Burn wood with heptane as starter.

[SD]

Hi all,

I am a beginner in FDS. I have fds6 installed. I have tried to look at the FDS User's guide, but it didnt help in resolving my issue, or I may have overlooked the section or misinterpreted it. I tried playing with some of the fds codes available online, but most of them are fds5 input files and it is tricky to get them working in fds6. I have tried 3 approaches. In one of my approaches, I have the following issues as listed below.

GOAL

----------

My goal is to burn a stack of wood using a liquid heptane in a pan. I believe that as soon as I introduce heptane, it instaneously starts burning (by default) and I hope to use this as an accelerant to burn a stack of wood.

I am not sure where best location for the heptane pan is, but at the moment, it resides right on the top surface of the block of wood. 

Eventually, I want to use water sprinklers to see how fast the fire extinguishes.

PROCEDURE USED

-------------------------------

In order to achieve my goal, I use a couple of fds sample codes and combined them. As a result I have 2 REAC lines in my fds input file. I have read in some forums that fds6 doesnot support more than 1 REAC line ( not sure if earlier versions of fds support this).

I have the properties of wood and the properties of heptane. I am not sure how I can use heptane to burn wood. This is what I have so far and it doesnt work:

---------------------------------

&HEAD CHID='room_fire2', TITLE='ATF Room Fire Test, SVN $Revision: 13189 $'  / 

&MESH IJK=52,54,24, XB=0.0,5.2,-0.8,4.6,0.0,2.4 / 

&TIME T_END=300.0 / 

&REAC FUEL       = 'POLYURETHANE'

      FYI        = 'C_6.3 H_7.1 N O_2.1, NFPA Handbook, Babrauskas'

      SOOT_YIELD = 0.10

      N          = 1.0

      C          = 6.3

      H          = 7.1

      O          = 2.1  /

&REAC FUEL               = 'N-HEPTANE'

      FYI                = 'Heptane, C_7 H_16'

      HEAT_OF_COMBUSTION = 44400.

  SOOT_YIELD         = 0.037 

      O                  = 0.

      C                  = 7.

      H                  = 16./

  

 %SURF ID='BURNER', HRRPUA=1000., COLOR='RASPBERRY' - Don't want to use HRRPUA%

&MATL ID                     = 'N-HEPTANE LIQUID'

      EMISSIVITY             = 1.

      NU_SPEC                = 1.

      SPEC_ID                = 'N-HEPTANE'

      HEAT_OF_REACTION       = 364.9

      CONDUCTIVITY           = 0.14

      SPECIFIC_HEAT          = 2.2464

      DENSITY                = 684.

      ABSORPTION_COEFFICIENT = 100. 

  BOILING_TEMPERATURE    = 98.5   / 

 &MATL ID            = 'STEEL'

      EMISSIVITY    = 1.0

      DENSITY       = 7850.

      CONDUCTIVITY  = 45.8

      SPECIFIC_HEAT = 0.46 /

&SURF ID        = 'N-HEPTANE POOL'

      COLOR     = 'YELLOW'

      MATL_ID   = 'N-HEPTANE LIQUID'

      THICKNESS = 0.1 /

&SURF ID        = 'STEEL SHEET'

      COLOR     = 'BLACK'

      MATL_ID   = 'STEEL'

      BACKING   = 'EXPOSED'

      THICKNESS = 0.003 /

 

&MATL ID                    = 'FABRIC'

      FYI                   = 'Properties completely fabricated'

      SPECIFIC_HEAT         = 1.0

      CONDUCTIVITY          = 0.1

      DENSITY               = 100.0

      N_REACTIONS           = 1

      NU_SPEC               = 1.

      SPEC_ID               = 'POLYURETHANE'

      REFERENCE_TEMPERATURE = 320.

      HEAT_OF_REACTION      = 3000.

