Difference between revisions of "Multi-inlet CH 4/Air flame with scheme GRI12"

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Line 1: Line 1:
 
== '''Objectives''' ==
 
== '''Objectives''' ==
  
−
The Stochastic_GRI12 test case describes a reduction of the GRI1.2 scheme for a 0D 2-inlet configuration. Starting with 32 species and 177 reactions, we reduce to 12 transported species, 2 species in quasi steady assumption and 29 reactions.
+
The Stochastic_GRI12 test case describes a reduction of the GRI1.2 scheme for a 0D 2-inlet configuration. Starting with 32 species and 177 reactions, we reduce to 12 transported species, 2 species in quasi steady state assumption and 28 reactions.
  
 
== '''Key parameters''' ==
 
== '''Key parameters''' ==
  
−
The target species considered for this test case are O2, CO and CO2. We are at atmospheric pressure, and the fuel is injected in its gaseous form (no evaporation model). The inputs of the 3 inlets (oxidiser, fuel and burned gases) are displayed below :  
+
The target species considered for this test case are O2, CO and CO2. We are at atmospheric pressure, and the fuel is injected in its gaseous form (no evaporation model). The inputs of the 3 inlets (oxidiser, fuel and burned gases) are displayed below (from the input_file.ini):  
  
  
−
Characteristics of the air inlet :
+
//------Inlets------//
−
  listInlets.push_back(new MultipleInlet(
+
new Inlet 0 : Air
−
                /*Temperature*/ 700,
+
  T = 700
−
                /*Pressure*/ 1E+05,
+
  Pressure = 1E+05
−
                /*Mass flow rate*/ 0.500,
+
  MassFlowRate = 0.500
−
                /*Xk*/ "O2:0.21, N2:0.79",
+
  Xk = O2:0.21, N2:0.79
−
                /*Yk*/ "",
+
  // the composition can also be added with molar fractions, for that replace "Yk" by "Xk" 
−
                /*Evaporation model*/ false,
+
  EvaporationModel = false
−
                /*Droplet diameter*/ 0.0,
+
  DropletDiameter = 0.0
−
                /*Evaporation time*/ 0.0,
+
  EvaporationTime = 0.0
−
                /*Liquid density*/ 0.0,
+
  liquidDensity = 0.0
−
                /*Evaporation latent heat*/ 0.0));
+
  EvaporationLatentHeat = 0.0
 +
//EndInlet
  
−
Characteristics of the fuel inlet :
 
−
  listInlets.push_back(new MultipleInlet(
 
−
                /*Temperature*/ 450,
 
−
                /*Pressure*/ 1E+05,
 
−
                /*Mass flow rate*/ 0.02,
 
−
                /*Xk*/ "CH4:1.0",
 
−
                /*Yk*/ "",
 
−
                /*Evaporation model*/ false,
 
−
                /*Droplet diameter*/ 0.0,
 
−
                /*Evaporation time*/ 0.0,
 
−
                /*Liquid density*/ 0.0,
 
−
                /*Evaporation latent heat*/ 0.0));
 
  
−
Characteristics of the burned gases inlet :  
+
new Inlet 1 : Fuel
−
  listInlets.push_back(new Characteristics_MultipleInlet(
+
  T = 450
−
                /*Temperature*/ 2500,
+
  Pressure = 1E+05
−
                /*Pressure*/ 1E+05,
+
  MassFlowRate = 0.017
−
                /*Mass flow rate*/ 0.200,
+
  Xk = CH4:1.0 
−
                /*Xk*/ "N2:0.76308, O2:0.093573, H2O:0.072355, CO2:0.070468",
+
  // the composition can also be added with molar fractions, for that replace "Yk" by "Xk" 
−
                /*Yk*/ "",
+
  EvaporationModel = 0
−
                /*Evaporation model*/ false,
+
  DropletDiameter = 0.0
−
                /*Droplet diameter*/ 0.0,
+
  EvaporationTime = 0.0
−
                /*Evaporation time*/ 0.0,
+
  liquidDensity = 0.0
−
                /*Liquid density*/ 0.0,
+
  EvaporationLatentHeat = 0.0
−
                /*Evaporation latent heat*/ 0.0));
+
//EndInlet
−
                /*tau_t*/ 2e-04,
+
 
