Combustion Simulation using Ansys Fluent
Aim:
CFD Analysis of Combustion using Ansys Fluent
Objectives:
- To understand the combustor model and species formation in combustion.
- To observe the different species such as CO2, H2O, CH4, N2, O2, NOx emissions & Soot formation at different location.
- To recognize the effects of water content on the pollution emissions.
Introduction:
In this system, CH4 inlet is given at small size and air inlet is given at large size. Because of the turbulent mixing of this two, there will be combustion present. This will produce different pollutants such as CO2, H2O, CH4, N2, O2, NOx emissions & Soot formation at outlet. If the water is used by mole fraction with inlet fuel then there will be reduction in the pollutants at outlet.
Simulation Procedure:
Step: 1 Geometry Preparation
First of all, the 2d geometry is created in Spaceclaim which is given below:
Figure: 2d Sketch of Model
Figure: 2d Model
Step: 2 Meshing
In this, the meshing is generated with enabling Proximity after giving Name Selections.
Figure: Meshing
Step: 3 Set-up
General:
Energy Equation is enabled
Viscous Model:
Species Model:
NOx model:
Soot Model:
Boundary Conditions
Air Inlet Velocity: 0.5 m/s
Air Inlet Temperature: 300 K
Species Mass fraction at Air Inlet: O2 = 0.23
Fuel Inlet Temperature: 300 K
Fuel Inlet Velocity: 80 m/s
Species Mass Fraction at Fuel Inlet: CH4 = 1
Initialization: Hybrid
Step: 4 Results
Part 1:
In this part, H2O is not mixed with inlet fuel. Total Mass fraction of CH4 is only used as inlet fuel.
Contours:
Figure: Temperature Contour
Figure: CH4 Contour
Figure: CO2 Contour
Figure: H2O Contour
Figure: N2 Contour
Figure: O2 Contour
Figure: Pollutant Contour
Figure: Soot Contour
Figure: Line plot of CH4 Mass fraction
Figure: Line plot of CO2 Mass fraction
Figure: Line plot of H2O Mass fraction
Figure: Line plot of N2 Mass fraction
Figure: Line plot of O2 Mass fraction
Figure: Line plot of Pollution NO Mass fraction
Figure: Line plot of Soot Mass fraction
Part 2:
In this part, H2O is mixed with inlet fuel in terms of mole fractions from 0 % to 30 % to determine the effects on the amount of pollutants and soot formation at outlet.
5 % H2O Volume fraction:
Figure: Temperature Contour
Figure: CH4 Contour
Figure: CO2 Contour
Figure: H2O Contour
Figure: N2 Contour
Figure: O2 Contour
Figure: Pollutant Contour
Figure: Soot Contour
Figure: Line plot of Pollution NO Mass fraction
Figure: Line plot of Soot Mass fraction
15 % H2O Volume fraction:
Figure: Temperature Contour
Figure: CH4 Contour
Figure: CO2 Contour
Figure: H2O Contour
Figure: N2 Contour
Figure: O2 Contour
Figure: Pollutant Contour
Figure: Soot Contour
Figure: Line plot of Pollution NO Mass fraction
Figure: Line plot of Soot Mass fraction
30 % H2O Volume fraction:
Figure: Temperature Contour
Figure: CH4 Contour
Figure: CO2 Contour
Figure: H2O Contour
Figure: N2 Contour
Figure: O2 Contour
Figure: Pollutant Contour
Figure: Soot Contour
Figure: Line plot of Pollution NO Mass fraction
Figure: Line plot of Soot Mass fraction
Table of Results:
|
Sr. No.
|
% Mole Fraction of H2O in Fuel at inlet |
CH4 Emissions |
CO2 Emissions |
CO Emissions |
H2O Emissions |
N2 Emissions |
O2 Emissions |
Pollutants (NO) Emissions |
Soot Emissions |
Temperature at Outlet (K) |
Maximum Temperature (K) |
|
1. |
0 |
0.0363731 |
0.144119 |
-- |
0.117984 |
0.701516 |
8.19055e-06 |
0.000201854 |
0.0837272 |
2104.5 |
2272.13 |
|
2. |
5 |
0.0316571 |
0.141887 |
0.00180101 |
0.123475 |
0.70118 |
9.09389e-08 |
0.000159574 |
0.0616964 |
2109.95 |
2261.56 |
|
3. |
15 |
0.0227737 |
0.142044 |
0.0015493 |
0.133233 |
0.700399 |
2.37996e-07 |
0.000156562 |
0.0552994 |
2128.95 |
2244.60 |
|
4. |
30 |
0.00955721 |
0.142438 |
0.00100731 |
0.147775 |
|
3.75511e-06 |
0.000164192 |
|
2157.57 |
2208.88 |
Conclusion:
In this simulation, we can see that combustion will occur because of turbulent mixing of CH4 fuel and air. This will produce pollutants and soot at outlet. If we mix H2O with CH4 fuel at inlet then it will delay ignition and provide more time to mix two fuels. This will reduce maximum temperature of combustion and pollutants and soot formation at outlet.