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
Journal of Applied Fluid Mechanics,
Год журнала:
2023,
Номер
17(1)
Опубликована: Ноя. 6, 2023
For
the
purpose
of
automatic
generation
control
(AGC),
a
portion
propeller
hydro-turbine
units
in
China
is
adjusted
to
operate
within
restricted
range
75%-85%
load
using
computer-controlled
AGC
strategies.
In
engineering
applications,
it
has
been
observed
that
when
unit
operates
under
off-design
conditions,
large-scale
vortex
rope
would
occur
draft
tube,
leading
significant
pressure
fluctuations.
Injecting
air
into
tube
reduce
amplitude
fluctuations
common
practice,
but
its
effectiveness
not
proven
on
units.
this
study,
CFD
model
was
established,
and
15
cases
with
different
guide
vane
openings
(GVO,
between
31°
45°)
unsteady
conditions
were
calculated
studied.
Two
admission
measures
introduced
suppress
oscillation
mitigate
The
reason
for
additional
energy
loss
due
then
explained
by
entropy
production
theory,
value
quantified.
This
study
points
out
injecting
air,
necessary
first
consider
whether
will
obstruct
flow
tube.
Finally,
based
simulation
experimental
data
various
fluctuation
analysis
(based
fast
Fourier
transform,
FFT)
conducted
assess
measures.
can
provide
an
option
balancing
efficiency
stability
scheduling
strategy.
Processes,
Год журнала:
2023,
Номер
12(1), С. 72 - 72
Опубликована: Дек. 28, 2023
Hydraulic
vibrations
in
Francis
turbines
caused
by
cavitation
profoundly
impact
the
overall
hydraulic
performance
and
operational
stability.
Therefore,
to
investigate
influence
of
phenomena
under
high-load
conditions,
a
three-dimensional
unsteady
numerical
simulation
is
carried
out
for
turbine
with
different
head
operating
which
combined
SST
k-w
turbulence
model
two-phase
flow
capture
evolution
conditions.
Additionally,
utilizing
entropy
production
theory,
losses
during
development
are
assessed.
Contrary
pressure-drop
method,
theory
can
quantitatively
reflect
characteristics
local
loss
distribution,
calculated
error
coefficient
τ
not
exceeding
2%.
The
specific
findings
include:
primary
sources
energy
inside
airfoil
vortex
rope,
constituting
26%
71%
total
losses,
respectively.
According
comparison
tests,
vapor
volume
fraction
(VVF)
draft
tube
fluctuates
periodically
causing
low-frequency
pressure
pulsation
turbine’s
power,
rate,
other
external
characteristic
parameters
at
0.37
Hz,
runner
radial
force
frequency
1.85
Hz.
Engineering Science and Technology an International Journal,
Год журнала:
2024,
Номер
53, С. 101685 - 101685
Опубликована: Апрель 9, 2024
As
a
auxiliary
braking
device
in
vehicle's
downhill
process,
parallel
hydraulic
retarder
has
strict
requirements
for
its
rapidity
of
response
performance
and
accuracy
torque.
The
uses
high-pressure
gas
as
the
control
medium,
which
pushes
oil
into
working
chamber
through
high-speed
on/off
valve.
Because
filling
process
is
an
indirect
complicated
gas–liquid
movement
during
period
affects
process.
In
this
paper,
mechanical
characteristics
valve
had
analyzed
by
computational
fluid
dynamics.
system's
analyzed,
verified
experimental
data.
Compared
with
three
dimensional
method
to
directly
analyze
charging
discharging
system,
it
simplicity
fast
calculation.The
modeling
used
paper
mainly
suitable
system
air
pressure
liquid
medium.
This
integration
model
can
obtain
group
more
accurately
certain
novelty
rather
than
Theoretical
formula
calculation.
Then
influence
different
input
speed
on
transient
discussed
analyzed.
results
showed
that
shortest
opening
time
1.49
s
when
3.2
bar.
With
decrease
amount
speed,
oil-discharging
increases
gradually.
When
1800
rpm
rate
25
%,
discharge
reaches
5.48
s.
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
