rotorcraft center of excellence helicopter blade lag damping using embedded inertial dampers 2004...

Rotorcraft Center of ExcellenceRotorcraft Center of Excellence

Helicopter Blade Lag Damping Using Helicopter Blade Lag Damping Using Embedded Inertial DampersEmbedded Inertial Dampers

2004 National Rotorcraft Technology Center Review2004 National Rotorcraft Technology Center Review

May 3, 2005May 3, 2005

Jason S. PetrieJason S. PetrieMSMS

[email protected]@psu.edu

Dr. George A. LesieutreDr. George A. LesieutreProfessor of Aerospace Professor of Aerospace


Dr. Edward C. SmithDr. Edward C. SmithProfessor of Aerospace Professor of Aerospace



Presentation OutlinePresentation Outline

BackgroundBackground Embedded Damper ConceptEmbedded Damper Concept ObjectivesObjectives Technical ApproachTechnical Approach AccomplishmentsAccomplishments

Embedded Fluidlastic Damper DesignEmbedded Fluidlastic Damper Design Experiment Hardware and ResutsExperiment Hardware and Resuts ConclusionsConclusions


Aeromechanical InstabilitiesAeromechanical Instabilities

Major design considerations in the Major design considerations in the development of both Articulated and development of both Articulated and

Hingeless Rotor Systems areHingeless Rotor Systems are

Aeromechanical Instabilities Aeromechanical Instabilities (Ground Resonance and Air Resonance)(Ground Resonance and Air Resonance)

An effective method to avoid these An effective method to avoid these instabilities is the addition of instabilities is the addition of

Blade Lag Damping

Lag DamperLag Damper


State-of-the-Art Lag DampersState-of-the-Art Lag Dampers

Extremely High MaintenanceExtremely High Maintenance

Many Critical Flight Conditions / LoadsMany Critical Flight Conditions / Loads

Limited Life / High Cost of ReplacementLimited Life / High Cost of Replacement

Stroke Limits for Elastomeric DampersStroke Limits for Elastomeric Dampers

No Breakthrough Advances in Passive Rotor No Breakthrough Advances in Passive Rotor Blade Lag Damper Technology in the Last 20 YearsBlade Lag Damper Technology in the Last 20 Years


Embedded Inertial DampersEmbedded Inertial Dampers

Simplified Hub Design Simplified Hub Design Fewer PartsFewer PartsLess Constraints Less Constraints

Embedded Damper SystemEmbedded Damper System

Blade CavityBlade Cavity

MassMass

Elastomeric Elastomeric SpringSpring

Chordwise Motion of the Mass Chordwise Motion of the Mass Out of Phase with Rotor Blade Out of Phase with Rotor Blade

Lag MotionLag Motion

MMaa

Restoring Inertial Restoring Inertial Moment about Moment about the Lag Hingethe Lag Hinge

Large Large Moment Moment

ArmArm

Hebert, Lesieutre & Zapfe (1996 – 1998) Hebert, Lesieutre & Zapfe (1996 – 1998)


Embedded Inertial DampersEmbedded Inertial Dampers

Embedded DampersEmbedded Dampers

DamperMMkm +=+ &&

Viscous Root End DampersViscous Root End Dampers

Mkcm =++ &&&( )eRamM aaDamper −= &&


Embedded Dampers vs Root End DampersEmbedded Dampers vs Root End Dampers

Root End DamperRoot End Damper Embedded Inertial DamperEmbedded Inertial Damper

Difficulties with the Geometry Difficulties with the Geometry of the Blade or Hubof the Blade or Hub

YesYes(Especially with Bearingless Rotors)(Especially with Bearingless Rotors)

YesYes(Small Blade Cavity)(Small Blade Cavity)

Amount of Lag DampingAmount of Lag Damping Small - ModerateSmall - Moderate

Hub LoadsHub Loads Increases MIncreases MLagLag

Moderate - LargeModerate - Large

Possibly Reduce MPossibly Reduce MLagLag

(Stiff In-Plane?)(Stiff In-Plane?)

