1. The available head of a Francis Turbine is 100 m. Velocity of the flow at the runner inlet is 15 m/s. Find the flow ratio.
a) 0.33
b) 0.45
c) 0.67
d) 0.89
Explanation: Flow ratio is given by ψ = Vf1 / sqrt(2gH). Substituting the given values and taking the value of g = 10 m/s2, we get ψ = 0.33.
2. How does the flow ratio (ψ) of a Francis turbine vary with available head (H)?
a) ψ α H
b) ψ α 1/H
c) ψ α sqrt (H)
d) ψ α 1/(sqrt (H))
Explanation: Flow ratio is given by ψ = Vf1 / sqrt(2gH). Hence, the flow ratio is inversely proportional to the square root of available head.
3. What is the typical value for flow ratio in a Francis turbine?
a) 0.05 – 0.1
b) 0.15 – 0.30
c) 0.35 – 0.45
d) 0.50 – 0.60
Explanation: Flow ratio denoted by ψ is given by Vf1 / sqrt(2gH). Sqrt (2gH) is called the spouting velocity. The practical values of the flow ratio for Francis turbine lie in the range of 0.15 – 0.3
4. The available head of a Francis Turbine is 120 m. The blade velocity is given 35 m/s. Find the speed ratio of the turbine.
a) 0.56
b) 0.61
c) 0.71
d) 0.81
Explanation: The speed ratio φ = U/ sqrt(2gH). Hence, substituting the given values into this equation, we get φ = 0.71.
5. The speed ratio (φ) varies directly with which of the following parameters?
a) Vw1
b) V1
c) N (RPM)
d) H (Available head)
Explanation: The speed ratio is given by φ = U/ sqrt(2gH). Speed ratio directly depends upon U which in turn depends directly upon RPM of the turbine (N).
6. The typical value range of speed ratio for a Francis turbine is:
a) 0.3 – 0.6
b) 0.5 – 0.6
c) 0.1 – 0.4
d) 0.6 – 0.9
Explanation: Speed ratio denoted by φ is given by U / sqrt(2gH). Sqrt (2gH) is called the spouting velocity. The practical values of the speed ratio for Francis turbine lie in the range of 0.6 – 0.9.
7. In a Kaplan turbine, what is the direction of water flow?
a) Axial and then axial
b) Radial and then axial
c) Tangential and then axial
d) Tangential and then radial
Explanation: The Kaplan turbine is an axial flow reaction turbine. The water inlet is axial and the water outlet is axial too.
8. For which of the following values of available heads may Kaplan turbine be used?
a) 250 m
b) 100 m
c) 80 m
d) 50 m
Explanation: The Kaplan turbine is said to be a Low head turbine. The low head ranges from 0 to 60 m. Only 50 m falls in this range and hence, it’s the correct option.
9.In this type of low head turbine, the guide vanes are fixed to the hub of the turbine and are not adjustable. What is this type of turbine called?
a) Francis turbine
b) Kaplan Turbine
c) Propeller Turbine
d) Pelton turbine
Explanation: In a Kaplan turbine, the guide vanes are adjustable and not fixed to the hub of the turbine. Francis and Pelton turbines are not low head turbines. In a propeller turbine, the guide vanes are fixed to the hub of the turbine.
10.The velocity of flow through a Kaplan turbine is 10 m/s. The outer diameter of the runner is 4 m and the hub diameter is 2 m. Find the volume flow rate of the turbine in m3/s?
a) 95
b) 75
c) 85
d) 105
Explanation: The volume flow rate is given by
Substituting the given values in the above equation, we get Q = 95 m3/s.