In the near future, combustion dynamics is expected to become a more critical issue in operation of lean premixed gas turbines. Firstly, due to the lack of a quality harmonization code for the gas injected in the distribution network: this increases fuel composition variability at the inlet of gas turbine combustors. Secondly, due to the increasing share of renewable sources of energy in the electricity grid: this causes more likely power fluctuations. Gas turbines will be required to perform quicker loading and unloading phases than current ones (while maintaining their stability and low pollutant emissions) to guarantee the grid stability. Such a scenario highlights the importance of developing reliable and robust combustion instability sensing techniques to be integrated into control systems. Besides, it also shows the need for new and more efficient gas turbine “parking” strategies with lower minimum environmental loads. With these needs in mind, this work compares an optical device (ODC, Optical Diagnostics of Combustion) with standard high-temperature pressure-transducers while monitoring the stable and unstable conditions of an experimental combustor equipped with an ANSALDO-SIEMENS V64.3A burner fed with lean CH4/Air mixtures. Pressure and flame radiant energy signals are compared in terms of frequencies and associated amplitudes. It is also suggested how they can be used for the early detection of thermo-acoustic instabilities, i.e., for the real-time identification of instability precursors. Then, tests are repeated at the same conditions using a V64.3A burner modified to operate in the volumetric combustion regime. Tests prove its enhanced stability, thus suggesting volumetric combustion as a strategy to operate gas turbines at lower loads.

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