Reheat flames response to entropy waves

Sequential combustion architectures rely on auto-ignition flame stabilization in the second stage combustor. Due to exponential temperature dependence of ignition delay time flames can respond hot spots generated by unsteady first combustion. In this paper, response is investigated extending an existing analytical model for acoustic waves so that it also accounts entropy waves. Explicit expressions transfer functions and linear non-linear transition thresholds are derived. Results different operating conditions, forcing amplitudes frequencies discussed. For this, three computational domains increasing complexity considered validation: a 2D duct, 3D backward facing step, finally full-scale Ansaldo Energia GT26 sequential Unsteady Reynold-averaged Navier–Stokes as well large-eddy simulations performed. Acoustic entropic contributions separated means system identification techniques. Finally, identified. It observed gains linearly increase with excitation frequency non-linear, dependent effects already small amplitude levels excitation.