1. Right-click Mesh and select Import Mesh > CFX Mesh.

   The Import Mesh dialog box appears.

2. Configure the following setting(s):

   Setting	Value
   File name	CoalCombustion.gtm

3. Click Open.

4. Right-click a blank area in the viewer and select Predefined Camera > Isometric View (Z up) from the shortcut menu.

1. Open CoalCombustion_Reactions_Materials.ccl with a text editor and take the time to look at the information it contains.

   The CCL sets up the following reactions:

   • Fuel Gas Oxygen

   • HC Fuel Char Field

   • HC Fuel Devolat

   • Prompt NO Fuel Gas PDF

   • Thermal NO PDF.

   The CCL also sets up the following materials:

   • Ash

   • Char

   • Fuel Gas

   • Gas mixture

   • HC Fuel

   • HC Fuel Gas Binary Mixture

   • Raw Combustible

   The reactions Prompt NO Fuel Gas PDF and Thermal NO PDF are used only in the third simulation. Other pure substances required for the simulation will be loaded from the standard CFX-Pre materials library.

2. In CFX-Pre, select File > Import > CCL.

   The Import CCL dialog box appears.

3. Under Import Method, select Replace.

   This will replace the materials list in the current simulation with the ones in the newly imported CCL.

4. Under Import Method, select Auto-load materials.

   This will load pure materials such as CO2, H2O, N2, O2, and NO — the materials referenced by the imported mixtures and reactions — from the CFX-Pre materials library.

5. Select CoalCombustion_Reactions_Materials.ccl (the file you reviewed earlier).

6. Click Open.

7. Expand the Materials and Reactions branches under Simulation to make sure that all the materials and reactions described above are present.

Create a new domain named Furnace as follows:

1. Right-click Simulation > Flow Analysis 1 in the Outline tree view and click Insert > Domain.

2. Set Name to Furnace.

3. Click OK

4. On the Basic Settings, tab under Fluid and Particle Definitions, delete Fluid 1 and create a new fluid definition named Gas Mixture.

5. Click Add new item   and create a new fluid definition named HC Fuel.

6. Configure the following setting(s):

   Tab	Setting	Value
   Basic Settings	Location and Type > Location	B40
   	Fluid and Particle Definitions	Gas Mixture
   	Fluid and Particle Definitions > Gas Mixture > Material	Gas Mixture [ a ]
   	Fluid and Particle Definitions > Gas Mixture > Morphology > Option	Continuous Fluid
   	Fluid and Particle Definitions	HC Fuel
   	Fluid and Particle Definitions > HC Fuel > Material	HC Fuel [ b ]
   	Fluid and Particle Definitions > HC Fuel > Morphology > Option	Particle Transport Solid
   	Fluid and Particle Definitions > HC Fuel > Morphology > Particle Diameter Change	(Selected)
   	Fluid and Particle Definitions > HC Fuel > Morphology > Particle Diameter Change > Option	Mass Equivalent[ c ]
   Fluid Models	Multiphase > Multiphase Reactions	(Selected)
   	Multiphase > Multiphase Reactions > Reactions List	HC Fuel Char Field, HC Fuel Devolat
   	Heat Transfer > Option	Fluid Dependent
   	Turbulence > Option	k-Epsilon
   	Combustion > Option	Fluid Dependent
   	Thermal Radiation > Option	Fluid Dependent
   Fluid Specific Models	Fluid	Gas Mixture
   	Fluid > Gas Mixture > Heat Transfer > Heat Transfer > Option	Thermal Energy
   	Fluid > Gas Mixture > Thermal Radiation > Option	Discrete Transfer
   	Fluid > Gas Mixture > Thermal Radiation > Number of Rays	(Selected)
   	Fluid > Gas Mixture > Thermal Radiation > Number of Rays > Number of Rays	32 [ d ]
   	Fluid	HC Fuel
   	Fluid > HC Fuel > Heat Transfer > Heat Transfer > Option	Particle Temperature
   Fluid Pair Models	Fluid Pair	Gas Mixture | HC Fuel
   	Fluid Pair > Gas Mixture | HC Fuel > Particle Coupling	Fully Coupled
   	Fluid Pair > Gas Mixture | HC Fuel > Momentum Transfer > Drag Force > Option	Schiller Naumann
   	Fluid Pair > Gas Mixture | HC Fuel > Heat Transfer > Option	Ranz Marshall
   	Fluid Pair > Gas Mixture | HC Fuel > Thermal Radiation Transfer > Option	Opaque
   	Fluid Pair > Gas Mixture | HC Fuel > Thermal Radiation Transfer > Emissivity	1 [ e ]
   	Fluid Pair > Gas Mixture | HC Fuel > Thermal Radiation Transfer > Particle Coupling	(Selected)
   	Fluid Pair > Gas Mixture | HC Fuel > Thermal Radiation Transfer > Particle Coupling > Particle Coupling	Fully Coupled
   Click the Ellipsis   icon to open the Material dialog box, then select Gas Mixture under the Gas Phase Combustion branch. Click OK. Click the Ellipsis   icon to open the Material dialog box, then select HC Fuel under the Particle Solids branch. Click OK. The use of the Mass Equivalent option for the particle diameter is used here for demonstration only. A physically more sensible setting for coal particles, which often stay the same size or get bigger during combustion, would be the use of the Swelling Model option with a Swelling Factor of 0.0 (the default) or larger. Increasing the number of rays to 32 from the default 8, increases the number of rays leaving the bounding surfaces and increases the accuracy of the thermal radiation calculation. With this setting, the particles are modeled as black bodies.

