Fig. 1. Experimental setup

Fig. 2. Fluorescence spectra of 500 ppm CH₄/N₂ flow field

Fig. 3. Signal intensity attenuation curve at different CH₄/N₂ concentrations

Fig. 4. Location diagram of marker molecule

Fig. 5. Images with different laser energies and delay times

Fig. 6. Velocity measurement results of different laser energy and delay time

Fig. 7. Signal intensity vs. delay times with CH₄ concentration of 2 000 ppm

Fig. 8. Signal intensity vs. delay times with CH₄ concentration of 500 ppm

Fig. 9. Signal-to-noise ratio vs. delay time at different CH₄ concentrations