Oscillations, glow and ignition in carbon monoxide oxidation in an open system II. Theory of the oscillatory ignition limit in the c. s. t. r

The oxidation of carbon monoxide in the presence of hydrogen can produce a single ignition pulse in a closed vessel and repetitive, i. e. oscillatory, ignition in an open system. It is possible to predict the locus of critical conditions on a map of reactant pressure, p , against vessel temperature, T a , in a flow system by a treatment based on the change in local stability of the stationary state. Even the very simplest kinetic model for the CO + H 2 + O 2 reaction allows satisfactory predictions of the dependence of the critical pressure on T a , and of the displacement of such p – T a peninsulae as the mixture composition (CO : H 2 ratio) is varied. Many of the results can be obtained in terms of simple algebraic expressions. The relation between this approach and classical treatments of criticality based on the unbounded growth of the steady-state radical concentration or on tangency conditions (chain–thermal theory) is investigated. Oscill­atory periods (the interval between successive ignition pulses) are calcu­lated, and the variation in the mean residence time arising from the change in the number of moles during reaction and the accompanying self-heating is discussed.