Heat of combustion

DRAKE JONES

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Mar 19, 2021, 7:03:17 AM3/19/21

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Hi all,

I am simulating the cone calorimeter scenario of a material in FDS using HRRPUA model. The heat release rate is proportional to the effective heat of combustion. However, when I used the EHOC from the experiment, the heat release rate in FDS model is not same as that of FDS. So I calibrated my EHOC in such a way that my heat release rate matched with my experiment. The calibrated EHOC is 6000 kJ/kg more than what was measured from the experiment. This was the case with few other materials of mine. Why FDS is not able to predict the heat release rate properly when using EHOC from the experiments?. I am attaching the heat release rate curves form the experiment, FDS( with experimental EHOC and calibrated EHOC). TIA

Capture.PNG

dr_jfloyd

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Mar 19, 2021, 11:08:01 AM3/19/21

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Without knowing how you are attempting to model the cone experiment, it is not possible to tell you what might be wrong. Please provide a simple input file showing how your are trying to model the cone test.

DRAKE JONES

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Mar 19, 2021, 1:16:43 PM3/19/21

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please find attached the snippets from my code

1.PNG

2.PNG

dr_jfloyd

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Mar 19, 2021, 2:03:05 PM3/19/21

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Please provide a complete input file and attach it as a text file. I can't run FDS with a partial input file and I can't run a PNG file as the input.

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Kevin

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Mar 19, 2021, 3:09:44 PM3/19/21

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I ran your case. It appears that you have specified a heat release rate per unit area (HRRPUA) that follows a ramp and peaks at about 96 kW/m2. Is this not the case?

DRAKE JONES

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Mar 19, 2021, 9:24:40 PM3/19/21

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Yeah Kevin, that is the case

dr_jfloyd

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Mar 20, 2021, 7:44:38 AM3/20/21

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Your heat of combustion is 14.6 MJ/kg. Your fuel needs ~2.3 kg of O2 per kg of fuel to burn which gives you an EPUMO2 of 6.2 MJ/kg which is very low. Your fuel chemistry on REAC may not be correct. Having such a low EPUMO2 means the extinction model is preventing combustion. Either adjust your chemistry or set SUPPRESSION=F on MISC. When you increased the heat of combustion of your fuel on REAC, you eventually reached a point where the extinction model allowed combustion to happen.

DRAKE JONES

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Apr 13, 2021, 4:43:43 AM4/13/21

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May I know how did you arrive at the value of 2.3? Does EPUMO2 value is stored by FDS in the any of the output files? TIA

dr_jfloyd

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Apr 13, 2021, 6:59:02 AM4/13/21

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Write out the stoichiometric reaction for your REAC input. Use the molecular weights of the fuel and oxygen along with the stoichiometric coefficients to determine the kg of O2 required per kg of fuel. Divide the fuel heat of combustion by this value.

Hannah 11

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May 13, 2021, 4:16:48 AM5/13/21

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Dear all,

where can I refer this extinction model in detail?

dr_jfloyd

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May 13, 2021, 8:27:51 AM5/13/21

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The FDS Technical Reference Guide discusses the details of the extinction models available in FDS.

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