SPPU Question Papers
Class: TE Mechanical (2015 Course)
Subject: Turbo Machines
Unit IV: Steam Turbines
March 2015
Q. 5. a)
Define Nozzle and discuss effect of friction through convergent-divergent
nozzle with the help of T-S diagram. [4
marks]
Q. 5. b)
For certain stage of a 50% reaction axial steam turbine the mean rotor diameter
is l.35 m and speed ratio is 0.69. The rotor speed is 3000 rpm and the outlet
blade angle is 55°. Calculate: [6 marks]
i)
Inlet blade angle
ii)
Blade efficiency and
iii)
Maximum blade efficiency. All the angles are measured with respect to axial
direction.
(OR)
Q. 6. a)
What is compounding? Explain need of compounding? State methods of compounding?
[4 marks]
Q. 6. b)
Explain: [6 marks]
i)
Blade efficiency
ii)
Stage efficiency
iii)
Nozzle efficiency
May 2015
Q. 3. b) Steam
issues from the nozzle at an angle of 22° with a velocity of 430 m/s. The
friction factor is 0.9. For a stage turbine designed for maximum efficiency, find:
[6 marks]
i)
The blade velocity
ii)
Moving blade angles for equiangular blades
iii)
Power developed
(OR)
Q. 4. a) Prove
that for Parson’s reaction turbine moving & fixed blades are symmetrical in
shape. [6 marks]
December 2015
Q. 3. b) Derive
an expression for maximum utilization factor (Diagram efficiency) of Parson’s
reaction turbine in terms nozzle angle? [6
marks]
(OR)
Q. 4. b) Explain
with neat sketch throttle governing of steam turbines? [4 marks]
March 2016
Q. 5. a)
Steam issues from the nozzles of an impulse steam turbine with a velocity of
1200 m/s. The nozzle angle is 20°, the mean blade speed is 400 m/s and the
inlet and outlet angles of moving blades are equal. The mass of steam flowing
through the turbine is 900 kg/hr. Assume friction factor is 0.8.
Determine: [8 marks]
i.
The tangential forces on the blades.
ii.
Power developed.
iii.
The blade efficiency.
Q. 5. b)
Explain the need of compounding in steam turbines. [2 marks]
(OR)
Q. 6. a)
In Parson’s reaction turbine running at 500 rpm with 50% reaction turbine
develops 75 kW per kg of steam. The exit angle of the blades is 20° and steam
velocity is 1.5 times the blade velocity.
Determine:
[6 marks]
i.
Blade velocity
ii.
Inlet angle of moving blades
Q. 6. b)
Explain the method of nozzle control governing. [4 marks]
May 2016
Q. 3. b)
In a De Laval turbine, steam is issued from the nozzle with a velocity of l500
m/s whereas the mean blade velocity is 500 m/s. The nozzle angle is 20° and the
inlet and outlet angles of blades are equal. The mass of the steam flowing
through the turbine is at the rate of l200 kg/hr. Assuming blade velocity
coefficient k = 0.8, draw the velocity diagram and determine: [6 marks]
i)
The blade angles.
ii)
The power developed by turbine.
iii)
The blade efficiency.
