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Vijayamangalam – 638 056

Department of Mechanical Engineering

Effective Study Material

ME 660 – !a" Dynamic" and #et $ropul"ion

$repared %y

&'(avindiran' ME')

*""i"tant $rofe""or)

Department of Mechanical Engineering)

Sa"urie &ollege of Engineering'


2/56

Vijayamangalam – 638 056

Department of Mechanical EngineeringSubject Name: Gas Dynamics and Jet Propulsion

+,-. -

/*S-& &,&E$.S *,D -SE,.($-& 12S

Energy and momentum equations of compressible fluid flos ! Stagnation states" Mach a#es

and Mach cone ! Effect of Mach number on compressibility ! $sentropic flo through #ariable

ducts ! No%%le and Diffusers

$*(.4*

' Define compressible flo and Mach number& *pril7May 059 *pril7May 009

:ey ;int<

&ompre""i%le flo=<

• 'he density of the fluid changes from point to point ()≠ *onstant+ mar>9

Mach num%er<

'he ratio of the fluid #elocity to the #elocity of sound

M =c

a

mar>9

,& Define stagnation state& ,ov7Dec 09 *pril7May 009:ey ;int<

$t is obtained by decelerating a gas isentropically to %ero #elocity at %ero ele#ation&

mar>"9

-& Distinguish beteen no%%le and diffuser& May7#une 09:ey ;int<

,o??le<

$t is used to increase the #elocity and decrease the pressure of fluids& mar>9

Diffu"er<

• $t is used to increase the pressure and decrease the #elocity of fluids& mar>9

.& /hen does ma0imum flo occur for an isentropic flo ith #ariable area duct1

May7#une 09 ,ov7Dec 09

:ey ;int<

Mass flo rate ill be ma0imum at throat section here the Mach number is one&

mar>"9


3/56

2& Define %one of action and %one of silence& ,ov7Dec 039

:ey ;int<

@one of action<

•'he region inside the Mach cone& mar>9

@one of "ilence<

• 'he region outside the Mach cone& mar>9

3& Name the different regions of compressible fluid flo& ,ov7Dec 039 May7#une 09

:ey ;int<

• $ncompressible flo region

• Subsonic flo region

• 'ransonic flo region

• Supersonic flo region

• 4ypersonic flo region mar>"9

5& /hat are the basic differences beteen compressible and incompressible flos1

May7#une 039

:ey ;int<

&ompre""i%le flo=<

• 'he density of the fluid changes from point to point ()≠

*onstant+ mar>9

-n &ompre""i%le flo=<

•'he density of the fluid is constant ()

≠ *onstant+

mar>9

6& /hat is the cross section of the no%%le required to increase the #elocity of compressible

fluid flo from (a+ Subsonic to supersonic" (b+ Subsonic to sonic& May7#une 09

:ey ;int<

'he cross section of the no%%le is decided based on the equation"dA

A 7dc

c (M, ! 8+

a9 Su%"onic to "uper"onic< *on#ergent 9 Di#ergent mar>9

Su%"onic to "onic< *on#ergent mar>9

& /hat is subsonic" sonic and supersonic flo ith respect to Mach number1 *pril7May

09 *pril7May 009

:ey ;int<

Su%"onic


4/56

• Super"onic< ;luid #elocity is more than the sound #elocity mar>"9

891or Diffu"er< =rea ! $ncreases

>elocity ! Decreases mar>988& ?one of silence is absent in subsonic flo& /hy1 May7#une 09

:ey ;int<

$t is obser#ed that the a#e fronts mo#e ahead of the source of disturbance and therefore

the %one of silence is absent& mar>"9

8,& Name the four reference #elocities that are used in e0pressing the third #elocities in non9

dimensional form& May7#une 039

:ey ;int<

8& @ocal #elocity of sound&

,& Stagnation #elocity of sound&-& Ma0imum #elocity of fluid&

.& *ritical #elocity of fluid& mar>"9

8-& /hat is mean by gas dynamics1 *pril7May 059

:ey ;int<

Gas dynamics deals ith the study of motion of gases and its effects&

mar>"9

8.& E0press the stagnation enthalpy in terms of static enthalpy and #elocity of flo& ,ov7Dec

00A9 :ey ;int<

h0=h+1

2c2

mar>"9

82& /hat is the ad#antage of using MA (second Bind of Mach number+ instead of M (@ocal

Mach Number+ in some cases1 May7#une 00A9 ,ov7Dec 0089

:ey ;int<

• =t high #elocities M approaches infinity but MA gi#es a finite #alue&

• M is proportional to the fluid #elocity and sound #elocity" but M A is proportional

to the fluid #elocity alone& mar>"9

$art – /


5/56

8& = conical diffuser has entry and e0it diameters of 82cm and -


6/56

M,7

c2

a2

c, 7 65,&6 ms mar>"9

m 7 )=cm

A=1040.96 kg/ sm2

mar>"9

-& =ir (78&." 7,65JBgC+ enters a straight a0isymmetric duct at -


7/56


8/56

p0− p

p ×γ

2 M

2

=1+ M

2

4+ (2−γ )

24 M

4

mar>"9

M =c

a

p×γ

2 M

2=1+ M

2

4+

(2−γ )24

M 4

mar>"9

p0− p

1

2 ρc

2

=1+ M

2

4+ M

4

40

mar>"9

3& =n air jet at ."9


9/56

5& =n aircraft flies at a #elocity of 5


10/56

c2 7 .,&- ms mar>"9

m 7 ),=,c,

m 7 36&65 Bgs mar>"9

(b+ M, 7 "9

+,-. --

12 .;(+!; D+&.S

;los through constant area ducts ith heat transfer (ayleigh flo+ and ;riction (;anno flo+ !