Rotor WeightRotor Weight Moderate IncreaseModerate Increase Small IncreaseSmall Increase(Utilized Leading Edge Mass)(Utilized Leading Edge Mass)

Complexity of Rotor HubComplexity of Rotor Hub IncreasesIncreases Does Not Affect HubDoes Not Affect Hub

Rotor Hub DragRotor Hub Drag IncreasesIncreases Does Not Affect HubDoes Not Affect Hub

SizeSize Moderate to LargeModerate to Large SmallSmall

High Centrifugal Force High Centrifugal Force LoadingLoading NoNo YesYes


Embedded DevicesEmbedded DevicesEmbedded mechanical Embedded mechanical devices have been devices have been successfully integrated successfully integrated into full scale rotor blades. into full scale rotor blades.

An embedded inertial An embedded inertial damper will be subject to damper will be subject to similar loads and similar loads and geometric constraints as geometric constraints as existing embedded existing embedded devices.devices.Reference: DARPA - Smart Rotor Program - 2004Reference: DARPA - Smart Rotor Program - 2004


ObjectivesObjectives

Initial research shows that embedded inertial dampers Initial research shows that embedded inertial dampers may be promising for lag damping of rotor blades. In may be promising for lag damping of rotor blades. In addition, embedded inertial dampers may utilize part of addition, embedded inertial dampers may utilize part of the leading edge weight of the blade and simplify the the leading edge weight of the blade and simplify the rotor hub considerably.rotor hub considerably.

Theoretical and experimental investigation of the feasibility Theoretical and experimental investigation of the feasibility of blade lag damping using embedded inertial dampersof blade lag damping using embedded inertial dampersDevelop a physical understanding of blade lag damping Develop a physical understanding of blade lag damping with embedded inertial dampers (modal properties, stability, with embedded inertial dampers (modal properties, stability, and response)and response)Establish design guidelines for rotor blade lag damping Establish design guidelines for rotor blade lag damping with embedded inertial damperswith embedded inertial dampers

Current Research Objectives:Current Research Objectives:


Technical ApproachTechnical Approach

Theoretical Investigation of Blade Lag Damping Using Theoretical Investigation of Blade Lag Damping Using Embedded Inertial DampersEmbedded Inertial Dampers

Develop Aeromechanical Stability Analysis for the Rotor-Fuselage-Develop Aeromechanical Stability Analysis for the Rotor-Fuselage-Damper SystemDamper SystemAeroelastic and Aeromechanical Stability Analysis of Rotor System Aeroelastic and Aeromechanical Stability Analysis of Rotor System with Embedded Damperwith Embedded DamperParametric StudyParametric Study

Analysis Validation and Experimental Investigation of Analysis Validation and Experimental Investigation of Blade Lag Damping Using Embedded Inertial DampersBlade Lag Damping Using Embedded Inertial Dampers

Isolated Blade Lag DampingIsolated Blade Lag DampingAeromechanical Stability of Rotor System Aeromechanical Stability of Rotor System

Embedded Inertial Damper Device Design and TestEmbedded Inertial Damper Device Design and Test


2004 RCOE Review2004 RCOE Review

External InteractionsExternal Interactions

Lord CorporationLord Corporation

US ArmyUS ArmySikorskySikorskyBell HelicopterBell Helicopter


2001 - 2002 Accomplishments2001 - 2002 AccomplishmentsIsolated Blade Lag Damping ExperimentIsolated Blade Lag Damping Experiment

Validated the Analytical Model and ConceptValidated the Analytical Model and ConceptRevealed the Excessive Static Displacement of the Damper MassRevealed the Excessive Static Displacement of the Damper MassIdentified the Technical BarriersIdentified the Technical Barriers

Developed an Understanding of the Design Issues Developed an Understanding of the Design Issues Related to Embedded Chordwise Inertial DampersRelated to Embedded Chordwise Inertial Dampers

