Hypergolic propellants are widely used in liquid rocket propulsion. Instantaneous control of combustion, lack of requirement of an ignition system, and storability for long durations are the major advantages of hypergolic propellants. The propellant community is on the lookout for replacements for the currently utilized toxic hydrazine and its derivatives. Energetic hypergolic ionic liquids are excellent candidates for such replacement. However, their high viscosity and surface tension render atomization difficult, and hence, increase the ignition delays in the combustion chamber and reduce combustion efficiency. The current study focuses on the geometrical aspects of injector design and other injection conditions that control the ignition process and combustion efficiency. These mainly depend on the extent of mixing and atomization. Shadowgraphy and patternator-based experiments were performed on doublet and triplet impingement injectors under variable injection conditions, such as impingement angle, jet diameters, and injection velocities. A blend of 50% unsymmetrical dimethylhydrazine in the energetic ionic liquid hydroxyethylhydrazinium nitrate (UHN50) shows a promising candidate as a replacement for hydrazine. A blend of 38% ethanol in glycerol (GE6238) was used as a surrogate for UHN50, whereas water was used as a surrogate for nitrogen tetroxide. The effect of variation of injection conditions was found to be contradictory for achieving atomization and mixing. An optimum criterion from both the perspectives of atomization and mixing is jet impingement angle of 60°, intermediate injection velocities, and momentum ratio close to unity.

中文翻译：

---

混合型高能离子液体羟乙基肼硝酸盐的雾化与混合

自燃推进剂广泛用于液体火箭推进。自燃推进剂的主要优点是即时控制燃烧、无需点火系统以及可长期储存。推进剂界正在寻找目前使用的有毒肼及其衍生物的替代品。高能自燃离子液体是这种替代品的绝佳候选者。然而，它们的高粘度和表面张力使得雾化变得困难，因此增加了燃烧室中的点火延迟并降低了燃烧效率。目前的研究重点是喷射器设计的几何方面以及控制点火过程和燃烧效率的其他喷射条件。这些主要取决于混合和雾化的程度。在可变喷射条件（例如冲击角度、喷射直径和喷射速度）下对双态和三态冲击喷射器进行了基于阴影成像和图案化的实验。50% 不对称二甲肼在高能离子液体硝酸羟乙基肼 (UHN50) 中的混合物显示出作为肼替代品的有前途的候选者。38% 乙醇的甘油混合物 (GE6238) 用作 UHN50 的替代物，而水则用作四氧化二氮的替代物。发现喷射条件的变化对于实现雾化和混合的影响是矛盾的。从雾化和混合的角度来看，最佳标准是射流冲击角为60°、喷射速度中等、动量比接近1。