De-aeration of air-water flows in the tailwater channels of Pelton turbines

摘要

Pumped-storage developments currently under construction will be equipped with Pelton turbines working under permanent backpressure conditions. Knowledge of the length required for air recovery in the free-flow tailrace of the turbine is important to ensure the safe and economical operation of the plant. This paper discusses the results of basic hydraulic scale-model tests to study the hydrodynamic processes in the turbine housing and tailrace, as well as the results of tests carried out to determine the rise velocity of air bubble swarms. Also presented are the void fractions and flow velocities measured in the tailrace channels of three hydropower plants in Austria.