Investigation of the sampling nozzle effect on laminar flat flames

Sampling probes used for the mass spectrometric sampling of a flame can affect the flame's flow field. Although this effect is already compensated for by heuristic correction functions, state of the art 3-D simulations may permit an even better consideration of this effect. This work has investigated the perturbations induced by sampling probes in burner-stabilized, laminar, flat flames using numerical simulations. Any deviations in the flow and temperature fields from the ideal, one-dimensional flat flame were generated here by a perforated burner plate; they are also examined. Corresponding mass spectrometric measurements were performed in flames of CH4/O-2/Ar and H-2/O-2/N-2. burning under atmospheric conditions. In the present study, heat transfer from the flame to the sampling nozzle was studied with a conjugate heat transfer model. Combustion was described using a finite rate chemistry model, employing a detailed reaction mechanism for a H-2/O-2/N-2 flame and a reduced mechanism for a CH4/O-2/Ar flame. Compared to the ideal, one-dimensional, and unperturbed flame, the probe was found to affect the measurements of the concentrations of some species by up to 50%. The results highlight the value of supporting numerical simulations of both the flow and combustion for such measurements with invasive probing. (C) 2014 The Combustion Institute. Published by Elsevier Inc. All rights reserved.