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.
This
study
examines
the
S-characteristic,
a
key
factor
affecting
safe
grid
connection
and
operation
of
pumped-storage
units,
its
significant
impact
on
safety
power
stations.
We
conducted
numerical
simulations
model
experiments
to
investigate
vortex
motion
characteristics
in
vaneless
space
runner
passage
pump-turbines
operating
within
S-shaped
region,
along
with
an
analysis
pressure
pulsation
characteristics.
The
accuracy
these
was
validated
through
laser
Doppler
velocimetry
experiments,
particle
image
were
used
capture
space.
observed
that
vortices
generated
guide
vane
side
follow
flow
direction,
blocking
passage,
while
those
by
blades
move
opposite
direction.
Employing
entropy
production
theory
Liutex
method,
we
investigated
distribution
hydraulic
loss
region.
results
show
reduced
rates
lead
area,
which
become
main
contributors
energy
this
These
vortices,
mainly
arise
from
separation
blade
surfaces
due
suboptimal
inflow
conditions.
also
identifies
fluctuations
space,
induced
rotating
stall,
as
most
phenomenon,
significantly
impacts
performance
unit
both
upstream
downstream
directions.
International Journal of Thermofluids,
Год журнала:
2024,
Номер
22, С. 100689 - 100689
Опубликована: Май 1, 2024
Various
engineering
applications,
such
as
heat
exchangers,
air
conditioning
systems,
chemical
reactors,
and
refrigeration
make
use
of
enhanced
transfer
surfaces.
Numerous
methods
have
been
explored
to
improve
rates
reduce
the
size
cost
equipment
involved,
particularly
in
exchangers.
This
review
comprehensively
assesses
multiple
continuous
discrete
swirl-inducing
techniques
for
enhancing
transfer,
achieved
through
geometry
alterations
or
flow
deflectors.
The
study
showed
that
all
angles
device
effectively
promoted
fluid
mixing,
reduced
thermal
boundary
layers,
created
turbulent
eddies
due
swirl
flows
vortices.
While
solid
may
impede
local
performance
by
trapping
low-velocity
heated
fluids
within
these
move
downstream,
they
lead
improved
transport
over
large
areas.
paper
explores
application
other
specific
work
environments.
Heliyon,
Год журнала:
2024,
Номер
10(4), С. e26084 - e26084
Опубликована: Фев. 1, 2024
Pumps
as
Turbines
(PATs)
are
known
for
their
ability
to
replace
conventional
turbines
in
Pico/micro-hydropower
plants.
However,
selecting
a
suitable
pump
and
estimating
its
performance
reverse
mode
is
challenging
task.
The
overall
efficiency
of
PATs
also
lower
when
compared
purpose-made
turbines.
Numerous
attempts
have
been
made
analyze
the
PAT
power-generating
applications,
many
scholars
presented
research
on
improvement
economic
analysis.
In
this
paper,
detailed
review
conducted
show
historical
development
current
status
technology.
presents
findings
prediction,
techniques,
results
literature
survey
demonstrate
that
choice
an
appropriate
specific
application
significantly
affects
system.
Among
various
options,
Shear
Stress
Transport
(SST)
k-ω
standard
k-ε
turbulence
models
widely
used
simulating
turbine.
Blade
grooving
blade
tip
rounding
recognized
most
promising
techniques
improving
efficiency,
with
gains
4.91%
4.00%,
respectively.
Except
impeller
diameter
trimming,
modification
proposed
by
significant
impact
PATs;
however,
further
needed
investigate
advantages
modification.
Energies,
Год журнала:
2025,
Номер
18(2), С. 394 - 394
Опубликована: Янв. 17, 2025
As
the
core
for
energy
conversion
in
pumped
storage
plants,
pump
turbine
is
also
a
key
component
process
of
building
clean
power
grid,
owing
to
its
fast
and
accurate
load
regulation.
This
paper
introduces
current
status
research
development
turbines
from
perspectives
significance,
design
optimization,
operational
performance,
advanced
methods,
etc.
Internal
external
characteristics
such
as
transient
flow
evolution,
structural
vibration,
flow-induced
noise,
etc.,
not
only
reflect
performance
(hydraulic,
cavitation,
sediment
abrasion,
stability
etc.)
but
directly
affect
safe
efficient
operation
system.
It
worth
mentioning
that
space-time
evolution
internal
an
emerging
direction,
results
which
can
be
used
predict
conditions
turbines.
Moreover,
application
intelligent
condition
monitoring
fault
diagnosis
aim
prevent
failures
accidents
plants.
Axial
hydraulic
thrust
is
a
crucial
factor
contributing
to
the
unstable
operation
of
pump-turbine
especially
under
off-design
conditions.
Pressure-balance
pipe
can
effectively
achieve
axial
balance
pump-turbine.
In
this
study,
impact
diameter
and
location
pressure-balance
on
runaway
condition
investigated.
The
influence
mechanism
pressure
distribution
internal
flow
patterns
further
explored.
results
show
that
pipes
have
relatively
minor
while
increase
in
causes
rise
thrust.
Compared
with
outer
pipe,
inner
demonstrates
more
significant
effect
force
runner.
Additionally,
low-frequency
components
at
0.6
times
runner
rotational
frequency
are
observed,
which
indicate
occurrence
stall
vaneless
area.
variation
also
affects
number
passages
vortices,
as
well
quantity
vortices.
With
diameter,
backflow
phenomena
negative
regions
gradually
emerge
result
chaotic
flow.
The
flow
pattern
evolution
is
particularly
complicated
in
the
low
specific
speed
impeller
of
ultrahigh-head
pump
turbines.
To
reveal
mechanism
pressure
pulsation
induced
by
inter-blade
flow,
load
rejection
process
an
prototype
turbine
was
numerically
calculated
using
one-
and
three-dimensional
coupled
compressible
simulation
methods.
analyzed
time-frequency
analysis
visualization
method
field.
investigation
captured
two
high-amplitude
low-frequency
components
pulsations
during
turbine.
suggested
that
first
frequency
were
unique
to
They
approximately
sevenfold
rotation
frequency,
which
are
caused
separation
vortices
impeller.
Other
near
speed-no-load
condition
unstable
transitions
backflow
close
high-pressure
entrance
This
study
found
patterns
turbines
could
cause
pulsations.
However,
stable
flow-vortex
structures
cannot
apparent
findings
this
provide
a
theoretical
basis
for
suppressing
controlling
complex
flows
Energies,
Год журнала:
2025,
Номер
18(7), С. 1642 - 1642
Опубликована: Март 25, 2025
In
order
to
study
the
influence
of
split
blades
on
turbine
force
characteristics
and
fluid–structure
coupling
pumps,
this
paper
selected
IS
80-50-315
centrifugal
pump,
used
as
a
reverse-acting
hydraulic
turbine,
research
object,
optimized
original
pump-acting
impeller,
adopted
different
combinations
long
short
blades.
Based
SIMPLE
algorithm
RNG
k–ε
turbulence
model,
complete
three-dimensional
unsteady
numerical
simulation
was
conducted
internal
flow
field
pump-turbine.
The
results
show
that
reduce
radial
axial
forces.
deformation
patterns
rotor
components
in
two
pump
types
models
were
similar,
with
gradually
decreasing
from
inlet
outlet
impeller.
equivalent
stress
distribution
law
has
also
been
found
be
maximum
occurring
at
connection
between
front
rear
cover
plates
minimum
area
impeller
shaft
diameter
shaft.
blade
model
smaller
than
those
model.
