ECN 3: Combustion Indicator- Experiment and Modeling 1/85 April 2014 ECN 3 Subtopic 2.1: Combustion...
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ECN 3: Combustion Indicator- Experiment and Modeling 1/85 April 2014 ECN 3 Subtopic 2.1: Combustion Indicators Experiment and Modeling 3rd Workshop of the Engine Combustion Network April 4-5, 2014, Ann Arbor, USA Gianluca D’Errico, Seong-Young Lee, Michele Bardi, Jose M. Garcia-Oliver
ECN 3: Combustion Indicator- Experiment and Modeling 1/85 April 2014 ECN 3 Subtopic 2.1: Combustion Indicators Experiment and Modeling 3rd Workshop of
ECN 3: Combustion Indicator- Experiment and Modeling 1/85 April
2014 ECN 3 Subtopic 2.1: Combustion Indicators Experiment and
Modeling 3rd Workshop of the Engine Combustion Network April 4-5,
2014, Ann Arbor, USA Gianluca DErrico, Seong-Young Lee, Michele
Bardi, Jose M. Garcia-Oliver
Slide 2
ECN 3: Combustion Indicator- Experiment and Modeling 2/85 April
2014 Topic 2.1 Combustion Indicator- OUTLINE 1.Introduction of
Combustion Indicator o Objectives and Questions to be Addressed
2.Experimental Part o Institutions, Techniques and Operating
Conditions 3.Comparison for Global Indicators of Experiment vs.
Experiment o Standard measurement for LOL, ID to confirm trend
variation o LOL from OH-PLIF comparison o New measurement- FL, Sr,
peak concentration in OH-PLIF image 4.Modeling Part o Institutions,
models and operating conditions 5.Comparison for Global Indicator
of Model vs. Model o Parameters: ID, LOL, FL, Sr, maxOH, maxCH2O:
more detail from groups 6.Comparison of Model vs. Experiment in
Quantitative Data o Experimental data with modeling data from
various groups 7.Comparison of Model vs. Experiment in Time
Resolved Data o Heat Release Rate and Flame Tip Srt 8.Conclusion
Remarks o Future work and Information for upload data and data
availability
Slide 3
ECN 3: Combustion Indicator- Experiment and Modeling 3/85 April
2014 Objectives/ Questions to be Answered OVERALL OBJECTIVES
Analyze model and experimental results to determine different
parameters that can serve for a global description of the
combustion process, namely: Ignition Delay Lift-off Length Reactive
Spray Penetration Heat Release Rate OVERARCHING QUESTIONS TO BE
ADDRESSED What is the measured and computed dependency of the main
combustion indicators on the recommended parametric variations of
the operating conditions? What are the differences among
experiments, among models and between models and experiments? What
are the reasons for these differences? What is the influence of the
chemical mechanism? What is the influence of the
turbulence-chemistry interaction?
Slide 4
ECN 3: Combustion Indicator- Experiment and Modeling 4/85 April
2014 TECHNIQUES AND INDICATORS New CI Conventional CI
Slide 5
ECN 3: Combustion Indicator- Experiment and Modeling 5/85 April
2014 EXPERIMENT
ECN 3: Combustion Indicator- Experiment and Modeling 7/85 April
2014 INDICATOR CONTRIBUTIONS LOLIDFL LOL Sr OH* Time avg OH*
Transient Broad band OH* Transient
PressureBroadbandOH-PLIFSchlieren SNL X (O) X X CMT (O) X X IFPEN X
(O) X (OH-LIF/ OH*) TUe (O) X (O) (O) X (OH- LIF/OH*) X ECN3 (Data
from Sandia Web) X: New CI X: Conventional CI 1.Ambient temperature
[K]: 900 800 1000 1100 2.Injection pressure [MPa]: 150 100 - 50
3.Oxygen concentration [%]: 15 21 17 13 4.Ambient density [kg/m 3
]: 22.8 15.2 30.4 7.6 5.Injector:210677, 210675, 210678
Slide 8
ECN 3: Combustion Indicator- Experiment and Modeling 8/85 April
2014 COMPARISON BETWEEN INSTITUTIONS AND ANALYSIS Ignition Delay
(ID) and Lift-off Length (LOL) Reactive Spray Penetration (Sr)
Flame length (FL) Heat Release Rate (HRR)
Slide 9
ECN 3: Combustion Indicator- Experiment and Modeling 9/85 April
2014 SOC_CL Ignition Delays by T amb at Various Institutions SOC_P
SOC_CL: strong and non-linear temperature dependency while ID slope
decreases with increasing ambient temperature SOC_P: strong and
non-linear temperature dependency All ignition delays tend to
