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omTtme Allowed 3 hours MaXJmwn Marks 200

Canchdates should attempt any FIVE quesl!ons Asswne swtable data, Jj necessary, and mdJcate them clearly Use of Steam Tables, Psychrometnc Chart and Rejhgeratwn Tables Js permllted

ForatrR=O 287k.Jikg-K, Cp= 1 005kJ!kg-K

(= 1 4, M = 28 966 kg/kg-mole

(a) Denve the followmg Clapeyron and Clausms-Clapeyron equahons

dp hfg and dp = hfg di dT T(v, v1 ) p RT'

Explam the phySical SJgmficance of these equahons

(1 0)

(b) A heat pump operates between two idenhcal bodies In the beg1mung, both the bodies are at the same temperature T1 but operahon of heat pump cools down one of the body to temperature T3 Show that for the operat10n of heat pump the nummum work mput needed by the heat pump for uru t mass is given

Wmn=c[i>T,-2T1]

where c 1S the specific heat ofbod!es

DiScuss whether the system sahsfies first and second law ofthermodynanucs or not

(1 0)

(c) A large vessel contams steam at a pressure of 20 bar and a temperature of350°C Tius large vessel!S connected to a steam turbme through a valve followed by a smallimhally evacuated tank W!th a volume of 0 8m3 Dunng emergency power reqmrement, the valve 1S opened and the tank fills W!th steam unhl the pressure 1S 20 bar The temperature of the tank 1S then 400'C Assume that the filhng process takes place achabahcally and the changes m potenhal and kmehc energies are negligible By draWing the control volume, calculate the amount of work developed by the turbine m kJ

(2 0)

(a) What does a catalyst perform in a catalyhc convertor? Discuss the oX!dahon and reduchon reachons that are takmg place in a convertor Why it 1S preferred to use unleaded petrol in cars eqmpped W!th a catalyhc convertor system?

(1 5)

(b) "Factors wluch increase detonahon m S I engme tends to reduce knockmg m C I engmes", diScuss the valid! ty of the statement

(0 5)

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(c) A SIX cyhnder, four stroke spark-!gmhon engme of 10 em x 12 em (bore/stroke) With a compress10n raho of 6 1S tested at 4800 rpm on a dynamometer of arm 55 em Dunng a 10 mmutes test, the dynamometer reads 45 kg and the eng~ne consumed 5 kg of petrol of calonfic value 45 MJ/ kg The carburetorrecetves the a1r at 29° C and 1 bar at the rate of 10 kg/mm Calculate

(1) the brake power

(11) the brake mean effechve pressure

(111) the brake spec1fic fuel consumphon

(1v) the brake spec1fic a1r consumphon

(v) the brake thermal effic1ency

(m) the a1r fuel raho

(2 0)

(a) List the factors wluch are conSidered m the ophmum deSign of fins

(')

(b) An electromc senu-conductor demce generates heat equal to 480 x 10-3 W In order to keep the surface temperature at the upper safe hnut of 70 °C, the generated heat has to be d!SS!pated to the surroundmg w!uch" at 30°C To accomplish tlus task, alumm1um fins of 0 7 mm square and 12 nun long are attached to the surface The thermal conduchmty of alummmm fins 1S 170 W/mK If the heat transfer coeffiaent 1S 12 W/m2K, calculate the number of fins reqmred Assume no heat loss from the hp of fins

(c) A commerc1al aeroplane 1S modelled as a flat plate wlu ch 1S 1 5 m Wide and 8 m long m S!ze It" ma1nta1ned at 20°C The aeroplane" fl)'!ng at a speed of 800 kmib m a~r at ooc and 60 em of Hg pressure Calculate the heat loss from the Wlng 1fthe flow 1S made parallel to the Width of the Wing Take thermo-phySical properhes of a1r at the mean film temperature of 10 oc. K=2511x10-2 W/mK,

W= 14 16x 10-6m2/s, P,=0705

(1 5)

(d) An electr1cally heated mdustnal furnace cav1ty 1S modelled 1n the form of a cylmder hamng d1ameter 10 em and length 20 em It 1S opened at one end of surroundmgs that are at a temperature of 300 K The electncally heated Sides and the bottom of the cav1ty wluch are wellmsulated and may he approXimated as black bodies are ma1nta1ned at a temperature of 1800 K and 2000 K, respechvely By shoWing the sketch of the furnace, find the power reqmred to ma1nta1n the surface at tlus cond1hon Take shape factor from the bottom surface to surroundmgs as 0 06

