Study of stability limits and emission characteristics in premixed ammonia-methane-air swirling flames in low swirl configurations

doi:10.11949/0438-1157.20241165

Abstract

Abstract:

A combination of experiments and numerical simulations was employed to investigate the effects of low swirl configurations on the flame stability limits and emissions of ammonia-methane-air premixed swirling flames. The results indicated that high pollutant emissions were observed under all conditions in high swirl combustion, particularly unburned ammonia, carbon monoxide, and nitrogen oxides. In contrast, the low swirl configuration effectively reduced these pollutant emissions with only slightly narrowing the stability limits. However, ammonia-methane-air flames under low-swirl configurations produced higher levels of nitrous oxide $(N ₂ O)$ , which can be attributed to the lower flame temperature that inhibited the thermal decomposition of $N ₂ O$ . When the non-swirling flows were further increased, the stability limits became very narrow, even though emissions were further reduced. Overall, the low-swirl configuration achieves an optimal balance between pollutant emissions and flame stability, making it suitable for combustion applications requiring reduced pollutant emissions. In general, the low swirl configuration can achieve an optimal balance between pollutant emissions and flame stability, and is suitable for combustion application scenarios that require reducing pollutant emissions.

Key words: ammonia combustion, low swirl configuration, stability limits, flame topology, flow structures, emissions

摘要：

通过实验与数值模拟相结合的方法，系统研究了低旋流配置对氨-甲烷-空气预混旋流火焰稳定性极限及污染物排放方面的影响。结果显示，高旋流配置下，各种工况均表现出较高的污染物排放，尤其是未燃氨、一氧化碳和氮氧化物。而低旋流配置显著降低了这些污染物的排放，仅略微缩小了火焰稳定性极限。然而，低旋流配置下的氨-甲烷-空气火焰产生了较高的氧化二氮，这归因于低旋流配置降低了火焰温度，抑制了氧化二氮的热裂解。此外，随着非旋流气流比例的增加，尽管污染物排放量进一步减少，但火焰稳定性极限显著收缩，这与低旋流下火焰结构和流场结构的变化密切相关。综合而言，低旋流配置在污染物排放与火焰稳定性之间可以达到较优的平衡，适用于需要降低污染物排放的燃烧应用场景。

关键词: 氨燃烧, 低旋流配置, 稳定性极限, 火焰拓扑, 流动结构, 污染物排放

CLC Number:

TK 16

Haojie YANG, Chunyu LIU, Xuejiao LI, Liang YU, Xingcai LYU. Study of stability limits and emission characteristics in premixed ammonia-methane-air swirling flames in low swirl configurations[J]. CIESC Journal, 2025, 76(6): 3029-3040.

杨浩杰, 刘春雨, 李雪娇, 于亮, 吕兴才. 低旋流配置下氨-甲烷-空气预混旋流火焰稳定性和排放特性[J]. 化工学报, 2025, 76(6): 3029-3040.

Figures/Tables 15

Fig.1 Schematic of the swirler configurations

Table 1 Geometric dimensions of the swirlers

参数	LSI₁	LSI₂	HSI
旋流数S_N	0.6	0.6	0.6
叶片角度θ/(°)	40	40	40
叶片数N_b	8	8	8
中心通孔个数N_h	39	55	—
通孔直径d/mm	2	2	—
旋流器内径R_i/mm	10	12	7
旋流器外径R_o/mm	16	16	16
非旋流与旋流气体的质量流量之比R_m /%	25	49	0

Fig.2 Schematic of experimental equipment

Fig.3 Schematic of model structure and mesh distribution

Fig.4 Mesh independence verification

Table 2 Operating conditions

参数	数值
热功率P	20 kW
甲烷流量U_m	16.1~33.5 SLPM
氨气流量U_a	0.0~44.8 SLPM
空气流量U_air	180~600 SLPM
氨气体积分数 $η N H 3$	0~75%

Table 2 Operating conditions

参数	数值
热功率P	20 kW
甲烷流量U_m	16.1~33.5 SLPM
氨气流量U_a	0.0~44.8 SLPM
空气流量U_air	180~600 SLPM
氨气体积分数 $η N H 3$	0~75%

Fig.5 Verification of the accuracy of the swirl flame simulation

Fig.6 Model accuracy validation

Fig.7 Numerical simulation of the flow field structure

Fig.8 Numerical simulation temperature contour plots for different NH3 volume fractions

Fig.9 NH3-CH4-air flame stability limits for three different swirler configurations

Fig.10 Numerical simulation of NO mass fraction distribution for three swirler configurations(ηNH3=50% and φ = 0.9)

Fig.11 Average mass fraction distribution of NO and OH in HSI configuration(ηNH3=50% and φ = 0.9)

Fig.12 Scatter plots of OH-T and NH-N in flame zone

Fig.13 Plots of emissions as a function of φ and ηNH3 for three swirler configurations(HSI is used as the refence for subtraction)

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