Experimental and simulation study of lean-burn laminar flow of ammonia-methanol high-pressure mixture

doi:10.11949/0438-1157.20250118

Abstract

Abstract:

To investigate the lean combustion and emission characteristics of ammonia-methanol mixed fuels under high pressure, a visual study of their laminar flame propagation characteristics was conducted in a constant-volume combustion chamber. Additionally, chemical reaction kinetics analysis was performed based on a self-developed mechanism. It was found that as the methanol energy proportion increased, the laminar flame propagation speed significantly increased, and the stability of the flame improved. When the methanol energy proportion increased from 20% to 50%, the laminar combustion speed at Φ=0.7 and Φ=0.8 increased by 110% and 99.6%, respectively. In terms of emissions, the main formation pathways of NO are HNO+M $̿$ H+NO+M and HNO+H $̿$ H₂+NO, while the main consumption pathways of NO are NH₂+NO $̿$ NNH+OH and NH₂+NO $̿$ N₂+H₂O. Under lean-burn conditions, the presence of intermediates like HNO leads to an increase in NO emissions. Comprehensive analysis shows that under lean-burn conditions, NO generation is mainly carried out through the oxygen enrichment reaction pathway, and fuel-type NO is dominant. Therefore, although increasing methanol content can improve laminar burning velocity, it is necessary to balance this with NO emissions.

Key words: ammonia/methanol co-firing, high-pressure lean-burn, kinetic model, laminar flow, NO formation, alcohol

摘要：

为探究高压下氨-甲醇混合燃料的稀薄燃烧和排放特性，在定容燃烧弹中对其层流火焰传播特性进行了可视化研究，并基于自主开发的机理开展了化学反应动力学分析。研究发现，随着甲醇能量占比的增加，层流火焰传播速度显著提高，且火焰的稳定性得到改善，当甲醇能量占比由20%增加至50%时，Φ=0.7和Φ=0.8的层流燃烧速度分别增加了110%和99.6%。排放方面，NO的生成途径主要有HNO+M $̿$ H+NO+M和HNO+H $̿$ H₂+NO，而NO的消耗途径主要为NH₂+NO $̿$ NNH+OH和NH₂+NO $̿$ N₂+H₂O，稀燃条件下HNO等中间体的存在使NO排放增加。综合分析表明，稀燃条件下NO的生成主要通过增氧反应路径进行，燃料型NO占主导地位。因此，虽然增加甲醇含量可以提高层流火焰速度，但需权衡NO排放。

关键词: 氨/甲醇混燃, 高压稀燃, 动力学模型, 层流, NO生成, 醇

CLC Number:

TK 411

Chen HE, Mingfei LU, Lingjin WANG, Xiaoying XU, Pengbo DONG, Wentao ZHAO, Wuqiang LONG. Experimental and simulation study of lean-burn laminar flow of ammonia-methanol high-pressure mixture[J]. CIESC Journal, 2025, 76(8): 4248-4258.

何晨, 陆明飞, 王令金, 许晓颖, 董鹏博, 赵文涛, 隆武强. 氨-甲醇高压混合气稀燃层流实验与模拟研究[J]. 化工学报, 2025, 76(8): 4248-4258.

Figures/Tables 15

Fig.1 Schematic diagram and physical image of the constant-volume combustion bomb experimental setup

Table 1 Stretch flame extrapolation model

外推方法	拟合公式
LS	$S b = S b 0 - L b κ$
LC	$S b = S b 0 - L b S b 0 2 R f$
NQ	$S b S b 0 2 l n S b S b 0 2 = - 2 L b κ S b 0$

Table 1 Stretch flame extrapolation model

外推方法	拟合公式
LS	$S b = S b 0 - L b κ$
LC	$S b = S b 0 - L b S b 0 2 R f$
NQ	$S b S b 0 2 l n S b S b 0 2 = - 2 L b κ S b 0$

Fig.2 Verification of laminar burning velocity for ammonia/methanol/air mixtures

Table 2 The modified reaction kinetics data

反应		反应参数
		原始机理			改进机理
		A	β	E_a/(J/mol)	A	β	E_a/(J/mol)
1	NNH $̿$ N₂+H	3.00×10⁸	0	0	6.50×10²	0	0
2	NH₂+NO $̿$ NNH+OH	4.30×10¹⁰	0.294	-866	8.30×10¹⁰	0.31	-866
3	HNO+H $̿$ H₂+NO	9.00×10¹¹	0.72	660	5.20×10¹²	0.72	660
4	HNO+OH $̿$ NO+H₂O	1.30×10⁷	1.90	-950	1.30×10⁶	2.10	-950
5	H+NO+M $̿$ HNO+M	4.48×10¹⁹	-1.32	740	5.60×10¹⁹	-1.290	740

Table 2 The modified reaction kinetics data

反应		反应参数
		原始机理			改进机理
		A	β	E_a/(J/mol)	A	β	E_a/(J/mol)
1	NNH $̿$ N₂+H	3.00×10⁸	0	0	6.50×10²	0	0
2	NH₂+NO $̿$ NNH+OH	4.30×10¹⁰	0.294	-866	8.30×10¹⁰	0.31	-866
3	HNO+H $̿$ H₂+NO	9.00×10¹¹	0.72	660	5.20×10¹²	0.72	660
4	HNO+OH $̿$ NO+H₂O	1.30×10⁷	1.90	-950	1.30×10⁶	2.10	-950
5	H+NO+M $̿$ HNO+M	4.48×10¹⁹	-1.32	740	5.60×10¹⁹	-1.290	740

Fig.3 Comparison of ignition delay time simulation and experimental[23] results for ammonia/methanol mixtures

Fig.4 Flame variation at different equivalence ratios with 20% methanol energy fraction

Fig.5 Laminar burning velocity and Markstein length at 20% methanol energy fraction

Fig.6 Flame images at R = 20 mm for different methanol energy fractions and equivalence ratios

Fig.7 Flame images for methanol energy fractions of 30%, 40% and 50%(Φ= 0.6, R = 20 mm )

Fig.8 Laminar burning velocity and Markstein length at different methanol energy fractions

Fig.9 Comparison of NO emissions from ammonia-hydrogen combustion at different pressures with experimental data[37]

Fig.10 Mole fraction distribution of NO and N2O at different methanol energy fractions during lean-burn

Fig.11 NO rate of production (ROP) under different methanol energy fractions

Fig.12 NO sensitivity analysis during lean-burn at different methanol energy fractions

Fig.13 Comprehensive condition analysis under lean-burn conditions

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