Optimisation of a distribution pipeline

In April 2001 the Institute for Hydraulic Fluid Machinery was mandated to examine the design of a distribution pipeline. Additionally, the development and examination of alternative geometries, which should be compared by means of CFD calculations, were ordered. The final target was the development of the ideal geometry for an optimum flow to the turbines

Apart from a height difference of nearly 8 m and a horizontal distance of more than 45m between pressure tunnel and connection to the turbine spiral, an angle of 18°has to be realised in the distribution pipeline. These geometric conditions cause two deviations of the flow thus getting imposed a swirl. However, as the flow towards the turbines should be as even as possible, apart from a low-loss flow situation the main focus was on a swirl reduction at the entrance into the turbine spiral.

Besides a modification of the flow guidance and the installation of various fittings into the bends, the installation of double-decker butterfly valves functioning as shut-off valves in front of the turbines should reduce the swirl.

Elaborate tests proved that the installation of these double-decker butterfly valves is the most efficient solution to reduce the swirl and to keep losses on a minimum level at the same time. As a result, not only an optimised low-loss flow towards the spiral could be realised but the also a more compact construction.

Additional measures such as modified branch angles and diameter, the integration of a cone and the geometrically more favourable realisation of the flow deviations provided further improvements.