COMBUSTION SIMULATION USING ANSYS FLUENT

                                                                                                                 COMBUSTION SIMULATION

Combustion is a process in which the fuel is oxidized and large amount of chemically bound energy is released. This energy heats the products and combustion of fuel such as methane with air leads to a flame temperature of around 1900 °C (2173 K). In the combustion of methane and air, the main products are carbon dioxide and water. However, the formation of these products is very complex and hundreds of different species such as H, O, OH, CH, CH3 etc are intermediated in the combustion process. Besides carbon dioxide and water, a large number of pollutants are formed as, for instance, nitorgen oxides, carbon monoxide and soot particles. The efficiency of the combustion process depends on several parameters, such as oxygen supply, temperature history and mixing properties. 

The aim of this project is to perform a combustion simulation on a combustor model and to plot the variation of mass fraction of the different species.

1.Model:-

 

                                                               (fig. 1.1)                                                                                                                                      (fig. 1.2)

Since running the simulation for the entire 3D model requires lot of time and a powerful computer. Using split body tool the 2D view of the model is extracted for further processing. The 2D model is as follows:

                                                                                                (fig. 1.3)

2.Meshing:-

The 2D model is then further meshed using triangles method and element size of 2.5 mm. The total elements are 23550

 

                                                                                  (fig. 2.1)                                                                                    

   

                                              (fig. 2.2)                                                                                          (fig. 2.3)

Using edge selection tool, the edges are named as follows:

 

                                                           (fig. 2.4)                                                                                                                                    (fig. 2.5)             

 

                                                            (fig. 2.6)                                                                                                                                        (fig. 2.7)

 

                                                        (fig. 2.8)

The simulation is run for 2 parts as follows:

Part 1:- Perform a combustion simulation on the combuster model and plot the variation of the mass fraction of the different species in the simulation using line probes at different locations of the combuster.

The simulation is setup as steady state, pressure based with absolute formation. The energy is enabled and standard k-epsilon viscous mode is selected. 

In the species model the species transport is selected with volumetric reaction. The inlet diffusion and diffusion energy source is enabled. 

The mixture material used is methane-air

And the Turbulence chemistry interaction is set to eddy dissipation.

The Boundary conditions are set as:-

Air inlet - velocity = 0.5m/s ; Temperature = 300k; Species : O2=0.23

Fuel inlet - velocity = 80m/s; Temperature = 300k; Species : Ch4 = 1

The solution is run for 1500 iterations and the results are as follows:

                                                                  (fig. P1.1)

 

The maximum temperature attained during combustion is 2310k.

Mass Fraction:-

In a mixture, mass fraction is the amount of mass of one substance divided by the mass of the total misxture.

Following are the contours of mass fraction of different species:-

                                                        (fig. P1.2)                                                                                                                                    (fig. P1.3)

 

                                                          (fig. P1.4)                                                                                                                                    (fig. P1.5)

 

                                                            (fig. P1.6)                                                                                                                                (fig. P1.7)

 

                                                          (fig. P1.8) 

 

Line probes are created at a distance of following values from the origin (left side)

line 1 = 0.1m

line 2 = 0.248m

line 3 = 0.396m

line 4 = 0.593m

line 5 = 0.790m

                                                                                  (fig. P1.9)

 

The plot for various species, Nox emissions and soot formations are as follows:

In these plots the abscissa is taken as the mass fraction of the species and the ordinate as the vertical distance along the respective line probe.

Also,

Series 1 = Line 1

Series 2 = Line 2

Series 3 = Line 3

Series 4 = Line 4

Series 5 = Line 5

  

                                                           (graph. P1.1)                                                                                                                                (graph. P1.2)

 

 

                                                                (graph. P1.3)                                                                                                                          (graph. P1.4)

 

 

                                                              (graph. P1.5)                                                                                                                            (graph. P1.6)

 

                                                              (graph. P1.7)

 

 

Part 2: The Soot and Nox formation has many harmful effects on the environment and humans. In the this part the effect of adding water in the fuel is checked.

Case 1:- 5% water content in the fuel.

The simulation is setup as steady state, pressure based with absolute formation. The energy is enabled and standard k-epsilon viscous mode is selected. 

In the species model the species transport is selected with volumetric reaction. The inlet diffusion and diffusion energy source is enabled. 

The mixture material used is methane-air-2step (this allows to add water in the fuel)

And the Turbulence chemistry interaction is set to eddy dissipation.

The Boundary conditions are set as:-

Air inlet - velocity = 0.5m/s ; Temperature = 300k; Species : O2=0.23

Fuel inlet - velocity = 80m/s; Temperature = 300k; Species : Ch4 = 0.95  , H2O = 0.05

The solution is run for 1500 iterations and the results are as follows:

                                                                (fig. P2- C1.1)

The maximum temperature attained during combustion is 2300k.

