Investigation on flame dynamic characteristics to air-inlet excitation in a gas turbine model combustor

The combustion characteristics for a gas turbine (GT) model combustor in air-inlet excitation are studied by Large Eddy Simulation (LES). Time series of heat release rate (HRR) fluctuation is captured during simulation. The precessing vortex core (PVC) structure is shown by pressure iso-surface, and the single/double helix branches of PVC alternately evolve in one forcing cycle. With the rotation of PVC, the high-speed ring zone (HSRZ) is periodically squeezed, and large-scale vortex roll-up results from that. The flame root structure is also significantly affected by PVC, which is one of the reasons for the HRR fluctuation. With the increase of the forcing amplitude, the flame response is divided into three parts. The linear growth zone and secondary rising zone are separated by saturation plateau. The flame dynamics analysis shows that the change of the flame structures and flame front oscillation modes are the apparent mechanism of the nonlinear flame response appearance.

Automated summary

The combustion characteristics of a gas turbine model combustor under air-inlet excitation are studied using Large Eddy Simulation (LES). The results show the presence of a precessing vortex core (PVC) structure, which alternately evolves into single and double helix branches during one forcing cycle. The rotation of the PVC causes periodic squeezing of the high-speed ring zone (HSRZ), resulting in large-scale vortex roll-up. The flame root structure is also significantly affected by the PVC, contributing to the fluctuation in heat release rate (HRR). The flame response can be divided into three parts with increasing forcing amplitude, characterized by a linear growth zone, saturation plateau, and secondary rising zone. The change in flame structures and flame front oscillation modes are identified as the apparent mechanism for the nonlinear flame response appearance.