Physics of Fluids,
Год журнала:
2024,
Номер
36(12)
Опубликована: Дек. 1, 2024
This
paper
examines
the
instability
and
energy
dissipation
of
a
high-head
Francis
turbine
during
shutdown
using
improved
delayed
detached
eddy
simulation,
which
involves
linearly
reducing
guide
vane
opening
from
9.84°
(best
efficiency
point)
to
0.8°
[Spin-No-Load
(SNL)].
The
results
demonstrate
linear
increase
in
water
head,
with
hydraulic
dropping
93%
30%.
Pressure
fluctuations
vaneless
space
are
mainly
due
blade
passing
frequency
low-frequency
components
at
SNL.
High-amplitude
pressure
occur
below
37.4%
draft
tube,
dominant
under
0.32
times
frequency.
Three
vortex
structures
identified
within
columnar
rope
first
stage,
multiple
helical
ropes
second
discrete
third
stage.
most
significant
axial
radial
velocity
evident
stages.
Turbulent
kinetic
generation
work
done
by
Reynolds
stress
main
sources
power
loss.
Energy
primarily
occurs
outlet
runner
blades,
while
it
corresponds
positions
suggesting
that
flow
primary
mechanism
turbine.
study
introduces
numerical
model
dynamic
mesh
technique,
clarifies
relationship
between
performance
parameters,
identifies
three-stage
evolution
mechanisms,
offering
novel
insights
into
transient
instabilities
turbines.
Energies,
Год журнала:
2024,
Номер
17(10), С. 2402 - 2402
Опубликована: Май 16, 2024
The
internal
flow
of
a
pump
turbine
is
unstable
in
part-load
mode
for
small
guide-vane
openings,
and
the
strong
vibration
caused
by
pressure
pulsation
related
to
safe
stable
operation
unit.
A
with
six-splitter-blade
runner
was
chosen
unsteady
simulation
analyses.
standard
k-epsilon
turbulence
model
adopted
study
mode.
predicted
results
show
that
draft
tube
splitter
blades
relatively
blade-to-blade
channel
symmetrical.
When
inlet
outlet
velocity
distribution
vanes
not
uniform,
vortex
began
form
stay-vane
domain.
reason
this
formation
explained,
it
pointed
out
existence
backflow
leads
uneven
distribution.
calculation
showed
pressure-pulsation
peak-to-peak
amplitudes
vaneless
area
guide
were
much
higher
than
those
other
monitor
points
because
rotor–stator
interference
between
rotating
vanes.
In
addition,
characteristics
at
different
circumferential
positions
region
quite
different.
area,
gradient
along
direction
very
large,
there
phenomenon
backflow.
Also,
0.2
times
rotational
frequency,
blade-passing
frequency
third-order
frequency.
At
vane,
mainly
low
complex
flow.
Finally,
decrease
rapidly
region.
Journal of Marine Science and Engineering,
Год журнала:
2024,
Номер
12(9), С. 1654 - 1654
Опубликована: Сен. 14, 2024
During
the
operation
of
a
reversible
pump-turbine,
hump
area
can
easily
appear
under
pump
condition,
which
will
greatly
affect
performance
storage
unit,
with
pressure
pulsation
being
key
factor
for
stable
pump-turbine.
Therefore,
in
order
to
explore
characteristics
each
flow
component
area,
this
paper
first
compared
full
model
test
different
working
conditions,
and
then
it
analyzed
characteristics.
By
analyzing
unit’s
rates
rule
pump-turbine
running
was
revealed.
It
found
that
peak-to-peak
value
draft
tube
smallest
optimal
increased
along
direction,
rotor
stator
interaction
(RSI)
effects
continuously
enhanced.
When
away
from
runner
basin,
influence
RSI
gradually
weakened
after
leaving
runner.
No
low
frequency
traffic.
The
condition
distribution
not
uniform.
main
whole
basin
relatively
complex,
indicating
water
unstable
partial
load,
resulting
during
unit
operation.
research
results
provide
theoretical
reference
improving
stability
pump-turbines.