converge as the temperature increases except for Sandia data at
1100K due to the different criterion, 0.03 kPa as threshold No
significant variation with different institutions and injector
models
Slide 10
ECN 3: Combustion Indicator- Experiment and Modeling 10/85
April 2014 T amb Effect on ID and Uncertainty Ignition Delay (All
Data)Uncertainty Ignition delays appear collapse single profile
while there are scatters at lower ambient temperature, 800K
Uncertainty is estimated by the ratio of one-sigma over averaged
ignition delay at a fixed ambient temperature Above T amb =900K,
uncertainty is approximately below 10% for SOC_CL while large
uncertainty is observed in SOC_P
Slide 11
ECN 3: Combustion Indicator- Experiment and Modeling 11/85
April 2014 T amb Effect on LOL and Uncertainty Lift-off length
(LOL)Uncertainty OH*-LOLs converge one single profile with very low
uncertainty, below 10% LOL profile shows non-linear behavior,
similar to the ID profile No significant deviation in various
institutions and injector models
Slide 12
ECN 3: Combustion Indicator- Experiment and Modeling 12/85
April 2014 LOL Dependency of Ta, O2, Density and P inj All data
(ECN3) were compiled to build an empirical relationship to predict
LOL variations There is a general good agreement with the
literature It will provide a guideline for modeling of spray
dynamics abcd SAE 2005-01-3843-3.74-0.851 Benajes et al. 2013,
CMT-3.890.54 ECN3-4.01-1.22--1.04 [150MPa 15% 22.8kg/m 3 ] [150MPa
900K 22.8kg/m 3 ] [150MPa 900K 15%] [900K 15% 22.8kg/m 3 ]
Slide 13
ECN 3: Combustion Indicator- Experiment and Modeling 13/85
April 2014 [150MPa 15% 22.8kg/m 3 ] [150MPa 900K 22.8kg/m 3 ]
[150MPa 900K 15%] [900K 15% 22.8kg/m 3 ] SOC_CL Dependency of Ta,
O2, Density and P inj All data (ECN3) were compiled to build an
empirical relationship to predict SOC_CL v ariations There is a
general good agreement and It will provide a guideline for
prediction of flame ignition abcd ECN3-6.03-1.42--0.94
Slide 14
ECN 3: Combustion Indicator- Experiment and Modeling 14/85
April 2014 COMPARISON BETWEEN INSTITUTIONS AND ANALYSIS Ignition
Delay (ID) and Lift-off Length (LOL) Reactive Spray Penetration
(Sr) Flame length (FL) Heat Release Rate (HRR)
Slide 15
ECN 3: Combustion Indicator- Experiment and Modeling 15/85
April 2014 Reactive Flame Tip Penetration (Sr) There is a general
good agreement among the institutions and among various injection
duration Range of penetration scattering at fixed time is about 3-4
mm Significantly lower penetration by Tu/e over the injection
period Diverging penetration when Sr>80mm. Methodology:
Schlieren imaging Institution comparison at Ref condition (Spray
A)
Slide 16
ECN 3: Combustion Indicator- Experiment and Modeling 16/85
April 2014 Reactive Flame Tip Penetration (Sr) Methodology:
Schlieren imaging Inert and Reactive penetration comparison
Reactive and inert penetration at a certain ASOI time after the
ignition are diverging The information is not representative of the
start of ignition. This information can be useful when modeling
spray morphology at reacting conditions The indicator Sr/Si can
bring valuable information Ignitionc Desantes et al. Combustion and
Flames, 2014
Slide 17
ECN 3: Combustion Indicator- Experiment and Modeling 17/85
April 2014 Reactive Flame Tip Penetration (Sr) Methodology:
Schlieren imaging Inert and Reactive penetration This parameter has
been obtained at different conditions It provides important
guidelines on the spray morphology Important information if we are
attempting to model spray chemistry! It give consistent results
between different institutions (even when the penetration showed
some discrepancies)
Slide 18
ECN 3: Combustion Indicator- Experiment and Modeling 18/85
April 2014 COMPARISON AND ANALYSIS Ignition Delay (ID) and Lift-off
Length (LOL) Reactive Spray Penetration (Sr) Flame Length (FL) Heat
Release Rate (HRR)
Slide 19
ECN 3: Combustion Indicator- Experiment and Modeling 19/85
April 2014 Flame Length (FL) Methodology: Broadband chem./OH *chem.
