INTERNAL COMBUSTION ENGINES By İbrahim H. YILMAZ

EARLY HISTORY 1700s - Steam engines (external combustion engines) Lenoir engine (η = 5%) Otto-Langen engine (η = 11%, 90 RPM max.) Otto four stroke “spark ignition” engine (η = 14%, 160 RPM max.) 1880s - Two stroke engine Diesel four stroke “compression ignition” engine Wankel “rotary” engine

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

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

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.

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

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

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

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

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

1.Types of Ignition 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.

2.Engine 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.

3.Valve Location Valves in head (overhead valve) Valves in block (flat head) One valve in head and one in block

4.Basic Design ReciprocatingRotary

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.

5.Position & Number of Cylinders of Reciprocating Engines Single Cylinder In-Line V Engine Opposed Cylinder Engine W Engine Opposed Piston Engine Radial Engine

6.Air Intake Process Naturally Aspirated SuperchargedTurbocharged Crankcase Compressed

Naturally Aspirated No intake air pressure boost system

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

Turbocharged 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.

7.Method of Fuel Input for SI Engines Carbureted 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.

8.Fuel Used Gasoline Diesel Oil or Fuel Oil Gas, Natural Gas, Methane LPG Alcohol – Ethyl, Methyl Dual Fuel Gasohol

9.Application Automobile, Truck, Bus LocomotiveStationaryMarineAircraft Small Portable, Chain Saw, Model Airplane

9.Type of Cooling Air Cooled Liquid Cooled, Water Cooled

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 Engine 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). spark plugspark plug

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 Engine 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 Engine Cycle

COMPRESSION RATIO This is defined as the ratio of the volume of the cylinder at the beginning of the compression stroke (when the piston is at BDC) to the volume of the cylinder at the end of the compression stroke (when the piston is at TDC). This is defined as the ratio of the volume of the cylinder at the beginning of the compression stroke (when the piston is at BDC) to the volume of the cylinder at the end of the compression stroke (when the piston is at TDC). The higher the compression ratio, the higher the air temperature in the cylinder at the end of the compression stroke. Higher compression ratios, to a point, lead to higher thermal efficiencies and better fuel economies. Diesel engines need high compression ratios to generate the high temperatures required for fuel auto ignition. In contrast, gasoline engines use lower compression ratios in order to avoid fuel auto ignition, which manifests itself as engine knock or pinging sound. Common spark ignition compression ratio: 8:1 to 12:1 Common compression ignition ration: 14:1 to 25:1

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

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

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

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

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

IGNITION SYSTEM

TRANSMISSION SYSTEM

HOW CLUTCH WORKS

TRANSMISSION

MANUAL TRANSMISSION

DIFFERENTIAL SYSTEM

DUAL FUEL TECNOLOGY

CATALYTIC CONVERTER

SUSPENSION SYSTEM

CAR ENGINE MANUFACTURE

THE END

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