斜坡限制域对脱体火焰宏观形状和燃烧振荡影响实验研究

Combustion instability is a common unsteady process in lean premixed flame，which is dangerous to the combustor and should be carefully suppressed. Specifically，lifted flame has advantages in reducing NO_x emission，but tends to undermine the combustion instability behaviors. In the present work，the passive control of slope confinements on combustion instabilities for the lifted flame is studied experimentally in a centrally-staged combustor. Time-averaged flame macrostructures and transient images are captured by a single-lens reflex camera and a high-speed camera，respectively. The flame dynamics are analysed by phase-averaged flame images and proper orthogonal decomposition. The results show that slope confinements with step height equal to 0 mm and multiple angles can significantly suppress combustion instability. Although the suppressing effect on combustion instabilities becomes weak with the increase of the step height in a 30° slope confinement，the amplitude decreases significantly compared with the conventional dump confinement.