automotive fuel tank sloshing analysis

8/11/2019 Automotive Fuel Tank Sloshing Analysis

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Fuel Tank Sloshing Simulation Analysis

utilizing MSC.Dytran

Igor Demin , TI Automotive

Edwin Spencer , MSC Software


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Abstract

Predicting sloshing noise as early as possible during the design process hasbecome an increasingly desired simulation for fuel tank suppliers. It enablessuppliers to build products directly to customer specifications, at the minimumcost, in a shorter timeframe. Ideally, it needs to be run during the quote stage toavoid hidden obstacles later. All known solutions take from five to nine days to runthe slosh test to completion. The method that has been developed at TI

Automotive together with MSC Software is based on utilizing MSC.Dytran as aHydro code and requires only few hours to run. It allows reasonably quicksimulations to study the effects of varying parameters such as the accelerationfield, fuel level and internal baffles on the noise generated.

The results can be presented as an animation of the fuel sloshing in the tankand/or pressures on the surface of the tank. The time histories of points on the

tank can be used to help predict sound problems within the tank.


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TI Automotive Business Profile

Only global supplier of fully integrated automotive fluid systems.

The leading supplier of fluid carrying systems applications to automakersworldwide.

Approximately two-thirds of the worlds vehicles built every year rely on fluidstorage, carrying and delivery technology from TI Automotive. TI Automotive products and technology are present on over eighty of the top one

hundred vehicle platforms.

Annual sales of $2.5B

Employs over 18,000 people Has more than 130 facilities

Present on 6 Continents

Operates in 28 countries


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TI Automotive Market Strategy

Automotive Fluid Systems

HVAC FluidSystems

Powertrain

Components

TankSystems

Fluid CarryingSystems

Pump & ModuleSystems


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DIVE: Design Intelligently in a Virtual

Environment

Blow Mold

Simulations

Reverse

Design and

Engineering

Drop Test

Simulations

Sag AnalysisSimulations

Pressure

Vacuum Test

Simulations

Burst Test

Simulations

IV TM

Design / Engineering

and Manufacturing
http://localhost/var/www/apps/conversion/tmp/Documents%20and%20Settings/bbrandner/DOCUME~1/tjp/LOCALS~1/Temp/TEMP/Sag.avihttp://localhost/var/www/apps/conversion/tmp/Documents%20and%20Settings/bbrandner/DOCUME~1/tjp/LOCALS~1/Temp/TEMP/ReverseEng.jpghttp://localhost/var/www/apps/conversion/tmp/Documents%20and%20Settings/bbrandner/DOCUME~1/tjp/LOCALS~1/Temp/TEMP/PV.jpghttp://localhost/var/www/apps/conversion/tmp/Documents%20and%20Settings/bbrandner/DOCUME~1/tjp/LOCALS~1/Temp/TEMP/Sag.avihttp://localhost/var/www/apps/conversion/tmp/Documents%20and%20Settings/bbrandner/DOCUME~1/tjp/LOCALS~1/Temp/TEMP/Burst.avihttp://localhost/var/www/apps/conversion/tmp/Documents%20and%20Settings/bbrandner/DOCUME~1/tjp/LOCALS~1/Temp/TEMP/Drop.mpghttp://localhost/var/www/apps/conversion/tmp/Documents%20and%20Settings/bbrandner/DOCUME~1/tjp/LOCALS~1/Temp/TEMP/BlowMold.avi


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Process Standardization

Standard processwizards

Make complex simulationprocesses to everydayengineers

Ensure reliable resultsthrough use of validatedmethods

Uses technology fromspecialized solutions insingle common interface

Molding simulation

Nonlinear simulation

Thermal-structural

simulation


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Process Automation

Automatically meshes CADgeometry

Automatically runsmanufacturing simulation

Automatically runs standardtests to each OEM specs

Static Loads

Drop Test

Sag Test

Burst Test

Pressure-Vacuum Test

Automatically couples multi-

discipline simulations as molded wall thicknesses

Fluid-structure interactions

Thermal-structural interactions

Automatically extracts results


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Data Management

Automatically captures models andresults for all simulations

Organizes simulation information toenable evaluation of multipledesign variations efficiently

