Identification And Evaluation Of Near-term Opportunities .
Identification and evaluation of near-term opportunitiesfor efficiency improvementPresented by K. Dean EdwardsRobert M. WagnerRon L. GravesOak Ridge National LaboratoryDOE Management Team:Steve Goguen, Gurpreet SinghU.S. Department of EnergyOffice of Vehicle Technologies14th Diesel Engine-efficiency and Emissions Research Conference4-7 August 2008Managed by UT-Battellefor the Department of Energy
IntroductionIdentifyIdentify andand prioritizeprioritize opportunitiesopportunities forfor efficiencyefficiencygainsgains inin internal-combustioninternal-combustion enginesengines throughthroughcompletecomplete thermodynamicthermodynamic analysisanalysis ofof experimentalexperimentalengineengine datadata andand modelmodel simulations.simulations.Near-termNear-term PathwaysPathways Waste-heatWaste-heat recoveryrecovery–– BottomingBottoming cyclescycles–– Turbo-compoundingTurbo-compounding–– Thermo-electricsThermo-electrics ReduceReduce heatheat lossloss–– AdvancedAdvanced combustioncombustion modesmodes–– AdvancedmaterialsAdvanced materialsLong-termLong-term PathwaysPathways ReductionReduction ofof combustioncombustion alcombustionwith unconventional combustion–– Counter-flowCounter-flow PreheatingPreheating withwith ChemicalReaction and Thermo-Chemical RecuperationRecuperation(CPER-TCR)(CPER-TCR)–– StagedStaged CombustionCombustion withwith OxygenOxygen TransferTransfer(SCOT)(SCOT) ReduceReduce frictionfriction losseslosses–– AdvancedAdvanced lubricantslubricants–– ElectrificationElectrification ofof accessoriesaccessoriesPerformPerform thermodynamicthermodynamic analysisanalysis toto evaluateevaluatepotentialpotential successsuccess ofof thethe recoveryrecovery techniques.techniques.2Managed by UT-Battellefor the Department of Energy
Light-duty diesel platforms at ORNLMBMB 1.7-L1.7-L 4-cylinder4-cylinder common-railcommon-railGMGM 1.9-L1.9-L 4-cylinder4-cylinder common-railcommon-rail 19991999 versionversionWAVEWAVE modelmodelModificationsModifications includeinclude VGT,VGT, electronicelectronic EGR,EGR, EGREGRcooler,cooler, throttlethrottleHighHigh- andand low-pressurelow-pressure EGREGR circuitscircuitsFull-passenginecontrolFull-pass engine controlVariableVariable CRCR versionversion availableavailableNumber of Cylinders3Managed by UT-Battellefor the Department of Energy 420052005 andand 20072007 versionsversionsGT-PowerGT-Power modelmodelOEMOEM hardwarehardware includesincludes VGT,VGT, electronicelectronic EGR,EGR, EGREGRcooler,cooler, throttlethrottle“Open”“Open” ECUECU andand full-passfull-pass engineengine controlcontrol unitunitCommonplatform:ORNL(multi-cyl),SNLCommon platform: ORNL (multi-cyl), SNL (1-cyl(1-cyl optical),optical),UWiscUWisc (1-cyl(1-cyl opticaloptical andand metal)metal)Number of Cylinders4Bore, mm80.0Bore, mm82.0Stroke, mm84.0Stroke, mm90.4Compression Ratio19.0Compression Ratio17.5Rated Power, kW66Rated Power, kW110Rated Torque, Nm180Rated Torque, Nm315
Overview of thermodynamic analysis of experimental data – Mass flow rates of fuel, air, andcoolant– Brake work and indicated work(from cylinder pressure)– Exhaust composition– EGR mass fraction– Temperatures: exhaust, EGR,block, & coolant n of fuel energy/availabilityapportioned to––––––4: thermocouple: pressure transducer: gas samplingAnalysis based on experimentalmeasurements ofBrake workExhaustFriction lossesEGR and charge-air cooler losses(gas-side)Losses to coolant losses (from block)“Other”: combustion irreversibility,convective and radiant heat loss,mixing, flow losses, etc.Managed by UT-Battellefor the Department of EnergyAirExhaustWaterLFE
Overview of thermodynamic analysis for model results Thermodynamic analysis is performed on the engine system as a whole and onindividual components (turbocharger, intercooler, individual cylinders, etc.). Our analysis requires evaluation of property balances for mass, energy, entropy, andavailability (a.k.a. exergy) for all elements in the engine model at all timesteps in thecycle simulation. WAVE provides all information necessary to perform the analysis except for entropyand availability which must be calculated from the working-fluid composition andthermodynamic properties. GT-Power provides entropy and (as of Version 6.2, Build 9) physical availability flux.The addition of chemical availability, control-volume availability (including incylinder), and user-defined dead-state is planned for a future release.Q.m, h, ke,s, af5Managed by UT-Battellefor the Department of Energy.W.m, u,ke, s,am, h, ke,s, af