      HEAT_OF_COMBUSTION    = 15000. /

&MATL ID                    = 'FOAM'

      FYI                   = 'Properties completely fabricated'

      SPECIFIC_HEAT         = 1.0

      CONDUCTIVITY          = 0.05

      DENSITY               = 40.0

      N_REACTIONS           = 1

      NU_SPEC               = 1.

      SPEC_ID               = 'POLYURETHANE'

      REFERENCE_TEMPERATURE = 320.

      HEAT_OF_REACTION      = 1500.

      HEAT_OF_COMBUSTION    = 30000. /

&MATL ID            = 'GYPSUM PLASTER'

      FYI           = 'Quintiere, Fire Behavior'

      CONDUCTIVITY  = 0.48

      SPECIFIC_HEAT = 0.84

      DENSITY       = 1440. /

&MATL ID                    = 'CARPET PILE'

      FYI                   = 'Completely made up'

      CONDUCTIVITY          = 0.16

      SPECIFIC_HEAT         = 2.0

      DENSITY               = 750.

      N_REACTIONS           = 1

      NU_SPEC               = 1. 

      SPEC_ID               = 'POLYURETHANE'

      REFERENCE_TEMPERATURE = 290.

      HEAT_OF_COMBUSTION    = 22300.

      HEAT_OF_REACTION      = 2000. /

&SURF ID             = 'UPHOLSTERY'

      COLOR          = 'PURPLE'

      BURN_AWAY      = .TRUE.

      MATL_ID(1:2,1) = 'FABRIC','FOAM'

      THICKNESS(1:2) = 0.002,0.1 /

&SURF ID             = 'WALL'

      DEFAULT        = .TRUE.

      RGB            = 200,200,200

      MATL_ID        = 'GYPSUM PLASTER'

      THICKNESS      = 0.012 /

&SURF ID              = 'CARPET'

      MATL_ID         = 'CARPET PILE'

      COLOR           = 'KHAKI'

      BACKING         = 'INSULATED'

      THICKNESS       = 0.006 /

&OBST XB= 1.50, 3.10, 3.80, 4.60, 0.00, 0.40 /

&OBST XB= 1.50, 3.10, 3.80, 4.60, 0.40, 0.60, SURF_ID='UPHOLSTERY', BULK_DENSITY=41.176 / Couch, seat cushions

&OBST XB= 1.30, 1.50, 3.80, 4.60, 0.00, 0.90, SURF_ID='UPHOLSTERY', BULK_DENSITY=41.176 / Couch, armrest

&OBST XB= 3.10, 3.30, 3.80, 4.60, 0.00, 0.90, SURF_ID='UPHOLSTERY', BULK_DENSITY=41.176 / Couch, armrest

&OBST XB= 1.50, 3.10, 4.40, 4.60, 0.60, 1.20, SURF_ID='UPHOLSTERY', BULK_DENSITY=41.176 / Couch, back cushions

VENT XB= 2.40, 2.60, 4.30, 4.40, 0.60, 0.60, SURF_ID='BURNER' / Ignition source on couch

&OBST XB=2.60, 2.80, 4.30, 4.40,0.60,0.65, SURF_IDS='N-HEPTANE POOL','STEEL SHEET','STEEL SHEET' /

&OBST XB=2.60, 2.80, 4.30, 4.40,0.60,0.70, SURF_ID='STEEL SHEET' /

&OBST XB=2.60, 2.80, 4.30, 4.40,0.60,0.70, SURF_ID='STEEL SHEET' /

&OBST XB=2.60, 2.80, 4.30, 4.40,0.60,0.70, SURF_ID='STEEL SHEET' /

&OBST XB=2.60, 2.80, 4.30, 4.40,0.60,0.70, SURF_ID='STEEL SHEET' /

 