Soot incandescence radiation penetrates until a certain distance
depending on injection pressure conditions This distance is related
with spray stoichiometric surface, flame length Flame length is
independent of injection pressure CMT 675 - Spray A - 21% O2 CMT
675 - Spray A - 15% O2 CMT 675 - 21% O 2 /150 MPa Ignition
Slide 20
ECN 3: Combustion Indicator- Experiment and Modeling 20/85
April 2014 SCALING LAWS FOR SPRAY LENGTHS CMTSNLTU/e (OH* chem) FL
(mm)98.890>95 Similar measurements from all the
institutions
Slide 21
ECN 3: Combustion Indicator- Experiment and Modeling 21/85
April 2014 SCALING LAWS FOR SPRAY LENGTHS
Slide 22
ECN 3: Combustion Indicator- Experiment and Modeling 22/85
April 2014 SCALING LAWS FOR SPRAY LENGTHS
Slide 23
ECN 3: Combustion Indicator- Experiment and Modeling 23/85
April 2014 Flame Length (FL) CMTSNLTU/e (OH* chem) FL
(mm)98.890>95 SNL900 K1000K1100K FL90 mm88.5 mm84.6 mm Effect of
temperature: flame length decrease at higher ambient temperature
Similar measurements from all the institutions
Slide 24
ECN 3: Combustion Indicator- Experiment and Modeling 24/85
April 2014 Important remarks: To the moment the FL determination is
based on thresholds that has to be further discussed Important
fluctuations are involved in the measurement The long distance
needed for the flame to stabilize makes FL measurable only at
certain conditions The approach needs further discussion but it
shows promising results The relationship between Sr, Si and FL and
the related test conditions needs further understanding (new
challenges for modelers!) Flame Length (FL)
Slide 25
ECN 3: Combustion Indicator- Experiment and Modeling 25/85
April 2014 COMPARISON AND ANALYSIS Ignition Delay (ID) and Lift-off
Length (LOL) Reactive Spray Penetration (Sr) Flame length (FL) Heat
Release Rate (HRR)
Slide 26
ECN 3: Combustion Indicator- Experiment and Modeling 26/85
April 2014ECN 3 26/4 Apr 2014 Pressure Trace Constant threshold for
ignition delay analysis yields inconsistent results at high ambient
temperature due to the effect of ringing Shortly after high-T
ignition, ringing causes pressure traces to drop below zero. Use of
averaged and smoothed trace requires a lower threshold at this
ambient temperature to capture correct ignition timing. T amb press
* chemi 9000.41 (>3kPa)0.40 10000.37 (>3kPa) 0.23 (>1.5
kPa) 0.27 11000.39 (>3kPa) 0.16 (>1.2kPa) 0.20 12000.39
(>3kPa) 0.15 (>1kPa) 0.15 *The pressure shown in parenthesis
indicates the threshold used for analysis
Slide 27
ECN 3: Combustion Indicator- Experiment and Modeling 27/85
April 2014 Pressure measurement for ID could give trouble
especially when the ID premixed phase is reduced (i.e. short ID).
