TED-AJ03-249 ON RADIATIVE EDGE DIFFUSION FLAMES

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概要

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• The edge of a nitrogen-diluted hydrogen flame burning in air is modeled numerically using a constant density, one-step reaction model in a plane two-dimensional counterflow configuration. An optically thin assumption is used to investigate the effects of radiation on the flame dynamics, structure, and extinction. As found before, there exist dual extinction limits for the 1D radiative flame response, namely high-stretch (small Damkohler number) blow-off extinction and low-stretch (large Damkohler number) radiative quenching. Although the hydrogen flame is of sub-unity Lewis number, it is found that when the 1D radiative extinction flame exhibits oscillatory flame response. This demonstrates that diffusion flame oscillation can also be triggered by radiative heat loss. These oscillations are found to have increasing amplitude and decreasing frequency as the stretch rate is decreased. Flame oscillation eventually leads to permanent extinction eventhough the stretch rate is smaller than the corresponding steady-state radiative extinction limit. A previous study on adiabatic flames using the same configuration showed the existence of cellular flame structures close to the 1D adiabatic blow-off extinction limit. Moreover, the flames were found to resist quenching by stretch, thereby exhibiting two-dimensional flame structures for Damkholer numbers less than the 1D blow-off extinction [figure]value. This bifurcation of the two-dimensional flame branch from the one-dimensional flame response curve at the neutral stability point near the 1D blow-off extinction limit is also found to exist for high-stretch flames with radiative heat loss. Towards the low-stretch radiative extinction limit, the low-stretch two-dimensional radiative edge flames are found to exhibit transient cellular structures close to 1D radiative extinction limit. For Damkholer numbers higher than the 1D radiative extinction limit, steady cellular flamelet structures are observed. The size and spacing of the flamelets are found to depend on the Damkholer number, with the spacing increasing with increasing Damkholer numbers. The existence of two-dimensional flame structures beyond the 1D radiative extinction limit suggests that possibility of a bifurcation of the two-dimensional flame branch from the one-dimensional flame branch at the neutral stability point near the 1D low-stretch radiative extinction limit.[figure]

• 一般社団法人日本機械学会の論文

著者

• Nanduri Jagannath

  Department Of Mechanical And Aerospace Engineering National Center For Microgravity Research In Flui

• SUNG CHIH

  Department of Mechanical and Aerospace Engineering National Center for Microgravity Research in Flui

• TIEN JAMES

  Department of Mechanical and Aerospace Engineering National Center for Microgravity Research in Flui

• Sung Chih

  Department Of Mechanical And Aerospace Engineering National Center For Microgravity Research In Flui

• Tien James

  Department Of Mechanical And Aerospace Engineering National Center For Microgravity Research In Flui

• Tien James

  Department Of Mechanical And Aerospace Engineering Case Western Reserve University

関連論文

• TED-AJ03-249 ON RADIATIVE EDGE DIFFUSION FLAMES
• TED-AJ03-327 A COMPUTATIONAL STUDY ON FLAME RADIATION-SURFACE INTERACTION IN FLAME SPREAD OVER THIN SOLID-FUEL

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