Governing equations (neglecting potential energy)Mass BalanceεError terms, & , in the numericalsolutions for mass and energyare on the order of theconvergence criteria for thesolver.dm m& m& ε&massdt CV inoutEnergy Balanced [m(u ke )] m& (h ke ) m& (h ke ) Q& W& ε&energydtinoutCVEntropy BalancedSdtCVQ&I& m& s m& s Tw inTooutIrreversibility is a measure ofthe useful work that could havebeen done, but was not.I& To S& genAvailability (Exergy) Balance To & &dAdV 1 Q W Po m& a f m& a f I&dt CV Tw dt in outAvailability is the potential to douseful work due to physical andchemical differences betweenthe working fluid and thesurroundings.where,ACV m [achem (u uo ) To (s so ) ke] Po (V Vo )a f achem (h ho ) To (s so ) ke6Managed by UT-Battellefor the Department of Energy Subscript o denotes dead-state(i.e., ambient) properties. Tw wall temperatureEdwards, et al., SAE 2008-01-0293
Evaluation of thermodynamic propertiesProperties not provided by GT-Power and WAVE are determined from the NIST-JANAFtables for each gaseous component and known fuel properties. Dead state defined as air at ambient (not Standard) conditions–Working fluid composition frozen–Properties of working fluid at ambient conditions evaluated using NIST-JANAF tables–Chemical availability accounts for differences between chemical composition of the workingfluid and ambient environment (air)Chemical availability only dependent upon chemical composition–Sum of chemical availability of each gaseous species and fuelo–Chemical availability of each gaseous specieso–Ahrendts (1977) “Die Exergie Chemisch Reaktionsfähiger Systeme”, see Bejan, Tsatsaronis, Moran (1996)Chemical availability of fuel based on lower heating value and fuel composition (H/C, O/C, S/C)o7Bejan, Tsatsaronis, Moran (1996) Thermal Design and OptimationRodríguez (1980) “Calculation of Available-Energy Quantities” Thermodynamics – Second Law Analysis,American Chemical Society Symposium, Series No. 122.(u ke) (h ke) PV Total internal energy: Wall temperature of each element used as boundary temperature at which heattransfer from that element occursManaged by UT-Battellefor the Department of EnergyEdwards, et al., SAE 2008-01-0293
Assessment of opportunities to recover and reduce losses Recovering exhaust availabilityrequires cycle compounding. Reducing heat transfer dependsupon the materials and combustiondetails and results in increasedexhaust availability. Recovering wall heat transferrequires cycle compounding oncoolant (e.g., refrigerant in vaporpower cycle). Reducing the combustionirreversibility requires afundamental change to thecombustion process.8Managed by UT-Battellefor the Department of EnergyOctane-fueled spark-ignition engineCaton, SAE 2000-01-1081ENERGY or AVAILABILITY (%)Largest thermodynamic losses inIC engines are typically due towall heat transfer, unrecoveredexhaust energy, and combustionirreversibility.100Destructiondue toInlet ctiondue toCombustion(20.6%)8060(40.0%)Net TransferOut Dueto atedWork20(29.7%)(30.6%)01Energy(1st Law)2Availability(2nd Law)
Prioritizing waste-heat recovery efforts 1st Law analysis shows that 14% of the fuel energy is lost by heat transfer through the exhaustmanifold and intercooler (7% each) suggesting equal priority. 2nd Law analysis shows that 4% of fuel availability is lost by radiant and convective heat lossthrough the exhaust manifold. Less than 1% of fuel availability is lost through the intercooler. Unlike the charge air, the hot exhaust gases in the exhaust system have significant availabilitywhich should not be squandered through unrecoverable heat loss to the environment.Tintake 22oC, Un-insulated exhaust manifold, peak efficiency, WAVE MB modelnd Law22ndLaw AnalysisAnalysis11stst LawLaw AnalysisAnalysis 1%7%Intercooler Turbo17%Exhaust Flow7%Exh Manifold2%Friction40%HeatLoss 1% each3%7%Intercooler, Throttle,TurboEGR Valve & Cooler, Exh ManInt Man, Tailpipe10%Exhaust ck & Head2%Tailpipe1%EGR Cooler9Managed by UT-Battellefor the Department of Energy4%Exh Man41%Brake Work13%HeatLoss9%Block & HeadEdwards, et al., SAE 2008-01-0293 1% eachTurbo, Intercooler,Throttle, Int Man,EGR Valve & Cooler38%Brake Work
