A jet of water is striking at the centre of a curved vane moving with a uniform velocity in the direction of jet. For the maximum efficiency, the vane velocity is ________ of the jet velocity
One-half
One-third
Two-third
Three-fourth
Correct Answer :
B. One-third
Related Questions
Which of the following statement is wrong?
The reaction turbines are used for low head and high discharge.
The angle of taper on draft tube is less than 8°.
An impulse turbine is generally fitted slightly above the tail race.
A Francis turbine is an impulse turbine.
For centrifugal pump impeller, the maximum value of the vane exit angle is
10° to 15°
15° to 20°
20° to 25°
25° to 30°
Medium specific speed of turbine implies it is
Propeller turbine
Francis turbine
Impulse turbine
Any one of the above
A hydraulic accumulator is a device used to store ________ energy which may be supplied to a machine later on.
Strain
Pressure
Kinetic
None of these
The speed of a turbine runner is
Directly proportional to H1/2
Inversely proportional to H1/2
Directly proportional to H3/2
Inversely proportional to H3/2
Kinematic similarity is said to exist between the model and the prototype, if both of them
Have identical velocities
Are equal in size and shape
Are identical in shape, but differ only in size
Have identical forces
In impulse Turbine, energy available at the inlet is in the form of
Potential Energy
Strain Energy
Kinetic energy
None of these
Which of the following turbine is preferred for a specific speed of 60 to 300 r.p.m.?
Pelton wheel
Francis turbine
Kaplan turbine
None of these
The ratio of actual work available at the turbine to the energy imparted to the wheel is known as ________ efficiency.
Hydraulic
Mechanical
Overall
None of these
Casting of a centrifugal pump is designed so as to minimize
Friction loss
Cavitations
Static head
Loss of kinetic energy
The discharge of a double acting reciprocating pump is (where L = Length of stroke, A = Cross-sectional area of piston, and N = Speed of crank in r.p.m.)
L.A.N
2 L.A.N
(L.A.N)/60
(2 L.A.N)/60
The force exerted (in Newton) by a jet of water impinging normally on a fixed plate is (where w = Specific weight of water in N/m3, a = Crosssectional area of jet in m², and V = Velocity of jet in m/s)
waV / 2g
waV / g
waV² / 2g
waV² / g
A Pelton wheel is
Tangential flow impulse turbine
Inward flow impulse turbine
Outward flow impulse turbine
Inward flow reaction turbine
The angle of taper on draft tube is
Greater than 15°
Greater than 8°
Greater than 5°
Less than 8°
Reaction turbines are used for
Low head
High head
High head and low discharge
Low head and high discharge
Specific speed for reaction turbines ranges from
0 to 4.5
10 to 100
80 to 200
250 to 300
The cavitation in a hydraulic machine
Causes noise and vibration of various parts
Reduces the discharge of a turbine
Causes sudden drop in power output and efficiency
All of the above
A centrifugal pump will start delivering liquid only when the pressure rise in the impeller is equal to the
Kinetic head
Velocity head
Manometric head
Static head
In a centrifugal pump casing, the flow of water leaving the impeller, is
Rectilinear flow
Radial flow
Free vortex motion
Forced vortex
Impulse turbine is generally fitted
At the level of tail race
Little above the tail race
Slightly below the tail race
About 2.5 m above the tail race to avoid cavitations.
Puck up the wrong statement about centrifugal pump
Discharge a diameter
Head a speed²
Head a diameter
Power a speed⁴
Which of the following pump is successfully used for lifting water to the boilers?
Centrifugal pump
Reciprocating pump
Jet pump
Airlift pump
In a centrifugal pump, the liquid enters the pump
At the top
At the bottom
At the canter
From sides
The efficiency of a Pelton wheel working under constant head ________ with the increase in power.
Remain same
Increases
Decreases
None of these
The discharge through a reaction turbine with increase in unit speed
Increases
Decreases
Remain unaffected
First increases and then decreases
The number of buckets on the periphery of a Pelton wheel is given by
(D/2d) + 5
(D/2d) + 10
(D/2d) + 15
(D/2d) + 20
Which of the following pump is suitable for small discharge and high heads?
Centrifugal pump
Axial flow pump
Mixed flow pump
Reciprocating pump
The hydraulic efficiency of a reaction turbine, is the ratio of
Power produced by the turbine to the energy actually supplied by the turbine
Actual work available at the turbine to energy imparted to the wheel
Workdone on the wheel to the energy (or head of water) actually supplied to the turbine
None of the above
Reciprocating pumps are no more to be seen in industrial applications (in comparison to centrifugal pumps) because of
High initial and maintenance cost
Lower discharge
Lower speed of operation
Necessity of air vessel
The depth of the bucket for a Pelton wheel is generally ________ the diameter of jet.
Equal to
1.2 times
1.8 times
Double