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INTERNAL COMBUSTION

ENGINES

By İbrahim H. By İbrahim H. YILMAZYILMAZ

EARLY HISTORYEARLY HISTORY

1700s - Steam engines (external combustion engines)1860 - Lenoir engine (η = 5%)1867 - Otto-Langen engine (η = 11%, 90 RPM max.)1876 - Otto four stroke “spark ignition” engine (η = 14%, 160 RPM

max.)1880s - Two stroke engine1892 - Diesel four stroke “compression ignition” engine1957 - Wankel “rotary” engine

ENGINE TYPESENGINE TYPES

External Combustion Engines (ECE)External Combustion Engines (ECE)Internal Combustion Engine (ICE)Internal Combustion Engine (ICE)

External Combustion EnginesExternal Combustion Engines ((EECE)CE)

Combustion takes place outside the Combustion takes place outside the mechanical engine (include steam engines and mechanical engine (include steam engines and gas turbine engines etc.)gas turbine engines etc.)

IInternal nternal CCombustion ombustion EEnginengine (ICE) (ICE)

The The internal combustion engineinternal combustion engine (ICE) is a (ICE) is a heat engine that converts chemical energy in a heat engine that converts chemical energy in a fuel into mechanical energy, usually made fuel into mechanical energy, usually made available on a rotating output shaft.available on a rotating output shaft.

Chemical energy of the fuel is first converted Chemical energy of the fuel is first converted to thermal energy by means of combustion or to thermal energy by means of combustion or oxidation with air inside the engine.oxidation with air inside the engine.

This thermal energy raises the temperature This thermal energy raises the temperature and pressure of the gases within the engine, and pressure of the gases within the engine, and the high-pressure gas then expands and the high-pressure gas then expands against the mechanical mechanisms of the against the mechanical mechanisms of the engine.engine.

This expansion is converted by the mechanical This expansion is converted by the mechanical linkages of the engine to a rotating crankshaft, linkages of the engine to a rotating crankshaft, which is the output of the engine.which is the output of the engine.

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

CAR ENGINE MAIN CAR ENGINE MAIN STRUCTURE COMPONENTSSTRUCTURE COMPONENTS

Engine Block (Motor bloğu)Engine Block (Motor bloğu)Camshaft (Kam mili yada eksantrik mili)Camshaft (Kam mili yada eksantrik mili)Carburetor (Karbüratör)Carburetor (Karbüratör)Catalytic converter (Katalitik konvertör)Catalytic converter (Katalitik konvertör)Combustion chamber (Yanma odası)Combustion chamber (Yanma odası)Connecting rod (Biyel kolu)Connecting rod (Biyel kolu)Connecting rod bearing (Biyel kolu rulmanı)Connecting rod bearing (Biyel kolu rulmanı)Cooling fins (Soğutucu genişletilmiş yüzey)Cooling fins (Soğutucu genişletilmiş yüzey)

Crankcase (Karter)Crankcase (Karter)Crankshaft (Krank mili)Crankshaft (Krank mili)Cylinders (Silindir)Cylinders (Silindir)Exhaust manifold (Egzoz manifoldu) Exhaust manifold (Egzoz manifoldu) Exhaust system (Egzoz sistemi)Exhaust system (Egzoz sistemi)Fan (Pervane)Fan (Pervane)Flywheel (Volan)Flywheel (Volan)Fuel injector (Yakıt enjektörü)Fuel injector (Yakıt enjektörü)Fuel pump (Yakıt pompası)Fuel pump (Yakıt pompası)Engine head (Motor üst kapağı)Engine head (Motor üst kapağı)Head gasket (Üst kapak contası)Head gasket (Üst kapak contası)

Intake manifold (Emme manifoldu)Intake manifold (Emme manifoldu)Oil pump (Yakıt pompası)Oil pump (Yakıt pompası)Oil sump (Yakıt haznesi)Oil sump (Yakıt haznesi)Piston (Piston)Piston (Piston)Piston rings (Segman)Piston rings (Segman)Push rods (Külbütör çubuğu)Push rods (Külbütör çubuğu)Rocker arm (Piyano parmağı)Rocker arm (Piyano parmağı)Radiator (Radyatör)Radiator (Radyatör)Spark plug (Buji)Spark plug (Buji)Supercharger (Süperşarj)Supercharger (Süperşarj)Throttle (Kelebek)Throttle (Kelebek)

