|Extinction of lean near-limit methane/air flames at elevated pressures under normal- and reduced-gravity|
|Zhang H; Fan R; Wang SF(王双峰); Tian XQ; Xu K; Wan SX(万士昕); Egolfopoulos FN
|Source Publication||Proceedings of The Combustion Institute
|Abstract||perimentally at evaluated pressures and under normal- and micro-gravity conditions utilizing the 3.5 s
drop tower of the National Microgravity Laboratory of China. The results showed that under micro-gravity
conditions the natural convection is minimized and the flames become more planar and symmetric compared
to normal gravity. In both normal- and micro-gravity experiments and for a given strain rate and
fuel concentration, the flame luminosity was found to enhance as the pressure increases. On the other hand,
at a given pressure, the flame luminosity was determined to weaken as the strain rate decreases. At a given
strain rate, the fuel concentration at extinction was found to vary non-monotonically with pressure, namely
it first increases and subsequently decreases with pressure. The limit fuel concentration peaks around 3 and
4 atm under normal- and micro-gravity, respectively. The extinction limits measured at micro-gravity were
in good agreement with predictions obtained through detailed numerical simulations but they are notably
lower compared to the data obtained under normal gravity. The simulations confirmed the non-monotonic
variation of flammability limits with pressure, in agreement with previous studies. Sensitivity analysis
showed that for pressures between one and 5 atm, the near-limit flame response is dominated by the competition
between the main branching, H + O2 ? OH + O, and the pressure sensitive termination,
H+O2+M? HO2 + M, reaction. However, for pressures greater than 5 atm it was determined that
the HO2 kinetics result in further chain branching in a way that is analogous to the third explosion limit
of H2/O2 mixtures.
2010 The Combustion Institute. Published by Elsevier Inc. All rights reserved.|
|WOS Keyword||FLAMMABILITY LIMITS
; PREMIXED FLAMES
|WOS Research Area||Thermodynamics
; Energy & Fuels
; Energy & Fuels
; Engineering, Chemical
; Engineering, Mechanical
|Corresponding Author||Zhang H|
Zhang H,Fan R,Wang SF,et al. Extinction of lean near-limit methane/air flames at elevated pressures under normal- and reduced-gravity[J]. Proceedings of The Combustion Institute,2011,33(1):1171–1178.
Zhang H.,Fan R.,王双峰.,Tian XQ.,Xu K.,...&Egolfopoulos FN.(2011).Extinction of lean near-limit methane/air flames at elevated pressures under normal- and reduced-gravity.Proceedings of The Combustion Institute,33(1),1171–1178.
Zhang H,et al."Extinction of lean near-limit methane/air flames at elevated pressures under normal- and reduced-gravity".Proceedings of The Combustion Institute 33.1(2011):1171–1178.