为解决环保和碳减排等问题，目前我国正在研发民用航空发动机新型贫油低NO_X洁净燃烧技术和替代燃料燃烧技术，军用飞机正在寻求飞行高度新的突破，这些都加剧高空低温低压极端环境燃烧室再点火难度。与地面环境相比，高空环境低温、低压、空气稀薄，导致燃料雾化和混合变差，造成燃料蒸发和化学反应速率降低，使得高空点火困难。因此，为了深入研究高空环境对燃烧室点火过程的影响机制，探索新的有效可行的点火方式，本文采用数值模拟计算的方法，研究航空发动机高空熄火后，燃烧室进气特性、煤油雾化特性和单液滴着火特性，并研究了利用航天级过氧化氢分解产生的高温富氧射流的点火方式。

本文根据标准大气模型和航空发动机结构特征，建立了航空发动机高空熄火后，燃烧室进口参数的计算模型。结果表明，航空发动机高空熄火后燃烧室进气温度、压力和进气量骤降；飞行高度7 km，飞行马赫数0.7时，燃烧室进口温度降为266 K，压力下降到标准大气压的0.48倍，进气量下降到巡航状态的1/10。航空发动机空中熄火后，可以采取俯冲策略，将飞机的重力势能转化为飞机的动能，降低飞行高度的同时提高飞行马赫数，从而改善高空再点火环境。

本文以CFM56-7发动机单头燃烧室为研究对象，采用数值模拟计算的方法，建立了压力旋流雾化模型，开展了航空发动机燃烧室高空熄火后煤油雾化特性研究，分析了飞行高度和飞行马赫数对煤油雾化的影响。研究结果表明，煤油雾化在喷嘴下游11倍喷嘴直径的距离之内完成；在飞行马赫数为0.7时，随着飞行高度增大，煤油雾化粒径增大的幅度更加明显，煤油雾化恶化加剧，增大了航空发动机高空再点火的难度；在飞行高度为7 km下，当飞行马赫数大于0.7时，煤油雾化粒径较小，且马赫数变化对煤油雾化粒径影响较小，当飞行马赫数小于0.7时，马赫数的变化对煤油雾化粒径影响显著；降低飞行高度使得煤油雾化粒径分布指数增大，煤油雾化粒径分布均匀。

本文采用数值模拟计算的方法，建立了静止环境煤油单液滴着火计算模型，开展了高空环境煤油单液滴着火特性研究。研究结果表明，在相对较低的高温环境下，化学动力学控制液滴着火；在相对较高的高温环境下，传热传质控制液滴着火。研究了环境温度、氧气质量分数、环境压力和液滴初温对煤油单液滴的着火特性的影响。研究结果表明，提高环境氧气质量分数、增加液滴初始温度可以降低液滴着火延迟时间；提高环境氧气质量分数和环境压力可以拓宽液滴着火直径范围。

本文采用数值模拟计算的方法，开展了利用航天级过氧化氢分解产生的高温富氧射流进行高空再点火。高温富氧射流不仅可以提供点火能量，而且可以提供富氧环境，有利于低温低压极端环境的高空再点火。该点火过程可以分为三个阶段：局部高温区初步建立、煤油蒸汽快速积累和火焰快速传播。点火过程包括两条火焰传播路径：当点火射流动压较大时，煤油蒸汽在火焰筒内侧积累，火焰从火焰筒内侧发展；当点火射流动压较小时，煤油蒸汽在火焰筒外侧积累，火焰从火焰筒外侧发展。研究结果表明，在温度为288K，压力为7.4 × 10⁴ Pa的高空条件下，利用98%过氧化氢分解的高温富氧射流进行高空点火，当空燃比为13.4且射流与气膜冷却空气的动压比大于0.374，或者空燃比为17.4且射流与气膜冷却空气的动压比大于0.281时，高空再点火成功；在可以成功点火的空燃比下，存在点火成功的动压比下极限，动压比小于此极限的富氧射流点火失败，空燃比越低，此极限越低。

In order to solve environmental pollution and reduce carbon emission, clean low-NO_X combustion technologies and alternative fuel of civil aviation engines are currently being developed, and military aircraft are seeking new breakthroughs in flight envelope, which result in the difficulty of high-altitude relight of aero-engine in the low-temperature and low-pressure extreme conditions. Compared with the ground environment, the low-temperature low-pressure and rarefied air at high-altitude causes poor atomization and mixing of kerosene in combustion chamber and results in the decrease of the rates of fuel evaporation and combustion, which makes high-altitude relight difficult. In order to study the influence mechanism of high-altitude environment on ignition process in combustion chamber and explore new effective and feasible ignition methods, this thesis adopted numerical simulation calculation method to investigate the intake characteristics of combustion chamber, the atomization characteristics of kerosene and the ignition characteristics of single drop after flameout of aero-engine and a novel method of high-altitude relight was presented, using the high-temperature and oxygen-enriched jet generated by the decomposition of high-concentration hydrogen peroxide.

