it contains complete information about aero engines- theory, components, working etc.

1. 1
IINNTTRROODDUUCCTTIIOONN TTOO AAEERROO
EENNGGIINNEESS
SSoommee ddeeffiinniittiioonnss rreellaatteedd ttoo jjeett eennggiinnee
11.. EEnnggiinnee:: EEnnggiinnee iiss aa mmaacchhiinnee wwhhiicchh ccoonnvveerrttss cchheemmiiccaall eenneerrggyy ooff ffuueell iinnttoo hheeaatt eenneerrggyy
ttoo ddoo wwoorrkk..
22.. AAeerroo eennggiinnee:: AAeerroo eennggiinnee iiss aa mmaacchhiinnee wwhhiicchh ttrraannssffoorrmmss ppootteennttiiaall eenneerrggyy ccoonnttaaiinneedd iinn
tthhee ffuueell aanndd aaiirr iinnttoo kkiinneettiicc aanndd // oorr mmeecchhaanniiccaall eenneerrggyy..
33.. GGaass TTuurrbbiinnee EEnnggiinnee:: AA ttyyppee ooff eennggiinnee wwhhiicchh ttrraannssffoorrmmss eenneerrggyy bbyy mmeeaannss ooff aa
ccoommpprreessssoorr,, ccoommbbuussttiioonn cchhaammbbeerr aanndd ttuurrbbiinnee..
44.. TTuurrbbiinnee:: TTuurrbbiinnee iiss aa wwhheeeell wwhhiicchh ddeerriivveess iittss ppoowweerr ffrroomm tthhee mmoottiioonn ooff aa fflluuiidd..
55.. PPrrooppuullssiioonn:: IImmppaarrttiinngg aacccceelleerraattiioonn ttoo aa cceerrttaaiinn mmaassss..
66.. TThhrruusstt:: AA ggaass jjeett eexxhhaauussttiinngg aatt hhiigghh vveelloocciittyy ffrroomm aa nnoozzzzllee ggeenneerraattiinngg aa ffoorrccee iinn tthhee
ooppppoossiittee ddiirreeccttiioonn iiss tteerrmmeedd aass tthhrruusstt..
77.. TTuurrbboo jjeett:: AAllll aaiirr ffllooww ggooeess tthhrroouugghh aa ggaass ggeenneerraattoorr ii..ee.. ccoommpprreessssoorr,, ccoommbbuussttiioonn
cchhaammbbeerr aanndd ttuurrbbiinnee..
88.. BByyppaassss TTuurrbboo jjeett:: IItt aaddmmiittss mmoorree aaiirr tthhaann nneecceessssaarryy ffoorr GGaass GGeenneerraattoorr,, aaddddiittiioonnaall ffllooww
bbyy--ppaassssiinngg tthhee GGaass GGeenneerraattoorr..
99.. TTwwiinn ssppooooll bbyyppaassss TTuurrbboo jjeett:: AA ggeenneerraattoorr iinnccoorrppoorraatteess ttwwoo iinnddeeppeennddeenntt rroottaattiinngg
aasssseemmbblliieess.. AA llooww pprreessssuurree ttuurrbbiinnee aanndd hhiigghh pprreessssuurree ttuurrbbiinnee sshhaafftt rruunnss ccooaaxxiiaallllyy ee..gg..
AALL--3311FFPP,, RRDD--3333 eennggiinnee..
1100.. TTuurrbboo pprroopp:: AA ggaass ttuurrbbiinnee eennggiinnee ddrriivviinngg aa pprrooppeelllleerr ee..gg.. AAVVRROO,, AANN--3322 aaiirrccrraafftt..
1111.. TTuurrbboo SShhaafftt:: AA ggaass ttuurrbbiinnee eennggiinnee ssuuppppllyyiinngg mmeecchhaanniiccaall eenneerrggyy oonn aa sshhaafftt ffoorr
vvaarriioouuss aapppplliiccaattiioonnss,, ee..gg.. HHeelliiccoopptteerr rroottoorrss,, eelleeccttrriicc ggeenneerraattoorrss..
1122.. FFrreeee ttuurrbbiinnee ttuurrbboo sshhaafftt:: PPoowweerr ttuurrbbiinnee iiss mmeecchhaanniiccaallllyy iinnddeeppeennddeenntt ooff GGaass
GGeenneerraattoorr,, ee..gg.. TTuurrbboo ssttaarrtteerr GGTTDDEE 111177--11MMOO..
1133.. MMoodduullee:: AAnn iinnddeeppeennddeenntt ssuubb aasssseemmbbllyy wwhhiicchh ccaann bbee eeaassiillyy rreemmoovveedd ffrroomm ootthheerr
aasssseemmbbllyy.. MMoodduullaarr ddeessiiggnn ppeerrmmiittss rreeppllaacceemmeenntt ooff aa mmoodduullee bbyy uusseerr wwiitthhoouutt rreettuurrnniinngg
ccoommpplleettee aasssseemmbbllyy ttoo ffaaccttoorryy..

