Francis Turbine topics include: Francis turbine velocity diagrams, francis turbine work and efficiency. A Francis turbine is a type of reaction turbine invented by James B. Francis around 1855. It is the most common type of turbine used today. Francis turbines are used in about 60% of the world's hydropower capacity.  Here's how a Francis turbine works: Water enters the turbine in a radial direction, flowing towards its axis. The water is deflected 90 degrees in the runner, which sets the runner and the generator in a rotary motion. The energy released in this way can achieve an... Show more

Francis Turbine topics include: Francis turbine velocity diagrams, francis turbine work and efficiency.

A Francis turbine is a type of reaction turbine invented by James B. Francis around 1855. It is the most common type of turbine used today. Francis turbines are used in about 60% of the world's hydropower capacity. 

Here's how a Francis turbine works:
Water enters the turbine in a radial direction, flowing towards its axis.
The water is deflected 90 degrees in the runner, which sets the runner and the generator in a rotary motion.
The energy released in this way can achieve an efficiency of up to 95%. 

Here are some other features of Francis turbines:
They have a radial flow runner with fixed buckets, usually nine or more.
The turbine must be completely immersed when in operation.
The wicket gate around the outside of the turbines rotating runner controls the rate of water flow through the turbine for different power production rates.
The turbine runner is connected to an electrical generator by a common shaft.
As the runner rotates, so does the generator rotor.
The rotor rotates through an electromagnetic field, which induces current in the stator windings.

Show less

Hydraulic Machines Practice Test: Francis Turbine

Time left 00:00

25 Questions

1. The input water power of the Francis turbine is 1.25 times the runner power. What would be the hydraulic efficiency of the turbine (in %)?

60809070

2. Work done per second by a Francis turbine can be given by ρAVf (Vw1u1 + Vw2u2).

FalseTrueDon't KnowMaybe

3. Which of the following efficiencies for Francis Turbine is described as the ratio between total quantity of water over runner blades to total quantity of water supplied to turbine?

Hydraulic efficiencyMechanical efficiencyOverall efficiencyVolumetric efficiency

4. Which of the following runner types will have the highest vane angle at inlet (β1 value)?

Medium RunnerSlow RunnerFast RunnerVane angle is defined only for Kaplan Turbines and not Francis turbines

5. Water flow velocity is given 10 m/s. The runner diameter is 3 m and the width of the wheel is 25 cm. Find the mass of water (kg) flowing across the runner per second.

7500π50πRPM of the turbine needs to be given300π

6. A student performs an experiment with a Francis turbine. He accidently set the RPM of Francis turbine to 1400 rpm instead of 700 rpm. He reported the power to be 1 MW. His teacher asks him to perform the same experiment using the correct RPM. The student performs the same experiment again, but this time the erroneously doubled the flow velocity. What does the student report the power to be?

0.5 MW2 MW1 MW0.25 MW

7. 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.

0.330.670.890.45

8. The desired hydraulic efficiency of a turbine is 80% at a whirl velocity of 20 m/s and a head of 100 m. What should be the blade velocity of the turbine at inlet in m/s?

25408060

9. Why does the cross sectional area of the Spiral casing gradually decrease along the circumference of the Francis turbine from the entrance to the tip?

To reduce material costs in order to make the turbine more economicalTo ensure constant velocity of water during runner entryTo prevent loss of efficiency of the turbine due to impulsive forces caused by extra areaTo prevent leakage from the turbine

10. The whirl velocity at inlet is 15 m/s and blade velocity is 10 m/s. The volume flow rate of water in 20 m³/s. Find the power output available at the shaft if the mechanical efficiency is 95% (in MW)?

0.2856.553.0752.85

11. The power available at the shaft of a Francis turbine is 1 MW. The volume flow rate of water in 25 m³/s, whirl velocity at inlet is 10 m/s and blade velocity is 5 m/s. Find the mechanical efficiency (in %)?

75809065

12. What is the water flow direction in the runner in a Francis turbine?

Radial and then axialTangential and then axialAxial and then tangentialAxial and then radial

13. Velocity of whirl at the runner inlet is given to be 10 m/s and blade velocity to be 5 m/s. The volume flow rate of water in Francis turbine is given to be 25 m³/s. Find the power generated by the turbine?

1000 HP3400 HP1700 HP800 HP

14. The hydraulic efficiency of a Francis turbine is 90%, the mechanical efficiency is 95% and the volumetric efficiency is assumed to be 100%. Fine the overall efficiency (in %)?

83.385.58087.5

15. How does the flow ratio (ψ) of a Francis turbine vary with available head (H)?

ψ α 1/Hψ α Hψ α sqrt (H)ψ α 1/(sqrt (H))

16. The volumetric efficiency of a given turbine is 80%. If volume flow rate of water in given to be 30 m³/s, find the volume of water (m³) NOT flowing over the runner blades per second?

126105

17. Which of the following terms is considered to be zero while deriving the equation for work done per second for Francis Turbine?

Vr1Vw2Vf2Vr2

18. What is the typical value for flow ratio in a Francis turbine?

0.15 – 0.300.50 – 0.600.05 – 0.10.35 – 0.45

19. In case of a Medium runner, tan (α1) CANNOT be given by (α1 = Guide vane angle at inlet)?

Vw1 / u1Vf1 / Vw1Vr1 / u1Vr1 / Vw1

20. Which of the following is true in case of flow of water before it enters the runner of a Francis Turbine?

Available head is entirely converted to velocity headAvailable head is partly converted to pressure head and partly to velocity headAvailable head is entire converted to pressure headAvailable head is neither converted to pressure head nor velocity head

21. In the figure shown below,which of the following angles replace the question mark?

Guide vane angle at inletBlade angle at outletVane angle at inletBlade angle at inlet

22. The typical value range of speed ratio for a Francis turbine is:

0.1 – 0.40.6 – 0.90.3 – 0.60.5 – 0.6

23. Power developed by Francis turbine are calculated for a certain set of conditions. Now, the inlet whirl velocity is doubled, the blade velocity at inlet is doubled and the flow velocity is quartered. The power developed:

Is 4 times the original valueIs same as the original valueIs ½ times the original valueIs 2 times the original value

24. The volumetric efficiency of a Francis turbine is given to be 90%. If the volume flow rate through the turbine is 25 m³/s. What is the flow rate of water over the runner blades (in m³/s)?

21.52522.520

25. In which of the following type of runners the velocity of whirl at inlet is greater than the blade velocity?

Medium RunnerSuch a case is practically impossibleSlow RunnerFast Runner