Question

The specific speed of a turbine is the speed of an imaginary turbine, similar 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

Answer 1

Hint: The specific speed value for a turbine is defined as the speed of a geometrically identical turbine which can be used to produce unit power or we can say one kilowatt under unit head or we can say one meter. The specific speed of a turbine is mentioned by the manufacturer itself along with other ratings. And it will be always known as the point at which maximum efficiency is occurring. These all may help us to solve this question.

Complete step-by-step answer:
Specific speed is basically an index helpful in predicting desired pump or turbine performance. It can be used to assume the basic shape of a pump's impeller. This impeller’s shape is able to predict its flow and head properties so that the designer can then select a pump or turbine most appropriate for a certain application. The specific speed of a turbine is mentioned by the manufacturer itself along with other ratings. And it will be always known as the point at which maximum efficiency is occurring.
The speed of an imaginary turbine which is identical with a certain given turbine, can develop a unit power under a unit head. This is the definition for the specific speed of the turbine. Therefore the correct answer is option C.

Note: The unit of specific speed is given as rotation per minute or abbreviated as RPM. A geometrically similar impeller will be required to operate for delivering one litre per second of fluid at a head of one metre. The specific speed of the Pelton turbine is the slowest.