Download Visvesvaraya Technological University (VTU) BE ( Bachelor of Engineering) ME (Mechanical Engineering) 2015 Scheme 2020 January Previous Question Paper 5th Sem 15ME53 Turbo Machines
'7
US\
15ME53
Fifth Semester B.E. Degree Examination, Dec.20197Jan.2020
Turbo Machines
Time: 3 hrs. Max. Marks: 80
Note: Answer any FIVE full questions, choosing ONE full question from each module.
=
Find:
s ;
(i) Inlet total temperature
s
......:
-
:J.
x
(ii) Actual exit total temperature
:-._-
_ fz, (iii) Actual exit static temperature if the velocity is 100 m/s
= --1-
(iv) Total to static efficiency (08 Marks)
P ^.)
u ''
?= a)
= ?L OR
0
6'
.
=
2 a. Show that for a turbine polytropic efficiency is given by
o -o
where n is index of polytropic process, y is ratio of specific heats. (08 Marks)
c
-o
tiO
5
=
? ,
al al
b. A turbine is to operate under a head of 25m at 200 rpm. The discharge is 9 m
3
/s. If the
.?. r
o
efficiency is 90%, determine the performance of the turbine under a head of 20 m. (08 Marks)
L
,;
,. _
Module-2
3 a. Show that the alternate form of Euler's turbine equation can be expressed as follows
W =
\---
4)
CS
.: e .
2
2
> c.,
cri ,... Draw the relevant velocity triangles. (08 Marks)
... _
c ...
z
Show that for maximum utilization factor of an axial flow machine with R =
1
. The speed 7
8
72
b.
4
to
c to
? g
:- ration (I).-
2
cosa , where R is degree of reaction and a
l
is nozzle angle with respect to
- c .....
z. '
3 P >
o2
>,
tangential direction at inlet. (08 Marks)
8
OR
O
4 a. A radial outward flow turbo machine has no whirl at inlet. The blade speed at exit is twice
that at inlet. The radial velocity remains constant. Inlet blade angle is 45?. Show that the
0
degree of reaction for this machine is given by R =
2+ cot 13
4
where R is degree of reaction
and 132 is blade angle at exit.
(08 Marks)
Module-1
1 a. Enumerate the difference between positive displacement machine and turbo machine.
(04 Marks)
b. Define static and stagnation states. (04 Marks)
c. Air flows through an air turbine where its stagnation pressure is reduced in the ratio 5:1. The
total to total efficiency is 80%. The air flow is 5 kg/s. If the total power output is 500 KW.
ri
p
=
( n -1)
r
7
n ) 7 -1)
(vi
v2 .)+ (
u
2
1 u,
)
+
0
1,
2 ..2
V
r
I of 3
FirstRanker.com - FirstRanker's Choice
1
'7
US\
15ME53
Fifth Semester B.E. Degree Examination, Dec.20197Jan.2020
Turbo Machines
Time: 3 hrs. Max. Marks: 80
Note: Answer any FIVE full questions, choosing ONE full question from each module.
=
Find:
s ;
(i) Inlet total temperature
s
......:
-
:J.
x
(ii) Actual exit total temperature
:-._-
_ fz, (iii) Actual exit static temperature if the velocity is 100 m/s
= --1-
(iv) Total to static efficiency (08 Marks)
P ^.)
u ''
?= a)
= ?L OR
0
6'
.
=
2 a. Show that for a turbine polytropic efficiency is given by
o -o
where n is index of polytropic process, y is ratio of specific heats. (08 Marks)
c
-o
tiO
5
=
? ,
al al
b. A turbine is to operate under a head of 25m at 200 rpm. The discharge is 9 m
3
/s. If the
.?. r
o
efficiency is 90%, determine the performance of the turbine under a head of 20 m. (08 Marks)
L
,;
,. _
Module-2
3 a. Show that the alternate form of Euler's turbine equation can be expressed as follows
W =
\---
4)
CS
.: e .
2
2
> c.,
cri ,... Draw the relevant velocity triangles. (08 Marks)
... _
c ...
z
Show that for maximum utilization factor of an axial flow machine with R =
1
. The speed 7
8
72
b.
4
to
c to
? g
:- ration (I).-
2
cosa , where R is degree of reaction and a
l
is nozzle angle with respect to
- c .....
z. '
3 P >
o2
>,
tangential direction at inlet. (08 Marks)
8
OR
O
4 a. A radial outward flow turbo machine has no whirl at inlet. The blade speed at exit is twice
that at inlet. The radial velocity remains constant. Inlet blade angle is 45?. Show that the
0
degree of reaction for this machine is given by R =
2+ cot 13
4
where R is degree of reaction
and 132 is blade angle at exit.
(08 Marks)
Module-1
1 a. Enumerate the difference between positive displacement machine and turbo machine.
