The integrated afterburner has received increasing attention because of its unique advantages, including low pressure loss, high flame intensity, and reduced combustor length. The present work focuses on the combustion dynamics and instabilities of an integrated afterburner with strut and cavity using the Eulerian-Lagrangian large-eddy simulation (LES). Two closely-coupled fuel injection schemes with different momentum flux ratios are proposed to investigate the influence of fuel distribution. The flame response characteristics are also obtained by applying external excitations. The results show that a higher momentum flux ratio leads to asymmetric large-scale flame shedding due to Bénard-von Kármán (BVK) instability, and a lower momentum flux ratio exhibits symmetric flame with small fluctuations. The main heat release region is concentrated in the shear layers of the recirculation zone (RZ) and the edges of the vortices in the wake region, where the premixed combustion mode is dominant. The non-premixed combustion mode mainly exists in RZ and the farfield wake region. Flame in the cavity propagates towards the bluff body and tends to enhance a bluff-body stabilized flame. Part of the hot products in the strut recirculation zone (SRZ) are transported to the cavity via vortical interactions with the cavity recirculation zone (CRZ), which further improves the cavity flame stability. For the flame response with external excitations, the maximum peak of the gain occurs at around 330 Hz and corresponds to the characteristic frequency of BVK instability of the bluff body.
Wang et al. (Sat,) studied this question.
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