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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

Correct Answer :

C. 0.46


Related Questions

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4

In order to avoid cavitation in centrifugal pumps

A. The suction pressure should be high

B. The delivery pressure should be high

C. The suction pressure should be low

D. The delivery pressure should be low

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4

Low specific speed of turbine implies it is

A. Propeller turbine

B. Francis turbine

C. Impulse turbine

D. Any one of the above

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4

The specific speed from 160 to 500 r.p.m. of a centrifugal pump indicates that the pump is

A. Slow speed with radial flow at outlet

B. Medium speed with radial flow at outlet

C. High speed with radial flow at outlet

D. High speed with axial flow at outlet

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4

In a centrifugal pump, the regulating valve is provided on the

A. Casing

B. Delivery pipe

C. Suction pipe

D. Impeller

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4

The impeller of a centrifugal pump may have

A. Volute casing

B. Volute casing with guide blades

C. Vortex casing

D. Any one of these

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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

Puck up the wrong statement about centrifugal pump

A. Discharge a diameter

B. Head a speed²

C. Head a diameter

D. Power a speed⁴

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4

In axial flow fans and turbines, fluid enters and leaves as follows

A. Radially, axially

B. Axially, radially

C. Axially, axially

D. Radially, radially

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4

In a centrifugal pump casing, the flow of water leaving the

A. Radial

B. Axial

C. Centrifugal

D. Vortex

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4

According to fan laws, for fans having constant wheel diameter, the air or gas capacity varies

A. Directly as fan speed

B. Square of fan speed

C. Cube of fan speed

D. Square root of fan speed

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4

The force exerted by a jet of water impinging normally on a plate which due to the impact of jet, moves in the direction of jet with a velocity v is

A. [wa (V - v)]/2g

B. [wa (V - v)]/g

C. [wa (V - v)²]/2g

D. [wa (V - v²)]/g

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4

If the ratio's of the corresponding forces acting at corresponding points are equal, then the model and the prototype are said to have.

A. Geometric similarity

B. Kinematic similarity

C. Dynamic similarity

D. None of these

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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

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

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 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

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

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

For centrifugal pump impeller, the maximum value of the vane exit angle is

A. 10° to 15°

B. 15° to 20°

C. 20° to 25°

D. 25° to 30°

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4

The centrifugal pump preferred for a specific speed between 80 to 160 r.p.m. is

A. Slow speed with radial flow at outlet

B. Medium speed with radial flow at outlet

C. High speed with radial flow at outlet

D. High speed with mixed flow at outlet

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4

The specific speed of turbine is defined as the speed of a unit

A. Of such a size that it delivers unit discharge at unit head

B. Of such a size that it delivers unit discharge at unit power

C. Of such a size that it requires unit power per unit head

D. Of such a size that it produces unit horse power with unit head

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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

Manometric head, in case of a centrifugal pump, is equal to

A. 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

B. Workdone per kN of water Losses within the impeller

C. Energy per kN at outlet of impeller Energy per kN at inlet of impeller

D. All of the above

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4

Which of the following pump is successfully used for lifting water to the boilers?

A. Centrifugal pump

B. Reciprocating pump

C. Jet pump

D. Airlift pump

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4

Delivery head of a centrifugal pump is

A. Directly proportional to N

B. Inversely proportional to N

C. Directly proportional to N²

D. Inversely proportional to N²

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4

Which of the following is not a reaction turbine?

A. Fourneyron turbine

B. Journal turbine

C. Thomson's turbine

D. Pelton wheel

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4

Medium specific speed of a pump implies it is

A. Centrifugal pump

B. Mixed flow pump

C. Axial flow pump

D. Any one of the above

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4

The maximum hydraulic efficiency of an impulse turbine is (where φ = Angle of blade tip at outlet)

A. (1 + cos φ)/2

B. (1 - cos φ)/2

C. (1 + sin φ)/2

D. (1 - sin φ)/2

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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

Saving of work done and power by fitting an air vessel to double acting reciprocating pump is of the order of

A. 39.2 %

B. 49.2 %

C. 68.8 %

D. 84.8 %