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BULB TURBINES & GENERATORS

General Concept ofBulb Turbines

Today low heads can be used for powergeneration very economically feasible. More than 300 units supplied by VA TECH HYDRO for heads up to 30 m, a maximum runner diameter of 7,700 mm and outputs up to 55 MW testify the experience in this seg- ment ofhydropower generation. VA TECH HYDRO is the leader in Bulb-turbine/Generator units with a market share of more than 50% in the last decades. The application range includes direct-driven units, pit turbines using a step-up gear to the generator and the so called STRAFLO™ turbines, a special de- velopment by VA TECH HYDRO. The to- tal installed capacity worldwide amounts to approximately 4,500 MW. Bulb turbines have the advantage of a straight inflow to the distributor and runner and also the outflow through the conical draft tube has no bend. This results in a minimum of losses in the entire application range and therefore higher efficiencies. In VA TECH HYDRO’s hydraulic test lab-oratory in Linz, Austria, Bulb turbines areoptimized in this respect to ensure high- est energy generation for all applications. Bulb turbines can be double or single regulated as far as the wicket gates or the runner blades are concerned. Directly coupled Bulbturbine/Generatorunits are economically feasible for high- er heads of up to 25 m thus offering a suf- ficent high generator speed. For lower heads pit turbines with step-up gears can be used to allow for high turbine effi- ciencies at low speeds. High speed gen- erators need less space and are also cheaper. For low heads and small outputs Bulb turbines with bevel gears are used in accordance with our COMPACT HYDRO turbine program. For special applications Bulb turbines with S-shaped draft tubes can be used with the advantage of having the generator outside the waterway.
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