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B. Tech. (Sixth Semester) Examination Nov-Dec 2010Subject: Turbo machineryBranch: Mechanical En.'o

Code: ME 10612

Max Marks:8{}Min Pass N,Iarks: 28

Time: Three Hours

(a)Ql

Note: Use of Steam table & Mollier chart is permitted.

What is the difference between impulse & reaction turbine? Show thepressure & velocity distribution.Find expressions for the force, work done, diagram efficietrcy, gross stageefficiency & axial thlust for an impulse turbine.

OR

The velocity of stearn entering a simple in'rpulse turbine is 1000 nt/s, andnozzle angle is 200. The mean peripheral velocity of blades is 400 m/s arrdthe blades are symmetrical. if the steam is to enterthe blades without shock.what will be the biade arrgles?

(i) Neglecting the fi'iction effects on the blades, calculate tiretangential force on the blades and the diagram power for a ntassflora' of 0.75 Kg/s. Estimate also the axial t}u'ust & diagranrefficiencl.

(ii) if the relative velocity at exit is reduced by friction to 80% ofthat at inlet, estimate the axial thrust. diagram power anddiagram efficiency. I0

r)?Y.- (a)

(b)

Describe the various losses taking place in a steam turbine.

For a 50o/o reaction turbine, derive an expression fbr the maxi:llu-r'rtheoretical stage & blade efficiencies. l0

OR

The ar-rgles at inlet & discl'rarge of the blading of a50oh reactir.rr-r turbine are350 & ?00. respectively. The speed of rotation is 1500 rpm and at apalticr-rlal stage, the mean ring diameter is 0.67 m and the steam condition isat I5 bar, 0.96 dry. Estimate

(i) The required height of blading to pass 3.6 Kg/s of steam and(ii) The power developed by the ring. 10

PTO

06

10

(b)

(b)

06

Q.3 (a) For rrultistage turbine, show that RF is always greater than 1nit1,.

(b) Describe nozzle controj governing.OR

Stearn at 20 bar,4000C expands in a steam turbine to 0.1 bar. Ther-e are fonrstages irt the turbine arrd the total enthalpy drop is divided equally amongthe stages. The stage efficiency is75Yo and it is the sante in all the sta-e,es.Determine the inter stage pressures. the reheat factor & the tulbine internalefficiency.

Q.4 (a) Derive the explession for specific work output and the efficiency ol asinlple cycle with a heat exchanger. Draw their trends as a luncliorr ofpressure ratio.

OR

Delive the expression for specific work or:tput and the efficiency of asimple cycle with reheat and heat exchange. Draw theil tlencls as a fr;nctionof pressure ratio.

(b) A gas turbine with a regenerator lias got the followirrg data:Contpressor inlet temp: 290 KCompressor Outlet tem: 460 KInlet temperature of the turbine: 9000COutlet temperature of the turbine 4670C Calculate -

(i) The pressure ratio of the compressoland turl'rine(ii) The specific power output.(iii) The over all efficiency of the cycle(iv) The work required to drive the compressor.

Q.5 (a) What is a surging? Explain it with neat sketches.

OR

(a) With a neat sketch explain the inlet & exit velocity triangles 1br varioustypes ofblades. 06

(b) A 50% reactiott, axial flow compressor runs at a mean blade speed of 200m/s. The pressllre ratio developed by the machine is 1.3. Deternrine theblade and air angle if the rnean flow velocity was 200 m/s. Condition atinlet are I bar and 300 K.

06

l0

10

08

08

08

06

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CSVTTI Code: ME 10612

a91.\r9f'\

Max Marks: 80Min Pass Marks: 28

B. Tech. (Sixth Semester) Exam Apr-May 2010Subject: Turbo Machinery

Branch: lllech. Engg.

Time: Three Hours

I{ote: Attempt any Jive questions. All parts of a question should be answered together. IJse of steam table& Mollier chart is permitted.

