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1

PyroSim / Soot yield from burnable surfaces part 2

« on: December 02, 2021, 04:44:38 am »

Dear all,
I am using pyrosim software to investigate the impact of fire in a room with wooden lining. I want to model the development of the smoke layer height.  

Setup: My room is 20x30x7 m, burner vent constant at 800 kW. Material is yellow pine, surface of the reaction allow obstruction to burn away, ignition temperature 225?C, HRRPUA=120kW/m2.

My problem: the production of soot from the burnable lining. The lining burns - it ignites and contributes to the total HRR. The total HRR rises to 2000 kW over 250 s, making the wooden surface contribute with 1200 kW compared to the reference case (concrete, without lining). Smoke view visualises a production of soot from the wooden surface. However, height measuring device's results show no significant contribution of soot. How can the soot yield for burnable surfaces be changed?
 
I have tried the "Species Injection" tab in the surface, but it seems to crash if soot yield is added in the respective settings (linked to a material).  Different room sizes have been tested and the trend is same.

Thanks in advance

2

PyroSim / Soot production from burnable objects

« on: November 29, 2021, 01:29:48 pm »

Hi

I'm still a little new to the pyrosim software so sorry if I am making a beginner mistake with this question. I am a student who is trying to investigate the increase of danger (severity of fire and time to critical smoke layer height) by using wooden lining in a room in comparrison to non-burnable surfaces. I have an issue with the smoke/soot production of programming this burnable lining: I seem to have been able to program the lining to be burnable as it ignites after it heats and it contributes to the total HRR of the model (Burner vent is constant at 800 kW and with the wooden surface, the total HRR rises to 2000 kW over 250 s, making the wooden surface contribute with 1200 kW). And in smoke view, the wooden surface seems to burn and produce smoke. All of this seems great.
My problem starts when my layer height measuring device's results does not seem differ significantly from a room without a burnable lining. My sample room is 20x30x7 m and the time to critical smoke layer height in the room with no burnable surface is 322 s, and with the burnable surface is 318 s. A little less of an increase than what I would expect. It has to be said that I have tried different room sizes and the trend seems the same.
 
I see that I haven't been able to give my surface a soot yield coefficient, I have just linked it to a material of "yellow pine", and given the surface the reaction of being burnable with an ignition temperature and a HRRPUA. Is there anywhere I should insert the soot yield for this burnable surface? I have tried the "Species Injection" tab in the surface, but it seems to crash if I put a soot yield in those spaces while it is linked to a material. What should my approach be if I want a more accurate meassurement?

I have read a post about the smoke layer zoning device not being all that reliable, and other critical condition should be considered instead. Is this an area where I have overestimated the capabilites of this too?
https://forum.thunderheadeng.com/index.php/topic,2371.msg3731.html?fbclid=IwAR3tzdQG1dbh1ACaZGrOxB4cxuRILdL-baZPiMByTcFDCmkDaK0U3p5lc4E#msg3731

Thanks in advance