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Hydraulic Machines
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Hydraulic Machines
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The hydraulic efficiency of an impulse turbine is the
ratio of the actual power produced by the turbine to the energy actually supplied by the turbine
None of the above
ratio of the actual work available at the turbine to the energy imparted to the wheel
ratio of the Work done on the wheel to the energy of the jet
The speed ratio in case of Francis turbine varies from
0.6 to 0.9
0.4 to 0.5
1 to 1.5
0.15 to 0.3
The specific speed of a hydraulic turbine depends upon
speed and power developed
speed, power developed and head of water
discharge and power developed
speed and head of water
Head developed by a centrifugal pump is
None of the above
proportional to diameter of impeller
proportional to diameter and speed of impeller
proportional to speed of impeller
Theoretical power required (in watts) to drive a reciprocating pump is (where w = Specific weight of liquid to be pumped in N/m3, Q = Discharge of the pump in m3/s, Hs = Suction head in metres, and Hd = Delivery head in metres)
wQ(Hs - Hd)
wQHd
wQ(Hs + Hd)
wQHs
In a reciprocating pump, air vessels are used to
smoothen the flow
reduce acceleration head
reduce suction head
increase delivery head
A Pelton wheel develops 1750 kW under a head of 100 metres while running at 200 r.p.m. and discharging 2500 litres of water persecond.
The unit speed of the wheel is
80 r.p.m.
40 r.p.m.
20 r.p.m.
10 r.p.m.
In a centrifugal pump, the regulating valve is provided on the
casing
suction pipe
delivery pipe
impeller
A turbine is required to develop 1500 kW at 300 r.p.m. under a head of 150 m. Which of the following turbine should be used
Kaplan turbine
Pelton wheel with two or more nozzles
Francis turbine
Pelton wheel with one nozzle
Slip of a reciprocating pump is negative, when
suction pipe is short and pump is running at low speeds
delivery pipe is long and pump is running at high speeds
suction pipe is long and delivery pipe is short and the pump is running at high speeds
suction pipe is short and delivery pipe is long and the pump is running at low speeds
A Pelton wheel working under a constant head and discharge, has maximum efficiency when the speed ratio is
0.56
0, 46
0.26
0.36
For 450 m head of water, __________ shallbeused
NONE OF THESE
Pelton wheel
Francis turbine
Kaplan turbine
Which of the following turbine is preferred for a specific speed of 60 to 300 r.p.m
Kaplan turbine
Francis turbine
Pelton wheel
NONE OF THESE
Which of the following turbine is preferred for 0 to 25 m head of water
Pelton wheel
Kaplan turbine
Francis turbine
NONE OF THESE
If Hg is the gross or total head and hf is the head lost due to friction, then net or effective head (H) is given by
H = Hg x hf
H = Hg + hf
H = Hg - hf
H = Hg/hf
Geometric similarity is said to exist between the model and the prototype, if both of them
are identical in shape, but differ only in size
have identical forces
have identical velocities
are equal in size and shape
Which of the following statement is correct as regard to water wheels
They have slow speeds.
They give constant efficiency, even if the discharge is not constant
All of the above
They are suitable even for low water heads.
Power required to drive a centrifugal pump is directly proportional to __________ of its impeller
fourth power of diameter
diameter
square of diameter
cube of diameter
The hydraulic efficiency of an impulse turbine is maximum when velocity of wheel is __________ of the jet velocity,
One-fourth
double
Three-fourth
one-half
The cavitation in a hydraulic machine
causes noise and vibration of various parts
All of the above
causes sudden drop in power output and efficiency
reduces the discharge of a turbine
If the ratio's of the corresponding forces acting at corresponding points are equal, then the model and the prototype are said to have
dynamic similarity
NONE OF THESE
kinematic similarity
geometric similarity
The overall efficiency of a reaction turbine is the ratio of
workdone on the wheel to the energy (or head of water) actually supplied to the turbine
power produced by the turbine to the energy actually supplied by the turbine
None of the above
actual work available at the turbine to the energy imparted to the wheel
The speed of an imaginary turbine, identical with the given turbine, which will develop a unit power under a unit head, is known as
specific speed
NONE OF THESE
normal speed
unit speed
The cavitation in a hydraulic machine is mainly due to
Low pressure
Low velocity
high velocity
high pressure
If the net positive suction head (NPSH) requirement for the pump is not satisfied, then
excessive power will be consumed
no flow will take place
efficiency will be low
cavitation will be formed
The power developed by a turbine is (where H = Head of water under which the turbine is working)
inversely proportional to H1/2
directly proportional to H1/2
inversely proportional to H3/2
directly proportional to H3/2
A hydraulic press is a device used
All of the above
to lift larger load by the application of a comparatively much smaller force
to store pressure energy which may be supplied to a machine later on
The specific speed of a centrifugal pump, delivering 750 litres of water per second against a head of 15 metres at 725 r.p.m., is
82.4 r.p.m.
48.2 r.p.m
24.8 r.p.m.
248 r.p.m
Which of the following hydraulic unit is used for transmitting increased or decreased torque to the driven shaft
Hydraulic torque converter
Hydraulic accumulator
Hydraulic intensifier
hydraulic ram
If the ratio of all the corresponding linear dimensions are equal, then the model and the prototype are said to have
kinematic similarity
geometric similarity
dynamic similarity
NONE OF THESE
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