Stores all information in centraldatabase


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Sloshing Simulation

9-Oct-14 99-Oct-14 9

Based on physical testing

Developed in joint efforts between TI Automotiveand MSC

Optimized upon available resources and provenknowledge

Requires additional software to post process
http://localhost/var/www/apps/conversion/tmp/scratch_4/Sloshing_Study.pdfhttp://localhost/var/www/apps/conversion/tmp/scratch_4/Nissan-sae.pdfhttp://localhost/var/www/apps/conversion/tmp/scratch_4/audi_sloshtest.pdfhttp://localhost/var/www/apps/conversion/tmp/scratch_4/XMA%2008MAR19%20Bench%20slosh%20noise%20test(YEKIM).pdf


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Simulation Challenges CAD/CAE disconnect

Translations and healing from native CAD to finite elements

Limited Simulation Capability Verification onlyno design guidance

Limited simulation resources1 expert analyst

Complex Simulation Requirements Multi-discipline interaction

Manufacturing & performance dependencies (as molded thickness)Fluid-Structure Interaction

Thermal-Structural Interaction

Highly nonlinear effectsManufacturing simulationmaterial phase change

Drop TestExplicit dynamics & contact

Sag/Creepnonlinear material behavior

Multiple specialized tools (software) required

Predicting design behavior is a best guess on past experience

It is knowledge that many times was not captured and regarded as an Art

Frequent late design changes

Many physical prototypes and tests required


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Fuel Tank Sloshing Test

11


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Fuel Tank Sloshing Noise Types

Low Frequency Hit Noise

This is created by wave frontshitting the tank wall. It tends to behigher sound pressure levels thanthe splash noice and is moreprominent at lower frequencies.The sound transmitted into the

passenger compartment dependsstrongly on the acousticcharacteristics of the wall, such asits damping and Eigenmodes.

High Frequency Splash Noise

This is created by two wave frontssloshing into each other. It tendsto have lower sound pressure levelthan hit noise and is more

prominent at higher frequencies.

9-Oct-14 139-Oct-14 13

CAE 11-002


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Fuel Tank Sloshing Noise Types

Low Frequency Clonk Noise

This is created when sloshing fluidcompresses an air volumeabrubtly. This noise has the lowestfrequency compared to hit and

splash

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Slosh Test Customer Specs

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CAE 11-002


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Slosh Test Customer Specs

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The CAE analysis is performed as per specification below:

Fuel slosh noise : At 100%, 80% and 50% of nominal volume, apply fuel tank in the horizontal

state the forward/backward acceleration of 0.2g, 0.4g, 0.6g and thenforward moving with back incline of 3and backward moving with frontincline of 3should be maintained at the end of acceleration.

The pressure gauge should be installed equally spaced at front 3 points,upper 9 points, back 3 points of the upper PNL of fuel tank

The pressure change (difference between first pressure and peak pressure)at each side should be less than 1000Pa.


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Slosh Test Simulation Workflow

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Tank

Math

Model

TankShellMesh

SloshModelPrep

TankFEModel

Slosh_run

.dat

EulerianMeshPrep

CouplingSurfacePrep

SloshEulerianMesh .bdf

SloshCouplingFaces .bdf

SloshSimulation

slosh_run.out

slosh_runeuler .arc

Slosh_run.ths

Slosh.mpg

slosh_run

tank .arc

Timegraph

included

included

included

ResultsMSC.Patran MSC.Dytran

CADMSC.Patran


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Slosh Test Simulation Workflow

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CAE 11-002

Tank Math Model obtained from CAD has to be prepared for meshing.

The pre-processor used is MSC.Patran and the analysis solver used is MSC.Dytran.