Managing exhaust energy for WHR and aftertreatment Insulating the exhaust manifold to reduce heat loss produces an exhaust streamwith more energy and higher availability to maximize potential gains from a wasteheat recovery system or to increase exhaust gas temperarture for downstreamaftertreatment devices. Note that in this example, the VGT rack position was increased to maintainequivalent boost and mass flow.Tintake 22oC, peak efficiency, WAVE MB modelUn-insulatedUn-insulated exhasutexhasut manifoldmanifold 1% each3%7%Intercooler, Throttle,TurboEGR Valve & Cooler, Exh ManInt Man, TailpipeInsulatedInsulated exhaustexhaust manifoldmanifold10%Exhaust rboExh Man14%Exhaust Flow 1% eachIntercooler, Throttle,EGR Valve & Cooler,Int Man, Tailpipe2%Friction25%Cylinders4%Exh Man13%HeatLoss36%Irreversibility9%Block & Head10 Managed by UT-Battellefor the Department of Energy 1% eachTurbo, Intercooler,Throttle, Int Man,EGR Valve & Cooler38%Brake Work10%HeatLoss9%Block & Head 1% each Turbo, Intercooler,Throttle, Int Man, EGR Valve& EGR CoolerEdwards, et al., SAE 2008-01-029338%Brake Work
Experiments make use of modal conditions representative oflight-duty diesel drive cycle Considered representative speed-load points for light-duty diesel engines. Does not include cold-start or other transient phenomena. Represents method for estimating magnitude of drive-cycle emissions.PointSpeed / LoadWeightFactorDescription11500 rpm / 1.0 bar400Catalyst transitiontemperature21500 rpm / 2.6 bar600Low speed cruise32000 rpm / 2.0 bar200Low speed cruise withslight acceleration42300 rpm / 4.2 bar200Moderate acceleration52600 rpm / 8.8 bar75Hard accelerationFor more information:SAE 1999-01-3475SAE 2001-01-0151SAE 2002-01-2884SAE 2006-01-3311 (ORNL)ORNLORNL isis workingworking withwith thethe ACECACEC TechTech TeamTeam toto proposepropose aa newnew setset ofof operatingoperating conditionsconditions forfor entsfromadvancedenginetechnologies.in characterizing efficiency & emissions improvements from advanced engine technologies.11 Managed by UT-Battellefor the Department of Energy
Analysis of representative speed/load modal pointsPeak Efficiency, 2250 rpm, 18 barMultiple strategies for waste-heat recovery may beneeded to improve efficiency over the wholespeed/load range due to variations in quality ofavailability streams.11stst LawLawFrictionExhaustEGR CoolerOther (Heat Loss, Combustion Irreversibility, etc.)1500 rpm, 2.6 bar49.2%40.5%1.1%Brake Work1500 rpm, 1.0 bar40.4%27.5%Fraction of Fuel Energy/Availabilitynd Law22ndLaw31.0%1.1%2000 rpm, 2.0 bar2300 rpm, 4.2 bar9.2%2600 rpm, 8.8 bar1st .3%14.3%17.1%11.4%14.5%10.6%9.9%2nd 2%12 Managed by UT-Battellefor the Department of Energy24.4%6.8%9.0%2.1%11.5%7.7%1.9-L GM engine, experimental data6.3%5.7%2.0%7.1%2.8%2.2%
Energy and availability maps Energy and availability maps show how fuel energy and availability are apportionedacross the speed/load range. Similar maps can be made for each energy/availabilty stream.Exhaust Availability(Fraction of Fuel Input)(Fraction of Fuel Availability)0.400.40Exhaust Energy0 .30 .3 20.3 00.3 00.2 00.100 .40 .3 80.3800 .340 .3 80 .3 240 .2 00.34000 .480.340 .30.360 .40.380.360.360.380 .3 60.360 .30 .30 .3 240 .3 20.3 00 .2 00.3 40.3 00 .2 00.10Solid contour lines correspond to BTE, GM 1.9-L engine data13 Managed by UT-Battellefor the Department of Energy60160 .40 .40.310.30 .40.3 60 .3
Potential improvements in BTE estimatedwith partial recovery of exhaust availability Maps of brake thermal efficiency (BTE). All on same scale. Estimated BTE of combined engine/WHR system usingexhaust availability estimations from across thespeed/load range. WHR efficiency is assumed fixed across the speed/loadrange for simplification of the estimates. Note that WHR may change the BTE/speed/loadrelationship.30% recovery14 Managed by UT-Battellefor the Department of Energy50% recoveryContours correspond to BTE, GM 1.9-L engine dataBase condition100% recovery
Must balance energy use and recovery over speed/load rangeEGR HXNEngine CoolantShaft WorkExhaust HXNTurboExhaustAftertreatmentAir15 Managed by UT-Battellefor the Department of EnergyAir HXN
PCCI combustion approach Baseline conditions approximated with OEM calibration parameters. HECC modes achieved withHigher dilution, higher fuel injection pressure, & proper combustion phasing (singleevent, timing before but near TDC).BSFC similar for OEM & HECC calibrations.908886848280270HECC (PCCI)Heat Release RateAVL Noise (dB)92BaselineHeat Release RateExample from MB 1.7-L engine(1500 rpm, 2.6 bar BMEP)275280285BSFC (g/kW-hr)290295-40-20020406080Crank Position (CAD)16 Managed by UT-Battellefor the Department of Energy100 120
