest advantage. Since it is powered by a belt, it always produces boost, even at low RPM.

Turbo Charger

For efficiency the turbocharger should be more economical as it operates through energy created by exhaust gases that would otherwise be lost.

The turbo Needs to spool up its turbine before making boost, which creates lag.

The bigger the turbo the higher the lag.

Classification of Internal Combustion Engine

Method of Fuel Input for SI Engine • Carburetted • Multipoint Port Fuel Injection • Throttle Body Fuel Injection

Fuel-Air Mixing

In spark ignition engines the air and fuel are usually mixed prior to entry into the cylinder.

The ratio of mass flow of air to the mass flow of fuel must be held roughly constant at about 15 for proper combustion.

Initially a purely mechanical device known as a carburettor was used to mix the fuel and the air.

Most modern cars use electronic fuel-injection systems.

Basic CarburettorThe carburettor has

two swivelling valves above and below the venturi. At the top, there's a valve called the choke that regulates how much air can flow in. If the choke is closed, less air flows down through the pipe and the venturi sucks in more fuel, so the engine gets a fuel-rich mixture.

Fuel Injection SystemA fuel injector is nothing but an Electronically Controlled Valve.

It is supplied with pressurized fuel by the fuel pump in your car, and it is capable of opening and closing many times per second.

When the injector is energized, an electromagnet moves a plunger that opens the valve, allowing the pressurized fuel to squirt out through a tiny nozzle. The nozzle is designed to atomize the fuel to make as fine a mist as possible so that it can burn easily.

The amount of fuel supplied to the engine is determined by the amount of time the fuel injector stays open. This is called the pulse width, and it is controlled by the ECU.

The injectors are mounted in the intake manifold so that they spray fuel directly at the intake valves. A pipe called the fuel rail supplies pressurized fuel to all of the injectors.

In order to provide the right amount of fuel, the engine control unit is equipped with a whole lot of sensors.

Diesel Fuel Injection System

With diesel engines fuel is sprayed directly into the cylinders power is varied by metering the amount of fuel added (no throttle)

Diesel fuel injection systems operate at high-pressure.fuel pressure must be greater than the compression pressureneed high fuel jet speed to atomize droplets small enough for rapid

evaporation

Direct Injection (DI) Engine

Hybrid engines that combines the best features of SI and CI engines:operate at optimum compression

ratio (12-15) for efficiency by injecting fuel directly into engine during compression (avoiding knock associated with SI engines with premixed charge)

ignite the fuel as it mixes (avoid fuel-quality requirement of diesel fuel)

control engine power by fuel added (no throttling no pumping work)

Need bowl in piston design with high swirl in order to achieve rapid fuel-air mixing

Direct-Injection Stratified-Charge Engines Create easily ignitable fuel-air mixture at the spark plug and a

leaner fuel-air mixture in the rest of the cylinder. Lean burn results in lower emissions.

Classification of Internal Combustion Engine

Fuel Used

GasolinDiesel Oil of Fuel OilGas, Natural Gas,

MethaneLPGAlcohol – Ethyl,

MethylDual FuelGasohol

Application

Automobile, Truck, Bus

LocomotiveStationaryMarineAircraftSmall Portable,

Chain Saw, Model Airplane

Type of CoolingAir Cooled.Liquid Cooled,

Water Cooled.

What are the five basic parts of any engine?

Cylinder Head Function

The cylinder head is made up of many channels or passageways. These passageways are used as a conduit to enable air and fuel, a fluid mixture vital to efficient engine operation, to reach the combustion chamber. Exhaust fumes also exit the combustion chamber and reach the exhaust valve via these passageways.

Cylinder Function

A cylinder is the central working part of a reciprocating engine or pump, the space in which a piston travels. Multiple cylinders are commonly arranged side by side in a bank, or engine block

Cylinder Arrangement

Flat Inline

V

Piston Function

It is the moving component that is contained by a cylinder and is made gas-tight by piston rings. In an engine, its purpose is to transfer force from expanding gas in the cylinder to the crankshaft via a piston rod and/or connecting rod. 

Connecting Rod Function

The connecting rod connects the piston to the crankshaft. It can rotate at both ends so that its angle can change as the piston moves and the crankshaft rotates.

Connecting rods are commonly made from cast aluminum alloy and are designed to withstand dynamic stresses from combustion and piston movement.

Crankshaft Function

The crankshaft transforms the linear motion of the pistons into a rotational motion that is transmitted to the load.  

Other important components Spark Plug

To produce the sparks necessary to ignite the gas and air in the engine, initiating a combustion reaction that provides energy to run the engine

Valves

Engine valves are located in the cylinder head. The main function of the engine valves is to let air in and out of the cylinders. That air is used to help ignite the fuel which will drive the pistons up and down.

There are two types of engine valves; intake and exhaust valves.

Intake valves: Let air in

Exhaust valves: To let exhaust air out

Air Cleaner Function

Prevents abrasive particulate matter from entering the engine's cylinders, where it would cause mechanical wear and oil contamination.

THANK YOU