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Physical sub-models to be included in the main model

Physical sub-models to be included in the main model. In Physical Modelling the conservation equations (mass, momentum, energy) are solved. Observations, experiments, and modelling show that there is gas flow. ... ahead of the flame near the fuel bed. Bellemare, 2000.

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Physical sub-models to be included in the main model

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  1. Physical sub-models to be included in the main model In Physical Modelling the conservation equations (mass, momentum, energy) are solved Observations, experiments, and modelling show that there is gas flow ... ... ahead of the flame near the fuel bed ... Bellemare, 2000 ... and inside the porous fuel bed Obviously, there is also flow inside shrubs and inside foliage Fire Star conclusive symposium: Marseille March 18th 2005

  2. Physical sub-models to be included in the main model Several sub-models are used to deal with a number of phenomena The temperatures of fuel bed, shrubs, foliage, and of the gas that flows inside them are not necessarely the same • heat transfer between the gas and these fuel matrixes occurs This energy exchange plays an important role in the decrease of fuel moisture content and in the fuel pyrolysis The flow inside the fuel matrices is subjected to aerodynamic drag • sub-models for heat transfer and aerodynamic drag are, • therefore, necessary Fire Star conclusive symposium: Marseille March 18th 2005

  3. Physical sub-models to be included in the main model There is no data on porous beds similar to forest fire fuel matrices Data on packed beds from chemical engineering have been used ... chemical packed beds are very different from the forest fuel matrices But ... Objective : • to measure the heat transfer coefficient h and pressure drop • through matrices of forest fuels Fire Star conclusive symposium: Marseille March 18th 2005

  4. heating elements working section + 2 Existing wind tunel heating elements (used for aerodynamic studies  very good performance) + honeycomb pine needles + honeycomb 1 honeycomb 3 heating elements working section + o o o o o o 4 thermocouple honeycomb pine needles pressure tap Physical sub-models to be included in the main model Section 1 : electric resistances (5 kW) to heat the flow Section 2 : working section packed with pine needles or twigs and leaves or just twigs 1000 x 160 x 240 mm (l x h x w) insulated walls 6 thermocouples and pressure taps Fire Star conclusive symposium: Marseille March 18th 2005

  5. Physical sub-models to be included in the main model Thin thermocouples had to be “inserted” at the fuel surfaces Thicker wire (250m) to which the thin wire is attached 125m K type thermocouple “inserted” at the fuel particle’s surface 125m K type thermocouple in the air at the vicinity of the fuel particle Fire Star conclusive symposium: Marseille March 18th 2005

  6. D 4 / SVR h = Nu = Nu k k Physical sub-models to be included in the main model Examples of the curves obtained for h and for pressure drop Pressure drop per unit length for Quercus coccifera Nu as a function of Re for Pinus pinaster and Quercus coccifera Influence of the strata location and existence (or not) of leaves Fire Star conclusive symposium: Marseille March 18th 2005

  7. Experimental fires in the INIA wind tunnel • Experimental fires in the wind tunnelwere devoted to: • Validate the behaviour model of wildland fire • Analyse effectsof • Wind speed • Shrub moisture content • Width of a discontinuity • on the fire behaviour • in a fuel complex of Pinus pinaster litter • and Chamaespartium tridentatum shrubs General view of INIA wind tunnel Fire Star conclusive symposium: Marseille March 18th 2005

  8. C. tridentatum shrubs P. pinaster litter Experimental fires in the INIA wind tunnel • Example of test : • Wind speed = 1 m/s • Shrub m.c.: 40 % • Width of discontinuity = 0 m Fire Star conclusive symposium: Marseille March 18th 2005

  9. Experimental fires in the INIA wind tunnel • Example of Test on discontinuous fuel: • Wind speed = 0 m/s • Shrub m.c.: 40 % • Width of discontinuity = 2 m Fire Star conclusive symposium: Marseille March 18th 2005