−
                /*delta_t*/ 1e-05,
+
 
−
                /*nbIterations*/ 200,
+
new Inlet : GB
−
                /*BurnedGases*/ true));
+
  T = 2500
 +
  Pressure = 1E+05
 +
  MassFlowRate = 0.2
 +
  Xk = N2:0.76308, O2:0.093573, H2O:0.072355, CO2:0.070468  
 +
  // the composition can also be added with molar fractions, for that replace "Yk" by "Xk" 
 +
  EvaporationModel =  0 ///1 to activate the model
 +
  DropletDiameter = 0.0
 +
  EvaporationTime = 0.0
 +
  liquidDensity = 0.0
 +
  EvaporationLatentHeat = 0.0
  
 
== '''Results''' ==
 
== '''Results''' ==
Line 57: Line 55:
 
While running the DRGEP species step, your terminal should display the following information :
 
While running the DRGEP species step, your terminal should display the following information :
  
−
  Reading initial mechanism "mechanisms/gri12.xml" with description "gri12" ----------> OK
+
 
−
Number of species: 32
+
 
−
Number of reactions: 177
+
  MECHANISM:------------------------------------------------------------------------------------------------------
−
Set the mole fraction of inlet 0
+
            Reading initial mechanism "mechanisms/gri12.xml" with description "gri12" ----------> OK
−
Set the mole fraction of inlet 1
+
              Number of species: 32
−
Set the mole fraction of inlet 2
+
              Number of reactions: 177
  
  
 
  Composition to enter  For the equilibrium computation to get the Burned gases  
 
  Composition to enter  For the equilibrium computation to get the Burned gases  
−
  Compo_H_mixed 334274
+
  Compo_H_mixed 525637
 
  X_O2: 0.16931
 
  X_O2: 0.16931
 
  X_H2O: 0.019848
 
  X_H2O: 0.019848
Line 72: Line 70:
 
  X_CO2: 0.0193304
 
  X_CO2: 0.0193304
 
  X_N2: 0.749689
 
  X_N2: 0.749689
−
  T_mixed 1063.63
+
  T_mixed 1212.8
 
  Nb particles  0  500
 
  Nb particles  0  500
 
  Nb particles  1  17
 
  Nb particles  1  17
Line 85: Line 83:
  
 
  0  AR
 
  0  AR
−
  2.3181e-16 C
+
  1.41837e-05 HCCOH
−
  2.44619e-09 CH
+
  0.000287651 C
−
  2.59722e-09 HCCOH
+
  0.000489111 CH2CO
−
  5.68614e-09 C2H
+
  0.000498049 C2H
−
  1.49031e-08 CH2CO
+
  0.00327403 C2H2
−
  1.27776e-07 C2H2
+
  0.00356528 CH2OH
−
  2.68843e-07 HCCO
+
  0.00476023  CH
−
  3.69712e-05 C2H3
+
0.00528262 HCCO
−
  7.25527e-05 CH2OH
+
  0.0119242 H2O2
−
  0.00365571 H2O2
+
  0.0130846 C2H3
−
  0.00537274 C2H4
+
  0.0164568 CH3OH
−
  0.00537274 C2H5
+
  0.0358106 C2H4
−
  0.00543792 CH2(S)
+
  0.0358106 C2H5
−
  0.00598963 CH2
+
  0.0380984 CH2(S)
−
  0.0100589 CH3OH
+
  0.0394904 CH2
−
  0.0179344 H2
+
  0.0692651 H2
−
  0.0199904 HCO
+
  0.120645 C2H6
−
  0.0576166 O
+
  0.144271 HCO
−
  0.145908 CH3O
+
  0.146106 CH2O
−
  0.342307 H
+
  0.193431 CH3O
−
  0.373973 C2H6
+
  0.345988 O
−
  0.460535 OH
+
  0.699261 H
−
0.483807  CH2O
+
  0.699262 OH
 
  0.999998  HO2
 
  0.999998  HO2
 
  0.999999  CH3
 
  0.999999  CH3
Line 116: Line 114:
 
  1  CO2
 
  1  CO2
 
  1  N2
 
  1  N2
−
 
  
 
From a detailed 32 species scheme, we obtain reduced schemes (31 to 11 species). and we choose the one with 14 species for the next step. With 13 species and less, the trajectories of the targets and the temperature are too different from the detailed ones to be easily optimised.
 
