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Direct impact of the Precessing Vortex Core in swirl stabilized flames

© TUB Kilian Oberleithner
© TUB Kilian Oberleithner

Since the discovery of the precessing vortex core (PVC), as the dominant coherent structure in swirling flows, numerous investigations have been conducted to study its properties in non-reacting [1-2] and reacting [3-4] 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, funded by the DFG, 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 a foregoing project, findings of the linear hydrodynamic stability analysis about the formation of the PVC are applied in this context [2-3]. 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 which serves as a proof of concept of different actuator concepts and sensor arrangements. The following investigations employing feed-back control allow for effective suppression of the PVC [5]. 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 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.

To evaluate the impact of the controlled PVC on flame and flow field, especially optical (laser-based) measurement techniques are utilized in connection with sensor-based pressure measurements. Time-resolved (Stereo-) Particle Image Velocimetry (PIV) measurements are conducted to investigate the flow field, whereas OH-Planar Laser Induced Fluorescence and OH*-chemiluminescence measurements generate data to characterize flame-shape and –dynamics.

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