#ariation of flo properties&

8& /hat is meant by stagnation pressure1 *pril7May 059:ey ;int<

$t is the pressure of the gas hen it is isentropically decelerated to %ero #elocity at %ero

ele#ation& mar>"9

,& Gi#e =ssumptions made on ayleigh ;lo& May7#une 09 ,ov7Dec 039 May7#une

09

:ey ;int<

• 89D steady flo&

• ;lo in constant area&

•

'he gas is perfect&

• =bsence of orB transfer across the boundaries& mar>"9

-& Define critical condition in ;anno flo& May7#une 09

:ey ;int<

Due to friction in subsonic or supersonic flo in a constant area duct" flo ill reach

the critical condition here M 7 8& mar>"9


11/56

.& /hat is impulse function and gi#e its uses1 May7#une 039:ey ;int<

'he sum of pressure force and impulse force gi#es impulse function& mar>"9

2& Gi#e the e0pression for

T 0

T and

T ¿

T for isentropic flo through #ariable area in terms

of Mach number& May7#une 039:ey ;int<

T 0

T =1+

γ −12

M 2

mar>9

T ¿

T =

2

γ +1+γ −1γ +1

M 2

mar>9

3& Define ;anno flo and hat are the assumptions made for ;anno flo1 *pril7May 059

,ov7 Dec 09 ,ov7 Dec 039 ,ov7 Dec 09 *pril7May 09

:ey ;int<

1anno flo=<

;lo in a constant area duct ith friction and ithout heat transfer& mar>9

*""umption"<

• 89D steady flo

• ;lo taBes place in constant sectional area&

• 'here is no heat transfer&

• 'he gas is perfect ith constant specific heats& mar>9

B' Gi#e to practical e0amples for ;anno flo and ayleigh flo analysis& ,ov7 Dec 0)

*pril7May 09

:ey ;int<

1anno flo=<

;lo in air breathing engines&

;lo in refrigeration and air conditioning& mar>9

(ayleigh flo=<

•;lo in combustion chamber&

• ;lo in heat e0changers& mar>9

8' /here are the con#ergent no%%les and con#ergent ! di#ergent no%%les used1 *pril7May009

:ey ;int<

&onvergent no??le"


12/56

• Subsonic and sonic flos&

$t is used as flo measuring and flo regulating de#ices& mar>9

&onvergent – divergent no??le"<

• Supersonic flo& mar>9

A' /hat is chocBed flo through a no%%le1 ,ov7Dec 039

:ey ;int<

'he ma0imum mass flo conditions are reached hen the throat pressure ratioachie#es critical #alue& =fter that there is no further increase in mass flo ith decrease in

bacB pressure& mar>"9

8"9

88& @ist some flo properties& May7#une 09

:ey ;int<

• Mass density&

• Specific #olume

• Specific eight• 'emperature

• Specific gra#ity mar>"9

8,& Gi#e the assumption made in $sothermal flo&

:ey ;int<

• Ine dimensional flo&


13/56

• *onstant area duct&

• 'he gas is perfect&

;rictional flo at constant temperature& mar>"9

8-& /rite don the e0pression for the pressure ratio of to sections in terms of Mach number

in ayleigh flo&

:ey ;int<

p2

p1

=1+γ M 1

2

1+γ M 2

2

mar>"9

8.& /hat are the three equation go#erning ;anno Process1

:ey ;int<

• Energy equation

• *ontinuity equation

• Equation of state& mar>"9

82& Define fannings coefficient of sBin friction&

:ey ;int<

$t is the ratio beteen the all shear stress and dynamic head& mar>"9

$art – /

8& = circular duct passes 6&,2 Bgs of air at an e0it Mach number of


14/56

L=305.59m mar>"9

(iii+ ;rom ;anno flo table" 7 8&. " M, 7


15/56

T

T ¿ =0.953

', 7 8388&-2C

cc

¿ =0.625

c, 7 282&88 ms mar>"9

'< ma0 7 '


16/56

T 1

T 01=0.444,

p1

p01=0.0585

'8 7 ,.


17/56

p1

p1

¿ =2.207, p

0

p0

¿ =1.217,T

1

T 1

¿ =0.305,T

0

T 0

¿ =0.252

p, 7 -&-bar" ', 7 .."9

∆ p0= p01− p02

∆ p0=0.735 ¿̄

mar>"9

Q=m c p(T 02−T 01)

Q=962.3 kJ / kg mar>"9

3& = con#ergent ! di#ergent no%%le is pro#ided ith a pipe of constant cross section at its

e0it& 'he e0it diameter of the no%%le and that of the pipe is ."9

4 f́ L

D =[

4 f́ Lmax

D ]

M 1

−[ 4 f́ Lmax

D ]

