Fig. 1. Structure diagram of central drain pipe of floating-roof tank

Fig. 2. Physical model

Fig. 3. Model validation

Fig. 4. Concentration change curves of each monitoring point at different leak locations

Fig. 5. Schematic diagram of laser detection experimental system

Fig. 6. Picture of experimental system

Fig. 7. Original absorption spectral-line waveform

Fig. 8. Voigt linear function fitting residual

Fig. 9. Inversion results of CH₄ concentration at different flow rates