Modified Design Analysis to Capture Realistic PhysicsModified Design Analysis to Capture Realistic PhysicsNon-Linear Effects of the Static Lag Angle on Damper ResponseNon-Linear Effects of the Static Lag Angle on Damper Response

Investigated Additional Conceptual Design ParametersInvestigated Additional Conceptual Design Parameters Angular and Radial Damper ResponseAngular and Radial Damper Response

Conducted an Initial Investigation of Blade Lag Damping Using Conducted an Initial Investigation of Blade Lag Damping Using Embedded Fluid Elastic DampersEmbedded Fluid Elastic Dampers

Developed a pure lag blade-embedded damper modelDeveloped a pure lag blade-embedded damper modelConducted a parametric study Conducted a parametric study


2003 Accomplishments2003 AccomplishmentsConducted Initial Simulation of Rotor Blade Loads and Hub Conducted Initial Simulation of Rotor Blade Loads and Hub Vibration in Forward FlightVibration in Forward Flight

Refined Fluid Elastic Damper Model to Include All Necessary Fluid Refined Fluid Elastic Damper Model to Include All Necessary Fluid Motion Dynamics and AttributesMotion Dynamics and Attributes

Conducted a Study of Blade Lag Damping Using Embedded Fluid Conducted a Study of Blade Lag Damping Using Embedded Fluid Elastic DampersElastic Dampers

Conducted a parametric study to determine the effects of the fluid elastic Conducted a parametric study to determine the effects of the fluid elastic element on rotor blade lag damping and the damper responseelement on rotor blade lag damping and the damper responseCompared the use of fluid elastic inertial dampers with elastomeric dampers Compared the use of fluid elastic inertial dampers with elastomeric dampers previously investigatedpreviously investigatedConducted feasibility study of embedded fluid elastic inertial dampersConducted feasibility study of embedded fluid elastic inertial dampers

Completed Initial Design of Fluid Elastic Damper with the Lord Completed Initial Design of Fluid Elastic Damper with the Lord Corporation for Full Scale and Model RotorsCorporation for Full Scale and Model Rotors


2004-05 Accomplishments2004-05 Accomplishments

Development of a New test facility to evaluate Lag DamperDevelopment of a New test facility to evaluate Lag DamperTechnologiesTechnologies

Completed Detailed Design of Fluid Elastic Damper with the Lord Completed Detailed Design of Fluid Elastic Damper with the Lord Corporation for Full Scale and Model RotorsCorporation for Full Scale and Model Rotors

Fabrication of Second Generation (Fluid Elastic) Embedded Fabrication of Second Generation (Fluid Elastic) Embedded Inertial Damper Inertial Damper

Benchtop and initial rotor testing completedBenchtop and initial rotor testing completed

Published AIAA and AHS Conference Papers, MS Thesis, andPublished AIAA and AHS Conference Papers, MS Thesis, andAIAA Journal of Aircraft paperAIAA Journal of Aircraft paper



BackgroundBackground Embedded Fluidlastic Damper DesignEmbedded Fluidlastic Damper Design Experiment Hardware and ResutsExperiment Hardware and Resuts ConclusionsConclusions


Elastomeric Damper DesignElastomeric Damper Design

( ) ( ) ( ) 0222 =++Ω+Ω−Ω+−−− ∗akaamemaamermam aoaaoaaaa ξξξ &&&&&

( )( )22

2

ω

ξω

+Ω−

−= ∗

aa

aadynamic mk

erma2

20

Ω−Ω

=∗

aa

astatic

mk

maa

Damper Equation of Motion:Damper Equation of Motion:

Damper Response:Damper Response:

aaoo

aa

mmaa

CGCG

yy

kkaa**


Elastomeric Damper Design IssuesElastomeric Damper Design Issues

1)1) The static displacement of the embedded inertial damper may be The static displacement of the embedded inertial damper may be excessiveexcessive

2)2) A low damper tuning frequency is required to produce a suitable damping A low damper tuning frequency is required to produce a suitable damping band for aeromechanical stability of systemband for aeromechanical stability of system

