Limiting Phenomena. Self-Ignition Peninsula

Curve 1 slow reaction curve 2 slow reaction with a cool flame flash (the maximum in the curve designates a degenerate explosion) curve 3 reaction ending in explosion. All the curves refer to slightly different mixture compositions 

It was stated above that, at ea 1, the reaction rate tends with time to a constant value w = Woa/(l — sa) (the rate of a stationary reaction). For a branched chain reaction at as 1, the kinetic equation (35.5) becomes 

The degenerate chain reactions also follow this equation (w exp 9t) but with a very low value of 9 (often varying from 10 to 10 s ). 

The rate of a branched chain reaction increasing according to exp 9t after a certain time becomes so high that the reaction ends in explosion. However, this occurs only if the value 9 is positive (ea 1) throughout the reaction. 

It should be added that the transition to the explosion region is often favoured by the heating which is already observed at a relatively low reaction rate and accelerates the reaction up to a thermal explosion (see Section XII.43). 

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