Steady glow

Linnett and various co-workers [57, 58] also observed oscillatory glow, somewhat intermittently, in their studies of the reaction with extensively-dried reactants (see above) in vessels with untreated surfaces. These authors unfortunately used the phrase multiple explosions to describe the phenomenon which they observed only by eye. Later, meticulous work exploiting instrumental monitoring of the reaction by Bond et al. [59, 60] revealed that the ignition limit reported by the Linnett group on the basis of a detectable emission actually corresponds to the limit for steady glow. 

In well-stirred flow reactors, the CO + O2 reaction supports five different modes of response [63,64] steady slow reaction, steady glow, oscil-... 

Fig. 5.31. The co-existence of (a) steady glow and (b) oscillatory glow for the CO -I- O2 reaction (dry mixtures) in an ageing reactor. (Reprinted with permission from reference [60], Royal Society of London.)...

Fig. 5.43. Schematic bifurcation diagram for CH3CHO + O2 reaction showing separate branches corresponding to dark reaction and steady glow, with upper branch losing stability at a Hopf bifurcation as Ta is reduced to give limit cycle (cool-flame) oscillations. The simple limit cycle also loses stability as is reduced further and a complex oscillation corresponding to the multi-stage ignition will emerge but cannot be adequately represented...

As these extra sources of electrons become more important, the glow increases and, along region F-G, it becomes steady and similar to that shown in Figure 6.4. (It is known as the normal glow.)... 

Fig. 3. Formation of a pulsating negative sheath on a capacitively coupled surface in an rf glow discharge [after Butler and Kino ] a) initial application of rf voltage b) steady-state application of rf voltage...

Experimentally, the moment of ignition is recorded according to the appearance of light emission or a rapid rise of the temperature in the oxidation zone. The ignition is considered established as soon as the combustion process becomes steady. Shortterm glow is regarded as a flash. In the steady-state combustion the heat flux from the exothermal reaction zone to the fresh polymer surface makes up for all the heat necessary for the self-sustaining reaction. 

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