M 2

Lmax=968cm mar>"9


18/56

;rom ;anno table" 7 8&." M8 7 8&6

p1

p¿ =0.474,

T 1

T 1

¿ =0.728

p¿=4.405 ¿̄

T 1

¿ =500.275 K mar>"9

5& 'he stagnation temperature of air is raised from 62"9

6& 'he Mach number at inlet and e0it for a ayleigh flo are - and 8&2 respecti#ely& =t inlet

static pressure is 2


19/56

T 1

T 01=0.357,

p1

p01=0.0272

ayleigh flo table" 7 8&. and M8 7 -"

p1

p1

¿ =0.176, p

0

p0

¿ =3.424,T

1

T 1

¿ =0.281,T

0

T 0

¿ =0.654

ayleigh flo table" 7 8&. and M, 7 8&2" p

2

p2

¿ =0.578, p

0

p0

¿ =1.122,T

2

T 2

¿ =0.753,T

0

T 0

¿ =0.909

p2=1.64 ,̄ T

2=282.19 K , c

2=505.56m/s

3 mar>"9

p1

p01=0.0272

p"9

p2

p1¿¿

¿ γ −1γ

¿T 2

T 1¿

s2−s1=c p ln¿


20/56

s2−s

1=649.51 J /kgK

3 mar>"9

'he heat transfer rate is positi#e" it is cooling process mar>"9

+,-. – ---

,(M*2 *,D /2-C+E S;&:S

Go#erning equations ! >ariation of flo parameters across the normal and oblique shocBs !

Prandtl ! Meyer relations ! =pplications&

$*(. *

8& /hat is Iblique shocB1 *pril7May 059 ,ov7Dec 09 *pril7May 09

:ey ;int<

• /hen the shocB a#e is inclined at an angle to flo& mar>"9

,& /rite the Prantl ! Meyer relation1 *pril7May 059 ,ov7Dec 09

:ey ;int<

a¿ 2=c x c

M x¿

×M ¿ =1

mar>"9

-& /hy the efficiency of a machine" e0periencing shocB a#e is considerably lo1

May7#une 09

:ey ;int<

• ShocB may cause boundary layer separation and de#iation of flo from its designed

direction&

• 'here ill be a loss in stagnation pressure and increase in entropy across the shocB

a#e& mar>"9

.& /hat is the use of pitot tube in supersonic flo1 May7#une 09

:ey ;int


21/56

• $ntroduction of the pitot tube produces a cur#ed shocB a little distance upstream of its

mouth&

• 'herefore it measures the stagnation pressure donstream the shocB a#e& mar>"9

2& /hat are the beneficial and ad#erse effects of shocB a#es1 May7#une 09:ey ;int<

/eneficial effect"<

• = strong a#e is utili%ed to accelerate the flo to a high Mach number in a shocB tube&

• sed in supersonic compressor to obtain considerably high pressure ratio in one stge&

*dver"e effect"<

$t cause undesirable interference ith normal flo beha#ior& 'herefore" the efficiency

of turbo machineries decreases&

$t create sonic flos in supersonic aircraft and damage the flo passage& mar>"9

3& /hy the shocB a#es cannot be de#eloped in subsonic flo1 *pril7May 09:ey ;int<

>elocity of fluid is less than the #elocity of sound& Due to this reason deceleration is

not possible in subsonic flo& mar>"9

5& Mention the useful applications of shocB a#e& *pril7May 009

:ey ;int<

• Jet engines

• ShocB tubes

• Supersonic ind tunnel

• Practical admission turbines& mar>"9

6& /hat are the situations here shocBs are undesirable1 *pril7May 009

:ey ;int<

• 'hey interfere ith the normal flo beha#ior& 'hus the efficiencies of turbo machines

e0periencing shocB a#es are considerably lo&

• 'he sonic boom created by supersonic aircraft and the blast a#es generated by an

e0plosion& mar>"9

& Gi#e the difference beteen normal and oblique shocBs&,ov7Dec 09

:ey ;int<

S' ,o' ,ormal "hoc> %liue "hoc>

8ShocB a#e is right angle to

the flo

ShocB a#e is inclined at an angle

to the flo

, Ine dimensional flo 'o dimensional flo

mar>"9


22/56

89

No& Since the fluid properties liBe pressure" temperature and density are changed during

normal shocB& mar>9

88& Define compression and rarefaction shocBs& ,ov7Dec 039:ey ;int<

&ompre""ion "hoc>"<

= shocB a#e hich is at a higher pressure than the fluid into hich it is mo#ing&

mar>9

(arefaction "hoc>"<

= shocB a#e hich is at a loer pressure than the fluid into hich it is mo#ing& $t is

not possible& mar>9

8,& /hat are the assumptions used for oblique shocB flo1 ,ov7Dec 039

:ey ;int<• ;lo is steady" adiabatic and frictionless&

• 'he gas is perfect ith constant specific heats&

• =bsence of orB transfer across the boundaries&

• =bsence of body forces& mar>"9

8-& Define the strength of shocB a#e&

:ey ;int<

'he ratio of difference in donstream and upstream shocB pressures to upstream shocB

pressure& mar>"9

8.& State the necessary conditions for a normal shocB to occur in compressible flo&

:ey ;int<

i& 'he compression a#e is to be at right angle to the compressible flo&

ii& ;lo should be supersonic& mar>"9

82& *alculate the strength of shocB a#e hen normal shocB appears at M 7 ,&


23/56

:ey ;int<

!= p − p x

p x mar>9

efer normal shocBs table for M0 7 ," 7 8&."

p p x

=4.5

!=3.5 mar>9

$art – /

8& Deri#e the e0pression for anBine ! 4ugoniot Equations& ,ov7Dec 09 ,ov7Dec 0089

M:9 69

:ey ;int<

ρ= p

RT ρ

ρ x=

p

p x×

T x

T mar>"9

M x2=

γ +12γ (

p

p x )+γ −12γ

T

T x=

p

p x [γ −1γ +1

× p

p x+1]

p

p x+ γ −1

γ +1

mar>"9


24/56

p

p x×

T x

T =

p

p x+γ −1γ +1

1+γ −1γ +1

× p

p x

ρ

ρ x=

γ −1γ +1

× p

p x+1

γ −1γ +1

× p

p x

6 mar>"9

p

p x=

ρ

ρ x [γ +1γ −1 ]−1

γ +1γ −1

− ρ ρ x

mar>"9

,& = gas at a pressure of -.< mbar" temperature of -22C and entry Mach number of 8&. ise0panded isentropically to 8."9


