关键词: 自燃推进剂;凝胶推进剂;燃烧;雾化;可视化

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.

Key words: Hypergolic propellants;Gel propellant;Combustion;Spray;Visual