Tracer-free liquid-vapor imaging using lifetime-filtered planar laser-induced fluorescence

Area of Science:

• Combustion science
• Optical diagnostics
• Aerospace engineering

Background:

• Traditional laser-induced fluorescence (LIF) methods struggle to separate liquid and vapor fuel signals due to tracer coevaporation and signal disparities.
• Accurate fuel spray characterization is crucial for optimizing combustion processes and reducing emissions in aviation.

Purpose of the Study:

• To develop and demonstrate a tracer-free technique for differentiating liquid and vapor phase LIF signals in fuel sprays.
• To enhance the accuracy of fuel spray diagnostics by overcoming limitations of existing LIF methods.

Main Methods:

• Implementation of lifetime-filtered LIF, utilizing prompt detection for liquid phase and time-delayed detection for vapor phase signals.
• Application to Jet-A fuel sprays in oxygen-free environments.
• Development of a scaled liquid signal subtraction algorithm to mitigate vapor phase contamination from large droplets.

Main Results:

• Successful separation of liquid and vapor phase LIF signals without the need for tracer species.
• Demonstration of effective removal of vapor signal contamination using the subtraction algorithm.
• Validation of the lifetime-filtered LIF technique for Jet-A fuel.

Conclusions:

• Lifetime-filtered LIF offers a robust and accurate method for distinguishing liquid and vapor fuel spray components.
• This tracer-free approach simplifies experimental setups and enhances the reliability of fuel spray diagnostics.
• The technique holds significant potential for advancing combustion research and engine development.