Flammability limits of simple chemical reactions

Although gaseous fuels such as methane and propane are commonly referred to as flammable, their mixtures with oxygen or air will only burn if the fuel concentration lies within sharply defined limits, known as the lower (fuel-lean) and upper (fuel-rich) flammability limits. Outside of these limits ignition and flame propagation can not be initiated by the application of an external stimulus. Even should a reaction mixture lay within its flammability limits ignition requires the input of sufficient energy in a suitable form. (It should be noted that the phenomenon of flammability is distinct from, although related to, autoignition).

The aim of this work is to identify the flammability limits of simple chemical reaction schemes and to investigate how the geometry of the test method used to measure them changes their value. To this end we are working with simple idealised chemical schemes. It is then proposed to use the techniques developed to examine flammability limits in the hydrogen-oxygen reaction.

A goal of this work is to explore the use of continuously-stirred tank reactors in investigating the flammability of gases produced by the decomposition of polymers. A long-term goal is to investigate the interaction between heterogeneously catalysed and homogeneous combustion reactions.

Highlights of research on flammability limits

  1. I have shown that flammability limits correspond to either limit-points (more cursory, more detailed) or Hopf points (more cursory, submitted) on an isola as the reaction composition is varied. If the Hopf bifurcation is supercritical then there is a parameter region in which oscillations of near-extinction flames are observable.
  2. I have suggested how the identification of flammability limits with appropriate bifurcations points on an isola can be used as a basis for investigating gas-phase active fire retardants using dynamical systems methodology. (submitted)

My collaborators in modelling flammability limits

Dr. G.N. Mercer 1999-Present
Dr. J. Sexton 2000-Present
Dr. H. Sidhu 1999-Present
Dr. R.O. Weber 1999-Present.

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Page Created: 18th April 2002.
Last Updated: 22nd February 2003.