Laser Rayleigh scattering for flame thermometry in a toroidal jet stirred combustor

Area of Science:

• Combustion science
• Laser diagnostics
• Turbulence

Background:

• Measuring instantaneous flame temperatures in turbulent flows is challenging due to poor optical access and interfering radiation.
• Existing methods struggle with background noise and laser-induced glare.

Purpose of the Study:

• To develop and validate a novel method for obtaining instantaneous flame temperatures in turbulent combustors.
• To overcome challenges posed by poor optical access, black body radiation, and laser-induced glare.
• To accurately determine the probability density functions (PDFs) of fluctuating temperatures.

Main Methods:

• Utilized pulsed laser Rayleigh scattering for temperature measurements.
• Developed a novel polarization-based technique to extract Rayleigh scattering signals.
• Applied shot noise correction to observed PDFs to obtain actual temperature PDFs.

Main Results:

• Successfully obtained instantaneous flame temperatures in a turbulent flow combustor.
• The polarization method effectively isolated Rayleigh scattering from background noise and glare.
• Accurate probability density functions (PDFs) of fluctuating temperatures were derived for ethylene-air combustion.

Conclusions:

• The novel polarization-based pulsed laser Rayleigh scattering technique is effective for measuring flame temperatures in challenging combustor environments.
• This method provides accurate PDFs of fluctuating temperatures, crucial for understanding turbulent combustion dynamics.
• The developed technique enhances diagnostic capabilities for combustion research.