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.
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
