Spontaneous ignition and stability in closed and open systems. Part 1.—Foundations: first-order reactions in the adiabatic case

Abstract

When a first-order, exothermic reaction is carried out in a closed vessel, thermal explosion may result. For well stirred systems of high exothermicity, reactant consumption can be ignored and the value of a single parameter (the Semenov number) determines the course of events, and calculation of its critical value permits the prediction of the pressure–temperature boundary between quiescent and explosive behaviour. When the same reaction is studied in an open system so contrived as to operate adiabatically there is no such (P_cr, T_cr) boundary. There is, however, another single parameter (the Zel'dovich number) which determines whether slow reaction or fast reaction or jumps from one state to another occur. Calculation of this number allows the prediction of critical flow rates for ignition and extinction. This case is presented here as the foundation of a broader study of unstable behaviour in open systems.