(04 Marks)
b. Define static and stagnation states. (04 Marks)
c. Air flows through an air turbine where its stagnation pressure is reduced in the ratio 5:1. The
total to total efficiency is 80%. The air flow is 5 kg/s. If the total power output is 500 KW.
ri
p
=
( n -1)
r
7
n ) 7 -1)
(vi
v2 .)+ (
u
2
1 u,
)
+
0
1,
2 ..2
V
r
I of 3
151k,
b. A single stage air blower with no inlet guide vanes is running at 3600 rpm. The me,
diameter of rotor is 16 cm and mass flow rate of air through the blower is 0.45 kg/s. In the
rotor the air is turned through an angle of 20? towards the axial direction during the passage
through the rotor at mean diameter. Assume that the axial component of fluid velocity
remain constant. Determine the power input and degree of reaction. Assume that the density
of air is constant at 1.185 kg/m
3
and area of flow is 0.02 m
2
. (08 Marks)
Module-3
5 a. What is need for compounding in stream turbines? Explain velocity compounding. (04 Marks)
b. For a 50% reaction turbine show that a
l
= 13
2
and oc, = 131 where co and ot, are inlet and
outlet angles of fixed blades and 131 and 13, are inlet and outlet angles of moving blades.
(04 Marks)
c. In a single stage impulse turbine the nozzle angle is 25?. The absolute velocity of stream at
exit is 300 m/s in a direction 120? to the direction of motion of blades assuming no axial
thrust. Determine: (i) the blade angles and (ii) power developed. (08 Marks)
OR
6 a. Show that the maximum utilization factor of blade efficiency with equiangular blades is
given by = cos
2
a
l
where ai is the nozzle angle. (08 Marks)
b. The following data refers to a stage of a reaction turbine. Rotor diameter 1.5 m, speed ratio
0.72, outer blade angle 20? rotor speed 3000 rpm. Determine:
(i) Diagram efficiency
(ii) Percentage increase in diagram efficiency and rotor speed. If the rotor is designed to run
at the best theoretical speed. Assume symmetric velocity triangles. (08 Marks)
Module-4
7 a. Show that the maximum hydraulic efficiency of pelton wheel turbine is given by
1+ Kcosi3
2
h max
2
where K is blade velocity coefficient, 132 is blade discharge angle. (08 Marks)
b.
The following data refers to a Francis turbine:
Net head = 60 m, speed = 700 rpm, shaft power = 294.3 KW, overall efficiency = 84%,
hydraulic efficiency = 93%, flow ratio = 0.20, breadth ratio = 0.1, outer diameter of runner
equal twice the inner diameter. The thickness of the vane occupy 5% of circumferential area
of the runner, velocity of flow is constant at inlet and outlet and the discharge is radial at
outlet. Determine :
(i) Guide blade angle
(ii) Runner vane angle at inlet and outlet
(iii) Diameter of runner at inlet and outlet
(iv) Width of the wheel at inlet (08 Marks)
OR
8 a. Explain with neat sketch working of Francis turbine. Mention the functions of draft tube.
(08 Marks)
b
.
A pelton wheel is to be designed for a head of 60 m when running at 200 rpm. The pelton
wheel develops 95.65 KW shaft power. The velocity of buckets = 0.45 times the velocity of
jet, overall efficiency = 0.85 and coefficient of velocity = 0.98. Find:
(i) The diameter of jet
(ii) Diameter of wheel
(iii) Size of buckets
FirstRanker.com - FirstRanker's Choice
1
'7
US\
15ME53
Fifth Semester B.E. Degree Examination, Dec.20197Jan.2020
Turbo Machines
Time: 3 hrs. Max. Marks: 80
Note: Answer any FIVE full questions, choosing ONE full question from each module.
=
Find:
s ;
(i) Inlet total temperature
s
......:
-
:J.
x
(ii) Actual exit total temperature
:-._-
_ fz, (iii) Actual exit static temperature if the velocity is 100 m/s
= --1-
(iv) Total to static efficiency (08 Marks)
P ^.)
u ''
?= a)
= ?L OR
0
6'
.
=
2 a. Show that for a turbine polytropic efficiency is given by
o -o
where n is index of polytropic process, y is ratio of specific heats. (08 Marks)
c
-o
tiO
5
=
? ,
al al
b. A turbine is to operate under a head of 25m at 200 rpm. The discharge is 9 m
3
/s. If the
.?. r
o
efficiency is 90%, determine the performance of the turbine under a head of 20 m. (08 Marks)
L
,;
,. _
Module-2
3 a. Show that the alternate form of Euler's turbine equation can be expressed as follows
W =
\---
4)
CS
.: e .
2
2
> c.,
cri ,... Draw the relevant velocity triangles. (08 Marks)
... _
c ...
z
Show that for maximum utilization factor of an axial flow machine with R =
1
. The speed 7
8
72
b.
4
to
c to
? g
:- ration (I).-
2
cosa , where R is degree of reaction and a
l
is nozzle angle with respect to
- c .....
z. '
3 P >
o2
>,
tangential direction at inlet. (08 Marks)
8
OR
O
4 a. A radial outward flow turbo machine has no whirl at inlet. The blade speed at exit is twice
that at inlet. The radial velocity remains constant. Inlet blade angle is 45?. Show that the
0
degree of reaction for this machine is given by R =
2+ cot 13
4
where R is degree of reaction
and 132 is blade angle at exit.
