Microgravity diffusion flame spread over a thick solid in step-changed low-velocity opposed flows

doi:10.1016/j.combustflame.2019.03.040

	Microgravity diffusion flame spread over a thick solid in step-changed low-velocity opposed flows
	Zhu F(朱凤); Lu ZB; Wang SF(王双峰); Yin YL
刊名	COMBUSTION AND FLAME
	2019-07-01
卷号	205 页码:55-67
关键词	Opposed-flow flame spread Thick solid Microgravity Radiation-controlled regime Diffusive-thermal instability
ISSN号	0010-2180
DOI	10.1016/j.combustflame.2019.03.040
通讯作者	Wang, Shuangfeng(sfwang@imech.ac.cn)
英文摘要	We report results from a microgravity combustion experiment conducted aboard the SJ-10 satellite of China, focusing on the structure and dynamics of diffusion flames spreading over a thick PMMA in low-velocity opposed flows. The width of the PMMA sample is chosen to be as large as possible in order to minimize the side diffusion effects of oxygen, and for each of the four oxygen concentration cases considered, four decrementally changing gas flow velocities are imposed such that a wide range of parameter values are spanned near the quenching limit. Two distinct flame spread modes are identified near the quenching limit, namely the continuous flame mode for gas flow velocities greater than an oxygen-concentration dependent critical value, and the flamelet mode for subcritical gas flow velocities. The transition process between these two spread modes due to a step change in the gas flow velocity is usually accompanied by flame oscillations, and diffusive-thermal instability of the leading flame front is identified as the mechanism controlling such transition. A correlation of the flame spread rate data among different oxygen concentrations indicates that, in the presently considered radiation-controlled regime the normalized flame spread rate deviates from the predictions of the thermal theory and decreases monotonically with the increase in the flame Damkohler number. Meanwhile, with the decrease in the flame spread rate, the standoff distance and the inclination angle at the flame leading edge show an increasing and decreasing trend, respectively. An energy balance analysis across the fuel surface beneath the flame leading edge indicates that the variation of the heat absorbed by the solid for vaporization is sub-linear with respect to the flame spread rate, thereby implying that the fuel regression depth has a tendency to increase with decreasing flame spread rate. Moreover, the energy balance analysis suggests that the quenching boundary and the marginal stability boundary identified on the flammability map are, respectively, intrinsically associated with a certain specific ratio of the overall heat losses to the total heat conducted from the flame, or equivalently, associated with a certain specific value of the flame spread rate. (C) 2019 The Combustion Institute. Published by Elsevier Inc. All rights reserved.
分类号	一类/力学重要期刊
资助项目	National Natural Science Foundation of China[U1738117] ; Strategic Priority Research Program on Space Science ; Chinese Academy of Sciences[XDA04020410] ; Chinese Academy of Sciences[XDA04020202-10]
WOS关键词	TEMPERATURE-MEASUREMENT ; STABILIZATION ; PREDICTION ; NUMBER ; MODEL ; EDGE
WOS研究方向	Thermodynamics ; Energy & Fuels ; Engineering
语种	英语
WOS记录号	WOS:000471742000007
资助机构	National Natural Science Foundation of China ; Strategic Priority Research Program on Space Science ; Chinese Academy of Sciences
其他责任者	Wang, Shuangfeng
内容类型	期刊论文
源URL	[http://dspace.imech.ac.cn/handle/311007/79364]
专题	力学研究所_国家微重力实验室
推荐引用方式 GB/T 7714	Zhu F,Lu ZB,Wang SF,et al. Microgravity diffusion flame spread over a thick solid in step-changed low-velocity opposed flows[J]. COMBUSTION AND FLAME,2019,205:55-67.
APA	朱凤,Lu ZB,王双峰,&Yin YL.(2019).Microgravity diffusion flame spread over a thick solid in step-changed low-velocity opposed flows.COMBUSTION AND FLAME,205,55-67.
MLA	朱凤,et al."Microgravity diffusion flame spread over a thick solid in step-changed low-velocity opposed flows".COMBUSTION AND FLAME 205(2019):55-67.