Turbocharger (Turboşarj)Turbocharger (Turboşarj)Valves (Sübap)Valves (Sübap)Water jacket (Su gömleği)Water jacket (Su gömleği)Water pump (Su pompası)Water pump (Su pompası)Wrist pin (Krank pimi)Wrist pin (Krank pimi)

ENGINE CLASSIFICATIONSENGINE CLASSIFICATIONS

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

1.1. Types of IgnitionTypes of Ignition

Spark Ignition (SI)Spark Ignition (SI)Compression Ignition(CI)Compression Ignition(CI)

Spark Ignition (SI)Spark Ignition (SI)

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

Compression Ignition(CI)Compression Ignition(CI)

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

2.2. Engine CycleEngine Cycle

Four-Stroke CycleFour-Stroke CycleTwo-Stroke CycleTwo-Stroke Cycle

Four-Stroke CycleFour-Stroke Cycle

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

Two-Stroke CycleTwo-Stroke Cycle

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

3.3. Valve LocationValve Location

Valves in head (overhead valve)Valves in head (overhead valve)Valves in block (flat head)Valves in block (flat head)One valve in head and one in blockOne valve in head and one in block

4.4. Basic DesignBasic Design

ReciprocatingReciprocatingRotaryRotary

ReciprocatingReciprocating

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

RotaryRotary

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

5.5. Position & Number of Cylinders of Position & Number of Cylinders of Reciprocating EnginesReciprocating Engines

Single CylinderSingle CylinderIn-LineIn-LineV EngineV EngineOpposed Cylinder EngineOpposed Cylinder EngineW EngineW EngineOpposed Piston EngineOpposed Piston EngineRadial EngineRadial Engine

6.6. Air Intake ProcessAir Intake Process

Naturally AspiratedNaturally AspiratedSuperchargedSuperchargedTurbochargedTurbochargedCrankcase CompressedCrankcase Compressed

Naturally AspiratedNaturally Aspirated

No intake air pressure boost system No intake air pressure boost system

SuperchargedSupercharged

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

TurbochargedTurbocharged

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

Crankcase CompressedCrankcase Compressed

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

7.7. Method of Fuel Input for SI EnginesMethod of Fuel Input for SI Engines

CarburetedCarburetedMultipoint Port Fuel InjectionMultipoint Port Fuel InjectionThrottle Body Fuel InjectionThrottle Body Fuel InjectionDirect InjectionDirect InjectionIndirect InjectionIndirect Injection

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

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

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

8.8. Fuel UsedFuel Used

GasolineGasolineDiesel Oil or Fuel OilDiesel Oil or Fuel OilGas, Natural Gas, MethaneGas, Natural Gas, MethaneLPGLPGAlcohol – Ethyl, MethylAlcohol – Ethyl, MethylDual FuelDual FuelGasoholGasohol

9.9. ApplicationApplication

Automobile, Truck, BusAutomobile, Truck, BusLocomotiveLocomotiveStationaryStationaryMarineMarineAircraftAircraftSmall Portable, Chain Saw, Model AirplaneSmall Portable, Chain Saw, Model Airplane

9.9. Type of CoolingType of Cooling

Air CooledAir CooledLiquid Cooled, Water CooledLiquid Cooled, Water Cooled

BASIC ENGINE CYCLESBASIC ENGINE CYCLES

Four-Stroke SI Engine CycleFour-Stroke SI Engine CycleFour-Stroke CI Engine CycleFour-Stroke CI Engine CycleTwo-Stroke SI Engine CycleTwo-Stroke SI Engine CycleTwo-Stroke CI Engine CycleTwo-Stroke CI Engine Cycle

Four-Stroke SI Engine CycleFour-Stroke SI Engine Cycle

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

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

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

http://www.howstuffworks.com/ignition-system2.htm

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

Four-Stroke CI Engine CycleFour-Stroke CI Engine Cycle

Intake StrokeIntake Stroke : : The same as the intake stroke The same as the intake stroke in an SI engine with major difference : in an SI engine with major difference : no no fuel is added to the incoming air.fuel is added to the incoming air.

