Document Type
Article
Publication Date
1-1-2021
Abstract
This study investigates the impact of pressure and dilution on combustion behavior of C2H6/air/N2 mixtures within an externally heated micro-tube using both experimental and analytical techniques. Experiments are conducted for pressures up to 10 bar at multiple dilution levels and document three flame regimes, i.e. weak flames, FREI and normal flames. Characteristic temperatures for flame stabilization, as well as ignition and extinction are obtained by applying a novel thin filament pyrometry method (TFP), which uses a thin silicon carbide (SiC) filament that enables temperature measurements for both reacting and non-reacting cases. Results show a decrease of characteristic temperatures with increasing pressure, which can be partially compensated by a decrease of O2 content. Further, regime transitions occur at lower velocities as the pressure increases, whereas weak flame positions are insensitive to dilution at a given pressure. Predictions from an analytical model compare favorably with experimental results. The most prominent finding is that as dilution increases, the transition from weak flame to FREI becomes less abrupt and is completely lost for high dilution levels (i.e. low O2 content). Both experimental and analytical results indicate that the unstable FREI combustion regime does not exist at high dilution levels, i.e. weak flame and normal flame regimes are no longer clearly separated. As FREI correspond to a cyclic transition from an ignition zone to a propagating flame, results for highly diluted conditions are interpreted as a combustion regime where classical flame propagation ceases to exist.
Publication Source (Journal or Book title)
Proceedings of the Combustion Institute
First Page
6695
Last Page
6702
Recommended Citation
Isfahani, S., Sauer, V., & Schoegl, I. (2021). Effects of dilution and pressure on combustion characteristics within externally heated micro-tubes. Proceedings of the Combustion Institute, 38 (4), 6695-6702. https://doi.org/10.1016/j.proci.2020.06.090