2. 2
DESCRIPTION OF AERO-ENGINE:
TThhee aavviiaattiioonn ggaass ttuurrbbiinnee eennggiinnee iiss ccaatteeggoorriizzeedd aass aa hheeaatt eennggiinnee.. IItt uusseess ggaass aass iittss wwoorrkkiinngg
fflluuiidd aanndd pprroodduucceess ((mmeecchhaanniiccaall)) sshhaafftt ppoowweerr aanndd tthhrruusstt.. GGeenneerraattiinngg tthhrruusstt,, iinn ppaarrttiiccuullaarr,,
iiss ppoossssiibbllee oonnllyy iiff tthhee eexxhhaauusstt vveelloocciittyy ooff ggaass iiss hhiigghheerr tthhaann tthhee vveelloocciittyy aatt wwhhiicchh aaiirr
eenntteerrss tthhee eennggiinnee.. IInn oorrddeerr ttoo aacccceelleerraattee tthhee ggaass,, eenneerrggyy mmuusstt bbee aaddddeedd ttoo tthhee aaiirrffllooww
wwiitthhiinn tthhee eennggiinnee wwhhiicchh ccaann tthheenn bbee ccoonnvveerrtteedd iinnttoo kkiinneettiicc eenneerrggyy..
IInn aa ggaass ttuurrbbiinnee eennggiinnee,, tthhee iinnccrreeaassee ooff eenneerrggyy iiss aaccccoommpplliisshheedd iinn ttwwoo ccoonnsseeccuuttiivvee
sstteeppss,, aanndd bbyy ttwwoo ddiiffffeerreenntt,, tthhoouugghh aaddjjaacceenntt,, eennggiinnee ccoommppoonneennttss.. FFiirrsstt,, pprreessssuurree ooff tthhee
aaiirrffllooww iiss rraaiisseedd bbyy aaccttiioonn ooff mmeecchhaanniiccaall sshhaafftt ppoowweerr.. TThhiiss iiss ddoonnee iinn tthhee ccoommpprreessssoorr
sseeccttiioonn.. AAfftteerr iittss ddiisscchhaarrggee ffrroomm tthhee ccoommpprreessssoorr,, tthhee pprreessssuurriizzeedd aaiirr eenntteerrss iinn tthhee
ccoommbbuussttiioonn cchhaammbbeerr,, wwhheerree tthhee ffuueell aanndd pprreessssuurriizzeedd aaiirr bbuurrnnss,, tthheerreebbyy tteemmppeerraattuurree ooff tthhee
ggaass iiss sstteeeeppllyy rraaiisseedd ((dduuee ttoo cchheemmiiccaall rreeaaccttiioonn ooff aaiirr aanndd ffuueell mmiixxttuurree))..
TThhee ggaass iiss nnooww ssuuffffiicciieennttllyy pprroocceesssseedd ttoo pprroovviiddee pphhyyssiiccaall wwoorrkk ffoorr tthhee ttuurrbbiinnee,, tthhee
ffiirrsstt ssttaattiioonn wwiitthhiinn tthhee eennggiinnee wwhheerree wwoorrkk eexxttrraacctteedd ffrroomm tthhee hhoott ggaass iiss ttuurrbbiinnee.. AAss tthhee
ggaass eexxppaannddss aanndd aacccceelleerraatteess,, iitt rroottaatteess tthhee ttuurrbbiinnee wwhhiicchh iinn ttuurrnn rroottaatteess tthhee ccoommpprreessssoorr aass
ttuurrbbiinnee iiss ddiirreeccttllyy ccoouupplleedd ttoo tthhee ccoommpprreessssoorr bbyy aa sshhaafftt ((ssppooooll)).. AAfftteerr ddiisscchhaarrggiinngg ffrroomm
tthhee ttuurrbbiinnee,, tthhee ggaass iiss ffuurrtthheerr aacccceelleerraatteedd iinn tthhee eexxhhaauusstt nnoozzzzllee,, wwhheerree aallll rreemmaaiinniinngg
uussaabbllee hheeaatt eenneerrggyy iiss ccoonnvveerrtteedd iinnttoo kkiinneettiicc eenneerrggyy wwhhiicchh pprroodduucceess tthhrruusstt ffoorr mmoovviinngg tthhee
aaiirrccrraafftt ffoorrwwaarrdd ((NNeewwttoonn TThhiirrdd LLaaww))..

