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SPENN TATE
1 8 5 5
Center for Acoustics and Vibration
Rotorcraft Acoustics and Dynamics
Group Activities
Edward C. Smith, Professor
Director, Penn State Vertical Lift Research Center
2012 CAV Workshop
SPENN TATE
1 8 5 5
• Group Highlights
• 2011-2016 VLRCOE Renewal Proposal
• Review of ongoing group research projects
• Individual Project Highlights
- Coupled Fluidic Vibration Isolators
for Multi-Harmonic Loads Reduction
Presentation Outline
SPENN TATE
1 8 5 5
Interaction with Other PSU
Research Centers
Vertical Lift
Research Center
of Excellence
National Center for Advanced
Drivetrain Technology
ARL
Condition Based
Maintenance Dept.
Center
for Acoustics and
Vibration
Institute for
Computational
Science Composites Manufacturing
Technology
Center
ARL
ARL
iMAST
SPENN TATE
1 8 5 5
Vertical Lift Center Tech Base
25
Faculty
40 +
Graduate
Students
100
Undergraduate
Students (Freshman Sem, AHS Chapter,
Senior Class, Design projects)
40 Continuing Education Students
(Short course)
4
Res Assoc
Penn State ARL
NRTC CRI
SBIR Programs
apply &
transition
SPENN TATE
1 8 5 5
Vertical Lift Center Faculty @ PSU
Ed Smith Dynamics, aeromechanics
Ken Brentner Aeroacoustics, VLRCOE Admin
Farhan Gandhi Dynamics and smart structures, VLRCOE Education
Joe Horn Flight mechanics and control
Sven Schmitz Applied and computational aero, wind energy
Mark Maughmer Airfoil design, aerodynamics
Jack Langelaan Guidance, navigation, and controls
Rob Kunz (ARL) CFD, multi-phase flow, propulsion and gears
Ralph Noack (ARL) CFD, Overset grids, multiphase flows
Brian Elbing (ARL) Fluid mechanics
Dennis McLaughlin Experimental aerodynamics and aeroacoustics
Cengiz Camci Experimental fluid mechanics and heat transfer
Barnes McCormick Aerodynamics, stability & control
Directors
Affiliated Faculty - Aerodynamics, Aeroacoustics, and Flight Controls
Deputy Directors
Administrative Aides
Debbie Mottin, Barbara Kepinska
Stephen Conlon (ARL) SHM, HUMS, sensors, structural acoustics
SPENN TATE
1 8 5 5
Vertical Lift Center Faculty @ PSU
George Lesieutre Structural dynamics, materials
Bob Bill Propulsion and powertrains
Jose Palacios Icing, smart structures, experimental mechanics
Zihni Saribay Drive systems and rotordynamics
Jianhua Zhang Rotor dynamics and design
Chris Rahn (ME) Controls and structural dynamics
Chuck Bakis (ESM) Composite structures
Joe Rose (ESM) Ultrasound, NDE, guided waves
Cliff Lissenden (ESM) SHM, fatigue and fracture, composites
Tom Donnellan (ARL) Manufacturing, advanced composites
Kevin Koudela (ARL) Composite structures, nano-materials, FEM
Steve Hambric (ARL) Structural acoustics
Mike Yukish (ARL) Crashworthiness, optimal design
Suren Rao (ARL) Drivetrain technologies, manufacturing
Doug Wolfe (ARL) Coatings, materials and manufacturing
Tim Eden (ARL) Cold spray forming, materials and manufacturing
Jim Adair (Mat Sci) Nano-materials
Affiliated Faculty and Research Scientists - Structures and Dynamics
Karl Reichard (ARL) HUMS, signal, processing
Jeff Banks (ARL) HUMS system integration
Affiliated Faculty and Research Scientists - Condition Based Maintenance
SPENN TATE
1 8 5 5
VLRCOE Renewal Award
12 Separate Tasks
14 Pis
20 Graduate Students
5 years (20011-2016)
$7.5 M Total
Partners (cost share)
LORD Corp Sikorsky
Goodrich Bell
Timken Aerospace Gyrodyne
Penn State Univ
Group Highlights
SPENN TATE
1 8 5 5
VLRCOE Renewal tasks
Aeromechanics: Higher speeds, better fuel efficiency,
all weather
• Unsteady airfoil design methods
• Rotor hub flow physics for drag reduction
• Icing physics, modeling, detection
