Francis turbine: Definition of speed ratio. Speed ratio is defined relative to the runner peripheral (rim) speed at inlet and the ideal jet/stream velocity √(2gH). State whether the given definition is correct. Choose the correct option.
Mechanical Engineering
Hydraulic Machines
Difficulty: Easy
Choose an option
-
ACorrect — speed ratio = theoretical jet velocity / peripheral speed
-
BIncorrect — speed ratio = peripheral speed / theoretical jet velocity (u / √(2gH))
-
CDepends on specific speed; no fixed definition
-
DValid only for Pelton wheels, not Francis turbines
Answer
Correct Answer: Incorrect — speed ratio = peripheral speed / theoretical jet velocity (u / √(2gH))
Explanation
Definition
- For reaction turbines (e.g., Francis), speed ratio φ = u / √(2 g H), where u is runner peripheral speed and √(2 g H) is the ideal velocity head equivalent.
ReasoningThe statement reverses numerator and denominator. The correct ratio places runner speed in the numerator.
Final AnswerIncorrect — speed ratio = u / √(2gH)