Lw. Kostiuk et Knc. Bray, MEAN EFFECTS OF STRETCH ON LAMINAR FLAMELETS IN A PREMIXED TURBULENT FLAME, Combustion science and technology, 95(1-6), 1994, pp. 193-212
A new approach to modeling the mean effects of stretch on laminar flam
elets in a premixed turbulent flame is explored which uses statistical
results of direct numerical simulation of the distributions of strain
and curvature on a propagating surface. These statistics are combined
to estimate the distribution of stretch rates experienced by the flam
e and hence the mean rate at which the turbulent flame converts reacta
nts to products per unit of flame surface area. The results are presen
ted as a function of the Karlovitz number ranging from zero to unity.
The distribution of stretch rates on the flamelet surface reveals that
a large proportion (30-50%) of the flame is under compression (i.e.,
negative stretch rates) at any time. The mean rate of conversion from
reactants to products per unit area tends to decreases with increasing
Karlovitz number. Certain combinations of modeled parameters lead to
a prediction that the mean reaction rate per unit area can be greater
than that in an unstretched flame. Using results from a laminar flamel
et library for stoichiometric methane:air flames the effect of stretch
on the mean rates of reaction is estimated.