Applied Sciences,
Год журнала:
2024,
Номер
14(11), С. 4450 - 4450
Опубликована: Май 23, 2024
The
flow
in
the
draft
tube
of
water
turbine
is
affected
by
upstream
and
inherent
structure
accompanied
various
undesirable
characteristics,
affecting
efficient
stable
operation
turbine.
Changing
downstream
runner
an
important
measure
to
reduce
hydraulic
loss
improve
stability.
In
this
study,
three
structures
runner,
namely,
non-locking
nut,
small
locking
extended
nut
are
numerically
calculated
verified
using
experimental
results.
unstable
characteristics
analyzed
variations
swirling
flow,
backflow,
pressure
gradient,
vortex
strip.
results
show
non-negligible
effect
which
significantly
reduces
rotational
momentum
flux
at
inlet,
accelerates
decay
rate
suppresses
generation
axial
low
pressure.
shortens
backflow
zone,
decreases
velocity.
zone
some
sections
straight
section
but
prolongs
increases
Water,
Год журнала:
2025,
Номер
17(1), С. 113 - 113
Опубликована: Янв. 3, 2025
With
the
requirement
of
flexible
operation
hydraulic
turbine
units,
Francis
units
have
to
adjust
their
output
into
extended
operating
ranges
in
order
match
demand
power
grid,
which
leads
more
off-design
conditions.
In
conditions,
excitation
causes
excessive
stress,
pressure
pulsation,
and
vibration
on
machines.
Different
designs
turbines
cause
different
excitations
vibrational
behaviors.
To
conduct
better
condition
monitoring
fault
prognosis,
it
is
paramount
importance
understand
behavior
a
machine.
reveal
influence
factors
Francie
field
tests
been
conducted
two
similar-designed
features
compared
this
research.
The
installed
same
station
under
condition.
Field
performed
researched
has
using
spectrum
analysis
method.
indicators
are
extracted
from
test
data
variation
rules
compared.
By
comparing
machines,
design
installation
difference
machines
analyzed.
This
research
reveals
effects
installations
performance
prototype
units.
obtained
results
give
guidance
designers
operators
Engineering Applications of Computational Fluid Mechanics,
Год журнала:
2023,
Номер
17(1)
Опубликована: Янв. 13, 2023
Precessing
vortex
rope
(PVR)
plays
a
key
role
in
inducing
hydraulic
resonance
Francis
turbines
operating
at
partial
load,
possibly
degrading
power
plant
stability
and
availability.
Air
injection
into
the
runner
cone
is
suitable
mitigating
alternative;
however,
influence
mechanism
of
air
on
PVR
remains
unclear.
The
principal
objective
this
study
was
to
establish
response
relationships
between
characteristic
parameters
by
method
computational
fluid
dynamics
(CFD)
considering
components
water,
water
vapour
air.
findings
show
that
cavitation
flow
can
be
completely
suppressed
slight
injection;
helical
structures
are
persisted
1.0%
2.0%
volume
fractions,
static
pressure
recovery
improved
together
with
increase
loss.
At
3.0%
fraction,
structure
disappears,
leaving
an
umbrella-shaped
structure,
no
vibration
arising
turbine.
Moreover,
physical
reducing
amplitudes
clarified.
This
results
clarify
PVR,
contribute
steadily
extending
flexibility
range
turbine
during
engineering
application.
Energies,
Год журнала:
2023,
Номер
16(13), С. 5131 - 5131
Опубликована: Июль 3, 2023
This
review
addresses
the
current
state
of
research
into
active
control
and
suppression
vortex
rope
in
hydroturbines
under
off-design
operating
conditions.
Only
methods
that
can
be
“switched
on”
when
required
conditions
are
considered
this
work.
The
focuses
on
air
addition
flow,
as
well
various
auxiliary
fluid
jets.
It
includes
all
best
practices
for
numerical
experimental
studies.
inferred
from
a
modern
flow
system
should
comprehensive,
designed
specific
hydroturbine
geometry,
obtain
feedback
flow.
Injecting
~2%
impeller
fairing
cone
appears
optimal
suppressing
pressure
pulsations
without
significant
efficiency
loss.
cost
injection
is
rarely
estimated,
but
use
an
automatic
venting
minimize
overheads
potentially
improve
efficiencies
at
low
gas
contents.
Fluid
jets
ranging
3%
to
12%
main
rate
efficiently
suppress
pulsations,
their
high
energy
requirements
limit
use.
Azimuthal
perturbation
promising
it
does
not
require
loss,
practical
implementation
remains
challenging
one
needs
accurately
know
dynamics
capable
real-time
manipulation
A
self-induced
instability
known
as
vortex
rope
enhanced
by
cavitation
usually
occurs
at
part
load
operation
conditions
in
the
draft
tube
and
negatively
affects
normal
of
Francis
turbines.
In
present
study,
turbine
was
simplified
modeled
a
diffuser
with
swirling
flow
to
analyze
understand
patterns
cavitating
turbulent
strong
oscillation.
The
numerical
simulation
used
modified
shear
stress
transport
partially
averaged
Navier–Stokes,
i.e.,
MSST
PANS
turbulence
model,
Zwart–Gerber–Belamri
model
investigate
characteristics
different
swirl
numbers.
precession
surge
predicted
simulations
agree
available
experimental
data,
indicating
applied
method
is
suitable
for
study.
results
reveal
that
smaller
number
larger
promote
vortical
oscillations,
which
induce
pressure
fluctuations
diffuser.
Furthermore,
can
be
increase
number,
frequency
amplitude
dominant
pulsation
component
significantly
number.
It
also
depicted
interaction
between
directly
determines
conditions.
analysis
based
on
vorticity
equation
indicates
stretching
term
has
an
extremely
important
effect
production
evolution
under
