MECHANICAL GNGINGGLLNG 2007

TimeAH<med: 3 hours IIIIximum IIIIrks 300
Candidates should attempt Questions Nos. 1 and 5 which are compulSLLl, and any three 01 the remaining questions selectiBlat least one question lrom each Section.
IIany data is considered insuflicient, assume suitable value.
Newton may he convened to kg using the equalityl kiloNewton(11111) 100 kg, illound necessa/y.

SECllDN A
Answer any three of the folloWlng
Define pressure angle for a cam follower mecharusm Explam its lmportance m the deSign of cam profile

A plate cam dnves a radial translating follower with cyclO1dal motion at 1000 rpm Rise and return strokes are each 120° with two equal dwells. Follower is retamed agamst the cam by a compreSSiOn spnng with a scale of 15 N/mm. Spnng lS compressed by 2.5 mm m assembly to provlde an mitialload. For anse of 10 mm and a follower mass of 1 8 kg, compute the radial component of the cam force and the cam shaft torque at a pomtlo cated at 1000 m the ascenllng stroke

A machine, of mass 17 kg, lS mounted on a spnng havmg stiffness 1 N/nun A plston within the machine of mass 2 kg has a reclprocating motion with a stroke of 75 mm and a speed of 5000 rpm. Assunung the motion to be SHM, detemune amplitude0fmotionofthemachine force transmitted to the ground Dampmg ratio may be taken as 0.20

Under which conlltion of the state of stress at a pomt m the two dimensions, the Mohr's clrcle Will be reduced to a point?
How much change ln volume would a 100 nun Side cube of steel will have when itlS kept at a depth of 2 km m sea water? Assume speafic graVity of sea water equal to 1.02, modulus of elasticity equal to 2.08 GPa and POisson's ratio equal to 0.29

With the help of a neat sketch, explam the folloWing tenns Crystallographic axes, Primitives and Interfaclal angles
Compare 8CC and FCC structures
What lS sol1d solution? Explam with the help of neat sketches the different lGIes of sol1d solutions

Explam the concept of controlling force m connection with a centrifugal governor and state ltS lmportance m detemumng the stability 0f a centrifugal type governor

In a spnng loaded governor of Hartnell type, the mass of each balllS 1 kg. The length of the vertical arm of the bell crank everlS 100 nun and that ofhonzontal armlS 5Omm.TheIIstance0fthefulcrum ofeachb ell cranklever lS80mm110mtheaxlSof rotation of the governor The extreme ralll of rotation of the balls are 75 mm and 112.5 mm The maxtmum equil1bnum lIeed lS 5 per cent greater than the nummum which lS 360 rpm. Find Initial compreSSiOn of the spnng and mass of the sleeve neglecting obliquity of the arms. Also find the equilibnum speed corresponding to the radius of rotation equal to 100 mm

WhatlS creep 0f beltm a b elt dnve? Explam It with the help 0f a neat sketch
A leather belt 100 nun Wide and 10 nun thick lS transmitting power at 1000 m/mm The net dnvmg tenSion lS 1 8 times the tensiOn on the slack Side. If the safe p ernussible stress on the belt section lS 1 6 calcul ate the maxtmum power that can be transmitted at this speed. Assure the density of leather equal to 1000 kg/m3

A steel bolt of diameter 1 8 cm passes coaxtally through a copper tube of mner diameter 2 cm and outer diameter 3 cm. The length 0 f the tub e lS 50 cm. Washers are placed at b oth ends of the tube. The bolt has threads at one end havmg pitch equal to 0.24 cm. The nutlS turned on the bolt through 45° agamst the washer to tighten the assembly. Detenmne the stress develofed m the bolt and thetube. Assume the modulus of elastiaty of steel to be 2 x N/mm and mo dulus 0 f el ashClty 0 f copp er lS half that 0 f steel

The section ofa beam lS square of 10 cm Side with one diagonal vertical 1tlS subjected to a transverse shear force of magnitude F Detenmne the problem of the layer at which the transver shear stress lS mffil1murn

A solid circular steel shaft lS encased m a hollow copper shaft so as to make a compound shaft. The diameter of the steel shaft lS 8 cm and the outSide diameter of the copper shaft lS 11 em. The compound shaft of length 2 m lS subjected to an axtal torque of 8 kNm Deternune the nuXlmurn shear stress In steel and copper Given" G 2G <OW" 80

4. Explam the method of controllmg the gram Size m a polyaystalline matenal

What do you mean by 'stellite'? What are the Important properties possessed by this matenal? Write doWll the uses of stellite m the englneenng applications

How are plastics broadly clasSified? What are the advantages and disadvantages of plastic matenals?