&PART ID='ignitor particle', SURF_ID='ignitor', STATIC=.TRUE. /

&SURF ID='ignitor', TMP_FRONT=1000., GEOMETRY='CYLINDRICAL', LENGTH=0.15, RADIUS=0.01 /

&INIT XYZ=2.45,4.35,0.65, DX=0.1, PART_ID='ignitor particle', N_PARTICLES=3 /

&OBST XB= 4.00, 4.60, 3.80, 4.60, 0.00, 0.40 /

&OBST XB= 4.00, 4.60, 3.80, 4.60, 0.40, 0.60, SURF_ID='UPHOLSTERY', BULK_DENSITY=41.176 / Chair, back corner, seat cushion

&OBST XB= 3.80, 4.00, 3.80, 4.60, 0.00, 0.90, SURF_ID='UPHOLSTERY', BULK_DENSITY=41.176 / Chair, back corner, right armrest

&OBST XB= 4.60, 4.80, 3.80, 4.60, 0.00, 0.90, SURF_ID='UPHOLSTERY', BULK_DENSITY=41.176 / Chair, back corner, left armerest

&OBST XB= 4.00, 4.60, 4.40, 4.60, 0.60, 1.20, SURF_ID='UPHOLSTERY', BULK_DENSITY=41.176 / Chair, back corner, back cushion

 OBST XB= 1.60, 3.00, 2.80, 3.60, 0.40, 0.60, SURF_ID='SPRUCE' / Table

&OBST XB= 0.00, 0.80, 2.00, 2.60, 0.00, 0.40 /

&OBST XB= 0.00, 0.80, 2.00, 2.60, 0.40, 0.60, SURF_ID='UPHOLSTERY', BULK_DENSITY=41.176 / Chair, left wall, seat cusion

&OBST XB= 0.00, 0.80, 1.80, 2.00, 0.00, 0.90, SURF_ID='UPHOLSTERY', BULK_DENSITY=41.176 / Chair, left wall, right armrest

&OBST XB= 0.00, 0.80, 2.60, 2.80, 0.00, 0.90, SURF_ID='UPHOLSTERY', BULK_DENSITY=41.176 / Chair, left wall, left armrest

&OBST XB= 0.00, 0.20, 2.00, 2.60, 0.00, 0.90, SURF_ID='UPHOLSTERY', BULK_DENSITY=41.176 / Chair, left wall, back cushion

&OBST XB= 1.80, 3.80, 0.00, 1.00, 0.00, 0.20, SURF_ID='UPHOLSTERY', BULK_DENSITY=41.176 / Futon on floor?

&OBST XB= 2.00, 2.40, 1.60, 2.00, 0.00, 0.40 /

&OBST XB= 2.00, 2.40, 1.60, 2.00, 0.40, 0.60, SURF_ID='UPHOLSTERY', BULK_DENSITY=41.176 / Small chair, room center, seat cushion

&OBST XB= 1.80, 2.00, 1.60, 2.00, 0.00, 0.80, SURF_ID='UPHOLSTERY', BULK_DENSITY=41.176 / Small chair, room center, left armrest

&OBST XB= 2.40, 2.60, 1.60, 2.00, 0.00, 0.80, SURF_ID='UPHOLSTERY', BULK_DENSITY=41.176 / Small chair, room center, right armrest

&OBST XB= 1.80, 2.60, 1.40, 1.60, 0.00, 0.80, SURF_ID='UPHOLSTERY', BULK_DENSITY=41.176 / Small chair, room center, back cushion

 OBST XB= 4.40, 5.20, 1.00, 2.00, 0.00, 0.80, SURF_ID='SPRUCE' / TV cart?

