INTERNAL COMBUSTION ENGINES...The following is a list of major components found in most reciprocating internal combustion engines (see Fig. 5). Fig.5: Cross-section of four-stroke

Lecture 2 ENGINE COMPONENTS

Automobile Department Engineering Technical College / Najaf Al-furat Al-awsat Technical University

By

INTERNAL COMBUSTION ENGINES

Lecturer

Dr. Hyder H. Balla

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1.4 ENGINE COMPONENTS

The following is a list of major components found in most reciprocating

internal combustion engines (see Fig. 5).

Fig.5: Cross-section of four-stroke cycle S1 engine showing engine components;

(A) block, (B) camshaft, (C) combustion chamber, (D) connecting rod, (E)

crankcase, (F) crankshaft, (G) cylinder, (H) exhaust manifold, (I) head, (J) intake

manifold, (K) oil pan, (L) piston, (M) piston rings, (N) push rod, (0) spark plug, (P)valve, (Q) water jacket.

Internal Combustion Engines L (2) A.Lecturer: Dr. Hyder H. Balla

9

Fig.5: Side view of four-stroke cycle S1 engine

Fig.5: A four-stroke cycle S1 engine


01

1.Block: Body of engine containing the cylinders, made of cast iron or

aluminum. In many older engines, the valves and valve ports were contained

in the block. The block of water-cooled engines includes a water jacket cast

around the cylinders. On air-cooled engines, the exterior surface of the block

has cooling fins.

2.Camshaft : Rotating shaft used to push open valves at the proper time in

the engine cycle, either directly or through mechanical or hydraulic linkage

(push rods, rocker arms, tappets). Camshafts are generally made of forged

steel or cast iron and are driven off the crankshaft by means of a belt or

chain (timing chain).

3.Combustion chamber: The end of the cylinder between the head and the

piston face where combustion occurs.

4.Connecting rod: Rod connecting the piston with the rotating crankshaft,

usually made of steel or alloy forging in most engines but may be aluminum

in some small engines.

5.Crankcase: Part of the engine block surrounding the rotating crankshaft.

In many engines, the oil pan makes up part of the crankcase housing.

6.Crankshaft: Rotating shaft through which engine work output is supplied

to external systems. Most crankshafts are made of forged steel, while some

are made of cast iron.

7.Cylinders: The circular cylinders in the engine block in which the pistons

reciprocate back and forth. The walls of the cylinder have highly polished

hard surfaces.

8.Exhaust manifold: Piping system which carries exhaust gases away from

the engine cylinders, usually made of cast iron.

9.Head: The piece which closes the end of the cylinders, usually containing

part of the clearance volume of the combustion chamber. The head is usually

cast iron or aluminum, and bolts to the engine block. The head contains the

spark plugs in SI engines and the fuel injectors in CI engines and some SI

engines.

Head gasket: Gasket which serves as a sealant between the engine block and

head where they bolt together.


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10.Intake manifold: Piping system which delivers incoming air to the

cylinders, usually made of cast metal, plastic, or composite material.

11.Oil pan: Oil reservoir usually bolted to the bottom of the engine block,

making up part of the crankcase. Acts as the oil sump for most engines.

Oil pump: Pump used to distribute oil from the oil sump to required

lubrication points. The oil pump can be electrically driven, but is most

commonly mechanically driven by the engine.

12.Piston: The cylindrical-shaped mass that reciprocates back and forth in

the cylinder, transmitting the pressure forces in the combustion chamber to

the rotating crankshaft. Pistons are made of cast iron, steel, or aluminum.

Iron and steel pistons.

13.Piston rings: Metal rings that fit into circumferential grooves around the

piston and form a sliding surface against the cylinder walls.

14.Push rods: Mechanical linkage between the camshaft and valves on

overhead valve engines with the camshaft in the crankcase.

15.Spark plug: Electrical device used to initiate combustion in an SI engine

by creating a high-voltage discharge across an electrode gap. Spark plugs are

usually made of metal surrounded with ceramic insulation.

Glow plug: Small electrical resistance heater mounted inside the combustion

chamber of many CI engines, used to preheat the chamber enough so that

combustion will occur when first starting a cold engine. The glow plug is

turned off after the engine is started.

16.Valves: Used to allow flow into and out of the cylinder at the proper time

in the cycle.

17.Water jacket: System of liquid flow passages surrounding the cylinders,

usually constructed as part of the engine block and head. Engine coolant

flows through the water jacket and keeps the cylinder walls from

overheating.


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Starter: Several methods are used to start IC engines. Most are started by

use of an electric motor (starter) geared to the engine flywheel. Energy is

supplied from an electric battery.

Supercharger Mechanical compressor powered off of the crankshaft, used

to compress incoming air of the engine.

Throttle: Butterfly valve mounted at the upstream end of the intake system,

used to control the amount of air flow into an SI engine. Some small engines

and stationary constant-speed engines have no throttle.

Turbocharger: Turbine used to compress incoming air into the engine. The

turbine is powered by the exhaust flow of the engine and thus takes very

little useful work from the engine.

Water pump: Pump used to circulate engine coolant through the engine and

radiator. It is usually mechanically run off of the engine.


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1.5 BASIC ENGINE CYCLES Most internal combustion engines, both spark ignition and compression

ignition are operating on either a four-stroke cycle or a two-stroke cycle.

These basic cycles are fairly standard for all engines, with only slight

variations found in individual designs.

Four-Stroke SI Engine Cycle


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Four-Stroke CI Engine Cycle

1. First Stroke: Intake Stroke The same as the intake stroke in an SI

engine with one major difference: no fuel is added to the incoming air.

2. Second Stroke: Compression Stroke The same as 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.

3. Combustion: Combustion is fully developed by TDC and continues at

about constant pressure until fuel injection is complete and the piston

has started towards BDC.

4. Third Stroke: Power Stroke The power stroke continues as

combustion ends and the piston travels towards BDC.

5. Exhaust Blowdown Same as with an SI engine.

6. Fourth Stroke: Exhaust Stroke same as with an SI engine.

Two-Stroke SI Engine Cycle


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Two-Stroke CI Engine Cycle

The two-stroke cycle for a CI engine is similar to that of the SI engine,

except for two changes. No fuel is added to the incoming air, so that

compression is done on air only. Instead of a spark plug, a fuel injector is

located in the cylinder. Near the end of the compression stroke, fuel is

injected into the hot compressed air and combustion is initiated by self-

ignition.


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INTERNAL COMBUSTION ENGINES...The following is a list of major components found in most reciprocating internal combustion engines (see Fig. 5). Fig.5: Cross-section of four-stroke