COMBUSTION SIMULATION ON A COMBUSTOR MODEL

1. TYPES OF COMBUSTION SIMULATIONS IN FLUENT

BASED ON MIXING

• NON-PREMIXED COMBUSTION: In this type of combustion simulation, the fuel and oxidizer enter the reaction zone in distinct streams. Mixing takes place at the time of combustion.
• PRE-MIXED COMBUSTION: In this type of combustion simulation, the fuel and oxidizer are mixed at the molecular level before ignition.
• PARTIALLY MIXED COMBUSTION: In this type of combustion simulation, the fuel and oxidizer are partially pre-mixed at non-uniform ratios before combustion.

BASED ON PHASE

• FLUID PHASE (VOLUMETRIC REACTIONS): When combustion takes place in the fluid phase.
• WALL (SURFACE REACTIONS): When combustion takes place on the wall.
• PARTICLES (SURFACE REACTIONS): Combustion taking place on the surface of the particles.
• POROUS REGIONS: Combustion taking place inside the pores.

2. COMBUSTION SIMULATION ON A COMBUSTOR MODEL

2.1. 3D MODEL OF THE COMBUSTOR

2.2. 2D GEOMETRY EXTRACTED FROM THE 3D MODEL

2.3. MESHING:

Number of nodes: 35300

Number of elements: 17181

2.4. ELEMENT QUALITY:

2.5. BOUNDARY CONDITIONS

• The turbulence model used here is a k-epsilon model.
• Mass Fraction of CH4: 1
• Mass Fraction of O2: 0.23
• Inlet velocity of fuel: 80m/s.
• Inlet velocity of air: 0.5m/s.
• A pressure Based Solver is used for the simulation.
• Chemical energy interaction is governed by EDDY DISSIPATION MODEL.

2.6. TEMPERATURE CONTOUR:

2.7. MASS FRACTIONS OF DIFFERENT SPECIES

2.7.1. MASS FRACTION OF CH4

2.7.2. MASS FRACTION OF CO2

2.7.3. MASS FRACTION OF H2O

2.7.4. MASS FRACTION OF N2

2.7.5. MASS FRACTION OF O2

2.8. LINE PROBES ARE USED TO ANALYSE THE LINE AVERAGED MASS FRACTION OF DIFFERENT SPECIES AT DIFFERENT LOCATIONS

The lines are drawn from the inlet at a distance of 0.1m, 0.2m, 0.3m and 0.4m.

THE LINE AVERAGED MASS FRACTION OF DIFFERENT SPECIES AT FOUR DIFFERENT LOCATIONS ARE SHOWN BELOW:

2.8.1. VARIATION IN CH4 MASS FRACTION

2.8.2. VARIATION IN CO2 MASS FRACTION

2.8.3. VARIATION IN N2 MASS FRACTION

2.8.4. VARIATION IN H2O MASS FRACTION

2.8.5. VARIATION IN O2 MASS FRACTION

We did not get any mass fractions of NOx from the simulation. This is because N2 is an inert gas. Therefore the NOx concentration is very low to a negligible value. There are methods to find the NOx mass fraction which are discussed below.

2.9. CALCULATION FOR MASS FRACTION OF NOx

The variation in NOx species cannot be determined in the above method. Because during the simulation, the NOx equation in the solver was turned off. In order to determine the NOx mass fraction, the Equation was turned on. The simulation was done on post-processing mode, where all other equations other than NOx equations were turned off.

2.9.1. NOx MASS FRACTION

2.9.2. VARIATION IN NOx MASS FRACTION AT DIFFERENT LOCATIONS

2.10. CONCLUSION

• The combustion simulation on the given combustor model was completed successfully.
• The mass fraction of all the given species was found.
• The highest temperature is 2257k
• Since N2 is an inert gas the NOx concentration is negligible.
• The mass fraction of NOx was found by turning on the NOx model (equations) in the solver and by running the solver in post-processing mode.