Engine.

Engine.

An engine is a mechanical device which is design to convert one form of energy into mechanical energy.

Example.

·        Heat engine is use to convert heat energy into mechanical energy.

·        Electric meter is use to convert electrical energy into mechanical energy.

·        Hydraulic meter is used to convert pressure fluid into some mechanical work.

·        Molecular motor found in living things use chemical reaction to do useful work.

Part of engine.

Engine is used to produce some power, there are many part of an engine bolted together, they are used to do some work in connection with each other.

Cylinder block or cylinder.

Cylinder block is main part of an engine in which combustion (burning of fuel) take place many other parts such as piston, connecting rods, crankshafts are bolted in it.

Piston.

Piston is connected with cylinder block. It move freely up and down. It compress air fuel mixture and convert fuel energy into mechanical energy. It transmit power to the crankshaft.

Cylinder head.

Cylinder head is fitted on the top of cylinder block and the function of cylinder head is to seal the working end of cylinder block and not to permit entry and exit of gases, valve, cam shaft, and spark plugs are fitted on it.

Connecting rod.

It connects piston to the crankshaft and transmit motion.

Classification of I.C engine.

Classification of I.C engine are defined below.

1.                According to the design of the engine.

a)    Reciprocating engine (petrol engine).

a.     in reciprocating engine the pressure force is generated by combustion is exerted on the piston and it transmit the pressure force to crankshaft through connecting rods, so the crankshaft start to rotate the wheel of vehicle.

b)    Rotary engine (winkle engine).

a.     In rotary engine a rotor is used which is free to move when pressure force is exerted on the rotor. It start to rotate and thus rotate the crankshaft.

2.                 According to the type of fuel used.

a)     Diesel engine (I.C engine). 
b)    Petrol engine (S.I engine). 
c)     Gas engine (hot spot engine).

3.                 According to the stroke.

a)     Two stroke engine. 
b)    Four stroke engine. 
c)     Six stroke engine.

4.                 According to number of cylinder.

a)     Single cylinder engine. 
b)    Multi cylinder engine.

5.                 According to arrangement of cylinder.

a)     Inline cylinder. 
b)    V type cylinder. 
c)     Opposed type cylinder. 
d)    W type cylinder. 
e)     Radial engine.

Spark ignition (S.I) engine.

Spark ignition engine generally known as petrol/gasoline engine in an I.C engine, where the combustion process of air fuel mixture is ignited by spark from spark plug. S.I engine can run on fuel other than petrol such as auto gas (L.P.G), compressed natural gas (C.N.G), hydro gas, nitro methane in racing cars.

Ignition compression (I.C) engine.

I.C engine are commonly known as diesel engine in an I.C engine in which combustion take place due to high temperature which the gas (air) achieve when greatly compressed. Diesel engine work by compressing air, this this increase the air temperature to such an high extend that it ignite the fuel, diesel engine may be design either two stroke or four stroke cycle.

Spark ignition (S.I) engine	Ignition compression (I.C) engine
S.I engine work on Otto cycle or constant volume heat addition cycle.	I.C engine work on diesel cycle or constant pressure heat addition cycle.
S.I engine uses petrol as working fuel. It is highly volatile fuel.	I.C engine uses diesel as working fuel. It is nonvolatile fuel.
In S.I engine a carburetor is used for air fuel mixture.	In I.C engine fuel is injected directly into combustion chamber with a high pressure thus it consist of fuel pump and injector.
In S.I engine ignition is carried out with the help of spark plug.	In I.C engine ignition is carried out due to high compression of air.
In S.I engine compression ratio varies from 6 to 10.	In I.C engine compression ratio varies from 16 to 20.
Due to the lower compression ratio its thermal efficiency is lower	Due to higher compression its thermal efficiency is higher.

Two stroke cycle engine.

In a two stroke cycle engine the working cycle is completed in two stroke of a piston or one revolution of crankshaft. This is archive by carrying out suction, compression process in one stroke, expansion and exhaust process in second stroke.

Four stroke cycle engine.

In four stroke cycle engine, the working cycle is completed in four strokes of piston or two revolution of crankshaft, this is achieved by carrying out suction, compression, power and exhaust in each stroke.

two stroke cycle petrol engine.

Advantages.

·        A two stroke cycle engine gives twice the no. of power stroke than four stroke cycle engine at the same engine speed. Theoretically two stroke cycle engine should develop twice the power as that of four stroke.

·        For the same power developed, a two stroke is lighter, less bulky and occupy less floor area.

·        A two stroke cycle engine has lighter flywheel, thus it lead to higher mechanical efficiency as compare to four stroke cycle engine.

·        Initial cost of two stroke cycle engine is less than four stroke cycle engine.

·        The mechanism of two stroke cycle engine is much simpler than four stroke cycle engine.

·        The two stroke cycle engine are easier to start.

Disadvantages.

·        Thermal efficiency of two stroke cycle engine is less than four stroke cycle engine because of less compression ratio as compare to four stroke cycle engine.

·        Overall efficiency of two stroke cycle is less than four stroke cycle engine because in a two stroke inlet and exhaust ports remain open, at the time small quantity of charge lost from engine cylinder.

·        The consumption of lubricating oil is large in two stroke cycle engine as compare to four stroke cycle engine.

·        The exhaust gas in two stroke cycle engine create noise because of short time available for exhaust.

Four stroke cycle petrol engine.

It is also known as Otto cycle, it require four stroke of a piston to complete a cycle. The four stroke of petrol engine are described below.

1.    Suction stroke.

In this stroke, the inlet valve opens and charge is sucked into the cylinder as the piston move downward from TDC (top dead center) it continues till the position reaches BDC (bottom dead center)

2.    Compression stroke.

In this stroke both inlet and exhaust valve are closed and the charge is compressed as the piston moves from BDC (bottom dead center) to TDC (top dead center). As a result the pressure and temperature increased, this complete one revolution of crankshaft.

3.    Expansion or power stroke.

In this stroke shortly before the piston reaches TDC (top dead center) (during compression) the charge is ignited with the help of spark plug, it suddenly increases the pressure and temperature of product of combustion, due to rise in pressure the piston is pushed down with the great force. Hot burnt gases expend due to high speed piston, during this stroke both valves are closed and the piston moves from TDC (top dead center) to BDC (bottom dead center).

4.     Exhaust stroke.

In this stroke, exhaust valve is open as piston moves from BDC (bottom dead center) to TDC (top dead center). This movement of piston pushes burnt gases out from the engine cylinder. This compile the cycle and engine cylinder is ready to suck new charge again.