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M. Schulze, M. Zahn, M. Schmid, T. Sattelmayer
The dynamic flame response to acoustic excitation is numerically analyzed for a typical rocket engine application with supercritical H2/O2 combustion in a coaxial injector configuration. To reduce numerical efforts the frame of consideration is restricted to only a single flame, leading to low computational times and to the possibility of applying fast turnaround times. In each simulation, the single flame is subjected to an artificially generated acoustic field for a single-frequency excitation and is studied in terms of fluctuating heat release rates and governing periodic field structures. Parameter studies are carried out to analyze the coupling mechanisms, which are responsible for the fluctuating nature of the heat release rate. Studies show that the flame response depends on excitation frequency, which is varied between 8 000 and 16 000 Hz, and load point. Further investigations show that two different coupling mechanisms are present in the chamber which can be spatially distinguished. In the region close to the injector, the convective transport of periodically oscillating vortices is dominant. In the remaining region further downstream baroclinic effects due to strong density gradients in combination with axial acoustic pressure gradients govern the the periodic generation of vortices, which, in turn, lead to a fluctuating heat release rate. Those two mechanism provide unequal contributions to the total fluctuating heat release rate, providing different driving potentials for thermoacoustic instability.
Deutscher Luft- und Raumfahrtkongress 2014, Augsburg
Deutsche Gesellschaft für Luft- und Raumfahrt - Lilienthal-Oberth e.V., Bonn, 2014
21,0 x 29,7 cm, 14 Seiten
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