(OR)
Q. 4. b)
A Parsons turbine runs at 400 rpm with 50% reaction and it develops 75 kW of
power per unit mass of steam flow per second. The exit angle of the blades is
20° and the steam velocity is l.4 times the blade velocity. Find: [6
marks]
i)
Blade velocity and
ii)
Inlet angle of the blades
December 2016
Q. 4. a)
Define the following terms: [4 marks]
i)
Diagram efficiency
ii)
Nozzle efficiency
Q. 4. b)
In a Parson’s turbine running at l500 rpm, the available enthalpy drop for an
expansion is 63 kJ/kg. If the mean diameter of the rotor is l00 cm, find the
number of moving rows required. Assume that efficiency of a stage is 0.8, blade
outlet angle 20º and speed ratio 0.7. [6
marks]
March 2017
Q. 5. a)
What do you mean by compounding of steam
turbine? Discuss any one method. [4 marks]
Q. 5. b)
A single stage steam turbine is supplied
with steam at 5 bar & 200º at the rate of 50 kg/min. It expanse into
condenser at a pressure of 0.2 bar. The blade speed is 400 m/s, the nozzle are
inclined at an angle is 20º to the plane of the wheel and the outlet blade
angle is 30º. Neglecting frictional losses, determine the power developed,
blade efficiency and stage efficiency. [6
marks]
(OR)
Q. 6. a)
Define the following as related to steam turbines. [4 marks]
i)
Speed ratio
i)
Blade velocity coefficient
iii)
Diagram efficiency
iv)
Stage efficiency
Q. 6. b)
In an Impulse turbine the diameter of the blade is l.05 m and the speed is 3000
rpm. The nozzle angle is l8º, the ratio of the blade speed to steam speed is
0.42 and the ratio of the relative velocity at outlet from the blades to that
at inlet is 0.84 the outlet angle of blade is to be made 30º less than that at
the inlet angle. The steam flow is l0 kg/sec. Draw velocity diagram for blades
and calculate: [6 marks]
i)
Tangential thrust on the blades
ii) Axial thrust on the blades
iii)
Power developed in the blades
May 2017
Q. 3. b)
Steam issues from the nozzle of an impulse steam turbine with a velocity of l200
m/s. The nozzle angle is 20°. The mean blade speed is 400 m/s and inlet &
outlet angles of moving blades are equal. The mass of steam flowing through the
turbine is 900 kg/hr. Assume friction factor =0.8
Determine:
[8 marks]
i)
Blade angles
ii)
Power developed
iii)
Blade efficiency
(OR)
Q. 4. b)
Explain: [4 marks]
i)
Blade efficiency
ii)
Stage efficiency
December 2017 (2012 Pattern)
Q. 3. b)
Explain with suitable sketch different methods of compounding of steam turbines.
[6 marks]
(OR)
Q. 4. a)
The following particulars refer to a stage if Parson’s turbine comprising one
ring of fixed blade and one blade of moving blades; Mean diameter of the blade
ring = 70 cm, RPM = 3000, steam velocity at exit from blade = l60 m/s, blade
outlet angle = 20º, steam flow through blades = 7 kg/s. Draw the velocity diagram
and find following: [6 marks]
i)
Blade inlet angle,
ii)
Tangential force on the ring of a moving blade,
iii)
Power developed in a stage
Q. 4. b)
What is cavitation? On what factors does the cavitation in reaction turbines
depend? [4 marks]
December 2017 (2015 Pattern)
Q. 5. a)
Write difference between throttle and nozzle governing used in steam turbines
and explain with neat sketch of nozzle governing. [8 marks]
Q. 5. b)
Steam issues from the nozzles of an angle of 20° at a velocity of 440 m/s, the
friction factor is 0.9, for a single stage turbine designed for a maximum
efficiency determine: [8 marks]
i)
Blade velocity
ii)
Moving blade angles for equiangular blades
iii)
Blade efficiency
iv)
Stage efficiency if the nozzle efficiency is 93% & power developed for mass
flow rate of 3 kg/s
(OR)
Q. 6. a)
Discuss reheat factor with the help of T.S. diagram. [6 marks]
Q. 6. b) Following
data refer to the single row of impulse steam turbine mean diameter of the
blade ring = l.l m, Speed = 3000 rpm, Nozzle angle = l7 deg., ratio of blade
velocity to the steam velocity = 0.45, blade friction factor = 0.82, Blade
angle at exit is less by 3 deg. to that at inlet, steam mass flow rate = l0.2
kg/s. Draw a velocity diagram and find the following: [8 marks]
(i) Blade angles at
inlet and outlet
(ii) Tangential force
(iii) Axial force
(iv) Resultant force
(v) Power developed.
