ENGINE & WORKING PRINCIPAL OF IC ENGINE

Engine & working principle of ic engine

A heat engine is machine .Which converts heat energy into mechanical energy .The combustion of fuel such a petrol,diesel generates heat.This heat is supplied to a working substance at high temperature .By  the expansion of this substance in suitable machine,heat energy is converted into useful work .Heat engine can be further divided into two types.
1. External combustion
2. Internal combustion
In a steam engine the combustion of fuel takes place outside the engine and the steam thus formed is used to run the engine.Thus it is known as external combustion engine .In the case of internal combustion engine.The combustion of fuel takes place inside the engine cylinder itself .

The IC engine can be further classified as;
1. Horizontal and vertical
2. Low, medium or high speed



                                                        HEAT ENGINE 
1.External combustion -
                       Steam engine

2.Internal combustion -
               2.1 Reciprocating
                      CI engine  - Two stroke ,Four stroke
                      SI engine  - Two stroke ,Four stroke


MATERIAL USED FOR ENGINE

Name of the parts	Material of constructions
Cylinder head	Cast iron , Cast Aluminium
Cylinder liner	Cast steel , Cast iron
Engine block	Cast iron , Cast aluminium ,Welded steel
Piston	Cast iron , Aluminium alloy
Piston pin	Forged steel ,Aluminium alloy
Connecting rod	Forged steel , Aluminium alloy
Piston rings	Cast iron , Pressed steel alloy
Connecting rod bearings	Bronze , White metal
Main bearings	White metal , steel backed Babbitt base
Crankshaft	Forget steel , Cast steel
Camshaft	Forged steel , Cast iron , Cast steel
Timing gears	Cast iron , Fiber, Steel forging
Push rods	Forged steel
Engine valves	Forged steel ,Steel, alloy
Valves springs	Carbon spring steel
Manifolds	Cast iron , Cast aluminium
Crankcase	Cast iron, Welded steel
Flywheel	Cast iron
Studs and bolts	Carbon steel
Gaskets	Cork , Copper, Asbestos

Principal of operation of IC engine
1. Two stroke cycle diesel engine 
Two cycle of the four stroke of the piston (the suction , compression, power and exhaust strokes)
is completed only in two strokes in the case of a two strokes engine.The air is dawn into the crankcase due to the suction created by the upward stroke of the piston. On the down stroke of  the piston it is compressed in the crankcase.The compression pressure is usually very low , being just sufficient to enable the air to flow into the cylinder through the transfer port when the piston reaches near the bottom of its down stroke .
The air thus flows into the cylinder where the piston compresses it as it ascends, till the piston is nearly at the top of its stroke.The compression pressure is increased sufficiently high to raise the temperature of the air above the self ignition point of the fuel used .The fuel is injected into the cylinder head just before the completion of the compression stroke and only for a short period .The burnt gases expand during the next downward stroke of the piston .These gases escape into the exhaust pipe to the atmosphere through the piston uncovering the exhaust port.