Modern gas turbines need to fulfill increasingly stringent pollutants emission targets. Ansaldo Energia GT26 and GT36 respond to this by means of the lean-premixed combustion technology and a sequential combustion system. In particular, the second combustion chamber relies on the autoignition principle for flame stabilization. To guarantee high efficiency and, at the same time, ensure operational flexibility it is necessary to study the thermoacoustics of these flames. In this paper, we make use of the linearized Rankine-Hugoniot conditions, a commonly used theoretical approach for propagation flames, to predict an autoignition flame transfer matrix. In particular, we derive the linearized Rankine-Hugoniot jump conditions taking into account the presence of a moving discontinuity and upstream entropy inhomogeneities. The obtained analytical expression is compared with large eddy simulations with good agreement. Physical differences with propagation flames are pointed out.
