Download VTU BE 2020 Jan ME Question Paper 17 Scheme 6th Sem 17ME53 Turbomachines

Download Visvesvaraya Technological University (VTU) BE ( Bachelor of Engineering) ME (Mechanical Engineering) 2017 Scheme 2020 January Previous Question Paper 6th Sem 17ME53 Turbomachines

USN
o
ft

1:7
f 17M E53
Fifth Semester B.E. Degree Examination, Dec.2019/446
1
20
Turbomachines
Time: 3 hrs. Max. Marks: 100
Note: Answer any FIVE full questions, choosing ONE full question from each module.
Module-1
,...
0
I a. Define Turbomachine. With neat sketch, explain the parts of Turbomachine. (04 Marks)
-
rq b. Define specific speed of pump. Derive an expression for the same in terms of discharge
VI
-c
1.) c. A Fransis turbine model is built to scale 1:5 the data for the model is P = 4kW, N = 3500rpm
H = 2m and prototype H = 6m. Assume that the overall efficiency of the model as 70%.
i1J1) 2
Calculate: i) Speed of the prototype ii) Power of the prototype. Use Moody's equation.
'5 =
t--5
(10 Marks)
1 c5 OR
Z. '
c,c
u
2 a. Define Polytropic Efficiency of turbine. Show that the Polytropic Efficiency during
,sb

_ +
In ?
T2

,-,3
= .4
s
v
0
Expansion process is given by ri
p
=
1
T,
P,
(10 Marks)
=

?
c
.
.
In
0

Y
P
1
= c
b. In a three stage turbine the pressure ratio of each stage is 2 and stage efficiency is 0.75.
Calculate overall efficiency and reheat factor. (10 Marks)
Module-2
?
O-0
r..1) 3 a. Derive alternate form of Euler's turbine equation and explain the significance of each energy
;e
.
component. (10 Marks)
3 :4
==.
b. At a 50% reaction stage axial flow turbine the mean blade diameter is 0.6mts. The maximum t
.e

utilization factor is 0.85 and steam flow rate is I 2kg/sec. Calculate the inlet and outlet
absolute velocities and power developed if the speed is 2500rpm. (10 Marks)
g c
r
i"
4 a.
8
o
cz
-)
b.
c ?o
=
3
?
22.
6
<-4
Module-3 ??
5 a. Why compounding of steam turbine necessary? Describe the velocity compounding of steam
turbine with neat sketch. (08 Marks)
O b. Show that for a two row Curtis steam turbine stage in the absence of friction for axial
COM
discharge at exit under maximum utilization condition U /V, = 4 where U = blade
speed V
1
= absolute velocity at inlet at = nozzle angle at inlet. (12 Marks)
l oft
OR
In a turbomachine prove that the maximum utilization factor is given by
24 cos a,
E
ms
= where (I) = speed ration, R = degree of reaction, al = nozzle angle.
1 + 24R Cosa.,
(10 Marks)
Draw the velocity triangles at inlet and outlet of an axial flow compressor from the
following data. Degree of reaction 0.5 inlet blade angle 45?. Axial velocity of flow which is
constant throughout 120m/sec, speed of rotation 6500rpm, radius of rotation 20cm, blade
speed of inlet is equal to blade speed at outlet. Calculate angles at inlet and outlet. Also
calculate power needed to handle 1.5kg/s of air. (10 Marks)
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USN
o
ft

1:7
f 17M E53
Fifth Semester B.E. Degree Examination, Dec.2019/446
1
20
Turbomachines
Time: 3 hrs. Max. Marks: 100
Note: Answer any FIVE full questions, choosing ONE full question from each module.
Module-1
,...
0
I a. Define Turbomachine. With neat sketch, explain the parts of Turbomachine. (04 Marks)
-
rq b. Define specific speed of pump. Derive an expression for the same in terms of discharge
VI
-c
1.) c. A Fransis turbine model is built to scale 1:5 the data for the model is P = 4kW, N = 3500rpm
H = 2m and prototype H = 6m. Assume that the overall efficiency of the model as 70%.
i1J1) 2
Calculate: i) Speed of the prototype ii) Power of the prototype. Use Moody's equation.
'5 =
t--5
(10 Marks)
1 c5 OR
Z. '
c,c
u
2 a. Define Polytropic Efficiency of turbine. Show that the Polytropic Efficiency during
,sb