&OBST XB= 0.00, 5.20, -0.20, 0.00, 0.00, 2.40 / Front wall

&HOLE XB= 4.00, 4.90, -0.20, 0.00, 0.00, 2.00 / Door

&VENT MB='YMIN',SURF_ID='OPEN' / 

&VENT XB=0.00,5.20,0.00,4.60,0.00,0.00, SURF_ID='CARPET' / 

&BNDF QUANTITY='GAUGE HEAT FLUX' / 

&BNDF QUANTITY='WALL TEMPERATURE' / 

&BNDF QUANTITY='BURNING RATE' / 

&SLCF PBX=2.60, QUANTITY='TEMPERATURE' /

&SLCF PBX=2.60, QUANTITY='HRRPUV' / Heat Release Rate per Unit Volume

&SLCF PBX=4.45, QUANTITY='TEMPERATURE' /

&SLCF PBX=4.45, QUANTITY='HRRPUV' / Heat Release Rate per Unit Volume

&DEVC XYZ=2.6,2.3,2.1, QUANTITY='TEMPERATURE' /

&DEVC XYZ=2.6,2.3,1.8, QUANTITY='TEMPERATURE' /

&DEVC XYZ=2.6,2.3,1.5, QUANTITY='TEMPERATURE' /

&DEVC XYZ=2.6,2.3,1.2, QUANTITY='TEMPERATURE' /

&DEVC XYZ=2.6,2.3,0.9, QUANTITY='TEMPERATURE' /

&DEVC XYZ=2.6,2.3,0.6, QUANTITY='TEMPERATURE' /

&DEVC XYZ=4.5,0.3,2.1, QUANTITY='TEMPERATURE' /

&DEVC XYZ=4.5,0.3,1.8, QUANTITY='TEMPERATURE' /

&DEVC XYZ=4.5,0.3,1.5, QUANTITY='TEMPERATURE' /

&DEVC XYZ=4.5,0.3,1.2, QUANTITY='TEMPERATURE' /

&DEVC XYZ=4.5,0.3,0.9, QUANTITY='TEMPERATURE' /

&DEVC XYZ=4.5,0.3,0.6, QUANTITY='TEMPERATURE' /

&DEVC XYZ=0.3,4.3,2.1, QUANTITY='TEMPERATURE' /

&DEVC XYZ=0.3,4.3,1.8, QUANTITY='TEMPERATURE' /

&DEVC XYZ=0.3,4.3,1.5, QUANTITY='TEMPERATURE' /

&DEVC XYZ=0.3,4.3,1.2, QUANTITY='TEMPERATURE' /

&DEVC XYZ=0.3,4.3,0.9, QUANTITY='TEMPERATURE' /

&DEVC XYZ=0.3,4.3,0.6, QUANTITY='TEMPERATURE' /

&DEVC XYZ=2.6,2.3,0.0, QUANTITY='RADIATIVE HEAT FLUX', IOR=3 / 

&TAIL /

---------------------------------

If someone can point me to the right source in user guide or point my mistakes in this code, I would appreciate it.

Thanks much.

[SD]

I forgot to mention that the error I get when I run this is "ERROR: The default EXTINCTION MODEL is designed for 1 reaction. See Tech Guide"

[Craig Weinschenk]

Currently the extinction model will only work with one gas phase reaction.

On Fri, Mar 14, 2014 at 6:35 PM, SD <sai....@gmail.com> wrote:

I forgot to mention that the error I get when I run this is "ERROR: The default EXTINCTION MODEL is designed for 1 reaction. See Tech Guide"

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www.cweinschenk.com

[SD]

I should have also mentioned earlier that

1. I am currently using 'POLYURETHANE' instead of wood. But if this program works, then my intention later is to replace 'POLYURETHANE' with WOOD by defining the properties of WOOD.

2. The code currently uses 'ignitor particles' with N_PARTICLES=3 to burn the wood, but I dont think it is helping the POLYURETHANE to burn much. I do not understand how these particles work. I see that these are particles at 1000 deg C, but I am not sure what N_PARTICLES=3 means (Question-1). I am confused.

Sorry for digressing.

Craig:  Firstly, to understand what you said,  it seems reasonable that only one gas phase reaction can be handled by the extinction model. Can it handle one gas phase and one solid phase reaction (total of two)?  I am assuming burning polyurethane is a solid phase model. How does FDS know which is a gas phase model and which is a solid phase (Question-2). Or, is the solid phase pyrolysis of polyurethane also modeled as gas phase reaction as the volatile gases are released?