3. 3
Types of aero engines
There are mainly three types of aero gas turbine engines. Those are:
Turbojet:
A turbojet engine is a gas turbine engine that works by compressing airwith an inlet and a
compressor (axial, centrifugal or both), mixing the fuel with compressed air, burning the
mixture in the combustor, and then passing the hot, high pressure air through a turbine,
which extracts energy from the expanding gas passing through it. The engine converts
internal energy in the fuel to kinetic energy in the exhaust, producing thrust.
Turbofan:
A turbofan engine is a gas turbine engine that is very similar to the turbojet. Like a
turbojet it uses the gas generator core (compressor, combustor, turbine) to convert
internal energy in fuel to kinetic energy in the exhaust. Turbofans differ from turbojets in
that they have an additional component, a fan. Like the compressor the fan is powered by
the turbine section of the engine. Unlike the turbojet some of the flow accelerated by fan
bypasses the gas generated core and is exhausted through a nozzle making the thrust
produced by the fan more efficient than that produced by the core.

4. 4
Turboprop:
It is a type of gas turbine engine. In turboprop engines, a portion of the engine’s thrust is
produced by spinning a propeller, rather than relying solely on high speed jet exhaust. As
their jet thrust is augmented by a propeller, turboprops are occasionally referred to as a
type of hybrid jet engine.
AAiimm ooff jjeett eennggiinnee
AAiimm ooff jjeett eennggiinnee iiss ttoo ggeenneerraattee hhoott ggaasseess aatt aa pprreessssuurree mmuucchh hhiigghheerr tthhaann aammbbiieenntt
pprreessssuurree ffoorr eexxppaannssiioonn iinn aa nnoozzzzllee ttoo pprroodduuccee tthhrruusstt.. CCeennttrraall eelleemmeenntt ooff jjeett eennggiinnee iiss ggaass
ggeenneerraattoorr wwhhiicchh ccoommpprriisseess ooff ccoommpprreessssoorr,, ccoommbbuussttiioonn cchhaammbbeerr aanndd ttuurrbbiinnee.. BByy aaddddiinngg
aann iinnlleett aanndd aa nnoozzzzllee,, aa ttuurrbboojjeett rreessuullttss..

5. 5
Major parts and their functions of
Aero gas turbine engine:
AIR IN TAKE SYSTEM
Air intake of any turbojet powered aircraft has to carry out the very
important function of converting type kinetic energy of air flow to pressure energy
by compressing the air to a sufficiently high degree before it reaches the
compressor face. The engine performance i.e. thrust and specific fuel consumption
will depend upon the affiant conversion of this energy. At subsonic flight speeds,
the compression takes place mainly on the compressor. However, with the increase
in flight speeds more and more compression takes place in the air intake duct. At
Mach 2 the degree of compression in the air intake and the compressor is almost
equal.
Operation of air intake is quit complex for a supersonic aircraft due to
the wide range of the operating flight spectrum. As a component in the engine
aircraft system, the intake must satisfy a number of requirements such as:
a. Delivering the correct amount of air to the engine face as correct
speed with minimum loss of total energy contents.
b. Operating with a uniform discharge velocity profile as the
compressor surface.
c. Maintaining surge free steady flow in the air intake.
d. Creating maximum external drag due to airflow.
PRESSURE RECOVERY
In order to obtain high thrust, it is necessary to recover the full energy
of free system with minimum of pressure loss. The pressure losses occur due to
friction, eddy loss and shows. At the supersonic speed pressure loss due to friction
and eddies is less compared to the loss across the shock system. Pressure loss
across the shock system is highest if declaration of flow is achieving by normal
shock and is reduce if it is achieved through series of oblique shocks. A shock
system for minimum pressure loss as a particular Mach no. can always be design.
Reducing the slow speed and channel length reduces the frictional losses.
Adequate lip contouring reduces Eddy losses.

