Internal combustion engine

Prepared by

Gaurav Bhati

SOT, PDPU

ENERGY CONVERSION The distinctive Feature of our civilization today , one that

makes it different from all others, is the wide use of mechanical power.

At one time the primary source of power was chiefly man’s muscles.

The great step was taken in this direction when man learned the art of Energy convrsion from one form to another.

The machine which does the job of energy conversion is called an ENGINE.

Definition of Engine A device that transforms one form of energy into other

form of energy.

HEAT ENGINE:

A device that transforms chemical energy of fuel into thermal energy which is utilized to perform useful mechanical work.

Heat engine can be broadly classified into two categories:

(i) Internal Combustion Engines

(ii) External Combustion Engines

History The first working internal combustion engine for

automobiles was Francois Isaac of Switzerland in 1807. Mixing hydrogen and oxygen for fuel.

The first gasoline powered engine was built in 1864 by Siegfried Marcus and was said to be the forerunner to the modern automobile.

In 1876 two of the greatest engines were invented, i-e two stroke engine by Nikolaus Otto and four stroke engine by Dougald Clerk. This started the rise of better and more efficient engines.

CLASSIFICATION OF HEAT ENGINESHEAT ENGINES

IC ENGINES EC ENGINES

ROTARY RECIPROCATINGROTARY RECIPROCATING

Open CycleGas Turbine

WankelEngine

GasolineEngine

DieselEngine

Steam Turbine

Gas Turbine

SteamEngine

StirlingEngine

Advantage of Reciprocating IC engine The most widely used are the reciprocating internal

combustion engine, The Gas turbine and Steam turbine.

The reciprocating internal combustion engine have absence of heat exchangers in the passage of the working fluid.

This result in a considerable mechanical simplicity and improved power plant efficiency of the IC engine.

All its component work at an average temperature which is much below the maximum temperature of the working fluid in the cycle.

Disadvantage The main disadvantage of this type of engine is the

problem of vibration caused by the reciprocating components.

Also, it is not possible to use a variety of fuels in these engines.

These fuels are relatively more expensive.

CLASSIFICATION OF IC ENGINES IC Engines

4-Stroke 2-Stroke

SI CI

Petrol GasDual Fuel

Divided Chamber

Injection TypeCarburetor Type

Magneto IgnitionBattery IgnitionSwirl

ChamberPre

Chamber

Air CoolWater Cool

Reciprocating Muti-cylinder Reciprocating Single Cylinder Rotary (Wankel)

V-Cylinder(4/6/8/12)

Inclined –Cylinder( 2/4/6)

Opposed Cylinder(2/4/6)

Reciprocating IC engines Reciprocating internal combustion engines uses

one or more reciprocating pistons to convert pressure

into a rotating motion.

Types of reciprocating IC engines:

Spark ignition (SI)

Compression ignition (CI)

Engine Components•Cylinder BlockMain supporting structure

•CylinderWhere piston makes a reciprocating motion

•PistonCylindrical component fitted into the cylinder which forms the first link in transmitting the gas forces to the output shaft.

•Combustion ChamberSpace enclosed in the upper part of the cylinder, by the cylinder head and piston top

•Inlet ManifoldPipe which connects the intake system to the inlet valve

Engine Components•Inlet and Exhaust ValvesProvided on the cylinder head or on the side of the cylinder

•Spark Plug Located on cylinder head

•Connecting RodInterconnects the piston and the crankshaft

•CrankshaftConverts the reciprocating motion into useful rotary motion of the output shaft

•Piston RingsFitted into the slots around the piston, provide a tight seal between piston and the cylinderwall

Engine Components•Gudgeon PinForms the link between the small end of CR and the piston

•CamsIntegral part designed to open the valves at correct timing

•Fly WheelTo achieve a uniform torque

NomenclatureCylinder Bore (d) •The nominal inner diameter of the working cylinder (mm).

Piston Area (A)• The area equal to cylinder bore (cm2) .

Stroke (L) • Nominal distance through which a working piston moves L and is expressed usually in millimeter (mm).

Stroke to Bore Ratio(L / d) • If d < L, under-square engine

• If d = L, square engine

• If d > L, over-square engine

•An over stroke can operate at higher speeds because of larger bore and shorter stroke

NomenclatureDead Centre •The position of the at either end of the stroke.

•Top Dead Centre (TDC) :

When the piston is farthest from the crankshaft

•Bottom Dead Centre (BDC): when the piston is nearest to the crankshaft

Swept Volume (Vs) •Nominal volume swept by the working piston when travelling from one dead centre to the other. It is expressed in terms of cubic centimeter (cc)

and given by

Nomenclature Cubic Capacity or Engine Capacity

Displacement volume of a cylinder multiplied by number of cylinders . If there are K cylinders in an engine, then

Cubic capacity = Vs x K

Clearance Volume (Vc)

The nominal volume of the combustion chamber above the piston when it is at the top dead centre is the clearance volume.

Nomenclature Compression Ratio (r)

It is the ratio of the total cylinder volume when the piston is at the bottom dead centre, Vr, to the clearance volume, Vc.

r = VT/Vc = Vc+Vs / Vc