Comparison between CARS and corrected thermocouple temperature measurements in a diffusion flame

Area of Science:

• Chemical Physics
• Spectroscopy
• Combustion Science

Background:

• Accurate temperature measurement is crucial for understanding combustion processes.
• Traditional methods like thermocouples face limitations in harsh flame environments.
• Coherent anti-Stokes Raman spectroscopy (CARS) offers a non-intrusive alternative for temperature determination.

Purpose of the Study:

• To determine radial temperature profiles in an axisymmetric methane diffusion flame using CARS.
• To compare CARS temperature measurements with conventional thermocouple measurements.
• To assess the capabilities and limitations of CARS for flame temperature diagnostics.

Main Methods:

• Utilized Coherent anti-Stokes Raman Spectroscopy (CARS) for temperature measurements.
• Analyzed background-free nitrogen Q- and O-branch spectra.
• Employed a nonlinear least-squares CARS fitting program for spectral analysis.
• Compared CARS data with radiation- and conduction-corrected thermocouple measurements.

Main Results:

• CARS successfully obtained radial temperature profiles in the methane diffusion flame.
• Excellent agreement was observed between CARS and thermocouple measurements in regions of stable temperature.
• Discrepancies arose in areas with steep temperature gradients, indicating a need for higher CARS spatial resolution.

Conclusions:

• CARS is a viable technique for non-intrusive temperature measurements in flames.
• CARS performance is comparable to corrected thermocouples in uniform temperature zones.
• Enhanced spatial resolution in CARS is necessary for accurate measurements near significant temperature gradients.