LIU, F. ... et al, 2012. Onset of cellular instabilities in spherically propagating hydrogen-air premixed laminar flames. International Journal of Hydrogen Energy, 37 (15), pp.11458-11465.
Using high-speed Schlieren and Shadow photography, the instabilities of outwardly
propagating spherical hydrogen-air flames have been studied in a constant volume
combustion bomb. Combustion under different equivalence ratios (0.2 w 1.0), temperatures
(298 K w 423 K) and pressures (1.0 bar w 10.0 bar) is visualized. The results show that
flames experience both unequal diffusion and/or hydrodynamic instabilities at different
stages of propagation. The critical flame radius for such instabilities is measured and
correlated to the variations of equivalence ratio, temperature and pressure. Analysis
revealed that equivalence ratio affects unequal diffusion instability via varying the Lewis
number, Le; increased temperature can delay both types of instabilities in the majority of
tests by promoting combustion rate and changing density ratio; pressure variation
has minor effect on unequal diffusion instability but is responsible for enhancing
hydrodynamic instability, particularly for stoichiometric and near-stoichiometric flames.