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针对自燃推进剂接触就能着火燃烧的特点,设计实现了高压飞滴及常压挂滴两套单液滴燃烧实验系统,并开展了有机凝胶偏二甲肼(UDMH)液滴在四氧化二氮(NTO)氧化剂环境中着火燃烧的实验研究,深入分析了其着火燃烧特性及NTO氧化剂浓度、温度、压力、对流速度、液滴初始尺寸的影响。结果表明:有机凝胶UDMH液滴表面液体燃料耗尽后会形成弹性胶凝剂膜,促使液滴内部出现沸腾蒸发及非稳态蒸汽喷射,导致燃烧火焰出现剧烈扰动。NTO浓度升高,增大了扩散燃烧火焰范围,加速液滴表面燃料蒸汽分解燃烧,有利于提高燃烧速率。NTO温度越低,着火延迟时间越长,并容易导致熄火。NTO对流速度越大,也会增加着火延迟时间,且更容易形成脱体火焰,使其燃烧速率降低。凝胶液滴尺寸越大,其着火延迟时间受对流速度的影响明显减小。NTO压力升高会抑制燃料蒸汽喷射强度,形成更稳定且更靠近液滴表面的双火焰结构。
In view of the characteristics of ignition and ignition of spontaneous combustion propellant, two sets of single droplet combustion experiment system of high pressure droplet and atmospheric droplet are designed and implemented, and the droplet of UDMH (organic dimethylpolysiloxane) Nitrogen (NTO) oxidant environment, the ignition and combustion characteristics of NTO oxidant, the concentration of NTO oxidant, temperature, pressure, convection velocity and initial droplet size were analyzed. The results show that the liquid gel of UDMH droplets forms an elastic gel film when the liquid fuel is depleted, causing boiling evaporation and unsteady steam injection inside the droplet, resulting in severe disturbance of combustion flame. Increasing the concentration of NTO increases the diffusion combustion flame range and accelerates the fuel vapor decomposition and combustion on the droplet surface, which is beneficial to improve the combustion rate. The lower the NTO temperature, the longer the ignition delay, and can easily lead to flameout. The larger the convection velocity of NTO, the longer the fire delay time will be, and the easier it is to form an off-body flame and reduce its burning rate. The larger the droplet size of the gel, the more the ignition delay time is affected by the convection velocity. Increasing NTO pressure suppresses the fuel vapor injection intensity, creating a more stable, two-flame structure closer to the droplet surface.