1. The velocity of the flow at the inlet of Kaplan turbine is V. In an experimental setup, what could be the possible value of the velocity of the flow at the outlet of Kaplan turbine?
a) V
b) 0.8V
c) 1.2V
d) 2V
Explanation: The flow velocity of turbine at the outlet of the Kaplan turbine will be lesser than that of the inlet due to effects of friction in the blade. Hence, practically a lower value would be obtained. 0.8V is the only option lower than V.
2. Which of the following turbines will have the lowest number of blades in it?
a) Pelton turbine
b) Steam turbine
c) Francis turbine
d) Kaplan turbine
Explanation: As the head for Kaplan turbine is low, the discharge of water through the turbine is high and hence, blade resistance should be low. That’s why Kaplan turbine will have the lowest number of blades.
3. The velocity of the flow through the Kaplan turbine is 25 m/s. The available head of the turbine is 60 m. Find the flow ratio of the turbine (take g = 10 m/s2).
a) 0.65
b) 0.72
c) 0.69
d) 0.75
Explanation: Flow ratio is given by ψ = Vf1 / sqrt(2gH). The given of head and flow velocity must be substituted in this equation to obtain the flow ratio which comes out to be 0.72.
4. A Kaplan turbine requires a speed ratio of 2. The available head of the turbine is 5 m. What should be the blade velocity of the turbine such that a speed ratio of 2 is maintained (take g = 10 m/s2)?
a) 75.75 m/s
b) 63.25 m/s
c) 23.35 m/s
d) 50.00 m/s
Explanation: The speed ratio φ = U/ sqrt(2gH). Substitute the value for speed ratio and available head in this equation and rearrange to find U = 63.25 m/s.
5. The flow ratio of a Kaplan turbine is given as 0.7. The available head is 30 m. The outer diameter of the runner is 3.5 m and the hub diameter is 2 m. Find the volume of water flowing through the turbine per second (m3/s)?
a) 90
b) 111
c) 125
d) 168
Explanation: We know that
We can write V as ψ*(sqrt(2gH)). Now, substitute the values in the modified equation to find Q which comes out to be around 111 m3/s.
6. In which of the following type of runners in a Kaplan turbine the velocity of whirl at inlet is smaller than the blade velocity?
a) Such a case is practically impossible
b) Slow Runner
c) Medium Runner
d) Fast Runner
Explanation: Considering the velocity diagram of a Kaplan turbine at the inlet for a fast runner, we notice that the whirl velocity is lower the blade velocity along the same direction. They are equal in case of a medium runner.
7.In the outlet velocity triangle of a Kaplan turbine, β2 = 30o. Vf2 = 5 m/s. What is the relative velocity of the flow at outlet?
a) 10 m/s
b) 5.77 m/s
c) 8.66 m/s
d) 2.88 m/s
Explanation: In the outlet velocity triangle, sin (β2) = Vf2/ Vr2. Therefore, Vr2 = 5/sin(30) = 10 m/s.
8. In the inlet velocity triangle of a Kaplan turbine, α1 = 45o. The velocity of flow at inlet = 10 m/s. Find the whirl velocity of water at the inlet of Kaplan turbine?
a) 5 m/s
b) 10 m/s
c) 12.5 m/s
d) 15 m/s
Explanation: In the inlet velocity triangle, tan (α1) = Vf1/ Vw1. Since α1 = 45o, Vf1 = Vw1 = 10 m/s.
9. The whirl velocity of water at the inlet of the Kaplan turbine is 15 m/s. The velocity of water at inlet of the turbine is 20 m/s. Find the guide vane angle at inlet (In degrees).
a) 53.13
b) 36.86
c) 45
d) 41.41
Explanation: cos (α1) = Vw1/ V1 = 15/20 = ¾. Hence, α1 = cos-1(3/4) = 41.41o.
10. The relative velocity of water at the inlet of the Kaplan turbine is 7 m/s. β1 = 75o. The whirl velocity of the water at inlet is 10 m/s. Find the blade velocity of the turbine?
a) 26.124 m/s
b) 40 m/s
c) 36.124 m/s
d) 60 m/s
Explanation: cos (β1) = (u – Vw1)/ Vr1. Substituting the given values in the above equation and rearranging to find the value of u, we get 36.124 m/s.