Effects of transverse injection distribution scheme of dual flames on thermoacoustic instability in a Rijke tube

Low emission or even zero carbon emission has bring major challenge for aero engines, in which thermoacoustic instability is often difficult to control due to the lean premixed combustion technology. The multi flame scheme is typical for injectors utilized in aero engines and landed gas turbines. It is of practical significance to study effects of transverse injection distribution schemes on thermoacoustic oscillations. In this study, oscillation characteristics for different dual flame schemes are experimentally investigated. The transverse injection distribution scheme includes two parts: transverse distance and injection angle. Nonlinear dynamic analysis methods are applied to analyze acoustic pressure signals detected by microphone. Proper orthogonal decomposition method is used to capture flame front dynamic mode. Results indicate that there is the optimum transverse injection distance for direct injection dual flames that can cause more unsteady flame heat releases, and can be more inclined to induce thermoacoustic oscillations. Although oscillation amplitudes of dispersed injection dual flames are relatively low, intermittent oscillations and more oscillation frequencies can be induced by dual flames with large injection angles. Nonlinearity of dual flame front dynamic behavior can be enhanced by the increase of injection angle and the position of the dual flame in the Rijke tube.