Eventos Anais de eventos
COBEM 2023
27th International Congress of Mechanical Engineering
Analytical and Numerical Determination of Acoustic Modes of 25 kN Liquid Propellant Rocket Engine
Submission Author:
Maurício Sá Gontijo , DF
Co-Authors:
Maurício Sá Gontijo, Mateus Sant'Ana, Priscila Yamada, Renato Filho, Anieli Schrammel, Olexiy Shynkarenko, Jungpyo Lee, Artur Elias De Morais Bertoldi
Presenter: Anieli Schrammel
doi://10.26678/ABCM.COBEM2023.COB2023-1464
Abstract
Liquid propellant rocket engines are complex devices that work under extreme conditions and a wide range of pressure and temperatures. During operation, this type of engine is subject to several types of combustion instabilities, divided in low, intermediate and high frequency instabilities (in general, defined as 10 to 400 Hz, 400 to 1000 Hz and greater than 1000 Hz, respectively). These kinds of oscillations may cause chamber pressure peaks, which are a threat to the engine's performance and the thrust chamber and/or the vehicle's structural integrity. Thus, great efforts were conducted over the years to predict and suppress those phenomena. High frequency instabilities are commonly suppressed with baffles and acoustic cavities. In order to determine the necessity of those devices, acoustic analyses on the chamber are performed, since acoustic resonance might occur. In this work, a complete process of theoretical acoustic characterization was made on the new 25 kN Liquid Oxygen/Ethanol. This engine is being designed to be used on the new training rocket for launch centers, supported by the Brazilian government through the MCTI (Ministry of Science, Technology and Innovation), AEB (Brazilian Space Agency), FINEP (Financier of Studies and Projects) and FNDCT (National Fund for Scientific and Technological Development), and executed by DeltaV Engenharia Espacial. In this characterization, analytical calculations were validated with numerical simulations, with finite element method. Those results will be used to, if necessary, design baffles or resonators. The eigenfrequencies were obtained analytically trough the based on the Helmholtz equation for a cylindrical combustion chamber closed at both sides (injector and throat), obtaining the roots of the Bessel function first derivative. In future works, the model will be validated with experimental tests and, finally, the obtained data will be used to design the rocket's structure and the test bench, to avoid its natural frequencies. The used methodology provides frequencies of the longitudinal, tangential and radial acoustic modes, both in hot and cold conditions. Cold condition is also of great interest, since it can contribute with relevant data and with fast and simple tests.
Keywords
Liquid Propellant Rocket Engines, Vibro-acoustics, Numerical analysis
