模型燃烧室内不稳定燃烧发展过程的数值分析

为了对自燃推进剂燃烧室内出现的不稳定燃烧现象进行详细分析,采用欧拉-拉格朗日方法对该燃烧室内的气液两相非稳态燃烧过程进行了数值模拟,计算得到的压力振荡幅值和频谱特性与实验结果吻合较好,在此基础上对不同燃烧阶段内的压力和释热变化规律进行了分析。结果表明:在压力振荡幅值超过10%的不稳定燃烧阶段,压力振荡主频为9 200 Hz,燃烧室内横向压力分布与1阶切向振型一致,仿真中再现了1阶切向自激高频不稳定燃烧的产生及发展过程;稳定燃烧向不稳定燃烧转变早期,压力振荡从部分燃烧释热波动中获得能量,压力振荡幅值缓慢增长;随着燃烧进行,燃烧释热波动与压力振荡之间相位和频谱特性逐渐趋于一致,压力振荡幅值开始急剧增大;当二者完全耦合时,燃烧室内压力振荡幅值达到极限饱和状态,此时压力振荡幅值超过了平均室压的200%。 

Numerical analysis of unstable combustion developing process in model combustor

Gas-liquid two-phase unsteady combustion process was simulated with the Euler-Lagrange method to analyze the combustion instability, which was observed in hypergolic propellant combustor. The pressure oscillations amplitude and spectral characteristics agreed with the experimental results. And the variation rule of pressure and heat release in different combustion stages was analyzed. The results indicate that, while the pressure oscillation amplitudes exceed 10% of the average pressure, the pressure oscillation frequency is 9 200 Hz, and the transverse pressure distribution is in accordance with the first-order tangential vibration mode. The generation and developing process of the first-order tangential self-excited high frequency unstable combustion have been reproduced in simulation. At the early stage of the change from stable to unstable combustion, the pressure oscillation obtains energy from part of the combustion heat release fluctuations and the pressure oscillation amplitude increases slowly. With the combustion, the phase and spectral characteristics between the combustion heat release and pressure oscillation tend to be the same, and the pressure oscillation increases sharply. When they are fully coupled, the pressure oscillation amplitude in combustion chamber exceeds 200% of average chamber pressure and reaches the limits of saturation.