IAS Mains Mechanical Engineering 1987

8/11/2019 IAS Mains Mechanical Engineering 1987

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2/7

4

5.

6.

7

a)

b)

A shaft

12

em external diameter and 8 em internal diameter is subjected to a bending moment

of

300 kgf-m, twisting moment

of

100 kgf-m and a direct thrust

of

10000 kgf. Determine the

maximum principa stress and direction in which

it

acts with reference to the axis

of

the shaft

at the endpoints P and Q of diameter PQ as shown in Fig. I.

l ig.

J

compound cylinder is formed by shrinking a tube 16cm 0 al elia and 12 em internal eli a

on to another tube which has an internal

clia of

8 c . er shrinking, the radial

compression at the common surface is 300

k g f l m

cumferential stress a; the

inner and outer surfaces and at the common surface.

words):

a) What is the principle

of

Location . xpl

a1

the various lo eating and clamping devices used in

practice and their choice.

b) Explain the field n carbides, coated carbides, ceramics and diamonds as

cutting tool materials 1tion

tr

relative advantages and performances.

c) Where do you l ~ o ~ arators ? Mention the names of the various comparators used in

practice. Expl ai c struction and working of sigma-comparator.

(d) Explain th imp o

of

Regression Analysis. How is it suitable for the best curve fitting ?

a) t tl:ircle diagram, derive the equations to find-

a)

n and shear stresses on rake end shear - planes;

specific energy

of

cutting, shear and friction

kinetic coefficient of friction.

Explain the need for unconventional machining processes. How are the Lasers and Plasmas

produced ? Mention their field

of

application.

Indicate the directions

in

which new metal-forming processes are being developed What are

the main advantages

of

the High Energy Rate Forming processes and their applications ?

With the help of a neat sketch, show the different tones of an operating characteristics curve

(OC) for an attribute sampling plan, and explain the characteristics

of

the curve.

b) what are the limitation

of

X and R charts and how do you compare p chart with X and R

chart?


3/7

8.

c) PI ot the control charts for X and R using the following sample data and sample size of five.

a)

b)

From the chart see if the pro cess is under control for the averages. Also find the process

capability. Give d

2

= 2.326)

Sub Group

No.

2 3

4

5 7

8 9 10

x ~

5.004 5.204 5 014 5 008 5 009 5 016 5 030 5 010 5 016 5 ~

0

0.02 0.08 0 03 0 04 0 04 0 09 0 04

DofiM

..

l l o ~ o g

~ p h o

U

lmo

prog

o

i) Uniqueness

ii) Degeneracy,

t

'v

A soft drinks firm has two bottling ~ ~ o c t e d at M and the other at N. Each plant

produces three different soft drinkA B . C The capacities of the two plants in number

of bottles per day are as given a . A market survey indicates that dw1ng the month

ofApril there will be adem ~ bottles ofA 16000 bottle of B and 480 00 bottles of

400 How many days s ,j:h

rlfi

rm run each plant m Apnl

so

that production cost ts

muunuzed while sttl h7 market demand?

C Tho opo,.;og :: , iog plmu M md N

' ' ' '

Ro 600

Ro

N

3000 1000

B

1000 1000

c

2000 6000


4/7


5/7

4

b)

A conical section has been fabricated out of pyroceram. It is of circular cross-section with

diameter D =ax, where a= 0.25. The small end is located at x

1

=50 mm and the large end at

x

2

=

250

mm. The end temperatures are T

1

= 400 K and T

2

= 600 K while the lateral surface

is well-insulated.

a)

(i) Derive an expression for the temperature

clistri

bution T(x) assuming one-dimensional

con

eli

tion.

(ii) Calculate the heat rate q through the cone.

A shell and tube heat exchanger must be designed to heat 2. 5 kg/s of water to

160

C, through the shell side of the exchanger. The oil is known to ovid an average

convection coefficient of 345 kcal/m

2

hC on the outside of the tub en 1b are used to

pass the water through the shelL Each tube

is

thin-walled of eli amet 25m and makes eight

passes through the

shelL

(i)

If

the

o111s

to leave the exchanger at 100C, what flpw rate?

ii)

How''

'

'

'

=mphoh

C

or engme

01 Cv

= 560 callkg C

For water Cv I 000 cal/kg C

V1scos1ty

=

54

8 x I 0

6

kg/s m '

V

Thermal conductnnty= 0 553

Pr

=

3 56

Assume that the correct on factor - 87

(25)

(b)

ir

at a 11

ri

and a temperature of 3 00C flows wtth a veloc1ty of

I 0 mls over

~

of length 0 5 m Est1mate the

co

ohng rate per umt wtdth of

plate ~

t a m

1t at a surface temperature of 27 C.

h for air

at)

v 5.21 x10_.m

2

s

th. stated conditions

P

= 0. 687

K =

0.0

313 lccallmh C

(25)

c) perature profile at a particular x location in a thermal boundary layer is givenby T(y)

y

+

Cy

2

,

where A, B and C are constants. Obtain an expression for the corresponding

at transfer coefficient.

