Ignition theory, activation-energy

Mallard-Le Chatelier theory, Semenov assumed an ignition temperature, but by approximations eliminated it from the final equation to make the final result more useful. This approach is similar to what is now termed activation energy asymptotics. 

Recent theories of knock (4, 33, 45, 207) have emphasized the role played by the hydroperoxy radical (H02-) under incipient knock conditions. H02 radicals would be formed by Reactions 9", 11, and 9-4. Reaction 9, with an activation energy of 40 kcal. (204), might be the reaction required to trigger ignition. The yields of both hydrogen peroxide (207) and hydrogen (107) have in fact been observed to increase rapidly near autoignition. 

The temperature instability of a two-dimensional reactive fluid of N hard disks bounded by heat conducting walls has been studied by molecular dynamics simulation. The collision of two hard disks is either elastic or inelastic (exothermic reaction), depending on whether the relative kinetic energy at impact exceeds a prescribed activation barrier. Heat removal is accomplished by using a wall boundary condition involving diffuse and specular reflection of the incident particles. Critical conditions for ignition have been obtained and the observations compared with continuum theory results. Other quantities which can be studied include temperature profiles, ignition times, and the effects of local fluctuations. 

---