(1 5)

(a) DiScuss m deta~l the factors affechng the performance of vapour compresS! on refngerahon cycle

(1 5)

(b) Expla1n how a refngerant produces co ohng effect What are the good qual1 hes of refngerant? N arne the refngerant wh1ch does not destroy ozone layer

(1 0)

(c) 10 tons ofrefngerahon 1S reqmred for a food storage space to keep the food stuff cool The refngerant used m the plant" Freon-12 and " subcooled by 5°C before entenng m the

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expanSion valve The temperature of evaporator and condenser are --t'C and 30°C respecl!vely The vapour " superheated to 6°C before leavmg the evaporator c01l The compressor 1S of two cyhnders, smgle actmg type havmg stroke equal to 1 5 l!mes the bore The compressor runs at 800 rpm and the compresSion 1S assumed to be 1Sentrop1c Esl!mate the followmg

(1) refngeral!ng effect per kg

(11) mass flow rate oftherefngerant

(111) theorel!cal p!Ston d!Splacement

(1v) theorel!cal power

(v) COP and

(v1) theorel!cal bore and stroke of the compressor

(1 5)

(a) Obtam an express10n for diScharge through an onfice meter

(1 0)

(b) A hollow cyhnder of 1m long has an mtemal d1ameter and external d1ameter equal to 0 4 m and 0 6 m, respecl!vely and both ends are open Assummg the we1ght of the cyhnder as 700 M, analyse whether the cyhnder would be stable wlule flo atmg m water W!th 1ts ax!S veri! cal

(1 0)

(c) Show that the hydraJJhc effic1ency of a Pelton turbme 1S max1mum when penpheral wheel velo c1ty 1S half the absolute veloc1ty of Jet at mlet

1+Kcos,B Further, showthal'lh,==

2 '

where K 1S the fncl!on factor

Menl!on the en ten a for selecl!ng water turbmes for hyde! power plant

(a) Develop an express10n for the pressure loss across a corneal contract10n of d1ameter D1 and D, m a g!Ven length L for alammar flow Explam the phySical SJgmficance of equahon

(1 0)

(b) Do you need pnmmg m a gear pump ? G1ve the reasons for your answer

(o)

(c) Explam the separahon of flow and diScuss the methods used for controlling of separahon m a d1ffuser

(1 0)

(d) A centnfugal pump 1S to diScharge 0 2m3/sat a speed of 1400 rpm agamst ahead of 25m The 1mpeller d1ameter 1S 0 3 m, 1ts Width at outlet 1S 0 05 m and the manometnc effiaency 1s 8 0% Determme the vane angle at the outer p enphety of the 1mp eller and label the angle by sketclung the 1mp eller

(1 5)

(a) What do you mean by supersaturated flow through steam nozzles ? DiScuss the causes of super -saturahon phenomena

(1 0)

(b) What 1S the baS!c pnnc1ple of regenerahve feed heahng m steam power plant cycle? Sketch a prachcal feed heahng system for a 500 MW steam turbme and label1t

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(1 0)

(c) A blade group m a Parson's reach on steam turbme 1S of constant height The turbme develops 6 0 MW ruruung at 3 00 0 rpm The itu hal steam pressure and temperature entenng the turbme are 50 bar and 400°C and the back pressure" 70 em Hg The effiaency raho ofturbme" 70% The mean blade velocity m the group 1S 120 rrJs The average specific volume of steam m the group may be taken as 0 62 m3ikg By drawmg the veloaty diagram, calculate the followmg

(i) mass flow rate of steam

(11) he1ght of blade

(111) drum d!ameter

(iv) movmg outlet blade angle

Assume the raho of blade veloaty to steam velocity as 0 55 and the nozzle (fixed blade) angle" 20° Neglect the hp leakage and mecharucallosses

(2 0)

(a) Why should no moiSture flow along W!th steam from the drum to the superheater and why 1S no vapor bubble deS!fed to flow along W!th saturated water from the drum to the down comers?