What lS tempenng of steel? How lS it camed out? Differentiate between Cyarucl1ng and Nitriding

SECTION II

Answer any three of the folloWlng
5. WhatlS pnnaple of location? What are the vanous degrees of freedom for a body m space? DistingUish between aJig and a Fixture

(b)What lS ultrasoll1c machimng? Draw a neat sketch shoWing the Important parts of an ultrasoll1c machine, label the parts Which matenals are normally machined usmg ultrasoll1c machill1ng?

The store ofan od engme repalr shop has ten items whose details are shoWllm Table below Apply ABC analySiS to items of store. Does it satisfy pnnaple of ABC analySiS?


With a neal sketch briefly explam orgatl1zah on 0f digital compuler

Write down the general structure of a lOgical IF statement m modem FORTRAN language Differentiale between a function sub pro gramme and sub-routine



WhatlS the difference between laser welding and plasma welding? Draw aneal sketch of a plasma lorch, lab el the vanous parts




Denve an equation for the average diepressureln open die forgmg ofa CIrcular disc Explam the assumptions made m denvmg the equation. The solution may be found only for the sliding conditi on 0 f friction




Four different castings are to be machined on four machines, one casting on each machine,


,...

Price "til.
P<lclOog stod COO
eo, T"""" bolt
out " ""
eo, Bu,h 1000
eo" eo, l'UIllP-.llr111 lI)Q _rings 7000 500D "" JOOJ ,000

because set-up cost and time are too high to pemut a casting bemg worked on more than one machine. Table below shows time of machimng each casting on each machine. ASSign the Jobs on machines and show that the problem is multi-optimal solutions Obtam sequential solution


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Construct ProJ ect network


Find the expected duration and van ance 0f each activity
Find the critical path and expected project completion time



WhatlS the probability of completing the project on or before 30 weeks?



What do you understand by the abbrevlation HSS TWist drills are used for making holes m machine parts, label the vanous features of a twist drill Used for making holes ln nuld steet What are the tools used for firushing the holes? Make neat sketches to illustrate your
answers


Describ e step s to be foll owed dunng "Time Study"


In a turning shop, a direct time study was on a step tummg The study was conducted by an expenenced mdustrial engmeer and one lnexpenenced engmeer. They agreed preciSely on cycle, time shoWllln Table below, but thelr opmlOn on rating 0f workers was differed. The expenenced engmeer rated the worker 100% and the other engmeer rated the worker 120% They used 0 10 allowance fraction


or
TIII1C!l cm..v.d
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Deternune the standard I1me usmg rahng of each engineer

MECHANICAL ENCINEERING

TimeAH<med: 3 hours IIIIximum IIIIrks 300
Candidates should attempt Questions Nos. 1 and 5 which are compulsory, and any three of the remaining questions selecting at least one question from each Section.
Ifany data is considered insufficient, assume suitable value. Use ofpsychometric chait is permitted.
Answer any three of the followmg parts (answer to each part should not exceed 200 words) (20x3=60)

ConSider a Carnal cycle heal enllne operating m the outer space. Heal can be rejected from Ills engme only by thermal radiation, wllch is proportional to the radiator area and the fourth power of the absolute temperature of the radiator Show that for a given engme work oUllul and liven temperature of the IIgher temperature reservOlr the radiator area will be a ffilll1ffiUm when the ratioT,/TH=3/4


A fhll conlamed m a honzonla! cylinder fitted with a frictionless leak-pro of PiStOn, is continuously agitated by means of stirrer passmg through the cylinder cover The cylmder diameter lS 0.40 m Dunng the stimng process lasting 10 mmutes, the plSton slowly moves out a distance of 0.485 m agamst the atmosphere. The net work done by the flmd dunng the process lS 2 kj The speed of the electric motor dnVlng the stirrer IS 840 rpm Detenmne the torque m the shaft and the power oUllut of the motor


A S!mple carburetor has a ventun throat diameter of 20 mm and the coeffiCient of flow lS 0.8 The diameter of the fuel onfice lS 1 14 mm and the coeffiCient of fuellS 0.65. The gasolme surface lS 5 mm below the throat Calculate­


