Hydraulic turbines

Hydraulic turbines

1. Hydraulic Turbines

2. Hydraulic Machines It is defined as those machines which convert either hydraulic energy into mechanical energy (i.e. turbines) or mechanical energy into hydraulic energy ( i.e. pumps). Turbines It is defined as the hydraulic machines which converts hydraulic energy into mechanical energy . Head of Turbines Gross Head ( ) Net Head ( H ) Head loss ( )  

3. Power of Turbines Water Power ( WP ) Runner Power ( RP ) Shaft Power ( SP ) Efficiencies of Turbines Hydraulic Efficiency ( ) = Mechanical Efficiency ( ) = Overall Efficiency ( ) = Volumetric Efficiency ( ) = = Amount of water striking per sec Q = Amount of water supplied per sec by jet  

4. C lassification of Hydraulic Turbines According to the type of energy at inlet (a) Impulse turbine (ex – Pelton wheel) (b) Reaction turbine (ex – F rancis turbine, Kaplan turbine etc ) According to the direction of flow through runner ( a) Tangential flow turbine (ex – Pelton wheel) (b) Radial flow turbine (ex – Francis turbine) (c) Axial flow turbine (ex –Kaplan turbine) (d) Mixed flow turbine (ex – ModernFrancis ) According to the head at the inlet of the turbine ( a) High head turbine (more than 250 m. ex – Pelton wheel ) (b) Medium head turbine (60 m to 250 m. ex – Francis turbine ) (c) Low head turbine (less than 60 m. ex –Kaplan turbine ) According to the specific speed of the turbine ( a) High specific speed turbine (less than 30 single jet, 30 to 50 multi jet pelton wheel) ( b) Medium specific speed turbine (50 to 260 Francis turbine) (c) High specific speed turbine (260 to 860 Kaplan turbine)

5. Pelton Wheel (or turbine) Components of Pelton Wheel 1 . Nozzle and Flow Regulating Arrangement ( Spear ) 3. Casing and 2 . Runner and Buckets 4 . Breaking Jet

6. Pelton Wheel (or turbine) Shape of bucket

7. Reaction Turbine In reaction turbine, water at the inlet of the turbine possesses kinetic energy as well as pressure energy. As water flows through runner, a part of pressure energy goes on changing into kinetic energy. Thus the water through runner is under pressure and the runner is completely enclosed in an air-tight casing. Casing and the runner is always full of water . Radial Flow R eaction turbine In radial flow reaction turbine the water flows in the radial direction. If the water flows from outward to inwards through the runner, the turbine is known as inward radial flow turbine. If the water flows from inward to outwards through the runner, the turbine is known as outward radial flow turbine.

8. Francis turbine Components of Francis turbine 1. Scroll casing 2. Guide mechanism 3. Runner 4 . Draft tube

9. Kaplan turbine Components of Francis turbine 1. Scroll casing 2. Guide mechanism 3. Hub with vanes or runner 4 . Draft tube

10. Governing of Pelton Wheel

11. Governing of Francis Turbine

12. Characteristic Curves of Hydraulic Turbines The turbines are generally designed to work at particular designed conditions. But often the turbines are required to work at different conditions. Therefore it is essential to determine the exact behavior of the turbines under the varying conditions. “ Characteristic curves of a hydraulic turbine are the curves, with the help of which the exact behavior and performance of the turbine under different working conditions can be known .” The following are the important characteristic curves for a hydraulic turbine: 1. Main Characteristic Curves or Constant Head Curves 2. Operating Characteristic Curves or Constant Speed Curves 3. Constant Efficiency Curves

13. 1. Main Characteristic Curves Main characteristic curves are obtained by maintaining a constant head and a constant gate opening on the turbine. The characteristic curves drawn are: a) Unit discharge vs unit speed b) Unit power vs unit speed c) Overall efficiency vs unit speed Unit discharge vs unit speed

14. Unit power vs unit speed Overall efficiency vs unit speed

15. 2. Operating Characteristic Curves

16. 3 . Constant Efficiency Curves

17. Centrifugal Pump Main parts of a centrifugal pump are: Impeller Casing Suction pipe Delivery pipe

18. Types of Casing Volute casing Vortex casing Casing with Guide blades

19. Characteristic Curves of Hydraulic Pumps Characteristic curves of centrifugal pumps are defined those curves which are plotted from the results of a number of tests on the centrifugal pump. These curves are necessary to predict the behavior and performance of the pump when the pump is working under different flow rate, head and speed. The followings are the important characteristic curves for pumps: 1 . Main Characteristic Curves 2 . Operating Characteristic Curves 3 . Constant Efficiency Curves

20. 1 . Main Characteristic Curves

21. 2. Operating Characteristic Curves

22. 3 . Constant Efficiency Curves