Ice Lecture 1

Ir. TRI TJAHJONO, MT/INTERNAL COMBUSTION ENGINE

INTRODUCTION 1. HEAT ENGINE (MESIN KALOR) A heat engine is a device which transforms the chemical energy of fuel into thermal energy and uses this energy to produce mechanical work. Heat engine are divided into two broad classes (2 kelompok besar): (a) External combustion engines, and (b) Internal combustion engines. •

External combustion engines :

The product of combustion of air and fuel transfer heat to second fluid which is the working fluid of the cycle. Example: Steam Turbine

STEAM TURBINE

Steam Engine:

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Ir. TRI TJAHJONO, MT/INTERNAL COMBUSTION ENGINE

Gas Turbine:

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Internal combustion engines :

2. CLASSIFICATION: •

Classification of heat engines

Classification

Internal combustion engines

Name of Engines

Reciprocating or rotary

Maximun size in hp

Gasoline or petrol engine (SI)

Reciprocating

5 000

Gas engine (SI)

Reciprocating

5 000

Diesel engne (CI)

Reciprocating

50 000

Rotary

5 00

Rotary

20 000

Electric power, aircraft

Rotary No Mechanism

10 000 very big

Aircraft Missiles, space travel

Reciprocating

5 000

Wankel engine Open cycle gas turbine Jet engine Rocket Steam engine

External combustion engines

Steam tubine Rotary 500 MW Stirling or hot air Reciprocating 1 000 engine Closed cycle gas Rotary turbine 100 000 SI = spark ignition CI = compression ignition

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Principal Use

Remaks

Road vihicles, small industrial, small marine, aircrafts Industrial, electric power Road vihicles, industrial, locomotives, electric power, Under development marine. Road vehicles

Locomotive, ships Electric Power, large marine Under development Experimental, power in space, vehicle Electric power, marine

IC engine classification

The IC engine can be classified on the basis of cycle operation in cylinder, type of ignition, etc. On the basis of cycle operation: 1. Otto cycle engines (spark-ignition or SI engines), and Diesel cycle engines (compression ignition or CI engines). 2. Four-strokes engines and two-stroke engines (both SI and CI engines) 2

Ir. TRI TJAHJONO, MT/INTERNAL COMBUSTION ENGINE

Further classification of spark-ignition engines: (a) On the basis of fuel used: Gas engines and petrol engines. (b) On the basis of method of supply of fuel: 1. Carbureted types: Fuel supplied through carburetor. 2. Injection type: (ii)

Fuel injected into inlet ports or inlet manifold.

(iii)

Fuel injected into the cylinders before ignition.

(c) On the basis of method of ignition: Battery ignition and magneto-ignition. Further classification of compression-ignition engines: (i)

Normally type, using liquid fuel, i.e. light diesel oil (LDO), high speed diesel oil (HSD), heavy oil

(ii)

Dual-fuel type, using liquid fuel for ignition, with supplementary gaseous fuel, either injected or carbureted.

3. PART OF ENGINE: Intake of suction manifold

Cylinder head Suction valve

Exhaust valve

Exhaust manifold

Clearance volume, Vc

Top dead center, TDC

Piston Stroke volume, VS

Gudgeon or wrist pin

Cylinder volume, V

Cylinder Bottom dead center, BDC Connecting rod Crank case

Crank pin Crank

Crank shaft Check ANIMASI

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Ir. TRI TJAHJONO, MT/INTERNAL COMBUSTION ENGINE

 Cylinder volume (V). The sum of piston swept volume and clearance volume. V = VS + VC  Compression ratio (CR or r). The numerical value of the cylinder volume is divided by the numerical value of the combustion space volume. Compressionratio r =

V VC

Comparison of four-stroke and two-stroke cycle engines

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Four-stroke cycle The cycle is completed in four strokes of the piston or in revolutions the crank shaft. Thus one power stroke in every two revolutions of the crank shaft. Because of the above, turning movement is not so uniform and hence hevier flywheel is needed. Again, because of one power stroke for two revolutions, power produced for the same size of engine is small, or for the same power the engine is heavy and bulky. Because of onepower stroke in revoutions, lesses cooling and lubrication requirements. Lesser rate of wear and tear. The four-stroke engine contains valves and valve mechanism. Because of the heavy weight and and complication of valve mechanism. Higher in initial cost. Volumetric efficiency more due to more time induction. Thermal efficiency higher, part load efficiency better than two stroke cycle engine.

Use where efficiency is important, in cars, buses, trucks,tractors, industrial engines, aeroplanes, power generation, etc.

Two-stroke cycle the cycle is completed in two strokes of the piston or in one revolution of the crankshaft. Thus one power stroke is optained in each revolution of the crankshaft. More uniform turning movement and hence lighter flywheel is needed. Because of one power stroke for one revolution, power produce for same size of engine is more (theoretically twice, actually about 1:3 times), or for the same power the engine is light and compact. Because of one power stroke in one revolution greater cooling and lubrication requirement. Greater rate of wear and tear. Two-stroke engines have no valves but only ports (some two-stroke engines are fitted with conventional exhaust valve or reed valve. Because of light weight and simplicity due to the absence of valve mechanism, cheaper in initial cost. Volumetric efficiency less due to lesser time for induction. The thermal efficiency lower, part load efficiency lesser than four-stroke cycle engine.In two stroke petrol engines some fuelis exhausted during scavenging. Used where (a) low cost, and (b) copactness and lightweight important. Two-stroke (air -cooled) petrol engine used in very small size only: own movers, scooters, motor cycles, etc. (Lubricating oil mixed with petrol). Two-stroke engines have no valves but only ports (some two-stroke engines are fitted with conventional exhaust valve or reed valve.

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Ir. TRI TJAHJONO, MT/INTERNAL COMBUSTION ENGINE

Comparison of SI and CI engines 1

Description Basic cycle

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Fuel

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Introduction of fuel

SI Engine Based or Otto cycle. Petrol (gasoline). Hight selfingintion temperature desirable Fuel and air introduced as a gaseous mixture in the suction stroke. Carburator nessesary to provide the mixture. Throtle controls the quantity of mixture introduced.

CI Engine Based on Diesiel cycle. Diesel oil. Low self-ignition temperature desirable Fuel is injected directly into combustion chamber at high pressure at of compression stroke. Carburator is eliminated but a fuel pump and injector necessary. Quality of fuel regulated in pump.

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Ignition

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Compression ratio rage

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Speed

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Efficiency

Ignition due to high temperatur, Required an ignition system caused by high compression of with spark plug in the air, when fuel is injected. combustion chamber. Ignition system and spark plug is eleminated. 14 to 22. Upper limit of CR is 6 to 10.5. Upper limit of CR limited by the rapidly increasing fixed by anti-knock quality of weight of the engine structure fuel. as the compression ratio is further increased. Higher maximum revolution per minute due to lighter Maximum r.p.m lower weight. Maximum efficiency lower Higher maximum efficiency.

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Weight

Lightrer

Heavier due to higher pressures

SI Engine Classification by Valve Location

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Ir. TRI TJAHJONO, MT/INTERNAL COMBUSTION ENGINE

Basic Type of Arrangements

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