分级旋流火焰的燃烧不稳定性及火焰动力学

The combustion instability and flame dynamics characteristics of the lean premixed graded swirl flame were experimentally studied. The experiment was carried out on a laboratory bench at room temperature and pressure fueled by methane. By means of fast Fourier transform (FFT) analysis of dynamic pressure and heat release rate, inverse Abel transformation of flame image, heat release integral, and proper orthogonal decomposition (POD) analysis, the effect of grade ratio on combustion instability was emphatically studied. The experimental results showed that the proportion of pilot stage fuel played an important role in flame stabilization mechanism, heat release distribution and flame stability. As the grade ratio increased, the flame changed from an unstable detached flame or mushroom flame to a stable and compact Ⅴ-shaped flame, with the heat release center of the flame moving towards the nozzle. POD analysis showed that when the grade ratio was relatively large, the pilot stage flame reduced the periodic expansion and contraction of the flame surface by improving the flame stability at the flame root, and finally inhibited the combustion instability.