引入熔融糊状区的PMMA逆流火蔓延数值模拟

doi:10.16511/j.cnki.qhdxxb.2020.21.013

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摘要

该文通过数值模拟研究了聚甲基丙烯酸甲酯（PMMA）板材逆流火蔓延过程，将PMMA火蔓延过程中的糊状区熔融相变传热过程引入到材料的能量方程，并建立气相燃烧反应的组分方程和传热微分方程。通过在材料上边界局部位置施加固定热流以实现点火过程，研究相变材料由点火、非稳定火蔓延到稳定火蔓延过程中的典型特性。基于凝聚相温度场，获得了糊状区和熔融相界面的形态。结果表明：火焰前缘附近的糊状区较薄，火焰前锋下游糊状区呈缓慢增厚趋势，火焰前锋附近的液相熔融界面较浅；随着与火焰前锋距离的增大，熔融深度逐渐加深。基于模拟结果和尺度分析，表明熔融界面形态近似呈二次函数发展。

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	罗圣峰
	谢启源
	张辉
	王光健

关键词 ：聚甲基丙烯酸甲酯(PMMA), 火蔓延, 数值模拟, 熔融相变

Abstract：

The opposed-flow flame spreading along a polymethyl methacrylate (PMMA) sheet was investigated numerically. The melting process included a mushy transition region in the energy equation during the flame spreading. The fuel was ignited by applying a fixed heat flow at one position on the upper boundary of the material. The results show the typical procedures of ignition followed by unstable to stable flame spreading. The morphology of the mushy zone and the molten phase thickness were obtained based on the temperature field. The results show that the mushy zone is thin near the flame front and gradually thickens downstream of the flame front. Additionally, the melt region is shallow near the flame front and gradually deepens with increasing the distance from the flame front. The numerical results and a scale analysis show that the melt interface location can be approximated by a quadratic function.

Key words： polymethyl methacrylate (PMMA) flame spread numerical simulation melt transition

收稿日期: 2020-04-27 出版日期: 2020-10-14

通讯作者: 谢启源,张辉 E-mail: xqy@ustc.edu.cn;zhhui@tsinghua.edu.cn

引用本文:

罗圣峰,谢启源,张辉,王光健. 引入熔融糊状区的PMMA逆流火蔓延数值模拟[J]. 清华大学学报（自然科学版）, 2020, 60(12): 1039-1046.
Shengfeng LUO,Qiyuan XIE,Hui ZHANG,Guangjian WANG. Numerical simulation of opposed-flow flame spread of PMMA with melting mushy zone. Journal of Tsinghua University(Science and Technology), 2020, 60(12): 1039-1046.

链接本文:

http://jst.tsinghuajournals.com/CN/10.16511/j.cnki.qhdxxb.2020.21.013 或 http://jst.tsinghuajournals.com/CN/Y2020/V60/I12/1039

模型主要物性参数

热塑性材料受热熔融相变过程和火蔓延过程示意图
10.16511/j.cnki.qhdxxb.2020.21.013.T001表 1

参数	数值
固相导热系数k_s/(W·m^-1·K^-1)	0.2
固相密度ρ_s/(kg·m^-3)	1 190
液相导热系数k_l/(W·m^-1·K^-1)	0.36
固相线温度T_s/K	440
热解活化能E_c/(J·mol^-1)	129 872.9
气体导热系数k_g/(W·m^-1·K^-1)	0.041 1
热解反应热q_c/(J·kg^-1)	9.41×10⁵
燃烧热q_g/(J·kg^-1)	-2.59×10⁷
初始氧质量分数Y_{o, ∞}	0.3
可燃气反应当量比u_f	1
PMMA比热容C_ps/(J·kg^-1·K^-1)	1 460
液相密度ρ_l/(kg·m^-3)	1 500
液相线温度T_l/K	500
热解指前因子A_c/(J·mol^-1)	2.82×10⁹
渗透系数K_e	0.95
气体比热容C_pg/(J·kg^-1·K^-1)	1 007
初始温度T_∞/K	300
发射系数ε	0.84
氧气反应当量比u_o	4

模型主要物性参数

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