SPPU Question Papers
Class: TE Mechanical (2015 Course)
Subject: Turbo Machines
Unit II: Impulse Water Turbines
Q. 1 b)
Sketch Pelton wheel bucket giving its approximate dimensions and answer following
questions in brief: (l) the ideal jet deflection angle is l80°, however bucket
deflects the jet through l60° to l65°. [4
marks]
OR
Q. 2 a) A
Pelton wheel is supplied with water under an effective head of 97 m at the rate
of l020 liters/s. The buckets deflects the jet through an angle of l63°. The
mean speed of the bucket is 23 m/s. Find: [6
marks]
i)
Mass flow rate of water
ii)
Velocity of jet
iii)
Hydraulic Power output, assume coefficient of velocity of jet, Cv = 1 and
friction factor of bucket is k = l.
Q. 2 b) Define:
[4 marks]
i)
Gross Head
ii)
Jet Ratio
May 2015
Q. 1 b) Explain
the function of following: [4 marks]
i)
Casing of Pelton Wheel
ii)
Notch of bucket
December 2015
Q. 1 a) Derive
an expression of maximum hydraulic efficiency of Pelton Wheel? [6 marks]
Q. 1 b) Explain
the following terms: [4 marks]
i) Specific speed
ii)
Run – away speed
Q. 3 a) Explain
the classification of water turbines with examples. [4 marks]
OR
Q. 4 a) Derive
expressions of Unit quantities. [6
marks]
March 2016
Q. 1 a)
A Pelton wheel is having a mean bucket diameter of 1 m and is running at 1000
rpm. The net head on the Pelton wheel is 700 m. If the side clearance angle is
15° and discharge through the nozzle is 0.1 m3/s. Determine: [6 marks]
i)
Power available at the nozzle
ii)
Hydraulic efficiency of the turbine
Q. 1 b)
Explain the classification of hydraulic turbines in detail with examples. [4 marks]
OR
Q. 2 b)
Define the following terms: [4 marks]
i) Gross head ii)
Net head
iii) Hydraulic efficiency iv) Mechanical
efficiency
Q. 3 b) Derive the expression of Unit speed and Unit
discharge. [4 marks]
May 2016
Q. 1 a)
State the advantages of using draft tube and justify not using it in Pelton
Wheel. [4 marks]
Q. 1 b) A
Pelton wheel operates with a jet of 15 cm in diameter under a head of 500 m.
Its mean runner diameter is 2.25 m and it rotates with the speed of 375 rpm.
The outlet angle of bucket tip is 15°, the coefficient of velocity as 0.98,
Mechanical efficiency as 97% and buckets are smooth. Determine the shaft power,
hydraulic efficiency and power lost in bucket. [6 marks]
December 2016
Q. 1 a) A
Pelton turbine develops 3000 kW under a head of 400 m. The overall efficiency
of the turbine is 87%. If the speed ratio is 0.48 and the coefficient of
velocity is 0.96 and specific speed 18, Find: [6 marks]
i) Diameter of the turbine
ii)
Diameter of the jet
OR
Q.
2 b)
Define specific speed of turbine & state its significance. [4
marks]
March 2017
Q. 1 b)
A Pelton wheel develops 8421 kW of shaft power under a head of 320 m speed of
rotation of wheel is 700 rpm and its overall efficiency is 87%. Assuming the
coefficient of velocity of jet as 0.98, speed ratio as 0.45 and jet ratio as 6,
find: [6 marks]
i)
Wheel Diameter
ii)
Jet ratio
iii)
Number of jets required
Q. 4 b)
What is the significance of specific speed? Derive the relation for the same. [4 marks]
May 2017 (2012
Pattern)
Q. 1 b) The
mean velocity of the bucket of the wheel is 10 m/s. The jet supplies the water
at 0.7 m3/s under the head of 30 m. The jet is deflected through an
angle of 160° by the bucket. Find the power developed by the Pelton wheel and
Hydraulic efficiency. Take CV = 0.98 & neglect the losses in the
bucket. [6 marks]
OR
Q. 2 a) How
do you classify water turbines? What is the difference between the impulse &
reaction turbine? [4 marks]
Q. 4 a) Derive an expression of specific speed of
hydraulic turbines. [6 marks]
August 2017 (2015 Pattern – Insem.)
