Calibration-free imaging thermometry via two-line atomic fluorescence in combustion processes

Area of Science:

• Combustion Science
• Laser-Induced Fluorescence Spectroscopy
• Thermometry

Background:

• Accurate temperature measurement is crucial for understanding combustion processes and flame dynamics.
• Particle-laden flames present unique challenges for traditional thermometry techniques.
• Indium atomic fluorescence offers a promising route for non-intrusive temperature measurements.

Purpose of the Study:

• To demonstrate a novel calibration-free imaging technique for full-frame temperature field measurements in particle-laden flames.
• To utilize two-line atomic fluorescence (TLAF) of indium for precise thermometry.
• To validate the technique's performance across various flame conditions.

Main Methods:

• Implementation of two-line atomic fluorescence (TLAF) using indium atoms.
• Excitation of specific indium atomic transitions (52P3/2 → 62S1/2 and 52P1/2 → 62S1/2) with narrowband external cavity diode lasers (ECDLs).
• Formation of excitation lasers into a light sheet for imaging thermometry on a laminar, premixed flat-flame burner.

Main Results:

• Successful calibration-free, full-frame temperature field imaging was achieved.
• Temperature distributions were accurately measured in laminar premixed flames with added indium precursor aerosol.
• Measurements were performed for varying air:fuel ratios (0.7, 0.8, and 0.9).

Conclusions:

• The developed TLAF technique provides a robust method for temperature imaging in particle-laden flames.
• The results demonstrate the technique's capability and potential for future applications.
• This method shows promise for applications such as flame synthesis of indium-containing nanoparticles.