25/56

-& =n oblique shocB a#e occurs at the leading edge of a symmetrical edge& =ir has a Mach

number of ,&8 and deflection angle of 82


26/56

M 2=0.619

mar>"9

;or strong eaB a#e"

M x= M 1 sin"

p

p x=

p2

p1=2.219

mar>"9

ρ= p

RT

ρ2

ρ1=1.741

T

T x=

T 2

T 1=1.274

mar>"9

M 2= M

sin ( " −# )

M 2=1.548

mar>"9

.& 'he ratio of the e0it to the entry area in a subsonic diffuser is .&


27/56

T x

T 0 x=0.508,

p x

p0 x=0.0935

;rom normal shocB tables" 7 8&." M0 7 ,&,"

My 7


28/56

M 2=2.64,

T 2

T 02=0.417,

P2

P02=0.0471

mar>"9

', 7 ,2"9 M =0.5

'y 7 25"9c = M ×a

c =239.32m/s mar>"9

3& Starting from energy equation deri#e Prandtl9Mayer equation& May7#un 039 ,ov7Dec09 !:9 69

:ey ;int<

Stagnation Enthalpy relation"

h0=

a2

γ −1+c2

2=

1

2 ( γ +1γ −1 )a¿2 mar>"9Hefore shocB a#e"


29/56

a x2

c x=( γ +12 ) a

¿2

c x−

γ −12

c x

mar>"9

=fter shocB a#e"

a 2

c =( γ +12 ) a

¿2

c −

γ −12

c

mar>"9

m

A= ρ x c x= ρ c

γ p x

ρ x c x−

γ p

ρ c =γ (c −c x)

mar>"9

a x2

c x−

a 2

c =γ (c −c x )

a¿ 2=c x c mar>"9

M x¿×M

¿ =1 mar>"9

5& (i+ Deri#e the equation for static pressure ratio across the shocB a#es& May7#un 09

,ov7Dec 00A9 !:9 89

:ey ;int<

; 7 pO)c,

p

p x=

1+γ M x2

1+γ M 2

mar>"9

p p x

=(1+γ M x

2 )( 2γ γ −1 ) M x2−1γ +1γ −1

[ γ M x2+1 ]


30/56

p

p x=

2γ

γ +1 M x

2−( γ −1γ +1 ) mar>"9

(ii+ 'he #elocity of a normal shocB a#e mo#ing into stagnant air (p78&"9c = M ×a

c + =c x−c

c + =222.05m/s mar>"9

M + =

c +

a

M + =0.571 mar>9

;rom isentropic tables M + =0.571

T T 0

=0.939

T 0 + =400.56 K

mar>9


31/56

6& = con#erging9di#erging no%%le has an e0it area to throat area ratio of ,& =ir enters this

no%%le ith a stagnation pressure of 3&2bar and a stagnation temperature of -"9

;rom normal shocB tables" 7 8&." M0 7 8&2" My 7 "9

p =4.345 ¿̄

T =332.86 K 6

mar>"9

+,-. – -V

#E. $($+2S-,

'heory of jet propulsion ! 'hrust equation ! 'hrust poer and propulsi#e efficiency ! Iperating

principle" cycle analysis and use of stagnation state performance of ram jet" turbojet" turbofan

and turbo prop engines&

$*(.4*

8& Define propulsi#e efficiency& *pril7May 059

:ey ;int<

'he ratio of propulsi#e poer to the poer output of the engine& mar>"9


32/56

,& /hat is the type of compressor used in turbo9jet1 *pril7May 059:ey ;int<

otary compressor is used due to its high thrust and high efficiency& mar>"9

3' Define thrust poer and propulsi#e efficiency of aircraft engine& May7#une 09

:ey ;int<

.hru"t po=er<

• 'he product of thrust and flight speed& mar>9

$ropul"ive efficiency<

'he ratio of propulsi#e poer to the poer output of the engine& mar>9

.& /hy a ram jet engine does not require a compressor and turbine1 May7#une 09

,ov7Dec 09 ,ov7Dec 039

:ey ;int<

Due to supersonic and subsonic diffuser" the static pressure of air is increased to

ignition pressure& mar>"9

2& @ist out the different types of jet engines& May7#une 039

:ey ;int<

• amjet engine

• Pulse jet engine

• 'urbo jet engine mar>9

• 'urboprop engine

• 'urbo fan engine& mar>9

3& Gi#e the components of a turbo jet& May7#une 039

:ey ;int<

• Diffuser

• otary compressor

• *ombustion chamber mar>9

• 'urbine

• E0haust no%%le mar>9

5& /hat are the benefits of thrust augmentation in a turbojet engine1 May7#une 09

*pril7May 09

:ey ;int<

• Short taBe9off distance& mar>9


33/56

• 4igh climb rate to #ery high altitude& mar>9

6& /hat is a bypass engine and define bypass ratio& *pril7May 09

:ey ;int<

/ypa"" engine<

'urbo fan engine& = portion of the total flo of air bypass part of the compressor&

mar>9

/ypa"" ratio<

'he ratio of the mass flo rates of cold air and the hot air is Bnon as Hypass ratio&

mar>9

& Define speed ratio in propulsi#e system ,ov7Dec 09

:ey ;int<

'he ratio of flight speed to the jet #elocity mar>"9

8"9

88& ;ind the optimum propulsi#e efficiency hen the jet #elocity is 298,& /hat is thrust augmentation1 *pril7May 09