Comparison of combustion modes Availability recovered in one component tends to show up as losses elsewhere inthe system. In this example, transitioning to High-Efficiency Clean Combustion (HECC) modereduces losses through the exhaust but increases losses through the EGR coolerand to the coolant.1500 rpm, 2.6 bar BMEP – 2nd Law Analysis of Experimental Data from MB 1.7-LConventionalConventionalHECCHECCEGR CoolerEGR % Exhaust52.4%Exhaust4.2% EngineCoolant2.2%2.8% EngineCoolant8.6%Friction &Accessories10.9%Friction &AccessoriesOther includes combustion irreversibilities, heat transfer, mixing, etc.17 Managed by UT-Battellefor the Department of Energy
Combustion irreversibility is the least understood of themajor losses Irreversibility is caused bycombustion reactions occurring farfrom chemical & thermalequilibrium (unrestrained chemicalreactions)Molecular-scale gradients result inentropy generation,* reducingavailability–Internal heat transfer–Molecular rearrangements–Gradients in chemical potentialdSdtCV Q& I& m& s m& s TToinoutwPath IndependentTcoolPathDependentTmaxTadiabaticLost availability can never berecovered (2nd Law)Daw, et al. (2006) International Journal of Hydrogen Energy, 3118 Managed by UT-Battellefor the Department of Energy* Dunbar & Lior, (1994) Combustion Science and Technology, 103.
Combustion irreversibility is essentially unchanged forHCCI and HCCI-like modes Comparison of conventional and HCCIH2 combustion in adiabatic engine Even with homogeneous combustion(no macroscopic spatial gradients),irreversibility substantial Reactions still occurring far fromchemical and thermal equilibrium(unrestrained) (HCCI)(flame)ExhaustavailabilityPiston workEntropy generation and availabilityloss effectively unchangedCombustionirreversibilityChakravarthy, et al. (2006) “Second Law Comparison of Volumetric and FlameCombustion in an Ideal Engine with Exhaust Heat Recovery,” The Combustion Institute2006 Central States Meeting.19 Managed by UT-Battellefor the Department of Energy
Combustion irreversibility minimized by stoichiometricfueling, but at expense of reduced expansion workCombustion irreversibility isreduced for stoichiometricequivalance ratio.––– Reactions still unrestrainedbut with fewer moleculesLess dilution of reactionproductsLower entropy generationEffect is masked in traditionalICEs by reduced expansionwork extraction forstoichiometric mixture.Recovering higher availabilityfrom stoichiometriccombustion will require cyclecompounding.1Fraction of Original Fuel Energy irreversibility0.9total bility0.70.6ideal gas expansion work0.50.40.50.60.70.8Fuel-to-Air Equivalence Ratio0.9Plot details: Ideal adiabatic combustion of iso-octane and air Fully expanded Otto cycle with initialcompression ratio 1020 Managed by UT-Battellefor the Department of Energy1
Summary Operation across the speed-load range produces sizable variations in theavailability of the different waste energy streams. Management strategies will be needed to recover energy from multiple wastestreams and to balance the different thermal requirements of aftertreatment,turbochargers, advanced combustion modes, and waste-heat recovery efforts.Higher-impact paths:Lower-impact paths: Waste heat recovery–From multiple streams (exhaust, EGR,coolant)–Turbocompounding–Bottoming cycles–Over-expanded cycles Stoichiometric combustion (withexhaust heat recovery) Reduced wall heat transfer (withexhaust heat recovery) Staged combustion, with nearequilibrium reactions (reduction ofcombustion irreversibility)21 Managed by UT-Battellefor the Department of EnergyHCCI, HECC, PCCI, etc.–Unless resulting in reduced heat lossesor aftertreatment fuel penalties Lean-burn Matching reaction rates to workextraction CR 10
Primary Contacts Ron Graves (FEERC Program Manager)gravesrl@ornl.gov, 865-946-1226 Robert Wagner (Light-duty diesel program)wagnerrm@ornl.gov, 865-946-1239 Dean Edwards (Thermodynamic analysis, GT-Power/WAVE simulation)edwardskd@ornl.gov, 865-946-121322 Managed by UT-Battellefor the Department of Energy
Properties of working fluid at ambient conditions evaluated using NIST-JANAF tables – Chemical availability accounts for differences between chemical composition of the working fluid and ambient environment (air) Chemical availability only dependent upon chemical composition – Sum of chemical availability of each gaseous species and fuel o
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