2018

An IH-QCL based gas sensor for simultaneous detection of methane and acetylene

An IH-QCL based gas sensor for simultaneous detection of methane and acetylene

G. Zhang, K. Khabibullin, A. Farooq

Proceedings of the Combustion Institute, (2018)
G. Zhang, K. Khabibullin, A. Farooq
QCL, Shock tube, Methane, Acetylene, Absorption spectroscopy
2018

Fig. Simulated spectra for a 2.5% CH4, 1.5% C2H2, balance air mixture. T = 1800 K, P = 1 atm, L = 14 cm.
Extended wavelength tuning of an IH-QCL (integrated heater quantum cascade laser) is exploited for simultaneous detection of methane and acetylene using direct absorption spectroscopy. The integrated heater, placed within few microns of the laser active region, enables wider wavelength tuning than would be possible with a conventional DFB (distributed feedback) QCL. In this work, the laser current and heater resistor current are modulated simultaneously at 25 kHz to tune the laser over 1279.6–1280.1 cm−1, covering absorption transitions of methane and acetylene. The laser is characterized extensively to understand the dependence of wavelength tuning on modulation frequency, modulation amplitude and phase difference between laser/heater modulation. Thereafter, the designed sensor is validated in both room-temperature static cell experiments and non-reactive high-temperature-measurements in methane-acetylene-argon gas mixtures in the shock tube. Finally, the sensor is applied for simultaneous detection of methane and acetylene during the high-temperature pyrolysis of iso-octane behind reflected shock waves.​
DOI: 10.1016/j.proci.2018.06.062