Tech Briefs Magazine - August 2022 - 33

Anti-Phase Noise Suppression Rotor Technologies
Acoustic optimization for anti-phase asymmetric rotor.
Armstrong Flight Research Center, Edwards, CA
R
otor noise and vibration are two sources
of operational challenges for all aircraft
operating with open rotors such as helicopters,
unmanned aerial vehicles (UAVs),
urban air mobility personal air vehicles,
drones, and aircraft operating with ducted
fans, such as passenger aircraft. One key
disadvantage of convention rotor design is
the noise due to noise-induced shed vortices
generated by rotor blades. NASA Ames
Research Center has developed a novel
patent-pending design and method for reducing
rotor blade vibration and acoustic
signatures in rotor systems using anti-phase
blade vortex suppression design concepts.
The design objective is to maximize reduction
of noise perceived by the community
while maintaining the aerodynamic thrust.
These designs could be applicable in any
system that uses rotor blades.
The unique problem with rotor noise
and vibration is the periodic blade passage
that results in a harmonic reinforcement
and causes the rotor blades to vibrate and
generate noise.
This NASA technology seeks to optimize
the implementation of anti-phase
trailing edge designs and asymmetric blade
tip treatments for rotor noise suppression
and integrated aircraft noise solutions by
incorporating the anti-phase rotor design
concepts into an aircraft flight control system
to reduce the noise footprint.
There are several embodiments of the
invention, which include the following: (1)
an anti-phase trailing edge design whereby
the trailing edge pattern of the leading
rotor blade is offset by a phase shift from
the trailing edge pattern of the following
blade; (2) an anti-phase rotor design implementing
asymmetric blade tips with
inverted airfoil; and (3) other anti-phase
enabled concepts such as unequal blade
length, ducted rotors with non-radial unequally
spaced struts, and multi-axis tilt
rotor design incorporating the anti-phase
rotor design.
The designs could be applicable in any system that
uses rotor blades, such as drones. (Image: NASA)
The technology has applications in rotorcraft
like helicopters, drones and unmanned
aerial vehicles (UAVs), urban
air mobility vehicles (UAMVs), military/
commercial/passenger aircraft gas turbine
engines and wind turbines, as well as industrial
systems that use rotor blades.
NASA is actively seeking licensees to
commercialize this technology. Please
contact NASA's Licensing Concierge at
Agency-Patent-Licensing@mail.nasa.gov
or call at 202-358-7432 to initiate licensing
discussions. For more information, visit
https://technology.nasa.gov/patent/
TOP2-297.
Improved Fixed-Wing Gust Load Alleviation Device
Enabling thinner, lighter fixed wings for novel aircraft design.
Langley Research Center, Hampton, VA
G
ust load alleviation is an increasing
concern for the design of fixed-wing
aircraft with ultra-high aspect wings. It
may have detrimental impacts on flight including
increased structural and aerodynamic
loads, structural deformation, and
decreased flight dynamic performance.
Innovators at NASAs Langley Research
Center have developed a mechanical solution
to control gust-load on fixed plane
wings enabling significant improvement
over alleviation devices currently in use.
By manipulating the wings natural response
to gust loads, the technology may
minimize aerodynamic and structural
loads and improve flight efficiency of
future aircraft. Current computer-controlled,
active gust-alleviation devices delay
the wing response such that gust loads
experienced are mitigated less than 10
percent while the present invention has
demonstrated the ability to improve gust
load alleviation up to 30 percent. Along
with the reduced response time that alleTech
Briefs, August 2022
viates gust load, NASA's mechanical innovation
offers the advantage of a simplified
design and potentially improves passenger
flight experience during turbulence.
This technology has been demonstrated
to improve current gust load allevia3/25/19
- St. Dev Accel#1 , Mass = 1g
st.dev vs Wind Speed - 240s record
1.4
1.2
1
0.8
0.6
0.4
0.2
20
30
40
50
60
70
Wind Speed (ft/s)
Standard deviation of the wing tip acceleration
time of the free-to-rotate, passive gust load alleviation
device, by comparison to the locked,
current gust alleviation device. (Image: NASA)
www.techbriefs.com
Upon gust impact, the mass balance shifts the
center of gravity in front of the hinge line to illicit
an opposing aerodynamic force, reducing
load. (Image: NASA)
33
80
90
100
Locked
Unlocked
accelerometers
tion by use of a trailing-edge, free-floating
surface control with a mass balance.
Immediately upon impact, the inertial
response of the mass balance shifts the
center of gravity in front of the hinge
control surface
mass balance
control surface
locking pin
St. Dev Accel (G)
beam spar
hinge line
https://technology.nasa.gov/patent/TOP2-297 https://technology.nasa.gov/patent/ http://www.techbriefs.com
Tech Briefs Magazine - August 2022

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