Flame transfer function measurement of a sequential combustor fuelled with natural gas and hydrogen

The flame transfer function (FTF) relates acoustic perturbations and the coherent heat release rate response. This frequency-dependent function governs the thermoacoustic stability of a combustor. The FTF measurement is therefore of great interest for predicting the stability of the practical combustor connected to the engine’s compressor and turbine. So far, the FTFs of the second stage of constant pressure sequential combustors (CPSC) have only been obtained from numerical simulations. In this study, second-stage FTFs are measured experimentally. The thermal power of the first- and second-stage flames is configured to be equal. The effects of hydrogen blending in the first- and second-stage fuel mixtures on the sequential FTF are analyzed. The FTF of the sequential flame is fitted with a distributed time delay (DTD) model with two pulses. The trends of the model parameters obtained are consistent with the chemiluminescence of the sequential flame.