희박 예혼합 다단 연소기에서의 주파수 동조에 의한 연소불안정 증폭

Abstract

The self-excited dynamics of a lean-premixed axially-staged combustor, with respect to the characteristic acoustic frequency, were experimentally investigated by varying the hydrogen mole fraction in the primary flame while maintaining the fuel composition of the secondary flame constant. It is observed that the dominant instability frequency transitions from lower to higher acoustic modes with varying hydrogen concentrations during single-flame combustion. We demonstrate that under axially-staged conditions, the more complex instabilities can be triggered and sustained by the combination of local heat release fluctuations generated from the primary flame and secondary transverse reacting jets. When the instability frequencies of the primary and secondary flames synchronize with each other, especially within the same acoustic mode, the amplitudes of pressure fluctuations are significantly amplified compared to those observed with single flame condition.