Combustor model for simulation of combustion instabilities and their active control

The development and application of a numerical model of an actively control led combustor are described. The! main objective was to develop a model tha t could be used as a platform for studying closed-loop control of unstable combustors. The model uses a heuristic approach and global kinetics to desc ribe mixing and combustion processes in a one-dimensional gaseous combustor . initially, the model is used to investigate a combustor's response to ope n-loop excitation by periodic fuel injection. The numerical model's predict ion that 1) the pressure oscillation amplitude decreases and 2) the phase s hift between the fuel injection rate and heat-release oscillations increase s linearly, as the frequency of fuel injection rate increases, are in good agreement with experimental data from a gas rocket. Nest, closed-loop contr ol is studied. The investigated controller determines the characteristics o f the most unstable mode in real time and damps the instability by modulati ng the injection rate of a fraction of the injected fuel to excite a second ary combustion process within the combustor out of phase with respect to th e most unstable mode of pressure oscillations. Active control examples incl ude the study of the dependence of the controller's performance on the amou nt of fuel pulsed.