Question

What is the range of the speed ratio for a Francis turbine?
1. 0.10 to 0.30
2. 0.60 to 0.90
3. 0.85 to 0.90
4. 1.40 to 2.45

Answer 1

Correct Answer - Option 2 : 0.60 to 0.90

Explanation:

Speed ratio: 

• It is defined as the ratio of tangential velocity or circumferential velocity to its spout velocity and denoted b.
• ϕ = \(\frac{U_1{}}{\sqrt{2gH}}\) Where, U₁ = Tangential velocity, \({\sqrt{2gH}}\) = Spout velocity
• Speed ratio varies from ie 0.6 ≤  ϕ ≤ 0.9

Flow ratio:

• It is defined as the ratio of flow velocity at the inlet to the spout velocity.
•  ψ = \(\frac{V_{f1}}{\sqrt{2gH}}\) Where, V_f1 = Flow velocity at inlet and \({\sqrt{2gH}}\) = Spout velocity.
• Flow value varies from ie 0.15 ≤ ψ ≤ 0.3

Turbine Name	Specific Speed (NS), MKS
Pelton wheel turbine (Single jet)	10 - 35
Pelton wheel turbine (Multiple jets)	35 - 60
Francis turbine	60 - 300
Kaplan turbine	> 300