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PHD THESIS
Background
Traditionally speaking, the runners of hydraulic
turbines have always been designed to operate
at synchronous speed. This is governed by the
fact that the generator has a certain number
of poles and it has to rotate at a certain
synchronous speed in order to produce the
required grid frequency. This is crucial for
uninterrupted electricity production.
On the other hand, synchronous speed turbines
have certain challenges when they are operated
at off-design load. Nowadays, turbines are
indeed required to operate at either part-load
or full-load much more frequently than before.
Despite the decreased efficiency at these
operating points, there is a higher dynamical
load present on the runner as well, which can
lead to severematerial cracks, expensive repairs
and decreased power plant reliability in general.
Therefore, it’s considered that variable speed
operation can improve efficiency and stability of
the turbine.
The idea of using variable speed generators is
relatively old but opens future prospects only
because the price of such generators are getting
lower nowadays. But, as reported in previous
research, not all turbine runners can gain
benefit from operating at variable speeds.
Both the idea and objective of this research is to
develop new tools and methodology for design-
ing a turbine that will operate at variable speeds
almost exclusively. A better understanding of
the design philosophy is then required in order
to sustain the parametric study needed. Finally,
a model runner will be produced and tested in
order to compare the performance against the
existing Francis-99 runner.
Department of Energy and
Process Engineering
2016-2019
Design of a High-
Head Francis Turbine
for Variable Speed
Configurations
Supervisor:
Ole Gunnar Dahlhaug
Co-supervisor:
Chirag Trivedi
Igor Iliev
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