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Topic 1.2: Near field spray development and coupled nozzle flow and spray simulationsAlan Kastengren*: Argonne National LaboratoryQingluan Xue: Argonne National LaboratoryJulien Manin: Sandia National LaboratoryChawki Habchi: IFPEN

Modeling PartFacilitate dynamic coupling of in-nozzle flow and external spray approachesCompare the different coupling approaches of in-nozzle flow and external sprayStudy the capability of the different modeling approaches (Lagrangian-Eulerian, Eulerian-Eulerian) and CFD frameworks (RANS, LES, DNS) for the simulation of the primary atomization and the cavitationEncourage high-fidelity simulations near nozzle sprays and liquid jet atomizationInstitutionModel approachCFD Code Compressibility Turbulence modelArgonneSingle-mixture EulerianCONVERGEIncompressible liquidCompressible gas (EOS)RANSStandard k-epsilonCMTSingle-mixture EulerianOpenFOAM (ESA)Compressible liquid (function of pressure & temperature) and gas (EOS)RANSSST k-omegaIFPENTwo-Fluid multi-species EulerianIFP-C3DCompressible liquid and gasLiquid : Stiffened gas EOS Gas : Perfect gas EOSLES SmagorinskySandiaMultiphase/multicomponent with transcritical thermodynamics Raptor (CRF-Sandia)Compressible liquid and gasLESdynamic SmagorinskyUMassSingle-mixture EulerianOpenFOAM (HRMFoam)Compressible liquid and gasLESone-eq. eddyModel descriptionECNSpray AInstitutionMesh resolutionNeedle motionInitial conditions inside injector2-D or 3-DArgonne10 m inside nozzle and first 6mm; fixed embeddingTransient needle motion with wobbleFuel filled sac and orifice; 150 MPa and 343 K in Sac and orifice

3-DHeight=200mm; D=50mm

CMTAbout 30 m uniformFixed needle lift at 100 mFuel filled sac and orifice: 150 MPa and 343 K in sac and orifice2-D axisymmetricHeight = 12 mmWidth = 6 mmIFPENNon-uniform hexahedra : Minimum cell size=(5m in the hole,2m in the seat, 15m near-nozzle region)With needle motion - Without wobble(LVF,P,T)=Chamber-needle-seat : (0.99, 150 Mpa, 343K)Sac and hole : (0.0001,2MPa,, 343K)Chamber : (0.0001,2MPa,303K)3D configuration including:The needle (15 cm) control volumeChamber (bore=6 cm, height =6cm)Sandia4 m close to injector; stretched fixed mess

Plug-flow BC used a few nozzle diameter upstream of nozzle exit; needle not simulatedGas filled sac and orifice; 6MPa and 900K3-Dheight=90mmDiameter=45mmUMassAbout 12 m cross nozzle and 50 m for sprayWithout needle motion; fixed needle lift at 100 mGas filled with sac and orifice at 2MP and 346K3-DHeight = 9 mmDiameter = 2 mmSimulation set up (Spray A)ECN5InstitutionGeometry (210675)Total number of computational cellsComputational time for first 100 microseconds (CPU hours) ArgonneLow resolution4.50 millions 12,288CMTLow resolution0.09 millions100IFPENHigh-resolution (CNRS scanned)1.10 millions6,144SandiaLow resolution50.00 millions 140,000UMassLow resolution 2.80 millions50,000Spray A: Computational time (first 100s)Note: the computational domain size, initial conditions, and needle motions are different for the institutionsECN

Computational domain (Spray A)CMTIFPENSandiaThe inflow boundary conditions are specified at upstream for all simulations Argonne

UMASS

ECNSpray A (675) modeling resultsMass flow rate at the nozzle exitFuel spray penetration vs. time (0.1% liquid mass fraction)Contour plots of projected density in the 0plane at 0.1 and 0.5 ms after actual SOIProjected fuel mass/density (ug/mm2) profiles across nozzle axis at 0.5 ms after SOIx = 0.1, 0.6, 2, 6, and 10 mm downstream to nozzle exit@ x= 0.6 and 6 mm, @ 0.75 ms and 1 ms after SOI2D contours of liquid volume fraction at x = 0.1, 0.6, 2, 6, 10 mmTransverse integrated mass profiles at 0.5 ms after SOI: x = 0.1 mm, 0.6 mm, 2 mm, 6 mm, and 10 mm Mean droplet size (SMD) at x = 1, 4, 8 mm at 0.5 ms after SOIMean SMD at the above axial positions vs. axial positionDistributions of SMD vs. radial position at the above axial positionsDynamics: peak projected density and Full Width Half Maximum (FWHM) of distribution at x = 0.1, 2, 6 mm from nozzle for entire duration of the injection event (in intervals of 20 s)ECNSpray A: Predicted mass flow rate at nozzle exitAll simulations predict similar mass flow rates as the ROI from CMTs Virtual generatorThe transient process at the start of injection is different from the modeling groups since the minimum or fixed needle lift used are differentStarting from empty sac, initial LES penetration for IFPEN (up to 10 s) compares well with the ROI from CMTs generator, but it is oscillating; LES for UMass under-predictsEnlarged @ first 0.1ms

The start of injection is defined as first evidence of liquid outside of the nozzle exitECNSpray A: spray penetrationNote: Sandia simulated conditions (Ambient=N2@900K and 60bar); Standard conditions for topic 1.2 are (Ambient=N2@303K and 20bar) The data measured by Argonne and SandiaArgonne, CMT and IFPEN: The liquid penetration defined by 0.1% mass fractionSandia: Mixture-fraction of 0.79 cut-off for the dense flow modelInitially Sandia simulations over-predict penetration but the liquid length is lowerCMT predict higher mass flow rate but lower penetration compared to Sandia Argonne over-predict penetration due to high initial minimum needle lift

