限制域形状对分层火焰和燃烧不稳定性的影响

本文在中心分级燃烧室中研究限制域形状对火焰结构及燃烧不稳定性的影响。实验过程中，使用带有CH*滤镜的相机拍摄火焰图像，使用动态压力传感器测量压力脉动。结果表明，突扩限制域和斜坡限制域中的时均火焰结构相似。但突扩限制域中的火焰动态结构呈现出周期性变化，并伴随着压力振荡。而斜坡限制域中的火焰动态结构基本不变，且压力脉动接近于零，主要原因是斜坡限制域中的旋涡脱落过程受限，旋涡与火焰的相互作用被大幅削弱。通过改变主燃级通道流速调节延迟时间，发现突扩限制域中会出现压力振幅的周期性变化，而斜坡限制域中始终保持稳定燃烧。本文的研究表明使用斜坡限制域有潜力成为在宽工况范围内有效抑制燃烧不稳定的被动控制方法。

Effects of Confinement Shapes on Stratified Flames and Combustion Instabilities

The effect of the confinement shape on flame structures and combustion instabilities in a centrally-staged burner was investigated in this paper. During the experiments, cameras equipped with CH* filters were used to capture flame images. Besides, pressure signals were synchronously collected by dynamic pressure sensors. The results show that time-averaged flame structures in the dump confinement and slope confinement are similar. The dynamic flame in the dump confinement shows periodic changes, accompanied by pressure oscillations. However, the dynamic flame in the slope confinement is basically unchanged with very small pressure fluctuations, which is attributed to the weakened vortex-flame interaction due to the limited vortex shedding within the slope confinement. Changing the flow speed in the main stage could adjust the delay time. It is found that the pressure amplitude shows periodic changes in the dump confinement, while the combustion is always stable for the slope confinement case. The present study illustrates that using the slope confinement has the potential to become a passive control method to effectively suppress combustion instabilities in a wide range of operating conditions.