It takes 14 steps in MSC.Patran from creating of fuel tank mesh to writing out aMSC.Dytran analysis deck.

If the fuel tank has a baffle it essentially splits the Euler domain in two, therefore the

adaptive Euler mesh is defined twice to cover the fluid on either side of the baffle. The MESH cards define the adaptive Euler mesh for the fluid domains on either

side of the tank which gets generated automatically for each tank location during theanalysis.

The COUPLE card defines the coupling surface between each Euler domain andthe fuel tank.

The tank is treated as rigid, therefore tank deformations are not accounted for in thisanalysis.

The entire process ( pre-processing , solving, post-processing) takes less than 15hrs


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Dytran Solver

Dytran uses the Eulerian FV approach to simulate the fluid flow and

Lagrangian FE solver for the Structure.

Gas Tank or other structure entities functioning as flow boundaries arerepresented by Lagrangian surface (shell or membrane) elements.

Dytran adopts a tightly-coupled approach to tie the motion of the structure withthe fluid motion.

This Coupling algorithm does not change Euler mesh connectivity therefore iscomputationally efficient.

The Euler mesh adaptively changes based on the motion of the fuel tank. TheEuler mesh is created by the solver during run time.

Dytran allows to model multiple compartments tied to their own fluid domain.

All the aforementioned traits make Dytran particularly suited for SloshingAnalysis.


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Fluid-Structure Interaction

Lagrangian and Eulerian meshes can be used in the same analysis and

coupled together allowing the solution of Fluid-Structure Interaction problems.

Arbitrary Motion

The coupling surfaces can be of any shape and can undergo arbitrary motions

The Euler mesh loads the structure resulting in new grid pointaccelerations and velocities for the structural nodes.

The Lagrange mesh acts as a boundary to the flow of materials in theEuler mesh. Consequently, the volume of each fluid element changesresulting in change in density and pressure of the fluid element.

FSI - General Coupling


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Sloshing Analysis Results

Maximum Fluid Pressure (Pa) versus Time (Sec.)


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CUSW AWD 64L Sloshing Analysis No Baffle

Pressure (Pa) versus Time (Sec.)


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CUSW AWD 64L Sloshing Analysis With Baffle

Pressure (Pa) versus Time (Sec.)


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Sloshing Analysis Results

Tank Surface Pressure and Fluid Pressure (Pa)

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Sloshing Analysis Conclusions

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MSC Dytran can accurately simulate the Fluid Structure Interaction in a

sloshing process.

Dytrans automatic Adaptive Fluid Elements creation during run timemakes pre-processing easy as the user does not need to create theelements upfront for the entire space in which the structure moves. Theentire pre-processing and analysis setup takes less than 2 hrs.

The Fast coupling FSI algorithm in the Dytran allows faster computationtimes ( 5 sec simulation computation in less than 12 hrs).

Future work will involve implementation of this process in DIVE and alsotaking the current results as input in to an acoustic package to predict the

noise outside the tank.


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Work Flow For Future Tasks Exterior Acoustics

Sloshing AnalysisSolverDytran

Fuel TankRigid

Output

Pressure on the tank

Vibration AnalysisSolverNastranFuel TankElasticCoupling Analysis with Fuel

Transformation of Nastran Input

OutputTime domain Acceleration on

the tank

Acoustic AnalysisSolverActranUsing IFEM

OutputSPL

Punch Output


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Nastran Mode

Pressure Input

Z Constraint

X,Y,ZConstraint

Support Condition


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Nastran Model

Fuel

Empty Fuel 21L(1)

Fuel 21L(2) Fuel 44L


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Actran Model


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Actran Model

Point1

Point2

Point3


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ReferenceTime Step


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ReferenceFrequency Analysis


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Calculation Time

Nastran 5 minutes

Actran 5 ninutes

HardwareNastran

CPU Intel 3.16GH

MEM 8GB

OS Windows XP 64bit

HardwareActran

CPU Intel 2.1GH

MEM 2GB

OS Windows XP 32bit