2

20

Ω−Ω

=∗

aa

astatic

mk

maa

( )( )22

2

ω

ξω

+Ω−

−= ∗

aa

aadynamic mk

erma

An ideal embedded chordwise inertial damper for helicopter blade lag An ideal embedded chordwise inertial damper for helicopter blade lag damping would have both a high static stiffness and a low dynamic stiffnessdamping would have both a high static stiffness and a low dynamic stiffness


Fluid Elastic DamperFluid Elastic Damper

Outer Outer CylinderCylinder MassMass

ElastomerElastomer

Inner Inner CylinderCylinder

Fluid Fluid ChamberChamber

Tuning PortTuning Port

Damper Damper AmplitudeAmplitude

Conceptual Conceptual Device Device

High Static StiffnessHigh Static Stiffness Low Dynamic StiffnessLow Dynamic Stiffness

As a result of blade lag motion, the As a result of blade lag motion, the damper mass oscillates in the lag damper mass oscillates in the lag direction and the fluid in the tuning direction and the fluid in the tuning port is pumped through the inner port is pumped through the inner chamber.chamber.

Fluid motion creates a force which Fluid motion creates a force which reduces the effective stiffness of the reduces the effective stiffness of the damper. The fluid force increases damper. The fluid force increases as the frequency of the system as the frequency of the system increases.increases.

References:References:• Halwes (Bell Helicopter) 1980Halwes (Bell Helicopter) 1980• McGuire (Lord Corp.) 1994McGuire (Lord Corp.) 1994• Kang (PSU) 2001Kang (PSU) 2001


Fluid Elastic Damper ModelFluid Elastic Damper Model

mmpp

mmttkkaa**

bb

aa

aapopo

aapp

aatt

aatoto

Mass-Spring Equivalent of a Fluid-Elastomer DamperMass-Spring Equivalent of a Fluid-Elastomer Damper

mmpp = Damper Primary Mass = Damper Primary Mass

mmtt = Tuning Mass = Fluid Mass = ALρ = Tuning Mass = Fluid Mass = ALρ

A = Tuning Port Cross Sectional AreaA = Tuning Port Cross Sectional AreaL = Length of Tuning PortL = Length of Tuning Portρ = Density of Fluidρ = Density of FluidG = b/a = Outer Cylinder-Tuning Port Area RatioG = b/a = Outer Cylinder-Tuning Port Area Ratio

Parameters:Parameters:

aatt = (G-1)a = (G-1)app

Reference: Reference: Halwes (Bell Helicopter) 1980Halwes (Bell Helicopter) 1980


Fluid Elastic Damper DesignFluid Elastic Damper Design

Tuning Tuning FrequencyFrequency MassMass

Fluid MassFluid Mass

StiffnessStiffnessTuning Port Tuning Port Area RatioArea Ratio

Establish an appropriate tuning frequency in order to maintain the Establish an appropriate tuning frequency in order to maintain the aeromechanical stability of the rotor systemaeromechanical stability of the rotor system

Step 1Step 1






Establish the amount of mass that can be used within the blade Establish the amount of mass that can be used within the blade cavity for the damper devicecavity for the damper device

Embedded inertial dampers are intended to utilize part of the leading Embedded inertial dampers are intended to utilize part of the leading edge mass or part the tip mass of a rotor blade edge mass or part the tip mass of a rotor blade

Step 2Step 2






Step 3Step 3

Set the stiffness of the elastomer such that the device will be able to Set the stiffness of the elastomer such that the device will be able to resist the centrifugal force at rotor speeds that correspond to the resist the centrifugal force at rotor speeds that correspond to the tuning frequency of the devicetuning frequency of the device






Step 4Step 4

The fluid mass and the tuning port area ratio are then determined The fluid mass and the tuning port area ratio are then determined based on the equation for the elastomer stiffness based on the equation for the elastomer stiffness






The device must be able to The device must be able to fit within the bladefit within the blade

