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Current Affairs January 2024

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4

If the net positive suction head (NPSH) requirement for the pump is not satisfied, then

A. No flow will take place

B. Cavitation will be formed

C. Efficiency will be low

D. Excessive power will be consumed

Correct Answer :

B. Cavitation will be formed


Related Questions

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4

The speed of a turbine runner is

A. Directly proportional to H1/2

B. Inversely proportional to H1/2

C. Directly proportional to H3/2

D. Inversely proportional to H3/2

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4

A Pelton wheel working under a constant head and discharge, has maximum efficiency when the speed ratio is

A. 0.26

B. 0.36

C. 0.46

D. 0.56

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4

The cavitation in reaction turbines is avoided, to a great extent by

A. Installing the turbine below the tail race level

B. Using stainless steel runner of the turbine

C. Providing highly polished blades to the runner

D. All of the above

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4

The overall efficiency of a reaction turbine is the ratio of

A. Power produced by the turbine to the energy actually supplied by the turbine

B. Actual work available at the turbine to the energy imparted to the wheel

C. Workdone on the wheel to the energy (or head of water) actually supplied to the turbine

D. None of the above

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4

The jet ratio is defined as the ratio of the

A. Diameter of jet to the diameter of Pelton wheel

B. Velocity of jet to the velocity of Pelton wheel

C. Diameter of Pelton wheel to the diameter of jet

D. Velocity of Pelton wheel to the velocity of jet

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4

The speed ratio in case of Francis turbine varies from

A. 0.15 to 0.3

B. 0.4 to 0.5

C. 0.6 to 0.9

D. 1 to 1.5

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4

For very high discharge at low pressure such as for flood control and irrigation applications, following type of pump is preferred

A. Centrifugal

B. Axial flow

C. Reciprocating

D. Mixed flow

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4

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 per second. The unit discharge of wheel is

A. 0.25 m3/s

B. 0.5 m3/s

C. 1.5 m3/s

D. 2.5 m3/s

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4

The power developed by a turbine is (where H = Head of water under which the turbine is working)

A. Directly proportional to H1/2

B. Inversely proportional to H1/2

C. Directly proportional to H3/2

D. Inversely proportional to H3/2

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4

A ship with jet propulsion draws water through inlet orifices at right angles to the direction of its motion. The propelling force of the jet is (where a = Area of the jet, Vr = Relative velocity of the jet and ship = V + v, v = Velocity of the ship, and V = Velocity of the jet issuing from the ship)

A. waVr /g × (Vr + v)

B. waVr /g × (Vr - v)

C. waVr /g × (Vr + v)²

D. waVr /g × (Vr - v)²

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4

The hydraulic efficiency of an impulse turbine is maximum when velocity of wheel is _______ of the jet velocity,

A. One-fourth

B. One-half

C. Three-fourth

D. Double

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4

The ratio of quantity of liquid discharged per second from the pump to the quantity of liquid passing per second through the impeller is known as

A. Manometric efficiency

B. Mechanical efficiency

C. Overall efficiency

D. Volumetric efficiency

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4

A hydraulic accumulator is a device used to store ________ energy which may be supplied to a machine later on.

A. Strain

B. Pressure

C. Kinetic

D. None of these

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4

In an inward flow reaction turbine

A. The water flows parallel to the axis of the wheel

B. The water enters at the centre of the wheel and then flows towards the outer periphery of the wheel

C. The water enters the wheel at the outer periphery and then flows towards the centre of the wheel

D. The flow of water is partly radial and partly axial

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4

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)

A. waV / 2g

B. waV / g

C. waV² / 2g

D. waV² / g

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4

In a centrifugal pump, the liquid enters the pump

A. At the top

B. At the bottom

C. At the canter

D. From sides

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4

Mechanical efficiency of a centrifugal pump is the ratio of

A. Energy available at the impeller to the energy supplied to the pump by the prime mover

B. Actual workdone by the pump to the energy supplied to the pump by the prime mover

C. Energy supplied to the pump to the energy available at the impeller

D. Manometric head to the energy supplied by the impeller per kN of water

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4

High specific speed of turbine implies it is

A. Propeller turbine

B. Francis turbine

C. Impulse turbine

D. None of the above

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4

The working of which of the following hydraulic units is based on Pascal's law?

A. Air lift pump

B. Jet pump

C. Hydraulic coupling

D. Hydraulic press

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4

The specific speed of a turbine is the speed of an imaginary turbine, identical with the given turbine, which

A. Delivers unit discharge under unit head

B. Delivers unit discharge under unit speed

C. Develops unit power under unit head

D. Develops unit power under unit speed

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4

An impulse turbine is used for

A. Low head of water

B. High head of water

C. Medium head of water

D. High discharge

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4

Impulse turbine is generally fitted

A. At the level of tail race

B. Little above the tail race

C. Slightly below the tail race

D. About 2.5 m above the tail race to avoid cavitations.

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4

The efficiency of jet propulsion for a ship with inlet orifices at right angles to the direction of motion of ship is given by

A. [2(Vr - v) v]/ Vr²

B. 2(Vr + v) v]/ Vr²

C. [(Vr - v) v]/ Vr

D. [(Vr + v) v]/ Vr

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4

The maximum number of jets generally employed in impulse turbine without jet interference is

A. 4

B. 6

C. 8

D. 12

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4

The specific speed (Ns) of a centrifugal pump is given by

A. (N√Q)/H2/3

B. (N√Q)/H3/4

C. (N√Q)/H

D. (N√Q)/H5/4

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4

The flow ratio of Francis turbine is defined as the ratio of the

A. Velocity of flow at inlet to the theoretical jet velocity

B. Theoretical velocity of jet to the velocity of flow at inlet

C. Velocity of runner at inlet to the velocity of flow at inlet

D. None of the above

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4

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?

A. Pelton wheel with one nozzle

B. Pelton wheel with two or more nozzles

C. Kaplan turbine

D. Francis turbine

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4

Reciprocating pumps are no more to be seen in industrial applications (in comparison to centrifugal pumps) because of

A. High initial and maintenance cost

B. Lower discharge

C. Lower speed of operation

D. Necessity of air vessel

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4

By fitting an air vessel to the reciprocating pump, there is always a saving of work done and subsequently saving of power. This saving in case of a single acting reciprocating pump is

A. 39.2 %

B. 48.8 %

C. 84.8 %

D. 88.4 %

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4

Motion of a liquid in a volute casing of a centrifugal pump is an example of

A. Rotational flow

B. Radial

C. Forced spiral vortex flow

D. Spiral vortex flow