From a detailed 32 species scheme, we obtain reduced schemes (31 to 11 species). and we choose the one with 14 species for the next step. With 13 species and less, the trajectories of the targets and the temperature are too different from the detailed ones to be easily optimised.
Line 126: Line 123:
  
 
From the reduced scheme with 14 species, the DRGEP reaction step displays the associated 42 reactions (forward, reverse and global) with their rank. The global reactions are displayed below :
 
From the reduced scheme with 14 species, the DRGEP reaction step displays the associated 42 reactions (forward, reverse and global) with their rank. The global reactions are displayed below :
 +
 +
Reaction 11  7.11815e-05
 +
Reaction 2  9.22955e-05
 +
Reaction 1  9.5273e-05
 +
Reaction 18  0.002098
 +
Reaction 31  0.00268202
 +
Reaction 10  0.00415073
 +
Reaction 6  0.00453937
 +
Reaction 12  0.0058625
 +
Reaction 22  0.00631152
 +
Reaction 7  0.0107781
 +
Reaction 8  0.0107783
 +
Reaction 34  0.0154049
 +
Reaction 19  0.0177938
 +
Reaction 29  0.0220001
 +
Reaction 25  0.0269477
 +
Reaction 24  0.0322283
 +
Reaction 37  0.0341651
 +
Reaction 40  0.0553785
 +
Reaction 9  0.0611019
 +
Reaction 32  0.0701004
 +
Reaction 39  0.0765675
 +
Reaction 38  0.148919
 +
Reaction 35  0.164745
 +
Reaction 3  0.165682
 +
Reaction 14  0.166509
 +
Reaction 30  0.173203
 +
Reaction 23  0.250228
 +
Reaction 21  0.364056
 +
Reaction 36  0.459012
 +
Reaction 26  0.491301
 +
Reaction 5  0.494067
 +
Reaction 28  0.550285
 +
Reaction 20  0.606395
 +
Reaction 42  0.607008
 +
Reaction 15  0.736774
 +
Reaction 17  0.754281
 +
Reaction 16  0.791332
 +
Reaction 41  0.855392
 +
Reaction 33  0.948061
 +
Reaction 13  0.969153
 +
Reaction 4  0.974258
 +
Reaction 27  0.992507
  
 +
After this step, by comparing the reference trajectories with the new ones, we choose to delete 13 reactions, so the next step is performed with 14 species and 28 reactions. Indeed, with 27 and less species, the final state of the trajectories is not well predicted and difficult to represent even with the optimisation step.
  
−
Reaction 11  6.97477e-05
+
[[File:14sp_28R.png|600px|center]]
−
Reaction 2  8.75759e-05
+
−
Reaction 1  8.98678e-05
+
−
Reaction 18  0.00213229
+
−
Reaction 31  0.00291462
+
−
Reaction 6  0.00363456
+
−
Reaction 10  0.00375711
+
−
Reaction 22  0.00511265
+
−
Reaction 12  0.00898034
+
−
Reaction 7  0.0106843
+
−
Reaction 8  0.0106849
+
−
Reaction 34  0.0173608
+
−
Reaction 19  0.0185876
+
−
Reaction 25  0.0221759
+
−
Reaction 29  0.0222202
+
−
Reaction 37  0.0372901
+
−
Reaction 24  0.0446721
+
−
Reaction 9  0.0449009
+
−
Reaction 40  0.0555031
+
−
Reaction 32  0.0696855
+
−
Reaction 39  0.0865175
+
−
Reaction 3  0.144344
+
−
Reaction 30  0.156095
+
−
Reaction 14  0.166212
+
−
Reaction 35  0.167587
+
−
Reaction 38  0.178616
+
−
Reaction 23  0.250862
+
−
Reaction 36  0.357038
+
−
Reaction 21  0.360875
+
−
Reaction 26  0.419329
+
−
Reaction 28  0.459053
+
−
Reaction 5  0.487659
+
−
Reaction 42  0.602514
+
−
Reaction 20  0.633343
+
−
Reaction 15  0.740476
+
−
Reaction 16  0.789885
+
−
Reaction 17  0.828505
+
−
Reaction 41  0.846392
+
−
Reaction 33  0.948112
+
−
Reaction 13  0.969275
+
−
Reaction 4  0.971434
+
−
Reaction 27  0.992353
+
−
 
