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

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