Flight Dynamics & control: autonomy, safety, new configs
• Autonomous multi-lift systems
Structures: Lower weight, more reliability
• Nano-tailored composites for improved toughness and
thermal conductivity
SPENN TATE
1 8 5 5
Design Concepts: Speed, range, altitude
• Aeroelastically tailored wing extensions and winglets for
Large Civil Tiltrotors
• Control redundancy on compound rotorcraft for
performance, HQ, and survivability
Vibration & Noise Control: Active rotors, variable W rotors
• Physics of active rotors for performance and acoustics
VLRCOE Renewal tasks
SPENN TATE
1 8 5 5
Propulsion and Drive Systems: weight, reliability, noise
reduction
• Comprehensive analysis of gearbox loss of lubrication
Affordability: condition-based maintenance, SHM
• Health monitoring for joints in composite structures
Maritime Operations: improving safety / reliability for manned
and autonomous operations in the dynamic interface
• Advanced response types / cueing systems for naval ops
• Autonomous shipboard take-off and landing
VLRCOE Renewal tasks
SPENN TATE
1 8 5 5
Other CAV Group/VLRCOE Projects
LORD Corp
• Conceptualization, Modeling, and Characterization of a CF Driven Multi-
State Lead-Lag Bypass Damper
• Vibration Control via Coupled Fluidic Pitch Links
NASA
• Acoustically Tailored Panels for Low Cabin Noise (Hambric & Koudela)
NASA
• High Fidelity CFD Analysis and Validation of Rotorcraft Gear Box
Aerodynamics (Kunz)
GE Global Research
• Wind Turbine Ice Protection Coating Performance Evaluation (Palacios)
• Ice Accretion Shapes to Wind Turbine Airfoils (Palacios)
• Ice Accretion to Cascade Flow Configurations of Engine Compressors
(Palacios)
SPENN TATE
1 8 5 5
Other CAV Group/VLRCOE Projects
Vertical Lift Consortium (Army, Navy + Industry)
• Durability Evaluation of Single Crystal Energy Harvesters
(Conlon, Reichard, Smith)
• Evaluation of Pericyclic Transmission Concepts (Rao, Saribay, Bill, Smith)
• Static and Dynamic Characterization of Composite Materials for Future
Driveshaft Systems (Bakis and Smith)
• Centrifugally Driven Pneumatic Actuators for Active Rotors (Palacios, Smith)
• Modeling of Rotor Blade Ultrasonic Deicing and Experimental Comparison
with Electrothermal Ice Protection Systems (Palacios, Smith)
FBS Inc/NAVAIR SBIR
• A Multi-Functional Ultrasonic Sensor System for Composite Rotor
Blade Ice Protection, Ice Sensing, and Structural Health Monitoring
Bell Helicopter TEXTRON
• Civil Certification Noise Prediction Tools (Brentner)
• Analysis of Rotor Startup/Shutdown in Complex Winds (Smith, Kunz)
• Alternate Control Laws for Fly-by-Wire Helicopters (Horn)
SPENN TATE
1 8 5 5
Penn State VLRCOE - New Facilities
• Water Tunnel for Hub Drag flow visualization
• Upgrades to Flight Simulation Facility
• New rotary-wing UAV for autonomous flight
research
• 2011 DURIP Awards
Laser Vibrometer (ONR): Profs. Capone and Conlon
Rotor Rig Upgrades (ARO): Lesieutre and Smith
Adaptive Flight Inc., Hornet Mini
SPENN TATE
1 8 5 5
• Group Highlights
• 2011-2016 VLRCOE Renewal Proposal
• Individual Project Highlights
- Coupled Fluidic Vibration Isolators
for Multi-Harmonic Loads Reduction
Presentation Outline
SPENN TATE
1 8 5 5
Coupled Fluidic Vibration Isolators
for Multi-Harmonic Loads Reduction
Lloyd Scarborough, Nicolas Kurczewski, and Dr. Christopher Rahn
Department of Mechanical and Nuclear Engineering
Dr. Edward Smith Dr. Kevin Koudela
Department of Aerospace Engineering Applied Research Laboratory
May 14, 2012
CAV Workshop: Rotorcraft Acoustics and Dynamics Group
SPENN TATE
1 8 5 5Fluidic Vibration Isolator
• Objective: minimize fout(t) for a
given input force, fin(t) = sin(ωt).