6. 6
MASS FLOW
The mass flow coefficient is the ratio of actual mass flow captured by
the intake to the maximum mass flow corresponding to check operation. The
operation of the air intake is said to be subcritical if the ratio is less than one and is
said to be super critical if the ratio is one or more. If the air supply is less than
engine requirement, then auxiliary profile must be provided so that engine does not
flame out. Such condition occurs during takeoff. The air is inducted through the
take of shutter which opens automatically during takeoff due to the difference in
the pressure between the outside air and air inside the channel. If supply is more
this extra air is must bypass to atmosphere before it reaches as the engine speed
increases the air requirement increases. In order to provide the correct amount of
air, it is necessary to contend the lip area.
DRAG OF INTAKE
Drag of intake consists of frictional drag. Low pressure drags additive
drag due to spillage of flow and shock drag. Additive drag is zero if mass flow co-
efficient is unity skin friction drag and pressure drag are generated due to the air
flow over the internal and external surface of the air channel. These drag forces
reduce the net thrust available on the aircraft.
To reduce the drag, it is necessary to reduce the fontal size of air
intake to minimum. The air spillage reduce the shock strength contour the lip
geometry properly avoid sudden turning of flow in the channel and use adequate
boundary air bleed.
ACCESSORY DRIVE
LP compressor shaft provides the drive for following accessories through
suitable gear train and quill shaft.
a) Front scavenging oil pump.
b) Up compressor rotor with techno meter generator.
c) Centrifugal governor of main fuel regulating pumps.
HP turbine shaft provides the drive to the accessory gearbox through a
bevel gear train and coupling shaft from where the drive from the following
accessories is taken through and work of gear train and shafting.
 Starter generator
 Fuel regulating pump

7. 7
 Hydraulic pump
 Fuel booster pump
 Oil unit
 De-aestor
 Breather
 Air craft generator
 HP rotor tachometer generator
COMPRESSOR
Axial flow compressor is used in aero engine because in centrifugal
compressor the compression ratio is fixed. But in axial flow compressor C.R is
very high. There are two types
1. Single spool (Only one shaft is used)
2. Double spool (Two shafts are used)
Compressor has basically –
(i) Rotor blades (ii) Stator blades
Rotor blades add kinetic energy to the suction air, stator blades
converts the kinetic energy into pressure energy.
COMPRESSOR CASING
It consists of a distance ring, front casing, middle casing, split casings
(IVth, Vth, Vith, stage rotor) and rear casing (VIth stage stator).
DISTANCE RING
Distance ring provides smooth entry of air into the compressor and
also helps to couple the engine to the aircraft intake through the air radiator of
intake. The rear flange of the casing is bolted to the front casing.
FRONT CASING
The front casing houses the 1st stage rotor blades, which are in, turn
bolted to the front bearing housing. The IInd stage casing comprises of the outer
and inner rings and IInd stage stator blades spot-welded to the rings.
MIDDLE CASING
Middle casing houses IIIrd stage stator blades, which are welded as
the outer radius. At the inner radius, a flange ring is welded to the stator blades. Air
is tapper from inter space between the inner ring of the middle casing and IVth
stage rotor assembly for various purposes such as pressurization of HP compressor

