Combustion characteristics of inverse diffusion flame in CO₂ atmosphere

The flame configuration and luminous emission properties of laminar inverse diffusion flames in CO₂ and N₂ atmosphere were experimentally investigated. The concentrations of fuel and oxidizer were varied by the dilution with CO₂ or N₂ while those velocities were kept constant for all flames. A video camera with Image Intensifier (I.I.) unit, UV lens and short-pass filter was used to measure the OH radical chemiluminescence and that with 680 nm long-pass filter was used to collect luminous intensity distribution from the soot radiation. The spectroscope was also used to detect flame emission spectrum. In CO₂ atmosphere, the flame height became longer than that in N₂. The emissions from intermediate species such as HCO and CH₂O, and chemiluminescence from CO₂* was enhanced in CO₂ atmosphere. This implies that some reactions were strongly enhanced by the presence of CO₂. In addition, the intensity of soot radiation luminosity in CO₂ atmosphere was less than half of that in N₂. This result indicates that the soot formation was suppressed in CO₂.