Js. Ervin et Sp. Heneghan, THE MEANING OF ACTIVATION-ENERGY AND REACTION ORDER IN AUTOACCELERATING SYSTEMS, Journal of engineering for gas turbines and power, 120(3), 1998, pp. 468-473
Global reaction mechanisms and rate constants are commonly used in com
putational fluid dynamics models that incorporate chemical reactions t
o study aviation fuel thermal and oxidative thermal stability. Often t
hese models are calibrated using one set of conditions, such as flow r
ate and temperature. New conditions are then calculated by extrapolati
on using the global expressions. A close inspection of the origin of g
lobal oxidation rate constants reveals that in systems that undergo au
tocatalysis or auto inhibition, a simple overall global activation ene
rgy and reaction order are not good descriptors of the reaction proces
s. Furthermore, pseudo-detailed chemical kinetic modeling of a fuel th
at experiences autocatalysis showy that the observed reaction order fo
r oxygen consumption varies with initial oxygen concentration, extent
of reaction, and temperature. Thus, a simple global rate expression us
ed to describe oxygen consumption in an autoaccelerating system is ins
ufficient to allow extrapolation to different temperature or time regi
mes.