外激作用下自激热声系统的非线性动力学响应

Nonlinear dynamic responses of a self-excited thermoacoustic system subjected to acoustic forcing

在高温高压燃烧实验台上,以频率ff为78~716Hz,幅值A为0.026~0.629的外激信号激励有自激响应的同心分层旋流部分预混预蒸发火焰热声系统,研究其非线性动力学响应。结果表明:系统的自激频率fn为366.85Hz;当外激频率和自激频率的比值为1.022,幅值A为0.629时,火焰主要被外激频率其谐波控制,其状态轨迹密集在很窄的封闭带中;当外激频率和自激频率的比值与A在其他的范围时,火焰不仅在ff和fn处响应,还在谐频、结合频和分频处响应。说明当外激幅值足够大并且外激频率靠近自激频率时,火焰发生锁相;当火焰未锁相时,出现了谐频、结合频以及分频的非线性响应,火焰准周期振荡。受迫范德波尔振荡器模型能够预测锁相、奇数谐频以及结合频2fn±ff。

On the combustion experimental platform of high temperature and pressure,the thermoacoustic system with a concentric stratified swirl-stabilized partially premixed-prevaporized flame with self-excited response was excited by external-excited signal with frequency ffof 78-716 Hz and amplitude A of 0.026-0.629,and its nonlinear dynamic responses were studied.It was found that the system self-excited frequency fnwas 366.85 Hz;when the ratio of external-excited frequency to self-excited frequency was 1.022 and amplitude A was 0.629;the flame was dominated by the harmonic frequency and its state trajectory was dense in a very narrow closed zone.When the ratio of external-excited frequency to self-excited frequency and A was in other ranges,the flame responded not only at ffand fn,but also at the harmonic,combining and divided frequencies.It showed that when amplitude A was large enough and external-excited frequency was close to the self-excited frequency,the flame was phase-locked.When the flame was not phase-locked,the nonlinear responses of the harmonic,combining and divided frequencies appeared,and the flame oscillated quasiperiodically.Forced van Der Pol oscillator model can predict phase-locked,odd harmonic frequencies and combining frequencies 2 f_n±f_f.