氢气超声速燃烧过程的多步简化反应机理数值模拟

doi:10.13209/j.0479-8023.2017.050

摘要/Abstract

摘要：

摘要为了减少燃烧试验次数和改进超燃冲压发动机结构设计, 采用大型模拟软件Fluent, 对氢气和空气在超燃冲压发动机内的超声速流动与燃烧过程进行数值模拟。首先对空气和燃料在发动机中的冷混流动进行模拟, 然后分别采用一步总包或多步简化化学反应机理, 模拟超声速燃烧过程。结果显示, 采用一步总包反应机理时, 燃料点火容易, 得到的燃烧效率也比较高, 但是得到的温度偏高; 采用多步简化反应机理, 不容易点火, 模拟过程中火焰易灭, 模拟所需要的时间也比较长, 但得到的流场与实验过程更接近。

关键词: 超燃冲压发动机, 超声速流动, 燃烧, 反应机理

Abstract:

In order to reduce the combustion experiments and improve the scramjet structure design, the supersonic flow and combustion process of hydrogen and air in the scramjet are simulated with the large-scale simulation software Fluent. Firstly the cooling mixed flow of air and fuel in the scramjet is simulated, then supersonic combustion process is simulated with one-step or multi-step reduced chemical reaction mechanism respectively. The simulation results show that when using one-step global reaction mechanism, the fuel can be ignited easily, and the combustion efficiency is also relatively high, but the temperature obtained is higher. Simulation with the multi-step reduced reaction mechanism is closer to the actual combustion experiments, but the fuel may be ignited harder, the flame may easy to destroy during the simulation, and the time of simulation may relatively longer.

Key words: scramjet, supersonic flow, combustion, reaction mechanism

兰中秋, 邓彤天, 钟晶亮, 孙智利. 氢气超声速燃烧过程的多步简化反应机理数值模拟[J]. 北京大学学报自然科学版, 2017, 53(3): 397-404.

Zhongqiu LAN, Tongtian DENG, Jingliang ZHONG, Zhili SUN. Multi-step Reduced Reaction Mechanism Simulation of Hydrogen Supersonic Combustion Process[J]. Acta Scientiarum Naturalium Universitatis Pekinensis, 2017, 53(3): 397-404.

图/表 11

图1 双模态超燃发动机模型

Fig. 1 Dual-modal scramjet model

图2 网格划分示意图

Fig. 2 Schematic diagram of grid distribution

表1 来流条件和喷流条件

Table 1 Inflow and jet flow condition

表2 氢气燃烧化学反应机理

Table 2 H2 Combustion chemical reaction mechanism

序号	反应步数	组元数	各组元分子式
1	1	4	H₂ O₂ H₂O N₂
2	8	7	H₂ O₂ H₂O H OH O N₂^[14]
3	19	9	H₂ O₂ H₂O HO₂ H₂O₂ O H OH N₂^[15]
4	19	10	H₂ O₂ H₂O H O OH HO₂ H₂O₂ Ar N₂^[16]
5	19	13	H₂ O₂ H₂O H O OH HO₂ H₂O₂ Ar He CO CO₂ N₂^[17]

表3 氢气燃烧效率

Table 3 H2 combustion efficiency

反应机理或实验	燃烧效率
1	0.453
2	0.28
3	0.155
4	0.467
5	0.572
实验值	0.78^[12]

图3 中心下壁面压强沿流向分布

Fig. 3 Pressure distribution on bottom of central cross section

图4 面积加权平均压强沿流向分布

Fig. 4 Pressure distribution of area weighted average

图5 冷混流以及各反应机理的速度分布

Fig. 5 Velocity distributions of cold mixed flow and different reaction mechanisms

图6 冷混流以及各反应机理的温度分布

Fig. 6 Temperature distributions of cold mixed flow and different reaction mechanisms

图7 冷混流以及各反应机理的H2质量分数分布

Fig. 7 H2 mass fraction distributions of cold mixed flow and different reaction mechanisms

表4 推力统计

Table 4 Thrust result

燃烧模式	推力/N
1	304.04
2	100.36
3	-50.89
4	10.31
5	278.48

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