Q. 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? (Solved)
1. To ensure constant velocity of water during runner entry
2. To prevent loss of efficiency of the turbine due to impulsive forces caused by extra area
3. To prevent leakage from the turbine
4. To reduce material costs in order to make the turbine more economical
- a. To ensure constant velocity of water during runner entry