Feed-back control of the precessing vortex core in swirl-stabilized flames to exploit its direct impact on flame dynamics, thermoacoustic instabilities and emissions.

• Applicant: Professor Dr.-Ing. Kilian Oberleithner
• Subject Area: Fluid Mechanics
• Term: from 2013 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 247226395

Since the discovery of the precessing vortex core (PVC), as a typical coherent structure in swirling flows, numerous investigations have been conducted to study its properties in reacting and non-reacting flows. Until today, there is no clear evidence concerning directly usable effects of this fluid dynamic phenomenon on swirl-stabilized combustion as it is applied in industrial gas turbines. The primary reason for this knowledge gap is connected to the lack of possibilities to control the PVC precisely. The present research project aims to develop a feed-back control system, which allows for experimental control of the PVC at its point of origin in a targeted and precise way. Based on the foregoing project, findings of the linear hydrodynamic stability analysis about the formation of the PVC are applied in this context. After construction, implementation and calibration of the active flow control system in the generic combustion chamber test rig, experiments on turbulent swirl-stabilized flames will be conducted. Applying the control system for open-loop measurements provides insight into the lock-in behaviour of the PVC and serves to find the optimal position for actuation. The following investigations employing feed-back control allow for effective suppression of the PVC. The PVC can be described as a stable limit cycle; therefore, the system dynamics can be brought to its unstable fixed point by feed-back control. For this reason, different states of the PVC can be investigated so that this type of active flow control enables the chance to employ the PVC as an additional control parameter for the properties of reacting and non-reacting swirl-stabilized flows. In the following course of the project, the explicit influence of the PVC on flame dynamics, thermoacoustic instability and pollutant formation in swirl-stabilized combustion will be investigated.

• DFG Programme: Research Grants
• Co-Investigators: Professor Dr.-Ing. Jonas Moeck; Professor Dr.-Ing. Christian Oliver Paschereit