凹腔结构对正丁烷部分预混火焰可燃极限的影响

doi:10.11949/0438-1157.20240143

摘要/Abstract

摘要：

部分预混火焰的稳定性对燃烧装置的安全、高效、低排放运行影响重大。以带有凹腔/无凹腔的微型圆柱燃烧器为目标模型，以正丁烷为目标燃料，通过实验和数值模拟相结合的方法，研究了在典型一次空气系数条件下，部分预混火焰在这两种燃烧器中的可燃极限范围。结果表明，第一，凹腔燃烧器的火焰稳定范围要远大于无凹腔燃烧器（相差约2个数量级），特别是对于吹熄极限的影响更为显著，这主要得益于凹腔燃烧器特有的双火焰结构（驻涡火焰+外火焰）。第二，凹腔燃烧器在外火焰发生回火或脱火后，凹腔内的驻涡火焰仍可以在一定的范围内继续存在。第三，驻涡火焰对壁面的加热是外火焰稳定的关键。上述结论对部分预混燃烧装置的设计有一定的指导意义。

关键词: 稳定性, 燃料, 可燃极限, 双火焰结构, 数值模拟

Abstract:

The stability of partially premixed flame has a great influence on the safety, efficiency and emission of combustion device. This paper studies the flammability limit of n-butane partially premixed flame in cavity and non-cavity burner at a constant primary air coefficient by experiment and numerical simulation. The results show that, first, the flame stabilization range of the cavity burner is much larger than that of the non-cavity burner (a difference of about 2 orders of magnitude), especially with a more significant impact on the blow-out limit, which is mainly due to the unique double flame structure of the cavity burner (stuck vortex flame + external flame). Second, the trapped vortex flame in the cavity burner can continue to exist within a certain range after flashback or blowout of the external flame. Third, the key of the stabilization of the external flame is the heating of the wall by the trapped vortex flame. Such conclusions are intended to provide guidance for the design of partially premixed combustion units.

Key words: stability, fuel, flammability limit, dual flame structure, numerical simulation

中图分类号:

TK 1

李静, 张方芳, 王帅帅, 徐建华, 张朋远. 凹腔结构对正丁烷部分预混火焰可燃极限的影响[J]. 化工学报, DOI: 10.11949/0438-1157.20240143.

LIJing, Fangfang ZHANG, Shuaishuai WANG, Jianhua XU, Pengyuan ZHANG. Effect of cavity structure on flammability limit of n-butane partially premixed flame[J]. CIESC Journal, DOI: 10.11949/0438-1157.20240143.

图/表 9

图1 燃烧器示意图(a)和实验系统图(b)

Fig.1 Schematic diagram of burner (a) and experimental system (b)

图2 计算区域(a)和网格(b)

Fig.2 Computational domain (a) and mesh (b)

图3 模型验证

Fig.3 Model validation

图4 凹腔(a)/无凹腔(b)燃烧器的温度及释热率分布，以及凹腔(c)/无凹腔(d)在各个速度下的最大释热率

Fig.4 Distributions of temperature and heat release for cavity (a) and non-cavity burners (b), respectively，and maximum heat release at different velocity for cavity (c) and non-cavity burners (d) , respectively

图5 凹腔/无凹腔燃烧器的可燃极限

Fig.5 Flammability limits for cavity and non-cavity burners

图6 凹腔燃烧器在外火焰脱火(a)/回火(b)后驻涡火焰的温度及释热率分布，以及外火焰脱火(c)/回火(d)后驻涡火焰在各个速度下的最大热释率

Fig.6 Distributions of temperature and heat release of trapped vortex flame after blowoff (a)/flashback (b) of external flame for cavity burner, and maximum heat release at different velocity for blowoff (c)/flashback (d) of external flame

图7 V=0.6m/s条件下的凹腔/无凹腔燃烧器的各变量分布

Fig.7 Distributions of several variables for cavity and non-cavity burners at V=0.6m/s

图8 V=0.6m/s条件下凹腔/无凹腔燃烧器外壁面温度及其梯度分布

Fig.8 Distributions of out-wall temperature and its gradient for cavity and non-cavity burners at V=0.6m/s

图9 不同入口速度条件下凹腔燃烧器壁面温度(a)及其梯度(b)的分布

Fig.9 Distributions of out-wall temperature (a) and its gradient (b) for cavity burner at different velocities

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