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8/16/2019 Vigne Węgrzyński SFPE2016 JVVA

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Influence of Variabil ity of Soot Yield Parameter in AsseSafe Evacuation Conditions in Advanced Modelling A

Results of Physical and Numerical Modelling Comp

Gabriele Vigne

Director JVVA Fire & RiskUniversity of Jaén, Spain

11th CONFERENCE ON PERFORMANCE-BASED CODES AND FIRE SAFETY DESIG

23-25 MAY, WARSAW, POLAND

Wojciech Wę

Building Research Polan


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PRESENTATION• Background

• Objectives

• Previous Analysis

• Building Research Institute (ITB) Experiment

• Numerical Analysis

• Validation & Verification

• Conclusions & Future Work


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BACKGROUND

• In many of today’s construction project the Fire Engineerinplays a fundamental role, especially when it comes to pbased design.

• A natural part of the performance based design process nowuse of advanced modelling.

• It is of utter importance to understand the limitations and thethe model parameters on the final results.


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OBJECTIVE

• This presentation shows the analysis and the results from a rewith the objective to evaluate the sensitivity of visibility when va

critical parameters that have a direct influence on the same: Ys, K

mass extinctioncoefficient (Km)

VISIBILITsoot yield (Ys)

Visibility factor (C)


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WHY?

• Visibility is one of the most critical output when con

ASET/RSET analysis

• Very often 10m is used to identify for how long tenable coreached into a certain domain and consequently define the Available Safe Egress Time to evacuate the domain


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Visibility

• Estimates of visibility through smoke can be made byequation:

S = C/K

• C = 8 for a light-emitting sign and C = 3 for a light-reflectinK is the Light Emission Coefficient:

K = Km ρ YS

km is the mass extinction coefficient and ys the soot yield


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Visibility

The light dampening effect through the smoke, as an outcome

scattering and other phenomena, follows the law of Lambert-B

be written in general form, or related to the local mass density o

I0 – light intensity,I – light intensity after distance l in the smoke,Km - mass extinction coefficient [m-1]

Ms –

mass density of smoke

= 0−


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Visibility

• C is the visibility factor (C = 8 for a light-emitting sign andlight-reflecting sign)

• Km is the mass extinction coefficient. The default value is 8value suggested for flaming combustion of wood and plastic

• Ys is the soot yield and represents the fraction of fuelconverted to soot when using a simple chemistry approach.


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In January 2013 researchers from the University of Jaén, The Univ(ICAI) with the collaboration of the Imperial College of London, MAfire consultancy JVVA Fire and Risk have undertaken several full sc

the Fire Atrium test facility in Murcia (Spain).

Previous Analysis

Statistical analysis to determine the most important input parameter• Ys: 0.015g/g, 0.120g/g and 0.230 g/g• Km: 7600 m²/kg, 8700 m²/kg and 9800 m²/kg• C: 3 and 8

Analysis shown that soot yield is the most influential parameter provuser of a CFD model


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Metal Technology Center (CTM) in Murcia

Previous Analysis


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The Murcia Fire Atrium is a full-scale facility consistingof a prismatic structure of 19.5 m x 19.5 m x 17.5 mand a pyramidal roof raised 2.5 m at the centre.

The walls and roof are made of 6 mm thick steelsheets whilst the floor is made of concrete.

The atrium is provided with four exhaust fans (with twovelocity, provided by Sodeca) installed on the roof,each with a nominal flow rate of 9.2m3/sapproximately.

As per make up air, there are eight grilled ventsarranged at the lower parts of the walls.

Previous Analysis


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Previous Analysis

Influence of Soot Yield and Mass Extinction Coeffic ient on Visibi


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• Based on above findings a new test facility was used,Research Institute (ITB) in Warsaw, Poland and in collaWojciech Węgrzyński, a new set of fire tests were conduc

• The following materials were chosen for assessment:

Building Research Institute (ITB) Exper

• methyl alcohol, Ys = 0.001 g/g• propane alcohol, Ys = 0.015 g/g

• heptane, Ys = 0.035 g/g• toluene, Ys = 0.178 g/g


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Building Research Institute (ITB) Expe

• A test chamber in ITB with

dimensions of 10 x 10m and height of

4m was equipped with mechanicalsmoke exhaust system.• The system was scaled in a way, that

a state of equilibrium was achieved inthe room for fires with power rangingfrom 130 to 160kW, i.e the sameamount of smoke is exhausted, as

enters the smoke layer, and theheight of layer is stable.