The air-fuel ratio for apressure drop of 0.08 bar when the nozzle tip lS neglected;


The air-fuel ratio when the nozzle tip lS taken mto account;




The ffilmmum velocity of air or cntical air velocity reqUired to start the fuel flow when the nozzle tip lS proVIded Assume the density of air and fuel to be 1 20 kg/m3 and 750 kgim3 respectively

ConSlder a diffuse Circular disc of diameter D and area Aj and a plane diffuse surface of area « Ai The surface are parallel and lS located at a distance L from the centre of Aj Obtam an expressiOn for view factor


The configuration of a furnace can be approXimated as an equilateral triangular duct which lS suffiCiently long that the end effects are neglillble. The hot wall is maintained atT, 900 K and has an effilsSlvity 0.8 The col d walllS at 4 00 K and has an emlSS! vity co 0.8 The third walllS reradiating zone for which Q3 0 The accompanymg sketch illustrates the configuration Calcul ate the net radiation heat flux 1eavmg the hot wall


l.B
The diagram shows a truncated conical section fabncated from a matenal of thennal conductivity K The circular cross-section of the comcal section has the diameter D ax, where alS a constant and x lS the aXial distance of the section from the apex of the cone. The temperatures at the two end faces of the comcal section (at distances and from the apex) are respectively and while the lateral surface of the truncated cone lS thennally msulated


Denve an expreSSiOn for the temperature distribution m symbol1c fonn assunung one­dimenSl onal steady-state conditions. Sketch the temperature di stribution


Calculate the heat rate through the cone m x-direction


A refrigeration system operates usmg SImple saturated cycle with a certam refrigerant The condensmg and evap orating temp eratures for the refrigerant are 35°C and _15°C resp ectively Deternune the COP of the system If a liqUId vapour heat exchanger is mstalled m the system, with the temp erature of the vap our leavmg the heat exchanger at 15°C, what will be the change m the COP? Use the followmg data for the refrigerant used



"
" 69.5
181.0

SUpellleall!d


2Q K




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0.731

0.663g i 216.4
0,7052


10 cu m of almosphenc atr at 25°C DBT and 12°C WBT is flOWIng per nunute through a duct Dry saturated steam at 100 DC lS mJected through the duct Dry saturated steam at 100 °C 1SmJ ecled mto the air stream with a rate of 1 2 kg/mm


What 1s the temp erature 0f air after m1Xmg the steam?


What 1s the relative hunudity of air after nuxmg the steam?




Sketch the axial-flow turbme cascade. Show the veloCIty with Its components at enlly exit mdicating the forces exerted by the flow on blades. State the expreSSiOn of Ideal lift m tenns of flow angles and show that itlS equal to pCm where Cm 1Sthe mean velo city and llS the circulation


The first aXial-flow air compressor stage Wlthoutmlet gUIde vanes lS operating at a speed of 15000 r.p.m m the almosphenc conditions of To 288 Po 101 bar. The rotor mean blade nng diameter lS 0.34 m and hub to tip ratio lS 0.5 Almosphenc air enters the stage with a velocity of 150 m/s. ConSlder constant 8111al velocity through the stage and take stage effiCIency as 0 86, mecharucal effiCIency as 0.97, work done factor as 0.97, Cp 1 005 kJ/kg/K and R 0 287 kJikg/K Sketching the 8111al compressor stage WIth velocity diagrams and labelling with most general notations used m practice, detennme the folloWIng for atlallllng relative velocity rali on across rotor (de Hall er numb er) 0f 0.73


Mass flow rate m kg/s


M8Xlmum Mach numb er at rotor blade at enlly




Angles made by relative and absolute veloCIty at rotor entry and exit with axial directi on

Power reqrnred to drive the compressor


Stage pressure ratio




SECTION II
Answer any three questions (20x3=60)
Sketching 'load curve' and 'load duration curve explam the1f purposes Define also 'demand factor' and 'plant-use factor The loads for certam mdustnes are tabulated below for 24 hours. Dunng load duration and 10 ad curve, find power reqUired for 40% 0f the time of the day If the capacity 0f the power pI antlS 35 MW, find the cap acity factor 0f the power plant
Time 6AM 8AM 9AM IIAM 2AM
o to to to to
8AM 9AM I lAM 2AM 5AM
Load 18 26 30 22 24
(in M1N)
Time 5PM 8PM 12PM 5PM
to to to to
8PM 12PM 5PM 6PM
Load 30 20 15 16
(in M1N)

