The effect of main stage flow velocity on thermoacoustic instability of stratified swirl burner

In this paper, two group experiments were conducted to study the effect of the main stage flow velocity on thermoacoustic instability and flame macrostructure. The experiments were carried out under atmosphere condition, and namely the pilot stage flame mode and the stratified swirl flame mode. The experimental results show that in the pilot stage flame mode, the thermoacoustic oscillation amplitude remains constant (around 1000 Pa) with the decrease of the main stage flow velocity. But when the velocity is zero (without main stage air), the thermoacoustic instability disappeared. In the stratified swirl flame mode, the amplitude of thermoacoustic instability is the largest (around 300 Pa) when the main stage flow velocity is 6.2 m/s, and the amplitude is slightly smaller in other working conditions. The time-averaged flame shape under the two flame modes is recorded and discussed. This paper highlights the effect of interactions between the pilot stage flame and main stage air or flame on thermoacoustic instability.