高温气流下温度敏感型航空煤油凝胶液滴变形及破碎机理研究

Abstract: The affinity of gellant of the gelled temperature-sensitive kerosene for the kerosene substrate changes with temperature. The gelled droplets can convert into solution with a viscosity decrease by 3-4 orders of magnitude, which greatly accelerates the atomization of the gelled kerosene droplets during the process of spray and combustion. Therefore, it is expected to achieve high-efficiency atomization of the gelled kerosene to a large extent and solve the low-efficiency combustion problem, indicating a broad application prospect in Ramjet. On this condition, study on the mechanism of deformation and breakup of the gelled temperature-sensitive kerosene droplet will be conducted in high-temperature airflow based on the constitutive characterization and phase transition model of the temperature-sensitive kerosene gel. The effect of air parameters on the gel droplet motion and deformation is studied. The deformation mechanism of the droplet is revealed when phase change occurs by establishing corresponding deformation model. An uniform determination model of breakup mode and related breakup models are built through measuring the breakup mode, characteristic parameters and their variation trend to find out the breakup mechanism of the gelled temperature-sensitive kerosene droplets in high-temperature airflow and the effect rules of air temperature and droplet phase change on the droplet atomization. The research of this project has a high academic significance and value for promoting atomization and combustion efficiency of the gelled kerosene in ramjet engines and improving engineering application level.

摘要：温度敏感型航空煤油凝胶所用胶凝剂对煤油基体的亲疏性会随着温度发生转变。在喷雾燃烧过程中受高温气流的影响，液滴的凝胶体系可相变为溶液，粘性降低3-4个数量级，这大大促进了液滴的雾化过程。因此，有望在较大程度上实现煤油凝胶的高效雾化，解决目前面临的低燃烧效率问题，在冲压发动机中具有广泛的应用前景。以此为背景，本项目拟在温度敏感型煤油凝胶本构表征和相变模型基础上，开展高温气流作用下凝胶液滴的变形和破碎机理研究，获得气流参数对凝胶液滴运动和变形过程的影响规律，建立相应的变形模型，揭示液滴发生相变时的变形机理；测量凝胶液滴的破碎模态、破碎特征及其变化规律，建立统一的模态判定模型和相应的破碎模型，揭示温度敏感型煤油凝胶液滴在高温气流中的破碎机理以及气流温度和液滴相变对凝胶液滴雾化效率的影响规律。本项目对于促进煤油凝胶在冲压发动机中的雾化燃烧效率，提升工程化应用水平，具有较高的学术研究意义和价值。

本项目以温敏型凝胶煤油为研究对象，针对凝胶推进剂燃烧应用中雾化效率低的问题，开展了凝胶液滴变形破碎机理以及非敏感凝胶和敏感凝胶的机理和动力学特性研究。通过实验得到了其变形和破碎特性，并得到了不同的破碎模式。本项目还建立了包含液滴固体核心，不同模式下的变形破碎模型。研究结果表明：本项目采用的无机凝胶剂凝胶煤油的温敏性较弱，而以蓖麻油和氨基酸为基础的凝胶煤油具有良好的热敏性；并建立了较为准确的本构方程。不同温度下的变形特性基本相似，因为内部液滴可能没有受到传热的影响，温度变化不明显，粘度基本不变。建立的含固体核心TAB模型可以讨论气流温度的影响，尽管由于TAB模型本身的局限性导致精度较低，但仍可为进一步的研究打下良好的基础；与非温度敏感凝胶相比，敏感凝胶的相变We大大降低。同时，由于高温增加了减薄效应，温度越高，凝胶液滴越容易转变。.因此，对热敏凝胶进行加热可以促进其雾化效果，有望提高凝胶推进剂雾化的基础研究水平，为实现凝胶高效雾化提供技术手段。