考虑喷注流强分布的纵向稳定性建模与分析

喷注器流强分布是除声学阻尼装置以外使液体火箭发动机稳定工作的重要措施，通过控制喷注流强分布使推进剂的燃烧尽量远离主要振型的波腹区，减少热声耦合振荡的能量源，从而达到抑制高频振荡的效果。因此，建立喷注流强分布与稳定性之间的综合分析模型，研究流强分布的不稳定性抑制特性具有重要实际意义。针对采用自击式喷嘴器、液滴蒸发作为燃烧速率控制过程的某自燃推进剂缩尺燃烧室高频纵向燃烧不稳定问题，近似采用蒸发速率峰值区代替集中燃烧释热区，引入燃烧室三维声学控制方程以考虑多喷嘴条件下燃烧响应空间分布，建立了针对喷注器流强分布条件下的高频纵向燃烧稳定性分析模型，并对喷注流强的稳定性抑制特性进行了分析，给出了不同分布流强下燃烧室一阶纵向信号的增长率变化规律。研究表明，喷注流强分布有利于燃烧室稳定，"驼峰区"喷注孔径的增大对改善高频纵向不稳定性更为显著，"驼峰区"流强增加30%，相应的增长率降低15%。

Modeling and analysis of longitudinal stability considering injection intensity distribution

Apart from acoustic damping devices, injection intensity distribution is a main method for the stabilization of liquid rocket engines. Through injection intensity distribution control, propellant combustion moves far away from the node of the main acoustic mode, decreasing the coupled energy driving thermo-acoustic instability and thereby suppressing high frequency combustion instability. Therefore, it is highly significant to build a comprehensive analysis model between injection intensity distribution and instability. For the hypergolic sub-scaled combustor adopting a self-impinging injector and droplet vaporization as the rate-control process, the concentrated combustion zone can be approximately replaced by the area with the highest evaporation rate in analysis of high longitudinal combustion instability. To build a theoretical model for high longitudinal combustion instability considering injection intensity distribution and analysis of its instability suppression capability for injection intensity distribution, a three-dimensional thermo-acoustic equation for the combustion chamber with multiple injectors is introduced for spatial distribution of concentrated combustion response. Finally, the growth rates representing combustion instability of the first longitudinal mode with different injection intensity distributions are computed. Results indicate that the injector with higher injection intensity in the hump zone is more stable than that with lower intensity, with a typical result of 30% gain from injection intensity in the hump zone leading to a 15% reduction in the growth rate.