Simulation, Rheology and Efficiency of

Polymer Enhanced Solutions March 2018

AshlieMartini,UmaRamasamy,DuvalJohnsonUniversityofCaliforniaMerced

MercyCheekolu,PawanPanwar,PaulMichael

MilwaukeeSchoolofEngineering

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Background •  Higherefficiencyhydraulicfluidstypicallycontainpolymeric

additives(viscosityindeximproversorVIIs)thatthickenoilathightemperatures

•  Polymeradditivesaresusceptibletopermanentandtemporaryviscositylossduetoshear

•  Polymeradditivesthatresistsheararerequiredtoassurethattheviscosityofthefluidstaysingrade

•  However,stillnotfullyunderstoodare:•  Therelationshipbetweenshearstabilityandhydraulicefficiency

•  Themechanismsofthickeningfordifferentpolymersandtheeffectofshearonthatbehavior

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Research Strategy ProjectGoal:Bridgethegapbetweenfundamentalbehaviorofpolymerenhancedfluidsandtheperformanceofcomplexfluidpowersystems

HydraulicEfficiency

SolutionRheology

MolecularProperties

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Shear Stability

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Correlating Viscosity to Efficiency

Viscosity:•  Lowshearbeforetest•  Lowshearaftertest•  Highshearbeforetest•  Highshearaftertest•  AfterSonicShear•  AfterKRL

Efficiency:•  Flowloss•  Motortorqueloss

•  Pumpinlettorque

?

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Viscosity Index •  Measurementsperformedwithtwostraightgradefluids(AandB)andtwofluidswithPAMAVII(CandD)

•  AdditionoftheVIIreducesflowloss

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Measurements •  PermanentViscosityLoss

•  Sonicshearstabilitytest•  KRLtest•  Lowshearviscosityofsamplestakenduringdynamometertesting

•  TemporaryViscosityLoss•  Viscosityofsamplespriortotestingmeasuredatarangeoftemperatures

andshearrates

•  HydraulicEfficiency•  Flowloss•  Motortorque•  Inputpower

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Permanent Viscosity Loss •  FluidswithVIIhavesignificantviscosityloss,butthemoreshearstablepolymer(D)performsbetter

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Temporary Viscosity Loss

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Danfoss Series 45 Pump Modified ISO 4409 Axial piston pump Variable displacement 50⁰C and 80⁰C inlet temp Danfoss Series 90 Motor Modified ISO 4392-1 Axial piston motor 1000 to 4000 psi 1 to 1400 RPM

Dynamometer

•  Studied change in system flow losses over time •  Flow losses = internal leakage that is lost kinetic energy that doesn’t produce work •  Flow losses = pump and motor case drains + pressure compensator + valves •  35 Data sets •  328 combinations of pressure, speed and temperature for each data set •  11,480 measurements

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Circuit Schematic

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Flow Loss •  Measurementsperformedwithtwostraightgradefluids(AandB)andtwofluidswithPAMAVII(CandD)

•  AdditionoftheVIIreducesflowloss

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Model Theperformanceofhydraulicpumpsandmotorsisaffectedbyfriction,viscousdrag,fluidcompressibilityandpressuredrivenflowlosses

𝑄↓𝑙 = 𝐶↓𝑜 + 𝐶↓𝜇 ∆𝑃/𝜇+ 𝐶↓𝜌 √�∆𝑃/𝜌 + 𝐶↓𝐾 𝜔∆𝑃/𝐾

LaminarFlowLoss TurbulentFlowLoss CompressibilityLoss

Flowlossdatawasfittothisequationwithviscositiesmeasureddifferentways

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Model Fit •  ExampleofdatafitwithviscosityfromtheSonicSheartest•  Repeatedwithothermeasuresofviscosityandgoodnessof

fitquantifiedforeach

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Shear Rate? •  Flowlossesofusedfluidscorrelatebetterwithviscosity

measuredathighershearrates,i.e.subjecttotemporaryviscosityloss

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Motor Torque Losses •  Torquelossesinthemotorarenotproportionaltoviscosity,but

ratherexhibitspeed-dependentbehavior

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Pump Inlet Torque •  Contrarytoconvention,anincreaseinviscosityatlower

temperaturereducestorqueduetolowerleakageflow

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Summary of Power and Losses •  Pumpefficiencyexhibitsnegligiblechangewithinputpower•  Thisillustrateswhy“losses”tendtobeabetterindicatorofthe

effectsoffluidonsystemperformancethanefficiency

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Simulation Contribution •  Experimentalresultsclearlyshowtheimportantroleofviscosity

modifiersinhydraulicefficiency•  Howdoviscositymodifiersperformthisfunctionandcanthey

befurtheroptimizedtoimproveperformance?

NoVM PAMAVM•  CoilExpansion

•  Aggregation/Association

•  Alignment

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Simulation Tool-Set RandomEthylene-PropyleneCopolymer(OCP)

PolydodecylMethacrylate(PMA)

Styrene-Butadiene(SB)

Polyisobutylene(PIB)

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Testing the Expansion Mechanism Modelpolymerinbasefluidmoleculesandsimulatedynamics

Calculatetheradiusofgyrationfromatompositions

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Testing the Expansion Mechanism Characterizethedistributionofcoilsizesduringthesimulationat40Cand100C

PAMA OCP

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Testing the Expansion Mechanism

M.J. Covitch, K.J. Trickett, Adv. Chem. Eng. Sci., (5), 134-151 (2015)

C. Mary et al., Tribol. Lett., (52) 3, 357-369 (2013)

OCP PAMA1 PAMA2 OCP

PAMA

OCP

PMA

ExperimentsusingdirectandindirectcoilsizemeasurementsandsimulationsshowPAMAexpandswithtemperaturebutOCPdoesnot

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Publications •  PMichael,MCheekolu,PPanwar,MDevlin,RDavidson,DJohnson,A

Martini,TemporaryandPermanentViscosityLossCorrelatedtoHydraulicSystemPerformance,TribologyTransactions,InPress

•  MLen,USRamasamy,SLichter,MartiniA,(2018)ThickeningMechanismsofPolyisobutyleneinPolyalphaolefin,TribologyLetters,66,5

•  USRamasamy,MLen,AMartini,(2017)CorrelatingMolecularStructuretotheBehaviorofLinearStyrene–ButadieneViscosityModifiers,TribologyLetters,65,147

•  AMartini,USRamasamy,MLen,ReviewofViscosityModifierLubricantAdditives,TribologyLetters,InPress(InvitedReview)

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Thank you for your kind attention!

Acknowledgements

•  CenterforCompactandEfficientFluidPower

•  NationalFluidPowerAssociation•  PascalSociety•  DonorsoftheAmericanChemicalSocietyPetroleumResearchFund(#55026-ND6)