微米铝粉具有很高的能量密度，微米铝与液态水的燃烧反应在水下推进和空间推进中应用前景广阔。微米铝/液态水的燃烧反应过程和机理十分复杂，目前相关的实验数据严重不足，对燃烧特性和规律没有形成系统而深入的认识；同时，包括铝粉在内的水反应金属燃料用于推进面临着燃烧组织方式的困扰，缺乏可能实用化的推进剂设计形式，使实际技术应用存在很大困难。加强微米铝-液态水燃烧特性研究，并探索可能的铝-水燃烧组织方式，对于掌握有关燃烧基础规律、促进微米铝-液态水燃烧应用具有重要意义。

本论文针对微米铝粉与液态水燃烧特性和机理开展了较为系统的实验和数值模拟研究。实验方面，观测和分析了三种不同组织形式的铝-水体系的燃烧：（1）准均质铝粉/液态水（Al/H₂O(q)）混合物，该体系中，铝粉在液态水中均匀分散，代表着较为理想的铝-水混合状态；（2）铝粉/树脂吸附微水体（Al/H₂O(a)）混合物，由铝粉微团与树脂吸附微水体构成，具有快速制备的实用化特点；（3）铝蜂窝与Al/H₂O(q)或Al/H₂O(a)构成的复合体系（Al/H₂O/AlFoil），以铝蜂窝提供结构骨架并调节体系的燃烧速率，是另外一种可能实用的铝-水燃烧组织方式。利用发明的全新点火方法，实现了铝-水体系的点火，对燃烧过程和燃烧特性进行了系统观测，并建立模型分析火焰传播规律。数值模拟方面，对Al/H₂O/AlFoil体系的燃烧过程进行分析，特别考察蜂窝骨架的作用机理；对铝-水燃烧环境中单个铝颗粒的气相燃烧行为进行探讨，分析粒径和环境条件（气流速度、环境温度及气体组分）的影响机理，并与所建立的非均相反应模型的分析结果进行对比。实验结果与数值分析相结合，获得了微米铝-液态水燃烧的基本规律，以及组织形式影响燃烧特性的控制机制。论文主要内容及研究结果如下：

1）实验研究了准均质微米铝粉/液态水（Al/H₂O(q)）混合物的燃烧特性，包括可燃极限、燃烧速率、火焰温度、燃烧效率以及添加剂的影响，铝粉粒径3.5-25 μm。Al/H₂O(q)具有较大的可燃范围，对于所有粒径（D_Al）的铝粉，燃烧速率（r_b）随着当量比（φ）的增加先增大再减小，最大值出现在φ = 1.7-2.0处。燃烧速率与粒径的关系遵循幂次律r_b ~ D_Al^−0.18，表明燃烧反应受到化学动力学控制。φ > 0.7时，随着φ的增加，燃烧产物中铝的残留量逐渐增大，燃烧效率下降。典型添加剂的影响表现为：氟化钠（NaF）通过破坏铝颗粒表面氧化膜促进燃烧；氟化铝钠（Na₃AlF₆）可溶解燃烧产物中的氧化铝，从而减少相变放热，对燃烧产生抑制；氯化钠（NaCl）对燃烧速率没有明显影响。基于火焰传播的传热机制建立了一维火焰传播模型，较好地预测了铝粉粒径和混合物当量比等主要因素对燃烧速率的影响，并用于分析火焰热结构的变化规律。

2）提出铝粉/树脂吸附微水体（Al/H₂O(a)）混合物这一新的铝-水燃烧组织形式，并对其燃烧特性进行实验研究。Al/H₂O(a)的贫燃极限接近Al/H₂O(q)，富燃极限则显著扩大。随着φ的增加，Al/H₂O(a)的燃烧速率也表现出先增大再减小的非单调变化，但在燃烧速率增大的区间（φ从0.6至2.0-2.5），燃烧速率-当量比曲线先后呈现两个变化速率不同的阶段，后者的增长速率更大，与Al/H₂O(q)相比，Al/H₂O(a)的最大燃烧速率显著提高。在实验研究的参数范围内，铝粉粒径对Al/H₂O(a)的燃烧速率没有规律性影响。当量比一定时，Al/H₂O(a)表现出与Al/H₂O(q)相近的燃烧效率。考虑Al/H₂O(a)中铝粉颗粒和液态水的分布特点及燃烧过程中混合物的结构变化，对体系导热系数及颗粒团燃烧时间进行分析，利用火焰传播模型揭示了当量比对Al/H₂O(a)燃烧速率的影响机制，表明导热系数的显著增大是该体系相比Al/H₂O(q)燃烧速率增加的主要原因。