7. Click OK.

1. Click Solver Control  .

2. Configure the following setting(s):

   Tab	Setting	Value
   Basic Settings	Convergence Control > Max. Iterations	600
   	Convergence Control > Fluid Timescale Control > Timescale Control	Physical Timescale
   	Convergence Control > Fluid Timescale Control > Physical Timescale	0.005 [s] [ a ]
   Particle Control	Particle Coupling Control > First Iteration for Particle Calculation	(Selected)
   	Particle Coupling Control > First Iteration for Particle Calculation > First Iteration	25 [ b ]
   	Particle Coupling Control > Iteration Frequency	(Selected)
   	Particle Coupling Control > Iteration Frequency > Iteration Frequency	10 [ c ]
   	Particle Under Relaxation Factors	(Selected)
   	Particle Under Relaxation Factors > Vel. Under Relaxation	0.75
   	Particle Under Relaxation Factors > Energy	0.75
   	Particle Under Relaxation Factors > Mass	0.75
   	Particle Ignition	(Selected)
   	Particle Ignition > Ignition Temperature	1000 [K]
   	Particle Source Smoothing	(Selected)
   	Particle Source Smoothing > Option	Smooth
   Advanced Options	Thermal Radiation Control	(Selected)
   	Thermal Radiation Control > Coarsening Control	(Selected)
   	Thermal Radiation Control > Coarsening Control > Target Coarsening Rate	(Selected)
   	Thermal Radiation Control > Coarsening Control > Target Coarsening Rate > Rate	16 [ d ]
   Based on the air inlet speed and the size of the combustor. The First Iteration parameter sets the coefficient-loop iteration number at which particles are first tracked; it allows the continuous-phase flow to develop before tracking droplets through the flow. Experience has shown that the value usually has to be increased to 25 from the default of 10. The Iteration Frequency parameter is the frequency at which particles are injected into the flow after the First Iteration for Particle Calculation iteration number. The iteration frequency allows the continuous phase to settle down between injections because it is affected by sources of momentum, heat, and mass from the droplet phase. Experience has shown that the value usually has to be increased to 10 from the default of 5. The Target Coarsening Rate parameter controls the size of the radiation element required for calculating Thermal Radiation. Decreasing the size of the element to 16, from the default 64, increases the accuracy of the solution obtained, while increasing the computing time required for the calculations.

3. Click OK.

1. Click Define Run  .

2. Configure the following setting(s):

   Setting	Value
   File name	CoalCombustion_nonox.def

3. Click Save.

   CFX-Solver Manager automatically starts and, on the Define Run dialog box, Solver Input File is set.

4. Quit CFX-Pre, saving the simulation (.cfx) file.

1. Right-click a blank area in the viewer and select Predefined Camera > Isometric View (Z up).

   This orients the geometry with the inlets at the top, as shown at the beginning of this tutorial.

2. Edit Cases > CoalCombustion_nonox_001 > Furnace > Symmetry Plane 1.

3. Configure the following setting(s):

   Tab	Setting	Value
   Color	Mode	Variable
   	Variable	Temperature
   Render	Show Faces	(Selected)
   	Lighting	(Cleared) [ a ]
   Turning off the lighting makes the colors accurate in the 3D view, but can make it more difficult to perceive depth. As an alternative to turning off the lighting, you can try rotating the view to a different position.

4. Click Apply.

   As expected for a non-swirling case, the flame appears a significant distance away from the burner. The flame is likely unstable, as evidenced by the rate of solver convergence; the next simulation in this tutorial involves swirl, which tends to stabilize the flame, and has much faster solver convergence.

