Day 37-Oct 27-worksheet-Diploma-Turbines

The primary reason for limiting the divergence angle of a straight divergent draft tube to nearly 8° is to

• Reduce friction losses

• Avoid flow separation and eddy formation

• Increase velocity at outlet

• Prevent cavitation

A Pelton wheel does not require a draft tube because

• The pressure at runner exit is above atmospheric

• The jet strikes the bucket tangentially and leaves at atmospheric pressure

• The casing maintains vacuum

• Tailrace is at higher level

The specific speed of Kaplan turbine is high mainly because

• It handles low head and low discharge

• It handles high head and low discharge

• It handles low head and high discharge

• It handles high head and high discharge

The conversion of velocity head into pressure head in a reaction turbine happens

• Inside the runner

• In the penstock

• In the draft tube

• In the scroll casing

For maximum efficiency in Pelton turbine, the ratio of bucket speed to jet speed should be

A mixed flow turbine changes direction of flow from

• Tangential to radial

• Radial to tangential

• Radial to axial

• Axial to tangential

Reaction turbines operate completely under atmospheric pressure throughout the flow.

• True

• False

Assertion (A): The Kaplan turbine is provided with adjustable runner blades. Reason (R): It allows the turbine to maintain efficiency only at the design load.

• Both A and R are true, and R is the correct explanation

• Both A and R are true, but R is not the correct explanation

• A is true but R is false

• A is false but R is true

Expansion of water in the draft tube converts into .

• kinetic energy, pressure energy

• pressure energy, kinetic energy

• potential energy, heat energy

• kinetic energy, potential energy

Specific speed of a turbine increases as discharge ______ and head ______