Measurements of 3D flame edge dynamics were made on a high-speed jet diffusion flame to assess the global/local hydrodynamic instability. The flame was generated by issuing high-speed ethylene (U_j = 170 m/s) into a low-speed vitiated hot coflow (U_c = 1.5 m/s), resulting in a hydrodynamic shear layer instability at the interface between combustion products and ambient flow. The measurements used a high-speed camera combined with nine-headed fiber endoscopes to simultaneously collect both the soot radiation and chemiluminescence projections of the flame from nine views, based on which 3D flame edges were obtained via computed tomography at 15 kHz. The measurements clearly capture the time-varying, 3D instantaneous flame edge structures with fine-scale corrugations, enabling the observation of small-scale vortices' evolution. The flame edge deformations induced by those vortices were calculated globally and locally to infer the relationship between global and local flame edge oscillations. Results show that various local oscillation frequencies exist at different locations along the flow direction for such a highly sheared flame. They are dominated by the periodical formation and motion of various localized, small-scale vortices. The local oscillations are much severer than the global oscillation, indicating a self-suppression of the instabilities between these local oscillations. The suppression mechanism is attributed to the constructive and destructive interference behavior of the local disturbances. The global oscillation of the flame edge turns out to be the linear superposition of local oscillations at different locations.

在高速射流扩散火焰上进行了3D火焰边缘动力学的测量，以评估整体/局部流体动力学的不稳定性。火焰是通过将高速乙烯（U _j  = 170 m / s）释放到低速的热热气流中（U _c = 1.5 m / s），导致燃烧产物和环境流之间的界面处的流体动力剪切层不稳定。测量使用了高速摄像头和九头光纤内窥镜，从九个视图同时收集了火焰的烟尘辐射和化学发光投影，并基于15 kHz的计算机断层扫描技术获得了3D火焰边缘。这些测量清楚地捕获了随时间变化的3D瞬时火焰边缘结构和细小波纹，从而可以观察到小尺度涡旋的演变。整体和局部计算了由这些涡流引起的火焰边缘变形，以推断整体和局部火焰边缘振荡之间的关系。结果表明，对于这种高剪切火焰，在沿着流动方向的不同位置存在各种局部振荡频率。它们受各种局部小规模涡旋的周期性形成和运动支配。局部振荡比全局振荡严重得多，这表明这些局部振荡之间的不稳定性是自我抑制的。抑制机制归因于局部扰动的相长干涉和相消干涉行为。火焰边缘的整体振荡被证明是在不同位置的局部振荡的线性叠加。局部振荡比全局振荡严重得多，这表明这些局部振荡之间的不稳定性是自我抑制的。抑制机制归因于局部扰动的相长干涉和相消干涉行为。火焰边缘的整体振荡被证明是在不同位置的局部振荡的线性叠加。局部振荡比全局振荡严重得多，这表明这些局部振荡之间的不稳定性得到了自我抑制。抑制机制归因于局部扰动的相长干涉和相消干涉行为。火焰边缘的整体振荡被证明是在不同位置的局部振荡的线性叠加。