Impact of local secondary gas addition on the dynamics of self-excited ethylene flames

Advanced combustion strategies for gas turbine applications, such as lean burn operation, have been shown to be effective in reducing NOx emissions and increasing fuel efficiency. However, systems are susceptible thermo-acoustic instabilities which can lead deterioration engine performance. This paper will focus on one of the common industrial techniques controlling instabilities, secondary injection, is addition small quantities combustor. approach has often employed industry a trial-and-error basis using primary injection. Recent advances fuel-flexible turbines offers possibility use other gases injection mitigate instabilities. explore effectiveness hydrogen this purpose. The experiments presented study were carried out laboratory scale bluff-body combustor consisting centrally located conical bluff body. Three different gases, ethylene, nitrogen, added locally turbulent imperfectly-premixed ethylene flames. total calories mixture momentum ratio kept constant allow comparison flame response. heat release fluctuations determined from OH* chemiluminescence, while velocity perturbations estimated pressure measurements two-microphone method. results showed that was most magnitude self-excited oscillations. Nitrogen had negligible effect, only an effect at high flow rates resulted sooty