Secondly, I am trying to understand how FDS interprets the input file picks the fuel. Based on the code I pasted earlier, FDS looks at the following sequence below as pointed out in order to choose the fuel and start the reaction process:

OBST (3D volume) -->SURF_ID -->UPHOLSTERY-->FABRIC & FOAM -->POLYURETHANE --> FUEL

OBST (2D Area) -->SURF_IDS-->'N-HEPTANE POOL'-->'N-HEPTANE LIQUID'-->'N-HEPTANE' --> FUEL   (Can this OBST 2D area be a 3D volume representing a pool of heptane?)

Am I right (Question-3)?

I am sorry I have so many questions, but the code is so perplexing to me that I want to clarify if I am interpreting the code correctly even before I implement the physics correctly.

[Craig Weinschenk]

The solid phase reaction will convert the fuel into a gas phase quantity - so you will end up with 2 fuels in the gas phase. There is some development into handling multiple fast chemistry reactions with gas phase extinction, but that work isn't ready yet. You are right with your question 2. 

With respect to multiple reactions - FDS reads the &REAC lines and grabs the fuels from there. In your case, it sees two fast chemistry reactions and then shoots an error message that extinction cannot have two reactions. It does not look at what the source of the fuel is.

[SD]

Craig,

Thanks for  patiently answering my questions. These questions were lingering in my head for a while and it feels good to have them clarified and I cannot appreciate you enough.

So, now that I know we cannot have two &REAC lines in the code, how can I use heptane liquid fuel to burn solid  'POLYURETHANE' ?

What are my options or alternatives? How can I achieve my GOAL as described in my first email? 

Can you give me any suggestions or point me to any resources?

[dr_jfloyd]

You cannot use the simple chemistry approach (c,h,o,n inputs) with more than one fuel. If you want more than one for you need to explicitly define your own reactions.

[brad c]

&HEAD CHID='sd', TITLE='sd'/
&TIME T_BEGIN=0, T_END=100, WALL_INCREMENT=1/
&MESH IJK= 40,40,40 XB= -1,1,-1,1,0,2/
&VENT MB='XMIN', SURF_ID='OPEN'/
&VENT MB='XMAX', SURF_ID='OPEN'/
&VENT MB='YMIN', SURF_ID='OPEN'/
&VENT MB='YMAX', SURF_ID='OPEN'/
&REAC FUEL= 'PROPANE', SOOT_YIELD=.01/
&MATL ID='stuff',
      SPECIFIC_HEAT=1.0,
      CONDUCTIVITY=0.05,
      DENSITY=100.0,
      N_REACTIONS=1,
      NU_SPEC=1.
      SPEC_ID='PROPANE'
      HEAT_OF_COMBUSTION=30000,
      HEAT_OF_REACTION=100.0,
      REFERENCE_TEMPERATURE=100.0/
&SURF ID             = 'log'
      MATL_ID        = 'stuff'
      THICKNESS      = 0.01
      BURN_AWAY=.TRUE./

&PART ID='ignitor particle', SURF_ID='ignitor', STATIC=.TRUE./

&SURF ID='ignitor', TMP_FRONT=1000., GEOMETRY='SPHERICAL', RADIUS=0.01/
&PROP ID='BALL', SMOKEVIEW_ID='SPHERE', SMOKEVIEW_PARAMETERS(1)='D=0.01'/
&INIT XYZ=0,0,.1, PART_ID='ignitor particle', N_PARTICLES=1/
&SPEC ID='WATER VAPOR'/
&PART ID='water_drops',  SPEC_ID='WATER VAPOR', SAMPLING_FACTOR=1,
QUANTITIES='PARTICLE DIAMETER', DIAMETER=2000./
&DEVC ID='sprinkler', PROP_ID='QR', XYZ=0,0,1.9/
&PROP ID='QR',
      QUANTITY='SPRINKLER LINK TEMPERATURE',
      ACTIVATION_TEMPERATURE=73.9,
      RTI=50.0
      FLOW_RATE=.375
      PARTICLE_VELOCITY=10.
      PART_ID='water_drops'/
&OBST XB=-.1,.1,-.1,.1,.2,.3, SURF_ID='log'/
&TAIL /

