基于经验模态分解的燃烧不稳定性分析

Analysis on combustion instability based on empirical mode decomposition

实验研究了在常温常压条件下贫燃预混旋流火焰的燃烧不稳定性,发生燃烧不稳定性时其压力脉动表现为非平稳信号.利用一种基于经验模态分解(EMD)的希尔伯特-黄变换(HHT)算法对在当量比分别为0.71和0.80工况下的压力脉动信号进行了时频分析.针对压力脉动信号进行经验模态分解,选取主要的固有模态函数(IMF),对IMF通过HHT变换得到瞬时频率并进行统计分析.结果表明:在当量比为0.71时,压力信号呈间歇式的脉动,其振型为拍振;在当量比为0.80时,脉动压力信号则呈现出极限环振型.在基于EMD的HHT变换中,IMF体现了燃烧不稳定性的固有模态且具有自适应性强的特点.

An experimental study was conducted in the lean-premixed swirl-stabilized combustor at atmospheric pressure and temperature in order to analyze the pressure oscillation in occurrence of the combustion instability.The fluctuating pressure signals exhibited as non-stationary signals.A new method using Hilbert-Huang transform（HHT）based on empirical mode decomposition（EMD）and intrinsic mode function（IMF）reconstruction was investigated.This method was applied to demonstrate the characteristics of pressure oscillations in the lean-premixed combustor when the equivalent ratio was at 0.71 and 0.80.The pulsating signals were decomposed with EMD,and IMF containing specific frequencies was obtained.Through the HHT and statistical analysis,the instantaneous frequency of the IMF was analyzed.The results show that the pressure oscillations display the characteristics of intermittent pulsating,and present the beat at the equivalent ratio of 0.71;whereas at the equivalent of ratio 0.80,the pressure oscillations feature the limit cycle.The validity of this method proves that the IMF reflects the inherent mode when the combustion instability occurs,and it has a strong adaptability.