Following are the contours of mass fraction of different species:-

 

                                                      (fig. P2- C1.2)                                                                                                                              (fig. P2- C1.3)

 

 

                                                            (fig. P2- C1.4)                                                                                                                        (fig. P2- C1.5)

 

 

                                                      (fig. P2- C1.6)                                                                                                                                (fig. P2- C1.7)

 

 

                                                    (fig. P2- C1.8)                                                                                                                                  (fig. P2- C1.9)

 

Line probes are created at a distance of following values from the origin (left side)

line 1 = 0.1m

line 2 = 0.248m

line 3 = 0.396m

line 4 = 0.593m

line 5 = 0.790m

                                                                    (fig. P2- C1.10)

 

The plot for various species, Nox emissions and soot formations are as follows:

In these plots the abscissa is taken as the mass fraction of the species and the ordinate as the vertical distance along the respective line probe.

Also,

Series 1 = Line 1

Series 2 = Line 2

Series 3 = Line 3

Series 4 = Line 4

Series 5 = Line 5

 

                                                        (graph. P2- C1.1)                                                                                                                            (graph. P2- C1.2)

 

 

                                                          (graph. P2- C1.3)                                                                                                                             (graph. P2- C1.4)

 

 

                                                      (graph. P2- C1.5)                                                                                                                          (graph. P2- C1.6)

 

                                                      (graph. P2- C1.7)

 

 

Case 2:- 10% water content in the fuel.

The simulation is setup as steady state, pressure based with absolute formation. The energy is enabled and standard k-epsilon viscous mode is selected. 

In the species model the species transport is selected with volumetric reaction. The inlet diffusion and diffusion energy source is enabled. 

The mixture material used is methane-air-2step (this allows to add water in the fuel)

And the Turbulence chemistry interaction is set to eddy dissipation.

The Boundary conditions are set as:-

Air inlet - velocity = 0.5m/s ; Temperature = 300k; Species : O2=0.23

Fuel inlet - velocity = 80m/s; Temperature = 300k; Species : Ch4 = 0.90  , H2O = 0.10

The solution is run for 1500 iterations and the results are as follows:

                                                               (fig. P2- C2.1) 

 

The maximum temperature attained during combustion is 2290k.

Following are the contours of mass fraction of different species:-

 

                                                          (fig. P2- C2.2)                                                                                                                                (fig. P2- C2.3)

 

 

                                                        (fig. P2- C2.4)                                                                                                                                      (fig. P2- C2.5)

 

 

                                                      (fig. P2- C2.6)                                                                                                                                    (fig. P2- C2.7)

 

 

                                                        (fig. P2- C2.8)                                                                                                                                      (fig. P2- C2.9)

 

Line probes are created at a distance of following values from the origin (left side)

line 1 = 0.1m

line 2 = 0.248m

line 3 = 0.396m

line 4 = 0.593m

line 5 = 0.790m

                                                                              (fig. P2- C2.10)

 

The plot for various species, Nox emissions and soot formations are as follows:

In these plots the abscissa is taken as the mass fraction of the species and the ordinate as the vertical distance along the respective line probe.

Also,

Series 1 = Line 1

Series 2 = Line 2

Series 3 = Line 3

Series 4 = Line 4

Series 5 = Line 5

 

                                                          (graph. P2- C2.1)                                                                                                                            (graph. P2- C2.2)

 

 

                                                          (graph. P2- C2.2)                                                                                                                                (graph. P2- C2.3)

 

 

                                                      (graph. P2- C2.4)                                                                                                                                  (graph. P2- C2.5)

                                                            (graph. P2- C2.7)

 

Case 3:- 15% water content in the fuel.

The simulation is setup as steady state, pressure based with absolute formation. The energy is enabled and standard k-epsilon viscous mode is selected. 

In the species model the species transport is selected with volumetric reaction. The inlet diffusion and diffusion energy source is enabled. 

The mixture material used is methane-air-2step (this allows to add water in the fuel)

And the Turbulence chemistry interaction is set to eddy dissipation.

The Boundary conditions are set as:-

Air inlet - velocity = 0.5m/s ; Temperature = 300k; Species : O2=0.23

Fuel inlet - velocity = 80m/s; Temperature = 300k; Species : Ch4 = 0.85  , H2O = 0.15

The solution is run for 1500 iterations and the results are as follows:

                                                                      (fig. P2- C3.1) 

The maximum temperature attained during combustion is 2280k.

Following are the contours of mass fraction of different species:-

 

                                                          (fig. P2- C3.2)                                                                                                                              (fig. P2- C3.3) 

 

 

                                                          (fig. P2- C3.4)                                                                                                                              (fig. P2- C3.5)

  

 

                                                            (fig. P2- C3.6)                                                                                                                              (fig. P2- C3.7)                                 

 

 

                                                        (fig. P2- C3.8)                                                                                                                                      (fig. P2- C3.9)

  

Line probes are created at a distance of following values from the origin (left side)

line 1 = 0.1m

line 2 = 0.248m

line 3 = 0.396m

line 4 = 0.593m

line 5 = 0.790m

                                                                      (fig. P2- C3.10) 

 

The plot for various species, Nox emissions and soot formations are as follows:

In these plots the abscissa is taken as the mass fraction of the species and the ordinate as the vertical distance along the respective line probe.