SD,

Here is an igniter particle under a piece of combustible stuff and a sprinkler. The values and dimensions are not very realistic, but should give you something to start with. In this example, it is not clear whether the sprinkler extinguishes the fire before the fuel is consumed, but looking at the HRR curve there appears to be a level period before it drops to 0. I cut this example (and changed material properties so it would run faster) from my questioning, not of "how long will it take the sprinkler to extinguish the fire", but, "what water application rate will be in equilibrium with what HRR". I think that is what the level part of the curve is and I call it "Control Mode". You can ramp the TEMP_FRONT of the igniter particle to better simulate a match or other ignition source. You do not need a liquid fuel to start a fire.

Good luck and Have fun,

brad c

ps-- I think the N in N_Particles means  'how many are there"? 

[SD]

Dr. Jfloyd,

Thanks for your comment. Section 12.2.2 (Multiple Chemical Reactions) of the User Guide has an example considering two simultaneous, mixing-controlled reactions of polyurethane and wood. It uses a lumped species approach to define the species and then two &REAC lines are defined corresponding to polyurethane and wood respectively.

Is this the approach you are suggesting?

Is simple chemistry combustion model a subset of 'mixing-controlled' model? Because both section 12.1 (single step) and Section 12.2.2 (multiple chemical reactions) are referred to as 'mixing-controlled' models.

If I may, I also want to share with you another approach that a colleague of mine used in FDS5. I haven't understood it to the full extent, but it looks like there is a point source of heptane and then there is wood stacked. The heptane burns and then burns the wood. I tried running the same case in FDS6, but I was unable to run it. It gives me an error "ERROR: Problem with PROP number  1". I tried changing the &PROP line to 

&PROP ID='nozzle', PART_ID='heptane droplets', FLOW_RATE= 30, FLOW_RAMP='fuel',

      PARTICLE_VELOCITY=10., SPRAY_ANGLE(1:2,1)=0.,45., SMOKEVIEW_ID='nozzle', PARTICLES_PER_SECOND=500 /

so that it complies with FDS6, but I was unsuccessful. I am including this FDS5 input file below:

------------------------------------- Start of FDS5 input file-----------------------------

&HEAD CHID='Test-Fire10',  TITLE='10 L Gasoline with stacked wood' /

&TIME DT= 0.1, T_END= 100 /

&MESH IJK= 40,60,20,   XB=0.0 , 10.0 , 0.0 , 15.0 , 0.0 , 5.0  /

MISC SURF_DEFAULT='CONCRETE', /

&REAC ID='HEPTANE'

FUEL='N-HEPTANE'

      FYI='Heptane, C_7 H_16'

HEAT_OF_COMBUSTION=44000

      C=7.

      H=16.

      CO_YIELD=0.008

      SOOT_YIELD=0.015 /

&DEVC ID='nozzle_1', XYZ= 5.50 , 7.0 , 0.13, PROP_ID='nozzle', QUANTITY='TIME', SETPOINT=0. /

