基于二次燃料喷射的预混燃烧室热声振荡主动控制方法

Active control of thermoacoustic oscillations in premixed combustor based on secondary fuel injection

为了实现热声振荡的主动控制,基于燃气轮机模型燃烧室,实验研究了二次燃料喷射对热声振荡的影响。采用高频压力传感器和光电倍增管同步测量了燃烧室内压力振荡和CH*表征的释热脉动,采用高速相机捕捉了火焰结构,通过对实验数据的分析获得了热声振荡的产生机理和二次燃料喷射解耦热声耦合的作用机制。结果表明:涡流效应会引起火焰的周期性卷曲,导致火焰面积的变化,引发释热率的脉动,激发并维持热声振荡。二次燃料喷射可以显著降低热声振荡水平,当二次燃料占比5.0%时,声压幅值和均方根压力幅值分别降低了32%和35%;当二次燃料占比10%时,声压幅值和均方根压力幅值降低到噪声水平。二次燃料喷射可以改变火焰形态,随着二次燃料占比的增加,火焰抬升高度和火焰宽度相应增加,释热区域向燃烧室下游延展,火焰的非定常特性减弱。二次燃料喷射可以打破燃烧室压力和释热率之间的相位耦合,实现对热声振荡的主动控制。

To achieve active control of thermoacoustic oscillations,the effects of secondary fuel injection on thermoacoustic oscillations were experimentally investigated based on a gas turbine model combustor.Highfrequency pressure transducers and photomultiplier tubes were used to synchronously measure the pressure oscil⁃lations and heat release rate(HRR)disturbances characterised by CH*.High-speed camera was used to capture the flame structure.The mechanisms of the thermoacoustic oscillations and secondary fuel injection decoupling thermoacoustic process were obtained through theanalysis of the experimental data.The results show that the vor⁃tex effect causes the periodic flame roll-up,which leads to the change of the flame area and makes HRR distur⁃bances,and further induces and maintains the thermoacoustic oscillations.The level of thermoacoustic oscilla⁃tions can be significantly weakened by the secondary fuel injection.The peaks of sound pressure level and root mean square pressure are reduced by 32%and 35%,respectively,at 5.0%proportion of secondary fuel,and drop to noise levels at 10%proportion of secondary fuel.The flame structure can be changed by the secondary fu⁃el injection.As the proportion of secondary fuel increases,the lift height and width of the flame increase accord⁃ingly.The heat release area extends downstream of the combustor,and the unsteady characteristics of the flame are weakened.The secondary fuel injection can break the phase coupling between pressure and HRR in the com⁃bustor,and achieve the active control of thermoacoustic oscillations.