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Four Stroke Engines, Two Stroke Engines
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WHAT IS HEAT ENGINE?
The device which is able to derive heat
energy from the combustion of the fuel and
able to transfer this heat energy in to
mechanical energy is known as a heat
engine.
There are two types of heat engines.
External Combustion Engine
Internal Combustion Engine
CLASSIFICATION OF I.C. ENGINES
Types of Fuel used as:
Petrol Engine
Diesel Engine
Gas Engine
Nature of Thermodynamic cycle as:
Otto cycle Engine
Diesel cycle Engine
Duel cycle Engine
CLASSIFICATION OF I.C. ENGINES
Number of strokes per cycle as:
Four stroke engine
Two stroke engine
Method of ignition as:
Spark ignition engine
Compression ignition engine
CLASSIFICATION OF I.C. ENGINES
Method of cooing as:
Air cooled engine
Water cooled engine
Speed of the engine as:
Low speed engine
Medium speed engine
High speed engine
CLASSIFICATION OF I.C. ENGINES
Number of cylinder as:
Single cylinder engine
Multicylinder engine
Position of cylinder as:
Inline Engine
V-Engine
Radial Engine
Opposed cylinder engine
Opposed piston engine
ENGINE COMPONENTS
Cylinder
Cylinder head Piston Piston ring Piston pin Connecting rod Crank & Crank shaft Valves Flywheel Crank case
Carburetor Fuel Pump Fuel injector Spark plug
ENGINE COMPONENTS
Cylinder & Cylinder head: It is the heart of the engine in which the fuel is
burnt and the power is developed. It has to withstand very high pressure and
temperature because the combustion of fuel is carried out within the cylinder. Therefore cylinder must be cooled.
Piston reciprocates inside the cylinder. Cylinder head covers top end of cylinder. It
provides space for valve mechanism, spark plug, fuel injector etc.
ENGINE COMPONENTS
Piston: The function of the piston is to transmit the
gas force to connecting rod, hence to the crank.
It slides in the cylinder. Pistons are generally made of aluminum alloys
and cast steel.
ENGINE COMPONENTS
Piston rings: The piston rings are metallic rings inserted
into circumferential grooves provided at the top of the piston. This rings maintain gas tight joint between the piston and the cylinder while piston is reciprocating inside the cylinder.
Piston rings made of cast steel are provided to prevent the leakage of gas to crank case. Upper
rings are called compression rings. Lower piston rings are oiling rings.
ENGINE COMPONENTS
Piston pin or Gudgeon pin: It connects the piston to small end of the
connecting rod. It is made of hardened steel in the shape of
spindle. Connecting rod: As the name suggests, it connects piston on
one side through piston pin and crankshaft on other side through crank pin.
It forms the main link for converting reciprocating motion of piston in to rotary motion of crankshaft.
It is usually made of steel forging.
ENGINE COMPONENTS
Crank and Crank Shaft: The crank is a leaver that is connected to big
end of connecting rod by pin joint with its other end connected rigidly to a shaft called crank shaft.
As piston reciprocates in cylinder, crank rotates about the axis of crankshaft.
Crankshaft is supported by bearings.
ENGINE COMPONENTS
Valves and valve gear mechanism: Engine has intake valve and exhaust valve. They are operated by valve gear mechanism. Valves controls the flow of intake air and
exhaust gases to and form engine cylinder. Flywheel: A heavy rotating mass is attached to
crankshaft outside the crankcase called flywheel.
The function of the flywheel is to smooth out the cyclic fluctuations of torque developed by the reciprocating engine during cycle.
ENGINE COMPONENTS
Crank case: It is the lower part of the engine, serving as
an enclosure of the crank shaft and also as a sump for the lubricating oil.
Carburetor: It is used in petrol engine and its function is to
prepare proper mixture of air and petrol. Spark plug: It is used in petrol engine to produce high
intensity spark for ignition of air petrol mixture in the cylinder.
ENGINE COMPONENTS
Fuel Pump: It is used in diesel engine for increasing
pressure of fuel and controlling quantity of fuel supplied to injector.
Fuel injector: It is used to inject diesel in the form of fine
atomized spray in the cylinder.
I.C. ENGINE TERMINOLOGY
Bore (D):The inner diameter of cylinder is called a bore.
Dead Centres: In case of vertical engines, Top most position
of piston is called top dead centre (T.D.C.). In case of vertical engines, Bottom most
position of piston is called bottom dead centre (B.D.C.).
I.C. ENGINE TERMINOLOGY
Dead Centres: In case of horizontal engines, inner most
position and outer most position of the piston are called inner dead centre (I.D.C.) and outer dead centre (O.D.C.) respectively.
Stroke (L): Travel of piston from one dead centre to other
dead centre is termed as stroke.
I.C. ENGINE TERMINOLOGY
Clearance Volume (Vc ): The volume contained in the cylinder above
the piston from its top dead centre position is called clearance volume. It is denoted by Vc.
The volume between cylinder head and piston when piston is at top dead centre is called clearance volume.
I.C. ENGINE TERMINOLOGY
Stroke Volume: The volume displaced by the piston, when it
moves from TDC to BDC is called stroke volume. It is denoted by Vs.
Vs = π/4 × d2 × l
Where, d = Bore l = Stroke
I.C. ENGINE TERMINOLOGY
Compression Ratio (r): The ratio of cylinder volume to clearance
volume is called the compression ratio of the engine.
I.C. ENGINE TERMINOLOGY
Piston speed:It is the average speed of piston. It is equal to 2LN. Unit is m/min. Where, N = Speed of crank shaft in
rpm, Piston speed Vp = 2LN/60 m/sec
FOUR STROKE SINGLE CYLINDER PETROL ENGINE
The cycle of operation in a four stroke petrol engine is completed in two revolutions of crank shaft or four strokes of piston.
There are basic four strokes: a) Suction stroke b) Compression stroke c) Expansion stroke (Working stroke) d) Exhaust stroke
TWO STROKE SINGLE CYLINDER PETROL ENGINE
The cycle of operation in a two stroke petrol engine is completed in one revolutions of crank shaft or two strokes of piston.
There are basic four strokes: a) Suction stroke b) Compression stroke c) Expansion stroke (Working stroke) d) Exhaust stroke