3.1. Effects of mixture composition on local flame
structure and laminar flame speed
Fig. 4 shows the CCD camera captured flame images for stoichiometric
syngas/air mixtures at different XH2 . Significant
reduction in flame front area is observed with increasing XH2 .
Furthermore, the perceptual bluish flame luminosity
decreases and becomes increasingly pinkish with the increase in XH2 . Flame height decreases with increasing XH2 due to the
increase in flame speeds since the Reynolds number of
upstream flows keeps constantly and flow rates of different
mixtures are almost the same. As XH2 increases, the burned
gas flame propagation speed is increased, pushing the flame
front toward the upstream direction for flow balance. Due to
distinction of different flame emissions, flame radiation color
can be distinguished from each other. For example, for low XH2
flame, major emission is CO2; while for high XH2 flame, water
vapor becomes the major emission. Those emissions influence
the visible light of flames, and result in the differences of
flame shape and color.