Q. 3 a) Sketch
Pelton wheel bucket giving its approximate dimensions and answer question in
brief: The ideal jet deflection angle is 180 degree, however bucket deflects
the jet through 160 to 165 degree. [4
marks]
Q. 3 b)
A Pelton wheel of 2.5 m diameter operates under the following conditions: Net
available head = 300 m; Speed = 300 rpm. Blade angle at outlet = 165°; CV
of nozzle = 0.98; Mechanical Efficiency = 95%. Determine: i) The Power
developed ii) Specific speed iii) Hydraulic Efficiency. [6 marks]
OR
Q. 4 a) Define:
[4 marks]
(1)
Gross head (2) Jet ratio (3) Hydraulic efficiency (4) Mechanical efficiency
Q. 4 b) Show
that the maximum efficiency of the Pelton wheel is given by:
(1
+ k cosϕ) / 2 , Where k = bucket friction factor, ϕ = Bucket outlet angle. [6
marks]
December 2017 (2012 Pattern)
Q. 1 b) A
Pelton turbine is to be designed for the following specifications: [6 marks]
Power
to be developed = 120 MW,
Net
head available = 500 m,
Speed
= 200 RPM,
Ratio
of Jet diameter to wheel diameter = 1/10,
Hydraulic
efficiency = 86 %,
Velocity
coefficient = 0.98,
Speed
Ratio = 0.46.
Calculate:
i)
Volume
flow rate of water required
ii)
Number
of jets
iii)
Diameter
of each jet
December 2017 (2015 Pattern)
Q. 1 b)
What is the difference between the impulse and reaction turbine. [4 marks]
OR
Q. 2 a) Classify
water turbines in brief. [4 marks]
Q. 2 b) The
mean bucket speed of a Pelton wheel is 40 m/s and the discharge is 1.2 m3/s.
The head over the turbine is 385 m. The head loss due to friction in penstock
is 9 m. The bucket deflects the jet through 165°. If the coefficient of velocity
of nozzle is 0.9. Determine (i) Power developed by the turbine and (ii)
hydraulic efficiency of the turbine. Neglect bucket friction. [6 marks]
Q. 3 a)
Discuss main characteristics of the Pelton wheel. [4 marks]
May 2018
Q. 1 b) A
Pelton turbine develops 3000 kW under the head of 300 m, the overall efficiency
of the turbine is 83 %. If the speed ratio is 0.46, coefficient of nozzle Cv = 0.98
and specific speed is 16.5, find: (i) diameter of the turbine (ii) diameter of
the jet. [6 marks]
OR
Q. 2 a) Define:
[4 marks]
i)
Unit speed
ii)
Unit discharge
iii) Unit power
State
its significance.
August 2018
Q. 3 a) Two
jets strike the buckets of a Pelton wheel, which generates shaft power of l5450
kW. The diameter of each jet is given as 200 mm. If the net head on the turbine
is 400 m, find the overall efficiency of the turbine. Take Cv = l.0. [6 marks]
Q. 3 b) Derive
an expression for Unit Discharge and Unit Power and state their significance. [4 marks]
OR
Q. 4 a) A
Pelton wheel is required to develop 6 MW when working under a head of 300 m. It
rotates with a speed of 550 rpm. Assuming jet ratio as l0 and overall
efficiency as 85 %. Calculate:
i) Diameter of wheel
ii) Quantity
of water required
iii) Number of jets.
Assume
coefficient of velocity for nozzle = 0.96 & speed ratio = 0.46. [6 marks]
Q. 4 b) Compare
Impulse and Reaction Turbines. [4 marks]
December 2018
Q. 1 b) A
Pelton wheel has to develop 13250 kW under a net head of 800 m at a speed of
600 rpm. The coefficient of velocity for the jet is 0.97. The peripheral
velocity is 0.46√(2gH). The diameter of the jet is not to
exceed one sixteenth the wheel diameter. Find the discharge, the wheel
diameter, the jet diameter and the number of jets required. Assume the overall
efficiency to be 85 %. [6 marks]
May 2019
Q. 1 b) A
double jet Pelton Wheel has a specific speed of 14 and is required to deliver
1000 kW. The turbine is supplied through pipeline from a reservoir whose level
is 400 m above the nozzles. Allowing 5% for frictional loss in the pipe,
calculate:
i) Speed in RPM
ii) Diameter of jets
iii) Mean Diameter of Bucket circle
Take
Cv = 0.98, speed ratio = 0.46 and overall efficiency = 85%, the specific speed
is based on power output per jet. [6
marks]
OR
Q. 2 b) Define
unit quantities for the turbines. [4
marks]
