不同直径圆球诱导燃烧的振荡机制与频率特性

In order to analyze the law of oscillating combustion induced by spheres with different diameters and to reveal the inherent effect of sphere size on the oscillation phenomenon, numerical simulations are carried out to investigate the oscillating combustion phenomenon in a H₂/air premixed gas mixture induced by spheres with different diameters, by solving the two-dimensional axisymmetric Euler equations along with a detailed combustion mechanism. Results show that as the sphere diameter increases, the frequency of oscillating combustion does not decrease continuously, but with two abrupt drops, which implies that there exist three modes in the high-speed sphere-induced oscillating combustion phenomenon, namely the superhigh-frequency mode, the high-frequency mode, and the low-frequency mode. During the transition of two modes, there exists a metastable oscillating state of double-frequency coupling before the oscillation reaches its stable state. Moreover, the appearance of these three different modes is affected by different oscillation mechanisms, and the double-frequency coupling phenomenon during the transition of two modes is resulted from the competition of two mechanisms.