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Methanol, Ys = 0.001 g/g Propanol, Ys = 0.015 g/g

Heptane, Ys = 0.035 g/g Toluene, Ys = 0.178 g/g


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• In order to analyze a wider range of soot yields, a numerical abeen performed.

• Two software have been selected as ones of the most used a

in the Fire Engineering Community, ANSYS Fluent (v.17) andDynamics Simulator (v.6.4.0).

• Twenty (20) models have been processed both in Fluent and soot yield range between 0.01 g/g and 0.2 g/g using the Heptas a base.

Numerical Analysis


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Numerical Analysis

Numerical model used -

ANSYS Fluent

Numerical model used

Fire Dynamics Simula


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• A preliminary validation has been performed in order tperformance of the numerical models used.

• The results show a relative good agreement to the experimentdata for Heptane and Propanol with a maximum discrepancyHigh discrepancy has been found for Methanol and Tolueneassessed by new experiments to be conducted in summer 201

• Heptane showed to be the most stable fuel when it comes towas then used as a base for a wider range of numerical model

VALIDATION & VERIFICATION



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VISIBILITY VS SOOT YIELD


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VISIBILITY VS. SOOT YIELD

Visibili ty range vs. Soot Yield (Ansys Fluent) Visibility range vs. Soot Yield (Fire


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VISIBILITY VS. SOOT YIELD

Soot Yield (g/g) 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0

Visibility (m) – FDS* 14.87 10.90 7.34 5.39 4.29 3.55 2.98 2Visibility (m) – Fluent* 15.15 7.64 4.91 4.04 2.96 2.44 2.12

Soot Yield (g/g) 0.11 0.12 0.13 0.14 0.15 0.16 0.17 0

Visibility (m) – FDS* 1.85 1.71 1.56 1.43 1.31 1.21 1.14 1

Visibility (m) – Fluent* 1.34 1.30 1.23 1.09 1.02 N/A 0.91 0

S i U


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Summing Up

• Four (4) Experimental tests have been performed in 2016 in the ITB

Centre of Warsaw, Poland, using for different fuels with a wide range

(from 0.001 g/g for Methanol to 0.178 g/g for Toluene)

• The results have been compared to four (4) numerical models proce

Ansys Fluent and Fire Dynamics Simulator

• Good agreement has been found for Heptane and thus this fuel was

for a numerical study looking at 20 different cases, each one with a s

difference of 0.01 g/g (from 0.01 g/g to 0.20 g/g)

CONCLUSIONS AND FUTURE WO


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CONCLUSIONS AND FUTURE WO

• The numerical analysis, both for Ansys Fluent and FDS, show an hy

of the Visibility when increasing the soot yield with a cut-off point aro

where a variation of the soot yield can produce a relevant (below 0.negligible (above 0.12 g/g) change in the Visibility.

• The implications of choosing for the same fire scenario a reaction in

another can lead to a huge over prediction of the Visibility and there

under estimation of the Fire Safety.

CONCLUSIONS AND FUTURE WOR


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• Unless the materials (and thus the chemical reactions) in the bube assessed by a Fire Engineering analysis are well known, val

soot yield below about 0.10 g/g should be used with extremely cwhen performing an ASET/RSET exercise.

• Although the overall conclusions still be valid, more accurateexperiments will be performed in order to better understand thedeviation from the numerical results.

CONCLUSIONS AND FUTURE WOR


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THANK YOU FOR YOUR ATTENT

Gabriele Vigne

Director JVVA Fire & Risk

University of Jaén, Spain

11th CONFERENCE ON PERFORMANCE-BASED CODES AND FIRE SAFETY DESI

23-25 MAY, WARSAW, POLAND

Wojciech Węg

Building Research In

Poland

vigne węgrzyński sfpe2016 jvva

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