The fluid mass and the tuning port area ratio will affect the overall The fluid mass and the tuning port area ratio will affect the overall size of the embedded fluid elastic dampersize of the embedded fluid elastic damper



Conceptual Device Conceptual Device

LORD CORPORATIONLORD CORPORATION

Practical Device Practical Device


Fluid Elastic Embedded DamperFluid Elastic Embedded Damper

•

Outer Cylinder

Inner Cylinder

Helical Tuning Port

Elastomer Element

Spar (10 lbs)Spar (10 lbs)

Damper Damper (1 lb)(1 lb)

HubHub


Lord Corp. Helical Tuning PortLord Corp. Helical Tuning Port

Enables very highEnables very highTuning port ratiosTuning port ratios(G = 50+)(G = 50+)

Suited for compactSuited for compactembedded designsembedded designs

Elastomeric Element:

The average stiffness was 2058 lbs/in at +- .010" and 5 Hz. Loss factor = .042


Benchtop Damper TestBenchtop Damper Test

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

- Clear tuning frequency at 7.5 Hz- Clear tuning frequency at 7.5 Hz- This shows fluid amplification effect- This shows fluid amplification effect


Fluid Elastic Damper ExperimentFluid Elastic Damper Experiment

Phase #2 – Bench Top TestPhase #2 – Bench Top Test

Full Scale Full Scale Embedded Fluid Embedded Fluid Elastic Inertial Elastic Inertial Damper for Damper for Commercial Rotor Commercial Rotor Blade SystemBlade System

Examine the Stiffness Characteristics of the DamperExamine the Stiffness Characteristics of the DamperValidate Analytical Model and Damper DesignValidate Analytical Model and Damper Design

Measure Static and Dynamic Measure Static and Dynamic Stiffness of DeviceStiffness of Device

Phase #1 – Spin TestPhase #1 – Spin Test

Scale Model Scale Model Embedded Fluid Embedded Fluid Elastic Inertial Elastic Inertial Damper for New PSU Damper for New PSU Lag Test StandLag Test Stand

Measure Blade Lag Damping Measure Blade Lag Damping and Frequencyand Frequency



Test Stand PropertyTest Stand Property ValueValue

Mass Per RadiusMass Per Radius mm 0.0627 slugs/ft0.0627 slugs/ft

RadiusRadius RR 4.00 ft4.00 ft

Lag Hinge OffsetLag Hinge Offset ee 10% R10% R

Non-Rotating FrequencyNon-Rotating Frequency ωωoo 4.00 Hz4.00 Hz

Blade Damping CoefficientBlade Damping Coefficient CCξξ 00

Chord (Actual)Chord (Actual) cc 0.1667 ft0.1667 ft

Chord (Theoretical)Chord (Theoretical) cc 0.600 ft0.600 ft

Number of BladesNumber of Blades NNbb 22

Rotor SpeedRotor Speed ΩΩ 0 0 ΩΩ 450 RPM 450 RPM

RotorRotor

Support Support StructureStructure

Hydraulic Hydraulic MotorMotor

Slip RingSlip Ring

HubHub

FlexureFlexure BladeBladeActuatorActuator



Steel FlexuresSteel FlexuresDictates Lag FrequencyDictates Lag FrequencyInterchangeableInterchangeableAdds StrengthAdds Strength



Embedded ActuatorEmbedded ActuatorExcites BladeExcites BladeTunableTunableAdds VersatilityAdds Versatility


Lag Damping Test RigLag Damping Test Rig


Fluid Elastic Design - Full ScaleFluid Elastic Design - Full Scale

• Simulated Annealing Algorithm (derived from RCOE Mount Task)• “Comanche-’like” rotor properties (R = 20ft, Lag freq = 3.5 Hz)• 3% critical damping• Absorber tuning Freq = 4.9 Hz (based on 220 RPM crossing)• Damper limit of 10% blade mass, 1%chord dynamic stroke


Fluid Elastic Design - Full ScaleFluid Elastic Design - Full Scale

• Target Damping Level Achieved within realistic constraints

• Other variations possible based on modified objectives


Fluid Elastic Damper- Model Test PredictionsFluid Elastic Damper- Model Test Predictions

