同轴离心式喷嘴噪声引发燃烧不稳定分析和预测

以氧化剂和燃料的混合比作为系统控制参数，研究同轴离心式喷嘴燃烧动力学过程。混合比增加和减少过程中，燃烧噪声和振荡燃烧状态间转变的混合比不同，说明系统出现了亚临界Hopf分叉现象，且在双稳定区内出现了燃烧噪声引发的振荡燃烧。利用临界慢化理论，分析3种表征参数:延迟为1自相关系数、方差和条件异方差（CH）对噪声引发不稳定的预警效果。结果表明:延迟为1自相关系数在噪声引发不稳定前出现明显的上升趋势且非随机现象，具有较可靠的指示作用。方差对噪声引发不稳定性的预示性较差。条件异方差在不稳定发生前振荡上升，可以作为辅助判断条件。基于Kendall秩相关系数趋势评估方法，提出一种在线预测噪声引发不稳定的判断准则，具有较好的适应性和可靠性。 

Analysis and prediction of noise-induced combustion instabilities of coaxial swirl injector

The combustion dynamics of a coaxial swirl injector was investigated with the mixture ratio of oxidant and fuel as the system control parameter.The mixture ratios at which the transitions between combustion noise and oscillatory state occurred were different for the forward path and for the reverse path.This difference indicated that the transition to the oscillatory state observed was subcritical Hopf bifurcation in nature.Noise-induced instabilities were observed in the bistable regime.The viability of three early warning measures such as lag-1 autocorrelation，variance and conditional heteroskedasticity （CH） to predict transition in the combustor was analyzed based on critical slowing down theory.It was found that lag-1 autocorrelation showed an increasing trend as the critical point was approached，enabling to predict catastrophic transitions as early warning signals.Variance may be less generic as an indicator of noise-induced instability.Significant CH showed an increasing trend，which can be used as an auxiliary judgment condition.An online prediction method of good adaptability and reliability for noised-induced instability based on Kendall rank correlation coefficient was proposed.