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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

Correct Answer :

A. The suction pressure should be high


Related Questions

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4

The specific speed of a turbine is given by the equation

A. N√P / H3/2

B. N√P / H²

C. N√P / H5/4

D. N√P / H3

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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

The water in a jet propelled boat is drawn through the openings facing the direction of motion of the boat. The efficiency of propulsion is given by

A. 2V/(vr - v)

B. 2V/(vr + v)

C. V/(vr - v)

D. V/(vr + v)

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4

Which of the following statement is correct?

A. In an impulse turbine, the water impinges on the buckets with pressure energy.

B. In a reaction turbine, the water glides over the moving vanes with kinetic energy.

C. In an impulse turbine, the pressure of the flowing water remains unchanged and is equal to atmospheric pressure.

D. In a reaction turbine, the pressure of the flowing water increases after gliding over the vanes.

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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

Braking jet in an impulse turbine is used

A. To break the jet of water

B. To bring the runner to rest in a short time

C. To change the direction of runner

D. None of these

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4

The specific speed of a hydraulic turbine depends upon

A. Speed and power developed

B. Discharge and power developed

C. Speed and head of water

D. Speed, power developed and head of water

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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

Which of the following pump is suitable for small discharge and high heads?

A. Centrifugal pump

B. Axial flow pump

C. Mixed flow pump

D. Reciprocating pump

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4

The cavitation in a hydraulic machine is mainly due to

A. Low velocity

B. High velocity

C. Low pressure

D. High pressure

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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

Pressure intensifier increases the pressure in proportion to

A. Ratio of diameters

B. Square of ratio of diameters

C. Inverse ratio of diameters

D. Square of inverse ratio of diameters

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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 flow rate in gear pump

A. Increases with increase in pressure

B. Decreases with increase in pressure

C. More or less remains constant with increase in pressure

D. Unpredictable

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4

In a single casing, multistage pump running at constant speed, the capacity rating is to be slightly lowered. It can be done by

A. Designing new impeller

B. Trimming the impeller size to the required size by machining

C. Not possible

D. Some other alterations in the impeller

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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 %

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4

Head developed by a centrifugal pump depends on

A. Impeller diameter

B. Speed

C. Fluid density

D. Both (A) and (B) above

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4

The mechanical efficiency of an impulse turbine is

A. Ratio of the actual power produced by the turbine to the energy actually supplied by the turbine

B. Ratio of the actual work available at the turbine to the energy imparted to the wheel

C. Ratio of the Work done on the wheel to the energy of the jet

D. None of the above

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4

Kinematic similarity is said to exist between the model and the prototype, if both of them

A. Have identical velocities

B. Are equal in size and shape

C. Are identical in shape, but differ only in size

D. Have identical forces

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4

Which of the following pump is preferred for flood control and irrigation applications?

A. Centrifugal pump

B. Axial flow pump

C. Mixed flow pump

D. Reciprocating pump

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4

Casting of a centrifugal pump is designed so as to minimize

A. Friction loss

B. Cavitations

C. Static head

D. Loss of kinetic energy

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4

A hydraulic coupling belongs to the category of

A. Power absorbing machines

B. Power developing machines

C. Energy transfer machines

D. Energy generating machines

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4

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

A. Same

B. 0.75 B.H.P.

C. B.H.P./0.75

D. 1.5 B.H.P.

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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

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

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

The number of buckets on the periphery of a Pelton wheel is given by

A. (D/2d) + 5

B. (D/2d) + 10

C. (D/2d) + 15

D. (D/2d) + 20

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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

High 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

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

A. Rectilinear flow

B. Radial flow

C. Free vortex motion

D. Forced vortex