有机凝胶偏二甲肼液滴着火燃烧特性及影响因素实验研究

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。

Experimental study on the characteristics and influence factors of organic gel UDMH droplet burning

Two sets of single droplet combustion experiment system for flying droplet in high pressure and suspended droplet in room pressure are built respectively.The experiments of organic gel UDMH droplet auto-ignition and burning in NTO oxidizer are carried out,and the effects of NTO oxidizer concentration,temperature,pressure,convection velocity and droplet size on its combustion characteristics are deeply analyzed.The results show that an elastic gel film would form after the liquid fuel near the droplet surface is exhausted.It induces droplet interior boiling evaporation and unsteady vapor bursting,which results in violent distortion of combustion flame.Increasing the NTO concentration would enlarge the diffusion combustion flame area and enhance the surface fuel vapor decomposition combustion,which is in favor of droplet burning rate.Decreasing the NTO temperature would prolong the ignition delay time and make flame extinction more easily.Higher NTO convection velocity would also prolong the ignition delay time and form wake flame,resulting in the reduction of droplet burning rate.Increasing the droplet size would remarkably reduce the effect of convection velocity on its ignition delay time.Higher NTO pressure could suppress the strength of burst and form much more stable double flame structure.