This has been observed at high ambient temperature An adjustable
polynomial fitting has been employed to fit raw data by SNL
(filtering method developed at ETH) The sensitivity is high until
the first peak in pressure, then the following fluctuation are
heavily filtered Results are to the smoothed signal from the
ensemble average Methodology: narrow range pressure sensor in CV
vessel (Lillo et al. SAE 2012-01-1239) Pressure Rise and ROHR
Slide 28
ECN 3: Combustion Indicator- Experiment and Modeling 28/85
April 2014 Pressure Rise and ROHR Methodology: narrow range
pressure sensor in CV vessel (Lillo et al. SAE 2012-01-1239) By
obtaining the ROHR by the smoothed curve, we defined the ignition
delay as the instant corresponding to the highest peak in the ROHR
curve The method still needs to be applied to more test conditions
SNL800 K900 K1100 K ID Chem [ms]0.920.390.2 ID PR [ms]0.850.410.15
ID ROHR [ms]0.940.410.24
Slide 29
ECN 3: Combustion Indicator- Experiment and Modeling 29/85
April 2014 LOL CORRELATION BETWEEN OH* AND OH-LIF TUe (201.02) HS
OH* images Schlieren movies at injection pressure of 50/100/150 MPa
OH-LIF images Laser beam corrected images at 50/100/150MPa at
1100us and 5000us IFPEN (201.01) OH-LIF images Laser beam corrected
images of AR, O1, O3, T2, T3 at 150MPa at 5000us AR: [201.01 900K
15% 150MPa] O1: [201.01 900K 13% 150MPa] O3: [201.01 900K 21%
150MPa] T3: [201.01 1000K 15% 150MPa] T2: [201.01 800K 15% 150MPa]
I1: [201.02 900K 15% 50MPa] I2: [201.02 900K 15% 100MPa] AR:
[201.02 900K 15% 150MPa]
ECN 3: Combustion Indicator- Experiment and Modeling 31/85
April 2014 SENSITIVITY ANALYSIS of OH-LIF Threshold % of OH Max
Intensity with Various Background Subtraction BG Subtraction
Imax=55.6 Due to Background Interference Detection of OH Signal
Start 4% 13.7 mm 17 mm 18.9 mm 25% Background Subtraction
Background subtraction (% of maximum intensity) from raw image and
normalization Apply 10% max OH to track the location of threshold
from injector tip and define the LOL Note that relatively high
noise level after laser beam correction
Slide 32
ECN 3: Combustion Indicator- Experiment and Modeling 32/85
April 2014 Relation between OH* and OH-LIF- TU/e A very good
agreement of LOL between OH* and OH-LIF
ECN 3: Combustion Indicator- Experiment and Modeling 34/85
April 2014 10% threshold of OH max intensity Sensitivity Analysis
of 150MPa OH at 4700us- IFPEN BG Subtraction Imax=4747 [201.02 900K
15% 150MPa] LOL variation from 0% to 36 % background subtraction is
about 16%
Slide 35
ECN 3: Combustion Indicator- Experiment and Modeling 35/85
April 2014 LOL Comparison of OH-LIF and OH*- IFPEN Background 5%
subtraction were applied to all cases considered A very good
agreement of LOL between OH* and OH-LIF
Slide 36
ECN 3: Combustion Indicator- Experiment and Modeling 36/85
April 2014 CONCLUSIONS ON EXPERIMENTAL PART The newly established
experiment provides the rich database for the predictive model
development and serves as the benchmark data for modeling
Experimental data including quantitative and time-resolved global
indicators are available Uncertainty for LOL and ID o LOL variation
shows below 10% over various parametric sweeps o Chem-base ID
relatively is reliable that Press-base ID o LOL and ID variations
are minimal under various institutions and injector models Heat
release rate can be used for the definition of ignition delay
LOL-OH-LIF shows fairly good agreement with LOL OH* with limited
conditions
Slide 37
ECN 3: Combustion Indicator- Experiment and Modeling 37/85
April 2014 MODELLING
Slide 38
ECN 3: Combustion Indicator- Experiment and Modeling 38/85
April 2014 Objectives/ Questions to be Answered OVERALL OBJECTIVES
Analyze model and experimental results to determine different
parameters that can serve for a global description of the
combustion process, namely: Ignition Delay Lift-off Length Reactive
Spray Penetration Heat Release Rate OVERARCHING QUESTIONS TO BE
ADDRESSED What is the measured and computed dependency of the main
combustion indicators on the recommended parametric variations of
the operating conditions? What are the differences among
experiments, among models and between models and experiments? What
are the reasons for these differences? What is the influence of the
chemical mechanism? What is the influence of the
turbulence-chemistry interaction?
