TY - JOUR
T1 - Influence of scaling rules on loss of acoustic energy
AU - Morgenweck, Daniel
AU - Sattelmayer, Thomas
AU - Fassl, Felix
AU - Kaess, Roland
N1 - Funding Information:
Financial support has been provided by the German Research Council (DFG) in the framework of the Sonderforschungsbereich Transregio 40. We would like to thank Astrium, GmbH, for providing us data and counsel for this work. The Leipniz– Rechenzentrum is gratefully acknowledged for providing computational resources. Additional thanks go to the DLR, German Aerospace Center, Braunschweig, for granting us access to the acoustic solver PIANO.
PY - 2011
Y1 - 2011
N2 - The damping of acoustic oscillations in two different design concepts of rocket engine demonstrators is assessed. Both engines represent different scaling strategies for subscale demonstrators. In this context, one major question is which of the two designs are less prone to combustion instabilities. Different methods are presented to show the influence of geometry on the loss of acoustic energy. The decay coefficient is determined, which accounts for the overall loss of acoustic energy independent of the physical mechanism. The admittance at the intersection of the combustion chamber and nozzle is evaluated. The acoustic flux is calculated and divided into different kinds of contributions. In this regard, the importance of the relation between pure acoustic transport and convective transport is emphasized. It shows that the pure acoustic transport is directed into the combustion chamber. However, its fraction of acoustic energy is compensated by the convective transported acoustic energy, which is convected out of the thrust chamber. Thus, the overall acoustic energy in the system is decaying. The two designs show different damping characteristics for different modes. The photoscaled design is less stable for longitudinal modes but more stable for transverse modes. The first transverse mode in the Mach-scaled design is barely damped.
AB - The damping of acoustic oscillations in two different design concepts of rocket engine demonstrators is assessed. Both engines represent different scaling strategies for subscale demonstrators. In this context, one major question is which of the two designs are less prone to combustion instabilities. Different methods are presented to show the influence of geometry on the loss of acoustic energy. The decay coefficient is determined, which accounts for the overall loss of acoustic energy independent of the physical mechanism. The admittance at the intersection of the combustion chamber and nozzle is evaluated. The acoustic flux is calculated and divided into different kinds of contributions. In this regard, the importance of the relation between pure acoustic transport and convective transport is emphasized. It shows that the pure acoustic transport is directed into the combustion chamber. However, its fraction of acoustic energy is compensated by the convective transported acoustic energy, which is convected out of the thrust chamber. Thus, the overall acoustic energy in the system is decaying. The two designs show different damping characteristics for different modes. The photoscaled design is less stable for longitudinal modes but more stable for transverse modes. The first transverse mode in the Mach-scaled design is barely damped.
UR - http://www.scopus.com/inward/record.url?scp=79958037654&partnerID=8YFLogxK
U2 - 10.2514/1.48334
DO - 10.2514/1.48334
M3 - Article
AN - SCOPUS:79958037654
SN - 0022-4650
VL - 48
SP - 498
EP - 506
JO - Journal of Spacecraft and Rockets
JF - Journal of Spacecraft and Rockets
IS - 3
ER -