+
−
 
+
−
After this step, by comparing the reference trajectories with the new ones, we choose to delete 13 reactions, so the next step is performed with 14 species and 29 reactions. Indeed, with 28 and less species, the final state of the trajectories is not well predicted and difficult to represent even with the optimisation step.
+
−
 
+
−
[[File:14sp_29R.png|600px|center]]
+
  
−
Fig2 : Comparison between the reference trajectories of the target species and the temperature (in black), and the trajectories computed with the reduced mechanism with 14 transported species and 29 reactions (in red) for the fuel inlet.
+
Fig2 : Comparison between the reference trajectories of the target species and the temperature (in black), and the trajectories computed with the reduced mechanism with 14 transported species and 28 reactions (in red) for the fuel inlet.
  
 
=== QSS Step ===
 
=== QSS Step ===
Line 182: Line 177:
 
While running the QSS step, your terminal should display the following information :
 
While running the QSS step, your terminal should display the following information :
  
−
  Species H  0.00707074
+
  Species H  0.00794323
−
  Species O  0.00347138
+
  Species O  0.00490131
 
  Species O2  1
 
  Species O2  1
−
  Species OH  0.00238597
+
  Species OH  0.00320187
−
  Species H2O  0.0394215
+
  Species H2O  0.0582805
−
  Species HO2  0.0120837
+
  Species HO2  0.012535
−
  Species CH3  0.0951441
+
  Species CH3  0.0853549
−
  Species CH4  0.774634
+
  Species CH4  0.794206
 
  Species CO  1
 
  Species CO  1
 
  Species CO2  1
 
  Species CO2  1
−
  Species HCO  0.00480146
+
  Species HCO  0.00362124
−
  Species CH2O  0.178736
+
  Species CH2O  0.181152
−
  Species CH3O  0.00520346
+
  Species CH3O  0.00472456
 
  Species N2  1
 
  Species N2  1
  
−
  Interactions with species H  with QSS Criteria 0.00707074
+
  Interactions with species H  with QSS Criteria 0.00794323
−
  H2O:2  HO2:1  CH3:1  CH2O:2  CH3O:1
+
  H2O:2  HO2:1  CH3:1  CH2O:2  CH3O:1
  
−
  Interactions with species O  with QSS Criteria 0.00347138
+
  Interactions with species O  with QSS Criteria 0.00490131
−
  OH:1  H2O:1  HO2:1  CH3:1  CH2O:1  CH3O:1
+
  OH:1  H2O:1  HO2:1  CH3:1  CH2O:1  CH3O:1
  
−
  Interactions with species OH  with QSS Criteria 0.00238597
+
  Interactions with species OH  with QSS Criteria 0.00320187
−
  O:1  OH:2  HO2:1  CH3:2  HCO:2 CH2O:2  CH3O:1
+
  O:1  OH:2  HO2:1  CH3:2  HCO:1 CH2O:2  CH3O:1
  
−
  Interactions with species H2O  with QSS Criteria 0.0394215
+
  Interactions with species H2O  with QSS Criteria 0.0582805
−
  H:2  O:1  HO2:1  CH3:1  HCO:2
+
  H:2  O:1  HO2:1  CH3:1  HCO:2
  
−
  Interactions with species HO2  with QSS Criteria 0.0120837
+
  Interactions with species HO2  with QSS Criteria 0.012535
−
  H:1  O:1  OH:1  H2O:1  CH3:2  CH2O:1
+
  H:1  O:1  OH:1  H2O:1  CH3:2  CH2O:1
  
−
  Interactions with species CH3  with QSS Criteria 0.0951441
+
  Interactions with species CH3  with QSS Criteria 0.0853549
−
  H:1  O:1  OH:2  H2O:1  HO2:2  HCO:1  CH2O:1
+
  H:1  O:1  OH:2  H2O:1  HO2:2  HCO:1  CH2O:1
  