If the load lS supplied by two power one lS acting as a base load planthavmg capaCIty of25 MW and other as peak load planthavmg capacity of 10 MW, find load factor, capaCIty factor and use factor for both power plants
The stator blades of a gas turbine are supplied with gas whose stagnation enthalpy ho and stagnation temperature To with radius r There is cylindncal flow through the stator blades lS reversible and adiabatic Show that, m the cross-sectional plane at exit from the stator blades

.. O"""a +Cdo
Hence, when the gas can be assumed to be a perfect gas and the stagnation pressure Po lS constant over the annulus, show that


A quarter-scale turbme modellS tested under a head of 10.8 m. The full-scale turbine lS reqUired to work under a head 0f 30 it and to run at 7. I4 rev/s. At what sp eed the model must run? Ifit (model) develops 100 kW and uses I 085 m3 of water per second at this speed, what power wlll be obtamed from the full-scale turbme, its efficiency bemg 3°10 better than that of model? WhatlS the dimensiOnless sp eCifi c speed 0f Full-scale turbme?


Steel ball beanngs 50 a =1.3 x 10.5 haVing a diameter of40 mm are heated to a temperature of 650°C and then quenched m a tank of oil at 55°C. If the heat transfer coefficient between the ball beanngs and the olllS 300 detenmne


the duration 0f time the beanngs must remam m 011 to reach a temp erature 0f 200°C;


the total amount of heat removed from each beanng dunng this time;




the mstantaneous heat transfer rate from the beanngs when they are first immersed m oil and when they reach 200°C

Define Rayletgh flow and mention its govemmg relations. Usmg them, establish the expreSSiOn for the flow m the form p Const, where G lS the mass flow rate per unit

area. Show the plot of this equation on h-s and p-v planes. Show also that at maximum enthalpy state


For the Rayleigh flow, establish the expression for TiT* tenns 0f Mach numb er, M


Air enters a 5 em diameter frictionless duct with a Mach number 2. Its static temperature lS 250°C and stagnation pressure 6 bar. For increasmg Mach number to find the amount of heat to be transferred and change m static temperature You may use the followmg table for


airhavmgy= 1.4
N TIT* PolPo ToiTo*
2 05289 0.3636 1503 0.7934
3 02803 0.1765 3.424 06534


Why lS the use of dust collector necess"'Y m case of thermal power plant? Discuss the location of electrostatic precipitator with reference to sulphur content of coal and flue gas temp erature


From the followmg data for the underfeed stoker boiler, find draft requued m mm of water colunm and power requued to dnve the fan


Mean temperatures of flue gases passmg through duct 227 °C PI enum pressure I 5 cm 0 f water Atmosphenc pressure 75 cm of Hg Mean velocity of flue gases m duct 900 m1nun Length of the duct 150m Mean Size ofthe non-circular duct 75 Numberof900bends 4 Numberof45°bends 4 Loss 0fdraftmevery90°bend 0 Icm 0fwater Draft avatlable from chimney I 5 cm of water Fuel bed reSiStance for underfeed stoker I 0 cm 0 f water Fan efficiency 60% Motor efficiency 92.5% Assummg that 45° bend is eqU1valentto one-half of 90° bend, reSiStance offered by non­circular duct lS 20% higher than a Similar circular duct, friction factor for arcular duct lS 0.006, find draft reqU1red to be produced by fan and the fan power for flue gases Take R 294.353ikg-K
To avOid havmg additional mlet and outlet pipes through the wall of the pressure vessel of
pressunsed water nuclear reactors, itlS usual to employ a steam -heated reheat cycle. Steam lS bled from the boiler delivery main to reheat the steam leaVing the high-pressure turbme before it enters the low-pressure turbme. The data for the cycle are as follows
Boiler outlet condition Saturated steam at 60 bar
turbme mlet pressure 5 bar
Condenser pressure 0 05 bar
HP turbine isentropic efficiency 0 80 bar
LP turbme lSentropic effiaency 0 87 bar
Reheat temp erature 270°C

The feed pump tenns can be neglected, and it may be assumed that the bled steam leaves the reheater at a temp erature equal to that at the high-pressure turbine exit, Determme the dryness fractions at the high-and low-pressure turbine exit and the cycle efficiency
Also detennme these quantities if no reheating were used. Comment bnefly on the result

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