Slide 39
ECN 3: Combustion Indicator- Experiment and Modeling 39/85
April 2014 CONTRIBUTIONS ECN3: topic 2.1 Modelling contributions
ANL: Argonne National Laboratories (Som, Pei) ETH: Swiss Federal
Institute of Technology in Zurich (Bolla) POLIMI: Politecnico di
Milano (DErrico, Lucchini) TUE: Technische Universiteit Eindhoven
University of Technology (Somers) UNSW: The University of New South
Wales (Hawkes, Chishty) WISC: University of Wisconsin, ERC (Wang)
CONTRIBUTOR2.1 T sweep O2 sweep Pinj sweep Rho sweep 2.22.3 ANL
(1.5 ms) XXXXXX ETH XXXXXX POLIMI XXXXXXX TUE XXXX X UNSW XXXXX X
WISC XXXX X X
Slide 40
ECN 3: Combustion Indicator- Experiment and Modeling 40/85
April 2014 CODE(S)Turbulence model(s)Scalar transport ANLCONVERGE
RNG k- Gradient ETHStarCD RNG k- Gradient PoliMiOpenFOAM + LibICE
k- Gradient TUEStarCD k- (high Re) Gradient UNSWFluent k- , with
round jet adjustment m0: Gradient m1: Weiner process (i.e.
gradient) WISCKIVA-3vr gRNG k- Gradient Models
Slide 41
ECN 3: Combustion Indicator- Experiment and Modeling 41/85
April 2014 ChemistryTurbulence chemistry interaction ANL Luo et
(111 species)Transient multiple representative interactive
flamelets (T-RIF). 1 flamelet every 0.075 ms, flamelet creation
based on fuel mass. ETH Luo et al. (106 species)Conditional Moment
Closure. Equations solved for conditional moments of species and
temperature as function of mixture fraction, space and time. POLIMI
Luo et (111 species)Transient multiple representative interactive
flamelets (T-RIF). 1 flamelets every 0.1 ms, flamelet creation
based on fuel mass. TUE Narayanaswamy (255 species) Flamelet
generated manifolds. Tabulation on mixture fraction and progress
variables. Beta PDFs for both. UNSW Pei et al (88
species)Transported PDF method. Lagrangian solution of full joint
composition mass density function. Well-mixed for comparison. WISC
Wang et al.(106 species)Well-mixed.
Slide 42
ECN 3: Combustion Indicator- Experiment and Modeling 42/85
April 2014 Grid type Grid rangeTime discretisation scheme Time step
ANL3D, structured with AMR 0.25 mm - 4mmPISO5e-7s variable with max
Courant 0.75 ETH2D axisymmetric0.5 mm - 2.0 mmPISO1e-06s CFD 1e-07
s CMC POLIMI2D axisymmetric0.1 mm - 1mmPIMPLE2.50e-7 s TUE3D,
uniform Cartesian, sector 0.5mm X 0.5mm X 0.25 mm PISO5.0e-6 s
UNSW2D, structured0.25 mm - 1mmSIMPLE4e-06 s WISC2D axisymmetric0.5
mm-1.5 mmSIMPLE5e-07 s
Slide 43
ECN 3: Combustion Indicator- Experiment and Modeling 43/85
April 2014 Injection/ Break-up CollisionDrag/ Dispersion Heat
transfer/ evaporation ANL Inj: Blob Break-up: KH-RT without breakup
length Collision: no time counter algorithm Drag: Dynamic model
Dispersion: Stochastic HT: Ranz-Marshall Evap: Frossling ETH Inj:
Blob Break-up: Reitz-Diwakar ORourkeDrag: Dynamic Dispersion:
Stochastic HT: Ranz-Marshall Evap: Ranz-Marshall POLIMI Inj: Blob
Break-up: KH-RT without breakup length NoDrag: Dynamic Dispersion:
Stochastic HT: Ranz-Marshall Evap: Spalding TUE Inj: Nozzle flow
model - Modified MPI* Break-up: Reitz-Diwakar ORourkeDrag: Star-CD
standard Dispersion: Stochastic HT: Ranz-Marshall Evap: Standard
UNSW Inj: Group Break-up: No (inject small droplets) ORourkeDrag:
Stokes-Cunningham Dispersion: stochastic HT: Ranz-Marshall Evap:
Frossling WISC Inj: Blob Break-up: KH-RT ORourkeDrag: Dynamic model
Dispersion: none HT: Han and Reitz Evap: Discrete Multi-
Component
Slide 44
ECN 3: Combustion Indicator- Experiment and Modeling 44/85
April 2014 Models for turbulence-chemistry interaction Well-mixed
(UNSW, WISC): Mixing is fast relative to chemistry. Fast mixing
causes the scalar PDFs to be close to -functions. Presumed
PDF/flamelet approaches (ANL, POLIMI, TUE): The thermochemical
state-space is low-dimensional and described by a few parameters.