_ +
In ?
T2

,-,3
= .4
s
v
0
Expansion process is given by ri
p
=
1
T,
P,
(10 Marks)
=

?
c
.
.
In
0

Y
P
1
= c
b. In a three stage turbine the pressure ratio of each stage is 2 and stage efficiency is 0.75.
Calculate overall efficiency and reheat factor. (10 Marks)
Module-2
?
O-0
r..1) 3 a. Derive alternate form of Euler's turbine equation and explain the significance of each energy
;e
.
component. (10 Marks)
3 :4
==.
b. At a 50% reaction stage axial flow turbine the mean blade diameter is 0.6mts. The maximum t
.e

utilization factor is 0.85 and steam flow rate is I 2kg/sec. Calculate the inlet and outlet
absolute velocities and power developed if the speed is 2500rpm. (10 Marks)
g c
r
i"
4 a.
8
o
cz
-)
b.
c ?o
=
3
?
22.
6
<-4
Module-3 ??
5 a. Why compounding of steam turbine necessary? Describe the velocity compounding of steam
turbine with neat sketch. (08 Marks)
O b. Show that for a two row Curtis steam turbine stage in the absence of friction for axial
COM
discharge at exit under maximum utilization condition U /V, = 4 where U = blade
speed V
1
= absolute velocity at inlet at = nozzle angle at inlet. (12 Marks)
l oft
OR
In a turbomachine prove that the maximum utilization factor is given by
24 cos a,
E
ms
= where (I) = speed ration, R = degree of reaction, al = nozzle angle.
1 + 24R Cosa.,
(10 Marks)
Draw the velocity triangles at inlet and outlet of an axial flow compressor from the
following data. Degree of reaction 0.5 inlet blade angle 45?. Axial velocity of flow which is
constant throughout 120m/sec, speed of rotation 6500rpm, radius of rotation 20cm, blade
speed of inlet is equal to blade speed at outlet. Calculate angles at inlet and outlet. Also
calculate power needed to handle 1.5kg/s of air. (10 Marks)
17N.
OR
6 a. Define degree of reaction for reaction turbine and derive an expression for the some for 50,
reaction turbine. (10 Marks)
b. In a Parson's turbine, the axial velocity of flow of steam is 0.5 times the mean blade speed.
The outlet angle of the blade is 20? diameter of the blade ring is 1.3m and rotational speed
3000rpm. Determine inlet blade angles, power developed for steam flow of 65kg/sec and
isentropic enthalpy drop, if the stage efficiency is 80%. (10 Marks)
Module-4
7 a. Show that the specific speed of Pelton wheel is given by n, = 206.63 ? where n = number
m
of jets used for the flow, m = wheel diameter to jet diameter ratio. Assume the jet velocity
coefficient as 0.97 speed ratio as 0.45 and efficiency of the turbine as 0.89. (08 Marks)
b. A double overhung Pelton wheel unit is to produce 30000 kW of a generator under an
effective head 300m at the base of the nozzle. Find the size of the jet. Mean diameter of the
runner speed and specific speed of each Pelton turbine. Assume generator ri = 93% Pelton
wheel rl = 0.85 speed ratio = 0.46 jet velocity co-coefficient = 0.97 and jet ratio = 12.
(12 Marksl
.

OR
8 a. Draw a neat sketch of Francis turbine. Explain the function of draft tube. Also draw the
typical velocity triangles of Fransis turbine. (08 Marks)
b. A Kaplan turbine working under head of 20m develops 11772kW of shaft power. The outer
diameter of the runner is 3.5m and hub diameter is 1.75m. The guide blade angle of the
extreme edge of the runner is 35?. The hydraulic and overall efficiencies of the turbine are
88% and 84% respectively. If the velocity of whirl is zero at outlet, determine: i) Runner
vane angle at the inlet and outlet at the extreme edge of the runner ii) Speed of turbine.
(12 Marks)
Module-5
9 a. Show that the pressure rise in the impeller of a centrifugal pump when the frictional and
other losses in the impeller are neglected is given by Ap
2
[
vf,
2 u2, -
Vf? cosec
2
P
2
].
Vf, and Vf, are velocity of flow at inlet and outlet of the impeller U2 = tangential speed of
impeller at exit, (32 = exit blade angle. (10 Marks)
b. A centrifugal pump is running at 1000 rpm. The outlet vane angle of the impeller is 45? and
the velocity of flow of the outlet is 2.5m/sec. The discharge through the pump is 0.2m
3
/sec.
When the pump is working against a head of 20m. If the monometric efficiency is 80% draw
the outlet velocity diagram and calculate : i) The diameter of the impeller at the outlet
ii) width of impeller at the outlet. (10 Marks)
OR
10 a. With reference to centrifugal air compressor, explain the following:
i) PreWhirl ii) Surging iii) Slip factor iv) Choking. (10 Marks)
b. A centrifugal compressor runs at a speed of 15000rpm and delivers air at 30kg/sec, exit
radius is 0.35m, relative velocity and vane angles at exit are 100m/s and 75? respectively.
Assuming axial inlet and inlet stagnation temperature and pressure as 300K and 1 bar
respectively, calculate: i) Torque ii) The power required to drive compressor
iii) The ideal head developed iv) The workdone v) The exit total pressure
(cp)
ajr
= 1.0051d/kgK. (10 Marks)
2 of 2
if --if
". ? i
t
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