The excitation and evolution characteristics thermoacoustic instability in syngas micromixed combustion

This paper presents an experimental study of thermoacoustic oscillations of synthetic gas (syngas) micromixed combustion, in which the excitation and evolution characteristics of thermoacoustic oscillations were obtained as a function of flame equivalence ratio. The results show that the flame initiates thermoacoustic oscillations when the equivalence ratio drops below 0.80, with the oscillations undergoing mode transferring as the flame equivalence ratio decreases. When the equivalence ratio is 0.70, the second-order mode of thermoacoustic oscillation begins to dominate. At an equivalence ratio of 0.50, the second-order oscillation mode (640 Hz) begins to dominate the first-order oscillation mode (320 Hz). Flame flashback coexists with thermoacoustic oscillation starting at an equivalence ratio of 0.5, where the chemiluminescence distribution of the flame indicates that the flame heat release rate pulsation is maximal at the burner outlet, and other radicals vary with the equivalence ratio. Low equivalence ratio promotes the generation of amino group radicals, thereby interfering with the production of nitrogen oxides. The flame shape also depends on the flame equivalence ratio. The flame is initially conical and flattens as the equivalence ratio decreases. The innovation of this study lies in its first exploration of the thermoacoustic oscillations and flashback characteristics of syngas micromixed combustion, which contributes to the formulation of design criteria for micromixed burners. These results clarify the evolution of syngas micromixed combustion and facilitates the prediction and control of flashback or thermoacoustic oscillations.