The forms of the parameter PDFs are known and described by a small
number of moments usually two, e.g. beta functions, Gaussian or
one, e.g. delta function. There is some way of obtaining
thermochemical state conditional on the parameters.
Slide 45
ECN 3: Combustion Indicator- Experiment and Modeling 45/85
April 2014 Models for turbulence-chemistry interaction Presumed
PDF/flamelets (ANL, POLIMI, TUE): Chemistry is fast relative to
mixing. Ignition of a one-dimensional laminar non-premixed
stagnation flow. (Or an approximation to this.) Different table
parameter choices possible. TUe - mixture fraction and progress
variables. Beta PDFs for both. ANL, POLIMI transient multiple
representative interacting flamelet with a beta PDF. Chemistry in
online solved in the mixture fraction space. Each flamelet is
representative of a fraction of the injected fuel mass. Average
stoichiometric scalar dissipation rate values are passed to each
flamelet.
Slide 46
ECN 3: Combustion Indicator- Experiment and Modeling 46/85
April 2014 Conditional Moment Closure (ETH) Chemistry Conditional
turbulent flux Species Molecular mixing Conditional velocity Models
for turbulence-chemistry interaction Equations are solved for
species and temperature, conditionally averaged on mixture
fraction. Conditional fluctuations are assumed to be small. Mixture
fraction PDF is presumed as a beta function. In some respects
similar to flamelets but the tabulation evolves in time and space.
(In space, on a coarser grid than the CFD.)
Slide 47
ECN 3: Combustion Indicator- Experiment and Modeling 47/85
April 2014 Models for turbulence-chemistry interaction Transported
PDF approaches (UNSW)
Slide 48
ECN 3: Combustion Indicator- Experiment and Modeling 48/85
April 2014 Comparison among used kinetic mechanisms Constant volume
homogeneous ignitions were modelled using SENKIN. Ignition was
defined computationally as the time of the maximum rate of change
of temperature. The following three chemical mechanisms were
compared: - Narayanaswamy et al.: a 255 species mechanism. -Som et
al.: 111 species skeletal mechanism (based on Luo et al. with the
skeletal mechanism for OH* added). -Pei et al.: an 88 species
reduced mechanism (quasi-steady state assumptions to the 111
species mechanism). The model was compared with ignition delays
from shock tubes: o Pfahl et al. : n-decane, pressure = 50 bar, phi
= 0.67, 1.0 and 2.0 o Zhukuv et al. : n-decane, pressure = 80 bar,
phi = 1.0 o Vasu et al. : n-dodecane, pressure = 20 bar, phi =1.0.
(The raw data were scaled to 20 bar) Separately Wang provided
information on the validation of 106 species mechanism formulated
at UW-ERC, showing good agreement with Narayanaswamy et al,
especially at high temperatures. Chemical mechanisms
Slide 49
ECN 3: Combustion Indicator- Experiment and Modeling 49/85
April 2014 Chemical mechanisms Comparison among used kinetic
mechanisms Results from Som et al. and Pei et al. are nearly
identical. The Som et al. mechanism and the Narayanaswamy et al. do
not significantly differ at low temperatures. The main difference
is in the high temperature range. For 50 bar or higher pressure, at
temperatures below ~900K the mechanisms all over- predict the
ignition delay, and there is little to distinguish between the
mechanisms. This is significant because the spray A baseline
ignites at a phi > 2.0 where the temperature is under 850K.
Narayanaswamy et al. mechanism mainly improves the high temperature
behaviour relative to the starting detailed mechanism of Som et
al.
Slide 50
ECN 3: Combustion Indicator- Experiment and Modeling 50/85
April 2014 Modelling definitions
Slide 51
ECN 3: Combustion Indicator- Experiment and Modeling 51/85
April 2014 Models for turbulence-chemistry interaction Parametric
variations Models vs Experiments First Ignition Delay/LOL analyis
is shown for: 1. Ambient Temperature [K]: 900 800 1000 1100 2.
Injection pressure [MPa]: 150 100 - 50 3. Oxygen concentration [%]:
15 21 17 13 4. Ambient density [kg/m 3 ]: 22.8 15.2 30.4 7.6 For
each operating point, one value of experimental data is reported
with the observed scatter of data among different
institutions.