−
  Interactions with species HCO  with QSS Criteria 0.00480146
+
  Interactions with species HCO  with QSS Criteria 0.00362124
−
  OH:2 H2O:2  CH3:1
+
  OH:1 H2O:2  CH3:1
  
−
  Interactions with species CH2O  with QSS Criteria 0.178736
+
  Interactions with species CH2O  with QSS Criteria 0.181152
−
  H:2  O:1  OH:2  HO2:1  CH3:1
+
  H:2  O:1  OH:2  HO2:1  CH3:1
  
−
  Interactions with species CH3O  with QSS Criteria 0.00520346
+
  Interactions with species CH3O  with QSS Criteria 0.00472456
 
  H:1  O:1  OH:1
 
  H:1  O:1  OH:1
  
 
We choose to put the species CH3O and HCO in QSS hypothesis due to their low QSS coefficient.
 
We choose to put the species CH3O and HCO in QSS hypothesis due to their low QSS coefficient.
  
−
In order to obtain the trajectories of the 12-transported species 29-reactions reduced scheme, we run the getQSSfile step and we observe that the final state and the shape of the trajectories are conserved. It is under these conditions that the optimisation step will be efficient.
+
In order to obtain the trajectories of the 12-transported species 28-reactions reduced scheme, we run the getQSSfile step and we observe that the final state and the shape of the trajectories are conserved. It is under these conditions that the optimisation step will be efficient.
  
−
[[File:12sp_29R.png|600px|center]]
+
[[File:12sp_28R.png|600px|center]]
  
−
Fig3 : Comparison between the reference trajectories of the target species and the temperature (in black), and the trajectories computed with the reduced mechanism with 12 transported species and 29 reactions (in red) for the fuel inlet.
+
Fig3 : Comparison between the reference trajectories of the target species and the temperature (in black), and the trajectories computed with the reduced mechanism with 12 transported species and 28 reactions (in red) for the fuel inlet.
  
 
=== Optimisation Step ===
 
=== Optimisation Step ===
  
  
−
The final step of the ORCh method, the genetic algorithm, enables to recover the trajectories of the target species. Firstly, we allowed a 10 % variation on the pre exponential factor, the temperature exposant and the energy activation in order to find their optimal values.
+
The final step of the ORCh method, the genetic algorithm, enables to recover the trajectories of the target species. We allowed a 10 % variation on the pre exponential factor, the temperature exposant and 6 % on the energy activation in order to find their optimal values.
  
−
A population of 40 elements was used during 38 generations.
+
A population of 40 elements was used during 40 generations.
  
−
Secondly, in order to obtain more precise trajectories, we allowed a 1 % variation on the pre exponential factor, the temperature exposant and the energy activation. 42 more generations were performed in that case.
 
  
−
The following trajectories of the temperature, the flame speed and the target species match perfectly the ones of the reference detailed scheme with only 12 transported species and 29 reactions.
+
The following trajectories of the temperature, the flame speed and the target species match perfectly the ones of the reference detailed scheme with only 12 transported species and 28 reactions.
  
  
 
[[File:optim_stoch_GRI.png|600px|center]]
 
[[File:optim_stoch_GRI.png|600px|center]]
  
−
Fig4 : Comparison between the reference trajectories of the target species and the temperature (in black), and the trajectories computed with the reduced mechanism with 12 transported species and 29 reactions (in red) after optimisation for the fuel inlet.
+
Fig4 : Comparison between the reference trajectories of the target species and the temperature (in black), and the trajectories computed with the reduced mechanism with 12 transported species and 28 reactions (in red) after optimisation for the fuel inlet.

Latest revision as of 16:59, 31 January 2019

Objectives

The Stochastic_GRI12 test case describes a reduction of the GRI1.2 scheme for a 0D 2-inlet configuration. Starting with 32 species and 177 reactions, we reduce to 12 transported species, 2 species in quasi steady state assumption and 28 reactions.