Q.r (a)

(b)

Why are steam turbines compounded? Describe pressure velocity compounding by

drawing stages and draw distribution of pressure and velocity along the axis of the turbine.

An inrpulse steam turbine is supplied with steam at 35 bar,3500C, the condenser pressure

being 0.07 bar. The first stage of the turbine is velocity compounded with two rings of

moving blades separated by a ring of fixed guide blades. The isentropic enthalpy drop for

this stage is % of that for the whole turbine. The nozzle angle is 200 and the nozzle

efficiency is 88%. The mean blade velociry of both the moving rings of blades is 0.2 of the

velocity of steam leaving the nozzle. The exit blade angles for both fixed and moving

blades ur"'300 and the blade friction coefficient for all blades is 0.9. If the internal

efficiency of the turbine is 1\Yo,'calculate the efficiency of the first stage and the

percentage of the totalpower developed by'the turbine in this stage.

Shorv that in a 50%o reaction steam turbine stage, the maximum stage efficiency is

ZCr;s2 a

-

Where a is the nozzle angle.I+Cos-a

The first stage of a steam turbine is a two row velocity compounded impulse wheel. The

steam velocity at inlet is 600 m/s and the mean blade velocity is 120 m/s. The nozzle angle

is 160 and the exit angles of the first row of moving blades. Fixed blades, and second row'\of moving blades are 180,210 and 350, respectively. The steam flow rate is 5 Kg/s and the

' *'t i'- l' i

nozz,le.height is 25 mm. Neglecting the nozzle wall thickness, estimate the length of the

nozzle arc. The specific volume of steam leaving the nozzles is 0.375 m'/kg. Assuming

that all the blades have a pitch of 25 mm and an exit tip thickness of 0.5 mm, Calculate the

blade height at exit from each row. Take Ku-as 0.9 fbr all blades.

What do you mean by state point locus? Explain nozzle control governing with sketches.

Steam at 20 bar, 4000C expands in a steam turbine to 0.1 bar. There are four stages in the

turbine and the total enthalpy drop is divided equally among the stages" The stage

efficiency is 75% and it is the same in all the stages. Determine the inter stage pressures,

the reheat factor and the turbine internal efficiency.

Derive the expression for specific work output and the efficiency of a simple cycle with

inter cooled and heat exchanger. Draw their trends as a function ofpressure ratio.

Q.2 (a)

(b)

Q.i (a)

,(b\4

Q,4 (a)

PTO

(tr) An open cycle regenerative gas turbine plant of S IAW capacity consists of two stages

compressor with perfect inter cooling, a compressor turbine and separate power turbine.

The maximum cycle temperature is limited to 1000 K and pressure ratio is limited to 5.S

The gases ooming out from the compressor turbine are reheated in a direct combustion

chamber to 1000 K. The pressure and temperature of the air entering into compressor are 1

bar & 300 K.

Isentropic efflrciency of each stage of compression

Isenttopic efficiency of both turbines

Mechanical efficiency

Combustion efficiency ii, Uottl combustion chambers

Effectiveness of the regenerator

Lou'er heating value of the fuel used

Co air: 1.005 & Cor: 1 .147, y uo:7,4 & y r=(i) overall efficiency of the plant,

(ii) Mass flow rate through the plant &

(iii) Specific fuel consumption.

Show that the specific r,l'ork out put of the brayton c-vcle is maximum when the pressure

ratio is such that the compressor outlet & turbine outlet temperatures are equal.

A compressor & turbine have an isentropic efficiency of 0.85 at a pressure ratio of 4.0.

Calcuiate the corresponding polytropic efficiency and thence the plot the variation of

isentropic efficiency over a range of pressure ratio from 2.0 to 10.0. Also deduce the

expression which is used for calculation.

Show that when the degree of reaction is 50% the blades are symmetrical.

