燃烧条件下凝胶自燃推进剂雾化特性试验研究

Experimental Study on Spray Characteristic of Gelled Hypergolic Bipropellants in Hot-Fire Test

关键词:  自燃推进剂  凝胶推进剂  燃烧  雾化  可视化

Key words:  Hypergolic propellants  Gel propellant  Combustion  Spray  Visual

摘要:

为了研究凝胶自燃推进剂的雾化特性及敏感因素，在单互击式喷嘴矩形燃烧室内进行了凝胶一甲基肼/四氧化二氮（MMH/NTO）喷雾燃烧过程可视化试验，采用光源后置消光法湮灭火焰自然辐射发光，采用彩色高速摄影获取了燃烧条件下的高质量雾场阴影图像，通过图像处理，有效提取了雾场的雾化锥角、破碎长度、液丝直径及液丝运动速度，分析了撞击角、射流速度和动量比的影响。结果表明，凝胶MMH/NTO稳态燃烧时可观察到液膜、贯穿视场的液丝和红棕色NO ₂气体，推进剂混合燃烧不充分；撞击角从75°增大到105°，凝胶MMH/NTO撞击后的破碎长度、液丝直径减小，视场内可视红棕色NO ₂气体变少，撞击角为105°时，推进剂会附着在喷注面上，从而影响液膜横向铺展，雾化锥角反而最小，建议撞击角选取90°。燃料射流速度从23m/s增大到45m/s，凝胶MMH/NTO撞击后的雾化锥角及液丝运动速度增大，破碎长度及液丝直径减小，雾化模式发生改变。动量比从1.04增大到1.52，凝胶MMH/NTO撞击后的雾化锥角及液丝运动速度增大，视场内红棕色NO ₂气体变少。故一定量程内增加撞击角、射流速度、动量比有助于凝胶MMH/NTO推进剂混合燃烧。

Abstract:

Aiming at elucidating the spray characteristic and effect factors of gelled hypergolic bipropellants, visual experiment was conducted to investigate the phenomena involved in the spray and combustion processes of gelled methylhydrazine/nitrogen tetroxide(MMH/NTO) in a square combustion chamber with a single unlike-impinging injector. Back illumination light extinction was used to neutralize the influence of flame in this experiment, so high-quality spray images of gelled MMH/NTO in hot-fire were obtained with the help of high-speed camera. Spray cone angle, breakup length, diameter and velocity of liquid ligaments were obtained by image processing technology, then the effects of impinging angle, jet velocity and momentum ratio were discussed in the study. The results show that the co-combustion of gelled MMH/NTO is not efficient, liquid sheets, ligaments throughout the entire field of view and reddish-brown NO ₂ unreacted could be seen clearly in shadow images. The breakup length, diameter of ligaments and reddish-brown NO ₂ decrease with the increasing impinging angle from 75° to 105°, however, liquid propellants would accumulate on the wall of injector and influence the expansion of liquid sheets when impinging angle is 105°，and lead to the spray cone angle decrease, so 90°impinging angle is suggested. The spray angle and velocity of ligaments increase when jet velocity of fuel increase from 23m/s to 45m/s, and the breakup length and diameter of ligaments decrease at the same time, moreover, the breakup pattern is changed possibly with the increasing fuel jet velocity. With the momentum ratio of oxidizer to fuel changing from 1.04 to 1.52, the spray cone angle and velocity of ligaments increase, and the reddish-brown NO ₂ decrease. Therefore, the increasing of impinging angle, jet velocity and momentum ratio in certain range could improve the spray and combustion of gelled MMH/NTO.