Key parameters

The target species considered for this test case are O2, CO and CO2. We are at atmospheric pressure, and the fuel is injected in its gaseous form (no evaporation model). The inputs of the 3 inlets (oxidiser, fuel and burned gases) are displayed below (from the input_file.ini): 


//------Inlets------//
new Inlet 0 : Air
 T = 700
 Pressure = 1E+05
 MassFlowRate = 0.500
 Xk = O2:0.21, N2:0.79  
 // the composition can also be added with molar fractions, for that replace "Yk" by "Xk"   
 EvaporationModel = false
 DropletDiameter = 0.0
 EvaporationTime = 0.0
 liquidDensity = 0.0
 EvaporationLatentHeat = 0.0
//EndInlet



new Inlet 1 : Fuel
 T = 450
 Pressure = 1E+05
 MassFlowRate = 0.017
 Xk = CH4:1.0  
 // the composition can also be added with molar fractions, for that replace "Yk" by "Xk"   
 EvaporationModel = 0
 DropletDiameter = 0.0
 EvaporationTime = 0.0
 liquidDensity = 0.0
 EvaporationLatentHeat = 0.0
//EndInlet



new Inlet : GB 
 T = 2500
 Pressure = 1E+05
 MassFlowRate = 0.2
 Xk = N2:0.76308, O2:0.093573, H2O:0.072355, CO2:0.070468 
 // the composition can also be added with molar fractions, for that replace "Yk" by "Xk"   
 EvaporationModel =  0 ///1 to activate the model
 DropletDiameter = 0.0
 EvaporationTime = 0.0
 liquidDensity = 0.0
 EvaporationLatentHeat = 0.0

Results

DRGEP Step

While running the DRGEP species step, your terminal should display the following information : 


MECHANISM:------------------------------------------------------------------------------------------------------
           Reading initial mechanism "mechanisms/gri12.xml" with description "gri12" ----------> OK
              Number of species: 32
              Number of reactions: 177



Composition to enter  For the equilibrium computation to get the Burned gases 
Compo_H_mixed 525637
X_O2: 0.16931
X_H2O: 0.019848
X_CH4: 0.0418227
X_CO2: 0.0193304
X_N2: 0.749689
T_mixed 1212.8
Nb particles  0  500
Nb particles  1  17
Nb particles  2  200
Nmix 35
Set the mole fraction of inlet 0
Set the mole fraction of inlet 1
Set the mole fraction of inlet 2


followed by the the species associated with their rank : 

0  AR
1.41837e-05  HCCOH
0.000287651  C
0.000489111  CH2CO
0.000498049  C2H
0.00327403  C2H2
0.00356528  CH2OH
0.00476023  CH
0.00528262  HCCO
0.0119242  H2O2
0.0130846  C2H3
0.0164568  CH3OH
0.0358106  C2H4
0.0358106  C2H5
0.0380984  CH2(S)
0.0394904  CH2
0.0692651  H2
0.120645  C2H6
0.144271  HCO
0.146106  CH2O
0.193431  CH3O
0.345988  O
0.699261  H
0.699262  OH
0.999998  HO2
0.999999  CH3
1  O2
1  H2O
1  CH4
1  CO
1  CO2
1  N2

From a detailed 32 species scheme, we obtain reduced schemes (31 to 11 species). and we choose the one with 14 species for the next step. With 13 species and less, the trajectories of the targets and the temperature are too different from the detailed ones to be easily optimised.

14sp 42R.png

Fig1 : Comparison between the reference trajectories of the target species and the temperature (in black), and the trajectories computed with the reduced mechanism with 14 transported species and 42 reactions (in red) for the fuel inlet.