• fin(t) induces fluid flow in the
fluid track.
• The fluid’s inertance and
accumulator’s capacitance
dictate the isolation frequency.
16
fout(t)
fin(t)
Pump
Fluid
track
Accumulator
Mass
SPENN TATE
1 8 5 5Fluidic Vibration Isolator
Can isolate only
one frequency!
17
fout(t)
fin(t)
Spring-only
isolator
Fluidic
isolator
The fluidic isolator achieves the
same reduction at 16 Hz, but
with 7 times the static stiffness
of the spring-only isolator.
SPENN TATE
1 8 5 5Vibration Isolator Examples
• Dynamic Antiresonant Vibration Isolator (DAVI) [Flannelly 1967]
• Liquid Inertia Vibration Eliminator (LIVE®), LORD Corporation’s Fluidlastic devices
[Halwes 1980, McGuire 2003]
18
Images from McGuire, D. P., “High Stiffness (“Rigid”) Helicopter
Pylon Vibration Isolation Systems,” AHS 59th Annual Forum,
Phoenix, Az., 2003.
SPENN TATE
1 8 5 5Motivation: Pitch Link Loads Reduction
• The pitch link connects the swashplate to the blade root to provide cyclic blade pitch given by the pilot’s control input.
• Aerodynamic blade loads cause fatigue damage.
• Excitation frequencies are harmonics of the constant main-rotor speed:
– Cyclic blade pitch control: 1/rev
– Aerodynamic blade excitations: 2, 3, 4, 5,…/rev 19
From Burkhard Domke
Pitch link
Blade root
Swashplate
SPENN TATE
1 8 5 5
Project Objectives
• Explore new pitch link devices for multi-
harmonic loads reduction.
• Develop a series of analytical models suitable
for design.
• Validate concepts and models via bench-top
experiments.
20
SPENN TATE
1 8 5 5Motivation for Coupling Isolators
• Each blade sees the same loading, just offset
in time.
fin(t) = A sin (ω t – φ), where φ = 2 π / Nb
Nb is the number of blades.
• Replace rigid pitch links with fluidic isolators.
Utilize odd-harmonic loading to pump fluid
back and forth between two pitch links on
opposite sides of the swashplate.
21
SPENN TATE
1 8 5 5Coupled Fluidic Vibration Isolators
22
Mass
fin1(t) fin2
(t)
fout1(t) fout2
(t)
Elastomer
Piston
Fluid
track
SPENN TATE
1 8 5 5Odd and Even Harmonic Forcing
23
Fluid flow
Out-of-phase forcing (Odd Harmonic)
One isolation frequency
fin(t)
No fluid flow
In-phase forcing (Even Harmonic)
No isolation
(direct load transmission)
fin(t) fin(t) fin(t)
SPENN TATE
1 8 5 5Experimental Setup
24
Isolators
Fluid
track
Shakers
Load cell
(output load)
Load cell
(input load)
Masses
Rubber
diaphragm
Stinger
SPENN TATE
1 8 5 5Odd Harmonic Results from Experiment
25
Theory
Experiment Baseline 20” Fluid track 23” Fluid track 25” Fluid track
Isolation
Isolation frequency
decreases with
increasing fluid
track length.
Experimental
results match
the theory well.
SPENN TATE
1 8 5 5Even Harmonic Results from Experiment
26
Baseline 20” Fluid track 23” Fluid track 25” Fluid track
Theory
Experiment
Direct load
transmission
SPENN TATE
1 8 5 5
Design Requirements and Possible Fluidic
Circuit Configurations
• Design requirements
– Symmetric circuit
• All pitch links should behave identically.
– Statically stiff
• Pitch links must transmit the 1/rev control loads.
