Francis Turbine

Francis Turbine Working & Improvement

1. PRESENTED BY TAMOOR KHALIL UW-14-MET-BSC-011 M ZUBAIR UW-14-MET-BSC-032 MATTI ULLAH UW-14-MET-BSC-018 FRANCIS TURBINE SUBMITTED TO Mr. Umer Sohail

2. Francis turbine Francis Turbine is an Inward Flow Reaction Turbine having Radial Discharge at Outlet. (i.e. = 0). Modern Francis Turbine is a mixed flow type turbine (i.e. Water enters the runner of the turbine in the radial direction and leaves the runner in the axial direction).

3. Francis turbine

4. Working Of Francis turbine In the Francis turbines the water must be enter into inlet nozzle and the velocity must be decreases. Then the water moves in the forward direction in the turbine but continuous decrease in the spiral casing area must be happened. With the constant speed the water strikes the turbine blades. On the runner the blades are mounted. The blades are designed like a thin air foil. So due to the design the water flow occurs at low pressure at one point and other side it creates a low pressure.

5. Working Of Francis turbine So the motion takes place from the high pressure to the low pressure. Inside the blade it looks like a bucket it using the impulsive force for rotation of water. If the flow rate of water changes then by using the governing mechanism we can set the angle of attack of the water on the blade. At that case the turbine works properly. Initially the water passes from the blades and next later enters into the draft tube, where we can notice the continuous increment in the area and velocity of the water must be decreases. Cont..

6. Francis turbine Medium head(45m to 250m) Reaction(K.E.+P.E) mixed flow(radial + axial) medium specific speed(50 to 250) disposition of shaft of runner is vertical

7. Francis turbine

8. Main P arts Penstock-it is a large size conduit which conveys water from upstream to the dam/reservoir to the turbine runner spiral casing- it constitutes a closed passage whose cross section area gradually decrease along flow direction area is maximum at inlet and nearly zero at exit guide vanes-these vanes direct the water on the runner at an angle appropriate to the design, controlled by hand wheel or governor

9. Cont.. Governing mechanism-it changes the position of guide vanes to affect a variation in water flow rate, when the load condition on the turbine changes Runner and runner blades-the driving force on the runner is both due to impulse and reaction effect(usually runner blades 16-24). Draft tube-it is generally an expending tube which discharges the water, passing through the runner to the tail race.

10. PARTS OF FRANCIS TURBINE

11. Efficiencies Of Turbine Hydraulic Efficiency - It is ratio of power developed by the runner of a turbine to the power supplied by the water at the inlet . Mechanical Efficiency – It is ratio of power available at the shaft to power developed at the runner.  

12. Volumetric Efficiency - It is ratio of volume of the water actually striking the runner to the volume of water supplied to the turbine. Overall Efficiency - It is ratio of power available at the shaft of the turbine to the power supplied by the water at the inlet of the turbine .   Cont..

13. Disadvantages Water wheels of different types have been used historically for over 1000 years to power mills of all types, but they were relatively inefficient.  Nineteenth-century efficiency improvements of water turbines allowed them to replace nearly all water wheel applications and compete with steam engines wherever water power was available.  After electric  generators were developed in the late 1800s turbines were a natural source of generator power where potential hydro-power sources existed . Improvement

14. Improvement Pawtucket Gatehouse in Lowell, Massachusetts; site of the first Francis turbine

15. Improvement

16. Disadvantages In 1826 Benoit Fourneyron developed a high efficiency (80%) outward-flow water turbine. Water was directed tangentially through the turbine runner, causing it to spin.  Jean-Victor Poncelet designed an inward-flow turbine in about 1820 that used the same principles . In 1848 James B. Francis, while working as head engineer of the Locks and Canals company in the water wheel-powered textile factory city of Lowell, Massachusetts, improved on these designs to create more efficient turbines.   He applied scientific principles and testing methods to produce a very efficient turbine design. More importantly, his mathematical and graphical calculation methods improved turbine design and engineering .  His analytical methods allowed confident design of high efficiency turbines to precisely match a site's water flow and pressure (water head). Improvement

17. Advantage It is most widely used turbine in world (70-80%). Effective use of water pressure as well as velocity. It is American standard turbine. Very good efficiency (80-94%). Advantage

18. Disadvantages Cost is high. Due to it’s complex design and large no of moving parts, maintenance and repair is difficult and costly. It is applicable to flow of medium head only . Cavitation is also a big problem. Disadvantages