May 2018
Q. 5. a)
Explain the term Reheat Factor in steam turbines. [6 marks]
Q. 5. b)
In a stage of a Turbine with Parson's blading delivers dry saturated steam at 2.7
bar from the fixed blades at 90 m/sec. The mean Blade height is 40 mm, and the
moving blade exit angle is 20°. The axial velocity of steam is 3/4 of the blade
velocity at the mean radius. Steam is supplied to the stage at the rate of 9000
kg/hr, the effect of the blade tip thickness on the annulus area can be
neglected. Calculate: [10 marks]
i)
Wheel speed in RPM
ii)
The diagram power
iii)
The diagram efficiency
iv)
The enthalpy drop of steam in the stage
(OR)
Q. 6. a)
Explain why subsonic nozzle is convergent while supersonic nozzle is divergent.
[4 marks]
Q. 6. b)
Derive
an expression for diagram efficiency of single stage Impulse Turbine. Obtain
the Condition for Maximum efficiency & its value. [6 marks]
Q. 6. c) In a single stage impulse turbine
the mean diameter of the blade ring is l m and the rotational speed is 3000
rpm. The steam is issued from the nozzle at 300 m/sec and nozzle angle is 20°.
The blades are equiangular. If the friction loss in the blade channel is l9% of
the kinetic energy corresponds to relative velocity at the inlet to the blades.
What is the power developed in the blading when the axial thrust on the blades
is 98 N. Solve the problem graphically. [6
marks]
December 2018
Q. 5. a)
Explain the pressure compounded impulse turbine showing pressure and velocity
variations along the axis of the turbine. [6
marks]
Q. 5. b)
In a single stage steam turbine saturated steam at 10 bar (absolute) is
supplied through a convergent divergent steam nozzle. The nozzle angle is 20º
and mean blade speed is 400 m/s. The steam pressure leaving the nozzle is 1 bar
(absolute). Find:
i)
The best blade angles if the blades are equiangular
ii)
The maximum power developed by the turbine if number of nozzles used are 5 and
the area at the throat of each nozzle is 0.6 cm2.
Assume
nozzle efficiency 88%, blade friction coefficient of 0.87 and index of
expansion n = 1.4. Solve using graphical method. [10 marks]
(OR)
Q. 6. a)
Enumerate the energy losses in steam turbine. [6 marks]
Q. 6. b)
A
50% reaction turbine (with symmetrical velocity triangles) is running at 400
rpm has the exit angle of blades as 20º and the velocity of the steam relative
to the blades at the exit is 1.35 times the mean blade speed. The steam flow
rate is 8.33 kg/s and at a particular stage the specific volume is 1.381 m3/kg.
Calculate for the stage: [10 marks]
i)
A suitable blade height, assuming the rotor mean diameter 12 times the blade
height.
ii)
The diagram work
May 2019
Q. 5. a)
Compare impulse turbine & reaction steam turbine. [4 marks]
Q. 5. b)
Explain the need of compounding in steam turbines. Discuss any one method. [4 marks]
Q. 5. c)
Steam issues from the nozzles at angle of 20° at a velocity of 440 m/s. The
friction factor is 0.9. For a single stage turbine designed for maximum
efficiency, determine: [8 marks]
i)
The blade velocity
ii)
Moving blade angles for equiangular blades
iii)
The blade efficiency
iv)
The stage efficiency if the nozzle efficiency is 93%
v)
Power developed for a mass flow rate of steam of 3 kg/s.
(OR)
Q. 6. a)
For a certain stage of 50% reaction turbine, the mean root diameter is 1.35 m
and speed ratio is 0.69. The rotor speed is 3000 rpm and outlet blade angle is
55°. Find: [8 marks]
i)
Inlet blade angle
ii)
Blade efficiency and maximum blade efficiency
Q. 6. b) Define
the following terms: [4 marks]
i) Diagram efficiency
ii) Nozzle efficiency
Q. 6. c) Explain
with neat sketch throttle governing of steam turbine. [4 marks]
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