Slide 52
ECN 3: Combustion Indicator- Experiment and Modeling 52/85
April 2014 Ignition delay/LOL Temperature sweep For the
experimental data, a mean value for each operating condition is
shown with a scatter bar of all data collected at different
institutions. All models over-predict the ignition delay, while LOL
is generally better estimated. Computed and experimental trends are
generally in good agreement.
Slide 53
ECN 3: Combustion Indicator- Experiment and Modeling 53/85
April 2014 Ignition delay/LOL Results do not explicitly depend on
the chemical scheme ETH and TUE have a lower ID for the baseline
condition, but this is not confirmed for other operating
conditions. POLIMI and UNSW have a similar trend and values. ANL
has globally the lower ID for all conditions. Temperature sweep
(ID) The over-prediction of ID by all groups is consistent with the
chemistry sub-models over- predicting the ignition delay at high
pressures and temperatures less than around 900K. Models show that
the ignition shifts to richer (and thus cooler) regions as ambient
temperature is increased, such that the ignition still occurs at a
temperature less than 900K. This effect is due to the NTC.
Slide 54
ECN 3: Combustion Indicator- Experiment and Modeling 54/85
April 2014 Ignition delay/LOL Overall trends are good, but
differences among models are significant. POLIMI and UNSW have
generally the closer values to the measured data. Most relevant
errors are WISC at 900 K, ANL at 800 K and TUE at 1100 K not a
unique worse condition! Absolute values might depend on the
definition Temperature sweep (LOL)
Slide 55
ECN 3: Combustion Indicator- Experiment and Modeling 55/85
April 2014 Ignition delay/LOL Higher Error in the prediction of the
ignition delay than of the lift-off length (chemistry?) There is no
evident correlation between the two combustion indicators in any of
the models.
Slide 56
ECN 3: Combustion Indicator- Experiment and Modeling 56/85
April 2014 Ignition delay/LOL Do the conclusions depend on the ID
definition? ETH and TUE provided results with both definitions: -
OH mass fraction: First time at which Favre-average OH mass
fraction reaches 2% of the maximum in the domain after a stable
flame is established. -Temperature rise: Time of maximum rate of
rise of maximum temperature Results are the same with both
definitions.
Slide 57
ECN 3: Combustion Indicator- Experiment and Modeling 57/85
April 2014 Ignition delay/LOL Do the conclusions depend on the LOL
definition? ANL and UNSW provided results with two definitions (2%
and 14% of max OH). Computed trends are similar with an obvious
shift towards higher values with the 14% maxOH definition. This
difference is more significant for ANL results than UNSW.
Slide 58
ECN 3: Combustion Indicator- Experiment and Modeling 58/85
April 2014 Is it possible to use a LOL definition based on OH*?
Ignition delay/LOL POLIMI - AR OH OH* Trend seems to captured
despite the very low values. A different threshold would be needed
to be consistent with the OH based definition.
Slide 59
ECN 3: Combustion Indicator- Experiment and Modeling 59/85
April 2014 Ignition delay/LOL What about turbulence-chemistry
interactions? Only UNSW provided results with both TCI (Tpdf) and
well-mixed approach, while WISC provided results only with
well-mixed. Ignition delay (UNSW) does not depend significantly on
TCI. In literature and at ECN2 some groups had shown opposite
conclusions. UNSW well-mixed results are different from WISC. LOL
with the well-mixed approaches for WISC and UNSW are closer.
Slide 60
ECN 3: Combustion Indicator- Experiment and Modeling 60/85
April 2014 Ambient oxygen sweep Ignition delay/LOL Ignition delay
Overall over-estimation is confirmed. ANL and POLIMI (both mRIF)
have similar trends (and values). UNSW and TUE have similar trends
(not values).
Slide 61
ECN 3: Combustion Indicator- Experiment and Modeling 61/85
April 2014 Ambient oxygen sweep Ignition delay/LOL Lift-off Overall
good prediction also quantitative (apart from WISC with well-mixed
approach). ETH, POLIMI and UNSW have similar trends in good
agreement with the experimental values.
Slide 62
ECN 3: Combustion Indicator- Experiment and Modeling 62/85
April 2014 Other indicator Position of maximum OH and CH2O Apart
from the 800 K (where some results might not be stable yet):
-POLIMI and UNSW have similar locations of OH and CH2O, either as
trends and as absolute values. - TUE predicts a longer distance
between OH and CH2O. -ETH results predicts very close locations for
the AR case.
