French
English
In the current energy transition scenario, CH4−H2 mixture combustion is attractive in terms of lean-premixed conditions and reduction of NOxand CO2emissions, but it can significantly trigger combustion instabilities. Although gas turbines burners are designed to operate with different fuels (natural gas, syngas, biogas, etc.), they allowminimal variations in the fuel properties with respect to the design one (reducedfuel-flexibility).Actually, thermoacoustic instabilities result in one of the major drawbacks in gas turbine combustors.Then, the need to control and limit such a deleterious phenomenon is mandatory to avoid structural damage of the burner.From an acoustic point of view, combustor liner couldbe approximated by a perforated plate crossed by bias flow. Then, studying perforated plates traversed by bias flow can give a useful insight on sound absorption properties of liners, rather than investigate complex geometries, which require high computational cost simulations.The proposed seminar aims to show ongoing numerical and experimental research on the characterization of passive damping devices for acoustic oscillations inside gas turbine combustor chambers.Regarding the numerical activity, a numerically cost-effective CFD analysis will be presented to predict the acoustic impedance of perforated plates traversed by bias flow. Hypotheses, boundaries and operating conditions will bedescribed, focusing on the role of the Non-Reflecting-Boundary-Condition (NRBC) and the Transparent-Flow-Forcing condition in treating acoustic waves. Numerical results are compared both with linear analytical models and experimental data, by proving a fast and reliable prediction of the acoustic response.Finally, regarding the experimental research activities, the test rig of the Impedance Tube at the PolytechnicUniversity of Bari will be showed withthe experimental characterization of anHelmholtz resonator designed ad hocfor a real combustor chamber.
Dr. Michele Stefanizzi
Research Fellow at the Department ofMechanics, Mathematics and Management, Polytechnic University of Bari, Italy