:ey ;int<

'o achi#e better taBe9off performance" additional fuel is burnt in the tail pipe beteen the

turbine e0haust section and entrance section of the e0haust no%%le& 'hrust augmentation

increases the jet #elocity and is Bnon as after burning& $t is used for fast and easier taBe off&

mar>"9

8-& /hat is ram effect1

:ey ;int<

$n ramjet engine the subsonic and supersonic diffusers are used to con#ert the Bineticenergy of the entering air into pressure energy& 'his energy transformation is called ram

effect& mar>"9

8.& Gi#e the e0pression for the thrust de#eloped by a turbojet engine&

:ey ;int< F = ḿ c − ḿa-

mar>"9


34/56

82& /hat is scram jet1

:ey ;int<

= supersonic combustion ramjet engine is Bnon as scramjet& mar>"9

$*(. – /

8& Deri#e the e0pression for the jet thrust" propeller thrust" propulsi#e efficiency" thermalefficiency" o#erall efficiency and the optimum #alue of flight to jet speed ratio for a turbo jet

engine& ,ov7Dec 09 May7#un 09 M:9 69

:ey ;int<

#et thru"t

Mass flo rate of no%%le at e0it of the no%%le 7ḿa+ ḿf

Net thrust 7 Momentum thrust OPressure 'hrust

Net thrust(;+ 7 ( ḿa+ ḿf ) c)− ḿa ×- 3 mar>"9

$ropeller thru"t

Net thrust considering mass of fuel (;+ 7 ( ḿa+ ḿf )c)− ḿa×-

c)=c

; 7m(¿c −-)

¿́ (or+


35/56

; 7 ḿa(c −-) 3 mar>"9


p

= P%&p-/s01) p&()% (¿ )Th%-s$ p&()%

P&()%&-$p-$ &f $h))'g0')

p= 2-

c +-

, p= 2"

1+" 3

mar>"9

.hermal efficiency<

P&()% 0'p-$

,$ = P&()% &-$p-$ &f $h) )'g0')

¿ $h) )'g0') $h%&-ghf-)/ ¿

1

2

´m(¿c 2−-2)

ḿf ×2.3

$ =¿

3 mar>"9

verall efficiency<

P&()% 0'p-$

0= P%&p-/s01) p&()% (¿ )Th%-s$ p&()%

¿ $h))'g0') ¿

´m(¿ c −-)×-

ḿf ×2.3

0=¿

,0=, p × ,$ mar>"9


36/56

Effecti#e speed ratio" =

F/0gh$ sp))d

J)$1)/&c0$

" = -

c

mar>"9

,& E0plain ith neat sBetches the principle of operation of (i+ 'urbo fan engine and (ii+ 'urbo jetEngine& May7#un 059 ,ov7Dec 039 ,ov7Dec 09 *pril7May 09 M:9

69

:ey ;int<

.ur%o fan engine<

*ombination of turboprop and turbo jet engine& =ir from the atmosphere enters into turbofan

engine" employing a lo pressure ducted fan& 'he air after passing through the fan is di#ided

into to streams" namely primary air and secondary air&

'he primary air flo through the turbofan engine consisting of compressor" combustion

chamber" turbine and e0haust no%%le& *ombustion taBes place in the combustion chamber

and the thrust is produced in the opposite direction& 'he thrust de#eloped by the secondary air is at loer #elocity& 3 mar>"9

=ir and the thrust de#eloped by the primary air is at much higher #elocity& 'he total thrust produced in this engine is the sum of thrust produced by the primary air and the secondary air&

'his total thrust propels the aircraft& mar>"9


37/56

3 mar>"9

.ur%o jet Engine<

(i+ Diffuser 9 'he function of the diffuser is to con#ert the Binetic energy of the entering air

into pressure energy&

(ii+ otary compressor ! 'he air passes through the rotary compressor in hich the air isfurther compressed& mar>"9(iii+ *ombustion chamber 9 4igh pressure air flos into the combustion chamber& $n thecombustion chamber" the fuel is injected by suitable injectors and the air9fuel mi0ture is burnt&

4eat is supplied at constant pressure&

(i#+ 'urbine 9 'he highly heated products of combustion gases are then enters the turbine and

partially e0panded&

(#+ E0haust no%%le9 'he function of the no%%le is to con#ert the pressure energy of the

combustion gases into Binetic energy& 3 mar>"9

3 mar>"9

-& E0plain the orBing principle of the ramjet engines ith neat sBetch and state its ad#antages

and disad#antages& May7#un 039 *pril7May 009 May7#un 00A9 M:9 69

:ey ;int<

mar>"9


38/56

'he function of supersonic and subsonic diffusers are to con#ert the Binetic energy of the

entering air into pressure energy& 'his energy transformation is called ram effect and the

pressure rise is called the ram pressure.