Slide 63
ECN 3: Combustion Indicator- Experiment and Modeling 63/85
April 2014 Ignition delay/LOL What about turbulence-chemistry
interactions now? Some differences arise in the ignition delay
(UNSW) for the oxygen sweep. LOL with the well-mixed approaches for
WISC and UNSW are closer for the oxygen sweep too.
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April 2014 Ambient density sweep Ignition delay/LOL Ignition delay
and Lift-off All models show similar trends for ID and LOL as
function of ambient density.
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April 2014 Fuel injection pressure sweep Ignition delay/LOL
Ignition delay and Lift-off have opposite trend as function of the
injection pressure Some results (ANL, ETH, POLIMI, TUE) capture
(with different degree of accuracy) both trends. Very interesting
conditions to understand the flame stabilization mechanisms.
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April 2014 Other indicators Reactive spray penetration: temperature
sweep Experimental reactive spray penetration were compared at 1.5
ms with the modelling results. Absolute values depend on the
capability of the model to well describe the transient evolution of
the flame. For this aspect, the good set-up of the spray model has
a great influence too. Some institutions provided time resolved
data which can help to understand the differences, as we will see
later.
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April 2014 Other indicators Reactive spray penetration: oxygen
sweep This sweep is very interesting for RSP data since it is done
at constant thermodynamic conditions. POLIMI and WISC results are
in good agreement with the measured data. Other models show a weak
dependency of the RSP on the oxygen concentration.
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April 2014 Other indicators Reactive spray penetration: ambient
density sweep All models are able to well capture the dependency of
the RSP on the ambient density as trend.
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April 2014 Other indicators Reactive spray penetration: fuel
injection pressure sweep ANL results have an opposite trend with
the injection pressure. All other models well predict this
dependency with particularly good agreement for POLIMI and
WISC.
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April 2014 Other indicators: time-resolved Reactive spray
penetration: reacting baseline (AR) The time-resolved RSP data
helps in understanding the observed differences among models. In
the baseline case, the differences due to the spray model set-up
are particularly evident.
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April 2014 Other indicators: time-resolved Reactive spray
penetration: reacting vs non-reacting For two models, it was
possible to compare the Spray penetration computed in the
non-reacting (topic 1.2) and reacting cases under the same
thermodynamic conditions. POLIMI results are in good agreement with
the measured data.
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April 2014 Heat release rate Other indicators: time-resolved
Comparison for the baseline reacting case (AR) ETH, POLIMI and WISC
have a similar steady value of HRR, which is lower (why?) than the
measured data. UNSW has an increase of HRR after 2 ms (numerical
issues with the pdf method?) Models with TCI have a similar
description of the initial stages of combustion (cool flame,
premixed, mixing-controlled).
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April 2014 Heat release rate Other indicators: time-resolved
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April 2014 Time-resolved Conclusions on the modelling part (#1)
GLOBAL INDICATORS The available experimental database allows an
extended validation of the model capability to well predict
ignition delay and lift-off length. Generally all models tend to
over-estimate the ID for all conditions. -Need more shock tube and
flow reactor data in spray A relevant conditions to improve current
kinetic mechanisms. -Current chemical mechanism give comparable
results when applied to Spray A conditions. Models with TCI showed
a good capability of predicting LOL absolute values and trends.
Well-mixed approaches can capture the qualitative trend.
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April 2014 Time-resolved Conclusions on the modelling part (#2)
TIME RESOLVED RESULTS Time resolved spray penetrations computed by
all groups differ significantly. Models need to be well set-up
under non reacting conditions first to well capture the transient
behavior the flame. If properly set-up, model can capture the
effect of the reactions on the spray penetration evolution. The
comparison of heat release rate between models and experiments,
showed some discrepancies not only in the ignition prediction but
also in the steady state rate of combustion. More investigation is
required.
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April 2014 BACK-UP SLIDE
Slide 77
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April 2014 IFPEN TUe OH*OH-LIF HS-OH*OH-LIF Fueln-dodecane
Injector201-02 201-01 Injection pressure1500 bar 500/1000/1500 bar
Injection duration 5 ms Laser-Q1(6):282.92 nm -Q1(9):283.928nm
Energy-11 -17 mJ/pulse -11 mJ/pulse Laser sheet length (width)-20
mm (