  10. Variation of Maximum Temperatures with Height Experimental fires in the INIA wind tunnel Examples of results obtained at INIA wind tunnel Width of discontinuity = 0 m Variation of Rate of Spread with Wind Speed Similar set of results are available for: * Flame height * Byram´s fireline intensity Fire Star conclusive symposium: Marseille March 18th 2005

  11. Visible TIR (8-12 m) MIR (3-5 m) Multi- spectral TIR MIR • LIR-UC3MFire parameters obtained by IR Spectral Imaging • Equipment set up and Images Acquisition • Tunnel and lab meas.: 2 cameras one for each band (MIR &TIR). • Field measurements: 1 camera: up to 4 MIR sub-bands Infrared images are simultaneous, co-registered and calibrated (brightness temperatures) Bi-spectral images (MIR & TIR bands) Multispectral images (4 MIR bands) Fire Star conclusive symposium: Marseille March 18th 2005

  12. T (K) LIR-UC3MFire parameters obtained by IR Spectral Imaging 2. Pixel Classification and image processing IR image: Physical parameters measured • Brigthness temperatures • Scene classification • Rate of spread • IR flame height • Instantaneous Radiated power • Estimation of: • Total released power (roughly, 17% of the power released is radiated) • Fire front intensity • Heat released per unit area MIR Bi-spectral image T (K) TIR Class map (For multispectral images is analogous) In collaboration with INIA and CIF-Lourizan Fire Star conclusive symposium: Marseille March 18th 2005

  13. gases CO2 CO IR emitter FTIR Fuel sample Heater CH4 LIR-UC3M Fuel Pyrolysis Studies based on FTIRS- Fourier Transform IR Spectrometry: 1. Schematics and aims spectral absorbance •  Objective: to gain knowledge on the pyrolysis chemistry • FTIR spectrometry: a) identification of gases by the spectral location of absorbance bands b) determination of gas concentration from the band depth • c) acquires simultaneously information on the whole spectral range (2-16 mm) • Gases under study: CO2 , CO , CH4 , NH3 In collaboration with INIA Fire Star conclusive symposium: Marseille March 18th 2005

  14. combustion efficiency • - clear correlation of NH3 with CO emissions • data dispersion • low rate of CH4 emission LIR-UC3M Fuel Pyrolysis Studies based on FTIRS 2. Some remarkable results In collaboration with INIA Fire Star conclusive symposium: Marseille March 18th 2005

  15. INRA DESIRE bench 5 thermocouplesonto a vertical Sketch of the experiment UP VIEW median axis of DESIRE camera field of view DESIRE plate infrared camera SIDE VIEW Fire Star conclusive symposium: Marseille March 18th 2005

  16. INRA DESIRE bench 1 pixel of the infrared image solid fuel temperature comparison of time signals Comparison of infrared signal and thermocouple temperature near fire front position of the cotton thread position du fil de coton thermocouple at 5 cm high gas temperature thermocouple à 5 cm de haut  température du gaz Fire Star conclusive symposium: Marseille March 18th 2005

  17. INRA DESIRE bench Time evolutions of solid fuel and gas temperature – Slope 0° Slope 0° Pente 0° Moyenne mobile des données de température the thermocouple ‘enters’ the flame le thermocouple ‘entre’ dans la flamme Pre-heating of the litter Préchauffage de la litière solid fuel temperature  gas temperature Breaking of the cotton thread Coupure du fil de coton Fire Star conclusive symposium: Marseille March 18th 2005

  18. INRA DESIRE bench Time evolutions of solid fuel and gas temperature – Slope 30° Slope 30° Pente 30° the thermocouple ‘enters’ the flame le thermocouple ‘entre’ dans la flamme Pre-heating of the litter Préchauffage de la litière solid fuel temperature  gas temperature Breaking of the cotton thread Coupure du fil de coton Fire Star conclusive symposium: Marseille March 18th 2005

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