Parameter Fluid Elastic DamperProperty

_bo (Hz) 4

mp (slugs) 0.0373 Mb

ra (ft) R

f (Hz) 5.63η0.21

mt (slug )s 0.335 mp

G 68ak′ (lbf/ft) 2.64 (104)

• Prototype damper fabricated at Lord Corp


Fluid Elastic Damper- Model Test PredictionsFluid Elastic Damper- Model Test Predictions

• Very low static displacement (no instability)

• Proper tuning freq and low dynamic stroke



BackgroundBackground Rotor Loads and Vibration SimulationRotor Loads and Vibration Simulation Embedded Damper DesignEmbedded Damper Design Elastomeric Damper vs. Fluid Elastic DamperElastomeric Damper vs. Fluid Elastic Damper Fluid Elastic Damper Design and ExperimentFluid Elastic Damper Design and Experiment ConclusionsConclusions


ConclusionsConclusions An embedded fluid elastic inertial damper is capable of An embedded fluid elastic inertial damper is capable of

producing rotor blade lag damping within a desirable frequency producing rotor blade lag damping within a desirable frequency band for aeromechanical stability of the system.band for aeromechanical stability of the system.

The static stiffness of a fluid elastic inertial damper is large The static stiffness of a fluid elastic inertial damper is large enough to maintain a reasonable static amplitude.enough to maintain a reasonable static amplitude.

aaStaticStatic / a / aoo < 5% of the Chord< 5% of the Chord

Static Instability Problem Resolved!Static Instability Problem Resolved!


ConclusionsConclusions

A new lag damping test rig was successfully designed A new lag damping test rig was successfully designed and brought onlineand brought online

Detailed Design and Fabrication of a Compact Second Detailed Design and Fabrication of a Compact Second Generation (Fluid Elastic) Embedded Inertial Damper Generation (Fluid Elastic) Embedded Inertial Damper was completedwas completed

Benchtop testing of the new device confirmed the Benchtop testing of the new device confirmed the dynamic characteristics predicted by design analysisdynamic characteristics predicted by design analysis


Publications and PresentationsPublications and Presentations

• AIAA SDM Conference (April 2002)AIAA SDM Conference (April 2002)• Lord Corporporation (May 2002)Lord Corporporation (May 2002)• Sikorsky (June 2002)Sikorsky (June 2002)• ARO Aeroelasticity Workshop (November 2003)ARO Aeroelasticity Workshop (November 2003)• Lord Corporation (February 2004)Lord Corporation (February 2004)• AIAA Journal of Aircraft Paper (Accepted March 2004)AIAA Journal of Aircraft Paper (Accepted March 2004)• AIAA SDM Conference (April 2004)AIAA SDM Conference (April 2004)• Jason Petrie MS Thesis (August 2004)Jason Petrie MS Thesis (August 2004)• Boeing, Mesa (January 2005)Boeing, Mesa (January 2005)• Lord Corporation R&D Center (March 2005)Lord Corporation R&D Center (March 2005)•• AHS Forum (June 2005)AHS Forum (June 2005)


2005 Plans2005 Plans

Complete spin testing of embedded damper devicesComplete spin testing of embedded damper devices

Complete additional analysis of vibratory hub loads Complete additional analysis of vibratory hub loads

and chordwise blade loads in forward flight and chordwise blade loads in forward flight

(Dr. Zhang)(Dr. Zhang)

Explore opportunities for industry team for further Explore opportunities for industry team for further

development of full scale prototype (including development of full scale prototype (including

designs effective for both articulated and BMR)designs effective for both articulated and BMR)


