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Acoustic characteristics of a rocket combustion chamber: radial baffle effects

Farshchi, M ; Sharif University of Technology | 2009

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  1. Type of Document: Article
  2. DOI: 10.1016/j.apacoust.2009.03.001
  3. Publisher: 2009
  4. Abstract:
  5. This paper describes methods used for determining the characteristic acoustic modes and frequencies of a liquid-propellant rocket-motor combustion chamber and effects of radial baffles on the chamber's acoustic field. A multi-point sensing experimental setup, including stationary and moving sensors, was used to measure characteristic frequencies and mode shapes of a combustion chamber. A new technique based on the comparison of signal phase angles from stationary sensors to that of a moving sensor was used to map complex characteristic mode shapes of a combustor. A three-dimensional Helmholtz acoustic solver was also developed using an efficient finite volume approach for complex geometries to simulate the acoustic field inside a combustor. Using this approach the effects of the convergent section of the nozzle and the number of radial baffles on the chamber's dominant acoustic modes with no mean flow were investigated. We have shown that the classical reduction of characteristic frequency of tangential modes caused by radial baffles is due to longitudinalization of tangential modes and is a function of the blade length and weakly dependent on the number of blades. Also, conjugate spinning modes are decoupled and do not spin in any baffled combustor, independent of the number of blades. On the other hand the converging nozzle section of a combustion chamber modifies pure longitudinal modes in the radial direction and pure tangential modes in the longitudinal direction. Existence of some mixed tangential-longitudinal modes in a combustor is dependent on the ratio of the nozzle throat diameter to the combustor head plate diameter. © 2009 Elsevier Ltd. All rights reserved
  6. Keywords:
  7. Combustion chamber ; Acoustic characteristics ; Acoustic modes ; Characteristic frequencies ; Characteristic mode shapes and frequencies ; Complex characteristics ; Complex geometries ; Conjugate modes ; Converging nozzles ; Experimental set-up ; Finite volume approaches ; Helmholtz ; Longitudinal directions ; Longitudinal modes ; Mean flows ; Mode shapes ; Moving sensors ; Multi-point sensing ; Nozzle throats ; Radial baffles ; Radial directions ; Rocket combustion chambers ; Signal phase ; Spinning modes ; Tangential modes ; Acoustic field measurement ; Acoustic fields ; Acoustic waves ; Combustion chambers ; Combustors ; Nozzles ; Rockets ; Sensors ; Smoke ; Structural panels ; Thermochemistry ; Three dimensional ; Combustion
  8. Source: Applied Acoustics ; Volume 70, Issue 8 , 2009 , Pages 1051-1060 ; 0003682X (ISSN)
  9. URL: https://www.sciencedirect.com/science/article/abs/pii/S0003682X09000590