Modeling complex exhaust gas aftertreatment by Star-CD/axisuite coupling

Transcription

1 Modeling complex exhaust gas aftertreatment by Star-CD/axisuite coupling Theodoros Atmakidis Exothermia SA Greece Dr. Onoufrios Haralampous Technological Educational Institute of Larissa Greece Dr. Grigorios C. Koltsakis Laboratory of Applied Thermodynamics, Aristotle University Thessaloniki Greece 22-Mar-2011 STAR European Conference 2011

2 Introduction After-treatment modeling basics 22-Mar-2011 STAR European Conference

3 Scope of the problem Targets of the CFD engineer working on exhaust after-treatment: Improve after-treatment performance by reducing non-uniformities Temperature Concentration Flow Reduce backpressure penalty Reduce space requirements Control/eliminate deposits Audi Q7 V6 CleanDiesel Target of present work: Ref: Faurecia presentation CTI conference Jan 2011 Development of a tool suitable for the study of the above using the necessary input from the catalyst/filter technology department 22-Mar-2011 STAR European Conference

4 Exothermia brief profile Spin-off of Laboratory of Applied Thermodynamics/Aristotle University Thessaloniki (LAT/AUTh), established in 2007 Area of activity: Exhaust after-treatment simulation Development and maintenance of software products User support Engineering studies Market sectors Automotive OEMs Engine suppliers Exhaust system manufacturers Substrate manufacturers Catalyst coaters Automotive engineering service suppliers 4

5 axisuite overview +1D modeling captures and reveals in-depth processes Captures complex 3D effects System performance analysis/design 22-Mar-2011 STAR European Conference

6 axitrap mathematical model Ref: SAE papers , , Mar-2011 STAR European Conference

7 Recent references for axisuite validation Koltsakis, G. C., Dardiotis, C. K., Samaras, Z. C., Frey, M., Wenninger, G., Krutzsch, B., Haralampous, O. A., Modelbased Optimization of Catalyst Zoning in Diesel Particulate Filters, SAE , 2008 Koltsakis G. C., O. Haralampous, Z. C. Samaras, L. Kraemer, F. Heimlich. K. Behnk: Control Strategies for Peak Temperature Limitation in DPF Regeneration Supported by Validated Modeling, SAE Transactions, Journal of Fuels and Lubricants, Koltsakis G.C., Margaritis N., Haralampous O.: NOx Trap Modeling and Experimental Validation Using Ultra-fast Analyzers, Topics in Catalysis, Vol. 42, No. 1-4, pp Kalogirou M., Katsaounis D., Koltsakis G.C, Samaras Z. C.: Measurements of Diesel Soot Oxidation Kinetics in an Isothermal Flow Reactor Catalytic Effects Using Pt-based Coatings, Topics in Catalysis, 2007 Frey M., Wenninger G., Krutzsch B., Koltsakis, G.C, Haralampous O., Samaras Z. C.: 2D Simulation of the Regeneration Performance of a Catalysed DPF for Heavy-Duty Applications., Topics in Catalysis, Koltsakis G.C, Margaritis N. K., Haralampous O. A., Samaras Z. C.: Development and Experimental Validation of a NOx Trap Model for Diesel Exhaust, SAE Transactions, Journal of Fuels and Lubricants (SAE paper ), Koltsakis G.C, Haralampous O. A, Margaritis N., Samaras Z. C., Vogt C.D., Ohara E., Watanabe Y., Mizutani T.: 3- dimensional Modeling of the Regeneration in SiC filters, SAE Transactions, Journal of Fuels and Lubricants, Mar-2011 STAR European Conference

8 Exhaust engineering work-flow WLNT-WSCR WLNT SCR LNT DPF SCR Characterization of aftertreatment devices System concept analysis Detailed system analysis System control Application Feedback axisuite Computational fluid dynamics System control software Different modeling levels and tools are necessary in each step Easy transition from one modeling tool to another is necessary 22-Mar-2011 STAR European Conference

9 Exhaust engineering work-flow WLNT-WSCR WLNT SCR Characterization of aftertreatment devices LNT DPF SCR System concept analysis Detailed system analysis System control Application Feedback axisuite Coupling Computational fluid dynamics System control software Different modeling levels and tools are necessary in each step Easy transition from one modeling tool to another is necessary 22-Mar-2011 STAR European Conference

10 Axisuite/Star-CD coupling approaches Approach User subroutines Es-aftertreatment Package Included in Star-CD Extra package developed by CD-adapco Concept Exothermia provides user subroutines for direct coupling of axisuite solvers Coupling with 3rd party single-channel tools Control volume Porous medium approach Representative channels Information exchange Time-dependent source terms and flow resistances from axisuite library Device mesh Imported from axisuite Built-in channel mesh generation Energy Solved by axisuite Solved by Star-CD Porous medium 22-Mar-2011 STAR European Conference