(I 0)

SEC11 N B

5. Answer any three of the following four parts (Answer to each part should not exceed 200 words):

a) Give a list

of

the thermometers

you

would employ to measure temperatures ranging between

-100 c and 3000C.

(20)

b) Explain

the

salient features of Clapeyron equation. Calculate the change in melting point of

ice when it is subjected to a pressure of I 0 0 atrno spheres.


6/7

6.

Density of ice= 0.917 gm/cm

3

Latent heat of ice = 80. 3 cal/gm

20)

(c) Compare the performance of various types of fuel injectors for fuel injection in Combustion

Chambers

of

gas turbines.

(d)

(a)

(b)

(c)

In relation to steam turbines explain the purpose of the following:

i)

ii)

iii)

Velocity compounding

Pressure compounding

Pressure-Velocity compounding.

Explain the principle of working of he following

20)

(1)

Once through, Super

en

ical bo1ler

u) Steam generation by nuclear reactor

~

20)

Steam 1s supphed to a turbme at a pressure

and a temperature of 500 C

Steam 1s bled for feed heating at pressures

~

4 em and 5 10 kgflcm

2

The condenser

pressure 1s 0 510 kgflcm

2

The stage effia yo ea section of the turbme can be taken as

82 In the feed heaters the feed water ~ nthalpy rat sed to that of the bled steam

The bled steam 1s condensed, but no oled and m this state, on leavmg the feed

heater,

1s

pumped mto the feed mat

The effect of reheating on plan efficiency

Mass of steam heater

tn

kg/kg of supply steam

111)

Thermal

e f f i a : i g e m e n t

(1)

u)

; r

30)

Steam enters a convergent-divergent nozzles at a pressure of 22 5 kgflcm

2

and 1Mth

a temperature o 0 Eqwhbn

u

exp ans1on through the nozzles to an ex1t pressure of 4

kgflcm

2

? \ to

the roat

of the

nozzle

the

flow can be constdered as frictionless From the

xtt,i towever, there 1s an efficiency

of exp

ans1on

of

85 . The rate

of

steam

f

ow

thr zles is kgls. Determine the throat and exit velocities and the throat and exit

ar s.

I 0)

the following

25)

(1) Destgn of solar collectors

ii) Choice of refrigerants.

(b)

A turbine model having the following specifications has been constructed

to

predict the

behaviour

of

an actual turbine:

Power=

15

HP

Head=12m

N=474r p m


7/7

(c)

8. (a)

(b)

(c)

n=

10

Determine the speed

of the

actual turbine runner and its power

if

the overall efficiency of

turbine is equal

to

that of the model. Find the type

of

turbine for which the model was

constructed.

(20)

n axial compressor is fitted with half-reaction blading, the blade inlet and out et angles

being 5

o

and

5

when measured from the axial direction. The mean diameter

of

a certain

blade pair is

85

em and the rotor turns at 5500 r.p.m. Calculate the necessary isentropic

efficiency of

the

stage

if

the pressure ratio

of

compression is

to

be

1.4

e

temperature 1s 25C. '

[Cp=0.24.y=1.4] G

(15)

Discuss the essential differences in working principles off heat engi he pump and

refrigerating machine. ~ (12)

Describe a summer air conditioning system with ventilation.

n

air handling unit in air conditioning pi ant supplies a

to

. ;(4

50

0 m /s

of

ry air which

compn ses by we1ght 20% fresh atr at 4oc DBT and 27 ~ 8 0 recirculated atr at

25C D BT and 50%

RH

The atr leaves the

co

ohng

C urated Calculate the total

coohng load and room heat gatn

The followtng data can be used

Cond1t1on DBT WBT RH Sp f ' ~ Enthalpy

c c % ~ vapour) kcallkg

k dry air d. a

Outside 40 27 17.

20.3

Inside 25 .0 12.15

ADP 13

' '

v 9 4 8.85

Sp

volume

of

air

oling coil =

0. 86

9 m

3

1kg d. a. (2 0)

A vapour o p ~ efrtgerator uses methyl chloride and operates between pressure limits

of

180.54 kgflm d

6.3

kgflm

2

. At entry

to

the compressor the methyl chloride is dry

s a t u r a t

dafter c mpression has a temperature of I 02C. The compressor has a bore and

stroke

5

m runs at 8 rev/s with a volumetric efficiency of 80%. The temperature of

the erant as it leaves the condenser is

35 c

and its specific heat cap city is

0. 38

8

k k g ~ The specific heat capacity of the super-heated vapour may be assumed to be

n ant. Determine------

(i) refrigerator

COP.

(ii) mass flow rate of refrigerant.

(iii) cooling water required by the condenser if its temperature rise is limited

to

12c

Specific heat capacity ofwater= I kcalikg C

Relevant properties

of

methyl chloride are as follows:

Sat Temp Press ~ e c Vol ~ e Enthalpy Spec Entropy

-10

45

cf kg/1m

2

m

3

/kg kcallkg kcalikg C

180.54

986.3

v, v, h, hg

s

s,

0.00102 0.233 I 0.8 110.0 0.044 0.42

0.00115 0.046 318 115.6 0.116 0.38

(28)

Documents

IAS Mains Mechanical Engineering 1987