OH-Planar Laser-Induced Fluorescence Measurements in Laminar Diffusion Flames of N-Heptane with Coflow Air Diluted by N2 and CO2.

The distribution of hydroxyl (OH) radicals in the laminar diffusion flame of n-heptane was studied by planar laser-induced fluorescence (PLIF). The influences of nitrogen (N2) and carbon dioxide (CO2) dilution on the formation and distribution of OH radicals were analyzed. The corresponding dilution ratios (volume fractions) of both N2 and CO2 vary from 0 to 5%. The results show that for the n-heptane flame, the OH radical is mainly concentrated in the two wings of the flame, presenting a radially approximate symmetrical distribution. Both N2 and CO2 dilutions decrease the intensity of the maximum OH radical fluorescence and the total OH radical fluorescence. Moreover, the flame temperature decreases more significantly with the CO2 dilution ratio due to the combination of the dilution effect and thermal effect.