Exhaust Aftertreatment Modelling

1
Exhaust Aftertreatment Modelling

• University of Thessaly
• Mechanical Engineering Department
• Prof. Dr-Ing. A.M. Stamatelos
• Status March 2004

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Otto Diesel Exhaust Aftertreatment Modelling

• The Laboratory of Thermodynamics Thermal
  Engines of the University of Thessaly, Mechanical
  Industrial Engineering Department, possesses
  and further develops CAE methodologies and tools
  regarding the modelling of Automotive Exhaust
  Aftertreatment Systems comprising Catalytic
  Converters Diesel Filters.
• Our computational tools are characterized by an
  engineering approach in the chemical reaction
  modelling, relying on apparent kinetics, partly
  tunable to the results of routine full scale
  tests (engine bench or chassis dyno tests).

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Automotive Exhaust Aftertreatment In-house CAE
Software Tools
University of Thessaly Mechanical Industrial
Engineering Department Laboratory of
Thermodynamics Thermal Engines (LTTE)

• HEATRAN Exhaust Systems Heat Transfer Modeling
  Software
• CATRAN 3-Way Catalytic Converter Modeling
  Software
• CATRAN NOx Adsorber Catalytic Converter Modeling
  Software
• CATWALL Diesel Particulate Filter Regeneration
  Modeling Software 1D or 3D with ANSYS-CATWALL
  interfacing
• KONSTAN Exhaust emissions test data quality
  assurance software
• DARWIN Kinetic Parameter Estimation Software
  (based on GAs)

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RD Activities /funding in Automotive Exhaust
After-Treatment CAE

• University of Thessaly
• Mechanical Industrial Engineering Department
• Laboratory of Thermodynamics Thermal Engines
• (LTTE)

• Fundamental Research (Long Term)
• Funding provided by EC and interested
  Industrial Partners
• Development of Computer-Aided Engineering
  Methodologies
• (Medium Term)Funding provided by EC and
  Industrial Partners
• Transfer of CAE Software and Knowhow (Short
  Term) Against
• payment of license fees and charging of
  man-hours allocated to project
• Consulting Services and Design Optimization Case
  Studies (Short
• Term) Charging fees based on man-hours
  allocated to project

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Transfer of knowhow

• Transfer of software and knowhow to certain
  automotive, exhaust systems and catalytic
  converters manufacturers is in progress
• This transfer includes understanding from our
  industrial partners, of the algorithm and the
  input and output data structures of our catalytic
  converter, filter heat transfer modelling
  software
• Cooperation with industrial partners also covers
  the definition and customization of experiments
  and tests that support the modelling of different
  types of catalytic converter, filter exhaust
  piping

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Automotive Exhaust Aftertreatment CAE Current
state of the art

• Requirements of exhaust aftertreatment systems
  performance are continuously increasing, with
  increasingly stringent legislation
• Computer-Aided Engineering Methodologies are
  introduced to reduce development and testing
  time. They are based on in-house software
• Keeping an acceptable accuracy in the prediction
  of emissions over the NEDC and FTP-75 cycles,
  becomes increasingly difficult
• Commercial software (CFD) cannot be conveniently
  extended to cover prediction of transient exhaust
  emissions at converter exit

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LTTE in-house CAE methodologies

• The LTTE in-house software is tailored to the
  needs of the automotive and exhaust systems
  designer
• The basic points of its underlying philosophy
  are
• recognition of the minimum required degrees of
  freedom
• ability to fastly and efficiently perform
  transient simulations
• employment of routine test results in model
  tuning. Quality assurance of test data.
• integrated system optimization based on a modular
  software structure that covers a wide range of
  aftertreatment devices

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Basic Features of LTTE Catalytic Converter
Diesel Filter Models

• Kinetics reduced pragmatic net reaction rates
• Diffusion Thiele modulus approach
• Activity profiles lumped into net reaction rates
• Washcoat layers lumped into net reaction rates
• Heat mass transfer 1-D, Nu /Sh approach
• Cell shape lumped into effectiveness
• Washcoat shape lumped into effectiveness
• Canningincluded (2-D for converters, 3-D for
  filters)
• Exhaust piping included (1-D)
• Monolith shape and cpsi included
• Effect of Precious metal loading empirical
  approach
• Exhaust gas maldistribution included (2-D, 3-D)
• Typical input data 1-10 Hz test cycle modal data
• Front-end MS EXCEL macros or MATLAB/SIMULINK

9
Experimental input to CAE Tools

• LTTE in-house CAE methodologies use apparent
  kinetics and rely on full scale tests for model
  tuning (engine bench or chassis dyno tests,
  legislated cycles or parts thereof)
• The results of laboratory experiments and tests
  that provide fundamental data (i.e. light-off,
  lambda sweep, oxygen storage assessment tests
  etc) may also be processed and taken into account
  in model tuning.

10
Further development of LTTE in-house CAE
Methodologies

• Our CAE methodologies are already being employed
  in automotive exhaust after-treatment design, and
  transferred to industrial partners
• They are complete methodologies in the sense that
  they support the design optimization of exhaust
  after-treatment systems starting from routine
  engine bench/chassis dyno tests results
• Based on this experience, our kinetics tuning,
  pre- and post-processing tools and methodolo-gies
  are further developed and customized