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摘要以自建的超细水雾发生装置为基础对超细水雾与杯式燃烧器中火焰相互作用的规律进行了实验和计算机模拟研究。全混流反应器模型对于熄灭甲烷、乙醇和正庚烷火焰所需的临界平均雾化速率的预测值分别为 6.236g/min、11.427g/min 和8.239g/min。当超细水雾浓度达到熄灭乙醇和正庚烷火焰的最低灭火浓度时，超细水雾发生装置的平均雾化速率分别为 7.590g/ min和 6.817g/ min。通过对模型假设的分析，确定了使模型误差增大的主要因素。在不同的超细水雾浓度下，研究了火焰的外部特征、脉动频率及火场温度，并利用 Fluent 模拟了载气中无灭火剂工况和存在 1g/min 超细水雾工况下正庚烷的燃烧。模拟结果与实验现象相符：1）当超细水雾浓度较低时，超细水雾在火焰面附近蒸发，置换氧气使火焰轴向拉长，碳烟增多，温度升高；2）当其浓度较高时，部分水雾进入火焰面，对火焰面流场产生干扰，火焰根部产生褶皱和振荡；3）当超细水雾接近灭火浓度时，其冷却作用使火焰最高温度降至临界温度，火焰根部悬举、振荡并最终吹熄。 59692
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毕业论文关键词 超细水雾 灭火 最低灭火浓度 杯式燃烧器 全混流反应器 CFD 建模
Title An study on the interaction of ultra fine water mist and flame in a cup burner
Abstract An experimental and numerical study was carried out on the interaction of ultra fine water mist with cup burner flame. The predicted minimum extinguishment concentrations (MECs) of ultra fine water mist(UFM) extinguishing methane, ethanol and n-heptane flame were 6.236 g/ min, 11.427 g/ min and 8.239 g/ min. The measured MECs of the UFM extinguishing ethanol and n-heptane flame were 7.590 g/ min and 6.817 g/ min respectively. A further study on the model reveals the main factors causing the gaps between the experimental results and predicted values. An analysis was conducted on the flame image，flame oscillation frequency and temperature of the flame and plume when the flame interacted with the UFM. The subsequent Fluent simulations of the n-heptane cup burner flame were agree with the experimental phenomenon. The interaction process is postulated as follows: 1) when the mist is introduced to the flame, it evaporates before entering into the flame boundary, displaces the oxygen, intensifies the flame and elongates its axial length; 2) with more mist interacts with the flame, a portion of water droplets penetrates the flame, disturbing the fluid field and destabilizing the flame base; 3) when water mist concentration closes to MEC, its cooling effect decreases the flame temperature to its critical value, where the flame oscillates and drifts downstream.
Keywords Ultra-fine water mist; Flame extinction; Minimum extinguishing concentration; Cup burner; Perfectly stirred reactor; CFD modeling
目 次
1 绪论 . 1
1.1 背景和意义 . 1
1.3 主要工作和研究内容 4
2 实验准备 .. 4
2.1 氮气灭火系统 4
2.2 超细水雾灭火系统 . 5
2.3 超声波雾化装置的标定 .. 6
2.4 实验系统的校正 .. 7
2.5 灭火实验步骤 8
3 超细水雾最低灭火浓度的预测和测定 .. 9
3.1 PSR 模型预测超细水雾最低灭火浓度 .. 9
3.2 超细水雾最低灭火浓度的实验测定 . 12
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