8. 8
lubricating oil seals, cooling and seal pressurization for the turbine assembled and
thrust balancing of the HPCR.
SPLIT CASING
Split casings accommodate IVth and Vth stage stator blades, which
are welded to them. The casings are bolted to the middle casing at one end to the
load ring of the rear casing at the other end.
REAR CASING
The rear compressor casing houses the VIth stage stator blades, which
are bolted to the outer casing which at the inner radius. They are bolted to the rear
casing diaphragm flange.
COMPRESSOR ROTOR
The rotor assembly consists of individual discs with each set of HP
and LP spools forming ad room type construction except the 1st stage compressor
disc. The 1st stage disc is mounted as a cantilever on the LP compressor shaft with
the help of involute splined joint. The disc is located on the shaft by a splined lock
bolt. The nose bullet is of double construction and is given hydro phobic enamel
coating to prevent ice formation and erosion.
The rotor blades of 1st, 2nd and 3rd stages are secured in the
respective discs by dove tailed locks. The axial movement is restricted either by
retaining dowels or by blades retaining rings or by both. HP compressor assembly
is built as an integral unit with the journal. The journal in the main torque
transmitting member and is fitted in the center bearing housing in two radial thrust
half bearings.
COMBUSTION CHAMBER
The combustion chamber is can annular type with ten straight flame
tubes, which are arranged between the combustion chamber outer casing and the
surround of the rear casing. Each flame tube consists of a conical section followed
by five cylindrical liners followed by one rear transition liner which are seem
welded to each other. The conical section has a vanned swirler and a deflector and
is spot-welded to the liner.
The combustion liners are provided with 12 slots in welded zone to
reduce thermal stresses and for a closer fit of the welded surfaces. The outer wall

9. 9
of conical section has holes for providing air for cooling the deflector. The
deflector itself has two rows of holes. Holes on 3rd, 4th, 5th liners are suitably at
the shoulders of the liners (near welded section) for cooling liner walls. The air
form these holes are made to flow along the circumference by the extension of
liners. Flame tubes are inter connected by the inter connector tubes located in the
conical section. The inter connectors between flame tubes I, II, IX and X are
provided with fuel connection to receive the two ignitor connections. Flame
propulsion and pressure equalization among the flame tube is effected by the inter
connectors. The ignition assembly is mounted on the compressor chamber outer
casing and has three connections, one for supply of starting fuel to the inner cavity
of ignitors another for location of spare plug and the other for oxygen supply
required for flight relighting. The extended steam of ignitor has four holes to
provided P2 air supply to inner cavity. A deflector provides in the cavity gives P2
air and upward motion.
The front end of flame tube rest on burners to spherical to incorporate
in the swirlers and at the rear end the flange of the flame tube is redidity secured to
the common ring. Combustion chamber outer casing is fabricated from the sheet
metal sections and is provided with three flanges, front flange for securing the
C.C.O.C to the stator none of six stage compressor, middle and front flanges serve
for mounting the bracket of accessory drive gearbox assembly and rear flange is
connected to turbine nozzle diaphragm assembly. For inflight relighting oxygen at
7-9 kg/cm2
at the rate of 0.95 to 1.2 gm/sec/ignitor, which is taken from oxygen
bottles in aircraft. Flame tubes are made up of Ni base alloy and coated with
spherical enamel to improve heat and corrosion properties. The C.C.O.C and
C.C.I.C are made up of S.S
TURBINE
The function of the turbine is to drive the compressor and accessories
by extracting pressure and kinetic energy from high temperature gases coming
from C.C. Based on the flow of gases on the gas turbine it is classified into
1. Axial flow turbines
2. Radial flow turbines
In axial flow turbine gas enters and leaves axially where in radial flow
turbine gas enters radially and leaves axially and vice-versa. The axial flow turbine
consists of two main elements consisting of a set of stationary vanes and one or
more turbine rotors. In stationary vanes the pressure energy is converted to K.E
and the same is converted into mechanical energy with rotary blades. Nozzle vanes
either cast or forged. Some vanes are made hollow to allow cooling using pump,
bleed air. The blades of turbine are two basic types.