ECN

Mass/area(g/mm2)

RANSLESSpray A: projected mass density 0.1ms ASOIX-raydataArgonneCMTIFPENAll simulations predict quite different liquid jetsA dense liquid core near nozzle region is captured by all simulationsAll simulations over-predict liquid penetrationRANS models tend to be overly diffusive compared to LESLES over-predict the core length and some averaging to be comparable to x-ray results

SandiaECN

Spray A: projected mass density 0.5ms ASOIX-rayArgonne

CMTIFPEN

Mass/area (g/mm2)At steady-state, the observations are consistent with earlier injection time (0.1ms)LES simulation captures the fact that spray is off-axis, because IFPEN consider a more detailed geometry with finer mesh

GeometryRANSLESUMASS

ECN

Spray A: IFPEN calculation @ 0.5ms Velocity vector plots in 3-D (left) and 2-D show the asymmetric distributionsGeometry effect on downstream spray predictedECN

Spray A: projected mass density 0.5ms ASOIArgonne

CMTIFPENRANS simulations tend to over-predict radial diffusion; LES simulations tend to over-predict liquid core lengthIFPEN consider a more detailed geometry with finer mesh and predict off-axis spray

GeometryRANSLESSandia@0.25ms

UMASS

ECN

Spray A: 2-D (YZ) Liquid Volume Fraction (LVF)Argonne

Very high LVF (close to 1) are seen from Tomographic reconstruction x-ray dataRANS results are symmetric due to symmetric geometry usedAsymmetric liquid jet is shown from LES due to asymmetric geometry used Low LVF (max=0.65) obtained LES results due to the presence of gaseous cavitation in the [0.1,2] mm region.

X=0.1mm

X=0.6mm

X=2mm

RANS

0.5ms ASOI

LESIFPENSandiaTomographicReconstruction from x-rayGeometryIFPENOthers

ECNSpray A: Radial profiles of projected density density 0.5ms ASOI 0 degree view from x-ray is asymmetric at all locationsArgonne and CMT use the same geometry, and fair comparison between the EE model is obtained Sandia and UMass LES predict quite symmetric with the geometry usedAll simulations capture the shape of the radial profile, however, significant differences in the peak values and tails (IFPEN GERM model predicts some gaseous cavitation in the [0.1,2] mm region)Note: The profiles from simulations are shifted to have the same phase as the x-ray data

0.5ms ASOIECNSpray A: Radial profiles of projected density Multiple realizations are necessary for LES to get smoother profilesSignificant difference between Argonne and CMT, although the similar EE model used (some difference in details)Suggest to use the new geometry for the RANS cases in future work

0.5ms ASOI

ECNSpray A: Projected fuel density 0.5, 0.75, 1.0 ms Argonne RANS predicts liquid jet reaches steady-state after 0.5 ms ASOI similar than x-ray experiments.IFPEN Single-realization LES shows liquid jet reaches steady state after 0.5 ms, and may be at 0.75 ms

LESRANSECNSpray A: Transverse Integrated Mass (TIM)TIM increases with axial distance, all the simulations capture this trendAll simulations over-predicted the TIM which may be due to over dispersion in the radial directionTIM at nozzle exit corresponds with the mass flow rate trends from topic 1.1CMT profile is not monotonic perhaps due to initial conditions

0.5ms ASOI

ECNSpray A: peak density & FWHM vs. timeSimilar peak values predicted by ANL and CMT at 0.1mm and 2.0mm, IFPEN under-predictedWe see variations from RANS results from CMT due to pressure wave and compressibility effectFluctuations are expected from LES @ SGS which may enhance primary atomization

PeakprojecteddensityFWHMECN

Spray A: SMD at first 50 s for IFPENSub-microns droplets observed for IFPEN simulation which is consistent with x-ray measurementECNSpray A: EE vs. LE at Argonne

Projected mass density along spray axisMass-averaged velocity along axisEulerian model is better than traditional Lagrangian approach in the near nozzle region Lagrangian simulations: 62.5m minimum resolution, blob injection model, 300,000 parcels

X-ray dataEulerianLagrangianECNSpray B

Spray B: Internal flow to external spray

Hole 1Hole 2Hole 3UMass contribution

Mass fraction of gasHole # 3 has wider distribution Phoenix geometryECNSpray B: spray velocity at 100 s ASOI

Hole #1Hole #2Hole #3

Argonne contributionPreliminary results for 3-D transient simulation at 10 microns resolutionZoomed-in view shows holes #3 has wider spray compared to other holesThe effect of geometry, needle wobble, grid alignment and resolution to be investigated in the future workCONVERGE reduced High-resolutiongeometryECNConclusionsEulerian model is suitable for the coupling nozzle and near-field dense sprayFor the first time, quantitative data on spray morphology in the near nozzle region was extracted from simulationSignificant insight from different simulation approaches were obtained when compared against experimental dataThe Eulerian simulations seem to work better than Lagrangian simulations in the near nozzle regionA few key challenging areas for modeling:Liquid compressibilityTemperature variationGas in the sacGrid resolution2-D results are good and computationally cheap, needle off-axis motion and geometric asymmetries need 3-D simulationsECNAll Contributors:

Argonne National Laboratory: Qingluan Xue, Michele Battistoni, Sibendu SomCMT - Motores Trmicos: Pedro Mart, Ral PayriIFPEN: Chawki Habchi, Rajesh KumarSandia National Laboratories: Guilhem Lacaze, Joseph C. OefeleinUniversity of Massachusetts Amherst: Maryam Moulai, David P. SchmidtAcknowledgementsECN