Bluff-body flame instabilities are experimentally investigated under varying turbulence conditions during lean blowout. For all turbulence conditions, the blowout process is induced through a temporal reduction of the fuel flow rate to capture the flame-flow dynamics approaching blowout. Simultaneous high-speed particle image velocimetry (PIV), stereoscopic PIV, and C₂*/CH* chemiluminescence imaging are employed, along with an independent CH* imaging system, to capture flame-flow instabilities. Proper orthogonal decomposition (POD) and dynamic mode decomposition (DMD) techniques are used to identify prominent flame oscillations and evaluate recurring spatiotemporal modes during blowout. The results reveal that the dominant flame oscillations and wrinkling characteristics are directly dependent on the turbulence conditions in the combustor. Specifically, the flame-flow oscillations are strongly coupled with the integral length scales, which were able to collapse the oscillation frequencies to a unified value. The turbulence-driven flame-flow oscillations are shown to largely impact the magnitude, temporal evolution, and oscillatory behavior of the flame strain rate. As the turbulence intensity is increased, the oscillation of the flame strain rate increases in frequency, making it more likely for localized extinctions to occur. Additionally, the magnitude of the flame strain rate increases at high turbulence intensities and accelerates the lean blowout process.

在贫燃期间，在变化的湍流条件下，对钝体火焰的不稳定性进行了实验研究。对于所有湍流条件，通过暂时降低燃料流量来引发爆燃过程，以捕获接近爆燃的火焰流动动力学。同时高速粒子图像测速（PIV），立体PIV和C ₂* / CH *化学发光成像与独立的CH *成像系统一起使用，以捕获火焰流动的不稳定性。正确的正交分解（POD）和动态模式分解（DMD）技术用于识别突出的火焰振荡并评估井喷过程中的时空模式。结果表明，主要的火焰振荡和起皱特性直接取决于燃烧室中的湍流条件。具体而言，火焰流振荡与整体长度标度紧密相关，该整体长度标度能够将振荡频率压缩为一个统一的值。湍流驱动的火焰流振荡显示出对火焰应变率的大小，时间演化和振荡行为有很大影响。随着湍流强度的增加，火焰应变率的振荡频率增加，从而更可能发生局部灭绝。另外，火焰应变率的大小在高湍流强度下会增加，并会加速稀薄吹出过程。