Comparison Among Thermal, Kinematic and Acoustic Spectra in a Gas Turbine Burner Model

Flame temperature measurements have been performed by means of Multi-wavelength pyrometry (MWP). The followed procedure to obtain the above results, consists on putting solid particles inside the flame (by means of alumina seeding distributed in the air incoming into the burner). Thermal radiance of alumina particles allows to diagnose flame temperature, due to agreement between temperature of flame and particles co- flowing in it. In combustion research last challenge is to perform, in the same time, flame temperature and velocity measurements with high time resolution. MWP was applied on flames, together with LDA (Laser Doppler Anemometer, a technique applied for velocity measurements) and sound analyzer, without problems, in a large range of flame working conditions. A final comparison among thermal, kinematic and acoustic spectra showed the rule of velocity field (together with vorticity, too) on temperature and sound, in the range of frequency lower than 1000 Hz. Harmonics, common to the three fields, where due to combustion chamber shape and the generation of stationary waves. Frequencies present in spectrum of velocity field where common to spectrum of temperature, owed to combustion extinction and reburning forced by velocity fluctuation generated by vortex evolutions. Finally some temperature frequencies, absent in the other fields, were due to front flame stretching or variation in chemical composition, smoothed by air inertia (for small wave lengths) or covered by room noise (for long waves)