The influence of the blockage ratio on low-swirl flame dynamics was experimentally investigated in a lean-premixed combustor. Here we test five different swirl injectors, one with high swirl and four with low swirl, all with different blockage ratios (β). We analyze a large experimental dataset of self-excited instability measurements, and show that instability amplitudes for the case of β = 0.75 tend to be remarkably attenuated.
This is attributed to the development of out-of-phase modulations between the jet-stabilized flame in the inner section and the swirl-stabilized flame in the outer section.