A centrifugal compressor has a pressure ratio of 4:1 w'ith an isentropic efficiency of 80%

wlren running at I 5000 rpm and inciuding air at 293 K. curved vanes at inlet give the air a

prervhirl of 250 to the axial direction at all radii and the mean dia of eye is 250 mm. The

absolute air velocity at inlet is 150 m/s. hnpeller tip dia is 600 mm. Calculate the slip

factor.

Write short notes on:

Surging in centrifugal compressor

Different losses in the turbine.

Effectiveness of velocity compounded turb ine.

Deviation of practical gas power cycles from ideal cycles.

80% .*

850A;'::'

98Vo'

97%

7 5o/o

42,000 KJ/Kg

1.33. Calculate:

(a)

(b)

Q.5

(a)

(b)

Q.6

Q.7

,t6(ii)

(iii)

(iv)

Jos3g04a30i4$lti@{*si6:1'"

CSVTU Code: ME 09612

B. Tech.( Sixth Semester) Examination Nov-Dec 2009Subject: Turbo MachineryBranch: Mechanical Ettgg.

Time: Three hours

Note: Use of steam table & mollier chart is permitted.

Max Marks:80Min Pass Marks: 28

Q' 1 (a) Write the differences between pressrro cr:mpounding & veiocity compounding. 06

(b) Find the expressions for the force e, workdone, diagram efficiency, gross stage

r0efficiency & thrust (axial) for an impulse turbine.

ORSteam issues from the nozzles of de-Level turbine with a velocity of 1200 m/s.

The nozzle angle is 200C, the mean blacle velocity is 400 m/s, and the inlet and

outlet angle of blades are equal. The mass of steam following through the turbine

per hour is 900 kg. Caicuiate;

(i) the blade angles

i.ii) the relative velocity of steam entering the blades,

iiii) tangential force on the blades

(iv) the power deveioped

(v) the blade effrciency.

Assume that K:0.8Q.2 (a) Find the optirnum velocity ratio for 5Ao/o reaction stage" 06

(b) tsriefly describe the various losses taking place in steam turbine. 10

ORThe angles at inlet & discharge of the blading af a 50Yo reaction turbine are 350

&,20o,respectiveiy. The speed of rotation is 1500 rpm and at a particular stage,

the mean ring diameter is 0.67 m and the steam condition is at 1.5 bar, 0.96 dry.

Estimate

(i) the required height of blading to pass 3.6 kgis. of stearn , and

(ii) the power developed by the ring .

Q.3 (a) Prove that Reheat factor is greater than unity for multistage turbine. 06

(b) Describe nozzle & throttle governing. l0

PTO

Q.4 (a)

(b)

Q -5 (a)

(b)

OR

A turbine is supplied with steam at 35 bar and a temperature of 4350C" It isexpanded in four stages to the condenser of 0.04 bar. The pressure-at the end ofstages are 5, I.2 & 0.25 bar respectively. Loss due to friction through out the

expansion is 24Yo. Determine-

(i) the Isentropic enthalpy drop in each stage.

(ii) the enthalpy drop tbr the turbine if friction is neglected

(iii)the work done in kJ/kg of floiv neglecting all losses other than the one

stated above

(iv)the reheat factor and

(v) the specific steam consumption in kg/kWh.

What are the various methods which are used to improve the efficiency & output

of a gas turbine?

Derive an expression for specific work output & efficiency of an ideai gas power

cycle with reheating.

,., oRA gas turbine operates on a pressure ratio of 6.0. The inlet air temperature to the

conipressor is 300 K and the air entering the turbine is at a temperature of 5770C.

If the volume rate of air eniering the r:ompressor is 240 m3ls, calcuiate the net

power output of the cycle in MW. Also compute the efficiency. Assume that the

cycle operates under ideal conditions.

What is a slip factor? What is its cffect on the flow & the pressure ratio in the

stage?

Derive the general energy transfer equation for a rotating machine.

OR

A Centrifugal compressor 30 kg of air per second at a rotational speed of 15000

ryni, The air enters the compressor axially and the condition at the exit section

are radius : 0.3 m, relative velocity of air at the tip : 100 m/s at an angie of 800C

with respect to plane of rotation. Take por : 1 bar & Tor : 300 K. Find the

torque & power required to drive the compressor and also the ideal head

developed.

