The process, which causes the air to enter the impeller blades of a centrifugal compressor at ________ velocity (without effecting the mass of air to flow and velocity of flow) is known as prewhirl.

The blades of a centrifugal impeller are said to be curved forward, if the __________ of the motion of impeller blades.

A

Inlet tip of a blade curves in a direction opposite to that

B

Outlet tip of a blade curves in a direction opposite to that

C

Inlet tip of a blade is towards the direction

D

Outlet tip of a blade is towards the direction

In a centrifugal compressor, the flow of air is ________ to the axis of compressor.

A

Parallel

B

Perpendicular

C

Inclined

D

None of these

In an axial flow compressor, the ratio of pressure in the rotor blades to the pressure rise in the compressor in one stage is known as

A

Work factor

B

Slip factor

C

Degree of reaction

D

Pressure coefficient

Consider a centrifugal pump having a specific impeller diameter, fixed impeller speed pumping a liquid of constant density at a particular discharge capacity. With decrease in the capacity of the pump, the __________ decreases.

A

NPSH required

B

BHP required by the pump

C

Head of the liquid pumped

D

All of the above

The variable required to be known in correlations used for estimating the horse power of a centrifugal gas compressor and hence its cost are P. Inlet pressure Q. Compressor rpm R. Delivery pressure S. Volumetric flow rate at inlet.

A

P, Q and R

B

P and R

C

R and S

D

P, R and S

Axial flow compressor has the following advantage over centrifugal compressor

A

Larger air handling ability per unit frontal area

B

Higher pressure ratio per stage

C

Aerofoil blades are used

D

Higher average velocities

Height of liquid in agitation tank is normally maintained equal to the tank diameter. However, if the tank is too tall and a large liquid hold up is desired, then two or more impellers mounted on the same shaft may be used. The clearance between the tank bottom and the bottom most impeller should be about (where, D = impeller diameter)

A

0.5 D

B

D

C

1.5 D

D

2 D

Horsepower increase of a centrifugal gas compressor without altering the volumetric flow rate will __________ the gas discharge pressure.

A

Increase

B

Decrease

C

Not change

D

Exponentially decrease

If the flow of air through the compressor is parallel to its axis, then the compressor is

A

Reciprocating compressor

B

Centrifugal compressor

C

Axial flow compressor

D

Turbo compressor

The ratio of outlet whirl velocity to blade velocity in case of centrifugal compressor is called

A

Slip factor

B

Velocity factor

C

Velocity coefficient

D

None of the above

The process, which causes the air to enter the impeller blades of a centrifugal compressor at ________ velocity (without effecting the mass of air to flow and velocity of flow) is known as prewhirl.

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