Propene concentration sensing for combustion gases using quantum-cascade laser absorption near 11 μm

R. S. M. Chrystie, E. F. Nasir, A. Farooq
Applied Physics B, vol. 120, issue. 2, pp. 317-327, (2015)

Propene concentration sensing for combustion gases using quantum-cascade laser absorption near 11 μm

Keywords

Propene concentration sensing

Abstract

​We report on a strategy to measure, in situ, the concentration of propene (C3H6) in combustion gases using laser absorption spectroscopy. Pyrolysis of n-butane was conducted in a shock tube, in which the resultant gases were probed using an extended cavity quantum-cascade laser. A differential absorption approach using online and offline wavelengths near λ = 10.9 μm enabled discrimination of propene, cancelling the effects of spectral interference from the simultaneous presence of intermediate hydrocarbon species during combustion. Such interference-free measurements were facilitated by exploiting the =C–H bending mode characteristic to alkenes (olefins). It was confirmed, for intermediate species present during pyrolysis of n-butane, that their absorption cross sections were the same magnitude for both online and offline wavelengths. Hence, this allowed time profiles of propene concentration to be measured during pyrolysis of n-butane in a shock tube. Time profiles of propene subsequent to a passing shock wave exhibit trends similar to that predicted by the well-established JetSurF 1.0 chemical kinetic mechanism, albeit lower by a factor of two. Such a laser diagnostic is a first step to experimentally determining propene in real time with sufficient time resolution, thus aiding the refinement and development of chemical kinetic models for combustion.

Code

DOI: 10.1007/s00340-015-6139-4

Sources

Website PDF

See all publications 2015