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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

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• 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

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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

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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

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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

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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

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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

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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

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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

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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

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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)

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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)

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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

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• Group Highlights

• 2011-2016 VLRCOE Renewal Proposal

• Individual Project Highlights

- Coupled Fluidic Vibration Isolators

for Multi-Harmonic Loads Reduction

Presentation Outline

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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

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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

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1 8 5 5Fluidic Vibration Isolator

Can isolate only

one frequency!

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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.

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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]

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Images from McGuire, D. P., “High Stiffness (“Rigid”) Helicopter

Pylon Vibration Isolation Systems,” AHS 59th Annual Forum,

Phoenix, Az., 2003.

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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

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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.

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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.

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1 8 5 5Coupled Fluidic Vibration Isolators

22

Mass

fin1(t) fin2

(t)

fout1(t) fout2

(t)

Elastomer

Piston

Fluid

track

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1 8 5 5Odd and Even Harmonic Forcing

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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)

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1 8 5 5Experimental Setup

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Isolators

Fluid

track

Shakers

Load cell

(output load)

Load cell

(input load)

Masses

Rubber

diaphragm

Stinger

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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.

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1 8 5 5Even Harmonic Results from Experiment

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Baseline 20” Fluid track 23” Fluid track 25” Fluid track

Theory

Experiment

Direct load

transmission

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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

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Air accumulator

Soft-tubing

accumulator

Inertance and

resistance

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Add Vertical Fluid Track with Accumulator (One degree-of-freedom evident for both odd and even forcing)

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• 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)

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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

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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

)

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Two Vertical Fluid Tracks (Two degrees-of-freedom evident for even forcing, one for odd forcing)

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Ia1 , Ra1

Ia2 , Ra2

Qa2(t) Qa1

(t)

Ca1 , pa1

Ca2 , pa2

fin1(t) fin2

(t)

fout1(t) fout2

(t)

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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

)

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In-line accumulators

(flexible tubing)

Two In-line Accumulators (Two degrees-of-freedom evident for odd forcing, one for even forcing)

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I3 , R3

Q3(t)

Ca , pa

fin1(t) fin2

(t)

fout1(t) fout2

(t)

I , R

Q1(t) Q2(t)

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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!

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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.

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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

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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.

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