A Theoretical Model of Major Fire Spread in a Tunnel

Abstract

A model of major fire spread in a tunnel is described. It employs the concepts of non-linear dynamical systems theory and identifies the onset of instability with major fire spread in a tunnel. In particular, the model associates the existence of a fold bifurcation with dramatic fire spread from an initial fire to a 'target object'. The purpose is to identify the thermo-physical and geometrical conditions which lead to instability and sudden fire spread. Flame impingement on the target object is assumed not to exist; fire spread is assumed to be by spontaneous ignition only.The case considered assumes the existence of a longitudinal forced ventilation and predicts the critical heat release rate needed for a fire to spread from an initial fire to an item with a given assumed shape. The target object may be taken to approximate a vehicle. The illustrative case approximating fire spread from an initial fire to a heavy goods vehicle (HGV) within the Channel Tunnel is presented ; it is not restricted to this case, however. The model is identified with the name FIRE-SPRINT A3, which is an acronym of Fire Spread in Tunnels, Model A, Version 3. It is a development of an earlier model, FIRE-SPRINT A2. The current model takes greater account of thermal radiation than was done in the earlier work and also assumes a more extensive flame volume for a downstream flame section.

Road tunnel fire safety and risk: a review

“…Hansen andIngason (2011, 2012) have developed a method for calculating the critical heat flux for ignition according to mechanism 3 above. Beard (2006) has developed a non-linear model called FIRE-SPRINT to identify the onset of instability with major fire spread according to either mechanism 1 or 3 above, see (Grant and Jagger 2012;Charters 2012) for an overview.…”

Handbook of Tunnel Fire Safety, 2nd edition

“…The only comprehensive treatment of fire spread in a tunnel has been that due to Beard (Beard, 1997(Beard, , 1998(Beard, , 2001(Beard, , 2003Beard et al, 1995). He has developed a suite of non-linear models of thermal instability in fires to examine the ignition of objects downwind of an existing fire in a tunnel.…”

State of the Art of Tunnel Fire Research

“…It is, however, assumed that this thermal instability corresponds to one mechanism of fire spread. The tunnel model has been developed further since this groundbreaking work (FIRE-SPRINT A2 [7,34]), where the flames extend downstream from the initial fire and over the entire length of the target object without impinging on it. There is also a third version, FIRE-SPRINT A3 [35], available which makes the same assumptions as A2 but includes a thicker flame section between the initial fire and target fire.…”