Approach for a quantitative on-the-fly fluorescence diagnostic in combustion systems

Area of Science:

• Combustion diagnostics
• Laser-induced fluorescence spectroscopy
• Atmospheric chemistry

Background:

• Accurate measurement of species concentration is crucial for understanding combustion processes.
• Sodium atom fluorescence is a common tracer for flame studies, but its measurement is affected by quenching.
• Existing methods for sodium concentration measurement can be time-consuming and sensitive to flame conditions.

Purpose of the Study:

• To develop a rapid and robust method for determining sodium atom concentration in flames.
• To utilize a megahertz repetition rate laser system for time-resolved fluorescence measurements.
• To establish a measurement technique independent of the flame's quenching environment.

Main Methods:

• Employed a megahertz repetition rate, picosecond dye laser system for excitation.
• Utilized gated photon counting detection for high temporal resolution.
• Analyzed sodium atom fluorescence lifetimes in seeded atmospheric pressure flames (CH(4)/O(2)/diluent).

Main Results:

• Achieved data acquisition times as short as 1 millisecond with a 3.8-MHz laser repetition rate.
• Demonstrated that the ratio of the integrated fluorescence signal to the fluorescence lifetime is independent of the quenching environment.
• Successfully obtained sodium atom fluorescence lifetimes in various flame conditions.

Conclusions:

• The developed method allows for rapid, on-the-fly measurements of sodium concentration.
• This technique offers a significant advantage by eliminating the need for quenching corrections.
• The findings have implications for real-time combustion monitoring and analysis.