06

l0

06

10

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ts, Tech"(Sixth Semesfer) Examination Aprybfiay 200gSubject: Turbo Flaehinery !

Braneh: Mechanieal EngineeriugTimc: Three hours Max kfarks: 80

Pass Marl{s: 28

Note: Attempt all questions, All questions carry equal marks. Assume suitnble data ifneeessary " Use of,IVIollier chnrt nnd steam tahle is permitted,

Q.l (s) What is the prineiple of operation of steam turbines? Differentiate between

impulse and reaction twbine.

OR

compare the sJage eqthalpy egplgLuqp@,iw9 row c"rttq-{5020 Reaerio4

stagds.

(b) The following partieulars appty to a two row veloerty compounded impulse

stage of a turbine: Nozzle angle 170, mean blade rp""a rzs mA, exit'angles ofthe first row moving blades, the fixed blades, and the second row moving

blades P!, zao & 3--f , respectively; blade friction factor for each row 0.9" '

Assume that the absolute veloeity of stearn leaving.the stage is in the axial

direction" Draw the velocity diagraruo for the stage and obtair (i) the absolute.\., velociry of steam leaving the stage, (ii) ttre diagram wgrk , and (iii) the diagrarn

effioiency" :

effieiency is

@

Q.2 (a) Define diagram efficiency. earry over coefficient. Find the optimum ratio of\:-/blade speed to steam speed for a veloeiff eompounded impulse turbine"

OR

Show that in a Parson's reaction steam turbine stage, the nnaximum stage

ffi where s is the nozz.eangle, / is ear* over

factor and r7^is blade efficiency"

(b) The Farsons reaetion turbine running at 400 rpm develops 5 h{w using

6 kg/kwh of steam flow" The exit angle of the blades is 200 and the veloeiy ofsteam relative to the blades at exit is 1.35 tinrues the mean blade spced. At a

PTO

A.&-dsX

(b)

padioular stage in the expansion the pressttre is 1'2 bar and the steam quahty is

0"g5. ealoulatc for this stage (i) a suitable blade height, assuming the ratio of

D*/Trs as 12, andthe diagrarn power" #

What are the methods to rbduee leaving loss? Enlist the vansus losses taking

place in a steam turbine"

Steam at 20 bar , 4000e expatlds rn a steam turbinc to 0.1 bar. There are four

stages in the turpine and the total enthalpy drop is divided equally among the

stages. The sta€e effieieney is 75% and it is the same in all the stages"

Detennine the inter stage presstres, the reheat f,actor and the turbine intetnal

effieiency.

OR

Establish relations between stage effigle3gr, internal effieiency and reheat

factor of a multistage impulse turbine.

Q"4 (alz- Derive the expression for speeifi.c work ouSut and the effieiency of a simple\-/

gas turbine eyele with a heat exchanger. Drair their trends as a funetion of

r Pressure ratio.ioR;-

. , ,Degive*he:boridition for. b;rt p"ffiion for division of the expansiOii-into rwo*' > '-+t '"i,*-- '---- ". -

* - :-

stages for maxineum ou$rut of a gas turbine using a reheater"

(b) A gas turbine plant operates on the Brayton eyele between Tryrn : 300K and

Tmax : 1073K" Furd the max' work done_per hS of alr, and the correspondrng

&<

cyele effieiency oe.erating betwTpjth.g p1e rwo temperatures"

Q.5 (a) Show that the index of cqmpression for a polytropie process is given by

(rr *t\ ( v -t\ I

I o J"=17)u.e*' Explain the phehomenon ofsurging and chgckiilg in eentrifugal eonrpressor.

OR

What arc the fimstions of the impellpr & diffuser in'a cenrifugal compressor?

Sketeh the variation of veloeity & pressure along the impeller.