&PART ID='heptane droplets',FUEL=.TRUE.,DENSITY=688.,

      QUANTITIES(1:3)='DROPLET_DIAMETER','DROPLET_TEMPERATURE','DROPLET_AGE',

      DIAMETER=500.,HEAT_OF_COMBUSTION=44500.,SAMPLING_FACTOR=1 /

&PROP ID='nozzle', PART_ID='heptane droplets', FLOW_RATE= 30, FLOW_RAMP='fuel',

      DROPLET_VELOCITY=10., SPRAY_ANGLE=0.,45., SMOKEVIEW_ID='nozzle', DROPLETS_PER_SECOND=500, /

&RAMP ID='fuel', T= 0.0, F=1 /

&RAMP ID='fuel', T=20.0, F=1 /

&RAMP ID='fuel', T=21.0, F=0 /

&RAMP ID='fuel', T=31.0, F=0 /

&RAMP ID='fuel', T=40.0, F=0 /

&MATL ID            = 'CONCRETE'                                                                    

      FYI           = 'Quintiere, Fire Behavior'                                                    

      SPECIFIC_HEAT = 0.88                                                                          

      DENSITY       = 2100.                                                                         

      CONDUCTIVITY  = 1.0 / 

&MATL ID            = 'TILE MATERIAL'                                                                                      

      FYI           = 'UL Report NC987-96NK37863'

      DENSITY       = 313.          

      SPECIFIC_HEAT = 0.753

      CONDUCTIVITY  = 0.0611 /

&MATL ID                    = 'Wood'

      FYI                   = 'Wood'

      SPECIFIC_HEAT         = 0.00017

      CONDUCTIVITY          = 0.35

      DENSITY               = 650.0

      N_REACTIONS           = 1

      NU_FUEL               = 1.

      REFERENCE_TEMPERATURE = 350.

      HEAT_OF_REACTION      = 2500.

      HEAT_OF_COMBUSTION    = 16000. /

&SURF ID             = 'WALL'

      RGB            = 150,150,150

MATL_ID = 'CONCRETE'

THICKNESS =0.1

Transparency = .3  /

&SURF ID        = 'FLOOR'                                                              

      RGB       = 150,150,150                                                                

      MATL_ID   = 'CONCRETE'                                                                    

      THICKNESS = 0.1 

Transparency = .3  /    

&SURF ID        = 'CEILING'

      RGB       = 230,230,230   

      MATL_ID   = 'TILE MATERIAL'

      BACKING   = 'EXPOSED'

      THICKNESS = 0.016 

Transparency = .3  /

&VENT MB='YMIN', SURF_ID='OPEN', /

&VENT MB='YMAX', SURF_ID='OPEN', /

&VENT MB='XMIN', SURF_ID='WALL' /

&VENT MB='XMAX', SURF_ID='WALL' /

&VENT MB='ZMIN', SURF_ID='FLOOR' /

&VENT MB='ZMAX', SURF_ID='CEILING' /

&SURF ID             = 'UPHOLSTERY'

      COLOR          = 'PURPLE'

      BURN_AWAY      = .TRUE.

      MATL_ID = 'Wood'

THICKNESS=0.125 /

&OBST XB= 3.5, 7, 5, 5.75, 0.5, .750, SURF_ID='UPHOLSTERY'/

&OBST XB= 3.5, 7, 6.5, 7.25, 0.5, .750, SURF_ID='UPHOLSTERY'/

&OBST XB= 3.5, 7, 8, 8.75, 0.5, .750, SURF_ID='UPHOLSTERY'/

&OBST XB= 4, 4.5, 5, 9, 0.750, 0.875, SURF_ID='UPHOLSTERY'/

&OBST XB= 5, 5.5, 5, 9, 0.750, 0.875, SURF_ID='UPHOLSTERY'/

&OBST XB= 6, 6.5, 5, 9, 0.750, 0.875, SURF_ID='UPHOLSTERY'/

&OBST XB= 3.5, 7, 5, 5.75, 1, 1.25, SURF_ID='UPHOLSTERY'/

&OBST XB= 3.5, 7, 6.5, 7.25, 1, 1.25, SURF_ID='UPHOLSTERY'/

&OBST XB= 3.5, 7, 8, 8.75, 1, 1.25, SURF_ID='UPHOLSTERY'/

&TAIL /

-------------------------------------End of FDS5 input file-----------------------------

Can I use this approach in FDS6 and make the above FDS5 input file work in FDS6? This input file works in FDS5.

