Gas Turbine Single Annular Combustor Sector: Combustion Dynamics

This paper investigates the combustion dynamics of a single cup gas turbine combustor sector, a swirl-stabilized burner with dilution and cooling air holes. The burner was fueled by natural gas and was operated at one atmospheric pressure with various air inlet temperatures, air pressure drops, and air–fuel ratios. Acoustic emissions as functions of operating conditions were measured. Chemiluminescence imaging with a high-speed CCD camera and simultaneous dynamic pressure measurements has been used to characterize the combustor’s behavior. Imaging of the combustion energy release rate has provided an insight on the flame structure and its interaction with the dilution air jets. The combustion dynamics were correlated well with the heat release rate in the primary zone or in the dilution air jet region. Two low-frequency combustion dynamics modes (fuel-rich combustor domes with frequency around 420Hz, and fuel-lean combustor domes with frequency around 280 Hz) were identified by a dynamic microphone, dynamic pressure transducers, and a high-speed CCD camera. A two-dimensional distribution of the heat release rate dynamics (amplitude and phase angle) reveals different combustion dynamics driving mechanisms for fuel-lean and fuel rich modes. The acoustic emissions for the fuel-lean combustion mode correlated well with the energy release rate dynamics of the swirling jet inside the combustor dome. The acoustic emissions for the fuel-rich mode were associated with the unsteady chemical energy release rate from interactions between the dilution air jets and the fuel-rich mixture convected from the combustor dome.