Encyclopaedia Index

WORKSHOP - Combustion: SCRS

Overview

The case below exemplifies how the Simple Chemical Reaction Scheme can be applied to a combustion chamber. The flow is turbulent and the reaction-rate is physically controlled by means of the Eddy-Breakup Model.

The geometry is shown below:

The combustion chamber has an inlet (not visible) for the premixed fuel-oxygen which lies at the top of the dark-grey blockage at the lower right corner; two secondary oxygen inlets (purple colour) on the right and a dilution inlet (purple colour) on the left. There is a blocked region (orange colour on the far right) near the fuel-oxygen inlet and the outlet is on the far left.

Summary of the input data

The following input data are used for this case:

  1. Molecular weight (gm/mole): W(air)=29.0; W(fuel)=16.0; W(product)=28.0
  2. Stoichiometric ratio: 17.24
  3. Mixture fraction: Fstoich = 1./(1.+ Stoich) = 0.054825
  4. Specific heat (J/kg/K): CP(air) =1500.; CP(pr) =1500.; Cp(fu)=1500.
  5. Heat of Combustion (J/kg): H(fu) = 4.9E7
  6. KE and EP values at the Inlet boundary
    TKEIN = 2.5E-05*VIN(fu)*VIN(fu)
    EPSIN = 0.09*TKEIN**2./(9.59*ENUL)
  7. Enthalpy value at the Inlet: HIN(fu) = CP(fu)*T(fu)+FIN(fu)*H(fu)

A complete step-by-step guide, showing how to set the case from the default mode of operation, is provided.

Accessing PHOENICS-VR.

From the system level:

To enter the PHOENICS-VR environment, click on the PHOENICS icon on the desktop, or click on Start, programs, PHOENICS, PHOENICS.

From the commander level:

To enter the PHOENICS-VR environment, click on the 'Run vre' icon in the left column.

In PHOENICS-VR environment,

Start with an 'empty' case - click on 'File' then on 'Start New Case', then on 'Core'', then click on 'OK'; to confirm the resetting.

To enter VR Editor:

This is the default mode of operation.

Within VR Editor.

Set the domain size and grid numbers:

Click on 'Menu' (Main Menu) on the VE-Editor panel;

Set 'Combustion SCRS' as the Title;

Click on 'Geometry'.

Click on 'Cartesian' under co-ordinate system; and select 'Cylindrical-polar' and then on 'OK'.

Leave 'Inner radius' at 0.0 and 'tolerance' at 1.e-3.

Change the x-domain size to 0.628 radians.

Change the y-domain size to 0.065 m.

Change the z-domain size to 0.245 m.

Set 'number of cells' to 8 in x-direction, 10 in y-direction and 25 in z-direction.

Click on 'OK' to close the Grid mesh settings dialog.

Click on 'OK' to exit from 'Menu'.

Click on 'Reset' button on the movement panel.

Click on 'Fit to Window'

Click on 'Mouse' button (or use the Arrow buttons) on the movement panel;then use mouse to position the Y-direction of the coordinate upright and Z-direction pointing to the left.

Activate solution of the required variables and models

Click on 'Menu'; and the on 'Models'.

Click on ENERGY EQUATION; and then choose ENTHALPY and toggle STATIC to TOTAL.

Click on 'Turbulence models' and choose the KEMODL.

Click on COMBUSTION and choose 3_GASES_KINETIC.

If "settings" for 3_GASES_KINETIC model is clicked, a sub-panel appears that shows the following model settings:

  1. Stoichiometric ratio: 17.24
  2. Heat of Combustion: 4.9E7 J/kg
  3. Specific heats and Molecular weights for Fuel, Oxidant and Product
  4. Reaction Type: Kinetically-controlled
  5. Reaction source: Eddy_breakup

Specify properties

Click on 'Properties'.

Turn 'Use property table' to OFF. The density will be automatically set to 3_GASES.

Turn (Density) 'Storage' to ON

Check that 'Temperature' should now be 3_GASES-KINETIC and 'Specific Heat' is 3_GASES.

Click 'Page down' and continue the settings.

Change 'Reference Pres (Pa) to 8E5 and Reference Temp(K) to 0.0.

Click 'Page up'.

Set Initial values

Click on 'Initialisation'.

Set the following initial (FIINIT) values

Enter numerical settings

Click on 'Numerics'.

Set 'Total number of iterations' to 150.

Click 'Relaxation control' and then click on 'Limits on variables'

Change VARMAX of P1 to 1E5 and VARMAX of DEN1 to 4.0

Change VARMIN of TMP1 to 273 and VARMIN of H1 to 1.0

Click 'Previous panel'

Click on 'Top menu' and then on 'OK' to exit from 'Menu'.

Create Objects and specify boundary conditions

Create Blockages for combustion chamber

Click on 'Settings', 'New' and 'New Object' on the top bar of the VR-Editor. This will bring up the object specification dialog box.

Change name to CMP1.