'he high pressure air flos into the combustion chamber& $n the combustion chamber" the

fuel is injected by suitable injectors and the air fuel mi0ture is burnt& 3 mar>"9

'he highly heated products of combustion gases are then alloed to e0pand in the e0haust

no%%le section&

'he function of no%%le is to con#ert pressure energy of gas into Binetic energy& Due to high#elocity of gases coming out from the unit" a reaction or thrust is produced in the opposite

direction& 'his thrust propels the air craft& 3 mar>"9

*dvantage"<

• amjet engine is #ery simple and does not ha#e any mo#ing part&

• *ost is lo

• @ess maintenance

• 'he specific fuel consumption is better than other gas turbine poer plants at high

speed&

• 'here is no upper limit to the flight speed& 3 mar>"9

Di"advantage"

• Since the taBe9off thrust is %ero" it is not possible to start a ramjet engine ithout

an e0ternal launching de#ice&

• 'he combustion chan:ber required flame holder to stabili%e the combustion due

to high speed of air &

• $t is #ery difficult to design a diffuser hich ill gi#e good pressure reco#ery

o#er a ide range of speeds&• $t has lo thermal efficiency& 3 mar>"9

.& = turbo jet flies at a speed of 65


39/56

ḿa=41.9 kg/ s 3 mar>"9

F = ḿ c − ḿa-

; 7 882-6 N& 3 mar>"9

F sp= F

ḿ

F sp=268.95 4 /( kgs ) 3 mar>"9

5 sp= F

ḿg

5 sp=27.41 s mar>"9

P 7 ; 0 u

P 7 ,&56 0 8"9

T6F2 = ḿf F

T6F2 =0.312 kgh− 4 3

mar>"9

2& =n air craft propeller flies at a speed of ..< Bmph& 'he diameter of the propeller is .&8m and

the speed ratio is


40/56

; 7 .8335 N 6 mar>"9

P 7 ; 0 u

P 7 2&


41/56

p=66.6

1

2

´m(¿c 2−-2)

ḿf ×2.3

$ =¿

$ =12.65

,0=, p × ,$

,0=8.42

mar>"9

5& (i+ Differentiate turbo jet and turboprop engines ith suitable diagrams& May7#une 09

!:9 9

:ey ;int<

.ur%o jet Engine<

(i+ Diffuser 9 'he function of the diffuser is to con#ert the Binetic energy of the entering air

into pressure energy&

(ii+ otary compressor ! 'he air passes through the rotary compressor in hich the air isfurther compressed&

(iii+ *ombustion chamber 9 4igh pressure air flos into the combustion chamber& $n the

combustion chamber" the fuel is injected by suitable injectors and the air9fuel mi0ture is burnt&

4eat is supplied at constant pressure& (i#+ 'urbine 9 'he highly heated products of combustion gases are then enters the turbine and

partially e0panded&

(#+ E0haust no%%le9 'he function of the no%%le is to con#ert the pressure energy of the

combustion gases into Binetic energy& 3 mar>"9

3 mar>"9

.ur%oprop Engine


42/56

'he angular #elocity of the shaft is #ery high& Hut the propeller cannot run at

higher angular #elocity& So a reduction gear bo0 is pro#ided before the poer is transmitted

to the propeller& the turbine dri#es the compressor and propeller&

Propeller is used to increase the flo rate of air hich results in better fuel economy&

Due to high #elocity of gases coming out from the unit" a reaction (or+ thrust is producedin the opposite direction&

'he total thrust produced in this engine is the sum of the thrust produced by the propeller and the thrust produced by the no%%le& 'his total thrust propels the air craft&

3

mar>"9

3 mar>"9

(ii+ /rite the equations to calculate propulsi#e efficiency and thermal efficiency of an aircraft&

May7#une 09 !:9 9

:ey ;int<


p= P%&p-/s01) p&()% (¿ )Th%-s$ p&()%

P&()%&-$p-$ &f $h) )'g0')

p= 2-

c +-

mar>"9


43/56

.hermal efficiency<

P&()% 0'p-$

,$ = P&()% &-$p-$ &f $h) )'g0')

¿ $h) )'g0') $h%&-gh f-)/ ¿

1

2

´m(¿c 2−-2)

ḿf ×2.3

$ =¿

mar>"9

6& = turbo jet engine operating at a Mach number of


44/56

, p= 2-

c +-

p=31.97 mar>"9

1

2

´m(¿c 2−-2)

ḿf ×2.3

$ =¿

,$ =33.04 mar>"9

,0=, p × ,$

0=10.57 mar>"9


45/56

+,-. – V

S$*&E $($+2S-,

'ypes of rocBet engines ! Propellants9feeding systems ! $gnition and combustion ! 'heory of

rocBet propulsion ! Performance study ! Staging ! 'erminal and characteristic #elocity !

=pplications ! space flights&

$*(. *

8& /hat is mono propellant1 Gi#e E0amples& *pril7May 059 May7#une 039 *pril7May09

:ey ;int<

= liquid propellant hich contains both the fuel and the o0idi%er in a single chemical&

mar>9

Eample<

• Nitroglycerine&

• Nitro methane& mar>9

,& /hy rocBet is called as non ! breathing engine1 *an rocBet orB at #acuum1 May7#une

09

:ey ;int<

• *ombustion taBes place by using its on I0ygen supply instead of atmospheric air&

• $t can orB at #acuum& mar>"9

-& /hat is the use of inhibitors in solid propellants1 May7#une 09

:ey ;int<

'o regulate the burning of propellant& mar>"9

' /hat are the types of rocBet engines based on source of energy employed1 *pril7May