From the reduced scheme with 14 species, the DRGEP reaction step displays the associated 42 reactions (forward, reverse and global) with their rank. The global reactions are displayed below : 

Reaction 11  7.11815e-05
Reaction 2  9.22955e-05
Reaction 1  9.5273e-05
Reaction 18  0.002098
Reaction 31  0.00268202
Reaction 10  0.00415073
Reaction 6  0.00453937
Reaction 12  0.0058625
Reaction 22  0.00631152
Reaction 7  0.0107781
Reaction 8  0.0107783
Reaction 34  0.0154049
Reaction 19  0.0177938
Reaction 29  0.0220001
Reaction 25  0.0269477
Reaction 24  0.0322283
Reaction 37  0.0341651
Reaction 40  0.0553785
Reaction 9  0.0611019
Reaction 32  0.0701004
Reaction 39  0.0765675
Reaction 38  0.148919
Reaction 35  0.164745
Reaction 3  0.165682
Reaction 14  0.166509
Reaction 30  0.173203
Reaction 23  0.250228
Reaction 21  0.364056
Reaction 36  0.459012
Reaction 26  0.491301
Reaction 5  0.494067
Reaction 28  0.550285
Reaction 20  0.606395
Reaction 42  0.607008
Reaction 15  0.736774
Reaction 17  0.754281
Reaction 16  0.791332
Reaction 41  0.855392
Reaction 33  0.948061
Reaction 13  0.969153
Reaction 4  0.974258
Reaction 27  0.992507

After this step, by comparing the reference trajectories with the new ones, we choose to delete 13 reactions, so the next step is performed with 14 species and 28 reactions. Indeed, with 27 and less species, the final state of the trajectories is not well predicted and difficult to represent even with the optimisation step.

14sp 28R.png

Fig2 : Comparison between the reference trajectories of the target species and the temperature (in black), and the trajectories computed with the reduced mechanism with 14 transported species and 28 reactions (in red) for the fuel inlet.

QSS Step

While running the QSS step, your terminal should display the following information : 

Species H  0.00794323
Species O  0.00490131
Species O2  1
Species OH  0.00320187
Species H2O  0.0582805
Species HO2  0.012535
Species CH3  0.0853549
Species CH4  0.794206
Species CO  1
Species CO2  1
Species HCO  0.00362124
Species CH2O  0.181152
Species CH3O  0.00472456
Species N2  1

Interactions with species H  with QSS Criteria 0.00794323
H2O:2  HO2:1  CH3:1  CH2O:2  CH3O:1

Interactions with species O  with QSS Criteria 0.00490131
OH:1  H2O:1  HO2:1  CH3:1  CH2O:1  CH3O:1

Interactions with species OH  with QSS Criteria 0.00320187
O:1  OH:2  HO2:1  CH3:2  HCO:1  CH2O:2  CH3O:1

Interactions with species H2O  with QSS Criteria 0.0582805
H:2  O:1  HO2:1  CH3:1  HCO:2

Interactions with species HO2  with QSS Criteria 0.012535
H:1  O:1  OH:1  H2O:1  CH3:2  CH2O:1

Interactions with species CH3  with QSS Criteria 0.0853549
H:1  O:1  OH:2  H2O:1  HO2:2  HCO:1  CH2O:1

Interactions with species HCO  with QSS Criteria 0.00362124
OH:1  H2O:2  CH3:1

Interactions with species CH2O  with QSS Criteria 0.181152
H:2  O:1  OH:2  HO2:1  CH3:1

Interactions with species CH3O  with QSS Criteria 0.00472456
H:1  O:1  OH:1

We choose to put the species CH3O and HCO in QSS hypothesis due to their low QSS coefficient.

In order to obtain the trajectories of the 12-transported species 28-reactions reduced scheme, we run the getQSSfile step and we observe that the final state and the shape of the trajectories are conserved. It is under these conditions that the optimisation step will be efficient.

12sp 28R.png

Fig3 : Comparison between the reference trajectories of the target species and the temperature (in black), and the trajectories computed with the reduced mechanism with 12 transported species and 28 reactions (in red) for the fuel inlet.

Optimisation Step

The final step of the ORCh method, the genetic algorithm, enables to recover the trajectories of the target species. We allowed a 10 % variation on the pre exponential factor, the temperature exposant and 6 % on the energy activation in order to find their optimal values.

A population of 40 elements was used during 40 generations.


The following trajectories of the temperature, the flame speed and the target species match perfectly the ones of the reference detailed scheme with only 12 transported species and 28 reactions.


Optim stoch GRI.png

Fig4 : Comparison between the reference trajectories of the target species and the temperature (in black), and the trajectories computed with the reduced mechanism with 12 transported species and 28 reactions (in red) after optimisation for the fuel inlet.

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