MECHANICAL ENGINEERING
PAPER · II
SECTION A
.n. "
5 of'S
Answer any four pansc
Two C'amot engines won: in series between the sourt:e and sink temperatures of 600 K and
300 K If both engines develop equal power. detemtine the intermediate rempemture

Show that the compression ratio for the maximum work to be done per kg of air in an
Otto cycle betWeen upper and lower limi Is of absolute temperaru res T_. and T1 is given by the
expression
1
An ideal gas is healed at coostam volume until its temperature is 3 times dte original
temperature, then it is expanded isothermally till it reaches irs original pressure, the gas is
then restored to lts original state. Oetentline the expression of net work done.

:lOO kJ/sec of heat is supplied at a constam fixed temperature of2 90°C to a heal engine.
The heat rejection rakes place at s.5•c The fo llowing results were obtained
215 kJ/s of heat is rejected
150 kJ/s of heat is rejected
(Il 75 kJis of heat is rejected
Using Clausius int'quality which of the results report a reversible cycle or irroversible cycle.
or impossible resul t7

What is HUCR (H.ighesl usetitl compression ratio) V LSxplain the terms, Octane number
and Celane number

What is petrol infection What are its advantages and disadvantages?

Make a detailed r<lmparisotl of Sl and Cl engines with respt'Ct to ba.sic cyclo, fuel,
introduction of fuel in the cylinder, ig11ition, compression ratio and weighl
1
Two parallel flat plates of equal areas 0 5m2 each face other. These are· at 1000 K and 500 K
respectively Shape factor between them F 11 F21 0,285, These are placed in a room whose
walls are at 300 K Find rdtional hat transfer rate between the plates. and between the plates
and wall Asswne tltat omcr pan of both the plates is insulated. Stefan-13oltzmann constant
5.67 X w·• W/K-m2•


What is detonation? ·Factors leading lo increase detonation In Sl engines lend to reduce
knock in Cl engines.' Discuss the validity nf the two phenomena stated above in the light of
differences in their nature. Indi cate the methods to reduce knock in Cl engines.

3
4.
6 oi'M
Determine the diameter of a fuel orifice for a ei1Sine working on diesel cycle
developing 18 kW per cylinder at 2000 utions per minute. using 0.27 kg/kW"-hr fuel of
API. The duration of the crank injection is J0° of crank travel. The fuel injection pressure.
is 125 bar and the combustion chamber pressure is 35 bar lake velocity coefficient as 0 9
and
141..5
131.6+ API

What is stoichiometric air requirement and eJ<cess afr fa at or?
What de you understand by higher calorific value and lower caiOii lic value? Explain the
methods to ensure Otem.
15)
Determine the air-fuel rat1o at 6000 m altinode in a carburettor adjusted to given an nir-fuel
ratio of 15 I at sea levd wheo·e rhe air tem perature is 300 K and pressure t.O 13 bar

The remperature.of air decreases with altitude and is given by tlte eKprcssh:)O
r t,=00065 h
Where hIs alrirude in n1erres and t.is rhe lemperanrre at sea level in "C
The air pressure decreases wirh alritude as 11er the relation
h 19220 t01r10 J
Where, p Js in a
What remedies "'ould you suggest to compensate fm the decrease iu aiJ.fuel ratio al heigbl
alritudes1 Discuss them justitlc>ction

Show that lhu guvetuing equatiotl fur loUJpermur., distribution i u a fUJ of uniform cross·
Is given 1/y
d
2a "" m. v
ds.'
wh•.re,aa and m1
Fur01er. show that the solution or boundary condirions at 6 at K 9 M x Lis
ll [61 sin h oLx Bo sin h m x 11 sin h mL
tl
Water flows in the tube and brine llows in the annulus of a double"tube heat exchanger
Water at the rate orO. IS kg/s is cooled from 30°C to 29°C and temperature of briue increases
ll·om -15°C to -5°C. The illncr and ttu terdiameters ofwater-can)'ing tube are 25 tum and 30
mm respectively and thermal conductivity of nre1al is 45 Wlm-K. Tlre convective
transfer coefficients on the brine and water side are 2700 and 2LOO W/m1 respecti vely.
Jlind overall heat transfer coefficient and rhen the length of the heat e-Xchanger for parallel
A ow and counter. now. Specific lreni of water= 4.18 kJ