Click on 'Size' and set SIZE of the object as:

Xsize: 0.628

Ysize: 0.013

Zsize: 0.025

Click on 'General'.

Define Type: Blockage.

Click 'OK' to exit from the Object specification Dialogue Box.

Click on 'Settings', 'New', and 'New Object'.

Change name to CMP2.

Click on 'Shape'

Find POLWE2 in the subdirectory public/shapes; and then select and click on 'Open'

Click on 'Size' and set SIZE of the object as:

Xsize: 0.628

Ysize: 0.052

Zsize: 0.025

Click on 'Place' and set POSITION of the object as:

Xpos: 0

Ypos: 0.013

Zpos: 0

Click on 'General'.

Define Type: Blockage

Click 'OK' to exit from the Object specification Dialogue Box.

Create the Fuel Inlet

Click on 'Settings', 'New' and 'New Object'.

Change name to INLET.

Click on 'Size' and set Size of the object as:

Xsize: 0.628

Ysize: 0

Zsize: 0.004

Click on 'Place' and set POSITION of the object as:

Xpos: 0

Ypos: 0.013

Zpos: 0.009

Click on 'General'.

Define Type: INLET.

Click on 'Attributes'

Toggle Inlet density to User-set and then set density to 3.606 and temperature 773K

Click on 'Gas composition' and set FUEL to 0.0548; Oxidant to 0.9452

Click on 'Apply' and 'OK'

Set velocity in Y-direction at 100 m/s.

Toggle 'Object side' to High

Click on 'OK' twice to exit from the Object Specification Dialogue Box.

Create the secondary air inlets

Click on 'Settings', 'New' and 'New Object'.

Change name to SIN1.

Clicl on 'Size' and set Size of the object as:

Xsize: 0.10

Ysize: 0

Zsize: 0.0245

Clicl on 'Place' and set POSITION of the object as:

Xpos: 0

Ypos: 0.065

Zpos: 0.0735

Click on 'General'.

Define Type: INLET

Click on 'Attributes'.

Set Temperature at 773K.

Set velocity in Y-direction at -40. m/s

Click on 'OK' and check the position and size again.

Click on 'OK' to exit from the Object Dialogue Box.

Click on 'Settings', 'New' and 'New Object'.

Change name to SIN2.

Click on 'Size' and set Size of the object as:

Xsize: 0.1

Ysize: 0

Zsize: 0.0245

Click on 'Place' and set POSITION of the object as:

Xpos: 0.314

Ypos: 0.065

Zpos: 0.0735

Click on 'General'.

Define Type: INLET

Click on 'Attributes'.

Set Temperature at 773K and click 'OK'

Set velocity in Y-direction at -40. m/s

Click on 'OK' and check the position and size again

Click on 'OK' to exit from the Object Dialogue Box.

Create the dilute air inlet

Click on 'Settings', 'New' and 'New Object'.

Change name to DIN.

Click on 'Size' and set Size of the object as:

Xsize: 0.1

Ysize: 0

Zsize: 0.0245

Click on 'Place' and set POSITION of the object as:

Xpos: 0.0

Ypos: 0.065

Zpos: 0.15

Click on 'General'.

Define Type: INLET

Click on 'Attributes'.

Set Temperature at 773K and click 'OK'

Set velocity in Y-direction at -40. m/s

Click on 'OK' and check the position and size again.

Click on 'OK' to exit from the Object Dialogue Box.

Create the outlet

Click on 'Settings', 'New' and 'New Object'

Change name to Outlet.

Click on 'Size' and set Size of the object as:

Xsize: 0.628

Ysize: 0.065

Zsize: 0.0

Click on 'Place' and set POSITION of the object as:

Xpos: 0.0

Ypos: 0.0

Zpos: 0.245

Click on 'General'.

Define Type: OUTLET

Click on 'Attributes' and then change coefficient to 1.0.

Click on 'OK' twice to exit from the Object Specification Dialogue Box.

Adjust grid distribution in Z-direction

Click on 'Mesh toggle' button, and the grid will appears on the screen.

Click on the first three regions, 1, 2 and 3 in Z-direction and set 3 cells in each region and click on 'OK'.

Running the Solver.

In the PHOENICS-VR environment, click on 'Run', 'Solver'(Earth), and click on 'OK'; to confirm running Earth.

Using the VR Viewer.

In the PHOENICS-VR environment, click on 'Run', 'Post processor',then GUI Post processor (VR Viewer) Viewer)'. Click 'OK' on the file names dialog to accept the default files.

To view:

The image below shows the product (PROD) mass-fraction distribution.

To select the plotting variable:

To change the direction of the plotting plane, set the slice direction to X, Y or Z slice direction (927 bytes)

To change the position of the plotting plane, move the probe using the probe position buttons

probe position (927 bytes).

Saving the results.

In the PHOENICS-VR environment, click on 'Save as a case', make a new folder called 'COMBUST', select the new folder, and save as 'SCRS'.