(08 Marks)
Module-1
1 a. Enumerate the difference between positive displacement machine and turbo machine.
(04 Marks)
b. Define static and stagnation states. (04 Marks)
c. Air flows through an air turbine where its stagnation pressure is reduced in the ratio 5:1. The
total to total efficiency is 80%. The air flow is 5 kg/s. If the total power output is 500 KW.
ri
p
=
( n -1)
r
7
n ) 7 -1)
(vi
v2 .)+ (
u
2
1 u,
)
+
0
1,
2 ..2
V
r
I of 3
151k,
b. A single stage air blower with no inlet guide vanes is running at 3600 rpm. The me,
diameter of rotor is 16 cm and mass flow rate of air through the blower is 0.45 kg/s. In the
rotor the air is turned through an angle of 20? towards the axial direction during the passage
through the rotor at mean diameter. Assume that the axial component of fluid velocity
remain constant. Determine the power input and degree of reaction. Assume that the density
of air is constant at 1.185 kg/m
3
and area of flow is 0.02 m
2
. (08 Marks)
Module-3
5 a. What is need for compounding in stream turbines? Explain velocity compounding. (04 Marks)
b. For a 50% reaction turbine show that a
l
= 13
2
and oc, = 131 where co and ot, are inlet and
outlet angles of fixed blades and 131 and 13, are inlet and outlet angles of moving blades.
(04 Marks)
c. In a single stage impulse turbine the nozzle angle is 25?. The absolute velocity of stream at
exit is 300 m/s in a direction 120? to the direction of motion of blades assuming no axial
thrust. Determine: (i) the blade angles and (ii) power developed. (08 Marks)
OR
6 a. Show that the maximum utilization factor of blade efficiency with equiangular blades is
given by = cos
2
a
l
where ai is the nozzle angle. (08 Marks)
b. The following data refers to a stage of a reaction turbine. Rotor diameter 1.5 m, speed ratio
0.72, outer blade angle 20? rotor speed 3000 rpm. Determine:
(i) Diagram efficiency
(ii) Percentage increase in diagram efficiency and rotor speed. If the rotor is designed to run
at the best theoretical speed. Assume symmetric velocity triangles. (08 Marks)
Module-4
7 a. Show that the maximum hydraulic efficiency of pelton wheel turbine is given by
1+ Kcosi3
2
h max
2
where K is blade velocity coefficient, 132 is blade discharge angle. (08 Marks)
b.
The following data refers to a Francis turbine:
Net head = 60 m, speed = 700 rpm, shaft power = 294.3 KW, overall efficiency = 84%,
hydraulic efficiency = 93%, flow ratio = 0.20, breadth ratio = 0.1, outer diameter of runner
equal twice the inner diameter. The thickness of the vane occupy 5% of circumferential area
of the runner, velocity of flow is constant at inlet and outlet and the discharge is radial at
outlet. Determine :
(i) Guide blade angle
(ii) Runner vane angle at inlet and outlet
(iii) Diameter of runner at inlet and outlet
(iv) Width of the wheel at inlet (08 Marks)
OR
8 a. Explain with neat sketch working of Francis turbine. Mention the functions of draft tube.
(08 Marks)
b
.
A pelton wheel is to be designed for a head of 60 m when running at 200 rpm. The pelton
wheel develops 95.65 KW shaft power. The velocity of buckets = 0.45 times the velocity of
jet, overall efficiency = 0.85 and coefficient of velocity = 0.98. Find:
(i) The diameter of jet
(ii) Diameter of wheel
(iii) Size of buckets
15ME53
Module-5
9 a. When the pumps are arranged in series and in parallel? Explain any one arrangement.
(04 Marks)
b. Explain the phenomenon of surging in centrifugal compressors. (04 Marks)
c. An air compressor has eight stages of equal pressure ratio 1.35. the flow rate through the
compressor and its overall efficiency are 50 kg/s and 82% respectively. If the conditions of
air at entry are 1.0 bar and 40?C. Determine:
(i) State of air at exit of compressor
Polytropic efficiency
(iii) Efficiency of each stage
(iv) Power required to drive the compressor, assume overall efficiency of drive as 90%.
(08 Marks)
OR
10 a. Define slip and slip coefficient with respect to centrifugal compressor. (02 Marks)
b. Draw the velocity diagrams at exit of a centrifugal pump for forward, radial and backward
curved vanes. (06 Marks)
c. A centrifugal pump impeller has radial vanes from inner radius of 8 cm to outer radius of
24 cm. The width of the impeller is constant and is 6 cm between the shrouds. If the speed of
the pump is 1500 rpm and discharge is 250 lit/s. Find:
(i) Change in enthalpy
(ii) The outlet pressure if the inlet pressure is 0.8 kPa and water flow is outward. (08 Marks)
3 of 3
FirstRanker.com - FirstRanker's Choice
This post was last modified on 02 March 2020