10. 10
1. Impulse turbine
2. Reaction turbine
The turbine is of axial flow reaction type T3 maximum is limited to 936°c.
Turbine needed cool to avoid over heating of components. A rotor assembly are
supported by radial thrust ball bearings and cylindrical roller bearing as the
compressor and turbine and respectively. Fixed vanes are arranged radially
between concentric rings.
1st stage NGVS are made of hollow for cooling air in investment
casting. These are sliding fit over the spokes arrange radially between the internal
and external rings.
ROTORS
Discs of L.P.T and H.P.T are presses fitted into the shaft are fastened
together by means of radial pins, which ensures concentricity of disc and shaft.
Blades are fixed in broached fire-tree slots in the disc and are lock by plate locks.
Blades are cropped at the tip in order to eliminate occurrence of cracks due to
unfavorable resonance vibration at the railing edge. LP blades are placed together
at about 2/3 of the blade height to avoid resonance vibration. Where the lace passes
extra material is provided and this locally thickened area blends itself with aerofoil
to minimize aerodynamic losses. No hairline cracks and under cuts is permitted at
this place. Natural frequency limits of H.P.T.R blades are 1130 - 1190 LPS.
Frequencies of higher order should not be less than 9200 cps.
Delta turbine temperature= 278°c
Turbine efficiency = 0.9
Pressure ratio at turbine = 3.43
AFTER BURNER AND JET NOZZLE
To provide higher thrust for short durations such as during take-off,
acceleration, climb and combat after burner are made use of a higher thrust engine
without thrust augmentation would mean a higher of the basic engine large fontal
area and high A/F ratio in gas turbines. Levels sufficient amount of unburnt
oxygen is made use of for burning consist of introduction and burning of fuel
between turbine and jet nozzle. The engine after burner system comprises of the
following.
1. DIFFUSER
A diffuser serves to reduce the velocity of gases from the turbine to a
level suitable the flame. It consists of outer shell and an inner shell or truncated
cone, supported by five aerofoil shaped fairings.

11. 11
2. REHEAT PILOT COMBUSTION CHAMBER
Installed in the truncated cone of the diffuser, this provided the hot
stream of the pilot flame to light of the after burner fuel. This comprises of an
ignitor head with ignitor plug and ignitor case with nozzle. Electric current is fed to
the ignitor housing is coated with heat resistant enamel. Also cooling is provided
by air at P2.
3. AFTER BURNER MAIN FOLDS
It consists of an outer manifold with 60 burners (40 shaped on ring
and 20 shaped on pipes burning offering) and an inner manifold with 40 burners
(30 on ring and 10 on pipes along with two starting burners). The burners are of
simplex type and all supply atomized fuel against the direction of gas flow except
the starting burners, the starter burners supply fuel into the proposating the pilot
flame.
4. FLAME STABILIZER
Flame stabilizers are of radial type, which serves as flame holder and
are mounted near the out let of the diffuser.
5. VARIABLE AREA JET NOZZLE
It is a convergent nozzle, which increases the velocity of gases leaving
the after burner, thereby increasing thrust. The high mass flow and temperature of
exhaust gases during reheat requires the nozzle to be opened up, which is not done
result in unstable operation of the engine. This explains the need for variable area
jet nozzle. Nozzle flaps 18 in number are provided for this purpose with the flap
control ring being actuated by the cylinders.
SOME MORE TERMS RELATED IN VARIOUS SYSTEMS TO AN
AEROENGINE:
GAS TURBINE ENGINE: - An engine in which the working fluid is heated by
internal combustion be expanded through a turbine.
AERO ENGINE: An engine used to provide the main propulsive or lifting power
for aircraft.
CONSUMPTION: The total quantity of fuel consumed per hour.
SPECIFIC CONSUMPTION: - The weight propellant or fuel consumed per Kg of
thrust per hour.

12. 12
ACCESSORY GEARBOX: - An engine drives the gearbox driving accessories.
ENGINE RATING: - A statement of the guaranteed minor alternately the average
performances of the engine, including output r.p.m specific fuel consumption, gas
temp, time limit and other relevant data specified conditions.
HEIGHT POWER FACTOR: - The ratio of power or thrust developed at a
specified attitude to that which would be developed at standard sec level it applied
to maximum power or thrust conditions of fuel throttle.
POWER UNIT: - An engine or two more engines complete with all components
and accessories used as fitted into an aircraft.
DRY WEIGHT: - The weight of an aero engine without liquid but including all
accessories essential to its running and any drives incorporated it for non-essential
accessories.
WEIGHT PER KG THRUST: - The dry weight of an engine divided by the
maximum permissible thrust under standard sec level conditions.

