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Francis Turbine
The Francis turbine is a mixed-flow reaction turbine that was developed by James B. Francis in 1849. It operates in a water head from 60 to 250 meters. Water enters the runner radially at the outer periphery and exits axially at the center. It uses both the kinetic and pressure energy of water to drive the turbine. Key components include a spiral casing, stay vanes, guide vanes, runner blades, and a draft tube. The guide vanes direct water onto the runner blades to efficiently convert the hydraulic energy of water into mechanical rotation of the shaft and electrical energy via a generator. The speed of the turbine is maintained constant via a governing mechanism that controls the guide vanes.
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Francis Turbine
- 1. FRANCIS TURBINE Working andGoverning Mechanism. Santosh Kurre Sharad Walia Professor B. Tech (Mechanical) UPES, Dehradun UPES, Dehradun
- 2. TURBINE • A hydraulicturbine is a machine that uses the potential and kinetic energy of water and converts it into usable mechanical energy. • This mechanical energy is used in running an electric generator which is directly coupled to the shaft of the turbine, thus this mechanical energy is converted into electrical energy
- 3. Types of turbine (basedontheactionofwaterflowingthroughtheturbinerunners) •IMPULSE TURBINE •Only kinetic energy of water is used to drive turbine. • e.g. - Pelton Turbine •REACTION TURBINE • Kinetic energy as well as Pressure energy of water is used to drive turbine. • e.g.- Francis Turbine
- 4. FRANCIS TUBINE • Francisturbine is a mixed flow type of reaction turbine. • Francis turbine is a mixed flow type as water enters the runner radially at its outer periphery and leaves axially at its centre. • In today’s use, Francis turbines are the most common water turbine. • They operate in a water head from 60 to 250 metres.
- 5. Sir James B.Francis • The Francis turbine was developed by James B. Francis in Lowell, Massachusetts, USA. • Sir Francis was the first to develop an inward radial flow type of reaction turbine in 1849.
- 6. Layout of ahydroelectric power plant
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- 10. Components • Penstock: Itis a large size conduit which conveys water from the upstream of the dam to the turbine runner. • Spiral Casing: It constitutes a closed passage whose cross- sectional area gradually decreases along the flow direction. It ensures that the velocity of water is constant along its path. • Stay Vanes: Stay vanes and guide vanes guides the water to the runner blades. Stay vanes remain stationary at their position and reduces the swirling of water due to radial flow, as it enters the runner blades. Thus making turbine more efficient.
- 11. Flow throughstay andguidevanes.
- 12. Cont… • Guide Vanes:These vanes direct the water onto the runner at an angle appropriate to the design. • Guide vanes only swing around their own axes and this helps to bring about a change in the flow area between two consecutive runner blades. • The configuration and arrangement of the guide vanes is such that the energy of the water is not consumed by eddies and other undesirable flow phenomenon causing energy loss. • Motion is given to the guide vanes either by means of a hand wheel or automatically by a governor.
- 13. Cont… • Runner andRunner Blades: The driving force on the runner is both due to impulse and reaction effect. • Design of the runner blades decides how well a turbine is going to perform. • Runner blades of mixed flow turbine can be divided into two parts, the upper part of the blades use the reaction force of water flowing through it and the lower half is in the shape of a small bucket using the impulse action of water flowing through it. These two forces together makes the runner to rotate. • The runner is keyed to the shaft which may be of vertical or horizontal disposition, the shafts are mostly vertical.
- 14. Flow of waterthrough Runner
- 15. Cont… • Draft tube:After passing through the runner, water is discharged to the tail race through a gradually expanding tube, called the draft tube. • The free end of the draft tube is submerged deep into the tail race.
- 16. Governing of Francisturbine
- 17. Governing of Francisturbine • Speed of the turbine runner is required to be maintained constant so that the electric generator coupled directly to the turbine shaft runs at constant speed under varying load conditions. • This task is accomplished by governing mechanism.
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