• Fluidic circuit configurations
27
Air accumulator
Soft-tubing
accumulator
Inertance and
resistance
SPENN TATE
1 8 5 5
Add Vertical Fluid Track with Accumulator (One degree-of-freedom evident for both odd and even forcing)
28
• Ca - capacitance
• R - flow resistance
• I - inertance
• Q – flow
• p – internal pressure
m m
k k
D D
p1(t) p2(t)
Ca , pa
fin1(t) fin2
(t)
fout1(t) fout2
(t)
Ia , Ra
I, R
Q1(t) Q2(t)
Qa(t)
pm(t)
SPENN TATE
1 8 5 5Transfer Functions
• Odd forcing ( fin1 = - fin2
):
– One complex pole, one complex zero
• Even forcing ( fin1
= fin2 ):
– One complex pole, one complex zero
29
ksARsIAm
ksARsIA
F
F
in
out
222
222
1
1
)(
aaa
aaa
in
out
CAksARRsIIAm
CAksARRsIIA
F
F
/)()]([
/)()(2222
2222
222
222
1
1
2
4D
πA
SPENN TATE
1 8 5 5Example Plots – Force Transfer Function
30
Odd Forcing
Even Forcing
0 10 20 30 40-40
-20
0
20
40
|Ft1
/F1| (d
B)
0 10 20 30 40
-150
-100
-50
0
frequency (Hz)
phase a
ngle
(deg)
0 10 20 30 40-40
-20
0
20
40
0 10 20 30 40
-150
-100
-50
0
frequency (Hz)
Same as
before
(no flow into
accumulator)
D = 0.197 ft
m = 83.7 lbs
k = 35,100 lb/ft
I = 894 lb·s2/ft5
Ia = 1,030 lb·s2/ft5
Ca = 3.69e-7 ft5/lb
Fluid density:
1.55 slugs/ft3
Fluid track diameter:
0.040 ft
Flow resistance:
12,000 lb·s/ft5/ft 0 10 20 30 40-40
-20
0
20
40
|Ft1
/F1| (d
B)
0 10 20 30 40
-150
-100
-50
0
frequency (Hz)
phase a
ngle
(deg)
0 10 20 30 40-40
-20
0
20
40
0 10 20 30 40
-150
-100
-50
0
frequency (Hz)
Zero for
even
forcing frequency (Hz)
|Fo
ut 1
/ F
in1|
(dB
) |F
ou
t 1 /
Fin
1|
(dB
)
SPENN TATE
1 8 5 5
Two Vertical Fluid Tracks (Two degrees-of-freedom evident for even forcing, one for odd forcing)
31
Ia1 , Ra1
Ia2 , Ra2
Qa2(t) Qa1
(t)
Ca1 , pa1
Ca2 , pa2
fin1(t) fin2
(t)
fout1(t) fout2
(t)
SPENN TATE
1 8 5 5
32
Example Plots – Force Transfer Function
Odd Forcing
Even Forcing
0 10 20 30 40-40
-20
0
20
40
|Ft1
/F1| (d
B)
0 10 20 30 40
-150
-100
-50
0
frequency (Hz)
phase a
ngle
(deg)
0 10 20 30 40-40
-20
0
20
40
0 10 20 30 40
-150
-100
-50
0
frequency (Hz)
Two zeros
Ia1 = 4,110 lb·s2/ft5
Ca1 = 7.38e-9 ft5/lb
Ia2 = 2,060 lb·s2/ft5
Ca2 = 7.24e-7 ft5/lb
(All other values are
the same as in the
previous example.)
0 10 20 30 40-40
-20
0
20
40
|Ft1
/F1| (d
B)
0 10 20 30 40
-150
-100
-50
0
frequency (Hz)
phase a
ngle
(deg)
0 10 20 30 40-40
-20
0
20
40
0 10 20 30 40
-150
-100
-50
0
frequency (Hz)
Same as
before
(no flow into
accumulator)
frequency (Hz)
|Fo
ut 1
/ F
in1|
(dB
) |F
ou
t 1 /
Fin
1|
(dB
)
SPENN TATE
1 8 5 5
In-line accumulators
(flexible tubing)
Two In-line Accumulators (Two degrees-of-freedom evident for odd forcing, one for even forcing)
33
I3 , R3
Q3(t)
Ca , pa
fin1(t) fin2
(t)
fout1(t) fout2
(t)
I , R
Q1(t) Q2(t)
SPENN TATE
1 8 5 5
34
Example Plots – Force Transfer Function
Odd Forcing
Even Forcing
0 10 20 30 40-40
-20
0
20
40
|Ft1
/F1| (d
B)
0 10 20 30 40
-150
-100
-50
0
frequency (Hz)
phase a
ngle
(deg)
0 10 20 30 40-40
-20
0
20
40
0 10 20 30 40
-150
-100
-50
0
frequency (Hz)
Two zeros
I3 = 1030 lb·s2/ft5
Ca = 1.11e-7 ft5/lb
(All other values
are the same as in
the previous
examples.)
