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
Energies,
Год журнала:
2023,
Номер
16(6), С. 2661 - 2661
Опубликована: Март 12, 2023
The
expanding
role
of
renewable
energy
sources
in
the
electricity
market
share
implies
increasing
hydropower
and
exploitation
unharnessed
hydraulic
potential,
scope
sustainability
net
zero
emissions.
Hydro-turbine
design
practices
are
expected
to
expand
beyond
achieving
high
efficiency
goals,
multi-objective
criteria
ranging
from
efficient
reversible
operation
fish-friendly
concepts.
present
review
paper
outlines
fundamental
characteristics
hydropower,
summarizing
its
potential
impact
toward
aquatic
life.
Estimates
lethality
for
each
damage
mechanism
discussed,
such
as
barotrauma,
blunt
shearing,
along
with
relevant
advances
experimental
techniques.
Furthermore,
numerical
techniques
simple
particle
tracking
fully
coupled
six-degree-of-freedom
tracking,
which
can
be
used
investigate
candidate
designs
their
performance,
presenting
advantages
disadvantages.
Subsequently,
a
link
individual
mechanisms
is
established,
proposed
holistic
performance
metrics,
useful
providing
estimates
fish-friendliness
given
installation.
Finally,
recent
developments
turbine
concepts
presented.
Applied Sciences,
Год журнала:
2021,
Номер
11(12), С. 5529 - 5529
Опубликована: Июнь 15, 2021
To
understand
the
hydraulic
vibration
characteristics
in
a
traditional
hydropower
system
and
identify
possible
exciting
sources
that
may
induce
serious
vibrations
flow
passage,
experimental
tests
numerical
calculations
were
conducted
for
different
operating
conditions.
The
results
show
pressure
fluctuations
are
mainly
related
to
vortex
rope
phenomena
draft
tube,
dominant
frequency
of
fluctuation
is
0.2~0.4
times
runner
rotational
(fn).
all
attenuating
factors
negative,
which
indicates
itself
stable
on
condition
elements
have
steady
performance.
free
analyses
confirm
range
tube
partly
overlaps
natural
frequencies
system.
Apart
from
rope,
another
common
approximately
equal
10th
mode.
From
mode
shapes,
it
inferred
small
disturbance
its
close
or
specific
could
large
oscillations
tail
tunnel.
In
light
system’s
response
forcing
frequencies,
formed
under
off-design
conditions
verified
be
potential
source
system,
0.2
fn
much
more
dangerous
than
other
disturbances
Chemical Engineering Communications,
Год журнала:
2023,
Номер
211(2), С. 192 - 204
Опубликована: Июль 6, 2023
Most
of
the
mediums
in
chemical
industry
exhibit
shear-thinning
property,
i.e.,
effective
viscosity
decreases
with
increasing
shear
rate.
In
this
work,
effect
property
on
vortex
structure
evolution
and
induced
pressure
fluctuation
an
axial
flow
pump
is
numerically
studied.
The
CMC
solution
used
as
fluid,
viscous
Newtonian
fluid
(viscosity
equals
apparent
index
1)
adopted
for
comparison.
results
show
that
variation
guide
vane
more
obvious
than
impeller.
case,
two
passage
vortexes
are
found
outlet,
but
only
one
larger-scale
exists
fluid.
Meanwhile,
enhances
interaction
between
vortices
mainstream,
leading
to
higher
fluctuation.
Different
from
rotor-stator
play
a
dominant
role
fluctuation,
can
arouse
low-frequency
components.
Machines,
Год журнала:
2024,
Номер
12(6), С. 392 - 392
Опубликована: Июнь 7, 2024
Unstable
flows
in
the
runner
of
water
turbines,
such
as
reverse
flow,
vorticity
and
flow
direction
transition,
are
main
factors
causing
increased
losses
decreased
efficiency,
changing
geometry
structure
downstream
is
an
important
means
mitigating
these
instabilities.
The
different
fields
runners
induced
by
locking
nut
structures
numerically
calculated
verified
experimental
results.
states
evaluated
terms
characteristic
quantities
pressure
gradient,
swirling
vorticity.
results
show
a
non-negligible
effect
nut,
which
leads
to
more
uniform
distribution,
increases
descending
speed
rate,
reduces
volume
strength
vortex.
small
significantly
weakens
top
zone,
decreases
vortex
at
blade
passage
outlet
size
disturbance
extended
lock
growth
rate
generation
partial
vortex,
but
range
high-pressure
bottom
increasing
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:
2022,
Номер
15(11), С. 3956 - 3956
Опубликована: Май 27, 2022
Utilizing
the
flexibility
of
hydropower
to
integrate
more
intermittent
renewable
energy
into
power
grid
requires
hydro
units
expand
operating
range;
this
duty,
however,
a
continuous
improvement
their
stability
during
part-load
conditions.
This
study
focuses
on
performance
generation
systems
(HGS)
flexible
operation.
First,
dynamic
model
HGS
that
reflects
characteristics
conditions
is
established
by
introducing
pressure
pulsation
in
draft
tube.
Second,
coupled
with
shafting
system
investigate
vibration
property
unit.
Then,
validity
coupling
verified
comparing
it
traditional
and
actual
data.
Finally,
some
possible
ways
mitigate
instability
caused
operation
are
explored.
The
results
show
accompanied
significant
response
fluctuations
(5%).
Moreover,
interaction
effect
multiple
sources
condition
investigated.
paper
expected
provide
support
for
improving
offer
useful
insights
exploiting
potential
HGS.