13. 13
PRINCIPLE OF FLIGHT
Four forces come into action in an aero engine while flying.
1) Lift
2) Gravity
3) Thrust
4) Drag
1) LIFT
It is produced by a lower pressure created on the upper surface of an
airplane’s wings compared to the pressure on the wing’s lower surface, causing the
wing to be lifted upwards. Lift depends upon: -
i) Shape of the airfoil.
ii) The angle of attack.
iii) The area of the surface exposed to airstream.
iv) The square of the air speed.
v) The air density.
2) GRAVITY
It is due to weight of the plane itself that acts vertically downwards
from the center of gravity of the airplane.
3) THRUST
It is the forward direction pushing or pulling force created by the air
passing through the adjustable nozzle. This includes reciprocating engines, turbojet
engines and turboprop engines.
4) DRAG
Drag is the force which opposes the forward motion of airplane. It is a
retarding force acting upon a body in motion through a fluid, parallel to the
direction of motion of a body. It is created by air impact force, skin friction and
displacement of air.

14. 14
PRINCIPLE OF JET ENGINE/GAS TURBINE
ENGINE
Modern gas turbine engines follow the Brayton Cycle. An engine cycle is named after
George Brayton (1830-1892), the American Engineer who developed it originally for use
in piston engines, although it was originally proposed and patented by Englishman John
Barber in 1791.
The ideal Brayton cycle in gas turbine engine consists of three components:
1. A gas compressor
2. A burner (or combustion chamber)
3. An expansion turbine
The processes involved in Ideal Brayton cycle are:
Isentropic process- ambient air is drawn into the compressor where it is pressurized.
Isobaric process- the compressed air then runs through a combustion chamber, where
fuel is burned, heating the air- a constant pressure process, since the chamber is open to
flow in and out.
Isentropic process- the heated, pressurized air then gives up energy, expanding through a
turbine. Some of the work extracted by the turbine is used to drive the compressor
Isobaric process- heat rejection (in the atmosphere).
The processes involved in Actual Brayton cycle are:
Adiabatic process- compression
Isobaric process-heat addition
Adiabatic process-expansion
Isobaric process-heat rejection
Brayton Cycle

