Water hammer calculation for hydro power plant project
The planners of a hydro power plant engaged the Institute or Hydraulic Fluid Machinery to realise water hammer calculations for a cross-border hydro power plant project which should produce clean energy for approximately 90.000 private households. A 20 km head race tunnel provides water to the surge tank. Furthermore, a penstock to the power plant building with the two installed Francis turbines was built.
With the help of instationary, one-dimensional numerical calculations the transient behaviour of the power plant’s hydraulics should be investigated whereas mass oscillations as well as the maximum water hammer are of interest. For the relevant power plant components specially programmed software modules were used in order to allow for in illustration of the plant scheme as detailed as possible. Thus, certain phenomena and parameters such as the rotational speed of the machine at load rejection or a possible separation of free water levels in the surge chamber can be depicted.
The questions and load cases dealt with include the start-up of the plant from a standstill to full load operation, the guide vane emergency shutdown of both turbines, the simultaneous load rejection of both turbines, the periodic operation of the plant in response to the surge chamber oscillations and the restart of the plant to full load after an emergency shutdown or a load rejection.
As this power plant project is still in its planning stage, additionally to the above-mentioned charges the maximum internal pressures within the pipes to be expected are of importance in order to be able to correctly dimension these pipes and /or their wall thickness.
On the one hand the results of the water hammer calculations provide the customer with information on the pressure losses to be expected and thus on the possible plant performance. On the other hand important information is gathered on the surge chamber behaviour which influences the feasible operational modes of the power plant. Furthermore, planning also reflects all these findings which have an influence on the final realisation of the surge chamber.