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,, 20CSVTU Code: ME08612M f, AL' '

B.Tech (Sixth Semester) Examination Apr-May-0g L'

Subject: Tur.bo MachineryBranch : Mechanical Engi.neering

Time: Three Hours Max Marks:g0lVlinirnum Marks:28

NOTE: All questions carry equal marks. Use of steam table & Mollier chart ispermitted

H*'n"*9k

'Yh3t is the purpose of compounding of Impulse turbine? what is thedifference between pressure compounding & velocity compounding?

ql:f,(b)

0"wd*'{

Find the optimum velocity ratio for a single stage Impulse turbine? plotthe variation of diagram efficiency with ratio of blade effrciency tosteam velocity for single stage impulse turbine with & without frictionon the blades.

The following particulars refer to a two-row vetrocity compoundedirnpulse wheetr:

steam vel. at nozzle exit =-600m/s, nozzle angle : 16o, Mean blade vel.= tr2Om/s,

Exit angles: First row moving blades: 1go, fixed guide blade :22o,second row moving blades = 36o..Stearn flow: SKg/s, bldb* {lictiar cc*fEsier*.," S.g5.D.etermine (i) The tangential thrust, (ii) The axial thrust,(iii) The power developed, (iv) The diagram efficiency.

conrpare the stage enthalpy drops of rmpulse, two row curtis wtd 50%reaction stages.

OR

compare the diagram effrciencies of impulse, two-row curtis anj 50%reaction stages.

Q,2 (a) ,*K,

t$'-x?"h\q,f"

rbabt ltearn expands in a -turbine from 4a bar, 500oc to 0.10 barotr-9! "^qrrsentropically. Assuming ideal conditions, determine the rnean diameter\ - h.*

uof the wheel,if the turbine were of (i) singte stageo (ii) single 50%, t action stage, (iii) four pressure stages, (ivfone tio row curtis stage,

.pd ^L_. ffitJIJr::* 50% reaction stages. Take the nazzleangle as 16o and N1s

^ ,$ tFKoT1", (i) with rrr" n"tp'orneat skerches exptain nazztecontrol sovernins.

\ 94= (ii) Prove that RF>l for multistage turbine. \rS 9th ,g"wii.L e

*t_, (b) Steam which is initially dry and saturated at an absolute temperatureTy

2d\" expands in a turbine to an absolute temperature T2, the stage efficiency1, \, tO being qr. Assuming a very large number of stages and that for

-pt' I > - condition curve on the T-S chart is a straight line, show that the reheat

" \S factor,{-J [,

\ ,"q RF : r' +r'

" Y{<"U 2r' +4'(r' -r')

P.T.O.

K inS.$\ Er\A turbiit is suiplied withw

JP-

expanded in four stage toat 35 bar and a temp. of 435oC" It is

condenser pressure of 0.04 bar" Thepressure at the end of stages are 5, 1.2 and 0.25 bar respectively. Lossdue to friction thr..,ugh out the expansion is 24o/s. Determine, (i) T'heisentropic enthalpy drop in each stage, (ii) the enthalpy drop for theturbine if friction is neglected, (iii) the work done in kJ/Ie of flowneglecting all losses other than the one stated above, (iv) the steamflow required to obtain one KWh of work from the turbine.

what is the purpose of adding a heat exchanger in simple Braytoncycle? Explain the details with suitable sketches"

In a gas turbine plant air at pressure p, and temperature T1 iscompressed to RP1 and then heated to temperature Tr. The air is thanexpanded in a two stage turbine such that the pressure ratio is the samein each stages. The air is reheated between the turbine stages to thetemperature T3. Assuming that the working fluid is a perfect gas havinga ratio of specific heats equal to y and that the compression and bothexpansion are isentropic shnw that the net outpulKg of working fluidwill be maximum when R is given by