15. 15
WWoorrkkiinngg ooff aa jjeett eennggiinnee // ggaass
ttuurrbbiinnee eennggiinnee
TThhee aavviiaattiioonn ggaass ttuurrbbiinnee eennggiinnee iiss ccaatteeggoorriizzeedd aass aa hheeaatt eennggiinnee.. IItt uusseess ggaass aass iittss
wwoorrkkiinngg fflluuiidd aanndd pprroodduucceess ((mmeecchhaanniiccaall)) sshhaafftt ppoowweerr aanndd tthhrruusstt.. GGeenneerraattiinngg tthhrruusstt,, iinn
ppaarrttiiccuullaarr,, iiss ppoossssiibbllee oonnllyy iiff tthhee eexxhhaauusstt vveelloocciittyy ooff ggaass iiss hhiigghheerr tthhaann tthhee vveelloocciittyy aatt
wwhhiicchh aaiirr eenntteerrss tthhee eennggiinnee.. IInn oorrddeerr ttoo aacccceelleerraattee tthhee ggaass,, eenneerrggyy mmuusstt bbee aaddddeedd ttoo tthhee
aaiirrffllooww wwiitthhiinn tthhee eennggiinnee wwhhiicchh ccaann tthheenn bbee ccoonnvveerrtteedd iinnttoo kkiinneettiicc eenneerrggyy..
IInn aa ggaass ttuurrbbiinnee eennggiinnee,, tthhee iinnccrreeaassee ooff eenneerrggyy iiss aaccccoommpplliisshheedd iinn ttwwoo ccoonnsseeccuuttiivvee
sstteeppss,, aanndd bbyy ttwwoo ddiiffffeerreenntt,, tthhoouugghh aaddjjaacceenntt,, eennggiinnee ccoommppoonneennttss.. FFiirrsstt,, pprreessssuurree ooff tthhee
aaiirrffllooww iiss rraaiisseedd bbyy aaccttiioonn ooff mmeecchhaanniiccaall sshhaafftt ppoowweerr.. TThhiiss iiss ddoonnee iinn tthhee ccoommpprreessssoorr
sseeccttiioonn.. AAfftteerr iittss ddiisscchhaarrggee ffrroomm tthhee ccoommpprreessssoorr,, tthhee pprreessssuurriizzeedd aaiirr eenntteerrss iinn tthhee
ccoommbbuussttiioonn cchhaammbbeerr,, wwhheerree tthhee ffuueell aanndd pprreessssuurriizzeedd aaiirr bbuurrnnss,, tthheerreebbyy tteemmppeerraattuurree ooff tthhee
ggaass iiss sstteeeeppllyy rraaiisseedd ((dduuee ttoo cchheemmiiccaall rreeaaccttiioonn ooff aaiirr aanndd ffuueell mmiixxttuurree))..
TThhee ggaass iiss nnooww ssuuffffiicciieennttllyy pprroocceesssseedd ttoo pprroovviiddee pphhyyssiiccaall wwoorrkk ffoorr tthhee ttuurrbbiinnee,, tthhee
ffiirrsstt ssttaattiioonn wwiitthhiinn tthhee eennggiinnee wwhheerree wwoorrkk eexxttrraacctteedd ffrroomm tthhee hhoott ggaass iiss ttuurrbbiinnee.. AAss tthhee
ggaass eexxppaannddss aanndd aacccceelleerraatteess,, iitt rroottaatteess tthhee ttuurrbbiinnee wwhhiicchh iinn ttuurrnn rroottaatteess tthhee ccoommpprreessssoorr aass
ttuurrbbiinnee iiss ddiirreeccttllyy ccoouupplleedd ttoo tthhee ccoommpprreessssoorr bbyy aa sshhaafftt ((ssppooooll)).. AAfftteerr ddiisscchhaarrggiinngg ffrroomm
tthhee ttuurrbbiinnee,, tthhee ggaass iiss ffuurrtthheerr aacccceelleerraatteedd iinn tthhee eexxhhaauusstt nnoozzzzllee,, wwhheerree aallll rreemmaaiinniinngg
uussaabbllee hheeaatt eenneerrggyy iiss ccoonnvveerrtteedd iinnttoo kkiinneettiicc eenneerrggyy wwhhiicchh pprroodduucceess tthhrruusstt ffoorr mmoovviinngg tthhee
aaiirrccrraafftt ffoorrwwaarrdd ((NNeewwttoonn TThhiirrdd LLaaww))..
EExxppllaannaattiioonn ooff wwoorrkkiinngg pprriinncciippllee..
AA.. TThhee aaiirr ffrroomm aattmmoosspphheerree iiss
ttaakkeenn iinn tthhrroouugghh aa ssiimmppllee oorr
ccoommpplleexx aaiirr iinnttaakkee ddeeppeennddiinngg oonn
tthhee fflliigghhtt ssppeeeedd aanndd ggeeoommeettrryy ooff
tthhee aaiirrccrraafftt aaiirr iinnttaakkee..
BB.. AAiirr iiss ccoommpprreesssseedd iinn aa cceennttrriiffuuggaall
oorr aaxxiiaall ffllooww ccoommpprreessssoorr ttoo iinnccrreeaassee
tthhee pprreessssuurree aanndd tteemmppeerraattuurree ooff aaiirr..
CC.. CCoommpprreesssseedd aaiirr eenntteerrss iinn
ccoommbbuussttiioonn cchhaammbbeerr wwhheerree ffuueell
iiss iinnjjeecctteedd aanndd bbuurrnneedd,, tthhuuss aaddddiinngg
mmoorree eenneerrggyy ttoo aaiirrffllooww.. TTeemmppeerraattuurree ooff ggaass
iinnccrreeaasseess wwhheerree aass pprreessssuurree rreemmaaiinnss
ccoonnssttaanntt..

16. 16
DD.. PPaarrtt ooff tthhee eenneerrggyy ggeenneerraatteedd
iiss uusseedd ttoo rruunn aa ttuurrbbiinnee wwhhiicchh
pprroovviiddeess ppoowweerr ffoorr rruunnnniinngg tthhee
ccoommpprreessssoorr aanndd aallssoo ssoommee
aacccceessssoorriieess nneecceessssaarryy ffoorr eennggiinnee
ooppeerraattiioonn..
EE.. TThhee rreemmaaiinniinngg eenneerrggyy ooff ggaass
ssttrreeaamm iiss ccoonnvveerrtteedd iinnttoo kkiinneettiicc
eenneerrggyy bbyy eexxhhaauusstt nnoozzzzllee ttoo pprroodduuccee
tthhrruusstt.. HHiigghh eexxhhaauusstt vveelloocciittyy iiss
pprreerreeqquuiissiittee ttoo ggeenneerraattiioonn ooff tthhrruusstt..

17. Thank You