弹射救生数值仿真及不利姿态下救生性能分析

 国内弹射座椅救生性能预测分析主要依赖地面弹射试验。由于国内相关试验设备的缺乏,不利姿态下弹射座椅的救生性能很难通过试验获得,因此国内不利姿态下弹射座椅救生性能的分析研究比较薄弱。采用数值仿真的方法对弹射座椅的救生性能进行预测和分析,针对弹射座椅弹射过程的4个阶段分别建立了数学模型,其中自由飞阶段采用四元数法代替欧拉速率方程,以解决传统的六自由度方程出现的奇异性问题。采用四阶龙格-库塔法对数学模型进行求解,计算结果与地面弹射试验结果吻合较好。在此基础上,对某新型弹射座椅的弹射姿态轨迹进行计算,分析研究了弹射座椅在不利姿态下的救生性能,得到不利姿态下弹射座椅救生性能不佳的主要原因是座椅高速稳定性差以及飞机向下的牵连速度和飞机滚转角的影响,并根据分析结果提出了改善弹射座椅不利姿态下救生性能的基本方法。

Numerical Simulation of Ejection Seat and Analysis of Performance Under Adverse Attitudes

The escape performance evaluation of an ejection seat in China depends mainly on sled tests which may take a long time. Due to the limits of available experimental facilities, research of ejection seat perfor-mance under adverse attitudes is rarely done. In this article, a numerical simulation method is developed to evaluate and analyze the escape performance of ejection seats under adverse attitudes. The ejection progress fell into four phases. The mathematic models of each phase are built. The quaternion method rather than the Euler angular velocity equation is adopted in the free flight phase to resolve the singularity problem of a traditional 6 degree of freedom equation. The mathematic models are solved using four-order Runge-Kutta methods. The computational results agreed well with the sled test experiment data. The ejection seat attitude and trajectory are calculated and analyzed to study the performance of a escape system in adverse attitude conditions. The major causes of poor performance of an escape system under adverse attitude conditions are the instability of the seat at high speed and the influence of aircraft embroiling movement. Some basic methods to improve the escape performance of ejection seats under adverse attitudes are proposed according to the analysis.