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Computational modelling as an alternative to full-scale testing for tunnel fixed fire fighting systems

Computational modelling as an alternative to full-scale testing for tunnel fixed fire fighting systems . Kenneth J. Harris & Bobby J. Melvin Parsons Brinckerhoff Sacramento, CA USA E-mail: harris@pbworld.com Presented By Aaron McDaid. Key modeling bases.

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Computational modelling as an alternative to full-scale testing for tunnel fixed fire fighting systems

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  1. Computational modelling as an alternative to full-scale testing for tunnel fixed fire fighting systems Kenneth J. Harris & Bobby J. Melvin Parsons Brinckerhoff Sacramento, CA USA E-mail: harris@pbworld.com Presented By Aaron McDaid

  2. Key modeling bases • Fundamental energy analysis can be used to estimate water application rates. • Subroutines that model the key elements of solid and liquid vaporization have been written. • Subroutines that model the key elements of combustion energy have been written.

  3. Dynamics of Fire and Extinguishment

  4. Water Application Rate Equation

  5. Comparison of two identical fire test set-ups

  6. Flaming Radiative Heat Flux & Pyrolysis Model

  7. Common Heat Flux Levels

  8. Description of LTA Fire Tests

  9. Tabulation and comparison of fuel quantities

  10. Fuel Properties

  11. Comparison of model and test results for unsuppressed fire

  12. Comparison of model and test results for 12 mm/min. suppressed fire

  13. Peak heat flux and FHRR for various leakage rates

  14. Comparison of model and test results for unsuppressed and 12 mm/min. suppressed fire

  15. Dynamics of Fire and Extinguishment

  16. Water application rate for external heat flux only

  17. Vaporized water heat flux

  18. Water Application Rate 2 mm/min

  19. Water Application Rate 4 mm/min

  20. Main/Target Rate 4/0 mm/min

  21. Conclusion • Computer modelling provides a more cost-effective means of demonstrating proposed system performance. • The fuel vaporization process is well-defined in fire science and the computer models can be set up to utilize this approach. • Some significant differences in modelling are required for this approach. • The fuel properties and structure must be explicitly defined. • Comparison with a test is beneficial to calibrate the model.   • Modelling of the unsuppressed fire in particular can produce results very close to that shown in testing. • Modelling of fire suppression can provide results that give a reasonable degree of confidence of what can be expected of the system. • Computer modelling can be used to model the interaction of water and fire for design purposes, making individual full-scale testing unnecessary and making FFFS more likely to be implemented in road tunnels. • Pyrolysis-based input rather than fire heat release rate input should be used to more accurately model the effects of water and fire interaction.

  22. FSI 2014 Fire Sprinkler International • Thank you

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