The deregulated electricity market in Europe opens new potential for the construction of pump storage hydropower plants. Optimum turbine efficiency under high head conditions for the various operation modes is achieved by the use of Pelton turbines. In order to reduce the shaft length between the storage pump and pelton runner in the power cavern (or power-house), it is possible is to place the Pelton runner below the water level of the lower reser-voir. This kind of arrangement requires that the water level below the runner is pressed down by means of overpressure.
Pelton-Turbine, working in back-pressure mode
When the water - flowing out from the nozzles - hits the runner buckets and falls down into the tailwater channel, considerable amounts of air are dragged into the water. This air must be separated from the fluid before the flow reaches the pressurized conduit system. In case that the de-aeration length of the tailwater channel is to small, air is conveyed towards the reser-voir. In order to maintain air volume in the tailwater channel, additional air has to be pumped into the tailwater channel which may cause disadvantageous technical and economical situa-tions for the whole system. The objective of the research work is to establish design guide-lines for choosing the geometrical dimensions of the tailwater channels.
The work is divided into three phases:
- Phase 1 Prototype measurements
- Phase 2 Physical model tests
- Phase 3 Computational modul (CFD), Design guidelines