3）对铝蜂窝与Al/H₂O(q)或Al/H₂O(a)构成的复合体系（Al/H₂O/AlFoil）的燃烧特性进行实验，并通过数值模拟对铝蜂窝及其主要参数的作用机理进行分析。实验结果表明，铝蜂窝的存在能显著改变铝-水的燃烧速率，特别是在φ = 0.6-2.0的范围内，相比于铝/水混合物，Al/H₂O/AlFoil的燃烧速率更大，最大燃烧速率发生在更小的当量比（φ = 1.0-1.3），其数值提高了1-2倍；蜂窝孔径为3.47 mm和5.20 mm时，燃烧速率基本不受孔径影响，壁厚的增加使φ = 1.0附近的燃烧速率增大。结合实验结果，对Al/H₂O/AlFoil燃烧的数值模拟分析得到以下认识：铝片介质主要通过增强火焰向未燃区的导热能力，使体系的燃烧速率增大；蜂窝角区的温度场受到相邻蜂窝壁的共同影响，该作用机制促进火焰传播，随着孔径的增大，角区的影响程度趋于稳定，继续增大孔径对燃烧速率不产生显著影响；蜂窝壁厚的增加使火焰向未燃区的导热加快，从而增大燃烧速率；蜂窝壁厚越小，蜂窝参与燃烧的程度对燃烧速率的影响越小。

4）利用所建立的单膜模型对单颗粒铝的非均相燃烧进行分析，同时，利用CFD模型对单颗粒铝的均相燃烧进行数值模拟，考察燃烧环境中粒径以及环境参数对铝颗粒燃烧特性的影响机制。非均相燃烧时，反应主要受化学动力学控制，颗粒燃烧速率受环境温度和水蒸气浓度的影响较大，受气流速度的影响较小；在环境条件一定时，颗粒表面温度随粒径增大而增加，当粒径达到某一临界值后，颗粒表面温度达到铝的汽化温度。与非均相燃烧相比，气相燃烧时颗粒燃烧速率受水蒸气浓度的影响较小，受气流速度的影响较大；随着气流速度的增加，颗粒燃烧速率先增大再减小，对于所考察的两种粒径（25 μm和200 μm）铝颗粒，燃烧速率均在颗粒雷诺数Re = 0.03时达到最大，当Re > 0.16时气相燃烧无法维持；在一定流动和温度环境条件下，随着粒径的减小，当燃烧控制机理由氧化剂扩散控制向化学动力学控制转变时，火焰温度降低，可能存在维持单颗粒铝气相燃烧的临界粒径；上述结果说明，为了实现铝颗粒的均相燃烧，需要根据流场和温度场合理选择粒径。

Micron-sized aluminum (μAl) powder has a high energy density, and its reaction with liquid water (H₂O) has a promising application prospect in underwater propulsion and space propulsion. The combustion reaction process and mechanism of μAl and H₂O are extremely complicated. At present, the relevant experimental data are very limited, and there is no systematic and in-depth understanding of its combustion characteristics and laws. At the same time, the use of hydroreactive metal fuels, including Al powder, for propulsion faces the issue of combustion organization, and the lack of possible feasible design forms of propellants makes practical technology applications extremely difficult. Therefore, it is of great significance to strengthen the research on the combustion characteristics of μAl-H₂O and explore the possible Al-H₂O combustion organization for mastering the basic law of combustion and promoting the application of μAl-H₂O combustion.

In this paper, systematic experimental and numerical simulation research on the combustion characteristics and mechanism of micron-sized aluminum powder and liquid water was carried out. In terms of experiment, the combustion of three kinds of Al-H₂O systems was observed and analyzed: (1) Quasi-homogeneous aluminum powder and liquid water (Al/H₂O(q)) mixture, in which Al powder is uniformly dispersed in liquid water, representing an ideal Al-H₂O mixing state. (2) Aluminum powder and resin adsorbed micro-water (Al/H₂O(a)) mixture, composed of Al powder micro-clusters and resin adsorbed micro-water, has the practical characteristics of rapid preparation. (3) A composite system (Al/H₂O/AlFoil) composed of aluminum honeycomb and Al/H₂O(q) mixture or Al/H₂O(a) mixture, in which aluminum honeycomb provides the structural framework and adjusts the burning rate of the system, is another possible practical Al-H₂O combustion organization. A novel ignition method was used to realize the ignition of the Al-H₂O systems. The combustion process and characteristics were systematically observed, and some models were established to analyze the flame propagation law. In terms of numerical simulation, the combustion process of Al/H₂O/AlFoil system was analyzed, especially the influence mechanism of honeycomb skeleton; the gas-phase combustion behavior of a single Al particle in an Al-water combustion environment was discussed, and the influence mechanisms of particle size and environmental conditions (airflow velocity, ambient temperature, and gas composition) were analyzed and compared with the established heterogeneous reaction model. Combining the experimental results with numerical analysis, the basic combustion law of μAl-H₂O and the control mechanism of organizational form affecting combustion characteristics were obtained. The main contents and research results are as follows:

