Experimental study on combustion instability of lean premixed swirl flame

An experimental study was conducted on combustion instabilities in a lean-premixed swirl-stabilized combustor at atmospheric pressure and temperature.The result shows that the combustion instability occurred in the model combustor is self-excited under longitudinal oscillation mode,the premixing section resonates with the combustor at the unstable mode of the system,and the oscillation frequency depends on the whole system.The equivalence ratio was identified to have major impact on the onset of instabilities.With equivalence ratio increase,the combustion was transited from stable to unstable states,and reached a limit cycle at last.In the occurrence of instability,the flame became much shorter and penetrated into the corner recirculation.The instability mechanism probably stems from the strong interaction between flame dynamics and flow oscillations inside the combustor,but more work is needed to provide an in-depth physical understanding of the mechanisms to initiate and sustain combustion instabilities.