The Alestle - Vol. 60 No. 22 - 10/25/2007

Vol. 60 No. 2

Experimental and theoretical comparison of spatially resolved laser-induced incandescence signals in a sooting flame

A detailed experimental and theoretical investigation has been made on the use of Laser-Induced Incandescence (LII) in two configurations; right-angle LII and backward LII. Both right-angle and backward LII imaging measurements were conducted in simultaneous experiments at various pulse energies. The theoretically calculated LII signals were based on a heat transfer model for soot particles exposed to laser radiation, and were compared with the experimental LII images. Both the experimental and theoretical results from this initial comparison showed similar general behaviour, for example the broadening of the spatial LII distribution and the hole-burning effect at centre for increasing laser pulse energies

A comprehensive protocol for chemical analysis of flame combustion emissions by secondary ion mass spectrometry

International audienceRATIONALE. Time of flight secondary ion mass spectrometry (ToF-SIMS) is used to provide detailed information on the surface chemical composition of soot. An analytical protocol is proposed and tested on a laboratory flame, and the results are compared with our previous measurements provided by two-step laser mass spectrometry (L2MS). METHODS. This work details: (1) the development of a dedicated apparatus to sample combustion products from atmospheric flames and deposit them on substrates suitable for ToF-SIMS analysis; (2) the choice of the deposition substrate and the material of the sampling line, and their effect on the mass spectra; (3) a method to separate the contributions of soot and condensable gas based on impact deposition, and finally (4) the post-acquisition data processing. RESULTS. Compounds produced during flame combustion are detected on the surface of different deposition substrates and attributed a molecular formula based on mass defect analysis. Silicon and titanium wafers perform similarly, while the surface roughness of glass microfiber filters results in a reduced mass resolution. The mass spectra obtained from the analysis of different locations of the deposits obtained by impaction show characteristic patterns that are attributed to soot/condensable gas. CONCLUSIONS. A working method for the analysis of soot samples and the extraction of useful data from mass spectra is proposed. This protocol should help avoiding common experimental issues like sample contamination, while optimizing the setup performance by maximizing the achievable mass resolution

Mesure de concentration d'especes dans une flamme par fluorescence saturee induite par laser : une nouvelle approche

SIGLECNRS T Bordereau / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Mesure quantitative d'espèces traces par des méthodes combinées de spectroscopie laser (LIF et CRDS)

National audienc

In situ LIF and ex situ CRDS applied to NO measurement in flames: probe perturbation and absolute quantification

International audienceFlame-sampling experiments allow describing the species profiles as function of the height above the burner. However, the so-measured species profiles are perturbed by the heat losses due to the probe, and/or species losses inside the probe. In order to attempt to clarify the perturbations induced by a microprobe, NO species profiles were obtained in a stoichiometric low-pressure flame by using in situ and ex situ measurements. An unperturbed NO species profiles was measured locally by LIF. Two shapes of microprobes were used to perform ex situ measurements by CRDS after gas probe sampling. The comparison of the profiles shows that the profiles obtained after probe sampling are shifted downstream, and that the absolute mole fraction of NO may be drastically affected during the sampling

Species concentration monitoring in flames by cavity ring-down spectroscopy : a study of the spatial resolution and of the detection limit in hostile environments

International audienc

Species concentration monitoring in flames by cavity ring-down spectroscopy : a study of the spatial resolution and of the detection limit in hostile environments

International audienc

Imagerie de NO par fluorescence induite par laser dans un moteur à allumage commandé

LILLE1-BU (590092102) / SudocSudocFranceF