reactive flows and complex chemistry in...
TRANSCRIPT
-
Reactive flows and complex
chemistry in DARS
Karin Fröjd
-
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
Why DARS?
-
What is DARS BasicTM?
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
Standalone software for 0D and 1D analyses of chemical reactions
DARS Basic v2.10 released!
- Focus on library generation for STAR-CCM+ and STAR-CD
-
Import any mechanism in DARS Basic
Analyse the chemistry in reactors and flames
Understand reaction pathways through species flow analysis
Chemistry analysis
Ignition delay times as function of
temperature for n-heptane
n-heptane decompositionCO production in fuel rich combustion of n-heptane
-
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
Mechanism reduction
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:
– 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
6Mechanism reduction panel – choose reduction limit here
DARS workbench – read mechanism, constant
pressure and reduce mechanism modules
-
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 CHEMKINTM formatted mechanism from literature can be used
Chemistry mechanisms
Flow analysis for n-heptane
decomposition
-
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.
DARS Basic - catalyst
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
parameters for reduced schemes.
Study emission conversion as
function of
– Catalyst length
– Exhaust gas temperature
– Exhaust species composition10
0
200
400
600
800
1,000
1,200
-30 20 70 120 170 220
Tem
per
atu
re [
K]
/ C
on
cen
trat
ion
(p
pm
)
Time [min]
InletT[K]
NO_GasOut
NO2_GasOut
N2O_GasOut
NH3_GasOut
Ammonia SCR for a temperature ramp
C3H6 inhibition of NO oxidation
under lean conditions in Nox-
storage catalyst
-
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
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
fuel/oxidant mixture
– Any CHEMKIN™ format chemistry
can be used
Improve species prediction
– Choose species for postprocessing
in STAR-CCM+.
Ignition process for n-heptane combustion at
various equivalence ratios
CO mass fraction during n-heptane combustion at
various equivalence ratios
-
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
13
The gas composition panel, used for specification of
parameter range and grid
Soot surface growth as function of mixture fraction for n-heptane
combustion at various strain rates
-
Thank you for your attention
www.cd-adapco.com/dars