Schedule and MilestonesSchedule and Milestones

TasksTasks 20012001 20022002 20042004 20052005

STAGE ONESTAGE ONEFundamental Study Fundamental Study

System ModelingSystem Modeling

Stability AnalysisStability Analysis

Blade Lag Damping TestBlade Lag Damping Test

STAGE TWOSTAGE TWO

Model RefinedModel Refined

Parametric StudyParametric Study

Concept Design of AbsorberConcept Design of Absorber

Fluid Elastic Damper TestFluid Elastic Damper Test

STAGE THREESTAGE THREEDesign of Absorber Design of Absorber

Rotor Loads & Vibration Rotor Loads & Vibration

Report, Guideline of DesignReport, Guideline of Design

Long TermLong Term

20032003

CompletedCompleted Short TermShort Term


Helicopter Blade Lag Damping Using Helicopter Blade Lag Damping Using Embedded Fluid Elastic Inertial DampersEmbedded Fluid Elastic Inertial Dampers

Questions?Questions?

This project is co-funded by the Lord Corporation (Project Technical This project is co-funded by the Lord Corporation (Project Technical Monitors: John Heilman, Monitors: John Heilman,

Denny McGuire)Denny McGuire)


Previous AccomplishmentsPrevious AccomplishmentsBasic Study of Blade Lag Damping Using Embedded Basic Study of Blade Lag Damping Using Embedded Inertial Dampers Inertial Dampers ((Kang, Smith & Lesieutre 1999 – 2001)Kang, Smith & Lesieutre 1999 – 2001)

Rigid Blade/Embedded Rigid Blade/Embedded Damper ModelDamper Model aaoo

aa

yy

Parametric StudyParametric Study

Developed an analytical model of a rotor system with an embedded damperDeveloped an analytical model of a rotor system with an embedded damperDemonstrated that an elastomeric device could produce blade lag dampingDemonstrated that an elastomeric device could produce blade lag damping


Previous AccomplishmentsPrevious AccomplishmentsAeromechanical Stability Analysis for Rotor – Fuselage – Aeromechanical Stability Analysis for Rotor – Fuselage – Embedded Inertial DamperEmbedded Inertial Damper (Kang, Smith & Lesieutre 2001 - 2002)(Kang, Smith & Lesieutre 2001 - 2002)

Damper Mass:Damper Mass: 0.1 (M0.1 (Maa/M/Mbb) )

Location:Location: 1.0R 1.0R Tuned Frequency: Tuned Frequency: 13.95 Hz (0.8413.95 Hz (0.84ΩΩ00))

Loss Factor:Loss Factor: 0.50.5

Consider a Hingeless Rotor Consider a Hingeless Rotor System with Embedded Inertial System with Embedded Inertial

Damper (AFDD Rotor)Damper (AFDD Rotor)

Indicated that embedded chordwise dampers had the potential Indicated that embedded chordwise dampers had the potential to maintain the aeromechanical stability of helicoptersto maintain the aeromechanical stability of helicopters


Previous AccomplishmentsPrevious AccomplishmentsIsolated Blade Lag Damping Tests Isolated Blade Lag Damping Tests (Kang, Smith & Lesieutre 2001 – 2002)(Kang, Smith & Lesieutre 2001 – 2002)

Number of BladesNumber of Blades 22

Radius, inRadius, in 19.519.5

Chord, inChord, in 0.50.5

Rotation Speed, RPMRotation Speed, RPM 0-3000-300

Nonrotating Lag Freq., HzNonrotating Lag Freq., Hz 4, 6.54, 6.5

Lag Damping, % CriticalLag Damping, % Critical 0.30.3

Blade PropertiesBlade Properties

Mass (lbm)Mass (lbm) Frequency Frequency Loss FactorLoss Factor

11 0.03550.0355 8.9 Hz 8.9 Hz 0.380.38

22 0.0420.042 7.6 Hz 7.6 Hz 0.390.39

33 0.0420.042 6.3 Hz 6.3 Hz 0.420.42

44 0.04850.0485 5.5 Hz 5.5 Hz 0.410.41

Damper PropertiesDamper Properties


Previous AccomplishmentsPrevious Accomplishments

RREESSUULLTTSS

rotorcraft center of excellence helicopter blade lag damping using embedded inertial dampers 2004...

Documents