Location of Repository

Gas-phase and heat-exchange effects on the ignition of high- and low-exothermicity porous solids subject to constant heating

By A.A. Shah, J. Brindley, A. McIntosh and J. Griffiths


This article investigates the ignition of low-exothermicity reactive porous solids exposed to a maintained source of heat (hotspot), without oxygen limitation. The gas flow within the solid, particularly in response to pressure gradients (Darcy’s law), is accounted for. Numerical experiments related to the ignition of low-exothermicity porous materials are presented. Gas and solid products of reaction are included. The first stage of the paper examines the (pseudo-homogeneous) assumption of a single temperature for both phases, amounting to an infinite rate of heat exchange between the two. Isolating the effect of gas production and flow in this manner, the effect of each on the ignition time is studied. In such cases, ignition is conveniently defined by the birth of a self-sustained combustion wave. It is found that gas production decreases the ignition time, compared to equivalent systems in which the gas-dynamic problem is effectively neglected. The reason for this is quite simple; the smaller heat capacity of the gas allows the overall temperature to attain a higher value in a similar time, and so speeds up the ignition process. Next, numerical results using a two-temperature (heterogeneous) model, allowing for local heat exchange between the phases, are presented. The pseudo-homogeneous results are recovered in the limit of infinite heat exchange. For a finite value of heat exchange, the ignition time is lower when compared to the single-temperature limit, decreasing as the rate of heat exchange decreases. However, the decrease is only mild, of the order of a few percent, indicating that the pseudo-homogeneous model is in fact a rather good approximation, at least for a constant heat-exchange rate. The relationships between the ignition time and a number of physico-chemical parameters of the system are also investigated

Topics: Q1
Year: 2006
OAI identifier: oai:eprints.soton.ac.uk:44775
Provided by: e-Prints Soton

Suggested articles



  1. Aldushin AP (2003) Effects of gas-solid non-equilibrium in filtration combustion.
  2. (1999). Analysis of ignition of a porous energetic material.
  3. Chemical Team Leader, Process Hazard Section, Syngenta. private communication
  4. (1981). Evolution of a deflagration in a cold combustible subjected to a uniform energy flux.
  5. (1981). Flame propagation and combustion processes in solid propellant cracks.
  6. (1999). Ignition analysis of a porous energetic material: II. Ignition at a closed heated end.
  7. (1991). Ignition of condensed systems with gas filtration.
  8. (1999). Ignition of porous materials by gas filtration (unsteady downstream filtration). Combus Explos Shock Waves 35:43–52
  9. (2001). Ignition phenomenology and criteria associated with hotspots embedded in a reactive material. Chem Engng Sci 56:2037–2046
  10. (1998). Influence of pressure-driven gas permeation on the quasi-steady burning of porous energetic materials.
  11. (2001). Influence of sublimation and pyrolysis on quasi-steady deflagrations in confined porous energetic materials.
  12. (2003). Influence of subsurface gaseous combustion on the burning of confined porous energetic materials.
  13. (1999). Initiation of combustion waves in solids and the effect of geometry.
  14. (2002). Intrusive-limit deflagrations in confined porous energetic materials.
  15. (1999). Long-term flow/chemistry feedback in a porous medium with heterogeneous permeability: kinetic control of dissolution and precipitation.
  16. (1989). On the tortuosity and the tortuosity factor in flow and diffusion through porous media.
  17. (2001). Potential hazards from spherical hotspots in reactive solids.
  18. (1992). Propagation of the front of an exothermic reaction through porous media under blow-through gas conditions. Soviet Phys Doklady
  19. (1981). The effect of deformation on flame spreading and combustion in propellant cracks.
  20. (2003). The effect of oxygen starvation on ignition phenomena in a reactive solid subject to a constant heat flux.
  21. (2004). The ignition of reactive solids by constant heating.
  22. (1991). The model for combustion of porous propellants subjected to fragmentation. Combust Explos Shock Waves
  23. (1971). Theory of ignition of a reactive solid by constant energy flux.

To submit an update or takedown request for this paper, please submit an Update/Correction/Removal Request.