Also,

Series 1 = Line 1

Series 2 = Line 2

Series 3 = Line 3

Series 4 = Line 4

Series 5 = Line 5

 

                                                            (graph. P2- C3.1)                                                                                                                        (graph. P2- C3.2) 

 

 

                                                                (graph. P2- C3.3)                                                                                                                      (graph. P2- C3.4) 

 

 

                                                          (graph. P2- C3.5)                                                                                                                              (graph. P2- C3.6)

  

                                                        (graph. P2- C3.7) 

 

Case 4:- 20% water content in the fuel.

The simulation is setup as steady state, pressure based with absolute formation. The energy is enabled and standard k-epsilon viscous mode is selected. 

In the species model the species transport is selected with volumetric reaction. The inlet diffusion and diffusion energy source is enabled. 

The mixture material used is methane-air-2step (this allows to add water in the fuel)

And the Turbulence chemistry interaction is set to eddy dissipation.

The Boundary conditions are set as:-

Air inlet - velocity = 0.5m/s ; Temperature = 300k; Species : O2=0.23

Fuel inlet - velocity = 80m/s; Temperature = 300k; Species : Ch4 = 0.80  , H2O = 0.20

The solution is run for 1500 iterations and the results are as follows:

                                                                (fig. P2- C4.1)

The maximum temperature attained during combustion is 2260k.

Following are the contours of mass fraction of different species:-

 

                                                        (fig. P2- C4.2)                                                                                                                                (fig. P2- C4.3)         

 

 

                                                      (fig. P2- C4.4)                                                                                                                                (fig. P2- C4.5)

 

 

                                                        (fig. P2- C4.6)                                                                                                                                (fig. P2- C4.7)

 

 

                                                      (fig. P2- C4.8)                                                                                                                                  (fig. P2- C4.9)

 

Line probes are created at a distance of following values from the origin (left side)

line 1 = 0.1m

line 2 = 0.248m

line 3 = 0.396m

line 4 = 0.593m

line 5 = 0.790m

                                                                              (fig. P2- C4.10)

 

The plot for various species, Nox emissions and soot formations are as follows:

In these plots the abscissa is taken as the mass fraction of the species and the ordinate as the vertical distance along the respective line probe.

Also,

Series 1 = Line 1

Series 2 = Line 2

Series 3 = Line 3

Series 4 = Line 4

Series 5 = Line 5

 

                                                            (graph. P2- C4.1)                                                                                                                        (graph. P2- C4.2)

 

 

                                                      (graph. P2- C4.3)                                                                                                                                (graph. P2- C4.4)

 

 

                                                    (graph. P2- C4.5)                                                                                                                                (graph. P2- C4.6)

 

                                                  (graph. P2- C4.7)

 

Case 5:- 25% water content in the fuel.

The simulation is setup as steady state, pressure based with absolute formation. The energy is enabled and standard k-epsilon viscous mode is selected. 

In the species model the species transport is selected with volumetric reaction. The inlet diffusion and diffusion energy source is enabled. 

The mixture material used is methane-air-2step (this allows to add water in the fuel)

And the Turbulence chemistry interaction is set to eddy dissipation.

The Boundary conditions are set as:-

Air inlet - velocity = 0.5m/s ; Temperature = 300k; Species : O2=0.23

Fuel inlet - velocity = 80m/s; Temperature = 300k; Species : Ch4 = 0.75  , H2O = 0.25

The solution is run for 1500 iterations and the results are as follows:

                                                           (fig. P2- C5.1)

The maximum temperature attained during combustion is 2250k.

Following are the contours of mass fraction of different species:-

 

                                                        (fig. P2- C5.2)                                                                                                                                (fig. P2- C5.3)

 

 

                                                      (fig. P2- C5.4)                                                                                                                                  (fig. P2- C5.5)        

 

 

                                                    (fig. P2- C5.6)                                                                                                                                    (fig. P2- C5.7) 

 

 

                                                  (fig. P2- C5.8)                                                                                                                                        (fig. P2- C5.9)

 

Line probes are created at a distance of following values from the origin (left side)

line 1 = 0.1m

line 2 = 0.248m

line 3 = 0.396m

line 4 = 0.593m

line 5 = 0.790m

                                                                              (fig. P2- C5.10)

 

The plot for various species, Nox emissions and soot formations are as follows:

In these plots the abscissa is taken as the mass fraction of the species and the ordinate as the vertical distance along the respective line probe.

Also,

Series 1 = Line 1

Series 2 = Line 2

Series 3 = Line 3

Series 4 = Line 4

Series 5 = Line 5

 

                                                        (graph. P2- C5.1)                                                                                                                              (graph. P2- C5.2)

 

 

                                                          (graph. P2- C5.3)