On the effect of injector temperature on the flame transfer functions of laminar premixed flames

This paper investigates the effect of injector panel temperature on the flame transfer function (FTF) for different fuel/air mixtures, including methane/air, propane/air, and hydrogen/air, by combining numerical simulations with system identification (SI) techniques. Under steady conditions, increasing the injector panel temperature leads to a reduction in the flame stand-off distance. A small amplitude Gaussian impulse is introduced to perturb the oncoming flow velocity, and once the flame returns to steady behavior, the FTF is extracted over a range of frequencies using system identification. The resulting FTFs are validated against those obtained using the conventional sinusoidal forcing method. The results show that increasing wall temperature enhances the peak gain of the FTF and shifts the peak frequency to higher values. In addition, variations in flame stand-off distance influence the phase characteristics of the FTF. Extra flame oscillations give rise to sub-peaks in the FTF spectrum, and the magnitude of these oscillations is modulated by the stand-off distance.