In order to avoid cavitation in centrifugal pumps
The suction pressure should be high
The delivery pressure should be high
The suction pressure should be low
The delivery pressure should be low
Correct Answer :
A. The suction pressure should be high
Related Questions
The force exerted by a jet of water (in a direction normal to flow) impinging on a fixed plate inclined at an angle θ with the jet is
waV/2g × sinθ
waV/g × sinθ
waV²/2g × sin2θ
waV²/g × sinθ
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
Mechanical efficiency of a centrifugal pump is the ratio of
Energy available at the impeller to the energy supplied to the pump by the prime mover
Actual workdone by the pump to the energy supplied to the pump by the prime mover
Energy supplied to the pump to the energy available at the impeller
Manometric head to the energy supplied by the impeller per kN of water
A hydraulic intensifier normally consists of
Two cylinders, two rams and a storage device
A cylinder and a ram
Two coaxial rams and two cylinders
A cylinder, a piston, storage tank and control valve
Manometric head, in case of a centrifugal pump, is equal to
Suction lift + Loss of head in suction pipe due to friction + Delivery lift + Loss of head in delivery pipe due to friction + Velocity head in the delivery pipe
Workdone per kN of water Losses within the impeller
Energy per kN at outlet of impeller Energy per kN at inlet of impeller
All of the above
The width of the bucket for a Pelton wheel is generally ________ the diameter of jet.
Double
Three times
Four times
Five times
Discharge of a centrifugal pump is (where N = Speed of the pump impeller)
Directly proportional to N
Inversely proportional to N
Directly proportional to N²
Inversely proportional to N²
Saving of work done and power by fitting an air vessel to double acting reciprocating pump is of the order of
39.2 %
49.2 %
68.8 %
84.8 %
Which of the following pump is successfully used for lifting water to the turbines?
Centrifugal pump
Reciprocating pump
Jet pump
Air lift pump
If a pump is handling water and is discharging a certain flow Q at a constant total dynamic head requiring a definite B.H.P., the same pump when handling a liquid of specific gravity 0.75 and viscosity nearly same as of water, the horse power required will be
Same
0.75 B.H.P.
B.H.P./0.75
1.5 B.H.P.
The efficiency of a hydraulic press is given by (where W = Weight lifted by ram, P = Force applied on plunger, A = Area of ram, and a = Area of plunger)
(W/p) × (A/a)
(p/W) × (a/A)
(W/p) × (a/A)
(p/W) × (A/a)
High specific speed of turbine implies it is
Propeller turbine
Francis turbine
Impulse turbine
None 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
Medium specific speed of turbine implies it is
Propeller turbine
Francis turbine
Impulse turbine
Any one of the above
The flow ratio in case of Francis turbine varies from
0.15 to 0.3
0.4 to 0.5
0.6 to 0.9
1 to 1.5
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
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
Which of the following pump is successfully used for lifting water to the boilers?
Centrifugal pump
Reciprocating pump
Jet pump
Airlift pump
The discharge through a reaction turbine ________ with the increase in unit speed.
Decreases
Increases
Remain same
None of these
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?
Pelton wheel with one nozzle
Pelton wheel with two or more nozzles
Kaplan turbine
Francis turbine
In impulse Turbine, energy available at the inlet is in the form of
Potential Energy
Strain Energy
Kinetic energy
None of these
Multistage centrifugal pumps are used to obtain
High discharge
High head
Pumping of viscous fluids
High head and high discharge
Head developed by a centrifugal pump depends on
Impeller diameter
Speed
Fluid density
Both (A) and (B) above
The unit discharge through the turbine is
Q/√H
Q/H
Q/H3/2
Q/H²
In a Francis turbine runner, the numbers of blades are generally between
2 to 4
4 to 8
8 to 16
16 to 24
A hydraulic coupling belongs to the category of
Power absorbing machines
Power developing machines
Energy transfer machines
Energy generating machines
Which of the following statement is correct?
In an impulse turbine, the water impinges on the buckets with pressure energy.
In a reaction turbine, the water glides over the moving vanes with kinetic energy.
In an impulse turbine, the pressure of the flowing water remains unchanged and is equal to atmospheric pressure.
In a reaction turbine, the pressure of the flowing water increases after gliding over the vanes.
In order to avoid cavitation in centrifugal pumps
The suction pressure should be high
The delivery pressure should be high
The suction pressure should be low
The delivery pressure should be low
The maximum number of jets, generally, employed in an impulse turbine without jet interference are
Two
Four
Six
Eight
The overall 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 the 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