1. Change the variable used for coloring the plot to Radiation Intensity and click Apply.

   This plot is directly related to the temperature plot. This result is consistent with radiation being proportional to temperature to the fourth power.

2. When you are finished, right-click Symmetry Plane 1 in the Outline tree view and select Hide.

1. Edit Cases > CoalCombustion_nonox_001 > Res PT for HC Fuel.

2. Configure the following setting(s):

   Tab	Setting	Value
   Color	Mode	Variable
   	Variable	HC Fuel.Temperature

3. Click Apply.

   Observing the particle tracks, you can see that coal enters the chamber at a temperature of around 343 K. The temperature of the coal, as it moves away from the inlet, rises as it reacts with the air entering from the inlet. The general location where the temperature of the coal increases rapidly is close to the location where the flame appears to be according to the plots created earlier. Downstream of this location, the temperature of the coal particles begins to drop.

1. Change the plot of the particle tracks so that they are colored by HC Fuel.Ash.Mass Fraction.

   The ashes form in the flame region, as expected.

2. Quit CFD-Post, saving the state (.cst) file at your discretion.

1. Create a domain interface named Periodic.

2. Configure the following setting(s):

   Tab	Setting	Value
   Basic Settings	Interface Type	Fluid Fluid
   	Interface Side 1 > Region List	PeriodicSide1
   	Interface Side 2 > Region List	PeriodicSide2
   	Interface Models > Option	Rotational Periodicity

3. Click OK.

1. Click Define Run  .

2. Configure the following setting(s):

   Setting	Value
   File name	CoalCombustion_nonox_swirl.def

3. Click Save.

   CFX-Solver Manager automatically starts and, on the Define Run dialog box, Solver Input File is set.

4. Quit CFX-Pre, saving the simulation (.cfx) file.

1. Right-click a blank area in the viewer and select Predefined Camera > Isometric View (Z up).

2. Edit Cases > CoalCombustion_nonox_swirl_001 > Furnace > Periodic Side 1.

3. Configure the following setting(s):

   Tab	Setting	Value
   Color	Mode	Variable
   	Variable	Temperature
   Render	Show Faces	(Selected)
   	Lighting	(Cleared)

4. Click Apply.

   As expected, the flame appears much closer to the burner than in the previous simulation, which had no swirl. This is due to the fact that the swirl component applied to the air from Air Inlet tends to entrain coal particles and keep them near the burner for longer, therefore helping them to burn.

1. Change the variable used for coloring the plot to Radiation Intensity and click Apply.

2. When you are finished, right-click Periodic Side 1 in the Outline tree view and select Hide.

1. Edit Cases > CoalCombustion_nonox_swirl_001 > Res PT for HC Fuel.

2. Configure the following setting(s):

   Tab	Setting	Value
   Color	Mode	Variable
   	Variable	HC Fuel.Temperature

3. Click Apply.

1. Change the plot of the particle tracks so that they are colored by HC Fuel.Ash.Mass Fraction.

2. Quit CFD-Post, saving the state (.cst) file at your discretion.

1. Edit Simulation > Flow Analysis 1 > Furnace.

2. Configure the following setting(s):

   Tab	Setting	Value
   Fluid Specific Models	Fluid	Gas Mixture
   	Fluid > Gas Mixture > Combustion > Chemistry Post Processing	(Selected)
   	Fluid > Gas Mixture > Combustion > Chemistry Post Processing > Materials List	NO
   	Fluid > Gas Mixture > Combustion > Chemistry Post Processing > Reactions List	Prompt NO Fuel Gas PDF,Thermal NO PDF

   These settings enable the combustion simulation with nitrogen oxide (NO) as a postprocessing step in the solver. The NO reactions are defined in the same way as any participating reaction but the simulation of the NO reactions is performed after the combustion simulation of the air and coal. With this one-way simulation, the NO will have no effect on the combustion simulation of the air and coal.

3. Click OK.

4. Edit Simulation > Flow Analysis 1 > Furnace > Air Inlet.

5. Configure the following setting(s):

   Tab	Setting	Value
   Boundary Details	Component Details	NO
   	Component Details > NO > Mass Fraction	0.0

6. Click OK.

7. Edit Simulation > Flow Analysis 1 > Furnace > Coal Inlet.

8. Configure the following setting(s):

   Tab	Setting	Value
   Boundary Details	Component Details	NO
   	Component Details > NO > Mass Fraction	0.0

9. Click OK.

1. Click Define Run  .

2. Configure the following setting(s):

   Setting	Value
   File name	CoalCombustion_noxcpp_swirl.def

3. Click Save.

4. Quit CFX-Pre, saving the simulation as CoalCombustion_noxcpp_swirl.cfx.