Thanks much,

Sai.

[dr_jfloyd]

"simple chemistry" is mixing controlled combustion but limited to one REAC where the fuel chemistry is limited to C,H,O, and N.  

Yes, I was referring to the examples you found in 12.2.2

In your FDS5 input file, you are using simple chemistry (REAC has inputs of C,H,O, and N).  Therefore, all the fuel is being considered heptane in the gas phase. The solid phase is computed using the solid phase properties you give, but all the fuel that is pyrolyzed is then treated as heptane.  There are a number of changes that were made to inputs in going from FDS5 to FDS6, but if you make the needed changes the file you show should run in FDS6.

[SD]

Bradc,

Thanks for taking the time to review my fds input file and providing a simpler version. I appreciate the time you are taking to assist me. I have several beginner questions that hopefully you can help me with if you have time. I am including them in the attached file so as to not annoy the rest of the thread contributers with the lengthy questions.

Thanks,
Sai. 

[brad c]

My pleasure Sai.

I hesitate to answer questions off forum though because I am likely to lead you astray, but I will read and think about your questions and try and discover a subtle concept that might be a 'hump' for you, and I will try to remember how I got over it. I always start out doing as little as possible, actually, with small, simple examples-- there is a world of difference for me between THINKING about it and DOING (something, anything) about it :).

BTW-- I re-ran the simple example I posted and I miss spoke even about it, and that is what I mean by 'lead you astray'.

Brad

[brad c]

&REAC FUEL='SAI STUFF',C=6.3,H=7.1,O=2.1,N=0.0/

&MATL ID='stuff',
      SPECIFIC_HEAT=1.0,
      CONDUCTIVITY=0.05,
      DENSITY=100.0,
      N_REACTIONS=1,
      NU_SPEC=1.

      SPEC_ID='SAI STUFF'
      HEAT_OF_COMBUSTION=30000,
      HEAT_OF_REACTION=100.0,
      REFERENCE_TEMPERATURE=100.0/

Sai,

I believe if you change the &REAC and &MATL lines to the above some of the fog might lift for you-- you could no longer say "...log(propane)" and know it is a liquid fuel. From the user's guide, 8.5.7:  "The inclusion of BOILING_TEMPERATURE on the MATL line tells FDS to use its liquid pyrolysis model".

The SPEC_ID='SAI STUFF' ties the products of the combustion of 'stuff' to the chemistry in the REAC line. If you are interested in getting output for these products, and want SOOT and CO as well, you would give the yields for SOOT and CO (0 by default) as well, on the REAC line.

question 1(b) Yes-- the fuel mass would increase from .16 kg to .32 kg.

I would like to wait on other questions until you have studied the user's guide a little more and I have given more thought, except ramping igniter particle, try this:

...TEMP_FRONT=1000, RAMP_T='match'...

&RAMP ID='match',T=0,F=0/

&RAMP ID='match',T=1,F=1/

&RAMP ID='match',T=35,F=0/

The sprinkler flow rate is unrealistically low. If you change it to 56.7 (and the velocity to 1, which is unrealistically low but I did it anyway) you will see the fire is extinguished before the fuel is consumed.

thanks, Brad

[brad c]

correction on match ramp:

&RAMP ID='match',T=0,F=0/

&RAMP ID='match',T=1,F=1/

&RAMP ID='match',T=30,F=1/

&RAMP ID='match',T=35,F=0/

And I wanted to add, if you still want to use heptane to burn wood, you can do that by replacing the igniter particle with a material with the properties for heptane. You should place it under the stack though, otherwise it would burn away without heating the wood. I think using one REAC line is best thought of as describing the predominate fuel in your model, and the products of combustion based on the chemical make-up of that fuel. You can also give other values like H_O_C. If a MATL has a different H_O_C than given on REAC, it will override REAC.

Brad