059 May7#une 039:ey ;int<

• *hemical rocBet engine

• Solar rocBet engine mar>9

• Nuclear rocBet engine

• Electrical rocBet engine mar>9


46/56

2& = rocBet flies at 89

3& Mention any four applications of rocBet& May7#une 09:ey ;int<

• Military

Space mar>9

• =ircraft

*ommunication& mar>9

5& /hat is meant by hypergolic propellant1 *pril7May 009

:ey ;int<

4ypergolic propellant do not require ignition mar>"9

6& E0plain chemical rocBet propulsion system& ,ov7Dec 09

:ey ;int<

4igh pressure and high temperature gases are produced in combustion chamber due to

chemical reaction& mar>"9

& /hat are the properties of solid propellants1 ,ov7Dec 09

:ey ;int<

• $t should release large amount of heat during combustion&

• Physical and chemical properties should not change during processing& mar>9

• $t should ha#e high density&

• $t should be non9corrosi#e and non9reacti#e ith components of the engine&

mar>9

8


47/56

88& /hat are the ad#antages of a hybrid rocBet1 ,ov7Dec 039:ey ;int<

• Speed regulation is possible

• 4igh load capacity& mar>9

• @ighter than liquid propellant rocBet

• 4igh fuel density&

• 'here is no chemical deterioration beteen fuel and I0idi%er& mar>9

8,& /hat is specific impulse of a rocBet1

:ey ;int<

'he thrust de#eloped per unit eight flo rate of the propellant is Bnon as specific

impulse& mar>9

5 sp= F

7 p

mar>9

8-& /hat is bipropellant1

:ey ;int<

$f the fuel and o0idi%er are different from each other in its chemical nature" then the

propellant is called bipropellant& mar>"9

8.& Define specific propellant consumption&

:ey ;int<

'he propellant consumption rate per unit thrust is Bnon as specific propellant

consumption& mar>9

6P2 =7 P

F mar>9

82& Name some propellants for space application&

:ey ;int<

• Nitroglycerine&

• Nitromethane&

• 4ydra%ine&

• 4ydrogen pero0ide& mar>"9

$*(. – /

8& @ist the main components of liquid propellant rocBet engine and e0plain& *pril7May 059

M:9 69

:ey ;int


48/56

• @iquid fuel (refined petrol" liquid hydrogen" hydra%ine" etc+ and liquid o0ygen are used in

this engine& @iquid fuel and liquid o0ygen are stored separately in to different tanBs&

• Preheater is used to heat the fuel and o0idi%er& No%%le is used to increase the #elocity

and decrease the pressure of the gases& mar>"9

mar>"9

• @iquid fuel and liquid o0ygen are pumped separately into a combustion chamber through

control #al#es&

• 'he preheated fuel9o0idi%er mi0ture is injected into the combustion chamber through

suitable injector and combustion taBes place&

• /hen the combustion taBes place in the combustion chamber" #ery high pressure and

#ery high temperature gases are produced&

• 'he highly heated products of combustion gases are then alloed to e0pand in the

no%%le section&

• Due to high #elocity of gases coming out from the unit" a force (or+ thrust is

produced in the opposite direction& 'his thrust propels the rocBet&

mar>"9

*dvantage"

• @iquid propellant engines can be reused after reco#ery& So it is economical&

• *ombustion process is controllable i&e., it is easy to stop the combustion by closing the

fuel #al#e (or+ o0idi%er #al#e&

• Speed regulation i.e., increase and decrease of speed is possible&

• 4igh specific impulse& 3 mar>"9

Di"advantage"

• *onstruction is more complicated compared to solid propellant rocBet&

• Manufacturing cost is high&

• 'here are additional handling and safety problems if the propellants are poisonous

and corrosi#e&


49/56

• 'he si%e and eight of the engine is more compared to solid propellant rocBet&

• 4igh #ibration& 3 mar>"9

,& = rocBet engine has the folloing data: Effecti#e jet #elocity 7 8,"9

p= 2"

1+" 2

p=98 3 mar>"9

$ =c 2+-2

2×2.3

$ =0.477 3 mar>"9

,0=, p × ,$

0=46.8

3 mar>"9


50/56

-& E0plain the orBing of a turbo ! pump feed system used in a liquid propellant rocBet&

May7#un 09 *pril7May 009 M:9 69

:ey ;int<

• $n this system" liquid fuel and the liquid o0idi%er are stored in a separate tanB at

lo pressure&

• @iquid fuel and liquid o0idi%er are forced into the combustion chamber at high

pressure by the fuel and o0idi%er pumps&

• Gas turbine is used to operate the fuel and o0idi%er pumps&

• @iquid hydrogen pero0ide (4,I,+ from the tanB is decomposed by

a catalyst such as calcium or sodium permanganate& Due to this" steam

and o0ygen are generated& 'his steam is used to dri#e the turbine&

• Hecause of the third liquid" the gas turbine" the pumps and additional lines are

necessary& So the pump pressuri%ation system is considerably more comple0

than gas pressuri%ation system&

•Design of pump is a greatest problem that ill handle the liquids safely andithout leaBs& 6 mar>"9

mar>"9

• *ombustion of a liquid propellant (fuel and o0idi%er mi0ture+ in the combustion

chamber requires the folloing basic processes &

(i+ $njection(ii+ =tomi%ation

(iii+ Mi0ing

(i#+ >apori%ation(#+ $gnition

(#i+ *hemical reaction beteen fuel and o0idi%er 3 mar>"9

• 'he propellants are injected into the combustion chamber through fine orifices for

proper atomi%ation& >arious methods are folloed to atomi%e and mi0 the fuel and

o0idi%er&


51/56

• 'he combustion starts ith the arri#al of one of the propellants& $n order to

obtain a lo #alue of the o0idi%er fuel ratio" the fuel jet is alloed to enter the

combustion chamber first&

• 'he combustion pressure and temperature depends on the flo rates of the propellants"

the combustion rate and the gas flo rate through the e0haust no%%le& 3 mar>"9

.& Describe the important properties of liquid and solid propellants desired for rocBet propulsion