(o)

(b) With the help of a neat sketch diScuss the workmg pnncipl e o fV elox high pressure boiler

(1 5)

(e) A Simple open cycle gas turbme has a compressor turbme and a free power turbme It develops electncal power output of 250 MW The cycle takes in u at 1 bar and 288 K The total compressor pressure raho 1S 14 The turbme mlet temperature 1S 1500 K The total to total iSentropic efficiency of compressor and turbme at 0 86 and 0 89, respechvely The mechanical efficiency of each shaft 1S 0 98 Combushon efficiency 1S 0 98 willie combustor pressure loss 1S 3% of compressor dehvery pressure The exhaust pressure loss 1S 0 03 bar Alternator efficiency 1S 0 98 Take calonfic value of fuel equal to 42,000 kJ!kg, Cp, = 1 005 kJ/kgK and Cpg = 1 15 kJ!kgK

Calculate the folloWing ,,, a1r-fuel raho

(u) specific work output

(111) specific fuel consumphon

(iv) mass flow rate ofa1r ,,, cycle thermal efficiency

(2 0)

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IIIGCHANICAL GNGINGGICNG

Ttme Allowed 3 hours MaXimum Marks 200

Canchdates should attempt Question 1 m Sect! on 'A' winch Js compulsory, TWO ~Qestwns from Sect! on 'B' and TWO ~Qestwns from Sect! on 'C'

Question 1 Js of short answer type, hmltmg answer of each part to 30 words Assume swtable data, Jj necessary andmcbcate the same clearly

SECnONA

(a) Wluch one of the three shafts h sted here has the h1ghest ul hmate tensile strength 7 What 1S the approXimate carbon content m each steel ?

(1) Mild steel

(11) Cast 1ron

(111) Spnng steel

(b) State the Von - M!Ses' s theoty Glso g1ve the mathemah cal express10n

(c) Why are shafts not made out of cast 1ron?

(d) When are I -Secl!ons preferred m engmeenng apphcah ons? Elaborate your answer

(e) For the three veloaty ral!os 11eaf1ed below wlnch one of the followmg gear dnve would be preferable for transm!ttmg power With reduchons at4, 20 and 70 ?

The dnves are smgle stage spur gear reduchon, smgle start warm dnve and tnple start warm dnve

(f) In a smgle mvolute gear already manufactured of the three diameters given below two are pre-determmed

Wluch are those two? Substanhate your answer The three diameters g!Ven are adandem circle diameter, pitch circle diameter and base circle diameter

(g) In an epicychc gear tram the number of planets m any row has to be more than one Do you agree or disagree Why?

(h) In a typical power transm!SS!on from an induchon motor runrung at 1440 rpm to an ou11ut speed of 1 rpm Wluch order of reduchon of the three dnves hsted below 1S preferred? Why?

War gearreduchon, belt reduchon and spur gear reduchon

(i) Is the Cam m mesh W!th the follower a case of complete constramt? Substanhate your answer

6) Do you agree that in a four stroke four cylmder I C engme the pnmary forces and the pnmary couples are in balance? Substanhate your answer

(k) D!Shngmsh between urulateral and bilateral tolerances for the dimens10ns Indicate the tolerance zones for each by takmg an example

(1) What is the who! e b as!S and shall baS! s of fits? Which one is preferred m practice and why?

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(m) Wnte the chem1cal equahon for the reachon gomg on m the oxy-acetylene flame Where do you get the most part of the oxygen, 1S 11 from the cyhnder or the ahno sphere?

(n) Clearances have to be prov1ded on the press tools, what 1s the order of clearances for sheanng operat10n and deep drawmg operahon? On what tool W!ll you prov1de the clearance m

(1) Punclung operahon

(11) Blankmg operat10n

( o) What 1S a three h1gh rolhng m1ll? Ind1cate the movement of rolls and the work p1ece

(p) What 1S the baS!S for Selechve Inventory Control? Menhon four apphcahons of the same m the Inventory Management

(q) What 1S the d!Stnbuhon followed by the achv1ty durahons of a PERT network? Menhon 1ts mean and standard demahon

(r) What do you understand by trackmg S!gnalm forecashng? How 1S 11 computed?

(s) D!Shngmsh between P-.system and Q-system m Inventory Control

(t) What are the charactenshcs of cellular manufactunng system?

(2x20=40)

SEC:TION B

(1) An antnfichon b eanng used m a gear box has a sp ec1ficahon 6 1 0 8 What do the numbers 6, 1 and 08 S!grufy?