In this thesis, according to the standard atmosphere model and the structural characteristics of the aero-engine, the computational model of the combustion chamber inlet parameters after the aero-engine flameout at high altitude was established. The results show that the combustion chamber inlet temperature, pressure and airflow plummet after an aero-engine flameout at high altitude. At a flight altitude of 7 km and a flight Mach number of 0.7, the inlet temperature of the combustion chamber drops to 266 K, the pressure drops to 0.48 times the standard atmospheric pressure, and the airflow drops to 0.1 times the cruise state. After the aero-engine flameout at high altitude, a dive strategy can be adopted to convert the aircraft's gravitational potential energy into the aircraft's kinetic energy, reducing the flight altitude while increasing the flight Mach number, thus improving the high-altitude re-ignition environment.

Taking the single-head combustion chamber of CFM56-7 engine as the research object, this thesis established a pressure-swirl atomization model by numerical simulation, and studied the characteristics of kerosene atomization in the combustion chamber of an aeroengine after high-altitude flameout, and analyzed the influence of flight altitude and flight Mach number on kerosene atomization. The results indicate that kerosene atomization is completed within a distance of 11 times the nozzle diameter downstream of the nozzle. At the flight Mach number of 0.7, with the increase of flight altitude, the increase of kerosene atomization particle size is more obvious, and the deterioration of kerosene atomization is aggravated, which greatly increases the difficulty of the aero-engine re-ignition at high altitude. Under the flight altitude of 7km, when the flight Mach number is greater than 0.7, the kerosene atomized particle size is small, and the change of Mach number has less effect on the kerosene atomized particle size; when the flight Mach number is less than 0.7, the change of Mach number has significant effect on the kerosene atomized particle size. Reducing the flight altitude results in an increase in the kerosene atomization particle size distribution index and a uniform kerosene atomization particle size distribution.

A single drop ignition calculation model of kerosene in static environment was established by numerical simulation. This thesis studied the characterization of single droplet ignition of kerosene in high altitude environment, and the results show that chemical kinetics controls droplet ignition at relatively low high temperature environment, and heat and mass transfer controls droplet ignition at relatively high temperature environment. The effects of ambient temperature, oxygen mass fraction, ambient pressure and droplet initial temperature on the ignition characteristics of kerosene single droplets is investigated. The results show that increasing the ambient oxygen mass fraction and the droplet initial temperature can reduce the droplet ignition delay time, and increasing the ambient oxygen mass fraction and pressure can widen the range of droplet ignition diameters.

This thesis adopted numerical simulation to investigate the law of high-altitude relight using the high-temperature oxygen-enriched jet produced by the decomposition of high-concentration hydrogen peroxide. The high-temperature and oxygen-enriched jet can not only provide ignition energy, but also provide an oxygen-enriched environment, which is conducive to high-altitude relight in extreme environments. The novel relight process can be divided into three stages: ignition core formation, kerosene vapor accumulation and rapid flame propagation. There are two flame propagation paths in combustion chamber during high-altitude relight: at high dynamic pressure of the ignition jet, kerosene vapor accumulates on the inside of the flame tube, and the flame propagates from the inside of the flame tube; at low dynamic pressure of the ignition jet, kerosene vapor accumulates on the outside of the flame tube, and the flame propagates from the outside of the flame tube. Under the high-altitude conditions at a temperature of 288 K and a pressure of 7.4 × 10⁴ Pa, the high-temperature and oxygen-enriched jet generated by the decomposition of 98% hydrogen peroxide is utilized for high-altitude relight. The results show that when the air-fuel ratio is 13.4 and the dynamic pressure ratio of the jet to film cooling air is greater than 0.374 or the air-fuel ratio is 17.4 and the dynamic pressure ratio of the jet to film cooling air is greater than 0.281, the high-altitude relight is successful, and under the air-fuel ratio that can be successfully ignited, there exists a limit for the dynamic pressure ratio below which ignition with the oxygen-enriched jet fails. The lower the air-fuel ratio, the lower this limit.