Detection of OH in flames by using polarization spectroscopy

Area of Science:

• Combustion science
• Laser spectroscopy
• Chemical physics

Background:

• Nonlinear laser spectroscopy offers advanced diagnostic capabilities for combustion analysis.
• Hydroxyl (OH) radicals are key intermediates in combustion processes, making their detection crucial.
• Understanding flame chemistry and dynamics requires precise measurement of radical species.

Purpose of the Study:

• To investigate the application of polarization spectroscopy for detecting OH molecules in flames.
• To analyze the spatial distribution of OH radicals within different flame types.
• To explore the signal saturation behavior of polarization spectroscopy with varying laser intensities.

Main Methods:

• Utilized polarization spectroscopy, a nonlinear laser spectroscopy technique.
• Applied the method to detect OH molecules in a premixed acetylene-oxygen flame and a propane-air flame.
• Recorded polarization spectra in the OH A (2)Sigma-X(2)Pi(0, 0) band.
• Measured the spatial distribution of OH and investigated signal saturation.

Main Results:

• Successfully demonstrated the detection of OH molecules using polarization spectroscopy in both flame types.
• Obtained spatial distribution maps of OH radicals within the flames.
• Characterized the signal saturation dependence on laser pulse intensity.

Conclusions:

• Polarization spectroscopy is a viable and powerful technique for OH radical detection in combustion environments.
• The method provides valuable insights into OH spatial distribution and reaction dynamics.
• Further studies can leverage this technique for detailed combustion analysis.