(1 2)

(11) Menhon three d1fferent methods used to prevent an anhfncl!on beanng from shdmg =ally m a shaft at the 1tu1errace and m a bore at the outer race

(1 8)

(111) Wh1ch one of the three beanngs hsted below wdl you choose to take a heavy ax:1alload on thebeanng

(1) self al1 gmng ball b eanng

(11) deep groove ball beanng

(111) Thrust heanng

G1ve reasons for your selechon

(1 0)

A smgle cyhnder engme and a four cyhnder m !me four stroke engme (both honzontal) are tu!Ulmg at speed of 15 00 rpm Crank radms and co!Ulechng rod for both are 1 0 0 and 5 00 mm respecl!vely Rec1procahng parts for the Single cylmder engme we1gh 160 Nand for each of the four cyhnders of the four cyhnder eng1ne we1gh 40 N Revolvmg masses for both smgle and four cyhnder engmes work out to 160 N W!th a net eccentnc1ty ofO 1 nun Compute the folloWing for both the engmes

(1) Magrutude, frequency and duechon of the predonunant unbalanced force due to the rec1pro cahng parts

(1 8)

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(u) Magrutude, frequency and direchon of the unbalanced force due to the revolvmg ,~,

(1 8)

(111) If a mbrahon pick up 1S used to measure the mbrahon Signals on the frame of the engme, d!rechon m which the Signals W!ll be predommant

Express10n for the p!Ston accelerahon 1S g!Ven by co',(ao + a1 cos 8 + a, cos 28 + a,

cos 48) where OJ 1S the crank speed m rad/s, r crank rad!us, a, = 0, a1 = 1, a,= 0 2 and a,= 002, 8-the crank angle

A hot rolled steel shaft 1S subJected to a tomonalload that vanes from 300 KNmm clockWise to 100 KNmm anhclockw:tse as an apphed bendmg moment at a cnhcal sechon vanes from +400 KNmm to -200 KNmm The shaft 1S of umform cross-sechon and no key-way 1S present at the cnhcal sechon Determme the reqU1red shaft d!ameter by takmg factor of safety 1 5 For the matenal, take ulhmate tenSile stress as 560 MPa, stress at yield pomt 420 MPa deSign stress 1S 280 MPa Also take the mod1ficat10n factor as 0 62, S!ze correchon factor as 0 85, the load factor for bend!ng as 1 and the load factor for tors10n as 0 58

( 4 0)

SECniiN C

(a) What are the velocihes wlnch come mto eX!stence when a metal!S cut orthogonally? Show these veloahes graphically on a velocity d!agram and detenrune the mathemahcal relat10nslnp m terms of shear and rake angles

(b) Dishngmsh between a Jig and fixture, Wl th the help of diagrams for at least five each

( 4 0)

(a) What are the steps mvolved m mahng of carbide tool bits? What do you understand by the green denSity of a metal powder compacted part? What are the chiefments of a bush made by metal powder compachon?

(2 0)

(b) The demand for a product dunng the last 10 years 1S given below Estimate the demand for the next two years by the method of regresS! on

Ye. ' ' ' ' ' ' ' ' ' w

Uruts '" m '" '" '" '" '" '" "' '" (1 5)

(c) Define Value Engmeenng What are the cond!hons conducive to take up V A!VE study

(o)

(a) In a machme shop, certam type of machmes break -down at an average rate of 6 per hour The breakdowns are m accordance W!th P01sson process The eshmated costs of idle machme 1S Rs 1 5 per hour Two repairmen A and B W!th d! fferent skills are b emg conSidered to be hired as repairmen Repairman A takes S!X mmutes on an average to repair a machme and ills wages are Rs 8 per hour, whereas the repairman B takes five mmutes to rep atr and the wages

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are Rs 10 per hour Wluch repamnan's semce should be used and why? Assume the work sluftof8hours

(2 0)

(b) For xyz company, the aruma! reqmrement of an 1tem 1S 2400 umts Each 1tem costs the company Rs 6 The supplier offers a d!scount of 5% 1f 500 or more quanl!hes are purchased The ordenng cost!S Rs 32 per order and the average1nventoty cost 1S 16% Is 1t admsable to accept the diScount 7 Comment on the result?

(2 0)