Physics of Fluids,
Год журнала:
2024,
Номер
36(10)
Опубликована: Окт. 1, 2024
Sediment
erosion
poses
a
significant
challenge
for
hydraulic
turbines
in
sediment-laden
rivers.
This
paper
investigates
the
patterns
high-head
Francis
using
numerical
simulations.
It
analyzes
how
sediment
concentration,
particle
size,
and
operating
conditions
affect
wear
on
turbine
components.
The
results
identify
trailing
edges
of
guide
vanes,
intersection
runner
blade
edge,
band
as
primary
zones.
Higher
concentrations
increase
intensity
extend
range
upstream.
Small
particles
uniformly
both
pressure
suction
sides
blades,
while
larger
concentrate
near
edges.
flow
rate
has
greater
impact
than
water
head,
with
lower
rates
reducing
side
but
initially
increasing,
then
decreasing
erosion.
Additionally,
study
proposes
multi-objective,
multi-condition
optimization
design
method
that
balances
resistance
energy
efficiency.
optimized
reduces
maximum
by
23.91%
limiting
weighted
efficiency
loss
to
under
0.1%.
improved
high
areas
sides,
particularly
speeds
Sensitivity
analysis
reveals
trade-off
between
minimizing
maintaining
efficiency,
highlighting
importance
span
height
at
75%
controlling
Changes
circumference
angle
generally
reduce
may
also
Overall,
this
research
demonstrates
successful
reduction
preserving
offering
valuable
guidance
anti-erosion
sediment-heavy
environments.
Energies,
Год журнала:
2024,
Номер
17(12), С. 2957 - 2957
Опубликована: Июнь 15, 2024
Unstable
flow
in
a
pump-turbine
can
cause
pressure
pulsation,
and
the
resulting
vibration
deteriorates
stability
operating
safety
of
unit.
This
study
conducted
three-dimensional
numerical
calculations
overall
passage
with
splitter
blades
under
small
guide
vane
opening,
unsteady
characteristics
turbine
were
investigated.
The
results
showed
that
fluctuation
was
more
severe
at
lower
head
conditions
efficiency,
especially
vaneless
area
(the
runner
blade
passages).
Under
condition,
proportion
12
times
rotational
frequency
(12
f/fn)
increased
area,
amplitude
1
f/fn
as
well
2
became
larger
channel,
space
occupied
by
vortices
reflux
areas.
A
spiral
vortex
rope
formed
draft
tube,
increasing
0.4
0.7
pulses.
Physics of Fluids,
Год журнала:
2024,
Номер
36(12)
Опубликована: Дек. 1, 2024
This
paper
examines
the
instability
and
energy
dissipation
of
a
high-head
Francis
turbine
during
shutdown
using
improved
delayed
detached
eddy
simulation,
which
involves
linearly
reducing
guide
vane
opening
from
9.84°
(best
efficiency
point)
to
0.8°
[Spin-No-Load
(SNL)].
The
results
demonstrate
linear
increase
in
water
head,
with
hydraulic
dropping
93%
30%.
Pressure
fluctuations
vaneless
space
are
mainly
due
blade
passing
frequency
low-frequency
components
at
SNL.
High-amplitude
pressure
occur
below
37.4%
draft
tube,
dominant
under
0.32
times
frequency.
Three
vortex
structures
identified
within
columnar
rope
first
stage,
multiple
helical
ropes
second
discrete
third
stage.
most
significant
axial
radial
velocity
evident
stages.
Turbulent
kinetic
generation
work
done
by
Reynolds
stress
main
sources
power
loss.
Energy
primarily
occurs
outlet
runner
blades,
while
it
corresponds
positions
suggesting
that
flow
primary
mechanism
turbine.
study
introduces
numerical
model
dynamic
mesh
technique,
clarifies
relationship
between
performance
parameters,
identifies
three-stage
evolution
mechanisms,
offering
novel
insights
into
transient
instabilities
turbines.
