ABSTRACT
The distinction between isothermal chain branches and chain branching augmented by thermal feedback can then be investigated by ‘switching off’ the thermal contributions in the model. The relationships between thermal, chain branching and chain-thermal criticality are summarised, from which it is seen that both the thermal and the isothermal chain branching criteria are supercritical with respect to the conditions for chain-thermal criticality. The heat release from most combustion processes originates in a complex chemical mechanism, which includes chain branching. Thus an understanding of how free radical chain branching systems can behave underpins the interpretation of much combustion behaviour. A representative reaction scheme, appropriate to surfaces of low efficiency especially with respect to the destruction of HO2 and H2O2, must include quadratic interactions of free radicals. The main feature of a chain branching reaction is an exponential growth in reaction rate as a result of the multiplication of the primary propagating species.
