chemistry in DARS Karin Frjd Why DARS? Enabling detailed chemistry - PowerPoint PPT Presentation

Reactive flows and complex chemistry in DARS Karin Fröjd

Why DARS? Enabling detailed chemistry in your CAE simulations • Take the right design choices, including chemical effects • Faster and cheaper design cycles • Evaluation of entirely new designs

What is DARS Basic TM ? Standalone software for 0D and 1D analyses of chemical reactions Chemistry analyses Mechanism reduction Idealized reactors – Ignition delay time – Emission production – Flame speed calculations Library generation 1D & 0D PDF models for in-cylinder combustion and aftertreatment DAR ARS S Bas asic v2.10 0 releas ased! ! - Focus s on libr brar ary gene neration tion fo for r STAR AR-CC CCM+ M+ an and STAR-CD CD

Chemistry analysis Import any mechanism in DARS Basic Analyse the chemistry in reactors and flames Understand reaction pathways through species flow analysis Igniti tion dela lay y times s as functi ction of temperatu rature re for r n-hepta tane CO producti ction in fuel rich ch combusti stion of n-hepta tane n-hepta tane deco composit sitio ion

Mechanism reduction To avoid large CPU times the mechanism can be reduced Mechanism reduction through necessity analysis Visual analysis of the reaction scheme through flow analysis Steady state reduction through life- time analysis Flow analysis for n-heptane decomposition

Mechanism Reduction through necessity analysis Flow + sensitivity analysis used to detect the most unnecessary species in the mechanism Workflow: DARS workbench – read mechanism, constant pressure and reduce mechanism modules – Read detailed reaction scheme – Run relevant reactor conditions, with necessity analysis turned on. – Let DARS remove species with necessity lower than your defined threshold value – Check mechanism validity through rerun of relevant reactor conditions Mechanism reduction panel – choose 6 reduction limit here

Chemistry mechanisms DARS standard chemistry mechanisms – n-heptane – TRF (n-heptane/toluene) – PRF (n-heptane/iso-octane) – Natural gas Collaboration with prof. Lu, Univ. of Connecticut – n-dodecane – PRF (n-heptane/iso-octane) – Biodiesel – DME – Ethanol – Natural gas Any CHEMKIN TM formatted mechanism from literature can be used Flow analysis for n-heptane decomposition

DARS Basic - catalyst 1D channel model in DARS Basic – Thin film layer approach - transport to washcoat calculated – Surface chemistry in washcoat layer – Gas phase chemistry in gas – Detailed or global chemistry can be used. – Any CHEMKIN format chemistry can be used. washcoat Monolith wall

DARS Basic - catalyst

DARS Basic - catalyst Save time by analysing chemical reactions in 1D before employing full CFD – Is detailed chemistry needed for the CFD calculation? – Can a reduced scheme be used? – Optimization of chemistry C3H6 inhibition of NO oxidation parameters for reduced schemes. under lean conditions in Nox- storage catalyst Study emission conversion as 1,200 InletT[K] Temperature [K] / Concentration NO_GasOut function of 1,000 NO2_GasOut N2O_GasOut – Catalyst length 800 NH3_GasOut (ppm) – Exhaust gas temperature 600 – Exhaust species composition 400 10 10 200 0 -30 20 70 120 170 220 Time [min] Ammonia SCR for a temperature ramp

Library generation With DARS Basic v2.10 you can export – FGM libraries – Soot libraries – ECFM-3Z single/dual fuel libraries – ECFM-CleH single/dual fuel libraries – PVM-MF single/dual fuel libraries Straightforward parameter specification, designed for each library type – Set up a full library calculation in less than 10 minutes. Paralellization for efficient library generation

FGM libraries Simulate combustion accurately and fast – DARS Basic can now export FGM libraries for STAR-CCM+ – For non-premixed and partially premixed combustion Explore combustion of any Igniti tion proce cess ss for n-hepta tane combusti stion at fuel/oxidant mixture vario rious s equiva vale lence ce ratio ios – Any CHEMKIN ™ format chemistry can be used Improve species prediction – Choose species for postprocessing in STAR-CCM+. CO mass s fracti ction durin ing n-hepta tane combusti stion at vario rious s equiva vale lence ce ratio ios

Soot source term libraries DARS Basic v2.10 can export Soot sectional and moment method libraries – Flamelets are used to capture turbulence-chemistry interaction Specify ranges and grid in T, P, EGR and scalar dissipation rate Library set up ~ 10 min Library calculation: ~ 40 h on 16 cores for single fuel library The gas s composit sitio ion panel, l, use sed for r specif cifica icati tion of parame ramete ter r range and grid id Soot t surfa face ce growth wth as functi ction of mixtu ture re fracti ction for r n-hepta tane 13 13 combusti stion at vario rious s strain rate tes

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