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

Revision as of 16:54, 22 June 2017

Objectives

The Stochastic_GRI12 test case shows 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.

Principle

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 :

Characteristics of the air inlet :

  listInlets.push_back(new MultipleInlet(
               /*Temperature*/ 700,
               /*Pressure*/ 1E+05,
               /*Mass flow rate*/ 0.500,
               /*Xk*/ "O2:0.21, N2:0.79",
               /*Yk*/ "",
               /**/ false,
               /**/ 0.0,
               /**/ 0.0,
               /**/ 0.0,
               /**/ 0.0));

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*/ "",
               /**/ false,
               /**/ 0.0,
               /**/ 0.0,
               /**/ 0.0,
               /**/ 0.0));

Characteristics of the burned gases inlet :

  listInlets.push_back(new Characteristics_MultipleInlet(
               /*Temperature*/ 2500,
               /*Pressure*/ 1E+05,
               /*Mass flow rate*/ 0.200,
               /*Xk*/ "N2:0.76308, O2:0.093573, H2O:0.072355, CO2:0.070468",
               /*Yk*/ "",
               /**/ false,
               /**/ 0.0,
               /**/ 0.0,
               /**/ 0.0,
               /**/ 0.0,
               /*tau_t*/ 2e-04,
               /*delta_t*/ 1e-05,
               /*nbIterations*/ 200,
               /*BurnedGases*/ true));

Results

DRGEP Step

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
Set the mole fraction of inlet 0
Set the mole fraction of inlet 1
Set the mole fraction of inlet 2

Composition to enter  For the equilibrium computation to get the Burned gases 
Compo_H_mixed 334274
X_O2: 0.16931
X_H2O: 0.019848
X_CH4: 0.0418227
X_CO2: 0.0193304
X_N2: 0.749689
T_mixed 1063.63
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
2.3181e-16  C
2.44619e-09  CH
2.59722e-09  HCCOH
5.68614e-09  C2H
1.49031e-08  CH2CO
1.27776e-07  C2H2
2.68843e-07  HCCO
3.69712e-05  C2H3
7.25527e-05  CH2OH
0.00365571  H2O2
0.00537274  C2H4
0.00537274  C2H5
0.00543792  CH2(S)
0.00598963  CH2
0.0100589  CH3OH
0.0179344  H2
0.0199904  HCO
0.0576166  O
0.145908  CH3O
0.342307  H
0.373973  C2H6
0.460535  OH
0.483807  CH2O
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, the trajectories of the targets and the temperature are too different from the detailed ones to be easily optimised.

Comparison between the reference trajectory (in black) of the target species and the temperature, and the trajectories computed with the reduced mechanism (in red) with 14 transported species.

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

[insert screen shot]

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.

Comparison between the reference trajectory (in black) of the target species and the temperature, and the trajectories computed with the reduced mechanism (in red) with 14 transported species and 29 reactions.

QSS Step

Interactions with species H  with QSS Criteria 0.00707074
H2O:2  HO2:1  CH3:1  CH2O:2  CH3O:1  

Interactions with species O  with QSS Criteria 0.00347138
OH:1  H2O:1  HO2:1  CH3:1  CH2O:1  CH3O:1  

Interactions with species OH  with QSS Criteria 0.00238597
O:1  OH:2  HO2:1  CH3:2  HCO:2  CH2O:2  CH3O:1  

Interactions with species H2O  with QSS Criteria 0.0394215
H:2  O:1  HO2:1  CH3:1  HCO:2  

Interactions with species HO2  with QSS Criteria 0.0120837
H:1  O:1  OH:1  H2O:1  CH3:2  CH2O:1  

Interactions with species CH3  with QSS Criteria 0.0951441
H:1  O:1  OH:2  H2O:1  HO2:2  HCO:1  CH2O:1  

Interactions with species HCO  with QSS Criteria 0.00480146
OH:2  H2O:2  CH3:1  

Interactions with species CH2O  with QSS Criteria 0.178736
H:2  O:1  OH:2  HO2:1  CH3:1  

Interactions with species CH3O  with QSS Criteria 0.00520346
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 29-reactions reduced scheme, we run the getQSSfile step and we obtain the targets and observe that the final state and the shape of the trajectory is conserved, see for example the CO2 species  :

Optimisation Step