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• Water under pressure contains energy.
• Turbines convert the energy in water into rotating mechanical energy.
• Impulse turbines convert the kinetic energy of a jet of water to mechanical energy. • Reaction turbines convert potential energy in pressurized water to mechanical energy. Selected References
• Microhydro by Scott Davis
• Microhydro Design Manual by Adam
Harvey
• Waterturbine.com for picohydro units
• BC Hydro Handbook
• Idaho National Labs
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Impulse Turbines
• Tolerate sand.
• Easy to fabricate.
• Efficient at wide a range of head and flow.
• A nozzle converts pressurised water into a high-speed jet of water.
Pelton Turbine – Canyon Industries 3
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Impulse Turbines
• Pelton
– Low Flow
– Medium to High Head
• Turgo
– Medium Flow
– Medium to High Head
• Crossflow
– High Flow
– Low to Medium Head
Pelton Turbines
• At least one jet of water strike the buckets at atmospheric pressure.
• Maximum jet diameter about 1/3 bucket width.
• More jets increase flow and are used at low head. 5
0.61m Pelton – Dependable Turbines Ltd.
Multiple Runners
• Advantages
– Greater Flow
– Flow control
• May be placed in the same housing or separate housings.
1000 kW Twin Pelton – Canyon Industries 6
Turgo Turbines
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• Similar to Pelton runner, but a more complex blade design.
• Greater flow possible.
Multiple nozzles
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• Four to six nozzles may be added before splash interference occurs.
• Power output is proportional to the number of nozzles.
Spear Valves
• A spear valve changes the nozzle size without stopping the turbine.
• Expensive.
Spear Valve
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Deflectors
• Deflectors can be used to vary flow.
• Usually used for emergency stop without causing water hammer.
Deflector
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Crossflow Turbines
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• Banki or Mitchell turbine.
• Shaft oriented horizontally.
• Rectangular nozzle forms the jet. • Water strikes the blades twice.
• A control vane changes jet size.
Crossflow Turbines