May7#un 039 *pril7May 09 *pril7May 009 M:9 69

:ey ;int<

$($E(.-ES 1 2-C+-D $($E22*,.S

• Propellant should ha#e high calorific #alue&

• $t density should be high&

• $t should ha#e lo #alues of #apor pressure and #iscosity&

• $t should ha#e higher specific heat and thermal conducti#ity &• Products of combustion should ha#e lo molecular eight to produce high jet

#elocity&


• $t should not be poisonous and ha%ardous&

• $t should be cheap and easily a#ailable&

• Energy released during combustion per unit mass of the propellant

combination should be high&

• $t should be easily ignitable& 8 mar>"9

$($E(.-ES 1 S2-D $($E22*,.S

• $t should release large amount of heat during combustion&

• Physical and chemical properties should not change during processing&

• $t should ha#e high density&

• $t should not be poisonous and ha%ardous&

• $t should be cheap and easily a#ailable&


• StorageQ and handling should be easy& 8 mar>"9

2& Dra a neat sBetch e0plaining the general orBing of the hybrid propellant rocBet& ,ov7Dec

039 ,ov7Dec 09 M:9 69

:ey ;int


52/56

mar>"9

• 'he hybrid rocBet engines combine the ad#antages of both solid and liquid propellant

rocBets&

• $n this type" solid fuel along ith liquid o0idi%er is used as a propellant&

• Solid fuel is pacBed in the combustion chamber and the liquid o0idi%er is stored in the

separate tanB& mar>"9

or>ing

• 'he liquid o0idi%er hich is stored in the separate tanB is injected into the

combustion chamber&

• /hen liquid o0idi%er mi0es ith solid fuel in the combustion chamber" combustion

taBes place automatically&

• /hen the combustion taBes place in the combustion chamber" #ery high pressure

and #ery high temperature gases are produced&

• 'he highly heated products of combustion gases are then alloed to e0pand in the

no%%le section&

• $n the no%%le" pressure energy of the gas is con#erted into Binetic energy& So the

gases coming out from the unit ith #ery high #elocity&• Due to high #elocity of gases coming out from the unit" a force (or+ thrust is

produced in the opposite direction& 'his thrust propels the rocBet& mar>"9

*dvantage"

• Speed regulation is possible by regulating the supply of o0idi%er&

• 4igh load capacity&


53/56

• 4ybrid rocBets are lighter hen compared to the liquid propellant type rocBets&

• 4igher fuel density&

• Since the fuel and o0idi%er are Bept separately" there is no chemical deterioration

beteen fuel and o0idi%er&

• $n case of an accident or crash the e0plosion is less destructi#e compared to

the liquid propellant rocBet engines& mar>"9

Di"advantage

• No%%le erosion cannot be a#oided& mar>"9

3& Describe briefly the important applications of rocBet propulsion in the folloing fields& (i+

=ircrafts" (ii+ Military" (iii+ Space" (i#+ Scientific& May7#un 09 !:9 69:ey ;int<

i' *ircraft"<

(a+ Primary poer plants e&g&:9 German Mel 83- fighter used in $$ /orld ar R9 8 esearch engine (first to breaB the sonic barrier+

R 9 82 supersonic research aircraft

(b+ =u0iliary poer plants for super performance or impro#ing the performance

(speed" rate of climb+" assisted taBe9off& mar>"9

ii' Military<

(a+ ocBet projectiles (unguided missile+ 9 not accurate" payloads e0plosi#e

charges" smoBe charge" other military payloads (or mail carriers to reachremote #illages in mountain areas+

(b+ Guided missiles:9 similar to rocBet projectiles but bigger in si%e and thetrajectory is controlled 9 ground to ground" ground to air (aircraft+" air to air"

air to ground" ship to air and ship to ship missiles 9 payloads are atomiceapons& mar>"9

iii' Space<

(a+ Military purposes ! reconnaissance"

(b+ *ommercial purposes 9 communication and eather studies scientific purposes 9 lunar" space and planets

(c+ Manned and unmanned space #ehicles

(d+ Near earth" longer" interplanetary" trains9 solar systems(e+ ocBet engines are use to (8+ taBe9off from earth" ascend and achie#ement of

orbit (,+ altitude control" trajectory connections" reentry" attainment of lunar and planetary orbits and landing" separation of #ehicle stages" maneu#ers etc&

mar>"9

iv' Scientific'

(a+ ocBets hich carry instruments to measure meteorological and scientificdata at high altitudes may be guided or unguided&

(b+ ;or throing life line to ships" signal rocBets" antitanB rocBets" under ater

rocBets etc&


54/56

(c+ Miscellaneous 9 ejection or cre escape capsules and stores personnel

propulsion beltsT" mar>"9

5& = rocBet flies at 8"9

F = ḿ p c

F =7000 4

P&()%= F × -

P&()%=19.6 M7 3 mar>"9

*'g0')&-$p-$ = P&()%

p

*'g0') &-$p-$ =24.5 M7 3 mar>"9

,$ = c

2+-2

2×2 .3

,$ =75.38 3 mar>"9

,0=, p × ,$

0=0.603 mar>"9


55/56

6& = rocBet has the folloing data: *ombustion chamber pressure 7 -3 bar" *ombustionchamber temperature 7 -3"9

c F = F

p0 A¿

c F =2.96 mar>"9

c¿=

c

c F

c¿=945.45m /s mar>"9


56/56

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