ias mains mechanical engineering 2007

8/13/2019 IAS Mains Mechanical Engineering 2007

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IIIGCHANICAL GNGINGGLLNGTimeAH


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(u)

wh1ch 1S 360 rpm Fmd 1ruhal compress10n of the spnng and mass of the sleeveneglectmg obhqmty of the arms Also find the eqmhbnum speed correspondmg to therad us of rotal on equal to 10 0 mm (3 0)What 1s creep of belt m a belt dnve? Explam 1 W th the help of a neat sketchA leather belt 10 0 nun W de and 1 0 nun th1ck 1S transnuthng power at 1000 m/mmThe net dnvmg tenS on 1S 1 8 l mes the tens10n on the slack S de If the safepernusS ble stress on the belt sechon 1S 1 6 N/nun2, calculate the max:1mum power thatcan be transm lted at th S speed Assure the denSity of leather equal to 100 0 kg/m3(3 0)(a) A steel bolt of d1ameter 1 8 em passes coax:1ally through a copper tube of mner d1ameter 2 em

and outer d1ameter 3 em The length of the tube 1S 50 em Washers are placed at both ends ofthe tube The bolt has threads at one end havmg p1tch equal to 0 24 em The nut 1S turned onthe bolt through 45 agamst the washer to hghten the assembly Determme the stressdeveloyed m the bolt and the tube Assume the modulus of elast C Iy of steel to be 2 x 105N/mm and modulus of el ashc1ty of copper 1S half that of steel (2 0)(b) The sechon of a beam 1S square of 10 em S de W th one d1agonal verhcal It 1S subjected to atransverse shear force of magmtude F Determme the problem of the layer at wh1ch thetransver shear stress 1S max1mum (2 0)

(c) A sohd c1rcular steel shaft 1S encased m a hollow copper shaft so as to make a compoundshaft The d1ameter of the steel shaft 1S 8 em and the outS de d ameter of the copper shaft 1S11 em The compound shaft of length 2 m 1S subjected to an ax:1al torque of 8 kNmDeternune the nuX mum shear stress 1n steel and copperG1ven" G ,..,1 2 G ''PP" 80 kN/mm' (2 0)

(a) Explam the method of controllmg the gram S Ze m a polyaystalhne matenal1 5)(b) What do you mean by 'stelhte'? What are the 1mportant propert1es possessed by tlusmatenal? Wnte down the uses of stelhte m the n g ~ n n n g apphcahons1 5)(c) How are plast1cs broadly clasSified? What are the advantages and diSadvantages of plashcmatenals?1 0)(d) What 1S tempenng of steel? How 1S 11 earned out? D1fferenl ate between Cyarucung and

N1tndmg(2 0)

SEC nONAnswer any three of the folloWing(a) What 1S 3-2-1 pnnaple oflocahon What are the vanous degrees of freedom for a body mspace? D Shngmsh between aJ1g and a Fmture

(2 0)(b) What 1S ultrasoruc maclumng? Draw a neat sketch shoWing the 1mportant parts of anultrasoruc machme, label the parts Wh1ch matenals are normally machmed usmg ultrasorucmaclurung?

(2 0)(c) The store of an od engme repa1r shop has ten 1tems whose deta1ls are shownm Table belowApply ABC analySiS to 1tems of store Does 11 sahsfy pnnaple of ABC analySiS?

(2 0)


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(d)(u)(111)

W1th a neat sketch bnefly explam orgamzah on of d g1tal computerWnte down the general structure of a l o ~ cal IF statement m modem FORTRANlanguageD1fferenhate between a funchon sub pro gramme and sub-routme

(2 0)(a) What 1S the d1fference between laser weldmg and plasma weldmg? Draw a neat sketch of aplasma torch, label the vanous parts (3 0)

(b) Denve an equahon for the average d epressure1n open d1e forgmg of a arcular d Sc Explamthe assumphons made m denvmg the equahon The soluhon may be found only for theshdmg cond1h on of fuel on

(3 0)(a) Four different cashngs are to be machmed on four machmes, one cashng on each maclune,because set up cost and l me are too h1gh to penrut a cashng bemg worked on more than

one machme Table below shows hme of maclumng each cashng on each maclune AsSignthe Jobs on maclnnes and show that the problem 1S mulh-ophmal soluhons Obtam sequenhalsoluhon~ .' - ' ,.,, ,. '

' (3 0)ctMty mlo-' ' ' '' ' , '' , ' '' ' ' '' ' ' 's O ' ' '' ' ' '


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1 ) Construct ProJ eel network(u) F1nd the expected durahon and van ance of each achv1ty111) F1nd the cnhcal path and expected proJect complehon hme(1v) What 1S the probab1hty of complehng the proJect on or before 30 weeks?