0 10 20 30 40-40
-20
0
20
40
|Ft1
/F1| (d
B)
0 10 20 30 40
-150
-100
-50
0
frequency (Hz)
phase a
ngle
(deg)
0 10 20 30 40-40
-20
0
20
40
0 10 20 30 40
-150
-100
-50
0
frequency (Hz)
frequency (Hz)
|Fo
ut 1
/ F
in1|
(dB
) |F
ou
t 1 /
Fin
1|
(dB
)
35
Odd Forcing Even Forcing
|Fout1 /Fin1| (dB)
0 10 20 30 40-40
-20
0
20
40
|Ft1
/F1| (d
B)
0 10 20 30 40
-150
-100
-50
0
frequency (Hz)
phase a
ngle
(deg)
0 10 20 30 40-40
-20
0
20
40
0 10 20 30 40
-150
-100
-50
0
frequency (Hz)
0 10 20 30 40-40
-20
0
20
40
|Ft1
/F1| (d
B)
0 10 20 30 40
-150
-100
-50
0
frequency (Hz)
phase a
ngle
(deg)
0 10 20 30 40-40
-20
0
20
40
0 10 20 30 40
-150
-100
-50
0
frequency (Hz)
0 10 20 30 40-40
-20
0
20
40
|Ft1
/F1| (d
B)
0 10 20 30 40
-150
-100
-50
0
frequency (Hz)
phase a
ngle
(deg)
0 10 20 30 40-40
-20
0
20
40
0 10 20 30 40
-150
-100
-50
0
frequency (Hz)
0 10 20 30 40-40
-20
0
20
40
|Ft1
/F1| (d
B)
0 10 20 30 40
-150
-100
-50
0
frequency (Hz)
phase a
ngle
(deg)
0 10 20 30 40-40
-20
0
20
40
0 10 20 30 40
-150
-100
-50
0
frequency (Hz)
0 10 20 30 40-40
-20
0
20
40
|Ft1
/F1| (d
B)
0 10 20 30 40
-150
-100
-50
0
frequency (Hz)
phase a
ngle
(deg)
0 10 20 30 40-40
-20
0
20
40
0 10 20 30 40
-150
-100
-50
0
frequency (Hz)
0 10 20 30 40-40
-20
0
20
40
|Ft1
/F1| (d
B)
0 10 20 30 40
-150
-100
-50
0
frequency (Hz)
phase a
ngle
(deg)
0 10 20 30 40-40
-20
0
20
40
0 10 20 30 40
-150
-100
-50
0
frequency (Hz)
Multi-harmonic isolation demonstrated!
SPENN TATE
1 8 5 5
Conclusions
• Converting rigid pitch links to pumpers and
coupling them via a fluidic circuit provides isolation
at multiple harmonics.
• The inertances and capacitances of the fluidic
circuit dictate the number and the locations of the
isolation frequencies.
• Experimental results validate the analytical
predictions for the simplest fluidic circuit.
36
SPENN TATE
1 8 5 5On-Going Research
• Experimental validation of proposed fluidic
circuit configurations
– Pitch link loads reduction
• Explore potential for coupled fluidic pitch
links for higher-harmonic blade pitch control
– Tailor dynamic response to natural airloads
– Noise and vibration reduction
37
SPENN TATE
1 8 5 5
Acknowledgement
The authors would like to express their appreciation for
the financial support provided by LORD Corporation, the
Applied Research Laboratory (ARL) at The Pennsylvania State
University, and Dr. Patricia Gruber, director of the ARL
Exploratory and Foundational Graduate Assistant Program.
38