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

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

Exhaust StrokeExhaust Stroke : : Same as with an SI Same as with an SI engine.engine.

Two-Stroke Engine CycleTwo-Stroke Engine Cycle

COMPRESSION RATIOCOMPRESSION RATIO This is defined as the ratio of the volume ofThis is defined as the ratio of the volume of thethe cylinder at cylinder at

the beginning of thethe beginning of the compression stroke (when the piston compression stroke (when the piston is at BDC) to the volume of the cylinder atis at BDC) to the volume of the cylinder at the end of the the end of the compression stroke (when the piston is at TDC).compression stroke (when the piston is at TDC).

The higher the compression ratio, the higher the air temperature The higher the compression ratio, the higher the air temperature in thein the cylinder at the end of the compression stroke.cylinder at the end of the compression stroke.Higher compression ratios, to a point, lead to higher thermal Higher compression ratios, to a point, lead to higher thermal efficiencies andefficiencies and better fuel economies.better fuel economies.Diesel engines need high compression ratios to generate the Diesel engines need high compression ratios to generate the highhigh temperatures required for fuel auto ignition.temperatures required for fuel auto ignition.In contrast, gasoline engines use lower compression ratios in In contrast, gasoline engines use lower compression ratios in order to avoid fuelorder to avoid fuel auto ignition, which manifests itself as engine auto ignition, which manifests itself as engine knock or pinging sound.knock or pinging sound.

Common spark ignition compression ratio: Common spark ignition compression ratio: 8:1 to 12:18:1 to 12:1Common compression ignition ration: Common compression ignition ration: 14:1 to 25:114:1 to 25:1

SELF-IGNITION SELF-IGNITION && ENGINE KNOCK ENGINE KNOCK

If the temperature of an air-fuel mixture is If the temperature of an air-fuel mixture is raised high enough, the mixture will self-ignite raised high enough, the mixture will self-ignite without the need of a spark plug or other without the need of a spark plug or other external igniter. The temperature above which external igniter. The temperature above which occurs is called the occurs is called the self-ignition self-ignition temperaturetemperature (SIT). (SIT).

On the other hand, self-ignition is not On the other hand, self-ignition is not desirable in an SI engine, where a spark plug desirable in an SI engine, where a spark plug is used to ignite the air-fuel at the proper is used to ignite the air-fuel at the proper time in the cycle.time in the cycle.

When self-ignition does occur in an SI engine When self-ignition does occur in an SI engine higher than desirable, pressure pulses are higher than desirable, pressure pulses are generated. These high pressure pulses can generated. These high pressure pulses can cause damage to the engine and quite often cause damage to the engine and quite often are in the audible frequency range. This are in the audible frequency range. This phenomenon is often called phenomenon is often called knock knock oror ping ping..

OCTANE NUMBEROCTANE NUMBER

The fuel property that describes how well a fuel The fuel property that describes how well a fuel will or will not self-ignite is called the will or will not self-ignite is called the octane octane number number or justor just octane octane. . The higher the octane number of a fuel, the The higher the octane number of a fuel, the less likely it will self-ignite.less likely it will self-ignite.Engines with low compression ratios can use Engines with low compression ratios can use fuels with lower octane numbers, but high-fuels with lower octane numbers, but high-compression engines must use high-octane fuel compression engines must use high-octane fuel to avoid self-ignition and knock.to avoid self-ignition and knock.

CETANECETANE NUMBER NUMBER

In a CI engine, self-ignition of the air-fuel mixture is In a CI engine, self-ignition of the air-fuel mixture is a necessitity.a necessitity.The correct fuel must be chosen which will self-The correct fuel must be chosen which will self-ignite at the precise proper time in the engine cycle.ignite at the precise proper time in the engine cycle.The property that quantifies this is called the The property that quantifies this is called the cetane numbercetane number..The larger the cetane number, the shorter is the ID The larger the cetane number, the shorter is the ID and the quicker the fuel will self-ignite in the and the quicker the fuel will self-ignite in the combustion chamber.combustion chamber.