(3 0)(a) What do you understand by the abbrev1ahon HSS TW st dnlls are used for makmg holes mmaclnne parts, label the vanous features of a tw: st dnll Used for makmg holes 1n m1ld sleetWhat are the tools used for firushmg the holes ? Make neat sketches to 11lustrate your

answers

(u)(3 0)Descnb e steps to be followed dunng T1me Study

In a tummg shop, a duect hme study was on a step tummg The study was conductedy an expenenced mdustnal engmeer and one 1nexpenenced engmeer They agreedpreciSely on cycle, hme shown1n Table below, but the1r opm10n on ratmg of workers

was differed The expenenced engmeer rated the worker 100% and the other engmeerrated the worker 120% They used 0 10 allowance frachon

C);;e nm ~ u r t e r or(minutes; Time l cm v d''''Determ1ne the standard hme usmg rahng of each eng1neer

(3 0)


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MECHANICAL ENGINEERING:::: TimeAH


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where a S a constant and x 1S the aX al &stance of the sechon from the apex of the cone Thetemperatures at the two end faces of the comcal sechon (at diStances x 1 and x1 from the apex)are respechvely T1 and T, wh1le the lateral surface of the truncated cone 1S thermallymsulated

(1) Denve an express10n for the temperature d Stnbuhon T(X) m symbolic form assunung oned menS onal steady -state cond hons Sketch the temperature d stnbuhon11) Calculate the heat rate q, through the cone m x-d1rechon

(20+40)(a) A refngerahon system operates usmg Simple saturated cycle W th a certam refngerant Thecondensmg and evap orahng temperatures for the refngerant are 35 oc and -15 oc resp echvely

Deternune the COP of the system If a hqU1d vapour heat exchanger 1S mstalled m thesystem, W th the temperature of the vapour leavmg the heat exchanger at 15 C, what W ll bethe change m the COP?Use the folloWing data for the refngerant used

S'Jpemea l d' 2Q K '' ;' . . I ' '"'" '"' ~ ... ~ J i j q j k]ll


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(1v) Power reqmred to dnve the compressor(v) Stage pressure raho(10+50)

SECTIONAnswer any three queshons

(20x3=60)(a) Sketclung 'load curve' and 'load dural on curve explam thm purposes Define also 'demandfactor' and 'plant-use factor

The loads for certam mdustnes are tabulated below for 24 hours Dunng load durahon andload curve, find power reqmred for 40% of the hme of the day If the capac1ty of the powerplant 1S 35 MW, find the cap ac1ty factor of the power plantT1me 6AM 8AM 9AM lAM 2AM

0 Co Co Co CoCAM o M lAM CAM o MLoad M nm MW)

T1me M CCM 12 PM MCo Co Co Co

M 12PM O M O Mo ~ M M(m MW)

If the load 1S supphed by two power p l a n t ~ one 1S achng as a base load planthavmg capaatyof25 MW and other as peak load planthavmg capac1ty of 10 MW, find load factor, capaatyfactor and use factor for both power plants

(b) The stator blades of a gas turbme are supphed W lh gas whose stagnal on enthalpy h0 andstagnal on temperature To Va )' W lh radms r There 1S cyhndncal flow through the statorblades 1S reverSible and ad1abahcShow that, m the cross-sechonal plane at eX I from the stator blades~r ~ o.. za Cdo'ence, when the gas can be assumed to be a perfect gas and the stagnahon pressure Po 1Sconstant over the annulus, show that