1) The combustion characteristics of quasi-homogeneous micron-sized aluminum powder and liquid water (Al/H₂O(q)) mixture were experimentally studied, including flammability limits, burning rates, flame temperatures, combustion efficiencies, and the effect of additives. The particle size of aluminum powder is 3.5-25 μm. The Al/H₂O(q) mixture has a large combustible range. For all particle sizes (D_Al) of aluminum powder, the burning rate (r_b) increases first and then decreases with the increase of equivalent ratio (φ), with the maximum value appearing at φ = 1.7-2.0. The relationship between burning rate and particle size follows the power law r_b ~ D_Al^−0.18, indicating that the combustion reaction is controlled by chemical kinetics. When φ is greater than 0.7, with the increase of φ, the residual amount of Al in the combustion product increases gradually, and the combustion efficiency decreases accordingly. The influences of typical additives are as follows: the sodium fluoride (NaF) promotes combustion by destroying the oxide film on the surface of Al particles; the sodium aluminum fluoride (Na₃AlF₆) can dissolve alumina in the combustion products, thus reducing phase transition heat release and inhibiting combustion; the sodium chloride (NaCl) has no significant effect on burning rate. A one-dimensional flame propagation model was established based on the heat transfer mechanism of flame propagation, which successfully predicts the influence of main factors such as particle size and equivalence ratio on burning rate, and was used to analyze the variation of flame thermal structure.

2) A new Al-H₂O combustion organizational form, i.e., aluminum powder and resin adsorbed micro-water (Al/H₂O(a)) mixture, was proposed and its combustion characteristics were experimentally studied. The lean flammability limits of Al/H₂O(a) are similar to that of Al/H₂O(q) mixture, while the rich flammability limits are much larger than them. With the increase of φ, the burning rate of Al/H₂O(a) mixture also shows a non-monotonic change that increases first and then decreases. However, in the interval of increasing burning rate (φ from 0.6 to 2.0-2.5), the burning rate-equivalence ratio curve presents two stages with different change rates successively, and the growth rate of the latter increases sharply. The maximum burning rates are also higher than that of Al/H₂O(q) mixture. In the range of experimental parameters, the particle size of Al particle does not affect the burning rate of Al/H₂O(a). The combustion efficiencies of Al in Al/H₂O(a) are similar to that of Al/H₂O(q) mixtures at the same equivalence ratios. Considering the distribution characteristics of Al powder particles and liquid water in Al/H₂O(a) and the structural changes of the mixture during combustion, the thermal conductivity of the system and the burning time of particle cluster were analyzed. The influence mechanism of equivalence ratio on the burning rate of Al/H₂O(a) was revealed by using the flame propagation model. The significant increase of the thermal conductivity is the main reason for the increase of burning rate compared with Al/H₂O(q).

3) The combustion characteristics of the composite system (Al/H₂O/AlFoil) consisting of Al honeycomb skeleton and Al/H₂O(q) mixture or Al/H₂O(a) mixture were studied experimentally, and the mechanism of aluminum honeycomb and its main parameters was analyzed by numerical simulation. The experimental results show that Al honeycomb skeleton can significantly change the Al-H₂O burning rate. In the range of φ = 0.6-2.0, compared with the Al/H₂O(q) and Al/H₂O(a) mixture, the burning rates of Al/H₂O/AlFoil are larger, and the maximum burning rates occur at a smaller equivalence ratio (φ =1.0-1.3), and their values increase by 1-2 times. When the honeycomb aperture is 3.47 mm and 5.20 mm, the burning rate is basically not affected by the aperture, and the increase of Al foil thickness increases the burning rates near φ = 1.0. Combined with the experimental results, the numerical simulation analysis of Al/H₂O/AlFoil combustion has the following understanding: The Al foil medium increases the system's burning rate by enhancing the thermal conductivity of the flame to the unburned zone. The temperature field in the honeycomb corner area is affected by the adjacent honeycomb walls, accelerating flame propagation. As the aperture increases, the influence degree of the corner area tends to stabilize, and further increasing the aperture does not have a significant impact on the burning rate. The increase of honeycomb wall thickness further increases the heat conduction of the flame through the wall to the unburned mixture, thus increasing burning rate. The smaller the honeycomb wall thickness, the smaller the influence of the degree of honeycomb participation in combustion on burning rate.

4) The heterogeneous combustion of a single aluminum particle was analyzed by using the established single-film model. At the same time, the CFD model was used to simulate the homogeneous combustion of a single aluminum particle. The influence mechanism of particle size and environmental parameters on the combustion characteristics of aluminum particles in the combustion environment were investigated. In heterogeneous combustion, the reaction is primarily controlled by chemical kinetics. The ambient temperature and water vapor concentration have a large impact on the particle burning rate, while airflow velocity has a minor impact. The particle surface temperature rises as particle size increases when the environmental conditions remain constant. The particle surface temperature reaches the vaporization temperature of aluminum when the critical particle size is reached. Compared with heterogeneous combustion, in gas-phase combustion, the effect of water vapor concentration on the burning rate is relatively small, and the effect of airflow velocity is relatively large. The burning rate increases first and then decreases with increasing airflow velocity. For the two particle sizes (25 μm and 200 μm) of Al particles investigated, the burning rate reaches the maximum when the particle Reynolds number Re = 0.03, and the gas phase combustion cannot be maintained when Re > 0.16. Under certain flow and temperature environmental conditions, as the particle size decreases, the flame temperature decreases when the combustion control mechanism shifts from oxidant diffusion control to chemical kinetic control. There may be a critical particle size that makes the gas phase combustion of a single Al particle unsustainable. The results show that to achieve homogeneous combustion of Al particles, the appropriate particle size must be chosen based on the flow field and temperature field in practice.