11 User subroutines approach Concept Implementation Examples 22-Mar-2011 STAR European Conference

12 User subroutines concept Distributed as axisuite_starcd.so with implementations of user subroutines and axisuite solvers bcdefi, initfi, poros1, posdat, scalfn, sorent, sorsca Distributed scripts used for initialization Device setup imported from axisuite files Mesh generated automatically in axisuite and imported in starcd (nastran format) 22-Mar-2011 STAR European Conference

13 Balances in user subroutines approach Momentum Inlet flow rates Outlet pressures Momentum Porous medium parameters Species mass Gas energy Inlet concentrations Species source terms Inlet temperatures Heat source terms Species mass Gas energy Stored species Heat source terms Solid energy Ref: Koltsakis G C, Exothermia SA, SAE paper Mar-2011 STAR European Conference

14 DPF simulation - boundary conditions Wall boundary with constant temperature to account heat losses to the environment (T wall = 300 C) Outlet boundary Pout Inlet boundary T in v in C in Diffusers, pipes Cells DPF ~1000 channels 30 axial cells/channel Uncatalyzed 22-Mar-2011 STAR European Conference

15 DPF - Loading and regeneration scenario Loading Regeneration Increased soot emissions for accelerated loading 22-Mar-2011 STAR European Conference

16 DPF Loading Flow Soot loading 22-Mar-2011 STAR European Conference

17 DPF loading - Evolution of flow distribution Start of loading End of loading 22-Mar-2011 STAR European Conference

18 DPF loading - Final soot distribution 22-Mar-2011 STAR European Conference

19 DPF regeneration - Inlet temperature profile Calculated gas temperature profile at DPF inlet Temperature assumptions for internal wall of pipes and diffuser Uniform Constant 300 C 22-Mar-2011 STAR European Conference

20 DPF regeneration Flow Outlet temperature Soot loading 22-Mar-2011 STAR European Conference

21 DPF regeneration evolution Ref: Koltsakis G C et al., Exothermia SA, SAE paper

22 DPF regeneration: Non-uniformities Temperature distribution during peak Soot distribution at end of regeneration Normal stresses in axial direction during peak 22-Mar-2011 STAR European Conference

23 Es-aftertreatment approach Concept Implementation Examples CDPF DOC+DPF 22-Mar-2011 STAR European Conference

24 Es-aftertreatment approach Representative 1D channels One user subroutine esafter1d Called for each channel or device depending on mode Modes for Simulation initialization and termination Device initialization (using axisuite files) Conditions initialization (also restarting) Calculation of next or final iteration Thermo-physical properties exchange Built-in channel mesh generation 22-Mar-2011 STAR European Conference

25 Balances in user subroutines approach Momentum Inlet flow rates Outlet pressures Momentum Porous medium parameters Species mass Gas energy Inlet concentrations Species source terms Inlet temperatures Heat source terms Species mass Gas energy Stored species Heat source terms Solid energy Ref: Koltsakis G C, Exothermia SA, SAE paper Mar-2011 STAR European Conference

26 Balances in Es-aftertreatment approach Momentum Inlet flow rates Outlet pressures Momentum Flow resistance terms Species mass Gas energy Inlet concentrations Outlet concentrations Inlet temperatures Outlet temperatures Species mass Gas energy Stored species Solid energy Temperature field Heat source terms 22-Mar-2011 STAR European Conference

27 CDPF - Grid Same mesh for diffusers and pipes cells Representative channels 88 channels 100 axial cells/channel Coarse due to memory restrictions Cement elements are not taken into account Catalyzed 22-Mar-2011 STAR European Conference

28 CDPF Loading and regeneration scenario Loading Regeneration Increased soot emissions for accelerated loading 22-Mar-2011 STAR European Conference

29 CDPF loading Velocity and soot loading Start of loading (0g/l) End of loading (8g/l) Vel. [m/s] Soot [g/l] Mar-2011 STAR European Conference

30 CDPF regeneration Velocity and soot loading Wall temperature Peak of regeneration (t=260s) End of regeneration (t=600s) Vel. [m/s] Soot [g/l] Temp. [K] Mar-2011 STAR European Conference

31 Further Possibilities: DOC + DPF End of loading (8g/l) DOC DPF Vel. [m/s] Mar-2011 STAR European Conference

32 Comparison of coupling approaches Inherent advantages of esaftertreatment Integrated in Star-CD GUI Built-in parallelization Combined solution of energy in all solid elements (diffuser, canning, substrates) Shortcomings of current development status Support of segmented DPFs Imported mesh functionality Cement thermo-physical properties from axisuite 1d subroutine Speed Efficient memory management 22-Mar-2011 STAR European Conference

33 Conclusions Future prospects axisuite coupling with Es-aftertreatment shows potential to cover better all user needs Development from CD-Adapco and Exothermia reached a basic level for modeling sufficiently full scale geometries Further development is planned for detailed and speedy analysis support of segmented DPFs 22-Mar-2011 STAR European Conference

34 Thank you very much for your attention! Onoufrios Haralampous 22-Mar-2011 STAR European Conference