~ z( in a d +(c) A quarter-scale turbme model S tested under a head of 108m The full-scale turbme 1S

reqmred to work under a head of 30 11 and to run at 7 14 rev/s At what speed the model mustrun? If1t (model) develops 100 kW and uses 1 085 m3 of water per second at tills speed, whatpower wdl be obtamed from the full-scale turbme, 1ts effic1ency bemg 3lo better than that ofmodel? What 1S the d1menS1onless sp ec1fi c speed of Full-scale turbme?(d) Steel ball beanngs (K =50 W/m-K, =1 3 x 10-5 m2/s) hamng a d1ameter of 40 mm areheated to a temperature of 650 oc and then quenched m a tank of 01l at 55 oc If the heat

transfer coeff1c1ent between the ball beanngs and the od 1S 300 W/m2-K, detenmne(1) the durahon of hme the b eanngs must remam m od to reach a temperature of 20 0 C,(11) the total amount of heat removed from each beanng dunng tlns hme,(111) the mstantaneous heat transfer rate from the beanngs when they are first 1mmersed m01l and when they reach 20 0 oc

(a) Define Rayle1gh flow and menhon 1ts govemmg relahons Usmg them, estabhsh theexpress10n for the flow m the form p + G'v = Cons , where G 1S the mass flow rate per un1t


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area Show the plot of th S equahon on h-s and p-v planes Show also that at max:tmumenthalpy state

(b) For the Rayle1gh flow, estabhsh the express10n for TIT* terms of Mach number, M(c) Alr enters a 5 em d ameter fnchonless duct W lh a Mach number 2 Its stahc temperature S250 oc and stagnat10n pressure 6 bar For 1ncreasmg Mach number to 3, find the amount of

heat to be transferred and change m stahc temperature You may use the folloWing table fora1rhavmgy= 14N TIT* PIP* Po/Po To To*2 0 5289 0 3636 1 503 0 7934

0 2803 0 1765 3 424 0 6534(a) Why S the use of dust collector necessa )' m case of thermal power plant? DiScuss thelocahon of electrostahc prec1p1tator W th reference to sulphur content of coal and flue gastemperature(b) From the folloWing data for the underfeed stoker bo1ler, find draft requued m mm of watercolunm and power requued to dnve the fanMean temperatures of flue gasespassmg through ductPlenum pressureAhnosphenc pressureMean veloc1ty of flue gases m ductLength of the ductMean S ze of the non-c1rcular ductNumber of90 bendsNumber of45 bendsLoss of draft m evety 90 bendDraft available from ch1mneyFuel bed reSiStance for underfeed stoker

227 oc15cmofwater75 em of Hg900 m/nun150m75 em'

1 em ofwater1 5 em ofwater10cmofwater

Fan effic1ency 60%Motor effic1ency 92 5%Assummg that 45 bend eqU1valent to one-half of 90 bend, reSiStance offered by nonCircular duct S 20% h1gher than a S nular c1rcular duct, fnchon factor for arcular duct S0 006, find draft reqU1red to be produced by fan and the fan power for flue gases TakeR=294 35 3/kg-K

(20+40)To av01d havmg add1honal mlet and outlet p1pes through the wall of the pressure vessel ofpressunsed water nuclear reactors, S usual to employ a steam - heated reheat cycle Steam S bledfrom the bo1ler dehvety ma1n to reheat the steam leamng the h1gh-pressure turbme before entersthe low-pressure turbme The data for the cycle are as follows

B01ler outlet cond1hon Saturated steam at 6 0 barU turbme mlet pressure 5 barCondenser pressure 0 05 barHP turbme 1sentrop1c effic1ency 0 80 barLP turbme 1Sentrop1c effiaency 0 87 barReheat temperature 270 oc

The feed pump terms can be neglected, and may be assumed that the bled steam leaves the reheaterat a temperature equal to that at the h1gh -pressure turbme ex1t, Deternune the dryness frachons at thelngh- and low-pressure turb1ne ex1t and the cycle effic1encyAlso determme these quanhhes 1f no reheahng were used Comment bnefly on the result ( 60)


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Cumulahve d Stnbuhon funchon for the standard normal d stnbuhon (SND)

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ias mains mechanical engineering 2007

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