OR

Rr desigir point the ioiiownrg ,iata apply to a gas turbrne set emp,loyinga heat. exohanger. 4c * Sffi, rl* : 85%0, Mechanical ttansmissioneffi ciency(Ir) : 9904, combrntion effi ciencyr1o:98Yo, Heat exchanges etl'ectiveness (e) = 80% Pressure ratio : 4.0,Max. Cycle temperature : 1100K.Pressure losses:Combustion chamber -2o/o cornp. delivery pressureHeat exchanger airside - 3yo, comp. delivery pressureHeat exchanger gas side - 0.04 bar,Arnbient conditions - Olbar & 28SKTake Cp : l.005kJ/Kgk, y : 1"4 during compression,

Cp = 1 .147 kJlKgk, y: 1.333 during expansionHeating value of the fuel :43100kJ/Kg.Calculate specific work output, specific fuel consumption and cycleefficiency.

Derive the general energy transfer equation for a rotating machine.

OR

Show that cohen the degree of reaction is 507o, the blades aresymmetrical.

A centrifugal compressor has a preissure ratio of 4.1 with an isentropicefliciency of 80% when rurming at 15000 rprn and inducing air at293K. Curved vanes at inlet give the air a prewhirl of 25o to the axialdirection at all radii and the rnean dia of eye is 250mm. The absoluteair velocity at inlet is 150 m/r;. Impeller tip dia is 600mm. Calculate theelin fnnfnr

OR

steamthe

L4

Q.4 (a)

(b)

. .ii r j

R= l'5'}"'-'j{.4 I

Q.s (a)

(b)

C'otlc: 065026 S

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Subjcct :'l'tt llto N{ :rchi'nct'y

' Branch: Mcchanical Enginccring

'Iime: '['hrec l[oursIVlirx Marlrs: lt)()

Min I'uss Marks:J5

Notc:

-*n"#F#4w*

-41 efficicnoy.

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stcam table ontf Uoffitr chart is pcrmittcd'

marks. Usc of

rvith schemattc diagrattl

ul tls llllil

-.k=. ui;

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ixplain the compor'rndirlg ot'iniptrlsc ttrrbinc irr detail

compalc thc stage cnthalp;' ui?n; ,trf

it-nPulsc turbine', t\v0-lo\\' L

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cnthalpy clroll reclutrecl atld thc cliarg'r'lrrl.r l)owcr'

qrrf'{i#rr*":u:.*i,f..';l;*l::ltl,:li,ill'';' llili'*;ii*t-r'; - I)ciernritrc thc itrtcr stagc prcsstrr'(:s' illc

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isentropio cflioicncy. 12

Discuss t6e eff'ect of pressure ratio on thc efficiency of a rcgerlcrative lJraYtott0ticycle.

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LThe ratio ol. net worl( to tr.rrbilc u,clrk g1'an ideal gas it tilrbittc'l-alcc tlre inlet tclnpcratur0 to tire collrprcssor ils 3()0i<

temperatur4e clrop across thc tt-tt'bitle i1'thc thcrmal eI'licierle 1'

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W = u Vf (tan Br - tanBz), ,I

A centrifugal compressor has a pl'essurc ratio of 4:l rvith an ise tltropic

efficiency 6f AOrh when running at 15000 tPT^und.inducing air al 293K'

Curved oun6 at inlet give the aiia prewhirl of 25u to the axial direction at all

radii and the nrean dii of eye is 250mm. The absolute air velocity at inlct is

150 rn/s. Impeller tip dia is 600rnnr, Calcrrlatc thc slip factor.

Q,5 hV. G\ What are the lunctions ol' the impeller and diflirser in"-.r\,,,",,,,rr.r,q.r,r.'1 Sl<ctclr tltc vat'iirtiorr ctl'r',Jltrcity artd l)lcssLll'c lrltlttg

cfine slip 'aofor attcl clerive an exlllession f<lr tire

{ - '. P"f.r*,, lyf :!:l j ': l:;il"il il,:,1 ;iat cjo you mcan by statc l:6int lri,:r,s? f)raw a schenratic clilgranr o{',srure

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