Application of FRAME for Simultaneous LIF and LII Imaging in Sooting Flames Using a Single Camera

Area of Science:

• Combustion Science
• Optical Diagnostics
• Chemical Engineering

Background:

• Sooting combustion is a complex phenomenon crucial for energy production and pollutant formation.
• Accurate multi-species measurements in flames are challenging due to signal overlap and background noise.
• Understanding the spatial distribution of Polycyclic Aromatic Hydrocarbons (PAH) and soot is key to controlling combustion.

Purpose of the Study:

• To present and validate the Frequency Recognition Algorithm for Multiple Exposures (FRAME) technique for simultaneous multi-species measurements.
• To investigate the distribution of PAH and soot in ethylene/air diffusion flames.
• To improve the understanding of sooting combustion processes.

Main Methods:

• Simultaneous Laser-Induced Fluorescence (LIF) of PAH and Laser-Induced Incandescence (LII) of soot were performed.
• The FRAME technique was applied to spectrally isolate LIF and LII signals from a single acquired image.
• Image post-processing was used to suppress flame luminosity and background light, enhancing image contrast.

Main Results:

• The FRAME technique successfully isolated LIF (PAH) and LII (soot) signals.
• PAHs were found predominantly in the inner flame region, surrounded by soot.
• Hydroxyl (OH) radicals were mainly located at the outer flame edges, indicating reaction and soot oxidation zones.

Conclusions:

• The FRAME technique is effective for simultaneous PAH and soot imaging in diffusion flames.
• The findings provide insights into the spatial relationships between PAHs, soot, and OH radicals in sooting flames.
• This technique advances the study of combustion chemistry and soot formation mechanisms.