SECTION B
5 Answer any four pan!>.
The evaporator and rempemtures in a reverse Camot refrigera tion cycle of I TR
capacity are 263 K and J I J K respectively Tbe ouder or com pression is sarurated pour and
to turbine is satut'ated liquid_ Find Ute utass llmv rate. work done, condenser heat
and COP Propenles of refrigerant at saturarion in Sl units are as follows:
6.
7
t h h s s I 263 154.656 145d.22
313 :l90.587 149M2 1.64377 5,1558
1
10)
Air enters a cooling coil a1· Jo•c 75% rt)la tive humidity 111e appnmt11s dew-p0im is 12•c
BJld bypass factor is 0. 15. find temperature aud humidity ratio at outlel of cooling coiL u·
mass llow •·ate of air is 10 kg is, lind Ute coudensato and cooling capaci ty of cooling cuil
The partial pressures of wa1e1 vapuur at 12•C and aru I q017 <UJd 4,243 I kPa
respectively Am10spheric pressure is 101.325 kPa. Emhalpy of condensate at 12•c
kJ/kg.

Explain the nomenclature for CFCs and inorganic compounds What 1s meamhy ozone
deple.tlon 7 Name at leas1 two refrigerants that do not cause it.
I
Stare Buckingham's rr theorem Using Buckingham's it lheorem, obtain e"Pression for
drag force on a suumorg<'d bt>dy moving with a 1elati ve velocity V in a lluid. tJoe
other vari ables being linear dimensi<m 1., height of surface roug)mess the 11ldd p
ancl gravitational acceleration g.
tO)
tJ1e cri teria tor the sdootiun of site for steam and hydmelectric power plan!>.
Ia

A rcfrigcnuion system of 10 TR cooling capacity has condenser and evaporator Lemperntw·cs
nf 45"C and to•c respectively The vapour leaving !he evaporator subcools the liquid
leaving the oonde.nset from 45°C • 25"C schen1atic diagram and T-S diagram
considering isentropic compression, isobaric heat absorption and rejection. Determine mass
n9w rate, cqmpressor work, coudeoser heat rejection COP Use vapour specific heat at
oondon$er pressure to f:i nd adiabatic discharge temperature and entlla.lpy. The proporties in St
unhs at saturarion are:
t"7'.8
79.7
It,
178.7
:04.9

0.7088
0.6812
c,.
0.61
.15;
c
1.02

Oeline 1hennodynamic wet bulb 1emperarure t" and show thai humidi ty mtio may be
expressed as
fa)
w W .. .00&

where py l)f is expressed h I 005
J
Diabatic now of dry air takes place tltrough a frictionless constant area duct. At some
panicular section of the duct, the Mac.h number 4.0 vhile stagnation temperature rmd static
pressure are 280 K and 0,45 bar respectively, Calculate the stagnation temperature, staric and
stagnation pressures at a secrion where the Mach number is Also find the amount of hea1
u1111sfer whiclt causes d1is reduction in Mach numbeJ
'rake 0 l .O<)fi k.t/kg and y 1.4.
M Tfl'• T{r." P.fP:
l!.ll 11.361 0.529 6.793 1.503
4.0 0.1026 0..168 0.589 8.227
Explain what do you understand by specific spc.ed of a turbo machine. Give its importance ..
Calc.tolme tJ1e specific of tltc fo llowi ng cases:
8.
K of'S
A 2500 kW gas turbine is running at a speed of 18000 PM. ne entry and exit conditions
of the gas arcT1 J lOOK, 6obar, 30 bar
A centrifugal compressor develops a pressure ratio of I .5 while running at 24000 RPM
and discharging, 2.0 kg/s of air The entry conditions are p1 1.0 bar, 290 K For both
cases take
y 1.4, R 287 Jil<g·K,
1.005 kJ/kg·k

Explain clearly, 'J-Ieat rate curve' and Incremental rate cwve'. Show that the increme111al
rate curve crosses tbc heal rate curve at lowest value of heat rate.
The incrementalluel costs f1>r two generatiug units A and B of: a plant are given by
Pa 25
t=0.08p. +20
where F is fuel cost in Rs/hr and P is power output in MW Find·
the economic loading of the two units when the total load supplit'<l by the power plant is
160MW;
the loss in fuel costihrifthe load is shared equally by the units

Discuss importance of the terms, capacity factor and use factor from !Joe economic poilll
of view of the power plant,
A power stati011 is said to have a use factor of 50% lUld a capacity faclo1 nf 45% How rnany
hours the plant did not operate during lbe yea I"
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