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Effect of compressed air on mortality of fish passing through a model turbine. Prempridi, Thamrong

Abstract

Rates of mortality among young salmon passing through a high speed, model propeller, turbine operating under a 50 ft hydraulic head but under various, draft tube suctions are given. Effects, on both fish mortality and turbine performance, of admission of compressed air into the turbine at various locations to reduce the effect of cavitation (believed to be the major cause of fish mortality in the turbine) are discussed . At low turbine speed and low efficiency, admission of air immediately downstream from the blades reduced the mortality of fish substantially but at high turbine, speed, and high efficiency, the reduction was insignificant. At high turbine speed, the effect, on fish mortality, of admitting compressed air into the penstock and atmospheric air into the turbine draft tube through a 3" diameter steel pipe installed about 1 ft downstream of the blades are shown to be beneficial. Records of biological examination from some of the tests to determine the apparent type of injuries are included. An attempt has been made to correlate the turbine speed with the number of injuries likely to be caused by fish being hit by the blades.The effect of partial vacuum on fish is also given.

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