Diode laser-based thermometry using two-line atomic fluorescence of indium and gallium

Area of Science:

• * Laser-based diagnostics
• * Combustion science
• * Thermometry

Background:

• * Accurate temperature measurement is crucial for understanding reactive flows and combustion processes.
• * Traditional thermometry methods can be intrusive or require complex calibration.
• * Developing robust, calibration-free techniques for high-temperature environments is essential.

Purpose of the Study:

• * To investigate a calibration-free thermometric technique using diode lasers and two-line atomic fluorescence (TLAF).
• * To assess the performance of indium and, for the first time, gallium as atomic temperature markers in reactive flows.
• * To validate TLAF measurements against rotational Coherent Anti-Stokes Raman Spectroscopy (CARS) in methane/air flames.

Main Methods:

• * Employed a diode laser system for two-line atomic fluorescence (TLAF) excitation.
• * Utilized indium and gallium atoms as temperature-sensitive tracers in a multi-jet burner.
• * Generated methane/air flames with temperatures ranging from 1600 K to 2000 K.
• * Conducted simultaneous measurements using rotational CARS for validation.

Main Results:

• * TLAF thermometry with indium and gallium demonstrated robust performance in reactive flows.
• * Measured temperatures ranged from 1600 K to 2000 K with high accuracy (~2.7%) and precision (~1%).
• * Indium and gallium showed comparable accuracy and precision across the tested temperature range.
• * TLAF results were consistent with simultaneous rotational CARS measurements, confirming reliability.

Conclusions:

• * The developed TLAF technique offers a reliable, calibration-free method for temperature measurements in reactive flows at atmospheric pressure.
• * Indium and gallium are effective atomic tracers for TLAF thermometry in this temperature regime.
• * This technique provides a valuable tool for combustion research and diagnostics.