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Unknown ~ Water Turbines

Unknown ~ Water Turbines - Hydro-electric turbines of the...

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Water Turbines Water Turbines For Micro-Hydroelectric Power Impulse Wheels, Sort Of. .... Banki Mitchell Turbines The crossflow curbine actually had two inventors. The first was the Australian engineer A. G. M. Michell, who obtained a patent for it in 1903. The turbine was later invented independently in Germany by the Hungarian Prof. Donat Banki where it became known more widely between 1917 and 1919 through a series of publications. A working model of Banki's turbine is exhibited in the German Museum in Munich. Its runner is 8 inches in diameter and is about 4 inches wide and has 40 blades. The present more widespread use of the cross-flow turbine is largelydue to the efforts of the Ossberger concern in Weissenburg, Bavaria, who added a number of original ideas to Michell's design, based on their own research work. The various stages of this steady development are covered by world patents. Thousands of these crossflow turbines have been built by Ossberger. The main characteristic of the cross-flow turbine is that it uses broad rectangular jet of water that travels through the turbine only once but travels across each runner blade twice, once in each direction. The water flows through the runner blading first from the periphery towards the center, and then, after crossing the open center space, from the inside outwards. This machine is therefore a turbine with two velocity stages, the water filling only part of the runner at any one time. As far as energy utilization is concerned, the use of two velocity stages provides no immediate advantages. The arrangement represents, however. a very skillful design which removes the water in a simple manner after it has passed through the runner without producing any back pressure. The addition of a draft tube to the cross-flow turbine represents an improvement implemented by Ossberger to enhance the turbine's performance. Ossberger uses an air valve in the draft tube to help regulate the head by introducing air in the draft tube. The machine is normally classified as an impulse or free-jet turbine. In its original design this classification is not strictly correct since it was designed as a true constant-pressure turbine. A sufficiently large gap was left between the nozzle and the runner to ensure that the jet entered the runner without any static pressure. There 1 of 8 8/1/00 3:30 PM Hydro-electric turbines of the past and present file:///E|/Tech/Power/Hydro Power/Water_Turbines.html
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was also sufficient space in the runner itself to allow the jet to expand freely sideways. During the passage through the first stage conditions were therefore essentially the same as in the much older Zuppinger free-jet turbine. However, the present design in which the nozzle is shaped to follow the runner periphery closely giving better results. At full or nearly full gate there is a slight positive pressure in the gap. This can readily
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Unknown ~ Water Turbines - Hydro-electric turbines of the...

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