Time-resolved temperature measurements in a laboratory flame using the optoacoustic beam-deflection method

Area of Science:

• Combustion Science
• Optical Diagnostics
• Acoustic Thermometry

Background:

• Accurate, time-resolved gas temperature measurements are crucial for understanding combustion processes.
• Existing methods often lack the spatial resolution or temporal response needed for dynamic flame analysis.

Purpose of the Study:

• To develop and demonstrate a noncontact optical technique for high-repetition-rate, localized gas temperature measurements.
• To investigate thermal oscillations in a premixed propane-air flame using the developed method.

Main Methods:

• Utilized a laser-beam deflection technique, leveraging rapid heating at a gas-solid interface as an acoustic source.
• Achieved time-resolved temperature measurements at a repetition rate exceeding 1 kHz.
• Applied the method to a laboratory-scale premixed propane-air flame.

Main Results:

• Successfully acquired localized gas temperature values with high temporal resolution (>1 kHz).
• Observed a distinct 12.5-Hz thermal oscillation specifically at the edge of the propane-air flame.
• Found no significant thermal oscillation in the central region of the flame.

Conclusions:

• The developed laser-based acoustic thermometry method is effective for time-resolved combustion temperature diagnostics.
• The findings indicate localized oscillatory behavior at the flame edge, providing insights into flame stability and dynamics.
• This technique offers a valuable tool for studying transient phenomena in combustion environments.