Effects of equivalence ratio on combustion instability characteristics of staged swirl flame

In order to investigate the combustion instability characteristics of staged swirl combustor, dynamic pressure under different fuel air ratio and stage ratio were tested. Results show that when overall combustion equivalence ratio is 0.47~0.68 and the main stage equivalence ratio is 0.48~0.65, the amplitude of pressure pulsation increases with equivalence ratio increase. Relation of flame thickness, flame length, laminar flame speed and flow velocity is derived under the laminar flame model and hypothesis of local flame blow out. The conclusion is that pressure pulsation amplitude ps' is proportional to laminar flame speed SL0. With the fact that SL0 increases with equivalence ratio under lean combustion, ps' increases with equivalence ratio increases, thus the experiment result is well explained.