Intrinsic Instability Of Premixed Flame

Soledad

In premixed flames propagating with a subsonic velocity
(e.g., hydrogen–air or hydrocarbon–air flames), intrinsic
instability always appears. Three basic types of phenomena
are responsible for the intrinsic instability of premixed
flames, i.e. hydrodynamic, body-force, and diffusivethermal
effects.The hydrodynamic effect is caused by
thermal expansion through the flame surface, and it is most
essential to the flame instability, since the combustion
reaction is exothermic and all premixed flames are
accompanied by thermal expansion. Thus, it is not possible
to study the instability of premixed flames without
considering the hydrodynamic effect. The body-force effect,
together with the hydrodynamic effect, is important to
intrinsic instability. This effect is caused by the difference in
density between the upper and lower fluids, and it has a
destabilizing (stabilizing) influence on upward (downward)
propagating flames . The reason is that the upper
fluid—the unburned gas (burned gas)—is heavier (lighter)
than that of the lower fluid. The third effect is the diffusivethermal
effect, which is caused by the preferential diffusion
of mass versus heat. This effect has a destabilizing influence
when the Lewis number of the deficient reactant is lower
than unity Cellular flames are experimentally
observed in lean (rich) gas mixtures with light (heavy) fuel
In addition, the formation of cellular flames is
numerically observed at low Lewis numbers, which is based
on either the diffusive-thermal model equation with a
constant-density approximation  or the compressible
Navier–Stokes equation .

lhgmail

最好有中文介绍，省得大家浪费时间。